Why would "thickness" (as specified by the customer) be measured 
     before solder resist application?  The customer is designing around 
     and will receive a finished product (which includes solder resist) to 
     be installed in a higher-level assembly.
     
     What am I missing here?
     
     John R. Kretsch, P.E.
     Engineer, Design Assurance
     [log in to unmask]


______________________________ Reply Separator _________________________________
Subject: FAB:  PCB thickness
Author:  [log in to unmask] at internet-mail
Date:    06/04/96 12:30


Let me contribute my observations on thickness.
     
The quality manual here says (written by me) that boards will be built to 
class A tolerances in the latest revision of IPC-D-300, unless otherwise 
specified by the customer.
     
That said, I have questioned IPC about the meaning of "thickness".  David 
Bergman and Lisa Williams did some investigating and thinking and advised 
me that thickness was to be measured over plated copper, but before solder 
resist application.  They also told me that the committee responsible for 
D-300 planned on expanding upon the present statement on baords thickness 
in the standard, to direct the user to specify board thickness in any 
areas of importance.
     
Lou Hart
     
     
.