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Article

Meng-Ran Liao, Tang Chen and Wei-Jian Lv

In this study, the authors performed a numerical investigation on the heating of a hot cathode with a conical tip by atmospheric arc, taking into account of the two…

Abstract

Purpose

In this study, the authors performed a numerical investigation on the heating of a hot cathode with a conical tip by atmospheric arc, taking into account of the two temperature sheath effect for the first time.

Design/methodology/approach

The Schottky effect at cathode surface is considered, which is based on the analytic solution of a one-dimensional sheath model. The unified model allows one to predict the cathode-plasma heat transfer.

Findings

The total heat flux to cathode surface is smaller than its components’ heat flux due to electron back diffusion is as large as that due to ion flux with the increase of cathode length the total heat transported to the cathode body has an obvious decrease.

Originality/value

It is found that two kinds of solution exist for the cathode with a 140° conical tip; however, only one stable solution exists when the conical angle is reduced to 130°.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 30 no. 5
Type: Research Article
ISSN: 0961-5539

Keywords

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Article

J.L. Marshall, D.E. Miiller, J. Sees, S.E. Matteson, D. Weathers and L. Lichtenberg

A combination of analytical methods was used on printed circuit board coupons to conclude the following: (1) while steam ageing deteriorates solderability of tinned…

Abstract

A combination of analytical methods was used on printed circuit board coupons to conclude the following: (1) while steam ageing deteriorates solderability of tinned coupons, it does not increase the oxide thickness or tin‐lead ratio of the surface (top 50 Angstroms) of tinned coupons; (2) therefore, some other factor, probably oxidation of the copper or tin/copper intermetallic substrate, determines solderability of the coupons.

Details

Circuit World, vol. 18 no. 1
Type: Research Article
ISSN: 0305-6120

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Article

L.R. Lichtenberg, M. Sleiman and M.J. Harry

During the past few years, statistical process control and experiment design concepts have taken a prominent place within the industry. The use of such tools within the…

Abstract

During the past few years, statistical process control and experiment design concepts have taken a prominent place within the industry. The use of such tools within the Motorola, GEG manufacturing environment, has grown to the point where reflow and wave solder process development and optimisation has significantly benefited. The ability to evaluate statistically and model various known and unknown phenomena has provided GEG's manufacturing technology with a series of very powerful tools to aid in process control and development. The primary purpose of this paper is to present the various approaches used by GEG to implement the previously mentioned statistical tools, with respect to the development of infra‐red (I‐R) reflow solder processes and enhancement of certain quality characteristics associated with wave soldered printed wiring boards (PWBs). Beyond specific GEG applications, the paper discusses the role of statistically designed experiments and process control methods as a vehicle for providing answers to complex manufacturing problems. In addition, a discussion of the mathematical and graphical methods underlying the interpretation of quantitative data is presented. Perhaps the most important benefit derived from the use of statistics to solve manufacturing and quality problems is related to decision making. When experiments are conducted to isolate unwanted sources of process and product variation, decisions must be made to determine whether or not certain experimental effects are important. Through the application of statistics, the researcher can ascertain the mathematical probability associated with the random chance occurrence of various experimental effects. With this knowledge, the researcher can make decisions with known degrees of risk and confidence. Without such knowledge, an organisation might possibly expend valuable resources and derive no direct benefit. Ultimately, the principal reason for applying statistical methods and procedures is to increase quality and yield, while simultaneously reducing costs.

Details

Circuit World, vol. 12 no. 4
Type: Research Article
ISSN: 0305-6120

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Article

P.S. Braterman, J.L. Marshall, J. Sees, C. Tan and J. Zhao

The unique advantages of confocal microscopy are used to explore four cases of interest: (i) voids in solder (depth and surface texture determined), (ii) steam vs ambient…

Abstract

The unique advantages of confocal microscopy are used to explore four cases of interest: (i) voids in solder (depth and surface texture determined), (ii) steam vs ambient aged solder coupons (significant differences detected), (iii) integrated circuit construction (sub‐surface contamination by µm‐size particles observed) and (iv) circuit boards and solder pads (non‐destructive optical sectioning through no‐wash flux layers). It is shown that confocal microscopy strongly complements SEM (scanning electron microscopy); SEM alone presents an incomplete description of a solder surface and in fact can sometimes produce misleading results.

Details

Soldering & Surface Mount Technology, vol. 7 no. 2
Type: Research Article
ISSN: 0954-0911

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Book part

Victor Villarreal and Maria J. Castro

Although many educators feel insecure about reporting suspected child maltreatment, educators are in a unique position to identify and, subsequently, intervene in such…

Abstract

Although many educators feel insecure about reporting suspected child maltreatment, educators are in a unique position to identify and, subsequently, intervene in such cases. This is particularly true for those working in early childhood education settings, as the youngest children – those most vulnerable to the effects of maltreatment – are at the greatest risk for being victims of most types of maltreatment. Thus, early childhood educators should be familiar with child maltreatment and be prepared to act in these cases. The purpose of this chapter is to provide a general overview of child maltreatment. Definitions and prevalent issues will be discussed, and the potential effects of child maltreatment across a variety of domains, including cognitive, academic, social, and behavioral functioning, will be highlighted. Finally, the authors explore various responsibilities, such as mandated reporting and intervention and prevention activities, of early childhood educators.

Details

Discussions on Sensitive Issues
Type: Book
ISBN: 978-1-78560-293-1

Keywords

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Book part

Simona Giorgi, Margaret E. Guider and Jean M. Bartunek

We discuss a recent effort of institutional resistance in the context of the 2008–2011 Apostolic Visitation of U.S. women religious motivated by Vatican concerns about…

Abstract

We discuss a recent effort of institutional resistance in the context of the 2008–2011 Apostolic Visitation of U.S. women religious motivated by Vatican concerns about perceived secularism and potential lack of fidelity among Catholic sisters. We examined the process of and women’s responses to the Visitation to shed light on the institutional work associated with productive resistance and the role of identity and emotions in transforming institutions.

At a time when the male leadership can be blamed for leading the church to a state of crisis – a time when the voices of women are needed more than ever – even the modest roles accorded to female clerics have come under attack. The specific reasons for the investigation are unclear (or, more probably, not public), but the suspicion, clearly, can be put in the crassest terms: too many American nuns have gone off the reservation.

– Lisa Miller, Female Troubles, Newsweek, May 27, 2010

At a time when the male leadership can be blamed for leading the church to a state of crisis – a time when the voices of women are needed more than ever – even the modest roles accorded to female clerics have come under attack. The specific reasons for the investigation are unclear (or, more probably, not public), but the suspicion, clearly, can be put in the crassest terms: too many American nuns have gone off the reservation.

Details

Religion and Organization Theory
Type: Book
ISBN: 978-1-78190-693-4

Keywords

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Article

L.R. Lichtenberg and P.J. Gillespie

A new product design required the addition of a secondlayer of electronics to control a base module. This product was designed with significantoverhangs of heavy leads and…

Abstract

A new product design required the addition of a second layer of electronics to control a base module. This product was designed with significant overhangs of heavy leads and components which presented a significant challenge to many different solder assembly processes. Only the heated gas jet process was able to solder the product successfully without damaging the printed wiring boards.

To answer the challenge, a new machine was developed, combining dispensing of solder paste with hot gas jet reflow technology. This provided a combination of capabilities resulting in a flexible process which was significantly superior to alternative technologies.

Other soldering processes such as laser, focused xenon lamp, robotic soldering iron, and focused IR soldering technologies were evaluated. Each of these technologies causes some damage or defect to the assembly due to the heat sinking aspect of the circuit assembled. These alternative processes would create damage or defects to the assemblies by burning the laminate, delaminating the pads on the printed wiring board, or not soldering the pads.

Proof of concept tests before machine designs were initiated demonstrated the potential and capabilities of this technology for automated assembly soldering. Testing indicated that the heated gas jet processing would provide a means of soldering the assemblies at a controllable rate without damaging the circuit boards.

While evaluating the machine ion its design phase, a designed experiment was initiated to help understand the relationships between head temperature settings versus gas flow rates, the measurable output was time to reflow.

The process meets all expectations in terms of solder fillet appearance, volume, and overall visual quality while maintaining process cycle time requirements.

Details

Soldering & Surface Mount Technology, vol. 9 no. 1
Type: Research Article
ISSN: 0954-0911

Keywords

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Article

J.L. Marshall, J. Calderon and J. Sees

A mechanical and microstructural study was performed of 43/43/14 tin/lead/bismuth solder. This alloy melts lower than the commonly used tin/lead solders and therefore…

Abstract

A mechanical and microstructural study was performed of 43/43/14 tin/lead/bismuth solder. This alloy melts lower than the commonly used tin/lead solders and therefore holds promise as a useful material in two‐step soldering processes or in processes with thermally sensitive components. Mechanical testing of 43/43/14 tin/lead/bismuth showed a strength comparable to that of tin/lead solders but increased creep rate. Microstructural analysis (scanning electron microscopy/energy dispersive X‐ray) exhibited the same mechanism of fatigue as for tin/lead solders, viz., heterogeneous coarsening. Thermocyclic fatigue demonstrated that the long‐term reliability of 43/43/14 tin/lead/bismuth is comparable to that of tin/lead solders.

Details

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

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Article

R.J. Klein Wassink and M.M.F. Verguld

Drawbridging or Stonehenge Effect of leadless components (i.e., the standing up on their end faces) has been investigated. An explanation is offered based on a…

Abstract

Drawbridging or Stonehenge Effect of leadless components (i.e., the standing up on their end faces) has been investigated. An explanation is offered based on a straightforward theoretical model considering surface tension, sustained by a great amount of experimental evidence. The phenomenon is strongly associated with condensation reflow soldering, whereas the dimensions of the metallisation at the underside of the leadless components and the size of the solder lands on the board are major influencing factors. Practical hints are given to overcome the problem.

Details

Microelectronics International, vol. 3 no. 1
Type: Research Article
ISSN: 1356-5362

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Article

M.S. Setty

As announced in the May issue of Hybrid Circuits, ISHM‐Benelux is organising a one‐day conference on applications of hybrid circuit technology.

Abstract

As announced in the May issue of Hybrid Circuits, ISHM‐Benelux is organising a one‐day conference on applications of hybrid circuit technology.

Details

Microelectronics International, vol. 4 no. 3
Type: Research Article
ISSN: 1356-5362

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