B. Fiegl, M. Hibler, W. Kiffe, F. Koch, R. Kuhnert, R. Messer and H. Schwarzbauer
Module technology has become the most successful technology for power devices. The sandwich structure of the module serves as both an electrical insulator and heat sink to remove…
Abstract
Module technology has become the most successful technology for power devices. The sandwich structure of the module serves as both an electrical insulator and heat sink to remove the heat generated in the device. Typical heat fluxes of 200 W/cm2 through the chip substrate interface make it necessary to develop modules with a lower thermal resistance than those available today. With the recent advances in diamond technology, diamond substrates which have unique heat conducting properties are now available. Presented here are the first applications of diamond films in power device modules in combination with a new joining technology. The thermal behaviour of these modules has been simulated. Following the simulations, power device modules with a diamond film were produced. Investigations with a scanning acoustic microscope showed that there is good mechanical contact between the diamond and the adjacent layers. The thermal resistance of the modules was measured. The results are in good agreement with those of the simulations. They show that the application of diamond films in power modules for heat conduction and heat spreading is feasible. It is demonstrated that diamond films together with an advanced joining technology provide a considerable improvement in thermal management compared with state‐of‐the‐art technologies.
Qiaoran Zhang, Abdelhafid Zehri, Jiawen Liu, Wei Ke, Shirong Huang, Martí Gutierrez Latorre, Nan Wang, Xiuzhen Lu, Cheng Zhou, Weijuan Xia, Yanpei Wu, Lilei Ye and Johan Liu
This study aims to develop a bimodal nano-silver paste with improved mechanical property and reliability. Silicon carbide (SiC) particles coated with Ag were introduced in…
Abstract
Purpose
This study aims to develop a bimodal nano-silver paste with improved mechanical property and reliability. Silicon carbide (SiC) particles coated with Ag were introduced in nano-silver paste to improve bonding strength between SiC and Ag particles and enhance high-temperature stability of bimodal nano-silver paste. The effect of sintering parameters such as sintering temperature, sintering time and the proportion of SiC particles on mechanical property and reliability of sintered bimodal nano-silver structure were investigated.
Design/methodology/approach
Sandwich structures consist of dummy chips and copper substrates with nickel and silver coating bonded by nano-silver paste were designed for shear testing. Shear strength testing was conducted to study the influence of SiC particles proportions on the mechanical property of sintered nano-silver joints. The reliability of the bimodal nano-silver paste was evaluated experimentally by means of shear test for samples subjected to thermal aging test at 150°C and humidity and temperature testing at 85°C and 85 per cent RH, respectively.
Findings
Shear strength was enhanced obviously with the increase of sintering temperature and sintering time. The maximum shear strength was achieved for nano-silver paste sintered at 260°C for 10 min. There was a negative correlation between the proportion of SiC particles and shear strength. After thermal aging testing and humidity and temperature testing for 240 h, the shear strength decreased a little. High-temperature stability and high-hydrothermal stability were improved by the addition of SiC particles.
Originality/value
Submicron-scale SiC particles coated with Ag were used as alternative materials to replace part of nano-silver particles to prepare bimodal nano-silver paste due to its high thermal conductivity and excellent mechanical property.
Details
Keywords
Yansong Tan, Xin Li, Xu Chen, Zhenwen Yang and Guo-Quan Lu
This paper aims to use nano-silver paste to design a new bonding method for super-large-area direct-bonded-aluminum (DBA) plates. It compared several frequently used bonding…
Abstract
Purpose
This paper aims to use nano-silver paste to design a new bonding method for super-large-area direct-bonded-aluminum (DBA) plates. It compared several frequently used bonding methods and proved the feasibility of an optimized low-pressure-assisted double-layer-printed silver sintering technology for large-area bonding to increase the thermal conductivity of power electronic modules with high junction temperature, higher power density and higher reliability.
Design/methodology/approach
The bonding profile was optimized by using transparent glasses as substrates. Thus, the bonding qualities could be directly characterized by optical observation. After sintering, the bonded DBA samples were characterized by nondestructive X-ray computed tomography system, scanning electron microscopy equipped with an energy dispersive spectrometer. Finally, bonding stress evolution was characterized by shear tests.
Findings
Low-pressure-assisted large-area double-layer-printed bonding process consisting of six-step was successfully developed to bond DBA substrates with the size of 50.8 × 25.4 mm. The thickness of the sintered-silver bond-line was between 33 and 74 µm with the average porosity of 12.5 per cent. The distribution of shear strength along the length of DBA/DBA bonded sample was from 9.7 to 18.8 MPa, with average shear strength of 15.5 MPa. The typical fracture primarily propagated in the sintered-silver layer and partially along the Ni layer.
Research limitations/implications
The bonding stress needs to be further improved. Meanwhile, the thermal and electrical properties are encouraged to test further.
Practical implications
If nano-silver paste can be used as thermal interfacial material for super-large-area bonding, the thermal performance will be improved.
Social implications
The paper accelerated the use of nano-silver paste for super-large-area DBA bonding.
Originality/value
The proposed bonding method greatly decreased the bonding pressure.
Details
Keywords
Yunhui Mei, Gang Chen, Xin Li, Guo‐Quan Lu and Xu Chen
The purpose of this paper is to determine: how much the residual curvature could be formed in sintered nano‐silver assembly when it is cooled to room temperature from the…
Abstract
Purpose
The purpose of this paper is to determine: how much the residual curvature could be formed in sintered nano‐silver assembly when it is cooled to room temperature from the sintering temperature (normally 275°C); how the cyclic temperature load affects the residual curvature or stresses in sintered joint. Then the stress level and the reliability of sintered nano‐silver for high‐temperature applications can be understood.
Design/methodology/approach
5 mm * 2.5 mm silicon chip was bonded with 96 per cent Al2O3 substrate by sintering nanosilver paste. An optical system was developed to measure the curvature of the sintered assemblies. Reliability of the sintered assemblies was evaluated by temperature cycling of −40∼125°C. Finite element analysis was employed to simulate the behavior of the joint subjected to the temperature cycling from −40°C to 125°C by ANSYS. SEM images were taken to investigate the impact of temperature cycling on the reliability of sintered silver attachment.
Findings
This residual bending at room temperature was found concave towards the substrate (alumina) side. Also, with the bondline thickness increasing, the residual curvature decreases obviously. The severity of the residual bending in all the structures was mitigated to some extent with increasing number of cycles. There is no crack in the joint with the thickness of 25 μm. The drop of the residual curvature of the samples with bondline of 25 μm is caused mainly by stress relaxation in sintered silver before 300 cycles. Sample with thicker bondline is more susceptible to thermal cycling for the structure bonded with nanosilver than that with thinner bondline. The poor quality of bonding is due to the thicker sintered joint, which means that sintered nanosilver is not suitable for die‐attachment requiring thick bondline.
Originality/value
The paper describes: how a precise optical system was developed to measure the residual curvature of the sintered assemblies; how the evolution of the residual curvature of the sintered assembly with the temperature cycling was obtained by both experiment and simulation; and how microstructures of the sintered silver joint were analyzed for as‐sintered assembly and the sintered assembly after temperature cycling.
Details
Keywords
This paper aims to find proper technological parameters of low-temperature joining technique by silver sintering to eventually use this technique for reliable electronic packaging.
Abstract
Purpose
This paper aims to find proper technological parameters of low-temperature joining technique by silver sintering to eventually use this technique for reliable electronic packaging.
Design/methodology/approach
Based on the literature and author’s own experience, the factors influencing the nanosized Ag particle sintering results were identified, and their significance was assessed.
Findings
It has been shown that some important technological parameters clearly influence the quality of the joints, and their choice is unambiguous, but the meaning of some parameters is dependent on other factors (interactions), and they should be selected experimentally.
Originality/value
The value of this research is that the importance of all technological factors was analyzed, which makes it easy to choose the technological procedures in the electronic packaging.
Details
Keywords
Tonmoy Chatterjee and Nilendu Chatterjee
Forestry is an integral part of an economy. It not only maintains the balance of the ecosystem but provides sustainable livelihood to the forest-fringe dwellers, apart from being…
Abstract
Forestry is an integral part of an economy. It not only maintains the balance of the ecosystem but provides sustainable livelihood to the forest-fringe dwellers, apart from being a huge source of revenue for the government. Hence, proper management of the forest resources is an important concern for the economists. On the other hand, convergence of natural resources is one of the hot cakes of discussion for the economists. In this study, the authors have considered three forest regions of West Bengal; these three being the largest forest areas hold an important position in West Bengal’s economy. Here, the authors have considered the whole of dryland forestry that covers the arid and semi-arid districts of western part of the state. They have also considered the forestry of Jalpaiguri and Cooch Behar districts that cover the sub-Himalayan forestry of North Bengal and mangrove forestry of South 24 Parganas district. The authors have used time-series data for the time period 1980–2019 and performed the Absolute Beta Convergence and Sigma Convergence Analysis as well as Conditional Beta Convergence of the total forest products of these three regions. In this study, the authors have found the existence of both forms of beta convergence but for variations, a divergence has been observed. The authors have also used the data from 2000 to 2019 on various aspects of income from forestry and performed the three forms of tests, like that of total forest products and observed similar type of results, that is, beta convergence of both forms but sigma divergence. The findings of this study ask for serious steps by the government bodies, since the decreasing rates are the causes of worries.
Details
Keywords
A.O. Zubair, Mohd Alsaleh and Abdul Samad Abdul-Rahim
The purpose of this study is to evaluate the profit efficiency of bioenergy industry and its determinants in EU28 region roadmaps for the transition towards energy efficiency…
Abstract
Purpose
The purpose of this study is to evaluate the profit efficiency of bioenergy industry and its determinants in EU28 region roadmaps for the transition towards energy efficiency which is increasingly perceived by stakeholders, researchers and the public as a pathway to bring dependency on fossil resources to a significant reduction. Many studies overlooked the importance of profit efficiency as a factor for bioenergy industry business improvement. More so, external environmental variables can play a key role in achieving profit efficiency in the industry.
Design/methodology/approach
This paper seeks to answer the questions on the following: (1) the profit efficiency level using the data envelopment analysis (DEA) approach in the EU28 region during the period between 1990 and 2018; and (2) to explore the impacts of external environmental variables on the profit efficiency level using panel regression model in the EU28 region during the period between 1990 and 2018.
Findings
Results revealed that gross domestic product, size of biomass and investment are essential for the development of the bioenergy industry and positively influence on profit efficiency level. The increase in temperature change decreased the profit efficiency level during 1990–2018.
Research limitations/implications
For those profit-inefficient bioenergy industries in countries such as Cyprus and Ireland, participation in innovative programs, expanding a knowledge-based economic system and implementation of support policy for bioenergy technologies, by investing in biomass sources that are suitable for their respective renewable energy development will enhance specialization, resource efficiency and improved profitability can be expected in future.
Originality/value
Unlike other previous studies, this study investigated the profit efficiency by applying the DEA statistical method. Moreover, the authors have applied a second regression analysis to estimate the impacts of macroeconomic and microeconomic variables on the profit efficiency level. This study has focused on the EU28 region, including both developed and developing countries, to compare the level of profit efficiency levels in the selected sample. The authors have applied data panel analysis for the period from 1990 to 2018. No previous study has applied the methods, samples and periods as those used in this study. Therefore, this study contributes significantly to the bioenergy industry specifically and the renewable energy industry in general and to the associated extant research.
Details
Keywords
What is the current level of integration of the retail and wholesale banking sectors in the European Union (EU) countries, and what are the main factors and challenges affecting…
Abstract
Purpose
What is the current level of integration of the retail and wholesale banking sectors in the European Union (EU) countries, and what are the main factors and challenges affecting it? What are the solutions to promote the integration and convergence of the retail banking sector in the European countries?.
Design/methodology/approach
Evaluated the level of integration of the banking sector, focusing on the EU banking context, retail banking especially. The paper will adopt a comprehensive and multidimensional approach, considering different criteria and indicators of integration, such as price, quantity and information, as well as different segments and dimensions of the EU banking sector, such as wholesale and retail, assets and liabilities, products, services, price indicators and institutions and markets.
Findings
It reveals that while significant integration has been realized in domains like the money market and wholesale banking, it is less pronounced in the retail banking and capital markets.
Originality/value
This paper is an original research. The entire study belongs to me.
Details
Keywords
Augustino Mwogosi and Stephen Kibusi
This study aims to evaluate healthcare practitioners’ perceptions of electronic health record (EHR) systems and their effectiveness in supporting clinical decision-making in…
Abstract
Purpose
This study aims to evaluate healthcare practitioners’ perceptions of electronic health record (EHR) systems and their effectiveness in supporting clinical decision-making in Tanzanian Primary Healthcare (PHC) facilities.
Design/methodology/approach
A mixed-methods approach was employed, combining quantitative data from structured questionnaires and qualitative insights from open-ended responses. The study was conducted in the Dodoma region of Tanzania, focusing on a diverse representation of PHC facilities, including district hospitals, health centres and dispensaries. Data were analysed using multiple linear regression for quantitative data, and thematic analysis was applied to qualitative responses.
Findings
The results revealed that while EHR systems are widely used in Tanzanian PHC facilities, their impact on clinical decision-making remains limited. Only a moderate portion of practitioners perceived EHR systems as effective in decision support, and frequent system use was negatively correlated with user satisfaction. Challenges such as inadequate training and support, system crashes, slow performance and poor usability and integration into clinical workflows were significant barriers to effectively utilising EHR systems.
Originality/value
This study contributes to the limited literature on EHR system implementation in low-resource settings, specifically Tanzania, by focusing on decision-support features within EHR systems. The findings offer valuable insights for healthcare policymakers, system designers and practitioners to optimise EHR implementation and improve healthcare outcomes in resource-constrained environments.
Details
Keywords
Myriam Ertz, Shashi Kashav, Tian Zeng and Shouheng Sun
Traditionally, life cycle assessment (LCA) has focused on environmental aspects, but integrating social aspects in LCA has gained traction among scholars and practitioners. This…
Abstract
Purpose
Traditionally, life cycle assessment (LCA) has focused on environmental aspects, but integrating social aspects in LCA has gained traction among scholars and practitioners. This study aims to review key social life cycle assessment (SLCA) themes, namely, drivers and barriers of SLCA implementation, methodology and measurement metrics, classification of initiatives to improve SLCA and customer perspectives in SLCA.
Design/methodology/approach
A total of 148 scientific papers extracted from the Web of Science database were used and analyzed using bibliometric and content analysis.
Findings
The findings suggest that the existing research ignores several aspects of SCLA, which impedes positive growth in topical scholarship, and the study proposes a classification of SLCA research paths to enrich future research. This study contributes positively to SLCA by further developing this area, and as such, this research is a primer to gain deeper knowledge about the state-of-the-art in SLCA as well as to foresee its future scope and challenges.
Originality/value
The study provides an up-to-date review of extant research pertaining to SLCA.