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In this paper studies on the lab formulated fritless silver thick film paste with two different binder compositions that have been used to fabricate λ/2 microstrip rejection filter in the X and Ku band are reported. These have been compared with ESL (USA) paste and copper thin film metallization for the same circuit. The thick film circuits were overlayed with TiO₂ thick film of different thickness and changes in the characteristics studied. In the X band, the Q of the filter improves with overlay and is also dependent on the Ag paste formulation, whereas in the Ku band there are no thick film paste dependent properties observed due to overlay. Thickness of overlay and metallization paste formulation dependent factors should be taken into consideration during fabrication of high density and multi‐layer microwave integrated circuits.

The microwave properties of microstripline at S‐band and X‐band and ?/2 rejection filter with midband rejection at 3 GHz fabricated by thick film technology are studied. The effect of an overcoat of Ag thin film of thickness 2 µm deposited by ion plating and electroless plating on Ag and Pd‐Ag thick film circuits is reported. There is a drastic improvement in the performance of the thick film circuits after overcoating. This is attributed to the superior edge definition whereby losses are reduced. As the edge is smoother, especially at the coupling area of the filter, there is tighter coupling, thus increasing the Q of the filter. The overcoat may also reduce the large open areas of the thick film, giving a smoother upper surface finish. This type of metallic overcoat, i.e., hybrid of thick and thin film, may reduce the need for costly and time‐consuming functional trimming and expensive thick film materials.

Dr Setty reports from ISHM‐India, who had their first committee meeting on the 4th October 1985, that the Society is now off the ground and that the Symposium on Hybrid Microelectronics held on February 5th attracted considerable interest, some 150 persons attending. Dr Sonde was the organising committee Chairman and was fortunate in being able to persuade the Department of Electrical Communication Engineering of the Indian Institute of Science in Bangalore, which has set up its thin and thick film hybrid department, to host this important event. Papers were given by visiting speakers from the US, UK and West Germany as well as from India itself. Among the presentations given were papers introducing some of the country's facilities from which it can be seen that microelectronics has an important future here.

Thick film technology is increasingly used in hybrid microelectronic circuits throughout the world. It is entering areas of electronics hitherto dominated by other technologies. Materials are the most important parameter in any technological development. A single material can generate several technologies (e.g., silicon). The role of a Materials Scientist, particularly in the case of Thick Film Materials, has to be very comprehensive. A ‘Vertical Integration System’ is followed in the study and development of thick film materials. This has helped in understanding the complex reactions taking place and in rectifying the defects formed during thick film processing. It has been amply rewarded during the development of several conducting and resistive materials and while carrying out the basic studies of other materials as thick films. Some future trends in this area have been suggested for adapting this fascinating thick film technology.

In this research work thick‐film manufacturing technology on stainless steel baseplates was developed. Adequate adhesion of dielectric IP211 to the steel substrate was achieved only by sand blast roughening. Standard PdAg thick‐film conductors were not solderable to IP211. The solution was to have a separate multilayer dielectric under conductors to be soldered. The reliability of soft soldering and gold wire bonding of thick‐film metallisation on stainless steel and other baseplate materials was evaluated. The technology developed was applied to manufacturing an intelligent signal node. Present expertise enables the manufacture of thick‐film hybrids on stainless steel baseplates. Development of an industrial production line would, however, involve considerable effort.

On 20 April ISHM‐Benelux held its 1988 Spring meeting at the Grand Hotel Heerlen. This meeting was totally devoted to implantable devices, in particular to the technologies used for these high reliability, extremely demanding devices. For this meeting ISHM‐Benelux was the guest of the Kerkrade facility of Medtronic. Medtronic (headquartered in Minneapolis, USA) is the world's leading manufacturer of implantable electronic devices. Apart from the assembly of pacemakers and heart‐wires, the Kerkrade facility acts as a manufacturing technology centre for Medtronic's European facilities.

Knowledge of critical materials and process parameters necessary to fabricate quality copper thick film multilayer and hybrid circuits is being amassed and distributed throughout the industry via technical reports and presentations. Generally the information being provided in a single report deals with specific segments of the industry or only one or two specific nitrogen fireable materials. In order for hybrid manufacturers to commit themselves to the technology they need to know that sufficient flexibility exists to permit design of complex circuits and accommodate circuit design changes without imposing changes in basic process guidelines and controls. The OEM's concern, which is valid, has been that the investment required for capital equipment and establishing new processes must be fully supported by and provide reasonable return from the technology being initiated. This paper introduces new information on wire bonding in copper thick film circuits and some improvements in nitrogen fireable resistor characteristics and processing. Materials are available to produce a broad range of circuits without varying basic process parameters, and adding wirebonding as an interconnect capability further expands the circuit complexity and density achievable with copper thick films.

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

The purpose of this paper was to determine the complex permittivity of bismuth strontium manganites (Bi_1−xSr_xMnO₃) in the 8‐12 GHz range by using perturbation of Ag thick film microstrip ring resonator (MSRR) due to superstrate of both bulk and thick film.

The BSM ceramics were synthesized by simple low cost solid state reaction method and their fritless thick films were fabricated by screen printing technique on alumina substrate. A comparison has been made between the X band response of Ag thick film microstrip ring resonator due to perturbation of bulk and thick film Bi_1−xSr_xMnO₃ ceramic.

The bulk and thick film superstrate decreases the resonance frequency of MSRR. In this technique even minor change in the properties of superstrate material changes the MSRR response. Variation of strontium content also influences microwave conductivity and penetration depth of bulk and thick films.

The microwave complex permittivity decreases with increase in Sr content in bismuth manganite and it is higher for bulk as compared to its thick films. The superstrate on Ag thick film microstrip ring resonator is an efficient tool capable of detecting the composition dependent changes in microwave properties of ceramic bulk and thick films.

The University of Southampton Thick‐Film 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 thick‐film unit was initially used to explore the opportunities for fabricating low‐cost miniature and robust electronic interface circuits suitable for incorporation within transducers. The benefits to be derived from these thick‐film fabrication techniques soon become evident and the unit rapidly grew in stature with the commencement of several research programmes in the area of thick‐film 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 medium‐term scope for commercial exploitation. This prediction is rapidly being fulfilled with an ever increasing number of thick‐film sensors being made commercially available.