A movement of smt component is caused by solder tension during reflow stage. You could have two issues, reflow profile and board design layout. If a reflow profile is not good, it causes too much temperature delta difference among smt pads/ components. This means pads will be reflowd at different times. Please check your oven profile / your solderpaste mfg oven profile guideline and make sure boards don't get heat up too fast. If some of your R- pack component pads are too closely connected to heavy ground plane, th holes or heavy traces, it could again cause unequal thermal mass and cause pads to reflow at different times. Also pad size and geometry could cause component movement. Check board layout is acceptable for manufacturability (or follow IPC-782 guideline) If you are still using IR or vapor phase oven, the problem can be worse. Are you sure you have a good solder mask dams around smt pads? regard Matthew NII-Norsat International Inc. >>> Angie Marques <[log in to unmask]> June 10, 1998 8:22 am >>> To all, My R packs have a mind of there own, at pick and place they are aligned then during reflow they decided to move. What causes this and how can I prevent this? Thank you in advance Angie ################################################################ 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 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 web site (http://jefry.ipc.org/forum.htm) for additional information. For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312 ################################################################