An Adventure in self-fabricating PCBs

An Embedded Kitchen wouldn’t have been complete without the ability to fabricate circuit boards for rapidly prototyping circuits without waiting on the board house [fail fast, fail often applied to hardware design]. This week, it gained the capability to fabricate boards using the well-known toner transfer method.

I had done toner transfer first when I was at school, the results had been terrible. So terrible that I turned to wire-wrap prototyping for my circuits, even when I started using SMD components later. However the realization that dead-bugging SMD parts is too much effort which doesn’t scale brought me back to PCBs. This time because I couldn’t wait for two weeks to get my boards manufactured so I decided to take on toner transfer again. I knew the steps. Clean the board, print the design, iron it on. After the ironing when I rinsed the board under cold water, I was pleasantly surprised to see near-perfect pattern transfer from paper to board. Then I went on to etch them with ferric chloride.

The first boards to be so fabricated are an early stage prototype of my project Smarter Power Pack which uses spare laptop batteries to realize a better power bank (interested? here’s a link for further reading), and a respin of the LCD connector board for my BeagleBone LCD cape. Here are pics of the boards so fabricated:




After this was done, I threw in an additional step of tinning the whole board to protect it from tarnishing and also patch-up any imperfections in traces. Then placing components and reflowing the boards are usual. Here are the results.



They’re not as pretty as the ones got from the board house, but they’re beautiful in their own way. They’re cheaper in terms of money but more expensive in terms of extra effort (drilling and hole plating). And I don’t need to have 5 or 10 copies of tea coasters if I used a wrong footprint or inverted it. But in the end, it’s all worth it when you can get from an idea to prototype in days and not weeks.