Microelectronics International

Kirby, P.L.; Pagan, I.D.

1987 Microelectronics International

doi: 10.1108/eb044284

Surface Mounting is shown to be the fourth generation of electronic interconnection technology. It has several facets and is seen differently from various viewpoints in the assembly industry. A review of published papers shows that the subject grew during the 1970s with no single inventor and as a result of numerous developments which are now combining into a coherent technology with important compatibility with other recent innovations.

Hoffheins, B.S.; Lauf, R.J.; Siegel, M.W.

1987 Microelectronics International

doi: 10.1108/eb044285

An intelligent gas sensor has been developed using thickfilm techniques to create a semiconducting oxide surface with carefully varied catalytic properties. An integral heater causes the surface to react with combustible gases and the resulting resistance map of the surface forms a signature that can be related to the functional groups present in the gas. For example, alcohols, ketones and alkanes have distinct, recognisable signatures on one sensor model.

Fukuoka, Y.; Matsumoto, E.; Ishizuka, M.

1987 Microelectronics International

doi: 10.1108/eb044286

This paper describes one of the new package cooling technology concepts using low melting point alloys in order to perform high density packaging. Two kinds of cooling alloy materials, BiSnIn and BiPbSnln, whose melting points were less than 80C and whose costs were low, were selected. The experimental substrate sample was fabricated by greensheet technology on which a tungsten metallised resistor heater was formed. Two kovar weld rings were brazed together to the top side and back side surfaces of the substrate individually. One kovar metal shell was laser welded to the top side weld ring in order to protect many devices. Another kovar metal shell, with a hole in the centre, was laser welded to the back side weld ring. The low melting point alloy was melted and poured into the back side kovar shell through the hole in a liquid state. After it was cooled and changed into a solid state, the hole was sealed hermetically with a small kovar metal cap by a laser beam. The authors performed a thermal experiment and confirmed that the substrate back surface temperature was fixed at the cooling alloy material's melting point for several minutes by thermal absorption while the low melting point alloy phase changed from its original solid state into a liquid state. This new package cooling technology is extremely useful for a high power motor drive circuit package which consists of many high power transistor chips and other analogue IC chips, and whose motor drive operation is performed intermittently for several minutes with some interval times.

Barker, J.R.

1987 Microelectronics International

doi: 10.1108/eb044287

The stimulus of the successful semiconductor device miniaturisation programmes coupled to recent progress in synthetic chemistry and molecular engineering has led to the emergence of a new interdisciplinary activitymolecular electronicswhich holds longterm promise for a new range of electronic materials and devices. From very speculative origins the field has begun to generate important applications based on photoresists, LangmuirBlodgett films, electroactive polymers and photochromic materials. A selection of topics ranging from molecular switches, memories, sensors, and the biological interface to prospects for a molecular computer are discussed with special emphasis on features such as stability, selforganisation and selfassembly which are unique to molecular systems.

Hrovat, M.; Jan, F.

1987 Microelectronics International

doi: 10.1108/eb044288

Thick film resistor materials' microstructure, sheet resistivity and temperature coefficient of resistivity during the firing process in the temperature range between 350C and 950C were investigated. During firing the sheet resistivities at first decrease because of evaporation andor oxidation of the organic phase and later, at higher firing temperatures, increase due to sintering of the glass phase and the rearrangement of conductive particles. The TCR is negative for firing temperatures below 450C, due to the presence of partly pyrolysed organic vehicle, and positive for higher firing temperatures.

de Groot, P.

1987 Microelectronics International

doi: 10.1108/eb044289

Termination resistances can affect the behaviour of thinfilm resistors. Depending on the dimensions of a resistor both the TCR and the longterm stability will be affected, while the termination resistance forms part of the practical resistance value. This paper deals with the results of an investigation concerning the influence of termination resistances with respect to the behaviour of thinfilm resistors. Three thinfiim technologies were investigated. Values for the resistance, TCR and ageing drifts of both the bulk material and the terminations will be discussed. Some remarks on the structure of a termination will be mentioned.

Kidd, J.

1987 Microelectronics International

doi: 10.1108/eb044290

Screen printing for the fabrication of Thick Film microelectronic circuits is now a mature technology. A greater understanding of the processes and materials used has allowed the once black art to develop into the high precision, high yield process of todaywith circuits containing 250 m conductors on many levels being printed over large areas up to 6 in. 8 in. However, electronic systems designers are demanding more compact interconnections and screen printing technology must advance to meet this challenge. Encouraging research to date has demonstrated that 50 m lines and spaces are readily printable under controlled conditions, and a complete 120 m multilayer system is now a reality. Unfortunately, this rapid advance in the technology is likely to hit insurmountable barriers in the near future, and alternative patterning techniques may be required if Thick Film technology is to cope with the ultra high tracking densities that will soon be required.

Belcourt, F.J.; Lane, T.A.

1987 Microelectronics International

doi: 10.1108/eb044291

One of the most challenging problems facing the package designer today is how to predict electrical performance before committing a design to fabrication. One means of accomplishing this task is to employ computeraided design CAD tools that analyse performance from simulations done on models derived from the physical package structures. These models, when combined with the chip models, allow interactive simulation and timing analysis of an entire multilayer package. This paper describes a CAD approach for evaluating interconnect performance within multilayer package structures and presents several examples to show how the approach is applied.

Castelli, G.; Lovati, G.

1987 Microelectronics International

doi: 10.1108/eb044292

The paper describes the results obtained by the integration of Polymer Thick Film and Printed Circuit Technologies. Polymer Thick Film PTF Technology, applied to PCB manufacturing, helps the designer's task considerably and offers an interesting way to achieve time and cost reduction. The use of conductive and dielectric materials to generate crossovers and low interconnection density multilayers on epoxyglass substrates is shown and basic design rules are discussed. The performances of PTF conductive materials from two different suppliers are investigated in terms of conductivity, current carrying capacity and contact resistance with the copperclad layer. Surface and bulk insulation resistance, capacitance, loss factor and breakdown voltage are studied for dielectric materials from two different suppliers. The effects of environmental tests, i.e., thermal shocks, high temperature storage and temperaturehumiditybias test, on the performances of dielectric and conductive PTF are investigated by means of suitable test patterns. Application examples of Transmission System boards are discussed in terms of design and manufacturing times and costs.

Whalley, D.C.; Campbell, D.S.

1987 Microelectronics International

doi: 10.1108/eb044293

Thermal cycling tests for surface mounted components are usually taken around a mean temperature of approximately 35C e.g., 55C to 125C 40C to 110C. To test the effect of different maximum temperatures thermal cycling tests using a lower temperature of 55C have been conducted with aluminathick film zeroohm jumper chips with nickel barriers. These are connected in series chains and wave soldered on to FR4 test coupons 128 chipscoupon. The test regimes used were 55C to 5C 65C 95C, 110C and 125C. Resistance changes before and after cycling were observed at room temperature. After 100 cycles changes of approximately 200 m were observed against a total resistance of 55 . However, more detailed examination showed that a top temperature of 95C gives optimum results with a total change over 100 cycles of 49.

Baudry, H.

1987 Microelectronics International

doi: 10.1108/eb044294

This paper intends to demonstrate the feasibility of thick film piezoelectric layers on ceramic substrates. Advantages of this technology for the realisation and improvement of some devices, such as loudspeakers and couplers to be applied in a communication bus, are described.

Riches, S.T.; White, G.L.

1987 Microelectronics International

doi: 10.1108/eb044295

GaAs electronic devices are becoming increasingly used in the microelectronics industry especially in solid state microwave, ultra high speed digital processing and optoelectronic applications. However, in the manufacture of the GaAs devices, problems due to the inherent brittleness of the GaAs and batch to batch variability of the bond pad metallisation have commonly been experienced. This has resulted in some difficulties in wire bonding to GaAs devices with ultrasonic and thermocompression wire bonding techniques. This paper describes a programme undertaken to investigate Au wire bonding techniques to GaAs devices. Specifically, bonding trials have been performed on a range of GaAs substrates using pulse tip and continuously heated thermocompression bonding and ultrasonic bonding. The results of this work have shown that thermocompression and ultrasonic wire bonding techniques are cabable of producing acceptable bonds to GaAs devices, although some of the advantages and limitations of each technique have been demonstrated. Thermocompression bonding with a continuously heated capillary gave the most tolerant envelope of bonding conditions and highest bond strengths. Pulse tip thermocompression bonding gave a less tolerant envelope of acceptable bonding conditions, required a longer bonding time and the wire was weakened above the ball bond. Ultrasonic bonding did not require any substrate heating to give acceptable bonds. However, the choice of equipment can be critical if damage to the device is to be avoided.

Turnbull, Bob; Barnwell, Peter; Yates, Paul; Fairbairn, Alan; Waterfield, Brian; Waterfield, Mary

1987 Microelectronics International

doi: 10.1108/eb044296

The conference and exhibition got off to a good start with an official reception by the Mayor of Bournemouth on Tuesday evening where attendees could relax and chata pleasant way to meet old friends and to make new acquaintances.

Turnbull, Bob

1987 Microelectronics International

doi: 10.1108/eb044297

It was Monday, June 8th, and immediately after the Bournemouth Conference. The weather was unchanged, dull and with rain not far away and I was pleased to board the plane for Finland hopefully the long days at this time of year would give better weather. My hopes were soon realised and Helsinki looked bright and clear under the afternoon sun, the white Cathedral dominating the harbour skyline. The market by the South Harbour was crowded with shoppers and others just enjoying a stroll by the sea.

Setty, M.S.

1987 Microelectronics International

doi: 10.1108/eb044298

As announced in the May issue of Hybrid Circuits, ISHMBenelux is organising a oneday conference on applications of hybrid circuit technology.

1987 Microelectronics International

doi: 10.1108/eb044299

Mr Peter Lenk has transferred from the FraunhoferInstitut to mls munich laser systems since 1 July 1987. Prior to this move, Mr Lenk was employed at the Fraunhofer Institut fr Festkrpertechnologie in Munich, where he organised and set up the procedures for the Institute's thick film technology department, supervised the complete film processing for thick film technology and research to prove the authenticity of thick film resistors. Mr Lenk also supervised and conducted training in thick film technology.

1987 Microelectronics International

doi: 10.1108/eb044300

A new Laser Trimmer from DEK Printing Machines has been purposedesigned for small batch production. It is a complete selfcontained system, supplied with probes and a full test capability.