There is no very accurate standard for the temperature setting of the eight temperature zones of SMT reflow soldering, which is determined according to the quality of SMT solder paste, actual soldered products and SMT reflow soldering machine. It is usually set according to the actual soldering situation based on the temperature range given by the SMT solder paste manufacturer. The standard temperature standard for SMT reflow soldering in eight temperature zones can only have the highest temperature range. The maximum temperature of SMT reflow soldering with lead-free solder paste is about 245°C, and the maximum temperature of SMT reflow soldering with lead solder paste is about 215°C. If the temperature standard of the eight temperature zones of SMT reflow soldering is specifically given, it can only be a reference temperature curve.

Generally speaking, the standard SMT reflow soldering is the eight-temperature zone reflow soldering. This is based on the actual soldered products and the actual consideration of the SMT chip processing manufacturer. If the soldering quality of circuit boards is relatively high, there are more manufacturers of SMT reflow soldering in ten temperature zones and twelve temperature zones. Usually The common SMT reflow soldering on the market is the SMT reflow soldering in the eight temperature zones.

No matter how many temperature zones SMT reflow soldering is, their overall temperature zone is divided according to the four temperature zones: preheating zone, constant temperature zone, welding zone, and cooling zone. The temperature of the eight temperature zones of lead-free solder paste SMT reflow soldering is also divided according to these four temperature zones. The following are the four temperature standard reference for lead-free solder paste SMT reflow soldering.

1. Preheating zone: The preheating zone is heated to 175 degrees, and the time is about 100S. From this, the heating rate of the preheating zone can be obtained. In the preheating zone, the time is 146-46=100S, since the room temperature is 26 degrees, 175-26=149 degrees, and the heating rate is 149 degrees/100S=1.49 degrees/S).

2. Constant temperature zone: The high temperature of the constant temperature zone is about 200 degrees, the time is 80S, and the difference between the high temperature and the low temperature is 25 degrees.

3. Reflow zone: the high temperature of the reflow zone is 245 degrees, the low temperature is 200 degrees, and the time to reach the value is about 35/S; the heating rate of the reflow zone is: 45 degrees/35S=1.3 degrees/S According to (how to Correct set temperature curve), we can know that the time for this temperature curve to reach the value is too long. The whole reflow time is about 60S.

4. Cooling zone: The cooling zone takes about 100S, the temperature drops from 245°C to 45°C, and the cooling speed is: 245°C-45°C=200°C/100S=2°C/S.

SMT reflow soldering temperature settings in eight temperature zones: first zone 160°C, second zone 180°C, third zone 185°C, fourth zone 185°C, fifth zone 210°C, sixth zone 250°C, seventh zone 275°C , the eighth zone 250 ℃. Chain speed 50CM/MIN can try this furnace temperature, of course, it must be adjusted according to the reference value of the temperature curve given by the solder paste manufacturer and the actual production situation.