.int [log in to unmask] As I recall, the numbers are.005 for pwas less than 12" and .008 for larger pwas per some IPC spec. I did a post on this a few months ago and asked how can we do boards with .020 pitch when we allow .008 error to the master art. Never did get a good answer. Since the question is asked again I assume others are having problems. Question to the FAB guys. Without going to glass tooling, how close to master can you control feature location on large 16 x 15" boards? How good with glass tooling? Larry Sternig [log in to unmask] *** Original Author: [log in to unmask] 04/23/96 161919 Resent-Date: Tue, 23 Apr 1996 16:15:44 -0700 Resent-Sender: [log in to unmask] Old-Return-Path: <[log in to unmask]> From: "Yuen, Mike" <[log in to unmask]> To: "[log in to unmask]" <[log in to unmask]> Subject: RE: dimensional question Message-ID: <[log in to unmask]> Encoding: 36 TEXT X-Mailer: Microsoft Mail V3.0 Resent-Message-ID: <"Id2w31.0.seB.lIJVn"@ipc> Resent-From: [log in to unmask] X-Mailing-List: <[log in to unmask]> archive/latest/3601 X-Loop: [log in to unmask] Precedence: list Resent-Sender: [log in to unmask] Q: How much growth (or shrink) should one expect land-to-land over a 16" distance? This has nothing to do with drilling; just master pattern to actual board size... A: I believe that's called stretch effect, the bigger the board gets the more severe the growth (or shrinkage) it will have. The stretch also depends on the board house and board thickness. The best way to minimize stretch effect is to group components which require tight tolorance into the central location of the PCB. Thanks Michael Yuen ---------- From: TechNet-request To: technet Subject: dimensional question Date: Tuesday, April 23, 1996 11:07AM The proliferation of sub .5mm peripheral leaded SMD's is causing assembly people to look at the overall size relationship between the master data and the actual board. When solder paste is stenciled on larger boards (say, 12-16"), the stencil image many times will not match the land pattern, causing shorts in the fine pitch area. My question: How much growth (or shrink) should one expect land-to-land over a 16" distance? This has nothing to do with drilling; just master pattern to actual board size... Thanks, marko