Interposer for a system-on-chip cooling device

Abstract

A method of assembling a cooling device includes forming an interposer by plating a metallic material on a carrier to form a first metallic trace, forming a first layer of nonmetallic material around the first metallic trace to form a first interposer layer, and removing the first metallic trace to form a first fluid channel. The method further includes coupling a first side of the interposer to a first manifold including a second fluid channel to fluidly couple the first fluid channel to the second fluid channel.

Description

INTERPOSER FOR A SYSTEM-ON-CHIP COOLING DEVICEBACKGROUND

[0001] Electronic printed circuit boards (PCBs), integrated circuits, and systems-on-chip (SOCs), such as those used in computers or other electronic systems, commonly have a board with electronic components mounted thereon. The electronic components can generate a considerable amount of heat due to electrical power consumption. The heat may be dissipated from the components and the board to ensure proper functioning of the components and to prevent damage to any part of the SOC and the overall electronic system.BRIEF DESCRIPTION OF THE DRAWINGS

[0002] FIG. l is a side view of an example of a system-on-chip assembly including a cooling device;

[0003] FIG. 2 is a side view of an example of a system-on-chip assembly including a cooling device;10004] FIG. 3 is a side view of an example of a system-on-chip assembly including a cooling device;

[0005] FIG. 4 is an example of a method for manufacturing an interposer;

[0006] FIG. 5 is a side section view of an example of an interposer coupled to an example of a microchannel manifold;

[0007] FIG. 6 is a top view of the interposer of FIG. 5;

[0008] FIG. 7 is a bottom view of the interposer of FIG. 5;

[0009] FIG. 8 is a side section view of an example of an interposer coupled to an example of a microchannel manifold;

[0010] FIG. 9 is a top view of the interposer of FIG. 5;[0011 { FIG. 10 is a bottom view of the interposer of FIG. 5;[00121 FIG. 11 is a side section view of an example of an interposer coupled to an example of a microchannel manifold;

[0013] FIG. 12 is a side view of an example of a system-on-chip assembly including a cooling device;

[0014] FIG. 13 is a top view of an example of an interposer;

[0015] FIG. 14 is a side view of an example of a system-on-chip assembly including a cooling device;

[0016] FIG. 15 is an example of a method of manufacturing a cooling device.|0017] It will be recognized that the figures are schematic representations for purposes of illustration. The figures are provided for the purpose of illustrating the implementations with the explicit understanding that the figures will not be used to limit the scope of the meaning of the claims.DETAILED DESCRIPTION

[0018] Heat can be removed from a system-on-chip (SOC) using a variety of techniques. For example, the heat can simply be transferred by convection to ambient air. However, the amount of heat transferred using this method may be relatively low. To enhance the effectiveness of dissipation by convection, a fan can be added to force the air to flow over the component. A heat sink or heat spreader may be attached to the component to further enhance heat dissipation by conducting the heat away from the heat source to a large surface area from which the heat may be dissipated to the air. A heat sink may be a solid piece of material with high thermal conductivity, such as metal, with multiple fins extending from a base coupled to the SOC. The fins increase the surface area of the heat sink, increasing the amount of heat that can be carried away by convection as air or another fluid flows over the heat sink through the fins. For even greater heat dissipation, liquid-cooled heat dissipation systems can be used.

[0019] Liquid-cooled systems may include a pump or compressor, a cooling manifold including fluid channels, and a heat sink. The cooling manifold can be coupled to the SOC to allow the heat to transfer from the cooling plate to the cooling fluid. The compressor pumps the cooling fluid through the manifold channels and through pipes or conduits thatcarry the fluid to the heat sink at a location remote from the SOC. In some cases, the heat sink may include a compressor for active refrigeration of the cooling fluid.

[0020] A thermal interface material (TIM) may be positioned between the SOC and the heat sink or cooling manifold to improve the thermal conductivity and heat transfer therebetween. Numerous materials can be used as the TIM, including thermal grease, polymer-based TIMs, carbon-based TIMs, and metal -based TIMs. Metal-based TIMs may have the highest thermal conductivity, as well as low thermal contact resistance, and may thus provide the best heat transfer from the SOC to the heat sink or cooling manifold. These metal-based TIMs may include silver sintering paste, gallium-based liquid metal, solder material, or TIMS including gold, silver, or copper bond interfaces.

[0021] Referring now to FIG. 1, a SOC assembly 100 including an SOC 102 bonded to a liquid-cooled cooling device 202 is shown in a typical arrangement. The SOC 102 may include processing components 108 mounted to a substrate 110 (e.g., an organic or inorganic substrate). The cooling device 202 is bonded to the SOC 102 by a TIM 106. The cooling device 202 includes a silicon microchannel manifold (MCM) 204 bonded to a coolant distribution manifold (CDM) 208 by an adhesive bond layer 210. Cooling fluid (e.g., water, oil, etc.) may be supplied to the CDM 208 via a fluid inlet 211. The CDM 208 includes fluid channels that distribute the cooling fluid to smaller channels in the silicon MCM 204. The silicon MCM 204 may include multiple layers 205 of silicon (e.g., three layers, as shown), which may each be bonded to the adjacent layers 205 by an adhesive. The lower layer 205a of the silicon MCM 204 as shown includes microchannels extending therethrough. The ends of these microchannels are coupled to channels in the middle layer 205b as shown that extend to the top layer 205c. At the top layer 205c, the channels may extend to the upper surface of the silicon MCM 204 and be fluidly coupled to the channels of the CDM. Thus, the CDM 208 distributes fluid to the channels in the top layer 205c of the silicon MCM 204, which flows through the channels to the microchannels in the lower layer of the silicon MCM 204. After passing through the microchannels, the fluid continues to flow back through the middle and upper layers 205 of the silicon MCM 204, into the CDM 208, and out of the fluid outlet 213. The fluid may then be conveyed to a heat sink or refrigeration unit where it is cooled and recirculated back to the cooling device 202.[00221 The microchannels in the lower layer 205a of the silicon MCM 204 may be the smallest channels in the silicon MCM 204, may be tightly packed, and may extendsubstantially parallel to and near the lower surface of the lower layer 205a, which is bonded to the SOC 102 by the TIM 106. This arrangement allows the fluid in the microchannels to absorb as much heat from the SOC 102 as possible by maximizing the surface area of the fluid passing close to the SOC 102. Due to manufacturing constraints, it may be difficult to manufacture the channels of the CDM 208 (which may be made of a molded thermoplastic material) to accurately and precisely provide fluid directly to the microchannels of the lower layer 205a of the silicon MCM 204. Instead, the channels in the silicon MCM 204 may increase in size with each layer of the silicon MCM 204 approaching the CDM 208 to interface with the relatively large channels of the CDM 208. For example, the microchannels in the lower layer 205a may each be approximately 60 micrometers wide and 600 micrometers deep. The lower channels of the CDM 208 fluidly coupled to the silicon MCM 204 may be approximately 1.4 millimeters wide and 6.25 millimeters deep. The channels in additional layer 205 in the silicon MCM 204 increase in cross-sectional area until the channels in the upper layer 205 interface with (e.g., are fluidly coupled to) the channels of the CDM 208. The gradual increase in cross-sectional area of the channels allows the cooling device 202 to maintain high coolant flow through the channels, uniform coolant temperature distribution, and low coolant pressure drop at the coolant input and output ports.|0023] The additional layers also help to account for a mismatch in coefficients in thermal expansion (CTE) between the silicon MCM 204 and the CDM 208, which may be made of a thermoplastic material. For example, silicon has a CTE of about 3ppm / °C, and thermoplastic materials may have a CTE in the range of 25ppm / °C to 50ppm / °C. An excess increase in temperature of the CDM 208 may cause stress in the bond interface between the silicon MCM 204 and the CDM 208 (e.g., in the adhesive bond layer 210). The adhesive bond layer 210 may be made thicker, such that the adhesive can deform without cracking or imparting excess stress into the silicon MCMs 204 due to the differences in thermal expansion between the silicon MCM 204 and the CDM 208. The layer of the silicon MCM 204 closest to the SOC 102 may experience the highest temperature change due to its proximity to the SOC 102, while each subsequent layer approaching the coolant distribution manifold 208 may experience progressively lower temperature change, essentially insulating the CDM 208 from the SOC 102. This reduces the temperature change of the CDM 208, thus minimizing the effect of the CTE mismatch between the silicon MCM 204 and the CDM 208. Additional layers 205 of silicon may thus reduce the stress at the bond interface. However, silicon is arelatively expensive material, and additional layers 205 increase the height and overall size of the cooling device 202, which may be undesirable in electronics where space is a concern.

[0024] Referring now to FIG. 2, a SOC assembly 300 is shown, according to some examples. The SOC assembly 300 may be substantially similar to the SOC assembly 100 of FIG. 1, except as shown and described herein to reduce cost and the overall height of the cooling device 202, a layer 205 or layers 205 (e.g., the top layer 205c) of the silicon MCM 204 may be replaced by an interposer 309. The interposer 309 is positioned between the CDM 208 and silicon MCM 204. The interposer 309 may be bonded to the CDM 208 by a first adhesive bond layer 312 and bonded to the silicon MCM 204 by a second adhesive bond layer 313. The interposer 309 may include fluid channels (shown schematically as channels 348) that fluidly connect the fluid channels of the CDM 208 (shown schematically as channels 247) to the fluid channels of the silicon MCM 204 (shown schematically as channels 249) and become progressively larger moving from the silicon MCM 204 to the CDM 208. For example, the upper channels of the silicon MCM 204 may have a cross-sectional area approximately 10-15 times larger than the fluid channels (e.g., microchannels) in the lower layer 205a. The channels of the interposer 309 may increase in cross-sectional to about 5-10 times that of the upper channels of the silicon MCM 204, and the channels of the CDM 208 may increase in cross-sectional to about 10-15 times that of the upper channels of the interposer 309. The interposer 309 may also include electrical traces extending from the top to the bottom of the interposer 309, such that electrical connections can be made between the silicon MCM 204 and the CDM 208 through the interposer 309.

[0025] The interposer 309 may be made of an epoxy mold compound (EMC) and may be assembled using molded interconnect substrate technology. The EMC may be, for example, Ajinomoto Build-up Film (ABF) and may have a CTE of about 7 ppm / °C (e.g., between about 5 ppm / °C and about 9 ppm / °C, or between about 4 ppm / °C and about 10 ppm / 3C). Because the interposer 309 may have a CTE between that of the silicon MCM 204 (e.g., 3 ppm / °C) and the CDM 208 (e.g., 25-50ppm / °C), the interposer 309 may expand more than the silicon MCM 204 and less than the CDM 208. Thus, the interposer 309 may provide a transition layer that reduces stress at the interfaces (e.g., at the adhesive bond layers 312, 313) compared to a cooling device 202 in which the silicon MCM 204 and the CDM 208 are directly coupled together (e.g., as shown in FIG. 1). Because the adhesive bond layer 313 is applied in a very thin layer, such that the adhesive is not squeezed into the narrow fluid channels of theinterposer 309 and the silicon MCM 204 upon assembly, a close CTE match between the interposer 309 and the silicon MCM 204 may be desired. Because the channels are large at the interface of the interposer 309 and the CDM 208, a thicker adhesive bond layer 312 (e.g., thicker than the adhesive bond layer 313) may be used, which may deflect and deform under stress to account for the difference in CTE between the interposer 309 and the CDM 208. In some examples, the interposer 309 may include multiple layers 310, each of which may include a different formulation of EMC with a different CTE. For example, the layer 310a immediately adjacent the silicon MCM 204 may be made from an EMC with a CTE of 7 ppm / °C, a middle layer 310b may be made from an EMC with a CTE of 9 ppm / °C, and an upper layer 310c may be made from an EMC with a CTE of 11 ppm / °C. Thus, the interposer 309 may provide a gradual increase in CTE from the silicon MCM 204 to the CDM 208.

[0026] The interposer 309 may replace a layer 205 or layers 205 of a silicon MCM 204 with the lower-cost EMC while providing the same or more effective cooling. For example, as shown in FIG. 2, the cooling device 302 includes a silicon MCM 204 with two layers 205. Compared to the cooling device 202 of FIG. 1, the top layer 205c of the silicon MCM 204 has been eliminated and replaced by the interposer 309 with four layers (e.g., a bottom layer 310a, top layer 310c two intermediate layers 310b, 310b’). The complete cooling device 202 with two silicon layers 205 and an interposer 309 may provide equivalent or improved cooling compared to the cooling device with three silicon layers 205. The interposer 309 may also be thinner than the thickness of the top silicon layer 205c, resulting in a lower overall height of the cooling device 202. For example, each layer 205 of the silicon MCM may be approximately 420 micrometers thick, while each layer 310 of the EMC interposer may be approximately 70 micrometers thick (e.g., 30-140 micrometers thick). So, if a layer 205 of a silicon MCM 204 can be replaced by a three-layer interposer 309, the overall height of the cooling device 202 may be reduced by approximately 210 micrometers. In some examples, the interposer 309 may replace multiple layers 205 of a typical cooling device 202. For example, as shown in FIG. 3, the cooling device 302 may include a silicon MCM 204 with one layer 205 of silicon, with the interposer 309 replacing the middle and top layers 205 of the silicon MCM 204. Eliminating silicon layers 205 also eliminates the additional manufacturing step of bonding the layers 205 together. It should be understood that “replacing,” as used herein refers to the interposer 309 being included in the cooling device 202 in place of an additional layer or additional layers of silicon in the silicon MCM 204 that would provide the same or similar cooling. Thus, “replacing” does not mean that the layersof the silicon MCM 204 are removed from a silicon MCM 204 after the silicon MCM 204 is manufactured. The interposer 309 may include several thin layers 310 (e.g., thinner than the layers 205 of the silicon MCM 204), allowing for the fluid channels to fan out from the lower layer 310a adjacent the silicon MCM 204 to the layer 310c adjacent the CDM 208. Examples of interposers 309 bonded to silicon MCMs 204 are shown in further detail in FIGS. 5-10.[0027| Referring now to FIG. 4, an example method of manufacturing an interposer 309 is shown. At operation 402 of the method 400, a carrier 452 is provided. At operations 404 and 406 of the method 400, layers of dry film 454 and a second material 456 are applied (e.g., plated) to the carrier 452. The second material 456 may be a metallic material, such as copper or a copper alloy, which forms a metallic trace or trace portion on the carrier. The dry film 454 may allow the layers of the second material 456 to be supported as they are built up from the carrier 452. At operation 408 of the method 400, the dry film 454 may be removed, leaving the second material 456 on the carrier 452. At operation 410 of the method 400, the remaining second material 456 may be molded into a mold compound 458, which may be an epoxy mold compound (EMC) or other nonmetallic material, to form a layer surrounding the second material 456. At operation 412 of the method 400, additional layers of dry film 454 and the second material 456 may be applied on top of the EMC and lower layers of the second material 456 to form additional traces or trace portions of the second material 456. Some of the additional metallic material may be in contact with the metallic material plated applied in operations 404 and 406, such that a trace is formed from multiple trace portions. Traces may extend from the carrier 452 to the upper face of the interposer 309 after completion of the method 400. At operation 414 of the method 400, the dry film 454 may be removed. At operation 416 of the method 400, the additional layers of second material 456 may be molded into another layer of mold compound 458. The operations may be repeated as necessary to add additional layers of second material 456 and mold compound 458. At operation 418 of the method 400, the carrier 452 may be removed. At operation 420 of the method 400, a portion or all of the second material 456 may be removed, leaving an interposer 309 with channels 460 through the layers of mold compound 458. For example, if the mold compound 458 is EMC and the second material forming the traces is copper, selective chemical etching may be used to remove the copper and form the channels 460. This method 400 allows for very thin layers of mold compound 458 with precise and closely packed channels 460.[0028 | The method 400 also allows for some of the second material to remain in the interposer 309 without being removed, for example, by masking those portions of the second material during the chemical etching process (e.g., in operation 420). For example, copper traces may extend from an upper surface of the interposer 309 to a lower surface of the interposer 309 to conduct electrical signals through the interposer 309. The copper traces may be electrically connected to electrical contacts in the silicon MCM 204 and in the CDM 208 to conduct electrical signals between the MCM 204 and the CDM 208. The electrical contacts may be electrically coupled to an electrical component in the silicon MCM 204, such as a flow sensor, temperature sensor, pressure sensor, or other sensor or electrical component. For example, the CDM 208 may include or may be coupled to a controller communicably coupled to the electrical components via the traces. The controller may, for example, receive sensor data from the electrical components and use the sensor data to control aspects of the cooling device 302. For example, the controller may control the fluid pumps to increase the speed of the cooling fluid through the channels when an increase in temperature in the silicon MCM 204 is detected.[0029| An interposer 309 manufactured according to the method 400 may be desirable over potential alternatives for several reasons. For example, as discussed above, additional layers 205 of silicon in the silicon MCM 204 may add to the cost and overall size of the cooling device 202. The interposer 309, even with multiple layers 310, may be thinner than a single layer 205 of the silicon MCM 204. An interposer 309 manufactured according to the method 400 may also allow fine fluid pitch between channels and thinner slots than alternative manifolds, including injection-molded thermoplastic manifolds. For example, prototypes have been manufactured demonstrating a fluid channel pitch of less than 150 micrometers, with 73 micrometer-wide channels being separated by only 76 micrometers. Slots have also been formed as narrow as 43 micrometers. Injection-molded thermoplastic manifolds have a much higher minimum fluid channel pitch and minimum channel size (e.g., closer to 1 millimeter in width). Injection-molded thermoplastic manifolds also have relatively high CTE, a significant draft angle to allow for release from the mold, a low glass transition temperature, and a rough surface finish, and are not typically manufactured with multiple layers. In contrast, the interposer 309 may be made of a chemically robust ABF material, which can be smoothed with a grinding wheel to achieve a smooth surface finish to allow for a firm adhesive bond to the silicon MCM.[00301 Referring now to FIGS. 5-7, a side section view, a top view, and a bottom view, of an example interposer 309 are respectively shown. In the side section view of FIG. 5, the interposer 309 is shown coupled to a silicon MCM 204. The silicon MCM 204 includes two layers 205, and the interposer 309 includes three layers 310. The lower layer 205a of the silicon MCM 204 includes microchannels 252 extending therethrough, near the lower surface 254 of the silicon MCM 204, which may be bonded to an SOC 102. The microchannels 252 may be approximately 50 micrometers wide and 600 micrometers deep. The upper layer 205 of the silicon MCM 204 includes vertically-extending channels 256 fluidly coupling the microchannels 252 to the lower channels 352 of the lower layer 310a of the interposer 309. As shown in FIG. 5, the horizontal lower channels 352 extend from the lower face of the interposer 309 along the upper surface of the silicon MCM 204 and are fluidly coupled to vertically-extending channels 354 in the second layer 310b of the interposer 309 (e.g., an intermediate layer of the interposer 309). The vertically-extending channels 354 fluidly couple the lower channels 352 to larger fluid distribution channels 356 in the upper layer 310c of the interposer 309. For example, as shown in FIG. 6, multiple vertically-extending channels 354 may be coupled to one larger fluid distribution channel 356. The larger fluid distribution channels 356 extend to the upper face of the interposer 309 and may be fluidly coupled to the fluid channels of the CDM 208. The average cross-sectional area (e.g., along the fluid flow direction) of the lower channels 352 may be lower than the average cross- sectional area of the larger fluid distribution channels 356. As shown in the bottom view of FIG. 7, the lower channels 352 open to the bottom of the interposer 309, where they may be fluidly coupled to the vertically-extending channels 256 of the silicon MCM 204. As shown in FIG. 5, when the interposer 309 is coupled to the silicon MCM 204, the upper surface of the silicon MCM 204 forms a lower surface of the fluid channels 352, sealing the open channels 352 and fluidly coupling the vertically-extending channels 256 of the silicon MCM 204 to the vertically-extending channels 354 of the interposer 309.|0031] FIGS. 8-10 respectively show a side section view, a top view, and a bottom view, of another example interposer 309. The interposer 309 of FIGS. 8-10 may be substantially similar to the interposer 309 of FIGS. 5-7, except as shown and described herein. The interposer of FIGS. 8-10 includes four layers 310 and is shown coupled to the silicon MCM 204 including one layer 205. As in FIGS. 5-7, the layer 205 of the silicon MCM 204 includes microchannels 252 extending therethrough, near the lower surface 254 of the silicon MCM 204, which may be bonded to an SOC 102. However, rather than the silicon MCM 204including a second upper layer 205 with a vertically-extending channel 256, as shown in FIGS. 5-7, the interposer 309 includes a fourth layer at its lower end with a vertically- extending layer 358 fluidly coupling the microchannels 252 to the horizontal lower channels 353. Thus the horizontal lower channels 353 are not open to the open to the bottom of the interposer 309 as shown in FIGS 5 and 7. FIG. 10 shows the lower channels 358 open to the bottom of the interposer 309, where they may be fluidly coupled to the microchannels 252 of the single-layer silicon MCM 204. The top view shown in FIG. 9 is substantially the same as the top view shown in FIG. 6 (as the top layer 310c of each interposer 309 in these Figures is substantially the same), except that in FIG. 8, the upper surface of the lower layer 310a can be seen through the vertically-extending channels 354.[00321 The example interposers 309 shown in FIGS. 5-10 allow the number of layers 205 in the silicon MCM 204 to be reduced from three or more to two or even one. The layers 310 of the interposer may be thinner than the layer 205 of the silicon MCM 204, such that an interposer 209 with multiple layers 310 may be thinner than even a single layer 205 of the silicon MCM 204. Thus, replacing a layer 205 of the silicon MCM 204 with the interposer 309 may reduce the overall height of the cooling device 302. Replacing two layers 205 of the silicon MCM 204, such that the silicon MCM includes only a single layer, as shown in FIGS. 8-10, reduces the overall height of the cooling device 302 even more. This may allow the cooling device 302 to be more easily packaged into an electrical device, without driving up the size of the device housing. A single-layer silicon MCM 204 may also be more easily manufactures, as multiple layers would not have to be bonded together in an additional manufacturing step. Due to the costs involved with forming the fluid channels in the layers 205 of the silicon MCM 204 and bonding the layers 205 together, the manufacturing cost of a cooling device 302 with an interposer 309 and a silicon MCM 204 with one or two layers 205 may be lower than the manufacturing cost of a cooling device 202 without an interposer and with a silicon MCM 204 with three or more layers 205.

[0033] FIG. 11 shows a side section view of a portion of an example interposer 309 coupled to an example silicon MCM 204 (e.g., similar to the center portion of the interposer 309 of FIG. 5). As described above, the interposer 309 may be manufactured by molding a metallic material (e.g., copper) into an epoxy mold compound (e.g., ABF). Metallic material may then be removed (e.g., using selective etching) to form the fluid channels 352, 354, 356. However, some of the metallic material may remain in the interposer 309 to act as electrical traces 360.The electrical traces 360 may extend through the interposer 309 from the upper face 362 to the lower face 364, where they may be electrically connected to electrical contacts 260 in the silicon MCM 204. Each electrical contact 260 may be electrically coupled to an electrical component 262, such as a flow sensor, temperature sensor, pressure sensor, or other sensor or electrical component. The upper end of the electrical traces 360 may be electrically coupled to additional components in the CDM 208 to enable an electrical connection between the CDM 208 and the silicon MCM 204. For example, the CDM 208 may include or may be coupled to a controller communicably coupled to the electrical components 262 via the traces 360 and may, for example, receive sensor data from the electrical components 262. Any of the interposers 309 discussed herein may include electrical traces 360 as shown in FIG. 11.

[0034] Referring now to FIG. 12, a SOC assembly 500 with a cooling device 502 is shown, according to some examples. Due to manufacturing imperfections, the substrate 110 and the SOC 102 as a whole may bow when the temperature of the SOC 102 increases. This bow may become more pronounced in larger SOCs 102. A single, large silicon MCM 204 will resist the bending of the SOC 102, which causes stress in the TIM 206 and the bond interfaces of the SOC 102 and silicon MCM 204 with the TIM 206. To address this, the SOC assembly 500 includes multiple silicon MCMs 204 each bonded to the SOC 102 by separate TIMs 206. Each silicon MCM 204 may be spaced apart from the silicon MCMs 204, allowing each silicon MCM 204 to move relative to the other silicon MCMs 204. Because the silicon MCM 204 are separated from each other, as the SOC 102, silicon MCMs 204, and TIMs 206 heat up, the silicon MCMs 204 can expand toward each other and / or move vertically (as shown) relative to each other without imparting excess stress into the SOC 102, TIMs 206, or silicon MCMs 204. Because the space between the silicon MCMs 204 relieves stress caused by thermal expansion, rigid material, including metal-based TIMs such as silver sintering paste, can be used for the TIMs 206 rather than a more compliant TIM. The SOC assembly 500 thus allows for TIMs with very high thermal conductivity and very low contact resistance to be used, despite their rigidity. In some examples, the TIM 206 may be continuous while the silicon MCMs 204 are separated from each other. For example, the SOC assembly 500 may include a single section of TIM 206 bonded to two or more silicon MCMs 204, rather than including a separate section of TIM 206 for each silicon MCM 204. The separation of the silicon MCMs 204 may be sufficient to reduce stress without also separating the TIM 206 as shown in FIG. 12.

[0035] As shown in FIG. 12, all of the silicon MCMs 204 are coupled to one interposer 309. In other examples, less than all of the silicon MCMs 204 may be coupled to one interposer 309. For example, the cooling device 502 may include multiple interposers 309 each coupled to a subset of the silicon MCMs 204. As shown in FIG. 14, the SOC assembly 600 includes a cooling device 602 including a first interposer 309a with a flexible joint 311 and two bond portions 314 each coupled to a silicon MCM 204. The cooling device also includes a second interposer 309b that does not include a flexible joint 311 and is coupled to one silicon MCM. In some examples, there may be a separate interposer 309 coupled to each cooling unit. However, it may be desired to use one interposer 309 to couple together multiple silicon MCMs 204, so that the spaces between the silicon MCMs 204 can be tightly controlled. For example, it may be desired to have the silicon MCMs 204 very close together such that substantially an entire surface of the SOC 102 (e.g., the upper surface of the SOC 102 as shown in FIG. 3) is covered by the silicon MCMs 204, with the gaps positioned over an insubstantial portion of the surface. For example, the gap between each silicon MCMs 204 may be about 200 microns wide or less. Such a small gap may be difficult to maintain if each silicon MCM 204 is individually bonded to the SOC 102. Accordingly, each silicon MCM 204 may first be coupled to the interposer 309, maintaining a very small gap between the silicon MCMs 204, and the complete cooling device 202 can be to the SOC 102. This may also allow the cooling devices 202 to be pre-assembled for installation on existing SOCs 102, for example, to replace an existing heat sink. The cooling devices 202 may be manufactured and / or assembled using precision machinery to maintain the very small gaps between the silicon MCMs 204. However, if a rigid interposer 309 is coupled to multiple silicon MCMs 204, the interposer 309 may resist the ability of the silicon MCMs 204 to move relative to one another. If the TIM 206 is also rigid, this may cause stress at the interface between the silicon MCMs 204 and the SOC 102.

[0036] As shown in FIG. 12, the cooling device 502 includes an interposer 309 with flexible joints 311 in the areas between the silicon MCMs 204. The portions between the flexible joints 311, which may be referred to as bond portions 314 (e.g., interposer tiles, tile portions, etc.), may be coupled to the silicon MCMs 204. The flexible joints 311 may allow the silicon MCMs 204 to move relative to one another when the SOC 102 deforms. The interposer 309 may thus create insubstantial resistance to the movement of the silicon MCMs 204 relative to one another. However, because the interposer 309 still couples the silicon MCMs 204 together, the silicon MCMs 204 may be precisely positioned and coupled to the interposer309 to maintain tightly controlled gaps between the silicon MCMs 204. The flexible joints 311 may be, for example, in the form of partial or complete cuts in the interposer 309 or a combination of partial and complete cuts. Thus, the cross-sectional area of a flexible joint 311 (e.g., on a plane extending longitudinally through the flexible joint 311) may be lower than the cross-sectional area of an adjacent bond portion 314 on a parallel plane. FIG. 13 shows an example of an interposer 309 with ten bond portions 314 to be coupled to ten silicon MCMs 204. A flexible joint 311 is positioned between each of the adjacent bond portions314 of the ten bond portions 314. The flexible joints 311 include both through-cut portions315 and partial-cut portions 317. The through cut portions 315 provide no resistance to movement of the silicon MCMs 204 relative to each other. The partial cut portions 317 provide relatively insubstantial resistance to movement of the silicon MCMs 204 relative to each other while coupling the individual bond portions 314 together.

[0037] Referring now to FIG. 15, an example method 430 of manufacturing a cooling device (e.g., cooling device 202) is shown. At operation 432 of the method 430, an interposer 309 is formed according to the method 400. At operation 434 of the method 400, the interposer 309 may be cut to form a flexible joint between two adjacent tile portions. The flexible joints may be slots, through cuts, or a combination of the two. An interposer 309 with flexible joints is further discussed below with respect to FIGS. 13 and 14. In other examples, a flexible joint may be formed in the interposer 309 during operation 432. Instead of cutting the interposer, a metallic trace may be formed at a lower or upper face of the interposer 309, and the nonmetallic material may be formed around the trace. The metallic trace may be removed (e.g., by etching), leaving a depression or channel on the face of the interposer 309 that may act as a flexible joint, either alone or in cooperation with additional depressions or channels. In other examples, an interposer 309 may be formed and assembled into the cooling device 202 without any flexible joints. At operation 436 of the method 400, a first side of the interposer 309 is coupled to a first manifold (e.g., a silicon MCM 204) to fluidly couple fluid channels (e.g., microchannels) of the first manifold to fluid channels of the interposer 309. The interposer 309 may be coupled to the first manifold using an adhesive. Coupling the first manifold to the interposer 309 may include electrically coupling an electrical trace formed in the interposer 309 to an electrical contact in the first manifold to allow electrical signals to be sent to and from the first manifold through the interposer 309.

[0038] In examples in which a flexible joint has been formed in the interposer 309, the first manifold may be coupled to a first tile portion of the interposer 309, and the method 400 may further include operation 438. At operation 438, a second manifold (e.g., a silicon MCM 204) may be coupled to a second tile portion of the interposer on the first side of the interposer to couple fluid channels (e.g., microchannels) of the second manifold to fluid channels of the interposer 309. The interposer 309 may be coupled to the second manifold using an adhesive. The first manifold and the second manifold may be spaced apart from each other, with the flexible joint therebetween. At operation 440 of the method 400, a second side of the interposer 309 is coupled to a CDM 208 to fluidly couple fluid channels of the CDM 208 to fluid channels of the interposer 309, and thereby fluidly couple fluid channels of the CDM to fluid channels of the first manifold and, in some examples, fluid channels of the second manifold. The interposer 309 may be coupled to the CDM 208 using an adhesive or gasket. The method 400 may include additional operations not listed. For example, additional flexible joints may be formed in the interposer 309 to form additional tile portions and additional silicon MCMs 204 may be coupled to the additional tile portions. In some examples, the method 430 may not include some of the listed operations. For example, as discussed above, a flexible joint may not be formed in the interposer 309, and multiple silicon MCMs 204 may not be coupled to the interposer 309.

[0039] In an aspect, a method of assembling a cooling device is provided. The method includes forming an interposer by plating a metallic material on a carrier to form a first metallic trace, forming a first layer of nonmetallic material around the first metallic trace to form a first interposer layer, and removing the first metallic trace to form a first fluid channel. The method further includes coupling a first side of the interposer to a first manifold including a second fluid channel to fluidly couple the first fluid channel to the second fluid channel.

[0040] In some examples, the method further includes coupling a second side of the interposer to a coolant distribution manifold including a third fluid channel to fluidly couple the first fluid channel to the third fluid channel.

[0041] In some examples, the nonmetallic material is an epoxy mold compound and the metallic material includes copper, and removing the first metallic trace includes selectively etching the copper.

[0042] In some examples, the method further includes cutting the interposer to form a flexible joint between a first tile portion and a second tile portion adjacent the first tile portion and coupling a second manifold including a fourth fluid channel to the second tile portion on the first side of the interposer, wherein coupling a first side of the interposer to the first manifold includes coupling the first tile portion to the first manifold.

[0043] In another aspect, a cooling device for a system-on-chip is provided. The cooling device includes an interposer including a first layer with a first plurality of fluid channels extending from a first face of the interposer and having a first average cross-sectional area and a second layer coupled to the first layer and including a second plurality of fluid channels extending from a second face of the interposer, fluidly coupled to the first plurality of fluid channels, and having a second average cross-sectional area that is larger than the first average cross-sectional area. The cooling device further includes a microchannel manifold including a first side to be coupled to a system-on-chip, a second side coupled to the first face of the interposer, and a third plurality of fluid channels fluidly coupled to the first plurality of fluid channels; and

[0044] In some examples, the cooling device further includes a coolant distribution manifold coupled to the second face of the interposer and including a fourth plurality of fluid channels coupled to the second plurality of fluid channels.

[0045] In some examples, the cooling device further includes a first adhesive layer coupling the interposer to the microchannel manifold and a second adhesive layer coupling the interposer to the coolant distribution manifold, wherein the second adhesive layer is thicker than the first adhesive layer.

[0046] In some examples, the first layer of the interposer includes a first epoxy mold compound with a first coefficient of thermal expansion, and the second layer of the interposer includes a second epoxy mold compound with a second coefficient of thermal expansion that is higher than the first coefficient of thermal expansion.

[0047] In some examples, the interposer includes a metallic trace molded into an epoxy mold compound.

[0048] In some examples, the metallic trace extends from the first face of the interposer to the second face of the interposer to enable an electrical connection between a microchannelmanifold coupled to the first face and a coolant distribution manifold coupled to the second face.

[0049] In some examples, the interposer includes a plurality of tile portions to be coupled to a plurality of manifolds and a flexible joint between adjacent tile portions, the flexible joint having a lower cross-sectional area on a plane extending longitudinally through the flexible joint than an adjacent tile portion on a parallel plane.

[0050] In some examples, the interposer includes an intermediate layer between the first layer and the second layer, the intermediate layer including a fifth plurality of fluid channels fluidly coupling the first plurality of fluid channels to the second plurality of fluid channels.

[0051] In another aspect, a method of assembling a cooling device is provided. The method includes forming an interposer by plating copper on a carrier to form a first copper trace portion, forming a first layer of epoxy mold compound around the first copper trace portion to form a first interposer layer, plating copper on the first interposer layer to form a second copper trace portion in contact with the first copper trace portion, forming a second layer of epoxy mold compound around the second copper trace portion to form a second interposer layer, removing the first copper trace portion and the second copper trace portion to form a first plurality of fluid channels. The method further includes coupling a first side of the interposer to a first silicon microchannel manifold including a plurality of microchannels to fluidly couple the first plurality of fluid channels to the plurality of microchannels and coupling a second side of the interposer to a coolant distribution manifold including a second plurality of fluid channels to fluidly couple the first plurality of fluid channels to the second plurality of fluid channels.

[0052] In some examples, the method further includes cutting a slot in the interposer to form a flexible joint between a first tile portion and a second tile portion adjacent the first tile portion, and coupling the first side of the interposer to the first silicon microchannel manifold includes coupling the first tile portion to the first silicon microchannel manifold. And the method further includes coupling a second silicon microchannel manifold to the second tile portion spaced apart from the first tile portion with the flexible joint positioned between the first tile portion and the second tile portion.

[0053] In some examples, the method further includes plating copper on the carrier to form a third copper trace portion, wherein the first layer of epoxy mold compound is also formedaround the third copper trace portion, plating copper on the first interposer layer to form a fourth copper trace portion in contact with the third copper trace portion to form an electrical trace, wherein the second layer of epoxy mold compound is also formed around the fourth copper trace portion, and electrically coupling the electrical trace to an electrical contact of the first silicon microchannel manifold.

[0054] It should be noted that certain passages of this disclosure may reference terms such as “first” and “second” in connection with devices, surfaces or sides of devices, modes of operation, transmit chains, antennas, etc., for purposes of identifying or differentiating one from another or from others. These terms are not intended to merely relate entities (e.g., a first device and a second device) temporally or according to a sequence, although in some cases, these entities may include such a relationship. Nor do these terms limit the number of possible entities (e.g., devices) that may operate within a system or environment.

[0055] While this specification contains specific implementation details, these should not be construed as limitations on the scope of what may be claimed but rather as descriptions of features specific to particular implementations. Certain features described in this specification in the context of separate implementations can also be implemented in combination in a single implementation. Conversely, various features described in the context of a single implementation can also be implemented in multiple implementations separately or in any suitable sub-combination. Moreover, although features may be described as acting in certain combinations and even initially claimed as such, features from a claimed combination can, in some cases, be excised from the combination, and the claimed combination may be directed to a sub-combination or variation of a sub-combination.

[0056] As utilized herein with respect to structural features (e.g., to describe shape, size, orientation, direction, relative position, etc.), the terms “approximately,” “about,” “substantially,” and similar terms are meant to cover minor variations in structure that may result from, for example, the manufacturing or assembly process and are intended to have a broad meaning in harmony with the common and accepted usage by those of ordinary skill in the art to which the subject matter of this disclosure pertains. Unless otherwise noted, the use of the words “approximate,” “about,” “around,” “substantially,” etc., when used to refer to a numerical value mean plus or minus ten percent.

[0057] The term “coupled” and variations thereof, as used herein, means the joining of two members directly or indirectly to one another. Such joining may be stationary (e.g., permanent or fixed) or moveable (e.g., removable or releasable). Such joining may be achieved with the two members coupled directly to each other, with the two members coupled to each other using a separate intervening member and any additional intermediate members coupled with one another, or with the two members coupled to each other using an intervening member that is integrally formed as a single unitary body with one of the two members. If “coupled” or variations thereof are modified by an additional term (e.g., directly coupled), the generic definition of “coupled” provided above is modified by the plain language meaning of the additional term (e.g., “directly coupled” means the joining of two members without any separate intervening member), resulting in a narrower definition than the generic definition of “coupled” provided above. Such coupling may be mechanical, electrical, or fluidic.

[0058] References herein to the positions of elements (e.g., “top,” “bottom,” “upper,” “middle,” “lower,” “above,” “below,” vertical,” “horizontal,” etc.) are merely used to describe the orientation of various elements in the FIGURES. It should be noted that the orientation of various elements may differ according to other examples, and that such variations are intended to be encompassed by the present disclosure.

[0059] With respect to the use of substantially any plural and / or singular terms herein, those having skill in the art can translate from the plural to the singular and / or from the singular to the plural as is appropriate to the context and / or application. The various singular / plural permutations may be expressly set forth herein for the sake of clarity.

[0060] The foregoing description of illustrative examples has been presented for purposes of illustration and of description. It is not intended to be exhaustive or limiting with respect to the precise form disclosed, and modifications and variations are possible considering the above teachings or may be acquired from practice of the disclosed examples. It is intended that the scope of the claimed subject matter be defined by the claims appended hereto and their equivalents.

Claims

WHAT IS CLAIMED IS1. A method of assembling a cooling device, the method comprising: forming an interposer by: plating a metallic material on a carrier to form a first metallic trace; forming a first layer of nonmetallic material around the first metallic trace to form a first interposer layer; and removing the first metallic trace to form a first fluid channel; and coupling a first side of the interposer to a first manifold comprising a second fluid channel to fluidly couple the first fluid channel to the second fluid channel.

2. The method of claim 1, further comprising coupling a second side of the interposer to a coolant distribution manifold comprising a third fluid channel to fluidly couple the first fluid channel to the third fluid channel.

3. The method of claim 1, wherein the nonmetallic material is an epoxy mold compound and the metallic material comprises copper, wherein removing the first metallic trace comprises selectively etching the copper.

4. The method of claim 1, further comprising: cutting the interposer to form a flexible joint between a first tile portion and a second tile portion adjacent the first tile portion; and coupling a second manifold comprising a fourth fluid channel to the second tile portion on the first side of the interposer, wherein coupling a first side of the interposer to the first manifold comprises coupling the first tile portion to the first manifold.

5. A cooling device for a system-on-chip, the cooling device comprising: an interposer comprising: a first layer with a first plurality of fluid channels extending from a first face of the interposer and having a first average cross-sectional area; anda second layer coupled to the first layer and comprising a second plurality of fluid channels extending from a second face of the interposer, fluidly coupled to the first plurality of fluid channels, and having a second average cross-sectional area that is larger than the first average cross-sectional area; and a microchannel manifold comprising a first side to be coupled to a system-on-chip, a second side coupled to the first face of the interposer, and a third plurality of fluid channels fluidly coupled to the first plurality of fluid channels.

6. The cooling device of claim 5, further comprising a coolant distribution manifold coupled to the second face of the interposer and comprising a fourth plurality of fluid channels coupled to the second plurality of fluid channels.

7. The cooling device of claim 6, further comprising a first adhesive layer coupling the interposer to the microchannel manifold and a second adhesive layer coupling the interposer to the coolant distribution manifold, wherein the second adhesive layer is thicker than the first adhesive layer.

8. The cooling device of claim 5, wherein the first layer of the interposer comprises a first epoxy mold compound with a first coefficient of thermal expansion, and the second layer of the interposer comprises a second epoxy mold compound with a second coefficient of thermal expansion that is higher than the first coefficient of thermal expansion.

9. The cooling device of claim 5, wherein the interposer comprises a metallic trace molded into an epoxy mold compound.

10. The cooling device of claim 9, wherein the metallic trace extends from the first face of the interposer to the second face of the interposer to enable an electrical connection between a microchannel manifold coupled to the first face and a coolantdistribution manifold coupled to the second face.

11. The cooling device of claim 5, wherein the interposer comprises a plurality of tile portions to be coupled to a plurality of manifolds and a flexible joint between adjacent tile portions, the flexible joint having a lower cross-sectional area on a plane extending longitudinally through the flexible joint than an adjacent tile portion on a parallel plane.

12. The cooling device of claim 5, wherein the interposer comprises an intermediate layer between the first layer and the second layer, the intermediate layer comprising a fifth plurality of fluid channels fluidly coupling the first plurality of fluid channels to the second plurality of fluid channels.

13. A method of assembling a cooling device, the method comprising: forming an interposer by: plating copper on a carrier to form a first copper trace portion; forming a first layer of epoxy mold compound around the first copper trace portion to form a first interposer layer; plating copper on the first interposer layer to form a second copper trace portion in contact with the first copper trace portion; forming a second layer of epoxy mold compound around the second copper trace portion to form a second interposer layer; removing the first copper trace portion and the second copper trace portion to form a first plurality of fluid channels; coupling a first side of the interposer to a first silicon microchannel manifold comprising a plurality of microchannels to fluidly couple the first plurality of fluid channels to the plurality of microchannels; and coupling a second side of the interposer to a coolant distribution manifold comprising a second plurality of fluid channels to fluidly couple the first plurality of fluid channels to the second plurality of fluid channels.

14. The method of claim 13, further comprising: cutting a slot in the interposer to form a flexible joint between a first tile portion and a second tile portion adjacent the first tile portion, wherein coupling the first side of the interposer to the first silicon microchannel manifold comprises coupling the first tile portion to the first silicon microchannel manifold; and coupling a second silicon microchannel manifold to the second tile portion spaced apart from the first tile portion with the flexible joint positioned between the first tile portion and the second tile portion.

15. The method of claim 13, further comprising: plating copper on the carrier to form a third copper trace portion, wherein the first layer of epoxy mold compound is also formed around the third copper trace portion; plating copper on the first interposer layer to form a fourth copper trace portion in contact with the third copper trace portion to form an electrical trace, wherein the second layer of epoxy mold compound is also formed around the fourth copper trace portion; and electrically coupling the electrical trace to an electrical contact of the first silicon microchannel manifold.

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