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
>>> >
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>>
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