Sn-cu-based lead-free solder alloy for improving solder joint creep performance and its preparation process

Abstract

The invention provides a Sn-Cu based lead-free solder alloy which improves the creep performance of solder joints. The content of Cu in the solder alloy is 0.7 wt%, the content of Co is 0.5-0.05 wt%, and the content of Ni is 0.25 wt%. -0.025wt%, the content of P is 0.05-0.005wt%, and the balance is Sn. At the same time, a preparation process for making the above-mentioned lead-free solder alloy is also provided. The effect of the present invention is that by adding trace amounts of Co, Ni and P elements to the Sn-0.7Cu eutectic solder, the morphology of the interface compound is effectively improved, the supercooling degree of the alloy is reduced, and the oxidation resistance is improved. Furthermore, the growth of the interfacial compound layer Cu6Sn5 and the appearance of the brittle compound Cu3Sn on the side of the Cu substrate are suppressed in a high-temperature environment, thereby improving the high-temperature creep resistance of the welded joint. The alloy can be widely used in wave soldering and manual soldering processes in the field of electronic assembly.

Description

technical field [0001] The invention belongs to a lead-free solder alloy material for electronic packaging, and in particular relates to a Sn-Cu based lead-free solder alloy for improving the creep performance of solder joints and a preparation process thereof. Background technique [0002] With the full implementation of the lead-free process of electronic packaging, domestic and foreign experts have conducted a lot of research on the composition and soldering performance of lead-free solder. At present, the mainstream lead-free solder alloy systems mainly include Sn-Ag system, Sn-Cu system, Sn-Ag-Cu system and so on. Among them, the lead-free solder alloy based on Sn-Cu eutectic is widely used in wave soldering and manual soldering processes due to its low cost. However, the alloy still has problems such as poor creep performance, poor oxidation resistance and poor creep resistance of welded joints. [0003] ZL03111446.6 and ZL03134099.7 improve the oxidation resistance ...

AI Technical Summary

Problems solved by technology

[0005] The above-mentioned patents have better solved the oxidation resistance of Sn-Cu solder alloys, but none of them have solved the problem of soldering caused by the rapid growth of Cu6Sn5 compounds on the Sn-Cu / Cu interface under high temperature environment and the formation of Cu3Sn brittle compounds. The high-temperature creep performance of the joint is reduced, and the high-temperature creep resistance of the Sn-Cu solder has not been effectively improved

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