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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