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Date: | Tue, 24 Jul 2007 09:49:02 -0400 |
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Ralph
I presented a paper at IPC this spring on the variables which affect the
copper uniformity in PTHs. You can probably get a copy by contacting Tom
Newton at IPC.
It is difficult for me to imagine a greater copper thickness causing the
barrel to become more susceptible to cracks. The thicker the copper the
lower the stress for a given load and consequently the lower the strain.
What may be going on is the uniformity of the copper which causes stress
concentrations and the ductility of the plated copper. As I mathematically
demonstrated in my paper, the current density used in plating has a strong
impact on these parameters. The thicker the board the greater the need for
low current density.
I would ask the supplier to measure the ductility of the plated copper for
several current densities and draw your own conclusions.
Best regards
Lee
J. Lee Parker, Ph.D.
JLP Consultants LLC
804 779 3389
----- Original Message -----
From: <[log in to unmask]>
To: <[log in to unmask]>; <[log in to unmask]>
Sent: Tuesday, July 24, 2007 9:00 AM
Subject: RE: [TN] Question on plated through holes general
Lee,
Do you also have any inromation about max Cu thickness in the PTH? In
the recent past we had some cracks and the min was ok but the max showed
values aroung .045mm. Our supplier said that the crack was caused due to
too thick copper. The crack location was on the top just below the Cu
ring.
Do you or anybody else has a suggestion how to handle or specify this?
Regards
Ralph
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Lee parker
Sent: Friday, July 20, 2007 10:42 PM
To: [log in to unmask]
Subject: Re: [TN] Question on plated through holes general
David
I always advise one mil or more in the PTH. Given the non-uniformity
often seen in the PTH I would also spec the drill quality and the ratio
of the copper at the top of the hole and in the center.
Best regards
Lee
J. Lee Parker, Ph.D.
JLP Consultants LLC
804 779 3389
----- Original Message -----
From: "David Harman" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Friday, July 20, 2007 4:23 PM
Subject: [TN] Question on plated through holes general
I have a quick question and our standard that we have maybe an older
one. We currently use the ANSI/IPC-A-600 Rev E
Page 70 Micro section:
There is a table describing copper plating thickness min, requirements
Class 1
Class 2 Class 3
Average Min Thickness .020mm (0.0008in) 0.025mm
(0.001 in) 0.025 mm (0.001 in)
Minimum this area .0015 mm( .0006 in) 0.020 mm
(.0008 in) 0.020mm (.0008 in)
Can anyone tell me if this still is a current standards for copper
plating thickness measurements.
David Harman
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