Microelectronics International

Hrovat, M.; Bernik, S.; Kolar, D.

1988 Microelectronics International

doi: 10.1108/eb044316

A superconducting material with the composition YBa1.8Pb0.2Cu3O7 was synthesised. The influence of PbO addition on the sintering and formation of the superconducting compound YBa2Cu3O7 was investigated. A thick film paste, prepared from prereacted material and an organic vehicle, was fired on Al2O3 and ZrO2 substrates. The resistivity of samples on ZrO2 substrates decreased to zero around 90 K, while samples on Al2O3 substrates did not reach zero resistivity until 77 K, which is probably due to the differences in thermal expansion coefficient between Al2O3 and the superconducting material. Interactions between Pt alloy based thick film conductors and superconducting material were studied.

Donaldson, P.E.K.

1988 Microelectronics International

doi: 10.1108/eb044317

The UK Medical Research Council's Neurological Prosthesis Unit was formed on 1 October 1968. In this review, Peter Donaldson, who has been with the unit from the beginning, reflects on what seem to him to be the most important contributions to implant technology from the unit, and suggests some possible developments for the future.

Hartman, D.H.

1988 Microelectronics International

doi: 10.1108/eb044318

Fundamental engineering limits to very high speed electronics switching systems are employed. These limitations are caused by packaging and interconnection constraints, as well as device switching speed. From the device viewpoint, reactive parasitics caused by the packaginginterconnection scenario are discussed. From the systems level perspective, overall delay, delay variance and power consumption are explored. The important problem of clock distribution in high speed synchronous digital systems is discussed. These limitations are then revisited with photonics implementation in mind. Comparisons are made between the electrical and photonic approaches. Some engineering limits to the photonic alternative are laid out.

Oishi, T.; Kaneyasu, M.; Ikegami, A.

1988 Microelectronics International

doi: 10.1108/eb044319

An integrated sensor with three elements zinc oxide, tin oxide and tungsten oxide was fabricated by thick film techniques in order to develop a smell sensor. Using this sensor and pattern recognition method, the possibility of identifying 15 chemical compounds which belong to the alcohol, ester, ketone, benzene and hydrocarbon group was examined. The following results were obtained All 15 compounds have different patterns, so they can be individually identified compounds which have the same functional groups have similar patterns and, when gas sensitivity of three elements is displayed in a threedimensional space, the compounds with the same functional group form a specific closed space. This indicates that the sensor can identify functional groups of chemical compounds.

de Kluizenaar, E.E.

1988 Microelectronics International

doi: 10.1108/eb044320

Ultrasonic cleaning is an effective aid in the removal of flux residues from surface mounted circuits. However, an overintensive and too extended ultrasonic load of surfacemounted electronic circuits, on ceramic substrates, occasionally causes the fracture of component leads. In a metallurgical study, it was found that the fracture mechanism is fatigue. The fundamental cure for this problem is to limit the ultrasonic load to a level below the fatigue limit of the leads. This can be achieved by limiting the ultrasonic power input in the bath. Other beneficial measures are to limit the cleaning time and the ultrasonic frequency, and to prevent the components from coming into contact with other parts during cleaning.

Porter, M.

1988 Microelectronics International

doi: 10.1108/eb044321

This paper acts as an introduction to the work of the Microelectronics Technology Centre of British Aerospace at Hatfield. It concentrates, primarily, on the development of a CopperOnCeramic Technology. The philosophy of using BS 9450 principles to achieve a mature, fully documented process is outlined.

Tsunaga, M.; Kato, S.

1988 Microelectronics International

doi: 10.1108/eb044322

This paper describes a newly developed Copper PTF Polymer Thick Film which is characterised by direct solderability and high electrical conductivity. This Copper PTF claims to solve various problems existing in the conventional subtractive or firing process. It also realises new circuit production processes which are difficult to attain if conventional methods are applied.

Golonka, L.; Kozlowski, J.; Nitsch, K.

1988 Microelectronics International

doi: 10.1108/eb044323

The rapid assessment of thick film resistor reliability is presented. This relies on the application of constant power pulses. The longterm stability of the resistors is predicted on the basis of the value of the minimal destroyed power applied during the pulse. The results are compared with the longterm behaviour of the tested samples.

Kwikkers, T.

1988 Microelectronics International

doi: 10.1108/eb044324

For the production of sensor elements, thick film technology can be used. Advantages of this technology such as ease of production, low cost, high reliability and the possibility of integration with frontend electronic circuits, make the thick film sensor an interesting alternative to existing sensor elements. In this paper two examples of thick film thermal sensors are presented.

Tielemans, L.

1988 Microelectronics International

doi: 10.1108/eb044325

An evaluation of the feasibility of copper ballwedge bonding on Au, Cu thick film and aluminium metallisations was carried out. This evaluation is not merely a check for feasibility, but will also give more insight into the problems concerning copper ballwedge bonding. This article does not pretend to represent profound research on copper ball bonding, but will give qualitative insight. Copper ball bonding, without using cover gas, is possible, but the bond quality decreases. Extrusion and penetration of the ball bond in the substrates are caused by the hardness of the copper. This can only be avoided when the hardness of the substrate is matched to the hardness of the copper ballwire. Bonding mechanisms are similar for bonding on thick film to those for bonding on metallisations. Matching hardness of the substrate to the ballwire seems to be a necessity for proper ballwedge bonding.