SMT soldering excitement!

With my new SparkFun variable temperature regulated solder station from, I’ve been able to practice more SMT work without crummy  tools hampering my efforts. Following the tips from EEVblog, I’ve had some good success with the tack and reflow method. My square pad / through-hole combo proto boards offer a bit of a challenge in that the solder tries to escape through the holes when preparing the pad for an SMT component. A small bit of masking tape covering the other side stops this nicely.

Examining the “scrap” (there’s no visible damage) Solder: Time II board from Spikenzie, I was able to determine that it’s an older revision. Since the current schematic varies but the components are the same, I was easily able to determine the values of the resistors and capacitors. The main different in this older version is that each button uses its own pin on the ATMEGA328P, whereas the current revision sees the 2 buttons share one pin with a voltage divider. All easy enough to decipher with my VOM‘s continuity test.

SMD soldering work

Soldering the 10K 0805 resistors onto the Solder: Time II board

Everything tested out great on the first go. Neglected to solder down the other side of R4, but this will be a quick fix tomorrow. Will attempt to solder the ATMEGA TQFP at that point too.

I also changed the charge current limiting resistor on my TP4056 linear charger. The stock 0603 1.2K ohm resistor was replaced by a 5.1K 0805. “But Mr. King,” you might ask, “isn’t this a mismatch? 0603 and 0805?” Yes, I would reply. It is a mismatch, but it turns out that the pads are big enough to accommodate the slightly larger package. After removing the 0603, I sopped up the stock pasty solder and then applied flux. With just a small bit of solder onto the first pad, I placed the 0805, and tacked it down. Then a tiny bit of solder on the other pad. Straightforward!

TP4056 board with stock RPROG and its replacement placed beside it for comparison.

1.2K 0603 removed and RPROG pads exposed.

0805 5.1K ohm soldered in place.


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