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1 – 9 of 9Yang Liu, Hao Zhang, Lingen Wang, Xuejun Fan, Guoqi Zhang and F. Sun
Crack and stress distribution on dies are key issues for the pressure-assisted sintering bonding of power modules. The purpose of this research is to build a relationship among…
Abstract
Purpose
Crack and stress distribution on dies are key issues for the pressure-assisted sintering bonding of power modules. The purpose of this research is to build a relationship among stress distributions, sintering sequences and sintering pressures during the sintering processes.
Design/methodology/approach
Three sintering sequences, S(a), S(b) and S(c), have been designed for the double-side assembly of power module in this paper. Experiments and finite element method (FEM) analysis are conducted to investigate the crack and stress distribution.
Findings
The sintering sequence had significant effects on the crack generation in the chips during the sintering process under 30-MPa pressure. The simulation results revealed that the module sintered by S(a) showed lower chip stress than those by the other two sintering sequences under 30 MPa. In contrast, the chip stress is the highest when the sintering sequence follows S(b). The simulation results explained the crack generation and prolongation in the experiments. S(a) was recommended as the best sintering sequence because of the lowest chip stress and highest yield rate.
Originality/value
This study investigated the stress distributions of the double-side sintered power modules under different sintering pressures. Based on the results of experiments and FEM analysis, the best sintering sequence design is provided under various sintering pressures.
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Fabio Santagata, Jianwen Sun, Elina Iervolino, Hongyu Yu, Fei Wang, Guoqi Zhang, P.M. Sarro and Guoyi Zhang
The purpose of this paper is to demonstrate a novel 3D system-in-package (SiP) approach. This new packaging approach is based on stacked silicon submount technology. As…
Abstract
Purpose
The purpose of this paper is to demonstrate a novel 3D system-in-package (SiP) approach. This new packaging approach is based on stacked silicon submount technology. As demonstrators, a smart lighting module and a sensor systems were successfully developed by using the fabrication and assembly process described in this paper.
Design/methodology/approach
The stacked module consists of multiple layers of silicon submounts which can be designed and fabricated in parallel. The 3D stacking design offers higher silicon efficiency and miniaturized package form factor. This platform consists of silicon submount design and fabrication, module packaging, system assembling and testing and analyzing.
Findings
In this paper, a smart light emitting diode system and sensor system will be described based on stacked silicon submount and 3D SiP technology. The integrated smart lighting module meets the optical requirements of general lighting applications. The developed SiP design is also implemented into the miniaturization of particular matter sensors and gas sensor detection system.
Originality/value
SiP has great potential of integrating multiple components into a single compact package, which has potential implementation in intelligent applications.
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Yang Liu, Fenglian Sun, Cadmus A. Yuan and Guoqi Zhang
The purpose of this paper is to discuss the possibility of using soldering process for the bonding of chip-on-flexible (COF) light-emitting diode (LED) packages to heat sinks. The…
Abstract
Purpose
The purpose of this paper is to discuss the possibility of using soldering process for the bonding of chip-on-flexible (COF) light-emitting diode (LED) packages to heat sinks. The common bonding materials are thermal conductive adhesives. For thermal performance and reliability concerns, Tin-Bismuth (SnBi) lead-free solder paste was used for the connection of the COF packages and the Cu heat sinks by a soldering process in this study. Meanwhile, the geometrical effect of the SnBi solder layer on the thermal performance was also investigated.
Design/methodology/approach
The effects of the bonding materials and the area of the solder layers on the thermal performance of the LED modules were investigated by finite element simulation and experimental tests.
Findings
The SnBi soldered modules show much lower thermal resistance at the bonding layers than the adhesive-bonded LED module. Vertical heat transfer from the LED chips to the heat sinks is the primary heat dissipation mode for the SnBi soldered modules. Thus, the LED module with local solder layer shows similar LED thermal performance with the full-area soldered module. Meanwhile, the local soldering process decreases the possibility to form randomly distributed defects such as the large area voids and residue flux in the solder layers.
Research limitations/implications
The research is still in progress. Further studies mainly focus on the reliability of the samples with different bonding materials.
Practical implications
COF package is a new structure for LED packages. This study provides a comparison between SnBi solder and adhesive material on the thermal performance of the LED. Meanwhile, the authors optimized the geometrical design for the solder layer. The study provides a feasible bonding process for COF packages onto heat sinks.
Originality/value
This study provides a soldering process for the COF LED packages. The thermal performance of the LED light source was improved significantly by the new process.
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Mingzhi Dong, Fabio Santagata, Robert Sokolovskij, Jia Wei, Cadmus Yuan and Guoqi Zhang
This study aims to provide a flexible and cost-effective solution of 3D heterogeneous integration for applications such as micro-electro-mechanical system (MEMS) applications and…
Abstract
Purpose
This study aims to provide a flexible and cost-effective solution of 3D heterogeneous integration for applications such as micro-electro-mechanical system (MEMS) applications and smart sensor systems.
Design/methodology/approach
A novel 3D system-in-package (SiP) based on stacked silicon submount technology was successfully developed and well-demonstrated by the fabrication and assembly process of a selected smart lighting module.
Findings
The stacked module consists of multiple layers of silicon submounts which can be designed and fabricated in parallel. The bonding and interconnecting process is quite simple and does not require complicated equipment. The 3D stacking design offers higher silicon efficiency and miniaturized package form factor. The submount wafer can be assembled and tested at the wafer level, thus reducing the cost and improving the yield.
Research limitations/implications
The embedding design presented in this paper is applicable for modules with limited number of passives. When it comes to cases with more passive devices, new process needs to be developed to achieve fast, inexpensive and reliable assembly.
Originality/value
The presented 3D SiP design is novel for applications such as smart lighting, Internet of Things, MEMS systems, etc.
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Yijun Hou, Dongdong Wang and Guoqi Dong
The purpose of this paper is to take the early Permian no.6 coal seam in Jungar coalfield of North China as an example, this paper studied the net primary productivity (NPP) level…
Abstract
Purpose
The purpose of this paper is to take the early Permian no.6 coal seam in Jungar coalfield of North China as an example, this paper studied the net primary productivity (NPP) level of the early Permian peatland and its relationship with the atmospheric environment at that time, analyzed the influence of the atmospheric environment, and discussed its control factors.
Design/methodology/approach
First, geophysical logging signals were used for a spectrum analysis to obtain the Milankovitch cycle parameters in the no. 6 coal seam, including the eccentricity (95 ka); obliquity (35.6 ka); and precession (21.2 ka). These were then used to calculate the accumulation rate of the residual carbon in the no. 6 coal seam, which was determined to be between 49.44 and 50.57 gC/(m2 · a). The carbon loss could be calculated according to the density and residual carbon content of the no. 6 coal seam. Then, the total carbon accumulation rate of the peatland was further derived as being between 64.91 and 66.40 gC/(m2 · a). Also, the NPP of the peatland was determined to be between 129.82 and 132.8 gC/(m2 · a).
Finding
The result showed that the NPP of the early Permian peatland area was lower than that of the Holocene at the same latitude, and also lower than that of the later Permian of South China.
Originality/value
This study’s comprehensive analysis indicated that the temperature and humidity conditions, along with the oxygen and carbon dioxide levels in the atmosphere, were the main control factors of the NPP of the early Permian peatland. Also, wildfires were found to play a role.
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This paper aims to establish a theoretical framework that can comprehensively explain the executive compensation in state-owned enterprises (SOEs) within the context of socialism…
Abstract
Purpose
This paper aims to establish a theoretical framework that can comprehensively explain the executive compensation in state-owned enterprises (SOEs) within the context of socialism with Chinese characteristics.
Design/methodology/approach
The author develops a theoretical framework for executive compensation in SOEs from the perspective of Marxist economics and points out that the executives in SOEs are engaged in management labor, and their compensation should adhere to the principle of distribution according to labor contribution.
Findings
Based on this theory, the author posits that the continuous upward trend of executive compensation in SOEs, is consistent with the trend of SOEs' ongoing expansion, which reflects a continuous improvement of SOE executives' management labor in both quality and quantity.
Originality/value
It is necessary to start with Marxist economic theory and scientifically study the issue of SOE executive compensation, adhere to the principle of distribution according to work in the context of a socialist market economy and implement the specific guideline of the Party Central Committee; only in this way can the long-term healthy development of SOEs be promoted continuously.
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Xiaohua Yang and Clyde D. Stoltenberg
This paper aims to re-examine the role of institutions in the rise of made-in-China multinationals. Specifically, the paper seeks to understand how changes in the global…
Abstract
Purpose
This paper aims to re-examine the role of institutions in the rise of made-in-China multinationals. Specifically, the paper seeks to understand how changes in the global environment, especially global financial crisis, have solidified the Chinese government's role in pushing and encouraging Chinese firms to engage in outbound foreign direct investment (OFDI) activities.
Design/methodology/approach
This is a conceptual paper. The analysis is based on a large number of publicly available sources, including research papers, government documents, and reports. The paper strives to triangulate the validity of the data with multiple sources.
Findings
The study finds that while the role of the state in China has been evolving since the start of the economic reforms in 1978, by no means has it been lessened. Instead, the state has asserted its role specifically to grow Chinese multinationals in size and in number, by leveraging the financial resources accumulated over the last 30 years, by taking advantage of the cheap assets made available globally by the recent financial crisis and by institutionalizing its “Go Global” strategy.
Research limitations/implications
The study implies that the role of the state will be further solidified through China's national goal of enhancing competitiveness via knowledge acquisition through OFDI and simultaneously, multinationals’ OFDI initiatives and strategies will be reinforced by the state's economic policies and goals while their commercial interests will take on an increasing importance in the global marketplace and their behavior will co-evolve with and be reshaped by local, national, and international environments. The paper suggests that future studies employ co-evolutionary theory to investigate the role of state-owned enterprises (especially the functions of their CEOs) as well as non-state actors in shaping the institutional framework in China. Future studies should verify some of the ideas with empirical data and strive to triangulate different data sources to increase data quality.
Practical implications
The study also provides implications to Chinese policy makers on how to balance the government's role as conductor, enabler, protector, and constrainer while allowing Chinese multinationals to integrate into the global market for the benefit of both China and the world economy.
Originality/value
This study represents an original contribution to this topic. The research contributes to the study of globalization of Chinese enterprises by exploring the renewed dynamic relationship between the state and the firm after the 2008 global financial crisis.
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Rare earths are essential materials for many high-tech industries critical to both economic development and national defense. China, the world's dominant supplier of rare earths…
Abstract
Purpose
Rare earths are essential materials for many high-tech industries critical to both economic development and national defense. China, the world's dominant supplier of rare earths, has recently been imposing stricter controls over its production and export. The purpose of this paper is to examine the domestic roots of the changes in China's rare earth industry production and exports in its three-decade rise to the current global monopoly.
Design/methodology/approach
This paper adopts the historical institutionalism approach to analyze the trajectory of industry and trade development. The author analyzes data collected from government whitepapers and reputed scholarly and news sources.
Findings
This paper argues that the Chinese rare earth industry has gone through three periods of development, in which the state attempted to control the market and industry through reformulating rules and institutions to achieve state goals. Domestic state institutions, combined with macroeconomic environment and state governance strategy shaped the three-decade experience of rare earth industry and trade development in China.
Originality/value
This paper builds on existing findings about Chinese state regulations to provide a novel analytical framework to analyze the role of the state in industry and trade development in the rare earth industry. The focus on a single strategic industry seldom studied in the current literature also provides ample empirical value to further scholarly understanding about this industry.
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The purpose of this paper is to provide an overview of China's contemporary banking regulatory system, with particular focus on regulatory control of foreign banks trading in…
Abstract
Purpose
The purpose of this paper is to provide an overview of China's contemporary banking regulatory system, with particular focus on regulatory control of foreign banks trading in China. The paper addresses three aspects of Chinese banking regulation: what does China regulate; why does China regulate; and how does China regulate. Much of the discussion is concerned with China's regulatory agencies particularly with the role of the CBRC as the principal regulator in China's banking sector.
Design/methodology/approach
In the first instance the paper presents an overview of banking regulatory models gained from a review of theoretical literature in the area. Then through a wide ranging review of Chinese publications, both academic and official, the paper seeks to relate the course of regulatory reform in China, both in terms of compliance with orthodox regulatory theory, and the unique regulatory requirements of the Chinese banking system.
Findings
The paper recognises that China has embraced the need for banking regulation with the establishment of an institutional structure that is responsive to both banking supervision and government policy. Within that structure the role of the CBRC, the pervasive manner in which that agency operates, and the content of its regulatory output have been identified and critically reviewed.
Originality/value
In its review of the modernization of China's banking regulatory system, the paper achieves originality from the author's research into, and critical reflections on Chinese generated literature, both institutional and academic, which is then communicated in a manner that will be understood by readers familiar with Western banking regulatory theory.
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