Microelectronics International

Aleksi, O.S.; Nikoli, P.M.; Grozdi, T.D.; Lukovi,

1993 Microelectronics International

doi: 10.1108/eb044483

Various thick film varistor constructions were made and characterised sandwich, interdigitated and segmented varistors. The varistor active layer thickness, the electrode surface value and shape were varied. The Ul characteristics of these varistors were compared mutually, and with the Ul characteristics of the smallest chip varistors. In accordance with the results obtained, it has been shown that thick film printed varistors composed of ZnO and with additives could be applied as discrete components or integrated into a hybrid circuit.

Hill, G.W.

1993 Microelectronics International

doi: 10.1108/eb044484

As the hybrid market changes, many hybrid companies are being forced to adjust to reduced defence budgets and to the encroachment of epoxy board based SMT on traditional hybrid areas. This paper considers the establishment of an intelligent power module technology as a viable way to utilise the strengths of hybrid technology, in a field where there is an expanding market and, at present, not too much competition. The basic techniques are described, some of the potential pitfalls are highlighted, and the likely scale of technical and personnel investment is indicated.

Pickering, C.R.; Craig, W.A.; Barker, M.F.; Cocker, J.; Donohue, P.C.; Vanrietvelde, G.

1993 Microelectronics International

doi: 10.1108/eb044485

Complex mixed metallurgy multilayers require a very robust dielectric to withstand shorting or blistering effects, together with high density for longterm reliability in humid environments. The development and performance of a new multilayer dielectric which meets these needs is presented here. A dielectric frit chemistry has been developed with a view to eliminating short circuits and blistering induced by the proximity of dissimilar metallurgies on multiple refiring. Appropriate filler technology has also been developed to optimise dielectric density, toughness and lasertrim properties. High density has yielded excellent HBT High Bias Temperature and HHBT High Humidity Bias Test performance. Data on multilayer circuit bowing are presented which take account of the interaction of conductor frit and the dielectric on firing. Silver conductor is employed in inner layers to optimise conductivity and cost. A new 13 PdAg conductor for termination of components and resistors also permits heavy Al wire bonding with good aged performance. 25 m Au and 37 m Al wire bonding is facilitated by gold conductor on dielectric. The laser trim characteristics of a new resistor series on dielectric are described. The materials system has been tested in a complex multilayer structure which, with the use of a new silver via fill conductor, resulted in defectfree circuits with zero yield loss.

Dziedzic, A.; Nijs, J.; Szlufcik, J.

1993 Microelectronics International

doi: 10.1108/eb044486

Different techniques applied for the fabrication of thickfilm fine lines have been analysed. The basics, achievements, advantages and disadvantages of improved screen printing, screen printing with metal masks, the direct writing method, offset printing and photoformed or photoetched thickfilm are presented. In addition, current trends in front metallisation of silicon solar cells are described. Based on a critical review, the use of thickfilm fine lines for this purpose is discussed.

Atkinson, J.; Pitt, K.; Williams, K.

1993 Microelectronics International

doi: 10.1108/eb044487

The University of Southampton ThickFilm Unit TFU was originally established in the Department of Electronics in 1985 to service the requirements of a transducer research group. This group originally pioneered the concept of the intelligent transducer and the thickfilm unit was initially used to explore the opportunities for fabricating lowcost miniature and robust electronic interface circuits suitable for incorporation within transducers. The benefits to be derived from these thickfilm fabrication techniques soon become evident and the unit rapidly grew in stature with the commencement of several research programmes in the area of thickfilm sensors. The 1989 review of advanced sensor technologies undertaken by the DTI reported that the Southampton group was emerging as a centre of expertise in a technology offering significant short to mediumterm scope for commercial exploitation. This prediction is rapidly being fulfilled with an ever increasing number of thickfilm sensors being made commercially available.

De Meulemeester, B.; Van Calster, A.; De Bruycker, A.; Allaert, K.

1993 Microelectronics International

doi: 10.1108/eb044488

Since the first appearance of high density interconnection systems about ten years ago, researchers have tried to exploit this concept to the full. By introducing new technologies and materials, they have succeeded in building a module that equals wafer scale integration WSI in speed and efficiency. However, MCMs have not yet experienced rapid growth and acceptance as a result of the large capital investment and rather small volumes involved. This paper sets out to show that MCMs can be fabricated using technology and processes already in existence at most conventional IC and thinfilm production facilities.

Srensen, F.; Styhr Petersen, H.J.

1993 Microelectronics International

doi: 10.1108/eb044489

When providing substitutes for CFC113 in processes such as vapour phase soldering and removal of flux residues after soldering in the electronics industry, it is also important to avoid the use of other organic solvents at the same time. Vapour phase soldering can be replaced by soldering in an infrared belt oven or by using a closed wave soldering system with an inert gas such as nitrogen. The use of organic solvents in the removal of flux residues can be replaced by the following three procedures eliminating removal, by using a flux with a low residue content eliminating removal, by using a flux such as adipic acid and formic acid in a closed wave soldering system with an inert gas such as nitrogen and removal with water using a watersoluble flux.

Bjorneklett, A.; Halbo, L.; Kristiansen, H.; Nilsen, L.M.; Storfossene, T.; Tuhus, T.

1993 Microelectronics International

doi: 10.1108/eb044490

A new hybrid substrate technology for power electronic applications has been characterised by thermal resistance and mechanical stress measurements. The new substrate utilises thermal spray technology for deposition of dielectric layer and electrical conductors. The results are compared with the more established technology of alumina substrates with direct copper bonding DCB metallisation. Silicon test chips for thermal resistance and mechanical stress measurement were used for the characterisation. The experimental results were compared with finite element analysis and a reasonable agreement was found.

Fick, H.

1993 Microelectronics International

doi: 10.1108/eb044491

Power electronics used in consumer product assemblies require thermal management. Several current products rely on printed wiring designs. These have copper patterns separated from a metal substrate by a performance dielectric. The acceptance of this design concept ensures the availability of insulated metal substrates IMS for these applications. Available design guides do not describe the design constraints forced on these assembly designs by the physical characteristics of the materials in use. The following three design issues are discussed in this paper Dielectric strength testing does not relate to the proof stress testing required for product agency approval. There is a special case for conformal coating or the use of potting compounds when IMS assemblies are used. The choice of the metal substrate is based on quantity, thermal coefficient of expansion and thermal conductivity, often in that order.

George, Barry; Somora, M.

1993 Microelectronics International

doi: 10.1108/eb044492

On 8 October 1992 the ISHMBenelux Chapter organised a oneday conference entitled New Trends in Electronic Packaging and Interconnection which took place in the Holiday Inn, Gent, Belgium. This conference was attended by 45 participants from the Benelux countries and Great Britain.

Lowrie, Dave

1993 Microelectronics International

doi: 10.1108/eb044493

Selfcontained emergency lighting luminaires are mandatory in most countries for public buildings, offices and factories to ensure maximum safety in the event of a power failure. A major Netherlandsbased manufacturer, Blessing Electronics, Breda, produces a wide range of luminaires to suit most applications which are sold widely within Benelux and in other European countries.