Homebrew PCBs

Hi Adam

>What small copper wires are you talking about ?

Good question :) That's what someone told me they are used for. Well,
I used the station during some runs without those bags and could not
see a difference in the results. There are also no visible wires or
such, so maybe they surf another purpose - hell, most likely the one
you describe.

I also use brigthner and the anodes also became this dark "patina"
which I was told is good/important for the process. I do have the bags
mounted and since I have them I never felt motivated to try without.
Might be that I under estimate their effect. I must say though that I
don't use air agitation in my tanks.

Markus

> I thought 
>the anode and cathode (PCB) are well separated so there 
>cannot be any possibility of contact.
>
>Anode bags are very often used in many types of plating 
>baths. I know that for bright acid copper sulfate plating 
>the bags are used to inhibit solution flow around the anode 
>surface and preserve the black (or dark brown) film that 
>normally forms. I am using Macuspec 9241 brightener from 
>Macdermid and the data sheet stresses that anode bags must 
>be used. Well, since it didn't give any reasons why anode 
>bags must be used I didn't believe it and so I didn't use 
>any. Hmmm, yep, I soon learned why the bags are important. 
>The black film on anodes that's formed during plating is 
>very fragile and may easily strip off with air bubble 
>agitation. In these conditions the film is continuously 
>forming and releasing into the solution. After plating just 
>one PCB I could see enough precipitate produced that the 
>bottom of the tank was covered with a dark powder. I 
>installed the proper anode bags and it solved the problem 
>totally. I later read in plating books that the anode film 
>in bright acid copper plating is important for correct 
>dissolution of the anode.
>
>Interesting , originally when I was plating with no 
>additives (200g/L H2S04 , 75g/L CuS04.5H20), the anodes 
>would not form this dark brown film, and would be more 
>stable. But there were still some anode film and small 
>amount of copper powder would release into the bath.
>
>I also found that plating with low acid high copper
>(75g/L H2S04 , 200g/L CuS04.5H20) then anodes dissolve much 
>cleaner and remain pink, but of course this bath has 
>terrible plating uniformity and is why no one uses it to 
>plate PCBs.
>
>The anode bags are normally polypropylene fabric, that looks 
>very much like white denim. You could probably use 2 or 3 
>layers of 100% polyester fabric. I would first put it in 
>some 200g/L sulfuric acid for a week so that any thing in it 
>that might react with the acid will do so before in goes 
>into your plating tank.
>
>
>
>
>Be sure to visit the group home and check for new Bookmarks and files:
>http://groups.yahoo.com/group/Homebrew_PCBs
>
>To unsubscribe from this group, send an email to:
>Homebrew_PCBs-unsubscribe@yahoogroups.com
>
> 
>
>Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/ 
>