RE: Electronic/Circuit board experts, what causes this?

RE: Electronic/Circuit board experts, what causes this?

Over the last several years I’ve found too many failed circuit boards on Rheem/Ruud (specifically) gas package units. The solder on the back of the 9 or 12 pin molex plug cracks and the solder disappears. I don’t know if it’s overheating and vaporizing or… The cracking makes sense because package units are out in the weather, I’m in Tucson Arizona where the summers are 120° and winters get down into the 20’s on occasion. I’ve made temporary repairs by squeezing the pins with needle nose pliers long enough to get a replacement board. I could solder them but there’s a bit of liability there.

RE: Electronic/Circuit board experts, what causes this?

I’ve also found the same on Goodman furnaces, and Lennox, but it’s always on the back of the molex plug. Which is typically a safety circuit, or limit.

TimBagnall Junior Tech Asked on March 5, 2018 in Residential HVAC.
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6 Answers

It’s called a “cold” joint, because it either didn’t really get hot enough when the board was assembled, or the surfaces weren’t clean enough. Time/environment can cause the solder to crack and/or fall out. The boards are soldered with a wave bath, so the larger connections are harder to get hot without overheating the smaller connections.
Fixed far more than I can count on electronics, but I’m leery of fixing them on something like a furnace where it could cause a house to freeze or something of that nature where I could be held liable for a repair. But it can be done easily with a good pencil and rosin core solder.

Apprentice Answered on March 6, 2018.
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