Search results

1 – 10 of 81
Per page
102050
Citations:
Loading...
Access Restricted. View access options
Article
Publication date: 13 February 2007

Tong Fang, Sony Mathew, Michael Osterman and Michael Pecht

This paper aims to present a methodology for estimating the risk of component level electrical bridging failures from unattached conductive (tin) whiskers.

385

Abstract

Purpose

This paper aims to present a methodology for estimating the risk of component level electrical bridging failures from unattached conductive (tin) whiskers.

Design/methodology/approach

Based on experimental data an algorithm was developed and assessed by further experiments. The risk estimate is based on whisker parameters, generated from experiments over a period of time. A bridging failure risk is defined as the probability of a conductive whisker landing between two isolated electrical conductors. A probabilistic estimate for electrical bridging failure risk is achieved by randomly sampling distributions of conductive whisker length, deposition angle, and density for a defined electrical structure. A fine pitch quad flat package attached to a printed wiring board is used as test vehicle to verify the risk estimate.

Findings

The estimated risk is found to be higher than planned in the experimental test. The lower experimentally determined risk was found to be the result of high contact resistance between the conductive whisker and the electrical conductors that form the unintended circuit. Contact resistance between the whisker and electrical conductors was found to mitigate the whisker shorting risk.

Originality/value

This is the first attempt to quantify the risk failure due to unattached conductive whiskers in electronic products. A methodology for estimating electrical bridging risk due to unattached conductive whiskers is provided. Contact resistance of conductive whiskers is found to be a critical issue that may be mitigate failure risks.

Details

Circuit World, vol. 33 no. 1
Type: Research Article
ISSN: 0305-6120

Keywords

Access Restricted. View access options
Article
Publication date: 9 February 2010

Mohammed A. Alam, Michael H. Azarian, Michael Osterman and Michael Pecht

The purpose of this paper is to present an analytical approach to find the reduction in the required number of surface mount capacitors by the use of embedded capacitors in…

328

Abstract

Purpose

The purpose of this paper is to present an analytical approach to find the reduction in the required number of surface mount capacitors by the use of embedded capacitors in decoupling applications.

Design/methodology/approach

The analytical model used to perform decoupling is cavity model from theory of microstrip antenna and N‐port impedance matrix. The methodology involves addition of decoupling capacitors between the power and the ground plane such that the impedance between ports on the power‐ground plane becomes lower than the target impedance at that frequency. A case study is presented in which a 0.3 m×0.3 m power‐ground plane is decoupled by using various combinations of surface mount capacitors and embedded capacitors in the frequency range of 0.001‐1 GHz and at a target impedance of 0.1, 0.01, and 0.001 Ω. The total number of surface mount capacitors are compared in each case.

Findings

Use of embedded planar capacitors with a thin dielectric (about 8 mm) dampened board resonances at high frequency, as compared to a thick dielectric. Embedded capacitors are found to reduce the number of surface mount capacitors when the target impedance is low and the operating frequency is high.

Research limitations/implications

The methodology discusses in this paper is applicable to a simplified power‐ground plane (which has no cut‐outs and is rectangular in shape) as compared to actual digital circuits.

Originality/value

This methodology can be used as a quick preliminary tool to evaluate the decrease in the number of surface mount capacitors (by the use of embedded capacitors) as compared to complex and time consuming electromagnetic solvers.

Details

Circuit World, vol. 36 no. 1
Type: Research Article
ISSN: 0305-6120

Keywords

Access Restricted. View access options
Article
Publication date: 6 February 2009

Sony Mathew, Michael Osterman, Michael Pecht and Frank Dunlevey

The purpose of this paper is to present the results from work on a project aimed at evaluating six different copper alloy substrates coated with pure tin for tin whisker growth…

549

Abstract

Purpose

The purpose of this paper is to present the results from work on a project aimed at evaluating six different copper alloy substrates coated with pure tin for tin whisker growth. The influence of intermetallic growth between the copper alloy substrate and the tin‐plating on the growth of tin whiskers has been investigated.

Design/methodology/approach

The experiment consisted of six substrates of different alloys of copper, plated with bright tin including copper beryllium, cartridge brass, phosphor bronze, Cu‐Ni‐Si “7025” and Cu‐Ni‐Sn “spinodal”. The samples were mechanically stressed and then subjected to temperature humidity storage conditions for 1,000 h. These samples were then evaluated for tin whisker growth and intermetallic layer thickness.

Findings

Of the six samples five showed tin whisker growth. For these samples the intermetallic layer thickness has little effect on tin whisker growth. Sample with Cu‐Ni‐Sn “spinodal” alloy substrate showed very low whisker density and comparatively lower maximum whisker length than the other tested substrate material.

Research limitations/implications

More samples per condition should be evaluated to bolster the conclusions. For the sample without tin whisker growth, holes on the surface of the plating were observed. The holes in the plating provide an opportunity for stress relaxation after the plating process. Since stress in the plating layer is low, tin whiskers are not formed on the sample surface.

Originality/value

The paper details the tin whisker growth on six tin plated copper substrate samples. The intermetallic layer thickness for each copper alloy substrate is calculated. The relationship between the intermetallic layer thickness and tin whisker growth for the six substrates are discussed.

Details

Circuit World, vol. 35 no. 1
Type: Research Article
ISSN: 0305-6120

Keywords

Access Restricted. View access options
Article
Publication date: 23 August 2011

Bhanu Sood, Michael Osterman and Michael Pecht

This paper aims to present the results of physical analysis that was conducted on Toyota's electronic engine control system including accelerator pedal position sensors (APPSs)…

843

Abstract

Purpose

This paper aims to present the results of physical analysis that was conducted on Toyota's electronic engine control system including accelerator pedal position sensors (APPSs). The paper overviews the analyses and focuses on the discovery of tin whiskers found in the accelerator pedal assembly, which are an electrical failure concern.

Design/methodology/approach

Analytical techniques such as X‐ray fluorescence spectroscopy, scanning electron microscopy and energy dispersive spectroscopy are utilized to present a construction analysis of the APPS.

Findings

The use of a tin finish in the APPS is a cause for concern. Tin finishes are known to produce metal whiskers that are conductive and capable of creating unintended current leakage paths. In the analysis, a significant number of tin whiskers were found.

Research limitations/implications

The methodology discussed in this paper can be implemented to inspect for tin whiskers in the APPSs.

Originality/value

The paper begins a construction analysis of different parts of the Toyota engine control module and APPSs and then moves on to highlight electronics design issues that can comprise the engine control system and cause unintended consequences.

Access Restricted. View access options
Article
Publication date: 17 April 2007

Michael Osterman and Michael Pecht

The aim is to present temperature fatigue model constants for lead‐free tin‐silver‐copper solder derived from test data and demonstrate the validity of the model using published…

722

Abstract

Purpose

The aim is to present temperature fatigue model constants for lead‐free tin‐silver‐copper solder derived from test data and demonstrate the validity of the model using published experimental results.

Design/methodology/approach

Temperature cycle fatigue life data were collected from a controlled set of tests using ceramic leadless chip carriers. Using a regression algorithm, temperature cycle fatigue model constants were derived from fatigue life data. The model was then applied to a variety of package formats including ball grid arrays, quad flatpack and thin small outline packages to determine the validity of the model and constants.

Findings

The temperature cycle fatigue life experimental data were found to be in good agreement with the model with the derived model constants for various package types. Using this model, engineers can determine acceleration factors between test and field temperature cycle conditions.

Research limitations/implications

The technology has been used to ensure inner layer designs with nominal dimensions after the lamination stage. Further, development work should be undertaken to collate measured data from other parts of the PCB manufacturing process and model the material movement around all registration critical processes.

Originality/value

The paper details a temperature cycle fatigue life model and constants that allow engineers to predict field life expectancy and determine the acceleration factor between temperature cycle testing and field use conditions.

Details

Soldering & Surface Mount Technology, vol. 19 no. 2
Type: Research Article
ISSN: 0954-0911

Keywords

Access Restricted. View access options
Book part
Publication date: 16 July 2014

Derrick R. Brooms

This chapter reports on findings from a study that explored the experiences of African American young men who graduated from Du Bois Academy, an all-boys public charter secondary…

Abstract

This chapter reports on findings from a study that explored the experiences of African American young men who graduated from Du Bois Academy, an all-boys public charter secondary school in the Midwestern region of the United States. The chapter considers issues of African American male persistence and achievement and how they are impacted by school culture. Specifically, the author discusses how school culture can help shape these students’ educational experiences and aspirations. Using student narratives as the guide, a description of how Du Bois Academy successfully engaged these African American male students is provided. The students articulated three critical components of school culture that positively shaped their high achievement and engagement: (a) sense of self, (b) promotion of excellence, and (c) community building. The student narratives provided a frame for promoting positive school culture that enhances the educational experiences and academic aspirations of African American male students.

Details

African American Male Students in PreK-12 Schools: Informing Research, Policy, and Practice
Type: Book
ISBN: 978-1-78350-783-2

Access Restricted. View access options
Article
Publication date: 1 September 2006

Tong Fang, Michael Osterman, Sony Mathew and Michael Pecht

To present a methodology, including the algorithms, to quantify the risk of failure from tin whiskers and to present a dynamic risk trend based on the distribution of each of the…

788

Abstract

Purpose

To present a methodology, including the algorithms, to quantify the risk of failure from tin whiskers and to present a dynamic risk trend based on the distribution of each of the whisker growth parameters, generated from experiments over a period of time. This paper also aims to demonstrate the practical application of the methodology developed.

Design/methodology/approach

This paper has been written to provide a methodology to assess tin whisker risk due to fixed whiskers in electronic products. The risk assessment process has been detailed in the paper. To demonstrate the usefulness of the methodology, a tin whisker risk assessment was conducted for a printed circuit board (PCB) in operation.

Findings

Based on the experimental tin whisker growth data it is observed that growth rates of mean length and average density decrease with time. Based on the risk assessment, it was estimated that for the common matte tin over copper finish, the failure risk for the circuit card assembly was 4 per cent over 20 years. It was recommended that, for this product, components with bright tin lead finish should not be used. It was also found that the effectiveness of the conformal coating on this PCB is limited by the relative risk of the components on the board.

Originality/value

The paper provides a new methodology to assess fixed tin whisker risk in electronic products. The methodology provides a dynamic risk trend with time because the algorithm incorporates distributional data of whisker growth and the distributional data as a function of time. This type of assessment was lacking in the previous studies.

Details

Circuit World, vol. 32 no. 3
Type: Research Article
ISSN: 0305-6120

Keywords

Available. Content available
Article
Publication date: 10 May 2013

Martin Goosey

116

Abstract

Details

Circuit World, vol. 39 no. 2
Type: Research Article
ISSN: 0305-6120

Access Restricted. View access options
Book part
Publication date: 17 August 2016

Ruthanne Huising

Organizations that adopt new practices employ managers to make decisions about how to materialize these practices. I examine how these managers move between the meanings and…

Abstract

Organizations that adopt new practices employ managers to make decisions about how to materialize these practices. I examine how these managers move between the meanings and resources found in extra-local and local realms. I find that managers’ practices shift over time from adapting BPR practices to inhabiting BPR as an idea. Managers’ approaches are shaped by each organization’s history of efforts to introduce extra-local ideas. Rather than adapting BPR practices, managers draw on change tools, techniques, and methods that have worked in the organization and integrate BPR work into ongoing interactions, activities, and language in the local context.

Details

The Structuring of Work in Organizations
Type: Book
ISBN: 978-1-78635-436-5

Keywords

Access Restricted. View access options
Book part
Publication date: 22 September 2022

Robert N. Eberhart, Stephen Barley and Andrew Nelson

We explore the acceptance of new contingent work relationships in the United States to reveal an emergent entrepreneurial ideology. Our argument is that these new work…

Abstract

We explore the acceptance of new contingent work relationships in the United States to reveal an emergent entrepreneurial ideology. Our argument is that these new work relationships represent a new social order not situated in the conglomerates and labor unions of the past, but on a confluence of neo-liberalism and individual action situated in the discourse of entrepreneurialism, employability, and free agency. This new employment relationship, which arose during the economic and social disruptions in the 1970s, defines who belongs inside an organization (and can take part in its benefits) and who must properly remain outside to fend for themselves. More generally, the fusing of entrepreneurship with neo-liberalism has altered not only how we work and where we work but also what we believe is appropriate work and what rewards should accompany it.

Details

Entrepreneurialism and Society: New Theoretical Perspectives
Type: Book
ISBN: 978-1-80382-658-5

Keywords

1 – 10 of 81
Per page
102050