Time integration damage model for Sn3.5Ag solder interconnect in power electronic module

In this study, existing damage evolution models in the literature for solder layer in microelectronics have been reviewed. A two dimensional approximate semi-analytic time integration damage indicator model for Sn3.5Ag material solder interconnect in power electronic module has been proposed. The proposed time dependent damage model is dependent on the inelastic strain, the accumulated damage at previous time step and the temperature. The strains were approximated semi-analytically. A numerical modelling methodology combined with the data from public domain for crack initiation and crack propagation of Sn3.5Ag solder layer has been adopted to extract the parameter values of the proposed damage model. The proposed model has advantages over fatigue lifetime models as it instantaneously predicts the damage over time for any loading history. The damage model was compared with Ansys FEA tool based damage prediction using Coffin Manson and Paris law fatigue models. The predicted damage value by the model is slightly higher than those models. Furthermore, this damage model does not need a time consuming numerical simulation evaluating the damage model variables, which is an advantag

Modelling and analysis of vibration on power electronic module structure and application of model order reduction

Modelling and analysis of vibration of an IGBT power electronic module (PEM) structure were undertaken. PEM structure considered in this study was without molding compound and wirebonds. The most critical resonant frequency was identified by modal analysis. At the critical frequency of 1345Hz, for the vertical displacement of the base excitation, subsequent stress distribution on the PEM structure was analysed. Concurrent vibration and thermo-mechanical fatigue loads on the reliability of PEM structure solder interconnects were also estimated by widely used linear damage superposition approach. It was concluded that the at critical resonant frequency the vibration induced damage is more severe than the thermo-mechanical fatigue loading. In addition, a quarter car model (QCM) was used to mimic the dynamic interaction between the rough road surface and an electric vehicle (EV) in order to analyse the road surface roughness induced excitation on the PEM structure in the engine compartment. Stress and strain distribution on the PEM structure due to road surface roughness were analysed. Furthermore, three Krylov subspace based model order reduction (MOR) techniques were applied to the resulting dynamic system in vibration analysis. Due to the limits on computing resources, a submodel was utilized for MOR analysis. Within the three MOR techniques, Passive Reduced order Interconnect Macromodeling Algorithm (PRIMA) MOR technique performs better than the other techniques. Computational time ratio between reduced system iteration and the full system iteration is 1:53

Damage mechanics-based failure prediction of wirebond in power electronic module

A damage mechanics-based numerical approach for the prediction of the damage evolution in wirebond structures of the power electronic module (PEM) is presented. A simplistic damage evolution model is developed in an in-house finite element code, with a demonstration focused on the analysis of the wirebond damage evolution by thermally induced stresses in PEM subjected to varying thermal loads. The novelty of the proposed methodology is the damage evolution realized at the level of each discretised mesh element of the finite element model of the PEM structure in the numerical approach and the associated impact of damage on the mechanical material properties of that element. A simplified PEM structure is utilised as a case study to demonstrate the proposed damage evolution modelling. The thermal load of each discretised element of the PEM structure was imported from an external thermal code. From the thermally induced stresses, plastic strain rates were approximated and then, using these metrics a damage evolution metric was derived. The damage distribution plot of the wirebond structure for the applied load in the case study indicates that maximum damage accumulation at the heel structure reaches 2.4% of the total damage after 3 seconds. By extrapolating the trendline of damage evolution in wirebond, the time of the structural failure was also predicted. The maximum von Mises stress was observed on the busbar which reaches 64 MPa. The extreme stresses found at the busbar are attributed to the high value of the coefficient of thermal expansion of the busbar materia

Predicting damage and life expectancy of subsea power cables in offshore renewable energy applications

Subsea power cables are critical assets within the distribution and transmission infrastructure of electrical networks. Over the past two decades, the size of investments in subsea power cable installation projects has been growing significantly. However, the analysis of historical failure data shows that the present state-of-the-art monitoring technologies do not detect about 70% of the failure modes in subsea power cables. This paper presents a modelling methodology for predicting damage along the length of a subsea cables due to environmental conditions (e.g. seabed roughness and tidal flows) which result in loss of the protective layers on the cable due to corrosion and abrasion (accounting for over 40% of subsea cable failures). For a defined cable layout on different seabed conditions and tidal current inputs, the model calculates cable movement by taking into account the scouring effect and then it predicts the rate at which material is lost due to corrosion and abrasion. Our approach integrates accelerated aging data using a Taber test which provides abrasion wear coefficients for cable materials. The models have been embedded into a software tool that predicts the life expectancy of the cable and demonstrated for narrow conditions where the tidal flow is unidirectional and perpendicular to the power cable. The paper also provides discussion on how the developed models can be used with other condition monitoring data sets in a prognostics framework

Reduced order modelling for reliability optimisation of advanced micro-systems

This paper discusses the Design for Reliability of advanced electronics Micro-systems based on computational approach that integrates methods for high fidelity analysis, reduced order modelling, numerical risk analysis and optimisation. The methodology is demonstrated for the design of a System-in-Package (SiP) structure. System-in-Package is a technology that is developed on the basis of miniaturised integrated multi-functional electronics modules using 3D stacking of several silicon chips (Integrated Circuits, ICs). System-in-Package aims to provide fully functional electronic systems and sub-systems that integrate several functionally different devices, e.g. optical, MEMS, sensors and other components, into a single package. There is little understanding and knowledge how do the large die sizes in the SiP modules, the lead-free assembly, interfacial de-laminations and the utilisation of new materials affect the reliability of these electronics systems. In particular, the board level reliability of the package related to the thermal fatigue material degradation of solder interconnects is of a great concern. Understanding the performance, reliability and robustness of SiP modules is a key factor for the future development and success of the technology. The main focus in this study is on the techniques for reduced order modelling and the development of the associated models for fast design evaluation and analysis. The discussion is on methods for approximate response surface modelling based on interpolation techniques using Kriging and radial basis functions. The reduced order modelling approach uses prediction data for the thermo-mechanical behaviour of the SiP design obtained through non-linear transient finite element simulations, in particular for the fatigue life-time of the lead-free solder interconnects and the warpage of the package. The reduced order models are used for the analysis of the effect of design uncertainties on the reliability of these advanced electronics modules. To aid this assessment, different methods for estimating the variation of reliability related metrics of the electronic package are researched and tested. Sample based methods such as full scale Monte Carlo and Latin Hypercube, and analytical approximate methods such as First Order Second Moment (FOSM) and Point Estimation Method (PEM) are investigated and their accuracy is compared. The optimisation modelling addresses the probabilistic nature of the reliably problem of the SiP structures under investigation. Optimisation tasks with design uncertainty are formulated and solved using modified Particle Swarm Optimisation algorithms. The probabilistic optimisation deals with two different performance metrics of the design, the thermo-mechanical fatigue reliability of the board level interconnects and the thermally induced warpage of the package. The objective in this analysis is to ensure that the design has the required reliability and meets a number of additional requirements

Prognostics and health management of subsea cables

Subsea power cables are critical to bringing on shore the power from offshore renewable energy systems as well as maintaining supply to island communities from onshore generation.. Globally, the market in subsea power cables is growing expontentially due to their critical role in renewable and sustainable energy.. The integrity of national energy security, due to the expanding offshore renewable energy sector is highly dependent on their reliability. Recent investments in international subsea cable projects represent billions of dollars of investment, yet the state-of-the-art monitoring systems for subsea power cables do not monitor or predict the remaining useful life (RUL) associated with major subsea cable failure mechanisms, the majority of which aredue to environmental factors. Today’s technology, namely fibre optic sensing and online partial discharge monitoring, soley focus on internal breakdown mechanisms. This chapter presents the world’s first holistic and prognostic lifetime prediction model that provides an accurate forecast on cable health, which is vital for subsea cable asset management and planning. The model is sensor agnostic, thereby, suitable for expansion to include additional data types. A mathematical model and an associated software tool that can be used to predict cable damage and lifetime are outlined within this framework. For a defined cable layout on different seabed conditions and tidal flow inputs, the model calculates cable movement, taking into account scouring, and predicts the amount of cable wear that will occur over time due to both abrasion and corrosion. The modelling methodology provides utility and cable companies with the ability to predict cable lifetime taking into account scouring, corrosion, and abrasion for different cable constructions and environmental condition

Reduced order modelling for risk mitigation in design of miniaturised/integrated products

A numerical modelling methodology for the embodiment design of three-dimensional miniaturised/integrated products is developed and demonstrated. The focus is on the numerical techniques and methods that underpin the development of reduced order models (ROMs). These models are used together with methods for estimating variations in performance/quality characteristics and probabilistic optimisation to aid sensitivity, product capability and risk mitigation analyses. The numerical techniques comprising the design methodology are demonstrated with examples related to the design of a novel three-dimensional vibrating micro-probe

Numerical modelling methodology for design of miniaturised integrated products - an application to 3D CMM micro-probe development

This paper presents an integrated numerically-driven modelling methodology for the design of miniaturised/ integrated (Mintegrated) products and the selection/control of associated manufacturing processes. The focus is on the numerical techniques and methods that underpin several design procedures aiding the embodiment design stage of product development. A design assistant tool is developed as an end-user navigation interface that captures recommended design activities for the development of novel micro-integrated products and the supporting tools for their realisation. The main focus is placed on those design procedures comprising numerical methods for the simulation and modelling of the performance and behaviour of a product or process, and the analysis of their design in terms of risk of failure, capability of satisfying specification limits and optimality. The methodology enables an efficient and fast design process and can be applied to a wide range of microproduct developments. The applications range from the fabrication of micro- and nano-scale structures and components for heterogeneous systems, to micro-fluidics, metrology and embedded test devices. In this study, a number of design procedures and associated numerical techniques are demonstrated for the design of a new three-dimensional coordinate measuring machine (CMM) micro-probe developed at the National Physical Laboratory (NPL, UK)