The application of laser technology has recently become economically viable for microelectronics and surface mount technology. Semiconductor laser technology may prove to be the only technology capable of solving the assembly problems that will accompany further advances in microelectronics. Some characteristics of Nd‐YAG and CO2 lasers are compared with the performance of semiconductor diode lasers for soldering purposes. The early stages of evaluation of semiconductor diode lasers in an experimental soldering station at the University of Hull suggest that these lasers serve as an efficient selective, controllable and compact high power density heating source capable of meeting present and future microelectronics soldering requirements.
With the ever‐decreasing size of electronic components, examines the use of laser soldering, particularly of fine‐pitch, high value devices. Discusses the advantages and disadvantages of using lasers and the applications to which they are suited. Looks at the different types of lasers and how their different wavelength of operation affects the soldering process. Describes an experimental laser soldering station and its ability to solder circuit boards. Concludes that modern electronic component packaging technology is demanding new techniques for the interconnection of devices, and that the application of lasers to the traditional technique of soldering will enable this tested process to be applicable to the very fine pitch devices now being introduced.
THE greatly increased transition Reynolds numbers now attained in the boundary layers of cylinders having favourably shaped sections have renewed interest in the solution…
THE greatly increased transition Reynolds numbers now attained in the boundary layers of cylinders having favourably shaped sections have renewed interest in the solution of the equations of steady flow in a thin boundary layer. It is familiar that the scries solutions of Blasius and Hiemenz, improved by Howarth (ref. 1), and of Falkner (ref. 2) become severely restricted in range when applied to cylinders having other than bluff sections. But it appears that a series solution of substantially greater range is possible, at least for symmetrical flow, provided that the nose of the section is rounded. This problem forms the subject of Section I of the present paper.
AN approximate solution of the boundary layer equations recently completed involved the assumption of a velocity profile through the boundary layerdepending on two…
AN approximate solution of the boundary layer equations recently completed involved the assumption of a velocity profile through the boundary layerdepending on two parameters. As a result the problem was reduced to that of the construction and solution of two equations governing the variation of these parameters around the surface of the cylinder considered. Earlier solutions, such as Pohlhauscn's, have made use of a single parameter only and have employed Kármán's momentum integral for its determination, but the additional, parameter now introduced necessitates the use of a further equation. It is the purpose of the present note to discuss and illustrate the properties of the second condition that was selected.
ANOTHER paper (Ref. 1) establishes a new approximate solution of the boundary layer equations devised to meet difficulties that are encountered in applying earlier…
ANOTHER paper (Ref. 1) establishes a new approximate solution of the boundary layer equations devised to meet difficulties that are encountered in applying earlier solutions to laminar flow aerofoils and similarly thin cylinders. The advantage is in respect sometimes of accuracy, sometimes of applicability. The solution is a little unwieldy in its general form, however, and the present paper describes simplifications to facilitate rapid technical use. They are of two kinds, one being much more drastic than the other, and that first given, or both, may be used according to the nature of the problem and the accuracy required. Examples suggest that the resulting loss of accuracy and applicability will be small in most instances. This matter is described in Section I.
Britain's merchant navy dominated the international maritime trade in the 19th century. The strong ship owners' lobby imposed on the shippers the only choice to contract…
Britain's merchant navy dominated the international maritime trade in the 19th century. The strong ship owners' lobby imposed on the shippers the only choice to contract either under bills of lading drafted almost totally on the ship owners' terms or not to contract. The conflict between Britain and its rival the American merchant navy precipitated a movement for the use of model contracts of shipment (carriage) and towards standardisation of the liability of International liner carriers by legislative intervention. The bill of lading through its use in international trade gained the characteristic of being the document which incorporates the contractual terms. So, the orally agreed contract of carriage gave way to the contract of carriage in the form of a bill of lading.
Laser soldering provides a useful tool for the electronics manufacturer and has found a number of successful industrial applications. The laser provides highly…
Laser soldering provides a useful tool for the electronics manufacturer and has found a number of successful industrial applications. The laser provides highly controllable localised heating in a manner similar to hand soldering and has distinct advantages over other soldering methods. However, the heating processes that occur in laser soldering are complex making it difficult to predict whether a particular operation will be successful. Numerical modelling provides a valuable tool in answering such questions but the modelling process and the assumptions upon which it is based must be understood if the results are to be reliable.This paper explains the assumptions made in deriving a suitable model and describes the use of a commercial finite element modelling package to aid the understanding of laser soldering processes, with a particular emphasis on single and multi‐pass scanned beam soldering operations.
The purpose of this paper is to empirically investigate the quality tool’s impact on the effectiveness of the Hazard Analysis and Critical Control Point (HACCP)-based food…
The purpose of this paper is to empirically investigate the quality tool’s impact on the effectiveness of the Hazard Analysis and Critical Control Point (HACCP)-based food safety system and correlation studies between HACCP effectiveness and business performance in food and pharmaceutical industries.
A total of 116 survey responses of prominent food and pharmaceutical firms are used to fulfil the aim of this study. The principal component analysis (PCA) method was applied to classify quality tools into a finite number of groups. Further, multiple regression methods are employed to investigate the correlation between HACCP effectiveness and firm’s performance indicators.
Quality tools are classified into three categories on the basis of their application by using the PCA method: quality tools for hazard identification, quality tools for hazard analysis (QTHA) and quality tools for hazard control. The regression analysis revealed that QTHA has a substantial impact on HACCP objectives (hazard identification, hazard assessment and hazard control). Additionally, the results suggest that the successful implementation of HACCP-based food safety system also delivers a direct influence on the operational and financial performance of the food and pharmaceutical industries.
This paper contributes to the existing body of HACCP knowledge by providing a framework supported by an empirical case study. The case study clustered quality tools into three broad categories related to their application of a HACCP project. Study results can guide and motivate managers to use quality tools with the aim of successful implantation of the HACCP-based food safety system, especially in food and pharmaceutical industries.
I was fairly certain that I had explored most aspects of Whitehaven history. However this town of endless surprises had yet one more to spring on me. On his return my plumber friend unwrapped a parcel: it contained a ship's log — not the official one, but one kept by an apprentice on a voyage to the far east in the early nineteenth century — and the minute book of the Whitehaven Literary Society, 1820–1822. Of all the material things written about White‐haven very little has been said about its cultural activities. For the development of an interest in art it should be said by the way that the town owes a debt to William Gilpin of Scaleby Castle, the agent for Sir John Lowther of Whitehaven. Directly through his patronage of Matthias Read, and indirectly through his son and grandsons Gilpin contributed not a little to the promotion of painting in Cumberland and elsewhere.