Read "The Black Pad Failure Mechanism-From Beginning to End" by Ronald Bulwith, Michael Trosky, Louis Picchione, and Darlene Hug in the Sept. 2002 issue of Global SMT and Packaging. This is one of the clearest explanations as to the root cause of Black pad, but even they were not completely sure of all of the other variables that could also cause it. -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Ryan Grant Sent: Friday, August 12, 2005 2:42 PM To: [log in to unmask] Subject: Re: [TN] osp vs enig, black pad... - renamed Hi Cheryl, I'm afraid the information given to you is quite wrong. Black Pad is manifest as the plated Nickel having a high Phosphorous content when using Auger spectroscopy or some other similar analytical technique. High Phosphorous content is a red herring and high Phosphorous content in the Nickel bath actually PREVENTS black pad. The high Phosphorous in plated Nickel is due to removal of Nickel atoms during both Gold plating and during soldering; which changes the ratio of Nickel to Phosphorous. When this Nickel Phosphorous ratio reaches a catastrophic level, it is commonly called Black Pad. High Phosphorus Nickel plating baths control the loss of Nickel atoms by packing the Nickel nodules more densely so they are inaccessible to be removed. Apparently, and unfortunately, high Phosphorous content in the Nickel bath is believed to cause brittle Nickel failure, which is a different type of failure. Contamination of the plating baths by solder mask is just that, contamination of the plating bath; but NOT black pad. There is no such thing as a perfect plating finish for all applications... OSP will not work reliably as a contact pad. Your options pretty much amount to: ENIG, Nickel Palladium Gold, electrolytic Gold on the contact pads only if you can route the contact to a buss, immersion Silver, and Carbon. Immersion Silver usually does not cost more than OSP, whereas OSP + electrolytic Gold usually cost more than ENIG by itself. I wouldn't trust immersion Silver to make a rugged contact pad, but it could be used in situations that don't require a rugged contact. Myself, I use OSP + electrolytic Gold almost exclusively, but given the price parity of immersion silver with OSP, that has become a serious consideration to replace OSP. -Ryan -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Cheryl Johnson Sent: Friday, August 12, 2005 11:20 AM To: [log in to unmask] Subject: [TN] osp vs enig, black pad... - renamed Ellsworth, Thank you for your help. My biggest concern with the osp is that we have 18 contact pads, that must remain absolutely flat (so we are not wanting to just add solderpaste to them), so they need to be plated any way. With OSP, how would you recommend handling our contact pads? Having 2 processes would most likely void any potential cost savings.. Several years ago, when we were concerned with "black pad", I receive this information: "Black pad is the result of too high phosphorous content of the nickel bath and the organic leach out from the solder mask coating. If the phosphorous content is too high in the nickel coating Black Pad may result during thermal excursion in assembly. Suppliers of immersion gold have performed extensive testing to create the condition and remedies to eliminate the problem. They have reformulated the chemistries to better stabilize the prosperous levels and revised analytical and bath maintenance schedules at the user site. Solder mask is also known to be a contributor to black pad. Typical processing techniques allow for solder mask to be applied over the bare copper conductors prior to electroless nickel and immersion gold. We have heard of cases where the solder mask has contaminated the nickel bath with organics or leach out from the solder mask. The cause for the condition can be in the incompatibility of the solder mask and immersion gold process. A number of solder mask types have been reformulated and designated as "compatible" with immersion gold. It is important to emphasize adequate bath maintenance schedules to reduce the potential for the formation of Black Pad." As black pad is a process related issue, we believe our process has it under control (we have not had any issues.) Sincerely, ----------------------------------- Cheryl Johnson, C.I.D.+ Manager ExcelStor US Office, Engineering Services Email: [log in to unmask] Tel: (303) 684-7291 Fax: (303) 684-7268 Mobile: (303) 809-5815 ----------------------------------- -----Original Message----- From: TechNet [mailto:[log in to unmask]]On Behalf Of Ellsworth Berkowitz Sent: Friday, August 12, 2005 9:02 AM To: [log in to unmask] Subject: Re: [TN] <Misc>Re: [TN] <Misc>Re: [TN] RoHs board surface recommendations. In the early '97 timeframe we switched from HASL to ENIG, primarily to achieve "flat pads" for the increasing use of fine pitch & BGAs in our designs. Within several months of ENIG implementation, however, we experienced the "black pad" phenomenon. We went into scramble mode to find an alternative... After attending the IPC Surface Finishes conference that year, we selected OSP as our first choice finish. Immersion Ag looked very promising but we didn't believe it was as widely available; we did continue to monitor developments with this finish. OSP has worked very well in our process over these years. We started to migrate to immersion Ag in the past year, however, mostly due to issues with ICT probing of OSP test point pads. As the complexity of our products has increased, the designs have likewise migrated from reflow-wave to double-sided reflow & selective solder. Wave solder more effectively prepares the OSP test point for probing; solder paste & reflow presents more challenge to consistently cover our typical via-in-pad test points. A whole 'nother story... Generally we have reasonable inventory turnover, so OSP aging & degradation over time hasn't been a problem (in a few cases of slow moving product, we sent boards out to be re-OSP'ed). We have linked lines, so, when a work order starts it stays on the line until all assembly & soldering is finished (the chance for external Cu to oxidize after exposure to multiple thermal processes is therefore very limited; our boards don't wait in lengthy queue's after reflow or glue cure). Also, we don't bake boards. Solder joint integrity is excellent with OSP. We still specify OSP on low complexity designs (very few of those anymore...). Immersion Ag is working well; also, cost has been on par with OSP (our buyer does a great job working with the suppliers). Hope this helps. Contact me off-line if you have other questions. Ellsworth D. Berkowitz, P.E. On Thu, 11 Aug 2005 14:49:08 -0600, Cheryl Johnson <[log in to unmask]> wrote: >Well I am a wife, don't have a tail (hair down to my waist, though...) >In any case, I have been using ENIG for several years with no problems. > >HOWEVER, recently our off shore fab house is wanting us to go to "OSP over >copper". > >Any comments? Thank you! > >Sincerely, >----------------------------------- >Cheryl Johnson, C.I.D.+ >Manager >ExcelStor US Office, Engineering Services >Email: [log in to unmask] >Tel: (303) 684-7291 >Fax: (303) 684-7268 >Mobile: (303) 809-5815 >----------------------------------- > > >-----Original Message----- >From: TechNet [mailto:[log in to unmask]]On Behalf Of John Burke >Sent: Thursday, August 11, 2005 1:16 PM >To: [log in to unmask] >Subject: Re: [TN] <Misc>Re: [TN] <Misc>Re: [TN] RoHs board surface >recommendations. > > >Yup....................... > >Lets change the chemistry topic...............Ice cream anyone?? > >John > >------------------------------------ >Avanex >John Burke >Senior Manager RoHS Compliance >[log in to unmask] >40919 Encyclopedia Circle >Fremont >CA 94538 >tel: 510 897 4250 >fax: 510 979 0189 >mobile: 510 676 6312 >------------------------------------ > > >-----Original Message----- >From: TechNet [mailto:[log in to unmask]]On Behalf Of Stadem, Richard >Sent: Thursday, August 11, 2005 1:09 PM >To: [log in to unmask] >Subject: Re: [TN] <Misc>Re: [TN] <Misc>Re: [TN] RoHs board surface >recommendations. > > >It must be Friday for some of us:) > >-----Original Message----- >From: TechNet [mailto:[log in to unmask]] On Behalf Of Chris Ball >Sent: Thursday, August 11, 2005 2:48 PM >To: [log in to unmask] >Subject: Re: [TN] <Misc>Re: [TN] <Misc>Re: [TN] RoHs board surface >recommendations. > >......unnnnh........no tail.......wife..........must >resist.........arrrrgh.... > > > > > Steve Hodge > <[log in to unmask]> To: >[log in to unmask] > Sent by: TechNet cc: > <[log in to unmask]> Subject: Re: >[TN] <Misc>Re: [TN] > <Misc>Re: >[TN] RoHs board surface > 08/11/2005 03:36 PM recommendations. > Please respond to TechNet > E-Mail Forum; Please > respond to Steve Hodge > > > > > > > >George, I am sorry you feel you have to downgrade my opinion as being a >sales pitch or "wife's tail". I am stating data -substantiated facts and >I could care less about selling something to you or anyone else. A >wife's tail? What? My wife does not have a tail. I think it should be >"wive's tale" anyway. > >At 12:30 PM 08/11/2005, you wrote: >>John, >> >>Your opinionated! but then too so am I. However, it sounds like our >>opinions are based on data and not "wife's tails" or "sales pitches" >> >>Regards, >>George >>George M. Wenger >>Reliability / FMA Engineer >>Base Station and Subsystems Group >>Andrew Corporation, 40 Technology Drive, Warren, NJ 07059 (908) >>546-4531 [log in to unmask] >> >> >>-----Original Message----- >>From: TechNet [mailto:[log in to unmask]]On Behalf Of John Burke >>Sent: Thursday, August 11, 2005 2:16 PM >>To: [log in to unmask] >>Subject: Re: [TN] <Misc>Re: [TN] RoHs board surface recommendations. >> >> >>Very nice, >> >>Until you consider that ENIG infringes the design rules for at least >>one >of >>the top 3 global CM's due to the issues associated with it. >> >>If you want the number of their chief technologist who has to look at >enigma >>failures week in week out I will happily supply details off line. >> >>I personally have built hundreds of thousands of assemblies on ENIG as >well >>as Immersion AG. >> >>As for the rest, HASL is generally failure related to a complete lack >>of understanding of tin thickness and intermetallic growth rate, OSP >>failures generally are related to not understanding the degradation of >>that finish with multiple reflow cycling, and personally I would never >>use immersion >tin >>without some type of diffusion barrier between it and the copper if nay >time >>in storage was to be considered. >> >>The ENIG when it fails can be catastrophic............and in most cases >can >>be pointed back to the process at the fab house rather than what >>happened >to >>it during the assembly process, unlike most of the other finish >>defects, >and >>has to my knowledge resulted in multi million dollar lawsuits between >>companies in the bay area due to failures. >> >>If it doesn't fail - it is fine, but the joint shear strength is less >>than the equivalent HASL or immersion AG finish due to the Tin >>nickel/nickel copper crystalline structure, so taking into >>consideration the higher temperatures of lead free I would be vary >>careful using it for area array packages using this soldering >technology. >> >>For the record have been using immersion silver since 1996 as I >>produced >the >>first beta site production runs using alpha level, so perhaps my views >have >>a little more history. >> >>Call me opinionated - I'll take it. >> >>John >> >> >> >> >> >> >> >>------------------------------------ >>Avanex >>John Burke >>Senior Manager RoHS Compliance >>[log in to unmask] >>40919 Encyclopedia Circle >>Fremont >>CA 94538 >>tel: 510 897 4250 >>fax: 510 979 0189 >>mobile: 510 676 6312 >>------------------------------------ >> >> >>-----Original Message----- >>From: Steve Hodge [mailto:[log in to unmask]] >>Sent: Thursday, August 11, 2005 10:44 AM >>To: TechNet E-Mail Forum; John Burke >>Subject: Re: <Misc>Re: [TN] RoHs board surface recommendations. >> >> >>John, come on now. Anything can happen at any time. I have seen some >>reservations from the IS users as to silver migration possibilities and > >>shelf life/handling issues --you might say they have not seen them >--"yet". >>I have had more problems with HASL, OSP and IT than I have with ENIG. >>ENIG has longer data history than IS, so both shoes have already >>dropped so to speak. Three years without problems, is an eternity in >>this business, especially when we are expected to build custom >products in 24 hours. >> >> >>At 11:00 AM 08/11/2005, you wrote: >> >with it............YET.......... >> > >> >------------------------------------ >> >Avanex >> >John Burke >> >Senior Manager RoHS Compliance >> >[log in to unmask] >> >40919 Encyclopedia Circle >> >Fremont >> >CA 94538 >> >tel: 510 897 4250 >> >fax: 510 979 0189 >> >mobile: 510 676 6312 >> >------------------------------------ >> > >> > >> >-----Original Message----- >> >From: TechNet [mailto:[log in to unmask]]On Behalf Of Edwin Louis >> >Sent: Thursday, August 11, 2005 4:48 AM >> >To: [log in to unmask] >> >Subject: Re: [TN] RoHs board surface recommendations. >> > >> > >> >We have been using ENIG now for about three years and have had no bad > >> >experiences with it. NASA for one does not allow the use of silver . >> > >> >-----Original Message----- >> >From: TechNet [mailto:[log in to unmask]] On Behalf Of Werner Engelmaier >> >Sent: Wednesday, August 10, 2005 4:57 PM >> >To: [log in to unmask] >> >Subject: Re: [TN] RoHs board surface recommendations. >> > >> >Hi Steve, >> >I do not know about "bad-mouth ENIG"--I am a reliability consultant, >> >and have had plenty of calls because of ENIG related failures, but >> >not a one >about >> >iAg. On the other hand, I do not know about their respective >environmental >> >implications. >> > >> >Regards, >> >Werner Engelmaier >> >Engelmaier Associates, L.C. >> >Electronic Packaging, Interconnection and Reliability Consulting >> >7 Jasmine Run >> >Ormond Beach, FL 32174 USA >> >Phone: 386-437-8747, Fax: 386-437-8737, Cell: 386-316-5904 >> >E-mail: [log in to unmask], Website: www.engelmaier.com >> > >> > >> >--------------------------------------------------- >> >Technet Mail List provided as a service by IPC using LISTSERV 1.8e 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 >> >----------------------------------------------------- >> > >> >--------------------------------------------------- >> >Technet Mail List provided as a service by IPC using LISTSERV 1.8e 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 >> >----------------------------------------------------- >> > >> >--------------------------------------------------- >> >Technet Mail List provided as a service by IPC using LISTSERV 1.8e 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 >> >----------------------------------------------------- >> >> >>--------------------------------------------------- >>Technet Mail List provided as a service by IPC using LISTSERV 1.8e 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 >>----------------------------------------------------- >> >>---------------------------------------------------------------------- - >>------------------------- > >>This message is for the designated recipient only and may contain >>privileged, proprietary, or otherwise private information. >>If you have received it in error, please notify the sender immediately >>and delete the original. Any unauthorized use of this email is >>prohibited. >>---------------------------------------------------------------------- - >>------------------------- > >>[mf2] >> >>--------------------------------------------------- >>Technet Mail List provided as a service by IPC using LISTSERV 1.8e 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 >>----------------------------------------------------- > 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