In your former life...you must have seen a lot!
Yes, I was afraid of making a mistake too, so, in order to be sure, we'll do
FTIR.
The strange thing is, that these residues only appear on CBGAs. Other
components on the board never get such crystals. I have the book, and I
will have a look at the picture you mention.
Thanks/Ingemar
----- Original Message -----
From: "P. Langeveld" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Thursday, August 31, 2006 10:16 PM
Subject: Re: [TN] PbCO3
> Dear Ingemar,
>
> Are you sure it is PbCO3? Did you made a chemical analysis?
> What you describe sounds to me as recrystallization of colophony
> residues on the board.
> In my former life I also made that misinterpretation until my teacher
> Klein Wassink
> put me on the right direction. In his book there is a picture of it
> (page 218, 2nd edition).
>
> Regards,
> Peer Langeveld
> Consultant Soft Soldering Processes
> 5502 VH 8 The Netherlands
>
> 2006/8/31, Ingemar Hernefjord (KC/EMW) <[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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