Characterizing and modelling the behaviour of an isotropic conductive adhesive in view of electronic assembly fatigue life studies under thermal cycling

Abstract

Isotropic conductive adhesives (ICA) are now widely used in industry for a panel of applications such as space electronics manufacturing. Epoxy based adhesives are compliant enough to reliably bond bi-materials with an important coefficient of thermal expansion (CTE) mismatch. However, they are still under investigation for the characterization of their fatigue behaviour. Engineers lack of life prediction tools, although they are available for metallic materials. It is all the more necessary when it comes to severe on-ground qualification tests used to accelerate the demonstration of the die attachment reliability. This study deals with an epoxy based ICA with 80 wt% of silver flakes. The objectives are to characterize the glass/amorphous behaviour of the adhesive and to investigate its numerical implementation in ABAQUS for the on-ground test temperatures. The adhesive viscoelasticity becomes more preponderant with increasing of the temperature. For the time being it has been characterized between 20°C and 50°C. Tensile and creeps tests have been performed in different conditions identification purposes. A viscoelastoplastic model called Two-layers has been fitted to experimental results with success to get the evolution of the material coefficients in function of temperature. The next step consists in the implementation of the complete adhesive behaviour in an ABAQUS 20 model of the microelectronic components in thermal cycling.