Program of courses

One-day Short Course for Eurosime 2009

Who Should Attend
People involved with thermal management of electronic components, modules and systems would benefit from the course.
The main objective is to enable the attendees to understand the physics behind the often-used concepts underlying thermal analysis such as thermal resistance, heat spreading and experimental and numerical accuracy.
At the end of the course, the attendees will appreciate the big gap between what heat transfer handbooks teach and what real-life heat transfer is about.

Motivation
Everything must be made
as simple as possible
but not simpler.
Einstein

High temperatures have a negative influence on performance, reliability and safety for many electronic products, from ICs and LEDs to systems. The challenge for many designers is to estimate upfront what the temperatures will be in the final product, and the question is: which rules-of-thumb, handbooks and tools to use? There is always a big discrepancy between the textbook examples and the complexity encountered in practice. This is especially true in the thermal management of electronic parts and systems because of the complex geometries. This short course will address several topics, widely used, that cause trouble when trying to solve thermal problems in industry.

Course Description
The course covers the following aspects of thermal characterisation:

• Basics of industrial heat transfer: conduction, convection and radiation
• You sure you know what a thermal resistance is?
• Thermal characterisation and compact modeling
• Thermal standardisation from ICs to LEDs
• A few words on current progress in reliability analysis
• Heat spreading and its misconception
• You sure you know where the thermocouple voltage is generated?
• Conceivable accuracy of numerical analysis
• Correligion: the religious belief in correlations

The course material consists of the Lecture Notes.

Instructor
Clemens J.M. Lasance, Philips Research Laboratories, Eindhoven, The Netherlands

Clemens Lasance is a Principal Scientist at Philips Research in Eindhoven, the Netherlands. He has been on the Philips staff since 1969, when he received his physics degree at the Eindhoven Technical University. In 1980, he took up a post within the Heat Transfer Group at CFT. From 1984 onwards, his main focus has been the thermal management of electronic systems. He teached at the Summerschool of the NATO Advanced Institute of Technology in 1991. In 1996, he moved to Research, engaged with a long-term research program in the field of fluid dynamics and heat transfer with a special focus on electronic parts and systems. He has published over 70 conference and journal papers. He is an active participant in numerous professional and global industrial associations and an editor of Electronics Cooling magazine and Microelectronics Reliability. From 2000 to 2002, he led an EC-funded ten-partner consortium project called PROFIT. From 1995 to 2008 he acted as the co-program chair of THERMINIC and he was the General Chair of SEMITHERM 2003. He is the 2001 recipient of the SEMI-THERM Significant Contributor Award and the 2005 recipient of the Harvey Rosten Award. He won the Semitherm Best Paper Award in 1995 and 2009.

Course Scope:

Chip Scale Wafer Level Packaging is one of the fastest growing segments in semiconductor packaging industry due to the rapid advances in integrated circuit (IC) fabrication and the demands of a growing market for faster, lighter, smaller, yet less expensive electronic products with high performance and low-cost packaging. However, due to the intrinsic structural nature, most of failures occur at solder ball level. This includes solder ball thermal fatigue failures under thermal cycling, ball failures due to drop/impact loading, and the electromigration failures under high currents combined with thermal mechanical stresses. In order to improve solder ball reliability, several design considerations and processes have been implemented such as bump on I/O, bump on polymer, copper post structure, bump on RDL (redistribution layer), bump on UBM with polymer collar, and plastic cored solder ball applications. In addition, fan-out wafer level packaging concept extends the standard chip scale wafer level package to the next stage with unlimited potential applications in future. Different design structures and processes, UBM designs, solder materials, package structures, and bump structures present wide-spread reliability performances.

This course will present a state-of-art and in-depth overview of recent advances in design, reliability and electromigration considerations in chip scale wafer level packaging. Both ‘fan-in’ and ‘fan-out’ technologies will be reviewed. The emphasis will be given on the impacts of structural designs at both wafer and ball levels on reliability performances under various loading conditions. Three potential failure mechanisms, i.e, thermal fatigue of solder bulk, IMC failures under impact loading, solder ball voiding/cracking due to electromigration, will be described in details for different technologies. Previous studies on electromigration mostly concentrate on interconnects of integrated circuit such as Al-Cu alloy interconnect wire or pure Cu interconnect wire. This course will focus on the latest research results on electromigration occurring inside the solder adjacent to the under bump metallization (UBM) layer.

Course Objectives

• Provide an overview of Chip Scale Wafer Level Packaging Technologies including fan-in and fan-out technologies
• Fundamental understanding of the roles in wafer level structures on solder joint thermal cycling performance
• Understanding of failure modes of chip scale wafer level packaging under drop/impact
• Understanding of the failure mechanisms of electromigration in solder bumps
• Understanding of the application of finite element analysis to solder bump electromigration, with the coupled electrical-thermal-mechanical modeling to a package level system.

Outline

1.Introduction
2.‘Fan-in’ chip scale wafer level packaging
a.Standard bump on I/O
b.Bump on redistribution layer (RDL)
c.Bump on polymer
d.Copper post bump
e.Polymer collar
f.Bump on RDL pad
3.“Fan-out’ chip scale wafer level packaging
a.Infineon fan-out WLP
b.Redistributed chip packages
4.Typical failure modes at solder ball level for chip scale wafer level packaging
5.Reliability improvement of solder joints under thermal cycling
a.The role of copper post
b.The effect of redistribution layer
c.The effect of UBM structures
6.Underfill applications in chip scale wafer level packaging
a.Reliability improvement due to drop/impact loading
b.Underfill material selection
7.Plastic cored solder ball applications in chip scale wafer level packaging
8.Fundamentals of electromigration formulation at solder joints
a. Electromigration induced failure in solder bump of a package
b. Fundamentals of the migration driving force based theory
c. Void generation criteria
9.Electromigration modeling of solder bumps
a. Modeling methodologies
b. Void generation and growth algorithm
c. Time to Failure (TTF) modeling scheme
d. Correlation between modeling and test
10.Effect of electromigration on wafer level CSP reliability and design
a.Effect of electromigration on reliability of WL-CSP
b.UBM parameter design and its TTF
c.Solder bump parameter design and its TTF
11.Other failure modes in chip scale wafer level packaging (such as RDL interconnect failures)
12.Summary and references

Who should attend:

The course is designed for staff members, technical managers, design and manufacturing personnel, and reliability engineers in microelectronic companies. Although the course covers most recent advances in this area, the course does not assume prior knowledge of these issues and hence is of interest for both experts and new actors in this area.

Instructors’ Bio

Xuejun Fan is currently an Associate Professor in the Department of Mechanical Engineering at Lamar University, Beaumont, Texas. He was a Senior Staff Engineer at Intel Cooperation, Chandler, Arizona, from January 2004 to August 2007, a Senior Member Research Staff with Philips Research Lab at Briarcliff Manor, New York from 2001 to 2004, and a Member Technical Staff and Group Leader at the Institute of Microelectronics (IME), Singapore from 1997 to 2000. Dr. Fan’s interests and expertise lie in the areas of design, modeling, material characterization, and reliability in micro-/nano- electronic packaging and microsystems. He has given the short course on moisture related reliability several times at ECTC and the course was well received. He was invited to give a keynote presentation on Design and Reliability in Wafer Level Packaging at ICEPT-HDP in Shanghai in 2008. Dr. Fan has published more than 80 scientific papers and filed 14 patents in US patent office. In his earlier career he held a faculty position at Taiyuan University of Technology, Shanxi, China from 1989 to 1997. He received the Young Scientist Fellowship from Japan Society of Promotion of Science to spend a year at the University of Tokyo in 1993. He was a Visiting Professor at the University of British Columbia, Vancouver, Canada from 1996 to 1997. Dr. Fan was promoted to a Full Professor at Taiyuan University of Technology, Taiyuan, Shanxi in 1991, and became one of the youngest professors in China that year when he was 27. He was a nominee for the title of “1991 Ten Outstanding Youth of China”, and received Young Faculty Award in 1994 from Fok Ying-Tung Education Foundation.

Yong Liu has been with Fairchild Semiconductor Corp in South Portland, Maine since 2001 as a Senior Member Technical Staff from 2008, and a Member Technical Staff from 2004 to 2007, and a Principal Engineer from 2001 to 2004. He is now a Fairchild global team leader of electrical, thermal-mechanical modeling and analysis. His main interest area is IC packaging, modeling and simulation, reliability and material characterization. In last a few years he and his team have been working on the electromigration induced failures at solder bump level for chip scale wafer level packages, and a series of pioneering work have been carried out. He was invited to give a keynote presentation of electromigration in a solder joint reliability at Eurosime 2007 and an invited talk at TU Delft in 2008. One of his students in Fairchild-ZJUT Joint Lab on this topic received the ASE Best Paper Award at ICEPT-HDP in 2008. He has co-authored over 100 papers in journals and conferences and has filed over 30 US patents in the area of IC packaging and power devices. Dr. Liu was awarded Alexander von Humboldt Fellowship and studied at Tech University of Braunschweig, Germany in 1994. In 1997, he was awarded Alexander von Humboldt European Fellowship and studied at University of Cambridge, England. In 1998, he worked as a post-doctor research associate at Semiconductor Focus Center and Computational Mechanics Center, Rensselaer Polytechnic Institute (RPI). In 2000, he worked as a staff opto package engineer at Nortel Networks at Boston. Since he joined Fairchild in 2001, he was awarded the first Fairchild President Award in 2008, Fairchild Key Technologist in 2006, Fairchild BIQ award in product innovation in 2005, and Fairchild award for power of pen first place in 2004. Yong Liu is currently an IEEE Senior member and has been actively in technical committees of IEEE ECTC, EuroSime, EPTC and ICEPT.

Prognostics and health management (PHM) is a method that permits the assessment of the reliability of a product or system under its actual application conditions. Assessing the extent of deviation or degradation from an expected normal operating condition (i.e., health), and then the estimating the remaining life (prognostics) of products can be used to meet several critical goals, which include (1) advance warning of failures; (2) minimizing unscheduled maintenance, extending maintenance cycles, and maintaining effectiveness through timely repair actions; (3) reducing the life-cycle cost of equipment by decreasing inspection costs, downtime, and inventory; and (4) improving qualification and assisting in the design and logistical support of fielded and future products.

With increasing functional complexity of electronic products, there is an increasing demand for product health assessment, fault diagnostics, and prognostics. This is of special importance for soft faults and intermittent failures, some of the most common failure modes in today’s electronic products. This is also important because the traditional reliability prediction methods for electronic products (Mil-HDBK-217, 217-PLUS, Telcordia, PRISM and FIDES), should never be used, because they are inaccurate for predicting actual field failure events, and they are highly misleading, and can result in poor designs.

This presentation will discuss reliability prediction methods. There will be some discussion on qualification testing using accelerated means as a way to assess product reliability, but the focus will be on prognostics techniques.

Prof Michael Pecht has an MS in Electrical Engineering and an MS and PhD in Engineering Mechanics from the University of Wisconsin at Madison. He is a Professional Engineer, an IEEE Fellow, an ASME Fellow and an IMAPS Fellow. He served as chief editor of the IEEE Transactions on Reliability for eight years and on the advisory board of IEEE Spectrum. He is chief editor for Microelectronics Reliability and an associate editor for the IEEE Transactions on Components and Packaging Technology. He is the founder of CALCE (Center for Advanced Life Cycle Engineering) at the University of Maryland, College Park, where he is also a Chair Professor in Mechanical Engineering. He has written more than twenty books on electronic products development, use and supply chain management and over 400 technical articles. He has been leading a research team in the area of prognostics for the past ten years, and has now formed a new Prognostics and Health Management Consortium at the University of Maryland. He has consulted for over 50 major international electronics companies, providing expertise in strategic planning, design, test, prognostics, IP and risk assessment of electronic products and systems. He was awarded the highest reliability honor, the IEEE Reliability Societyʼs Lifetime Achievement Award in 2008. He has previously received the European Micro and Nano-Reliability Award for outstanding contributions to reliability research, 3M Research Award for electronics packaging, and the IMAPS William D. Ashman Memorial Achievement Award for his contributions in electronics reliability analysis.

Title: Mechanical dissipation in MEMS

Lecturers: Alberto Corigliano and Attilio Frangi

Affiliation: Department of Structural Engineering, Politecnico di Milano. Piazza Leonardo da Vinci 32, 20133, Milano, Italy.

Key words: MEMS, fluid damping, solid damping, BE and FE simulations

Abstract: The short course has the main objective to present an overview of dissipative phenomena which occur in MEMS mainly due to fluid-structure interaction (fluid damping) and to intrinsic solid dissipation mechanisms (solid damping).

After a description of the physical phenomena involved, details will be given in particular on the following subjects: computation of MEMS quality factor by means of an highly efficient numerical procedure based on the Boundary Element method; thermo-elastic damping and its numerical treatment; other possible sources of solid damping.

Topics addressed:

• Introduction and motivations. Quality factor and dissipation.
• Fluid dissipation at high/moderate pressure (continuum regime): Reynolds model and 3D Stokes approach. Introduction to numerical techniques: boundary elements and finite elements.
• Fluid dissipation at lower pressure (transition regime): introduction to the kinetic theory of rarefied gas dynamics (e.g. BGK). Methods of numerical solution. Simplified approaches based on corrected viscosity.
• Fluid dissipation in near vacuum (free-molecule flow): introduction and numerical models.
• Extension to high working frequencies and transient analysis
• Thermo-elastic damping
• Numerical evaluation of the thermo elastic quality factor and comparison with Zener’s formula
• Other sources of solid damping
• Case studies: linear accelerometers

References: Ardito R., C. Comi, A. Corigliano, A. Frangi – Solid damping in Micro Electro Mechanical Systems, Meccanica, 43, pp 419-428, 2008.

Corigliano A., F. Cacchione, S. Zerbini. Mechanical characterization of low dimensional structures through on-chip tests. In Micro and Nano Mechanical Testing of Materials and Devices, edited by F. Yang, J.C.M. Li, Springer, (2008).

Frangi A., Ye W., White J. Evaluating gas damping in MEMS using fast integral equation solvers, in Advances in Multiphysics Simulation of MEMS and NEMS edited by Frangi A., Aluru N., Cercignani C., Mukherjee S., Imperial College Press, London, 2008.

Frangi A., Aluru N., Cercignani C., Mukherjee S. eds., Advances in Multiphysics Simulation and experimental testing of MEMS, Imperial College Press , London, 2008.

Short CV Alberto Corigliano

Alberto Corigliano is full professor of "Scienza delle Costruzioni" (Structural Mechanics) at the Department of Structural Engineering of the Politecnico di Milano, member of the Council of PhD school in Structural, Earthquake and Geotechnical Engineering and vice-Director of the Department of Structural Engineering. He teaches courses of “Computational Mechanics”, “Advanced Structural Mechanics” and “Advanced Fracture Mechanics” to Graduate Engineers and PhD students and carries out his research activity at the Department of Structural Engineering. Since 2004 A. Corigliano is member of the technical committee of Eurosime (Thermal, mechanical and multi-physics simulation and experiments in micro-electronics and micro-systems). Since June 2006 is Associate Editor of the European Journal of Mechanics A/Solids. In 2006 he won the Bruno Finzi price for Rational Mechanics given by the “Istituto Lombardo Accademia di Scienze e Lettere”. He is (co-) author of more than 130 papers, published on international (more than 40) and Italian technical journals, books or on proceedings of Italian or international scientific congresses and co-author of two scientific monographs, one book for graduate students and of 3 invited chapters in books. During his research activity, Alberto Corigliano covered a wide range of subjects in the fields of structural and materials mechanics, with particular reference to theoretical and computational problems relevant to non-linear material responses. His main scientific interests are now focussed on Design and Reliability of Micro Electro Mechanical Systems (MEMS) and related multi-physics problems.

Short CV Attilio Frangi

Dr. Attilio Frangi is an Associate Professor at the Department of Structural Engineering of the Politecnico di Milano and at the Department of Mechanics, Ecole Polytechnique, Palaiseau (Paris). He is member of the International Advisory Board of the European Journal of Computational Mechanics. His research interests focus on the simulation of multiphysics phenomena for industrial electromagnetic applications and micro/nano structures. He has co-edited one scientific monograph on the multiphysics simulation of MEMS and NEMS and has (co-) authored one book on numerical analysis, 8 invited chapters in books, 37 papers published in international technical journals and more than 70 contributions in proceedings of scientific congresses. Attilio Frangi is the recipient of the Fondazione Confalonieri prize (1999) and of the Young Researcher Fellowship Award, MIT, Cambridge, 2001.

Experimental Mechanics Methods for Electronic Packaging

Instructor:

Jeffrey C. Suhling, Auburn University

Course Scope

Electronic packaging is a field in rapid evolution due to strong and competing customer demands for increased functionality and performance, further miniaturization, heightened reliability, and lower costs. Such product drivers cause a myriad of reliability challenges for the engineer involved in the mechanical design of electronic systems. Accordingly, advanced experimental techniques are in high demand, and several methods of experimental solid mechanics have become critical tools for design and development of electronic products. In this short course, a presentation is made of most important experimental techniques that are applied to packaging for measurements of stress, strain, and deformation including:

• Acoustic Microscopy (CSAM)
• Silicon Test Chips with Stress and Temperature Sensors
• Moiré Interferometry
• Digital Image Correlation (DIC)
• Photomechanics Methods for Characterization of Warpage
• Micromechanical Characterization of Solders, Underfills, and Thin Films

To begin the course, the mechanics and reliability issues for modern electronic systems will be reviewed, and the challenges facing the experimentalist in the packaging field discussed. For each experimental method, discussion will be given of the theoretical fundamentals and equations that form the basis of the technique, as well as of the practical approaches and “tricks of the trade” needed by the experimentalist for successful implementation to advanced electronic packages and assemblies. Designs for specialized instruments and testing systems based on these methods will also be shown. Finally, a comparison of the capabilities of the various methods will be made as well as identifying the best techniques for various applications. Several detailed examples for various important packaging measurements will be presented including:

• Delamination Detection at Material Interfaces in Flip Chip and Molded Packages
• Silicon Chip Stress Characterization (QFP, BGA, Flip Chip, etc.)
• Evaluation of Solder Joint Deformations and Strains in Area Array Packaging
• Warpage Measurements for Die, Components, and Substrates
• Evaluation of Transient Deformations and Strains During Drop Tests
• Material Characterization of Lead Free Solder Joints
• Material Characterization of Underfills and Thin Films

Instructor

Jeffrey C. Suhling received a Ph.D. degree in Engineering Mechanics from the University of Wisconsin, USA. He joined the Department of Mechanical Engineering at Auburn University in 1985, where he currently holds the position of Quina Distinguished Professor and was recently elected to be Department Chair. From 2002-2008, he previously served as the Director of the NSF Center for Advanced Vehicle Electronics (CAVE), which is an Industry University Cooperative Research Center (IUCRC) with 22 member companies. He was selected “Outstanding Mechanical Engineering Faculty Member” by the undergraduate students during 1990, received the College of Engineering Birdsong Superior Teaching Award in 1994, and received the College of Engineering Senior Research Award in 2001. His research interests include the application of analytical, numerical, and experimental methods of solid mechanics to problems in electronic packaging. In particular, Dr. Suhling has pioneered the method of on-chip piezoresistive stress sensors and their application for characterizing die stress distributions, as well as developing innovative methods for characterizing the material behavior and aging of lead free solders and underfills. He has authored or co-authored over 250 technical publications, including four papers selected as the Best of Conference. He has advised over 50 graduate students at Auburn University. Dr. Suhling is a member of ASME, IEEE, IMAPS, SEM, and SMTA. He served as Chair of the Electrical and Electronic Packaging Division of ASME during 2002-2003, and was on the EPPD Executive Committee from 1998-2003. Dr. Suhling was the Technical Program Chair of the InterPACK ‘07 Conference, and is the General Chair of the upcoming InterPACK ‘09 Conference to be held in July 2009. He currently serves on the Quality and Reliability Program Committee and Professional Development Course Committee of the IEEE Electronic Components and Technology Conference (ECTC).