How to Choose Reflow Welding Machine for SMT Electronics Factory

In recent years, the development of reflow soldering has been very rapid, and there have been many low-priced and low-quality reflow soldering equipment on the market. When electronic manufacturers choose reflow soldering machines, they are unsure where to start due to the significant price difference. They have doubts about how to choose a good reflow soldering machine. JEENOCE shares how to choose a reflow soldering machine.

1. A good reflow soldering machine has good insulation performance and high thermal efficiency, while a poor reflow soldering machine's insulation performance cannot meet the requirements. Although the thermal efficiency of the furnace is difficult to measure, the temperature can be determined by touching the outer shell of the reflow furnace and exhaust duct with your hand. Usually, this is the heat dissipation area. When you feel hot or hesitant to touch it with your hand, it indicates that the insulation performance of the furnace is poor and energy consumption is high. Normally, there is a slight feeling of heating by hand (about 50 degrees Celsius).

2. The evaluation of the furnace temperature of the reflow welding machine is an important step in selecting a reflow furnace, usually evaluated through the following methods:

(1) Uniformly adjust the temperature on the cross-section of the furnace chamber. Turn on the reflow welding machine track to the position, place a PCB, and set 5-6 test points along the cross-section of the furnace on the PCB. Measure the temperature difference on the board surface when unloaded, and the temperature difference should be less than 0.5 degrees Celsius. Then continuously place the PCB (at full load) and measure the temperature of one PCB surface to determine the temperature difference on the PCB at full load, usually around plus or minus 1 degree Celsius. Step three, place different analog IC blocks on the PCB and conduct testing. This judgment can effectively observe the temperature change when the reflow furnace is at full load, and at the same time, the actual temperature change displayed on the reflow soldering table should not exceed plus or minus 1 degree Celsius.

(2) If a 20cm * 20cm PCB is taken and placed on three thermocouples, the longitudinal (direction of motion) temperature resolution of the furnace chamber is measured, and the furnace temperature curve is tested. The measured temperature curve graph should clearly reflect the misalignment status of the thermocouple on the PCB, that is, the thermocouple in the front (direction of motion) first reaches the high temperature zone, and then reaches the high temperature zone, with a clear hierarchy.

3. The types of heaters can generally be divided into two categories. One is infrared lamps and adaptive tube heaters, which can directly radiate heat, also known as primary radiators; Another type is ceramic plate, aluminum plate, and stainless steel plate type heaters.

Tubular heater: It has the advantages of high working temperature, long radiation wave length, and fast heat response. However, due to the generation of light during heating, it has different reflection effects on welding components of different colors. At the same time, it is not conducive to matching with forced hot air.

4. The heat transfer system of the reflow welding machine must have 4-5 heating zones. At least a lower heater should be installed in the preheating zone of the reflow welding zone, and it should be able to independently control the temperature to ensure that the temperature can quickly reach the welding temperature in three ways: conduction, radiation, and convection.

5. The larger the volume of a reflow soldering machine, the longer the heating zone will be. The heating effect will be better than that of a smaller reflow soldering machine. So when choosing reflow soldering, the first thing to consider is the number of temperature zones, and then the heating length. For the same price, the longer the heating section, the higher the cost-effectiveness.

6. A good reflow welding machine has a very stable and non shaking mesh belt during operation. If the conveyor belt vibrates, it can cause welding defects such as displacement of welding points, suspension bridges, and cold welding.

7. Previously, the inner liner of the reflow soldering machine did not have a fan and directly used the heat dissipation function of the heating tube to heat the PCB. Later, it was improved to a more advanced thin tube blowing method called hot air micro circulation, which has a higher cost. Now, after so many years of production process improvement and continuous innovation, the domestic reflow soldering machine has a considerable technical foundation.