Mechanics of Microelectronics (eBook)

CONTENTS 6
PREFACE 12
MICROELECTRONICS TECHNOLOGY 15
RELIABILITY PRACTICE 49
THERMAL MANAGEMENT 79
INTRODUCTION TO ADVANCED MECHANICS 109
THERMO-MECHANICS OF INTEGRATED CIRCUITS AND PACKAGES 183
CHARACTERIZATION AND MODELLING OF MOISTURE BEHAVIOUR 295
CHARACTERIZATION AND MODELLING OF SOLDER JOINT RELIABILITY 391
VIRTUAL THERMO-MECHANICAL PROTOTYPING 483
CHALLENGES AND FUTURE PERSPECTIVES 551

Chapter 7
CHARACTERIZATION AND MODELLING OF SOLDER JOINT RELIABILITY (p. 378)

R. Dudek
Fraunhofer Institute Zuverlassigkeit und Mikrointegration, Gustav-Meyer-A - llee 25, 13355
Berlin, Germany

Abstract: This chapter addresses finite-element analyses (FEA) of solder fatigue phenomena caused by low-cycle thermo-mechanical loading. To begin with, an introduction to board level solder joint fatigue, characteristic thermal loading situations, the effects of thermal mismatch and analytical lifetime estimates is provided. Subsequently, challenges to the FE-based methodologies are discussed, which are particularly related to the non-linear mechanical properties of soft solders. Material constitutive models and the implementation of time and temperature dependent behaviours of leaded and lead-free solders are described. d Fatigue-life prediction modelling focuses on the strength of materials approaches, i.e., creep strain-based relations or energy-based relations. An overview on several fatigue-life prediction models from the literature is additionally provided. The FE-based methodology is applied to board-level solder joint reliability assessments for several components. Its wide applicability is illustrated by the choice of different types of components ranging from large t ceramic surface mount to small flip-chip assemblies on different types of substrates. For some of the application cases, results of parametric studies are presented and comparisons between failure prediction and testing results are made.

Key words: Solder fatigue, Finite Element simulations, solder plasticity, solder creep, primary and secondary creep, reliability predictions, coffin manson, board level test validation.

1. INTRODUCTION

The computational design of reliable microsystems, electronic packages as well as their interconnects can minimize expensive prototype development and testing. Accordingly, finite element (FE-) modelling is widely used to perform parametric studies on the thermo-mechanical behaviour of components like e.g., silicon microstructures, plastic packages, chip size/wafer level packages, or flip chip assemblies.

From a mechanical point of view all these structures include constituents, which are subjected to different loading conditions. The theoretical analysis of stresses within these constituents induced by environmental conditions requires the characterization of loads and material properties, respectively, as well as the knowledge of the appropriate failure criteria. Figure 1 provides an overview on the characteristic tasks to be performed for those thermomechanical finite element analyses (FEA).