Material–thickness response mapping and competing thermal-expansion mechanisms in polymer-lined Cu-filled through-glass vias

Polymer liners redistribute thermal-mismatch stress in Cu-filled through-glass vias (TGVs), but their stiffness, thermal expansion and thermal resistance have competing effects. A three-dimensional finite-element model of a 50 μm Cu core with fixed Co/TiW layers and a polymer liner was used to compare PI-2611, HD-4100, HD-8820 polybenzoxazole and benzocyclobutene (BCB). Fixed-thickness screening and 32 thickness-resolved designs were evaluated using glass-ring tensile stress and incremental thermal resistance relative to a polymer-free reference. A two-factor modulus–CTE study distinguishes stress relief due to compliance from stress induced by liner expansion. At an 8 μm thickness, the low-CTE PI-2611 liner reduces the hot-endpoint ring stress from 127.0 to 66.5 MPa despite its higher modulus. PI-2611 at 15 μm gives the lowest sampled stress, 50.7 MPa, with an incremental thermal resistance of 2428.0 K/W. BCB at 10 μm gives 80.6 MPa and 841.3 K/W, illustrating a lower-thermal-resistance trade-off rather than a unique optimum. Under assumed ±10% property perturbations, the stress envelope for PI-2611 remains distinct, whereas those for the other three polymers overlap. Additional controls assess how ring geometry, lateral domain size, interfacial tractions and cure preload affect the comparison. The results relate liner selection to competing thermal-expansion mechanisms and quantify stress–thermal trade-offs within the specified local TGV model.