Direct metalization of electrical circuit structures

Abstract

An electrical interconnect including a first circuitry layer with a first surface and a second surface. At least a first dielectric layer is printed on the first surface of the first circuitry layer to include a plurality of first recesses. A conductive material is plated on surfaces of a plurality of the first recesses to form a plurality of first conductive structures electrically coupled to, and extending generally perpendicular to, the first circuitry layer. A filler material is deposited in the first conductive structures. At least a second dielectric layer is printed on the first dielectric layer to include a plurality of second recesses generally aligned with a plurality of the first conductive structures. A conductive material is plated on surfaces of a plurality of the second recesses to form a plurality of second conductive structures electrically coupled to, and extending parallel to the first conductive structures.

Description

TECHNICAL FIELD

The present disclosure relates to a high performance electrical interconnect for electrically coupling least two circuit members using a unique fabrication technique that merges processes used in the printed circuit and semiconductor packaging industries with the flexibility of additive printing technology.

BACKGROUND OF THE INVENTION

Traditional printed circuits are often constructed in what is commonly called rigid or flexible formats. The rigid versions are used in nearly every electronic system, where the printed circuit board (PCB) is essentially a laminate of materials and circuits that when built is relatively stiff or rigid and cannot be bent significantly without damage.

Flexible circuits have become very popular in many applications where the ability to bend the circuit to connect one member of a system to another has some benefit. These flexible circuits are made in a very similar fashion as rigid PCB's, where layers of circuitry and dielectric materials are laminated. The main difference is the material set used for construction. Typical flexible circuits start with a polymer film that is clad, laminated, or deposited with copper. A photolithography image with the desired circuitry geometry is printed onto the copper, and the polymer film is etched to remove the unwanted copper. Flexible circuits are very commonly used in many electronic systems such as notebook computers, medical devices, displays, handheld devices, autos, aircraft and many others.

Flexible circuits are processed similar to that of rigid PCB's with a series of imaging, masking, drilling, via creation, plating, and trimming steps. The resulting circuit can be bent, without damaging the copper circuitry. Flexible circuits are solderable, and can have devices attached to provide some desired function. The materials used to make flexible circuits can be used in high frequency applications where the material set and design features can often provide better electrical performance than a comparable rigid circuit.

Flexible circuits are connected to electrical system in a variety of ways. In most cases, a portion of the circuitry is exposed to create a connection point. Once exposed, the circuitry can be connected to another circuit or component by soldering, conductive adhesive, thermo-sonic welding, pressure or a mechanical connector. In general, the terminals are located on an end of the flexible circuit, where edge traces are exposed or in some cases an area array of terminals are exposed. Often there is some sort of mechanical enhancement at or near the connection to prevent the joints from being disconnected during use or flexure.

In general, flexible circuits are expensive compared to some rigid PCB products. Flexible circuits also have some limitations regarding layer count or feature registration, and are therefore generally only used for small or elongated applications.

Rigid PCBs and package substrates experience challenges as the feature sizes and line spacing are reduced to achieve further miniaturization and increased circuit density. The use of laser ablation has become increasingly used to create the via structures for fine line or fine pitch structures. The use of lasers allows localized structure creation, where the processed circuits are plated together to create via connections from one layer to another. As density increases, however, laser processed via structures can experience significant taper, carbon contamination, layer-to-layer shorting during the plating process due to registration issues, and high resistance interconnections that may be prone to result in reliability issues. The challenge of making fine line PCBs often relates to the difficulty in creating very small or blind and buried vias.

BRIEF SUMMARY OF THE INVENTION

The present disclosure is directed to a high performance electrical interconnect that will enable next generation electrical performance. The present disclosure merges the long-term performance advantages of traditional PCB and semiconductor packaging with the flexibility of additive printing technology. By combining methods used in the PCB fabrication and semiconductor packaging industries, the present disclosure enables fine line high density circuit structures with attractive cost of manufacture.

The present disclosure includes plating surfaces of recesses in dielectric layers to create conductive structures, such as vias. A filler material is preferably located in the conductive structures. The present approach permits the material set to vary between layers and within layers.

The present approach also enables the production of very small low resistance vias to increase density and reduce line and feature pitch of the circuits as well as a host of electrical enhancements that provide an electrical interconnect that may prove to be superior to the traditional methods. The present disclosure uses contoured electro-less copper metalization of a dielectric surface, either entirely or selectively.

The present high performance electrical interconnect can be treated as a system of its own by incorporating electrical devices or other passive and active function, such as for example, ground planes, power planes, electrical connections to other circuit members, dielectric layers, conductive traces, transistors, capacitors, resistors, RF antennae, shielding, filters, signal or power altering and enhancing devices, memory devices, embedded IC, and the like. In some embodiments, the electrical devices can be formed using printing technology, adding intelligence to the interconnect assembly.

The present high performance electrical interconnect can be produced digitally, without tooling or costly artwork. The high performance electrical interconnect can be produced as a “Green” product, with dramatic reductions in environmental issues related to the production of conventional flexible circuits.

The vias and associated circuit geometry can be printed in a variety of shapes and sizes, depending on the terminal structure on the circuit members. The contact members and vias can be positioned at a variety of locations, heights, or spacing to match the parameters of existing connections making it easy to replace an existing interconnect without changing hardware or the PCB. The present disclosure permits the creation of blind or buried conductive structures on very tight pitch of about 25 microns or below without the use of laser ablation.

Traditional PCB and flex circuit fabrication methods take sheets of material and stack them up, laminate, and/or drill. The materials in each layer are limited to the materials in a particular sheet. Additive printing technologies permit a wide variety of materials to be applied on a layer with a registration relative to the features of the previous layer. Selective addition of conductive, non-conductive, or semi-conductive materials at precise locations to create a desired effect has the major advantages in tuning impedance or adding electrical function on a given layer. Tuning performance on a layer by layer basis relative to the previous layer greatly enhances electrical performance.

The present disclosure is directed to an electrical interconnect including a first circuitry layer with a first surface and a second surface. At least a first dielectric layer is printed on the first surface of the first circuitry layer to include a plurality of first recesses. A conductive material is plated on surfaces of a plurality of the first recesses comprising a first conductive structure electrically coupled to, and extending generally perpendicular to, the first circuitry layer. A filler material is deposited in the first conductive structure. A second dielectric layer is printed on the first dielectric layer to include a plurality of second recesses generally aligned with a plurality of the first conductive structures. A conductive material is plated on surfaces of a plurality of the second recesses comprising a second conductive structure electrically coupled to, and extending generally perpendicular to, the first conductive plating. A filler material is located in the second conductive structure. The filler material can be conductive or non-conductive.

The electrical interconnect optionally includes an IC device electrically coupled to a plurality of the second conductive structures. A second circuitry layer is optionally located on the second dielectric layer and electrically coupled with a plurality of the second conductive structures. A third dielectric layer is printed on the second dielectric layer to include a plurality of third recesses generally aligned with a plurality of the second conductive structures. Portions of the second circuitry layer located in the third recesses are etched away to expose a plurality of the second conductive structures.

A conductive material is optionally plated on surfaces of a plurality of the third recesses comprising a third conductive structure electrically coupled to, and extending parallel to the second conductive structures. An IC device including a plurality of contact pads is electrically coupled to a plurality of the third conductive structures, wherein the IC device is electrically coupled by one of a flip chip attachment directly to a plurality of third conductive structures, solder balls, or wire bonding.

A third circuitry layer is located on the third dielectric layer. A covering layer extends across the third circuitry layer. The covering layer includes a plurality of openings exposing contact pads on the third circuitry layer configured to electrically couple with an IC device.

A covering layer extends across the second surface of the first circuitry layer. The covering layer includes a plurality of openings exposing a plurality of contact pads on the first circuitry layer adapted to electrically couple with a PCB. A dielectric material is optionally printed in one or more of the recesses to surround one or more conductive structure.

The conductive material optionally includes one of sintered conductive particles or a conductive ink. At least one printed electrical device located on one of the dielectric layers and electrically coupled to at least a portion of the circuitry layers.

The present disclosure is also directed to a method of making an electrical interconnect including the steps of providing a first circuitry layer comprising a first surface and a second surface. At least a first dielectric layer is printed on the first surface of the first circuitry layer to include a plurality of first recesses. A conductive material is plated on surfaces of a plurality of the first recesses comprising a plurality of first conductive structures electrically coupled to, and extending generally perpendicular to, the first circuitry layer. A filler material is deposited in the first conductive structure. At least a second dielectric layer is printed on the first dielectric layer to include a plurality of second recesses generally aligned with a plurality of the first conductive structures. A conductive material is plated on surfaces of a plurality of the second recesses comprising a plurality of second conductive structures electrically coupled to, and extending parallel to the first conductive structures.

The method includes electrically coupling contact pads on an IC device to a plurality of the second conductive structures. The method also includes locating a second circuitry layer on the second dielectric layer and electrically coupling the second circuitry layer with a plurality of the second conductive structures. At least a third dielectric layer is printed on the second dielectric layer to include a plurality of third recesses generally aligned with a plurality of the second conductive structures.

One embodiment includes etching away portions of the second circuitry layer located in the third recesses to expose a plurality of the second conductive structures. A conductive material is plated on surfaces of a plurality of the third recesses comprising a plurality of third conductive structure electrically coupled to, and extending parallel to the second conductive structures. Contact pads on an IC device are electrically coupled to a plurality of the third conductive structures, wherein the step of electrically coupling comprises one of a flip chip attachment directly to a plurality of third conductive structures, solder balls, or wire bonding.

The method optionally includes locating a third circuitry layer on the third dielectric layer. A covering layer is attached to the third circuitry layer. The covering layer includes a plurality of openings exposing contact pads on the third circuitry layer configured to electrically couple with an IC device.

The method includes attaching a covering layer to the second surface of the first circuitry layer. The covering layer includes a plurality of openings exposing a plurality of contact pads on the first circuitry layer adapted to electrically couple with a PCB. The method optionally includes printing a dielectric material in one or more of the recesses to surround one or more conductive structures. At least one electrical device is printed on one of the dielectric layers and electrically coupling the electrical device to at least a portion of the circuitry layers.

The present disclosure is also directed to several additive processes that combine the mechanical or structural properties of a polymer material, while adding metal materials in an unconventional fashion, to create electrical paths that are refined to provide electrical performance improvements. By adding or arranging metallic particles, conductive inks, plating, or portions of traditional alloys, the high performance electrical interconnect reduces parasitic electrical effects and impedance mismatch, potentially increasing the current carrying capacity.

The present high performance electrical interconnect can serve as a platform to add passive and active circuit features to improve electrical performance or internal function and intelligence. For example, electrical features and devices are printed onto the interconnect assembly using, for example, inkjet printing technology or other printing technologies. The ability to enhance the high performance electrical interconnect, such that it mimics aspects of an IC package and a PCB, allows for reductions in complexity for the IC package and the PCB, while improving the overall performance of the interconnect assembly.

The printing process permits the fabrication of functional structures, such as conductive paths and electrical devices, without the use of masks or resists. Features down to about 10 microns can be directly written in a wide variety of functional inks, including metals, ceramics, polymers and adhesives, on virtually any substrate—silicon, glass, polymers, metals and ceramics. The substrates can be planar and non-planar surfaces. The printing process is typically followed by a thermal treatment, such as in a furnace or with a laser, to achieve dense functionalized structures.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1A is a cross-sectional view of a method of making a high performance electrical interconnects in accordance with an embodiment of the present disclosure.

FIG. 1B is a cross-sectional view of further steps of the method of making a high performance electrical interconnects of FIG. 1A.

FIG. 2 illustrates an optional additional layer on the high performance electrical interconnect of FIG. 1 in accordance with an embodiment of the present disclosure.

FIG. 3 illustrates application to a second circuitry layer to the high performance electrical interconnect of FIG. 1 in accordance with an embodiment of the present disclosure.

FIG. 4 illustrates an optional dielectric layer on the high performance electrical interconnect of FIG. 1 in accordance with an embodiment of the present disclosure.

FIG. 5 illustrates an optional etching step on the high performance electrical interconnect of FIG. 1 in accordance with an embodiment of the present disclosure.

FIG. 6 illustrates an electrical interconnect interfaced with a BGA device in accordance with an embodiment of the present disclosure.

FIG. 7 illustrates an electrical interconnect for a flexible circuit in accordance with an embodiment of the present disclosure.

FIG. 8 illustrates an electrical interconnect for an IC package in accordance with an embodiment of the present disclosure.

FIG. 9 illustrates an alternate electrical interconnect for an IC package in accordance with an embodiment of the present disclosure.

FIG. 10 is a side sectional view of an electrical interconnect in accordance with an embodiment of the present disclosure.

FIG. 11 is a side sectional view of an alternate electrical interconnect with printed compliant material in accordance with an embodiment of the present disclosure.

FIG. 12 illustrates an electrical interconnect with optical features in accordance with an embodiment of the present disclosure.

FIG. 13 illustrates an alternate high performance electrical interconnect with optical features in accordance with an embodiment of the present disclosure.

FIG. 14 illustrates an alternate high performance electrical interconnect with printed vias in accordance with an embodiment of the present disclosure.

FIG. 15 illustrates an alternate high performance electrical interconnect with printed electrical devices in accordance with an embodiment of the present disclosure.

FIG. 16 illustrates an alternate high performance electrical interconnect with printed compliant electrical pads to plug into another connector in accordance with an embodiment of the present disclosure.

DETAILED DESCRIPTION OF THE INVENTION

A high performance electrical interconnect according to the present disclosure may permit fine contact-to-contact spacing (pitch) on the order of less than 1.0 mm pitch, and more preferably a pitch of less than about 0.7 millimeter, and most preferably a pitch of less than about 0.4 millimeter. Such fine pitch high performance electrical interconnects are especially useful for communications, wireless, and memory devices.

The present high performance electrical interconnect can be configured as a low cost, high signal performance interconnect assembly, which has a low profile that is particularly useful for desktop and mobile PC applications. IC devices can be installed and uninstalled without the need to reflow solder. The solder-free electrical connection of the IC devices is environmentally friendly.

FIG. 1A is a side cross-sectional view of a method of making an electrical interconnect 50 using additive processes in accordance with an embodiment of the present disclosure. FIG. 1 shows the basic structure of copper foil circuitry layer 52A without optional base layer 54. In an alternate embodiment, the circuitry layer 52A can be applied to an optional base layer 54, such as a traditional PCB or laminated to a stiffening layer or core, such as glass-reinforced epoxy laminate sheets (e.g., FR4). The circuitry layer 52A can be preformed or can be formed using a fine line imaging step is conducted to etch copper foil as done with many PCB processes.

Dielectric material 56 is applied to surface 58 such that the circuitry 52A is at least partially encased and isolated. The dielectric material 56 can be a film or a liquid dielectric. The dielectric material 56 is typically imaged to create recesses 57 that expose the desired circuit locations 60. In some embodiments, it may be desirable to use a preformed dielectric film to leave air dielectric gaps between traces. Recesses 57 in the dielectric layer 56 that expose circuitry 52A can be formed by printing, embossing, imprinting, laser cutting, chemical etching with a printed mask, or a variety of other techniques.

The core dielectric material 56 is preferably processed for metalization by mechanical, chemical, and other means to promote plating adhesion to the side walls 64. Electro-less copper plating is applied to the side walls 64 of the recesses 57 to create conductive structures 62.

The shape of the conductive structure 62 is dictated by the shape of the recesses 57. A square recess 57 results in a square-shaped hollow conductive structure 62. In the illustrated embodiment, the conductive structure 62 is an annular-shaped via electrically coupled to the circuitry layer 52A with a center opening or recess 57. Once the surfaces 64 of the dielectric material 56 are plated, a higher deposition rate electroplate copper can be applied to build up the thickness or area of conductive structure 62 as desired.

As illustrated in FIG. 1B, the recesses 57 of the conductive structure or vias 62 are optionally filled with a conventional hole fill material 59 like that used for conventional laser drilled blind and buried vias. The fill material 59 can be conductive or non-conductive.

The plating process can be controlled to a certain degree, but in some cases with fine pitch geometries and high speed circuits, upper surfaces 66 of the copper via 62 and fill material 59 may vary in topography or height relative to the field, and the dielectric material 56 may vary in thickness slightly especially if liquid material is used. Consequently, it is preferred to planarize to surfaces 66 of the via 62 and the fill material 59, and the exposed surface 68 of the dielectric 56 between steps to control thickness and flatness of the electrical interconnect 50.

In the illustrated embodiment, additional foil layer 52B is applied and processed to create a circuit structure using any of the techniques discussed herein. The present method permits the material between layers and within each layer to be varied.

If the electrical interconnect 50 is to be part of a flexible circuit, the base layer 54 can be a material such as polyimide or liquid crystal polymer. If the final product is a rigid circuit board, the base layer 54 can be FR4 or one of many high speed laminates or substrates. If the final product is a semiconductor package, the base layer 54 can be a material such as FR4, BT resin of any one of a variety of laminate or substrate materials. If the final product is an electrical connector or socket, the base layer 54 can be molded LCP, machined plastic, or a variety of films or substrate materials.

FIG. 2 illustrates higher aspect ratio conductive structures 76 formed on the electrical interconnect 50 without the foil layer 50B. The process discussed above is repeated by applying another layer 70 of dielectric 72 that is imaged to created recesses 75 that expose the upper surface 66 of the copper via 62 and fill material 59. The surfaces 74 of the recesses 75 are then plated as discussed above to create conductive extension 76 of the via 62. Fill material 69 is then deposited and the top surface 78 is planarized as needed. The fill material 69 can be conductive or non-conductive.

In one embodiment, the conductive extensions 76 and fill material 69 are planarized to permit die attach point 82 to facilitate flip chip attach of the die 84 to the conductive extensions 76 directly. In another embodiment, exposed surfaces 86 of the plating can be enlarged to facilitate soldering of the die 84 to the conductive extensions 76.

FIG. 3 illustrates circuitry layer 80 is applied to the top surface 78 of the electrical interconnect 50 to create the base for additional routing layers and to facilitate vertical connection to subsequent layers in the stack in accordance with an alternate embodiment of the present disclosure.

FIG. 4 illustrates resist layer 90 added to the subsequent copper foil 80 in accordance with an alternate embodiment of the present disclosure. The resist layer 90 is imaged to create recesses 92 that expose portions 94 of the copper foil 80 that corresponds with the via extensions 76. The resist layer 90 protects the portions of the circuitry layers 80 that are not to be etched and provides access to the foil intimate to the conductive structures 62 and 76.

FIG. 5 illustrates a subsequent etch process that removes the copper foil 94 (see FIG. 4) located in the recesses 92 to allow access for the next plating step to join the layers together in accordance with an alternate embodiment of the present disclosure.

Depending on the resist material 90 and desired final construction, the resist layer 90 can be stripped to provide a level to be planarized as the base of further processing or the resist layer 90 can be left in place provided it is of the proper material type. The exposed regions that provided access for etch and plating can be filled with similar material to seal the layer which can be planarized for further processing if desired.

FIG. 6 illustrates one possible variation of the electrical interconnect 50. Recesses 92 are filled with a dielectric material 96 and the surface 98 is planarized to receive circuitry plane 100. Dielectric layer 102 is deposited on the circuitry plane 100 to expose selective regions 104. The selective regions 104 are configured to correspond to solder balls 120 on BGA device 122. In the illustrated embodiment, bottom dielectric layer 106 is optionally deposited on circuitry layer 52 in a manner to expose selective regions 108.

In one embodiment, the electrical interconnect 50 is further processed with conventional circuit fabrication processes to create larger diameter through vias or through holes plated 110 as needed, solder mask applied and imaged to expose device termination locations 104, 108, laser direct imaging, legend application etc.

FIG. 7 illustrate an alternate embodiment in which the electrical interconnect 50 is used in a flexible circuit applications. The electrical interconnect 50 is laminated with ground planes and cover layers 112, 114. In some applications the insulating layers 112, 114 are applied by jet printing of polyimide or liquid crystal polymers (LCP) inks as a final layer or as a combination of laminated film and jetted material.

FIG. 8 illustrates an electrical interconnect 150 for semiconductor packaging applications in accordance with an embodiment of the present disclosure. The stack 152 can be final processed with a variety of options to facilitate electrical connections to IC devices 162, 166, 172 and to system level attachment to PCB 158.

In one embodiment, the plating 160 is planarized to facilitate flip chip attach to the structure directly (see e.g., FIG. 2) or to receive BGA device 162. In other embodiment, plating 164 is extended to facilitate direct soldering of IC device die 166 with paste. In yet another embodiment, plating 168 is wire bonded 170 to the IC device 172.

The system interconnect side 180 can be processed to accept a traditional ball grid array attachment 182 for an area array configuration or plated with solder/tin etc. for a no lead peripheral termination. The system interconnect side 180 can also be fashioned to have plating or post extensions 184 to facilitate direct solder attach with paste and provide a natural standoff from the PCB 158.

FIG. 9 illustrates an electrical interconnect 200 for a semiconductor package 202 with dielectric materials 204 surrounding the conductive structures 206 in accordance with an embodiment of the present disclosure. Filler material 208 in the conductive structures 206 can be the dielectric material 204 or another filler material. Internal circuits and terminations may also be added by imaging or drilling the core material with a larger opening than needed and filling those openings with dielectric and imaging the desired geometry to facilitate conductive structure formation.

FIG. 10 illustrates an alternate electrical interconnect 230 with an insulating layer 232 applied to the circuit geometry 234. The nature of the printing process allows for selective application of dielectric layer 232 to leave selected portions 236 of the circuit geometry 234 expose if desired. The resulting high performance electrical interconnect 230 can potentially be considered entirely “green” with limited or no chemistry used to produce beyond the direct write materials.

The dielectric layers of the present disclosure may be constructed of any of a number of dielectric materials that are currently used to make sockets, semiconductor packaging, and printed circuit boards. Examples may include UV stabilized tetrafunctional epoxy resin systems referred to as Flame Retardant 4 (FR-4); bismaleimide-triazine thermoset epoxy resins referred to as BT-Epoxy or BT Resin; and liquid crystal polymers (LCPs), which are polyester polymers that are extremely unreactive, inert and resistant to fire. Other suitable plastics include phenolics, polyesters, and Ryton® available from Phillips Petroleum Company.

In one embodiment, one or more of the dielectric materials are designed to provide electrostatic dissipation or to reduce cross-talk between the traces of the circuit geometry. An efficient way to prevent electrostatic discharge (“ESD”) is to construct one of the layers from materials that are not too conductive but that will slowly conduct static charges away. These materials preferably have resistivity values in the range of 10⁵ to 10¹¹ Ohm-meters.

FIG. 11 illustrates an alternate high performance electrical interconnect 250 in accordance with an embodiment of the present disclosure. Dielectric layer 252 includes openings 254 into which compliant material 256 is printed before formation of circuit geometry 258. The compliant printed material 256 improves reliability during flexure of the electrical interconnect 250.

FIG. 12 illustrates an alternate high performance electrical interconnect 260 in accordance with an embodiment of the present disclosure. Optical fibers 262 are located between layers 264, 266 of dielectric material. In one embodiment, optical fibers 262 is positioned over printed compliant layer 268, and dielectric layer 270 is printed over and around the optical fibers 262. A compliant layer 272 is preferably printed above the optical fiber 262 as well. The compliant layers 268, 272 support the optical fibers 262 during flexure. In another embodiment, the dielectric layer 270 is formed or printed with recesses into which the optical fibers 262 are deposited.

In another embodiment, optical quality materials 274 are printed during printing of the high performance electrical interconnect 260. The optical quality material 274 and/or the optical fibers 262 comprise optical circuit geometries. The printing process allows for deposition of coatings in-situ that enhances the optical transmission or reduces loss. The precision of the printing process reduces misalignment issues when the optical materials 274 are optically coupled with another optical structure.

FIG. 13 illustrates another embodiment of a present high performance electrical interconnect 280 in accordance with an embodiment of the present disclosure. Embedded coaxial RF circuits 282 or printed micro strip RF circuits 284 are located with dielectric/metal layers 286. These RF circuits 282, 284 are preferably created by printing dielectrics and metallization geometry.

As illustrated in FIG. 14, use of additive processes allows the creation of a high performance electrical interconnect 290 with inter-circuit, 3D lattice structures 292 having intricate routing schemes. Conductive pillars 294 can be printed with each layer, without drilling.

The nature of the printing process permit controlled application of dielectric layers 296 creates recesses 298 that control the location, cross section, material content, and aspect ratio of the conductive traces 292 and the conductive pillars 294. Maintaining the conductive traces 292 and conductive pillars 294 with a cross-section of 1:1 or greater provides greater signal integrity than traditional subtractive trace forming technologies. For example, traditional methods take a sheet of a given thickness and etches the material between the traces away to have a resultant trace that is usually wider than it is thick. The etching process also removes more material at the top surface of the trace than at the bottom, leaving a trace with a trapezoidal cross-sectional shape, degrading signal integrity in some applications. Using the recesses 298 to control the aspect ratio of the conductive traces 292 and the conductive pillars 294 results in a more rectangular or square cross-section, with the corresponding improvement in signal integrity.

In another embodiment, pre-patterned or pre-etched thin conductive foil circuit traces are transferred to the recesses 298. For example, a pressure sensitive adhesive can be used to retain the copper foil circuit traces in the recesses 298. The trapezoidal cross-sections of the pre-formed conductive foil traces are then post-plated. The plating material fills the open spaces in the recesses 298 not occupied by the foil circuit geometry, resulting in a substantially rectangular or square cross-sectional shape corresponding to the shape of the recesses 298.

In another embodiment, a thin conductive foil is pressed into the recesses 298, and the edges of the recesses 298 acts to cut or shear the conductive foil. The process locates a portion of the conductive foil in the recesses 298, but leaves the negative pattern of the conductive foil not wanted outside and above the recesses 298 for easy removal. Again, the foil in the recesses 298 is preferably post plated to add material to increase the thickness of the conductive traces 292 in the circuit geometry and to fill any voids left between the conductive foil and the recesses 298.

FIG. 15 illustrates a high performance electrical interconnect 300 with printed electrical devices 302. The electrical devices 302 can include passive or active functional elements. Passive structure refers to a structure having a desired electrical, magnetic, or other property, including but not limited to a conductor, resistor, capacitor, inductor, insulator, dielectric, suppressor, filter, varistor, ferromagnet, and the like. In the illustrated embodiment, electrical devices 302 include printed LED indicator 304 and display electronics 306. Geometries can also be printed to provide capacitive coupling 308. Compliant material can be added between circuit geometry, such as discussed above, so the present electrical interconnect can be plugged into a receptacle or socket, supplementing or replacing the need for compliance within the connector.

The electrical devices 302 are preferably printed during construction of the interconnect assembly 300. The electrical devices 302 can be ground planes, power planes, electrical connections to other circuit members, dielectric layers, conductive traces, transistors, capacitors, resistors, RF antennae, shielding, filters, signal or power altering and enhancing devices, memory devices, embedded IC, and the like. For example, the electrical devices 302 can be formed using printing technology, adding intelligence to the high performance electrical interconnect 300. Features that are typically located on other circuit members can be incorporated into the interconnect 300 in accordance with an embodiment of the present disclosure.

The availability of printable silicon inks provides the ability to print electrical devices 302, such as disclosed in U.S. Pat. No. 7,485,345 (Renn et al.); U.S. Pat. No. 7,382,363 (Albert et al.); U.S. Pat. No. 7,148,128 (Jacobson); U.S. Pat. No. 6,967,640 (Albert et al.); U.S. Pat. No. 6,825,829 (Albert et al.); U.S. Pat. No. 6,750,473 (Amundson et al.); U.S. Pat. No. 6,652,075 (Jacobson); U.S. Pat. No. 6,639,578 (Comiskey et al.); U.S. Pat. No. 6,545,291 (Amundson et al.); U.S. Pat. No. 6,521,489 (Duthaler et al.); U.S. Pat. No. 6,459,418 (Comiskey et al.); U.S. Pat. No. 6,422,687 (Jacobson); U.S. Pat. No. 6,413,790 (Duthaler et al.); U.S. Pat. No. 6,312,971 (Amundson et al.); U.S. Pat. No. 6,252,564 (Albert et al.); U.S. Pat. No. 6,177,921 (Comiskey et al.); U.S. Pat. No. 6,120,588 (Jacobson); U.S. Pat. No. 6,118,426 (Albert et al.); and U.S. Pat. Publication No. 2008/0008822 (Kowalski et al.), which are hereby incorporated by reference. In particular, U.S. Pat. No. 6,506,438 (Duthaler et al.) and U.S. Pat. No. 6,750,473 (Amundson et al.), which are incorporated by reference, teach using ink-jet printing to make various electrical devices, such as, resistors, capacitors, diodes, inductors (or elements which may be used in radio applications or magnetic or electric field transmission of power or data), semiconductor logic elements, electro-optical elements, transistor (including, light emitting, light sensing or solar cell elements, field effect transistor, top gate structures), and the like.

The electrical devices 302 can also be created by aerosol printing, such as disclosed in U.S. Pat. No. 7,674,671 (Renn et al.); U.S. Pat. No. 7,658,163 (Renn et al.); U.S. Pat. No. 7,485,345 (Renn et al.); U.S. Pat. No. 7,045,015 (Renn et al.); and U.S. Pat. No. 6,823,124 (Renn et al.), which are hereby incorporated by reference.

Printing processes are preferably used to fabricate various functional structures, such as conductive paths and electrical devices, without the use of masks or resists. Features down to about 10 microns can be directly written in a wide variety of functional inks, including metals, ceramics, polymers and adhesives, on virtually any substrate—silicon, glass, polymers, metals and ceramics. The substrates can be planar and non-planar surfaces. The printing process is typically followed by a thermal treatment, such as in a furnace or with a laser, to achieve dense functionalized structures.

Ink jet printing of electronically active inks can be done on a large class of substrates, without the requirements of standard vacuum processing or etching. The inks may incorporate mechanical, electrical or other properties, such as, conducting, insulating, resistive, magnetic, semi conductive, light modulating, piezoelectric, spin, optoelectronic, thermoelectric or radio frequency.

A plurality of ink drops are dispensed from the print head directly to a substrate or on an intermediate transfer member. The transfer member can be a planar or non-planar structure, such as a drum. The surface of the transfer member can be coated with a non-sticking layer, such as silicone, silicone rubber, or Teflon.

The ink (also referred to as function inks) can include conductive materials, semi-conductive materials (e.g., p-type and n-type semiconducting materials), metallic material, insulating materials, and/or release materials. The ink pattern can be deposited in precise locations on a substrate to create fine lines having a width smaller than 10 microns, with precisely controlled spaces between the lines. For example, the ink drops form an ink pattern corresponding to portions of a transistor, such as a source electrode, a drain electrode, a dielectric layer, a semiconductor layer, or a gate electrode.

The substrate can be an insulating polymer, such as polyethylene terephthalate (PET), polyester, polyethersulphone (PES), polyimide film (e.g. Kapton, available from DuPont located in Wilmington, Del.; Upilex available from Ube Corporation located in Japan), or polycarbonate. Alternatively, the substrate can be made of an insulator such as undoped silicon, glass, or a plastic material. The substrate can also be patterned to serve as an electrode. The substrate can further be a metal foil insulated from the gate electrode by a non-conducting material. The substrate can also be a woven material or paper, planarized or otherwise modified on at least one surface by a polymeric or other coating to accept the other structures.

Electrodes can be printed with metals, such as aluminum or gold, or conductive polymers, such as polythiophene or polyaniline. The electrodes may also include a printed conductor, such as a polymer film comprising metal particles, such as silver or nickel, a printed conductor comprising a polymer film containing graphite or some other conductive carbon material, or a conductive oxide such as tin oxide or indium tin oxide.

Dielectric layers can be printed with a silicon dioxide layer, an insulating polymer, such as polyimide and its derivatives, poly-vinyl phenol, polymethylmethacrylate, polyvinylidenedifluoride, an inorganic oxide, such as metal oxide, an inorganic nitride such as silicon nitride, or an inorganic/organic composite material such as an organic-substituted silicon oxide, or a sol-gel organosilicon glass. Dielectric layers can also include a bicylcobutene derivative (BCB) available from Dow Chemical (Midland, Mich.), spin-on glass, or dispersions of dielectric colloid materials in a binder or solvent.

Semiconductor layers can be printed with polymeric semiconductors, such as, polythiophene, poly(3-alkyl)thiophenes, alkyl-substituted oligothiophene, polythienylenevinylene, poly(para-phenylenevinylene) and doped versions of these polymers. An example of suitable oligomeric semiconductor is alpha-hexathienylene. Horowitz, Organic Field-Effect Transistors, Adv. Mater., 10, No. 5, p. 365 (1998) describes the use of unsubstituted and alkyl-substituted oligothiophenes in transistors. A field effect transistor made with regioregular poly(3-hexylthiophene) as the semiconductor layer is described in Bao et al., Soluble and Processable Regioregular Poly(3-hexylthiophene) for Thin Film Field-Effect Transistor Applications with High Mobility, Appl. Phys. Lett. 69 (26), p. 4108 (December 1996). A field effect transistor made with a-hexathienylene is described in U.S. Pat. No. 5,659,181, which is incorporated herein by reference.

A protective layer can optionally be printed onto the electrical devices. The protective layer can be an aluminum film, a metal oxide coating, a polymeric film, or a combination thereof.

Organic semiconductors can be printed using suitable carbon-based compounds, such as, pentacene, phthalocyanine, benzodithiophene, buckminsterfullerene or other fullerene derivatives, tetracyanonaphthoquinone, and tetrakisimethylanimoethylene. The materials provided above for forming the substrate, the dielectric layer, the electrodes, or the semiconductor layer are exemplary only. Other suitable materials known to those skilled in the art having properties similar to those described above can be used in accordance with the present disclosure.

The ink-jet print head preferably includes a plurality of orifices for dispensing one or more fluids onto a desired media, such as for example, a conducting fluid solution, a semiconducting fluid solution, an insulating fluid solution, and a precursor material to facilitate subsequent deposition. The precursor material can be surface active agents, such as octadecyltrichlorosilane (OTS).

Alternatively, a separate print head is used for each fluid solution. The print head nozzles can be held at different potentials to aid in atomization and imparting a charge to the droplets, such as disclosed in U.S. Pat. No. 7,148,128 (Jacobson), which is hereby incorporated by reference. Alternate print heads are disclosed in U.S. Pat. No. 6,626,526 (Ueki et al.), and U.S. Pat. Publication Nos. 2006/0044357 (Andersen et al.) and 2009/0061089 (King et al.), which are hereby incorporated by reference.

The print head preferably uses a pulse-on-demand method, and can employ one of the following methods to dispense the ink drops: piezoelectric, magnetostrictive, electromechanical, electro pneumatic, electrostatic, rapid ink heating, magneto hydrodynamic, or any other technique well known to those skilled in the art. The deposited ink patterns typically undergo a curing step or another processing step before subsequent layers are applied.

While ink jet printing is preferred, the term “printing” is intended to include all forms of printing and coating, including: pre-metered coating such as patch die coating, slot or extrusion coating, slide or cascade coating, and curtain coating; roll coating such as knife over roll coating, forward and reverse roll coating; gravure coating; dip coating; spray coating; meniscus coating; spin coating; brush coating; air knife coating; screen printing processes; electrostatic printing processes; thermal printing processes; and other similar techniques.

FIG. 16 illustrates an alternate high performance electrical interconnect 320 with printed compliant material 322 added between circuit geometries 324, 326 to facilitate insertion of exposed circuit geometries 328, 330 into a receptacle or socket. The compliant material 322 can supplement or replace the compliance in the receptacle or socket. In one embodiment, the compliance is provided by a combination of the compliant material 322 and the exposed circuit geometries 328, 330.

Where a range of values is provided, it is understood that each intervening value, to the tenth of the unit of the lower limit unless the context clearly dictates otherwise, between the upper and lower limit of that range and any other stated or intervening value in that stated range is encompassed within the embodiments of the disclosure. The upper and lower limits of these smaller ranges which may independently be included in the smaller ranges is also encompassed within the embodiments of the disclosure, subject to any specifically excluded limit in the stated range. Where the stated range includes one or both of the limits, ranges excluding either both of those included limits are also included in the embodiments of the present disclosure.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the embodiments of the present disclosure belong. Although any methods and materials similar or equivalent to those described herein can also be used in the practice or testing of the embodiments of the present disclosure, the preferred methods and materials are now described. All patents and publications mentioned herein, including those cited in the Background of the application, are hereby incorporated by reference to disclose and described the methods and/or materials in connection with which the publications are cited.

The publications discussed herein are provided solely for their disclosure prior to the filing date of the present application. Nothing herein is to be construed as an admission that the present disclosure is not entitled to antedate such publication by virtue of prior invention. Further, the dates of publication provided may be different from the actual publication dates which may need to be independently confirmed.

Other embodiments of the disclosure are possible. Although the description above contains much specificity, these should not be construed as limiting the scope of the disclosure, but as merely providing illustrations of some of the presently preferred embodiments of this disclosure. It is also contemplated that various combinations or sub-combinations of the specific features and aspects of the embodiments may be made and still fall within the scope of the present disclosure. It should be understood that various features and aspects of the disclosed embodiments can be combined with or substituted for one another in order to form varying modes of the disclosed embodiments of the disclosure. Thus, it is intended that the scope of the present disclosure herein disclosed should not be limited by the particular disclosed embodiments described above.

Thus the scope of this disclosure should be determined by the appended claims and their legal equivalents. Therefore, it will be appreciated that the scope of the present disclosure fully encompasses other embodiments which may become obvious to those skilled in the art, and that the scope of the present disclosure is accordingly to be limited by nothing other than the appended claims, in which reference to an element in the singular is not intended to mean “one and only one” unless explicitly so stated, but rather “one or more.” All structural, chemical, and functional equivalents to the elements of the above-described preferred embodiment(s) that are known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the present claims. Moreover, it is not necessary for a device or method to address each and every problem sought to be solved by the present disclosure, for it to be encompassed by the present claims. Furthermore, no element, component, or method step in the present disclosure is intended to be dedicated to the public regardless of whether the element, component, or method step is explicitly recited in the claims.

Claims

1. A method of making an electrical interconnect comprising the steps of: providing a first circuitry layer comprising a first surface and a second surface;printing at least a first dielectric layer on the first surface of the first circuitry layer to include a plurality of first recesses;depositing a conductive material on surfaces of a plurality of the first recesses comprising a plurality of first conductive structures electrically coupled to, and extending perpendicular to, the first circuitry layer;printing a filler material in the first conductive structures;printing at least a second dielectric layer on the first dielectric layer to include a plurality of second recesses at least partially aligned with a plurality of the first conductive structures;depositing a conductive material on surfaces of a plurality of the second recesses comprising a plurality of second conductive structures electrically coupled to, and extending parallel to the first conductive structures; andprinting a dielectric material in one or more of the first and second recesses to surround one or more of the first and second conductive structures.

2. The method of claim 1 comprising electrically coupling contact pads on an IC device to a plurality of the second conductive structures.

3. The method of claim 1 comprising the steps of: locating a second circuitry layer on the second dielectric layer to electrically couple the second circuitry layer with a plurality of the second conductive structures; andprinting at least a third dielectric layer on the second dielectric layer to include a plurality of third recesses at least partially aligned with a plurality of the second conductive structures.

4. The method of claim 3 comprising etching away portions of the second circuitry layer located in the third recesses to expose a plurality of the second conductive structures.

5. The method of claim 3 comprising the steps of: plating a conductive material on surfaces of a plurality of the third recesses comprising a plurality of third conductive structures electrically coupled to, and extending parallel to the second conductive structures; andelectrically coupling contact pads on an IC device to a plurality of the third conductive structures, wherein the step of electrically coupling comprises one of a flip chip attachment directly to a plurality of third conductive structures, solder balls, or wire bonding.

6. The method of claim 3 comprising the steps of: locating a third circuitry layer on the third dielectric layer; andattaching a covering layer to the third circuitry layer, the covering layer comprising a plurality of openings exposing contact pads on the third circuitry layer configured to electrically couple with an IC device.

7. The method of claim 1 comprising attaching a covering layer to the second surface of the first circuitry layer, the covering layer comprising a plurality of openings exposing a plurality of contact pads on the first circuitry layer adapted to electrically couple with a PCB.

8. The method of claim 1 wherein at least one of the first and second conductive structures comprise a coaxial conductive structure.

9. The method of claim 1 comprising printing at least one electrical device on one of the dielectric layers and electrically coupling the electrical device to at least a portion of the circuitry layer.