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Article
Publication date: 1 February 1995

B.N. Ellis

Surface insulation, electrochemical migration and various other insulation resistances are terms which are often glibly used, sometimes even incorrectly. This paper categorises…

Abstract

Surface insulation, electrochemical migration and various other insulation resistances are terms which are often glibly used, sometimes even incorrectly. This paper categorises different types of insulation resistance and catalogues about twenty practical applications of insulation resistance measurement, each with its ideal general conditions of measurement (test voltage, bias voltage, bias polarity, test voltage period, test frequency, test duration, temperature, humidity, test pattern type, test pattern dimensions, voltage gradients, tolerances, etc.) This description is independent of any of the nearly forty known, often contradictory, standards, most of which no longer correspond to the practical printed circuit or assembly of today. Also discussed are the different technologies of insulation resistance measurement, starting with the original non‐electronic ‘Megger®’ types through to modern laboratory electrometers and, finally, instrumentation specific to the practical measurement of printed circuit insulation resistances, including static and dynamic types. The importance of automatic statistical analyses is emphasised, especially with production testing as well as qualification procedures. This paper is aimed not only at those wishing to learn what modern insulation resistance testing is all about, but also at experienced persons wanting to marshall their thoughts about the fundamental meanings of insulation testing for different applications and specifications.

Details

Circuit World, vol. 21 no. 2
Type: Research Article
ISSN: 0305-6120

Article
Publication date: 1 February 1991

B.N. Ellis

This paper outlines the composition of water soluble fluxes for the electronics industry and their methods of use when wave soldering and reflowing tinned coatings and solder…

Abstract

This paper outlines the composition of water soluble fluxes for the electronics industry and their methods of use when wave soldering and reflowing tinned coatings and solder pastes. Process optimisation is facilitated by the Taguchi method. Three types of cleaning machinery are evoked, with varying results. It is shown that the energy/time relationship is important to ensure adequate cleaning quality. A number of fallacious arguments are debunked. Methods of water purification and the problems of effluent treatment for all sizes of installation are addressed. Doubt is expressed as to the viability of closed‐circuit water recycling except for the largest installations or where exceptional conditions prevail. It is shown that water soluble fluxes and their subsequent aqueous removal are unlikely to make any significant contribution to the Greenhouse Effect. The overall cost of their use is substantially similar to that of rosin fluxes with CFC‐113 azeotropes at 1986 prices. Cleanliness control under production and laboratory conditions is discussed with reference to both ionic contamination testing, including its use for SMDs, and SIR analysis, especially at low voltages, including non‐destructive production SIR testing. Reliability of the assembled circuits is shown to be at least as good as that with more traditional soldering and cleaning methods, frequently better, and this is the case even for military and aerospace applications. The paper concludes that, now that quality water soluble solder pastes are available, this method is most likely to become the workhorse for the majority of electronics applications.

Details

Soldering & Surface Mount Technology, vol. 3 no. 2
Type: Research Article
ISSN: 0954-0911

Article
Publication date: 1 January 1994

This article has been withdrawn as it was published elsewhere and accidentally duplicated. The original article can be seen here: 10.1108/eb046243. When citing the article, please…

Abstract

This article has been withdrawn as it was published elsewhere and accidentally duplicated. The original article can be seen here: 10.1108/eb046243. When citing the article, please cite: B.N. Ellis, (1993), “A Voyage to the End of the World!”, Circuit World, Vol. 20 Iss 1 pp. 60 - 61.

Details

Soldering & Surface Mount Technology, vol. 6 no. 1
Type: Research Article
ISSN: 0954-0911

Article
Publication date: 1 March 1986

B.N. Ellis

This paper essentially describes what is believed will become the norm in contamination control over the next decade, as applied to laminate and PC manufacture, components…

Abstract

This paper essentially describes what is believed will become the norm in contamination control over the next decade, as applied to laminate and PC manufacture, components, assembly, soldering and protection. Particular attention is paid to the special requirements imposed by the increasing use of surface mount technology, especially when trying to extrapolate current techniques towards modern applications. Test methods are mentioned and these are also likely to undergo considerable development over the next few years but, above all, more precise, scientifically‐established standards are urgently needed for both ionic contamination and surface insulation resistance testing. Cleaning technology is, of course, an essential part of contamination control and future development of both solvent and aqueous methods will lie in a better understanding of the time‐energy relationship required to break contamination‐substrate bonds at a molecular level.

Details

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

Article
Publication date: 1 January 1987

B.N. Ellis

This paper discusses the requirements of quality assurance of electronics assemblies with respect to the surface conditions, and more particularly the problems introduced by…

Abstract

This paper discusses the requirements of quality assurance of electronics assemblies with respect to the surface conditions, and more particularly the problems introduced by modern assembly techniques. Ionic contamination testing and surface insulation resistance measurement are dealt with as complementary techniques. Particular emphasis is laid on the fact that standards related to both QC methods are inadequate and do not reflect modern needs. Cleaning, as a corollary to contamination, is touched upon without detail, other than a table comparing methods as a function of purchasing and operating costs, technical performance, etc.

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Circuit World, vol. 13 no. 2
Type: Research Article
ISSN: 0305-6120

Article
Publication date: 1 January 1988

B.N. Ellis

The use of surface insulation resistance testing has been restricted to QC laboratory applications. The extension of this technique to modern electronics and, in particular, to…

Abstract

The use of surface insulation resistance testing has been restricted to QC laboratory applications. The extension of this technique to modern electronics and, in particular, to contamination control of SMAs has forced the development of new methods of SIR measurement. These have revealed that existing standards are rapidly becoming obsolete because the premises on which they are founded are no longer valid. Even more alarming, it is revealed that we are rapidly reaching, not only the limit of our knowledge in the field, but also the technical limits of existing standard materials used in industry today. This paper is a warning against too much complacency, as the risk of running into real problems, at all process stages, will become very pertinent within a few years. The technical content of this paper is based on about three years' study of the subject resulting in the measurement of SIR at about 10 V, as opposed to the traditional values of 100 and 500 V, which have been proved to be of little value with conductor spacings such as are usual on SMAs.

Details

Circuit World, vol. 14 no. 2
Type: Research Article
ISSN: 0305-6120

Article
Publication date: 1 March 1994

B.N. Ellis

The need to use cleaning methods other than traditional CFC‐113 solvent for hi‐rel electronics imposes more rigid cleanliness testing. In the past, this was mainly limited to…

Abstract

The need to use cleaning methods other than traditional CFC‐113 solvent for hi‐rel electronics imposes more rigid cleanliness testing. In the past, this was mainly limited to ionic contamination control, but this is probably insufficient by itself when using other methods. This paper discusses the various methods for which instrumentation is available, from the practical standpoint. This should satisfy all the requirements of both procurement agencies and manufacturers. Particular emphasis is placed on the fact that most existing standards are out‐of‐date and should be urgently revised. It is suggested that the standards be based on statistically valid test results rather than the simpler, but risky, go/no‐go methods. These probability limit levels should be modulated according to the use to which the circuitry will be put and the technology used in its manufacture. Above all, emphasis is placed on testing methods that are more scientifically based with less empirical guesswork.

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Circuit World, vol. 20 no. 4
Type: Research Article
ISSN: 0305-6120

Article
Publication date: 1 February 1989

B.N. Ellis

This paper gives a general survey of the methods of contamination control related to assembled printed circuits. Particular emphasis is given to those aspects of the subject which…

Abstract

This paper gives a general survey of the methods of contamination control related to assembled printed circuits. Particular emphasis is given to those aspects of the subject which are currently in a state of change because of environmental difficulties, notably those due to the curtailment of use of chlorofluorocarbon solvents.

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Circuit World, vol. 15 no. 3
Type: Research Article
ISSN: 0305-6120

Article
Publication date: 1 April 1989

B.N. Ellis

This paper describes the current (April 1989) problems of finding substitutes for chlorofluorocarbon (CFC) solvents which are becoming regulated for environmental reasons. The…

Abstract

This paper describes the current (April 1989) problems of finding substitutes for chlorofluorocarbon (CFC) solvents which are becoming regulated for environmental reasons. The cleaning products discussed are hydrochlorofluorocarbons, hydrochlorocarbons, chlorocarbons, water, aqueous saponifiers, light hydrocarbons and terpene/surfactant mixtures. These are examined primarily from the points of view of air and water pollution and operator health and safety. Secondarily, the factors of cost and cleaning efficiency are discussed.

Details

Circuit World, vol. 16 no. 1
Type: Research Article
ISSN: 0305-6120

Article
Publication date: 1 March 1990

B.N. Ellis

That the provisions of the Montreal Protocol (1987) are inadequate is a well‐known fact. The first revision of the Protocol will be approved by the Parties in June 1990, but the…

Abstract

That the provisions of the Montreal Protocol (1987) are inadequate is a well‐known fact. The first revision of the Protocol will be approved by the Parties in June 1990, but the new provisions are still being discussed at the time of writing (December 1989). This paper discusses the various possibilities as to the available technologies which can replace current and future restricted cleaning solvents, as applied to the electronics assembly industry. It places particular emphasis on surface mount technology, as well as conventional assemblies.

Details

Circuit World, vol. 16 no. 4
Type: Research Article
ISSN: 0305-6120

1 – 10 of over 8000