Effect of reflow repair on interpretation of the quality of BGA rework station

Effect of reflow repair on interpretation of the quality of BGA rework station

BGA rework station need to set temperature curve according to the different curve of solder paste, so that

the welding disc temperature curve and solder paste rate of close. General use of multi zone heating method

is shown in Figure 1, the temperature curve is divided into preheating zone, active region, recirculation zone,

cooling zone.

(1) preheating zone, also known as the slope area, so that the temperature from the ambient temperature to

the solder temperature, damage to the metal oxide film to make the solder alloy powder surface clean, is

conducive to the formation of solder and solder joints. The heating rate in this area should be controlled in

the appropriate range, if the temperature is too fast, the substrate and the device may be damaged. If too

slow, there is not enough time to make PCB reach the active temperature, which leads to the evaporation of

the solvent, which affects the welding quality. The maximum temperature is 4 /sec, the usual temperature is

1 ~ 3 /sec.

(2) active region (Soak stage), sometimes called a warm zone, refers to the temperature increased from 140

DEG C to 170 DEG C, main purpose is the PCB component temperature tends to be uniform, and minimize

the temperature difference; allow the flux activity, the pad and the solder ball and the component pin removal

of oxides. This area generally accounts for the heating of the 33~50%, which requires 40~120s.