Environment-friendly lead-free soldering paste

Abstract

The invention discloses environment-friendly lead-free soldering paste which comprises, by weight, 70-90 parts of tin, 1-2 parts of lithium, 0.1-1 part of nickel, 0.1-1 part of rare earth, 0.1-3 parts of scaling powder, 5-10 parts of ethylene glycol butyl ether and 2-5 parts of polyamides. Tin lithium prepared according to the formula is lead-free soldering tin and is proper in melting point, a solid-liquid coexistence temperature interval is large, a typical solid-liquid coexistence temperature interval is about between 55 DEG C and 85 DEG C, meanwhile solid phase matter in a solid-liquid coexistence region generates solid phase matter with a higher proportion of a solid phase and a liquid phase along with temperature reduction (according to typical solid phase matter near a tin lithium eutectic line temperature, the solid phase accounts for about 45-60%, the liquid phase accounts for about 55-40%), solid-liquid coexistence matter at welding and cooling stages is properly high in viscosity and proper in mobility, changes of the proportion of the solid phase and the proportion of the liquid phase in the solidification process are appropriate, and solidification is carried out gradually at a moderate and stable speed.

Description

technical field [0001] The invention relates to a lead-free solder, in particular to an environment-friendly lead-free solder paste. Background technique [0002] Most of the existing solder materials are leaded solders. Various electronic products made of leaded solders are discarded or recycled, which will cause lead pollution to the environment and bring great harm to people's health. In order to reduce or even eliminate lead pollution caused by lead solder, the Ministry of Information Industry of my country promulgated the "Administrative Measures for the Prevention and Control of Pollution from Electronic Information Products" as early as 2003, which clearly stipulates that "producers should take measures to gradually reduce and eliminate electronic products. Content of lead, tribute, cadmium, hexavalent chromium, polybrominated biphenyl, polybrominated diphenyl ether and other toxic and harmful substances in information products." Therefore, lead-free solder must be gra...

AI Technical Summary

Problems solved by technology

[0002] Most of the existing solder materials are leaded solders, and various electronic products made of leaded solders are discarded or in the process of recycling, which will cause lead pollution to the environment and bring great harm to people's health