Wednesday, June 06, 2012


Printed Circuitry: All covered up

Since my last blog post I've done a few more experiments on the printed circuitry front.  Previously I've done some tests that indicate we really need to put a radius on track corners or else the track comes out a little blobby. I did do this in the print in my last post, however it was only 0.5mm. Since then I've redone the board with 1.5mm radii and result is much better.  Also where two sections of track meet I've also a radius to maximise the contact between the two sections of track and hopefully improve the reliability. Unlike last time I deposited the metal track first and inserted most of the components afterwards and soldered by hand. This is mainly as I wanted to test my theory about rounded corners without wasting components:

I've also had a go at covering up the entire board; I tried a few times using completely solid fill on the cover layer. However the boards always stopped working. They were as tested before covering so I suspect that the amount of heat was too much for the metal and the track was melting or the upper layer was shorting through the plastic where it wasn't supposed to. However as it is all covered I can’t physically check. I'm now doing a 0.5mm tall cover layer at 15% fill. This also means that I can still test the board mid build as the track is still exposed.  I've elected to do a 0.5mm tall layer as the track doesn't quite sit flush with the top of the board, and this ensures that the head doesn't collide with the track. I haven't quite nailed depositing the alloy on an upper layer yet. The problem is that I need a perfect plastic solid layer, and I only have one layer to achieve this in. Normally we have 3/4 layers to get a nice smooth finish on exposed layers but due to the geometry I can't do this.
I'm going to try fitting a fan to my machine and fiddling with the plastic print settings to see if I can improve things.  For the time being I've just deposited the solder by hand. However I've still managed to cover the board and it still works so I've proven porous fill isn’t damaging the metal.

VERY nice! :-)
100% Reprapable Repraps. I give it a year.
I have a question about your blog, do you think you could email me?
Could you extend this to 3d electronics? Unlike regular PCB's making it multi-layer is really cheap here so that might offer a way to hide complexity.

How wide / narrow can you get the printed tracks?
very nice work Rhys. This is the sort of thing that would go great with a robot hand I'm developing.
I wonder if a custom filling pattern would help produce a solid fill in one layer without damaging the traces? If the 15% infill seemed to work, how about seven passes of 15% infill starting at the same corner/edge for an interlace pattern? Might give things time to cool if heat is the problem.
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