Dear Mr. Fulton Feng, You have already pinpointed that the cause of the solder balls was due to misaligned print. I think you have to know the cause of misalignment, "is it the board"? or "is it the screen print machine set-up"?. Hope this would help... Bobby ################################################################ 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 ################################################################