Solder paste is mainly used for the welding of electronic components such as PCB surface resistance, capacitors and ICs in the SMT industry. Solder paste can be divided into many types due to the production process, processing method and melting point.
1. According to environmental protection standards, it is divided into two categories: lead-free solder paste and leaded solder paste.
2. Dispensing solder paste and printing solder paste according to the tin method.
3. According to the packaging method, canned solder paste and syringe solder paste.
Fourth, according to the halogen content, there are halogen solder paste and halogen-free solder paste.
5. According to the melting point temperature of alloy solder powder, it is divided into:
①The composition of the low-temperature solder paste alloy is tin 42, bismuth 58, and its melting point is 138 ℃.
②The alloy composition of medium temperature solder paste is tin 64 silver 1 bismuth 35, tin 63 lead 37, tin, silver, lead, etc., and its melting point is 172-183 ℃
③The alloy composition of high temperature solder paste is tin 99 silver 0.3 copper 0.7, tin 96.5 silver 3 copper 0.5, etc., and its melting point is 210-227 ℃
In the SMT chip process, the appropriate solder paste can be selected according to the temperature required for welding or the melting point temperature that the components can withstand.
6. According to the size of solder melting particles, it can be divided into: No. 3 powder solder paste, No. 4 powder solder paste, No. 5 powder solder paste, No. 6 powder solder paste, No. 7 powder solder paste, etc.
Seven, according to the different activity of the flux is divided into:
According to the activity of the flux, the solder paste can be divided into three grades: inactive (R), moderately active (RMA) and active (RA). In the mounting process, the suitable of solder paste. Generally, grade R is used for soldering of aerospace and avionics products, grade RMA is used for military and other high-reliability circuit components, and grade RA is used for consumer electronic products.
Eight, according to the viscosity of solder paste classification:
The viscosity of solder paste varies widely, usually 100~60OPa·s, and the highest can reach more than 1000Pa·s. The selection is made according to the different plastering process methods.
Nine, according to the flux cleaning method is divided into the following categories:
①Ordinary rosin cleaning type [into RA (ROSIN ACTIVATED) and RMA (ROSIN MILDLY ACTIVATED)]: This type of solder paste shows a better "tinning speed" during the welding process and can ensure a good "welding effect"; After the welding work is completed, there are relatively more rosin residues on the surface of the PCB, which can be cleaned with appropriate cleaning agents. After cleaning, the board surface is clean and free of residues, which ensures that the cleaned board surface has good insulation resistance and can pass various electrical properties. Technical testing ;
②No-clean solder paste [NC (NO CLEAN)]: After the solder paste is soldered, the surface of the PCB is relatively smooth and has less residue. At the same time, the production process is shortened and the production progress is accelerated; this solder paste is the most widely used and the most widely used.
③ Water-soluble solder paste [WMA (WATER SOLUBLE PASTES)] is also known as water-cleaning solder paste: in order to meet the needs of the market, water-soluble solder paste was produced. Cleaning, which not only reduces the production cost of customers, but also meets the requirements of environmental protection.
