Hi Earl - I think the jury is still out as to the impact of Phosphorus on the integrity of the solder joint for immersion gold/electroless nickel finishes. The latest information published by M. Zei of HP ( "The Effect of Electroless Ni/ Immersion Au Plating Parameters on PBGA Solder Joint Attachment Reliability) at the IPC Surface Finishes Conference in Austin Texas last month (prior to Texas becoming an extension of the Gulf of Mexico) was that "no clear relation between the P content and attachment strength". Zei also looked at some of the plating variables and reached the same conclusion. Looks like more testing and investigation is needed to uncover the answers. I have been using immersion gold/electroless nickel finishes on a couple of CSP applications successfully but I have talked with other folks who are having problems. Dave Hillman Rockwell Collins [log in to unmask] Earl Moon <[log in to unmask]> on 10/22/98 07:42:39 AM Please respond to "TechNet E-Mail Forum." <[log in to unmask]>; Please respond to Earl Moon <[log in to unmask]> To: [log in to unmask] cc: Subject: [TN] Percent Phosphorous in plating solution causing excess intermetal lics in Au/Ni/Cu solder joints Folks, Does anyone have information concerning the amount as percentage of phosphorous in electroless nickel solutions that correlates to excess intermetallic formations in electroless gold over electroless nickel over copper solder termination areas leading to SMT solder joint failure? Am I really seeing some people addressing this issue by saying under 7% is the maximum limit to ensure long term SMT solder joint reliability? Am I seeing some people saying this is possible and still provide an adequate nickel barrier between copper pads and the gold protecting them? Is there an answer to ensuring reliable solder joints using electroless Au/Ni or a much better alternative to it and HASL? Thank you, Earl Moon ################################################################ 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 ################################################################