Tin-zinc-bismuth-copper leadless solder with low cost and welding spot thereof

Abstract

The invention relates to a leadless solder with low cost, in particular to a tin-zinc-bismuth-copper leadless solder with low cost and a welding spot (or a welding seam) formed by the same, and belongs to the fields of the technique and the application of brazing materials. The solder comprises the following components by mass percent: 6.0-10.0% of Zn, 1.0-3.0% of Bi, 0.5-1.0% of Cu and the balance of Sn. Compared with an Sn-Pb solder and a traditional Sn-Zn solder, the invention provides leadless solder alloy which has no pollution and is easy to weld. The solder has the following advantages: (1) the melting point is lower than 200 DEG C, the temperature is lower than the heat resistance temperature of the packaging of an IC and approaches to the eutectic melting point of Sn-Pb, the properties of wetting and spreading are excellent, and the solder is easy to weld; and (2) the solder completely adopts alloying elements with low cost of raw materials. The welding spot (seam) formed by the solder has better bonding strength and use reliability.

Description

technical field [0001] The invention relates to a low-cost lead-free solder and its solder joints (or welds), in particular to a low-cost tin-zinc-bismuth-copper lead-free solder and its solder joints (or welds), which belong to brazing material technology and application field. Background technique [0002] In the electronics industry, traditional solders are based on tin-lead (Sn-Pb) alloys. Although Sn-Pb alloys have excellent wettability, mechanical properties, and low cost, because Pb and Pb compounds are one of the most harmful chemicals to humans and the environment, the use of lead-containing solders in countries all over the world There are clear legal and regulatory restrictions. As a major producer of various electronic products that consume electronic solder, my country's development of high-performance lead-free environmentally friendly solder that can be used to replace Sn-Pb solder is an important issue facing my country's electronics and information industr...

AI Technical Summary

Problems solved by technology

However, the main problems of Sn-Zn lead-free solder are relatively low solder wettability, poor oxidation resistance and corrosion resistance. Therefore, the performance is often improved by adding third and fourth elements, among which Sn-Zn -Bi(Cu) alloy is the most typical, such as Japanese patent 5718868, ZL95120505.6, in order to further improve its performance, often adopt a variety of micro-alloying methods, many of which add expensive alloying elements, such as: US patent 6649127 in Sn - Add Ge or Ag to Zn-Bi-Cu solder, Chinese patent 01139729.2 adds Ag to Sn-Zn-Bi-Cu solder, Japanese patent 126890 adds In, which not only increases the difficulty of alloy preparation and use (the more alloying elements, The more difficult it is to control the stability of its composition during solder preparation and use), it violates the original intention of Sn-Zn solder with low cost, and increases the long-term reliability of its application (requires long-term and a large number of experiments to prove its reliability) , and the extremely low content of some microalloying elements can greatly change the physical and chemical properties of the alloy, so it has not yet been applied on a large scale

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