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Sunday, 18 November 2012


I need to look up this and see what it does. Cool that you're doing your own boards, how do you make yours? I should soon be able to start building again and making my own boards is something I'd like to try, maybe even do on a regular basis.


I don't actually do my own board fab... not since I was a teenager, and certainly not for 4-layer boards such as this one. There are home etching kits that use laser-printed masks and are OK for coarse-featured, single-sided boards, and maybe 2-sided boards if you're very careful, but I haven't tried them - and the ferric chloride etchant doesn't work all that well. (Ammonium persulphate used to work very well indeed... until the mercuric chloride "activator" was banned. Without the mercury, it doesn't work at all.)

I design my boards in EAGLE (http://www.cadsoftusa.com/); I have the full-up professional version, which is great for small-business use, but for hobby purposes you'd probably want one of the downmarket editions.

Another option, popular with the open-hardware crowd, is KiCad (http://www.kicad-pcb.org/), which is free, but I haven't tried using it in several years and don't know what its current capabilities are nor what the UI looks like.

Anyway, once the board is all designed, I generate Gerber files and send them off to a fab house - there are several I use; the budget ones I've tried are BatchPCB (https://www.batchpcb.com/), which made the radio boards and most of my other summer gadgets, and OSH Park (http://oshpark.com/), which I've used once so far, getting a small 4-layer board done in 2 weeks (when the promised time was 6-7 weeks). Before the year is out, I expect to try one of the Eastasian* "10 copies of your board for 10 bucks, if you keep it down to 2 layers and under 5 x 5 cm" deals and see how that goes.

Using a commercial fab operation isn't as satisfying as doing the whole thing yourself, but it does get fairly repeatable boards with fine features, solder mask, silkscreened legends, plated-through holes, and suchlike niceties; in the SMD era, those are really useful things to have.

For SMT assembly, I'm mainly goobering solder paste onto and vaguely around the pads with a syringe and blunt needle, placing the parts with tweezers, and applying hot air (with a second-hand Hakko hot-air rework station) until the solder melts... and then, as needed, reheating selected parts and pushing them around with the tweezers to get them located properly, when surface tension has failed. I plan to start using solder stencils soon (to be the subject of a post, sometime after Beethoven's birthday), which should allow me to get a consistent layer of paste just where it belongs, and reduce the tendency of small parts to float around. I'm also thinking of building a benchtop reflow oven, to apply the correct hot-air profile somewhat more uniformly and avoid blown-around components and/or smoked boards.

* I forget; has Oceanea always been at war with Eastasia this week?

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