Search results

1 – 10 of 37
Per page
102050
Citations:
Loading...
Access Restricted. View access options
Article
Publication date: 1 December 2003

Cheng Bo, Wang Li, Zhang Qun, Gao Xia, Xie Xiaoming and Wolfgang Kempe

Flip chip on board (FCOB) solder joint reliability under thermal shock stress was investigated. With underfill materials, the solder joint lifetime was increased from 37 to…

350

Abstract

Flip chip on board (FCOB) solder joint reliability under thermal shock stress was investigated. With underfill materials, the solder joint lifetime was increased from 37 to 1,300/2,480 cycles depending on the particular underfill material used. Through the use of CSAM, SEM, dye penetration tests and cross sectioning, the reliability of a FCOB assembly under thermal shock stress was evaluated. Both dye penetration and SEM fracture analysis can be used to measure quantitatively the extent of crack propagation for assemblies without underfill. A new failure mechanism, PCB cracking was also observed and discussed.

Details

Soldering & Surface Mount Technology, vol. 15 no. 3
Type: Research Article
ISSN: 0954-0911

Keywords

Access Restricted. View access options
Article
Publication date: 1 December 2005

Junling Chang, Dirk Janz, W. Kempe and Xiaoming Xie

To investigate the degradation of lead free solder heat‐sink attachment by thermal shock. Samples with high voiding percentages were selected for the investigation in order to get…

591

Abstract

Purpose

To investigate the degradation of lead free solder heat‐sink attachment by thermal shock. Samples with high voiding percentages were selected for the investigation in order to get information on the significance of voids on the reliability of Sn‐Ag‐Cu heat‐sink attachment.

Design/methodology/approach

Through the use of X‐ray, C‐mode scanning acoustic microscopy, dye penetration, cross section and scanning electron microscopy/energy‐dispersive X‐ray tests, the degradation of Sn‐Ag‐Cu heat‐sink attachment during thermal shock cycling was evaluated.

Findings

The results showed that the Sn‐Ag‐Cu heat‐sink attachment where the area of voiding was 33‐48 per cent survived 3,000 thermal shock cycles, although degraded. The main degradation mechanism for the solder attachment was not solder fatigue but interface delamination due to Kirkendall voids at the Cu/Cu3Sn interface. It was found that the large voids in the Sn‐Ag‐Cu heat‐sink attachment were not significantly affecting the solder joint lifetime. Big differences of intermetallic compound growth behaviour and Kirkendall voids at device/solder and solder/Cu pad interfaces are found and the reasons for this are discussed.

Originality/value

This work has clarified the general perception that large voids affect the thermo‐mechanical lifetime of solder joint substantially and also provides further understanding of the Sn‐Ag‐Cu heat‐sink attachment degradation mechanism.

Details

Soldering & Surface Mount Technology, vol. 17 no. 4
Type: Research Article
ISSN: 0954-0911

Keywords

Access Restricted. View access options
Article
Publication date: 1 December 2000

Zhang Qun, Xie Xiaoming, Chen Liu, Wang Guozhong, Cheng Zhaonian and Wolfgang Kempe

The lifetime of flip chip solder joints can be greatly increased by applying underfill encapsulation. This paper presents a case study where the thermal cycle lifetime was…

285

Abstract

The lifetime of flip chip solder joints can be greatly increased by applying underfill encapsulation. This paper presents a case study where the thermal cycle lifetime was increased by more than 20 times, that is from ∼100 cycles to more than 2,000 cycles for a chip size of 5.6mm × 6.3mm. By combining electrical, acoustic and metallographic investigation, the degradation of the solder joints was monitored, some important factors relevant to solder joint reliability were analysed and discussed. Delamination was found not to be the dominant failure mode.

Details

Soldering & Surface Mount Technology, vol. 12 no. 3
Type: Research Article
ISSN: 0954-0911

Keywords

Access Restricted. View access options
Article
Publication date: 1 December 2003

Cheng Bo, Wang Li, Zhang Qun, Gao Xia, Xie Xiaoming and Wolfgang Kempe

Flip chip solder joint reliability under thermal shock stress was investigated both experimentally and by 2D finite element simulation. The results indicate that solder fatigue is…

327

Abstract

Flip chip solder joint reliability under thermal shock stress was investigated both experimentally and by 2D finite element simulation. The results indicate that solder fatigue is the dominant failure mode and that delamination has obvious adverse effects on the solder joint lifetime. Different material/process combinations (underfill, flux, reflow atmospheres) were designed in order to understand the role of material/process factors on the solder joint lifetime and the results are discussed.

Details

Soldering & Surface Mount Technology, vol. 15 no. 3
Type: Research Article
ISSN: 0954-0911

Keywords

Available. Content available
Article
Publication date: 1 August 2004

39

Abstract

Details

Soldering & Surface Mount Technology, vol. 16 no. 2
Type: Research Article
ISSN: 0954-0911

Access Restricted. View access options
Article
Publication date: 1 September 2019

Tong Wen, Wen Chen, Liang Zhang and Xiaoming Liu

Under the background of rapid urbanization, all kinds of urban water problems have gradually come into being: local flooding frequently happens, water environment is deteriorated…

104

Abstract

Under the background of rapid urbanization, all kinds of urban water problems have gradually come into being: local flooding frequently happens, water environment is deteriorated, water-supply is in tension, etc. Meanwhile, with rapid development of higher education in China, campus area and scale are gradually expanding, but traditional campus construction has many drawbacks. In order to promote sponge campus planning and construction of universities in hilly areas and provide demonstration windows for sponge city construction, based on deficiencies of campus construction of Hunan City University in the aspect of water resource utilization, we used ArcGis spatial analysis method, simulation method and comparative analysis method on Storm Water Management Model (SWMM) to establish sponge campus construction indexes, content system and optimal design strategies with objectives of campus water safety, water environment and water resource utilization. Results indicate that: difference between sponge campus planning and traditional campus planning mainly lies in rainfall management. We combed the design process of sponge campus planning in hilly areas from the perspective of rainfall management, and simulated the process of sponge facilities controlling the rainfall in the campus via computer model to verify reasonability of sponge facility planning and select the optimal planning and construction plan. This study has defined design process of sponge campus planning in hilly areas to a certain degree and provided a research basis for sponge campus planning and construction of universities, setting up a typical example and driving effects on solving urban local flooding problem and rainfall resource utilization in hilly areas.

Details

Open House International, vol. 44 no. 3
Type: Research Article
ISSN: 0168-2601

Keywords

Access Restricted. View access options
Article
Publication date: 8 May 2024

Mingge Li, Zhongjun Yin, Xiaoming Huang, Jie Ma and Zhijie Liu

The purpose of this paper is to propose a casting process for the production of double-chamber soft fingers, which avoids the problems of air leakage and fracture caused by…

94

Abstract

Purpose

The purpose of this paper is to propose a casting process for the production of double-chamber soft fingers, which avoids the problems of air leakage and fracture caused by multistep casting. This proposed method facilitates the simultaneous casting of the inflation chamber and the jamming chamber.

Design/methodology/approach

An integrated molding technology based on the lost wax casting method is proposed for the manufacture of double-chamber soft fingers. The solid wax core is assembled with the mold, and then liquid silicone rubber is injected into it. After cooling and solidification, the mold is stripped off and heated in boiling water, so that the solid wax core melts and precipitates, and the integrated soft finger is obtained.

Findings

The performance and fatigue tests of the soft fingers produced by the proposed method have been carried out. The results show that the manufacturing method can significantly improve the fatigue resistance and stability of the soft fingers, while also avoiding the problems such as air leakage and cracking.

Originality/value

The improvement of the previous multistep casting method of soft fingers is proposed, and the integrated molding manufacturing method is proposed to avoid the problems caused by secondary bonding.

Details

Robotic Intelligence and Automation, vol. 44 no. 3
Type: Research Article
ISSN: 2754-6969

Keywords

Access Restricted. View access options
Article
Publication date: 5 September 2018

Ying Huang, Chao Hao, Jian Liu, Xiaohui Guo, Yangyang Zhang, Ping Liu, Caixia Liu, Yugang Zhang and Xiaoming Yang

The purpose of this study is to present a highly stretchable and flexible strain sensor with simple and low cost of fabrication process and excellent dynamic characteristics…

509

Abstract

Purpose

The purpose of this study is to present a highly stretchable and flexible strain sensor with simple and low cost of fabrication process and excellent dynamic characteristics, which make it suitable for human motion monitoring under large strain and high frequency.

Design/methodology/approach

The strain sensor was fabricated using the rubber/latex polymer as elastic carrier and single-walled carbon nanotubes (SWCNTs)/carbon black (CB) as a synergistic conductive network. The rubber/latex polymer was pre-treated in naphtha and then soaked in SWCNTs/CB/silicon rubber composite solution. The strain sensing and other performance of the sensor were measured and human motion tracking applications were tried.

Findings

These strain sensors based on aforementioned materials display high stretchability (500 per cent), excellent flexibility, fast response (approximately 45 ms), low creep (3.1 per cent at 100 per cent strain), temperature and humidity independence, superior stability and reproducibility during approximately 5,000 stretch/release cycles. Furthermore, the authors used these composites as human motion sensors, effectively monitoring joint motion, indicating that the stretchable strain sensor based on the rubber/latex polymer and the synergetic effects of mixed SWCNTs and CB could have promising applications in flexible and wearable devices for human motion tracking.

Originality/value

This paper presents a low-cost and a new type of strain sensor with excellent performance that can open up new fields of applications in flexible, stretchable and wearable electronics, especially in human motion tracking applications where very large strain should be accommodated by the strain sensor.

Details

Sensor Review, vol. 39 no. 2
Type: Research Article
ISSN: 0260-2288

Keywords

Access Restricted. View access options
Article
Publication date: 6 November 2017

Jiayuan Hu, Zhixing Fang, Zhouhai Qian, Xiaoming Shen, Haifei Zhou and Dongchun Jin

The purpose of this paper is to study the cause of severe corrosion of the galvanized lightning rods in a 220 kV transformer substation, and to seek the effective corrosion…

141

Abstract

Purpose

The purpose of this paper is to study the cause of severe corrosion of the galvanized lightning rods in a 220 kV transformer substation, and to seek the effective corrosion inhibition measures for the hollow lightning rods.

Design/methodology/approach

The corrosion morphology and rust component of lightning rod was analyzed, and the corrosion process of lightning rod was researched by means of scanning electron microscopy (SEM), X-ray diffraction (XRD), ion chromatography and electrochemical tests.

Findings

The results indicated that the outer surface of hollow lightning rod was corroded slightly; however, its inner surface suffered severe corrosion because of a long time high-humidity environment inside the tube caused by the rainwater permeation. A rust layer consisted of Fe3O4 and a little FeOOH was accumulated on the inner surface of the hollow lightning rod. Moreover, Fe3O4 rust layer worked as a large cathode area which could promote the corrosion of metal substrate further. A self-accelerating corrosion process was formed on the inner surface, making the corrosion failure of lightning rod occurred and aggravated gradually.

Originality/value

The corrosion of inner surface of hollow lightning rod cannot be detected easily. More attention should be paid to the corrosion inhibition of lightning rod. The key of corrosion inhibition for the hollow lightning rod was to avoid the rainwater accumulation inside tube. The research results can provide guidelines on the corrosion inhibition measures selection of lightning rod in transformer substation.

Details

Anti-Corrosion Methods and Materials, vol. 64 no. 6
Type: Research Article
ISSN: 0003-5599

Keywords

Access Restricted. View access options
Article
Publication date: 10 December 2019

Xiaoming Zhang, Mingming Meng, Xiaoling Sun and Yu Bai

With the advent of the era of Big Data, the scale of knowledge graph (KG) in various domains is growing rapidly, which holds huge amount of knowledge surely benefiting the…

331

Abstract

Purpose

With the advent of the era of Big Data, the scale of knowledge graph (KG) in various domains is growing rapidly, which holds huge amount of knowledge surely benefiting the question answering (QA) research. However, the KG, which is always constituted of entities and relations, is structurally inconsistent with the natural language query. Thus, the QA system based on KG is still faced with difficulties. The purpose of this paper is to propose a method to answer the domain-specific questions based on KG, providing conveniences for the information query over domain KG.

Design/methodology/approach

The authors propose a method FactQA to answer the factual questions about specific domain. A series of logical rules are designed to transform the factual questions into the triples, in order to solve the structural inconsistency between the user’s question and the domain knowledge. Then, the query expansion strategies and filtering strategies are proposed from two levels (i.e. words and triples in the question). For matching the question with domain knowledge, not only the similarity values between the words in the question and the resources in the domain knowledge but also the tag information of these words is considered. And the tag information is obtained by parsing the question using Stanford CoreNLP. In this paper, the KG in metallic materials domain is used to illustrate the FactQA method.

Findings

The designed logical rules have time stability for transforming the factual questions into the triples. Additionally, after filtering the synonym expansion results of the words in the question, the expansion quality of the triple representation of the question is improved. The tag information of the words in the question is considered in the process of data matching, which could help to filter out the wrong matches.

Originality/value

Although the FactQA is proposed for domain-specific QA, it can also be applied to any other domain besides metallic materials domain. For a question that cannot be answered, FactQA would generate a new related question to answer, providing as much as possible the user with the information they probably need. The FactQA could facilitate the user’s information query based on the emerging KG.

Details

Data Technologies and Applications, vol. 54 no. 1
Type: Research Article
ISSN: 2514-9288

Keywords

1 – 10 of 37
Per page
102050