Homebrew PCBs

Hullo again all,, I am having a bit of a problem with figuring out 
how ,if anyway, one is able to do a touch up when making a transfer 
based on the UV developer method-- I realize that it is likely that 
there is no help there due to the nature of the process itself, but am 
hoping the assumption is wrong?

 I'm not in any trouble here, just curious-- I have way more experience 
with doing the plain-jane TT pcbs's but have most of the equip to do 
both methods (except for a good light source and the right transparency 
materials).

 Also, if there is no method to amend the mistake after making a foul-
up, how easy is it to remove the resulting transfer and just use the 
ol' fashion TT method thereafter? what is the best solvent to use for 
removal?

 Thanks in advance for the help, jd

----- Original Message ----- 

From: "timbomcnuckle" <jaydag71@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Tuesday, August 14, 2007 7:06 PM
Subject: [Homebrew_PCBs] UV developer re-do's....how to??


> Hullo again all,, I am having a bit of a problem with figuring out
> how ,if anyway, one is able to do a touch up when making a transfer
> based on the UV developer method-- I realize that it is likely that
> there is no help there due to the nature of the process itself, but am
> hoping the assumption is wrong?

How will you tell if the resist needs touching up?

>
> I'm not in any trouble here, just curious-- I have way more experience
> with doing the plain-jane TT pcbs's but have most of the equip to do
> both methods (except for a good light source and the right transparency
> materials).
>
> Also, if there is no method to amend the mistake after making a foul-
> up, how easy is it to remove the resulting transfer and just use the
> ol' fashion TT method thereafter? what is the best solvent to use for
> removal?

Sodium hydroxide solution (stronger than that used for development) will 
remove the resist in a few minutes, or you could rub the board with a paper 
towel and IPA.

Leon

> How will you tell if the resist needs touching up?
> 
hhhmmmm,, I dunno if I understand-- you mean how do I know if a 
mistake has been made after the developer? it would be obvious I 
assume once compared to the artwork. Things like creep, poorly filled 
areas, etc.(in most cases could be manually cirrected with additional 
re-touch work, but if not then...) A hypothetical problem that I 
assume would render the pcb unusable for developing thereafter,, 
correct? I mean to suggest that there are no re-dos for a 
presensitized PCB unless you have some UV sensitive material to 
spread back over the cleaned board? (I personally don't yet).

 What else can I use to get the resist off the PCB after development? 
I'm on a harsh budget so cannot go out and buy more chems than what I 
curentluy have on hand.

 Thanks in advance, Jd

--- In Homebrew_PCBs@yahoogroups.com, "Leon" <leon355@...> wrote:
>
> ----- Original Message ----- 
> From: "timbomcnuckle" <jaydag71@...>
> To: <Homebrew_PCBs@yahoogroups.com>
> Sent: Tuesday, August 14, 2007 7:06 PM
> Subject: [Homebrew_PCBs] UV developer re-do's....how to??
> 
> 
> > Hullo again all,, I am having a bit of a problem with figuring out
> > how ,if anyway, one is able to do a touch up when making a 
transfer
> > based on the UV developer method-- I realize that it is likely 
that
> > there is no help there due to the nature of the process itself, 
but am
> > hoping the assumption is wrong?
> 
> How will you tell if the resist needs touching up?
> 
> >
> > I'm not in any trouble here, just curious-- I have way more 
experience
> > with doing the plain-jane TT pcbs's but have most of the equip to 
do
> > both methods (except for a good light source and the right 
transparency
> > materials).
> >
> > Also, if there is no method to amend the mistake after making a 
foul-
> > up, how easy is it to remove the resulting transfer and just use 
the
> > ol' fashion TT method thereafter? what is the best solvent to use 
for
> > removal?
> 
> Sodium hydroxide solution (stronger than that used for development) 
will 
> remove the resist in a few minutes, or you could rub the board with 
a paper 

> towel and IPA.
> 
> Leon
>

----- Original Message ----- 

From: "timbomcnuckle" <jaydag71@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Wednesday, August 15, 2007 6:07 PM
Subject: [Homebrew_PCBs] Re: UV developer re-do's....how to??


>
>
>> How will you tell if the resist needs touching up?
>>
> hhhmmmm,, I dunno if I understand-- you mean how do I know if a
> mistake has been made after the developer? it would be obvious I
> assume once compared to the artwork. Things like creep, poorly filled
> areas, etc.(in most cases could be manually cirrected with additional
> re-touch work, but if not then...) A hypothetical problem that I
> assume would render the pcb unusable for developing thereafter,,
> correct? I mean to suggest that there are no re-dos for a
> presensitized PCB unless you have some UV sensitive material to
> spread back over the cleaned board? (I personally don't yet).

If your exposure and transparency are OK, and the transparency is in contact 
with the board, there shouldn't be any problems. If you do have problems 
with your process, they will rather extensive, and you won't be able to do 
much about them.


>
> What else can I use to get the resist off the PCB after development?
> I'm on a harsh budget so cannot go out and buy more chems than what I
> curentluy have on hand.

NaOh is cheap.

Leon
--
Leon Heller
Amateur radio call-sign  G1HSM
Yaesu FT-817ND transceiver
Suzuki SV1000S motorcycle
leon355@...
http://www.geocities.com/leon_heller