Hi Neil - the world of alternative finishes is so much fun! Because of your different finishes let me break my response into two sections: #1"Material: CuZn37-F37 Finish: 2 microns Silver Plated. Nominal 0.2 microns gold." * One problem you will have with this finish stackup is that the silver will quickly diffuse into the gold and then tarnish to a point were the solderability is lost. The gold/silver stackup was used briefly on connectors but then discontinued due to the diffusion problems. Check out this paper for more info: "Connector Reliability in the Military Environment", Connection Technology, May 1989, pages 19-22. The paper contains some good references too. #2 "Material: CuZn37-F37 Finish : Nominal 0.2 microns gold" * There are a couple of issues with this stackup. The copper will diffuse into the gold over time and become oxidized resulting in the loss of solderability. The second problem (which could also be occurring with finish stackup #1) is the diffusion of zinc to the copper/gold interface. A loss of solderability results from this mechanism too. Take a look at Klein Wassink's book, "Soldering In Electronics", ISBN # 0-901150-14-2, section 6.3.1.3 for more info. Many component suppliers put a barrier layer of copper to prevent the zinc diffusion but these components are intended for JIT operations due to the copper diffusion issues. Other suppliers use a nickel barrier which is much more robust. As for why the supplier is giving you two non-typical surface finishes on the same component- that is a mystery! A more standard finish such as tin/lead or gold/nickel would be more solderable than the finishes you have now. Good Luck. Dave Hillman Rockwell Collins [log in to unmask] Neil Atkinson <[log in to unmask]> on 10/01/98 02:00:51 AM Please respond to "TechNet E-Mail Forum." <[log in to unmask]>; Please respond to Neil Atkinson <[log in to unmask]> To: [log in to unmask] cc: Subject: [TN] Solderability Problems Technetters, This is the second time I have asked this question but so far I haven't had a reply. Maybe I'll ask in a different way this time! We are trying to solder a microswitch to a PCB and are having serious problems with dry joints (i..e de-wetting of the legs). Having spoken with the supplier of the switch he has informed me that the switch legs(there are two of them) have different platings these are: Material: CuZn37-F37 Finish: 2 microns Silver Plated. Nominal 0.2 microns gold. and Material: CuZn37-F37 Finish : Nominal 0.2 microns gold My questions are: What does the silver do to solderability? Why would a switch manufacturer use these finishes? Should the second leg have a barrier layer (Nickel?) between the brass and the gold? My swich supplier is willing to listen but what would be the best finish for us to solder whilst meeting the switch manufacturers requirements? HELP!!!! Neil Atkinson ################################################################ 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 ################################################################ ################################################################ 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 ################################################################