TREA

Direct CsI scintillator coating for improved digital X-ray detector assembly longevity

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Information

  • Patent Grant
  • 6720561
  • Patent Number
    6,720,561
  • Date Filed
    Thursday, December 6, 2001
    22 years ago
  • Date Issued
    Tuesday, April 13, 2004
    20 years ago
Information
Abstract
The present invention provides an X-ray detector assembly and a fabrication method, where the X-ray detector assembly comprises a scintillator material disposed on a detector matrix array disposed on a detector substrate; an encapsulating coating disposed on the scintillator material; a moisture resistant cover disposed over the detector substrate and the encapsulating coating, and an adhesive material disposed between the detector substrate and the moisture resistant cover so as to form a moisture vapor barrier. The adhesive material is disposed so that it is not in contact with the encapsulating coating. The fabrication method of the X-ray detector assembly includes the steps of disposing the encapsulating coating on the scintillator material and a portion of the detector substrate and removing the encapsulating coating from the portion of the detector substrate.
Description




BACKGROUND




This invention relates generally to the field of X-ray detector assemblies for medical imaging and more particularly to the construction of X-ray detector assemblies.




In an X-ray detector assembly, an amorphous silicon detector substrate is coated with a vapor phase deposited X-ray scintillator material. The scintillator material generates photons isotropically from the absorption of the X-rays. A reflective layer is required to reflect photons, which are emitted in a direction away from the detector substrate, back towards the detector substrate. A typical reflective layer (such as an Opticlad™ film, a registered trademark product available from the General Electric Company, Pittsfield, Mass.) covers the scintillator material. A detector matrix array subsequently measures the intensity of these photons. A moisture resistant seal is disposed between a moisture resistant cover and the detector substrate near the periphery of the X-ray detector assembly.




One important factor in medical imaging applications is in the detector spatial resolution. Photons, which are generated in the scintillator material over one detector pixel, must be counted only by that underlying pixel to obtain a high image resolution. Photons that are scattered to adjacent pixels reduce the clarity of the image. To this end, the scintillator material is vapor deposited in columnar or needle form. Individual needles are separated from one another and they possess aspect ratios (length/diameter) of 100 or greater. Photons traveling down the scintillator needles tend to be contained within the individual needle due to the higher refractive index of scintillator material over air, provided that the individual scintillator needles remain separated. The Cesium Iodide (CsI) scintillator material is known to be a very hydroscopic salt. Exposure of the CsI scintillator material to moisture can cause the CsI scintillator material to absorb the moisture, which further causes the individual CsI scintillator needles to fuse together.




One source of moisture that could effect the CsI scintillator material is the moisture that is contained in the pressure sensitive adhesive (PSA) layer of the Opticlad™ film that is used to attach the Opticlad™ film to the scintillator material. This Opticlad™ film reflective layer is placed over, and is in direct contact with, the CsI scintillator material.




However, applying the reflective layer reduces the detector image spatial resolution after the X-ray detector assembly is heated for several months at a temperature range between about 30 and about 35 degrees C. (e.g., conditions approximating normal operating environment). The MTF (Modulation Transfer Function) of the X-ray detector assembly is reduced, by a value of about 20% or greater, as a result of the moisture contained with in the PSA layer of the Opticlad™ film. The MTF is defined as the modulation of the image divided by the modulation of the object. Where:






Modulation
=



(


maximum
⁢

 

⁢
luminance

-

minimum
⁢

 

⁢
luminance


)


(


maximum
⁢

 

⁢
luminance

+

minimum
⁢

 

⁢
luminance


)


⁢

 

.











A second source of moisture is ambient environment moisture diffusion through the moisture resistant seal that bonds the moisture resistant cover to the detector substrate. This ambient environment moisture can degrade X-ray detector assembly performance. A third source of moisture is the moisture that is absorbed by the CsI scintillator material during X-ray detector assembly fabrication outside of the dry vacuum environment before sealing the detector substrate to the moisture resistant cover. Unless the X-ray detector assembly is sealed in a controlled, very low relative humidity ambient, the CsI scintillator material is exposed to moisture vapor during the assembly process during application of the moisture resistant seal. The CsI scintillator material has the potential to absorb moisture, which can degrade the performance of the X-ray detector assembly.




It is desirable to have an X-ray detector assembly design that minimizes the amount of moisture absorbed by the scintillator material from moisture sources inside the X-ray detector assembly. It is further desirable to have a robust seal assembly that protects the scintillator material and the structure holding the scintillator material from penetration by ambient moisture. It is further desirable to physically protect the X-ray detector assembly from damage caused by handling. It is also desirable that any encapsulating coating disposed over the scintillator material be easy to apply at temperatures less than about 250 degrees C. and the encapsulating coating fully contain the high aspect ratio scintillator needles. It is further desirable that any encapsulating coating forms a mold-like structure, reducing the moisture that can get into the CsI scintillator material, and constrain the CsI scintillator needles from touching adjacent scintillator needles to reduce X-ray picture degradation. It is further desirable that the encapsulating coating applies no distortion onto the scintillator material.




SUMMARY




The present invention provides an X-ray detector assembly and a fabrication method, where the X-ray detector assembly comprises a scintillator material disposed on a detector matrix array disposed on a detector substrate; an encapsulating coating disposed on the scintillator material; a moisture resistant cover disposed over the detector substrate and the encapsulating coating, and an adhesive material disposed between the detector substrate and the moisture resistant cover so as to form a moisture vapor barrier. The adhesive material is disposed so that it is not in contact with the encapsulating coating. The fabrication method of the X-ray detector assembly includes the steps of disposing the encapsulating coating on the scintillator material and a portion of the detector substrate and removing the encapsulating coating from the portion of the detector substrate.











DRAWINGS




These and other features, aspects and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:





FIG. 1

is a chart depicting an X-ray detector assembly relative image quality results with and without utilizing a mono-chloro-poly-para-xylylene material as the encapsulating coating disposed on the detector substrate adhesive bond area;





FIG. 2

is a chart depicting a two (2) step epoxy lap shear strength for the epoxy bond in moisture vapor barrier with and without utilizing a mono-chloro-poly-para-xylylene material as the encapsulating coating therebetween;





FIGS. 3 and 4

are cross sectional representations of X-ray detectors with a encapsulating coating disposed between a first epoxy layer and a second epoxy layer in moisture resistant dual epoxy seal in accordance with different embodiments of the test setups.





FIGS. 5

,


6


,


7


,


8


,


9


,


10


,


11


, and


12


are cross sectional representations of X-ray detectors in accordance with different embodiments of the present invention.











DETAILED DESCRIPTION OF THE INVENTION




The present invention provides an X-ray detector assembly that has a scintillator material disposed on a detector matrix array that is disposed on a detector substrate. An encapsulating coating is disposed on the scintillator material. A moisture resistant cover is disposed over the detector substrate and the encapsulating coating. An adhesive material is disposed between the detector substrate and the moisture resistant cover so as to form a moisture vapor barrier, wherein the adhesive material is disposed so that it is not in contact with the encapsulating coating.




The encapsulating coating is disposed directly onto the scintillator needles of the scintillator material to reduce scintillator performance degradation resulting from the scintillator material absorbing moisture when the scintillator material is exposed to moisture.




A successful encapsulating coating should possess a combination of properties including low stress, low moisture permeability, low X-ray, and light absorption, and non-reactivity with scintillator needles. Various mechanisms are envisioned by which these encapsulating coatings prevent degradation of scintillator performance resulting from the absorption of moisture during an exposure of the scintillator needles to moisture. The “encapsulating coating” as used herein is defined to mean that the encapsulating coating is deposited between the scintillator needle structure all the way to the bottom of each of the scintillator needles along all of the sidewalls of all of the scintillator needles. The encapsulating coating also has the ability to mold over the scintillator material to maintain a useful columinar scintillator structure even after the scintillator material has absorbed some moisture after having been exposed to moisture.




In all cases, the encapsulating coating should be deposited in a manner that does not substantially expose the scintillator material to a moisture-containing atmosphere either before or during the deposition process.




One suitable encapsulating coating comprises at least one polymer comprising para-xylylene moieties as structural units. In various embodiments, the polymers may comprise structural units derived from unsubstituted or substituted para-xylylene moieties. Illustrative examples of substituted para-xylylene moieties include but are not limited to mono-chloro-para-xylylene and di-chloro-para-xylylene. In the present invention the term parylene™, (a trademark of the Specialty Coating Systems, Inc. 5701 West Minnesota St. Indianapolis, Ind. 46241), is used to refer to both the polymers comprising structural units derived from unsubstituted or substituted para-xylylene moieties. In one embodiment of the present invention, and at least one polymer comprising para-xylylene moieties as structural units is typically vapor deposited. Alternatively, plasma polymerized hexamethyl disiloxane or a polymerized fluorine-containing hydrocarbon such as a polymerized fluoroethylene may be utilized as a suitable encapsulating coating. Alternatively, an inorganic barrier material such as MgF


2


, SiO, SiO


2


, TiO


2


or another inorganic material may be deposited using any of several deposition processes such as electron beam evaporation, sputtering, or chemical vapor deposition.




The encapsulating coating is directly deposited onto scintillator needles to prevent performance degradation of a scintillator material


3


of

FIG. 5

resulting from moisture exposure. CsI scintillator material was used in one embodiment of the present invention; however, other scintillator materials would also be acceptable. A parylene™ layer has been used as a common encapsulating coating in a particular embodiment of the present invention of the X-ray detector assembly. In one embodiment of the present invention the parylene™ layer is selected from a group consisting from a poly-para-xylylene material (parylene™ N), a mono-chloro-poly-para-xylylene material (parylene™ C), a di-chloro-poly-para-xylylene material (parylene™ D), and combinations thereof.




A series of six (6) tests were conducted using the mono-chloro-poly-para-xylylene material as the encapsulating coating.




In a test setup, a two step thermoset epoxy material with a curing temperature of less than about 100 degrees C. was utilized as an adhesive material. By way of example and not limitation, the herein arrangement is described with reference to

FIG. 5

to aid in presentation of the test data. A first epoxy layer (layer


11


of

FIG. 5

) was disposed onto a detector substrate adhesive bond area (area


7


of FIG.


5


). A second epoxy layer (layer


14


of

FIG. 5

) was disposed onto a moisture resistant cover adhesive bond area (area


9


of

FIG. 5

) so that second epoxy layer contacted first epoxy layer at an interface (interface


17


of FIG.


5


). In the first three tests, three different encapsulating coating configurations in the detector substrate adhesive bond area were tested to determine the mono-chloro-poly-para-xylylene material effect on the resulting epoxy bond strength in the moisture vapor dual epoxy barrier (barrier


16


in FIG.


5


).




In the first test, the baseline configuration was tested. In the baseline configuration, no encapsulating coating covered the scintillator material, and no encapsulating coating covered detector substrate adhesive bond area (area


7


as illustrated in FIG.


5


). Line


1


of

FIG. 1

depicts the decrease in relative image quality as a function of X-ray detector assembly operational hours.




In the second test, the encapsulating coating (similar to layer


4


of

FIG. 5

) was deposited on the scintillator material. The encapsulating coating was disposed in between a first epoxy layer (e.g., similar to layer


11


of

FIG. 5

) and detector substrate adhesive bond area (similar to area


7


of FIG.


5


). A second epoxy layer was then disposed on the moisture resistant cover and the cover was bonded to the first epoxy layer. The presence of the encapsulating coating in detector substrate adhesive bond area resulted in low epoxy bond strength in the moisture vapor barrier, as shown by Line


2


of FIG.


1


. The second test results indicate that poor epoxy bonding occurs between first epoxy layer and detector substrate, when encapsulating coating is disposed at detector substrate adhesive bond area. An X-ray detector assembly prepared in this manner failed life testing at 85 degrees C. and at 85 percent relative humidity after a few hundred hours. This low strength epoxy bond in the moisture vapor barrier was the result of having the first epoxy layer bonded to the encapsulating coating rather than having the first epoxy layer bonded to detector substrate adhesive bond area as in the baseline configuration (Line


1


of FIG.


1


).




In the third test, the encapsulating coating covered the scintillator material. However, encapsulating coating was not present in detector substrate adhesive bond area (area


7


of FIG.


5


). First epoxy layer was disposed on detector substrate adhesive bond area. Second epoxy layer was then disposed on moisture resistant cover and first epoxy layer so as to contact first epoxy layer at interface (interface


17


of

FIG. 5

) in the moisture vapor barrier. Line


3


of

FIG. 1

provides a depiction of the improvement in relative image quality as a function of X-ray detector assembly operational hours, compared to the baseline configuration (no mono-chloro-poly-para-xylylene material—Line


1


of

FIG. 1

) and the configuration with mono-chloro-poly-para-xylylene material in detector substrate adhesive bond area (Line


2


of FIG.


1


). When the mono-chloro-poly-para-xylylene material was not present in the detector substrate adhesive bond area, the X-ray detector assembly image quality did not substantially degrade over time, out through about 500 operational hours.




Three additional tests (


4


,


5


, and


6


) were performed with three different configurations of encapsulating coating at the interface (interface


17


of FIG.


5


), where the mono-chloro-poly-para-xylylene material was utilized as the encapsulating layer. This testing was designed to determine the effect of the mono-chloro-poly-para-xylylene material on the epoxy bond strength at interface


17


in the moisture vapor barrier. In all three of these tests, first epoxy layer was disposed on the detector substrate adhesive bond area prior to coating the scintillator material with the encapsulating coating. As learned from the first three test results, depositing first epoxy layer prior to applying mono-chloro-poly-para-xylylene material assisted in establishing good epoxy bond strength where first epoxy layer was disposed to detector substrate adhesive bond area. In test


4


, the encapsulating coating (layer


4


of

FIG. 3

) extended across the width of the interface (interface


17


of

FIG. 3

) by about 100% as illustrated in

FIG. 3

; in test


5


, the encapsulating coating (layer


4


of

FIG. 4

) extended across about 50% of the width of the interface (interface


17


of

FIG. 4

) as illustrated in

FIG. 4

; and in test


6


, the encapsulating coating (layer


4


of

FIG. 5

) was kept separate from the interface (interface


17


of FIG.


5


), as illustrated in FIG.


5


.




The fourth test was conducted with the mono-chloro-poly-para-xylylene material as the encapsulating coating


4


of

FIG. 3

covering about 100% of the width of interface


17


. Second epoxy layer


14


was disposed to the mono-chloro-poly-para-xylylene material at interface


17


and to moisture resistant cover


2


. The resulting epoxy bond lap shear strength of the moisture vapor dual epoxy barrier


16


is depicted as point


1


in FIG.


2


. It is believed that the low epoxy bond strength in the moisture vapor barrier


8


of

FIG. 3

at interface


17


was the result of the presence of encapsulating coating


4


disposed between first epoxy layer


11


and second epoxy layer


14


.




The fifth test was conducted with the mono-chloro-poly-para-xylylene material as the encapsulating material


4


of

FIG. 4

covering about 50% of the width of interface


17


. Second epoxy layer


14


was disposed to mono-chloro-poly-para-xylylene material and first epoxy layer


11


at interface


17


. Restricting the mono-chloro-poly-para-xylylene material to about 50% of the width of interface


17


provided improved epoxy bond lap shear strength in the moisture vapor dual epoxy barrier


16


as shown as point


2


in FIG.


2


. At point


2


of

FIG. 2

, the epoxy strength was higher than the test


4


(point


1


) results, where the mono-chloro-poly-para-xylylene material covered the entire interface


17


of FIG.


4


. It is believed that the resulting higher epoxy bond strength in the moisture vapor dual epoxy barrier


16


at interface


17


was the result of about half as much mono-chloro-poly-para-xylylene material disposed between first epoxy layer


11


and second epoxy layer


14


compared to the fourth test configuration.




The sixth test was conducted such that interface


17


of

FIG. 5

was not in contact with the mono-chloro-poly-para-xylylene material as the encapsulating material


4


in the moisture vapor dual epoxy barrier


16


. Second epoxy layer


14


and first epoxy layer


11


were disposed at interface


17


with no encapsulating coating present in interface


17


. Removing the encapsulating coating from interface


17


provided improved epoxy bond lap shear strength in the moisture vapor dual epoxy barrier


16


as shown as point


3


in FIG.


2


. Compared to both test


4


and test


5


results, it is understood that the improved epoxy bond lap shear strength in moisture vapor dual epoxy barrier


16


of

FIG. 5

at interface


17


was the result of ensuring that interface


17


was not in contact with the mono-chloro-poly-para-xylylene material.




Test results generated from tests


1


,


2


and


3


indicated that the decrease in relative image quality as a function of X-ray detector assembly operational hours is related to the amount of mono-chloro-poly-para-xylylene material in detector substrate adhesive bond area


7


of the moisture vapor dual epoxy barrier


16


when the mono-chloro-poly-para-xylylene material is utilized as the encapsulating coating. The test results of tests


4


,


5


, and


6


indicated that the decrease in epoxy bond lap shear strength in the moisture vapor dual epoxy barrier


16


is proportional to the amount of the mono-chloro-poly-para-xylylene material in interface


17


.




In one embodiment of the present invention, an X-ray detector assembly


1000


, comprises scintillator material


3


disposed on the detector matrix array


20


and the detector matrix array


20


is disposed on the detector substrate


1


(FIG.


6


). The encapsulating coating


4


, typically comprises at least one polymer comprising para-xylylene moieties as structural units, is disposed on scintillator material


3


and a detector substrate first portion


150


. Moisture resistant cover


2


is disposed over detector substrate


1


and is disposed over encapsulating coating


4


. As used herein, detector matrix array


20


typically refers to an array of photosensors disposed for detecting photons passing from the scintillator material


3


in response to incident radiation. Adhesive material


6


is disposed between detector substrate


1


and moisture resistant cover


2


so as to form a moisture vapor barrier


8


, adhesive material


6


is disposed so that it is not in contact with encapsulating coating


4


.




In the illustrations of the detector assembly


1000


in

FIGS. 3-12

, scintillator material


3


typically comprises a CsI material disposed in a CsI needle structure. The CsI needle structure commonly comprises a thallium doping material.




The encapsulating coating


4


typically comprises at least one polymer comprising para-xylylene moieties as structural units. In various embodiments, the polymers may comprise structural units derived from unsubstituted or substituted para-xylylene moieties. In one embodiment of the present invention, the encapsulating coating is selected form a group consisting of poly-para-xylylene material (parylene™ N), mono-chloro-poly-para-xylylene material (parylene™ C), di-chloro-poly-para-xylylene material (parylene™ D), and combinations thereof.




In another embodiment of the present invention, the encapsulating coating


4


of

FIG. 6

, further comprises a first encapsulating coating tier


122


of

FIG. 12

disposed on scintillator material


3


of

FIG. 6 and a

detector substrate first portion


150


. An inner reflective tier


124


of

FIG. 12

is disposed on first encapsulating coating tier


122


and a second encapsulating coating tier


126


of

FIG. 12

is disposed on inner reflective tier


124


.




First encapsulating coating tier


122


of

FIG. 12

typically comprises least one polymer comprising para-xylylene moieties as structural units. In various embodiments, the polymers may comprise structural units derived from unsubstituted or substituted para-xylylene moieties. In one embodiment of the present invention, the first encapsulating coating tier


122


is selected form a group consisting of poly-para-xylylene material (parylene™ N), mono-chloro-poly-para-xylylene material (parylener™ C), di-chloro-poly-para-xylylene material (parylene™ D), and combinations thereof. The inner reflective tier


124


typically comprises silver (Ag). The second encapsulating coating tier


126


typically comprises least one polymer comprising para-xylylene moieties as structural units. In various embodiments, the polymers may comprise structural units derived from unsubstituted or substituted para-xylylene moieties. In one embodiment of the present invention, the second encapsulating coating tier


126


is selected form a group consisting of poly-para-xylylene material (parylene™ N), mono-chloro-poly-para-xylylene material (parylene™ C), di-chloro-poly-para-xylylene material parylene™ D), and combinations thereof.




Detector substrate


1


of

FIG. 6

further comprises the detector substrate adhesive bond area


7


disposed on detector substrate


1


. Moisture resistant cover


2


further comprises the moisture resistant cover adhesive bond area


9


disposed on moisture resistant cover


2


. Adhesive material


6


is disposed between detector substrate adhesive bond area


7


and moisture resistant cover adhesive bond area


9


, where encapsulating coating


4


is not disposed therebetween. Detector substrate adhesive bond area


7


has a width designated “T


1


” in

FIG. 6

moisture resistant cover adhesive bond area


9


has a width designated “T


2


” in

FIG. 6

The detector substrate


1


, moisture resistant cover


2


, and adhesive material


6


are disposed to form a moisture vapor barrier


8


.




In another embodiment of the present invention, X-ray detector assembly


1000


of

FIG. 6

further comprises a reflective layer


5


disposed on encapsulating coating


4


. As noted herein, “on”, “over”, “above” and the like are used to refer to relative locations of items illustrated in the drawings and do not imply structural or operational limitations in the assembled device. Moisture resistant cover


2


is commonly disposed over reflective layer


5


covering detector matrix array


20


.




In the illustrations of the detector assembly


1000


in

FIGS. 5-7

, the moisture resistant cover


2


typically comprises a graphite/resin core


500


encapsulated by an aluminum foil


502


.




In one embodiment, the moisture resistant cover


2


of

FIG. 6

is disposed over encapsulating coating


4


and detector substrate


1


, so that a gap is disposed between moisture resistant cover


2


and encapsulating coating


4


. The gap is disposed between moisture resistant cover


2


and encapsulating coating


4


to have a width typically in a range between about 25 microns and about 125 microns. The range of the gap is provided for illustration purposes.




In another embodiment of the present invention, reflective layer


5


of

FIG. 6

is selected from a group consisting of silver (Ag), gold (Au), titanium dioxide (TiO


2


), Opticlad™ film, and combinations thereof. The Opticlad™ film is a polyester film with a layer of pressure sensitive adhesive, wherein the pressure sensitive adhesive further comprises about 40% by weight of titanium dioxide (TiO


2


).




In another embodiment of the present invention, the reflective layer


5


comprises silver (Ag).




In another embodiment of the present invention, an outer barrier


180


is disposed on an external adhesive material surface


190


of the adhesive material


6


, a portion of the moisture resistant cover bond area


9


and a portion of the detector substrate adhesive bond area


7


as shown in FIG.


6


. The outer barrier


180


is typically deposited by applying palladium acetate in range of between about 4 and about 6 weight percent chloroform solution and then nitrogen drying the chloroform solution. The chloroform solution is then typically irradiated with a UV248 excimer laser, to liberate the palladium. Electroless metal processing can then be used to deposit, as an example without limitation, boron nickel alloy as the outer barrier


180


. Alternatively, the outer barrier


180


is generated by metal sputtering, by way of example and not limitation, aluminum, palladium, titanium, and gold. In the metal sputtering embodiment, masking of the contact pads


21


is desired to protect the contact pads


21


against possible undesired shorting due to the sputtering process. Alternatively, an inorganic insulation material forms the outer barrier


180


. An example of an inorganic insulation material is without limitation a diamond-like carbon, such as Dylyn™ (a trademark of the Advanced Refractory Technology Inc. 699 Hertel Ave. Buffalo, N.Y. 14207).




In the illustration of the detector assembly


1000


in

FIG. 6

the adhesive material


6


commonly comprises a single step thermoset epoxy material with a curing temperature of less than about 100 degrees C.




In another embodiment of the present invention, an X-ray detector assembly


1000


of

FIG. 7

is described below with modifications noted with respect to the embodiment described above as FIG.


6


. X-ray detector assembly


1000


of

FIG. 7

further comprises a scintillator outer edge


19


on scintillator material


3


. Encapsulating coating


4


is deposited on scintillator material


3


to within a range (designated “T


4


” in

FIG. 7

) between about 0 microns and about 1500 microns of scintillator outer edge


19


. The T


4


range is provided for illustration purposes and is not intended to suggest a limitation.




Moisture resistant cover


2


is disposed over reflective layer


5


and detector substrate


1


, so that a gap is disposed between moisture resistant cover


2


and reflective layer


5


. The gap is disposed between moisture resistant cover


2


and reflective layer


5


to have a width T


3


.




Alternatively, as illustrated in

FIGS. 3-5

, first epoxy layer


11


and second epoxy layer


14


commonly comprise a two step thermoset epoxy material with a curing temperature of less than about 100 degrees C. When the encapsulating coating


4


of

FIG. 5

comprises at least one polymer comprising para-xylylene moieties as structural units, the encapsulating coating


4


does not extend over interface


17


.




In another embodiment of the present invention, when a two step epoxy comprising the first epoxy layer


11


of FIG.


5


and the second epoxy layer


14


are formed, the outer barrier


180


is disposed on an external first epoxy layer surface


210


of the first epoxy layer


11


, an external second epoxy layer surface


220


of the second epoxy layer


14


, a portion of the moisture resistant cover bond area


9


and a portion of the detector substrate bond area


7


. The outer barrier


180


deposition methods and materials used are described above.




In another embodiment of the present invention, shown in the

FIG. 7

, three epoxy layers commonly comprise the adhesive material


6


of

FIG. 6

, wherein the first epoxy layer


11


of

FIG. 7

is disposed to the detector substrate adhesive bond area


7


, the second epoxy layer


14


is disposed to the first epoxy layer


11


at the interface


17


, the third epoxy layer


300


is disposed to the second epoxy layer


14


at a second interface


315


and the third epoxy layer


300


is disposed to the moisture resistant cover adhesive bond area


9


. The moisture resistant cover


2


, third epoxy layer


300


, second epoxy layer


14


, first epoxy layer


11


and the detector substrate


1


are disposed to form the moisture vapor triple epoxy barrier


320


.




In another embodiment of the present invention, when three epoxy layers are disposed between the moisture resistant cover


2


and the detector substrate


1


, the outer barrier


180


shown in

FIG. 7

is disposed on the external first epoxy layer surface


210


of the first epoxy layer


11


, the external second epoxy layer surface


220


of the second epoxy layer


14


, an external third epoxy layer surface


310


of the third epoxy layer


300


, a portion of the moisture resistant cover bond area


9


and a portion of the detector substrate bond area


7


. The outer barrier


180


deposition methods and materials used are described above.




The number of epoxy layers disposed between the moisture resistant cover


2


and the detector substrate


1


is not limited to those discussed above. The single adhesive, two layer epoxy and three layer epoxy methods are provided for illustration and in no way implies a limitation. The final number of epoxy layers chosen is dependent on the X-ray detector assembly fabrication steps chosen and the final number of epoxy layers is left to the determination of the artisan.




A fabrication method for X-ray detector assembly


1000


of

FIG. 5

typically comprises the use of a two step epoxy material as the adhesive material


6


. Encapsulating coating


4


typically comprises at least one polymer comprising para-xylylene moieties as structural units in this application. Scintillator material


3


is deposited on detector matrix array


20


. Detector matrix array


20


is disposed on detector substrate


1


having contact pads


21


. First epoxy layer


11


is typically disposed on detector substrate adhesive bond area


7


prior to depositing the encapsulating coating


4


on scintillator material


3


, detector substrate first portion


150


, detector substrate second portion


160


, interface


17


, contact pads


21


, and a non-active underside


200


of detector substrate


1


. Encapsulating coating


4


is then removed from interface


17


, contact pads


21


, detector substrate second portion


160


and the non-active underside


200


of detector substrate


1


. Encapsulating coating


4


is removed by means of selective etching and the like, using a process such as Reactive Ion Etching (RIE) which utilizes an oxygen gas. Moisture resistant cover


2


, having moisture resistant cover adhesive bond area


9


, is disposed over detector substrate


1


and encapsulating coating


4


. Second epoxy layer


14


of

FIG. 5

is then disposed on moisture resistant cover adhesive bond area


9


so as to contact first epoxy layer


11


at interface


17


. Moisture resistant cover adhesive bond area


9


, detector substrate adhesive bond area


7


, first epoxy layer


11


, and second epoxy layer


14


form moisture vapor dual epoxy barrier


16


.




In another embodiment of the present invention the encapsulating coating


4


is also removed detector substrate second portion


150


(not shown in FIG.


5


).




The step of disposing the encapsulating coating


4


in the fabrication method for X-ray detector assembly


1000


of

FIG. 5

alternatively comprises disposing a first encapsulating coating tier


122


as shown in

FIG. 12

on scintillator material


3


of

FIG. 5

, detector substrate first portion


150


, detector substrate second portion


160


, interface


17


and contact pads


21


. Next, an inner reflective tier


124


as shown in

FIG. 12

is deposited on first encapsulating coating tier


122


; and then a second encapsulating coating tier


126


is disposed on inner reflective tier


124


.




A fabrication method for X-ray detector assembly


1000


of

FIG. 6

is described below with modifications noted with respect to the fabrication method described above for FIG.


5


. In the

FIG. 6

application, the detector assembly


1000


typically comprises the use of a single step adhesive material as the adhesive material


6


in the moisture vapor barrier


8


. The encapsulating coating


4


typically comprises at least one polymer comprising para-xylylene moieties as structural units. In various embodiments, the polymers may comprise structural units derived from unsubstituted or substituted para-xylylene moieties. In particular, the encapsulating coating


4


is selected form a group consisting of a poly-para-xylylene material (parylene™ N), mono-chloro-poly-para-xylylene material (parylene™ C), di-chloro-poly-para-xylylene material (parylene™ D), and combinations thereof. Typically, encapsulating coating


4


is initially deposited on scintillator material


3


, detector substrate first portion


150


, detector substrate second portion


160


, detector substrate adhesive bond area


7


, contact pads


21


and non-active underside


200


of detector substrate


1


. Encapsulating coating


4


is then removed from detector substrate adhesive bond area


7


, detector substrate second portion


160


, contact pads


21


, and non-active underside


200


of detector substrate


1


. Adhesive material


6


is disposed between detector substrate adhesive bond area


7


and moisture resistant cover adhesive bond area


9


so as to form the moisture vapor barrier


8


. Alternatively, the two epoxy layer approach as discussed above for

FIG. 5

can be used to comprise the adhesive material


6


that attaches the moisture resistant cover


2


to the detector substrate


1


.




In another embodiment of the present invention the encapsulating coating


4


is also removed from detector substrate second portion


150


(not shown in FIG.


6


). In the present invention a “portion” of the detector substrate is defined to be the detector substrate first portion


150


, detector substrate second portion


160


, detector substrate adhesive bond area


7


, contact pads


21


and non-active underside


200


of detector substrate


1


.




A fabrication method for X-ray detector assembly


1000


of

FIG. 7

is described below with modifications noted with respect to the fabrication method described above for the detector assembly of FIG.


5


. In the embodiment of the present invention shown in

FIG. 7

three epoxy layers are disposed between the moisture resistant cover


2


and the detector substrate


1


as discussed above. First epoxy layer


11


is typically disposed on detector substrate adhesive bond area


7


and the third epoxy layer


300


is typically disposed on the moisture resistant cover adhesive bond area


9


prior to depositing the encapsulating coating


4


on scintillator material


3


, detector substrate first portion


150


, detector substrate second portion


160


, interface


17


, contact pads


21


, and a non-active underside


200


of detector substrate


1


. The encapsulating coating


4


typically comprises at least one polymer comprising para-xylylene moieties as structural units. In various embodiments, the polymers may comprise structural units derived from unsubstituted or substituted para-xylylene moieties. In particular, the encapsulating coating


4


is selected form a group consisting of poly-para-xylylene material (parylene™ N), mono-chloro-poly-para-xylylene material (parylene™ C), a di-chloro-poly-para-xylylene material (parylene™ D), and combinations thereof. The encapsulating coating


4


is removed from a portion of scintillator material


3


covering a portion of detector substrate


1


typically that does not cover detector matrix array


20


. The encapsulating coating


4


is removed from the scintillator outer edge


19


towards detector matrix array


20


in a range (designated “T


4


” in

FIG. 7

) typically in a range between about 0 microns and 1500 microns. Encapsulating coating


4


is also removed from detector substrate first portion


150


, detector substrate second portion


160


, detector substrate adhesive bond area


7


, contact pads


21


, and non-active underside


200


of detector substrate


1


. The second epoxy layer


14


is disposed between the first epoxy layer


11


at interface


17


and third epoxy layer


300


at second interface


315


. Moisture resistant cover adhesive bond area


9


, detector substrate adhesive bond area


7


, second epoxy layer


14


, first epoxy layer


11


, and third epoxy layer


300


form the moisture vapor triple epoxy barrier


320


. Alternatively, the two epoxy layer approach as discussed above for

FIG. 5

can be used to attach the moisture resistant cover


2


to the detector substrate


1


, or the adhesive material


6


approach as discussed above for

FIG. 6

can be used to attach the moisture resistant cover


2


to the detector substrate


1


.




The step of disposing the encapsulating coating


4


in the fabrication methods for X-ray detector assembly


1000


of

FIGS. 5

,


6


and


7


alternatively comprises disposing a first encapsulating coating tier


122


as shown in

FIG. 12

on scintillator material


3


, detector substrate first portion


150


of

FIG. 7

, detector substrate second portion


160


, detector substrate adhesive bond area


7


, contact pads


21


and non-active underside


200


of detector substrate


1


. Next, an inner reflective tier


124


as shown in

FIG. 12

is deposited on first encapsulating coating tier


122


; and then a second encapsulating coating tier


126


is disposed on inner reflective tier


124


. Both the first encapsulating coating tier


122


and the second encapsulating coating tier


126


typically comprises at least one polymer comprising para-xylylene moieties as structural units. In various embodiments, the polymers may comprise structural units derived from unsubstituted or substituted para-xylylene moieties. In one embodiment of the present invention, the first encapsulating coating tier


122


and second encapsulating coating tier


126


are selected form a group consisting of poly-para-xylylene material (parylene™ N), mono-chloro-poly-para-xylylene material (parylene™ C), di-chloro-poly-para-xylylene material (parylene™ D), and combinations thereof.




In one alternative embodiment, the step of removing the encapsulating coating


4


in the fabrication methods for X-ray detector assembly


1000


of

FIG. 7

alternatively comprises placing a metallic hard mask (not shown) over the encapsulating material


4


such that the metallic hard mask does not cover the area designated as T


4


as described above, detector substrate first portion


150


, detector substrate second portion


160


, detector substrate adhesive bond area


7


, contact pads


21


and non-active underside


200


of detector substrate


1


. The encapsulating coating


4


is then typically removed by RIE utilizing an oxygen gas from the area designated as T


4


as described above, detector substrate first portion


150


, detector substrate second portion


160


, detector substrate adhesive bond area


7


, contact pads


21


and non-active underside


200


of detector substrate


1


. The metallic hard mask is then removed.




In another alternative embodiment, the step of removing the encapsulating coating


4


in the fabrication method for X-ray detector assembly


1000


of

FIG. 7

alternatively comprises, utilizing Opticlad™ as the reflective layer


5


and depositing the reflective layer


5


onto the encapsulating material


4


prior to removal of any excess encapsulating material


4


. The reflective layer


5


is deposited so as to cover the active portion of the detector substrate, but not cover the area designated as T


4


as described above, detector substrate first portion


150


, detector substrate second portion


160


, detector substrate adhesive bond area


7


, contact pads


21


and non-active underside


200


of detector substrate


1


. The encapsulating coating


4


is then typically removed by RIE utilizing an oxygen gas, where the Opticlad™ serves the function of the metallic hard mask, form the area designated as T


4


, detector substrate first portion


150


, detector substrate second portion


160


, detector substrate adhesive bond area


7


, contact pads


21


and non-active underside


200


of detector substrate


1


.




In the illustrations of

FIGS. 8-12

, a moisture resistant layer


40


or a combination of the moisture resistant layer


40


and planarized adhesive layer


80


are typically utilized in place of the moisture resistant cover


2


and adhesive material


6


. The encapsulating coating


4


typically comprises at least one polymer comprising para-xylylene moieties as structural units. In various embodiments, the polymers may comprise structural units derived from unsubstituted or substituted para-xylylene moieties. In one embodiment of the present invention, the encapsulating coating


4


is selected form a group consisting of poly-para-xylylene material (parylene™ N), mono-chloro-poly-para-xylylene material (parylene™ C), a di-chloro-poly-para-xylylene material (parylene™ D), and combinations thereof.




In another embodiment of the present invention, an X-ray detector assembly


1000


of

FIG. 8

is described below with modifications noted with respect to the embodiment described above as FIG.


6


. Reflective layer


5


is disposed on encapsulating coating


4


. A thin film mask


30


of

FIG. 8

is disposed on reflective layer


5


. The moisture resistant layer


40


is disposed on thin film mask


30


so as to extend over and terminate on detector substrate second portion


160


adjacent to reflective layer


5


. The moisture resistant layer


40


and detector substrate second portion


160


provide a humidity barrier


60


.




In another embodiment of the present invention, the encapsulating coating


4


of

FIG. 8

, further comprises the first encapsulating coating tier


122


of

FIG. 12

, the inner reflective tier


124


of FIG.


12


and the second encapsulating coating tier


126


of

FIG. 12

as described above for the

FIG. 6

embodiment.




Thin film mask


30


of

FIG. 8

is typically selected from the group consisting of aluminum (Al), magnesium fluoride (MgF), diamond-like carbon, boron carbide (B


4


C), boron nitride (BNO


2


), silicon nitrate (SiNO


3


), and silicon oxide (SiO).




Alternatively, X-ray detector assembly


1000


of

FIG. 8

may not have a thin film layer


30


disposed between reflective layer


5


and moisture resistant layer


40


. In this embodiment of the present invention, moisture resistant layer


40


is disposed on reflective layer


5


so as to extend over and terminate on detector substrate second portion


160


adjacent to reflective layer


5


.




X-ray detector assembly


1000


of

FIG. 8

commonly further comprises a corrosion protection layer


50


that is disposed on moisture resistant layer


40


so as to terminate on detector substrate second portion


160


adjacent to moisture resistant layer


40


.




Suitable material choices for corrosion protection layer


50


comprise materials having preferably low X-ray absorption, typically less than about 2% to reduce the degradation of the X ray detector assembly


1000


. These low X-ray absorption corrosion protection layer


50


materials typically have a thickness in range between about 1 micron and about 100 microns. The corrosion protection layer


50


materials are commonly selected from the group consisting of aluminum (Al), aluminum oxide (AlO), magnesium fluoride (MgF), diamond-like carbon, boron carbide (B


4


C), boron nitride (BNO


2


), silicon nitrate (SiNO


3


), silicon oxide (SiO), gold (Au), acrylic, at least one polymer comprising para-xylylene moieties as structural units, at least one polymer comprising structural units derived from unsubstituted, at least one polymer comprising substituted para-xylylene moieties. In one embodiment of the present invention, the corrosion protection layer


50


is selected form a group consisting of poly-para-xylylene material (parylene™ N), mono-chloro-poly-para-xylylene material (parylene™ C), di-chloro-poly-para-xylylene material (parylene™ D), and combinations thereof.




The combined width of detector substrate second portion


160


and detector substrate third portion


170


(designated as “T


6


” in

FIGS. 8-12

) typically has a range between about 3050 microns and about 4850 microns. The range of the T


6


width is provided for illustration purposes and the range of the T


6


width is not intended to suggest a limitation. In another alternative embodiment a planarized epoxy layer


80


is disposed over the detector substrate third portion


170


as depicted in

FIGS. 8 and 9

.




In another embodiment of the present invention when the corrosion protection layer


50


is not disposed on the moisture resistant layer


40


and the planarized adhesive layer


80


is not disposed on the detector substrate third portion


170


, X-ray detector assembly


1000


of

FIG. 8

further typically comprising a protective cover


100


and a protective cover epoxy


110


. Protective cover


100


is disposed over moisture resistant layer


40


and detector substrate third portion


170


. Protective cover epoxy


110


is disposed between detector substrate third portion


170


and protective cover


100


; protective cover epoxy


110


is disposed between moisture resistant layer


40


disposed over detector substrate second portion


160


and protective cover


100


. Encapsulating coating


4


is disposed so that it does not extend over detector substrate third portion


170


.




In another embodiment of the present invention when the corrosion protection layer


50


is disposed on the moisture resistant layer


40


and the planarized adhesive layer


80


is not disposed on the detector substrate third portion


170


, X-ray detector assembly


1000


of

FIG. 8

further typically comprising a protective cover


100


and a protective cover epoxy


110


. Protective cover


100


is disposed over corrosion protection layer


50


and detector substrate third portion


170


. Protective cover epoxy


110


is disposed between detector substrate third portion


170


and protective cover


100


; protective cover epoxy


110


is disposed between corrosion protection layer


50


disposed over detector substrate second portion


160


and protective cover


100


. Encapsulating coating


4


is disposed so that it does not extend over detector substrate third portion


170


.




In another embodiment of the present invention when the corrosion protection layer


50


is not disposed on the moisture resistant layer


40


and the planarized adhesive layer


80


is disposed on the detector substrate third portion


170


, X-ray detector assembly


1000


of

FIG. 8

further typically comprising a protective cover


100


and a protective cover epoxy


110


. Protective cover


100


is disposed over moisture resistant layer


40


and planarized adhesive layer


80


. Protective cover epoxy


110


is disposed between planarized adhesive layer


80


and protective cover


100


; protective cover epoxy


110


is disposed between moisture resistant layer


40


disposed over detector substrate second portion


160


and protective cover


100


. Encapsulating coating


4


is disposed so that it does not extend over planarized adhesive layer


80


.




In another embodiment of the present invention when the corrosion protection layer


50


is disposed on the moisture resistant layer


40


and the planarized adhesive layer


80


is disposed on the detector substrate third portion


170


, X-ray detector assembly


1000


of

FIG. 8

further typically comprising a protective cover


100


and a protective cover epoxy


110


. Protective cover


100


is disposed over corrosion protection layer


50


and planarized adhesive layer


80


. Protective cover epoxy


110


is disposed between planarized adhesive layer


80


and protective cover


100


; protective cover epoxy


110


is disposed between corrosion protection layer


50


disposed over detector substrate second portion


160


and protective cover


100


. Encapsulating coating


4


is disposed so that it does not extend over planarized adhesive layer


80


.




In another embodiment of the present invention, protective cover


100


of

FIGS. 8-12

is disposed over moisture resistant layer


40


with a gap disposed between protective cover


100


and moisture resistant layer


40


. The gap disposed between protective cover


100


and moisture resistant layer


40


is designated as “T


7


” in FIG.


12


.




In another embodiment of the present invention, protective cover


100


of

FIGS. 8-12

is disposed over corrosion protection layer


50


with a gap disposed between protective cover


100


and moisture resistant layer


40


. The gap disposed protective cover


100


and corrosion protection layer


50


is designated as “T


7


” in FIG.


8


.




The X-ray detector assembly


1000


as shown in

FIG. 8

typically is fabricated as follows: An adhesive material is deposited on the detector substrate


1


in detector substrate third portion


170


. In one embodiment of the present invention the adhesive material is an epoxy material. In one embodiment of the present invention the encapsulating coating


4


typically comprises at least one polymer comprising para-xylylene moieties as structural units. In various embodiments, the polymers may comprise structural units derived from unsubstituted or substituted para-xylylene moieties. In one embodiment of the present invention, the encapsulating coating is selected form a group consisting of poly-para-xylylene material (parylene™ N), mono-chloro-poly-para-xylylene material (parylene™ C), di-chloro-poly-para-xylylene material (parylene™ D), and combinations thereof.




The epoxy material is planarized with a Teflon™, (a trademark of the E. I. du Pont de Nemours and Company 1007 Market Street, Wilmington, Del. 19898), planarizing fixture (not shown) to form a planarized adhesive layer


80


that has a thickness designated as “T


5


” in

FIG. 8

The planarizing fixture is removed after planarized adhesive layer


80


has cured. A metal alloy Kovar™ (a trademark of the CRS Holdings, Inc. 209 Baynard Building 3411 Silverside Road, Wilmington, Del. 19810), (29% Ni, 53% Fe, 17% Co and 1% trace impurities) shadow mask (not shown) is laid down on planarized adhesive layer


80


, so that metal alloy shadow mask covers contact pads


21


and one edge of the metal alloy Kovar™ r shadow mask does not extend past a periphery of the detector matrix array


20


closest to the contact pads


21


. Scintillator material


3


is deposited onto metal alloy shadow mask and detector substrate


1


. Scintillator needles


120


grow to form scintillator material


3


and are in contact with detector matrix array


20


on detector substrate


1


. The metal alloy shadow mask is removed. Encapsulating coating


4


is deposited on scintillator material


3


, including coating between and along scintillator needles


120


of FIG.


12


. Encapsulating coating


4


is also deposited on detector substrate first portion


150


of

FIG. 8

, detector substrate second portion, planarized adhesive layer


80


and contact pads


21


. A contact shadow mask (not shown) is then laid down on the encapsulating coating


4


on planarized adhesive layer


80


, so that the contact shadow mask covers contact pads


21


and one edge of the contact shadow mask does not extend over detector substrate first portion


150


. The reflective layer


5


is deposited onto the encapsulating coating


4


covering scintillator material


3


and detector first portion


150


so as to not deposit reflective layer


5


on encapsulating coating


4


in detector substrate second portion


160


, planarized adhesive layer


80


and contact pads


21


. The thin film mask


30


is then deposited on the reflective layer


5


. The thin film mask


30


protects the reflective layer


5


when encapsulating coating


4


is removed by an oxygen RIE. The contact shadow mask is then removed. The encapsulating coating


4


is removed with RIE from detector substrate second portion


160


, planarized adhesive layer


80


, and contact pads


21


. A moisture resistant layer contact shadow mask (not shown) is then laid on planarized adhesive layer


80


, so that moisture resistant layer contact shadow mask covers contact pads


21


and one edge of moisture resistant layer contact shadow mask does not extend over the detector substrate second portion


160


. Moisture resistant layer


40


is deposited on thin film mask


30


and moisture resistant layer


40


terminates on detector substrate second portion


160


adjacent to thin film mask so as to form the humidity barrier


60


between moisture resistant layer


40


and detector substrate second portion


160


.




Alternatively, when the encapsulating coating removal process does not affect reflective layer


5


, the thin film mask


30


is not required; moisture resistant layer


40


is deposited on the reflective layer


5


and moisture resistant layer


40


terminates on detector substrate second portion


160


adjacent to reflective layer


5


.




In another embodiment of the present invention, the step of disposing encapsulating coating


4


of

FIG. 8

further typically comprises disposing first encapsulating coating tier


122


of

FIG. 12

on scintillator material


3


of

FIG. 8

, detector substrate first portion


150


, detector substrate second portion


160


, planarized adhesive layer


80


and contact pads


21


. Disposing inner reflective tier


124


of

FIG. 12

on first encapsulating coating tier


122


; and disposing second encapsulating coating tier


126


of

FIG. 12

on inner reflective tier


124


.




The X-ray detector assembly


1000


as shown in

FIG. 8

typically is fabricated as described above for the previous

FIG. 8

embodiment with the following modifications noted due to not disposing the planarized adhesive layer


80


on the detector substrate third portion


170


: The encapsulating coating


4


typically comprises at least one polymer comprising para-xylylene moieties as structural units. In various embodiments, the polymers may comprise structural units derived from unsubstituted or substituted para-xylylene moieties. In one embodiment of the present invention, the encapsulating coating


4


is selected form a group consisting of poly-para-xylylene material (parylene™ N), mono-chloro-poly-para-xylylene material (parylene™ C), di-chloro-poly-para-xylylene material (parylene™ D), and combinations thereof. The metal alloy Kovar™ shadow mask (not shown) is laid down on detector substrate


1


, so that metal alloy shadow mask covers contact pads


21


and one edge of the metal alloy Kovar™ shadow mask does not extend past a periphery of the detector matrix array


20


closest to the contact pads


21


. The scintillator material


3


is deposited as discussed above in the fabrication method embodiment as detailed for FIG.


8


. The metal alloy shadow mask is removed. Encapsulating coating


4


is deposited on scintillator material


3


, detector substrate first portion


150


, detector substrate second portion


160


, detector substrate third portion


170


and contact pads


21


. The contact shadow mask (not shown) is then laid down on encapsulating coating


4


on detector substrate third portion


170


, so that contact shadow mask covers contact pads


21


and one edge of the contact shadow mask does not extend over detector substrate first portion


150


. The reflective layer


5


is deposited onto the encapsulating coating


4


covering scintillator material


3


and detector first portion


150


so as to not deposit reflective layer


5


on encapsulating coating


4


in detector substrate second portion


160


, detector substrate third portion


170


and contact pads


21


. The encapsulating coating


4


is removed with RIE using an oxygen gas from detector substrate second portion


160


, detector substrate third portion


170


and contact pads


21


. The moisture resistant layer contact shadow mask (not shown) is then laid on detector substrate third portion


170


, so that moisture resistant layer contact shadow mask covers contact pads


21


and one edge of moisture resistant layer contact shadow mask does not extend over the detector substrate second portion


160


. The moisture resistant layer


40


is deposited as presented above in the

FIG. 8

fabrication method embodiment.




In another embodiment of the present invention, the step of disposing encapsulating coating


4


of

FIG. 8

further comprises disposing first encapsulating coating tier


122


of

FIG. 12

(not shown in

FIG. 8

) on scintillator material


3


of

FIG. 8

, detector substrate first portion


150


, detector substrate second portion


160


, detector substrate third portion


170


and contact pads


21


. Disposing inner reflective tier


124


of

FIG. 12

(not shown in

FIG. 8

) on first encapsulating coating tier


122


; and disposing second encapsulating coating tier


126


of

FIG. 12

(not shown in

FIG. 8

) on inner reflective tier


124


.




In a further embodiment, an X-ray detector assembly


1000


of

FIG. 9

is described below with modifications noted with respect to the embodiment described above as

FIG. 8

with planarized adhesive layer


80


disposed on detector substrate third portion


170


.




X-ray detector assembly


1000


of

FIG. 9

comprises moisture resistant layer


40


is disposed on reflective layer


5


and detector substrate second portion


160


so as to terminate on a planarized adhesive layer bond area


85


. Moisture resistant layer


40


, planarized adhesive layer


80


, and detector substrate third portion


170


are disposed to provide moisture resistant seal


70


. Encapsulating coating


4


is disposed so as to not to extend over planarized adhesive layer bond area


85


.




In another embodiment of the present invention, encapsulating coating


4


of

FIG. 9

further comprises the first encapsulating coating tier


122


of

FIG. 12

, the inner reflective tier


124


of FIG.


12


and the second encapsulating coating tier


126


of

FIG. 12

as described above in the

FIG. 8

embodiment.




X-ray detector assembly


1000


of

FIG. 9

typically further comprises thin film mask


30


disposed on reflective layer


5


. Moisture resistant layer


40


is disposed on thin film mask


30


and detector substrate second portion


160


so as to terminate on planarized adhesive layer bond area


85


.




Corrosion protection layer


50


commonly is disposed on moisture resistant layer


40


so as to terminate on planarized adhesive layer bond area


85


adjacent to moisture resistant layer


40


.




In another embodiment of the present invention, when the corrosion protection layer


50


is not disposed on the moisture resistant layer


40


, X-ray detector assembly


1000


of

FIG. 9

further typically comprising a protective cover


100


and a protective cover epoxy


110


. Protective cover


100


is disposed over moisture resistant layer


40


and planarized adhesive layer


80


. Protective cover epoxy


110


is disposed between planarized adhesive layer


80


and protective cover


100


. Protective cover epoxy


110


is disposed between moisture resistant layer


40


disposed over both detector substrate second portion


160


and detector substrate third portion


170


and protective cover


100


. Encapsulating coating


4


is disposed so that it does not extend over planarized adhesive layer


80


.




In another embodiment of the present invention when the corrosion protection layer


50


is disposed on the moisture resistant layer


40


, X-ray detector assembly


1000


of

FIG. 9

further typically comprising a protective cover


100


and a protective cover epoxy


110


. Protective cover


100


is disposed over corrosion protection layer


50


and planarized adhesive layer


80


. Protective cover epoxy


110


is disposed between planarized adhesive layer


80


and protective cover


100


. Protective cover epoxy


110


is disposed between corrosion protection layer


50


disposed over both detector substrate second portion


160


and detector substrate third portion


170


and protective cover


100


. Encapsulating coating


4


is disposed so that it does not extend over planarized adhesive layer


80


.




X-ray detector assembly


1000


as depicted in

FIG. 9

is fabricated as described above for fabrication method described for

FIG. 8

, except for the following fabrication steps described below.




Moisture resistant layer


40


is disposed on thin film mask


30


, detector substrate second portion


160


, and terminates on planarized adhesive layer bond area


85


. Moisture resistant layer


40


, planarized adhesive layer


80


, and detector substrate third portion


170


are disposed to form moisture resistant seal


70


. Alternatively, a corrosion protection layer


50


is commonly disposed on moisture resistant layer


40


and terminated on planarized adhesive layer bond area


85


adjacent to moisture resistant layer


40


.




In another embodiment, X-ray detector assembly


1000


is configured as illustrated in

FIG. 10

is described below with modifications noted with respect to the embodiment described above as FIG.


8


. Planarized adhesive layer


80


is disposed on detector substrate second portion


160


and detector substrate third portion


170


. First planarized adhesive layer bond area


86


is disposed over detector substrate second portion


160


. Second planarized adhesive layer bond area


87


is disposed over the detector substrate third portion


170


. Scintillator material


3


is deposited as described above for FIG.


8


. Encapsulating coating


4


is disposed on scintillator material


3


, detector substrate first portion


150


and first planarized adhesive layer adhesive bond area


86


, but not so as to extend over second planarized adhesive layer bond area


87


. Reflective layer


5


is disposed on encapsulating coating


4


. Thin film mask


30


is disposed on reflective layer


5


. Moisture resistant layer


40


is disposed on thin film mask


30


so as to terminate on second planarized adhesive layer adhesive bond area


87


adjacent to thin film mask


30


. Moisture resistant layer


40


, planarized adhesive layer


80


, detector substrate second portion


160


and detector substrate third portion


170


, provide moisture resistant seal


70


. This embodiment does not have the humidity barrier


60


of the

FIG. 8

embodiment, as the moisture resistant layer


40


does not contact the detector substrate


1


.




In another embodiment of the present invention, encapsulating coating


4


of

FIG. 10

further comprises a first encapsulating coating tier


122


of

FIG. 12

disposed on scintillator material


3


of

FIG. 10

, detector substrate first portion


150


and first planarized adhesive layer bond area


86


. Inner reflective tier


124


of

FIG. 12

disposed on first encapsulating coating tier


122


and a second encapsulating coating tier


126


of

FIG. 12

disposed on inner reflective tier


124


.




In another embodiment of the present invention, X-ray detector assembly


1000


of

FIG. 10

typically further comprises the protective cover


100


and the protective cover epoxy


110


. The arrangement of the protective cover


100


and the protective cover epoxy


110


are the same as presented above for FIG.


9


.




The X-ray detector assembly


1000


as depicted in

FIG. 10

is fabricated as described above for the

FIG. 8

fabrication method except for the following modified fabrication steps described below.




Planarized adhesive layer


80


is disposed on detector substrate second portion


160


and detector substrate third portion


170


. Encapsulating coating


4


is disposed on scintillator material


3


, detector substrate first portion


150


, detector substrate second portion


160


, first planarized adhesive layer bond area


86


, second planarized adhesive layer bond area


87


and contact pads


21


. A contact shadow mask (not shown) is then laid down on encapsulating coating


4


on planarized adhesive layer


80


, so that contact shadow mask covers contact pads


21


and one edge of contact shadow mask does not extend over first planarized adhesive bond area


86


of planarized adhesive layer


80


. The reflective layer


5


is then deposited onto encapsulating coating


4


so that no reflective layer


5


is deposited on encapsulating coating


4


that covers second planarized adhesive bond area


87


and contact pads


21


. The thin film mask is then deposited on to the reflective layer


5


so that no thin film mask


30


is deposited on encapsulating coating


4


that is deposited on the second planarized adhesive bond area


87


and contact pads


21


. The encapsulating coating


4


covering second planarized adhesive bond area


87


and contact pads


21


are removed. Moisture resistant layer contact shadow mask (not shown) is then laid on planarized adhesive layer


80


, so that the moisture resistant layer contact shadow mask covers contact pads


21


and one edge of moisture resistant layer contact shadow mask does extend past approximately one half of the width of the second planarized adhesive layer bond area


87


. Moisture resistant layer


40


is deposited on thin film mask


30


so as to terminate onto second planarized adhesive bond area


87


adjacent to thin film mask


30


. Moisture resistant layer


40


, planarized adhesive layer


80


, detector substrate second portion


160


and detector substrate third portion


170


form moisture resistant seal


70


. Corrosion protection layer


50


is typically disposed on moisture resistant layer


40


so as to terminate on second planarized adhesive layer bond area


87


adjacent to moisture resistant layer


40


.




An apparatus for an X-ray detector assembly


1000


of

FIG. 11

is described above in the

FIG. 10

description except as noted herein.




X-ray detector assembly


1000


of

FIG. 11

does not comprise the thin film mask


30


of

FIG. 10

; moisture resistant layer


40


is disposed on reflective layer


5


so as to terminate on second planarized adhesive layer bond area


87


adjacent to reflective layer


5


. The corrosion protection layer


50


is not disposed on moisture resistant layer


40


.




In another embodiment of the present invention, X-ray detector assembly


1000


of

FIG. 11

may alternatively further comprises protective cover


100


and protective cover epoxy


110


. The protective cover


100


and protective cover epoxy


110


has the same arrangement description as provided above for

FIG. 9

for the alternative where there is no corrosion protection layer


50


disposed on moisture resistant layer


40


.




In another embodiment of the present invention, X-ray detector assembly


1000


of

FIG. 11

the encapsulating coating


4


alternatively comprises the first encapsulating coating tier


122


of

FIG. 12

, the inner reflective tier


124


and the second encapsulating coating tier


126


arranged as described above in the

FIG. 10

embodiment.




An apparatus for an X-ray detector assembly


1000


of

FIG. 12

is described as above for the

FIG. 11

embodiment except as noted herein. In this embodiment there is no reflective layer


5


disposed between the encapsulating coating


4


and the moisture resistant layer


40


, where the encapsulating coating


4


is comprised of a multi-tiered encapsulating coating structure as described above in the

FIG. 10

description.




In another embodiment of the present invention, X-ray detector assembly


1000


of

FIG. 12

may alternatively further comprise the protective cover


100


and the protective cover epoxy


110


arrangement described above for the

FIG. 9

embodiment where the corrosion protection layer


50


does not cover the moisture resistant layer


40


.




A specific embodiment of a method and apparatus for utilizing the encapsulating coating


4


in conjunction with scintillator material


3


having a needle structure to produce the X-ray detector assembly


1000


according to the present invention has been described for the purpose of illustrating the invention and the fabrication for making the invention. It should be understood that the implementation of other variations and modifications of the invention and its various aspects will be apparent to one skilled in the art, and that the invention is not limited by the specific embodiments described. Therefore, it is contemplated to cover the present invention any and all modifications, variations, or equivalents that fall within the true spirit and scope of the basic underlying principles disclosed and claimed herein.




From the preceding description of various embodiments of the present invention, it is evident that the objects of the invention are attained. Although the invention has been described and illustrated in detail, it is to be clearly understood that the same is intended by way of illustration and example only and is not to be taken by way of limitation. Accordingly, the spirit and scope of the invention are to be limited only by the terms of the appended claims.



Claims
  • 1. An X-ray detector assembly comprising:a detector substrate; a scintillator material disposed on a detector matrix array disposed on said detector substrate; an encapsulating coating disposed on said scintillator material; a moisture resistant cover disposed over said detector substrate and said encapsulating coating; and an adhesive material disposed between said detector substrate and said moisture resistant cover so as to form a moisture vapor barrier; wherein said adhesive material is disposed so that it is not in contact with said encapsulating coating.
  • 2. The X-ray detector assembly as in claim 1, wherein said scintillator material has a plurality of scintillator needle structures, and wherein said encapsulating coating is deposited between said plurality of scintillator needle structures all the way to a bottom and along all sidewalls of each of said scintillator needle structures, so as to mold over said scintillator material.
  • 3. The X-ray detector assembly as in claim 1, wherein said encapsulating coating comprises at least one polymer comprising para-xylylene moieties as structural units.
  • 4. The X-ray detector assembly as in claim 3, wherein said para-xylylene moieties are comprised of structural units of unsubstituted para-xylylene moieties.
  • 5. The X-ray detector assembly as in claim 3, wherein said para-xylylene moieties are comprised of structural units of substituted para-xylylene moieties.
  • 6. The X-ray detector assembly as in claim 3, wherein said para-xylylene moieties are comprised of structural units of both substituted and unsubstituted para-xylylene moieties.
  • 7. The X-ray detector assembly as in claim 3, said encapsulating coating further comprising:a first encapsulating coating tier disposed on said scintillator material and a detector substrate first portion; an inner reflective tier disposed on said first encapsulating coating tier; and a second encapsulating coating tier disposed on said inner reflective tier.
  • 8. The X-ray detector assembly as in claim 7 wherein:said first encapsulating coating tier is selected from a group of a mono-chloro-poly-para-xylylene material, a di-chloro-poly-para-xylylene material, a para-xylylene material, and combinations thereof; said inner reflective tier comprises silver (Ag); said second encapsulating coating tier is selected from a group of said mono-chloro-poly-para-xylylene material, said di-chloro-poly-para-xylylene material, said para-xylylene material, and said combinations thereof.
  • 9. The X-ray detector assembly as in claim 3, wherein said adhesive material is disposed between a detector substrate adhesive bond area and a moisture resistant cover adhesive bond area, so that no said encapsulating coating is disposed therebetween.
  • 10. The X-ray detector assembly as in claim 3, wherein said adhesive material comprises a thermoset epoxy material with a curing temperature of less than about 100 degrees C.
  • 11. The X-ray detector assembly as in claim 10, wherein said adhesive material further comprises a first epoxy layer and a second epoxy layer; wherein said first epoxy layer is disposed on a detector substrate adhesive bond area so that no said encapsulating coating is disposed therebetween, wherein said second epoxy layer is disposed on said first epoxy layer at an interface so that no said encapsulating coating is disposed therebetween, wherein said second epoxy layer is disposed on a moisture resistant cover adhesive bond area so that no said encapsulating coating is disposed therebetween, wherein said first epoxy layer, said second epoxy layer, said detector substrate and said moisture resistant cover are disposed to form a moisture vapor dual epoxy barrier.
  • 12. The X-ray detector assembly as in claim 11 further comprising: an outer barrier, wherein said outer barrier is disposed on an external first epoxy layer surface of said first epoxy layer, an external second epoxy layer surface of said second epoxy layer, a portion of said moisture resistant cover bond area and a portion of said detector substrate adhesive bond area.
  • 13. The X-ray detector assembly as in claim 12, wherein said outer barrier is selected from a group consisting of a boron nickel alloy, Al, Pd, Ti, Ag, and an inorganic insulation material.
  • 14. The X-ray detector assembly as in claim 11, wherein said encapsulating coating is disposed so as to not extend over interface between respective layers of said two-step thermoset epoxy material.
  • 15. The X-ray detector assembly as in claim 10, wherein said adhesive material further comprises three epoxy layers; wherein a first epoxy layer is disposed on a detector substrate adhesive bond area so that no said encapsulating coating is disposed therebetween, wherein said second epoxy layer is disposed on first epoxy layer at an interface so that no said encapsulating coating is disposed therebetween, wherein a third epoxy layer is disposed on said second epoxy layer at a second interface so that no said encapsulating coating is disposed therebetween, and wherein said third epoxy layer is disposed on a moisture resistant cover adhesive bond area so that no said encapsulating coating is disposed therebetween, wherein said first epoxy layer, said second epoxy layer, said third epoxy layer, said detector substrate and said moisture resistant cover are disposed to form a moisture vapor triple epoxy barrier.
  • 16. The X-ray detector assembly as in claim 15, further comprising:an outer barrier, wherein said outer barrier is disposed on an external first epoxy layer surface of said first epoxy layer, an external second epoxy layer surface of said second epoxy layer, an external third epoxy layer surface of said third epoxy layer a portion of said moisture resistant cover bond area and a portion of said detector substrate adhesive bond area.
  • 17. The X-ray detector assembly as in claim 16, wherein said outer barrier is selected from a group consisting of a boron nickel alloy, Al, Pd, Ti, Ag, and an inorganic insulation material.
  • 18. The X-ray detector assembly as in claim 1, wherein said encapsulating coating is selected from a group consisting of a mono-chloro-poly-para-xylylene material, a di-chloro-poly-para-xylylene material, a poly-para-xylylene material, and combinations thereof.
  • 19. The X-ray detector assembly as in claim 1, further comprising:an outer barrier, wherein said outer barrier is disposed on an external adhesive material surface of said adhesive material, said moisture resistant cover bond area and said detector substrate adhesive bond area.
  • 20. The X-ray detector assembly as in claim 19, wherein said outer barrier is selected from a group consisting of a boron nickel alloy, Al, Pd, Ti, Ag, and an inorganic insulation material.
  • 21. The X-ray detector assembly as in claim 1, said X-ray detector assembly further comprising:a scintillator outer edge disposed around the circumference of said scintillator material; said encapsulating coating being disposed on said scintillator material so as to not overlie said scintillator outer edge.
  • 22. The X-ray detector assembly as in claim 1, said X-ray detector assembly further comprising:a reflective layer disposed on said encapsulating coating.
  • 23. The X-ray detector assembly as in claim 22, wherein said reflective layer is selected from a group consisting of silver (Ag), gold (Au), titanium dioxide (TiO2) and a polyester film with a layer of a pressure sensitive adhesive, and combinations thereof.
  • 24. The X-ray detector assembly as in claim 1, wherein said scintillator material comprises a cesium iodide (CsI) material disposed in a CsI needle structure.
  • 25. The X-ray detector assembly as in claim 24, wherein said CsI needle structure further comprises a thallium doping material.
  • 26. The X-ray detector assembly as in claim 1, wherein said moisture resistant cover comprises a graphite/resin core, encapsulated by an aluminum foil.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT

The United States Government may have certain rights in this invention pursuant to contract number 70NANB5H1148 awarded by the United States Department of National Institute of Standards and Technology.

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