Hi, hope all is well. Here is a direct quote from the article I referenced in an earlier post. "The immersion gold (IG) process provides a direct replacement of nickel surface atoms with gold atoms. The process is self limiting (diffusion is limited by nickel to the liquid interface) and provides a highly porous free protective barrier to passivation. Thus the IG process can be considered (loosely) as a controlled corrosion process. "There have been many investigations in recent years into the wettability of EN/IG surface finishes, also into the reliability, and failure modes of the EN/IG solder joints. The conclusions of these reports have, in general, had confounding results and no root cause for predominate failure mode(s) could be defined. The investigations did have one point in common in that they all reported a condition called "black pad". This condition was first reported by Puttlitz as defective joints that exhibit a dark gray-to-black appearance that would only partially wet. "This paper describes, in detail, the microstructure of the black pad defect and identifies as its root cause failure mode. The black pad defect was found to be due to a hyperactive "corrosive" IG process that changes the near surface microstructure of P-Ni into one with a marginal to a non-wetting state. The black pad defect shall be classified in terms of hyperactive corrosive activity. Furthermore, evidence shall be presented which shows that the black pad defect does not occur in a random of sporadic manner. Scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS), Auger spectroscopy and focus ion beam microbe (FIBM) are used to gain an understanding of this root cause effect." :Later in the article "It has been shown that the black pad defect is due to a hyper corrosive activity of the immersion gold process near the nickel surface. Eight levels of the defect activity have been identified. The lower activity levels do not present solder joint reliability issues. The highest activity level, black pad, creates an enriched phosphorous layer called black band. It has been shown that black band phosphorous enrichment is distinguishable from a thin layer of natural phosphorous enrichment created during Ni/Sn intermettalic formation." In the article there are many pictures of their results. They also managed to induce the phenomenon. Though they don't offer any solutions to prevent this from happening, I recommend anyone having this problem to get a copy of the article. It is on page 133 of "Future Circuits International", issue 5. Robert Peterson mailto:[log in to unmask] Alternate Final Finishes, Inc. 166 Middlesex St. N. Chelmsford MA 01863 Phone (978) 251-7429 Fax (978) 251-7219 http://www.AlternateFinalFinishes.com -----Original Message----- From: Richard Tilbrook [mailto:[log in to unmask]] Sent: Wednesday, October 13, 1999 3:57 AM To: [log in to unmask] Subject: [TN] Black Plague Forgive my ignorance, please define BLACK PLAGUE. Is it something I should be looking out for? Is it something we've already got and are suffering from???!!! Richard Tilbrook British Aerospace ############################################################## TechNet Mail List 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 web site (http://www.ipc.org/html/forum.htm) for additional information. If you need assistance - contact Gayatri Sardeshpande at [log in to unmask] or 847-509-9700 ext.5365 ############################################################## ############################################################## TechNet Mail List 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 web site (http://www.ipc.org/html/forum.htm) for additional information. If you need assistance - contact Gayatri Sardeshpande at [log in to unmask] or 847-509-9700 ext.5365 ##############################################################