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Drilling before exposing, & how long is it photosensitive?

2003-12-26 by sciciora

I just tried drilling a PCB before exposing it, and it didn't seem
like a better method. Spinning carbide drills at 30k rpm, the green
photosensitive coating flaked off near the holes. Just like sheering
the boards before exposing them. So, I think for the near future,
I'll expose, develop, etch, _then_ drill.

Does anyone know for how long they are photosensitive? Are they
still sensitive after develping? Do I have to etch in the dark?

Thanks!

- Steven Ciciora

Re: [Homebrew_PCBs] Drilling before exposing, & how long is it photosensitive?

2003-12-26 by Leon Heller

----- Original Message -----
From: "sciciora" <ciciora@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Friday, December 26, 2003 7:53 PM
Subject: [Homebrew_PCBs] Drilling before exposing, & how long is it
photosensitive?

> I just tried drilling a PCB before exposing it, and it didn't seem
> like a better method. Spinning carbide drills at 30k rpm, the green
> photosensitive coating flaked off near the holes. Just like sheering
> the boards before exposing them. So, I think for the near future,
> I'll expose, develop, etch, _then_ drill.
>
> Does anyone know for how long they are photosensitive?

I find that the resist seems to go off after about six months. I just buy a
couple of sheets of the pre-sensitised material at a time, so that it's
always reasonably fresh.

Are they
> still sensitive after develping?

It's probably a good idea to etch them fairly soon.

Do I have to etch in the dark?

Not for the ordinary stuff that is available.

Leon
--
Leon Heller, G1HSM
Email: aqzf13@...
My low-cost Philips LPC210x ARM development system:
http://www.geocities.com/leon_heller/lpc2104.html

Re: Drilling before exposing, & how long is it photosensitive?

2003-12-27 by Ted Inoue

I found: expose, develop, drill, etch worked best for me. When I
drilled after etching, I always seemed to screw up some pads.
Undoubtedly I was using too low an RPM or inadequate bits. However, I
never had problems drilling before etching. Gave much more room for
error.

-tdi

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--- In Homebrew_PCBs@yahoogroups.com, "sciciora" <ciciora@C...> wrote:
> I just tried drilling a PCB before exposing it, and it didn't seem
> like a better method. Spinning carbide drills at 30k rpm, the green
> photosensitive coating flaked off near the holes. Just like
sheering
> the boards before exposing them. So, I think for the near future,
> I'll expose, develop, etch, _then_ drill.
>
> Does anyone know for how long they are photosensitive? Are they
> still sensitive after develping? Do I have to etch in the dark?
>
> Thanks!
>
> - Steven Ciciora