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Using a Solder Paste Stencil

A project log for Vinduino, a wine grower's water saving project

Monitoring soil moisture at different depths to determine when to irrigate, and - more importantly - how much water is needed. Save 25%!

Reinier van der LeeReinier van der Lee 03/20/2016 at 17:373 Comments

For upcoming trial installations, I need 25 Vinduino printed circuit boards. Not a sufficient enough quantity for cost effective outsourcing of assembly. The new version of the Vinduino board has a good number of SMD components, and after building the first board with solder paste, toothpick, and hot air tool, I knew I had to find a faster way. So when I ordered PCBs @ Elecrow.com, I clicked on the option for having a 30 x 40 cm framed metal stencil. Added cost for the metal stencil is $18 + shipping, a bargain!

The PCBs and stencil arrived one week later, and I was pleased with the quality of the stencil and the frame. Now I was in the market for a stencil printer. A unit with good reviews will cost you over $500 + $200 shipping (weighs 17 kilo) from China. The $150 units on Ebay get mixed reviews, so was not sure if I wanted to squander HackaDay prize money on that.

I ended up not buying a stencil printer (for now), but instead made a $20 wooden positioning frame that works accurately, and gives repeatable results.

To fix the position of the PCB, I used iron-on edge tape. Then I moved the frame until it was perfectly aligned with the PCB pads. The frame position is fixed with pieces of wood glued to the base board.

For first tests, I used low temperature lead free solder paste, and a putty knife to apply the solder paste. One single pass should be enough.

The method gets me good solder paste dosage, and accurate alignment.

Fresh from the T962A oven, all solder pads passed visual inspection. Looks much cleaner than the manually applied solder paste build I did on the very first board.
No rework was needed.
After assembly of the top side through-hole components, all boards work as expected.

Discussions

Hans Christian wrote 02/11/2017 at 00:00 point

Nice idea for stencil alignment! You mentioned some stencil printers that have received good reviews. Could you share which ones, and where to buy them? Thanks :)

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Alex Rich wrote 03/20/2016 at 22:51 point

such a good idea for PCB houses to have a checkbox for adding a stencil, nice results!

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Reinier van der Lee wrote 03/21/2016 at 00:20 point

Agree, makes total sense to add the stencil as option as you are uploading the gerbers anyway.

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