New From OSH Park, Flexible PCBs!

Alasdair Allan
2 min readDec 30, 2018

Much like Linux on the desktop, whose time never really arrived, it always seems like it is next year that’s going to be the year wearables finally take off. My own view, is that wearables aren’t going to take off ’til they’re, well, more wearable. The current collection of smartwatches, and fitness trackers, aren’t wearables. Instead, they’re just things that people wear, which isn’t the same thing at all. But before wearables can make it into the mainstream, a whole technology stack needs to come together to make it easier to rapidly prototype products.

Over the last year or two we’ve started to see some of the elements of that stack mature, and become more readily available. Like ultra-low power microcontrollers and sensors, the “peace dividend” of the smartphone wars, that can now just about fit into energy budget of passive power sources like vibration harvesting and other energy harvesting techniques, which makes it possible to do away with the need for heavy batteries. Something that’s been holding back real wearables integrated into day to day clothing. However, there are still parts of the technology stack missing.

Which is why it’s really rather exciting to see that OSH Park has introduced new flexible PCBs.

Their flexible PCBs are made using a Polyimide substrate just 0.0762mm thick and can have one, or two, layers.

Costing $15 per square inch, which includes three copies of your board, the flexible PCB is about three times as expensive as traditional FR4 boards. Yet a lot more flexible, and while that does more wear and tear on solder joints, and although it’s always going to be design specific, OSH Park does have some suggestions for the minimum static and dynamic bend radius you can get from the new materials.

In other words, you need to think about positioning of your components, and the direction of the flex on the board that you’re expecting, as well as routing when you’re designing your boards.

The new OSH Park Flex PCB bending. (📷: OSH Park)

Full details of the new flexible PCBs can be found on the OSH Park site, along with the data sheet for the flexible laminate that they’re made from.

The one down side? Coloured masks made the PCBs too brittle, so unlike every other PCB that you’ll get from OSH Park, these new flexible ones aren’t purple. Yes, it pains them too.