Sungwon Han

Hygro-thermo-mechanical analysis and failure prediction in electronic packages by using peridynamics

This study presents an integrated approach for the simulation of hygro-thermo-vapor-deformation analysis of electronic packages by using peridynamics. This theory is suitable for such analysis because of its mathematical structure. Its governing equation is an integro-differential equation and it is valid regardless of the existence of material and geometric discontinuities in the structure. It permits the specification of distinct properties of interfaces between dissimilar materials in the direct modeling of thermal and moisture diffusion, and deformation. Therefore, it enables progressive damage analysis in materials or layered material systems such as the electronic packages. It describes the validation procedure by considering a particular package for each thermomechanical, hygromechanical deformation as well as vapor pressure predictions. Also, it presents results concerning failure sites and mechanisms due to hygro-thermo-vapor-deformation.

A Virtualized, Programmable Content Delivery Network

In this paper, we present an open platform of content delivery networks (CDNs), namely vCDN, by which a wide range of delivery strategies can be dynamically deployed via a centralized controller and a pool of geographically dispersed cloud resources. A control application can be written for representing a specific strategy w.r.t required scale, responsiveness, and security in content delivery, and then translated into a virtualized delivery network, a form of an overlay network on cloud storages and virtual machines. In doing so, we explore the unique combination of named data networking (NDN), software defined networking (SDN), and distributed monitoring so as to achieve to a certain extent programmability in content delivery. Different from traditional CDNs, the strategy of content delivery in vCDN is not statically fixed but can be tailored by each service provider via the deployment of its own control application. Throughout a few applications running on our test bed at 7 geographical locations with multiple cloud resources, we demonstrate the feasibility of the programmable CDN and the delivery performance enhancement by inter-cloud network route managements.

Peridynamic Direct Concentration Approach by Using ANSYS

Moisture can have damaging effects on electronic packages by inducing hygro-thermo-mechanical stresses and vapor pressure. Commonly accepted wetness approach for indirect calculation of moisture concentration can yield unrealistic results. Therefore, a direct concentration approach becomes unavoidable. This study presents the Peridynamic Direct Concentration Approach (PDCA) and its implementation in ANSYS, a commercial finite element software. Numerical results show that PDCA provides accurate predictions, and removes the anomalies associated with the wetness approach. Moreover, ANSYS allows the utilization of implicit time integration resulting in significant computational advantages.

Named data networking for infrastructure wireless networks

Named Data Networking(NDN) has emerged to support content-oriented services that are currently prevalent in the Internet. It successfully minimizes redundant transmission on wired links by adopting name-based access and in-network caching. In this paper, we discuss NDN in the IOT world, and propose its enhancement for efficient usage in IOT.

NDN-Based Pub/Sub System for Scalable IoT Cloud

The Internet of Things (IoT) has recently become mainstream, different from the incomplete realization of ubiquitous computing, sensor networks, and others in past that commonly shared the notion of visionary hyper-connectivity, i.e., everything is connected. Among many, one significant reason for this achievement of IoT is the nowadays availability of cloud computing which can cost effectively deal with the sheer number of globally distributed devices and data generated from those devices. In this paper, we address the issue of IoT scalability in cloud environments by proposing the unique integration scheme between pub/sub systems and Named Data Networking (NDN). While the pub/sub architecture has been applied in modern IoT cloud platforms, its implementation and deployment practice have not been fully studied for large scale IoT applications. Our approach concentrates on how to leverage the essential scalability of NDN for building pub/sub systems, thereby achieving scalable IoT cloud services.

Equivalent acceleration assessment of JEDEC moisture sensitivity levels using peridynamics

The moisture inside the IC packages induces the several deformation failures, such as popcorn crack and swelling during the solder reflowing process. In semiconductor industry, over the past few years, the equivalent acceleration time for JEDEC moisture sensitivity level has been updated based on the weight gain measurements when the package structure and materials were modified. It costs long test times which may induce the significant delay of new product development and reliability evaluation. Additionally, the weight gain equivalency may not be sufficient to determine the equivalent accelerated time. In this paper, the new approach for evaluating the equivalent acceleration test time for preconditioning is proposed using the numerical calculation by peridynamics (PD) theory. The essential of proposed method is analyzing a moisture concentration and a vapor pressure which can cause the moisture induced failure in IC packages without facing the discontinuity problems of moisture concentration along the interfaces.

Peridynamic wetness approach for moisture concentration analysis in electronic packages

Within the finite element framework, a commonly accepted indirect approach employs the concept of normalized concentration to compute moisture concentration. It is referred to as “wetness” approach. If the saturated concentration value is not dependent on temperature or time, the wetness equation is analogous to the standard diffusion equation whose solution can be constructed by using any commercial finite element analysis software such as ANSYS. However, the time dependency of saturated concentration requires special treatment under temperature dependent environmental conditions such as reflow process. As a result, the wetness equation is not directly analogous to the standard diffusion equation. This study presents the peridynamic wetness modeling for time dependent saturated concentration for computation of moisture concentration in electronic packages. It is computationally efficient as well as easy to implement without any iterations in each time step. Numerical results concerning the one-dimensional analysis illustrate the accuracy of this approach. Moisture concentration calculation in a three-dimensional electronic package configuration with many different material layers demonstrates its robustness.

A configurable web browser for heterogeneous consumer devices

A web browser has been one of the most popular applications commonly used on consumer devices. While web is definitely ubiquitous and content rich today, it becomes difficult to maintain web browsing experiences with much satisfaction and consistency across various consumer devices due to their inherent resource heterogeneity. In this paper, we present a configurable web browser which consumer devices of dissimilar specifications can cost-effectively embed.

Device/Cloud collaboration framework for intelligence applications

In this chapter, we present a novel framework for collaborative computing between devices and cloud. We show the benefits of our framework through the detailed case studies of selected real-world intelligence applications that were developed at Samsung Electronics. Applications that utilize our framework can process the user’s request more quickly. By leveraging the millions of smart mobile devices, the cost of managing the cloud can be reduced significantly as well. Besides the cost and performance benefit, the framework helps the applications protect privacy of the end users by processing personal data within a device or analyzing the obfuscated version of the personal data on cloud.