Repairing Flex Circuits By Accident

December 22, 2016 by Brian Benchoff 14 Comments

A while ago, [drygol] was asked to repair a few old Amiga keyboards. The key switches worked fine, but in the past decade or two, the flexible PCB ribbon connector has been mistreated, and was in an unworkable, nonfunctional state. The fragile traces underneath the green epoxy coating were giving way, but [drygol] found a few cool ways to repair these flex cables.

The end of this keyboard cable was beyond repair, but the Commodore engineers were gracious enough to leave a bit of slack in this keyboard connector. After cutting off the most damaged section, [drygol] had a strip of plastic, a few copper traces, and a green coating that had to be removed. The first attempt to remove this green covering used methanol, but that didn’t work. The next chemical attempt was with an epoxy solvent that contained nasty chemicals. This was applied to the end of the flex cable, with the remainder of the cable masked off by Kapton. It worked remarkably well.

In removing the Kapton masking tape, [drygol] discovered this green film sticks better to Kapton than it does to copper and plastic. A mechanical solution was found, allowing these keyboard cables to be easily repaired.

Of course, this was only half of the problems with these flexible circuits. Over the years, a few cracks appeared in the traces. To repair these broken traces, [drygol] turned to silver glue and a few laminations of Kapton to make this keyboard cable whole again. It worked, and the ancient keyboard was returned to service. Great work, and a fantastic observation for anyone with one of these keyboards sitting around: just grab a roll of Kapton to repair these circuits. It can’t get any easier than that.

Friendly Flexible Circuits: The Cables

February 7, 2024 by Arya Voronova 18 Comments

Flexible cables and flex PCBs are wonderful. You could choose to carefully make a cable bundle out of ten wires and try to squish them to have a thin footprint – or you could put an FFC connector onto your board and save yourself a world of trouble. If you want to have a lot of components within a cramped non-flat area, you could carefully design a multitude of stuff FR4 boards and connect them together – or you could make an FPC.

Flexible cables in particular can be pretty wonderful for all sorts of moving parts. They transfer power and data to the scanner head in your flat-bed scanner, for instance. But they’re in fixed parts too. If you have a laptop or a widescreen TV, chances are, there’s an flexible cable connecting the motherboard with one or multiple daughterboards – or even a custom-made flexible PCB. Remember all the cool keypad and phones we used to have, the ones that would have the keyboard fold out or slide out, or even folding Nokia phones that had two screens and did cool things with those? All thanks to flexible circuits! Let’s learn a little more about what we’re working with here.

FFC and FPC, how are these two different? FFC (Flexible Flat Cable) is a pre-made cable. You’ve typically seen them as white plastic cables with blue pieces on both ends, they’re found in a large number of devices that you could disassemble, and many things use them, like the Raspberry Pi Camera. They are pretty simple to produce – all in all, they’re just flat straight conductors packaged nicely into a very thin cable, and that’s why you can buy them pre-made in tons of different pin pitches and sizes. If you need one board to interface with another board, putting an FFC connector on your board is a pretty good idea.

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Building Circuits Flexibly

May 23, 2023 by Al Williams 20 Comments

You think of breadboards as being a flexible way to build things — one can easily add components and wires and also rip them up. But MIT researchers want to introduce an actual flexible breadboard called FlexBoard. The system is like a traditional breadboard, but it is literally flexible. If you want to affix your prototype to a glove or a ball, good luck with a traditional breadboard. FlexBoard makes it easy. You can see a short video below and a second video presentation about the system, also.

The breadboard uses a plastic living hinge arrangement and otherwise looks more or less like a conventional breadboard. We can think of about a dozen projects this would make easier.

What’s more, it doesn’t seem like it would be that hard to fabricate using a 3D printer and some sacrificial breadboards. The paper reveals that the structures were printed on an Ender 3 using ePLA and a flexible vinyl or nylon filament. Want to try it yourself? You can!

We know what we will be printing this weekend. If you make any cool prototypes with this, be sure to let us know. Sometimes we breadboard virtually. Our favorite breadboards, though, have more than just the breadboard on them.

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a flexible film with a matrix of illuminated color LEDs being stretched

Truly Flexible Circuits Are A Bit Of A Stretch

April 3, 2023 by Michael Shaub 5 Comments

Flexible PCBs have become increasingly common in both commercial devices and DIY projects, but Panasonic’s new stretchable, clear substrate for electrical circuits called Beyolex takes things a step further. The material is superior to existing stretchable films like silicone, TPU, or PDMS due to its high heat tolerance (over 160° C) for the purposes of sintering printable circuit traces.

But, a flexible substrate isn’t very useful for electronics without some conductive traces. Copper and silver inks make for good electrical circuits on stretchable films, and are even solderable, but increase resistance each time they are stretched. Recently, a team out of the University of Coimbra in Portugal has developed a liquid metal ink that can stretch without the resistance issues of existing inks, making it a promising pair with Panasonic’s substrate. There’s also certain environmental benefits of printing circuits in this manner over traditional etching and even milling, as you’re only putting conductive materials where needed.

After the break, check out Panasonic’s earlier videos showing some of their demo circuits that include a stretchable NFC antenna harvesting electricity even while submerged in water and an LED matrix performing while being, bent, rolled, and stretched. We’re excited to see where this technology leads and when we hackers will be able to create our own stretchable projects.

A great many flexible PCB projects have graced Hackaday, from early experiments to sophisticated flexible PCB projects. Heck, we had a whole Flexible PCB Contest with some awesome flexible projects.

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Circuit Boards You Can Stretch: Liquid Metal Nanomaterials Make A Strange Flex

November 19, 2020 by Dan Maloney 9 Comments

If you think polyimide-based flexible PCBs are cool, wait until you get a load of what polymerized liquid metal networks can do.

Seems like [CNLohr] has some pretty cool friends, and he recently spent some time with a couple of them who are working with poly LMNs and finding out what they’re good for. Poly LMNs use a liquid metal composed of indium and gallium that can be sprayed onto a substrate through a laser-cut stencil. This results in traces that show the opposite of expected behavior; where most conductors increase in resistance when stretched, pol LMNs stay just as conductive no matter how much they’re stretched.

The video below shows [CNLohr]’s experiments with the stuff. He brought a couple of traditional PCB-based MCU circuits, which interface easily with the poly LMN traces on a thick tape substrate. Once activated by stretching, which forms the networks between the liquid metal globules, the traces act much like copper traces. Attaching SMD components is as simple as sticking them to the tape — no soldering required. The circuits remain impressively stretchy without any apparent effect on their electrical properties — a characteristic that should prove interesting for wearables circuits, biological sensors, and a host of real-world applications.

While poly LMNs aren’t exactly ready for the market yet, they don’t seem terribly difficult to make, requiring little in the way of exotic materials or specialized lab equipment. We’d love to see someone like [Ben Krasnow] pick this up and run with it — it seems right up his alley.

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The Flexible Permanence Of Copper Tape Circuits

January 15, 2020 by Kristina Panos 23 Comments

Somewhere between shoving components into a breadboard temporarily and committing them to a piece of protoboard or a PCB lies the copper tape method. This flexible Manhattan-style method of circuitry formed the basis for [Bunnie Huang]’s Chibitronics startup, and has since inspired many to stop etching boards and start fetching hoards of copper tape.

[Hales] hit the ground running when he learned about this method, and has made many a copper tape circuit in the last year or so. He offers several nice tips on his site that speak from experience with this method, and he’ll even show you how to easily work an SMD breakout board into the mix.

Generally speaking, [Hales] prefers plywood as the substrate to paper or cardboard for durability. He starts by drawing out the circuit and planning where all the tape traces will go and how wide they need to be. Then he lays out copper traces and pads, rubs the tape against the substrate to make it adhere strongly, and reinforces joints and laps with solder before adding the components. As you can see, copper tape circuits can get pretty complicated if you use Kapton tape as insulation between stacked layers of traces.

Copper and Kapton (polyimide) tape are just two of the many useful tapes you may not be aware of. Stick with us a moment and check out [Nava Whiteford]’s exploration of various adhesive marvels.

Transparent And Flexible Circuits

May 17, 2019 by Al Williams 4 Comments

German researchers have a line on 3D printed circuitry, but with a twist. Using silver nanowires and a polymer, they’ve created flexible and transparent circuits. Nanowires in this context are only 20 nanometers long and only a few nanometers thick. The research hopes to print things like LEDs and solar cells.

Of course, nothing is perfect. The material has a sheet resistance as low as 13Ω/sq and the optical transmission was as high as 90%. That sounds good until you remember the sheet resistance of copper foil on a PCB is about 0.0005Ω.

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