Hi Werner, My problem is that I agree with you whole heartedly. Why come up with a complex explanation to a simple problem? We receive BGAs which have been pulled off of boards from all over. We see the same phenomenon on most components we receive. All from different sources and different manufacturers. At first I attributed the problem to the conversion of semiconductor assemblers to no-clean fluxes. Then I began looking into the possibility that they are just escapees which slip through the cracks. Now I am wondering if they made it out of assembly with good ball attach and then were degraded by test sockets which can stress the solder balls while they are at elevated temperatures. Regardless of what the root cause of the problem I guess the real question is: If you pull a BGA from a board (with a proper hot air reflow system) and find a bare nickel pad on the component who's fault is it? As long as it is not a function of the removal process then I believe the responsibility is that of the component manufacturer. I believe the failure analysis (at the board level) is complete. The component failed due to an open which was caused by a poorly attached solder ball (at the component). My experience tells me that the nickel should never become exposed just by heating the solder balls to the molten state and then lifting the component from the board. Do you see any reason why the board removal process would expose a bare nickel pad of a good BGA? -----Original Message----- From: [log in to unmask] [mailto:[log in to unmask]] Sent: Wednesday, February 17, 1999 6:43 PM To: [log in to unmask]; Russ Subject: Re: [TN] Defective BGAs? Hi Russ, Well, your problem comes down to two possible causes: 1) no solderability; your tests seem to exclude that. 2) inadequate soldering process; it certainly is possible that the solder balls were never properly attached to the component. Your problem is not likely related to shear strength of (or crack propagation in) nickel-tin intermetalics, but the absenceof any IMCs which are the by-product of a good intermetallic bond resulting from good wetting. Solder attachment strength to nickel is about half that to copper. Werner Engelmaier Engelmaier Associates, L.C. Electronic Packaging, Interconnection and Reliability Consulting 7 Jasmine Run Ormond Beach, FL 32174 USA Phone: 904-437-8747, Fax: 904-437-8737 E-mail: [log in to unmask] ################################################################ 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 ################################################################