For reflow soldering in today's changing component and soldering technology, requirements with respect to profiling seem to be difficult to determine and even harder to meet…
Abstract
For reflow soldering in today's changing component and soldering technology, requirements with respect to profiling seem to be difficult to determine and even harder to meet. State‐of‐the‐art reflow trackers can be of help here, but, without some knowledge of the fundamentals in profiling, it will be easy to misunderstand measurements. The use of nitrogen as a protective gas for reflow soldering can be advantageous for fine pitch technology, bare copper boards and low residue solder pastes. However, because reflow solder defects are related to more than just the use of nitrogen, one may find different benefits for the use of nitrogen, depending on how the investigations are carried out. Wetting under nitrogen is certainly better and more reproducible, while the near absence of oxygen is beneficial to oxidation‐related problems. For high numbers of solder joints per board, it is not easy to achieve an acceptable first pass yield. Only with low, controlled defect levels found within a robust reproducible process is it possible to achieve this. Using forced convection together with nitrogen for reflow soldering is becoming the preferred method.
Reflow soldering in a controlled O2 atmosphere will lead to practical benefits in the wettingbehaviour of solder pastes. The required O2 level and its control depend on the…
Abstract
Reflow soldering in a controlled O2 atmosphere will lead to practical benefits in the wetting behaviour of solder pastes. The required O2 level and its control depend on the solder paste used and the solderability of the materials to be joined. For a typical application with either fine‐pitch technology, multiple soldering or low residue solder paste, a lack of O2 control can cause soldering problems. Fine‐pitch solder pastes today still do not show an optimum slump behaviour, which is absolutely necessary to avoid bridging between IC leads and to reduce the formation of solder balls during reflow. Using a low O2 atmosphere to reduce these defects can make a difference, but an improved slump behaviour through predrying of the applied solder paste at 50°C or in a low pressure environment will be more effective. Spread of solder is in general better at lower O2 levels, but substantial improvements are only achieved if low residue pastes with low activation levels are reflowed. Even when the low residue paste is compatible with reflow in air, there is still a significant difference found between 20 and 200 ppm O2. Reflow systems which show variations up to 500 ppm in the preheat zones during loading, while maintaining 50ppm in the peak zone, will show non‐wetting or dewetting when a 100 ppm O2 solder paste is used. The visual cleanliness of solder joints is significantly improved at lower O2 levels because the flux residue will be distributed differently over the solder joints. Bridging is initially determined by the slump behaviour of the paste and the alignment of the paste pattern to the pads and the leads, but when the paste of adjacent pads slumps together before reflow, the tendency for the solder to pull back is influenced by the oxygen level. Wetting and spread of the solder on the lands are then an essential factor. All the proven benefits of a low O2 level are not worth the money spent on nitrogen if the consumption necessary to obtain the properly controlled O2 level is very high. When solderability or the solder defect level not an issue the benefits may not represent a value higher than the cost of the nitrogen consumed.
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Orbotech SA, Brussels, has announced the appointment of Kevin Smith as Sales Executive for its UK office. Mr Smith joints Orbotech with several years' experience in the…
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Orbotech SA, Brussels, has announced the appointment of Kevin Smith as Sales Executive for its UK office. Mr Smith joints Orbotech with several years' experience in the disciplines of CAD systems and networks and photoplotting. He will be based in the company's Rochdale office and will work with Rob Sawyer, UK Regional Manager, in selling Orbotech's AOI, CAM and Plotter products throughout the United Kingdom.
Martin Götz and Ernest H. O’Boyle
The overall goal of science is to build a valid and reliable body of knowledge about the functioning of the world and how applying that knowledge can change it. As personnel and…
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The overall goal of science is to build a valid and reliable body of knowledge about the functioning of the world and how applying that knowledge can change it. As personnel and human resources management researchers, we aim to contribute to the respective bodies of knowledge to provide both employers and employees with a workable foundation to help with those problems they are confronted with. However, what research on research has consistently demonstrated is that the scientific endeavor possesses existential issues including a substantial lack of (a) solid theory, (b) replicability, (c) reproducibility, (d) proper and generalizable samples, (e) sufficient quality control (i.e., peer review), (f) robust and trustworthy statistical results, (g) availability of research, and (h) sufficient practical implications. In this chapter, we first sing a song of sorrow regarding the current state of the social sciences in general and personnel and human resources management specifically. Then, we investigate potential grievances that might have led to it (i.e., questionable research practices, misplaced incentives), only to end with a verse of hope by outlining an avenue for betterment (i.e., open science and policy changes at multiple levels).
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Noel Scott, Brent Moyle, Ana Cláudia Campos, Liubov Skavronskaya and Biqiang Liu
Johnrev Guilaran and Hong An Nguyen
Disaster responders play a crucial role in providing aid to individuals and communities following catastrophic events. Being tasked to protect and preserve life and property…
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Disaster responders play a crucial role in providing aid to individuals and communities following catastrophic events. Being tasked to protect and preserve life and property, these groups of professionals are constantly exposed to various hazards, which puts them at risk of negative mental health consequences. This chapter describes and discusses these mental health effects and interventions for disaster responders in Southeast Asia. The chapter defines who the disaster responders are in Southeast Asian countries. Drawing from the literature, this chapter enumerates the various positive and negative psychological consequences of disaster response, and the risk and protective factors associated with disaster response work. This chapter also describes the different interventions, such as psychological first aid and psychotherapy, following the Inter-agency Standing Committee (IASC) (2007) guidelines on conducting mental health and psychosocial support services (MHPSS), and focusing on the Southeast Asian context. This chapter ends with a discussion of the different challenges of providing MHPSS in Southeast Asia and with some recommendations on how to improve the delivery of these services and the mental health of disaster responders in general.
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Smart card-based E-payment systems are receiving increasing attention as the number of implementations is witnessed on the rise globally. Understanding of user adoption behavior…
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Smart card-based E-payment systems are receiving increasing attention as the number of implementations is witnessed on the rise globally. Understanding of user adoption behavior of E-payment systems that employ smart card technology becomes a research area that is of particular value and interest to both IS researchers and professionals. However, research interest focuses mostly on why a smart card-based E-payment system results in a failure or how the system could have grown into a success. This signals the fact that researchers have not had much opportunity to critically review a smart card-based E-payment system that has gained wide support and overcome the hurdle of critical mass adoption. The Octopus in Hong Kong has provided a rare opportunity for investigating smart card-based E-payment system because of its unprecedented success. This research seeks to thoroughly analyze the Octopus from technology adoption behavior perspectives.
Cultural impacts on adoption behavior are one of the key areas that this research posits to investigate. Since the present research is conducted in Hong Kong where a majority of population is Chinese ethnicity and yet is westernized in a number of aspects, assuming that users in Hong Kong are characterized by eastern or western culture is less useful. Explicit cultural characteristics at individual level are tapped into here instead of applying generalization of cultural beliefs to users to more accurately reflect cultural bias. In this vein, the technology acceptance model (TAM) is adapted, extended, and tested for its applicability cross-culturally in Hong Kong on the Octopus. Four cultural dimensions developed by Hofstede are included in this study, namely uncertainty avoidance, masculinity, individualism, and Confucian Dynamism (long-term orientation), to explore their influence on usage behavior through the mediation of perceived usefulness.
TAM is also integrated with the innovation diffusion theory (IDT) to borrow two constructs in relation to innovative characteristics, namely relative advantage and compatibility, in order to enhance the explanatory power of the proposed research model. Besides, the normative accountability of the research model is strengthened by embracing two social influences, namely subjective norm and image. As the last antecedent to perceived usefulness, prior experience serves to bring in the time variation factor to allow level of prior experience to exert both direct and moderating effects on perceived usefulness.
The resulting research model is analyzed by partial least squares (PLS)-based Structural Equation Modeling (SEM) approach. The research findings reveal that all cultural dimensions demonstrate direct effect on perceived usefulness though the influence of uncertainty avoidance is found marginally significant. Other constructs on innovative characteristics and social influences are validated to be significant as hypothesized. Prior experience does indeed significantly moderate the two influences that perceived usefulness receives from relative advantage and compatibility, respectively. The research model has demonstrated convincing explanatory power and so may be employed for further studies in other contexts. In particular, cultural effects play a key role in contributing to the uniqueness of the model, enabling it to be an effective tool to help critically understand increasingly internationalized IS system development and implementation efforts. This research also suggests several practical implications in view of the findings that could better inform managerial decisions for designing, implementing, or promoting smart card-based E-payment system.