In a message dated 03/26/97 6:36:10 PM, you wrote: > Back in January I saw your informative message on the TechNet > regarding the soldering issues w/alloy 42. I archived it for future > reference, and had occasion to pull it out today, since we're having > some difficulties soldering an alloy 42 component (a 10BASE-T part > made in China). > > My question is this...what is the manufacturer's advantage in using > this alloy? From a contract assembler's perspective, it seems to have > little to recommend it. Profiles must increased, inspection stepped > up, etc. > > I suppose that it must be cheaper than a standard tin dipped copper > lead, but is that all there is to it? Is the use of this alloy > decreasing with time, remaining about the same, or increasing? > > > Bruce Tostevin > Lockheed Commercial Electronics Hi Bruce, The reason some component manufacturers use Alloy 42 as a lead frame material is because it makes the attachment of the die easier. The die has a CTE of about 2.8 and the Alloy 42 has a CTE of about 4.5; so die attach is easily accomplished with a thin rigid adhesive. Using a copper aloy lead frame requires a thicker more compliant adhesive to prevent die cracking. Alloy 42 is more difficult to solder to than copper; however, there is Alloy 42-- apparently coming from a South Korean mill--that is not solderable no matter what you do. HP ran into this material, and went public with their experience, as have others who chose not to publisize their experience. I do not know which mill produces this non-solderable Alloy 42, nor do i know whether the non-solderability comes in batches or affects all their output. The published experience of HP (Engelmaier, W., and B. Fuentes, "Alloy 42: A Material to be Avoided for Surface Mount Solder Component Leads and Lead Frames," Proc. Surface Mount International Conf., San Jose, CA, August-Septemb er 1994, pp. 644-655; also in Proc. Int. Electronics Packaging Conf. (IEPS), Atlanta, September 1994, pp. 503-516; also in Proc. 19th Ann. Electronics Manufacturing Sem., Naval Air Warfare Center, China Lake, CA, February 1995, pp. 5-20; also in Proc. NEPCON West '95, Anaheim, CA, February-March 1995, pp. 385-395; also in Soldering & Surface Mount Technology, No. 21, October 1995, pp. 20-25) has put some pressure on component manufacturers to change to copper-based leadframes, but not enough pressure. 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 subscribe/unsubscribe send a message <to: [log in to unmask]> * * with <subject: subscribe/unsubscribe> and no text in the body. * *************************************************************************** * 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] * ***************************************************************************