Bifu Xiong, Siliang He, Jinguo Ge, Quantong Li, Chuan Hu, Haidong Yan and Yu-An Shen
This paper aims to examine the effects of bonding temperature, bonding time, bonding pressure and the presence of a Pt catalyst on the bonding strength of Cu/SB/P-Cu/SB/Cu joints…
Abstract
Purpose
This paper aims to examine the effects of bonding temperature, bonding time, bonding pressure and the presence of a Pt catalyst on the bonding strength of Cu/SB/P-Cu/SB/Cu joints by transient liquid phase bonding (TLPB).
Design/methodology/approach
TLPB is promising to assemble die-attaching packaging for power devices. In this study, porous Cu (P-Cu) foil with a distinctive porous structure and Sn-58Bi solder (SB) serve as the bonding materials for TLPB under a formic acid atmosphere (FA). The high surface area of P-Cu enables efficient diffusion of the liquid phase of SB, stimulating the wetting, spreading and formation of intermetallic compounds (IMCs).
Findings
The higher bonding temperature decreased strength due to the coarsening of IMCs. The longer bonding time reduced the bonding strength owing to the coarsened Bi and thickened IMC. Applying optimal bonding pressure improved bonding strength, whereas excessive pressure caused damage. The presence of a Pt catalyst enhanced bonding efficiency and strength by facilitating reduction–oxidation reactions and oxide film removal.
Originality/value
Overall, this study demonstrates the feasibility of low-temperature TLPB for Cu/SB/P-Cu/SB/Cu joints and provides insights into optimizing bonding strength for the interconnecting materials in the applications of power devices.
Details
Keywords
Qiang Sun, Quantong Jiang, Siwei Wu, Chang Liu, Heng Tang, L. Song, Hao Shi, Jizhou Duan and BaoRong Hou
The purpose of this paper is to explore the effect of ZnO on the structure and properties of micro-arc oxidation (MAO) coating on rare earth magnesium alloy under large…
Abstract
Purpose
The purpose of this paper is to explore the effect of ZnO on the structure and properties of micro-arc oxidation (MAO) coating on rare earth magnesium alloy under large concentration gradient.
Design/methodology/approach
The macroscopic and microscopic morphology, thickness, surface roughness, chemical composition and structure of the coating were characterized by different characterization methods. The corrosion resistance of the film was studied by electrochemical and scanning Kelvin probe force microscopy. The results show that the addition of ZnO can significantly improve the compactness and corrosion resistance of the MAO coating, but the high concentration of ZnO will cause microcracks, which will reduce the corrosion resistance to a certain extent.
Findings
When the concentration of zinc oxide is 8 g/L, the compactness and corrosion resistance of the coating are the best, and the thickness of the coating is positively correlated with the concentration of ZnO.
Research limitations/implications
Too high concentration of ZnO reduces the performance of MAO coating.
Practical implications
The MAO coating prepared by adding ZnO has good corrosion resistance. Combined with organic coatings, it can be applied in corrosive marine environments, such as ship parts and hulls. To a certain extent, it can reduce the economic loss caused by corrosion.
Originality/value
The effect of ZnO on the corrosion resistance of MAO coating in electrolyte solution was studied systematically, and the conclusion was new to the common knowledge.
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Keywords
The purpose of this paper is to give a critical review of the City-State Theory by Wan Chin of Hong Kong. Chin is referred to as the “Father of Hong Kong Independence,” and his…
Abstract
Purpose
The purpose of this paper is to give a critical review of the City-State Theory by Wan Chin of Hong Kong. Chin is referred to as the “Father of Hong Kong Independence,” and his two books about the City-State Theory of Hong Kong are popular among the netizens in Hong Kong as a new model of Hong Kong-China (People’s Republic of China (PRC)), in which Hong Kong is considered a city-state and should be fully segregated from the PRC other than in seeking its help in military and diplomatic functions. This paper will aim to review his works with the view of nationalism and nativism theories.
Design/methodology/approach
This paper uses nationalism theories with particular focus on Benedict Anderson’s Imagined Communities and theories on American nativism. Then an effort is made to compare these theories against Chin’s arguments on his City-State Theory. This paper also compares his theories against China’s state-nationalism raised by Professors He and Guo.
Findings
This paper concludes that Chin advocates a “Hong Kong Nationalism,” a blend of traditional Chinese culture and moral values (he used the term Huaxia), but with a Western influence, into a typical Hong Kong culture. His theory fits into Anderson’s arguments of allowing Hong Kong citizens to imagine Hong Kong as a nation, through the “ramparts” of the city-state. His nativist advocacies also have shown strong nationalistic sentiments. He argues that China should be built in the Hong Kong model before the PRC intervention.
Originality/value
Despite his fame, this paper is the first comprehensive academic paper to review Chin’s theories. This paper introduced the notion of “ramparts” and how this has become the backbone of Chin’s nationalism advocacies.