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BLOG | Testing the Touch Board

Manufacturing PCBs in volume is a big challenge, even for boardhouses with years of experience. Increasing the yield and catching any errors is tricky, especially when time spent on inspection needs to be kept to a minimum (so we can get you your boards quickly). Solder shorts, unsoldered pins, faulty components, solder mask mis-alignment are all trying to slip through under the radar! Right now, the Bare Conductive Studio is all about test procedures and rigorous inspection as we look to ramp up production and streamline our design.

Up until recently we have been doing all of our testing in-house, which has been fine with small test batches. But now that we are expecting 60 Limited Edition Touch Boards to arrive soon we have had to work towards a more sophisticated testing procedure, not to mention the imminent order of several thousand!!

Enter the Touch Board Test Jig…

The above photo is the first prototype of our proposed Test Jig. This quick mock-up was constructed to check distances and tolerances and get a feeling for how it would work in practice. We wanted to make the operator’s job easy and minimise steps in the procedure. Basically, it’s a bed of pogo pins (temporary spring contacts – see http://en.wikipedia.org/wiki/Pogo_pin) sandwiched between a few PCB layers for stability. Using PCB is convenient, as we can solder the pin holders in place easily, as well as already having a manufacturing workflow for production. There’s also a small toggle clamp to hold the board in place and push it against the pogo pins during the test.

After this, some more rough sketches and measurements with a vernier we went to Eagle CAD and started working on the separate layers. This was quite a quick process as each layer is simply a variation on the layer below.

We could check that all the layers were as expected by printing them to scale on transparencies and placing them on top of one another. This also helps you double-check your land patterns against the physical objects you are fitting – very handy if you want something to work first time…

The active part of the test jig was developed as a separate board to the main stack and connects via a dense ribbon cable. We went old school on this board and used all through-hole components. This is partially for fun (we miss simpler times…) but also so that we could socket a lot of the components to make them easily replaceable for ease of maintenance. Again, reducing down-time helps keep the boards coming out.

The design files have been checked and checked again, and finally all the Test Jig Gerber files are ready to be sent off for fabrication on an express service arriving on Wednesday 2nd April. Our test code, written in a combination of Arduino and Processing, is being refined and is waiting for the jig to get back so it can work its magic. We’re looking forward to getting this show on the road!

Processing sketch working with the active component of the TestJig to perform automatic test procedures on a Touch Board held in the Test Jig and load the final code to ship.

Stay Tuned…

We hope you enjoyed this update. We’ll keep you posted on our progress as we go along. We’re expecting to get the Limited Edition Touch Boards in for testing next week and we want to show you the finished Test Jig, so stay tuned for more!