So I ordered a cheap SSR from Aliexpress and it finally arrived. I immediately disassembled it to look what's inside. It wasn't so bad -- BTA40-800, MOC3063.. assuming the components are not counterfeit of course. Pcb has some flux left and triac terminals were bent at some questionable angles and too close to the package.. but I can live with it. What surprised me though is how the triac was mounted.
SSR has an aluminum plate that you attach to the heatsink. I expected to see a screw, but there was none. The package (TOP3) was just soldered to the plate. Triac is 40A-rated, so maybe it's the way to minimize the thermal resistance. But I have questions.
1 Does the TOP3 package even allow that? I realize it's tab must be manufacturer-soldered for a reason, but the amount of the heat applied must be massive. I wonder if the triac is half-cooked already.
2 Will it last? Soldering aluminum is a tricky business, since the material is quite active chemically. So with the frequent heat-idle cycles, is there a danger it will "unstick"? Not unsolder due to the high temperature but just get off?