Guenter, It certainly takes time--and thermal energy--to allow gold/silver layers to disperse more or less uniformly throughout the solder joint to prevent embrittling concentrations. But you need to form intermetallics, otherwise you have no metallurgical bond. Cu/Sn intermetallics form much more rapidly than Ni/Sn intermetallics, because of the much higher dissolution rate of Cu in Sn. However, the danger of inadequate wetting (no intermetallics) is much greater for real product than the danger from excessive growth of the intermetallic layer(s). Regarding the IEEE Compliant Lead Task Force, I responded to a similar question from Dave Hillman with: Your second question is certainly a good one. There is a situation that shows how naive engineers can be. We had the catastrophic failures of the TI PLCC-J solder joints at IBM-Austin scaring everybody stiff. Consequently, the engineers from numerous competing companies formed the IEEE Compliant Lead Task Group with Jack Balde chairing. The idea was that everybody would contribute, we would test all submitted PLCCs, and evaluate and publish the results. Participating companies were Apple, AMP, AT&T (Bell Labs multiple locations), Burroughs, Bourns, DEC, Delco, Diacon, Fairchild, GTE, Hitachi, IBM, HP, IDC, Intel, ITT (US & England), Jade, Kyocera, Lockheed, LSI, Motorola, NCR, NEC, NSC, Signetics, Sperry, TI, T&B, United Technologies. There certainly was no lack of cooperation and most companies had at least one active participant. We published preliminary results from Phase I and other developments that occurred at different companies concurrently with the CLTF. You might my references interesting, if you can find them that is because some were only recorded on video tapes made during IEPS conferences: 1. Engelmaier, W., "Test Method Considerations for SMT Solder Joint Reliability," Proc. 4th Annual Int. Electronics Packaging Conf. (IEPS), Baltimore, MD, October 1984, pp. 360-369; also in Brazing & Soldering, No. 9, Autumn 1985, p. 40. 2. Engelmaier, W., "Solder Joint Reliability and Testing Considerations for Leaded Chip Carriers," Proc. Nepcon/West, Anaheim, CA, February, 1985, pp. 884-885; Presentation available on IEPS Videotape VR 001, Lead Compliance and Solder Integrity of Surface Mount Leaded Packages. 3. Engelmaier, W., "Interim Report on the Test Results of IEEE Compliant Lead Test Program," IEPS Videotape VR 004, IEEE Compliant Lead Task Force Results of Phase A, 1985. 4. Engelmaier, W., "IEEE Compliant Lead Task Force--Phase I: Correlation and Analysis of Solder Joint Fatigue Results Obtained at Different Cyclic Frequencies and Temperatures," Proc. 5th Annual Int. Electronics Packaging Conf. (IEPS), Orlando, FL, October 1985, p. 279; Presentation available on IEPS Videotape VR 002, Second Interim Report of the IEEE Compliant Lead Task Force. 5. Kotlowitz, R. W., and W. Engelmaier, "Impact of Lead Compliance on the Solder Attachment Reliability of Leaded Surface Mount Devices," Proc. 6th Annual Int. Electronics Packaging Conf. (IEPS), San Diego, CA, November 1986, p. 841. 6. Engelmaier, W., "Surface Mount Attachment Reliability of Clip-Leaded Ceramic Chip Carriers on FR-4 Circuit Boards," Proc. 7th Annual Int. Electronics Packaging Conf. (IEPS), Boston, MA, November 1987, p. 104; also in IEPS J., Vol. 9, No. 4, January 1988, p. 3; also in Proc. Nepcon/East, Boston, MA, June 1988, p. 121. 7. Engelmaier, W., "The Importance of Continuous Monitoring for SMT Solder Joint Failures During Accelerated Fatigue Testing," IPC Spring Meet., Hollywood, FL, April 1988. 8. Engelmaier, W., "IEEE Compliant Lead Task Force--A Progress Report," Proc. 8th Annual Int. Electronics Packaging Conf. (IEPS), Dallas, TX, November 1988, p. 891. 9. Engelmaier, W., "Surface Mount Solder Joint Reliability: Issues, Design, Testing, Prediction" Workshop Notes, Engelmaier Associates, Inc., Mendham, NJ, 1996. You will not, however, find the results from Phase III which included the fatigue test data for the components from all the participants that had submitted components. As is logical, the results were rank-ordered; that is when the lawyers of the two (2) companies on the bottom of the rank-order list got a hold of the data. Those two companies threatened to sue the IEEE and all other participants if the data were made public. Well guess what--they never saw the light of day. We could not even publish them without the company names, because the package designs had been thoroughly evaluated and the results together with all the design details published. The references listed above certainly contain the pertinent findings from the CLTF and the insights gained from this round robin--therefore, what is generally applicable has not been lost. Werner Engelmaier Engelmaier Associates, Inc. Electronic Packaging, Interconnection and Reliability Consulting 23 Gunther Street Mendham, NJ 07945 USA Phone & Fax: 201-543-2747 E-mail: [log in to unmask] *************************************************************************** * TechNet mail list is provided as a service by IPC using SmartList v3.05 * *************************************************************************** * To unsubscribe from this list at any time, send a message to: * * [log in to unmask] with <subject: unsubscribe> and no text. * *************************************************************************** * If you are having a problem with the IPC TechNet forum please contact * * Dmitriy Sklyar at 847-509-9700 ext. 311 or email at [log in to unmask] * ***************************************************************************