I got the boards back from OSHPark a while back, and got around to populating them. Though I have access to a real reflow oven, I’ve done boards like this with the heat gun method in the past, so I got out the solder paste, put it on the solder pads, put on the shift registers, and then went out to the garage.
I use an old license plate as a board holder, so the board goes on that.
Real reflow ovens use a time/temperature calibrated curve.
Basically, there’s a long soaking stage to gradually bring all the parts up to temp, a ramp up until the solder melts, and then a cooling-down period. I attempt to duplicate this with the heat gun, though it’s really not very precise.
The hard part with the heat gun is keeping it at a distance where it does not blow the parts around on the board; as the board heats up the flux will start to flow and the chips want to move. A little repositioning with a toothpick fixes that. You keep heating until you see the solder reflow, make sure it’s reflowed around all the parts, and then remove the heat.
And you get this:
The 34-pin connector and the two test point connections were hand soldered. I do need to test the board itself and then hook it up to the pin and see if it works.