Clint you asked about the temperature of soldering the surface mounted devices. Most of them are recommended to follow a heating curve that lasts about 2 or 3 minutes. Here is a url to a file that shows the preferred way to heat and cool them. It is for some capacitors,but other devices follow the same curve. This is for heating them up in something that resembles a toster oven. The professional devices have timmers and things like that to make the heat follow the curve.
We had a separate profile for every board we ran though the Heller Reflow oven at Microdyne. The operator selected the profile by the board type, and build number on a computer near the oven.
I bought a big toaster oven in 2007 to reflow PC boards stuffed with my P&P machine. I got a ramp and soak temperature controller on eBay and some micro-size thermocouple wire. I first tried doing the boards with the thermocouple just hanging in the air, but that ended up toasting the boards to a crisp! I then thought to poke the thermocouple junction into a through hole in one of the boards, and that has been working fine for years, now.
So, I can program in a ramp to 180 C, hold for one minute, then ramp to either 225 C (tin/lead) or 246 C (lead-free) and hold for one minute, then ramp rapidly to room temp. Sometimes the boards at the corners of the oven don't completely reflow all the way to the edges, but when I get the profile right, they come out looking quite professional, and with minimal rework.
If the boards have been sitting around for a while, I usually bake them at
50 C for a while, the up it to 75 C and hold for an hour or so. Otherwise, absorbed moisture can cause the boards to split internally and break vias.
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