Application of solder paste in SMT soldering process

Solder paste is an extremely important material that is indispensable in surface mount technology (SMT). It is composed of metal alloy powder and flux, which is used to solder electronic components and PCBs (printed circuit boards). However, the composition, physical properties and conditions of use of solder paste have a significant impact on the SMT manufacturing process. Moreover, different types of products require different types of solder paste. Therefore, it is important for SMT chip production and processing personnel to understand the different types of solder paste. Solder paste plays an irreplaceable role in the SMT process, from its composition to various classifications, to the precautions when using, all links are closely related to the final results of SMT chip processing.

1. Leaded solder paste and lead-free solder paste Solder paste is composed of metal alloy powder and flux. With the popularization of the concept of environmental protection, the composition of solder paste has gradually changed to lead-free solder powder. Currently, lead-free solder powders are available in a wide variety of compositions, among which tin-silver-copper (Sn-Ag-CuAlloys are the most widely used. In addition, the flux in the solder paste is also indispensable, and its main functions are to control the fluidity of the solder paste, remove oxides from the solder surface and the solder paste, improve the soldering performance, slow down the chemical reaction of the solder paste at room temperature, and provide the adhesion required for SMT patches. Leaded solder paste and lead-free solder paste have their own advantages and disadvantages, so the choice needs to be based on product requirements. First of all, solder paste is composed of metal alloy powder and flux, the composition of which has a significant impact on the SMT process. With the development of the concept of environmental protection, the composition of lead-free solder powders has increased, among which tin-silver-copper (Sn-Ag-Cu) alloys are widely used. Fluxes can control the flow of solder paste, remove oxides, improve soldering performance, and more. In terms of leaded and lead-free solder paste, the leaded solder paste commonly used by users is 6337 no-clean lead-free solder paste, and the lead-free solder paste has 0307 no-clean lead-free solder paste and 305 no-clean lead-free solder paste, which have different silver content and need to be selected according to industry requirements. The leaded solder paste often used by users is 6337 no-clean leaded solder paste, and the lead-free solder paste is 0307 no-clean lead-free solder paste and 305 no-clean lead-free solder paste. According to the silver content, 0307 contains 0.3 silver, 305 contains 3 silver, and the selection of leaded and lead-free solder paste should be based on the requirements of its own industry.

2. High-temperature solder paste, medium-temperature solder paste, low-temperature solder paste The temperature of solder paste refers to the melting point of solder paste. Generally speaking, the melting point of high-temperature solder paste is above 217 °C, and it is commonly used in lead-free solder paste; The melting point of medium-temperature solder paste is about 170 °C, and it is commonly used for lead-free medium-temperature solder paste; Low-temperature solder paste has a melting point of 138°C and is commonly used in products such as the LED industry that need to protect components that cannot withstand high temperatures. Choosing the right temperature of solder paste can improve the effect and quality of the mount. Secondly, the high-temperature, medium-temperature and low-temperature solder pastes classified according to temperature have different melting points and are suitable for different products. For example, high-temperature solder paste is often used for lead-free solder pastes with a melting point above 217°C; Medium temperature solder paste has a melting point of about 170 °C, and is used for lead-free medium temperature solder paste; The low-temperature solder paste has a melting point of 138°C, which is suitable for temperature-sensitive components such as the LED industry.  SMT production line

3. Tin powder particle size The size of tin powder particles of solder paste is also an important classification method. The solder powder in solder paste can be divided into 1, 2, 3, 4, 5,6 levels. Generally speaking, the more sophisticated the product, the more it is necessary to use smaller tin powder, but the smaller the tin powder, the corresponding increase in its oxidation area. At the same time, the shape of the tin powder is round and it is beneficial to improve the printing quality. The physical properties of solder paste include viscosity and viscosity. Solder paste is viscous, and the commonly used viscosity symbol is μ in kcp.s. The viscosity of the solder paste is an important property, which determines the flow of the solder paste during the printing process. The viscosity of solder paste is affected by a variety of factors, such as the powder content of the solder paste alloy, particle size, temperature, and shear rate. When purchasing solder paste, we should choose the appropriate solder paste according to the actual production needs, consider the printing accuracy, soldering performance and product cost and other factors, and select the appropriate solder paste alloy powder, granularity and flux ratio. Secondly, in the process of using solder paste, it is necessary to pay attention to the storage and use environment of solder paste, avoid too high or too low temperature and humidity to affect the performance of solder paste, and also pay attention to the shelf life of solder paste, and try to use fresh solder paste.

Overall, choosing the right solder paste has a big impact on the quality and cost of SMT chip processing. When selecting solder paste, it is necessary to classify it according to the product requirements, and at the same time select the appropriate solder paste according to the difficulty and requirements of SMT processing, so as to effectively improve the effect and quality of the product and reduce the cost. If you have friends who want to know, you can continue to pay attention. If you have any questions about reflow soldering, placement machines, semiconductor integrated circuits, chips, etc., please send us a private message or leave a message, and the TORCH technical team will also answer your questions! Solder paste plays an irreplaceable role in the SMT process, from its composition to various classifications, to the precautions when using, every link is closely related to the final effect of SMT chip processing. First of all, solder paste is composed of metal alloy powder and flux, and its composition has a significant impact on the SMT process. With the development of environmental protection concepts, the composition of lead-free solder powders has increased, among which tin-silver-copper (Sn-Ag-Cu) alloys are widely used. Fluxes can control the flow of solder paste, remove oxides, improve soldering performance, and more. In terms of leaded and lead-free solder paste, the commonly used leaded solder paste for users is 6337 no-clean lead-free solder paste, and lead-free solder paste includes 0307 no-clean lead-free solder paste and 305 no-clean lead-free solder paste, with different silver content, and the selection needs to be based on industry requirements. Secondly, the high-temperature, medium-temperature and low-temperature solder pastes classified according to temperature have different melting points and are suitable for different products. For example, high-temperature solder paste is often used for lead-free solder pastes with a melting point above 217°C; Medium temperature solder paste has a melting point of about 170 °C, and is used for lead-free medium temperature solder paste; The low-temperature solder paste has a melting point of 138°C, which is suitable for temperature-sensitive components such as the LED industry. In addition, the size of tin powder particles is also a classification method, divided into 1 - 6 grades, precision products tend to small tin powder, but the oxidation area of small tin powder will increase, round tin powder is conducive to printing quality. The viscosity and viscosity of solder paste are important physical properties, and viscosity is affected by factors such as alloy powder content, particle size, temperature, and shear rate. Finally, when purchasing solder paste, it is necessary to consider the printing accuracy, soldering performance and product cost, etc., pay attention to the storage and environmental conditions when using, avoid the influence of temperature and humidity, and pay attention to the shelf life. Choosing the right solder paste can improve the product effect and quality and reduce costs, and the TORCH technical team can also answer questions for friends who have questions about related fields. In addition, the size of tin powder particles is also a classification method, divided into 1 - 6 grades, precision products tend to small tin powder, but the oxidation area of small tin powder will increase, round tin powder is conducive to printing quality. The viscosity and viscosity of solder paste are important physical properties, and viscosity is affected by factors such as alloy powder content, particle size, temperature, and shear rate. Finally, when purchasing solder paste, it is necessary to consider the printing accuracy, soldering performance and product cost, etc., pay attention to the storage and environmental conditions when using, avoid the influence of temperature and humidity, and pay attention to the shelf life. Choosing the right solder paste can improve the product effect and quality and reduce costs, and the TORCH technical team can also answer questions for friends who have questions about related fields.