I've heard that the general rule limiting blind vias is a 1:1 aspect 
     ratio.  You are at it with the 16 mil holes & 16 mil depth.  It seems 
     like you are doing the right things (i.e. vibration, etc.) so I'm not 
     sure what else to suggest.
     
     
     MB
_____________________________ Reply Separator _________________________________
Subject: Blind vias & fine lines
Author:  [log in to unmask] at SMTPLINK-HADCO
Date:    2/12/97 10:07 PM


Techneters,
  Can anyone help? I am having two problem areas:
     
 1) Blind via holes 16 mil diameter 16 mil deep contacting with 4 
inner layers. I cannot always plate copper into all holes. If I do copper 
plate them I cannot tin plate all the holes. I have vibrators on the 
cathode movement frame and a giant to clout the fight bars with a 2 pound 
hammer. Is there anything else I can do?!?
     
 2) Circuits with 2 mil track and gaps. The finish required is 
electroless nickel/immersion gold. How can this be done without causing 
the tracks to short with nickel spikes?
     
  Thanks in advance,
   Roger Hammond
     
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