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 .