Sunday, April 26, 2009

DIY Electronics

So I've always been interested in electronics and all kinds of gizmos, but lately I've been playing with the idea of trying to come up with some cool stuff myself. Not quite sure what I'm going to make yet, but that'll come later.

There's a lot of great resources and inspiration out there, like Instructables, Hack a Day and Make Magazine. I know I would like to have a closer look at the Arduino and make something out of that, but since I haven't tinkered with electronics for years I found it best to start simple and refresh the basics. Sparkfun has a great tutorials section where they go through a bunch of stuff ranking simple to advanced.

There are basically two standard ways of making your own PCBs. The first is to use a laser printer to print out your circuitry and then transfer the toner to the PCB, clean it, etch it (using the toner as a mask) and then remove the toner with acetone. The second also uses a laser printer, but printing on a transparecy instead, using that as a mask while exposing the PCB to UV light before etching it. The main issue with both these methods is that you have to own a laser printer and one that uses enough toner to make the traces black enough that either etching fluid or UV light destroys the fine detail.

That got me thinking. Why isn't there an easier way of creating your own boards with as few steps as possible? Wouldn't it be nice to be able to draw up the ciruit using some form of laser?

Googling a bit I came over the macetech.com blog that proposed to use a laser to remove black paint from a PCB. The paint would take the place of the toner so you can skip that step entirely. Make has a similar article doing the same thing. As both of these posts mention, this method is not perfect. First of all using spray paint doesn't guarantee an even distribution of paint and the laser doesn't remove all of the paint as well - leaving you to wash of the rest. That again might destroy the any fine traces in the design. However; they both also mention that this method creates superb detail!

Taking it a step further a Polish research group came up with a way of doing Laser Direct Imaging (LDI) using UV laser a telescope and an optical scanner. Since they use a UV laser they rely on UV sensitive PCB's removing one more step; the toner/paint. The process is described in detail here and it was mainly created to be able to do ultra-fine traces for the circuitry of the future. In that aspect they succeded and while it's great a sollution it's not entirely feasible for us mere mortals.

Francois Dubrulle at HoloLab has made a UV photoplotter that does exactly what I want. Although his web-page lacks on details it shows it's possible. The main issue with this design, as he mention, is the low power of the laser (1mW) which limits the the speed of the print and it takes as much as two hours to finish one board. Doing prototyping and not volume production I don't mind waiting a bit to have PCB's produced this way since I can do something else in the meanwhile.

There are a lot of resources on making your own CNC mill and a 1mW UV diode has become pretty cheap so making one of these for myself should be feasible. Taking it one step further one could use the same CNC, switch out the UV lightsource with a laser and use that to make the screens for the solder and the laquer.

Maybe this will be my next project?
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