At 10:43 AM 10/10/96 -0700, you wrote:
>We are currently manufacturing M/L boards up to 10 layers.  I noticed that
>the IPC Multilayer Test Pattern (IPC-A-27) is for 6 or 10 layer boards. 
>What is used for layer counts in excess of 10 layers?  Are the coupon
>sections simply expanded and repeated to accomodate higher layer counts, or
>is something different used?
>
>Regards
>John Parsons
>Circuit Graphics Ltd.

John,

The IPC-A-27 Artwork contains test patterns for a specific type of 6 & 10
layer PWB.  Differences in Ground Planes, Pad & Line Geometries all require
adjustment of test coupons.  This severly limits the use of a single
specific coupon design for all PWB's.  I would suggest that you use the
guidelines of IPC-D-275 (Design Guide) for test coupon design.  This
document details the design requirements for PWB's and the test coupons
which accompany them on production PWB Panels.  

As for qualification at this time, all artwork that I am aware of has a ten
layer maximum (one size fits all).  You will be glad to hear that the next
revision of IPC-RB-276 which will be called IPC-6012, will allow the use of
Production Boards to "Qualify" specific attributes.  I am told by reliable
sources that IPC-6012 is on its way to the printer, and should be available
for use in the next couple of months.

Bob Neves
IPC Rigid Board Committee Chairman
Technical Director 
MICROTEK LABS
(714) 692-1000
[log in to unmask]
http://www.TheTestLab.com

.


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