An electrical resistance degradation model for thin film under fatigue loading

Abstract

While flexible electronics are ready for the market, keeping their good electric conductivity in long-term operation is still one of the inevitable challenges. This paper aims to develop a resistance degradation model based on the analysis of the observed fatigue behaviour of thin films and the premature electric failure of thin films. The material deterioration process due to fatigue is represented by the defined fatigue damage variation based on cracks initiation and growth, which establishes a connective relationship with electric resistance degradation. The developed model is validated to compare with experimental results, and numerical results show that it can accurately predict the fatigue life and electrical resistance degradation of thin films of different thicknesses; therefore, it could be a means to assess the electrical performance of thin films on flexible substrates.

Analysis of thermo-mechanical coupling damage behavior in long-term performance of microelectromechanical systems actuators

“…Although most of MEMS material is fabricated by polysilicon (Dellaert and Doutreloigne, 2014; Hussein et al., 2015; Kumar and Sharma, 2014), CDM can still be reasonably used into MEMS material. According to the applications of CDM, almost all materials can be applied to damage mechanics, such as metals (Cheng and Li,2020;Fan et al.,2020), polymers (Din et al., 2018), elastomers (Andriyana et al., 2015), composites (Fang et al., 2017), and concrete (Wu et al., 2020). Even if the failure mechanisms vary on the micro scale, they have more or less the same qualitative behaviors on meso- or macroscales (Lemaitre and Desmorat, 2005).…”

“…The long-term reliability curves (such as “S-N” curve) and the evolution process of microstructurally small cracks of silicon films and metal films are experimentally demonstrated to have remarkable similarities (Muhlstein et al., 2001, 2004). Therefore, it is reasonable to apply the methodology of CDM modeling of metal materials (Cheng and Li, 2020; Fan et al., 2020; Guo et al., 2020; Sun et al., 2019) to silicon materials.…”

“…Therefore, the modeling method of RVEs which has been successfully used to simulate the microstructure of metal films containing microcracks is applied to polysilicon. In other words, cracks occur in each element is used to simulate the cracking in each grain, and the grain boundary is the barrier to the propagation of microstructurally small cracks (Cheng and Li, 2020; Fan et al., 2020; Guo et al., 2020; Sun et al., 2019).…”

“…Based on the evolution law of cracks in solid materials (Cheng and Li, 2020; Miller, 1987; Miller and De Los Rios, 1986), the crack initiation rate n.N(c,t) and the propagation rate p.(c,t) are constructed as follows where Δε is the subjected strain. κ,α,β,A are model parameters.…”

“…Due to the electro-thermo-mechanical loads, several main failure modes can occur, including residual stresses due to a mismatch in the coefficients of thermal expansion, conductivity degradation due to thermal cycling, and melt of hot arms caused by electrical overstress, etc (Lu and Yeh, 2019; Weiss, 2007). In addition, because of humidity, high stress and high temperature, the failure mechanisms of the structure may involve oxidation, delamination and fracture (Cheng and Li, 2020; Schlacher et al., 2015). Due to the effects of multi-physics fields, the failure mechanisms also indicate the occurrence of degradation of electro-thermo-mechanical properties and unrecoverable deformation of structure.…”