Thanks Dave As always prince valiant-but Diet coke-I begin to doubt... When you come back from supper- What about the differences between immersion silver coating processes? What should I look for? Tested solderability from Two suppliers- both were OK, but then-x-rayed BGA's on the same board cat.no.- and PUFF! one had voids staying on the circuit pads SOOOOOO big, the other-just very few.Did them on a mixed batch concommitent. Gaby ----- Original Message ----- From: <[log in to unmask]> To: <[log in to unmask]> Cc: <[log in to unmask]> Sent: Tuesday, November 26, 2002 1:46 AM Subject: Re: [TN] Immersion Tin > > Hi Gaby! The Achilles heel of all tin finishes - immersion tin included - > has been its thermal degradation characteristics. Thermal excursions cause > two degradation mechanisms: 1) the growth of surface oxidation - as the SnO > oxide transforms to SnO2 oxide the solderability goes downhill very fast; > 2) the growth of copper/tin intermetallic phases - if the copper/tin > intermetallic phases (especially the Cu3Sn phase but also the Cu6Sn5 phase) > reach the surface and become oxidized then the solderability goes to zero. > Remember - the more active the flux system you use the less impact both > these mechanism have in your production process. What differentiates the > various available immersion tin chemistries from each other is how each of > the individual chemistry suppliers formulates their immersion tin bath to > account for these two degradation mechanisms. I agree with you on > procurement - if you need an immersion tin finish which will withstand > multiple thermal excursions then you should expect to pay more and have > fewer potential chemistry supplier choices. If you only need one thermal > excursion pass then more immersion tin possibilities exist. The needs of > the process should be matched to the characteristics of the surface finish > - and both the pwb fabricator and pwb user need to work together to meet > those goals. Enough said - I'm off to find a Diet Coke for supper! > > Dave > > > > > Gaby Bogdan <[log in to unmask]> on 11/25/2002 06:19:51 PM > > To: "TechNet E-Mail Forum." <[log in to unmask]>, > [log in to unmask] > cc: > > Subject: Re: [TN] Immersion Tin > > > Dave, > What is the cause of "degradation"? > Do you mean that this process is not the same from one supplier to the > other > ? And even more- that the procuring department should buy boards from > different suppliers according to their proven performance for each > finishing > process? > By the way- that's what we try to do. > Gaby > ----- Original Message ----- > From: "Dave Hillman" <[log in to unmask]> > To: <[log in to unmask]> > Sent: Monday, November 25, 2002 11:53 PM > Subject: Re: [TN] Immersion Tin > > > > Hi Yannick! Not all immersion tin chemistries are created equal - some > are > > much more robust in terms of thermal excursion degradation than others. I > > recommend you conduct a solderability test per JSTD-003 to determine if > > your solderability has gone south or if you are having a solder process > > issue. Good Luck. > > > > Dave > > > > > > > > > > Yannick Brisson <[log in to unmask]>@ipc.org> on 11/25/2002 07:03:35 AM > > > > Please respond to "TechNet E-Mail Forum." <[log in to unmask]>; Please > respond > > to Yannick Brisson <[log in to unmask]> > > > > Sent by: TechNet <[log in to unmask]> > > > > > > To: [log in to unmask] > > cc: > > > > Subject: [TN] Immersion Tin > > > > > > Hi, > > > > I made a board wich I plated with immersion Tin, I tought it should be > > the > > same result as we had with tin lead but we ran into a weird problem. We > > use > > a 63/37 no clean paste and on the Board with Immersion Tin the solder > just > > make a ball ON the pad...we ran the same profile with a board Tin-Lead > and > > we get almost a perfect solder joint. Because it's immersion tin should > we > > put our temperature higher? > > > > We try to solder with a iron and the paste can hardly wet all the pad > the > > fisrt time..if we do it a first time, cleand the pad and do it again it's > > more easy. If someone have work with it can give me some trick I would > > appreciate. > > > > Thanks You > > > > Yannick Brisson > > ============================ > > Technicien Ingénierie de Production > > Technician Production ingineering > > M2S Électronique > > 2855, Rue de Celles > > Québec, Québec > > G2C 1K7 > > Téléphone: (418) 842-1312 Ext: 264 > > Télécopie: (418) 842-0123 > > [log in to unmask] > > ============================ > > > > --------------------------------------------------- > > Technet Mail List provided as a free 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/html/forum.htm for > additional > > information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 > > ext.5315 > > ----------------------------------------------------- > > > > > > > > --------------------------------------------------- > > Technet Mail List provided as a free 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/html/forum.htm for > additional > > information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 > ext.5315 > > ----------------------------------------------------- > > > > > > > > --------------------------------------------------- Technet Mail List provided as a free 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/html/forum.htm for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 -----------------------------------------------------