bluuebunny/crossref_metadata_2025 huggingface dataset:
Commercial Production of Polymer Thick Film Resistors
Authors: Green W.J.
Published: February 2008

Polymer thick film resistors are selected for various commercial applications in view of their performance, reliability and cost advantages. They are, however, only as efficient as the processing procedures used in their production. This paper outlines the factors that require control and presents test data relating to the important parameters. The value of laser trimming of polymer resistors is assessed.
The Properties of Thick Film Resistors Fabricated on Various Dielectric Layers
Authors: Rzasa B. , Potencki J.
Published: February 2008

The paper presents a comparative analysis of the properties of ruthenate resistor layers produced on alumina substrates and on dielectric layers previously deposited on them. The effect of dielectric type and the peak firing temperature of ruthenate layers upon the value of their resistance and TCR (temperature coefficient of resistance) has been investigated. The reproducibility and stability of these parameters have been evaluated.
New Low Cost Substrate (Duroid) for Hybrid Microwave Integrated Circuits (MICs) in Wide Band
Authors: Ramy J.P. , Guena J. , Thebault C.
Published: February 2008

Because of its lower dielectric constant and loss tangent, and its greater surface smoothness, fused silica is very suitable for use in the KU band and above, but its cost is very high. The purpose of this paper is therefore to select a new substrate which competes with fused silica on the grounds of lower cost; to adapt the hybrid technology to this new substrate; to show ,comparing the measured performances of a filter realised on fused silica and on this new substrate, that the latter is suitable for MICs in the wide band, but not in the narrow band; and to describe an application of this substrate in the 22–24 GHz band. Thus, after an investigation of the electrical parameters and of the costs of different substrates, Duroid was selected and compared with silica. This substrate is composed of a non‐woven glass microfibre reinforced by polytetrafluorethylene; its microwave quality is theoretically almost similar to that of the fused silica one but its cost is much lower. The adaptation of hybrid technology on this substrate, notably in order to use beam lead and die semiconductor components with thermocompression bonding as a connection method, involved the use of a copper foil laminated on Duroid. This paper describes the process that has been perfected: selective electroplating of gold on copper, compatibility of etching solutions of gold and copper, attachment and connection methods of semiconductors, substrate attachment in a package, etc. A comparison of the performances of a filter realised on fused silica and on Duroid gives the following conclusion: Duroid is suitable for wide band circuits, but not for narrow band circuits because of its instability under stress test temperatures (−20 to 80°). In this last case, silica will be preferred. A transmitter‐receiver in the 22–24 GHz band for radio links is described.
ISHM news
Authors: Waterfield Brian , Herod B. , Moran Peter
Published: February 2008

The ISHM—Japan Chapter, comprising some 500 members, was represented at ISHM '84 by 60 members, 30 of whom attended as a group. Twelve papers were presented by Japanese delegates at the Conference held in the Loews Anatole Hotel from 17–19 October.
Solderable Polymer Thick Film Conductors for Surface Mount Technology
Authors: St. John F.
Published: February 2008

A new class of solderable PTF materials has been evaluated for SMDs on FR‐4 substrates. No etching or plating baths are required in this totally additive process. The materials are printed in the desired geometry, cured by heat or infra‐red followed by soldering and device mounting. The study examines processing variables and resultant cured film properties including solderability, conductivity and adhesion.
Surface Mount Technology Setting Up a Surface Mount Facility
Authors: Rowe G.L.
Published: February 2008

This paper presents the manufacturing methods used in the assembly of electronic circuits with surface mount components on planar printed wiring circuits. The manufacturing process flow is explored as a function of the design of the circuit as well as the selection of surface mount components. Equipment evaluation criteria are presented along with facilities' requirements in the area of utilities and floor space.
Creating Mechanical Stress in the Resistive Layer as a Method of Studying its Temperature Characteristics
Authors: Szymański D. , Achmatowicz S. , Bekisz J. , Szczytko B.
Published: February 2008

The separation of thick‐film resistor temperature characteristics into two components is presented. One of the components is a function of the resistive material, the other a function of the linear expansion coefficient mismatch between the substrate and the resistive layer. The analysis has been carried out by two methods: by taking the temperature characteristics of the resistive material in the form of pearls, and by generating compressive stress in the resistive layer corresponding to the stress created by the temperature rise.
Plasma Treatment in Hybrid and Conventional Electronic Assemblies
Authors: Booth R.N. , Ongley P.E.
Published: February 2008

Plasma chemistry is employed almost exclusively for etching, cleaning and deposition processes in semiconductor device fabrication technology. As a natural expansion of this successful technique, attention has been directed at similar processes for thick film ceramic, thin film hybrid and more generally printed circuit board electronic assemblies. This paper discusses a variety of applications, some established and some experimental, where plasma is offering the benefits which semiconductor engineers have enjoyed for many years. Such applications include general organic removal, i.e., flux residues, finger print contamination and the removal/reduction of oxides and glass on thick film conductors to promote improvements in solderability and wire bondability.
ISHM news
Authors: Moran Peter
Published: February 2008

A two‐day symposium will be hosted by the ISHM‐Can‐Am Chapter in Ottawa, Canada, on 19–20 June 1985. The event will concentrate on advances in Surface Mounted Technology and topics covered will include design rules and critical process parameters, multi‐stage attachment methods, advances in cleaning processes and fluids, robotic insertion of non‐standard components, automatic inspection, etc. A Tutorial will be held concurrently on rework techniques for surface mounted devices.
A New Dice Bonding Method for Hybrid Technology
Authors: Ramy J.P. , Demeure L.
Published: February 2008

The bonding of laser semiconductor dice for optical telecommunication systems is very difficult because of the fragility of these new components, the necessity to bond them with very high accuracy in their location, and the necessity to have a very homogeneous bond with a low thermal resistivity. A new bonding equipment has, therefore, been developed for this application: it can be used for preform, eutectic, or epoxy bonding, and naturally with many other components. Compared with other bonding equipment, such as preform or eutectic scrubbing, it presents the following advantages: the bonding is initiated and homogenised with an ultrasonic vibration of very small energy and amplitude which does not damage the laser dice; the workholder is built with a very small thermal inertia in order to prevent degradation of the bond when indium or tin alloy preforms are used; and it allows very high accuracy in the location of the dice. The results obtained with indium and epoxy bonding show that this equipment is particularly suitable for laser die bonding, and it permits the use of epoxy creams for this application in spite of their relatively low thermal conductivity.
Hermetic Sealing of Kovar Hybrid Packages by Laser Welding
Authors: Norrman S. , Torstensson P.A.
Published: February 2008

Laser welding of Kovar (54% Fe, 16% Co, 29% Ni, <1% Mn, Cr) has been evaluated in order to develop a reliable welding method for hermetic encapsulation of hybrid packages. In particular, the design of the welding joint and the impact of Au/Ni plating on the joint quality have been examined. It has been found that for the specific combination of case and lid used, the sealings are hermetic (leak rate <2 × 10−9 mbar l/s) if the following requirements are fulfilled: the contact area of the case against the lid is ground; the case and the lid are unplated or Ni electroplated (2–5 µm); when using a Nd‐YAG laser the pulse time is relatively long (furthermore the pulse power shall be low in order to avoid splatter of molten metal into the case); the welding is performed in a pure N2 gas flushed covered chamber; the joint is formed in such a manner that the molten metal ‘runs over’ the edge of the case. In addition, it was found that Au plating increases the probability of gross point leaks. When there is an increasing percentage of Au in the joint, the number and size of the leaks also tend to increase. Finally, material analysis including SEM and EDX is reported together with details of weld schedules, equipment and a comparison with the reviewed literature.
Future Trends and Developments in Circuit Technology
Authors: Barnwell P.G.
Published: February 2008

The effects and implications of current developments in interconnection technology on print and fire thick film hybrid manufacture are discussed. Particular emphasis is given to the fact that in many cases new techniques complement rather than compete with film hybrids. Alternative substrates, semiconductor packaging, semicustom integrated circuits, surface mount technology and polymer thick film are all included in the paper. Conclusions are drawn which indicate that although these technologies are all of crucial importance they will not replace current thick film technology.
High Speed Thick Film Fuses
Authors: Marriage A.J. , McIntosh B.
Published: February 2008

The increasing use of small, expensive, complex electronic systems using VLSI chips has created the need to develop fail‐safe protection devices with a fast acting response working in a low voltage and low current range that are compatible with modern assembly procedures. This paper shows that 3‐layer co‐fired thick film fuses are capable of very high speed protection for low voltage circuits. Their small size enables them to be incorporated in a total circuit or made as surface mounted chip components.
Drawbridging of Leadless Components
Authors: Klein Wassink R.J. , Verguld M.M.F.
Published: February 2008

Drawbridging or Stonehenge Effect of leadless components (i.e., the standing up on their end faces) has been investigated. An explanation is offered based on a straightforward theoretical model considering surface tension, sustained by a great amount of experimental evidence. The phenomenon is strongly associated with condensation reflow soldering, whereas the dimensions of the metallisation at the underside of the leadless components and the size of the solder lands on the board are major influencing factors. Practical hints are given to overcome the problem.
Protective Thin Film Coatings by Plasma Polymerisation
Authors: Sadhir R.K. , Saunders H.E.
Published: February 2008

The paper describes the plasma polymerisation process for depositing ultrathin films. Such films, deposited from monomers containing hydrophobic elements such as hexafluorobenzene and hexamethyldisiloxane, showed excellent water vapour barrier properties, due to dense, highly crosslinked and rigid structures of the films. The composition and structure of the plasma polymerised films have been elucidated by ESCA and infra‐red spectroscopy.
Low Temperature Co‐fired Tape Dielectric Materials System for Multilayer Interconnections
Authors: Steinberg J.I. , Horowitz S.J. , Bacher R.J.
Published: February 2008

Modern complex integrated circuits require more input/output connections and operate at faster switching speeds and higher power levels than was the case before LSI and VLSI devices. As a result, there is a need for packages with high electrical conductivity, low dielectric constant, high thermal conductivity, precise line resolution and low unit cost. Ideally, it should also be possible to include resistors and for the package to be manufactured in‐house for maximum control. Multilayer printed circuit boards, complex multilayer hybrid circuits and high temperature co‐fired ceramic packages have been used to accomplish the interconnection of complex ICs. A new technology has been developed which combines the benefits of thick film with the processing advantages of co‐fired ceramic. The thick film process begins with a bare substrate, usually 96% alumina, upon which gold, silver alloy or copper metallisation, and screen‐printable dielectric paste are applied. Processing is a series of printing and firing operations; the firing temperature is usually between 800°C and 1000°C. Interconnecting vias are typically formed by screen printing and are usually a minimum of 250 ?m (10 mil) in diameter. The high temperature co‐fired approach uses no substrate. Printing of tungsten, molybdenum or molymanganese metallisation is carried out on alumina tape dielectric. The vias are formed by mechanical punching and are typically a minimum of 200 ?m (8 mil) in diameter. A single firing is performed in a special atmosphere, usually at 1500°C. This paper describes a new materials system which consists of a tape dielectric and gold, silver and silver/palladium inner layer and via fill conductor compositions. Circuits and packages made with the system are fired in an air atmosphere in standard thick film furnaces and are compatible with other conventional thick film materials. The process for making these parts is described and critical process parameters are identified. The results of reliability testing under temperature, humidity and bias are discussed and supporting microstructural analysis is presented.
The Characterisation of Novel PWB Substrate Materials for Leadless Ceramic Chip Carrier Attachment
Authors: Brierley C.J. , Pedder D.J. , McCarthy J.P.
Published: February 2008

The problems associated with the direct attachment of leadless ceramic chip carriers (LCCCs) to conventional PWB structures subjected to ambient thermal and power (on/off) cycling are now widely documented. The reliability of LCCCs mounted on various novel substrate materials has been assessed here during ambient thermal cycling from −55° to 125°C and −20° to +70°C and during power heat cycling. Polyimide Kevlar material was rejected on the basis that microcracks, formed in the laminate during thermal cycling, propagated to the surface and resulted in copper track breakages. A flexible laminate interconnection structure for strain relief was found to be too cumbersome for most applications and gave only a small reliability improvement. Polyimide quartz and copper‐invar‐copper cored materials were both found to give a high degree of reliability in thermal cycling. The metal cored laminate is preferred because it is also a more rigid structure with the better thermal conductance needed for many high performance and reliability applications. An elastomer coated FR4 material also performed well during lower temperature thermal and power cycling tests and represents a reduced cost option for less severe environments.
The Interaction Between Thick Film Conductors and Low Ohmic Resistors
Authors: Hrovat M. , Jan F. , Kolar D.
Published: February 2008

For thick film resistor materials with low sheet resistivity (less than 10 ohm/□) sheet resistivity increases with decreasing resistor length, when terminated with Pd alloy based conductors. This is due to the reaction of palladium from the thick film conductor and bismuth ruthenate (Bi2Ru2O7), which is the active phase in thick film resistor material. The experimental results indicate the formation of Pd/Bi solid solution on the interface between the conductor and resistor. Because of its higher specific resistivity, this layer functions as an additional source of resistivity.
Piezoresistive Properties of Thick‐film Resistors An Overview
Authors: Prudenziati M. , Morten B.
Published: February 2008

The paper gives a review of the present knowledge of the piezoresistive properties of thick‐film resistors (TFRs) and shows how they have been exploited for the implementation of strain‐related physical‐quantities transducers. Two types of device are described in some detail. These achievements were made possible by a proper choice of resistive and conductive pastes and their firing conditions, since only in this case useful piezoresistive properties can be achieved that make TFR strain gauges competitive with metal and semiconductive materials. After examining some correlations between gauge factors, composition and structure of TFRs, new data are presented showing how the strain sensitivities may be changed by varying the peak firing temperature, dwell time and the nature of the chemical elements which diffuse from terminations in the films.
Wetting, Leaching and Solder Adhesion of Copper Thick Film Conductors on Alumina and Multilayer Glasses
Authors: Leibfried W.
Published: February 2008

This paper outlines methods and results of wetting, leaching and adhesion analyses on copper thick film conductors over alumina and multilayer glasses after different processing conditions. The intention is to provide a better background for evaluating and optimising materials and processing conditions in copper thick films and working out quick, reliable and quantitative methods for better characterisation of copper conductors in production. For these reasons the following methods were used: (a) wetting and leaching analyses with a scanning wetting balance, working in nitrogen, (b) pull tests with solder contacts on copper thick film conductors after soldering, ageing and thermal cycling, and (c) some additional surface analyses (REM, EDX, Auger) for a better understanding of copper pastes and their material interactions, when processed under different conditions. The results are summarised under three general aspects: surface structure and wetting of copper thick films, wetting and leaching of various copper thick films after different processing conditions, and finally the influence of different wetting properties of such surfaces on the solder adhesion strength after soldering, ageing and thermal cycling. The results give good insight into the various interactions of copper thick films with their substrate materials and confirm the ability of the described wetting and leaching analyses for these purposes.
Bond Strengths of Inner and Outer Leads on TAB Devices
Authors: Liljestrand L.‐G.
Published: February 2008

Chips with 43 leads mounted on three layer tapes were outer lead bonded to different substrates. The substrate materials were ceramics with Cu thick film, glass fibre reinforced epoxy, Cu‐lnvar‐Cu with polyimide coating and ceramics with polyimide coating. The strengths of the inner and outer leads were measured before and after storage at elevated temperature, vibration test and temperature cycling. The initial pull strength distributions of the outer lead bonds on the different substrates were analysed. The bond strength on ceramic substrates with Cu thick film was slightly lower than on the other substrates. TAB devices on all substrates endured 750 cycles or more when tested between −55°C and 125°C. Owing to the rather large difference in the coefficient of thermal expansion between the ceramics and the Cu leads, failures occurred first on the ceramic substrate. Storage at 200°C for 2000 h resulted in a somewhat reduced inner lead bond strength. Two mechanisms were responsible for this. The most severe process was interdiffusion between Al and Au across the barrier metal (Ti/W). The second process was diffusion between Cu and Au with the subsequent formation of Kirkendall pores in the Cu leads.
Thermal Management Evaluation of Large Size Thick Film Hybrids
Authors: Bilson R.T. , Allen R.W. , McCarthy J.P. , Stanley A.J.
Published: February 2008

Successive over‐relaxation methods have been applied to solutions of Poisson's equation for temperature distribution analysis of a number of metal reinforced and metal cored thick film substrate models. These include aluminium and copper clad invar reinforced alumina as well as dielectric coated steel and titanium substrates. The results of the computer analyses have been compared in some instances with actual measurements of temperature distributions in real structures. Some detailed inconsistencies have been found but good correlation has been shown in terms of ranked effectiveness.
Philosophy of Thick Film Materials Development
Authors: Setty M.S.
Published: February 2008

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.
ISHM news
Authors: Sinnadurai Nihal , Kersuzan G. , Sonde B.S. , Herod Boguslaw , Waterfield Brian C. , Knowles J.B. , Stein M.A.
Published: February 2008

I was an invited speaker to the ISHM‐Benelux meeting. As I arrived early, I also sat in on the committee meeting as an observer. Jos B. Peeters was the outgoing president and the incoming committee was widened to about 15 members compared with the previous 6. Following the unanimous election of all those nominated, the committee reconvened and elected Mr Kwikkers as the new president of ISHM‐Benelux. He is a professor at the Technische Hogeschole in Delft.
New U‐Cut Algorithmic Trimming for Lightning Protection
Authors: Lejeune B.
Published: February 2008

Large ohm film resistors that guard sensitive telecommunication devices against the hazards of lightning require a set of exacting characteristics for tolerance, endurance, and productivity. These characteristics largely depend on how the resistor is trimmed. Conventional laser trimming is unable to provide all the requirements for this important resistor application. A new technique developed by Teradyne Inc. called Algorithmic Trimming employs an algorithm and data base to calculate real‐time trim vectors that are used in a trimming hardware processor to overcome the drawbacks of conventional trimming. With this new technique 50‐ohm film resistors were trimmed to specification with 0·1% tolerance while attaining high resistor stability and a trim time of 300 milliseconds.
Hardness Measurements in a SEM as a Quality Test for Thin Films
Authors: Bangert H. , Kaminitschek A. , Wagendristel A.
Published: February 2008

Hardness testing using a SEM offers visual observation and measurement according to the hardness definition even for submicroscopic impressions. It can provide information on plasticity, homogeneity, adhesion etc. which cannot be obtained from depth measurements alone. The device described operates inside a SEM and offers a load between 10−2N and 10−5N. The influence of test load, rate of load increase and dwell time on the results was examined on various materials.
Noble Steel: A Suitable Substrate Material in Thick Film Technology?
Authors: Budweit M.
Published: February 2008

In various publications noble steel is mentioned as a possibility for use as a substrate in thick film technology processing. The possibility to cut, stencil and drill steel sheets to desired shapes and the attractive price difference compared with alumina as well as PC board materials justified an investigation. A variety of steel sheets in various formulations from various vendors is offered on the market as well as ceramic pastes for thick film applications. This investigation aims to find out the most suitable ceramic paste for coating steel substrates in a common thick film process.
Surface Mounting Reliability
Authors: Lynch J.T.
Published: February 2008

A review is given of the reliability of the ceramic chip carrier when solder‐attached to alumina thick film substrates. It is shown that no degradation occurs during humidity cycling or humidity steady state tests. Some diminution of the solder joint strength takes place during prolonged high temperature storage and temperature cycling but the effect is much more marked during power cycling. The effect of flux residues on thick film hybrids after solder reflow of surface mount components is assessed. No significant deterioration of any component, printed or discrete, that is attributable to flux is observed, given adequate cleaning techniques. The reliability of the ceramic leadless chip carrier is compared with both leaded ceramic and metal and plastic surface‐mountable components. The compliant leads of packages offer some advantages over the leadless chip carrier where thermal excursions are important but the leads themselves are easily damaged. Plastic packaging for surface‐mountable components continues to improve and become increasingly popular but potential reliability hazards associated with a thermal management performance inferior to that of ceramic and metal versions, moisture ingress and corrosion are seen to remain problem areas.
Atmospheric Corrosion Tests on Pd/Ag Thick Film Conductors
Authors: Hendriks A.H.C.
Published: February 2008

The influence of corrosive gases on the solderability of palladium/silver thick‐film conductors has been investigated. An experimental set‐up for atmospheric corrosion testing has been constructed in which atmospheres can be created comparable to a heavily polluted industrial environment. Various Pd/Ag thick‐film conductors have been submitted for 14 days to flowing atmospheres containing 1 ppm SO2, 15, 0·2 or 0·04 ppm H2S, 1 ppm NO2, 1 ppm O3 and 0·05 ppm Cl2, separately or in various combinations. When used separately, only H2S causes a poor solderability of the thick‐film conductors. This effect on the solderability turns out to be independent of the H2S concentration; even concentrations as low as 0·04 ppm cause identical corrosion phenomena. The other gases mixed with H2S have a synergistic effect on the corrosion process.
Company profile
Authors: Cullen Lorna , Waterfield Brian
Published: February 2008

The success of a company can be measured by many different yardsticks. Criteria taken into consideration may include for instance the ability to innovate and to develop high quality products; the expansion of a small group of products into a wide range that provides a complete package for a specific industry; the capacity to cater for a multiplicity of end applications; or growth in sheer physical size that necessitates a move to extensive purpose‐designed premises. Success can be reflected too in the acquisition of an ever expanding market in geographical terms, and in the gaining of a respected reputation worldwide.
Non‐conventional Applications of Thick‐film Technology
Authors: Dell'Acqua R.
Published: February 2008

Thick‐film technology to implement passive elements, network and hybrid circuits has been widely used for four decades and its importance is still growing. While on one hand the technology has been improved to meet the requirements for more sophisticated circuits, on the other hand a better knowledge of its outstanding properties has promoted its application to a certain number of sometimes exotic devices, many of which are in the sensor and actuator area. This paper presents examples of a variety of applications to illustrate what thick film technology can offer outside the familiar area, and to stimulate the imagination of scientists towards possible new applications.
From Soldering Iron to Laser A Review of Soldering Methods for Surface Mounting
Authors: Becker G.
Published: February 2008

Soldering techniques for surface mount technology are still in their early stages. Therefore, a survey is given of the main soldering methods which are currently used in research and production as well as those which are expected to come into use, such as wave soldering, infra‐red soldering, vapour phase soldering and laser soldering. These techniques are influenced by both the component and board design. Even in soldering surface mount components, a number of rules must be observed in order to produce a good solder joint.
A Test Substrate for Thermal Analysis of Hybrid Circuits
Authors: De Mey G. , Demolder S.
Published: February 2008

This paper describes a simple test configuration which allows an analytical solution for thermal analysis. Comparison with experimental measurements has been undertaken and complete agreement has been found.
Temperature Behaviour of the Bowing of Multilayer Thick Film Substrates
Authors: Storbeck I. , Leitner G.
Published: February 2008

The bowing of thick film substrates, wholly covered with copper pastes of the Du Pont base metal system DP 9922 and 9924, with one, four and ten layers has been measured from room temperature up to 700°C. It could be shown that the bowing does not, as expected, decrease uniformly with increasing temperature up to the softening point of the glass, but a change occurs in the curvature of bowing between about 80° and 100°C. By removing the copper layers the glassy interlayer could be investigated on the substrate. Its temperature behaviour is quite linear up to the softening point and the curvature is in contrast to that of the complete copper layer on the substrate. The superposition of the curvature of the metal and the glassy interlayer leads to the above‐mentioned change in the curvature of the complete copper layer. The deviation of the bowing that was found experimentally and that calculated by means of the plates theory, discussed in a previous paper, can therefore be explained by that change in the curvature and by a plastic deformation process in the copper. The values are caused by a reduction of stresses by plastic deformation in the metal during the cooling process. These results offer some possibilities for a reduction of the bowing of multilayer interconnection modules for use in hybrid microelectronics.
Surface Mount Design and Assembly for High Density Complex Modules
Authors: Anderson S. , St Jean J.
Published: February 2008

A packaging system has been developed using surface mounted components on ceramic substrates for conductive‐cooling applications. This has resulted in a high density, high reliability, and highly producible product. A 20 square‐inch module can mount up to 150 leadless chip carriers and can dissipate up to 30 W with a maximum junction temperature (Tj) of 90°C. Design guidelines, processing, and assembly techniques geared to surface mount devices for this high density ceramic thick‐film multilayer interconnect board will be presented. Constraints regarding the thermal characteristics and physical dimensions of the devices and the limitations of CAD routers, processing equipment, and automatic assembly equipment will also be discussed. Design guidelines regarding the electrical characteristics, such as capacitance and resistance in terms of layout and processing, will be defined. Timing criticality and busing layout guidelines will be discussed. Processing design considerations such as power and ground planes, conductor layers, layout boundaries, and surface mount footprints will be outlined. Other considerations taken during the placement, routing, and artwork phases will be presented, as well as those items to be considered during the processing flow. The assembly process will be discussed emphasising problems that can be encountered with tinning, placement, reflow, and cleaning. Rework of defective surface mount components will be reviewed in addition to considerations for design modifications.
A Review of Thin Film Resistors and their Assembly Problems
Authors: Hughes J.E.
Published: February 2008

This paper will be presented in two parts. Part 1, after an introduction to thin film resistor technology, gives a review of thin films and other resistors, followed by designer's considerations when using resistors and networks. Part 2 will deal with assembly problems.
Thick Film High‐power Attenuators for Microwave Frequency Range
Authors: Fitt J. , Reimann J. , Thust H.
Published: February 2008

Microwave and thermal problems in manufacturing high‐power microwave attenuators are considered and some proposals of thick film solutions are presented. Theoretical considerations have been confronted with the results of measurements.
The Origins of Surface Mounting
Authors: Kirby P.L. , Pagan I.D.
Published: February 2008

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.
Intelligent Thick‐film Gas Sensor
Authors: Hoffheins B.S. , Lauf R.J. , Siegel M.W.
Published: February 2008

An intelligent gas sensor has been developed using thick‐film 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.
New Package Cooling Technology Using Low Melting Point Alloys
Authors: Fukuoka Y. , Matsumoto E. , Ishizuka M.
Published: February 2008

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, Bi/Sn/In and Bi/Pb/Sn/ln, whose melting points were less than 80°C 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.
Prospects for Molecular Electronics
Authors: Barker J.R.
Published: February 2008

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 inter‐disciplinary activity—molecular electronics—which holds long‐term 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, Langmuir‐Blodgett 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, self‐organisation and self‐assembly which are unique to molecular systems.
Conventional Techniques for the Production of High Density Interconnects
Authors: Kidd J.
Published: February 2008

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 today—with circuits containing 250 µm 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 µm lines and spaces are readily printable under controlled conditions, and a complete 120 µm 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.
Automotive Electronics: Where Are We Going?
Authors: Dell'Acqua R. , Forlani F.
Published: February 2008

The need for better performance, safety and comfort is the driving force behind the dramatic growth in car electronics. The key to success depends mainly on system reliability and cost which in turn are related to the choice of technological approach. The basic topics to be investigated are, on the one hand, system architecture and, on the other, the implementation techniques involved. Large scale integration of a consistent portion of the system will be necessary but other factors such as interconnections, packages and so on must also be taken into account. The variety of boards, components and assembly techniques currently available are just adequate for present needs, but for the 1990s the continuously increasing complexity of automotive electronic systems will probably necessitate better use of what is available and possibly new ideas.
Copper Ball/Wedge Bonding to Copper Thick Film
Authors: Winkle R.V. , Cater S.R.
Published: February 2008

This paper describes the first of a two part study of copper ball/wedge thermosonic wire bonding and concentrates on the second wedge bond to copper thick film. Results of varying the bonding machine parameters of force, amplitude of vibration, weld time, substrate temperature and bonding direction on bond strength are discussed and optimum conditions to give maximum yield suggested. Methods of providing adequate gas shielding of the wire and substrate and the effect of wire ductility are also presented. Particular attention has been given to improving the accuracy and speed of testing of the loop pull test by correcting for variations in wire loop geometry. A method will be described for measuring loop height automatically during each test and the incorporation of a computer to obtain corrected values of force.
A Review of Thin Film Resistors and Their Assembly Problems
Authors: Mills D.
Published: February 2008

This paper has been presented in two parts. Part 1, after an introduction to thin film resistor technology, gave a review of thin films and other resistors, followed by designer's considerations when using resistors and networks. Part 2 will deal with assembly problems.
Thermal and Electrical Characteristics of Thick Film Overcurrent Protector with Self‐recovery
Authors: Sorimachi Y. , Tsubata I. , Miyauchi S.
Published: February 2008

A thick film overcurrent protector with self‐recovery has been developed using carbon black graft polymer. Carbon black graft polymer, henceforth called CG, is a thick film PTC thermistor material in which a polymer forms a three‐dimensional network structure around carbon blacks by graft‐copolymerising vinyl monomers. Since the CG material gives a large and stable positive temperature coefficient of resistance depending on the copolymer material, due to the difference of thermal expansion coefficient between carbon blacks and polymer, the stable thick film overcurrent protector with self‐recovery can be realised by using the CG material. The overcurrent protector utilises the dynamic current‐time characteristics of the CG element. When a very large current flows through the CG element, the temperature rises by self‐heating, and the resistance of the element increases dramatically; as a result it restrains the current at a lower level. Since this element is not destroyed after excess current flow, it can be used repeatedly, unlike a metal fuse. In this paper, the manufacturing process and thermal and electrical characteristics of the CG overcurrent protector are investigated, including an analysis of these characteristics.
Fatigue Fracture of Leads of SMT Components Caused by Ultrasonic Cleaning
Authors: de Kluizenaar E.E.
Published: February 2008

Ultrasonic cleaning is an effective aid in the removal of flux residues from surface mounted circuits. However, an over‐intensive and too extended ultrasonic load of surface‐mounted 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.
Copper‐On‐Ceramic Technology Development
Authors: Porter M.
Published: February 2008

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 Copper‐On‐Ceramic Technology. The philosophy of using BS 9450 principles to achieve a mature, fully documented process is outlined.
Copper Ball‐wedge Bonding and Its Problems
Authors: Tielemans L.
Published: February 2008

An evaluation of the feasibility of copper ball‐wedge 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 ball‐wedge 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 ball/wire. Bonding mechanisms are similar for bonding on thick film to those for bonding on metallisations. Matching hardness of the substrate to the ball/wire seems to be a necessity for proper ball‐wedge bonding.
Multichip Technology—Something for everyone?
Authors: Balde Jack
Published: February 2008

Each of the three major branches of interconnection technology has begun to focus its attention on Multichip Modules. The semiconductor manufacturers call the technology ‘The New Wafer Scale’ and use silicon‐on‐silicon constructions, but use organic insulating layers on the mother slice, permitting copper conductors instead of aluminium as used for the older silicon dioxide as the insulating material.
Economic Justification For Hybrid Substrate Testing
Authors: Crowley D.F.
Published: February 2008

This paper focuses on the economic justification for testing unpopulated hybrid substrates. The return on investment (ROI) for substrate testing is based on the high value added in material and labour after substrate fabrication. The data required to calculate the ROI on testing are presented. The factors influencing the selection of the test method are discussed.
Abruzzo, Italy
Authors: Turnbull R.B.
Published: February 2008

Terminal 1 at London's Heathrow Airport is not one of my favourite rendezvous locations, especially before 8.00 a.m. on a Sunday morning. However, Sunday 5th June was an exception; it was during the Anglo‐Italian week for the Abruzzo region and I was one of a mixed party representing industrial, banking, clothing, food and agriculture, tourism and, last but not least, the press. The objective was to learn something of what the region had to offer in preparation for 1992 when there will be free trade throughout Europe.
Company profile
Authors: Turnbull R.B.
Published: February 2008

We continued our brief visit to Germany with an easy day's drive through the Black Forest to Eastern Bavaria. From a good vantage point one could see the distant Alps with their air of peace and serenity. However, they seemed to represent a different world for we were in the centre of München (I wonder why we call it Munich?) with its complex motorway rings and busy traffic. Close to the inner ring is the Munich Technology Centre, a modern building housing a variety of high tech companies including Munich Laser Systems.
SMT/ASIC 88, Sindelfingen
Authors: Cullen Lorna
Published: February 2008

Mention Sindelfingen to anyone involved in the electronics industry and they spontaneously refer to IBM, who have a major presence in the Sindelfingen/Böblingen area. To many others, it immediately springs to mind as the ‘home’ of Daimler‐Benz. The district is, however, far from totally industrialised, as coniferous forests clothing the hillside and lining a stretch of the Autobahn offer superb scope for weekend walks in the environs of this small town to the south‐west of Stuttgart.
The Theoretical Fundamentals of the Screen Printing Process
Authors: Riemer D.E.
Published: February 2008

The basic parameters of screen printing are discussed, and an analytical model of the screen printing process is introduced. The ink roll in front of the squeegee is treated as a pump generating, close to the squeegee edge, high hydrostatic pressure which injects ink into the screen meshes. The shearing of the ink, the mechanics of screen snap‐off and the ink transfer taking place behind the squeegee are also analysed.