Not lemon juice, but citric acid was a common antitarnish when stripping print and etch innerlayers in caustic. Amines work better as an antitarnish, but they form complexes with dissolved copper and makes waste treatment very expensive. It reacts with the copper and forms a layer that resists oxidation reasonably well. After stripping these boards went through a black or red oxide treatment to enhance adhesion in multilayer boards. I seem to remember one or two shops that used citric acid in a chem clean line and I don't remember any adhesion problems with the photoresist.
----- Original Message -----
From: Tom
To: Homebrew_PCBs@yahoogroups.com
Sent: Friday, December 03, 2004 2:03 PM
Subject: [Homebrew_PCBs] Cleaning copper with lemon juice
Hi there, I'm new to etching PCBs and to the group.
Faced with some pretty tarnished copper clad I took the same approach
that I use for cleaning copper bottomed cookware, namely lemon juice
and a scotchbrite pad. Cleaned up all the oxidation very easily! Not
knowing if the lemon juice would leave any residue behind I finished
off by wiping the board with rubbing alchohol.
Just wondering if anyone else has tried lemon juice and/or has any
thoughts on how suitable it is for cleaning copper clad pcb material.
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