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A new corrosion test for assessing flux residues is applied to marginally cleaned water soluble fluxed test boards and low solids/no clean fluxed test boards. This test…
A new corrosion test for assessing flux residues is applied to marginally cleaned water soluble fluxed test boards and low solids/no clean fluxed test boards. This test method developed by Bono has been modified to accelerate the corrosion process. The corrosion mechanism observed in this study is conductive anodic filament (CAF), a corrosion mechanism proposed in 1979 by Lando et al. It is postulated that this degradation mechanism is due to the high bias voltage (190 V) coupled with the high humidity (85%) and high temperature (85°C) conditions used in this test. Important parameters in the test method are discussed and recommended refinements are given.
A binary choice model explaining the distribution of holidays abroad undertaken by UK residents is constructed and estimated. The foreign holiday demand function is…
A binary choice model explaining the distribution of holidays abroad undertaken by UK residents is constructed and estimated. The foreign holiday demand function is generated from a comparison of holiday costs and benefits, and stochastic behaviour is permitted. In addition, the effects of incomplete knowledge on holiday choice are incorporated in the model. It is shown that the empirical results support the theoretical framework and that the £50 foreign currency limit imposed by the British Government between 1966 and 1969 resulted in a shift in the distribution of foreign holidays.
Today's emphasis on alternative flux technology as an approach to eliminate the use of chlorofluorocarbons (CFCs) requires an understanding of the corrosion potential of…
Today's emphasis on alternative flux technology as an approach to eliminate the use of chlorofluorocarbons (CFCs) requires an understanding of the corrosion potential of the new fluxes. In 1989, Dr David Bono proposed that monitoring the effect of different soldering fluxes on the rate of corrosion of a copper wire printed on a circuit board would provide quantitative information on the corrosion potential of a flux. Further analysis of this testby Turbini et al. revealed that the degradation mechanism associated with Bono's test is the growth of conductive anodic filaments along the glass fibres of the epoxy‐glass boards. The original test method has been revised, and the test coupon redesigned with the goal of developing a standard, quantitative test method to characterise soldering fluxes. This paper will describe the equipment, test coupon and electrical circuitry associated with this proposed test method. Procedures chosen to reduce error sources associated with electrical noise will be reported and explained.
The corrosive power of solder pastes is studied by implementing a new method compatible with the common rules of use. The entire methodology is fully described. The…
The corrosive power of solder pastes is studied by implementing a new method compatible with the common rules of use. The entire methodology is fully described. The results show evidence of corrosion with some solder pastes that have been identified by microscopic and EDX analysis. The corrosion mechanism is ‘mouse bite’ and conductive anodic filaments. A ranking of the different solder pastes tested is given and pass criteria for this new method of evaluation are proposed.
For a number of years electronic manufacturers of printed circuit assemblies have used rosin‐based soldering fluxes. Post‐solder cleaning was accomplished with chlorinated…
For a number of years electronic manufacturers of printed circuit assemblies have used rosin‐based soldering fluxes. Post‐solder cleaning was accomplished with chlorinated or chlorofluorocarbon (CFC) solvents. With the elimination of these solvent options due to their destructive effect on the stratospheric ozone layer, manufacturers are considering alternative cleaners for rosin flux or new flux choices which can be cleaned with water or left uncleaned. Many of the flux formulations are relatively new and their long‐term effect on the performance of products manufactured with them is unknown. Although ionic contamination testers can alert one to the ionic levels remaining on an assembly, there is no direct relationship between the total ionic level and the corrosivity of the soldering flux. Surface insulation resistance testing is used in the industry, but the results are misunderstood by many. This is due to the fact that SIR data represent a complex dependency on a number of factors including (1) the test conditions (temperature, humidity, bias), (2) the area of interactions (often referred to as the number of squares), (3) the separation between lines on the interdigitated comb pattern, (4) the presence or absence of bias voltage during the test and (5) the nature of the substrate. All of these factors have been the driving force to develop a quantitative screening test for soldering flux residues. This test, originally reported by Dr David Bono, is being modified and developed at Georgia Tech to provide a quantitative evaluation of flux residue corrosivity. This work, in collaboration with the work being performed by the French UTE, will result in a new international standard. This paper reports the latest data on this important test development.
Under certain environmental conditions, printed wiring boards (PWBs) respond to applied voltages by developing sub‐surface deposits of copper salts extending from anode to…
Under certain environmental conditions, printed wiring boards (PWBs) respond to applied voltages by developing sub‐surface deposits of copper salts extending from anode to cathode along separated fibre/epoxy interfaces. These deposits are termed conductive anodic filaments (CAFs) and, in this work, the dimensions and growth patterns of a CAF have been determined by serial sectioning. The CAF growth pathway is characterised and the spatial distribution of the copper salts is quantified with scanning electron microscopy (SEM) using backscattered electrons. The chemical composition of the CAF is determined using energy dispersive X‐ray analysis (EDS). Prior research using high‐resolution non‐destructive X‐ray microtomography is correlated with the serial sectioning data. The failure phenomenon known as CAF may pose serious long‐term reliability concerns in electronics applications exposed to adverse and hostile environments.
This paper uses a probit model to analyse 100 observations in terms of three hypotheses about the formation of owners’ corporations in high‐density private housing estates…
This paper uses a probit model to analyse 100 observations in terms of three hypotheses about the formation of owners’ corporations in high‐density private housing estates in Hong Kong within the context of Mancur Olson’s group theory. The findings do not reject the theory, revealing that it is more likely for an older urban estate with fewer owners to form owners’ corporations. The discussion includes a brief introduction to Olson’s group theory and the development of the probit analysis. Some speculative thoughts about public participation in local level urban management and planning are offered in the conclusion.
Structural equation modelling (SEM) is a method that is very frequently applied by marketing and business researchers to assess empirically new theoretical proposals…
Structural equation modelling (SEM) is a method that is very frequently applied by marketing and business researchers to assess empirically new theoretical proposals articulated by means of complex models. It is, therefore, a logical thought that the quality of the new advances in marketing and business theory depends, in part, on how well SEM is applied. This study aims to conduct an extensive review and empirical analysis of a broad variety of classic and recent controversies and issues related with the use of SEM, in order to identify problematic questions and prescribe a compendium of solutions for its suitable application.
The main analyses were conducted on a sample of 191 SEM‐based papers and 472 applications, i.e. all the SEM‐based studies published in four leading marketing journals during the period 1995‐2007.
Despite the maturity of SEM, its application in marketing research still has notable room for improvement. This is a general conclusion based on numerous problems detected and discussed here.
The study provides plausible solutions to the problems identified, a useful guide that is easy to follow and to apply adequately to present SEM issues in marketing and business studies.
The sample of SEM‐based papers and applications is limited to four publication outlets. A wider set or/and other journals different to those analyzed here may be preferred.
This is a valuable and timely study of the application of SEM in marketing and business research, and is also useful as a guiding framework for good practice. Likewise, as the problems discussed here presumably occur in other areas of social science, this paper should be welcome beyond the borders of the business disciplines.
The purpose of this paper is to assess the reliability of a Portuguese version of the cooking skills scale (CSS) and to evaluate the association between cooking skills and…
The purpose of this paper is to assess the reliability of a Portuguese version of the cooking skills scale (CSS) and to evaluate the association between cooking skills and socio-demographic, psychological and other cooking-related variables.
The study was conducted as an online survey among 730 Portuguese university students. Translation and back-translation of the CSS were performed. Data were assessed in two stages (test and retest) and the psychometric properties of the CSS were analyzed. The effect of socio-demographic variables was assessed by binary logistic regression analysis. The odds ratios for upper tertile of the CSS score were calculated using the lower tertile as reference.
Cronbach’s α for the CSS was 0.90. In the analysis of test-retest reliability, Spearman’s rank correlation coefficient was 0.79 and Cohen’s κ (for tertiles) was 0.49. Cooking skills were higher in respondents cooking more often, feeling more confident, enjoying more and indicating the personal interest as the main motivation to learn how to cook. Cooking skills were significantly better in females, older students and those with more independent place of residence.
Very good psychometric properties of the Portuguese version of the CSS were found among university students, providing a proper and simple tool to measure cooking skills in future studies with similar populations. The interventions encouraging to acquire and improve cooking skills as part of promoting healthy eating should be targeted especially toward men and young adults.