Numerical study of thermomechanical fatigue influence of intermetallic compounds in a lead free solder joint

As electronics is increasingly present the reliability of automotive and aircraft equipment is linked to the reliability of electronic boards. Solder bumps are subjected to multiple stresses (e.g. mechanical, thermal, thermo-mechanical, coupled electro-thermal) due to usage conditions. In the scope of RoHS directive, solder joints are made of lead-free alloys. Very promising candidates to replacing standard SnPb solders in electronic assemblies are based on Tin-Silver-Copper alloys, commonly referred to as SAC. The intermetallic compounds (IMC) located at the interfaces of a lead free solder joint form a layer with usually different mechanical properties from the rest of the volume. They depend on the type of finishes and the solder alloy reacting together. The resulting compound is stiffer and more fragile than the solder itself. The IMC are of great concern when it comes to the thermomechanical fatigue characterization of a solder. Indeed, the thickness of the IMC layer increases in function of the exposure duration to high temperature due to atomic diffusion. The whole rigidity of the assembly increases and can lead to some changes in the solder behavior in the vicinity of the interfaces. Fatigue characterization requires to correlate the relevant failure mechanisms of a model in order to be predictive in different conditions. For that purpose, finite element analyses (FEA) must be accurate and representative. Therefore, it has been decided to evaluate the influence of IMC prone to be implemented in simulations. The drifting stiffness, the concentration of stress or the accumulation of viscoplastic strain near the interfaces are the main aspects investigated in this study using two different FE models made in ABAQUS. First, the simulation of a shear test performed on “grooved” single lap shear specimens 1 is used to quantify the error made on the shear modulus with different thicknesses of IMC. This model is also necessary to determine the creep behavior of the lead free solder in another study by fitting the response of such a stack to the experimental curves. A second model composed of a solder ball with its interfacial IMC has been made (cf. Figure 1). It is used to calculate the increasing in global stiffness due to IMC. The final purpose is to highlight the weaknesses to take into account in fatigue life design for which IMC could be responsible. In a final study this model is to be implemented with a proper nonlinear solder material behavior to correlate with thermomechanical fatigue tests of BGA components

Field return on a Chinese-French double graduation of an International Master in Microelectronics on the Base of the Bologna Process

International audienceWith the decrease in France of the number of students in the field of electrical engineering and information processing, that is unfortunately more and more common in Europe, several French Institutions are trying to build remote formations in Asia-Pacific region. This paper deals with the setup of a new master degree in the field of electrical and information engineering with two specialties, microelectronics and signal and image processing. It is a double diploma between South-East University (SEU) at Nanjing (China) and the University of Rennes 1, at Rennes (France), fully compatible with the Bologna process rules more especially in terms of ECTS. In this paper, some details on the structure and on the specific points that were solved are described and commented. In particular, the pedagogical program was built on the bases of the reciprocal competencies in order to take at the maximum the benefit of skills available on each side

Simulations and Measurements to Predict EMC Characteristics in Electronic Assemblies: Obsolescence Management

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Set-in LifeLong Learning for PhD students in Electrical and Information Engineering

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Proceedings of the 32nd European Symposium on the Reliability of Electron Devices, Failure Physics and Analysis

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Search for copper diffusion at hybrid bonding interface through chemical and electrical characterizations

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Editorial, Microelectronics Reliability, Volume 55, Issues 9–10, August–September 2015

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ELLEIEC implementation issues in EIE: State of advancement

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Proceedings of the 30th European Symposium on the reliability of electron devices, failure physics and analysis

International audienceThis special issue of Microelectronics and Reliability is devoted to the publication of the papers presented during the 30th European Symposium on Reliability of Electron Devices, Failure Physics and Analysis, ESREF 2019, in Toulouse (France) from September 23th to September 26th, 2019.This international symposium continues to focus on recent developments and future directions in quality and reliability management of materials, devices and circuits for micro-, nano-, and optoelectronics. It provides a European forum for developing all aspects of reliability management and innovative analysis techniques for present and future electronic applications.For this 30th edition, in addition to the core topics of the conference, we involved the major actors of aeronautics, space and embedded systems industry to provide specific topics such as radiation hardening, very long-term reliability, high/low temperature challenges, obsolescence and counterfeit issues, wide bandgap power devices for the more electric aircraft and other embedded system applications. A special session for space and aeronautic systems is proposed