Monday, 26 April 2010

Formica Expansion Boards Arrive!

As part of a final year group project I have been working to develop an expansion board for the Formica Robots. Over the Easter holidays I spent a considerable amount of time designing the PCB for the project. This is the first PCB which I have fully designed and had manufactured, so it was quite exciting. The boards arrived at the end of last week and so today (Monday) was the first chance I had to look at them and see if they work.
Here is the stack of ten boards fresh from PCB Train:




The white card behind them is a standard business card, which gives you some idea of how tiny these things are. These were then promptly cut with a PCB guillotine to separate the eyes from the expansion board:



Two eyes will stand vertically at the front of each expansion board, as the following mock up demonstrates:



The first problem experienced during construction is that the reverse of the inductor (shown in photo below) has a lot of exposed contact area. This is fine, except there is some ground plane and some signal lines routed directly under it on the board. To get around this I experimented with electrical tape stuck to insulate these tracks from the inductor.

LESSON #1: If you decide not to get a solder mask, be sure that you have not routed signals underneath components such as inductors, which have exposed conductive surfaces.



I have so far assembled only the DC-DC convert sub-circuit, due to the majority of the components being held captive by `stores' (My departments woefully inefficient system for ordering parts). Nonetheless, what has been built, works. This surprised me! The photo below shows the current state of assembly:

1 comment:

Jeff said...

Nice. Kapton tape is the correct stuff for that situation - much thinner than pvc tape, stronger and heat resistant. You can put it through a reflow oven, and it comes out unchanged!

eg. http://uk.farnell.com/3m/92-tape-12mm-x-33m/92-tape-kapton-12mmx33m-amber/dp/3309691