Kaustubh Ravindra Nagarkar

Reliability of POL-kw power modules

Wide band gap (WBG) semiconductor devices have demonstrated superior electrical and thermal performance, compared to their silicon-based counterparts. However, innovative power module packaging design and materials suitable to WBG devices are required. In this paper, the development of a new high power density module using the Power Overlay (POL) packaging platform is presented. The wirebond-less packaging platform has shown significantly reduced electrical parasitics, while providing a thin profile to allow double-side cooling and the integration of gate drive circuits. Thermal cycling and high temperature storage tests were conducted on specimens fabricated and assembled by production equipment. The results presented here were used to establish design guidelines for reliable operation of POL-based power modules.

Modeling the magnetic disturbance of pulsatile blood flow in a static magnetic field

Non-invasive continuous monitoring of blood flow may be particularly valuable for early detection of different anomalies such as hypovolemia and internal bleeding. Recent studies have demonstrated the potential clinical benefits of photo-plethysmography in detecting hypovolemia before the onset of cardiovascular decompensation. The magnetic sensing method bears advantages of size, weight, and cost along with less stringent body placement rules. In this work, a detailed three-dimensional mathematical model for the acquisition of the ventricular response using the disturbance created by magnetized blood undergoing a stationary permanent magnet is presented. The proposed model accounts for the different magnetic properties of the blood such as the relaxation time and the magnetic saturation. The blood flow is simulated by means of Navier-Stocks equations with pulsatile inlet pressure. The blood is assumed to be in the deoxygenated state and has a diamagnetic properties. Moreover, a moving mesh technique is implemented in the Finite-Element model to represent the idle and the moving states of the blood which provides the capability to model the magnetized blood as a moving magnet. The simulated magnetic field at different sensor locations is found to be in good agreement with experimental observations from the literature. The presented model can provide basis for understanding the magnetic modulated blood signal as well as the practical constraints that might be encountered in the design of such devices.

Reliability of compliant electrically conductive adhesives for flexible PV modules

Lightweight flexible Photovoltaic (PV) modules are an attractive product option in variety of markets including portable (to power IoT devices) and low load-bearing rooftop applications. The ease of transport, installation, integration, cost, and reliability/ruggedness are the primary drivers towards penetration of the lightweight flexible PV products in the market. Factors that enable the lightweight and flexibility features include the absence of a frame, no-glass encapsulation, and flexible interconnection. The impact of these factors on reliability needs careful attention as they significantly deviate from the traditional silicon PV module package. In this paper, we focus on the area of robustness of interconnections in thin film lightweight flexible PV modules. The use of flexible and more permeable polymer coversheets in these modules (rather than glass) present a greater challenge on the mechanical integrity and environmental stability of the interconnects.

Optical fiber reliability in subsea monitoring

Fiber optic cables have been successfully deployed in ocean floors for decades to enable trans-oceanic telecommunication. The impact of strain and moisture on optical fibers has been thoroughly studied in the past 30 years. Cable designs have been developed to minimize strain on the fibers and prevent water uptake. As a result, the failure rates of optical fibers in subsea telecommunication cables due to moisture and strain are negligible. However, the relatively recent use of fiber optic cables to monitor temperature, acoustics, and especially strain on subsea equipment adds new reliability challenges that need to be mitigated. This paper provides a brief overview of the design for reliability considerations of fiber optic cables for subsea asset condition monitoring (SACM). In particular, experimental results on fibers immersed in water under varying accelerated conditions of static stress and temperature are discussed. Based on the data, an assessment of the survivability of optical fibers in the subsea monitoring environment is presented.

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

Highly Manufacturable and Reliable CZT Detectors

Cadmium Zinc Telluride (CZT) based radiation detectors have been developed over the past decade and are, increasingly, being used in security and healthcare applications. Improvements in radiation detector performance, size, and cost have been achieved; however, the manufacturability and reliability of the individual CZT detector package continues to limit widespread use and new applications.To date, most CZT detector packages are designed, manufactured, and tested to requirements defined by manufacturers, rather than military, commercial, or industry standards, as is common for semiconductor packages. The lack of test standards has led to use restrictions and/or complex detector system design, as required to mitigate unknown or low detector package reliability. CZT detector packaging, as was the case for semiconductor packaging, has reached the point in technology maturation where a focus on optimizing detector design for manufacturability and reliability is appropriate and necessary.This paper reviews the systematic approach, including design, process development, and testing, utilized in the development and demonstration of a highly manufacturable and reliable (95% reliability at 1000 cycles) CZT detector package. Finite Element Model (FEM) based design and material trade-off studies, development of highly manufacturable and reliable commercial electronic assembly processes, failure mode identification and mitigation, selection and use of reliability test standards, and analyses are detailed for a flip-chip-CZT-on-ceramic substrate, detector package targeted for field deployment. As well, the next steps in package and system design, manufacturing, and reliability testing are proposed.Copyright