Mark, This is exactly what the article I have been referring to discusses. Did you need a copy as well? If you did I need your fax number. Technetters, I am receiving a lot of requests for the PCB Warpage article so it is taking some time to get to all of you. Please help me to ensure that I do not miss anyone. If you do not receive the article within 2 days of your request please remind me by e-mail. Thank you for your patience. Sincerely, Brian Stumm ETS >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 >################################################################ > > > ################################################################ 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 ################################################################