Another possible cause for this type of defect can be attributed to your PCB suppliers method of curing the Soldermask. If PCB's are cured vertically then it is extremely important that the support during the thermal cure does not allow the boards to sag. As the TG temperature of FR4 laminate (135 degC) in PCB construction is usually below that of the soldermask cure.(Normally 150 deg C) This would then allow the prepreg to assume the shape of the sag and once cooled will retain this bow. We have overcome this issue and if you need further details please contact me. I hope this is of some help. Mark Gillan Process Engineer Prestwick Circuits Scotland ---------- From: ririzarr To: TechNet Subject: Re: [TN] PCB warpage Date: 17 February 1998 10:04 This is due to thermal stresses in the PCB sometimes when they pass the oven they become more "soft" and they warp. Why don't you try some stiffeners to make the PCB strong enough to withstand the higher temperatures? Regards, Rub?n E. Irizarry-Guzm?n Operations Engineer [log in to unmask] on 02/16/98 04:52:39 PM Please respond to [log in to unmask]; Please respond to [log in to unmask] To: [log in to unmask] cc: (bcc: Ruben Irizarry) Subject: [TN] PCB warpage What causes PCBs to warp? How can we prevent this from happening? (Thanks to all responses in advance!) ################################################################ TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c ################################################################ To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE TechNet <your full name> To unsubscribe: SIGNOFF TechNet ################################################################ Please visit IPC web site (http://jefry.ipc.org/forum.htm) for additional information. For the technical support contact Dmitriy Sklyar at [log in to unmask] or 847-509-9700 ext.311 ################################################################ ################################################################ TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c ################################################################ To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE TechNet <your full name> To unsubscribe: SIGNOFF TechNet ################################################################ Please visit IPC web site (http://jefry.ipc.org/forum.htm) for additional information. For the technical support contact Dmitriy Sklyar at [log in to unmask] or 847-509-9700 ext.311 ################################################################ ################################################################ TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c ################################################################ To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE TechNet <your full name> To unsubscribe: SIGNOFF TechNet ################################################################ Please visit IPC web site (http://jefry.ipc.org/forum.htm) for additional information. For the technical support contact Dmitriy Sklyar at [log in to unmask] or 847-509-9700 ext.311 ################################################################