Hi Folks
I was guided here from the 1-Wire weather list[1], so I can stop posting
off-topic stuff there about board fabrication ;-)
Just by way of introduction, I'm a freelance web applications developer
(Perl, MySQL, a little PHP, somewhat less C) and general technology
consultant, having spent many years in IT/network/comms management in an
engineering multinational.
I have done hobby electronics on and off, in a rather half-hearted way,
since my early teens. My earliest days were spent working with
Veroboard which, in hindsight, seems to require more effort to plan,
assemble and debug than does making up a PCB. First attempts at PCB
fabrication were using a rub-down 'Letraset' system back in the early
1990s. I lost interest in this (too much like Hard Work) and only again
started on PCB fabrication about 7 years ago, when I moved to Australia.
This time around, I had the freeware version of Cadsoft's Eagle, running
on my Linux laptop. I experimented with printing using both laser and
inkjet printers, onto OHP transparency film. (I actually found that the
laser printer with the inkjet film seemed to produce the best results.)
I built myself a UV exposure box using an old file card drawer lined
with aluminium foil, a pair of UVB tubes and ballast, covered by a sheet
of thin glass, which sits on top of the rails that used to hold the file
dividers. This assembly is controlled by the digital timer from a
deceased microwave oven. (It even says "enjoy your meal" at the end of
the exposure, which I still find amusing, in a sad way.)
Transparencies are contact printed with the above onto Kinsten
pre-sensitised board and developed using sodium metasilicate. (I gave
up with caustic soda - often as not it would remove ALL the etch-resist,
exposed or not.)
I do my etching using a rocker dish (actually an old Ferrero Rocher box)
and ammonium persulphate. Having to use thrice-loathsome ferric
chloride near put me off for life - ammonium persulphate has been my
saviour.
After three or four years of being too busy/sick/otherwise engaged, I
find myself with a few projects requiring PCBs[2], so I am getting ready
to go again. I was going to treat myself to a bubble etch tank but it
seems that both my sources (at least sources charging sensible prices)
are out of stock for quite some time. I was rather looking forward to
the heated tank so that I wouldn't have to fish the PCB out half-way and
put the solution in the microwave - but looks like I'll just have to
carry on like that for a while longer.
The one thing that I have acquired this time round is the not-for-profit
'Standard' version of Eagle. Getting that extra board space is well
worth it, in my mind. Still waiting for the manuals, which were out of
stock when I ordered.
Holes are something I hate; I have been trying to use carbide drills in
a cheap-and-nasty, full-sized drill press. All I will say is that it is
very expensive in drills. Last week, I took delivery of a Dremel and
press - hopefully this process should get a bit easier for me. (I still
prefer larger SMDs though - anything that saves drilling is worth it!)
Issue that I will be needing to address:
∗ I'm still a little shaky when it comes to double-side boards; I have
yet to perfect a method of aligning top and bottom films in a way that
suits a) my UV exposure box and b) my shaky hands. If I can get away
with single-sided and a few jumpers, I generally will.
∗ Tinning boards. Tinning solution is just too expensive for what I am
doing. Hand-tinning with solder doesn't seem to suit smaller components.
∗ Making vias.
∗ Mounting SMDs with central pads (in addition to the side pads).
Haven't actually tried this yet, will probably just run a big pad end-to
end of the device, poking out either end, and put the iron on one of the
ends.
∗ Mounting SMDs with lots of small pins. At the moment, I'm just trying
to avoid them altogether. I've read about the toaster oven technique -
still sounds pretty tricky to me.
The above are challenges that I will be facing when I get back into it,
but am not worrying about unduly at the moment. When it comes to it, I
will ferret through stuff on the Group and tap into your combined wisdom...
Cheers
M
References
----------
1 - <
http://www.buoy.com/mailman/listinfo/weather>
2 - 1-Wire barometer, Nixie clock, isolation/level conversion boards for
GPS modules, (wired) remote control board for outside lighting, modified
quartz clocks that will read Tropical and Lunar years - and various
other stuff.
--
Matthew Smith
Smiffytech - Technology Consulting & Web Application Development
Business:
http://www.smiffytech.com/Personal:
http://www.smiffysplace.com/LinkedIn:
http://www.linkedin.com/in/smiffy