Temperature Setting for Each Temperature Zone of SMT Reflow Oven

 

When the PCB board enters the reflow oven zone, the temperature in the furnace rises rapidly to melt the solder paste, and the liquid solder forms solder joints to the components. The temperature of the reflow soldering oven zones is set relatively high, so that the temperature in the furnace rises rapidly to the peak temperature. The peak temperature is generally determined by the melting temperature of the solder paste and the heat resistance temperature of the PCB substrate and components. The temperature of the SMT reflow oven zone is from 217 ° C to Tmax to 217 ° C, and the entire interval is maintained at 60 to 90s. If there is a BGA, the peak temperature should be set within 240 to 260 degrees and maintained for about 40 seconds. In addition, it should be noted that in the reflow area, the reflow soldering time should not be too long, so as not to cause damage to the furnace, or cause the PCB board to be scorched or the component malfunctions.

 

The role of the cooling zone is to let the temperature drop to solidify the solder joint, and the cooling rate will affect the strength of the solder joint. If the cooling rate is too slow, it will cause eutectic metal compounds and large grains at the welding point, resulting in the strength of the welding point being too low. The temperature in this area is from Tmax to 180 ° C, and it is sufficient to cool at 75 ° C. The rate of temperature decrease should not exceed 4 ° C / s.

 

The temperature setting of each temperature zone also needs to pay attention to the following points:

1. The time for the internal temperature of the furnace to rise from room temperature to 250 ℃ cannot be higher than 6 minutes.

2. There is a temperature difference between the actual temperature in the reflow furnace and the temperature set by the system. The temperature curve setting recommended in this article is only for reference. The specific temperature curve provided by the solder paste factory and the actual situation of its own product need to be made adjustment.

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