Abstract
Intermetallic compounds (IMCs) formation between lead-free solder alloys (Sn-9Zn and Sn-8Zn-3Bi) and Ni/Au surface finish copper substrate were studied. Reaction between the solder and the substrate was carried out at regular soldering temperature, approx. 50 °C above the melting temperature of the solder alloys. Results indicated that Au-Zn was the IMC formed at the interface and the Au layer which is electro-plated on the substrate has completely dissolved into the solder alloys. The amount of Au available at the interface is an important factor that influent the morphology of the IMC with thicker Au layer on the substrate resulted in thicker layer of IMC at the interface. Although Bi does not taken part in the composition of IMC, it influent the formation of IMC, the IMC formed in the Sn9Zn/substrate interface was Au5Zn3, meanwhile it was g2-AuZn3 in the Sn-8Zn-3Bi/substrate interface.
Highlights
In electronic products, all the common base materials, coatings, metallizations such as Cu, Ni, and Au, form intermetallic compounds (IMCs) with Sn, which is generally accepted to be the major element in solder alloys [1,2,3,4]
A thin, continuous and uniform IMC layer is an essential requirement for good bonding
Knowledge of the solder/conductor metal interactions and phase evolution in the solder interconnections is important for the understanding of the reliability of the solder interconnections from the metallurgical viewpoint and for the optimization of the soldering process Ni/Au surface finish is one of the important types of surface finish that have been widely used in the electronic industry
Summary
All the common base materials, coatings, metallizations such as Cu, Ni, and Au, form intermetallic compounds (IMCs) with Sn, which is generally accepted to be the major element in solder alloys [1,2,3,4]. A thin, continuous and uniform IMC layer is an essential requirement for good bonding Due to their inherent brittle nature and the tendency to generate structural defects, too thick IMC layer at the solder/conductor metal interface may degrade the reliability of the solder joints [2,5,6,7,8]. Types of IMC formed at the solder/substrate interface and their morphology were extensively studied
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