Whilst I was with Dolby we actually moved to ImmAg from ENIG as a finish of preference for SMT/mixed technology when swapping over to RoHS compliant assembly = lead-free soldering (using SAC305 for SMT paste, SAC387 for wave/selective, SAC305 hand solder.) I was encouraged to try this having seen the Hillman/Pauls lead-free pony show at a SMART Group conference in the UK back in Nov 2004. With good PCB suppliers (able to meet and maintain IPC4553 thicknesses reliably) we had far fewer random or batch dependent solderability issues with ImmAg than ENIG. Also we saw an improvement in solder joint quality at wave solder (fewer bridges, better topside hole pull-thro'.) You just have to be a bit more careful with storage and keep sources of sulphur away. There was an increase in blowholes at wave solder, however, as the underlying nickel in ENIG seals the hole walls against micropores in the copper PTH, which the thin immersion Ag can't achieve. And concurrently the more robust PCB laminates used for lead-free are harder to drill and more prone to hole tear-out which can make hole wall problems more prevalent. Again, we worked with our supplier to understand and control these issues. We did have one supplier that routinely gave us ImmAg problems, but they were also responsible for most of the occasional ENIG solderability problems too which caused us to look at ImmAg in the first place. We stopped using them... I'm not a metallurgist but creating a solder joint with Ag over Cu on the PCB seems more logical using a Sn/Ag/Cu based solder alloy than introducing "foreign" elements Au and Ni into the mix. Nigel Burtt [log in to unmask] www.enjaybee.com --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 15.0 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 or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) 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/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 -----------------------------------------------------