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AN ENGINEER'S HANDBOOK OF ENCAPSULATION AND UNDERFILL TECHNOLOGY

by Martin Bartholomew

Code: EP37

Contents of this page:

Description
About the Author
Table of Contents

Description

The aim of this book is to assist personnel engaged in the design, development, and/or manufacture of glob-topped and underfilled components with the selection and use of encapsulant materials. There are a great many factors that have to be considered before even a short list of candidate materials can be drawn up. The requirements, in terms of materials properties, for typical glob-top and underfill applications are developed and discussed in relation to the performance of the extensive range of commercially available generic encapsulant materials.

The author makes no apologies for writing extensively on the many test methods that can be applied to encapsulants. It is hoped that the reader will be able to select test methods that are representative of his application, and be able to develop a focused, cost-effective test plan.

The author has attempted to cover the widest possible range of theoretical and practical topics associated with encapsulant materials and techniques. It has thus been necessary to limit the extensive organic chemistry background associated with the encapsulant materials to just the essentials, and avoid complex mathematical derivations. References are given at the end of each chapter to assist those who seek more detail on any topic.

About the Author

Martin Bartholomew obtained his BSc in Materials Science from the University of Bath in 1973. Since then he has worked in various roles related to semiconductor packaging, including process development, yield improvement, packaging development and quality engineering. His experience, gained while working for Plessey, GEC-Marconi, STC and Siliconix, covers a wide range of products, such as hermetic and plastic ICs, power MOSFETS, and optoelectronic components.

Before joining Multicore Solders as Market Development Manager (Advanced Products Division) in June 1996, Mr Bartholomew managed the technical activities in the EU 462 Pepite MCM programme at The Welding Institute (TWI). He also consulted for TWI’s member companies, and developed and conducted training courses in die attach and COB technologies. During that time, he carried out background research and performance evaluations on a range of industry-standard and novel encapsulation materials. This work resulted in his being awarded a Master’s Degree in Physics from the University of Warwick in the early part of 1998.

Mr Bartholomew is the author of several papers in the field of microelectronics packaging, and is a regular presenter at worldwide seminars conferences and workshops.

Table of Contents

Chapter One

INTRODUCTION TO GLOB-TOP AND UNDERFILL ENCAPSULATION MATERIALS AND TECHNIQUES

1.1 The use of resin encapsulants in semiconductor packaging: a historical perspective

1.2 Trends in semiconductor packaging

1.3 Overview of current organic resin encapsulant materials

Chapter Two

THE STRUCTURE AND PROPERTIES OF RESIN ENCAPSULANTS

2.1 Epoxies

2.1.1 Health and safety precautions

2.2 Silicones

2.3 Polyimides

2.4 Other candidates: Acrylates, Polyxylylenes, Urethanes

2.5 Effect of filler additions to encapsulants

Chapter Three

FAILURE MECHANISMS IN ENCAPSULATED SEMICONDUCTOR DEVICES

3.1 Die-related failure mechanisms

3.2 Package/operating environment-related failure mechanisms

3.2.1 Mechanical stress induced failures

3.2.2 Prediction of thermomechanical stresses

3.2.3 Metallurgical factors

3.3 Environmental factors/misuse of product

3.4 Discussion of Al metallisation corrosion mechanisms

3.5 Failure modes in underfilled flip-chipped components

3.5.1 Bump metallisation/die passivation effects

3.5.2 Fatigue of bump metallisation

3.6 Surface effects

 Chapter Four

MATERIAL PROPERTIES REQUIREMENTS FOR ENCAPSULANT MATERIALS

4.1 Results of literature survey

4.2 General material property requirements for encapsulants

4.2.1 Thermomechanical properties

4.2.2 Properties related to corrosion failure

4.2.3 Electrical/thermal/optical properties

4.2.4 Resistance to solvents

4.2.5 Mixing and storage

4.2.6 Rheology

4.2.7 Curing

4.3 Dual layer glob-top systems

4.4 Notes on the selection of encapsulant materials

Chapter Five

TEST METHODS FOR GLOB-TOP AND UNDERFILL ENCAPSULANTS

5.1 Tests carried out on encapsulants to determine their generic material properties

5.1.1 Adhesion

5.1.2 Young’s modulus

5.1.3 Hardness

5.1.4 Thermal coefficient of expansion

5.1.5 Glass transition temperature, cure sensitivity, and condition during storage

5.1.6 Dispensing and flow characteristics

5.1.7 Moisture content

5.1.8 Electrical properties

5.2 Tests on encapsulated components (test die, specially designed structures, or actual product)

5.2.1 Thermal shock/thermal cycling

5.2.2 Measurement of stress in encapsulated components

5.2.3 Relative electrical performance

5.2.4 Accelerated ageing tests

 5.2.5 Development of a salt cell test method

5.3 Failure analysis techniques

5.3.1 Introduction

5.3.2 Non-destructive inspection/test methods

5.3.3 Methods for encapsulant removal (decapsulation)

5.3.4 Inspection methods for use on decapsulated, or microsectioned, components

5.4 Guide to the analysis of failed components

Chapter Six

PROCESSING OF GLOB-TOP AND UNDERFILL MATERIALS

6.1 General issues

6.1.1 Preparation of Encapsulant Materials

6.1.2 Surface cleaning/verification methods

6.2 Glob-top dispensing

6.2.1 Manual syringe dispensing

6.2.2 Automated dispensing methods

6.2.3 Stencil printing

6.2.4 Control over glob-top morphology

6.3 Underfilling methods

6.4 Encapsulant curing methods

6.4.1 Thermal cure

6.4.2 Radiation cure (UV/visible light)

Chapter Seven

FUTURE TRENDS

Predeposited no-flow material. Self fluxing underfills

Reworkable materials. Advances in filler technology. Tests and standards

 

 

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 Page last revised 11.02.05

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