Hi Ken, I use a little handbook from the Zonk Group Inc., out of Richardson, TX, that recommends the following stack-up for soft material (i.e. Fr-4) mounted to soft or hard material: Fastener - Lock Washer - Flat Washer - PCB - Hard/Soft Material - Flat Washer - Nut The recommended torque that I start with is 70% of the maximum recommended torque for the particular fastener size. Continual monitoring of the deflection or compression of the board material, if any, is monitored while the torque is increased till the proper tightness is achieved (not to exceed the maximum recommended torque). Other references that may shed some light could be: Machinery's Handbook MIL-HDBK-60 ANSI SAE Hope this helps... good luck! Steve Sauer Mfg Engineer Northrop Grumman, Xetron -----Original Message----- From: Ken Carlile [mailto:[log in to unmask]] Sent: Tuesday, June 11, 2002 10:06 AM To: [log in to unmask] Subject: [TN] IPC Torque Specifications Does IPC have any Torque specifications for hardware mounting to FR-4? I have searched the archives and only find peoples opinions. If IPC doesn't have this does Mil Spec or ANSI? --------------------------------------------------------------------------------- Technet Mail List provided as a free service by IPC using LISTSERV 1.8d To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/html/forum.htm for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ---------------------------------------------------------------------------------