Effects of Thermal and Electrical Proper- Ties of Thin Metal Film in Photoinductive Field-mapping Technique for Eddy-current Probes

Photoinductive (PI) field mapping for eddy-current (EC) probes above a thin metal film was performed by multiphysics analysis with two-dimensional finite element method (FEM). The FEM model of PI method was used to observe how metal film properties affect the field-mapping signals of EC probes. The PI signal was tested for effects of resistivity, temperature coefficient of the resistivity, thermal conductivity, heat capacity, and thin film density The applicability of actual thin film materials for mapping the field of EC probe when using PI method was discussed. Field-mapping signals of EC probe coils with tilt angles of 0◦, 5◦, 10◦, 15◦, and 20◦ were also examined with appropriate metal film material. These experiments showed that the higher-resolution field-mapping signals of EC probes can be obtained by given a titanium thin film The resolution of field-mapping signals of EC probes correlated positively with resistivity, heat capacity, and density of thin film and correlated negatively with its thermal conductivity. Improved understanding of distinct field distribution of EC probes enables selection of optimal probes for EC inspection.