Printed Circuit Board Assembly & PCB Design SMT Electronics Assembly Manufacturing Forum

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


Stan

#16198

Soldering die to heatsinks | 16 April, 1998

Currently I am in the buisness of soldering bare die to the top surface of a copper heat sink. Is any one else have some exprience in this process that can help. We heat a copper slug through a contolled atmosphere, place a preform then a bare die. Problems: voiding, poor wetting, TCE mismatch.

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Earl Moon

#16199

Re: Soldering die to heatsinks | 17 April, 1998

| Currently I am in the buisness of soldering bare die to the top surface of a copper heat sink. Is any one else | have some exprience in this process that can help. We heat a copper slug through a contolled atmosphere, place a preform then a bare die. | Problems: voiding, poor wetting, TCE mismatch. TCE mismatch is an important issue as copper expands at approximately 17-19 ppm/C.. Also, preforms must be capable of "wetting" both solder termination surfaces. Often, voiding occurs as copper oxidizes immediately upon exposure to "normal" air. Scratch a penny and see how quickly this is effected. I must assume you are using an intert atmosphere in which to manage solder processes. Also, solder preforms are as specified to ensure effective solder process management. Earl Moon - Proof Of Design

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