Hello technetters,

Here's a question for the HMP reflow guru's.
We have a board that is polyimide material, 2 layers of copper invar, and an experimental paste composed of 85Pb 10Sb 5Sn. This paste goes liquidus at 255 degrees C. Reflow is recommended at less than 45 sec above liquidus at 285 degrees C. Adding to this is a recommended cooling rate of 4 degrees C/sec to achieve a fine grain structure. Greater than 4 deg/sec cooldown will cause a large grain structure, yielding a low fatigue resistance. My question is this: other than the issue of components being damaged due to this heat, will the invar layers help with TCE mismatch issues and/or board warpage.
Any replies are GREATLY appreciated.

Jason Gregory
Quality Manager
Electrospec
Houston, TX.
(713)784-4900
(713)784-1194 fax

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