Solder paste is a paste-like substance that plays two main roles in the process of removing oxides and reducing the surface tension of the welded material. Widely used in the brazing of clock instruments, precision parts, medical equipment, stainless steel crafts, tableware, mobile communications, digital products, air conditioning and refrigerator refrigeration equipment, glasses, knives, car radiators and various PCB boards and BGA solder balls. Solder paste has applications in various industries, so what is the role of solder paste?
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　　 The role of solder paste
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1. Remove surface oxides
Because of the oxygen in the atmosphere, various substances are actually surrounded by a layer of oxide with a thickness of approximately 2 × 10-9 to 2 × 10-8m. During soldering, the oxide film will inevitably prevent the solder from wetting the base material, and the soldering cannot be performed normally. Therefore, the flux must be coated on the surface of the base material to reduce the oxide on the surface of the base material, so as to achieve the purpose of eliminating the oxide film . On the other hand, the high temperature of welding easily oxidizes the surface of the welding material. Solder paste helps stop the oxidation process.
2. Reduce the surface tension of the material
The surface tension of the substance will affect the soldering quality, and another effect of the solder paste reduces the tension of the material. The surface tension of the molten solder will prevent it from flowing to the surface of the base metal and affect the normal progress of wetting. When the flux covers the surface of the molten solder, the surface tension of the liquid solder can be reduced, so that the wetting performance is significantly improved.
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　　 Selection of solder paste
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1. The melting point matches
In order to match the use of solder, the melting point of the selected solder paste should be 10-30 ° C lower than the melting point of the solder. If the melting point of the solder paste is too low than the melting point of the solder, it is easy to melt prematurely and lead to premature failure of the flux active ingredient.
2. According to the characteristics of the surface oxide film
For the alkaline oxide film, the acidic solder paste should be selected; for the acidic oxide film, the alkaline flux should be selected.
3. According to the brazing process
According to the specific process, choose different forms of solder paste, such as liquid solder paste for wave soldering, paste solder flux for high frequency or intermediate frequency induction brazing, and powder solder paste or paste flux for flame brazing and many more.
4. According to the characteristics of the substrate
Different substrate materials have large differences in the types of solder pastes due to the different surface oxide films, especially some difficult-to-weld metals, such as magnesium-containing aluminum alloys, stainless steel, and cemented carbide. In order to ensure the welding performance of magnesium-containing aluminum alloys, usually a more active flux is selected.
The above is to introduce to my friends about the role of solder paste and how to choose solder paste. Flux is harmful in use. Generally, if a skilled worker inhales vaporized steam into the human body when exposed to a high concentration environment, headaches and drowsiness may occur. Serious symptoms such as ataxia and irritation of eyes, nose and throat. Therefore, protective measures must be taken.
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