Search results

A new method of studying the accelerated ageing of interconnection materials is applied to a high‐stability thick film resistor system (the Du Pont HS‐80 system). The new method, referred to hereafter as the in‐situ method, allows measurement of the electrical resistance of a thick film resistor to a resolution of a few ppm during accelerated ageing. With the in‐situ technique, the electrical resistance measurements are performed at the elevated ageing temperature during the ageing treatment, whereas with the conventional ageing method the resistance measurements are carried out at room temperature, between subsequent annealing steps. The measuring resolution obtainable with the in‐situ method is orders of magnitude better than with the conventional method. The ageing kinetics can therefore be studied on a shorter time scale and in greater detail than with the conventional method. In this paper, the authors use the in‐situ method to study the accelerated ageing of the Du Pont HS‐80 thick film resistor system, encapsulated with a proper glaze. It will be shown that kinetics of the resistance drift observed in this system cannot be described by an Arrhenius‐type equation. The ageing data can only be interpreted in terms of a kinetic model incorporating a spectrum of activation energies for the ageing process. Such a model is given, and is shown to provide a good explanation of the observed ageing behaviour. The physical process that causes the observed ageing is most probably diffusion of silver from the contacting terminals into the amorphous matrix of the thick film resistor.

In this paper, it is shown that the so‐called in‐situ electrical measurement technique is a valuable tool for understanding failure mechanisms in thick film dielectrics. The technique makes it possible to measure important electrical characteristics of thick film dielectric systems in the temperature range from room temperature up to 900°C. This information is essential to understand failure mechanisms and to optimise the system with respect to quality and reliability. Mainly two electrical properties have been investigated: (i) the electrical resistance of the dielectric as a function of temperature and (ii) the spontaneous electromotive force occurring at higher temperatures between two metal layers with the dielectric in between. A significant result of the work is the observation of a close correlation between the leakage current measured through the dielectric at elevated temperatures, and the ability of the dielectric to resist shorting and blistering effects during the preparation of circuits. Secondly, from in‐situ voltage measurements, it was confirmed that the mixed metallurgy system Au(bottom)‐dielectric‐Ag(top) acts at 850°C as a spontaneous battery, and the battery voltage (i.e., the spontaneous electromotive force) was measured. Depending on the type of dielectric, a battery voltage up to 200 mV between the two metal layers was observed. As a result of this spontaneous electromotive force, blistering occurs. The battery voltage was shown to be much smaller in unmixed metallurgy systems with Ag(bottom)‐dielectric‐Ag(top) or Au(bottom)‐dielectric‐Au(top). However, if an external voltage of 300 mV is applied to such a system during a temperature profile up to 850°C, blisters can also be induced. This shows unambiguously that blistering is a voltage driven effect.

ISHM invites papers for the above Conference, to be held on 29–31 May 1991 in Rotterdam, The Netherlands. Papers should cover areas such as: design, manufacturing, packaging and interconnection, materials and processing, applications, reliability, components, new technologies, marketing and economics, optoelectronics. Summaries should be in English, length 200–300 words. The deadline for receipt of summaries is 30 September 1990. (For full details, see announcement on pp. 54–55.)

The purpose of this paper is to investigate oil-gas slug formation in horizontal straight pipe and its associated pressure gradient, slug liquid holdup and slug frequency.

The abrupt change in gas/liquid velocities, which causes transition of flow patterns, was analyzed using incompressible volume of fluid method to capture the dynamic gas-liquid interface. The validity of present model and its methodology was validated using Baker’s flow regime chart for 3.15 inches diameter horizontal pipe and with existing experimental data to ensure its correctness.

The present paper proposes simplified correlations for liquid holdup and slug frequency by comparison with numerous existing models. The paper also identified correlations that can be used in operational oil and gas industry and several outlier models that may not be applicable.

The correlation may be limited to the range of material properties used in this paper.

Numerically derived liquid holdup and holdup frequency agreed reasonably with the experimentally derived correlations.

The models could be used to design pipeline and piping systems for oil and gas production.

The paper simulated all the seven flow regimes with superior results compared to existing methodology. New correlations derived numerically are compared to published experimental correlations to understand the difference between models.

It has often been said that a great part of the strength of Aslib lies in the fact that it brings together those whose experience has been gained in many widely differing fields but who have a common interest in the means by which information may be collected and disseminated to the greatest advantage. Lists of its members have, therefore, a more than ordinary value since they present, in miniature, a cross‐section of institutions and individuals who share this special interest.

The implementation of public–private partnerships (PPPs), particularly in low- and middle-income countries, has been hampered by external stakeholders’ opposition leading to the failure of several projects. The purpose of this paper is to develop a framework to improve external stakeholder management in PPP projects.

Two case studies consisting of 23 interviews with a wide range of internal and external stakeholders were employed. This was supplemented with a focus group approach to validate the framework.

A new framework for the management of external stakeholders is developed. It encompasses new features such as the dynamic identification of stakeholders at each project phase and their corresponding interests.

The scope is road transportation projects in Nigeria and thus the recommendations may not be globally applicable.

The findings can help the public sector and their agencies to manage external stakeholders and maintain successful relationships on PPP projects.

The paper contributes to existing knowledge in four key areas: it confirms that the skill and actions of internal stakeholders are vital to the stakeholder management process; it shows that one-off stakeholder identification proposed in literature is a flawed approach; it proposes that the identification of external stakeholders’ interests be dynamic; and it adds the perspective of low- and middle-income countries in stakeholder management in PPP projects.

Aarhus Kommunes Biblioteker (Teknisk Bibliotek), Ingerslevs Plads 7, Aarhus, Denmark. Representative: V. NEDERGAARD PEDERSEN (Librarian).

This paper focusses on external stakeholders’ perspective of stakeholder management in public–private partnerships (PPP) projects within the context of developing countries where public opposition to PPP projects is prevalent. The purpose of this paper is to identify the key enablers to PPP projects’ success from the perspective of external stakeholders.

Data were collected from two case studies via semi-structured interviews in two PPP project locations in Nigeria. In total, 14 external stakeholders comprising community leaders, trade unionists and human right activist participated in the research.

Five key enablers of external stakeholder management were identified. These are as follows: the choice of project location; transparency of the internal stakeholders; timing of stakeholder engagement; knowledge of PPP; and relationship with internal stakeholders.

External stakeholders’ perspective of stakeholder management in PPP projects within the context of developing countries new to PPP has been established. The practical implications of the five enablers can be used by policy makers and industry professionals to ensure effective stakeholder management of PPP projects.

The purpose of this study was to determine the transaction cost (TC) contractors incur when tendering for a project as well as establish a correlation between the TC of tender and tender amount of projects procured through the national competitive bidding procurement method.

The research draws extensively documentary analysis, observation and interviews to collect cost data on 14 different tenders submitted by a D1/K1 contractor. Using TC theory, the data are analyzed and the actual cost is determined. Further, Spearman rank correlation is employed to establish a relationship between tender price (TP) and the cost of tender by the aid of Statistical Package for Social Sciences.

The research developed a tender preparation conceptual framework highlighting the components of TC in competitive tendering in Ghana and also revealed that, apart from the emotional and psychological costs, contractors in Ghana incur approximately Gh₵ 4,625 (US$ 925)–Gh₵ 2,520 (US$ 504) to prepare and submit a competitive tender. In relation to the tender figure, the TC of tender in Ghana ranges from 0.05% to 0.65% and an average of 0.33%. Also, there is an inverse correlation between TP and the percentage cost of tender.

The research relied on 14 competitive tenders and also limited to public sector works. Findings from the study should therefore be applied with caution.

This study is the only known research that has focused on assessing the TC of public sector competitive tendering from a contractor's perspective and within a developing sub-Saharan African context.

The performance of public–private partnerships (PPPs) can be determined by a variety of factors, i.e. influencing factors (IFs). This study is undertaken for a purpose of identifying how such factors determine the project's performance (i.e. factor transmission patterns), particularly from the key stakeholders' perspectives.

A hybrid approach, which comprises a Social Network Analysis, ISM (i.e. Interpretive Structural Modeling) and an improved DEMATEL (i.e. Decision-Making Trail and Evaluation Laboratory), was developed to analyze the causal relationships between the identified IFs as well as the transmission patterns of their impacts on PPPs. Data were collected from interviews and questionnaire surveys.

The transmission patterns of the identified IFs cascade from project environment and features and stakeholders' relationship to the project company capabilities and project process. It is identified that the public authority has a higher level than that of the private entity in PPPs.

It lacks longitudinal studies to investigate the dynamics of PPP stakeholder relationships and social networks. Future research needs to explore the transmission patterns of sub-factors affecting PPP performance and extend the applicability of the developed hybrid approach.

This research provides practitioners with a robust tool that is useful for and insights into enhancing the management of lifecycle performance. It ensures the public authorities and private entities embarking on PPPs will make an informed decision about the monitoring of the life cycle performance.

This study contributes to knowledge of managerial mechanisms that can be adopted to manage factors determining the performance of PPPs. It enables an understanding of stakeholders' roles in driving the life cycle performance of PPPs.