State-Aware Foldable Electronics Enters The Third Dimension

Still working with PCBs in 2D? Not [Yoav]. With some clever twists on the way we fab PCBs, he’s managed to create a state-aware foldable circuit board that responds to different configurations.

From his paper [PDF warning], [Yoav] discusses two techniques for developing foldable circuits that may be used repeatedly. The first method involves printing the circuit onto a flexible circuit board material and then bound front-and-back between two sheets of acrylic. Valid folded edges are distinguished by the edges of individual acrylic pieces. The second method involves laying out circuits manually via conductive copper tape and then exposing pads to determine an open or closed state.

Reconfigurable foldable objects may open the door for many creative avenues; in the video (after the break), [Yoav] demonstrates the project’s state-awareness with a simple onscreen rendering that echoes its physical counterpart.

While these circuits are fabbed from a custom solution, not FR1 or FR4, don’t let that note hold your imagination back. In fact, If you’re interested with using PCB FR4 as a structural element, check out [Voja’s] comprehensive guide on the subject.

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Make Flexible PCBs with Your 3D Printer

The last few years have seen great strides in budget printed circuit board manufacturing. These days you can have boards made in a week for only a few dollars a square inch. Flexible PCBs still tend to be rather expensive though. [Mikey77] is changing that by making flex circuits at home with his 3D printer. [Mikey77] utilized one of the properties of Ninjaflex Thermoplastic Elastomer (TPE) filament – it sticks to bare copper!

The TPE filament acts as an etch resist, similar to methods using laser printer toner. For a substrate, [Mikey77] lists 3 options:

.004″ thick “Scissor cut” copper clad board from Electronics Goldmine

.002″ thick pure copper polyester taffeta fabric from lessEMF.com

<.001″ Pyralux material from Adafruit, which is one of the materials used to make professional flex PCBs.

A bit of spray adhesive will hold the Flex PCB down on the printer’s bed. The only issue is convincing the printer to print a few thousandths of an inch higher than the actual bed level. Rather than change the home position on his Z axis, [Mikey77] used AutoDesk 123D to create 3D PCB designs. Each of his .stl files has a “spacer bar”, which sits at the bed level. The actual tracks to be printed are in the air a few thousandths of an inch above the bed – exactly the thickness of the substrate material. The printer prints the spacer bar on the bed, then raises its Z height and prints on the flexible PCB material. We’re sure that forcing the printer to print in mid-air like this would cause some printer software to throw errors, but the system worked for [Mikey77] and his Makerbot.

Once the designs have been printed, the boards are etched with standard etching solutions such as ferric chloride. Be careful though – these thin substrates can etch much faster than regular PCB.

Circuit Printer Doubles as a Pick and Place

Squink PCB printer and Pick and Place

Prototyping circuits is still a pain. The typical process is to order your PCBs, await their arrival, hand assemble a board, and start testing. It’s time consuming, and typically takes at least a week to go from design to prototype.

The folks at BotFactory are working on fixing that with the Squink (Kickstarter warning). This device not only prints PCBs, but also functions as a pick and place. Rather than using solder, the device uses conductive glue to affix components to the substrate.

This process also allows for a wide range of substrates. Traditional FR4 works, but glass and flexible substrates can work too. They’re also working on using an insulating ink for multilayer boards.

While there are PCB printers out there, and the home etching process always works, building the board is only half the battle. Hand assembly using smaller components is slow, and is prone to mistakes. If this device is sufficiently accurate, it could let us easily prototype complex packages such as BGAs, which are usually a pain.

Of course it has its limitations. The minimum trace width is 10 mils, which is a bit large. Also at $2600, this is an expensive device to buy sight unseen. While it is a Kickstarter, it’d be nice to see an all in one device that can prototype circuits quickly and cheaply.