How to control the process parameters of reflow soldering equipment

The main process parameters of reflow soldering equipment are heat transfer, chain speed control and wind speed and air volume control. Jeenoce Electronics will share with you in detail below.

1. Control of heat transfer in reflow soldering equipment

At present, many products use lead-free process, so the reflow equipment used now is mainly hot air reflow. In the lead-free welding process, we need to pay attention to the heat transfer effect and heat exchange efficiency. Especially for the components with large heat capacity, if they can not get sufficient heat transfer and exchange, the heating speed will obviously lag behind the components with small heat capacity, resulting in transverse temperature difference. The air transportation mode of reflow furnace directly affects the heat exchange rate. There are two hot air transmission modes for reflow soldering: microcirculation hot air transmission mode and small circulation hot air transmission mode.

The hot air in the microcirculation hot air is blown out from the hole of the heating plate, the flow of the hot air flows in a small range, and the surrounding heat transfer effect is poor. The design of small circulation is due to the concentrated flow of hot air and clear directionality. The heat transfer effect of such hot air heating increases by about 15%, and the increase of heat transfer effect will play a great role in reducing the transverse temperature difference of large and small heat capacity devices.

2. Control of chain speed of reflow soldering equipment

The control of chain speed of reflow soldering equipment will affect the transverse temperature difference of circuit board. Generally speaking, reducing the chain speed will give more heating time to devices with large heat capacity, so as to reduce the transverse temperature difference. However, after all, the setting of furnace temperature curve depends on the requirements of solder paste, so it is unrealistic to reduce the chain speed without limitation in actual production.

3. Control of wind speed and air volume of reflow soldering equipment

Keep other conditions in the reflow equipment furnace unchanged, and only reduce the fan speed in the reflow furnace by 30%, and the temperature on the circuit board will drop by about 10 degrees (Fig. 4). It can be seen that the control of wind speed and air volume is of great importance to the control of furnace temperature.

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 shall be controlled by frequency conversion to reduce the impact of voltage fluctuation on it;

b. Try to reduce the exhaust air volume of the equipment, because the central load of the exhaust air is often unstable, which is easy to affect the flow of hot air in the furnace.