In the soldering industry, each manufacturer’s solder paste formula is different, the production process is different, and the types will also have certain differences. According to the melting point of lead-free solder paste, it can be divided into low-temperature solder paste, medium-temperature solder paste and high-temperature solder paste. As the name suggests, solder paste is a solder paste with a low melting point temperature. It is mainly used in the SMT process of components that cannot withstand conventional high temperatures, such as LED or COM1 PCBs. Low-temperature solder paste is mainly composed of tin and bismuth alloys, and its melting point is 138 degrees. The bismuth component in low-temperature solder paste is a relatively brittle component, which means that the firmness after soldering is not good; low-temperature solder paste greatly improves the reliability of solder joints, and is mainly used in the soldering process of PCBs or components that are not resistant to high temperatures. The board surface reduces the requirements for welding equipment in the process, and the viscosity is moderate; it has high welding ability, and the solder joints are bright and full.

The advantages of low temperature solder paste are mainly reflected in the following aspects:

1. Good wettability, even and full solder joints.

2. The melting point is 138°C.

3. Fully compliant with RoHS standards.

4. No tin beads and tin bridges are produced during reflow.

5. Suitable for wide process and fast printing.

6. Long-term pasting life, steel screen printing life is long.

7. Excellent printability, eliminating omissions, depressions and agglomerations during the printing process.

Low-temperature solder paste is mainly used for radiator module welding, LED welding, high-frequency welding, etc., among which it is most widely used in the LED industry.

The above are the advantages of low-temperature solder paste. As the saying goes, there are advantages, but of course there are also disadvantages. Not only solder paste, but no one is perfect. There is no perfect person, and there is no perfect solder paste. Let's understand The so-called disadvantages of low temperature solder paste:

1. The main disadvantage of low-temperature solder paste is the Bi element in the composition. Bi is a relatively brittle component, which means that the firmness after soldering is not good;

2. The solderability of low-temperature solder paste is not as good as that of high-temperature solder paste, and the gloss of solder joints is dark.

3. The solder joints are very fragile, and are not suitable for products that require strength, especially for products that need to be plugged and unplugged for connecting sockets, which are easy to fall off.

So how should we deal with the disadvantages of low temperature solder paste:

1. First of all, the composition of low-temperature solder paste cannot be changed, and the firmness cannot be improved. We have to re-test the real temperature of the PCB board to choose the available ones such as medium-temperature solder paste and lower-temperature solder paste. The firmness should be higher, and you can choose high-temperature solder paste, which has good firmness and good welding effect.

2. If the components cannot withstand high temperature and can only choose low-temperature solder paste, then other processes must be used to improve the firmness after soldering.