Rick -
 
Negative etchback is a defect condition where the inner conductor layers of a multilayer board are recessed relative to the surrounding layers of base material.  First, it is indicative of a problem in the fabricators post drilling cleaning processes.  Second, it is an area which tends to produce faults in the bonding of the plated thru hole barrel to the inner conductive layers due to its propensity for retaining air bubbles or traces of chemicals not related to the plating bath.  The net effect tends to be latent board failures (also pronounced environmental test failures of assembled product or field failures).
 
Etchback is an option which may or may not be selected.  Negative etchback is a defect.  Do you have your term correct?
 
Regards - Kelly
----- Original Message -----
From: [log in to unmask]>Richard Jones
To: [log in to unmask]>[log in to unmask]
Sent: 7/11/01 3:08:38 PM
Subject: [DC] Etchback

Hello everyone,
 
 
Does anyone have any information and/or comments about the value of requiring
negative etchback on master drawings.
 
We are leaning toward waiving this requirement if possible.  Most of our
products are type class 2 and 3, type 3 products.
 
Thanks,
 
Rick Jones
Raytheon Systems
Baltimore, MD
 
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