Application of a high numerical aperture lens to visualize disbonding between metallic films and polymer substrates with SAM

Due to increased demand for design flexibility, in recent years engineers have progressively employed polymers in the design of electronics enclosures. As the circuits in these enclosures are miniaturized, dissipate more thermal energy and run at higher clock speeds, electromagnetic interference (EMI) and heat dissipation concerns become more apparent and are more problematic. The high thermal impedance of polymers slows their implementation in these situations. In addition, many electronics devices are subject to industrial and governmental regulations for EMI emission and isolation. To address these concerns it is becoming increasingly popular to apply conformal metallic films to polymer-based enclosures to increase EMI shielding and decrease thermal impedance through heat spreading. As with any coating, quality assurance of adhesion between the film and substrate is of immense importance. Without standardized testing procedures for assuring the quality of these processes, it is difficult to place them into practice. When new and alternative manufacturing processes are brought forth quality assurance is of paramount importance. The majority of existing commercial testing procedures for determination of adhesion quality for metallic films pertain to metallic substrates. This paper presents the application of a practical shear wave lens to overcome these issues. It will be demonstrated that the shear wave lens will provide sufficient resolution in this application to allow visualization of bond quality and determination of to what degree a conformal coating has been achieved.