Method of manufacturing a brazed micro-channel cold plate heat exchanger assembly

Abstract

The invention relates to a method of making a brazed micro-channel cold plate assembly for cooling a heat producing electronic component. The primary components of a cold plate assembly are a base plate, a manifold cover, and inlet/outlet pipes; wherein the individual components are assembled and brazed into an integral unit. The joining surfaces of the individual components have novel features that provide for permanent bonding of the joints by brazing and a hermetic seal along the joint seams. The novel features also forestall excess braze alloy from contaminating the interior surfaces of the assembled cold plate and obstructing the engineered flow channels.

1 . A method of manufacturing a heat exchanger assembly for a heat producing component, comprising the steps of:
 providing a base plate having a substantially central axis, wherein said base plate includes:
 an exterior surface adapted to engage with said heat producing component; 
 an interior surface having substantially parallel micro-fins and micro-channels, wherein said micro-fins have coplanar edges; and 
 a co-axial perimeter wall having an outer surface, an inner surface, and an end edge, wherein said perimeter wall is substantially parallel to said central axis; 
   providing a manifold cover having a substantially central axis, wherein said manifold cover includes:
 an interior manifold cover surface having a series of substantially parallel alternating inlet/outlet channels, wherein said inlet/outlet channels have coplanar edges adapted to engage with said coplanar edges of said micro-fins in a crossing pattern; and 
   a co-axial perimeter trough adapted to cooperate with said perimeter wall, wherein said perimeter trough has a trough first face, a trough second face, and a bottom, wherein the width of said bottom is greater than width of said perimeter wall;   arranging said base plate and said manifold cover so that said end edge of said perimeter wall is received in said trough of said manifold cover,
 wherein said coplanar edges of inlet/outlet channels are in intimate contact with said coplanar edges of micro-fins, 
 wherein said end edge of said perimeter wall is spaced apart from said bottom of said trough defining a gap, 
 wherein said outer surface of said perimeter wall is spaced apart from said trough first face defining an outboard radial clearance, and 
 wherein said inner surface of said perimeter wall is spaced apart from said trough second face defining an inboard radial clearance; 
 positioning a first braze alloy element said onto said outer surface of the perimeter wall proximate to said outboard radial clearance; 
   heating the arrangement to a temperature effective to melt said braze alloy, where upon the melted braze alloy is drawn into said outboard radial clearance by capillary forces and displaced air exits via the inboard radial clearance, thereby permitting said coplanar edges of micro-fins of base plate and said coplanar edges of inlet/outlet channels of manifold cover to remain in intimate contact; and   cooling the arrangement to solidify the braze alloy to bond said base plate to said manifold cover to form said assembly.   
   
   
       2 . A method of manufacturing a heat exchanger assembly of  claim 1  further comprising, prior to heating said assembly, the steps of:
 providing at least one inlet/outlet port through said manifold cover;   providing at least one inlet/outlet pipe amendable to brazing, wherein said inlet/outlet pipe comprises:
 a first exterior surface and a second exterior surface, wherein said first exterior surface is adapted to slidably insert into said inlet/outlet port while providing effective inlet/outlet pipe clearance to allow for capillary action to draw melted braze alloy, and 
 an annular exterior flange circumscribing said second exterior surface; 
 positioning a second braze alloy element on said second exterior surface of inlet/outlet pipe between said annular exterior flange and said first surface of inlet/outlet pipe; and 
 assembling said inlet/outlet pipe with said manifold cover by slidably inserting the first surface of said inlet/outlet pipe into said inlet/outlet port; 
   whereupon heating the arrangement to a temperature effective to melt said braze alloy, the melted braze alloy is drawn into said effective inlet/outlet pipe clearance by capillary forces.   
   
   
       3 . A method of manufacturing a heat exchanger assembly of  claim 2 , wherein said first exterior surface of inlet/out pipe has an annular notch to capture excess melted braze alloy. 
   
   
       4 . A method of manufacturing a heat exchanger assembly of  claim 1 , wherein said co-axial perimeter wall further has a rim extended substantially perpendicular to said central axis on interface of said outer wall and said end edge, wherein said rim retards melted braze flow into said gap during said heating of assembly. 
   
   
       5 . A method of manufacturing a heat exchanger assembly of  claim 1 , wherein said manifold cover has an exterior manifold cover surface and a substantially perpendicular force is applied onto said exterior manifold cover surface to ensure said coplanar edges of micro-fins of base plate and said coplanar edges of inlet/outlet channels of manifold-cover are in intimate contact during said heating and cooling of assembly. 
   
   
       6 . A method of manufacturing a heat exchanger assembly of  claim 5 , wherein a force is applied onto said inlet/outlet pipe toward said exterior manifold cover surface during said heating and cooling of assembly. 
   
   
       7 . A method of manufacturing a heat exchanger assembly of  claim 1 , wherein the volume of said braze element is less than the total volume of said outboard radial clearance and said gap. 
   
   
       8 . A method of manufacturing a heat exchanger assembly of  claim 1 , wherein said perimeter wall further comprises a shoulder extending from said outer surface and said braze element is positioned onto said shoulder and proximal to said outboard radial clearance. 
   
   
       9 . A method of manufacturing a heat exchanger assembly of  claim 3 , wherein the volume of said second braze element is less than the total volume of said inlet/outlet pipe clearance and said annular notch. 
   
   
       10 . A method of manufacturing a heat exchanger assembly for a heat producing component, comprising the steps of:
 providing a base plate having a substantially central axis, wherein said base plate includes:
 an exterior surface adapted to engage with said heat producing component; and 
 an interior surface having substantially parallel micro-fins and micro-channels, wherein said micro-fins have coplanar edges; and 
   providing a manifold cover having a substantially central axis, wherein said manifold cover includes:
 an interior manifold cover surface having a series of substantially parallel alternating inlet/outlet channels, wherein said inlet/outlet channels have coplanar edges adapted to engage with said coplanar edges of said micro-fins in a crossing pattern; 
 wherein one of said base plate or said manifold cover further comprises a co-axial perimeter wall having an outer surface, an inner surface, and an end edge, wherein said perimeter wall is substantially parallel to said central axis; and 
 wherein the other of said base plate or said manifold cover further comprises a co-axial perimeter trough adapted to cooperate with said perimeter wall, wherein said perimeter trough has a trough first face, a trough second face, and a bottom, and wherein the width of said bottom is greater than width of said perimeter wall; 
   arranging said base plate and said manifold cover so that said end edge of said perimeter wall in received in said trough of said manifold cover,
 wherein said coplanar edges of inlet/outlet channels are in intimate contact with said coplanar edges of micro-fins, 
 wherein said end edge of said perimeter wall is spaced apart from said bottom of said trough defining a gap, 
 wherein said outer surface of said perimeter wall is spaced apart from said trough first face defining an outboard radial clearance, and 
 wherein said inner surface of said perimeter wall is spaced apart from said trough second face defining an inboard radial clearance; 
   positioning a first braze element said onto said outer surface of the perimeter wall proximal to said outboard radial clearance, wherein said braze element is formed of a braze alloy;   heating the arrangement to a temperature effective to melt said braze alloy, where upon the melted braze alloy is drawn into said outboard radial clearance including portion of said gap by capillary forces and displaced air exits via inboard radial clearance, thereby permitting said coplanar edges of micro-fins of base plate and said coplanar edges of inlet/outlet channels of manifold cover to remain in intimate contact; and   cooling the arrangement to solidify the braze alloy to bond said base plate to said manifold cover to form said assembly.