The main process parameters of reflow soldering equipment are heat transfer, chain speed control and wind speed and air volume control.
1. Control of heat transfer in soldering oven.
At present, many products use lead-free technology, so the reflow soldering machine used now is mainly hot air reflow soldering. In the lead-free soldering process, it is necessary to pay attention to the heat transfer effect and heat exchange efficiency. Especially for components with large heat capacity, if sufficient heat transfer and exchange cannot be obtained, the heating rate will be significantly lower than that of devices with small heat capacity, resulting in lateral temperature difference. . The air flow mode of the reflow oven body directly affects the heat exchange speed. Two hot air transfer methods for reflow soldering are: micro-circulation hot air transfer method, and the other is called small-circulation hot air transfer method.
2. Control of chain speed of reflow soldering.
The control of the chain speed of the reflow soldering equipment will affect the lateral temperature difference of the circuit board. Generally speaking, reducing the chain speed will give the device with large heat capacity more time to heat up, thereby reducing the lateral temperature difference. But after all, the setting of the furnace temperature curve depends on the requirements of the solder paste, so it is unrealistic to reduce the chain speed without limit in actual production.
3. Control of air speed and air volume of reflow soldering equipment.
Keep the other conditions in the reflow oven unchanged and only reduce the fan speed in the reflow oven by 30%, the temperature on the circuit board will drop by about 10 degrees. It can be seen that the control of air speed and air volume is important to furnace temperature control.
In order to realize the control of wind speed and air volume, two points need to be paid attention to:
a. The speed of the fan should be controlled by frequency conversion to reduce the influence of voltage fluctuations on it;
b. Minimize the exhaust air volume of the equipment, because the central load of the exhaust air is often unstable, which easily affects the flow of hot air in the furnace.
Post time: Oct-14-2022