Patent Grant
7165831
The invention relates to micro-fluid ejection devices such as ink jet printheads and methods for making micro-fluid ejection devices having improved fluid flow characteristics.
A conventional micro-fluid ejection device such as an ink jet printhead generally has flow features either formed in a thick film layer deposited on a semiconductor substrate containing ink ejection devices or flow features ablated along with nozzle holes in a polymeric nozzle plate material. The term “flow features” is used to refer to fluid flow channels, fluid ejection chambers, and other physical features that provide a fluid such as ink to ejection devices on the semiconductor substrate. When both the nozzle holes and flow features are ablated in the nozzle plate material, a thick film material is typically not present. A disadvantage of forming the flow features and nozzle holes in the nozzle plate material is that the flow feature height and nozzle bore length are constrained by the nozzle plate material thickness. For micro-fluid ejection heads having a separate thick film layer and nozzle plate with the flow features formed in a thick film layer, the nozzle bore length is constrained to equal to the nozzle plate material thickness and the flow feature dimensions are determined by the thickness of the thick film layer.
With a trend toward increasing the functionality of micro-fluid ejection devices, it is desirable to provide fluid ejection devices on a single semiconductor substrate for ejecting different fluids having different drop masses. However, for largely disparate drop masses, the above constraints make the design of a single semiconductor substrate for multiple fluids difficult. For example, smaller droplet masses may be accommodated using flow features ablated in a nozzle plate material of a particular thickness. However, the larger droplet masses require additional flow features that cannot be ablated in a nozzle plate material suitable only for smaller drop masses. Alternatively, larger droplet masses may be accommodated using flow features formed in a thick film layer with nozzles ablated in a nozzle plate. However, the combined thickness of the thick film layer and nozzle plate degrades the ejection efficiency of the smaller droplet masses ejected from the same semiconductor substrate.
As the speed of micro-fluid ejection devices such as ink jet printers, increases the frequency of fluid ejection by individual ejection actuator elements must also increase requiring more rapid refilling of fluid ejection chambers. The requirement for more rapid refilling provides an incentive to devise a novel approach to providing flow features suitable for fluid ejection actuators for multiple size droplet masses on a single semiconductor substrate. Hence, there exists a need for improved micro-fluid ejection devices and methods for making the devices.
With regard to the foregoing, the disclosure provides an improved micro-fluid ejection head structure having multiple arrays of fluid ejection actuators. The structure includes a semiconductor substrate having a first array of fluid ejection actuators for ejecting a first fluid therefrom, and a second array of fluid ejection actuators for ejecting a second fluid therefrom. The first array of fluid ejection actuators is disposed in a first location on the substrate, and the second array of fluid ejection actuators is disposed in a second location on the substrate. A thick film layer having a thickness is attached adjacent the semiconductor substrate. The thick film layer has fluid flow channels formed therein solely for the first array of fluid ejection actuators. A nozzle plate is attached to the thick film layer opposite the semiconductor substrate. The nozzle plate having fluid flow channels formed therein for both the first array of fluid ejection actuators and the second array of fluid ejection actuators.
In another embodiment, there is provided a method of making a micro-fluid ejection head structure. The method includes the steps of providing a semiconductor substrate and forming a first array of fluid ejection actuators for ejecting a first fluid therefrom in a first location on the semiconductor substrate. At least a second array of fluid ejection actuators for ejecting a second fluid therefrom is formed in a second location on the semiconductor substrate. A thick film layer is deposited with a thickness adjacent the first and second arrays of fluid ejection actuators on the semiconductor substrate. Fluid flow channels are formed in the thick film layer solely for the first array of fluid ejection actuators. A nozzle plate material is provided for attachment to the thick film layer. Fluid flow channels are formed in the nozzle plate material for both the first and second arrays of fluid ejection actuators. The nozzle plate is attached to the thick film layer opposite the semiconductor substrate to provide the micro-fluid ejection head structure.
An advantage of the embodiments described herein is that it enables independent variation of fluid flow characteristics for multiple arrays of fluid ejection actuators on a single substrate. Independent variation of fluid flow characteristics is provided by combining fluid flow channels formed in thick film layer with fluid flow channels and nozzle holes formed in a nozzle plate material for at least one array of fluid ejection actuators. As a result of embodiments, fluid ejector arrays of different ejection volumes may be included on a single ejection head. For example, an ink ejection head may include ejection actuators for black ink that eject about four times the volume of ink ejected from cyan, magenta, and yellow ejection actuators on the same ejection head. Another advantage is that an ejection head having two different size ejection actuator arrays for a single fluid may be provided with a single fluid source without deleteriously affecting the fluid flow to the two actuator arrays. Such advantages are not easily provided by conventional ejection heads and fabrication methods.
Further advantages of the embodiments may be better understood by reference to the detailed description when considered in conjunction with the figures, which are not to scale and which are provided to illustrate the principle features described herein. In the drawings, like reference numbers indicate like elements through the several views.
With reference to
The ejection head 12 preferably contains a nozzle plate 16 containing a plurality of nozzle holes 18 each of which are in fluid flow communication with a fluid in the supply container 14. The nozzle plate 16 is preferably made of an ink resistant, durable material such as polyimide and is attached to a semiconductor substrate 20 that contains fluid ejection actuators as described in more detail below. The semiconductor substrate 20 is preferably a silicon semiconductor substrate.
Fluid ejection actuators on the semiconductor substrate 20 are activated by providing an electrical signal from a controller to the ejection head 12. The controller is preferably provided in a device to which the supply container 14 is attached, such as an ink jet printer. The semiconductor substrate 20 is electrically coupled to a flexible circuit or TAB circuit 22 using a TAB bonder or wires to connect electrical traces 24 on the flexible or TAB circuit 22 with connection pads on the semiconductor substrate 20. Contact pads 26 on the flexible circuit or TAB circuit 22 provide electrical connection to the controller in the printer for activating the fluid ejection actuators on the ejection head 12.
During a fluid ejection operation such as printing with an ink, an electrical impulse is provided from the controller to activate one or more of the fluid ejection actuators on the ejection head 12 thereby forcing fluid through the nozzles holes 18 toward a media. Fluid is caused to refill ink chambers in the ejection head 12 by capillary action between actuator activation. The fluid flows from a fluid supply in container 14 to the ejection head 12.
It will be appreciated that micro-fluid ejection devices such as ink jet printers continue to be improved to provide higher quality images. Such improvements include increasing the number of nozzle holes 18 and ejection actuators on a semiconductor substrate 20, reducing the size of the nozzle holes 18 and substrate 20, and increasing the frequency of operation of the ejection actuators.
One improvement includes providing an ejection head capable of ejecting multiple different fluids. Such an ejection head is provided by a substrate 28 containing multiple fluid supply slots 30, 32, 34, and 36 (
The frequency of fluid ejection from each of the arrays 38–46 depends on fluid flow characteristics of an ejection head containing the substrate 28. For example, the operational frequency of fluid ejection from each nozzle in a nozzle plate is limited by the time required to replenish fluid to a fluid chamber adjacent the fluid actuator 47. Fluid refill times are affected by the flow feature dimensions of the ejection head.
A portion of an ejection head 48 containing the substrate 28 and a nozzle plate 50 is illustrated in
A cross-sectional view, not to scale, of a portion of the ejection head 48 is illustrated in
As shown in
The flow features formed in the nozzle plate 50 may be formed as by laser ablating the nozzle plate material. Typically, the nozzle plate 50 is made of a polyimide material that is readily laser ablatable. Materials suitable for nozzle plate 56 according to the invention are generally available in thicknesses ranging from about 10 to about 70 microns. Commercially available nozzle plate materials have thicknesses of 25.4 microns, 27.9 microns, 38.1 microns, or 63.5 microns. Of the total thickness of the nozzle plate material, 2.54 or 12.7 microns may include an adhesive layer that is applied by the manufacturer to the nozzle plate material. It will be understood however, that the invention is also applicable to a nozzle plate material that is provided absent the adhesive layer. In this case, an adhesive may be applied separately to attach the nozzle plate 50 to the thick film layer 68.
The flow features may be formed in the thick film layer 68 as by a photolithographic technique. Typically, the thick film layer 68 is made of a photoresist material, either positive or negative photoresist, that is spin coated onto the substrate 28. In
A perspective view of arrays 38 and 42 is illustrated in
Having a single ejection head 48 containing multiple size fluid ejection actuators 47 and nozzle holes 78 and 80 provides increased versatility for use of the ejection head 48. For example, a multi-color ink jet printhead may include the ejection head 48, wherein black, cyan, magenta, and yellow inks are ejected from the ejection head 48. Each of the inks may have a different flow characteristic or volume requirement which may be achieved by variation in the fluid flow feature design of the ejection head 48 for each of the inks.
As will be further appreciated, providing a suitable thick film layer 68 and ablatable nozzle plate 50 enables tuning fluid flow characteristics for more efficient fluid ejection at higher frequencies. In embodiments described herein, the flow features for the fluid ejection arrays 38–46 are relatively independent of either of the thickness of the thick film layer 68 or of the thickness of the nozzle plate 50.
Variations in the flow feature dimensions between adjacent fluid flow channels 59 and 61 enable tuning of fluid flow to the fluid chambers 52 and 54. For example, even though fluid chamber 52 is relatively further away from the fluid supply slot 30 than fluid chamber 54, refill times for the fluid chambers 52 and 54 can be made similar by varying certain dimensions of the fluid flow channels 59 and 61 as herein described. With reference of
The foregoing modification of the fluid flow channel 59 is possible because the fluid flow channel 59 is formed in both the thick film 68 and in the nozzle plate 50. By contrast, the fluid flow channels 86 and 88 for nozzle holes 80 are formed only in the nozzle plate 50.
For further clarification, let CD4 (
To assure the most robust adhesion of the thick film layer 68 to the substrate 28, it is desirable to size CD2 such that WTF is greater than or equal to TF, where WTF is at least about 12 microns.
With regard to the above relationships, a comparison of the dimensions for ejector arrays 38 and 42 with reference to
In order to provide similar flow characteristics for chambers 52 and 54 in ejector arrays 38 and 40 (
For flow channels 59 and 61, the resistance of each channel is substantially the same as evidenced by the flow resistance ratio of about 1.0. Accordingly, the ejected mass of fluid from each channel 59 and 61 is approximately the same. It will be appreciated that the thick film layer 68 thickness (TF) may be decreased by increasing the choke widths (CD1 and CD3) for the channels and/or decreasing the choke lengths (L1 and L2). A reduced choke length (L1 and L2) enables use of a narrower substrate 28, thereby reducing the cost of a substrate 28 containing multiple fluid supply slots 30–36 for multiple fluids. However, the flow resistance of adjacent fluid flow channels 59 and 6i can be made substantially the same by varying the choke widths (CD1 and CD3) in the thick film layer 68 to provide equivalent jetting performance for the adjacent fluid chambers 52 and 54. Furthermore, an ejection head 48 for ejecting different volumes of different fluids may be provided using a combination of the thick film layer 68 of minimum thickness and the nozzle plate 50 wherein the fluid flow channels may be specifically configured for each array of fluid ejection actuators 38–46.
Having described various aspects and embodiments of the disclosure and several advantages thereof, it will be recognized by those of ordinary skills that the embodiments described herein are susceptible to various modifications, substitutions and revisions within the spirit and scope of the appended claims.
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