November 22, 2008
Tutorial - Solder Paste Stenciling
about 6 years ago
oops forgot to include a link to the pictures:
(click on the small icons on the right to browse).
Oh.. after making the 4" circle, i tried making a quick n dirty stencil for a 30mm circle project.. this time i simply applied some 2" wide kapton tape over the pcb, and cut out the pads.. took about 20 minutes.. VEEERRRY carefully removed the tape (actually i spread on paste on the first one) then moved the tape to a second board, and had two boards soldered with reflow heatplate in a matter of about 20 minutes including populating the boards (twice the performance of hand-soldering even with just two boards.. once i do a batch of 10 i expect 5x the performance!
I got my solder paste from stencils unlimited.. $25 for 200g. of course cost more in shipping than the paste.
Tutorial - Reflow Skillet
about 6 years ago
I bought the exact $20 target hot plate, and after a couple tests with layering different heat-spreader plates and testing different power levels (burned up one board pretty bad)… figured out a perfect solution.
I use a 1/8" piece of aluminum between the hotplate and circuit board to even out hot-spots..
I monitor the temperature either with IR thermometer or thermocouple with my fluke multimeter.
I use the profile shown here:
I start a stop watch and basically dial the power to achieve 150C in about 90 seconds, about 180C in 3 minutes…. then turning up power to full power for about 30 seconds and then off… it gives me a spike of about 220C, and has been working perfectly.
I made a test stencil myself.. see the stencil thread.
inspired by this thread, i did a ‘DIY’ stencil so i could test a pcb before ordering a real lasercut stencil. The step-by-step process i used is here:
1) convert my computer file of the PCB to one with outlines for the solder stencil.
2) print it out on label paper (half sheet in this case)
3) stick onto some appropriate 3mil film, i used some anti-stat plastic.. it was a bit softer/thinner than i wished, but all i had on hand… make sure that the label is bigger than the film.
4) stick label+film onto a backer, like ‘white cardboard’.
5) with some serious magnification and an x-acto, cut out all the holes
6) soak the label from the top with ‘goo gone’ or ‘goof off’ to release the adhesive
7) clean off the film of any residual adhesive.
baddabing.. saves $30-40 if you only need to make a handful of boards.. should be good for 10-20 boards if you are careful cutting. Also gives you instant gratification.
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