Thank you all for the numerous insights
offered on the issue of circumferential voids that we observed in our 10 mil
hole FR4 panels with aspect ratio of 10. I forgot to mention in my earlier note
that these voids were invariably in the center of the plated barrel. Based
on the analysis of the cross section and auditing of the processes, it
appears that it is either a drill parameter (including debris) issue or trapped
air bubble during copper/tin plating.
I would like some advice on panel agitation to
remove trapped air bubbles.
In order to remove air bubbles, I should do a good
agitation of the panels during plating.
1. At what tank(s) (acid clean or acid dip
or acid Cu or tin?) should I install the agitator? (The hole graphitization
line has ultrasonic vibration during several key stages, and it is unlikely
that graphitization did not occur).
2. Who supplies suitable vibrators for this type of
job?
I would deeply appreciate any and all
help.
Thanks.
Sandy