Flexible PCBs: Not Only For The Few

Flexible printed circuit boards are a fascinating technique for making electronics venture beyond the two-dimensional, but surprisingly they’re not something many of us have worked with. [Jessica Stanley] gave a talk at the recent Electromagnetic Field event in the UK, exploring the different ways to make your electronics bend.

She starts with an overview of flexible electronics, detailing the techniques used with conventional polyimide substrates and etched copper.  We’re particularly enamoured of a stretchable PCB made by coiling a flexible circuit round a piece of elastic. Since she’s looking for techniques accessible to everyone that don’t either cost a fortune or require dangerous chemicals we look at conductive paint and electrolysis, before arriving at using a vinyl cutter to create adhesive traces.

We’ve no doubt all noticed that flexible PCBs can be ordered from the usual fabrication houses at a price, but the value in this talk lies in reminding the viewer that this is not the only path. She demonstrates well that simple flexible PCBs can be within the reach of almost anyone, which is perhaps the encouragement needed for people to try this medium. The full talk is below the break.

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Saving Some Coin With 3D Printed Stencils

One of the extra tools someone might need when working with surface-mount components is a solder paste stencil, which not only simplifies the application of solder paste to a PCB but increases accuracy. These metal stencils can cost an annoying amount of money and take time to get delivered, so this group has developed a method to 3D print them instead.

Starting with a PCB design in one’s tool of choice, the Gerber files can be sent to the online Stenchill tool to generate the stencil. Alternatively, a KiCad plugin exists as well. The tool will output files for a 3D printer from there. An FDM printer is required, with either PLA or PETG filament, and some configuration in the slicer is needed to get the accuracy required for a useful stencil. But once that’s all set up, the printer can output a perfectly usable stencil at a fraction of the cost, and without having to wait days for delivery through the mail.

It’s not all upside, though. Although it might be better than applying solder paste with a syringe on a massive board or doing more than one smaller board by hand, it may not be as good as a metal stencil for extremely small pads. But for those who often find themselves using metal stencils and dealing with the downsides that come with them, this could be a viable alternative, especially when prototyping.

If you have a laser cutter handy, that opens up some additional options for stencil production.

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PCBs Straight From The Magazine

It’s never been easier to get a printed circuit board made. In fact, almost every electronics video out on the internet will incessantly remind you of this fact now. But making a custom PCB wasn’t always as straightforward as sending a KiCad file to a board house. Many DIY methods involve harsh chemicals and tedious processes, but did have the potential benefit of taking much less time than waiting on boards to arrive in the mail. [Bettina Neumryr] is demonstrating one of these older methods, called the toner transfer method, using a circuit that was printed directly in an old magazine.

The first part of the toner transfer method is to create an image that can be printed. Since this circuit came from a magazine, it is first scanned in to a computer and imported into GIMP, where it can be scaled to match the size of the components and then sharpened to make a crisp print. With the image ready, it’s time to print the image onto some toner transfer paper, ensuring that the printer in question is a laser printer which actually uses toner. From there, a sheet of blank copper PCB is prepared and then the toner is transferred by heating, in this case using a laminator. After that its etched, removing all of the copper not protected by the toner, and then the toner itself can be removed which leaves behind the copper traces.

For those of you who were around when toner transfer was in vogue, this video might not have much value. But for anyone who can’t use a board manufacturer for whatever reason or is looking for alternatives, a modern video showing the method could be much more useful and have better context for beginners than videos made a decade or more ago now. Some of those older methods include similar processes using inkjet printers instead, but there are more modern DIY methods as well using lasers or CNC machines too.

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DIY Ceramic Circuit Boards Surely Count As Solarpunk

Solarpunk is all about combining that DIY hacker ethos with sustainability and renewable resources. Our usual PCB manufacturing methods, with their bevy of chemical baths and petrochemical resins aren’t exactly the most sustainable. Digging up some clay and firing it into a circuit board? Very sustainable! And apparently doable, as demonstrated by [Emily Velasco] on Mastadon.

Of course anybody could take a ceramic wafer and call it a circuit board, but that’s only part of what [Emily] did. The ceramic wafer is apparently native clay, which is very cool. Even cooler is that she’s baked the traces into the pottery. While you could conceivably use some sort of conductive glaze for this, what [Emily] did was stamp her desired circuit into the unfired ceramic using a 3D-printed stamp, and then fill the depression with copper powder after the first firing. After that, a second firing is done in a reducing atmosphere to melt/sinter the copper together–it’s not totally clear which is happening here–without burning up.

The results speak for themselves; on the finished demo board, a pair of LEDs blink happily away, driven by the astable oscillator circuit baked right into the clay– and of course the components soldered to it. You’ll have to click through to see it, though.

Given those not-so-sustainable petrochemicals behind our favourite PCBs may be in short supply, this is a timely hack. If it seems familiar, that’s because we featured virtually the same technique last year, but using more-expensive silver powder instead of copper, and a campfire instead of a kiln.

Thanks to [smellsofbikes] for the tip!

Through-Glass Vias And The Long Road To Glass Substrates

Credit: Keith Best, Semiengineering.
Credit: Keith Best, Semiengineering.

Glass-based substrates are slowly beginning to push out organic substrates – as also commonly used in PCBs – due to often superior material properties for packaging. One area where glass substrates have however struggled is with through-hole vias and providing the conductive copper path through them. A 2024 article by [Keith Best] gives a good overview of the topic, with recent news showing how much companies like Intel are pushing for glass substrates, specifically for the packaging of dies.

One major advantage with vias in glass substrates is that they can be much smaller, enabling smaller than 0.1 mm diameter holes with far finer pitch. The challenge here is to make perfect holes with a laser that are defect-free, as well as have the intended diameter.

After that this through-glass via (TGV) has to be coated or filled with copper, much like their organic equivalent. Said TGV can be fully filled with copper, or use plating and add dielectric filler. Detecting flaws in such a finished TGV is important.

In a 2025 review article of glass substrate technologies by [Pratik Nimbalkar] et al. published in Chips the state of the art at the time was covered. The need for ever higher-density integration options with ASICs is highlight here, especially now that many chips today consist of multiple interconnected dies inside a single package.

The complications of creating TGVs with femtosecond laser pulses in Borofloat 33 glass are highlighted by [Daniel Franz] et al. in a 2025 research article, with microcracks and backside ablation observed without proper precautions, something which previously was often resolved by an etching step following said laser drilling. The main issue here is the post-drilling residual stress from the thermal shock, which the authors demonstrate can be largely prevented with careful tweaking of the laser drilling parameters.

As pointed out in a 2024 review article by [Chen Yu] et al. glass substrates are useful for far more than just high-density chip packaging. Glass substrates are also chemically resistant, have a higher heat resistance, are largely transparent to RF and can be hermetically sealed against outside influences. This makes them great for various advanced sensors and communication devices.

Meanwhile, if you wanted to do some metal-depositing on glass at home, we covered this recently.

A desk fan with an air filter. On the side, the final assembled PCB is visible.

Making A PCB The Old-Fashioned Way

Nearly all modern PCBs are designed with the help of EDA software, but not all of them. [ALTco] shows us the process of plotting out a board the old-fashioned way — by hand.

Back in the day, drawing out the traces on a PCB lead to beautiful, smooth lines that [ALTco] wanted to imitate. But first, he needed to figure out how the rest of the fabrication process worked. He starts by just experimenting, both with the “resist” markers and paint, and the etching compound. Things rarely work first-try, and neither did his home-made etchant. So then it was time to buy some ferric chloride, the standard copper etchant for PBCs. A few more tests sorted out which permanent marker worked best.

[ALTco] starts by thoroughly cleaning a raw copper-clad board so the marker sticks properly, then draws the circuit for a little analog fan controller. The board is then laid in a bath of the etchant for several minutes while gently rocking it to keep the reaction going. Finally the board is taken out, etchant stored for re-use, and the board washed with water and then presumably IPA to remove the remaining marker. Some assembly of the newly-printed circuit board later and you have a cute little smoke absorber for your soldering projects.

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Two printed circuit boards made from 3D prints and copper foil. One white and one black substrate.

Using 3D Printers To Make Circuit Boards

Custom printed circuit boards have become more and more accessible to the average hobbyist over the last decade. But one problem still remains: your circuits will take at least a couple days to make. But what if you needed some really rapid prototypes? [The Raccoon Lab] shows us how to do it with a 3D printer.

You start with the usual hobby PCB pipeline: take your idea, make a schematic, and then lay it out in KiCad. That’s where the changes start: to keep traces strong, they are made very thick. The PCB is then exported and opened in 3D CAD software, where the traces are extruded to be 2 mm tall. Off to the printer! The newly printed “circuit board” is made conductive by applying copper tape to it, and traces are cut out along their raised edges.

The result is a very quick and dirty PCB. Sure, it isn’t exactly production-ready, but for just about any simple microcontroller project it’ll do just fine, and it’s a whole lot more accessible than milling one using a CNC! We’ve seen a few variations on this approach recently, including some custom software designed to help along the process.
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