Thermomechanical Deformations of Power Modules with Sintered Metal Buffer Layers under Consideration of the Operating Time and Conditions | IEEE Conference Publication | IEEE Xplore

Thermomechanical Deformations of Power Modules with Sintered Metal Buffer Layers under Consideration of the Operating Time and Conditions


Abstract:

In this work an investigation of the thermomechanical deformation behaviour of power modules with sintered metal buffer layers is presented under consideration of the ope...Show More

Abstract:

In this work an investigation of the thermomechanical deformation behaviour of power modules with sintered metal buffer layers is presented under consideration of the operating time. The thermomechanical deformation is measured during active operation of the device using an optical measurement technique. The in-plane strain and the out-of-plane curvature were evaluated in dependency of the temperature by applying different operating conditions (IC, ton, toff). In addition, comparisons of the deformations of modules are shown, which on the one hand were measured directly after the production and on the other hand have passed through several thousand active load cycles until the end-of-life (EOL). Furthermore, the relevant electrical and thermal parameters (VCE,Sat, Tvj,max, ΔTvj, Rth) were recorded during the load cycles in order to analyse the failure mechanisms. The evaluation of the electrical measurement with regard to the failure mechanism correlates with the findings of the thermomechanical deformation. The uncertainty regarding the primary failure mechanism, which exists when evaluating only VCE and Rth, can be eliminated with the additional optical method without destroying the test module.
Date of Conference: 03-30 June 2020
Date Added to IEEE Xplore: 05 August 2020
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ISSN Information:

Conference Location: Orlando, FL, USA

I. Introduction

Conventional soldering is increasingly replaced by silver sintering as die attachment due to its outstanding reliability [1], [2]. With the substitution of the die attachment, however, the reliability problem has entirely shifted to the top-side electrical contacts, which are usually made of thick aluminium wire bonds [3]. The latest developments have therefore led to new material systems on top of the dies, e.g. sintered metal buffer layers with heavy copper wire bonds. This development improved the lifetime of the electrical contacts and thus of the entire system [4]. These introductions to the thermal layer stack also led to a change in the failure mechanisms and also induce changes to the thermomechanical behaviour of the systems [3]. One of the main root causes of failures of power electronic devices are the thermal strains and stresses caused by temperature variations. In order to contribute to a better understanding of the new failure mechanisms, the thermo-mechanical behaviour in active operation is therefore investigated. The investigations in this work were carried out with respect to the total operating time of the test module.

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