Effects of AlN Nanoparticles on the Microstructure, Solderability, and Mechanical Properties of Sn-Ag-Cu Solder
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I.
INTRODUCTION
CONVENTIONAL 60Sn-40Pb and 63Sn-37Pb solders have been widely used as bonding materials in microelectronic packaging industries for several decades, due to their outstanding properties, such as low melting point, and good mechanical and wetting properties. A solder material provides electrical continuity among various interconnecting networks in electronic devices. However, lead (Pb), which is toxic, from the Sn-Pb solder of electronic goods causes serious environmental problems, and contaminates underground water, causing decline in intelligence and the generative functions of the human body. Thus, restriction of hazardous substances (RoHS) and waste electrical and electronic equipment (WEEE) directives have been passed by the European Union to restrict lead usage in electronics manufacturing.[1] As a part of restricting Pb
DO-HYUN JUNG, ASHUTOSH SHARMA, DONG-UK LIM, and JAE-PIL JUNG are with the Department of Materials Science and Engineering, University of Seoul, Seoul 02504, Republic of Korea. Contact e-mail: [email protected] JONG-HYUN YUN is with KD One Co. Ltd., 22 Gukhoedaero 76-gil, Seoul 11560, Republic of Korea. Manuscript submitted November 16, 2016.
METALLURGICAL AND MATERIALS TRANSACTIONS A
in electronic packaging, various lead-free solders for soldering applications have been developed, such as Sn-Ag-Cu, Sn-Ag, Sn-Cu, Sn-Zn, and Sn-Bi), with the intention of providing superior strength and economically viable substitutes for the conventional Sn-Pb solder.[2–4] Although no such substitute of conventional Sn-Pb solder has so far been discovered, Sn-Ag-Cu lead-free alloy is considered one of the most outstanding candidates among the various lead-free solders known, due to its promising solderability, and low melting point in electronic packaging industries. Thus, research on leadfree SAC solders is an important issue for miniaturized electronic bonding materials, due to the replacement of Sn-Pb solder with lead-free solder alloys.[5,6] It is also noteworthy that the mechanical properties of lead-free SAC solder are of some concern because of the formation of large and brittle intermetallic Ag3Sn and Cu6Sn5 compounds (IMCs). As the IMCs grow, they may cause poor device performance, leading to the failure of the electronic device. IMCs such as Ag3Sn and Cu6Sn5 in lead-free SAC solder play an important role in bonding solder joints, and impart strength to the surrounding solder matrix.[7] In contrast, a large amount of IMCs may cause poor strength, due to their brittle nature. Therefore, new solder technologies that can reasonably control the growth of the IMCs and
microstructure have to be developed to address these issues satisfactorily. There are a few modern nanotechnologies for microstructural refinement and enhanced mechanical properties of lead-free solder alloys with nanoparticle additions, which are defined as nanocomposite solders.[8–11] The addition of intermetallic compounds in the solder matrix, like Cu6Sn5, Ni3Sn4, Ag3Sn, and CuAl2; metallic elements like Al, Ni, Ag, and Cu,
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