The melting point of lead-free solder paste is 217 degrees. The common composition of lead-free solder paste is: Sn/Ag/Gu, and its ratio is: 96.5/3.0/0.5. China PCBA factory SYS Technology takes tin-silver-copper solder paste as an example to explain what temperature set of the lead-free reflow soldering in each temperature zone.

1. Temperature setting of lead-free reflow preheating zone
The preheating zone is heated to 175 degrees, and the time is about 100S, from which the heating rate of the preheating zone can be obtained (because this tester uses an online test, it has not entered the preheating zone during the period from 0 to 46S, and the time is 146 -46=100S, since the room temperature is 26 degrees, the heating rate is 175-26=149 degrees; 149 degrees/100S=1.49 degrees/S).
2. Temperature setting of lead-free reflow soldering constant temperature zone
The maximum temperature of the constant temperature zone is about 200 degrees, the time is 80S, and the difference between the maximum temperature and the minimum temperature is 25 degrees.
3. Temperature setting of lead-free reflow soldering reflow zone
The highest temperature in the reflow zone is 245 degrees, the lowest temperature is 200 degrees, and the time to reach the peak is about 35/S; the heating rate in the reflow zone is: 45 degrees/35S=1.3 degrees/S. it can be seen that the time for this temperature curve to reach the peak is long. The whole reflow time is about 60S.
4. Lead-free reflow soldering cooling zone temperature setting
Cooling zone's time is
100s.