SLL45ssslcktih67laldll. Translated, this means no one knows what causes it precisely. Going way back with Boeing, and a nice guy named Phil Tjele (can't remember last name spelling but rhymes with jelly), he spent considerable time studying the phenomonon and concluded, as did many others, we don't know what causes it. What does IPC 600 say aboutit? Look it up please and tell us. MoonMan --------------------------------------------------------------------------------- Technet Mail List provided as a free service by IPC using LISTSERV 1.8d To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt delivery of Technet send the following message: SET Technet NOMAIL Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ---------------------------------------------------------------------------------