Screaming Circuits: QFP/SOIC/SSOP Mechanical Security

QFP/SOIC/SSOP Mechanical Security

I've written a lot about QFN footprint issues, but the venerable old leaded SMT configuration is still around. It gets its share of disrespect and questionable footprints too. When you give it a post-solder visual QFP fillet inspection, mostly what you see is the fillet "B" in my illustration. But, here's a question: which fillet is more important, A or B? The hidden fillet, A actually gives more of the mechanical strength then does B.

Most CAD library parts will have the proper footprint for these parts, but not all. Sometimes you have something close, but not exact. If that's the case, make sure the pad leaves room for a good fillet on both sides of the lead. Doing so will ensure that you have the best mechanical connection. Don't use red solder though. It might actually be Play-dough and Play-dough isn't a good conductor.

Duane Benson
Silly Putty won't work either


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Red loctite would work except it's too sticky so all of the electrons would get stuck and would stop moving in protest...

How about red loctite?! :D

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