Electromigration Analysis of Solder Joints for Power Modules Using an Electrical-Thermal-Stress Coupled Model

2021 ◽  
Author(s):  
Mitsuaki Kato ◽  
Takahiro Omori ◽  
Akihiro Goryu ◽  
Tomoya Fumikura ◽  
Kenji Hirohata
Keyword(s):  
Thermal Stress ◽  
Solder Joints ◽  
Coupled Model ◽  
Power Modules

Electromigration Analysis of Solder Joints for Power Modules Using an Electrical-Thermal-Stress Coupled Model

2021 ◽  
Author(s):  
Mitsuaki Kato ◽  
Takahiro Omori ◽  
Akihiro Goryu ◽  
Tomoya Fumikura ◽  
Kenji Hirohata
Keyword(s):  
Thermal Stress ◽  
Solder Joints ◽  
Coupled Model ◽  
Power Modules

Electromigration Analysis of Solder Joints for Power Modules Using an Electrical-Thermal-Stress Coupled Model

2021 ◽  
Author(s):  
Mitsuaki Kato ◽  
Takahiro Omori ◽  
Akihiro Goryu ◽  
Tomoya Fumikura ◽  
Kenji Hirohata
Keyword(s):  
Thermal Stress ◽  
Solder Joint ◽  
Power Output ◽  
Solder Joints ◽  
Vacancy Concentration ◽  
Inelastic Strain ◽  
Power Device ◽  
Power Module ◽  
Power Modules ◽  
Rate Of Increase

Abstract Power modules are being developed to increase power output. The larger current densities accompanying increased power output are expected to degrade solder joints in power modules by electromigration. In previous research, numerical analysis of solder for electromigration has mainly examined ball grid arrays in flip-chip packages in which many solder balls are bonded under the semiconductor device. However, in a power module, a single solder joint is uniformly bonded under the power device. Because of this difference in geometric shape, the effect of electromigration in the solder of power modules may be significantly different from that in the solder of flip chips packages. This report describes an electromigration analysis of solder joints for power modules using an electrical-thermal-stress coupled analysis. First, we validate our numerical implementation and show that it can reproduce the vacancy concentrations and hydrostatic stress almost the same as the analytical solutions. We then simulate a single solder joint to evaluate electromigration in a solder joint in a power module. Once inelastic strain appears, the rate of increase in vacancy concentration slows, while the inelastic strain continuously increases. This phenomenon demonstrates that elastic-plastic-creep analysis is crucial for electromigration analysis of solder joints in power modules. Next, the solder joint with a power device and a substrate as used in power modules was simulated. Plasticity-creep and longitudinal gradient generated by current crowding have a strong effect on significantly reducing the vacancy concentration at the anode edge over a long period of time.

Electromigration Analysis of Solder Joints for Power Modules Using an Electrical-Thermal-Stress-Atomic Coupled Model

2021 ◽  
Author(s):  
Mitsuaki Kato ◽  
Takahiro Omori ◽  
Akihiro Goryu ◽  
Tomoya Fumikura ◽  
Kenji Hirohata
Keyword(s):  
Thermal Stress ◽  
Solder Joint ◽  
Creep Strain ◽  
Current Density ◽  
Solder Joints ◽  
Vacancy Concentration ◽  
Size Ratio ◽  
Power Device ◽  
Current Crowding ◽  
Power Modules

Abstract Numerical analysis of electromigration in solder joints has mainly examined ball grid arrays (BGAs) in flip-chip packages, and few numerical study has been reported on solder joints in power modules. This report describes an electromigration analysis of solder joints for power modules with a Si-based power device, which are still widely used today, using an electrical-thermal-stress-atomic coupled analysis. To evaluate electromigration, a solder joint with a power device and a substrate as used in power modules was simulated. Due to current crowding, the current density at the edge of the solder joint exceeded the electromigration threshold even in Si-based power modules. Unlike general electromigration phenomena, the vacancy concentration increased at the center and decreased at the edges of the solder joint, regardless of whether it was on the cathode side or anode side. The vacancy concentration clearly increased with increasing current density and size ratio. Creep strain increased significantly with increasing current density, temperature, and size ratio. The largest change in vacancy concentration and creep strain was at the anode edge where current crowding occurred. In addition, we modeled the two-dimensional behavior of metal atoms passing through the interface of the solder joint. The expansion of intermetallic compound was accelerated by increasing the temperature and current density.

Investigation of rotor thermal stress in squirrel cage induction motor with broken bar faults

2016 ◽  
Vol 35 (5) ◽  
pp. 1865-1886 ◽  
Author(s):  
Ying Xie ◽  
Ze Wang ◽  
Xueting Shan ◽  
Yangyang Li
Keyword(s):  
Thermal Stress ◽  
Induction Motor ◽  
Coupled Model ◽  
Coupled Analysis ◽  
Content Type ◽  
Squirrel Cage ◽  
Squirrel Cage Induction Motor ◽  
And Performance ◽  
Cage Induction Motor ◽  
Good Agreement

Purpose Thermal stress of the rotor in a squirrel cage induction motor is generated due to the temperature rise, and the structure of the rotor will be destroyed if the stress acted on the rotor exceeds its limits, so the thermal stress is also one of the main causes led to broken bar fault. The purpose of this paper is to report the thermal stress coupled analysis for the induction motor with healthy and faulty rotor, and to find the variation tendency of the temperature and thermal stress due to broken bars, and the part most likely to break in the rotor as a result of the thermal stress load are identified. Design/methodology/approach The steady temperature and thermal stress of the rotor in the case of the healthy and faulty conditions are calculated by finite element method, and the 3D model of the motor used in the experiments is established and the experimental results are presented for both healthy and faulty machines. Findings The influence of the broken bars fault on the motor thermal profile and thermal stress can be found, and it explains why the breaking point always appears in the joint of the bars and end rings. Originality/value The paper presents the 3D thermal stress coupled model and performance characteristics of induction motor with broken bars. The reasonable constraint is established according to the contact of components each other, and more reasonable fracture location is selected. The results obtained by the simulation model are in a good agreement with practical situation, because the effect of skewed rotor were taken into consideration in the process of simulation.

A Comparison of Thermal Stress/Strain Behavior of Elliptical/Round Solder Pads

1999 ◽  
Vol 123 (2) ◽  
pp. 127-131 ◽  
Author(s):  
Kuo-Ning Chiang ◽  
Chang-Ming Liu
Keyword(s):  
Thermal Stress ◽  
Solder Joint ◽  
Solder Joints ◽  
Numerical Models ◽  
Ball Grid Array ◽  
Stress Strain ◽  
Restoring Force ◽  
Array Type ◽  
Finite Element Software ◽  
Area Array

As electronic packaging technology moving to the CSP, wafer level packaging, fine pitch BGA (ball grid array) and high density interconnections, the wireability of the PCB/substrate and soldering technology are as important as reliability issues. In this work, a comparison of elliptical/round pads of area array type packages has been studied for soldering, reliability, and wireability requirements. The objective of this research is to develop numerical models for predicting reflow shapes of solder joint under elliptical/round pad boundary conditions and to study the reliability issue of the solder joint. In addition, a three-dimensional solder liquid formation model is developed for predicting the geometry, the restoring force, the wireability, and the reliability of solder joints in an area array type interconnections (e.g., ball grid array, flip chip) under elliptical and round pad configurations. In general, the reliability of the solder joints is highly dependent on the thermal-mechanical behaviors of the solder and the geometry configuration of the solder ball. These reliability factors include standoff height/contact angle of the solder joint, and the geometry layout/material properties of the package. An optimized solder pad design cannot only lead to a good reliability life of the solder joint but also can achieve a better wireability of the substrate. Furthermore, the solder reflow simulation used in this study is based on an energy minimization engine called Surface Evolver and the finite element software ABAQUS is used for thermal stress/strain nonlinear analysis.

Supporting Structure Performances Analysis of Heavy-Duty Gas Turbine Based on Fluid-Solid Coupling Method

2015 ◽  
Author(s):  
Guohui Xu ◽  
Jian Zhou ◽  
Mingjian Lu ◽  
Haipeng Geng ◽  
Yanhua Sun ◽  
...  
Keyword(s):  
Thermal Stress ◽  
High Temperature ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Thermal Deformation ◽  
Coupled Model ◽  
Strength Analysis ◽  
Cooling Flow ◽  
Heavy Duty Gas Turbine ◽  
Steady State Heat Transfer

In order to achieve high working efficiency, modern gas turbines operate at high temperature which is close to the melting points of metal alloys. However, the support of turbine end suffers the thermal deformation. And the journal center position is also changed due to the effects of high temperature and shaft gravity. Tangential or radial supporting structures, which are composed of supporting struts, diffuser cones, hot and cooling fluid channel, are widely used in gas turbine hot end. Cooling technology is usually used to keep the bearing temperature in a reasonable range to meet requirements of strength and deformation of the supporting struts. In this paper, three major assumptions are proposed: (a) radiation is not considered, (b) cooling flow system is only partially modeled and analysis assumes significantly higher cooling flow that is not typical for current engines, and (c) only steady state heat transfer is considered. And a 3D fluid-solid coupled model based on finite-element method (FEM) is built to analyze the performances of both the tangential and the radial support. The temperature distribution, thermal deformation and stress of supports are obtained from CFD and strength analysis. The results show that either the tangential or radial support is used in a 270MW gas turbine; the thermal stress is about 90.3% of total stress which is produced by both thermal effects and shaft gravity. Comparing to the results from radial supports, it can be seen that the struts stress and position variation of journal center of tangential support are smaller. Due to a rotational effect of the bearing housing caused by the deformation of the tangential struts, the thermal stress in these tangential struts can be relieved to some extent. When both thermal effect and shaft gravity are considered, the stress of each tangential supporting strut is almost uniformly distributed, which is beneficial to the stability of rotor system in the gas turbine.

Electromigration Analysis of Solder Joints for Power Modules Using an Electrical-Thermal-Stress Coupled Model

2020 ◽  
Author(s):  
Mitsuaki Kato ◽  
Takahiro Omori ◽  
Akihiro Goryu ◽  
Tomoya Fumikura ◽  
Kenji Hirohata
Keyword(s):  
Solder Joint ◽  
Mechanical Stress ◽  
Solder Joints ◽  
Hydrostatic Stress ◽  
Vacancy Concentration ◽  
Intermetallic Layer ◽  
Current Crowding ◽  
Metal Atoms ◽  
Power Modules ◽  
Rate Of Increase

Abstract Power modules are being developed with the aim of increasing power output. Achieving this aim requires increased current density in power modules. However, at high current densities, power modules can degrade as a result of electromigration, which is a phenomenon where atoms move due to momentum transfer between conducting electrons and metal atoms. In addition, atoms are also moved by mechanical stress gradients and temperature gradients, so it is necessary to consider the combined effects of electrical, thermal, and mechanical stress. This report describes an electromigration analysis of solder joints for power modules. First, we validated our numerical implementation and showed that it could reproduce the distributions of vacancy concentrations and hydrostatic stress that were almost the same as those in previous studies. We then describe the effects of electromigration in a single solder joint. Due to the appearance of plastic and creep strains, the rate of increase in vacancy concentration was very slow and inelastic strain grew at an increasing rate. This result indicates that inelastic properties may strongly affect electromigration-induced degradation. Next, we present results for the solder joint with a SiC device and substrate. A current crowding appeared at the edge of the solder joint, and a vacancy concentration gradient was generated in not only the thickness direction but also the longitudinal direction. The absolute value of vacancy concentration increased significantly at the edge and did not reach a steady state even after a long time. These results indicate that peripheral components may strongly affect the electromigration-induced degradation. In addition, we modeled the behavior of metal atoms passing through the interface of the solder joint and simulated the growth of the intermetallic layer by electromigration.

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