Experimental and numerical estimation of ultrasonic attenuation in polymers based on wave transmission methods

Abstract

PI-film, also known as Kapton, is a widely used polymer in the production of electronic equipment. Its use in printed circuit boards and sensors is increasing. It is therefore important to have knowledge about ultrasonic attenuation in the polymer.

The main goal of this thesis was to investigate the attenuation of ultrasound through different polymers with different thicknesses. The presentation is divided into two parts based on the polymer thickness with respect to the applied wavelength. The attenuation was examined through both experimental methods and numerical studies were this was possible. Basic theory of waves, elastic materials and attenuation in polymers are presented, and theoretical models were applied to compare the attenuation found through experiments and simulation.

10 MHz transducers were applied in the experiments with thin Kapton-based samples. Based on the experiment, COMSOL Multiphysics was used to implement realistic models for numerical simulation. The amplitude spectra obtained through both experiments and simulations were compared to a corresponding theoretical spectrum. The model differences taken into consideration, the resulting amplitude spectra from the three methods were found to coincide. An experimental investigation at 10 MHz of the effects of surface treatment between layers in two PVDF-coated Kapton films were performed. At this frequency, no differences in transmission properties between the treated and untreated samples were detected.