Tin-zinc base plumbum-free solder alloy and its preparing technology

Abstract

The present invention relates to non-ferrous alloy material. The alloy contains Zn 4-11 wt%, P 0.001-1 wt%, except Sn, and may have some La and / or Ce. The preparation process of the alloy includes smelting Sn-Zn mother material with Zn content of 9.0 wt% and graphite protected surface in a resistive furnace; smelting intermediate alloy in a vacuum inducing furnace via adding La and Ce; melting the mother material inside a corundum crucible inside the resistive furnace and raising the temperature to 350 deg.c, pressing Sn foil coated intermediate alloy and red phosphorus powder into the melt quickly via stirring, maintaining the temperature for 10 min before reducing to 290-320 deg.c; and casting in iron mold into circular rod of 20 mm diameter. The alloy has copper moistening and spreading area greater than that of corresponding Sn-Zn alloy, up to 62 %.

Description

Technical field: [0001] The invention belongs to nonferrous alloy materials, and relates to a lead-free brazing material for electronic devices, in particular to a tin-zinc-based lead-free solder alloy and a preparation process thereof. Background technique: [0002] Various electronic devices, including microelectronic devices, generally use brazing as a means of circuit connection and assembly. For a long time, tin-lead eutectic and near-eutectic alloys have been used as brazing due to their low melting point and good wettability to copper bases. Welding materials are widely used. With the expansion of the production and application scale of electronic products, the acceleration of replacement and the enhancement of human environmental protection awareness, the potential harm of lead in a large number of discarded electronic products to the environment and human body has aroused great concern from the international community. Lead solder restriction regulations and set a ...

AI Technical Summary

Problems solved by technology

For these technologies, from the perspective of the current production and application status of lead-free solder and its technology itself, first, there is no large-scale commercial application, and the efforts of various countries to research and develop lead-free solder have never stopped, and new related patents are still emerging. Second, the alloys containing silver, bismuth, indium and phosphorus have the disadvantages of high raw material cost and complex process. In fact, when the content of silver, bismuth and indium exceeds 2%, the alloy can no longer be regarded as a simple Tin-zinc-based alloy; in the evaluation as silver-bismuth-indium-tin-zinc composite alloy category

The technology of coating tin film on the surface of tin-zinc powder also has the disadvantages of complicated process and increased cost

[0005] Also, it is known that adding bismuth at higher levels, e.g. more than 3% by total weight, improves the wettability of tin-zinc alloys and lowers the melting point of the alloy, but higher bismuth makes the alloy brittle , and bismuth resources are less, and there is a certain degree of toxicity itself, so a large amount of bismuth cannot be an ideal solution

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