I normally use stainless steel stencils, but for prototypes and one-off experiments it would be nice to be able to laser cut a stencil myself. In the past I cut stencils from clear Mylar using a CO2 laser cutter, but I currently only have access to a 445nm diode laser that won’t cut clear materials.
I know some companies produce cheap stencils cut from yellow Kapton film. eg, OSH Stencils, and I’ve seen it cut with a 10W diode laser on YouTube.
Has anyone here tried it with a diode laser, and can you recommend a cheap source of Kapton film sheets? All my searches bring up rolls of adhesive Kapton tape instead.
Like resistors, you’re paying more for handling the material than the material itself at low volumes…
$23.80 per sheet for an A4 sized sheet. $8.88 per sheet if you buy 100!
If you don’t mind a roll, you get more material for less.
150mm wide x 33m long is $139:
The downside is that kapton on a roll tends to curl a bit.
No idea on the diode laser – but if you have kapton adhesive tape already, I’d try a few test runs. You do need to watch you power and speed – I had a friend try to cut some thicker kapton I had some years ago and the result was a mess; it wasn’t worth our time to fine-tune it at the time, so I didn’t pursue it further and went to OSH Stencils. These days, I mostly get frameless stainless from China with my board order, though.
Ah, I hadn’t mentioned this to you! Bradan Lane tweeted about this adjustable stencil frame system and I ended up getting one: x.com
For doing short-runs on smaller boards (which the kapton laser cut would be for), where I am only likely to do five boards or so, it works well enough.
The stencils are not as square and tight as getting them with a frame – but when I’m done, the small frameless stencils don’t take up space.
I’m going through a downsizing thing right now, and one thing I did was to dump several cubic feet of old framed stencils. And I felt bad doing it because I didn’t want to just put it in the dumpster, but I’m not sure what else I could have done.
So this framing system is helping me with that issue.
For larger boards, especially when it’s dimension-critical (bunch of fine-pitched connectors spread out over longer distances), this system doesn’t work so well, and I would still get framed stencils.
We have also stuck with frameless stencils. We do a good amount of hand pasting using masking tape to hold the stencils.
We have a nice CO2 laser and it never made sense to do our own stencils vs getting stainless ones from PCBway bundled when we have the boards made (they are just so cheap framed or otherwise). Frameless, as you noted, reduces space and also shipping cost.
We’ve had moderately complex boards with QFN and “simple” BGAs with good success on the frameless and tape, otherwise we have a CM do the assembly.
Oh, nice. I think that Neoden one looks to be much easier to use than the system I have, which works well enough, but I find some aspects of it to be a little awkward…
I haven’t tried with a diode laser yet since we cut out own stencils out of stainless but one tip i found from a friend was that instead of using a cut to cut around the apertures using the engrave function produced a better result on the co2 the diode is probably the same… we have done kapton on the co2 as well in that way it seems counter intuitive but it worked
i had the other neoden one not the ‘precision’ one but it was basically junk put together with big box hardware store parts and i put it out on the street.
the big issue with frameless, especially when you have a lot is they are crazy sharp i always forgot to use gloves and slice a finger!
I don’t use the Stencil-Mate, but I have adopted their registration scheme and it’s a huge time-saver getting things lined up. Sometimes I barely need to twiddle the X-Y verniers.
Very interesting, thanks! I never would have thought of vellum paper. Can you remember a weight of paper that worked ok for a stencil? Did it need particular coating to scrape/wipe off excess solder paste, or just “standard” vellum tracing paper?
I had also made them from vellum using a cameo hobby cutter, see video here: https://www.youtube.com/watch?v=KqFHNe6nWpE . The associated blog post has some dead images which I’ve meant to fix, but it’s also all EOL equipment so it’s low on the priority list!
I used a “3mil drafting film” from a local art supply store.
No issues with using it as a stencil.
I do have a diode laser cutter & some kapton tape, so will see how it works out of interest! You can buy individual kapton film from McMaster-Carr but that also won’t be cheaper…
I only had some 1mil kapton/polymide tape here. It does cut but not fully clean, however part of the problem is the adhesive causes stuff to stick so it rips apart. The adhesive may also be causing more burning issues. I suspect straight film will be nicer, but will be a few days before I have any.
I’ve repeated the same pattern with some different kerf offsets, it’s 0603 & 0402 resistors + QFN + SOT23-5 packages (one of the QFNs dropped the leads entirely due to the kerf offset being too large).
This is with xtool S1 40W (~455nm) set to 40% power @ 300mm/s. It cut the tape down to 10% power with a slower speed. On the S1 the 40W head has a larger spot size than the 20W option, so a lower power version of the S1 may also perform better.
The quick story it’s it’s WAY easier to toggle the “order stencil with boards” button on jlcpcb and it looks a lot better
I was going to try some thicker polymide film as this had been on my todo list, so good excuse to test…
Some processing needed as I had to run the QFN leads in a single pass but the larger aperatures in 2 passes. This was without any automated postprocessing however, and just washing it in water to get the gunk out quickly. A few aperatures not fully clean here, but this was just a quick test so I didn’t spent too long optimizing it. You can see the edges are a bit “melty” here.
This was with ~8% power on a 40W laser, so presumably smaller ones will work well! The spot size is probably most important, the QFN leads here were done as basically a single line cut down the center.
