How to set the parameter to get the good reflow oven profile?

5.1 Setting of the Chain

The first parameter we should consider when setting reflow soldering temperature curve is the speed setting of transmission belt, which will determine the time spent by PCB passing through heating channel.

Through the specific calculation, we can get the setting of belt speed. Here we need to introduce an indicator, load factor. Load factor: F = L / (L + s) l = length of base plate, s = interval between base plate and base plate.

Transmission belt and chain

The load factor determines the influence of PCB in the furnace on the temperature in the furnace. The larger the load factor is, the more unstable the temperature in the furnace is. Generally, the value is between 0.5 and 0.9.

After weighing the efficiency and the stability of furnace temperature, the recommended value is 0.7-0.8. After knowing the length of the production board and the production beat, then we are able to calculate the transmission speed (the slowest value) of the conveyor belt.

Transmission speed (slowest value) = PCB length / 0.8/production beat. The characteristics of solder paste decides the transfer speed (the fastest value).

Most solder paste requires that the time from the beginning of temperature rise to the peak temperature in the furnace should not be less than 180 seconds.

By this way, the transfer speed (max.) = the length of the heating zone in the furnace / 180s can be obtained.

After obtaining two limit speeds, we can select the appropriate transmission speed according to the difficulty degree of the actual production products, generally taking the intermediate value.

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