ALBERT

Notes: In this work, commercial silver metal contacts welded on top of silver plated brass or brass substrates have been exposed to air rich in NaCl. Scanning electron microscopy and energy dispersive analysis of the exposed contact surfaces were performed to identify the corrosion by-products on top of the silver contacts, suspending wafers, and welding materials. Surface corrosion products were mainly found to consist of small spherules of Cu-Zn or Ag-Cu compounds which cover the surface of the contact proper with low adhesion properties. They mainly originate from the underplating wafer or welding materials. Electrical characterization of the contacting materials was based on dc temperature overheat tests, current switching cycle tests, and energy storage during ac current excitation. The experimental results display that the operating environment is indeed a very significant parameter determining the overall performance of the electrical contacts. New design rules as well as material selection properties may have to be systematically considered to allow for electrochemical induced degradation in saline operating environments.

Notes: This paper is concerned with the study of grease reaction by tribological stress. To observe the change of the viscoelastic properties by shearing the grease, rheometer tests were done. In addition to the flow behaviour, we investigated the friction process by using some tribometer. The tribological characteristics of the lubricant are determined with the help of energetic parameters. The interpretation of the results shows a correlation between viscoelastic properties and friction behaviour and an interesting dependence of storage modulus and shear stress. The results are considered to be useful information on the tribology of greases.

Notes: This paper discusses the lubrication of heavy load application and reports on a joint development project between the Technical University of Lulea in Sweden and Axel Christiernsson.

Notes: This report presents the results of a comparative test in which two similar new engines were run-in under identical conditions except that in one case a molybdenum disulphide suspension in oil was used as a crank case lubricant. The special testing rig is described and the results are presented in terms of comparative wear rates, determination of final ring profiles and SEM analyses of final ring surfaces. From this investigation it is concluded that the molybdenum disulphide additive is effective in modifying the mechanism of wear during running-in so that metal-to-metal contact is reduced and the change in surface topography is achieved mainly by plastic deformation rather than by an adhesive or abrasive wear process which mainly occurs when using conventional break-in oils.

Notes: Different percentages of calcium and lithium stearate greases were prepared using dimethyldi-2-ethyl-1-hexoxysilane and dimethyldi-1-dodecoxysilane as base oils by open kettle process and then were characterised. The performance of different greases has been studied by determining their apparent viscosity, consistency, dropping point, oxidation stability, anti-wear characteristics and moisture resistance. These properties are compared with those of tetra-2-ethyl-1-hexoxysilane and polydimethylsiloxane greases. Lithium stearate thickened greases exhibit better lubrication and heat resistance properties than those of calcium stearate and can be used for extreme temperature conditions in the range between –70°C and +220°C for automotive ball joints, aircrafts, antifriction, ball bearings etc.

Notes: Use of hydrotreated, hydrocracked and catalytically dewaxed base oils in hydraulic and industrial applications is increasing on a global scale. The hydrogenation and dewaxing processes involved in the manufacture of these products can result in base oils of exceptionally low aromatic content and sulphur level and raised viscosity index (VI). The aromatic content, sulphur level and VI are parameters used by the American Petroleum Institute (API) to categorize the base oils as Group II or Group III. The performance of additives in these Groups II and III base stocks differs from that in Group I base stocks. In addition, different processes used by different manufacturers will not only create different base stock oxidative stability and solvency from that of Group I base stocks, it will also create differences between Group II base stocks and between Groups II and III base stocks. Several different base stocks have been examined using methods including mass spectrometry and aniline point. Variations in properties, such as aromatic content, cycloparaffinic content and aniline point, appear to relate to differences in oxidation stability and solvency. With the improved response of Groups II/III base stocks to antioxidants, a performance level of 10,000 hours or greater in the ASTM D 943 is common. This necessitates addition of specific antioxidants which result in extended oxidation performance but lead in some cases to the formation of insoluble degradation products in Group II/III base stocks, and more so in Group I base stocks. Phenolic- containing and phenolic-free antioxidant systems have been identified that allow for extended oxidation stability in a wide range of Group II base stocks without sludge formation in either Group I, II or III base stocks.

Notes: The effect of different kind of pigments on the corrosion resistance properties of an epoxy paint has been investigated using electrochemical impedance spectroscopy and open circuit potential measurements. Painted naval steel samples were studied during the exposure to artificial sea water. The epoxy paint coatings were prepared employing red lead, zinc, red iron oxide or titanium dioxide as pigment with 0.8 of PVC/CPVC ratio. From the EIS and corrosion potential data analyis was found that the anticorrosive protection given by an anticorrosive (pigmented with red lead) and a top coat (pigmented with red iron oxide) epoxy painting scheme was both more lasting and more effective. This was attributed to the fact that both the effective adhesion provided by the chemical bonding between the steel surface and the epoxy paint groups and the constant high barrier effect afforded by this type of top coat were a perfect complement for the high corrosion inhibitive capacity of the red lead pigment.

Notes: Summarizes briefly the dramatic advances made in the reliability of mechanical seals for rotating shafts in the process chemical and petrochemical industries over the last 30 years. Shows that expected mean time before failure has improved from tens of days to years over that time.

Notes: Describes the structure and rheological characteristics of soap based greases and how the thickener retains the oil phase. Illustrates the thixotropic behaviour and effect of time of shearing on friction, film thickness, noise energy loss in grease lubricated contacts. Shows how friction can be less with grease than with oil.

Notes: Details the performance requirements of modern automotive engines and the role played by additives in fuels and in engine and transmission lubricants. Outlines problem areas needing attention.

Notes: Describes highly reactive polyisobutene production and use as an additive in automotive fuels and in a wide range of lubricants. Lists polyisobutene manufacturers and their productive capacities.

Notes: Outlines the history of BASF and details its production facilities including investment costs. Lists the products of the Antwerp plant with its integrated production. Details the production of highly reactive polyisobutene and its use within BASF for the production of polyisobutene amine.

Notes: Describes the testing and lubricating mechanisms of Slick 50, a solid lubricant engine oil additive containing PTFE for reducing friction and wear. Gives the results of long term engine tests by the Southwest Research Institute, Texas, monitored by radioactive tracer, exhaust emission analysis and fuel economy improvement. Offers Slick 50 as an alternative to zinc phosphorus additives.

Notes: Describes SKF's three new spherical roller bearings, E for smoother running, VA 405 to resist vibration and CARB for axial displacement and misalignment. Gives a paper mill as an example of the successful use of CARB.

Notes: External and internal gear, duocentric and sliding vane oil pumps used in internal combustion engines are illustrated and described briefly.

Notes: Details the friction and wear testing facilities offered to civilian customers by the DRA and lists recent projects. Cylinder and ball on plate fuel lubricity and fire resistant hydraulic fluid tests are described with line drawings and the results obtained tabulated.

Notes: A reciprocating sliding pad on plate boundary lubrication friction test is described. Typical friction waveforms are shown and compared with the output from an automated measuring system based on a digital storage oscilloscope.

Notes: Examines the issues surrounding fuel lubricity by explaining the background to the problems surrounding lubricity in diesel engines. As the need for low sulphur diesels arose it became clear that a universally accepted bench test was required and ISO working group SC7/WG6 was set up in 1992 to decide on a standard test. The group recommended that an HFRR (high frequency reciprocating rig) ball-on-flat test should be adopted. Describes the test methodology.

Notes: Outlines the history of the specialist lubrication group of the Institution of Mechanical Engineers - which was originally called the Lubrication Group and is now the Tribology Group. Describes how the organization was formed and lists its achievements, special activities and publications. Concludes by looking to the future, stating that the group has developed a dynamic five-year plan to take it into the next century.

Notes: Reports in improvements in the gear industry since 1993, and provides details of six projects carried out by the British Gear Association and the Gear Research Foundation. Briefly discusses the Navy and Vickers Gear Research Association research and the work of the Technical Committee. Finally discusses marketing strategy for Germany and Italy.

Notes: Describes various exhibits at the Coach and Bus 1995 exhibition. Discusses the development of liquid petroleum gas run vehicles, their benefits (reduced noise and pollution) and problems. Provides details of emission regulations for vehicles.

Notes: Discusses developments in coatings using high velocity oxyfuel (HVOF). Covers the basic process, comparisons with other thermal spraying processes and optimization of performance. Discusses industrial applications and new developments in the technology.

Notes: Provides a brief summary of the use of CFCs and HCFCs in general and marine refrigeration, and the ban on the use of CFCs. Discusses alternative refrigerants, and their advantages and disadvantages. Reviews refrigeration compressor lubrication and recent developments.

Notes: Modern engines place increasing demands on crankshaft systems, and thus bearings are required to have properties which conflict with the simultaneous need for strength and compliance under all operational conditions. Lists property requirements to describe bearing behaviour. Covers strengthening mechanisms for aluminium alloys, conformability tests, compatibility, metallurgical consequences.

Notes: Offers advice on lubricating roller chains which are widely used in mechanical handling and transmission systems. Despite their importance they are often a neglected component. Gives details of the most appropriate oils or other lubricants to use at varying temperatures and in different operating conditions.

Notes: Reviews recent advances in shaft sealing technology, aimed at reducing maintenance cost by improving reliability. Looks in detail at the evolution of the conical seal housing and the magnetic drive. Reports on a research programme initiated three years ago involving user representatives, mechanical seal manufacturers, pump manufacturers and the British Hydrodynamics Research Group. As a result, five different seal designs were tested. Concludes that magnetic drive pumps are very reliable and that ultimately the use of a mechanical seal or a magnetic drive rests with the user in discussion with the pump manufacturer.

Notes: Explains that metal has been replaced by plastic for some moving components in the engineering industry. However, conventional lubricants are inefficient or even damaging when used for plastics. Describes the range of lubricants developed by Molykote specifically for plastic components. Concludes with a brief history of Molykote's parent company in Germany.

Notes: Outlines the various testing procedures carried out by BICERI, including engine fuel and lubricant testing. Describes the universal wear machine, and explains the three test modes: pin-on disc, block-on-ring and pin-on-reciprocating plate.

Notes: Describes a number of new greases, developed by Total Lubricants, at present on extended trials. Sets out the advantages of the new synthetic greases and their application in industry, and reports on "green" greases.

Notes: Provides a brief history of Glacier Vandervell Europe. Describes the range of new materials developed, which are manufactured alongside the more traditional materials. The range includes copper lead and lead bronze, aluminium-based materials and polymer bearings. Details further research taking place into interactions between components in the bearing system. Summarizes the testing processes at the new laboratory in Kilmarnock.

Notes: Describes polytetrafluoroethylene (PTFE) bearing applications and details the fluorocarbon range of PTFE-based compositions. Outlines the fluorocarbon organization and activities.

Notes: Describes the basic orbital combustion process X engine and gives the specification of the lubricant required. Sets out the objectives of a programme for the development of a lubricant for the IAPAC two-stroke engine being developed in France and Italy. Also describes ELEVATE, another development engine.

Notes: Gives the results of trials conducted in China which show the use of top-grade, low smoke, part synthetic two-stroke oil gives better performance and four times longer engine life than the four-stroke engine oils generally used to lubricate two-stroke engines in China. Sets out existing and proposed international standards for two-stroke engine oils.

Notes: Outlines the use of rubber, ceramic, metallic and plastic coatings to protect pump components from corrosion and abrasive wear. Describes in detail the products of two specialist companies in this field and gives examples of their uses.

Notes: Uses the case of a continuous-flow travelling oven to illustrate the use of carbon bearings in adverse environments which preclude the use of lubricants. Gives more general information regarding the use of carbon-graphite bearing materials for a variety of applications.

Notes: Presents the comparative surface roughness measurement data from a paper on the wear of filled PTFE lip seals in contact with a variety of different surfaces, as reported in a paper from the University of Stuttgart Institute of Machine Elements.

Notes: The technical properties of Crambe abyssinica oil prompted the co-operation between a research institute and a lubricant producer to determine some possible industrial applications. The results confirm the special physico-chemical characteristics of crambe oil which, compared with some vegetable or synthetic oils, shows a higher heat removal capability and interesting lubrication characteristics. The research establishes that crambe oil could be a good hydraulic fluid. These findings led to the cultivation of a suitable area with Crambe abyssinica to obtain a sufficient amount of oil for lubricant formulation on a commercial scale.

Notes: The more frequently an engine oil is changed, the more the overhaul life of the engine is extended but with an increase in the cost both of the oil and of the oil drain services. If engine oil is changed less frequently the associated costs will decrease. In order to find the optimum drain interval, it is necessary to establish the relationship between the cost of the oil and oil drain services and the cost of more frequent overhauls. Presents an investigation into the degradation of a proprietary lubricant marketed in Turkey, and the wear rate of a petrol engine driven in urban traffic. Lubricant samples were examined approximately every 2,000km for deterioration of the lubricant and evidence of wear of the engine components. From the experimental results, determines the optimum oil drain period of the engine.

Notes: Summarizes the results of a recent study of the US industrial lubricants industry. Highlights the negative effect on volume gains that inevitably will occur following the institution of fluid management programmes incorporating recirculation and recycling efforts.

Notes: Defines the four main routes for reclaiming used oils - recovery as fuel; reconditioning on site; oil laundering and re-refining. Places used oil re-refining in its historical context and presents profiles of the (only) two used-oil re-refiners in the UK.

Notes: Discusses the properties of various asbestos-free gasket materials, in particular expanded PTFE. Presents the factors which need to be taken into account when choosing a gasket. Highlights the requirements of gaskets in the automotive industry and the conditions they have to withstand.

Notes: States that magnetic fluids, in a zero leakage, non-wearing seal, offer an innovative solution to the problems of harmful emissions from rotating process equipment. Discusses the properties and uses of the new GT series of ferrofluids from AP&T Ltd.

Notes: Outlines the development of National Vocational Qualifications (NVQs) in the petroleum industry. In recent years in this industry a number of clear trends have emerged. There was therefore a call for the development of a number of NVQs with relevance to particular areas of the industry. As a result NVQs were established covering occupations such as bulk liquid warehousing, refinery process operation, oil boiler installation and maintenance and forecourt management. The NVQ consists of five separate units and is designed to cover all aspects of lubricant manufacture.

Notes: A valve train system which could work in the absence of lubricants could reduce engine oil consumption. Routes to produce such a valve system have been explored, and composites, mostly powder metallurgy (PM) containing solid lubricants, have been tried. The expectation from utilizing these materials, keeping, at least, unchanged the life of engine components, is a reduction in oil consumption and oil fog in the cylinder head and a big environmental benefit. Various sintered materials for three different engine components - valve cap, valve seat and valve guide - have been developed and tested by disk-on-disk and fretting tests, in cold and hot conditions, respectively. Prototype components were produced, and the successful ones were then evaluated by an engine endurance test. The sintered valve cap and guide gave very interesting results in terms of friction coefficient and reduction of environmental pollution. Discusses the tribological characterization and the evaluation of these sintered materials.

Notes: Focuses on oleochemicals, a natural alternative to mineral oils for use in liquid lubricants, metal working coolants, quenchants and hydraulic fluids. Natural oil based products generally have many advantages over mineral oils, including lower volatility, better inherent lubricity, higher viscosity index, higher bulk modulus, better fire resistance and better solvency. Details the manufacturing process.

Notes: Lubricants for four-stroke motorcycles have traditionally been rebranded versions of those used for passenger car engine lubrication. Recent developments in passenger car engine oils with the intention of improving fuel utilisation efficiencies were not compatible with some of the specific requirements of four-stroke motorcycle powertrain lubrication. The effect of using such lubricants on the various components of the motorcycle powertrain, including the engine, clutch, gearbox, starter system drive and back torque limiter is described. The subsequent development of a new specification specifically for use in four-stroke motorcycles is described.

Notes: Summary of an International Symposium entitled "The European Downstream Industry: A Vision for 2010", organised jointly by AFTP (French Association of Petroleum Technicians and Professionals), IP (Institute of Petroleum) and DGMK (German Society for Petroleum and Coal Science and Technology), recently held in Paris. Summarises a presentation of particular interest by J. Davidson. (Mobil Europe Lubricants nv) and R.B. LaPierre (Mobil Technology Company).

Notes: Problems associated with inadequate fuel lubricity were identified in the aeronautical industry in the 1960s, following a succession of in-flight engine failures. The influence of fuel composition upon fuel lubricity was established, as was the effect of various lubricity additives. Problems associated with inadequate fuel lubricity were also subsequently identified in light-duty diesel engines when low-sulphur fuel was introduced. Again, the use of additives or modifications to the refining process overcame the problem at the time, but the continuing trend towards higher injection pressures may require further improvements in current fuel lubricity. The manufacture and use of biodiesel is described, together with the attendant benefits, including use as a lubricity additive in conventional diesel fuel, also disadvantages. The imminent introduction of direct-injection gasoline passenger car engines has now focused attention on the lubricity of gasoline, which is again likely to become a key issue. Two standardised test procedures for the measurement of fuel lubricities are described.

Notes: Some of the mechanisms involved in the microbial colonisation and biodeterioration of metalworking fluids are described in an attempt to design a more realistic and meaningful laboratory assay procedure. The history of bioassay techniques is reviewed and the nature and composition of metalworking fluids is examined. Maximisation of the performance of biocides against micro-organisms and the influence of tramp oil contamination is assessed.

Notes: Suggests that a very low volume of lubricant is enough to improve the cutting operation because the area that requires lubrication is small. An estimate of the volume of lubricant necessary has been carried out (7.2ml h-1) and some comments are presented about results of previous experiments using extremely low volumes of lubricant (108ml h-1). The low volume of lubricant is applied in the same way as the conventional system. In these previous experiments the effect of lubrication is measured by surface finish, cutting force and workpiece temperature. The improvement in surface finish when low volume of lubricant is applied is similar to the results obtained with tests carried out using the conventional cutting fluid system. This improvement is not due to lubrication on the rake face to avoid built-up edge, but action on the machined surface after it has been formed.

Notes: Deals with the tribological behaviour of some ferrous, non-ferrous and polymeric materials, used for various applications in machine tools in dry conditions and when using solid lubricants, and the development of an empirical relationship of wear and friction dependent on influencing parameters. Some "Iso-Wear" curves have also been plotted for the purpose of obtaining values of the parameters and their treatment combination for a specific wear rate.

Notes: Crankcase lubricants for automotive and commercial use are differentiated by their physico-chemical properties but more importantly by their performance in a series of engine test sequences. The sequences are devised by committees formed by representatives from the vehicle manufacturers, the oil companies and the additive suppliers. The article describes the sequences devised by the American Petroleum Institute and the European ACEA organisations, including some historical background as well as the current specifications. Methods of compliance monitoring and enforcement are also covered.

Notes: The various types and application of bonded coatings are described, and their ability to reduce friction and wear. The composition and nature of the active ingredients are also covered, together with brief details of manufacturing processes. Examples are given of typical current application areas, although the potential of these types of coatings is such that the number of new applications is escalating rapidly.

Notes: Manufacturing methods of white mineral oils are described, together with a summary of their major use areas. Recent toxicological studies using white mineral oils of various categories are covered. A summary of the current acceptable daily intake levels for such substances is included.

Notes: Despite their outstanding combination of properties, titanium and its alloys are very susceptible to severe adhesive wear in rubbing with almost all the engineering surfaces and can exhibit poor corrosion resistance in some aggressive environments. Surface engineering research centred at the University of Birmingham has been focused on creating designed surfaces for titanium components. Great progress has been made recently through the development of such novel surface engineering techniques as thermal oxidation, palladium-treated thermal oxidation, oxygen diffusion and duplex systems. Such advances thus provide scope for designing titanium components for a diversified range of engineering applications, usually as direct replacements for steel components. By way of example, some of our successful steps towards titanium designed surfaces are demonstrated. To date, the potential of these novel techniques has been realised first in auto-sport and off-shore industries.

Notes: The various approaches to achieving extended drain intervals in vehicle crankcase lubricants are described, with particular emphasis on commercial diesel engines. The various lubricant contaminants include soot, water, acids and particulate metals. Lubricant life may be prolonged by suitable design of the lubricant and of the engine, but more particularly by reducing the levels of contaminant in the lubricant such that the performance of the lubricant may be maintained. At the same time, wear rates within the engine must be within acceptable levels. The various options for reducing the levels of contaminant include lubricant by-pass filtration systems, including barrier filters, refiners and centrifugal filters.

Notes: Traditionally the development process has been used to optimise engine lubrication systems with a lot of hardware testing. This can lead to an expensive and time consuming process which can have major influences on the engine design. To complement engine development, design and analysis principles have been developed for further optimisation and understanding of the lubrication system. To demonstrate this a case study is used illustrating good use of analysis tools, offering clear ways towards system optimisation. In addition, while engine designers have been improving their techniques, new components and oil formulations have helped push the boundaries of the lubrication system, giving better wear and friction characteristics and also increasing oil life.

Notes: This paper describes the development of the use of lubricant analytical programmes and trend analysis to optimise oil change intervals and to predict equipment failure. The various analytical methods are covered, as are the most frequently occurring lubricant applications where such condition monitoring programmes are most appropriate.

Notes: The paper describes the evaluation of the fretting wear performance of diesel fuel additives as opposed to the sliding wear performance which is normally evaluated, and in fact forms part of the diesel fuel specification. Variations in load, frequency and running time were employed to ensure that all conditions which were like ly to be encountered were properly evaluated. Clear differences were observed between fretting wear performance and sliding wear performance, which is significant in view of the fact that fretting wear is often a factor for certain components of the fuel injection equipment. Further work on establishing the repeatability, reproducibility and participating in a "round robin" series of trials is indicated.

Notes: The function of lead additives in petrol is described, together with the effects on various engine components of their removal. The corrosive wear mechanisms are described in detail, and the effect of alternative additives in reducing corrosion and wear are covered. A number of field case histories are described, including experiences in Sweden, where lead replacement petrol was introduced in 1992. The article concludes with a series of recommendations designed to minimise possible damage to engines caused by substitution of leaded petrol by LRP.

Notes: The main role of the gears is to ensure smoothness and noiseless service, required power transmission, precision of processing, necessary degree of efficiency and so on. Lubrication is of significant importance to the protection of gears from tribological processes which cause failure of gears. The aim of this study is to investigate the influence of lubricating oils on the reliability of gears. The experimental investigation of the influence of some industrial oils on the tribological behaviour of gears of machine tools has been carried out at a metalworking factory. The paper presents the following: the classification of industrial oils for gears; the flow-chart of the choice of the industrial oil for gears; the analysis of the symptoms and the causes of failure to gears; the reliability curves of gears in the function of tribological properties of lubricating oils under the operating conditions of investigation here presented. The reliability of gears was found to be affected by both the type of lubricating oil and the viscosity grade.

Notes: This paper considers how the throughput of the component assembly process can be maximised by the use of software tools. Optimum results are achieved if the tools provide an automatic, detailed analysis of the assembly process while providing the engineer with the opportunity to use his experience to further enhance any automatically generated results. The tools must consider the assembly process as a whole, rather than each stage in the process independently, in order to gain maximum benefit. Finally, the tools must be flexible enough to be able to perform an accurate analysis for all assembly environments.

Notes: The microstructure of the Sn-3.5wt%Ag/Cu and Sn-9.0wt%Zn/Cu interfaces after soldering at 250°C was evaluated. The cross-sections were investigated using a scanning electron microscope and energy dispersive X-ray to determine the interface layer structure and composition. Even though the cooling rate from soldering temperature to room temperature is rapid, this study indicates that the intermetallic compound is formed at the interface between the solder and the copper substrate for both the Sn-3.5wt%Ag and the Sn-9.0wt%Zn lead-free solders.

Notes: This paper describes a technique for the monitoring and control of the reflow soldering process. The technique combines state-of-the-art infra-red (IR) sensor technology, coupled with application-specific process monitoring and control software, providing a unique capability both to monitor product temperatures during processing and to modify the process settings. The development of techniques to allow variation of the heat transfer from the oven to the in-process printed circuit assemblies (PCAs) provides the means to adjust the soldering oven's process settings for each individual PCA. This automatic profiling ensures consistent thermal histories and optimises oven energy consumption. Archiving of the reflow profiles along with temperatures recorded for each PCA provides full traceability to the reflow process settings for each individual PCA. The incorporation of IR sensing technology also provides a means to monitor the performance of the process.

Notes: In recent years, efforts to develop alternatives to lead-based solders have increased dramatically. These efforts began as a response to potential legislation and regulations restricting lead usage in the electronics industry. Lead is extremely toxic when inhaled or ingested. As researchers began to focus on Pb-free solders, they recognized their value in high temperature applications (e.g. automotive manufacturing) where Sn/Pb solders do not meet the requirements. There are many factors to consider when developing lead-free alloys: manufacturability, availability, reliability, cost and environmental safety. Of these, the most challenging and time consuming is the reliability of alternative solders. The lead-free alloys available cannot be used as a drop-in replacement for the SnPb or SnPbAg. The introduction of lead-free solder alloys may mean having to use alternative component and PCB metallizations, PCB materials, solder fluxes, etc.

Notes: A computational model was established in this study to simulate cavity-down plastic ball grid array (PBGA) assemblies. Stress analysis was performed to investigate the solder joint reliability of a PBGA-PCB (printed circuit board) assembly. The packages under investigation had two different body sizes and two kinds of ball population. The diagonal cross-section of the assembly was modeled by plane-strain elements and was subjected to a uniform thermal loading. The solder joints were stressed due to the mismatch of the assembly's coefficient of thermal expansion (CTE). The accumulated effective plastic strain was evaluated as an index for the reliability of solder joints. Effects on solder joint reliability such as package size and ball population were identified. Furthermore, it was found that, unlike conventional PBGA assemblies, the outermost solder ball has the highest plastic strain for all cases in the present study. This peculiar phenomenon was further discussed with the consideration of package deformation.

Notes: The benefits of a "no flow" process have been well documented in the recent past. The limitations of the previously reported materials in current use have been overcome via a unique chemistry which can be tailored to the application. Room temperature storage, effective fluxing, coupled with minimal outgassing, and a choice of reworkability after reflow or, if rework is not required, a full cure, can now be achieved within a single materials technology. This paper describes the properties of the new family of materials compared to conventional post-deposited underfills. The development sequence and the procedure for characterisation of material properties, including the evaluation of the effectiveness of the fluxing action on a range of solder alloys, is documented. A typical application is described, outlining how a minimum of two process steps can be eliminated and how improvements in materials handling, process robustness, and ultimate yield, have been realised. A simple rework regime is also proposed, and the almost "drop in replacement" aspect of the new material is discussed.

Notes: The efficiency of cleaning of flux residues after various periods of ageing was assessed by measuring the ionic contamination removed in an Ionograph 500 SMD. The flux residues were removed from bare boards, and boards with through hole and surface mount components. The effect of different ageing temperature was also investigated. The work has shown that there is a maximum time interval following assembly during which cleaning should be carried out. The ionic contamination of aged assemblies with through hole and surface mount components were cleaned with varying efficiencies. The surface mount components were more difficult to clean. The use of brushing and scrubbing proved particularly beneficial for the through hole components. A proprietary cleaner proved more effective than the generic alternatives considered.

Notes: An overview of the mechanical behaviour of commonsolder types is presented, with particular emphasis placed upon those properties relevant to theperformance of soldered joints in service. The requirements for more sophisticated and complexinformation are highlighted in order to assist design for the increasingly arduous demands associatedwith miniaturisation.

Notes: The advances in miniaturisation and ever increasing complexity of integrated circuitsfrequently mean an increase in the number of connections to a component with simultaneous reductionin pitch. For these emerging smaller contact geometries, micro-laser connection technologies arerequired. The reliability of the connection plays a decisive rôle. Theimplementation and reproducibility of laser connections technology in micro-electronics depend ongood thermal contact between the two parts and high quality absorption of the material surface used. Laser energy can cause local melting due to overheating of the lead becauseof the low distance between lead and bump. This effect influences the reproducibility of the contacts.Even the slightest interruption in the thermal contact of the parts cancause non-reproducibility of the contacts. Materials with a higher quality of absorption, for exampleSn(32% ), can be soldered with a good level of reproducibility. This clearly differs from gold (4% ) orcopper(7% ) surfaces. Due to the low absorption of these materials it is necessary to use a laserwith a higher intensity to produce the same energy. Irregularities in the quality of absorption, laserinstability and thermal contact can not guarantee reproducibility of the interconnections with this highlaser intensity. The FPC (fibre push connection) system offers severalsolutions to the problems mentioned. This system enables the laser to be transported by fibre to thecontact parts. The end piece of the fibre serves at the same time as a pushing unit. The advantage of this system is that the attenuation heat of the fibre end surface is alsoavailable for the connection. This improves the use of laser energy. As part of the laser energy at theend surface of the fibre is transformed into thermal energy, independently of the absorption quality ofthe material used, connection of a gold-plated contact part is possible. By pressing the connecting partswith the tip of the fibre, optimal coupling is achieved. The reproducibility of different metallisations and the reliability of connections with a pitchbelow 100 µm are presented as well as further applications of this system.

Notes: In a production environment, the first process applied to a bareprinted circuit board is generally the application of solder paste. It has been reported that 60% of allrework is attributable to poor quality solder paste deposition. If this process is not understood or theincorrect selection of paste, screen/stencil or squeegee is used, then regardless of technical capabilitiesof the printer, it will not be possible to achieve accurate and repeatable quality of work. This paper reports on the basics of solder paste deposition with mathematical formulasand diagrams to support the correct selection of criteria. Most importantly, it is intended to assist in theselection process and provide an understanding of the reasons for selecting a specificsolder/stencil/squeegee to be used in conjunction with the printer. Written and compiled from aproduction (real world) view-point, this paper recognises that it is certainly possible to use anon-standard process parameter, and still achieve ultra-fine pitch print capability in laboratory or smallbatch scenario. But primarily this paper is a guidance and recommendation to achieve excellent results,with as large a process window as is possible for production purposes.

Notes: Reflow soldering in a controlled O2 atmosphere will lead to practical benefits in the wettingbehaviour of solder pastes. The required O2 level and its control depend on the solderpaste used and the solderability of the materials to be joined. For a typical application with eitherfine-pitch technology, multiple soldering or low residue solder paste, a lack of O2 controlcan cause soldering problems. Fine-pitch solder pastes today still do notshow an optimum slump behaviour, which is absolutely necessary to avoid bridging between IC leadsand to reduce the formation of solder balls during reflow. Using a low O2 atmosphere toreduce these defects can make a difference, but an improved slump behaviour through predrying of theapplied solder paste at 50°C or in a low pressure environment will be more effective. Spread of solder is in general better at lower O2 levels, but substantial improvements are only achieved if low residue pastes with low activation levels are reflowed. Even when the low residue paste is compatible with reflow in air, there is still a significant difference foundbetween 20 and 200 ppm O2. Reflow systems which show variations up to 500 ppm inthe preheat zones during loading, while maintaining 50ppm in the peak zone, will show non-wetting ordewetting when a 100 ppm O2 solder paste is used. The visual cleanliness of solderjoints is significantly improved at lower O2 levels because the flux residue will bedistributed differently over the solder joints. Bridging is initially determined bythe slump behaviour of the paste and the alignment of the paste pattern to the pads and the leads, butwhen the paste of adjacent pads slumps together before reflow, the tendency for the solder to pull backis influenced by the oxygen level. Wetting and spread of the solder on the lands are then an essentialfactor. All the proven benefits of a low O2 level are not worth the money spent on nitrogen if the consumption necessary to obtain the properly controlled O2 level is very high. When solderability or the solder defect level not an issue the benefits may notrepresent a value higher than the cost of the nitrogen consumed.

Notes: A study was performed which investigated the wettability of 63Sn-37Pb and 96.5Sn-3.5Ag solders oncopper and gold -nickel plated Kovar ™ using a rosin -based, mildlyactivated (RMA) flux, a water soluble organic acid flux (WS ),and a lowresidue (LR) flux. The quantitative metric was the contact angle, c, measured by the meniscometer /wetting balance technique. The first part of thestudy (Part 1) examined wetting performance following continuous exposure to25°C prior to testing. Then, a preheating step was introduced into the experimentalprocedure after flux application, but preceding the actual wettability test in order to simulate afactory reflow process; these results are presented in Part II of this study. Contactangles for the 63Sn-37Pb solder (215°C) on copper were22±2° with the RMA flux, 12±5° for the WS flux, and31±6° for the LR flux. Increasing the 63Sn-37Pb solder temperature to245°C improved wettability with the RMA and LR fluxes, but no change was observedwith the WS fulx. Theii 96.5Sn-3.5Ag lead -free solder exhibited poorerwettability on copper compared with the 63Sn-37Pb alloy, with contact angles of41±2° (RMA), 63±15°(WS) and39±4°(LR). For the gold -nickel plated Kovar™substrates, the 63Sn-37Pb solder at 215° had contact angles of15±3°, 35±6° and 29±6° for the RMA, WS and LRfluxes, respectively. The values were reduced at the higher test temperature(245°). The 96.5Sn-3.5Ag solder also exhibited good wettingperformance on the gold -nickel plated Kovar™ specimens compared withcopper. Analysis of the interfacial tension parameters, ?SF-?SLand ?LF ,exemplified the importanceof ?LF as well as the condition of the surfaces (?SF ) on wettability performance. A so -called 'combinedanalysis' of the 63Sn-37Pb and 96.5Sn-3.5Ag wettability data oneither copper or gold - nickel plated Kovar™ substrates was used to predict thesolder temperature dependence of wettability for the three fluxes and two base materials.

Notes: A test procedure was developed to assess the capillary flow wettability of soldersinside a confined geometry. The test geometry comprised two parallel plates with a controlledgap of constant thickness (0.008 cm, 0.018 cm, 0.025 cm and 0.038 cm). Capillaryflow was assessed by: (1) the meniscus or capillary rise of the solder withinthe gap; (2) the extent of void formation in the gap; and (3)the time dependence of the risen solder film. Tests were performed with the lead-freesolders 95Sn-5Sb, 96.5Sn-3.5Ag, and 91.84Sn-3.33Ag-4.83Bi. The capillary rise of the lead-free solders was less than that observed with the 63Sn-37Pb control. Reducing the solder surfacetension and contact angle improved capillary flow. Void formation by the non lead soldersincreased as the gap became smaller. The extent of voiding was determined primarily by the gapsize rather than the wettability parameters (contact angle or surface tension) of theindividual alloys.

Notes: Since establishing a low volume, high reliability surface mount technology(SMT) facility, a number of problems have been overcome as part of the learningexperience. The tailoring of processes for a flexible assembly area brought to light a number ofissues that traditional SMT facilities do not face. This paper describes the many processesoptimised by the SMT facility team in becoming an on-time, high reliability producer. The topics include the development of design standards, forming, tinning, stencil printing, andcomponent placement. Several producibility enhancements are also described in acase-study of a solder mask evaluation project. The paper describes the many processimprovements implemented over the past few years.

Notes: The contamination onSMT assemblies caused by a number of flux/cleaning variation has been investigated, with severalanalysis methods used to quantify the contamination. The results from analysis of test printed circuitboards (PCBs) using anion separation, conductivity, ionic contamination measurement, visual and SEMinspection, microsections and surface insulation resistance (SIR) methods were compared. The bestcleaning result was observed with the combination of water soluble (WS) solder cream and watercleaning. The best measurement method for cleanliness of PCBs was considered to beSIR measurement. For WS fluxes, the iconic contamination test offers effective measurement of theamount of residues left on the PCBs.

Notes: This paper describes work which has been conducted to estimate the magnitudes of thermal stressesdeveloped in the solder joints of electronic components during service. Finite Element Analysis (FEA)has been employed to predict the level of stress and strain in computer simulations of joints and thesepredictions have been validated by experimental thermal cycling tests. Future work is outlined includingthe incorporation of microstructural features into the FEA models. The overall goal of this research is topredict the service lives of electronic components under various operating conditions, thus facilitatingthe introduction of novel components and materials.

Notes: The development and characterisation of a prototype solderability reference standard basedon a gold-plated nickel sample has been described previously. This material has nowbeen tested in an intercomparison with several European laboratories. The results presented here showthat a high degree of repeatability is achievable. These results substantiate earlier ones and confirm thismaterial's applicability as a solderability reference material.

Notes: SMT adhesives are applied to printed circuit boards by the following techniques: dispensing (c. 90% of all manufacturers use this technique at present), printing and pin transfer. The conventional dispensing method of applying adhesive utilises variations in dispense time, pressure and temperature combined with needle diameter to formdeposits of varying volume and geometry. Recently, the printing technique has attracted a lot ofinterest. This technique is well known from solder paste printing. The major driving force is the higherthroughput of this application method. moreover, a new printing technique with thick stencils allows thedeposition of glue dots with different diameters and different heights. Two printing methods will bediscussed: conventional printing technology and printing with thicker stencils.

Notes: This issue of the journal features the first part of a two-part serieswhich comprises Chapter 15 from Volume 1 of a recently published book 'AComprehensive Guide to the Manufacture of Printed Board Assemblies'*edited byW. MacLeod Ross. Volume 1, containing 800 pages, and Volume 2, scheduled to bepublished in the Spring of 1997 and estimated to contain around 900 pages, will, as far as thepublishers are aware, be the most comprehensive book ever published on the subject of printed boardsand printed board assemblies.

Notes: The comparatively new process of diffusion soldering combines themerits of Soldering and diffusion bonding. It is tolerant to surfaces that are not perfectly flat while, at flatwhile, at the same time, it is capable of producing large-area joints that are void free, a normal failing ofconventional soldering. Diffusion soldering processes have been successfully developed, based copper,silver and gold. The metallurgical principles behind the design of these processes are explained andprospective applications of each of the diffusion soldering systems are described. These range from theattachment of heat-sinks to silicon power devices, to jewellery and the fabrication of semiconductorpackaging.

Notes: As part of the portable product interconnects characterisation programme, the present investigation was conducted to determine the attachment integrity andlong-term reliability of Thin small Outline package (TSOP) solder joints. Accelerated thermal cyclingcombined with analytical modelling was used to evaluate the reliability for credit card sized DRAMmemory cards. The measured solder joint fatigue lifetimes varied from 645 to 830 thermal cycles forTSOP-II and I components, respectively. The modelling results corroborated the empirical findings.The solder joint thermal fatigue data were used to predict the card reliability under operating fieldconditions. The cards were found to be reliable for their intended use environment.

Notes: SMT stencil cleaning has traditionally been thought of as a'maintenance' procedure with little or no impact on production. Today, CFC and VOCcleaning processes are being replaced because of environmental concerns, and fine-pitch andultra fine-pitch assemblies are commonplace. These changes in cleaning processes andproduct specifications have shed new light on the importance of properly cleaning SMT screens andstencils in order to prevent damage to the stencil and potential production-related problems.This paper takes an unbiased look at the different stencil cleaning processes availablethrough the eyes of an SMT stencil manufacturer. The paper outlines the advantages and disadvantagesof using 'jet spray' washersvs 'ultrasonic' washers, aqueousand semi-aqueous vssolvent cleaning agents, and the effects of hot wash solutionsand hot drying air vsambient wash solutions and drying techniques.Specific criteria evaluated include: cleaning effectiveness of the process;potential adverse effects of the process on the integrity of the stencil; productiondown-time and other potential production-related problems; potential healthhazards to users; environmental impact of the process, and waste stream management.Magnified photography is used to demonstrate the relative effectiveness ofvarious cleaning technologies. Third party references of other industry experts, along with theauthor's own experiences, are cited to support the information provided.

Notes: Highly accelerated tests, while capable of producing failures in short test durations, cancause significant damage and failure as a result of damage mechanisms and/or material behaviournot present in the actual use of electronic product. This is particularly true for surface mount solderattachments. The results of low-acceleration reliability tests for the solderattachments of ball grid arrays (BGAs) and column grid arrays (CGAs) arereported in this paper. The tests were designed to mimic the thermal conditions of the use environmentof the product, including internal power dissipation within the grid array components, as closely aspractically possible. The test acceleration comes from two measures taken: (1)controlled reduced dwell times at the cyclic temperature extremes, thus allowing a higher cyclicfrequency, and (2) a controlled increased CTE-mismatch between the componentsand the test circuit board by an increase in the coefficient of thermal expansion (CTE) of thetest circuit boards relative to the product cirucit boards. Control test vehicles withproduct-like circuit board construction were also utilised. Theresults from the different test vehicle configurations are correlated and utilised to estimate the reliabilityof the product in the field.

Notes: The electronics industry seems to be under slightly less pressure, at present, to move to lead-freesolders. Nevertheless, many companies are interested in switching to comply with initiativesaimed at reducing the use of toxic materials such as lead. At the same time, these and othercompanies are hoping to use the improved properties of many lead-free solders toincrease solder joint reliability. While lead-free solders can indeed giveimproved properties in the proper system, using them with lead-containing materials canactually give poorer properties and uncertain reliability. It is important to understand thesematerials' interactions as thoroughly as possible before introducing new soldercompositions. To illustrate this point, some case histories will be presented, along with a generaldiscussion of how solders and substrates can and do interact.

Notes: The most commonly used solder for electricalinterconnects in electronic packages is the near eutectic 60Sn-40Pb alloy. This alloy hasa number of processing advantages(suitable melting point of 183°C and good wettingbehaviour). However, under conditions of cyclic strain and temperature(thermomechanical fatigue) the microstructure of this alloy undergoes aheterogeneous coarsening and failure process that makes the prediction of solder joint lifetimecomplex. A finite element simulation methodology to predict solder joint mechanical behaviour,that includes microstructural evolution, has been developed. The mechanical constitutivebehaviour was incorporated into the time-dependent internal state variable viscoplasticmodel through experimental creep tests. The microstructural evolution is incorporated through aseries of mathematical relations that describe mass flow in a temperature/strainenvironment. The model has been found to simulate observed thermomechanical fatiguebehaviour in solder joints.

Notes: Detailed studies to characterise the coarsening behaviour of eutecticSn-Ag and near-eutectic Sn-Pb-Ag solder joints were carriedout on samples reflow soldered and solidified at various cooling rates. Light and scanningelectron microscopy as well as EDS were used to study the microstructural evolution, whilemicrohardness measurements were used to monitor the change in the mechanical properties.Samples consisting of copper substrates and solder paste were reflow soldered about 30 °Cabove their melting points and then solidified at cooling rates ranging from furnace cooling torates associated with water quenching. Analysis of some of these samples showed that increasingthe cooling rate increased the quantity (volume fraction) of primarySn-dendrites, decreased the (EQ) intermetallic phase in the bulk solder, andresulted in finer microstructures with higher hardness. The microstructural evaluation involvedcharacterisation of bulk intermetallica and dendrite/eutectic ratios. Subsequent isothermalannealing of these reflow soldered joints at 125 °C for times between 0.25 h and 8 daysresulted in an initially fairly rapid decrease in hardness to a given level for each alloy and eachcooling rate.

Notes: The objective of this paper is to point out the limitations and ròles of DNP (distance to neutral point) on predicting the solder-joint thermal-fatigue life of area-array assemblies.

Notes: Provides a survey about a new process for dyeing synthetic fibres and fabrics. The use of disperse dyes in supercritical carbon dioxide as a dyeing medium completely avoids water pollution and the need for drying. Presents laboratory results showing excellent levelness and fastnesses on the dyeing of polyethylene terephthalate and on polyamides. Describes the state of technical development.

Notes: A neuro-fuzzy control model has been devised for the next generation of so-called "intelligent sewing machines". The model incorporates discrimination of material characteristics to be stitched by automatic determination of their properties. The fabric/machine interactions at different speeds have been computed in the form of linguistic rules of a fuzzy model and implemented in a neural network to allow for optimization of fuzzy membership functions and, subsequently, self-learning. The model is successfully applied to an instrumented industrial sewing machine.

Notes: Describes the FAST system, developed by CSIRO for quality control and assurance of fabrics. FAST, or Fabric Assurance by Simple Testing, consists of a series of instruments and test methods which are inexpensive, robust and simple to use. It measures properties which are closely related to the ease of garment making-up and the durability of worsted finishing. FAST-1 gives a direct reading of fabric thickness over a range of loads with micrometre resolution. FAST-2 measures the fabric bending length and its bending rigidity. FAST-3 measures fabric extensibility at low loads as well as its shear rigidity. FAST-4 is a quick test for measuring fabric dimensional stability, including both the relaxation shrinkage and the hygral expansion.

Notes: Follows a presentation at a symposium in 1993 where the authors presented an experimental investigation on a fluttering membrane for use in a wind-tunnel. Analyses the fluttering of an object by a theoretical method. Compares the experimental results with those of the theoretical and discusses their effectiveness. States that the present analysis is effective for approximate investigations.

Notes: Presents the influence of rheological properties of a sewing thread on its dynamical loads in a stitch formation process, or on change of thread strength as a consequence of dynamical loads in the sewing process, respectively. Research work shows the change in thread strength, as a result of the stitch formation process forming dynamic loads of a thread, as a function of rheological properties of a thread.

Notes: Reports the dynamic modelling of garments on synthetic humans. Develops the model based on a physical analogue to a deep shell system for describing and predicting the real 3-D shape of clothes. Determines the garment motion by fabric deformation energy, gravity and external constraints of the garment, such as collision forces, using the deformable node bar concept. Justifies the model by agreement between real fabric prediction of static and dynamic drapes using our newly developed drape metre. Demonstrates the garment simulation using garments from two different fabrics in a virtual fashion show. Also describes the work on modelling and animating a synthetic female. The advantages of this model are that engineering parameters can be used as model parameters directly and that the model is configured based on the surface co-ordinate system, which are important for the next generation of fashion CAD systems incorporating virtual fashion shows. This consideration is fundamental in the context of global retailing and becomes an integral part of intelligent textile and garment manufacture. Proposes the consequences of this work in cinema, TV, advertising and in graphics and animation are also important, but does not examine these.

Notes: Focuses on Korean garment manufacturing and the feasibility and benefits of introducing an expert system. Reviews previous literature on knowledge-based system and describes in detail the stages followed in developing, constructing, testing, evaluating, integrating, implementing and maintaining the expert system. Concludes that an expert system could be used to solve various garment manufacturing problems and would contribute to garment quality improvement through a standardized apparel production process.

Notes: Fully automating the apparel assembly process will require generic robotic manipulators which can be purchased as a complete unit and adapted to specific applications. A manipulator that can handle and position non-rigid fabric parts of inexact dimension is described. The XY-theta provides three directions of fabric positioning. Further, the manipulator can handle different sizes of a variety of styles. The aligning system is composed of three modules- vision, positioning and control, which exchange information and control signals via a 32-bit bus system. This combination of modules and bus system makes the aligning system very flexible which is represented by the ability to switch the type of microcontroller or motors used. Thus, the generic system can be adapted for specific applications.

Notes: Quality assessment and fault detection are important topics in textile research. Human assessment in this field, however, is subjective and slow. Presents an automatic assessment using two fundamentally different kinds of neural networks: the Kohonen Map (an unsupervised system) and the backpropagation network (supervised system). Evaluates two case studies using these techniques: assessment of carpet wear and the assessment of set marks. Both show good results when applied to the aforementioned problems. Makes a comparison between the two techniques and shows that the unsupervised system also gives an evaluation of the objectivity of the human experts.

Notes: Aims to analyse unique deformation properties of textile materials in terms of basic mechanical properties. Models fabric deformation as a nonlinear dynamical system so that a fabric can be completely specified in terms of its mechanical behaviour under general boundary conditions. Fabric deformation is dynamically analogous to waves travelling in a fluid. A localized two-dimensional deformation evolves through the fabric to form a three-dimensional drape or fold configuration. The nonlinear differential equations arising in the analysis of fabric deformation belong to the Klein-Gordon family of equations which becomes the sine-Gordon equation in three dimensions. The sine-Gordon equation has its origins in the study of Bäcklund Transformations in differential geometry. Describes fabric deformation as a series of transformations of surfaces, defined in terms of curvature parameters using Gaussian representation of surfaces. By considering a deformed fabric as a two-dimensional surface, algebraically constructs analytical solutions of fabric deformation by solving the sine-Gordon Equation. The theory of Bäcklund Transformations is used to transform a trivial solution into a series of solitary wave solutions. These analytical expressions describing the curvature parameters of a surface represent actual solutions of fabric dynamical systems.

Notes: Presents research into the improvement of flow-line assembly systems. Aims to understand and improve the design and control of manually intensive flow-line assembly in the clothing industry. A simulation model of the progressive bundle system has been constructed, incorporating operator performance variations and learning effects, machine failure and repair, operator absenteeism, quality failure and supervisory control. While the operator performance data and the stochastic variables are handled satisfactorily within the simulation, the problems of control are not handled well by conventional discrete event modelling techniques. Adopts a knowledge-based approach to control in which an online computerized supervisor exercises control over the execution of the simulation run. Complex system models are not easy to validate and a four-stage approach is used to demonstrate conformance with real-world systems: qualification; face validity; modular validation; and time-series system behaviour. Discusses applications of the model and the results of experiments with a line starting work on a new style.

Notes: Investigates the effects of moisture transfer on the compression properties and the volume change of wool, polyester and cotton futon padding by taking a series of creep measurements under three relative humidities and obtaining master creep curves from these curves at 20°C, 65 per cent RH. Discovers that the compression phenomena for wool, which absorbed the moisture from a drying state, were different from those obtained from desorption. Reveals that crimpy fibre assembly showed more volume change and better recovery than uncrimpy fibre assembly at high water content. Notes that the fibre crimp is also an important parameter for wool fibre assembly at high water content as well as standard condition.