Search results

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.

Held in the Cameo Room of the Metropole Hotel, Brighton, on the evening of 9th October, the Cahners Gala Awards Dinner sponsored by Electronics Weekly was attended by over 200 guests. Mr A. B. Nolan, Director Cahners Exhibitions Ltd, in welcoming those present to the 4th Annual Awards Dinner, explained that Internepcon was 18 years old; 31 of the original 54 exhibitors were still supporting the event, and the total number of exhibitors in 1985 amounted to 420.

During the first half of this year the Association has continued to expand its exhibition programme by increasing its presence at overseas shows. Two DTI sponsored joint venture groups have been formed, one to Nepcon West, the other to Nepcon Beijing. Anaheim saw the biggest UK group for over 10 years, with CEMA taking three separate blocks in different sectors of the show. There is no doubt from the reception we received that CEMA is now firmly established at Nepcon West. We enjoyed tremendous support from both the British Consulate and the British‐American Chamber of Commerce with their President making several visits to the CEMA booth.

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.

Discusses the 27 papers in ISEF 1999 Proceedings on the subject of electromagnetisms. States the groups of papers cover such subjects within the discipline as: induction machines; reluctance motors; PM motors; transformers and reactors; and special problems and applications. Debates all of these in great detail and itemizes each with greater in‐depth discussion of the various technical applications and areas. Concludes that the recommendations made should be adhered to.

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.

Coventry‐based Shipley Europe have appointed George Allardyce to the newly‐created position of European technical manager. The appointment further strengthens Shipley's research, development and technical support team serving the European marketplace.

Alpha Metals have introduced a revolutionary material to replace CFCs in PCB cleaning which is said to be environmentally safe. The new product, Bioact EC‐7, is a biodegradable, essentially non‐toxic, formula which has no ozone depletion potential.

A review of state‐of‐the‐art technology pertinent to tape automated bonding (for fine pitch, high I/O, high performance, high yield, high volume and high reliability) is presented. Emphasis is placed on a new understanding of the key elements (for example, tapes, bumps, inner lead bonding, testing and burn‐in on tape‐with‐chip, encapsulation, outer lead bonding, thermal management, reliability and rework) of this rapidly moving technology.