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This study aims to evaluate the effect of thermal aging temperature on the properties of Cu/Cu joints.

A new method that 1 um Zn-particles and Sn-0.3Ag-0.7Cu (SAC0307) with a particle size of 25–38 µm were mixed to fill the joint and successfully achieved the micro-joining of Cu/Cu under ultrasonic-assisted at low-temperature, and then the effect of thermal aging temperature on the properties of Cu/Cu joints was researched.

The composition of the intermetallic compounds (IMCs) on the upper and lower interfaces of Cu/SACZ/Cu joints remained unchanged, which was Cu₅Zn₈ in aging process, and the thickness of the IMCs on the upper and lower interfaces of the Cu/SACZ/Cu joints increased accordingly. Compared with the as-received joints, the thickness of the upper and lower interfaces IMCs of the soldering aged time for 24 h increased by 404.7% and 505.5% at 150ºC, respectively. The IMCs formation tendency and the IMCs growth rate of the lower interface are larger than those of the upper interface because the soldering seam near the IMCs at the upper and lower interfaces of the as-received joints were mostly white SAC0307 balls black Zn-particles, respectively. The growth activation energy of IMCs in the upper and lower interfaces is about 89.21 and 55.11 kJ/mol, respectively. Under the same aging time, with the increase of the aging temperature, the shear strength of Cu/SACZ/Cu joints did not change significantly at first before 150ºC. When the aging temperature reached 150ºC, the shear strength of the joints decreased significantly; the shear strength of the joints was the smallest at 150ºC for 24 h, which was 39.4% lower than that of the as-received joints because the oxidation degree of Zn particles in the joint with the increase of aging temperature and time.

Cu/Cu joints were successfully achieved under ultrasonic-assisted at low-temperature.

Low-Ag SAC solder will lead to a series of problems, such as increased the melting range and declined the solderability and so on. These research studies do not have too much impact on the improvement of solders’ performance but were difficult to achieve satisfactory results. It is urgent to develop new soldering technology to avoid the bottleneck of lead-free solder. low-temperature-stirring soldering and ultrasonic-assisted soldering was developed in the authors’ early work, but slag inclusion and pore would gather and grow up to lead decreasing of the shear strength. In this paper, Cu/SAC0307 +Zn power/Cu joints with ultrasonic-assisted at low-temperature was successfully achieved.

45um Zn-powder and SAC0307 No.4 solder powder were mixed to fill the Cu-Cu joint, and the content of Zn-powder were 0 and 5%, 7.5% and 10%, 12.5% and 15% respectively. During the soldering process under ambient atmosphere %252C the heating platform provided a constant 220%253 F and the ultrasonic vibrator applied a constant pressure of 4 MPa to the copper substrate. The soldering process was completed after holding 70 s at 300 W.

The Zn particles made the IMC at the joint interface and in the soldering seam from scallop-type Cu₆Sn₅ to flat-type Cu₅Zn₈. The shear strength of joints without Zn was only 12.43 MPa, the shear strength of joints with 10% Zn reached a peak of 34.25 MPa, and the shear strength of joints containing 10% Zn was 63.71% higher than that of joints without zinc particles, and then the shear strength decreased. In addition, with the increase of zinc content, the fracture mode of the joint changed from the brittle fracture of the original layered tears to the mixed tough and brittle fracture.

A new method that Zn micron-size powders and SAC0307 micron-size powders was mixed to fill the joint, and successfully achieved micro-joining of Cu/Cu under ultrasonic-assisted without flux at low-temperature.

This study aims to evaluate the effect of thermal aging temperature on the properties of Cu/Al joints.

A new method in which 1 µm Zn-particles and SAC0307 with a particle size of 25–38 µm were mixed to fill the joint and successfully achieved the micro-joining of Cu/Al under ultrasonic-assisted at 200°C, and then, the effect of aging temperature on the properties of Cu/Al joints at different aging times was researched.

The results showed that the Cu interface intermetallic compounds (IMCs) had the same composition and had two layers with Cu₅Zn₈ near the Cu substrate and CuZn₅ near the solder. As the aging time increased, CuZn₅ gradually transformed to Cu₅Zn₈, and the thickness of the CuZn₅ layer gradually decreased until CuZn₅ disappeared completely. There was a Sn–Zn solid solution at the Al interface, and the composition of the Al interface of the Cu/Al joints did not change with changing temperature. The IMC thickness at the Cu interface of the joints continued to increase, and the shear strength of the Cu/Al joints decreased with increasing aging temperature and time. Compared with the as-received samples, the IMC thickness of the Cu interface of joints increased by 371.8% and the shear strength of the Cu/Al joints was reduced by 83.2% when the joints were aged at 150°C for 24 h. With an increase in aging temperature, the fracture mode of the Cu/Al joints changed from being between solder balls and Zn particles to between Zn particles.

With increasing aging temperature, the shear strengths of the Cu/SACZ/Al joints decreased at the same aging time, the shear strength of Cu/SACZ/Al joints at 150°C for 24h decreased by 83.2% compared with that of the as-received joints.

The impact strength of solder joint under high strain rate was evaluated by board level test method. However, the impact shear test of single solder bump was more convenient and economical than the board level test method. With the miniaturization of solder joints, solder joints were more prone to failure under thermal shock and more attention has been paid to the impact reliability of solder joint. But Pb-free solder joints may be paid too much attention and Sn-Pb solder joints may be ignored.

In this study, thermal shock test between −55°C and 125°C was conducted on Sn-37Pb solder bumps in the BGA package to investigate microstructural evolution and growth mechanism of interfacial intermetallic compounds (IMCs) layer. The effects of thermal shock and ball diameter on the mechanical property and fracture behavior of Sn-37Pb solder bumps were discussed.

With the increase of ball size, the same change tendency of shear strength with thermal shock cycles. The shear strength of the solder bumps was the highest after reflow; with the increase of the number of thermal shocks, the shear strength of the solder bumps was decreased. But at the time of 2,000 cycles, the shear strength was increased to the initial strength. Minimum shear strength almost took place at 1,500 cycles in all solder bumps. The differences between maximum shear strength and minimum shear strength were 9.11 MPa and 16.83 MPa, 17.07 MPa and 15.59 MPa in φ0.3 mm and φ0.4 mm, φ0.5 mm and φ0.6 mm, respectively, differences were increased with increasing of ball size. With similar reflow profile, the thickness of IMC decreased as the diameter of the ball increased. The thickness of IMC was 2.42 µm and 2.17 µm, 1.63 µm and 1.77 µm with increasing of the ball size, respectively.

Pb-free solder was gradually used to replace traditional Sn-Pb solder and has been widely used in industry. Nevertheless, some products inevitably used a mixture of Sn-Pb and Pb-free solder to make the transition from Sn-Pb to Pb-free solder. Therefore, it was very important to understand the reliability of Sn-Pb solder joint and more further research works were also needed.

This study aims to research properties of Cu/SAC0307 mixed solder balls/Al joints with different bonding temperature under ultrasonic-assisted.

A new method that 1 mm Zn particles and Sn-0.3Ag-0.7 (SAC0307) with a particle size of 25–38 mm were mixed to fill the joint and successfully achieved micro-joining of Cu/Al under ultrasonic-assisted.

The results indicated that when the bonding temperature was 180°C, there was only one layer of CuZn₅ intermetallic compounds (IMCs) at the Cu interface. However, when the bonding temperature was 190°C, 200°C and 210°C, the Cu interface IMCs had two layers: for one layer, the IMCs near the Cu substrate were Cu₅Zn₈ and for another layer, the IMCs near the solder were CuZn₅. In addition, the thickness of the Cu interfacial IMCs increased with the bonding temperature. In particular, the thickness of IMCs at the Cu interface of the Cu/Al joints soldered at 210°C was 4.6 µm, which increased by 139.6% compared with that of the Cu/Al joints soldered at 180°C. However, there was no IMC layer at the Al interface, but there might be a Zn–Al solid solution layer. The shear strength of Cu/Al joints soldered at 180°C was only 15.01 MPa, but as the soldering temperature continued to increase, the shear strength of the Cu/Al joints increased rapidly. When the soldering temperature was 200°C, the shear strength of the Cu/Al joints reached the maximum of 38.07 MPa, which was 153.6% higher than that at 180°C. When the soldering temperature was 180°C, the fracture of Cu/Al joints was mainly on the Al side. However, when soldering temperature was 190°C, 200°C and 210°C, the fracture of Cu/Al joints was mainly broken in the Zn particles layer.

A new method that 1 mm Zn particles and Sn-0.3Ag-0.7 (SAC0307) with a particle size of 25–38 mm were mixed to fill the Cu/Al joint at 210°C.

This study aims to research properties of Cu/SAC0307 mixed solder balls/Cu joints with different Zn-particles content at low-temperature under ultrasonic assisted.

A new method that 1µm Zn particles and Sn-0.3Ag-0.7 (SAC0307) with a particle size of 25–38 µm were mixed to fill the joint and successfully achieved micro-joining of Cu/Cu under ultrasonic-assisted at low temperature.

The results showed that with a continuous increase in the Zn-particle content, the interfacial intermetallic compounds (IMCs) of the upper and lower interfaces of joints gradually changed from scallop-shaped Cu₆Sn₅ to wavy-shaped Cu₅Zn₈. Moreover, the IMC thickness of the upper/lower interface of joints first decreased and then increased with increasing Zn-particle content. The shear strengths of joints increased with Zn-particle content, the shear strength of joints went to a maximum of 29.76 MPa when the Zn-particle content was 40%, an increase of 62.6% compared to joints without Zn particles. However, as the Zn-particle content continued to increase, the shear strengths of the joints decreased. Additionally, when the Zn content increased to 50%, because the oxidation degree of Zn particles increased, the joints were mainly broken among Zn particles.

A new method that 1µm Zn particles and Sn-0.3Ag-0.7 (SAC0307) with a particle size of 25–38 µm were mixed to fill the Cu/Cu joint at 180°C.

With the rising of “religious fever” in China rural area, the authors inquire the reason why it happened. First, the authors explore the group characteristics which could affect both happiness and the religion belief of Chinese rural elderly. The authors analyze the micro-data of “thousand village surveys” data of Shanghai University of Finance and Economics by using Order Logit and Propensity Score Matching (PSM) method. These results show that when the elderly people have the following features related to health such as: feeling psychological loneliness, not obtaining the good management of chronic disease in the village, and not being participated in new rural cooperative medical system are more likely to believe in religious in the rural areas. And the authors also find these Chinese rural elderlies who believe in religion are less happy than atheism elderly actually (by PSM). Believing in religion is not the solution and maybe the way these elderly resorts to when they encounter health problem.

The quality of the unstructured mesh has a considerable impact on the stability and accuracy of aerodynamic simulation in computational fluid dynamics (CFD). Typically, engineers spend a significant portion of their time on mesh quality evaluation to ensure a valid, high-quality mesh. The extensive manual interaction and a priori knowledge required to undertake an accurate and timely evaluation process have become a bottleneck in the idealized efficient CFD workflow. This paper aims to introduce a neural network-based quality evaluation approach for unstructured meshes to enable higher efficiency and the level of automation.

The paper investigates the capability of deep neural networks for the quality evaluation of unstructured meshes. For training the network, we build a training dataset for mesh quality learning algorithms. The dataset contains a rich variety of unstructured aircraft meshes with different mesh sizes, densities, cell distribution, growth ratios and cell numbers to ensure its diversity and availability. We also design a neural network, AircraftNet, to learn the effect of mesh quality on the convergent properties of the numerical solutions. The proposed network directly manipulates raw point data in mesh source files rather than passing it to an intermediate data representation. During training, AircraftNet extracts non-linear quality features from high-dimensional data spaces and then automatically predicts the overall quality of the input unstructured mesh.

The paper provides a series of experimental results on GPUs. It shows that AircraftNet is able to effectively analyze the quality-related features like mesh density and distribution from the extracted features and achieve high prediction accuracy on the proposed dataset with even a small number of training runs.

Because of the limited training dataset, the research results may lack generalizability. Therefore, researchers are encouraged to test the proposed propositions further.

The paper publishes a benchmarking dataset for mesh quality learning algorithms and designs a novel neural network approach for unstructured mesh quality evaluation.

Value cocreation has become an important way to enhance the brand equity of a tourism destination. Different from common tourism contexts, agritourism has strong participatory and productive characteristics and is regarded as a critical platform of value cocreation. Therefore, this paper aims to explore the relationship between agritourism experience value cocreation and brand equity of rural tourism destinations from the perspective of tourists.

A questionnaire survey was conducted, and 602 valid questionnaires were collected by a random sample in 2021. Structural equation modeling was used to empirically analyze the data.

The results revealed that tourists’ participation, interaction and citizenship behaviors play a critical role in brand equity of rural tourism destinations. Meanwhile, tourists’ interaction and citizenship behaviors influenced brand equity of rural tourism destinations, via hedonic enjoyment and eudaimonia experience, and perceived experience value. Tourists’ participation behavior influenced brand equity of rural tourism destinations via hedonic enjoyment experience and perceived experience value.

This study focusing on agritourism as a critical platform of value cocreation explores the impact of agritourism experience value cocreation on brand equity of rural tourism destinations from the perspective of tourists. It enriches the existing literature on the relationship between value cocreation and brand equity of tourism destination, expands the research on value cocreation and happiness experience and also provides management basis for promoting brand equity of rural tourism destinations.

价值共创已成为提升旅游目的地品牌资产的重要途径。与一般的旅游情境不同, 农业旅游具有强烈的参与性和生产性特征, 被视为价值共创的重要平台。因此, 本文基于游 客视角探讨了农业旅游体验价值共创与乡村旅游目的地品牌资产之间的内在关系。

本文于2021 年实施问卷调查, 随机抽取602 份有效问卷。结构方程模 型用于实证分析数据。

游客参与、互动和公民行为对乡村旅游目的地品牌资产具有关键作用。同时, 游客互动和公民行为通过享乐型和实现型体验以及感知体验价值影响乡村旅游目的地品牌 资产。游客参与行为通过享乐型体验和感知体验价值影响乡村旅游目的地品牌资产。

本研究将农业旅游作为价值共创的重要平台, 基于游客视角探讨了农业旅游 体验价值共创对乡村旅游目的地品牌资产的影响, 丰富了价值共创与旅游目的地品牌资产 关系的文献, 拓展了价值共创与快乐体验的研究, 为促进乡村旅游目的地品牌资产提供了 管理依据。

La cocreación se ha convertido en una forma importante de mejorar el valor de marca de un destino turístico. A diferencia de los entornos turísticos comunes, el agroturismo tiene fuertes características participativas y productivas, y se considera una plataforma indispensable de cocreación de valor. Este artículo explora la relación entre la cocreación de valor de la experiencia de agroturismo y el valor de marca de los destinos de turismo rural desde la perspectiva de los turistas.

Se realizó una encuesta y se recogieron 602 cuestionarios válidos mediante un muestreo aleatorioa en 2021. Se utilizó un modelo de ecuaciones estructurales para analizar empíricamente los datos.

Los resultados revelaron que la participación e interacción de los turistas y los comportamientos de la ciudadanía juegan un papel crítico en el valor de marca de destinos de turismo rural. La interacción de los turistas y los comportamientos de la ciudadanía impactaron el valor de marca de destinos de turismo rural a través del disfrute hedónico, la experiencia eudaimonia y el valor percibido de la experiencia. El comportamiento de participación de los turistas influyó en el valor de marca de los destinos de turismo rural a través de la experiencia hedónica de disfrute y el valor percibido de la experiencia.

Este estudio, centrado en el agroturismo como plataforma importante para la cocreación de valor, explora el impacto de la cocreación de valor de la experiencia de agroturismo en el valor de marca de destinos de turismo rural desde la perspectiva de los turistas. Enriquece la literatura existente sobre la relación entre la cocreación de valor y el valor de marca de los destinos turisticos, expande la investigación sobre la cocreación de valor y la experiencia de felicidad, y ofrece también bases de gestión para promover el valor de marca de destinos de turismo rural.