My previous posting did not yield any suggestions. I'm submitting again and hope to have responses. >Date: Fri, 07 Feb 1997 10:25:09 -0500 >To: TECHNET >From: sam mccorkel <[log in to unmask]> >Subject: FR-4 material movement > >We experience up to .020" material movement on FR-4 materials.We ran some tests and measured after each operation and found that it began to move after etch, and moved a lot more after screen bakes and hot air leveling.We have not seperated panels by grain direction in our tests so far. We've tried baking before drilling and have not seen a significant difference from those not baked. The movement we experience causes major problems when we rout or score. We have to internally pin each piece to hold a ± .005" tolerance between a drilled hole and the edge of the part.We used to be able to pin externally with 4 pins to rout our boards and had no problems. Internally pinning adds a lot of labor with panels that have many parts on them. This problem cropped up on us about 10 months ago. Before that it wasn't a problem. Are other fabricators out there experiencing this same problem? Is there anything we can do to reduce the amount of movement? Should the material move this much with "normal" processing of 2-sided boards that are .062" thick? Do you have to internally pin each part on your panels? > *************************************************************************** * TechNet mail list is provided as a service by IPC using SmartList v3.05 * *************************************************************************** * To unsubscribe from this list at any time, send a message to: * * [log in to unmask] with <subject: unsubscribe> and no text. * *************************************************************************** * If you are having a problem with the IPC TechNet forum please contact * * Dmitriy Sklyar at 847-509-9700 ext. 311 or email at [log in to unmask] * ***************************************************************************