Dear colleagues,

let's take a board with SMT on both sides. Let's say that for particular reasons we have to solder the more thermally demanding side first.

The question is: when reflowing the second side, the one that requires lower temps because the components are less demanding, may the reflow recipe be colder? Will this affect the other side, that will reflow again, but at lower temps and for not as long? I mean the IMC is already formed; is there anything else that could go wrong?

Or, to generalize, a PCB with SMT parts that were properly reflowed once, can it be reflowed again at lower temperatures, without adverse effects on the metallurgy of the joints?

Thanks for your help,

Ioan

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