Metal Matrix Composite in Heat Sink Application: Reinforcement, Processing, and Properties

Heat sinks are commonly used for cooling electronic devices and high-power electrical systems. The ever-increasing performance of electronic systems together with miniaturization calls for better heat dissipation. Therefore, the heat sink materials should not only have high thermal conductivities, low densities, and cost, but also have coefficients of thermal expansion matching to those of semiconductor chips and ceramic substrates. As traditional materials fail to meet these requirements, new composite materials have been developed with a major focus on metal matrix composites (MMCs). MMCs can be tailored to obtain the desired combination of properties by selecting proper metallic matrix and optimizing the size and type, volume fraction, and distribution pattern of the reinforcements. Hence, the current review comprehensively summarizes different studies on enhancing the thermal performance of metallic matrices using several types of reinforcements and their combinations to produce composites. Special attention is paid to the types of commonly used metallic matrices and reinforcements, processing techniques adopted, and the effects of each of these reinforcements (and their combinations) on the thermal properties of the developed composite. Focus is also placed on highlighting the significance of interfacial bonding in achieving optimum thermal performance and the techniques to improve interfacial bonding.

Gradual Distance Dispersal Shapes the Genetic Structure in an Alpine Grasshopper

The location of the high mountains of southern Europe has been crucial in the phylogeography of most European species, but how extrinsic (topography of sky islands) and intrinsic features (dispersal dynamics) have interacted to shape the genetic structure in alpine restricted species is still poorly known. Here we investigated the mechanisms explaining the colonisation of Cantabrian sky islands in an endemic flightless grasshopper. We scrutinised the maternal genetic variability and haplotype structure, and we evaluated the fitting of two migration models to understand the extant genetic structure in these populations: Long-distance dispersal (LDD) and gradual distance dispersal (GDD). We found that GDD fits the real data better than the LDD model, with an onset of the expansion matching postglacial expansions after the retreat of the ice sheets. Our findings suggest a scenario with small carrying capacity, migration rates, and population growth rates, being compatible with a slow dispersal process. The gradual expansion process along the Cantabrian sky islands found here seems to be conditioned by the suitability of habitats and the presence of alpine corridors. Our findings shed light on our understanding about how organisms which have adapted to live in alpine habitats with limited dispersal abilities have faced new and suitable environmental conditions.

RDL Multilayer Metallization Approaches for TGV

Significant advances have been accomplished in the field of Through Glass Via (TGV) technology; enabling a new generation of electronic designs that achieve higher performance, while leveraging low cost system solutions. Through-hole creation methods in glass have been optimized for mass production with consistent via diameter, shape and wall chemistry/morphology. This has enabled the development of unique copper via metallization materials that exhibit very high conductivity, thermal expansion matching and hermeticity. This paper will discuss post via metallization processes for multilayer RDL (Redistribution Layer) metallization on both sides of the glass wafer. Unique Chemical Mechanical Polishing (CMP) development approaches for glass wafers with copper thick film vias will be explained. Thin film deposited adhesion layer on glass, followed by a deposited metallization layer will be described. Types of deposited adhesion layer on glass for optimized adhesion and electrical contact with the vias will be examined. Furthermore, copper plating approaches for higher conductivity and fine line circuit patterning are examined. Polymeric dielectric material systems for multilayer RDL on both sides of the glass will also be reviewed.

Semi-Analytical Solution of Optimization on Moon-Pool Shaped WEC

In order to effectively extract and maximize the energy from ocean waves, a new kind of oscillating-body WEC (wave energy converter) with moon pool has been put forward. The main emphasis in this paper is placed on inserting the damping into the equation of heaving motion applied for a complex wave energy converter and expressions for velocity potential added mass, damping coefficients associated with exciting forces were derived by using eigenfunction expansion matching method. By using surface-wave hydrodynamics, the exact theoretical conditions were solved to allow the maximum energy to be absorbed from regular waves. To optimize the ability of the wave energy conversion, oscillating system models under different radius-ratios are calculated and comparatively analyzed. Numerical calculations indicated that the capture width reaches the maximum in the vicinity of the natural frequency and the new kind of oscillating-body WEC has a positive ability of wave energy conversion.

Perturbation solutions for a micropolar fluid flow in a semi-infinite expanding or contracting pipe with large injection or suction through porous wall

We investigate an unsteady incompressible laminar micropolar flow in a semi-infinite porous pipe with large injection or suction through a deforming pipe wall. Using suitable similarity transformations, the governing partial differential are transformed into a coupled nonlinear singular boundary value problem. For large injection, the asymptotic solutions are constructed using the Lighthill method, which eliminates singularity of solution in the high order derivative. For large suction, a series expansion matching method is used. Analytical solutions are validated against the numerical solutions obtained by Bvp4c.