Study on the delamination between adhesive film and silicon in stacked-die packaging

The stacked-die packaging, one of the 3D packaging solutions, implements the vertical multi-die stacking. The technology reduces the footprint and improves packaging density effectively. In the stacked-die packaging, the dies designed with different size were connected in vertical direction by the die-attach films. The multi-layer structure is fixed on the substrate such as PCB/BT by the adhesive film. As the coefficient of thermal expansion (CTE) mismatch between dies and substrate is large, the delamination most likely takes place along the interface between the bottom die and the substrate when the stacked-die package is subject to thermal loadings. To improve the adhesion, the measurement of the interfacial fracture parameters should be setup. Moreover, the adhesion changes with environmental condition, i.e. moisture, should be clearly understood. In this study, the sample with interface between the adhesive film and the substrate was fabricated. The adhesive film was designed to be peeled off in testing. The peel stress was derived based on the testing data and the interface was characterized. The moisture was taken into account in the experiments for comparison. The results illustrated the peel stress range for interface between adhesive film and the substrate without/with moisture involved. The interface failure in the device and the moisture effect on the interface was discussed.