What are the Components of Low-Temperature Lead-Free Solder Paste?

2021-12-06

1. What is low-temperature lead-free solder paste?

Solder paste can be divided into leaded solder paste and lead-free solder paste. In recent years, due to the increasingly high environmental protection requirements of various countries, the use of lead-free solder paste has become mainstream. Lead-free solder paste is generally divided into high-temperature, medium-temperature, and low-temperature solder paste according to its alloy composition, melting point, and operating temperature. In fact, there is no standard specifying which melting point or temperature range belongs to low-temperature, but a solder paste with a melting point lower than138°C can be regarded as low-temperature solder paste.

Low-temperature lead-free solder paste SnBiAg

2. Why use a low-temperature solder paste?

When passing through the reflow oven. The temperature is inconsistent on the PCBs. The different sizes and the distribution of the components will cause the temperature difference of the PCBs. The complex and large PCB will have a peak temperature difference of 20 °C. In addition, it is necessary to consider the temperature measurement error and equipment stability. By accumulating all the differences. When using tin-silver-copper SAC305 solder paste, the lowest temperature of PCB should meet the minimum requirement of 240℃, and the highest temperature region can reach 265°C, which may exceed the temperature limit of the components. Even if the temperature limit is not exceeded, components and solder joints are also easily oxidized at high temperatures, and the degree of oxidation increases dramatically for every 10°C increase.

The low-temperature high-strength solders (solder paste, epoxy solder paste) FTP-170/180/200 and FTD-170/180/200 are made of Fitech’s low-temperature alloy powder FL170/FL180/FL200 by mixing with excellent zero-halogen flux. The peak reflow temperature is 170°C/180°C/200°C, and the soldering strength is excellent. It is an ideal material for low-temperature soldering and is very suitable for low-temperature components.

low-temperature lead-free solder paste FSA-170

Except for alloy solder powder, other components in solder paste belong to flux. There are various components of flux, which mainly protect alloy solder powder before soldering, remove the oxide layer during soldering, enhance wettability and solderability, and prevent secondary oxidation. Alloy solder powder and flux are both indispensable parts of solder paste.

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