E.B. Hakim, J. Fink, S.M. Tam, P. McCluskey and M. Pecht
For many years, the concern over the use of plastic encapsulated microcircuits(PEMs) has been their capability to survive in harsh environments over a long termwith continuous or…
Abstract
For many years, the concern over the use of plastic encapsulated microcircuits (PEMs) has been their capability to survive in harsh environments over a long term with continuous or intermittent operation. The issues centred around operational life limitation, due to failure mechanisms associated with internal corrosion, wires and wire bonds, and surface effects, It has now been conclusively demonstrated that best commercial practices will ensure that PEMs made using best commercial materials, processes, and quality techniques will permit devices to perform reliably in the most severe environments. Missile systems are low volume production items, which use relatively few microcircuits. They are required to operate for very short times after being unpowered (dormant) for very long times (10 to 20 years) and exposed to humidity, temperature cycle, and mechanical shock. This paper will address reliability concerns and provide data from studies which were performed to determine if PEMs could survive such long‐term unbiased applications. These studies include analysis of PEMs (some date coded 1968) from inventory or various storage locations and from applications where the electronic modules containing PEMs were stored for 10‐12 years in various environments. Regardless of the storage conditions, the significant factor is that these early vintage commercial grade PEMs, without screening or incoming inspection, survived assembly and extended storage.
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Military electronics have typically been isolated from mainstream developments due to military unique requirements,specifications and procurement policies. As a consequence…
Abstract
Military electronics have typically been isolated from mainstream developments due to military unique requirements, specifications and procurement policies. As a consequence, military electronics systems have not profited from many of the commercial technological advancements and the lessons learned. Based on an understanding of this problem, DoD policy directives are now changing, although there are attempts to resist or side‐step implementation. To understand the key issues affecting early affordable access to leading electronics technologies by the US military and government, it is necessary to understand those military and government policies, regulations and organisations that have influenced both directly and indirectly, purposefully and accidentally, electronics effectiveness and worth. This paper provides a perspective to some of the key issues and critical differentiators between US military/government and commercial approaches to electronics.
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G. Page and D.S. Campbell
A study has been undertaken into the use of thermal imaging techniques to determine the temperature distribution of electronic equipment. The suitability of such techniques was…
Abstract
A study has been undertaken into the use of thermal imaging techniques to determine the temperature distribution of electronic equipment. The suitability of such techniques was investigated to determine the level of confidence that could be established with regard to temperature readings obtained. The study consisted of the comparison of temperatures measured directly using fine wire thermocouples with those obtained from a thermal imaging system. Results showed that surface emissivity was a crucial factor in the determination of accurate temperatures by imaging techniques. However, by coating areas to be studied with a light deposit of aluminium chlorohydrate, a constant highly emissive surface could be obtained. This permitted temperature measurements to be made with an accuracy to within <±1 °C over the temperature range 30° to 90°C. The thermal imaging system was used to study the effect of component colour and of component density on temperature distribution. It was found, with respect to the component spacing, that the maximum component temperature was critically related to the spacing between the devices.
The paper describes two well‐known and occasionally confused mechanisms for degradation of electronic circuitry. Intended as a tutorial for individuals working in electronic…
Abstract
The paper describes two well‐known and occasionally confused mechanisms for degradation of electronic circuitry. Intended as a tutorial for individuals working in electronic packaging who have limited background in materials and little experience with these mechanisms, the paper defines and describes the two latent shorting phenomena. Major papers and conferences dealing with the phenomena are cited. Electrolytic or electrochemical shorting is an electrical field‐induced mechanism that can destroy the integrity of modern, densely packed circuits operated in the presence of moisture and ionic contaminants. Examples of copper migration to form electroplated shorts in both thick film hybrid multilayer and printed circuit multilayer boards are discussed, and common features to both systems are outlined. Related mechanisms that may occur with the simple electrochemical (metal plating) mechanisms to produce a broad array of electrical isolation breakdowns are also described. The closing of this part of the paper is a brief review of the Sarnoff‐developed RCA/GE multilayer copper materials system. By design this system solves the problems raised regarding thick film copper multilayer latent failure mechanisms. The discussion of whisker growth is limited to proper whiskers, including those that grow without the application of external stress, squeeze whiskers, and whiskers that result from classic electromigration. All of these grow from solid sources in contact with the whisker. The whisker growth direction is not electrical field related. Identification is made of Sn, Cd, Sb and Zn as the materials classically found to grow whiskers at room temperature. Avoiding the use of electroplated films of Cd, Sb and Zn in close proximity to electronic circuitry is encouraged, and the modern requirements that Sn films be used only after melting, or be alloyed with lead, and not on brass substrates are discussed. In more recent literature indium alloys have been identified as room temperature whisker growth systems. Finally, mechanical design to eliminate squeeze whisker shorting that can result from fasteners in contact with the above and other metals is briefly treated.
An investigation involving the use of thermal imaging has been undertaken, both on trimmed thick film resistors and on wave soldered joints to surface mounted devices. The surface…
Abstract
An investigation involving the use of thermal imaging has been undertaken, both on trimmed thick film resistors and on wave soldered joints to surface mounted devices. The surface mounted devices were ‘zero‐ohm’ jumpers which in themselves did not generate appreciable heat if current was passed through them, but also at the same time allowed the passage of DC current flow through the soldered joints. Thermal imaging results have shown the degree of current bunching obtained for thick film resistors trimmed using air abrasion. Appreciable changes in heating and hence in current density are not observed until the resistor has been trimmed with a cut extending into approximately 50% of the total width. In the case of soldered joints on surface mounted devices, it was found that thermal imaging techniques could not easily detect appreciable temperature changes and hence the current flow in joints which had previously been subject to stress due to one test or another. As a result, measurements were made on artificially damaged joints in order to determine the degree of damage that was needed for thermal imaging to show any noticeable effect. The joints were cut with a miniature PCB saw (1 mm wide) and it was not until the cut extended through approximately 60% of the soldered joint height that any appreciable thermal effects could be observed. Conclusions are drawn from these observations on the applicability of thermal imaging techniques to the assessment of trimmed resistors and soldered joint analysis.
The concept of green marketing has emerged as a panacea for reducing the negative impact of business activities on the environment. Many studies have investigated the impact of…
Abstract
Purpose
The concept of green marketing has emerged as a panacea for reducing the negative impact of business activities on the environment. Many studies have investigated the impact of green marketing on green purchase behavior, sustainable competitive advantage, etc., without much being explored about how green marketing translates into firms' profitability, particularly among small and medium enterprises (SMEs) in emerging markets. This study, therefore, investigates the influence of green marketing on perceived SME profitability alongside the mediating effect of green purchase behaviour.
Design/methodology/approach
A quantitative research approach was adopted, where a cross-sectional survey design was employed to collect the data from 400 SME owners/managers in Ghana. Using Statistical Package for Social Science, the data were analysed through descriptive statistics, correlation and macro Process version 3.4.1.
Findings
The results reveal that the dimensions (environmental knowledge, environmental concern, green price, green advertising and green product) of green marketing distinctively have significant positive effect on perceived SME profitability as well as green purchase behaviour. Furthermore, green purchase behaviour significantly mediates the relationship between green marketing dimensions and perceived SME profitability such that the indirect effects are far greater than the direct effects.
Practical implications
SME managers should include the green marketing dimensions in their business plans and develop strategies to implement them in order to enhance green purchase behaviour of their products and services which will, in turn, lead to profitability.
Originality/value
In augmenting green marketing literature, this study provides an insight into how SMEs can leverage on the distinct dimensions of green marketing to influence green purchase behaviour and profitability in an emerging market context.
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Abstract
This paper presents a study to determine the extent to which delamination at the die to encapsulant interface affects the package moisture content, and electrical failures when subjected to unbiased temperature‐humidity testing. Moisture absorption experiments showed that the presence of delamination did not significantly after the measurable moisture absorption characteristics of packages. Reliability testing indicated that although delamination is generally thought of as a reliability risk, it may not be a sufficient condition to promote damage in packages under dormant storage conditions. Experimental results showed no parametric or functional failures (or visible degradation) in packages with 100% die surface delamination after 1000 hours of unbiased testing at 140°C/85%RH.
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Guo‐Quan Lu, Xingsheng Liu, Sihua Wen, Jesus Noel Calata and John G. Bai
In this paper, some strategies taken to improve the reliability of solder joints on power devices in single device and multi‐chip packages are presented. A strategy for improving…
Abstract
In this paper, some strategies taken to improve the reliability of solder joints on power devices in single device and multi‐chip packages are presented. A strategy for improving solder joint reliability by adjusting solder joint geometry, underfilling and utilization of flexible substrates is discussed with emphasis on triple‐stacked solder joints that resemble the shape of an hourglass. The hourglass shape relocates the highest inelastic strain away from the weaker interface with the chip to the bulk region of the joint, while the underfill provides a load transfer from the joints. Thermal cycling data show significant improvements in reliability when these techniques are used. The design, testing and finite‐element analyses of an interconnection structure, termed the Dimple‐Array Interconnect, for improving the solder joint reliability is also presented.
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Post‐industrial predictions of a rapid growth in new technologyhomeworking have gained widespread currency to become part of theconventional wisdom. However the evidence…
Abstract
Post‐industrial predictions of a rapid growth in new technology homeworking have gained widespread currency to become part of the conventional wisdom. However the evidence, including primary research material, suggests that the claims for new technology homeworking, both regarding its extent and its alleged benefits, have been considerably overestimated. In particular, new technology homeworking by itself does not appear to open up opportunities for women to improve their position in the labour market; the demographic changes predicted for the 1990s may provide a better bet. Nevertheless, there is a danger in assuming that all firms apply the same strategy when employing homeworkers; at least three different variations can be identified and this has important implications for personnel managers. The overestimation of new technology homeworking stands in stark contrast to traditional homeworking where the extent has been considerably underestimated. This marginalisation of traditional homeworking stems in large part from the distortion caused by the conceptual split between private and public realms. The failure to find evidence to support the growth of new technology homeworking leads to a consideration of how the arguments may better be considered as rhetoric designed to advance a certain set of ideas – in particular that set associated with “privatisation” as a political ideology.