Low silver hypoeutectic Sn-Cu-Ag lead-free solder for electronic micro connection

Abstract

The invention provides a low-Ag hypo eutectic Sn-Cu-Ag lead-free solder the components of which are 0.5 to 0.65wt percent of Cu, 0.1 to 0.45wt percent of Ag, 0.001 to 0.1wt percent of Ni, 0.001 to 0.3wt percent of Sb, 0.001 to 0.2wt percent of Bi and / or In, 0 to 0.01wt percent of P, 0 to 0.03wt percent of Ge and the rest is Sn. The solder is further characterized in that (1) the content of Ag in the solder of Cu plus Ag is less than 1wt percent is not more than 0.45wt percent; (2) the gross of the microelements like Ni, Sb, Bi, In, P, and Ge, etc., that are added is not more than 0.5wt percent. The solder has the advantages of low cost and excellent oxidation, wettability and overflow resistances, can remarkably reduce the waste of the solder, improve the forming of the welding point, remarkably reduce the connecting defects of braze welding. The solder can replace a Sn-Cu-Ag hypo eutectic material and is suitable for the wave crest welding, dip soldering as well as manual welding and reflow soldering for electric products.

Description

technical field [0001] The invention relates to a lead-free solder used in the micro-connection of electronic products in the field of electronic materials. Background technique [0002] Micro-connection is mainly used in the connection and assembly of electronic products. It is characterized by the small and fine size of the connected objects. Therefore, dissolution, diffusion, surface tension, and strain, which can be ignored in traditional welding techniques, have become important influencing factors. For a long time, tin-based solders containing Pb have been mainly used in electronic micro-connections. Due to the environmental pollution of traditional lead-containing solders, since the 1990s, the world has set off a wave of greening electronic solders. In recent years, the micro-connection of electronic products is gradually promoting the use of lead-free solder, the most respected of which is Sn-Ag-Cu eutectic solder. [0003] The composition of Sn-Ag-Cu eutectic sold...

AI Technical Summary

Problems solved by technology

However, Sn-Ag-Cu eutectic solder is expensive, and it is seriously oxidized and wasted in a high-temperature liquid state. Its wettability, flowability and solder joint formation are worse than those of lead-containing solder, and it is easy to produce brazing defects such as pores.

Chinese patent ZL200410022637.7 reports the Sn-Cu eutectic lead-free solder with low silver content. Although it can significantly reduce the cost of solder, the process performance of the solder is such as oxidation resistance and wettability under high temperature liquid state. performance, flowability and solder joint formability are still not ideal

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