Detection of Sealant Delamination in Integrated Circuit Package Using Nondestructive Evaluation

This paper presents the development of a nondestructive evaluation method for delamination detection in integrated circuit (IC) packages. The developed method allows for quantitative detection of sealant delamination between integrated heat sink (IHS) and substrate, which is considered a potential failure mechanism in IC packages. The proposed method is expected to overcome the destructive nature of most existing techniques, while maintaining low cost of development. The reported development consists of the following processes: First, flash thermographic analysis is investigated and shown to be incapable of detecting a realistic sealant delamination. Then, ultrasonic guided waves (UGWs) are used as the chosen interrogation method due to their sensitivity to small-size damage and structural thickness variations. The complexity of the received ultrasonic signals caused by the geometric heterogeneity is resolved using a time–frequency signal processing technique. The extracted ultrasonic information, including time-of-arrival (TOA) and amplitude of wave modes received from different sensing paths under multiple excitation frequencies, is then used to construct a feature space. A multivariate Gaussian model is implemented as an information fusion and delamination detection tool, which investigates the distribution of feature space including correlations between features. Results from the developed model are compared with two existing evaluation methods, including pullout force measurement and a delamination metric. The developed method is seen to possess a similar level of accuracy with a nondestructive nature.