Coefficient of Thermal Expansion Compensation for Heat Exchangers

Abstract

Described herein are heat exchangers and heat source assemblies, which may be fabricated using electrochemical additive manufacturing (ECAM). A heat exchanger comprises a base and a heat-exchanging portion electrochemically deposited on and attached to the base and comprising heat-exchanging extensions with heat-exchanging surfaces. The combination of the heat-exchanging surfaces and the base forms openings (e.g., non-linear channels) for directing a heat transfer fluid through the heat exchanger. The openings may extend to the base for direct contact. The average CTE of the base may be closer to that of the heat source than the average CTE of the heat-exchanging portion. In some examples, the heat-exchanging portion comprises extension ends for thermal coupling to the heat source. Any dimension of each extension end may be less than a critical dimension, determined by adhesion, CTE mismatch, and temperature fluctuations.

1 . A heat exchanger for use on a heat source comprising a heat-transferring surface, the heat exchanger comprising:
 a base comprising a heat-receiving surface for thermal coupling to the heat-transferring surface; and   a heat-exchanging portion electrochemically deposited onto and attached to the base and comprising heat-exchanging extensions, wherein:
 the heat-exchanging extensions comprise heat-exchanging surfaces, 
 a combination of the heat-exchanging surfaces and the base forms opening for flowing a heat transfer fluid through the heat exchanger, 
 the opening extends to the base such that the heat transfer fluid is able to directly interface the base and the heat-exchanging surfaces while flowing through the heat exchanger, and 
 an average coefficient of thermal expansion (CTE) of the base is closer to an average CTE of the heat source than an average CTE of the heat-exchanging portion. 
   
     
     
         2 . The heat exchanger of  claim 1 , wherein the average CTE of the base is less than the average CTE of the heat-exchanging portion. 
     
     
         3 . The heat exchanger of  claim 1 , wherein the base comprises tungsten. 
     
     
         4 . The heat exchanger of  claim 1 , wherein the base further comprises copper, forming an alloy with tungsten. 
     
     
         5 . The heat exchanger of  claim 1 , wherein the base comprises one or more materials selected from the group consisting of silicon carbide (SiC), silver-diamond composite (AgD), and copper-diamond composite (CuD). 
     
     
         6 . The heat exchanger of  claim 1 , wherein the heat-exchanging portion is formed from copper. 
     
     
         7 . The heat exchanger of  claim 1 , wherein the heat-exchanging portion comprises a uniform material composition. 
     
     
         8 . The heat exchanger of  claim 1 , wherein:
 the heat transfer extensions comprise first extension ends and second extension ends such that the heat-exchanging surfaces extend between the first extension ends and the second extension ends, and   a material composition of the heat transfer extensions varies between the first extension ends and the second extension ends.   
     
     
         9 . The heat exchanger of  claim 8 , wherein the material composition of the heat transfer extensions gradually changes between the first extension ends and the second extension ends. 
     
     
         10 . The heat exchanger of  claim 8 , wherein the material composition of the heat transfer extensions changes in a step fashion between the first extension ends and the second extension ends. 
     
     
         11 . The heat exchanger of  claim 1 , wherein a cross-sectional shape of the heat transfer extensions with a plane parallel to the base is selected from the group consisting of an oval, a rectangle, a trapezoid, and a triangle. 
     
     
         12 . The heat exchanger of  claim 1 , wherein the heat transfer extensions have a height (H) of 30-200 micrometers. 
     
     
         13 . The heat exchanger of  claim 1 , wherein the heat transfer extensions have a thickness (T) of 30-200 micrometers. 
     
     
         14 . The heat exchanger of  claim 1 , wherein the heat transfer extensions have an average pitch (P) of 50-250 micrometers. 
     
     
         15 . The heat exchanger of  claim 1 , wherein the heat source is selected from the group consisting of a central processing unit (CPU), a graphical processing unit (GPU), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), a chipset, a power amplifier, a memory module, and a power management integrated circuit (IC). 
     
     
         16 . The heat exchanger of  claim 1 , further comprising a cover sealed against the base and forming a cavity thereby between, wherein the heat-exchanging portion extends within the cavity such that the opening is part of the cavity. 
     
     
         17 . The heat exchanger of  claim 16 , wherein the cover directly interfaces the heat-exchanging portion. 
     
     
         18 . The heat exchanger of  claim 16 , further comprising a cover gasket positioned between the cover and the heat-exchanging portion. 
     
     
         19 . A heat source assembly comprising:
 a heat source comprising a heat-transferring surface; and   a heat exchanger comprising a base and a heat-exchanging portion, wherein:
 the base comprising a heat-receiving surface mechanically adhered to the heat-transferring surface, 
 the heat-exchanging portion is electrochemically deposited on and attached to the base and comprises heat-exchanging extensions, 
 the heat-exchanging extensions comprise heat-exchanging surfaces, 
 a combination of the heat-exchanging surfaces and the base forms opening for flowing a heat transfer fluid through the heat exchanger, 
 the opening extends to the base such that the heat transfer fluid directly interfaces the base and the heat-exchanging surfaces while flowing through the heat exchanger, and 
 an average coefficient of thermal expansion (CTE) of the base is closer to an average CTE of the heat source than an average CTE of the heat-exchanging portion. 
   
     
     
         20 . The heat source assembly of  claim 19 , further comprising a thermal interface positioned between the base and the heat source and comprising one or more materials selected from the group consisting of silver epoxy and solder.