Rev. P05

19

VPN12AD02-FU

REFLOW PARAMETERS:

Lead-free soldering process is a standard of electronic products production. Solder alloys like Sn/Ag,

Sn/Ag/Cu and Sn/Ag/Bi are used extensively to replace the traditional Sn/Pb alloy. Sn/Ag/Cu alloy

(SAC) is recommended for this power module process. In the SAC alloy series, SAC305 is a very

popular solder alloy containing 3% Ag and 0.5% Cu and easy to obtain. Following figure shows an

example of the reflow profile diagram. Typically, the profile has three stages. During the initial stage

from room temperature to 150°C, the ramp rate of temperature should not be more than 3°C/sec. The

soak zone then occurs from 150°C to 200°C and should last for 60 to 120 seconds. Finally, keep at over

217°C for 60 seconds limit to melt the solder and make the peak temperature at the range from 240°C

to 250°C. It is noted that the time of peak temperature should depend on the mass of the PCB board.

The reflow profile is usually supported by the solder vendor and one should adopt it for optimization

according to various solder type and various manufacturers’ formulae.

FIG.39 Recommendation Reflow Profile