bluuebunny/crossref_metadata_2025 huggingface dataset:
Zero‐stress Film Adhesive for Substrate Attach
Authors: Leung L.M. , Chung K.K.T.
Published: February 2008

Traditional B‐staged epoxy film adhesives have been used as substrate attach adhesive for hybrid circuits. The advantages of using film adhesive instead of paste adhesive are precise bond‐line, clean operation, ease of application for larger bonding area and possibility to automate the process for large volume production. Epoxy, in general, is more stable than polyurethane and is better in adhesion with no contamination problems in comparison with silicone. Traditional epoxy, however, has high bond strength and is therefore limited only to substrates with matched thermal expansion properties. Combining the advantages of excellent adhesion of epoxy and flexibility of rubbery substance, a low glass transition temperature (Tg) epoxy which is flexible in nature has been developed for bonding substrates with mis‐matched thermal expansion coefficient. The new epoxy adhesive is also designed to meet the requirements of MIL‐STD‐883C/5011 in application without sacrificing ionic purity, low outgassing, thermal conductivity and long‐term dielectric or conductive properties. The new flexible film adhesive, in both its insulating and conductive forms, has attracted new applications and designs that were not previously feasible. For example, the flexible film adhesive can be used to bond ceramic hybrids directly to a lower cost metal substrate such as aluminium or copper. Testing has been performed by users on the combination of alumina/aluminium for over 1000 thermal cyclings and shocks from −55 to 150°C for large area bonding (up to a maximum of 6 x 6 inches square). The cured flexible epoxy adhesive, while very pliable, also exhibits more than 1,000 to 2,000 psi lap‐shear strength (depending on the type of substrate) and withstands more than 15,000 g acceleration test.
ISHM news
Authors: Forster G. , Jones Graham
Published: February 2008

Organised by ISHM‐France, this event is aimed at suppliers, manufacturers, and users of hybrid microelectronic circuits. The aim of the conference is to present information on the latest innovations and trends in microelectronics. Twelve technical papers selected by ISHM‐France will be presented in two sessions.
ISHM‐NORDIC Conference and Exhibition
Authors: R.B.T.  , S.J.M.
Published: February 2008

All Scandinavian cities seem to be close to water, if not the sea then there will be a lake or river. All too have that wonderful clear light in which the reflections sparkle and dance. Helsingør, the location for this year's ISHM‐Nordic event was no exception. It is just over half an hour by road from the capital city, Copenhagen, and the coastal route gives excellent views of the sea and the nearby coast of Sweden. Helsingør has many outstanding buildings dating from the middle ages, including St Olav Church and the nearby Carmelite monastery dating from around 1400. From 1660 to 1668 the famous composer Buxtehude was organist at the church. The town itself is dominated by the castle which was built in the Fifteenth century. The later alterations carried out by King Christian IV left the exterior virtually unchanged.
Design and Fabrication of an Ingestible Rechargeable Capsule for Thermal Monitoring
Authors: Lesho J.C. , Romenesko B.M. , Hogrefe A.F.
Published: February 2008

JHU/APL has developed and tested ingestible pills that telemeter core body temperature. The hybrids were manufactured as chip and wire on thick film ceramic substrates and surface mount on polyimide boards. The devices have potential applications for divers, astronauts, soldiers in combat, people working in hazardous conditions and people with hypothermia and hyperthermia. Descriptions of both circuit operation and packaging techniques are included.
Techniques for the Inspection of Flip Chip Solder Bonded Devices
Authors: Burdett P.A. , Lodge K.J. , Pedder D.J.
Published: February 2008

After a brief introduction to the advantages and method of construction of flip chip solder bond devices, this paper looks at different techniques that can be used to inspect these devices at various stages in their construction. These techniques include optical, infra‐red, acoustic and electron microscopy, radiograph, electrical and tensile testing. The advantages and limitations of each of the techniques are discussed and an outline inspection schedule is suggested.
Characterisation of Aluminium Nitride Ceramic Substrates
Authors: Norton M.G.
Published: February 2008

Aluminium nitride (AlN) is currently under investigation as a substrate material for use in microcircuit applications in particular where high thermal conductivity is required. Three commercially available substrate materials have been characterised using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X‐ray diffraction (XRD). The differences in thermal conductivity between the materials and also the difference from the theoretical thermal conductivity have been correlated to the presence of low thermal conductivity second phase regions between grains, defects within the crystal structure, the presence of oxygen impurities and poor sintering behaviour. The highest thermal conductivity substrate obtainable during this study was 140 W7m K. The substrates were identified as comprising hexagonal AIM having a wurtzite type structure. In addition, oxide and oxynitride phases were detected. The surface morphology of the substrates was also investigated, as it is the nature of the surface that will be of importance in determining the adhesion of applied films.
An Assessment of Thick‐Film Piezoresistors on Insulated Steel Substrates
Authors: White N.M.
Published: February 2008

The development of new, inexpensive, robust and miniaturised sensors is continuously being sought and it is believed that thick‐film technology can help to achieve these goals. A strain sensor utilising the piezoresistive properties of thick‐film resistors is described here. Characterisation of the sensing element has revealed that the gauge factor is significantly higher than that of metal foil strain gauges and the temperature coefficients are generally lower than those found for semiconductor strain gauges. Results show how the gauge factor can be optimised by varying the production parameters.
Assembly and Packaging Considerations for GaAs Microwave Power Devices
Authors: Tyler J.R. , Andrade D.K.
Published: February 2008

Recent developments in microwave GaAs technology are yielding devices with higher power capabilities and increased levels of integration. The mechanical and thermal properties of GaAs and other microwave materials play a key role in the design and assembly of microwave power circuits. Thermal management is a critical element of microwave power circuit design. Thermal properties of microwave materials are discussed and compared with standard microelectronic materials. Material selection criteria are described. Assembly and packaging techniques also affect the overall performance of the GaAs power circuit. The high operating frequencies of microwave circuits make ordinary circuit elements, such as wire bonds and printed conductors, reactive. In addition, electrical performance criteria, such as high current or low impedance, create unique assembly demands. The successful development of a GaAs‐based microwave product is dependent on careful attention to the material properties and precise assembly methods. Techniques of automated assembly and processing are discussed, with ah eye towards maintaining high quality and reliability.
Copper Thick Film—A Maturing Technology
Authors: Sayers P.
Published: February 2008

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.
A New Generation Multilayer System: Low Cost and High Reliability
Authors: Gilles T. , Reynolds Q. , Steinberg J.
Published: February 2008

The increasing complexity of hybrid circuits has led to a need for a reliable multilayer system. As well as reliability, the manufacturer will, of course, also attach considerable importance to material and production costs. Until now, thick film multilayer applications have been limited by the inability of existing technology to reduce their susceptibility to galvanic effects occurring between individual conductive layers during fabrication. Now, however, this company has developed a multilayer dielectric which prevents metal migration. The system is supported by conductor and resistor systems.
High‐density Multichip Module by Chip‐on‐Wafer Technology
Authors: Kimijima S. , Miyagi T. , Sudo T. , Shimada O.
Published: February 2008

A high‐density module for image processing was developed by chip‐on‐wafer technology. A silicon wafer was used as the substrate and the LSI chips were flip‐chip bonded to the silicon wafer by bumps in chip‐on‐wafer technology. A primary benefit of using a silicon wafer is the little induced thermal stress which affects the bumps. The module contained a digital signal processor, SRAMs and other peripheral LSls. A total of sixteen chips were bonded on the wafer. The LSIs were connected to each other by copper/polyimide multilayer interconnections consisting of eight copper conductive layers and polyimide dielectric layers. The characteristic impedance for the signal lines was controlled to 50 ohms. The LSIs were connected to the wafer electrically and mechanically by solder bumps, which were formed on the LSI bonding pads. A 188 pin AIN ceramic package was used for the module in order to obtain high heat radiation and high reliability. The occupied area for the module was reduced to 20%, compared with the size for conventionally assembled DIPs on a PC board.
Multichip Modules—The Hybrid for Wafer‐scale Integration
Authors: Sage M.G.
Published: February 2008

Existing IC packaging and interconnection is creating a barrier for advances taking place in IC technology. Wafer scale integration (WSI) is being proposed as the next major step in electronics, bringing with it the removal of a large number of these barriers. However, there are still major problems with WSI technology that are unlikely to be solved before the late nineties. In the meantime a new packaging and interconnection technology will be introduced—the multichip module (MCM), which will act as a hybrid for WSI. The MCM will not make the PCB obsolete, though it will pose threats and opportunities to important parts of the thick film hybrid industry. The MCM, for the purposes of this paper, is defined as a thin film multilayer interconnect structure utilising IC manufacturing type processes. MCM technology is not confined to high performance systems; it will be used across the whole of the electronics industry including the consumer sector, with a circuitised substrate world market of nearly $7 bn by 1997.
Bell Telephone Manufacturing, Ghent, Belgium
Authors: Waterfield B.C.
Published: February 2008

This visit was made to complete an unfulfilled invitation from the General Manager, Mr Van Neste, offered to the writer several years ago. It was a pleasure to find the time to make the trip and meet some old friends and to see actions taken to keep this company busy, efficient and profitable.
Quality Assurance in the Production of High‐quality Solder Powder—the Essential Prerequisite for Microelectronic Grade Solder Pastes
Authors: Ruthardt R.
Published: February 2008

The tremendous growth in the SMT market has led to a corresponding increase in demand for electronic‐grade solder pastes for the various reflow solder processes. The high quality standards imposed upon the basic solder powders are a reflection of these demanding applications. This means that informed choice and achievement of metallurgy, purity, morphology and a high level of quality must be maintained throughout the production process if present and future specifications are to be met. The manufacturing process for high reliability microelectronics soldering is eventually achieved by inert gas atomisation supported by advanced materials analyses, electron microscopy and laser granulometry.
Interface Reactions during Metal/Ceramic Diffusion Bonding
Authors: Qin C.D. , Derby B.
Published: February 2008

The strength of annealed ZrO2/Pd diffusion bonds was found to be weakened after annealing in both air and vacuum. Annealing in air reduces the strength much faster and more severely than in vacuum. Fracture surfaces of as‐bonded joints and those annealed in air and vacuum were studied to characterise the different effects of air and vacuum on the bonded interfaces. Various sizes of precipitates and voids were observed and their distribution on the fractured surfaces was examined by light microscopy. Large precipitates and voids were found close to the edges of the specimen. It is believed that the loss of strength after annealing is an effect of these defects at the highly stressed specimen edges. Transmission and analytical electron microscopy of as‐bonded joints show that an interface layer of very fine grains about 1 micron thick was formed during the bonding process. This layer has a different crystalline structure and composition from both Pd and ZrO2. Characterisation of this layer by electron microscopy is presented in this report. The formation of such a thick interface layer is probably not a pure diffusion process, rather a diffusion and melting process. From the Pd‐Zr phase diagram, there is a range of compositions near a eutectic point where a liquid phase is possible at the bonding temperatures used (1100°C). Taking the Pd‐Zr system as a qualitatively comparable system to Pd‐ZrO2, it is deduced that, at the very beginning of the bonding, Zr and Pd diffuse into each other until the melting composition is reached. The formation of the liquid phase will promote the contact and bonding processes dramatically. This explains why strong bonding cannot be achieved at lower bonding temperatures as was reported in an earlier paper. Similar experiments on Ni/ZrO2 diffusion bonds have also been studied to identify the mechanism of bonding and to compare it with Pd/ZrO2. No reaction was observed at the interface in Ni/ZrO2. Thus the wetting mechanism is absent which explains the formation of a large amount of interface voids and the much weaker bonding strength found in Ni/ZrO2 bonds.
Realisation of Hydrotalcite‐type Protonic Conductor Thick Films by the Screen‐printing Technique
Authors: Moneyron J.E. , de Roy A. , Besse J.P.
Published: February 2008

A new type of realisation of the hydrotalcite‐type lamellar compound Zn2AI(OH)6Cl.nH2O is described, using an original ink composed of a concentrated aqueous suspension of Zn2AI(OH)6Cl.nH2O powder, which, when applied by the screen‐printing technique, in particular environmental conditions—in a high relative humidity atmosphere—permits one to obtain very satisfactory deposits. Optical characterisation shows good resolution and levelling of the screen‐printed layer. X‐ray patterns show a high orientation of the (hkO) reticular planes of the screen‐printed material in a direction parallel to the substrate; this is a very interesting characteristic related to experiment on the electrical properties of this type of compound. Tests show the good adherence of the deposited layer on alumina or glass. Future applications are envisaged.
Ibiden Company Ltd, Ogaki, Japan
Authors: Lay H.T.
Published: February 2008

The visit to the Ibiden Company in Ogaki gave me the opportunity to see at first hand a part of the industry which has participated in the technological and economic miracle of post‐war Japan. It was a chance, too, to see something of the far‐reaching differences in working attitudes and methods which have no doubt contributed to this spectacular success, which has placed Japanese technological exports in a leading position in virtually every part of the world.
ISHM news
Authors: Binner H. , Law H.T. , Sinnadurai N. , Jones G. , Ongley P.E.
Published: February 2008

Following the discussion at our recent Annual General Meeting, a questionnaire was sent out to all members. Almost half of them replied despite the fact that the time allowed for returning the questionnaire had been kept very short. Some members even provided detailed comments.
Packaging Options for High Lead Count ASIC Devices
Authors: Riches S.T.
Published: February 2008

Selection of the correct interconnection technique for high lead count integrated circuits is dependent on technical and economic factors, in particular in small batch production of application specific devices (ASICs). This paper reviews some of the interconnection options and describes work where some advances in high density interconnection have been made.
Terpene vs. CFC Defluxing in Hybrid Circuits Manufacturing
Authors: Osvalder B.
Published: February 2008

Because of the influence of chlorofluorocarbon based solvents on the stratospheric ozone layer, electronics manufacturers worldwide are attempting to find new solvents or methods for defluxing printed wiring boards and hybrid circuits. In this report results are presented from an evaluation of terpene solvent (Bioact EC‐7), CFC‐113 (Freon TF) and ethylalcohol used as cleaning solvents for defluxing thick film substrates. From these results, it was found that terpene cleaning yields test results that are equal to or in some cases better than CFC cleaning. This paper also describes how the strength of adhesively mounted dies and ball‐bond wires on the substrates changes over time (1000 hours).
The Use of CAD in Advanced Ceramic Package Designs
Authors: Callahan R. , Ewanich J.
Published: February 2008

Being competitive in the high performance IC market requires package design concepts which keep pace with the rapid increase in device complexity. Devices operating in the 50 watt/500 MHz range impose stringent performance specifications on package designs. Rapid package designs are essential in keeping pace with device development. Accurate modelling of electrical, thermal and mechanical properties is also necessary. The use of CAD in advanced package design eliminates the need for each engineer to create a drawing to perform his specific design task. The design tape created by the packaging engineer can be used by the engineer performing the 3‐D electrical modelling functions. It can be used to display the package design at an off‐site product engineering review. The ceramic package manufacturer can use it in tooling the package. This paper discusses the use of CAD to design, model and manufacture a 169 lead ceramic pin grid array for an ECL standard cell application, and the advantages resulting from its use.
High Performance Electrically Conductive Silicone Adhesives
Authors: Lutz M.A. , Cole R.L.
Published: February 2008

Silicones have long been recognised as attractive materials for use in electronics applications because of their unique combination of properties. Now, technology which couples high electrical conductivity with silicone performance characteristics has been developed. The new silver‐filled silicone adhesives were processed and cured in a manner similar to that used in conventional heat cured silicone compositions. Resultant cured products were both highly flexible and highly conductive, exhibiting volume resistivities down to 2 × 10−4 ohm‐cm. Both flexibility and electrical conductivity were retained after extended periods at elevated temperature. The electrical performance obtained while the new adhesives were under strain (induced either mechanically or thermally) was attributed to changes in the spatial packing of the silver. Low temperature characterisation indicated that the materials remain soft and stress‐relieving even down to −60°C. Other physical characteristics of these compositions, such as high ionic purity, low moisture uptake and good adhesion, are typical of high performance electrically conductive adhesives. This combination of properties suggests that these new silicone adhesives should be attractive for the electrical interconnection of microelectronics substrates having a mismatch of thermal coefficients of expansion (TCE) which would normally lead to failure due to thermomechanical stresses, and for the manufacture of flexible circuitry.
ISHM news
Authors: Lantairès J. , Waterfield B.C. , Binner H. , Griffiths G. , Wright Maurice
Published: February 2008

ISHM invites papers for the above Conference, to be held on 29–31 May 1991 in Rotterdam, The Netherlands. Papers should cover areas such as: design, manufacturing, packaging and interconnection, materials and processing, applications, reliability, components, new technologies, marketing and economics, optoelectronics. Summaries should be in English, length 200–300 words. The deadline for receipt of summaries is 30 September 1990. (For full details, see announcement on pp. 54–55.)
Surface Mounted Joints on Different Substrate Materials
Authors: Rautioaho R.H. , Karjalainen L.P. , Lahdenperä M.K.
Published: February 2008

The deterioration of surface mounted solder and adhesive joints on different substrate materials under thermal cycling was investigated metallographically. Ceramic chip resistors and leadless chip carriers were soft‐soldered or glued onto alumina, FR‐4, aluminium or steel boards and the various cracking modes were observed. Fatigue cracking in the solder under the component (mode A) took place in the case of resistors on an Al substrate and carriers on all boards except alumina. Cracking on the outward surface near the upper and lower corners (mode B) occurred on all boards, but most notably on alumina. Adhesive joints seemed to offer the highest fatigue strength, but their electrical properties suffered continuously in the course of cycling even though cracking was not observed at all in many cases.
ISHM news
Authors: Binner H. , Setty M.S. , Collander P. , Garnett C.H.
Published: February 2008

A recent meeting involved co‐operation with the organisers of the Canadian High Technology Show and the local Chapter of the SMTA. The programme included an inspiring keynote address by Mr Frank J. Pipp, Xerox Corporation. The topic of the address was ‘Malcolm Baldridge National Quality Control and the Evaluation of Total Quality Control in Xerox Corporation.’
Optimised Nitrogen‐based Atmospheres for Copper Thick Film Manufacture
Authors: Rotman F. , Navarro D. , Mellul S.
Published: February 2008

This paper reports the results of development work conducted on nitrogen‐based atmospheres in order to improve the firing of copper thick film systems through continuous furnaces. The proposed solution is particularly suitable for industrial production conditions since it allows variations of the material quantity processed per unit time, resulting not only in an improvement in quality but also in productivity. Such improvements have been achieved by using a new gas distribution system which provides both zone control and regulation of oxygen additions in the nitrogen furnace atmosphere. An efficient set‐up of this system has become possible thanks to precise control of the oxygen profile in relation to the temperature cycle, taking into account various inks' characterisation, and owing to an extensive study of the effects of oxygen additions on copper thick film properties. The solution was tested in a muffle‐lined belt furnace with several commercial dielectric and copper inks, and for increasing oxygen additions into the furnace preheat zone. Different sample patterns were designed to test both monolayer and multilayer systems. The test programme includes measurements of resistivity, bondability, solderability, dielectric breakdown voltage and adhesion of copper films on alumina and on dielectric layers before and after ageing. Ink characterisation by thermogravimetry and by several gas analyses has confirmed that the organic vehicle removal mechanism under nitrogen atmospheres doped with oxygen is a burnout. Indeed, significant oxygen consumption occurs within the temperature range of the removal, as a function of the amount of ink processed. Oxygen additions in the furnace burnout zone greatly improve both the dielectric breakdown voltage and the adhesion of copper on alumina and on dielectric (especially after ageing), while sheet resistivity, wire bondability and soft solderability are not altered below a defined O2 level. It is therefore possible to determine an optimum oxygen addition range for which the thick films fired under such conditions will have the best characteristics. This optimum oxygen window is achieved thanks to a new regulation system which operates whenever variations occur in the quantity of paste processed.
Applications of Computer Algebra Techniques in Hybrid Circuit Design
Authors: De Mey G.
Published: February 2008

Computer algebra or symbolic manipulation is nothing else than performing analytical calculations with the help of a computer. This offers the advantage that lengthy and complicated calculations can be carried out without errors in a very short time. Computer algebra techniques have also been applied to solve electrical networks. This offers particular advantages for hybrid circuit design, as will be outlined extensively in this paper.
Industry news
Authors: Waterfield B.C.
Published: February 2008

Coors Ceramics has appointed Monika Sandoval as Account Manager for Germany, Austria and the German speaking part of Switzerland.
Investigations of Laser Soldered TAB Inner Lead Contacts
Authors: Zakel E. , Azdasht G. , Reichl H.
Published: February 2008

Tape Automated Bonding (TAB) is a modern technology which meets the requirements for micro‐connecting VLSI circuits. The limitations for gang bonding chips with high lead counts and reduced pitches are increased bond forces and induced mechanical stress. Laser soldering is an alternative for such contacts. Because microjoining of surfaces occurs via thermal energy from the laser beam, no mechanical pressure is necessary. Due to the optical properties of the laser beam and the possibility to reduce the laser spot, soldering of small pitches is possible. The results of TAB inner lead bonding with a pulsed Nd:YAG laser are presented. Tapes with three metallisations (Sn, Ni‐Sn and Au) were laser soldered to bumps consisting of gold and gold‐tin. The pull strength of laser soldered TAB‐contacts was optimised by variation of laser power and reliability investigations were performed. The metallurgy of laser soldering is different and more critical to long term reliability than that of gang bonded ILB‐contacts, even if identical tape and bump materials are applied. An accumulation of eutectic 80/20 Au‐Sn solder in the bonded interface results in a strong degradation due to Kirkendall pore formation in the ternary Cu‐Sn‐Au system. The application of a tape with a diffusion barrier of Ni inhibits this effect. But during thermal ageing these contacts show a strong degradation of pull forces which is attributed to the formation of brittle intermetallic compounds of the elements Ni, Sn and Au in the contact area. Laser soldering of Au‐plated tapes to Au‐Sn solder bumps is possible. The contacts show optimal pull forces and a minimal degradation after thermal ageing. This is attributed to the formation of an intermetallic compound with a high stability. The Zeta phase acts as a diffusion barrier between the copper lead and the eutectic Au‐Sn solder.
Optimised Nitrogen‐based Atmospheres for Copper Thick Film Manufacture
Authors: Mellul S. , Navarro D. , Rotman F.
Published: February 2008

This paper reports the final results of a development project conducted on nitrogen‐based atmospheres in order to improve the firing of copper thick films. Having shown that improvements in copper thick film performance can be obtained under production conditions by the control and regulation of oxygen additions during the first stages of firing, the authors studied the effects on copper thick film systems of other gaseous oxidisers (CO2, N2O, H2O) injected into the nitrogen furnace atmosphere either throughout the entire furnace or into its burnout zone only. SEM examinations of the microstructures of copper films, correlated with properties such as adhesion, solderability and resistivity, allow ideal firing atmosphere conditions for copper thick film manufacturing to be determined: it is necessary to restrict atmosphere doping to the burnout zone; oxygen and water vapour are the most effective gaseous dopants. Some specific equipments have been developed for controlling the injection of these dopants into the furnace atmosphere.
Development/Study of Thin Films for Electroluminescent Flat Panel Display
Authors: Natarajan P.V. , Vaiude D.G. , Rao B.M.
Published: February 2008

This paper concerns an all‐solid‐state, high‐contrast electroluminescent (EL) flat panel display which is becoming the potential for multifunctional avionic displays. In this ACTFEL (a.c. thin film electroluminescent flat panel) device, an active layer, doped with manganese (ZnS:Mn) is sandwiched between the two dielectric layers followed by conductive layers. All the layers are transparent except the back conductive layer. In the basic mode of operation, an alternating voltage is applied across any two crossing electrodes. When this voltage exceeds the ‘threshold voltage’, light is emitted from the active layer. EL mechanism (the generation of electrons, acceleration of these electrons to optical energies, and collision excitation of the Mn ions yielding light emission) occurs within the film or at the surface of the ZnS:Mn layer. A bright yellow light, in the visible region and with a relatively broad spectrum, is emitted. The TFEL display's thinness, compactness, low weight, moderately low power requirements and durability are its prime advantages. The characteristics of various thin films utilised in TFEL have been studied, and the data in this paper show the optimum requirements for luminance, efficiency and reliability of the light emission in ACTFEL.
Dendritic Growth from Dielectric Constituents in Thick Film ICs
Authors: Harsányi G.
Published: February 2008

Silver and other metals can exhibit dendritic short‐circuit growth caused by electrochemical migration in conductor‐insulator structures. Detailed analysis of migration‐free thick film systems using migration‐free conductors has demonstrated that not only metallic components, but also dielectric constituent materials can contribute to the formation of migrated shorts after a chemical reduction process.
Hybrid (and Multi‐chip Module) Design on the IBM‐PC Platform
Authors: Corless T.
Published: February 2008

The increased power and the memory available on IBM‐PC and compatible computers have led to the emergence of a wide range of engineering software. The large number of PCs offers an attractive market, with the result that software costs tend to be lower than those of similar packages on workstations. It is the purpose of this paper to describe an implementation of a hybrid/multi‐chip module design system, which runs on IBM‐PC compatible hardware.
ISHM news
Authors: Blancquaert Robert , Somora Miloš , Vijayaraghavan M.S. , Lowrie D.J.
Published: February 2008

ISHM‐Benelux has recently set up a permanent secretariat at the following address:
Factors in the Establishment of a Power Hybrid Manufacturing Facility
Authors: Hill G.W.
Published: February 2008

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.
New High Yield, High Reliability Materials System for Silver Multilayer Construction
Authors: Pickering C.R. , Craig W.A. , Barker M.F. , Cocker J. , Donohue P.C. , Vanrietvelde G.
Published: February 2008

Complex mixed metallurgy multilayers require a very robust dielectric to withstand shorting or blistering effects, together with high density for long‐term 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 laser‐trim 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 1:3 PdAg conductor for termination of components and resistors also permits heavy Al wire bonding with good aged performance. 25 µm Au and 37 µm 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 defect‐free circuits with zero yield loss.
Education in Hybrid Microelectronics
Authors: Atkinson J. , Pitt K. , Williams K.
Published: February 2008

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.
Cracking Behaviour during Au‐Au TAB Inner Lead Bonding
Authors: Baggerman A.F.J. , Kessels F.J.H.
Published: February 2008

Tape automated bonding (TAB) is an interconnection technique for integrated circuits (ICs) with a small lead pitch and a thin assembly thickness. During inner lead bonding the flying (Au plated Cu) leads of the TAB foil are connected to the Au bumps on the bondpads of an IC. The Au bumps are deposited in the openings of a thick Novolac based resist layer by electroplating. The resist is coated on a sputtered TiW‐Au metallisation; TiW is the barrier layer between Au bump and Al bondpad. Bonding of the leads to the Au bumps requires substantial plastic deformation of the bump and lead. As a result of this deformation, the TiW barrier layer underneath the bump may crack easily. A theoretical model has been used to describe the occurrence of these cracks. This theoretical model is compared with experimental results of deformation and cracking behaviour by visual inspection of the TiW barrier and the etched cross‐sections. Separate (single point) and simultaneous (gang) bonding techniques, different gold plating baths and TAB tapes are used to study the cracking behaviour.
Robust Aluminium Nitride Package Technology for Multichip Modules
Authors: Mather J.C. , Minogue G.R.
Published: February 2008

The advent of novel advanced packaging technologies such as multilayer thin‐film interconnect, combined with continuous improvements in IC clock speed and circuit performance, has placed extreme demands on electronics packaging and package materials. Aluminium nitride (AIN) ceramic offers significant opportunities and advantages for package design, particularly where the effective thermal management and overall reliability of large devices are a high priority. AIN has already been successfully employed at the substrate level for the enhanced thermal relief of power devices. Examples of these applications include heat sinks and device mounts for thyristor modules, power transistors, solid state relays, power SCRs, switching modules, LEDs and various RF package configurations. Both bare and metallised AIN substrates are beginning to find application as a substitute for beryllia (BeO) in mass market and high reliability automotive electronics applications. Successfully implementing AIN in a high level electronics packaging application requires a systems approach in which the intrinsic properties of AIN are considered as ‘first principles’ in shaping the package design process. The unique physicochemical and mechanical properties of AIN require the development of specialised metallisation and co‐firing processes to fabricate the advanced components necessary for hermetic packaging of complex devices and multichip modules. This paper presents a practical and mass manufacturable AIN‐based package tailored to these high level applications. The package design is unique in that it provides for the total separation of the electrical‐signal conduction from the mechanical support/mounting functions of the package. Such a separation of the functions improves both the package durability and reliability relative to currently available electronics packages of conventional designs.
Thermal Effects of Replacing Solder with Conductive Adhesives
Authors: Spalding O.
Published: February 2008

An important disadvantage of conducting adhesives is their inferior heat conductivity when compared with soft solder such as Sn60Pb40. Thermal simulations, however, show that, by using thinner layers of adhesive than of solder, the module's thermal resistance does not increase greatly. Test modules with four different silver filled epoxy adhesives and tin/lead solder were manufactured. These test modules contained power diodes, 30 A, 1000 V, die bonded onto Ag/Pt thick film conductors on alumina. The die bond adhesive layer thicknesses were typically 30 or 40 μm. For die bond solder layers the thickness was 90 μm. The alumina substrates were connected to 3 mm thick copper plates with filled epoxy or silicone adhesive. The thickness of these layers was 150 μm or 50 μm, respectively. Thermal resistance of the structures was measured. The results showed that good adhesion between joined surfaces is essential for optimised heat flow. The heat conductivity of an adhesive was only a secondary factor affecting the structure's thermal resistance. When the adhesive joint is of good quality, the replacement of solder with conductive adhesives does not increase the module's thermal resistance any more than as shown by the simulations. It should, however, be remembered that the printing of thin (< 20 μm) uniform layers is not always possible.
Bi/Pb‐Sr‐Ca‐Cu‐0 Based Thick Film Superconductors on Various Metal Substrates
Authors: Hrovat M. , Bernik S. , Rozman M. , Kolar D.
Published: February 2008

Thick film superconductors with the nominal composition Bi2Pb0.5Sr2Ca2.5Cu3.5Ox were fired on stainless steel substrates and on alumina substrates covered with silver or gold thick film conductors. Films on stainless steel substrates were semiconducting due to reaction between the superconducting film and oxidised chromium and iron from the steel. Tc(R=0) of films on silver was between 80 K and 90 K while Tc (R=0) on gold was below 60 K. The low Tc (R=0) of films on gold is attributed to the interaction between the gold layer and copper from the superconductor.
Technology of Optical Waveguide Thick Films
Authors: Keresztes‐Nagy Z. , Harsányi G.
Published: February 2008

In the last few years many new types of light‐guiding optical film structures have been developed. Several applications have been published in the field of optical and optoelectronic integrated circuits, sensor‐elements, etc. The basic component of these systems is the optical waveguide which can be realised with optical fibres or fabricated as a layer structure from different dielectrics and many kinds of glasses. The purpose of this paper is to describe some problems and solutions of optical waveguide thick film manufacturing and also connecting techniques with optical fibres.
A Reduction of a Thermal Model of Power Hybrid Circuits
Authors: Kos A.
Published: February 2008

The paper presents a two‐dimensional and three‐dimensional thermal model of the power hybrid circuit. Measurement of the accuracy of temperature computation using the two‐dimensional model is carried out. Based on both models, the AUTO_T program for thermal analysis is created. This program chooses the proper model according to the required accuracy of computation. The reduction of the computational time is evident.
Quality Issues in Chip‐on‐board (COB) Technology
Authors: Giani E. , Mathurin J.P.
Published: February 2008

Critical processing steps of COB manufacturing, as implemented at Epitek, are reported. They include testing of incoming boards, cleaning, bonding parameters, bonding defects and statistical process control.
Measurement of the Electrical Properties of High Performance Dielectric Materials for Multichip Modules
Authors: Laursen K. , Hertling D. , Berry N. , Bidstrup S.A. , Kohl P. , Arroz G.
Published: February 2008

Multichip modules provide short chip‐to‐chip interconnects in order to take advantage of the high speeds available in integrated circuits. One multichip approach utilises layers of embedded microstrip. In order to achieve the highest possible speed, it is necessary to use metals and dielectrics which have low relative dielectric constants and low loss. Polymer and polyimide dielectric materials hold great promise in MCM applications; however, their high frequency characteristics are often not well known. Since thin film dielectric properties may differ from the bulk properties, it is important to be able to determine the dielectric properties using on‐wafer measurement techniques rather than more conventional techniques. This paper focuses on some of the techniques available and discusses the advantages and shortcomings of different techniques for measuring dielectric properties.
MCM‐L Technology
Authors: Chandler N. , Tyler S.G.
Published: February 2008

Multichip modules using lamination techniques to make the substrate (MCM‐Ls) are a natural extension of printed circuit technology to meet the ever increasing demands of system integration and density. As with other forms of MCM, the interconnection density is so high that many circuits need only two signal layers. The substrate can also incorporate layers to control thermal expansion and extract heat. MCM‐L substrates are extraordinarily versatile; they can accommodate packaged ICs (e.g., fine pitch SMT), unpackaged ICs, other MCMs and odd‐form components. There is a large and growing number of MCM‐L suppliers offering solutions for a wide range of sizes, complexities, performance and market sectors at competitive prices.
Very Fine Line Photoimageable Thick Film Technology Developed at Hibridas
Authors: Minalgiene J. , Baltrushaitis V. , Muckett S.
Published: February 2008

The Microelectronics Division of the Radio Measurement Engineering Research Institute of Lithuania has developed a unique photoimageable thick film chemistry and process technology which has been in use since the mid‐1980s. The main application of the technology was for complex thick film microwave integrated circuits at lower cost than equivalent thin film devices. The paper describes the photoimageable materials and processing used at the Institute and also gives examples of suitable application in the microwave, high density interconnect, sensor and component fields.
Novel Techniques for Low‐cost, High Performance, Optoelectronic Component Assembly
Authors: Hall I.P.
Published: February 2008

The drive towards low unit cost in optoelectronics packaging is assisted by simple, rapid assembly processes, and by avoiding the need for hermeticity. This paper discusses the use of visible blue‐light cured resins as an important issue in assembly techniques. Results are also reported on trials of silicone gels as a means to produce hermetic equivalence performance in optoelectronic (O‐E) components and associated electronics. Photodiodes coated in these gels could be expected to have a service life of >60 years and results for coated lasers are encouraging with degradations of 4%/1000 h of damp heat stress, while GaAs ICs showed no degradation. The potential of these technologies has made possible the fabrication of a simple photodiode mount with coupling efficiencies approaching 100%. Low cost laser assembly has also been investigated. To demonstrate the feasibility of these technologies an O‐E transceiver module has been produced.
ISHM news
Authors: Hilley A.P. , Binner H. , Sung Oh Tae
Published: February 2008

‘The Choice between Chip and Wire and High Density Surface Mount Packages (MCM‐X, COB, etc.)’ was the title of the above event. One of a regular series held by ISHM‐France, this technical seminar was attended by over 100 members and non‐members of ISHM who were eager to hear of the latest developments in the field of multichip modules. The eight papers presented are summarised below:
A Cost‐effective High Efficiency LED Array Assembly Using Insulated Metal Substrates and Low Thermal Impedance SM Diode Encapsulation
Authors: Sawa H. , Kato K. , Asai S.
Published: February 2008

A surface‐mount in‐line light emitting diode (LED) array was developed for mounting an LED dot matrix display on a single‐sided insulated metal substrate (IMS). This LED array has heat dissipating cathode leads and an anode lead that works as a jumper wire. Good heat dissipation of the LED array was obtained on an aluminium IMS.
Essential Paste Properties for Fine Line Thick Film
Authors: Reynolds Q. , MacMahon H.G. , Freitag J.
Published: February 2008

The powder and rheology properties of a gold and a silver thick film ink are associated with its fine line performance. Printing 100 micron lines is shown to be straightforward and 75 microns is speculated as being feasible.
Thick‐film Laser Power Detector
Authors: Pércsi L. , Harsányi G.
Published: February 2008

Fabrication and performance characteristics of a thick‐film laser power detector are presented. The new sensor combines the advantages of a circular resistor and highly sensitive NTC resistor paste. As a consequence of the layout, the sensitivity of this sensor depends slightly on the eccentricity and positioning of the laser beam. Therefore the measurement is simpler and the linearity and the reliability of detector are of a high standard.
ISHM news
Authors: Lowrie D.J.J.
Published: February 2008

Two members of ISHM‐Hungary, Professor Zsolt Illyefalvi‐Vitéz, ELC representative, and Professor Gábor Harsányi, president and TPC representative, attended the NATO Advanced Research Workshop on MCM‐C/Mixed Technologies in Florida, USA, in May co‐sponsored by ISHM‐US and organised by: