So today was something of a downer.
I received my LGA-16 breakout board from proto-advantage.com yesterday, and decided to give reflow soldering another shot with my digital accelerometer, the LIS33DE.
The LIS33DE is the first 3V chip I’ve used that cannot also run at 5V. Because of this, I decided to re-do my breadboard and get myself a 3V power supply. I found an old PC power supply that can output 3.3 volts which is close enough. I’ve got some mounting posts that I’m planning on bolting to the power supply to make it a little easier to manage, but for tonight, I just used some alligator clips to bring the 3.3V to my board.
Now, along this process, I did a very stupid thing. I left my micro controller and temperature probe connected to the board. I’ve always been a fan of hot-plugging in the face of adversity, but in this case, I was a little too reckless, and not only killed another micro controller, but also the temperature probe!
Luckily, I had backups of both, and while desoldering a SOIC part is tedious, it’s by no means impossible.
What is very sad is my accelerometer. I’m not sure exactly what went wrong, but I was unable to get it to do anything intelligent. It wouldn’t even acknowledge its own address.
Concerned that maybe I had some shorts in my solder, I tried applying some heat to the traces and letting the solder move around. I even added more solder, concerned that there was an open somewhere. I finally just ripped the chip off the board and found that neither was an issue (testament to my awesome solder paste stenciling skills).
What I’m putting on the death certificate though is “Got Baked.”
I think I turned the toaster oven up a little too high (450F) for too long (like 10 minutes) and completely burned the chip up. I guess it makes sense that it’s a little more sensitive than a temperature probe, huh… That also explains why the toaster smelled not only like burned food bits (like usual), but also like burned plastic. The poor guy didn’t stand a chance.
I’m ordering a new chip and break out board. Proto-advantage usually takes like 2 weeks to deliver, so in the meantime, I’m going to continue working on the Real Time Clock, and the buzzers.
I’m going to be trying a different method for reflow in the future (especially before I even touch my $25 compass!) I’ve read on this page about doing reflow soldering in a skillet. The advantage here is that it will heat the chip from below and hopefully melt the solder paste before the chip gets too warm. Also, I learned that you’re pretty much supposed to remove the chip as soon as the paste turns liquid. Now, I didn’t really watch the chip when using the toaster oven in the first place, but the skillet should make the board much more visible.