Surface Mount Soldering

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Heating up Nicely

I’m making some more Cheesebox synthesizers. I’ve got a plan to make a monstrous device with pixel rings, grids and speakers. For the insides I’m assembling some circuit boards using surface mount technology. I’ve got a couple working so far, with a third just cooling down. These are the things I have learned today:

  • Surface mounting is very doable as long as you have the right stuff:

    • A little hotplate

    • Solder paste that melts at a low temperature in a syrninge

    • Some right angle tweezers

    • A trigger thing for your solder syringe. This makes it much easier to get exactly the right amount of solder paste on each pad.

    • No feeling in the tips of your fingers (you already have this if you have previously built and maintained a 3D printer)

  • When you are squirting solder paste onto a pad, lift the needle up vertically before moving it to the left or right towards the next pad. This will give you a good looking vertical “blob”. It’s a bit like icing a cake. Not that I’ve iced many cakes to be honest.

  • I set the heated bed temperature to 170 degrees, with my solder specified as melting at 128. This seemed to work OK for my oven. When the hotplate hit 170 degrees I turned it off. I then used a piece of card to slide the board off the hotplate onto card. A bit like how you move pizzas around.

  • Watching the solder melt and surface tension pull things into position is great. I put one of the leds in the wrong way round and it was fun to watch it try to rotate into the right position. It was an easy fix. I just picked the led up and dropped it back down in the right orientation.

  • The best way to find out if a circuit board is hot is not to touch it with your fingers.

YOu adjust the screw as the plunger goes into the syrninge

I bought the yellow trigger assembly on AliExpress. It is much easier to use than the plunger.

Tomorrow I’m going to put a couple of boards into cases and start working on the code.