This study investigated the effect of Ag addition on the morphology and growth rate of Cu5Zn8, Cu6Sn5 and Cu3Sn intermetallics in the Sn-8Zn-3Bi solder. The solder was prepared by mixing 1wt% of Ag into 99wt% of Sn-8Zn-3Bi solder. The intermetallics were formed by liquid-state aging, whereby the solders were reacted on Cu substrate above the melting temperature of the solder. The reflow was done at 250°C and 270°C at various soldering times. A scanning electron microscope (SEM) was used to observe the morphology of the intermetallic phase and energy dispersive X-ray (EDX) was used to identify the elemental composition. The Sn-8Zn-3Bi solder reacting with Cu substrate formed a single Cu5Zn8 intermetallic layer with a flat structure. On the other hand, the reaction between (Sn-8Zn-3Bi)-1Ag solder and Cu substrate produces Cu6Sn5 intermetallic. This Cu6Sn5 intermetallic has a scallop structure. As the soldering time increases, a second layer, identified as Cu3Sn starts to grow. The thickness of the intermetallics increases with aging temperatures and time. The addition of Ag into the Sn-8Zn-3Bi solder has significantly suppressed the formation of Cu5Zn8 intermetallic and promoted the growth of Cu6Sn5 intermetallic.

This study investigated the effect of Ni addition on intermetallic formation in the Sn-8Zn-3Bi solder under liquid state aging. The intermetallic compounds were formed by reacting the solder alloy with copper substrate. Different reflow time was used at temperature 220°C. Morphology of the phases formed was observed using scanning electron microscope (SEM) and in order to determine elemental compositions of the phases, energy dispersive x-ray (EDX) was used. The formation of the reaction layer led by Cu5Zn8 intermetallic and then followed by Cu6Sn5 and Cu3Sn when reflow time increases. Keywords: lead free solder, intermetallic, Cu5Zn8, Cu6Sn5, liquid state aging.

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This study investigated the effect of Ag addition on the formation of intermetallic compounds and joint strength of the Sn-Zn-Bi based alloys under liquid state aging. The intermetallic compounds were formed by reacting Sn-8Zn-3Bi and (Sn-8Zn-3Bi)-IAg lead free solders on copper substrate. Scanning electron microscope (SEM) was used to see the morphology of the phases and energy dispersive x ray (EDX) was used to estimate the elemental compositions of the phases. It was found that for Sn-8Zn-3Bi solder reacting with Cu substrate, the Cu5Zn8 intermetallic was formed. On the other hand, when 1 % Ag was added into the solder, the CU3Sn and CU6SnS IMC were formed. The morphology of the CusZng intermetallic was flat whereas for CU3Sn and CU6SnS were rather scallop. The addition of Ag into the Sn-Zn-Bi solder increases the shear strength of the solder joint. It is believed the scallop morphology of Cu Sn contribute to strengthening the (Sn-8Zn-3Bi)-IAg/Cu joints.