[sdiy] making PCBs, what's your method?

[Theo]

For me it depends on complexity and number of boards.
I used to do up to 30x16 cm double sided boards using 10mil traces (8mil
between pins of a soic) at home.
If you film is good and you use a (spray) etching machine this works.
However drilling all those holes is a pain in the but.
And not having though plated holes is a major pain in the but.
Now I just sent complex stuff to a PCB house. This saves a lot of trouble
except that it takes 2 weeks before the PCBs are ready.

However for small boards especially single sided stuff I still cook my own.
For home made I like to use 15 mil or wider tracks, this just makes things
less critical.
I use photo sensitive PCBs.
For the film I use plain paper from a laser printer, after printing I spray
the paper with synthetic lacquer.
This makes the paper translucent. Contrast of this "film" is quite
reasonable.
At first I used 2 to 3 minutes exposure time. But then I forgot to turn the
exposure unit off and found that 20 minutes worked even better :)
I still use the spray machine, but for the kind of boards I do now a plastic
bin in hot water would be good enough.

Unless you need the PCBs fast and are willing to invest in a exposure unit,
etching machine and miniature drill-stand, my advice would be to let someone
else make the PCB for you.
But if you plan to do simple boards, then a cheap miniature drill, a mini
solarium from a dump sale and some plastic bins may be all you need.

Making your film with a inkjet printer also works, but the "lines" of the
printer might be visible on the film. A work around could be to photo copy
the print from the inkjet. Didn't try this...

Some other tricks of the trade:

1) Wash the pcb with mild soap after exposure and before developing. This
gets rid of residue from the adhesive of the protecting film, resulting in
better development of the board. It's easy to scratch the photo lacquer, rub
with your fingers while washing, not with a kitchen brush.

2) Contra common believe, developer can be stored and used for months. Just
keep cool and closed from air. However the temperature while developing
should not get too low. 22C to 25C is about right. Under say, 20C results
get bad. When the developer gets older you may have to raise the temperature
a bit.
Most of the year room temp at my place is around 17C, so I heat the
developer "au bain Marie" and take bin with the developer in and out of the
hot water depending on how quickly things go.


Have fun.
Theo



----- Original Message -----
From: Charles Brodeur <orange_juice_man_returns at yahoo.com>
To: <synth-diy at dropmix.xs4all.nl>
Sent: Saturday, July 17, 2004 6:56 PM
Subject: [sdiy] making PCBs, what's your method?


> Hello all,
>  I want to start doing my projects on printed circuit boards (as
> opposed to perfboard), for a number of reasons. I'm still studying the
> different methods and products. I would liek to get some feedback from
> this group on how they make their boards. Any help would be greatly
> appreciated. Thanks.
>
> -Charles Brodeur
>
>
>
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