1. Reflow oven in each temperature zone temperature and chain speed stability, can be carried out after the furnace and test the temperature curve, from cold start the machine to the stable temperature usually in 20~30 minutes.
2. Technicians of SMT production line must record furnace temperature setting and chain speed every day or for each product, and conduct controlled test of furnace temperature curve measurement regularly to monitor the normal operation of reflow soldering. IPQC shall conduct inspection and supervision.
3. Lead-free solder paste temperature curve setting requirements:
3.1 The setting of temperature curve is mainly based on:
The recommended curve provided by the solder paste supplier.
B. PCB sheet material, size and thickness.
C. Density and size of components, etc.
3.2 Requirements for lead-free furnace temperature setting:
3.2.1. The actual peak temperature is controlled from 243 ℃ to 246 ℃, and there is no BGA and QFN IC within 100 spots, and there is no product with pad size within 3MM.
3.2.2. For the products with the size of IC, QFN, BGA and PAD above 3MM and below 6MM, the measured peak temperature shall be controlled at 245-247 degrees.
3.2.3 For some special PCB products with IC, QFN, BGA or PCB board thickness of more than 2MM and PAD size of more than 6MM, the measured peak temperature can be controlled from 247 to 252 degrees according to the actual needs.
3.2.4 When special plates such as FPC soft plate and aluminum base plate or parts have special requirements, it shall be adjusted according to the actual demand (the product process instructions are special, which shall be controlled according to the process instructions)
Remarks: In the actual operation, if there is any abnormality in the furnace, SMT technicians and engineers will give immediate feedback.
3.3 Basic requirements of temperature curve:
A. Preheating zone: the preheating slope is 1~3℃/SEC, and the temperature is raised to 140~150℃.
B. Constant temperature zone: 150℃~200℃, for 60~120 seconds
C. Reflux zone: above 217℃ for 40~90 seconds, with peak value of 230~255℃.
D. Cooling area: the cooling slope is less than 1~4℃/SEC (except PPC and aluminum substrate, the actual temperature depends on the actual situation)