Sunday 11 March 2012

Volte-Face on Toner Transfer

Politicians do it all the time - so why shouldn't I? I've made a u-turn. A 180. A policy reversal.

I guess it really started this week, when I was trying to make up a little PCB for work - only about an inch square with a few SMT components on it...

However, it seemed to lie at the extreme edge of the abilities of my "Toner transfer" backyard PCB manufacturing technology (
blogs passim). It took me a couple of tries to produce a satisfactory batch of boards and I just don't have that much time to waste!

Fortunately, a mention on the G-QRP Yahoo Group this week had drawn my attention to a website, enticingly called "Blondihacks", produced by a talented engineer who rejoices in the name "Quinn Dunki". The particular link was to Quinn's description of PCB production, in which she summarises her methods for producing PCBs using pre-coated photosensitive boards. Quinn's descriptions and the frustrations of my week persuaded me to give it a try - so I ordered some board and developer from Rapid (who - once again - lived up to their name).

OK - here we go... Deep intake of breath... I hereby renounce Toner Transfer methods of PCB production. They may be cheap, but they are rubbish, compared to what can easily be achieved using photo methods. The quality of my first optical board comfortably exceeded anything I've ever made using toner transfer...

Don't waste your time with irons or laminators. Don't waste time trying to get rid of those irritating chalky deposits from glossy photo paper that get trapped between traces, that fill holes and that mess up fine detail. Don't waste time trying to use old magazines and suffer porosity in the etch resist and consequent discontinuities in the copper. Get yourself kitted out with some photographic technology. Do you detect a whiff of the zeal of the newly converted? That's me!

All I used for exposure was a UV-rich florescent tube intended for aquaria and an old picture frame. I'll work it all up into a "proper" light box eventually!

I didn't follow Quinn's advice about etching - my bubble-tank full of ferric chloride has never been a problem.

Incidentally, the PCB in question is a development environment for the MTCLogic controller - it replaces (by plugging into its DIL socket) the 12F657 PIC with a richer processor, with extra I/O and the luxury of a CCP module - just right for PWM applications...

As you see, there's MIDI input and output, an ICSP interface (here seen with an FCC68 adapter going to the ICD2, but equally at home plugged directly into my PICkit2), a couple extra analog inputs (by which system parameters can be adjusted using the prsets) and 4 digital inputs (to select options). As you gather, there are lots of exciting developments in hand on the Leslie controller front!

Incidentally, I like the way our American cousins say "a couple extra analog inputs...", as distinct from the English equivalent "a couple OF extra analog inputs...".

Do yourself a favour - get yourself down to Blondihacks for some well crafted, witty American writing surrounding some interesting and educational projects.

Do yourself another favour - ignore any previous advice seen on these pages advocating toner transfer.

Anyone want a knackered laminator?
...-.- de m0xpd

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