Small chamber study of lead exposures from manual soldering of microelectronics

Airborne and surface Pb concentrations were measured inside a glovebox chamber with controlled inflow rate at 1.0 L/min of ultrapure air over a 4-hour period while an operator completed 1,680 solder connections using Sn63:Pb37 solder with rosin flux core. Chamber atmosphere showed released mean Pb mass of 0.0238 +/- 0.011 mu g and mean airborne concentration of 0.176 +/- 0.085 mu g/m(3). Of the total solder mass used in two trials, on average 4.65% was recovered from the tip cleaning sponge and 0.14% dropped onto the work surface, with a surface loading rate of 0.30-0.45 mu g/cm(2). The estimated fingertip surface area in contact with solder wire was 14.7 cm(2), with a measured average Pb mass of 14.9 mu g, and a corresponding dermal loading rate of 1.01 mu g/cm(2). The waste solder dross surface area determined from digital micrographs in each trial were 1.65 and 2.43 cm(2), with corresponding Pb density of 714 and 610 mg/cm(2) and >90% of the detected dross mass comprising particles >100 mu m in the widest dimension. Corresponding increases in blood Pb levels estimated using physiologically-based pharmacokinetic modeling were negligible compared with background. These findings demonstrate very low Pb emissions to air and surfaces during intensive manual microelectronic soldering activities.

Automated summary

During intensive manual microelectronic soldering activities, very low levels of lead emissions to air and surfaces were observed, especially in terms of lead released during soldering operations.