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Arthur T Knackerbracket [soylentnews.org] writes:

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Arthur T Knackerbracket has processed the following story [hackaday.com]:

While using a stencil should make solder paste application onto PCBs a simple affair, there are a number of “gotchas” that make it more art than science. Luckily, there are tools you can build, like this 3D-printed vacuum-assist stencil jig [hackaday.io], that take a little of the finesse out of the process.

For those who haven’t had the pleasure, solder paste stencils are often used to make the job of applying just the right amount of solder paste onto the pads of a PCB, and only on the pads. The problem is that once the solder paste has been squeegeed through the holes in the stencil, it’s not easy to remove the stencil without smearing. [Marius Heier]’s stencil box is essentially a chamber that attaches to a shop vac, along with a two-piece perforated work surface. The center part of the top platform is fixed, while the outer section moves up and down on 3D-printed springs.

In use, the PCB is placed on the center fixed platform, while the stencil sits atop it. Suction pulls the stencil firmly down onto the PCB and holds it there while the solder paste is applied. Releasing the suction causes the outer section of the platform to spring up vertically, resulting in nice, neat solder-covered pads. [Marius] demonstrates the box in the video below, and shows a number of adapters that would make it work with different sized PCBs.

If you think you’ve seen a manual vacuum stencil box around here recently, you’re right — we featured one by [UnexpectedMaker] [hackaday.com] not too long ago.

Personally I prefer using a magnetic chuck. The stainless steel stencils are fairly often magnetic and will sit firmly in place and are easy to just peel off without any smearing.

Vacuum chucks usually ends up with solder paste sneaking down some via or the like… Or smear out from the pads when the vacuum fades, I haven’t had any luck with it and magnets are so much more trivial and flawless in comparison. (except when one gets a non magnetic stencil.)

But for larger pads (in my case 0603), a bit of pressure from a finger or two is all that is needed for satisfactory results on most boards.

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