Xiuqi Wang, Fenglian Sun, Bangyao Han, Yilun Cao, Jinyang Du, Long Shao and Guohuai Liu
The purpose of this paper is to investigate the wetting behaviors of Sn-5Sb-CuNiAg solders on copper substrates in different soldering processes and the effects of alloying…
Abstract
Purpose
The purpose of this paper is to investigate the wetting behaviors of Sn-5Sb-CuNiAg solders on copper substrates in different soldering processes and the effects of alloying elements on the wettability.
Design/methodology/approach
Sn-5Sb-CuNiAg solder balls (750 µm in diameter) were spread and wetted on 40 × 40 × 1 mm copper plates, in different fluxes, soldering temperatures and time. The contact angles were obtained by a home-made measuring instrument. The samples were polished and deep etched before analyzed by scanning electron microscopy. Energy dispersive X-ray spectroscopy was used to identify the composition of the joints.
Findings
The effects of different soldering processes and alloying elements on the wetting behaviors of Sn-5Sb-CuNiAg solders on copper substrates were calculated and expounded. The rosin-based flux could effectively remove oxidation layers and improve the wettability of Sn-5Sb-CuNiAg solders. Then with the increase of soldering temperature and time, the contact angles decreased gradually. The soldering processes suited for Sn-5Sb-CuNiAg solders were RMA218, 280°C and 30 s. Considered the effects of alloying elements, the wettability of Sn-5Sb-0.5Cu-0.1Ni-0.5Ag was relatively favorable on copper substrates. Besides, Ni could accumulate at the solder/Cu interface and form a jagged (Cu,Ni)6Sn5 IMC.
Originality/value
This work was carried out with our handmade experiment equipment and the production of the quinary lead-free solder alloy used in wetting tests belongs to us. The investigated Sn-5Sb-CuNiAg alloys exhibited higher melting point and preferable wettability, that was one of the candidates for high-temperature lead-free solders to replace high-Pb solders, and applied extremely to high temperature and frequency working environments of the third-generation semiconductors components, with a greater potential research and development value.
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Md Jahidur Rahman and Xianxian Chen
This study aims to examine the effect of the chief executive officer (CEO) characteristics on corporate performance in private listed firms in China.
Abstract
Purpose
This study aims to examine the effect of the chief executive officer (CEO) characteristics on corporate performance in private listed firms in China.
Design/methodology/approach
Fixed effects regressions are used to explore the connection of CEO age, tenure, political connection, duality and gender with firm performance. The final panel data sample consists of 16,010 firm-year observations from 2010 to 2020, including A-share private firms listed in the Shenzhen and Shanghai Stock Exchanges.
Findings
Five hypotheses are proposed, and results show that certain CEO characteristics, such as age, tenure and political connection, are positively related to corporate performance. Contrary to expectations, CEO duality and gender do not affect firm performance.
Originality/value
Findings present implications for future research on corporate governance and political connections of private listed firms.