How to etch your own solder paste stencils

We’re kind of surprised we haven’t covered this concept before since it only uses techniques that are commonly avaialable for home PCB fabrication. [Ray] made this solder paste stencil out of a sheet of copper using the same etching techniques you would for a circuit board. He designed and printed a resist pattern, with toner everywhere except the places where there should be holes in the stencil. He transferred the toner to the copper using an iron.

The difference here should be obvious; this a thin copper sheet with no substrate. Because of that, you must protect the copper surface before etching. he covered the entire thing, both sides, in packing tape. After that it’s into the Cupric Chloride bath to dissolve the exposed parts. Once the tape and toner has been removed you can scree a precise amount of solder paste onto your boards.

This isn’t for everyone, but if you’re assembling many boards it’s not a bad approach. If the stencil is no longer used it can be recycled, but we do wonder how corrosion on the copper will affect the stencil’s performance.

The idea for this technique came to [Ray] from a guide that’s been around for years.

22 thoughts on “How to etch your own solder paste stencils

  1. A stencil made this way is likely going to be useful fewer times than even mylar. Copper bends too easily at these thicknesses and also work hardens to hold bends. You’ll end up with irregular shaped holes as the scraper drags the thin dividers between pads, and voids under the sheet where the copper does not lie flat. That’s why real stencils use stronger, springier metals like stainless steel, or stiff flexible plastics like mylar or kapton.

    1. You think it would really degrade that quickly? I wouldn’t worry about work hardening so much… Just hit it with a torch.

      You’re right that steel is a better choice, of course. No doubt about that. Luckily, you can etch steel fairly easily, which is what I plan to do when I need stencils.

      1. Excellent idea! In fact, I think I’ll make a prototype out of stainless, just to avoid all corrosion, or at least anything you can see or flake off in nasty chunks. :)

        Just an FYI to all, I won’t even try etching the stainless. I’ll send my CAD file to the machine shop and have them CNC it all out — likely, since I use components down to 0805 already, they’ll be milling or drilling holes instead of machining rectangles, since that will be easier & faster.

        Thanks for posting this, Mike! And thanks to Ray for sharing!

    2. If they’re cheap and/or easy enough, you might not care much about stencil lifetime. Framing the stencil and/or handling it with kid gloves would go far with stencils like these. A stencil that can’t be made to lay flat *is* fairly useless. The main trick is probably finding the right material thickness that gives you the longevity you need and an etch that yields clean, sharp apertures.

      1. @Steve-O-Rama yikes, i’d like to see the milling setup that can handle holes that tiny in thin stainless. I think you’d have to laser cut it.

  2. I’d swear that I saw something like this somewhere but using disposable aluminum dishes as the base material source.

    Why not use thick aluminum for stencil instead of copper?

    Duraluminum will be stronger than copper and easier to etch.

  3. Something isn’t right. You protected both sides by wrapping it in packing tape, before etching?

    Covered in tape, nothing should have etched.

    Unless I’m missing something.

    1. He covered the whole copper sheet – both sides and the edges – EXCEPT that he left the toner bare so that the little holes in the toner could be etched.

  4. The biggest problem with etched stencils is that the apertures come out rougher than the other methods used for higher-quality stencils (namely laser-cutting). Rough apertures produce less reliable solder paste releases which, besides getting the area vs. thickness equals volume right, is the biggest measure of usefulness/quality of a stencil. It’s pretty much all about the release.

  5. Assuming it’s cleaned after use and stored in a clean, dry place, there’s no reason the copper should corrode. Over time it will develop a dark patina, but that shouldn’t interfere with its use as a stencil.

  6. Just FYI, thin copper sheet in various thicknesses is readily available at hardware stores as copper flashing for roofing work.

    Aluminum is also available.

    1. Maybe where you live, but not everywhere I fear, still – thanks for telling people where to check, or alternatively where to look for it online.

    1. If you apply film photo-resist with a laminator first and apply tape to the back side, then expose it, develop, etch.. etc.. that should work well. I would do it that way since my laser printer does not print dark enough for direct transfer – I had problems doing toner transfer in the past.

    2. As I understand it, people have tried using laser printers to print directly on thin copper sheets and thin copper-clad substrates (Like DuPont Pyralux) and it doesn’t work for whatever reason. Something about the copper dissipating too well to fuse to.

      Inkjet is doable, but fraught with difficulties. (Ink coverage, beading, difficulties in drying the ink, etc.) Google ‘inkjet PCB resist’.

      But a solid ink printer, like a Xerox Phaser can do it. I saw something on HaD where a guy was directly printing sheets of Pyralux and then etching them. (It’s gotta be pretty flexible though.) I would so love one of those…

      I have a love/hate relationship with toner transfer; I love the idea of it being that easy, it hates the idea of ever working for me. ;)

      I’m trying to switch to photoresist, but I’ve had trouble getting started. (Okay, maybe I’m just goddamn incompetent afterall!)

  7. I tried using my CraftRobo to cut a solder paste stencil out of a laser transparency, but it caused too much drag on the blade and the holes came out somewhat misshapen. I could definitely do a perfectly precise one out of cardstock that’d be good for a couple-few applications though.

    Maybe I should try thin mylar film in a rigid frame? Isn’t that what some places make short-run stencils out of?

    For those who don’t know what a CraftRobo is, it’s an inexpensive computer-controlled X-Y swivel knife, basically. For cutting out papercraft models, die-cutting cards and stickers, and cutting vinyl graphics.

      1. I use a Silhouette SD, which is the newer re-branded replacement for the CraftRobo.

        I replaced the stock plastic blade holder (Which uses 3 different caps to determine depth of cut) with a CNC metal one from Specialty Graphics, featuring a twist-adjustable depth. (It also lets it take more generic blades)

        It’s a really handy thing to have around.

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