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JP-7856235-B2 - Heat pipes featuring matching thermal expansion coefficients and heat dissipation using the same

JP7856235B2JP 7856235 B2JP7856235 B2JP 7856235B2JP-7856235-B2

Inventors

  • ジン、アルフレッド エー．

Assignees

  • クプリオン インコーポレイテッド

Dates

Publication Date
20260511
Application Date
20220603
Priority Date
20210604

Claims (20)

  1. It is a heat pipe, A structure having a sealed outer shell containing a copper composite material comprising copper nanoparticles, micrometer-sized copper particles, and a coefficient of thermal expansion (CTE) modifier, A working fluid that is movable within the internal space defined within the sealed outer shell, Includes, The internal space includes a wicking structure inserted between the sealed outer shell and the hollow core, or a channel defined on the surface of the sealed outer shell. The copper composite material is formed by compaction of the copper nanoparticles with the micrometer-sized copper particles and the CTE modifier, and is a heat pipe.
  2. The heat pipe according to claim 1, wherein the wicking structure includes foam, wire mesh, multiple grooves, or any combination thereof.
  3. The heat pipe according to claim 1, wherein the sealed outer shell penetrates at least a portion of the wicking structure.
  4. The heat pipe according to claim 1, wherein a complementary portion contacts the sealed outer shell and seals the upper surface of the flow path.
  5. The heat pipe according to claim 1, wherein the copper composite material has a uniform nanoporosity of approximately 2% to approximately 30%.
  6. The heat pipe according to claim 1, wherein the CTE modifier comprises carbon fiber, W particles, Mo particles, diamond particles, boron nitride, aluminum nitride, carbon nanotubes, graphene, or any combination thereof.
  7. The heat pipe according to claim 1, further comprising a plurality of thermally conductive fibers extending from the end of the structure, wherein, optionally, at least a portion of the thermally conductive fibers extends into the internal space and comes into contact with the working fluid.
  8. A printed circuit board (PCB), A heat-generating component arranged on or at least partially embedded within an electrically insulating substrate, At least one heat pipe that is in thermal communication with the heat generating component, Equipped with, The at least one heat pipe is A structure having a sealed outer shell comprising a copper composite material containing copper nanoparticles, micrometer-sized copper particles, and a thermal expansion coefficient (CTE) modifier, A working fluid that is movable within the internal space defined within the sealed outer shell, Includes, The internal space comprises a wicking structure inserted between the sealed outer shell and the hollow core, or a channel defined on the surface of the sealed outer shell . The copper composite material is formed by compaction of the copper nanoparticles with the micrometer-sized copper particles and the CTE modifier , and is a printed circuit board (PCB).
  9. The PCB according to claim 8 , wherein the wicking structure includes foam, wire mesh, a plurality of grooves, or any combination thereof.
  10. The PCB according to claim 8 , wherein the sealed outer shell penetrates into at least a portion of the wicking structure.
  11. The PCB according to claim 8 , wherein the complementary portion contacts the sealed outer shell and seals the upper surface of the flow path.
  12. The PCB according to claim 8 , wherein the copper composite material has a uniform nanoporosity of about 2% to about 30%.
  13. The PCB according to claim 8, wherein the at least one heat pipe is bonded to the heat generating component via a bonding layer comprising a copper composite material CTE-matched to the copper composite material comprising the sealed outer shell.
  14. The at least one heat pipe is bonded to the upper surface of the heat generating component, One or more heat pipes are joined to the side surface of the heat generating component, The at least one heat pipe is bonded to the bottom surface of the heat generating component, and the at least one heat pipe extends through the electrical insulating substrate, The PCB according to claim 8 , or any combination thereof.
  15. The PCB according to claim 8 , wherein the CTE modifier comprises carbon fibers, W particles, Mo particles, diamond particles, boron nitride, aluminum nitride, carbon nanotubes, graphene, or any combination thereof.
  16. The PCB according to claim 8 , further comprising a plurality of thermally conductive fibers extending from the ends of the structure, wherein, optionally, at least a portion of the thermally conductive fibers extends into the internal space and comes into contact with the working fluid.
  17. It is a method, To provide an elongated wicking structure having an outer surface and an inner surface that define a hollow core, The application of a copper nanoparticle paste composition to the outer surface, wherein the copper nanoparticle paste composition comprises a plurality of copper nanoparticles, a plurality of micrometer-sized copper particles, and a thermal expansion coefficient (CTE) modifier. To form an outer shell sealed on the outer surface of the elongated wicking structure, the copper nanoparticles are compacted together with the micrometer-sized copper particles and the CTE modifier , The hollow core is partially filled with working fluid, Closing at least one end of the sealed outer shell to confine the working fluid within the hollow core, Methods that include...
  18. The method according to claim 17, wherein the at least one end is closed by applying a second portion of the copper nanoparticle paste composition to the at least one end and compacting the copper nanoparticles inside it .
  19. The method according to claim 18, further comprising arranging a plurality of thermally conductive fibers within the second portion of the copper nanoparticle paste composition and extending from at least one end thereof, wherein optionally at least a portion of the thermally conductive fibers extends into the hollow core and into contact with the working fluid.
  20. The method according to claim 17 , wherein the wicking structure includes a foam, a wire mesh, a plurality of grooves, or any combination thereof.

Description

Ineffective thermal communication between a heat source and a heatsink can hinder the dissipation of excess heat from a system. For example, heat-generating electronic components such as high-power LEDs (Light Emitting Diodes) and high-power circuits are constantly shrinking in size and becoming more powerful, thereby generating excessive heat loads concentrated in increasingly smaller spaces. As the generation and concentration of excess heat increases, effective heat removal becomes crucial, but can be particularly problematic. Failure to remove excess heat from an electronic system can lead to serious consequences, such as overheating, reduced conductivity, higher-than-normal power requirements, and/or the need for clock-down operation to avoid circuit board burnout and device failure due to the presence of hot spots. Ineffective heat conduction can be particularly prevalent in various types of circuit boards, especially printed circuit boards (PCBs). PCBs and similar circuit boards are insulators precisely because of the nature of their structure. Specifically, PCBs may use insulating substrates, such as glass fiber epoxy composites like FR4 with a thermal conductivity of approximately 0.25 W/m·K, on which appropriate electronic circuits and various board components are placed. The low thermal conductivity of PCB substrates can make it difficult to remove excess heat from electronic systems, as such PCB substrates cannot transfer a considerable amount of heat to a heat sink on their own. Due to their small size, lead wires or embedded metal traces can remove very little excess heat. Conventional lead solder is not particularly thermally conductive (for example, less than 1/10th the thermal conductivity of more thermally conductive metals such as copper). For example, package substrates containing heat-generating devices such as GaN and SiC systems, monolithic microwave integrated circuits (MMICs), and phased arrays, as seen in 5G base stations and power converters, may experience similar thermal conduction problems. Thermal vias are a method for removing excess heat generated by electronic components associated with printed circuit boards. However, the method of directly liquid casting high-melting-point metals into vias is incompatible with currently used substrate materials (substrates) (the metalworking temperature is >1000°C compared to the much lower polymer melting points of materials typically used as PCB substrates). Therefore, vias are often filled with rosin or similar fillers and then either galvanically end-protected at the ends with only a thick metal plating (e.g., copper) formed on the via wall (i.e., via barrel) to facilitate electrical communication through the PCB substrate, or left open. Galvanic end protection is a fairly slow process and may result in suboptimal thermal communication due to the relatively small metal area in contact with the heat source on the PCB substrate surface. Furthermore, galvanic via filling techniques may leave gaps within the metal plugs extending through the PCB, thereby further affecting thermal conductivity. An alternative method for filling vias using metal nanoparticles is described in U.S. Patent No. 10,616,994, incorporated herein by reference, which may promote more complete filling of via holes and result in higher thermal conductivity. Larger diameter vias may be suitable for such processes to provide more effective removal of excess heat. However, even thermal vias may be insufficient to remove a significant amount of excess heat. Thermal marcoins are an alternative method of heat dissipation that may be used when higher thermal conductivity than that provided by thermal vias is required. Thermal marcoins are typically metallic bodies 3-4 mm in diameter that are pressed into and extend through the plane of a PCB or similar substrate. While this can result in increased thermal conductivity compared to thermal vias, thermal marcoin size mismatches are common, and the thickness of the thermal marcoins and/or PCB substrate can vary, potentially leading to assembly problems when multiple PCB layers are stacked together. Heat pipes are an exceptional alternative heat transfer medium that can easily transfer large amounts of excess heat. While high thermal conductivity metals such as copper can only have thermal conductivity values in the range of several hundred W/m·K, heat pipes can offer much higher effective thermal conductivity values, ranging from several thousand W/m·K to even higher, such as approximately 10,000 W/m·K to approximately 100,000 W/m·K. Heat pipes have traditionally been used in applications where passive heat dissipation in harsh operating environments is desirable. Examples include satellite and spacecraft applications. Because heat pipes can operate independently of gravity and orientation, they can be advantageous in these and other zero-gravity applications. Miniaturized heat pipes have recently been used to dissipate excess h