Pete
I would suggest that you are not removing all the resist when you develop your board, they need longer and a good spray rinse. I get similar islands due to finger grease when I use toner transfer. I remove the board, rinse and scratch at the stubborn area with a blade, then back in the etch.
Malcolm
I don't suffer from insanity I enjoy it!
Mene, mene, tekel, upharsin
The writing is on the wall.
________________________________
From: Pete <
pete@...>
To:
Homebrew_PCBs@yahoogroups.com Sent: Sunday, March 4, 2012 10:45 PM
Subject: [Homebrew_PCBs] Etching problem - Help please
Hi,
I am trying to etch a small PCB and finding it etches unevenly leaving a small area of copper which is stubborn to remove. Just leaving in the etchant for longer starts to undermine the tracks that etched ok.
Here's what I do:
1. Print the track layout on inkjet printer using transparency film.
2. Lay the film ink side down onto a 3" x 2" single sided photo resist coated copper clad board (cut from a Maplin Size 4 ref KU14)
3. Expose in a home made LED Light box for 4 minutes
4. Develop in Universal Developer (PBD2) Sodium Metasilicate for 1 minute.
5. Etch in Ferric Chloride track side down for 16 mins, agitating every minute or so.
The result is most of the copper dissolves after 10 mins then it leaves a small area which refuses to disappear after waiting a further 5 minutes.
A photo of the etched board is here
https://picasaweb.google.com/109391378120539635298On close inspection of the board the unetched copper is left as stripes. So I am wondering if this is a board problem or the process.
Any help is appreciated.
Thanks
Pete
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