Gaby Some things to check: 1) thermal profile - ramp up rate. Your comment re the conductor area makes this suspicious. Also consider orientation in the oven - does one side reflow before the other? 2) is the oven running smoothly? (chain or conveyor vibration) 3) pads may be a factor, too much solder can do this. As a crude experiment you could try removing some of the paste from the pads before placement. 4) I am assuming you verify the accuracy of the placement before reflow, but if not it's also a possible problem. Also look at the accuracy of the screening onto the pads - if your paste is offset to the left and the part to the right... ** standard disclaimer, opinions are my own, etc.... ** regards, Graham Collins Process Engineer, Litton Systems Limited, Atlantic Division (902) 873-2000 ext 215 > -----Original Message----- > From: Gabriela Bogdan [SMTP:[log in to unmask]] > Sent: Tuesday, October 21, 1997 6:47 PM > To: [log in to unmask] > Subject: [TECHNET] Tombstoning > > Hello, Technetters! > I need infomation about Tombstoning of Surface mount components during > Reflow. > Does it occure on leadless components in general, disregarding size > and > number of connections? > If so, what are the rules for avoiding it?-Design of pads? > We encounter a problem which seems to be tombstoning with components > featuring 3+3 terminations .The corresponding pads on one side are > connected > to large conductor areas. The others are not. After reflow many > components are tipped on one side or misplaced. > Any suggestions? > Thank you, > Gaby > > ############################################################## > 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. > For the technical support contact Dmitriy Sklyar at [log in to unmask] or > 847-509-9700 ext.311 > ############################################################## ############################################################## 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. For the technical support contact Dmitriy Sklyar at [log in to unmask] or 847-509-9700 ext.311 ##############################################################