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Inclusions have been shown to be the most significant factor to decrease the low cycle fatigue (LCF) life in powder metallurgy (PM) alloys used by most of turbine discs for advanced turboengines. In this paper, effects of inclusions on PM alloys' LCF life are evaluated through the definition of initial damage value D₀ based on damage mechanics. By investigating the relationship between D₀ and characteristic dimension of inclusions, Bussac's probabilistic model is extended to consider surface and internal inclusions together.

This paper aims to review recent advances and applications of abrasive processes for microelectronics fabrications.

More than 80 patents and journal and conference articles published recently are reviewed. The topics covered are chemical mechanical polishing (CMP) for semiconductor devices, key/additional process conditions for CMP, and polishing and grinding for microelectronics fabrications and fan-out wafer level packages (FOWLPs).

Many reviewed articles reported advanced CMP for semiconductor device fabrications and innovative research studies on CMP slurry and abrasives. The surface finish, sub-surface damage and the strength of wafers are important issues. The defects on wafer surfaces induced by grinding/polishing would affect the stability of diced ultra-thin chips. Fracture strengths of wafers are dependent on the damage structure induced during dicing or grinding. Different thinning processes can reduce or enhance the fracture strength of wafers. In the FOWLP technology, grinding or CMP is conducted at several key steps. Challenges come from back-grinding and the wafer warpage. As the Si chips of the over-molded FOWLPs are very thin, wafer grinding becomes critical. The strength of the FOWLPs is significantly affected by grinding.

This paper attempts to provide an introduction to recent developments and the trends in abrasive processes for microelectronics manufacturing. With the references provided, readers may explore more deeply by reading the original articles. Original suggestions for future research work are also provided.

The abrasive wear performance of fly ash filled aramid fibre reinforced phenolic based composites has been investigated on a rubber wheel abrasive wear tester (RWAT). The design of the experiment approach which uses Taguchi’s orthogonal arrays is adopted to objectively evaluate and prioritize five influencing factors that are taken as experimental variables. A predictive mathematical model for damage assessment in wear rate is developed and validated by a well designed set of experiments. The study reveals that sliding distance, external abrading particle size and fly ash content show greater influence on the specific wear rate of the composites. An investigation on worn surface morphology with a scanning electron microscope (SEM) has been carried out to understand the plausible wear mechanisms. The study thus carried out has revealed the decisive role of quartz particles and photovoltaic (PV) conditions in terms of their influence not only on the alterations of topographical attributes, but also surface ploughing, micro-pitting and sub-surface damage as the various modes of wear of these composites.

COMMON to a diverse range of manufacturing industries, is the drive to miniaturise and produce higher precision products. Electric switches and relays, for example, operate faster when they are smaller. In turn this pushes forward the need for greater understanding of materials and processes at the molecular and atomic level.

WHEN the Harrier GR 5 begins operations, the Royal Air Force will have an aircraft of which one quarter of the structure weight is composites and one half of the structure area. Major primary structure components are fabricated from carbon fibre composites (CFC) whose characteristics are notably different from light alloys. These differences have to be taken into account when appreciating the problems of supporting such an aircraft and providing the best methods of effecting repairs to damaged structure.

Held at the NEC Birmingham, the Aerospace Technology Exhibition and Conference was sponsored by the Aerospace Industries Division of the Institution of Mechanical Engineers together with the Institutions of Electrical Engineers and Electronic and Radio Engineers. It attracted papers on a variety of subjects and gave companies the opportunity to show a range of products, many of which were related to safety matters or maintenance programmes.

Pitting Pitting is possibly the most expensive form of corrosion, in that one small hole can result in the failure or destruction of a process or plant. By its very nature it is a localised form of attack, the diameter of the resultant pit being approximately the same as its depth. Some materials are very prone to pitting—the pits are so close that the surface resembles a roughened specimen. The most important factor, that of pit depth, is sometimes referred to in terms of ‘pitting factor’. This relates the ratio of deepest pit to average metal penetration, the latter being derived from the weight loss of the specimen. Uniform corrosion has a pitting factor of unity.

Fine diamond powders, in some cases composed of particles smaller than one micron, are assuming ever increasing importance, especially as the cost of conventional abrasives rises disproportionately. This article looks at the advancing technology behind natural and synthetic micron diamond powders and their significance in the automated industry of today

In the present work, thixoformed AlSi8Cu3Fe alloy was investigated for its tribological properties. The tribological analysis reveals good sliding wear behaviour for thixoformed alloy due to thixotropic microstructural character. The results are compared with sliding wear behaviour of conventional gravity cast alloy. This paper aims to discuss these subjects.

In this study, thixoforming and gravity casting methods are used to produce materials. The ball-on-disc CSM tribometer was used to carry out the tribological tests that were performed under dry sliding conditions, under two different loads of 1N and 5N. Wear tests were performed first on the conventional gravity cast samples and then on the thixoformed counterparts in exactly the same fashion to facilitate a comparison. The microstructural characterizations are performed in optical microscopy, scanning electron microscopy and energy dispersive X-ray spectrometry.

Thixoformed samples have better wear resistance than conventional gravity cast samples. The wear performance improves in thixoformed AlSi8Cu3Fe alloy thanks to changing the microstructure. The superiority of the former is attributed to its structural features.

In this study, the thixoforming of AlSi8Cu3Fe alloy can provide important wear performance in comparison with conventional casting of AlSi8Cu3Fe alloy. This alloy is known to be used widely in automotive industry. Therefore, the alloy is highly exposed to wear and it is thought that thixoforming method can increase the wear resistant.

Lapping is a vital flattening process to improve the quality of processed semiconductor wafers such as single-crystal sapphire wafers. This study aims to optimise the lapping process of the fixed-abrasive lapping plate of sapphire wafers with good overall performance [i.e. high material removal rate (MRR), small surface roughness (Ra) of the wafers after lapping and small lapping plate wear ratio (η)].

The influence of process parameters such as lapping time, abrasive size, abrasive concentration, lapping pressure and lapping speed on MRR, Ra and η of lapping-processed sapphire wafers was studied, and the results were combined with experimental data to establish a regression model. The multi-evaluation index optimisation problem was transformed into a single-index optimisation problem via an entropy method and the grey relational analysis (GRA) to comprehensively evaluate the performance of each parameter.

The results revealed that lapping time, abrasive size, abrasive concentration, lapping pressure and lapping speed had different influence degrees on MRR, Ra and η. Among these parameters, lapping time, lapping speed and abrasive size had the most significant effects on MRR, Ra and η, and the established regression equations predicted the response values of MRR, Ra and η to be 99.56%, 99.51% and 93.88% and the relative errors between the predicted and actual measured values were <12%, respectively. With increased lapping time, MRR, Ra and η gradually decreased. With increased abrasive size, MRR increased nearly linearly, whereas Ra and η initially decreased but subsequently increased. With an increase in abrasive concentration, MRR, Ra and η initially increased but subsequently decreased. With increased lapping pressure, MRR and η increased nearly linearly and continuously, whereas Ra decreased nearly linearly and continuously. With increased lapping speed, Ra initially decreased sharply but subsequently increased gradually, whereas η initially increased sharply but subsequently decreased gradually; however, the change in MRR was not significant. Comparing the optimised results obtained via the analysis of influence law, the parameters optimised via the entropy method and GRA were used to obtain sapphire wafers lapping with an MRR of 4.26 µm/min, Ra of 0.141 µm and η of 25.08, and the lapping effect was significantly improved.

Therefore, GRA can provide new ideas for ultra-precision processing and process optimisation of semiconductor materials such as sapphire wafers.