Bouncing BGAs

I dropped my cellphone on the pavement the other day. That’s bad enough, but in my instinctive attempt to catch it, I actually hit it and increased its downward velocity. Luckily, everything still works. The odd thing is that I just assumed that it would still work. No real questions or doubts on that thought.

That realization got me thinking. (It happens now and then.) What other devices do I have that I automatically expect to survive a drop onto concrete? I have a carpenter’s hammer. I expect that to survive a drop intact. I would not expect my camera to survive such a drop intact, and have empirically verified that fact. A little car GPS? Probably not. Laptop; uh … no.

I’m sure there are some other devices that would easily survive. I just can’t think of any off the top of my head. I suspect that there are a lot of factors that go into making cellphones survivable. The case, the overall mass, the quality of solder joints.

Along those lines, some folks use an underfill glueish type substance to hold BGAs more securely. Some designers use pick and placeable solid underfill. Some just rely on extra good soldering and some leave it to luck. Of course, not all BGA installations require much shock resistance. How do you secure your parts when shock or vibration are serious concerns?

Duane Benson
Quick, where’s Henry? I need an inductor.