Homebrew PCBs

I've been pondering methods to improve/hasten/detoxify homemade PCBs, and had a thought occur yesterday: bead blasting. has anybody tried this or seen it done?

There are numerous types of photosensitive laminate out there, including hardier varieties created specifically for blast-etching. The same goes for blasting media, which is available a wide range of hardnesses and bead/shot size and shape.
Of course, really high density, fine-pitch traces may be quite difficult to do, but that's about the only real drawback I have been able to see so far. There are even mini-tabletop blasting chambers (or you can just do it outside if you feel like constantly buying new media).

Another cool possible benefit is to use it to drill! You would probably need to do the drill-blasting before the trace-blasting, and would need a drill stencil (I'm thinking a brass or nylon mask like a solder stencil but for the holes) and a jig to hold the nozzle perpendicular to the board. Adhere the stencil to the board (so the blast media doesn't creep between) then, using a fine hard grit, blast the holes. Then peel off the mask, use the photoresist as usual and blast the copper.

I'm sure it would be fun to try if nothing else. :)

~flight

> I've been pondering methods to improve/hasten/detoxify homemade PCBs, and
had a
> thought occur yesterday: bead blasting. has anybody tried this or seen it
done?
> 
> There are numerous types of photosensitive laminate out there, including
hardier
> varieties created specifically for blast-etching. The same goes for
blasting media,
> which is available a wide range of hardnesses and bead/shot size and
shape.
> Of course, really high density, fine-pitch traces may be quite difficult
to do, but that's
> about the only real drawback I have been able to see so far. There are
even mini-
> tabletop blasting chambers (or you can just do it outside if you feel like
constantly
> buying new media).
> 
> Another cool possible benefit is to use it to drill! You would probably
need to do the
> drill-blasting before the trace-blasting, and would need a drill stencil
(I'm thinking a
> brass or nylon mask like a solder stencil but for the holes) and a jig to
hold the nozzle
> perpendicular to the board. Adhere the stencil to the board (so the blast
media doesn't
> creep between) then, using a fine hard grit, blast the holes. Then peel
off the mask,
> use the photoresist as usual and blast the copper.
> 
> I'm sure it would be fun to try if nothing else. :)


Why not a water jet?  :)

The media usually isn't that fine, and anything capable of wearing away the
copper layer, and FR4 would probably eat thru the stencil as well.

That's not to say it can't be done, but you're going to need better gear
than what the typically hobbyist has, such as very fine media, tiny nozzles
and very high pressure (blasting is typically done at 60-100 PSI).

Tony

At 02:04 AM 3/12/2009, you wrote:

>I've been pondering methods to improve/hasten/detoxify homemade 
>PCBs, and had a thought occur yesterday: bead blasting. has anybody 
>tried this or seen it done?

yes, i do art glass carving and have such equipment. bead blasters 
will not cut materials and are used to clean motor parts, etc. 
silicon carbide (sand) blasters will quickly cut brittle substrates 
like glass, ceramics, etc but will only surface etch metals. it would 
not cut through the copper foil, but likely would attack the fiber 
board. the mask for sand carving must be very aggressive to withstand 
the blast, typically plotter-cut vinyl or photosensitive resists. the 
air pressure for 'pressure pot' blasting is hardly ever over 30 psi 
while 'siphon' blasters use much higher pressure and air flow. also 
you must use a blast chamber/dust collection system to contain the 
dust or risk silicosis of the lungs. good thought, but won't hasten 
and has some toxic attributes.


William Alford

GI Motility Medical Research Page
http://alford.grimtrojan.com/ 

[Non-text portions of this message have been removed]

--- In Homebrew_PCBs@yahoogroups.com, William Alford <walford@...> wrote:
... 
> you must use a blast chamber/dust collection system to contain the 
> dust or risk silicosis of the lungs. good thought, but won't hasten 
> and has some toxic attributes.

I can't say enough to warn about silicosis. Tiny bits of sharp glass that you can't cough out, that slowly work their way through your lungs, scarring and hardening the tissue. Your body can't eject it, encapsulate it, or absorb it.

In many ways, worse than smoking because one early exposure will theoretically keep causing damage your entire life.

Steve Greenfield