Greg; I will confuse you with another question : Why worry about ramp rate during reflow if bottom side ceramic capacitors has a ramp rate of 100 to 150C/sec during wave solder ???? ( This happens when they exit from pre heating and touch the molten solder during few seconds ) I believe who that could explain this too has the right answer ... Thanks > -----Original Message----- > From: Greg Jones [SMTP:[log in to unmask]] > Sent: 20 de Agosto de 1999 17:08 > To: [log in to unmask] > Subject: [TN] Thermal stress in reflow > > I am looking for a rule of thumb regarding the maximum ramp standard > components (chip capacitors) can tolerate without failure during the > reflow > process. The standard seems to be 3C\second, but this figure is generally > derived from the average ramp rate a product experiences during reflow. > Ex: A very light board spends 60 seconds in the first zone of a short > convection oven, which is set to 150C, and is at 150C at the end of that > zone. (Assume 30C ambient for simplicity) The averaged ramp rate for the > zone would be 2C\sec--an acceptable profile statistic . But what is > actually happening is the board is reaching 150C in the first 20 seconds > of > the profile, which gives an actual ramp rate of 6C\sec--well over any > established rule of thumb. > My question is: What is the ACTUAL ramprate, in Degrees C\second (and > duration at degrees\second), that chip capacitors can stand without > cracking, etc... > > Thanks, > Greg Jones > > ############################################################## > TechNet Mail List 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://www.ipc.org/html/forum.htm) for > additional > information. > If you need assistance - contact Gayatri Sardeshpande at [log in to unmask] or > 847-509-9700 ext.5365 > ############################################################## ############################################################## TechNet Mail List 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://www.ipc.org/html/forum.htm) for additional information. If you need assistance - contact Gayatri Sardeshpande at [log in to unmask] or 847-509-9700 ext.5365 ##############################################################