Reflow!

Finally got around to an attempt at reflowing some SMD components. I had some PCBs I got made at OSHPark and the half the parts to populate it about two months ago, and the last half of parts a couple of weeks ago (the part I needed was back in stock). It's supposed to be a header-less version of the Particle Battery Shield from Sparkfun.

I used some bismuth solder paste (featured on this CNLohr video) since it had a low reflow temperature of around 138 °C (~280 °F). I applied it using a toothpick, then placed all the components. The fuel gauge IC was in a rather unfriendly TDFN-8 package, and I was a little unsure of using in my first solder paste job. Oh well.

Applying paste and parts.

Skillet deals.

I put the PCB on the electric skillet, bought new from Sears for about $10 on Black Friday, and dialed in the temperature to 300 °F. After about a minute, I saw shiny joints being formed, and soon enough all the parts were secured. I turned off the skillet and let everything cool.

It wasn't as difficult as I thought it was going to be:

Done! :D

I could have definitely used a bit more solder paste on some parts, but the whole thing came out really well, even the TDFN-8! Probably could have left the board on the heat for a bit longer too.

It also works!

Well, the circuit mostly works. The battery charges, but the charging indicator LED flickers uncontrollably when done charging instead of turning off. If I push on the board in some places, the blinking stops. I think there might be a bad joint somewhere, but this is pretty good. I haven't tested if I can communicate with the battery gauge yet.

Time to use more SMD components in projects to further shrink PCBs, and save more money! Also time to practice more.