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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