Improved low-silver Sn-Ag-Au solder for microelectronic packaging and preparation method thereof

Abstract

The invention discloses improved low-silver Sn-Ag-Au solder for microelectronic packaging and a preparation method thereof. The solder comprises the following components of, by mass of 0.3%-1.0% of Ag, 0.5%-1.0% of Cu, 0.05%-0.5% of Nb and 97.5%-99.07% of Sn. The solder alloy has the advantage that the Nb element is added in trace on the premise of maintaining the good anti-drop performance of thelower-silver Sn-Ag-Cu solder alloy, so that dislocation movement is hindered, the normal temperature mechanical property of the solder is improved, and the creep resistance is greatly improved; an Zrelement is added, so that the synergistic effect of the Zr element and the Nb element can be achieved, further dispersed distribution of the Nb is promoted, meanwhile, the alloy structure is refined,and the strength and the hardness of the solder are improved; and the liquidity of liquid solder can be improved by addition of a rare earth element Yb, the wettability can be improved, and the creepresistance of brazing filler metal can be improved.

Description

technical field [0001] The invention relates to solder, in particular to a low-silver Sn-Ag-Cu solder for improving microelectronic packaging and a preparation method thereof. Background technique [0002] Surface mount technology (SMT) has experienced nearly half a century of development since its inception. It has not only become the mainstream of contemporary circuit assembly technology, but also is developing in depth, promoting electronic products to miniaturization, light weight, high precision and high reliability. The direction of development has increased the number of I / O pins in the circuit, the number of solder joints has increased, the size has become smaller, and the spacing has become narrower and narrower. The sharp reduction in the size of solder joints poses a challenge to the performance and reliability of electronic solder. Studies have shown that 70% of the failures of electronic devices are caused by the failures of packaging and assembly, among which ...

AI Technical Summary

Problems solved by technology

[0005] (1) The solder alloy composition deviates from the eutectic point, the melting point increases, the melting range increases, the fluidity and wettability of the molten pool during the welding process decrease, and the risk of oxidation increases, resulting in poor welding quality and reduced solderability ;

[0006] (2) The reduction of Ag content makes the strengthening phase in the matrix: Ag 3 The amount of Sn phase is greatly reduced, and the strengthening effect is reduced

The normal temperature mechanical properties of the alloy are reduced;

[0007] (3) The content of the soft primary β-Sn phase increases, which reduces the creep performance and thermal fatigue performance of the alloy, and greatly reduces the service reliability of the solder joint;

[0008] (4) The higher Sn content makes the interface intermetallic compound (IMC) layer grow rapidly during service, especially the interface Cu 3 The Sn layer grows rapidly, the thickness of the interface IMC layer increases, and the service reliability of the solder joint decreases.

However, compared with high-silver solder, low-silver solder has lower strength and hardness, higher melting point, poor wettability, and poor thermal fatigue, which cannot fully meet the needs of modern microelectronics industry production.

Images