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Date: | Wed, 23 Apr 1997 13:53:45 -0500 |
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Joef,
I used to have the same "inconsistencies" when I worked for a military shop. I found that by baking panels after drilling reduced the variation of the etchback. As for the gouging, this is probably drill quality. The baking after drill seemed to provide a more even "cure" of the laminate and the epoxy residue that was melted due to the heat generated by the drill. I don't know if you bake after drill but if you don't it is something to try.
Ed Cosper
Graphic Electronics,
Tulsa OK
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From: joef[SMTP:[log in to unmask]]
Sent: Friday, April 18, 1997 12:43 PM
To: [log in to unmask]
Subject: FAB: Etchback & NaMnO4 bath life
How does one determine when (if) a sodium permanganate bath is spent??
Problem: Our previously calibrated [Mil-class] etchback cycles for
various epoxies are now requiring 2-3 cycles; sections show too much
variability from .0005"-.0013"; lots of "gouging" into glass-rich
regions with lowest etchback at the copper interface.
Conditions are as follows:
- All chemistries (solvent swell, permanganate, glass etch) are within
vendor specs.
- NaOH normality: 1.2-1.3
- NaMnO4 concentration: 60-70 g/l
- MnO3 conc. 9 -12 g/l
- S.G.: 1.13
- 180 gal tank with 500A continuous electrolytic regeneration
- swell temp: 175 degF, permanganate temp: 185 degF
Vendor's tech service won't touch this one - if you want to do
chemical etchback "you're on your own"...
Any ideas out there before I dump this bath?
Thanks, Joe Felts
PC World, Toronto
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