As the precision of electronic products puts new demands on the reflow process, a general trend is to require reflow soldering to adopt more advanced heat transfer methods to achieve energy saving and uniform temperature, suitable for dual-panel PCB and new device packaging. Welding requirements.
The quality of reflow soldering has a very close relationship with the equipment and will directly affect the production process. So, when we choose a reflow soldering machine, what should we start with?
1, the heating part
Just open the lid and open the upper oven to see the heating element. Usually, small-scale economical reflow soldering is performed by a heating tube, and the heating tube has two types of heat sinks and a light rod. The performance of the heat sink is superior to that of the polished rod.
2, through the appearance of the volume
The larger the larger reflow soldering machine, the longer the heating zone will be. The heating effect will be better than the smaller reflow soldering. Therefore, when purchasing reflow soldering, the first thing to look at is the temperature zone. Look at the heating length. The same price, the longer the heating section, the higher the cost performance.
3. Transmission and transportation
Better reflow soldering is in operation. The mesh belt is very stable and does not shake. If the transmission has vibration, it will cause welding defects such as solder joint displacement, suspension bridge and cold welding.
4, the liner
The former furnace liner has no fan, and directly uses the heat dissipation function of the heating tube to heat the PCB. Later, it is improved to a more advanced thin tube blowing, called hot air microcirculation, and the cost of making hot air micro-circulation is high. After so many years of production process improvement and continuous innovation, welding has already had a considerable technical foundation. At present, many manufacturers in the furnace, in addition to some large reflow soldering equipment, small economical reflow soldering in order to reduce costs, low prices to attract customers.
The following parameters affect the quality of reflow:
1. It should have the temperature curve test function. If the equipment does not have this configuration, the temperature curve collector should be purchased.
PCB design and processing quality, components and solder paste quality are the basis for ensuring reflow quality. As long as the PCB design is correct, the quality of PCB, components and solder paste is qualified. The quality of reflow soldering can be printed, mounted, Reflow soldering is controlled by the process of each process.
2. The longer the length of the heating zone and the greater the number of heating zones, the easier it is to adjust and control the temperature profile. Generally, 5-6 temperature zones are selected for medium and small batch production, and a reflow furnace with a heating zone length of about 1.8 m can meet the requirements. Standard lead-free production We usually have 8 temperature zones, and there are touch, computer and button type controls. In addition, the heater should be independently temperature controlled to adjust and control the temperature profile.
3. The conveyor belt should be stable during operation, reflow soldering in the middle and low grade, the transmission mechanism is relatively simple, and there will be a little vibration. Conveyor belt vibration can cause welding defects such as displacement, suspension bridge, and cold welding.
4, different reflow soldering insulation performance is not the same, low-grade products generally not enough insulation layer, the maximum temperature is usually less than 300 degrees. The maximum heating temperature is generally 300~350 °C. If it is lead-free solder or metal substrate, it should be more than 350 °C.
5. Heat generation method and heat transfer method of reflow soldering
The heating wire type heating element has a relatively high exchange rate and a long service life; the heating tube type heating element has low heat generation efficiency, and if the hot air is not passed, the uniformity of the heating surface is not good; the infrared tube type heating body has a radiation type and uniformity, but will And the color temperature difference is mainly used for the thermal compensation zone, but not for the weld zone.
6, the conveyor belt width should meet the maximum PCB size requirements. The greater the width, the greater the reflow power, so choosing the right is the most important.
7, but also to save power, reflow is the power consumption of SMT equipment is amazing. So when choosing reflow soldering equipment, look at their insulation materials. Insulation materials have less heat loss, and reflow soldering saves power.
It seems that to choose a good reflow soldering machine, the brand is the key, the quality of the brand products is guaranteed, but the price will be higher. Secondly, look at the appearance, the appearance is beautiful, indicating that the manufacturer has a higher taste for product quality. Then there are energy saving, environmental protection and performance, and safety considerations.
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