There are many types of solder pastes, and there are many brands. Different solder paste materials used in different pcb boards are different. Solder pastes are classified into three types of solder pastes: R, RMA, and RA. So what is R, RMA, RA?
R means (inactive) The solder paste used in general military and aerospace pcb boards is very demanding, and it will use R type (water white rosin, inactive).
RMA stands for medium activity (rosin, non-ionic halide) and is generally used in military and other highly reliable circuit components.
RA stands for activity (rosin, ionic halide) and is generally used in consumer electronics.
However, in the pcb manufacturing industry, moderately active solder paste is commonly used.
Solder paste can be divided into high temperature solder paste (melting point greater than 250 ° C) and low temperature solder paste (melting point less than 150 ° C) according to the melting point. The commonly used solder paste has a melting point of 179 to 183 ° C and a composition of Sn63Pb37, Sn62Pb36Ag2 and the like.
(1) Lead: Sn60Pb40, Sn63Pb37, and Sn62Pb36Ag2. The melting point of Sn63Pb37 is 183 ° C, eutectic state, after the incorporation of 2% silver, the melting point is 179 ° C, eutectic state. Sn63Pb37 has good physical properties and excellent soldering properties, and is non-corrosive. It has a wide range of applications. Adding silver can improve the mechanical strength of solder joints.
(2) Lead-free: Sn96.5Ag3.0Cu0.5, Sn95.5Ag3.8Cu0.7, Sn42Bi58, Sn96.5Ag35, and the like.
Most of the pcb industry now uses more lead-free soldering processes.