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22 April 2011

PCB Fabrication - DIY or Commercial Services?

(At the time of writing it is Good Friday, so a Biblical start seemed appropriate)

In the beginning...

Was tagstrip and perfboard, which begat Veroboard, and it was good. Then the 1980s came along, and lo! Hobbyists didst discover copper clad and ferric chloride etchant, and there was much rejoicing.

I seem to remember my first printed circuit board used some of my mum's nail polish. Dalo pens then arrived in my toolbox, along with rub-down transfers, and my PCBs got a bit fancier.

I think it was some time around 1990 that I graduated to photo-etch. This meant I could use proper CAD tools and high resolution printed transparencies. An entire new world had suddenly opened up to me! With surface mount devices starting to become popular, it meant that I could lash up relatively quick prototypes without having to post a floppy to a commercial PCB house (even in the late 90s many still didn't use the Internet), wait for them to do whatever they do, and eventually post me the completed board complete with an invoice that would make Bill Gates wince.

Of course, self-made PCBs don't have through-plating (although in most instances there are work-arounds for this) and cannot normally be multi-layer, so that does limit what you can do, but for 1-off prototypes that don't have to be optimised for size and price (and indeed how they look) then self-made PCBs had a lot going for them.

Another decade went by, the 21st century arrived and things moved on again. Eastern Europe and China started to increase their influence and using commercial PCB houses not only became financially viable, but effectively relegated the UV exposure unit and bubble etcher to the store room. Then the world economy fell off a cliff, taking the exchange rates with it. PCB prototyping services once again started to look painfully expensive.

So, the market is changing once again. This time, the concept that is changing things, is that rather than selecting from the 200 dishes available on the restaurant menu, you can have a burger, or a quarter pounder burger. Companies like Itead are starting to fill that huge gap at the bottom of the market . In terms of bangs-per-buck they are great, but there obviously have to be compromises and limitations.

Itead and SeeedStudio charge a fixed fee, for which you get 5x5cm or 10x10cm of dual layer, green solder mask to play with, and you receive 10 PCBs, 5 of which are tested. Personally, I would prefer just 1 tested PCB, but the actual production process costs peanuts, the money goes in set-up costs. It is thought that these companies use spare board capacity on large panels that are already being used for other PCBs. Places like DorkBot create efficiency by waiting until they have enough to make up a big batch run, hence the lack of selection of finishes.

These processes don't have great tolerance (at $20 I wouldn't expect it anyway) and the size limitation can be a problem, but what are the options? Jon Chandler over at Digital-DIY has compiled an excellent run-down of the various PCB suppliers here

Having run my requirements through some of the web sites, there is a bit of a jump between the ultra low budget suppliers and the mainstream. For those times when 10x10cm isn't enough, and a fortnight turnaround is too long, I think I am going to give serious to consideration to dusting off the bubble etch tank and going back to making my own.

Interestingly, Itead are now doing PCBs at 5x15cm and 10x15cm. Sadly, that's just 1cm short of Eurocard size, but nevertheless it is a good amount of PCB real estate.

PCB Houses

    5x5cm (10 pcs) US$20 +$4 standard postage
    10x10cm (10 pcs) US$40 +$5 standard postage

    5x5cm (10 pcs) $12
    10x10cm (10 pcs) $28
Also now offering:
    5x15cm (10 pcs) $38
    10x15cm (5 pcs) $48



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