Morning Inge!
I have your pictures posted. I have never seen such stunning images! You
have opened my eyes to a strange new world! This looks like some bizzare
alien landscape. Even if I don't know exactly what they mean, I really
enjoy looking at them! Here they are for everyone to see:
http://stevezeva.homestead.com/files/daniel121b.jpg
http://stevezeva.homestead.com/files/daniel131b.jpg
http://stevezeva.homestead.com/files/daniel141b.jpg
-Steve Gregory-
> 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
>> >
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