Experience with nondestructive acoustic inspection of power IC's

A major aspect of thermal management is the thermal impedance of the package. The thermal impedance can be significantly degraded if there is an increase in the amount of voiding or delamination in the die attach medium. Therefore, for process optimization and reliability testing, a convenient and nondestructive technique for inspecting the die attach medium is important. In the case of plastic flange-mount packages, inspection by X-ray radiography is difficult because the high mass thickness of the metal heat sink results in poor contrast in the area of the die attach layer. In addition, X-ray radiography cannot easily detect cracks or delaminations in the die attach layer. C-mode acoustic microscopy has proven to be extremely valuable for the nondestructive inspection of die attach in power IC packages. However, the application of acoustic microscopy to die attach inspection is not always straightforward. A method for producing quantitative and reproducible die attach measurements is described.