Heat dissipation assembly

Abstract

A heat dissipating assembly including a layered stack of materials with a highly thermally conductive path for cooling a circuit, the stack including a structurally isolated material having a high coefficient of thermal expansion connected between materials having low coefficients of thermal expansion.

Having thus described various embodiments of the invention, what is claimed as new and desired to be protected by Letters Patent includes the following: 
     
         1 . An assembly for dissipating heat in an electronic circuit, the assembly comprising:
 a heat spreader having a high thermal conductivity for connecting to the circuit;   a substrate connected to the heat spreader on a first side of the substrate;   a heat slug having a high thermal conductivity and being connected to the heat spreader on a first side of the heat slug and adjacent to the substrate; and   a backplate having a high thermal conductivity and being connected to the substrate on a second side of the substrate opposite its first side and connected to the heat slug on a second side of the heat slug opposite its first side, the heat spreader, the substrate, and the backplate forming a layered stack of materials with a highly thermally conductive path for cooling the circuit, the heat spreader having a coefficient of thermal expansion (CTE) matching a CTE of the circuit and the substrate having a CTE matching a CTE of the backplate.   
     
     
         2 . The assembly of  claim 1 , wherein the substrate includes a cavity having a first opening and a second opening on opposite sides of the substrate, and the heat slug is disposed in the cavity and connected to the spreader near the first opening and connected to the backplate near the second opening. 
     
     
         3 . The assembly of  claim 1 , wherein the heat spreader is formed of a complex shape and the heat slug has a uniform cross sectional shape in at least one dimension. 
     
     
         4 . The assembly of  claim 1 , wherein the heat spreader is removable and the substrate, heat slug, and backplate collectively are reusable. 
     
     
         5 . The assembly of  claim 1 , wherein the substrate includes a ground plane, and the heat spreader is connected to the ground plane for minimizing electrical and radio frequency (RF) interference. 
     
     
         6 . The assembly of  claim 1 , wherein the ground plane is embedded in the substrate. 
     
     
         7 . The assembly of  claim 1 , wherein the heat spreader is shaped to have continuous RF grounding. 
     
     
         8 . The assembly of  claim 1 , wherein the substrate is connected to the circuit via a low inductance wire. 
     
     
         9 . The assembly of  claim 1 , wherein the heat spreader is bonded to the circuit, the substrate and the heat slug are bonded to the heat spreader, and the backplate is bonded to the substrate and the heat slug. 
     
     
         10 . The assembly of  claim 9 , wherein the bonding is effected by conductive epoxy. 
     
     
         11 . The assembly of  claim 9 , wherein the bonding is effected by solder. 
     
     
         12 . An assembly for dissipating heat in an electronic circuit, the assembly comprising:
 a heat spreader having a high thermal conductivity and high material strength for connecting to the circuit;   a substrate having a low thermal conductivity and being connected to the heat spreader on a first side of the substrate;   a heat slug having a high thermal conductivity and low material strength and being connected to the heat spreader on a first side of the heat slug and adjacent to the substrate; and   a backplate having a high thermal conductivity and high material strength and being connected to the substrate on a second side of the substrate opposite its first side and connected to the heat slug on a second side of the heat slug opposite its first side, the heat spreader, substrate, and backplate forming a layered stack of materials with a highly thermally conductive path for cooling the circuit, the heat spreader having a CTE matching a CTE of the circuit, the substrate having a CTE matching a CTE of the backplate, and the heat slug having a CTE that does not match the CTE of the circuit.   
     
     
         13 . The assembly of  claim 12 , wherein the heat slug and the substrate are preformed so that stresses induced when the layered stack is at a minimum temperature and the stresses induced when the layered stack is at a maximum temperature are of equal magnitude, so that the maximum induced stress is minimized. 
     
     
         14 . The assembly of  claim 12 , wherein the backplate includes a planar surface and the substrate and the heat slug are connected thereto. 
     
     
         15 . The assembly of  claim 12 , wherein the substrate is a printed wiring assembly. 
     
     
         16 . The assembly of  claim 12 , wherein the substrate is a low temperature co-fired ceramic material. 
     
     
         17 . The assembly of  claim 12 , wherein the heat spreader is formed of a Copper-diamond alloy. 
     
     
         18 . The assembly of  claim 12 , wherein the heat spreader is formed of a Copper-tungsten alloy. 
     
     
         19 . The assembly of  claim 12 , wherein the heat slug is formed of a material selected from the group consisting of a Copper-tungsten alloy, Kovar, Alloy 42, and Aluminum-silicon alloy. 
     
     
         20 . An assembly for dissipating heat in an electronic circuit, the assembly comprising:
 a heat spreader having a high thermal conductivity and high material strength for connecting to the circuit and being formed of a complex shape and removable from the circuit;   a substrate having a low thermal conductivity, having a cavity including a first opening and a second opening on opposite sides of the substrate, the substrate being bonded to the heat spreader on a first side of the substrate and connected to the circuit via a low inductance wire;   a heat slug having a high thermal conductivity, a low material strength, and a uniform cross sectional shape in at least one dimension and being disposed in the cavity and bonded to the heat spreader on a first side of the heat slug near the first opening; and   a backplate having a high thermal conductivity and high material strength and being bonded to the substrate on a second side of the substrate opposite its first side and being bonded to the heat slug on a second side of the heat slug opposite its first side and near the second opening, the heat spreader, substrate, and backplate forming a layered stack of materials with a highly thermally conductive path for cooling the circuit, the heat spreader having a CTE matching a CTE of the circuit, the substrate having a CTE matching a CTE of the backplate, and the heat slug having a CTE not matching the CTE of the circuit.