Nagaraj
As Warner mentioned plating is another issue you should consider with small holes. I presented a paper at IPC several years ago that mathematical examined the influence of hole size on the plating distribution in the barrel. An important result was that the ration of copper thickness at the top of the barrel to the center is a function of of the ratio (D/AR) squared. Obviously, small holes can cause large yield issues.
----- Original Message -----
From: Shanmugam, Nagaraj<mailto:[log in to unmask]>
To: [log in to unmask]<mailto:[log in to unmask]>
Sent: Thursday, February 11, 2010 1:18 AM
Subject: Re: [TN] High Aspect ratio issues
thanks for the answers.. Still I am looking for more information.
Say if my Aspect ratio is 12( assuming this is max capability of the FAB
house).
By Definition ; Aspect ratio = board thickness/ min drill size.
Can the Fab house able to make it drill with different board materials
like FR4, Teflon, Rogers - is the material strength of Prepregs not
considered?
Thanks,
Nagaraj
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Werner Engelmaier
Sent: Wednesday, February 10, 2010 9:03 PM
To: [log in to unmask]<mailto:[log in to unmask]>
Subject: Re: [TN] High Aspect ratio issues
Hi Nagaraj,
Indeed, drill bit yield/ hole wall quality goes down with smaller drill
diameters. Typically, your drill diameters are driven by the density of
your design.
Smaller holes are also more difficult to plate good copper into.
Werner
-----Original Message-----
From: Shanmugam, Nagaraj <[log in to unmask]<mailto:[log in to unmask]>>
To: [log in to unmask]<mailto:[log in to unmask]>
Sent: Wed, Feb 10, 2010 5:51 am
Subject: [TN] High Aspect ratio issues
Technetters:
I am working on the drill size selection I choose them based on
acceptable aspect ration by Fab house.
the reason being(to my knowledge) the drill bit yield reduces if we go
for higher aspect ratio -
Wondering what other cause prevent to go for high aspect ratio.
TIA,
Nagaraj
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