Oumphf!
You can't pronounce that? Like me not being able to see what strange
roses we find between the balls after BGA on FR4 after 10 minutes in a
REHM heat conveyour oven. Top temp is +230 / 1 minute. Preheat is
included in the 10 minutes. Kester 229D is used (if a Kester man reads
this, please give a line or two in response. The residues grow to
something that reminds of roses or cabbage! Colour in daylight is white,
but the residues do not seem to belong to the ordinary white residues
(Tin Abiate, polymerized rosin and lead salts). Flakes are <<1micron
thick and up to 50microns in diameter. EDAX gives 99%Lead and bal is
some Tin and Carbon and other random elements. Not soluble in the usual
solvents like Ethylene, Perclorethylene, Acetone etc. And that is
natural, as the residues are inorganic. Kester 229D is not QPL'd. Paste
Sn62Pb36Ag2 is screenprinted on traditional Cu/Ni/Sn-pads. We have used
this Kester formula for years for other products without seeing cabbage
nor roses. BGA is ceramic C4 from Mota, number of balls (bumps) approx.
25x25 matrix.

Can it be PbCO3?  The flux is RMA and contains clorides.

The line is stopped, nothing will be delivered until the cabbage growth
is eliminated. Special question to SIRguru labs: can we send this job to
you if our qualification does not cover the need?

Regards
Ingemar Hernefjord
Ericsson Microwave Systems