Werner,

What if the "finished hole diameter after plating" is how it is worded
on the drill drawing?  Can the fab house adjust the drill size dependant
on the amount of copper that will be plated into the holes?  We run 2, 4
and 6 ounce boards and our fab house will drill a larger hole to plate
more copper in the hole.  The logic being that if you are running 4
ounce copper and only having 1/4 or 1/2 ounce copper as a via or plated
hole won't cut the current load transfer from side to side.  

Phil  

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Werner Engelmaier
Sent: Wednesday, April 26, 2006 3:35 PM
To: [log in to unmask]
Subject: Re: [TN] Drill specification

Hi Jeff,
You say: "...the PCB house ... may opt to alter the drill size based on 
several factors -size, geometry, aspect ratio, etc."
This assumes, that the PCB house knows something about the operational
use of 
these PCBs-rarely the case, or that it knows more than the designer what
is 
needed-too often the case.
However, for knowledgeable designers that design a high-reliability
product, 
particularly for severe operational environments, and who know the 
capabilities of the PCB house, it is much better to specify the drilled
hole diameter-
again all too often not the case.

Werner

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