Thermal Stress Impact on Electrical Conductivity and Microstructure of Thin Aluminum Films Deposited on Polyethylene Terephthalate Substrates

Aluminum (Al) thin films are widely used in electronics due to their easy deposition on plastic boards and high electrical conductivity, but they are sensitive to thermal stresses. This study aimed to evaluate the thermal stresses on Al films on polyethylene terephthalate (PET). Two types of heat stresses are highlighted in this paper—continuous high heat stress (isothermal stress at 100 °C) and fluctuating low and high heat stress (thermal cycling stress at fluctuation temperature between 0°C and 100 °C). Electrical resistance was measured before and after applying thermal stress. Moreover, microstructure images were taken for all cases, and energy dispersive X-ray analysis (EDX) was performed to interpret the effects. It can be concluded that both types of thermal stresses increase the electrical resistance of thin films. Moreover, thermal aging also affected the relative change in electrical resistance, and we did not find this effect to be significant in the thermal cycling experiment. As shown in the microstructure images, thermal cycling led to microcracks on the films. The isothermal aging also increased the bonding between the nanoparticles of the film and increased the oxygen content of the film very slightly.