Since IC packages have been made thinner and smaller, the delamination and crack, which may be induced in the soldering process, have become important factors affecting the reliability of the package. The ability to penetrate deeply inside dielectric materials, and to reflect completely at the metal surface makes microwave inspection very suitable to detect such delamination. The authors have recently developed a new microwave imaging technique that uses an open-ended coaxial line sensor to detect the delamination in IC packages. The image was created by measuring the phase of the effective reflection coefficient at the aperture of the coaxial line sensor. For better evaluation of the shape and the size of the delamination, a method to further increase the spatial resolution of microwave imaging was studied in the present paper. The resolution affected by the dimensions of the sensor, the frequency of operation, and the standoff distance between the sensor and the sample was investigated by experiment. The experimental results indicate that microwave imaging is a promising technique for the integrity assessment of IC packages.
An Innovative Microwave-Imaging Technique for Nondestructive Evaluation: Applications to Civil Structures Monitoring and Biological Bodies Inspection