How to solve the problem of welding failure? Significance and purpose of solderability test

Date：2021-09-23 11:46:00Views：1367

Solderability test refers to the qualitative and quantitative evaluation of the solderability of components, PCB, pad, solder and flux by the principle of wetting balance method. Whether it is an obvious poor welding problem, or a problem that is not easy to detect or will affect the tin loading ability of the product, it can be found through the test and find out the root cause, so as to help the enterprise effectively determine the weldability and product quality after production and assembly.

Significance of solderability test

Solderability test is generally used to evaluate the solderability of components, printed circuit boards, solders and fluxes qualitatively and quantitatively. In the assembly and welding process of electronic products, the welding quality directly affects the quality of the whole machine. Therefore, in order to improve the welding quality, in addition to strictly controlling the process parameters, it is also necessary to carry out scientific solderability test on printed circuit boards and electronic components.

Purpose of solderability test

Through the implementation of weldability test, help enterprises determine the weldability and product quality after production and assembly. In practice, the core detection has further enriched the technical means of solderability testing of printed circuit boards and other components, defined the internal factors affecting solderability, and provided great help to the technical engineers in the manufacturing industry to improve product quality and zero defect welding process.

IEC, IPC, DIN, JIS and other major international standards organizations recommend various methods, such as edge immersion welding test, floating welding test, wave soldering test, wetting balance test and other six test methods. Common solderability problems include poor wetting, monument, crack, air hole, false welding, false welding, poor tin loading and slag inclusion defects. So what are the main reasons for the failure of welded structures?

1. The structural design is unreasonable. The welded structure is different from other structures, especially when the welded structure is used to replace the riveted structure, the design method of riveted structure can not be blindly copied to the welded structure.

The different characteristics of welded structure compared with riveted structure are:

1) High rigidity. Rigid connection during welding, and the connecting members are not easy to produce relative displacement; The riveted structure has a certain relative displacement, which can reduce its stiffness and reduce the additional stress.

2) Integrity. When the design is not appropriate, the integrity of the welded structure creates very favorable conditions for crack propagation. Once an unstable brittle crack appears in the welded structure, it may extend through the joint to the whole structure, resulting in all damage of the structure and catastrophic accidents; In riveted structures, when brittle cracks appear and extend to the joint, they will stop automatically, so greater disasters can be avoided.

2. Improper material selection reduces the service performance of base metal and the quality of welded joints.

3. The manufacturing process is unreasonable. The manufacturing of welded structure is composed of a series of processes, in which assembly welding is the most critical process; Therefore, whether the welding manufacturing process is reasonable or not is very important.

4. The influence of environmental factors refers to the environmental factors of welded structure in service, which will also have a significant impact on its service life. For example, the welded structure working at high temperature can lead to failure due to strong creep, which can make the joint brittle and produce brittle fracture. Welded structures working in various corrosive media can lead to premature failure due to corrosion.

5. Operation and management errors in production, due to careless operation or neglect of management, the failure of welded structure also occurs from time to time. Especially for some pressure vessels, the vessels burst due to failure to follow the operating procedures, serious overload, or failure to use the pressure reducing valve. Failure to pay attention to the floating amount of water level during boiler operation caused lower water level and even dehydration combustion, resulting in catastrophic accidents.

With the popularization of lead-free process, new requirements are put forward for welding materials and welding process. High quality interconnection technology and high-quality and zero defect welding process are required for level 1 (IC packaging) and level 2 (electronic components assembled to printed circuit board) processes in modern electronic industry. Weldability test, as a part of the quality management system, naturally began to become necessary! Therefore, in order to improve the welding quality of products, we need to conduct scientific solderability test on printed circuit boards!