レーザー衝撃波を用いた銅メッキの界面強度と耐久性の評価

抄録

This study aims to evaluate coating adhesion, i.e. the interfacial strength of coatings and thin films by using Laser Shock Adhesion Test (LaSAT). This method uses strong elastic wave induced by pulsed laser ablation. The elastic wave causes the coating delamination, when the maximum stress wave reaches the critical value (interfacial strength). In parallel, the out of plane displacement is measured by using a laser ultrasonic interferometer. The timing of delamination can be detected by the correlation coefficient calculated with a series of the out-of-plane displacement velocity waveform. Furthermore, computation of elastic wave propagation using FDTD (Finite difference time domain) is carried out to estimate tensile stress developed at the coating film/substrate interface. Based on the above results, the interfacial strength is estimated. In addition, the interfacial adhesion durability is evaluated by using repeated laser irradiation based on the above method (LaSAT). In this method, repetitive lower stress loading is applied to the interface. We evaluate the cycle number of repeated laser irradiation up to coating delamination, so that it may estimate the interfacial strength (adhesion) durability. It was found that delamination occurs at lower loading than the interface strength. This result may be useful for adhesion durability, when a coating is used in long time and subjected to cyclic loading.