On Thursday 22 May 2003 12:17, Marty Grove scribbled:
> Hello Neal.
>
> I'm assuming that you are asking how clean the lines are after etch (as
> opposed to how clean the etchant is after you have etched some boards). I
Yes, exactly.
> you are using the "swish the board around in the solution" method, I cannot
> say how the lines will turn out (I have practically no experience with that
> method of etching). I would imagine they would be okay down to a certain
> width, but at some point I would think that the "swish" method would
> produce ragged, uneven, and/or broken circuits for a number of reasons.
> poor chemistry distribution, chemistry out of range (out of specification),
> chemistry getting up-under the resist, etc.
I had been using a flat tray, with the board sitting flat on it, and I'd
heat/stir with a small hairdryer aimed so that the solution swirls in
circles. And I flip the board every few minutes. Got better results than
shaking manually every few minutes. Recently picked up an air pump for my
new PCB "system" so I expect better results.
> Our equipment was applying the chemistry to the board by spray. If all of
> the nozzles were properly clean, and the oscillation system that sprayed
> the chemistry was operating correctly (and the chemistry was in
> specification), the application of etchant was very evenly applied to the
> board(s). The impact of the spray on the board (the impingement) speeds up
> the etching process considerably. When using a high quality photo-resist
> and everything was working properly (including artwork, imaging, applying
> the resist, and developing), we were able to achieve line spaces and widths
> as small as 5 to 3 mil's with typically nice straight lines, and the
Interesting you mention spray. I was looking into this for rinsing my boards
(thinking ouf using spray nozzles from a car windshield washer) and thought a
about it for etchant, but decided to choose an etchant before investigating
if the etchant would corrode/damage the pump. I would ask what spray system
you use, but my guess is that anything industry-specific will be $$$.
> industry is currently trying to get even tighter tolerances. I once read
> that in another 8 to 10 years, the industry wants to consistently achieve 1
> mil lines and spaces. <whew>
Heard similar as well. I went to a PCB trade show late last year, and saw
some 3-mil boards, and 40-layer boards .... holy #$%∗&#@∗ !!!
Luckily I only need 10 mil for now, but need to get it consistent. I'd like
to make my system a "science" rather than an "art".
> I'm curious as to whether anyone has built their own home spray etcher (a
> small bench-top machine)? It would be fairly easy (albeit the time and
> components required).
Someday.
> Cheers to you too! I'm guessing you're in the U.K. I'll be visiting the
> U.K. in about two months. Although I've made several business trips over
> there, this will be my first vacation (holiday). I'm looking forward to
> it!
>
>
>
> Marty
>
Actually, I'm in the US, but not sure where I got cheers from. I lived in
London for a year a few years ago, but I was using cheers before that. And I
doubt that I got it from my original home in the Caribbean.
Cheers,
-Neil.