Hi David,
thx for rapid reflexions.
stock condition: 25 Centigrades @ 30-50 % RH unfiltered and common office
stored in ESD plastic bags
njet FTIR but EDAX will be done tomorrow Friday
photos to Steve tomorrow Friday
I hope the above isn't assendially unintelligiggle
Inge



----- Original Message -----
From: "David D. Hillman" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Thursday, August 31, 2006 1:24 PM
Subject: Re: [TN] PbCO3


> Hi Ingemar! I'll assume that your CBGA has a 90Pb10Sn solderball which
> would account for a large enough source of Pb to allow for the formation
> of
> PbCO3. What is puzzling is that Sn preferentially oxidizes before Pb which
> I would think would inhibit the formation of PbCO3 (e.g. competing surface
> species growth reactions). What type of environment is the CBGA exposed
> too? I can't image your stock room being an environment to promote the
> growth of PbCO3. What are the CBGAs stored in? Have you conducted an FTIR
> test to see if there is a flux residue film on the CBGA solderballs after
> cleaning? Oh, do you have any of your usual cool photos of the PbCO3 that
> Steve can post?
>
> Dave Hillman
> Rockwell Collins
> [log in to unmask]
>
>
>
>
>             "Ingemar
>             Hernefjord
>             (KC/EMW)"                                                  To
>             <ingemar.hernefjo         [log in to unmask]
>             [log in to unmask]>                                           cc
>             Sent by: TechNet
>             <[log in to unmask]>                                     Subject
>                                       [TN] PbCO3
>
>             08/31/2006 03:20
>             AM
>
>
>             Please respond to
>              TechNet E-Mail
>                   Forum
>             <[log in to unmask]>
>             ; Please respond
>                    to
>                 "Ingemar
>                Hernefjord
>                 (KC/EMW)"
>             <ingemar.hernefjo
>             [log in to unmask]>
>
>
>
>
>
>
>
> 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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