This paper presents an experimental study on the ageing of insulated-gate bipolar transistor (IGBT) power modules. The aim is to identify the effects of power cycling on these devices with high baseplate temperatures (60 °C to 90 °C) and wide temperature swings (60 °C to 100 °C). These values for thermal stresses have been defined according to automotive applications. The test conditions are provided by two types of test benches that will be described in this paper. The changes in electrical and thermal indicators are observed regularly by a monitoring system. At the end of the test (reaching damage criterion or failure), different analyses are performed (acoustic scanning and SEM imaging), and the damage is listed systematically. Nineteen samples of 600-V 200-A IGBT modules were thus aged using five different power-cycling protocols. The final summary of results shows that ageing mechanisms mainly concern wire bonds and emitter metallization, with gradual impact depending on protocol severity.

Ageing and Failure Modes of IGBT Modules in High-Temperature Power Cycling

In this paper a physical model for lifetime estimation of standard power modules is proposed. The lifetime prediction is based on the assumption that the solder interconnections are the weakest part of the module assembly and that the failure cause is the inelastic deformation energy accumulated within the solder material. Unlike the well-known Coffin-Manson model, the proposed model can be used to physically explain the dependency of lifetime on the various properties of a temperature profile i.e. frequency, dwell-ramp time, minimum/maximum temperature. The model is based on Clech's algorithm for simulation of stress-strain solder response under cyclical thermal loading and on the solder deformation mechanism map used to define the dominant failure mechanism under observed stress-temperature conditions. Either accelerated cycling tests or existing field databases are needed to parameterize the model. To verify the approach, the results of power cycling tests for a high power IGBT module found in literature are applied and the impacts of two mission profiles on the module lifetime are examined.

New physical model for lifetime estimation of power modules

................................................................................................................................... ii Dedication................................................................................................................................ iv Acknowledgments.................................................................................................................... v Vita........................................................................................................................................... vii List of Tables............................................................................................................................. xii List of Figures............................................................................................................................ xiv Chapter 1 ‐ Introduction........................................................................................................... 1 1.1 ‐ Microbial fuel cells.................................................................................................. 2 1.2 ‐ Microbial fuel cell applications............................................................................... 4 1.3 ‐ Research problems associated with MFC technology............................................. 5 1.4 ‐ Introduction to this research study......................................................................... 6 Chapter 2 ‐ Effects of Nano‐structure Enhanced Cathodes on Electricity Production of Two‐ Chamber Microbial Fuel Cells 2.1 ‐ Introduction............................................................................................................ 8 2.2 ‐ Materials and Methods........................................................................................... 16 2.2.1 ‐ Electrode construction Graphite bar anodes.......................................................................................... 18 Graphite bar cathodes....................................................................................... 20

In Partial Fulfillment of the Requirements for the Degree of

Applying Anand model to low-temperature sintered nanoscale silver paste chip attachment

The Anand viscoplastic constitutive model is often used to represent the deformation behavior of solders in electronic assemblies. In the Anand model, plasticity and creep are unified and described by the same set of flow and evolution relations. The nine parameters of the Anand constitutive model are typically determined from uniaxial stress-strain tests at several strain rates and temperatures using a standard multistep model parameter determination procedure. Conversely, creep data are often measured for solders, but typically are not used to determine Anand model constants.

Determination of Anand constants for SAC solders using stress-strain or creep data

A unified viscoplastic constitutive law, the Anand model, was applied to represent the inelastic deformation behavior for solders used in electronic packaging. The material parameters of the constitutive relations for 62Sn36Pb2Ag, 60Sn40Pb, 96.5Sn3.5Ag, and 97.5Pb2.5Sn solders were determined from separated constitutive relations and experimental results. The achieved unified Anand model for solders were tested for constant strain rate testing, steady-state plastic flow and stress/strain responses under cyclic loading. It is concluded that the Anand model can be applied for representing the inelastic deformation behavior of solders at high homologous temperature and can be recommended for finite element simulation of the stress/strain responses of solder joints in service. @DOI: 10.1115/1.1371781#

Applying Anand Model to Represent the Viscoplastic Deformation Behavior of Solder Alloys

A viscoplastic constitutive model, the Anand model, in which plasticity and creep are unified and described by the same set of flow and evolutionary relations, was applied to represent the inelastic deformation behavior for solder alloys. After conducting creep tests and constant strain rate tests, the material parameters for the Anand model of the Pb‐rich content solder 92.5Pb5Sn2.5Ag were determined from the experimental data using a nonlinear fitting method. The material parameters for 60Sn40Pb, 62Sn36Pb2Ag and 96.5Sn3.5Ag solders were fitted from the conventional model in the literature where plasticity and creep are artificially separated. Model simulations and verifications reveal that there is good agreement between the model predictions and experimental data. Some discussion on this unified model is also presented. This viscoplastic constitutive model for solder alloys possesses some advantages over the separated model. The achieved Anand model has been applied in finite element simulation of stress/strain responses in solder joints for chip component, thin quad flat pack and flip‐chip assembly. The simulation results are in good agreement with the results in the literature. It is concluded that the Anand model could be recommended as a useful material model for solder alloys and can be used in the finite element simulation of solder joint reliability in electronic packaging and surface mount technology.

G. Z. Wang

Papers

Applying Anand Model to Represent the Viscoplastic Deformation Behavior of Solder Alloys

Viscoplastic Anand model for solder alloys and its application