Binoy Milan Shah

Development of a Compliant Nanothermal Interface Material

The power density requirements continue to increase and the ability of thermal interface materials has not kept pace. Increasing effective thermal conductivity and reducing bondline thickness reduce thermal resistance. High thermal conductivity materials, such as solders, have been used as thermal interface materials. However, there is a limit to minimum bondline thickness in reducing resistance due to increased fatigue stress. A compliant thermal interface material is proposed that allows for thin solder bondlines using a compliant structure within the bondline to achieve thermal resistance <0.01 cm2 C/W. The structure uses an array of nanosprings sandwiched between two plates of materials to match thermal expansion of their respective interface materials (ex. silicon and copper). Thin solder bondlines between these mating surfaces and high thermal conductivity of the nanospring layer results in thermal resistance of 0.01 cm2 C/W. The compliance of the nanospring layer is two orders of magnitude more compliant than the solder layers so thermal stresses are carried by the nanosprings rather than the solder layers. The fabrication process and performance testing performed on the material is presented.Copyright

Novel Flexible Interconnects and Packaging for Minimally Invasive Medical Electronics

A novel interconnect approach was developed to enable packaging of miniature (<0.5 mm) MEMS pressure sensors for minimally invasive sensing applications. The interconnect approach is a variant of traditional flexible laminate circuits but does not require expensive patterning steps. It provides tight tolerance and assembly automation at relatively lower costs. In this paper, details of the novel interconnect and cabling approaches are disclosed. Examples of applications that benefit from this approach are also discussed. Experimental results on new ultra-miniature sensors utilizing the developed interconnect approach are presented.Copyright

Scaling and Hierarhical Structure of Cohesive Agglomerates of Nanoparticles

Aggregation of dry cohesive powders and dissipation of energy during loading of the aggregates are under consideration. Under the influence of interparticle adhesion, fine particles of the powders cluster together to form simple agglomerates. The simple agglomerates adhere together to form larger, complex agglomerates, which in turn, may adhere together and form a hierarchical structure. It is shown that contrary to diffusion-limited colloid aggregation, the simple agglomerates consisting of alumna or titanium dioxide particles are not mass fractals. The core structure of the simple agglomerates is described as a non-ordered homogeneous structure with a constant volume fraction, while the outer part (shell) can be considered as a rough surface that may have quite extended protuberances. It is shown that the total energy dissipated during relative motion between simple agglomerates depends on the amount of the primary cycles – “jump into contact – pull off” between cohesive particles. Finally, the specific properties of cohesive powder dampers are discussed.