Barbara, Look at Patent Number 5,764,071 dated June 9, 1998. IBM is patent holder and I was one of the author. The method allows monitoring of signals from the opposite side of PWB for a BGA or other modules. You have to contact IBM for permission to use the method described. Good luck -- _________________________ pratap singh tel/fax: 512-255-6820 email: [log in to unmask] WEB: www.rampinc.com --------------------------------------------------------------------------------- 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 e-mail to [log in to unmask]: SET Technet NOMAIL To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/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 ---------------------------------------------------------------------------------