What are the reasons for false soldering and false soldering? How to improve the faulty soldering of electronic parts?

Date：2022-07-25 16:14:05Views：1815

In the process of circuit board welding, it is easy to have poor welding conditions such as false welding and false welding. False welding and false welding will seriously affect the reliability of products and greatly improve the maintenance cost of products. Then, what are the reasons for false soldering and false soldering? How to improve the faulty soldering of electronic parts? In order to help you understand in depth, the following contents are sorted out by Chuangxin testing network for your reference.

1、 What is false soldering?

Faulty soldering is usually caused by oxidation or impurities at the welding point, poor welding temperature and improper method. The essence is that there is an isolation layer between the solder and the pin. They are not completely in contact. Generally, the naked eye cannot see its state. However, its electrical characteristics are not conductive or poorly conductive, which affects the circuit characteristics.

2、 What is false welding?

False soldering is similar to false soldering, which means that the circuit works normally in the initial stage, and the open circuit gradually appears in the later stage. In the welding process of electronic components, the solder joint seems to be successfully welded on the surface, but it is not welded in fact. Sometimes the lead wire can be pulled out of the solder joint with one hand. This phenomenon is called false welding.

3、 What is the reason for the faulty / false welding?

1. Pad and component pin oxidation

It is easy to cause that during reflow soldering, when the solder paste is liquefied, it cannot fully infiltrate the pad, and crawls tin, resulting in faulty soldering

2. Less tin

In the solder paste printing process, due to the small opening of the steel mesh or the small pressure of the scraper, there is less tin, so that when welding, the amount of solder paste is not enough, and the components cannot be fully welded

3. Temperature too high or too low

If the temperature is too high, not only the solder will flow, but also the surface oxidation speed will be increased, and false soldering may also occur.

4. Low melting point of solder paste

The melting point of low-temperature solder paste is relatively low, and the thermal expansion coefficient of the component pin and the plate used to fix the component are different. With the change of the working temperature of the component, the phenomenon of false soldering will occur under the force of thermal expansion and cold contraction.

5. Solder paste quality problems

Poor solder paste quality, easy oxidation of solder paste and loss of flux will directly affect the soldering performance of solder paste, resulting in false soldering / false soldering

4、 Methods to solve false welding

1. Moisture proof storage of components:

If the components are placed in the air for a long time, it will cause the components to absorb water and oxidize, resulting in the components can not fully remove the oxide during the welding process, and then produce false welding and false welding defects. Therefore, PCBA processing plants will be equipped with ovens, which can bake components with moisture during the welding process and replace oxidized components.

2. Choose well-known brand solder paste:

The defects of false soldering and false soldering in the process of PCBA welding have a great relationship with the quality of solder paste.

3. Adjust printing parameters:

Most of the problems of false soldering and false soldering are due to the lack of tin. During the printing process, the pressure of the scraper should be adjusted, and the appropriate steel mesh should be selected. The opening of the steel mesh should not be too small to avoid the situation of too little tin.

4. Adjust reflow temperature curve:

During the reflow welder procedure, the welding time should be well controlled. If the time in the preheating area is not enough, the flux cannot be fully activated and the surface oxide at the welding place can be removed. If the time in the welding area is too long or too short, it will cause false soldering and false soldering.

5. Select the appropriate testing equipment:

Select AOI detection equipment or X-ray detection equipment. When X-ray detection equipment can detect the parts of circuit board with weak soldering, circuit board cavity and circuit board fracture by detecting the difference of ray intensity of penetrating objects, it can detect the welding quality and reduce the outflow of defective products of weak soldering and false soldering.

5、 Hazards of faulty welding and false welding

Faulty welding and false welding reduce the reliability of products, cause unnecessary maintenance in the production process, increase production costs, reduce production efficiency, cause great quality and safety hazards to products that have left the factory, increase after-sales maintenance costs, increase customers' mistrust, reduce orders, and affect the company's image.

The above is related to the false soldering of electronic parts compiled by the core detection team. I hope it can help you. Shenzhen Chuangxin Online Testing Technology Co., Ltd. is a well-known professional testing institution for electronic components in China, with 3 standardized laboratories covering an area of more than 1000 square meters. The scope of testing services covers: electronic component testing and verification, IC authenticity identification, product design and material selection, failure analysis, function testing, factory incoming material inspection, component X-ray testing, taping and other test items.