Rev. B Solar Charger Board Received and Assembled

Rev. B Solar Charger Board

Rev. B Solar Charger Board

I received the Rev. B boards back from OSHPark a couple of weeks ago. I assembled one of them, this time using a stencil and squeegee just for the QFN IC and then a syringe to manually apply solder paste to the rest of the SMT components. I thought that might be the way to do it in order to get good results without needing a new stencil for the whole board. However, I found that my manual application of solder paste with the syringe left two shorts underneath two of the 0805 capacitors. Also, the soldering on this board looks a lot sloppier compared to the Rev. A board I assembled using only a stencil and squeegee. When I mentioned my latest attempt to a co-worker, he suggested using the stencil for the QFN and reflowing it by itself. Then, he said, just use flux and a soldering iron to manually solder the other SMT components, tacking down one end and then soldering the other. And finally, soak the board in 91% rubbing alcohol to remove the residual flux. I’ll try that method with the next board I assemble.

Also, I found that the large 1000uF capacitor I added in Rev. B encroached upon two other things: the “3.3V OUT” silkscreen for the 0.1″ header, and the smaller 0805 capacitor next to the big one. So I’ll need to address those layout changes on the next revision.

Next is debug and battery discharge/recharge plotting!