The advent of novel advanced packaging technologies such as multilayer thin‐film interconnect, combined with continuous improvements in IC clock speed and circuit…
The advent of novel advanced packaging technologies such as multilayer thin‐film interconnect, combined with continuous improvements in IC clock speed and circuit performance, has placed extreme demands on electronics packaging and package materials. Aluminium nitride (AIN) ceramic offers significant opportunities and advantages for package design, particularly where the effective thermal management and overall reliability of large devices are a high priority. AIN has already been successfully employed at the substrate level for the enhanced thermal relief of power devices. Examples of these applications include heat sinks and device mounts for thyristor modules, power transistors, solid state relays, power SCRs, switching modules, LEDs and various RF package configurations. Both bare and metallised AIN substrates are beginning to find application as a substitute for beryllia (BeO) in mass market and high reliability automotive electronics applications. Successfully implementing AIN in a high level electronics packaging application requires a systems approach in which the intrinsic properties of AIN are considered as ‘first principles’ in shaping the package design process. The unique physicochemical and mechanical properties of AIN require the development of specialised metallisation and co‐firing processes to fabricate the advanced components necessary for hermetic packaging of complex devices and multichip modules. This paper presents a practical and mass manufacturable AIN‐based package tailored to these high level applications. The package design is unique in that it provides for the total separation of the electrical‐signal conduction from the mechanical support/mounting functions of the package. Such a separation of the functions improves both the package durability and reliability relative to currently available electronics packages of conventional designs.
– The purpose of this paper is to study elastic properties of III-V nitride nanotubes (NNTs) using second generation (REBO) potential.
The purpose of this paper is to study elastic properties of III-V nitride nanotubes (NNTs) using second generation (REBO) potential.
In the present research paper elastic properties of BN, AlN and GaN nanotubes have been investigated, using the second generation REBO potential by Brenner and co-workers, which is a bond order potential earlier used for carbon nanostructures successfully. In the present calculation, the same form of potential is used with adjusted parameters for h-BN, h-AlN and h-GaN. In all these cases the authors have considered graphite like network and strongly polar nature of these atoms so electrostatic forces are expected to play an important role in determining elastic properties of these nanotubes. The authors generate the coordinates of nanotubes of different chirality’s and size. Each and every structure thus generated is allowed to relax till the authors obtain minima of energy. The authors then apply the requisite compressions, elongations and twists to the structures and compute the elastic moduli. Young’s Modulus, Shear Modulus and Poisson’s ratio for single-walled armchair and zigzag tubes of different chirality’s and size have been calculated. The computational results show the variation of Young’s Modulus, Poisson’s ratio and Shear Modulus for these NNTs with nanotube diameter. The results have been compared with available data, experimental as well as theoretical.
The authors have calculated bond length, cohesive energy/bond, Strain energy, Young’s Modulus, Shear Modulus and Poisson’s ratio.
To the best of the knowledge this work is the first attempt to study elastic properties of III-V NNTs using second generation REBO potential
This paper provides an overview of the different binding mechanisms in selective laser sintering (SLS) and selective laser melting (SLM), thus improving the understanding…
This paper provides an overview of the different binding mechanisms in selective laser sintering (SLS) and selective laser melting (SLM), thus improving the understanding of these processes.
A classification of SLS/SLM processes was developed, based on the binding mechanism occurring in the process, in contrast with traditional classifications based on the processed material or the application. A broad range of commercial and experimental SLS/SLM processes – found from recent articles as well as from own experiments – was used to explain the different binding mechanism categories.
SLS/SLM processes can be classified into four main binding mechanism categories, namely “solid state sintering”, “chemically induced binding”, “liquid phase sintering – partial melting” and “full melting”. Most commercial processes can be classified into the latter two categories, which are therefore subdivided. The binding mechanism largely influences the process speed and the resulting part properties.
The classification presented is not claimed to be definitive. Moreover some SLM/SLM processes could be classified into more than one category, based on personal interpretation.
This paper can be a useful aid in understanding existing SLS/SLM processes. It can also serve as an aid in developing new SLS/SLM processes.
Two die attach adhesive products, manufactured by Furane Products Co., claim to meet the military specification for epoxy electronic adhesives (MIL‐STD‐883C, Method 5011) without exception. The products are EPIBOND 7002 which is a thermally conductive adhesive and EPIBOND 7200, an electrically and thermally conductive die attach adhesive. Both are 100% solids and contain no solvents or diluents. Consequently, the likelihood of outgassing and void formation is greatly reduced. Both are extremely high purity systems, and have a hot die‐shear strength of over 6,000 N/M2 at 150°C. Both materials are screen printable and undergo virtually no bleed‐out during processing.
The complexity of microelectronic circuits, their scale of integration and clock speed requirements have been increasing steadily. All these changes have the effect of…
The complexity of microelectronic circuits, their scale of integration and clock speed requirements have been increasing steadily. All these changes have the effect of increasing the power density of the microcircuits. ICs with a power of several watts and an area of over a square centimetre are quite common. Thus, there is more heat generated per device at die, component and substrate‐attach levels of electronic packaging. In order to maintain reliability of finished products, the junction temperature of the constituent devices must be kept low. It has been demonstrated that thermal management can be one key to lowering the cost and increasing the performance life of microelectronic products. The cost‐effectiveness of lowering device temperature has been demonstrated to be dramatic compared with the cost of thermal management materials. Proper thermal management of advanced microelectronic devices has to be addressed at all levels. One should address the problem from the basic level of die‐attach, through component‐attach, and eventually substrate‐attach to thermal drains. Thermal management is almost invariably coupled with a thermally induced stress problem. The increase in temperature at the device level also means a larger fluctuation of temperature from the ambient. Each cycle of on‐off for the device represents one thermal cycle. Stress‐induced failure due to coefficient of thermal expansion (CTE) mismatch is much more acute for higher power devices. In this paper, the authors address the issue of thermally induced stress on the microelectronic product at all levels of packaging, with major emphasis on component and substrate levels. Various ways and examples of reducing or eliminating this stress, which is a major cause of device failures, will be demonstrated. One of the proven methods is through the use of low Tg epoxies with high thermal stability.
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…
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.
Because they offer many properties favourable forIC package construction, ceramics have been in widespread use as an electronic packagematerial since the early 1960s. In…
Because they offer many properties favourable for IC package construction, ceramics have been in widespread use as an electronic package material since the early 1960s. In recent years, with trends towards higher speed semiconductors generating up to 30‐40 watts power, packaging materials must possess excellent thermal, electrical and mechanical properties. Aluminium nitride, with a thermal conductivity of 170 W/m.K., high fracture strength and a thermal coefficient of expansion match with silicon, has been used to manufacture multilayer LGA (land grid array) packages for high performance applications. A 725 AIN LGA has been manufactured and its performance characteristics have been compared with those of an alumina (with copper/tungsten slug) packaging alternative. Because of the high thermal conductivity of aluminium nitride, all designs can be made in a cavity‐up configuration, resulting in significant package body size reduction. The area under the cavity can be used for increasing I/O number and a ground plane can be inserted under the cavity, reducing simultaneous switching noise. Aluminium nitride is particularly beneficial for flip‐chip interconnection. Its close TCE match to silicon eliminates the stress reduction requirement for die underfill.
The main types of fluid film bearing, irrespective of lubricant, are those relying on surface motion to generate the fluid film pressure and hence load capacity (hydrodynamic lubrication—or aerodynamic for gases), and those relying on an external supply of pressurized lubricant (hydrostatic or aerostatic lubrication). A bearing employing a mixture of the two lubrication modes is said to be hybrid. A special case of self‐acting bearings is the squeeze film bearing in which fluid pressure is generated due to the normal motion of the bearing surfaces. Particular bearing geometries will not be discussed.