It may end up being one of life's little unexplained mysteries.

David A. Douthit
Manager
LoCan LLC

==========================

Steve Gregory wrote:

 Hi David! I guess the reason I call this strange, is because I've had rework performed on literally hundreds of these type of parts, with the heat sink in the top, and haven't seen this problem before. When I say hundreds, I refer to a situation where a part was installed on an assembly, don't want to name names, at three-per, and the assembly didn't work. The manufacturer of the device says there was no die change, but for some reason, earlier date-code parts worked fine. So we changed out all these parts....same design, heat-sink in the top, but never saw cracking like this. To emphasize, this was just one part that did this, but it was so strange...I had to share. -Steve Gregory-

Steve,

You might consider the fact that metal will change temperature much faster than polymers.
This thermal gradient "split" can cause serious temporary CTE mismatches.

David A. Douthit
Manager
LoCan LLC

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