Effect of nano-Cu addition on microstructure evolution of Sn0.7Ag0.5Cu-BiNi/Cu solder joint

Purpose The purpose of this paper is to focus on the fabrication of SnAgCu (SAC) nanocomposites solder and study the effect of Cu nanopowders (nano-Cu) addition on the microstructure evolution of resultant nanocomposite solder after reflow and thermal aging. Design/methodology/approach Mechanical mixing is used in this work to incorporate nanoparticles into the solder and produce more homogeneous mixture. Standard metallographic procedures are applied for microstructural analysis of solder joints. Findings It is found that nano-Cu doped into Sn0.7Ag0.5Cu-BiNi solder has no appreciable influence on melting temperature of the composite solder. The addition of Cu nanoparticles refines the microstructure of bulk solder and suppresses the growth of interfacial intermetallic compound (IMC) layers. However, interfacial IMC grain size increases slightly after 1.0 per cent nano-Cu added. Originality/value The paper demonstrates a method of nano-composite solder paste preparation by means of mechanical mixing and a comparison study of the microstructure evolution of composite solder with the basic SAC solder.

Effects of Cobalt Nanoparticles Addition on Shear Strength, Wettability and Interfacial Intermetallic Growth of Sn−3.0Ag−0.5Cu Solder during Thermal Cycling

In the present study, Cobalt nanoparticles were synthesized and mixed with Sn-3.0Ag-0.5Cu solder (SAC305). The effect of 0.05 wt.%, 0.2 wt.%, 0.5 wt.% and 1.0 wt.% Co nanoparticles on the wettability, the shear strength as well as the growth of intermetallic compounds (IMCs) at composite solder/Cu interface during thermal cycling were investigated. Results show that Co nanoparticle addition can considerably improve wettability, increase the shear strength and suppress the growth of interfacial IMCs. The addition amount of Co nanoparticles have the consistent relation with the improvement extent of the wettability, shear strength and the growth rate of interfacial IMCs. Slight addition (0.05 wt.% and 0.2 wt.%) can significantly improve the properties of nanocomposite solder in all the three aspects. However, with excessive addition amount (0.5 wt.% and 1.0 wt.%) of Co nanoparticles, the improvement extent will decline. The Cross-section images of the interface of nanocomposite solder/Cu joint show that Co can form reinforcement particles in the solder and can act as the sacrificial element to substitute Cu to react with Sn. Excessive Co nanoparticles would form large amount of hard and brittle intermetallics which leads to decreasing shear strength of the composite solder.

Wettability, Electrical and Mechanical Properties of 99.3Sn-0.7Cu/Si3N4 Novel Lead-Free Nanocomposite Solder

A nanocomposite solder alloy with 99.3Sn-0.7Cu base alloy was successfully fabricated using the powder metallurgy route which consists of blending, compaction and sintering. Varying amount of nano size silicon nitride particulates were introduced as reinforcements to obtain a novel lead-free nanocomposite solder alloy. Following fabrication, the sintered nanocomposite solder were cut into thin solder disc and were analyzed in terms of their wettability, electrical and mechanical properties. Wettability, electrical and mechanical properties of the nanocomposite solder were compared to 99.3Sn-0.7Cu and 96.3Sn-3.0Ag-0.5Cu lead-free solder which were fabricated with the same method using powder metallurgy route. Wettability property of the nanocomposite solder was found to be in the accepted range with wettability angle below 45° similar to 99.3Sn-0.7Cu and 96.3Sn-3.0Ag-0.5Cu lead-free solder. Besides wettability, the results of electrical and mechanical properties analysis showed that additions of nano size Si3N4 had enhanced the strength and electrical conductivity of nanocomposite solder comparing to 99.3Sn-0.7Cu and 96.3Sn-3.0Ag-0.5Cu lead-free solder.