A review on silver-filled epoxy as die attach adhesive in LED package: thermomechanical characterisation methods and material models

The reliability of die attach adhesive is crucial for the proper functioning of a light-emitting diode (LED). Die attach failure, commonly found in the form of interfacial delamination is induced by thermomechanical stress. Thus, an understanding of the thermomechanical properties of adhesive is essential to accurately predict its reliability. The objective of this work is to provide a comprehensive evaluation of the existing thermal and thermomechanical characterisation methods, such as Differential Scanning Calorimetry (DSC), Dynamic Mechanical Analysis (DMA), Thermomechanical Analysis (TMA), and uniaxial tensile specifically for silver-filled epoxy emphasising challenges faced during characterisation, possible alternative equipment, and summarising test parameters for analysis. Moreover, material models implemented to describe silver-filled epoxy, such as linear elastic, elastoplastic, linear viscoelastic, and non-linear viscoelastic are discussed highlighting the applicability to describe elastic and plastic responses, as well as its time-, temperature-, and strain-dependent behaviour. This review serves as a key guide for researchers seeking to perform thermomechanical characterisation of silver-filled epoxy. This paper outlines the research gaps and suggests future research directions aimed at improving thermal and thermomechanical characterisation methods, laying the foundation for the development of robust material models for enhancing the reliability of LED packages.