Solder paste is used for soldering. One is the shielding gas to avoid air oxidation. In addition, it enhances capillary action, improves lubricity, and avoids empty soldering. Solder paste: white crystalline powder. The content is 99.0%, the acid value is 0.5 mgKOH/g, mp 112℃, soluble in alcohol, iso-guaranteed. It is generally used in organic chemistry, pharmaceutical intermediates, used in the production of fluxes and solder pastes. It acts as a surfactant, modifier, and has strong vitality. It has a certain effect on flashing spots and soldering roundness. It is the most excellent surface active additive among all fluxes. It is widely used as high- and mid-range energy-saving flux in precision processing electronic components.

Composition and function of alloy powder:

Solder powder alloy is the main component of solder paste, accounting for approximately 85% to 90% of the total mass of solder paste. The commonly used alloy combinations are as follows: tin-lead alloy (Sn-Pb), tin-lead-silver (Sn-Pb-Ag) alloy, tin-copper alloy (Sn-Cu), tin-silver-copper alloy (Sn-Ag-Cu) , Tin-bismuth alloy (Sn-Bi), tin-bismuth silver alloy (Sn-Bi-Ag), etc.

The composition, ratio, particle size and surface oxidation of alloy powder have the greatest influence on solder paste.

When the alloy content is relatively high, it can improve the slump of the solder paste and help to form a full and bright solder joint. At the same time, because the content of the flux decreases with the increase of the alloy content, the residue after soldering will also be reduced. It can effectively prevent the appearance of tin beads, but the disadvantage is that the requirements for printing and welding processes are relatively strict.

When the alloy content is relatively low, the printing performance will be better, the solder paste is not easy to stick to the squeegee, the wettability is good, the leakage plate has a long service life, and the processing is easier, but the disadvantage is that it is easy to collapse, and defects such as tin beads or bridging .

The composition of solder paste can be divided into two large parts, namely flux and solder powder.

The specific components of the flux are active agents, thixotropic agents, epoxy resins, and organic solvents.

Solder powder, also known as tin powder, is mainly composed of tin-lead alloy, generally accounting for 63/37; when there are special requirements, there is also tin powder that adds a certain amount of silver, bismuth and other metal materials to the tin-lead alloy.