First of all, the overall board thickness: consult your PCB manufacturer on his aspect ration limit: it can be anywhere between 1:7 to 1:14. The minimal hole diameter should not be less than the PCB depth divided by the aspect ration.
 
After this, consider the current capacity of every via: 0.01 mils via can carry 0.4 A; 0.012" via can carry 0.5A.
 
Third, consider signal integrity and skin effect. The difference should not be big in most cases, but RF boards and very high frequency digital boards may be affected.
 

Regards

Ofer Cohen

Quality Assurance Manager

Seabridge Ltd.

-----Original Message-----
From: Genny Gibbard [mailto:[log in to unmask]]
Sent: Wednesday, March 05, 2003 18:42
To: [log in to unmask]
Subject: [TN] info requested

We have an 8 layer board that we need to turn into a 10 layer board.  We have adjusted our layer stackup to accommodate the extra layers without any significant change in overall thickness, but we are still having trouble fitting everything we need onto the layout. 
What are the implications of going from a minimum .012" via to a 0.010" via?  What do we need to take into consideration?  What things might be critical to spec to the board fab house?

Genny Gibbard (mailto:[log in to unmask])

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