Surface-mount Soldering Info

For surface-mount stuff, we're going to use the hot plate upstairs. We have some syringes with solder paste in them (basically the same thing as the solder wire but in a different form factor. The process here is:

• Squeeze a little bit of solder paste onto each pad on the PCB for a given omponent. It doesn't take much. You can also use the microscope we have up in the lab if you're having trouble seeing things.
• Use tweezers to drop the component in place (it doesn't have to sit exactly in the right spot, but try your best to line the pins up with the pads). Again, the microscope can help here.
• You can do either the whole board at once, or you can do little sets of components at once. But be careful when moving/handling the board because the components can still slide around.
• Once you have things in place, we'll use the hot plate to melt the solder. Be careful because, like its name suggests, it gets hot.
  • Make sure the hot plate is on and hot (~185 is good).
  • Set the board down on the hot plate so that the whole thing is on there. Probably don't use your bare hands for this. We have pliers and stuff you can use.
  • When the solder melts, it'll happen in a couple of stages. First the thing will melt and it'll turn a dull grey and spread out. That's fine and normal, but you're not done yet at that point. Then, after a little while longer it'll sort of shrink down and get bright and shiny. At that point things are actually happy (you'll probably also see the components move a little bit, that's fine too, the solder is actually going to kind of pull them into place).
• Once that's ready, you can use your pliers or whatever to pull the board off the hot plate. Be careful to not burn yourself, and also be careful because at this point the solder will still be melted and the components can slide around; so grab onto the board itself with your pliers, ideally far away from any components.
• At this point, the board will also still be super hot, so set it down on the bench and let it cool for a while before handling it / testing / whatever.

Questions?

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