Inge "... we used a special tool to take samples from our balls. ... that something erects from the balls" Are you trying to turn this thread into p0rn? Brian Inge wrote: > TX John, > reminds me (short cut>short hand>key>morse) of 150 speed morse, when our > land based station sent this to me on the destroyer: "Is this Missis > Mississippihiss ?" - It was a test before sending 5 group codes. Not > appreciated at all. > >> Ahhhhhhhh Inge, >> >> That would be Miss Placed that young lady in the e-filed library. >> >> When you download it be sure to book mark it with a short cut......... >> >> John > > > About PbCO3, we used a special tool to take samples from our balls. The > following SEM/EDAX showed, with 95% confidence, that something erects from > the balls: Lead whiskers ! Starts with tiny, less than 0.1 um wide, > whiskers. They seem to grow in all three coordinates, until several um wide > and many um long. Close SEM images show how they protrude through the ball > surface, which is >95% Lead. Looks like a seal's periscope penetrating the > polar ice with Rock Hudson as captain. > > jk proposed, that the balls may be plated, and that this plating creates > mechanical tensions, which starts the whisker growth. Anyone heard of such > overplating for BGAs? Wafer bumps, yes, but not heard of such treatment for > BGAs. > > I'll send scary pics to Stefanos Gregorius. > > Inge > > > > > ----- Original Message ----- > From: "P. Langeveld" <[log in to unmask]> > To: <[log in to unmask]> > Sent: Monday, September 04, 2006 8:49 PM > Subject: Re: [TN] PbCO3 > > >> That guy is me: Peer Langeveld, Consultant Soft Soldering Processes, >> living at 5502 VH 8 The Netherlands, pupil of R.J. Klein Wassink, with >> 26 years of experience in soft soldering processes whereof 10 years in >> lead-free soldering (IDEALS project). >> >> By the way, CBGA's were not known in the early eighties of the last >> century. >> >> I just mentioned lead whisker growth as an option. A picture is known >> (Klein Wassink, page 295) and the needle form is simular to the SEM >> photo, combined with the EDAX analysis that only shows lead. And >> whiskers grow very fast under stress conditions. >> >> >> 2006/9/4, Ingemar Hernefjord (KC/EMW) <[log in to unmask]>: >>> Triple Hmmm! >>> >>> I used Gilette, which is little rough, but it works fine: dropped a >>> board in LN2. When at -196 knocked the backside of the board, and the >>> CBGA jumped off. Could then study the cleanliness. No flux residues or >>> whatsoever. >>> Yepp, Vigon is indeed very active, but why does the phenomenon appear >>> only on CBGAs? We have other BGAs on the board, and these have never >>> shown such growths. >>> >>> I'm attempted to go on quite another track for a while. One guy proposed >>> whisker growth. And, when you look at the SEM image, you find something >>> looking like pressing toothpaste out of its tube: whiskers? The guy (who >>> was it?) meant that CBGAs build up mechanical stress unlike other >>> components, and hence create whiskers. >>> >>> Lead whiskers? Quadruple Hmmm. The litterature is very thin about Lead >>> whiskers, not to say nearly non-existent. A few cases are reported, but >>> not regarding any BGAs, as far as I know. However, I will study the few >>> samples I got (am not allowed to touch the sharp boards)and see if it >>> can be Lead whiskers, or other type of Lead crystals. According to Sod's >>> law, I may be the one to be haunted by Lead whiskers... >>> >>> Inge >>> >>> >>> -----Original Message----- >>> From: TechNet [mailto:[log in to unmask]] On Behalf Of Mike Fenner >>> Sent: den 4 september 2006 09:38 >>> To: [log in to unmask] >>> Subject: Re: [TN] PbCO3 >>> >>> Double Hmmmm! >>> >>> Applying Occam's Razor to this. Put everything you have done to one side >>> for a moment and just imagine you were at the early stages of >>> investigating this problem. >>> You would describe a situation where you are using a reputable resin >>> based flux and then clean them in a reputable semi-aqueous cleaner. >>> Everywhere is OK, except under a large component. >>> My immediate thought would be that you are not cleaning under the >>> component as well as you think or at least are not washing/rinsing out >>> the cleaner. >>> Vigon is a very high pH material and therefore chemically active. >>> How do you know you have cleaned under the device? Are you lifting it >>> off to do something like ROSE? If there is a flush though problem then >>> ROSE will not detect it. >>> My apologies for pointing out what is basic stuff like this to someone >>> with your knowledge/experience, but sometimes it is easy to overlook >>> something when it is too simple. >>> >>> >>> Regards >>> >>> Mike >>> >>> >>> >>> -----Original Message----- >>> From: TechNet [mailto:[log in to unmask]] On Behalf Of Hfjord >>> Sent: Sunday, September 03, 2006 10:19 AM >>> To: [log in to unmask] >>> Subject: Re: [TN] PbCO3 >>> >>> Hmmm.... >>> >>> I have excluded residues that stem from reactions with the solder mask >>> and other reactions from solvents and fluxes. The reason is, that such >>> residues appear immediately after the soldering process, while our >>> residues GROW slowly during weeks and months. And only on CBGAs. >>> Furthermore, we have investigated the space between the CBGAs and the >>> board, and it's absolutely clean, because we use a very effective and >>> powerful Vigon 200 washing machine. >>> So, it is still a mystery. >>> >>> Inge >>> >>> >>> >>> ----- Original Message ----- >>> From: "Mike Fenner" <[log in to unmask]> >>> To: <[log in to unmask]> >>> Sent: Thursday, August 31, 2006 4:20 PM >>> Subject: Re: [TN] PbCO3 >>> >>> >>> >I can puzzle out how you could get carbonate but not how you would get >>> >lead carbonate. Lead is unreactive compared to other metals present >>> >and they would react in favour of the lead, or even if the lead >>> >reacted would displace it in the corrosion cell reaction. >>> > If you are getting significant carbonate formed so quickly then this >>> >would imply a fairly high acidity on the work, which is hard to relate >>> >>> >to that found in electronic grade fluxes. >>> > >>> > You have nothing to lose by trying an activated rosin base flux to >>> > reduce this stuff -whatever it is - and floating it away as a >>> > slag/dross in the rosin, but I doubt it would be effective unless you >>> re-melted the solder. >>> > If >>> > you were to do that it would be similar to some purification processes >>> >>> > for solders [and other metals,] >>> > >>> > >>> > Regards >>> > >>> > Mike Fenner >>> > Indium Corporation >>> > >>> > T: + 44 1908 580 400 >>> > M: + 44 7810 526 317 >>> > F: + 44 1908 580 411 >>> > E: [log in to unmask] >>> > W: www.indium.com >>> > Pb-free: www.Pb-Free.com >>> > >>> > >>> > >>> > -----Original Message----- >>> > From: TechNet [mailto:[log in to unmask]] On Behalf Of Ingemar Hernefjord >>> > (KC/EMW) >>> > Sent: Thursday, August 31, 2006 9:21 AM >>> > To: [log in to unmask] >>> > Subject: [TN] PbCO3 >>> > >>> > >>> > We got lots of such growth on CBGA balls recently. After >>> > soldering/cleaning: nada. After one week in stock: signs of growth. >>> > After one month: unacceptable crystals. Now, being insoluble in water >>> > and many solvents, some specialists advise you to mix an RA with >>> > ethanol, heat this mixture and dip the part until the crystals vanish. >>> > My question to TN is whether there is alternative methods? Some accept >>> > PbCO3 growth as being harmless, but this is not our intention, because >>> >>> > loose particles are semiconducting and can create leakage current >>> paths. >>> > >>> > Brian's book "Cleaning and Contamination of Electronics and >>> Assemblies" >>> > mention there are five groups of white residues, but, oddly enough, >>> > lead carbonate is not included. The chemistry world of soldering >>> > residues is so complicated, that I have to ask you for help. >>> > >>> > Thanks in advance >>> > Ingemar Hernefjord >>> > Ericsson Microwave Systems >>> > >>> > --------------------------------------------------- >>> > 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 email, its content and any files transmitted with it are >>> > intended solely for the addressee(s) and may be legally privileged >>> > and/or confidential. 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