Originally Posted by rohmell
Radio Shack sells thermal fuses, such as this one:
which looks like an ideal replacement for a coffee maker. I have used these in the past, with great success.
But, how did they solder the stainless steel contacts to the PCB? But seriously,a few taps with a Dremel equipped with a small abrasive disc will remove the plating/corrosion/oxidation that might be on the contacts, revealing a nice, solderable surface undeneath.
I watched the guy do the tiny spot weld. The little machine clamps the two parts together then the guy pressed a button. There was a little spark and the battery clip was weled to the contacts on the board. He told me the contacts are stainless steel and that explained why soft, lead based solder wouldn't adhere to it. You can't soft solder stainless steel.
The thermal fuses are also spot welded to the wire and contacts in coffee makers. You can solder those in but you have to use a high temp solder, something like 95/5 or the heat from the heating element will melt regular soft solder. 50/50 or 60/40 just won't do it.