Effect of Ultrasonic Bonding Parameters on the Contact Resistance and Bondability Performances of CIGS Thin Film Photovoltaic Solar Panel

This article aims to investigate the optimal ultrasonic bonding parameter namely bonding pressure, bonding energy, and bonding amplitude that can minimize the contact resistance (Rc), maximize the peel strength, and identify the possible failure modes of ultrasonic Al bond on Mo back contact layer of copper indium gallium (de)selenide (CIGS) thin-film photovoltaic (TFPV) solar panel. The transmission line method was used to measure Rc and a peel test was carried out to measure the peel strength and the possible failure modes of ultrasonic Al bond on the Mo layer. Design of experiment using D-optimal method was utilized to evaluate the effect of the ultrasonic bonding parameter toward the Rc and peel strength of the Al bond on the Mo layer. Individual and combination of the ultrasonic bonding parameter have a significant effect on the quality of Al bonds on Mo back contact layer of CIGS TFPV solar panel. Possible failure modes could be identified through the application of the higher value of individual ultrasonic bonding parameter while keeping constant other bonding parameters and through the qualitative result of the load-displacement profile obtained from the peel test. However, sample 2 with bonding pressure of 3 bar, bonding energy of 20 Ws, and bonding amplitude of 7.7 μm is the best-optimized bonding parameter window that can be applied to obtain ultrasonic Al bond with lower Rc and higher peel strength. It was noted that bonding pressure is the most sensitive bonding parameter followed by bonding amplitude and bonding energy.