Experimental and theoretical analyses of package-on-package structure under three-point bending loading

Abstract

High density packaging is developing toward miniaturization and integration, which causes many difficulties in designing, manufacturing, and reliability testing. Package-on-Package (PoP) is a promising three-dimensional high-density packaging method that integrates a chip scale package (CSP) in the top package and a fine-pitch ball grid array (FBGA) in the bottom package. In this paper, in-situ scanning electron microscopy (SEM) observation is carried out to detect the deformation and damage of the PoP structure under three-point bending loading. The results indicate that the cracks occur in the die of the top package, then cause the crack deflection and bridging in the die attaching layer. Furthermore, the mechanical principles are used to analyse the cracking process of the PoP structure based on the multi-layer laminating hypothesis and the theoretical analysis results are found to be in good agreement with the experimental results.

Evaluation of the critical stress of anodized coating-AZ91D substrate using SEM in-situ technology

“…A signal from the SEM was directly transferred to a computer via a direct memory access type A/D converter, making it possible to sample 9601280 frames of SEM images successively in in-situ observation during the bending test. All bending tests were controlled by a stroke ratio of 10 −4 mm/min Wang and Fan, 2006;Huang et al, 2007;Jia et al, 2012;Ren et al, 2013;Ren and Wang, 2014).…”

“…Therefore, to investigate failure issues of thin coating layers/substrates, experimental study is the best and directly approach (Wang and Xu, 2003;2004;2009;Li et al, 2008a;2008b;Dean et al, 2015). In addition, it is necessary to estimate the delivery criterion of stress close to the interface of thin anodized coatings and thick substrates using SEM in-situ technology Wang and Fan, 2006;Jia et al, 2012;Ren et al, 2013;Ren and Wang, 2014).…”