Search results

1 – 10 of 61
Per page
102050
Citations:
Loading...
Access Restricted. View access options
Article
Publication date: 1 April 1995

M. Nasta and H.C. Peebles

A good solder flux must simultaneously perform a number of important functions. It must promote thermal transfer to the area of the solder joint, enhance wetting of the solder on…

179

Abstract

A good solder flux must simultaneously perform a number of important functions. It must promote thermal transfer to the area of the solder joint, enhance wetting of the solder on the base metal, and prevent oxidation of the metal surfaces at soldering temperatures. However, its primary task is to remove the tarnish layer from the metal joint that is about to be soldered. Despite the fact that the process of soldering electronic devices is a part of a multi‐billion dollar industry, the actual chemical reactions that occur during this cleaning process are not well documented. In the case of organic acid or water‐soluble fluxes, the flux reactions can be modelled by considering the interactions at the metal/metal oxide/electrolyte solution interface. Although such modelling systems have not frequently been applied to the behaviour of solder and fluxes, they are common for a number of other closely related chemical systems which are of practical interest, e.g., passivation layers on metals, electrochemical cells and metal oxide semiconductors. There are two types of reactions that can occur at the oxide/solution interface: acid‐base reactions and oxidation‐reduction reactions. The factors which affect the reaction rates and mechanisms are such variables as the structure of the metal oxide, temperature, pH, concentration of the electrolyte, and the chemical nature of the solute and solvent. By combining information about flux behaviour with available models of surface reactions, it should be possible to develop the theory of the flux reactions and to gain a better understanding of the factors which control the process.

Details

Circuit World, vol. 21 no. 4
Type: Research Article
ISSN: 0305-6120

Access Restricted. View access options
Article
Publication date: 1 January 1990

M.A. Nasta, G.R. Hill and D. Campbell

The filterable particles found in electronic solder fluxes vary considerably in both concentration and chemistry. Four fluxes from three manufacturers were examined, including…

36

Abstract

The filterable particles found in electronic solder fluxes vary considerably in both concentration and chemistry. Four fluxes from three manufacturers were examined, including both rosin fluxes and mildly activated resin fluxes. Individual particles were examined by optical light microscopy (OLM) and scanning electron microscopy/energy dispersive X‐ray spectroscopy (SEM/EDX). Finally, an automated SEM/EDX system was used to collect and summarise information about the size and chemistry of a hundred or more particles from each flux. The number of particles per microgram of flux was found to vary by two orders of magnitude (0.004 to 0.4 per μg). The particle diameters ranged from 0.2–20 μm with averages of 1–3 μm. A large fraction of the particles (33–75% by number) were organic substances not soluble in the flux. The bulk of the inorganic particles were composed of sulphates, silicates and metal oxides. Thus, some solder fluxes may be introducing several contaminant particles into each solder contact. These contaminants may affect the quality of the solder joint depending on particle size and composition.

Details

Soldering & Surface Mount Technology, vol. 2 no. 1
Type: Research Article
ISSN: 0954-0911

Access Restricted. View access options
Article
Publication date: 5 June 2017

Kamila Piotrowska, Morten Stendahl Jellesen and Rajan Ambat

The aim of this work is to investigate the decomposition behaviour of the activator species commonly used in the wave solder no-clean flux systems and to estimate the residue…

406

Abstract

Purpose

The aim of this work is to investigate the decomposition behaviour of the activator species commonly used in the wave solder no-clean flux systems and to estimate the residue amount left after subjecting the samples to simulated wave soldering conditions.

Design/methodology/approach

Changes in the chemical structure of the activators were studied using Fourier transform infrared spectroscopy technique and were correlated to the exposure temperatures within the range of wave soldering process. The amount of residue left on the surface was estimated using standardized acid-base titration method as a function of temperature, time of exposure and the substrate material used.

Findings

The study shows that there is a possibility of anhydride-like species formation during the thermal treatment of fluxes containing weak organic acids (WOAs) as activators (succinic and DL-malic). The decomposition patterns of solder flux activators depend on their chemical nature, time of heat exposure and substrate materials. Evaporation of the residue from the surface of different materials (laminate with solder mask, copper surface or glass surface) was found to be more pronounced for succinic-based solutions at highest test temperatures than for adipic acid. Less left residue was found on the laminate surface with solder mask (∼5-20 per cent of initial amount at 350°C) and poorest acid evaporation was noted for glass substrates (∼15-90 per cent).

Practical implications

The findings are attributed to the chemistry of WOAs typically used as solder flux activators. The results show the importance WOA type in relation to its melting/boiling points and the impact on the residual amount of contamination left after soldering process.

Originality/value

The results show that the evaporation of the flux residues takes place only at significantly high temperatures and longer exposure times are needed compared to the temperature range used for the wave soldering process. The extended time of thermal treatment and careful choice of fluxing technology would ensure obtaining more climatically reliable product.

Details

Soldering & Surface Mount Technology, vol. 29 no. 3
Type: Research Article
ISSN: 0954-0911

Keywords

Access Restricted. View access options
Article
Publication date: 1 April 1995

J.E. Sohn and U. Ray

Weak organic acids (WOAs) are commonly used as activators in no‐clean fluxes. Surface insulation resistance (SIR) was determined as a function of WOA type and residue level…

116

Abstract

Weak organic acids (WOAs) are commonly used as activators in no‐clean fluxes. Surface insulation resistance (SIR) was determined as a function of WOA type and residue level through three temperature/humidity test environments. Acidic residue levels were determined after wave solder processing, and after exposure to each of the three test environments. With each of the WOAs studied, the greater the residue level, the lower the SIR. Chemical structure and physical property differences of the WOAs are discussed in the context of differences in SIR observed. WOA volatilisation is found to occur with all four WOAs when exposed to the highest test temperature (85°C). This work shows that testing WOA‐containing solder fluxes at 85°C may not be useful or appropriate.

Details

Circuit World, vol. 21 no. 4
Type: Research Article
ISSN: 0305-6120

Access Restricted. View access options
Article
Publication date: 2 September 2019

Kamila Piotrowska, Feng Li and Rajan Ambat

The purpose of this paper is to investigate the decomposition behavior of binary mixtures of organic activators commonly used in the no-clean wave flux systems upon their exposure…

161

Abstract

Purpose

The purpose of this paper is to investigate the decomposition behavior of binary mixtures of organic activators commonly used in the no-clean wave flux systems upon their exposure to thermal treatments simulating wave soldering temperatures. The binary blends of activators were studied at varying ratios between the components.

Design/methodology/approach

Differential scanning calorimetry and thermogravimetric analysis were used to study the characteristics of weak organic acid (WOA) mixtures degradation as a function of temperature. The amount of residue left on the surface after the heat treatments was estimated by gravimetric measurements as a function of binary mixture type, temperature and exposure time. Ion chromatography analysis was used for understanding the relative difference between decomposition of activators in binary blends. The aggressivity of the left residue was assessed using the acidity indication gel test, and effect on reliability was investigated by DC leakage current measurement performed under varying humidity and potential bias conditions.

Findings

The results show that the typical range of temperatures experienced by electronics during the wave soldering process is not sufficient for the removal of significant activator amounts. If the residues contain binary mixture of WOAs, the final ratio between the components, the residue level and the corrosive effects depend on the relative decomposition behavior of individual components. Among the WOA investigated under the conventional wave soldering temperature, the evaporation and removal of succinic acid is more dominant compared to adipic and glutaric acids.

Practical implications

The findings are attributed to the chemistry of WOAs typically used as flux activators for wave soldering purposes. The results show the importance of controlling the WOA content and ratio between activating components in a flux formulation in relation to its tendencies for evaporation during soldering and the impact of its residues on electronics reliability.

Originality/value

The results show that the significant levels of flux residues can only be removed at significantly higher temperatures and longer exposure times compared to the conventional temperature range used for the wave soldering process. The potential corrosion issues related to insufficient flux residues removal will be determined by the residue amount, its composition and ratio between organic components. The proper time of thermal treatment and careful choice of fluxing formulation could ensure more climatically reliable product.

Details

Soldering & Surface Mount Technology, vol. 32 no. 2
Type: Research Article
ISSN: 0954-0911

Keywords

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

Alyson DeSalvo, Sandi Binda Rest, Tammy Knight, Mary Nettleman and Steve Freer

Patients visit emergency rooms for urgent and non‐urgent care. Because emergency room visits are more costly than visits to primary care clinics and are less likely to involve…

667

Abstract

Patients visit emergency rooms for urgent and non‐urgent care. Because emergency room visits are more costly than visits to primary care clinics and are less likely to involve preventive care, third party payers and institutions have always tried to shift patients away from the emergency room and towards primary care clinics where appropriate. Hypothesizes that an intervention based in an adult primary care clinic might enable this, especially if it involved patients who used both the clinic and the emergency room. Surveys patients to determine why they used the emergency room and to identify barriers to using the primary care clinic instead. Based on the survey results, an intervention was developed to facilitate use of the primary care clinic. Discusses the methodology used in the survey and analyses results. Concludes that it is difficult to change patient behaviour to fit the demands of the health care system. Possibly, it would be better to change the system to fit the behaviour patterns of the patients.

Details

British Journal of Clinical Governance, vol. 5 no. 1
Type: Research Article
ISSN: 1466-4100

Keywords

Available. Open Access. Open Access
Article
Publication date: 13 February 2024

Luigi Nasta, Barbara Sveva Magnanelli and Mirella Ciaburri

Based on stakeholder, agency and institutional theory, this study aims to examine the role of institutional ownership in the relationship between environmental, social and…

4469

Abstract

Purpose

Based on stakeholder, agency and institutional theory, this study aims to examine the role of institutional ownership in the relationship between environmental, social and governance practices and CEO compensation.

Design/methodology/approach

Utilizing a fixed-effect panel regression analysis, this research utilized a panel data approach, analyzing data spanning from 2014 to 2021, focusing on US companies listed on the S&P500 stock market index. The dataset encompassed 219 companies, leading to a total of 1,533 observations.

Findings

The analysis identified that environmental scores significantly impact CEO equity-linked compensation, unlike social and governance scores. Additionally, it was found that institutional ownership acts as a moderating factor in the relationship between the environmental score and CEO equity-linked compensation, as well as the association between the social score and CEO equity-linked compensation. Interestingly, the direction of these moderating effects varied between the two relationships, suggesting a nuanced role of institutional ownership.

Originality/value

This research makes a unique contribution to the field of corporate governance by exploring the relatively understudied area of institutional ownership's influence on the ESG practices–CEO compensation nexus.

Access Restricted. View access options
Article
Publication date: 18 January 2008

Portia Bowen‐Chang and Marsha Winter

This paper intends to provide an annotated bibliographic guide for scholars and researchers studying the critical works of Samuel Selvon, one of the founding fathers of the…

1264

Abstract

Purpose

This paper intends to provide an annotated bibliographic guide for scholars and researchers studying the critical works of Samuel Selvon, one of the founding fathers of the Anglo‐Caribbean literary movement.

Design/methodology/approach

The authors identify and evaluate items from print bibliographies, online and card catalogues, electronic databases and the world wide web.

Findings

Numerous scholars have critically assessed the novels of Selvon and this is evident in the existence of published and unpublished works in English and other foreign languages.

Originality/value

The forte of the bibliography lies in the annotative aspect and the inclusion of unpublished works and non‐English speaking documents.

Details

Collection Building, vol. 27 no. 1
Type: Research Article
ISSN: 0160-4953

Keywords

Access Restricted. View access options
Book part
Publication date: 4 June 2024

Andy Goldhawk

This chapter discusses the findings of doctoral research into further education lecturers' and middle managers' perceptions of how Continuing Professional Development (CPD) in the…

Abstract

This chapter discusses the findings of doctoral research into further education lecturers' and middle managers' perceptions of how Continuing Professional Development (CPD) in the sector is planned and implemented. Thematic analysis revealed that mandatory CPD is perceived to: involve conflicting purposes between those planning it and its recipients (deriving from divergent understandings of professionalism and the role of CPD among stakeholders); and be characterised as mostly generic, didactic, and ineffective, leading lecturers to compensate by engaging in additional, separate forms of CPD. This chapter demonstrates the value of practice-based doctoral study in enabling the voices of educators to be positioned at the centre of an exploration of their own professional learning.

Details

Critical Perspectives on Educational Policies and Professional Identities
Type: Book
ISBN: 978-1-83753-332-9

Keywords

Available. Open Access. Open Access
Article
Publication date: 5 December 2022

Johanna Innerhofer, Luigi Nasta and Anita Zehrer

Although the role of human capital in the hospitality sector is critical, the industry faces challenges in attracting workers with a poor industry image frequently mentioned…

7644

Abstract

Purpose

Although the role of human capital in the hospitality sector is critical, the industry faces challenges in attracting workers with a poor industry image frequently mentioned regarding labor shortages. This research paper attempts to investigate the factors influencing labor shortages by presenting the perspectives of employees and employers.

Design/methodology/approach

Precisely 232 rural hospitality industry employees (n = 128) and employers (n = 104) in Northern Italy were surveyed using a written close-ended online survey and a quantitative research design as part of a convenience sampling approach. For hypotheses testing, Spearman's rho was used.

Findings

A relationship between the shortage of professional workers and a variety of factors was found, including professional, digital, social and green skills, industry-intrinsic characteristics and symbolic image attributes of the industry. The findings show that some factors are more important for employees, while others are more significant for employers.

Practical implications

This study demonstrates several practical implications for the hospitality sector by addressing the under-researched stakeholder group of existing hospitality employees, e.g. improving working conditions, reduction of manual operations through digital technologies, realistic career planning, employer branding, identification of skill deficiencies and provision of specialized trainings.

Originality/value

Most research on labor shortages in the hospitality industry has focused on the perspective of either employees or employers. This study compares both perspectives, including the industry image, to gain a realistic picture of the relevant factors for a rural tourism destination in Northern Italy.

Details

Journal of Hospitality and Tourism Insights, vol. 7 no. 1
Type: Research Article
ISSN: 2514-9792

Keywords

1 – 10 of 61
Per page
102050