The author of this video sent it to me after I had been complaining about my subpar technique on The Amp Hour. Crowdsourced knowledge, ftw!
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The real lesson here is that rigidly locking the stencil and PCB is generally more precise and repeatable than other methods. In most production environments this is accomplished by precisely manufactured ($$$$) frames, but for hobbyists this pin & registration hole method is doable and inexpensive.
To be sure, care is still required to prevent damaging the pins and holes - particularly in the stencil - in order to get long life (and repeatedly precise placement) out of stencils. Of course, the same is true with “tape and pray" methods, especially since we tend to have to have to repeat the stenciling process when we rely on tape for positioning.
I’ve never done this particular trick of soldering pins into a dummy board (which will get in the way of your paste squeegee) but I do regularly put alignment holes in my boards and stencils and stick temporary 2mm dowel pins through them to get close to alignment prior to using the vernier controls on my stencil fixture to finalize. The only problem is when an alignment pin happens to end up directly over a hole in the fixture’s matrix - oops! I must have half a dozen dowel pins inside the fixture by now.
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I came up with the poor man’s version of this on a very tiny board I am making that will have no room for additional pins. Instead, I was thinking of this video and I transferred the alignment pins on my tag connect to the top paste layer. Those will now be carved out of the stencil. I’ll be able to use the TC to line up the stencil, remove the TC, and then spread paste. The downside is that some amount of paste will go down into those alignment holes, but I will be able to just push that through to the bottom of the board before reflow. Maybe use similar sized pins to push that paste all the way through? (haven’t tried it yet) I was excited about this idea for not having to add additional stuff to this board. If this goes to production, I’ll put more realistic DFM elements onto the board and/or hand it off to an assembly house and let them impart their expertise.
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Alignment is always annoying, but if you make your boards at Eurocircuits, they have a really good system. You buy a $15 jig from them (reusable) that is a PCB without copper (glassfiber only) with holes drilled and some very precise metal pins. They then add a frame to your PCB’s that has holes that align with the pins and similar holes on the stencils. The stencils get cheaper since you don’t need a frame and can make them smaller. The system is 100% effortless to get right every time. You just drop the stencil on and it’s perfectly aligned. I really wish other PCB vendors used this system as well…
Here’s a video showing it in action: https://www.youtube.com/watch?v=HBWtqZro_fg
I use this system and Eurocircuits for all my prototype production where price isn’t critical. It never fails - though using old solder paste might. Highly recommended, but likely only if you’re in Europe where it makes sense to use Eurocircuits.
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@jensa never seen that before. Looks great thanks for sharing
Yeah, really good stuff! I haven’t ever gone for a board from eurocircuits, but everything i have seen from them has been impressive and well recommended.
Yeah. I wish Eurocircuits shared this setup with other vendors to make it an industry standard. I tried making some boards with this myself at JLC, but I didn’t manage to align things correctly. I gave up after one try, but this is many years ago. It’s a very good system.