Warp depends on: - how close the board gets to its Tg during the reflow cycle (the closer you get to the Tg the worse the warp gets) - the amount of copper on each side and the balance between the two - thickness of the board - overall length x width - time under temperature - rate of cool down Mutiple thermal cycles - such as rework - are never a good thing. My best suggestion - get the copper balanced and if possible go to higher Tg materials. Ted ---------- > From: Tempea, Ioan <[log in to unmask]> > To: [log in to unmask] > Subject: [TN] PCB specs > Date: Friday, May 21, 1999 1:58 PM > > Hi PCB fabs, > > this one's for you. > > I'm caught into a lot of fussing about whether my reflowing profiles warp > the boards or not. > > What I'd like to know is if the PCB manufacturers recommend optimal reflow > profiles for their boards or, at least, two things: > > 1. maximum temperatures the boards can withstand without warping or getting > damaged in any way > 2. maximum number of thermal cycles the board can take, including double > reflow, waving and some rework > > I don't mind if I hear from PCB users either. > > Have a good week-end after answering, Ioan > > ################################################################ > 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's web site (http://www.ipc.org) "On-Line Services" section for additional information. > For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312 > ################################################################ ################################################################ 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's web site (http://www.ipc.org) "On-Line Services" section for additional information. For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312 ################################################################