Criteria for classification and use of solder paste

As we all know, there are many types of solder paste, and the same solder paste can be classified into different types according to different methods. It is usually divided into two types: lead-free solder paste and leaded solder paste. According to the difference in working temperature, the same lead-free solder paste can be divided into lead-free high-temperature solder paste, lead-free medium-temperature solder paste and lead-free low-temperature solder paste. Is the classification standard commonly used by solder paste manufacturers consistent with that of the manufacturer? Here's an introduction:

1. Analysis of solder paste from the perspective of alloy classification:

 1. Leaded solder paste (generally applicable model: Sn63/Pb37) usually refers to the use of metallic lead as one of the combined materials in solder paste. In a way, all solder pastes will contain metallic lead, but in a different amount. Solder paste manufacturers classify leaded solder paste as a soldering process rich in metal lead, and the metal content in the solder paste is not low, and the commonly used product model is 6337, which is also the tin-lead ratio of eutectic solder.

2. Lead-free solder paste (generally applicable model: Sn99Ag0.3Cu0.7), the content of metal lead in this solder paste is low, and the content of metal lead in lead-free solder paste shall not exceed 1000pPM, that is, the content of metal lead in lead-free solder paste shall not exceed 1/1000. Lead-free solder paste conforms to the general trend of environmental protection and is widely used in the manufacture of various electronic products that require environmental friendliness. Among them, high-temperature lead-free solder pastes such as SAc0307 and SAc305, due to their high soldering temperature, are suitable for those electronic component connections that need to maintain good soldering performance in high-temperature environments, such as high-power chip soldering in some high-power electronic devices, which can ensure the firmness and conductivity of soldering at high temperatures.

2. Analysis of solder paste from the perspective of operating temperature:

1. Low-temperature solder paste (generally applicable model: Sn42Bi58), the soldering temperature of this solder paste is very low, the lowest measured by solder paste manufacturers can reach 149 degrees Celsius, and the main combination materials are metal tin and metal bismuth, of which the metal tin content is 42%, and the metal bismuth content is 58%. 2. Medium temperature solder paste (generally applicable model: Sn64Bi35Ag1.0), the soldering temperature of this solder paste is more suitable. The recommended use temperature of the solder paste manufacturer is 178 degrees Celsius, and its key combination materials are tin, bismuth and silver, of which the tin content is 64%, the bismuth metal content is 35%, and the silver content is 1%.

3. High-temperature solder paste (generally applicable models: SAc0307 and SAc305), these two types of solder paste belong to high-temperature solder paste, the main component is metal tin, and a small amount of metal silver composition. The actual soldering temperature measured by lead-free solder paste manufacturers is 217 degrees Celsius. SAC0307 is a lead-free solder paste with 99.7% metal tin and 0.3% metal silver, so it is also known as 03 silver lead-free solder paste; SAC305 is a lead-free solder paste with 97% tin and 3% silver, so it is also called 3 silver lead-free solder paste.

3. Analysis of solder paste from the perspective of solder powder diameter: No. 2 powder solder paste, the diameter of metal tin powder is: 45 - 75um, which usually means that the diameter of the metal tin powder composed of solder paste is in the range of 45 - 75 microns; No. 3 powder solder paste, the diameter of metal tin powder is: 25 - 45um, which usually means that the diameter of the metal tin powder that makes up the solder paste is between 25 - 45 microns; No. 4 powder solder paste, the diameter of metal tin powder: 20 - 38um, usually refers to the metal tin powder that makes up the solder paste The diameter is between 20 - 38 microns; No. 5 powder solder paste, the diameter of metal tin powder is: 15 - 25um, which usually means that the diameter of the metal tin powder that makes up the solder paste is between 15 - 25 microns.

Through the discussion of the actual situation of the above-mentioned lead-free solder paste manufacturers, it can be seen that the solder paste can be analyzed according to the different metal components used, the different working temperatures of the application, and the diameter of the metal tin powder applied. Even if there will be different types of solder paste according to different classification standards, there will still be a variety of different names, and the solder paste using these two names may belong to the same type. There are many classification criteria for solder pastes, covering aspects such as alloy composition, operating temperature, and solder powder diameter. From the perspective of alloy classification, leaded solder paste (such as Sn63/Pb37) contains more metallic lead, and lead-free solder paste (such as Sn99Ag0.3Cu0.7) has very low metallic lead content. In terms of working temperature, the soldering temperature is as low as 149 degrees Celsius for low-temperature solder paste (e.g., Sn42Bi58), 178 degrees Celsius for medium-temperature solder paste (e.g., Sn64Bi35Ag1.0), and 217 degrees Celsius for high-temperature solder paste (e.g., SAc0307 and SAc305). According to the diameter of the tin powder, there are No. 2 powder (45 - 75um), No. 3 powder (25 - 45um), No. 4 powder (20 - 38um) and No. 5 powder (15 - 25um) solder paste. Under different classification standards, the same solder paste may have different names, but it may belong to the same type, if you want to know more about the relevant expertise, you can pay attention to the online message interaction of Suzhou Norfil solder paste manufacturers.

In the actual production and use process, these different types of solder paste have their own unique application scenarios. For leaded solder paste, due to its high proportion of metallic lead, although it may have certain advantages in the soldering process, such as in some electronic product assemblies with high requirements for soldering firmness and less strict restrictions on lead content, but with the increasing environmental protection requirements, its scope of use is gradually shrinking.

The moderate soldering temperature of medium-temperature solder paste makes it excellent in the soldering of some temperature-sensitive electronic components, such as miniaturized and precise electronic circuit boards, which can not only ensure the quality of soldering, but also will not cause damage to the surrounding components due to excessive temperature. The low soldering temperature of low-temperature solder paste makes it play an irreplaceable role in the soldering of some extremely temperature-sensitive materials or electronic components that are not resistant to high temperatures, such as the soldering of some special plastic packaging electronic components or flexible circuit boards.

From the point of view of the diameter of the solder powder, the solder powder and solder paste with different particle sizes also have their scope of application. Due to its relatively large solder powder diameter, No. 2 powder solder paste is used in some soldering scenarios that do not require high solder paste fluidity and require large solder paste particles, such as soldering with large solder joints or some rough surfaces. The diameter of the solder powder is moderate, and it is widely used in general electronic soldering scenarios, which can provide good soldering results while ensuring a certain fluidity. Powder 4 and powder 5 solder paste, because of its small diameter of the powder, has good fluidity and fillability, especially suitable for the soldering of micro solder joints, such as the soldering of microchip pins or fine solder joints on high-density printed circuit boards.

To sum up, there are many types of solder paste according to different standards, and these types have their own advantages and disadvantages in practical applications, and it is necessary to comprehensively consider the selection of appropriate solder paste types according to specific production needs, electronic component characteristics, environmental protection requirements and other factors to ensure the efficiency, stability and quality of soldering work.