Making the Safe-T-Flow part II – Using it! An arduino controlled robotic skillet for SMT

In part two we use the Arduino controlled robot skillet to surface mount a chip on the USB Boarduino, 7 minute video – m4v. Here’s part one if you want to catch up!

Props to Ohararp for the idea of using kapton film instead of mylar. If you need stencils cut, because, say you don’t own a laser cutter, you should contact him!
The 2mil kapton/polyamide film was purchased from McMaster-Carr part #2271K2 for about $12/sqft. For a 35W Epilog laser, I used 100 speed, 15 power, 500 frequency to get a reasonably clean cut. The PCB holder is cut from everyday 1/16″ acrylic. Solder paste is from digikey, part# KE1507, you’ll want the nice rounded plunger from McMaster, part #66045A13 and ~22AWG needles such as #75165A682. While you’re at it, you’ll probably want to pick up a bottle of de-leading soap from Mcmaster, part # 7724T24

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  1. That’s a really awesome project. Great work!

  2. This is fascinating and fun. Is there some PID in your Arduino code?

  3. nope. its completely open loop. im going to fix that soon though. it works but i want something better (doesnt everyone?)
    i also should look up to really understand what the reflow profile means. i think i got it wrong 🙁

  4. I was very interested to see your technique with applying the solder mask, may I ask who your Kapton film provider is?

    Also, I think your doing great things with your products, keep up the good work.

  5. You are a rock star! I’d like to be friends.

  6. I see you posted your provider in another post, sorry about that.

  7. I’m curious as to why your solder stencil only has holes for the electrically connected pins, instead of all of them? Seems like it would be a good thing to trade a tiny amount of extra solder for a bit more mechanical security in the finished product.

  8. @jeremy mm, its right there under the video! 😉

    @jpeterson mostly because i was having solder bridging problems with the thicker mylar film. i may go back to that now that i have 2mil stencil material as i am not having any excess-solder bridging problems now!

  9. @Limor you should try raster engraving the stencil vs a vector cut. I am not at my laser now but I think I use 100 power|30 spd at 600 dpi on my 45W laser for 3 mil kapton. When you are producing bigger stencils with lots of pads this will save a ton of time on the laser.

  10. Great project! I was thinking the same thing that jpeterson mentioned. I have seen videos where people would simply use the syringe to deposit the solder paste to all of the pins not caring about the position of solder. I was surprised to hear that you had bridging issues. Would longer time in the skillet help or is it a different type of solder that was used in those other demonstrations where the solder removes itself from the solder mask and the part self centers with heat.

  11. well to be honest im not an SMT engineer. the problem went away when i went to 2mil kapton instead of 3mil mylar. it could also be my squeegee action >shrug<

  12. We solder surface mount chips like this by hand and its much faster. Your setup is super cool though.

  13. To solder a couple? yes it may be faster. To solder 100 in a row? I assure you that this is a hell of a lot faster and less prone to mistakes. And I have to do 100 at a time 🙂

  14. I’m wondering why one doesn’t just use stainless steel for the stencil like the big boyz/girlz do. I poked around the McMaster-Carr website (never been there before, and I can’t afford to go back, cuz it’s way too cool :-(), and 3mil 6″x10′ (unpolished) foil is about $35/(5*ft^2) or just over half the $/ft^2 of the Kapton you mentioned.

    Is it that one needs a laser cutter with that much more fry-power to get through 3mil SS? I did read somewhere that SS stencils can require post-processing (electroplating) to smooth out the rough edges, but perhaps for our (non-BGA & friends) purposes, a raw cut stencil would be just fine, if not better, than a polyfilm one.

    Life would seem to be much easier with SS. Seems like it would last a lot longer and wouldn’t need kid-glove treatment like I’d expect mylar/kapton might need. I do know that you can crimp mylar film if you’re not careful with it. And while you (certainly!) can’t tear it like masking tape, I’d still be concerned about ruining the interior detail of a cut stencil during use or clean-up — at least moreso than I’d expect with SS.

    Seems like if I had a cutter, I’d want to cut SS with it, but if I was kludging a stencil with some type of bladed tool, I’d opt for the polyfilm.

    If I’m off-base, someone feel free to tag me out.

    gards and re-gards,

  15. ‘commercial grade’ laser cutters cant cut through steel. youd probably want EDM or a vastly expensive industrial laser cutter probably going towards $100k. even if you cut 10 stencils from kapton, thats about $5

  16. $100K. ‘Nuf said!

    Can you solder with yours, or is that a no-no (hot flux sputtering around, or some other problems)? Seems like wattage would be about right.


  17. Limor,
    Thank you so much! This is simply amazing! My Hat Goes off to You

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