Electronic – How to hold SMD parts in place while soldering

solderingsurface-mount

I go through this every time I have PCBs I need to populate with SMD parts, and this has become more an issue as pin spacings have gotten tighter, and my hands have become less steady with age.

So far I've modified some curved tweezers with a rubber band for grip tension, to help hold a component in place until 1 or 2 pins can be soldered. It works but it can be cumbersome. The clamping force needs to be very light, and it seems one slight tap with a sharp iron tip will still move it. I've also tried various glues, placing a pin drop of glue in the center of where a component would go.

That sometimes works, but all the glues I've tried either waste my time waiting for it to dry, or dry (skin over) too quickly when grabbing some more. Worse, too often even a pin drop of glue will spread onto the pads, and then I have to waste more time cleaning things up.

If I had my druthers, all SMD pars would come with peel off self stick backing. But anyway, suggestions would be welcome. It will be a long time and many test markets before anything I'm doing will be populated for me with pro pick and place machines.

Best Answer

I just saw the SMD beak on Hack-a-day that looks like what you are looking for (I want one!)...

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http://vpapanik.blogspot.de/2015/02/the-smd-beak.html

I've also had luck...

  1. use a little piece of scotch or painter's tape on one side of a part to hold it down
  2. tack down a couple of leads with solder
  3. remove tape and solder down properly

For smaller parts (ie. SOT23)...

  1. tin one pad (typically a middle one)
  2. hold the part in exactly the right place with tweeters
  3. quickly touch the lead over the tinned pad with your iron to tack it down
  4. properly solder the other pins and work your way around back to the tacked one.

A nice feature of this technique is that you can rotate the part very precisely by moving your elbow (your arm acts like a big leaver). Even if you are a bit shaky, you can wait until the part happens to be perfectly aligned and then lock it down with the tack.

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