Microwave imaging for the integrity assessment of IC package

Since the package dimension has 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 IC package. Several techniques, such as scanning acoustic tomography have been used to evaluate the delamination in IC package. Unfortunately, the disadvantage of each technique limits their application in this respect. 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 which uses an open-ended coaxial line sensor to detect and evaluate the delamination in IC package. 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 delamination, a method to increase further the 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 lC package.