Microstructural Hierarchy Data Insights from Ag Paste and Cu-Cu Hybrid Bonding

The microstructural hierarchy descriptor (μSHD) method is applied to both cellular automata (CA) patterns and SEM images of Ag pastes and Cu-Cu hybrid bonding. CA patterns generated under different rule sets exhibit distinct μSHD profiles, establishing a quantitative link between simple rules and microstructural hierarchy. For Ag pastes, the μSHD value on scale J = 5 exhibits the highest sensitivity to processing parameters, and higher μSHD values on medium scales (J = 6 and J = 7) indicate a lower shear strength. In contrast, for Cu-Cu bonding, the limited available data suggest that higher μSHD values across smaller and larger scales are positively correlated with increased tensile strength. The μSHD curves of Class I and IV CA patterns can find their counterparts of the microstructures observed in both Ag pastes and Cu-Cu hybrid bonding.