Mechanical behavior of glass with different roughness and its influence on TGV reliability

Through-glass via (TGV) structures play a critical role in advanced 3D electronic packaging, offering superior electrical insulation and dimensional stability. Their mechanical integrity is critical to ensuring the long-term reliability of vertically integrated systems. As the demand for high-density, high-performance, and heterogeneous integration continues to grow, TGV technology is becoming increasingly important in enabling compact, thermally stable, and highly reliable 3D packaging solutions. Nevertheless, the surface roughness of glass significantly affects metal deposition, interface bonding, and mechanical behavior. Optical microscopy shows that smoother glass has smaller, denser particles, while rougher surfaces exhibit larger, irregular particles with clear boundaries. As the first exploration regarding the TGV glass material through scratch tests, this study investigates hardness, fracture toughness, friction, and interfacial bonding, elucidating how roughness affects mechanical properties of borosilicate glass. It also shows that smoother glass has uniform hardness and controllable crack propagation, thereby reducing stress concentration. Although rougher glass enhances mechanical interlocking and bonding strength, it often accumulates residual stress under thermal or mechanical loads. To unveil the underlying mechanism of the observation that rough surfaces increase the risk of microcracks, the finite element model (FEM) is established to study the force conditions of glasses with different roughnesses under scratch tests. These findings provide guidance for optimizing TGV processes, improving reliability, and supporting their applications in high-density ICs, 5G, and advanced optoelectronic packaging.