Should there be a spec for minimum solder joint height for leadless components?  An old paper from Werner (mid 90's, I believe) popped up on the Internet when I queried this, and Werner has a statement in it that joints less than about 50 microns thick are basically all intermetallics, but that is not necessarily a bad thing since the intermetallics are stronger than the solder (but more brittle).

I figured since we often try to get additional height for BGA joints to improve reliability, we should be concerned about QFNs and LCCs.

I grabbed a 1.5mil (37 micron) tungsten rod out of our cleanroom (used for clearing clogged wirebond capillaries)and started seeing if I could get that under my leadless components.  Couldn't get it under any of them, likewise with the QFNs.

Checked Technet archives and didn't see an obvious thread, but maybe I didn't have the correct search parameters--if you just enter "height" you get a couple of thousand hits.

Wayne Thayer

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