How does solder stick?

[icecycle66]

how does solder stick to other metal things?

Is it surface tension or some sort of chemical bonding? What's the science of what's going on in there?

[midwayfair]

It's mostly a chemical bond, basically the same type of chemical bond in whatever alloy the solder is. Surface tension mainly plays a roll in flowing the solder over the thing being soldered to. Both are reasons it's so difficult to solder parts to aluminum. It's also one of the reasons different types of solder are used in different types of work.

Some types of metals will form a chemical bond differently. Want to know why the copper tips on a cheap iron dissolve, especially when using tin/silver solder? It's because you're essentially performing a little bit of electroplating every time you use it.