Forming electrical interconnects using capillary microfluidics

Abstract

The present disclosure provides a method for manufacturing an electronic device, the method comprising: providing a substrate having a first major surface, the first major surface having a microchannel, wherein the microchannel has a first end and a second end; dispensing a conductive liquid in the microchannel so that the conductive liquid moves mainly by capillary pressure in a first direction toward the first end of the microchannel and in a second direction toward the second end of the microchannel; and hardening the conductive liquid to form a conductive trace, the conductive trace electrically connecting a first electronic device at the first end of the microchannel to a second electronic device at the second end of the microchannel.

Description

Background Art

[0001] Web-based printing of solid semiconductor dies combines the computing power of semiconductor technology with the high throughput and form factor flexibility of roll-to-roll manufacturing processes. Flexible hybrid electronics manufacturing requires that semiconductor dies be reliably and accurately aligned to printed traces on a moving web. Current alignment mechanisms suitable for wafer-based semiconductor devices may not be easily transferable to web-based processes.

[0002] Such techniques are needed to consistently and accurately achieve alignment between solid circuit dies and conductive interconnects on a substrate, particularly a moving flexible substrate used in a roll-to-roll manufacturing process, to a level less than about ten microns. Summary of the invention

[0003] In general, the present disclosure relates to articles and methods for providing automatic alignment via capillary liquid flow of conductive material to electrically interconnect aligned or aligned circuit traces or conductive contact pads of electronic components (such as, for example, circuit dies) disposed on a moving flexible substrate. The automatic alignment described herein can tolerate various sources of misalignment in web-based methods, such as, for example, substrate deformation due to in-line thermal cycling and / or tension control.

[0004] In one aspect, the present disclosure relates to a method for manufacturing an electronic device. The method includes: providing a substrate having a first major surface, the first major surface having a microchannel, wherein the microchannel has a first end and a second end; dispensing a conductive liquid in the microchannel so that the conductive liquid moves primarily by capillary pressure in a first direction toward the first end of the microchannel and in a second direction toward the second end of the microchannel; and hardening the conductive liquid to form a conductive trace, the conductive trace electrically connecting a first electronic device at the first end of the microchannel to a second electronic device at the second end of the microchannel.

[0005] In another aspect, the present disclosure relates to a method for manufacturing an electronic device, the method comprising: placing a solid circuit die on a first major surface of a substrate having a microchannel so that at least one contact pad on the solid circuit die resides in a first end of the microchannel, wherein a second end of the microchannel terminates in a hole extending between the first major surface of the substrate and an opposite second major surface thereof; aligning a conductive trace on the second major surface of the substrate with the hole at the second end of the microchannel; dispensing a conductive liquid in the microchannel between its first end and second end, wherein the volume of the conductive liquid dispensed in the microchannel is significantly greater than the volume of a portion of the channel below the dispensed conductive liquid; and causing the conductive liquid to flow primarily by capillary pressure in a first direction toward the contact pad and in a second direction toward the hole, wherein the conductive liquid directly contacts the contact pad on the solid circuit die and enters the hole to directly contact the conductive trace; and hardening the conductive liquid to form a conductive trace on the first major surface of the substrate, the conductive trace electrically connecting the contact pad on the solid circuit die to the conductive trace on the second major surface of the substrate.

[0006] In another aspect, the present disclosure relates to a method for manufacturing an electronic device, the method comprising: placing a solid circuit die on a first major surface of a substrate having a microchannel, the microchannel having a first end and a second end, wherein a contact pad on the solid circuit die resides in the first end of the microchannel, and wherein the second end of the microchannel terminates in a hole extending between the first major surface of the substrate and an opposing second major surface thereof, the hole comprising a first region proximate the first major surface of the substrate, the first region of the hole leading to a second region proximate the second major surface of the substrate; aligning a conductive trace on the second major surface of the substrate with the columnar region of the hole; dispensing a first conductive liquid in the microchannel between the first end and the second end thereof; causing the first conductive liquid to flow primarily by capillary pressure in the first region toward the contact pad; The method comprises applying a conductive liquid in a first direction and in a second direction toward the hole, wherein the conductive liquid directly contacts the contact pad on the solid circuit die and flows into the hole to reside on a shoulder in the first area of ​​the hole, so that the second area of ​​the hole is substantially free of the first conductive liquid; applying a sufficient amount of a second conductive liquid different from the first conductive liquid in the hole, so that the second conductive liquid flows into the second area of ​​the hole to directly contact the conductive trace and fills the hole to directly contact the first conductive liquid on the shoulder of the first area of ​​the hole, and wherein the microchannel on the first major surface of the substrate is substantially free of the second conductive liquid; and hardening the first conductive liquid and the second conductive liquid to form a conductive trace on the first major surface of the substrate, which connects the contact pad on the solid circuit die with the conductive trace on the second major surface of the substrate.

[0007] In another aspect, the present disclosure relates to an article comprising a flexible polymer substrate having a first major surface having at least one microchannel having a substantially constant width and depth and extending from a first end thereof to a second end thereof, wherein the second end of the microchannel terminates in a hole extending between the first major surface of the substrate and an opposing second major surface thereof. A solid circuit die resides on the first major surface of the substrate, wherein a contact pad of the solid circuit die resides in the first end of the microchannel. A first conductive trace resides on the second major surface of the substrate and is aligned with the hole at the second end of the microchannel. A conductive liquid is in the microchannel and in the hole, wherein the conductive liquid contacts the contact pad on the solid circuit die and the first conductive trace on the second major surface of the substrate.

[0008] In another aspect, the present disclosure relates to an article comprising a flexible polymer substrate having a first major surface having at least one microchannel having a substantially constant width and depth and extending from a first end thereof to a second end thereof, wherein the second end of the microchannel terminates in a hole extending between the first major surface of the substrate and an opposing second major surface thereof, the hole comprising a first region proximate the first major surface of the substrate, the first region leading to a second region proximate the second major surface of the substrate. A solid circuit die resides on the first major surface of the substrate, wherein a contact pad of the solid circuit die resides in the first end of the microchannel. A first conductive trace resides on the second major surface of the substrate, wherein the first conductive trace is aligned with a columnar region of the hole. A first conductive liquid is in the microchannel, directly contacting the contact pad on the solid circuit die and extending onto a shoulder in the first region of the hole, wherein the first conductive liquid does not extend into the second region of the hole; and a second conductive liquid, the second conductive liquid being in the second region of the hole and contacting the first conductive liquid and the first conductive trace.

[0009] The details of one or more embodiments of the present invention are shown in the following drawings and description. Other features, objects and advantages of the present invention will be apparent from the description and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 is a schematic top view of an embodiment of a substrate including microchannels.

[0011] Figure 2A A device having an electronic device disposed thereon Figure 1 Schematic top view of an embodiment of an article having a substrate.

[0012] Figure 2B yes Figure 2A A cross-sectional view of a product.

[0013] Figure 3A Yes Figure 2A Schematic top view of an embodiment of an article of a substrate with a conductive liquid disposed on a microchannel.

[0014] Figure 3B yes Figure 3A A schematic cross-sectional view of a product.

[0015] Figure 3C yes Figure 3A Schematic cross-sectional view of a channel in an article.

[0016] Figure 3D yes Figure 3A Schematic top view of a channel in an article of.

[0017] Figure 4A After the conductive liquid flows in the microchannel partly by capillary action Figure 3A Schematic top view of the product.

[0018] Figure 4B yes Figure 4A A schematic cross-sectional view of a product.

[0019] Figure 4C After the conductive liquid has hardened to form conductive traces in the microchannels Figure 4A Schematic cross-sectional view of a microchannel in an article.

[0020] Figure 5A is after applying a second conductive liquid in the hole at the second end of the microchannel Figure 4A Schematic top view of the product.

[0021] Figure 5B yes Figure 5A A schematic cross-sectional view of a product.

[0022] Figure 6 is a flow chart summarizing a method of manufacturing an electronic device according to an embodiment of the method of the present disclosure.

[0023] Figure 7 is a flow chart summarizing a method of manufacturing an electronic device according to an embodiment of the method of the present disclosure.

[0024] In the drawings, like symbols denote like elements. DETAILED DESCRIPTION

[0025] Figure 1A top view of an article 10 is shown, the article comprising a substrate 12 having a structured first major surface 14. In some embodiments, the substrate 12 can be a flexible substrate, such as a web of a polymeric material having an indefinite length. The flexible substrate 12 or web can be stretched (e.g., in the machine direction and / or in the transverse direction) while moving along a web path between rollers in, for example, a roll-to-roll manufacturing process. The substrate 12 can be made of any suitable material for forming features therein or thereon to support capillary fluid flow along the first major surface 14. In some embodiments, which are not intended to be limiting, the flexible substrate 12 is a polymer film comprising the following: polyesters (e.g., polyethylene terephthalate (PET), polyethylene naphthalate (PEN), and polycarbonate (PC)), polyolefins (e.g., linear, branched, and cyclic polyolefins), polyvinyl compounds (e.g., polyvinyl chloride, polyvinylidene chloride, polyvinyl acetal, polystyrene, polyacrylates, etc.), cellulose ester matrices (e.g., cellulose triacetate, cellulose acetate), polysulfones (such as polyethersulfone), polyimides, silicones, polyethylene, polystyrene, polyurethanes, and mixtures and combinations thereof. In some embodiments, the substrate 12 or a portion thereof may be rigid, and suitable rigid materials include, but are not limited to, bakelite, acrylonitrile-butadiene-styrene (ABS), cured epoxy resin systems, and the like.

[0026] The substrate 12 may optionally be treated before or after patterning using techniques such as, for example, solvent or chemical cleaning, heating, plasma treatment, ultraviolet radiation (UV)-ozone treatment, corona discharge, and combinations thereof.

[0027] In some exemplary embodiments, substrate 12 may have a thickness of, for example, 2 mm or less, 1 mm or less, 500 microns or less, or 200 microns or less.

[0028] At least one channel 16 is formed on the first major surface 14 and extends in length between a first end 16A and a second end 16B. The channel 16 may have any suitable dimensions and is not intended to be limiting. Figure 1 In some embodiments, the channel 16 has a substantially constant width w between the first end 16A and the second end 16B and a substantially constant thickness d of the channel wall 17. In various embodiments, the channel 16 formed on the major surface 14 is a microchannel having a minimum length of, for example, 500 microns or less, 300 microns or less, 100 microns or less, 50 microns or less, or 10 microns or less.

[0029] Channel 16 is configured to allow a conductive fluid deposited in region 26 between first and second ends 16A, 16B of channel 16 to flow in opposite directions 30A, 30B along channel 16 primarily by capillary forces to reach first and second ends 16A, 16B of channel 16 .

[0030] exist Figure 1 In the embodiment of the present invention, the channel 16 is open on its upper surface adjacent to the first major surface 14 of the substrate 12, but in alternative embodiments, all or part of the channel 16 can be formed by the upper wall ( Figure 1 (not shown) is closed. Figure 1 While one channel 16 is shown in the embodiment of FIG. 1 , it should be understood that any number of channels may be formed on the substrate 12 and that the channels may be fluidly connected in various configurations as desired to form electrical connections with circuit elements, electronic devices, and the like.

[0031] exist Figure 1 In some embodiments, channels 16 include indentations formed in major surface 14 of substrate 12, but in alternative embodiments, channels may include embossments (such as, for example, ridges) protruding above major surface 14. In some embodiments, channel walls 17 of channels 16 may be formed by adding material to major surface 14 by any suitable technique, including, for example, microreplication, hot embossing, molding, soft lithography, etching, flexographic printing, 3D printing, and the like.

[0032] In some embodiments, the channel 16 may include an optional upwardly protruding liquid flow control feature, such as a post 28, at any location along the channel 16 between the first end 16A and the second end 16B thereof. The post 28 may have any suitable shape to promote or guide capillary fluid flow of the conductive fluid in the channel 16 along the directions 30A, 30B. In various embodiments, the post 28 may have a shape such as, for example, a cube, a cuboid, a cylinder, a hemisphere, etc. In various embodiments, the channel 16 may include any suitable number of posts or other flow control features to promote or guide capillary flow of the conductive fluid in the channel 16.

[0033] The second end 16B of the channel 16 terminates in a hole 18 that extends through the first major surface 14 of the substrate 12 to its opposite second major surface 20. The hole 18 can be formed by any suitable technique, such as chemical etching, laser etching or drilling, mechanical punching, etc. The hole 18 includes a first region 22 proximal to the first major surface 14 of the substrate 12, which leads to a second region proximal to the second major surface 20 of the substrate 12. The hole wall 25 of the first region 22 includes a shoulder 24 at the transition between the first region 22 and the second region. In some embodiments, which are not intended to be limiting, the hole 18 is generally cylindrical, so that the hole wall 25 has a curvature, and when the hole wall 25 is at the first major surface 14 of the substrate 12, the hole 18 is generally cylindrical. Figure 1 When viewed from above, the opening of the hole 18 is circular or oval. In various embodiments, the first area 22 and the second area of ​​the hole 18 can have any suitable shape, and the shapes of the first area 22 and the second area can be the same or different.

[0034] See also FIG. 2A to FIG. 2B , the article 100 includes a solid circuit die 150 disposed on a first major surface 114 of a substrate 112. The solid circuit die 150 includes at least one contact pad 152 on its major surface 154. The contact pad 152 is positioned within a channel 116 in the surface 114 of the substrate 112. The configuration of the contact pad 152 on the circuit die 150 can vary widely, and in various embodiments, the contact pad 152 can be disposed along an edge 156 of the circuit die 150, or can be partially embedded in the circuit die 150 and have an exposed surface or portion adjacent to the edge 156. The contact pad 152 can be made of any suitable conductive material, such as, for example, a metal. Although the contact pad 152 is shown as having a bump-like shape, the contact pad can vary with the specific type of circuit die, and can include, for example, an elongated leg extending from the housing of the circuit die 150. In some embodiments, the contact pad 152 can include a plated metal (e.g., Cu / Au) on the surface of the housing of the circuit die 150.

[0035] In various embodiments, which are not intended to be limiting, the circuit die 150 may include a circuit chip, a rigid semiconductor die, a printed circuit board (PCB), a flexible printed circuit (FPC), or an ultra-thin chip having one or more contact pads arranged along its edge 156. In some embodiments, the circuit die 150 may have a thickness substantially the same as the depth d of the channel 116. In a non-limiting example, if the circuit die 150 is an ultra-thin chip having a thickness of about 2 microns to about 200 microns, about 5 microns to about 100 microns, or about 10 microns to about 100 microns, the depth d of the channel may be greater than the thickness of the circuit die 150, for example, by two, four, six, eight, or ten times. In some embodiments, the ultra-thin circuit die may be loaded on a removable handle substrate ( FIG. 2A to FIG. 2B) to facilitate its placement into channel 116.

[0036] In some embodiments, the surface 154 of the circuit die 150 may be optionally coated with an adhesive ( FIG. 2A to FIG. 2B 114 is attached to the first major surface 114 of the substrate 112 (not shown). Suitable adhesives include, but are not limited to, structural adhesives, acrylic adhesives, epoxy adhesives, polyurethane adhesives, optical adhesives, and mixtures and combinations thereof. In some embodiments, the adhesive may be a UV curable adhesive or an activated adhesive, such as, for example, a UV curable polyurethane. The adhesive should be applied precisely to attach the circuit die 150 to the major surface 114 without blocking the channel 116.

[0037] exist FIG. 2A to FIG. 2B In the embodiment of the present invention, the contact pad 152 is positioned at the first end 116A of the channel 116, but the contact pad 152 can be placed at any position between the first end 116A and the second end 116B of the channel 116. The second end 116B of the channel 116 terminates in a hole 118 that extends from the first major surface 114 of the substrate through the substrate 112 to the second major surface 120. The hole 118 includes a first region 122 proximal to the first major surface 114 of the substrate 112. The first region 122 includes a hole wall 125 that forms a shoulder 124 at the transition between the first region 122 and the second region 140, which extends from the first region 122 to the second major surface 120 of the substrate 112.

[0038] Conductive trace 160 is positioned adjacent second major surface 120 of substrate 112 and aligned with aperture 118. FIG. 2A to FIG. 2B In some embodiments, the conductive trace 160 is positioned so that at least a portion thereof is located below the region 140 of the aperture 118. The size and configuration of the conductive trace 160 can vary widely, and in some embodiments, the conductive trace can include a contact point or elongated strand of conductive material such as, for example, a metal used for circuit connection, such as copper, silver, gold, and mixtures and combinations thereof.

[0039] See now FIG. 3A to FIG. 3B In configuration 200 , conductive liquid 270 is dispensed along the direction of arrow A onto channels 216 formed on first major surface 214 of substrate 212 .

[0040] In various embodiments, the conductive liquid 270 can be any liquid composition that is conductive in the liquid state (e.g., a metal), or is non-conductive or weakly conductive in the liquid state and becomes conductive when hardened. The conductive liquid 270 includes a sufficient amount of a liquid carrier to make the conductive liquid flowable in the channel 216 primarily by capillary forces. In some embodiments, the conductive liquid 270 can be made to flow in the channel 216 by applying the conductive liquid under pressure in the channel 216 to enhance capillary flow.

[0041] Conductive liquid 270 contains a conductive material or a non-conductive material that can be converted into a conductive material, which is dispersed in a liquid using, for example, a coater or a sprayer to facilitate more uniform deposition on substrate 212. Suitable conductive materials for conductive liquid 270 include, but are not limited to, metal particles, nanowires, metal salts that are conductive at room temperature or become conductive when heated or otherwise reduced to metal, conductive polymers, and mixtures and combinations thereof. In some embodiments, conductive liquid 270 includes conductive inks that include conductive metals such as silver ink, silver nanoparticle ink, reactive silver ink, copper ink, and conductive polymer ink, as well as liquid metals or alloys (e.g., metals or alloys that melt at relatively low temperatures and harden at room temperature), etc. In some embodiments, liquid composition 270 is a conductive ink that can be cured with actinic radiation, such as, for example, UV-curable inks or activated inks.

[0042] In some embodiments, the conductive material in the conductive liquid 270 can be a blend of silver flakes or spheres, carbon / graphite particles, or a blend of silver flakes / carbon particles. The particle size is typically in the range of, for example, about 0.5 microns to about 10.0 microns in diameter. When these flakes or particles are suspended in a polymer binder, they are randomly spaced apart by the liquid. Once the solvent evaporates, they condense to form a conductive path or circuit. Among conductive materials, silver is the least resistive and the most expensive, while carbon / graphite provides the best combination of low resistance and low price. Suitable conductive inks are available from Tekra, Inc., New Berlin, WI, in New Berlin, Wisconsin.

[0043] Any non-corrosive liquid in which the conductive material can form a stable dispersion can be used in the conductive liquid 270, and suitable examples of liquid carriers include, but are not limited to, water, alcohols, ketones, ethers, hydrocarbons, or aromatic solvents (benzene, toluene, xylene, etc.). In some embodiments, the carrier liquid is volatile, having a boiling point of no more than 200 degrees Celsius (° C.), no more than 150° C., or no more than 100° C.

[0044] In addition, the conductive liquid 270 may contain additives or binders to control the viscosity, corrosiveness, adhesion and dispersibility of the conductive material. Examples of suitable additives or binders include, but are not limited to, carboxymethyl cellulose (CMC), 2-hydroxyethyl cellulose (HEC), hydroxypropyl methyl cellulose (HPMC), methyl cellulose (MC), polyvinyl alcohol (PVA), tripropylene glycol (TPG) and xanthan gum (XG), as well as surfactants such as ethoxylates, alkoxylates, ethylene oxide and propylene oxide and their copolymers, sulfonates, sulfates, disulfonates, sulfosuccinates, phosphates and fluorosurfactants (such as those available from DuPont under the trade name Zonyl).

[0045] In one example, the conductive liquid or "ink" contains, by weight, 0.0025% to 0.1% surfactant (e.g., a preferred range for Zonyl FSO-100 is 0.0025% to 0.05%), 0.02% to 4% viscosity modifier (e.g., a preferred range for HPMC is 0.02% to 0.5%), 94.5% to 99.0% solvent, and 0.05% to 1.4% conductive material. Representative examples of suitable surfactants include those purchased from DowDuPont, Wilmington, Delaware, under the trade names Zonyl FSN, Zonyl FSO and ZonylFSH, those purchased from Merck Millipore Sigma, St. Louis, MO, under the trade names Triton (x100, x114, x45), those purchased from Evonik Industries, Parsippany, NJ, under the trade names Dynol (604, 607), n-dodecyl bD-maltoside and Novek. Examples of suitable viscosity modifiers include hydroxypropyl methylcellulose (HPMC), methylcellulose, xanthan gum, polyvinyl alcohol, carboxymethyl cellulose, hydroxyethyl cellulose. Examples of suitable solvents that may be present in the nanowire dispersion containing the above-mentioned binder or additive include water and isopropanol.

[0046] In another embodiment, the conductive liquid may include a binder, such as, for example, a binder dissolved in a liquid solvent such as water acetone, toluene, methyl ethyl ketone (MEK), or the like.

[0047] The conductive liquid 270 may be cured, hardened, or hardened by removing at least a portion of the liquid carrier to leave a continuous layer of conductive material forming the conductive traces in the channel 216. The conductive liquid 270 may be cured and / or hardened, or sintered. "Curing or hardening" refers to a process in which the solvent or liquid carrier is removed from the conductive liquid 270 to form an interconnected circuit pattern. Suitable curing conditions are well known in the art and include, for example, heating, use of visible or ultraviolet (UV) light, electron beam irradiation, and the like. Alternatively, "hardening or hardened" may be caused by removing the solvent during drying without, for example, polymerization or crosslinking.

[0048] The conductive liquid 270 may be delivered at any location along the channel 216, but is typically deposited at the region 226 between the first end 216A and the second end 216B of the channel 216, such that the conductive liquid 270 may flow along the channel 216 in opposite directions 230A, 230B to reach the first end 216A and the second end 216B primarily by capillary forces. In some embodiments, the conductive fluid is dispensed onto the channel between the first end 216A and the second end 216B of the channel 216 in an amount sufficient to make the volume of the deposited conductive fluid significantly greater than the volume of the portion 226 of the channel 216 covered by the deposited conductive fluid. In various embodiments, the volume of the deposited conductive fluid is at least five times the volume of the lower portion 226 of the microchannel 216, or at least ten times the volume of the lower portion 226 of the microchannel 216. The conductive liquid 270 may be deposited by various methods, including, for example, pouring, funnel delivery, inkjet printing, piezoelectric dispensing, needle dispensing, microinjection, screen printing, flexographic printing, and the like.

[0049] exist FIG. 3A to FIG. 3B In some embodiments, the conductive liquid 270 is disposed directly on the major surface 214 in the region 226 so that the conductive liquid 270 can flow in opposite directions 230A, 230B along the channel 216. As described above, in some embodiments, the surrounding area of ​​the substrate can be selectively treated or patterned to enhance the gathering or flow of the conductive liquid 270 into the channel 216. For example, a suitable surface treatment or patterning method (including microreplication, flexographic printing, screen printing, gravure printing, etc.) can be used to produce one or more structures that are within or adjacent to the channel 216 and protrude away from or into the substrate 212 to promote or direct the flow of the conductive liquid 270. In an exemplary embodiment, an optional post 228 or arrangement of posts that protrude upward from the first major surface 214 of the substrate 212 can be formed in the channel 216 to control the flow of the conductive liquid 270, and in some embodiments, the posts 228 can be positioned to bisect the channel 216. The conductive liquid 270 can be deposited directly onto the posts 228, such as FIG. 3A to FIG. 3BAs shown, or may be deposited elsewhere in channel 216 so that liquid flows into or around pillars 228.

[0050] When the conductive liquid 270 is delivered into the channel 216, the conductive liquid 270 may be routed through the channel 216 primarily by capillary pressure in a first direction 230A toward the conductive pads 252 on the circuit die 250 proximate the first end 216A of the channel, and in a second direction 230B toward the holes 218 proximate the second end 216B of the channel 216. While not wishing to be bound by theory, currently available evidence suggests that a number of factors may affect the ability of the conductive liquid 270 to move through the channel 216 via capillary action. Such factors may include, for example, the size of the channel 216, the viscosity of the conductive liquid 270, the surface energy of the substrate 212, the surface tension of the conductive liquid 270, the drying conditions of the conductive liquid 270, and the like. Many of these factors are discussed in U.S. Pat. No. 9,401,306 (Mahajan et al.), which is incorporated herein by reference.

[0051] To generate effective capillary flow, the channel 216 can have any suitable dimensions (e.g., width, depth, or length), which can be determined in part by one or more of the above factors. As described above, in some embodiments, the channel 216 can be a microchannel having a width or depth in the range of, for example, about 0.01 micron to about 500 microns, about 0.05 micron to about 200 microns, or about 0.1 micron to about 100 microns.

[0052] See also FIG. 3C to FIG. 3D When the conductive liquid 270 moves into the channel 216 primarily via capillary action, the sidewalls 272 and bottom wall 274 of the channel 216 may be wetted by the conductive liquid 270 to form one or more curved menisci. The conductive liquid 270 should be delivered in an amount sufficient to cover a portion of the sidewalls 272 adjacent to the bottom wall 274. FIG. 3C to FIG. 3D As shown, the upper surface 271 of the conductive liquid 270 has a crescent-shaped concave shape. The edge 275 of the upper surface 271 can be used as a fixed contact line during the flow of the conductive liquid 270. Figure 3D As shown, the advancing front surface 276 of the conductive liquid 270 also has a crescent-shaped convex shape. The edge 277 of the front surface 276 can be used as a leading edge to guide the flow forward. The formation of the meniscus can generate a pressure gradient that can drive the flow downward along the capillary channel 216 using the viscous resistance provided by the friction at the channel wall 272.

[0053] See now FIG. 4A to FIG. 4B, the conductive liquid 370 is initially deposited on the first major surface 314 of the substrate 312 in the form of a laterally unconstrained droplet 380 and moves along the channel 316 in opposite directions 330A and 330B toward the first end 316A of the channel 316 and the second end 316B of the channel, respectively, via capillary action. At the first end 316A of the channel 316, the conductive liquid 370 contacts, spreads, and at least partially wets the exposed surface of the conductive pad 352 on the solid circuit die 350. At the second end 316B of the channel 316, the conductive liquid 370 flows into the first region of the hole 318. The conductive liquid 370 overflows the edge, flows along the hole wall 325 in the first region, and gathers on the shoulder 324 ... FIG. 4A to FIG. 4B In an embodiment, the dimensions (such as, for example, the shape of the edge, the width of the first region of the hole 318, and the dimensions of the hole wall 325) are proportional to the amount of conductive liquid 370 flowing into the region so that the conductive liquid 370 completely occupies the shoulder 324 but does not enter the cylindrical portion 340 of the hole 318. FIG. 4A to FIG. 4B In other embodiments not shown in FIG. 3 , the conductive liquid may overflow the shoulder 324 , down the wall 341 of the second region 340 of the hole 318 , and contact the conductive trace 360 ​​below the second region 340 .

[0054] See also Figure 4C In some embodiments, the conductive liquid 370 may be hardened, cured, hardened, etc. to form a conductive trace 390 deposited on both the sidewall 372 and the bottom wall 374 of the channel 316. Suitable methods that can be used to enhance the hardening of the conductive liquid 370 may include, for example, curing or evaporation by heating or radiation. In some embodiments, the curvature of the upper surface of the conductive trace may increase to form a new upper surface 373. During the hardening process, the fixed contact line 375 may induce liquid flow from the center of the channel 316 toward the sidewall 372. When the liquid carrier is removed from the conductive liquid 370, the volume of the conductive liquid decreases. The thickness of the deposited solid material left after the conductive liquid 370 hardens depends on the solid loading of the conductive liquid 370, but in some embodiments that are not intended to be limiting, the deposited solid material forming the conductive trace 390 may have a thickness of, for example, about 0.01 microns to about 200 microns, about 0.05 microns to about 100 microns, or about 0.1 microns to about 10 microns.

[0055] The hardening process may leave some void space in channel 316 below circuit die 350. In some embodiments ( FIG. 4A to FIG. 4C350 ), the void space may optionally be filled with an encapsulation material, for example, to protect the contact pad 352 from corrosion, or to enhance the structural strength of the construction 300. In various embodiments, the encapsulation material may include, for example, a dielectric material, a polymer material, etc. Examples of suitable encapsulants include, but are not limited to, polyurethanes, epoxies, polythiols, acrylates (including polyurethane acrylates), silicones, and polydimethylsiloxane (PDMS). In some embodiments, the encapsulation material may be delivered by capillary liquid flow to fill the open area of ​​the channel 316 after the conductive liquid 370 hardens. The liquid encapsulant may then be hardened to enhance the contact interface formed between the conductive traces and the contact pads 352 of the circuit die 350.

[0056] like FIG. 5A to FIG. 5B As shown in the configuration 400 in FIG. 1 , in some embodiments, a second conductive liquid 495 (which is different from the first conductive liquid ( 495 ) that has been previously hardened to form the conductive trace 490 in the channel 416) FIG. 4A to FIG. 4C )) is deposited in the direction of arrow B and backfilled in hole 418. Second conductive liquid 495 may include any of the conductive liquids discussed above, including conductive metals such as silver ink, silver nanoparticle ink, reactive silver ink, copper ink, and conductive polymer ink, as well as liquid metals or alloys (e.g., metals or alloys that melt at relatively low temperatures and harden at room temperature), etc. In some embodiments, second conductive liquid 495 is a molten metal or metal alloy, such as, for example, copper, silver, gold, and mixtures and combinations thereof. In some embodiments, second conductive liquid 495 is a conductive ink curable with actinic radiation, such as, for example, a UV curable ink or an activated ink.

[0057] The hole 418 may optionally be cleaned using a laser, chemical etching, or the like to ensure that the hole 418 is substantially free of the first conductive liquid and portions of the conductive trace 490 before the hole 418 is filled with the second conductive liquid 495. The second conductive liquid 495 flows into the first region 422 of the hole 418, substantially fills the second region 440 of the hole 418, and contacts the conductive trace 460 on the second major surface 420 of the substrate 412 to form an electrical connection with the conductive trace 460. Since the conductive trace 490 formed in the channel 416 substantially occupies the shoulder 424 of the first region 422 of the hole 418 and a substantial portion of the volume of the channel 416, the second conductive liquid 495 does not flow back into the channel 416, but is instead confined within the hole 418. In various embodiments, various properties of the conductive liquid 495, such as, for example, viscosity, may be selected to reduce the likelihood of backflow into the channel 416.

[0058] Then, the second conductive liquid 495 may be optionally hardened ( FIG. 5A to FIG. 5B416) to electrically connect the conductive traces 490 in the channel 416 to the conductive traces 460 on the second major surface 420 of the substrate 412, and thereby electrically connect the contact pads 452 on the solid circuit die 450 to the conductive traces 460. Suitable methods that can be used to optionally enhance the hardening of the conductive liquid 495 include, for example, curing or evaporation by heating or radiation. In various embodiments, the hardening method can be selected to quickly dry the conductive liquid 495, thereby reducing the possibility of backflow into the channel 416.

[0059] The present disclosure also provides a method for automatically aligning an electrical contact pad on an electronic component (e.g., a solid circuit die) with a conductive interconnect (such as, for example, a conductive trace). Generally, the solid circuit die is placed on a substrate so that the contact pad on the circuit die resides within a microchannel on a first major surface of the substrate. The conductive trace is formed in the channel by causing a conductive liquid in the channel to flow toward the contact pad on a first end of the channel to obtain automatic alignment with a conductive interconnect positioned on a second major surface of the substrate below a hole at a second end of the channel.

[0060] In some embodiments, the flexible substrate can be a web of polymeric material of indefinite length, and a suitable pattern of microchannels can be formed on or in a major surface of the web using, for example, a microreplication process such as embossing or via a printing process such as, for example, microcontact printing, screen printing, etc. The web with microchannels can be used in a high-speed roll-to-roll manufacturing process to electrically connect circuit components, thereby quickly producing low-cost circuits for electronic devices including, for example, radio frequency identification (RFID) tags, near field communication (NFC) circuits, Bluetooth circuits, Wi-Fi circuits, microprocessor chips, and the like.

[0061] In one embodiment of a method for making an electronic device, a substrate includes a first major surface having a microchannel having a first end and a second end. A conductive liquid is dispensed in the microchannel so that the conductive liquid moves primarily by capillary pressure in a first direction toward the first end of the microchannel and in a second direction toward the second end of the microchannel. The conductive liquid is hardened to form a conductive trace that electrically connects a first electronic device at the first end of the microchannel to a second electronic device at the second end of the microchannel.

[0062] exist Figure 6In another embodiment of the method 500 for manufacturing an electronic device as outlined in , a solid state circuit die is placed on a first major surface of a substrate in step 502. The first major surface of the substrate includes a configuration of microchannels having a substantially constant width and depth from a first end to a second end thereof. Contact pads on the solid state circuit die reside in the first end of the microchannel, and the second end of the microchannel terminates in a hole extending between the first major surface of the substrate and its opposing second major surface.

[0063] In step 504, the conductive traces on the second major surface of the substrate are aligned with the holes at the second end of the microchannel.

[0064] In step 506, a conductive liquid is dispensed in the microchannel between a first end and a second end thereof.

[0065] In step 508, the conductive liquid is caused to flow primarily by capillary pressure in a first direction toward the contact pads and in a second direction toward the holes, wherein the conductive liquid directly contacts the contact pads on the solid circuit die and enters the holes to directly contact the conductive traces.

[0066] In step 510, the conductive liquid is hardened to electrically interconnect the contact pads with the conductive traces.

[0067] exist Figure 7 In another embodiment of the method for manufacturing an electronic device 600 outlined in , in step 602, a solid circuit die is placed on a first major surface of a substrate. The first major surface of the substrate includes a microchannel having a substantially constant width and depth and extending from a first end of the microchannel to a second end. Contact pads on the solid circuit die reside in the first end of the microchannel, and the second end of the microchannel terminates in a hole extending between the first major surface of the substrate and an opposing second major surface thereof. The hole includes a first region proximate the first major surface of the substrate, and the first region leads to a second region proximate the second major surface of the substrate. In particular, as Figure 7 As shown in , in step 602, a solid circuit die is placed on a first major surface of a substrate so that a contact pad on the die resides in a first end of a microchannel on the substrate, and a second end of the microchannel terminates in a hole extending between the first major surface and the second major surface of the substrate, the hole including a tapered region proximal to the first major surface, the tapered region leading to a cylindrical region proximal to the second major surface.

[0068] In step 604, a conductive trace on the second major surface of the substrate is aligned with the second region of the hole.

[0069] In step 606, a first conductive liquid is dispensed in the microchannel between a first end and a second end thereof.

[0070] In step 608, the first conductive liquid is caused to flow primarily by capillary pressure in a first direction toward the contact pad and in a second direction toward the hole. The conductive liquid directly contacts the contact pad on the solid circuit die and flows into the hole to reside on the shoulder in the first region thereof, so that the second region of the hole is substantially free of the first conductive liquid. In particular, as Figure 7 As shown in FIG. 6 , in step 608 , a conductive liquid is flowed toward the contact pad and the hole so that the conductive liquid contacts the contact pad and flows into the hole to reside on a shoulder in a tapered region thereof, leaving the cylindrical region of the hole substantially free of conductive liquid.

[0071] In step 610, a sufficient amount of a second conductive liquid different from the first conductive liquid is applied to the hole so that the second conductive liquid flows into the second region of the hole to directly contact the conductive trace and fills the hole to directly contact the first conductive liquid on the shoulder of the first region, wherein the microchannel on the first major surface of the substrate is substantially free of the second conductive liquid. In particular, as Figure 7 As shown in , in step 610, the second conductive liquid is caused to flow into the pillar regions to contact the conductive traces and fill the holes to contact the first conductive liquid, so that the microchannels are substantially free of the second conductive liquid.

[0072] In step 612, the first conductive liquid and the second conductive liquid are optionally hardened to electrically interconnect the contact pads and the conductive traces.

[0073] In some embodiments of the method discussed above, the substrate may have: an alignment feature portion configured to receive an electronic component; and at least one channel configured to extend away from a region that corresponds to one of the contact points when the electronic component is disposed within the alignment feature portion.

[0074] In the present disclosure, the conductive liquid delivered into the channel can be automatically aligned with the circuit die by wetting the alignment features on the substrate and various surfaces of the circuit die (e.g., channel walls, side walls of a pit, side surfaces of the circuit die, etc.) via capillary action. The flow of the conductive liquid over the various capillary surfaces can be automatically directed at least in part by capillary forces, which allows the conductive fluid to be pumped toward the circuit die or conductive traces aligned with the substrate, optionally using a fluid pump, vacuum, etc. After the automatic alignment, the conductive liquid can be further hardened to form a solid continuous layer. The method can be repeated to form a multilayer structure aligned with the solid circuit die on the substrate.

[0075] In some embodiments, after forming the conductive traces in the channel, the channel may be optionally filled with an encapsulation material to protect the structure of the conductive traces or contact pads on the electronic device. The encapsulation material may include, for example, a dielectric material, a polymer material, etc. In some embodiments, the encapsulation material may be delivered via a capillary liquid flow to fill the channel. The encapsulation liquid may then be hardened to form an encapsulation material to protect the underlying traces, the circuit die, and the contact points formed between the traces and the circuit die.

[0076] When the conductive traces are formed and automatically aligned with the contact pads on the circuit die, the traces can be connected to other parts of the circuit or other circuits or devices at the same time or at a later time. In some embodiments, additional metal traces (e.g., Cu traces) can be patterned while aligned with the conductive traces. For example, in some embodiments, the conductive traces can be connected to the antenna coil of an electronic device (such as a receiver or transmitter). In some exemplary embodiments, which are not intended to be limiting, the methods described herein can be used to manufacture various chip-based circuits / devices, including, for example, radio frequency identification (RFID) tags, near field communication (NFC) circuits, Bluetooth circuits, Wi-Fi circuits, microprocessor chips, etc.

[0077] Implementation

[0078] Embodiment A. A method for manufacturing an electronic device, the method comprising:

[0079] providing a substrate having a first major surface including a microchannel, wherein the microchannel has a first end and a second end;

[0080] dispensing a conductive liquid in the microchannel such that the conductive liquid moves primarily by capillary pressure in a first direction toward a first end of the microchannel and in a second direction toward a second end of the microchannel; and

[0081] The conductive liquid is hardened to form a conductive trace that electrically connects a first electronic device at a first end of the microchannel to a second electronic device at a second end of the microchannel.

[0082] Embodiment B. The method of Embodiment A, wherein the volume of the conductive liquid dispensed in the microchannel is significantly greater than the volume of the portion of the channel below the conductive liquid dispensed therein.

[0083] Embodiment C. The method of any one of Embodiments A and B, wherein the microchannel has a substantially constant width and depth from the first end to the second end.

[0084] Embodiment D. The method of any one of Embodiments A to C, wherein the second end of the microchannel terminates in a hole extending from the first major surface of the substrate to a second major surface of the substrate opposite the first major surface.

[0085] Embodiment E. The method of embodiment D, wherein the first electronic device is on the first major surface of the substrate and the second electronic device is on the second major surface of the substrate and beneath the hole.

[0086] Embodiment F. The method of any one of Embodiments A to E, wherein the substrate comprises a flexible polymeric material.

[0087] Embodiment G. The method of Embodiment F, wherein the substrate comprises a web of polymeric material having an indefinite length.

[0088] Embodiment H. The method of any one of Embodiments A to G, wherein the first electronic component is a solid circuit die disposed on the first major surface of the substrate such that contact pads on the solid circuit die reside in the first end of the microchannel.

[0089] Embodiment I. The method of Embodiment H, wherein the solid state circuit die is a semiconductor die.

[0090] Embodiment J. The method of any one of Embodiments G to I, wherein placing the solid circuit die comprises mounting the solid circuit die on the first major surface of the substrate with an adhesive.

[0091] Embodiment K. The method of any one of Embodiments G to J, wherein the contact pad is located on a bottom surface of the solid circuit die.

[0092] Embodiment L. A method according to any one of Embodiments A to K, wherein the microchannel further comprises a feature protruding upward from the first major surface of the substrate to control the flow of the conductive liquid within the channel, wherein the feature is located between the first end and the second end of the microchannel.

[0093] Embodiment M. The method of any one of Embodiments A to L, wherein the conductive liquid comprises a conductive ink.

[0094] Embodiment N. The method of Embodiment M, wherein the conductive ink comprises a metal selected from the group consisting of copper, silver, gold, and mixtures and combinations thereof.

[0095] Embodiment O. A method for manufacturing an electronic device, the method comprising:

[0096] placing a solid circuit die on a first major surface of the substrate including the microchannel such that at least one contact pad on the solid circuit die resides in a first end of the microchannel, wherein a second end of the microchannel terminates in a hole extending between the first major surface of the substrate and an opposing second major surface thereof;

[0097] aligning the conductive trace on the second major surface of the substrate with the hole at the second end of the microchannel;

[0098] dispensing a conductive liquid in a microchannel between a first end and a second end thereof, wherein a volume of the conductive liquid dispensed in the microchannel is substantially greater than a volume of a portion of the channel underlying the dispensed conductive liquid; and

[0099] causing a conductive liquid to flow primarily by capillary pressure in a first direction toward the contact pads and in a second direction toward the holes, wherein the conductive liquid directly contacts the contact pads on the solid circuit die and enters the holes to directly contact the conductive traces; and

[0100] The conductive liquid is hardened to form conductive traces on the first major surface of the substrate that electrically connect contact pads on the solid state circuit die to conductive traces on the second major surface of the substrate.

[0101] Embodiment P. A method according to Embodiment O, wherein the microchannel has a substantially constant width and depth from its first end to its second end.

[0102] Embodiment Q. The method according to any one of Embodiments O to P, wherein the substrate P comprises a flexible polymer material.

[0103] Embodiment R. A method according to any one of Embodiments O to Q, wherein the substrate comprises a web of polymeric material having an indefinite length.

[0104] Embodiment S. The method of any one of Embodiments O to R, wherein the solid circuit die is a semiconductor die.

[0105] Embodiment T. The method of any one of Embodiments O to S, wherein placing the solid circuit die comprises mounting the solid circuit die on the first major surface of the substrate with an adhesive.

[0106] Embodiment U. The method of any one of Embodiments O to T, wherein the contact pad is located on a bottom surface of the solid circuit die.

[0107] Embodiment V. A method according to any one of Embodiments O to U, wherein the microchannel further includes a feature protruding upward from the first major surface of the substrate to control the flow of the conductive liquid within the channel, wherein the feature is located between the first end and the second end of the microchannel.

[0108] Embodiment W. The method of any one of Embodiments O to V, wherein the conductive liquid comprises a conductive ink.

[0109] Embodiment X. The method of Embodiment W, wherein the conductive ink comprises a metal selected from the group consisting of copper, silver, gold, and mixtures and combinations thereof.

[0110] Embodiment Y. The method of any one of Embodiments O to X, further comprising applying an encapsulating liquid to the microchannel after hardening the conductive liquid.

[0111] Embodiment Z. A method for manufacturing an electronic device, the method comprising:

[0112] placing a solid state circuit die on a first major surface of a substrate including a microchannel, the microchannel having a first end and a second end, wherein a contact pad on the solid state circuit die resides in the first end of the microchannel, and wherein the second end of the microchannel terminates in a well extending between the first major surface of the substrate and an opposing second major surface thereof, the well including a first region proximate the first major surface of the substrate, the first region of the well opening into a second region proximate the second major surface of the substrate;

[0113] aligning a conductive trace on the second major surface of the substrate with the cylindrical region of the hole;

[0114] distributing a first conductive liquid in the microchannel between a first end and a second end thereof;

[0115] causing a first conductive liquid to flow primarily by capillary pressure in a first direction toward the contact pad and in a second direction toward the hole, wherein the conductive liquid directly contacts the contact pad on the solid circuit die and flows into the hole to reside on a shoulder in a first region of the hole, such that a second region of the hole is substantially free of the first conductive liquid;

[0116] applying a sufficient amount of a second conductive liquid different from the first conductive liquid in the wells so that the second conductive liquid flows into the second region of the wells to directly contact the conductive traces and fills the wells to directly contact the first conductive liquid on the shoulders of the first region of the wells, and wherein the microchannels on the first major surface of the substrate are substantially free of the second conductive liquid; and

[0117] The first conductive liquid and the second conductive liquid are hardened to form conductive traces on the first major surface of the substrate that connect contact pads on the solid state circuit die with conductive traces on the second major surface of the substrate.

[0118] Embodiment AA. The method of Embodiment Z, wherein the volume of the conductive liquid dispensed in the microchannel is significantly greater than the volume of the portion of the channel below the dispensed conductive liquid.

[0119] Embodiment BB. The method of any one of Embodiments Z to AA, wherein the microchannel has a substantially constant width and depth from a first end to a second end thereof.

[0120] Embodiment CC. A method according to any one of Embodiments Z to BB, the method comprising hardening the first conductive liquid before applying the second conductive liquid to form a conductive trace on the first major surface of the substrate that is in direct contact with the contact pad on the solid circuit tube die, so that the subsequently applied second conductive liquid is in direct contact with the conductive trace on the first major surface of the substrate.

[0121] Embodiment DD. The method of any one of Embodiments Z to CC, wherein the substrate comprises a flexible polymeric material.

[0122] Embodiment EE. The method of Embodiment DD, wherein the substrate comprises a web of polymeric material having an indefinite length.

[0123] Embodiment FF. The method of Embodiment EE, wherein the method is performed on a roll-to-roll apparatus.

[0124] Embodiment GG. The method of any one of Embodiments Z to FF, wherein the solid circuit die is a semiconductor die.

[0125] Embodiment HH. The method of any one of Embodiments Z to GG, wherein the microchannel further comprises a flow control feature protruding upward from the first major surface of the substrate, wherein the flow control feature is located between the first end and the second end of the microchannel.

[0126] Embodiment II. The method of any one of Embodiments Z to HH, wherein the first conductive liquid comprises a conductive ink.

[0127] Embodiment JJ. The method of Embodiment II, wherein the conductive ink comprises a metal selected from the group consisting of copper, silver, gold, and mixtures and combinations thereof.

[0128] Embodiment KK. The method of any one of Embodiments Z to JJ, further comprising applying an encapsulating liquid to the microchannel after hardening the first conductive liquid.

[0129] Embodiment LL. An article comprising:

[0130] a flexible polymeric substrate having a first major surface including at least one microchannel having a substantially constant width and depth and extending from a first end thereof to a second end thereof, wherein the second end of the microchannel terminates in a well extending between the first major surface of the substrate and an opposing second major surface thereof;

[0131] a solid circuit die on the first major surface of the substrate, wherein a contact pad of the solid circuit die resides in the first end of the microchannel;

[0132] a first conductive trace on the second major surface of the substrate and aligned with the aperture at the second end of the microchannel;

[0133] A conductive liquid is in the microchannel and in the hole, wherein the conductive liquid contacts the contact pad on the solid circuit die and the first conductive trace on the second major surface of the substrate.

[0134] Embodiment MM. An article according to Embodiment LL, wherein the substrate comprises a web of polymeric material having an indefinite length.

[0135] Embodiment NN. The article of any one of Embodiments LL to MM, wherein the solid circuit die is a semiconductor die.

[0136] Embodiment OO. The article of any of Embodiments LL to NN, further comprising an adhesive layer between the solid circuit die and the first major surface of the substrate.

[0137] Embodiment PP. The article of any one of Embodiments LL to OO, wherein the contact pad is located on the bottom surface of the solid circuit die.

[0138] Embodiment QQ. The article of any of Embodiments LL to PP, wherein the conductive liquid comprises a conductive ink.

[0139] Embodiment RR. An article comprising:

[0140] a flexible polymeric substrate having a first major surface including at least one microchannel having a substantially constant width and depth and extending from a first end thereof to a second end thereof, wherein the second end of the microchannel terminates in a well extending between the first major surface of the substrate and an opposing second major surface thereof, the well including a first region proximal to the first major surface of the substrate that opens into a second region proximal to the second major surface of the substrate;

[0141] a solid circuit die on the first major surface of the substrate, wherein a contact pad of the solid circuit die resides in the first end of the microchannel;

[0142] a first conductive trace on the second major surface of the substrate, wherein the first conductive trace is aligned with the cylindrical region of the aperture;

[0143] a first conductive liquid in the microchannel, the first conductive liquid directly contacting a contact pad on the solid circuit die and extending over the shoulder in the first region of the aperture, wherein the first conductive liquid does not extend into the second region of the aperture; and

[0144] A second conductive liquid is in the second region of the aperture and contacts the first conductive liquid and the first conductive trace.

[0145] Embodiment SS. An article according to Embodiment RR, wherein the substrate comprises a web of polymeric material having an indefinite length.

[0146] Embodiment TT. The article of any one of Embodiments RR to SS, wherein the solid circuit die is a semiconductor die.

[0147] Embodiment UU. The article of any of Embodiments RR to TT, further comprising an adhesive layer between the solid circuit die and the first major surface of the substrate.

[0148] Embodiment VV. The article of any of Embodiments RR to UU, wherein the first conductive liquid and the second conductive liquid each comprise a conductive ink.

[0149] Embodiment WW. The article of any one of Embodiments RR to VV, wherein the first conductive liquid is a conductive ink and the second conductive liquid is a metal.

[0150] Various embodiments of the invention have been described. These and other embodiments are within the scope of the following claims.

Claims

1. A method for manufacturing an electronic device, the method comprising: placing a solid state circuit die on a first major surface of a substrate including a microchannel, the microchannel having a first end and a second end, wherein a contact pad on the solid state circuit die resides in the first end of the microchannel, and wherein the second end of the microchannel terminates in a well extending between the first major surface of the substrate and an opposing second major surface thereof, the well including a first region proximate the first major surface of the substrate, the first region of the well opening into a second region proximate the second major surface of the substrate; aligning a conductive trace on the second major surface of the substrate with a cylindrical region of the hole; distributing a first conductive liquid in the microchannel between a first end and a second end thereof; causing a first conductive liquid to flow by capillary pressure in a first direction toward the contact pad and in a second direction toward the hole, wherein the conductive liquid directly contacts the contact pad on the solid circuit die and flows into the hole to reside on a shoulder in the first region of the hole, such that the second region of the hole is free of the first conductive liquid; applying a second conductive liquid different from the first conductive liquid in the well, such that the second conductive liquid flows into the second region of the well to directly contact the conductive trace and fills the well to directly contact the first conductive liquid on the shoulder of the first region of the well, and wherein the microchannel on the first major surface of the substrate is free of the second conductive liquid; as well as The first conductive liquid and the second conductive liquid are hardened to form conductive traces on the first major surface of the substrate, the conductive traces connecting the contact pads on the solid state circuit die with conductive traces on the second major surface of the substrate. 2 . The method of claim 1 , wherein the volume of the conductive liquid dispensed in the microchannel is greater than the volume of a portion of the microchannel below the dispensed conductive liquid.

3. The method of claim 1, wherein the microchannel has a constant width and depth from a first end to a second end thereof. The method of claim 1 , wherein the substrate comprises a flexible polymer material.

5. A product, comprising: a flexible polymer substrate having a first major surface including at least one microchannel, the microchannel having a constant width and depth and extending from a first end thereof to a second end thereof, wherein the second end of the microchannel terminates in a well extending between the first major surface of the substrate and an opposing second major surface thereof, the well including a first region proximal to the first major surface of the substrate, the first region opening into a second region proximal to the second major surface of the substrate; a solid circuit die on the first major surface of the substrate, wherein a contact pad of the solid circuit die resides in a first end of the microchannel; a first conductive trace on the second major surface of the substrate, wherein the first conductive trace is aligned with the cylindrical region of the aperture; a first conductive liquid in the microchannel, the first conductive liquid directly contacting the contact pad on the solid circuit die and extending over the shoulder in the first region of the aperture, wherein the first conductive liquid does not extend into the second region of the aperture; and A second conductive liquid is in the second region of the hole and contacts the first conductive liquid and the first conductive trace.

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