Homebrew PCBs

Its a dry film negative acting materal. Please see
http://www.kepro.com/cprecut.htm for details.

How do you apply your own dryfilm, do you have a laminator, and if so how
big.. I can only buy it in huge rolls, and I'm worried about its shelf life
expiring. Or are you indicating that the shelf life starts once its applied?

I like the idea of your concept of appying the film one day and processing
the boards the same day. It would alleviate lots of problems.

Thanks
Ron
----- Original Message -----
From: "Adam Seychell" <adam_seychell@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Tuesday, January 21, 2003 7:29 PM
Subject: Re: [Homebrew_PCBs] Ferric Chloride


> I once tried to built a bubble agitated developer but found the
> bubbles could not reliably remove the dry-film from the board. In the
> end I found best results using something similar to what Tom described
>   with the brush.
> I also agree with Tom that you could be suffering dry-film residue,
> which is an invisible scum left behind after developing and is
> impermeable to the etchant. I am only familiar with negative dryfilm,
> are you sure the boards are this film or is it positive pre coated PCB
> material often sold at hobby shops ?
> The way to check if you have a residue problem is after about 1 minute
> in the etchant you should see the copper turn matte pink. If it still
> shows shinny scrubbing marks then its dry-film scum. This happens when
> the dry film has been on the board longer than a few weeks. I have
> some stuff that's over a year old and is a problem to develop. The way
> to develop these boards is to extend the developing time (brushing
> over the board for upto 3 minutes). I put it in the etcher and if the
> copper doesn't become matte pink over the entire board then I take it
> back to the developer and brush over it for another minute. The second
> pass usually gets it all. I apply my own dry-film these days and
> develop the board the same day so I never have residue problems.
>
> Ron Amundson wrote:
> > I'll give the brush solution a try tomorrow. As I purchase my boards pre
> > laminated with dry film, I'm sure cleanliness is not the issue, but
> > underdeveloped dry film resist probably is.
> >
> > I do my developing in a tray with agitation too, looks like I'll need to
set
> > up a simple to do spraying.
> >
> > Thanks
> > Ron
> > ----- Original Message -----
> > From: <twb8899@...>
> > To: <Homebrew_PCBs@yahoogroups.com>
> > Sent: Tuesday, January 21, 2003 10:09 AM
> > Subject: [Homebrew_PCBs] Ferric Chloride
> >
> >
> >
> >>Ron mentioned in a previous post that he was getting uneven etching
> >>with ferric chloride. When this happens it's usually due to under
> >>development of the photoresist. I am assuming that dry film resist is
> >>being used. The best way to develop dry film is with a spray tank set
> >>up with a 1% sodium carbonate (soda ash)solution. Find out how long
> >>it takes to "break through" to bare copper and then go about that
> >>same time again for final developing. For example if the bare copper
> >>shows up in 1 minute then continue the process for an additional 1
> >>minute and then you can etch.
> >>
> >>Another good idea is to make up a tray of weak etchant from a couple
> >>of ounces of ferric chloride in one gallon of water. If a developed
> >>board is put into this solution for a minute or so the areas that are
> >>fully developed will turn a dark color and the under developed spots
> >>will show bright copper. This will amaze you the first time you see
> >>it because the panel still has some dry film "scum" on the surface
> >>when the board looked like it was fully developed. If the board has
> >>scum, just put back in the developer for a bit longer and try again.
> >>When a uniform dark color appears across the entire surface you will
> >>be ready for final etching and obtain excellent results.
> >>
> >>If developemnt is being done in a tray, try using a very soft
> >>bristled brush to gently work the solution across the board surface.
> >>This will help to break through any scum on the board. The bottom
> >>line is that this scum must be removed or you will never obtain
> >>uniform etching. Hope this idea helps out.
> >>
> >>Tom
> >>
> >>
> >>
> >>
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> >>
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> >
> >
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