Archive of the former Yahoo!Groups mailing list: Homebrew PCBs

Hi,
I'm facing dry film tenting problems. It couldn't protect THP holes and tents start to break during developing. I did some googling and saw that this problem is known and according to Dupont technical articles, it is recommended to increase exposure duration to avoid tent break. I tried it and I saw great improvement.
Another recommendation was, to reduce roller pressure to avoid hole sharp edge cutting of the film. It is stated that pressure in the holes decreases after lamination and it sucks film (film is liquid during lamination) to the holes and because of that, sharp hole edges cut the film. This cut decreases film strength. Another advise was to decrease the lamination temperature. I also tested both, they helped but didn't solve the problem completely.

My second try was to use pattern plating method. I tried electroplated tin as a resist and ammonium persulfate as an etcher, it didn't act as an etch resist and etched away with copper.

Any ideas/suggestions or does anyone faced similar tenting problems?
Which etcher can be used for tin or nickel etch resist? Is there any practical formula for homebrewers?
I'll appreciate a lot on any guidance.
Thanks,

Volkan