Application of ZnO Nanoparticles in Sn99Ag0.3Cu0.7-Based Composite Solder Alloys

Olivér Krammer,Krzysztof Witek,Sebastian Wroński,Agata Skwarek,Balázs Illés,Tamás Hurtony,Krzysztof Górecki,Przemysław Ptak,Dániel Straubinger

doi:10.3390/nano11061545

Abstract

The properties of Sn99Ag0.3Cu0.7 (SACX0307) solder alloy reinforced with ZnO nanoparticles were investigated. The primary ZnO particle sizes were 50, 100, and 200 nm. They were added to a solder paste at a ratio of 1.0 wt %. The wettability, the void formation, the mechanical strength, and the thermoelectric parameters of the composite solder alloys/joints were investigated. Furthermore, microstructural evaluations were performed using scanning electron and ion microscopy. ZnO nanoparticles decreased the composite solder alloys’ wettability, which yielded increased void formation. Nonetheless, the shear strength and the thermoelectric parameters of the composite solder alloy were the same as those of the SACX0307 reference. This could be explained by the refinement effects of ZnO ceramics both on the Sn grains and on the Ag3Sn and Cu6Sn5 intermetallic grains. This could compensate for the adverse impact of lower wettability. After improving the wettability, using more active fluxes, ZnO composite solder alloys are promising for high-power applications.

Highlights

The transition to lead-free soldering technology in 2006 resulted in the widespread use of tin–silver–copper (SAC) solder alloys in microelectronics packaging, mostly Sn96.5Ag3Cu0.5(SAC305) and Sn95.5Ag4Cu0.5 (SAC405) alloys [1]
The addition of ZnO ceramic into the SACX0307 solder alloy resulted in refinement of the Sn grains in each case, from ~200–300 μ m2 to ~10–15 μ m2
No significant differences were found between the composite solders, and the Sn grain refinement did not depend on the ZnO particle size in the range investigated (50–200 nm)

Summary

Introduction

(SAC305) and Sn95.5Ag4Cu0.5 (SAC405) alloys [1] They have two significant drawbacks due to the relatively high silver content, namely their higher price and possible reliability problems. Over the past 5–10 years, the aim has been to reduce the silver content in SAC solder alloys while keeping the melting point between 217 and 227 ◦ C. A promising low-silver solder alloy is Sn99Ag0.3Cu0.7 (SAC0307), with the micro addition (

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