Immersion golds work by a displacement process; similar to if you place a piece of iron in a copper bath. The iron dissolves and the copper displaces it and covers the surface Electro less nickel baths by the nature of the reducing agent in them (which is generally sodium hypophosphite) have a final content of up to 14 % phosphorus and ends up similar to an alloy of nickel and phosphorous The "aggressiveness" of the immersion gold cannot alter the structure of the electro less nickel deposit Best bet is the electro less nickel has not been controlled properly with subsequent high phosphorus content If you are interested in further information I suggest you visit www.lea.co.uk and ask for information on "What is Electro less Nickel " They also hold a 2 day course every year in the UK on this technology -----Original Message----- From: TechNet [mailto:[log in to unmask]]On Behalf Of Robert Peterson Sent: 12 October 1999 18:31 To: [log in to unmask] Subject: Re: [TN] Black Plague Hi, There is an article by Nicholas Biunno of Hadco on page 133 of Issue 5 of "Future Circuits International" that covers the "Black Plague" quite thoroughly. Here is a very short over simplified summary: Everybody looks at the nickel but the cause turns out to be the immersion gold is too aggressive. The immersion gold works by corroding the nickel. If it is too aggressive it takes away the nickel and leave phosphorous behind. This makes it look like the phosphorous level is too high in the nickel bath. 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: Hollandsworth, Ron [mailto:[log in to unmask]] Sent: Tuesday, October 12, 1999 11:21 AM To: [log in to unmask] Subject: Re: [TN] Black Plague Importance: Low Franklin We are seeing the problem mainly at our wavesoldering operation. We have seen some, little, at the SMD workcell. We have checked our wavesolder process and profile and it has not changed. The problem is lot number dependent. A specific date code may have multiple lot numbers, and the issue show up on one lot number only and not every board in the lot. Bare board condition shows no early warning signs that we have detected at this time. We have cross sectioned some boards to see if there may be a tell tale sign, but nothing outstanding. We do have a couple boards in for that cross sectioning at the present time. No data back yet. Ron -----Original Message----- From: Franklin [mailto:[log in to unmask]] Sent: Tuesday, October 12, 1999 9:41 AM To: [log in to unmask] Subject: Re: [TN] Black Plague Ron, Where are you first seeing this condition? Is it on the bare boards? Are the the assembler or fabricator? How have you 'cleaned' these boards up in the past, if at all? (cleaned or made the gold look better) I'd like to offer whatever I can, your first message just did not have enough information. Franklin -----Original Message----- From: Hollandsworth, Ron < [log in to unmask] <mailto:[log in to unmask]> > To: [log in to unmask] <mailto:[log in to unmask]> < [log in to unmask] <mailto:[log in to unmask]> > Date: 12 October, 1999 7:54 AM Subject: Re: [TN] Black Plague Franklin, POD, & Paul You say there are ways to get around the Black Plague. Would you elaborate please. Once again I see messages where others are experiencing this problem but no absolute solutions. I have read the articles, tried the erasers, stronger fluxes, and pad scraping. No relief. I have learned to dislike Electroless Ni/ Immersion Au boards. I am thinking that HASL or precision pad technologies are much better. At least you can perform your soldering operation. A Circuit Card Assembly (CCA) with the Black Plague can run up scrap costs real fast. Not to mention the possibility of late shipment to the customer because of inability to solder. This is a real problem if you are using Ni/Au boards. So far there are few comments and the issue simply drops out of sight. Are platers/fabricators not controlling their processes or is this a inhouse process issue. We have checked our processes and find no change. Ron Hollandsworth ############################################################## 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] <mailto:[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 <http://www.ipc.org/html/forum.htm> ) for additional information. 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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 ##############################################################