In this study, properties of some selected, representative high density int
erconnect (HDI) materials (dielectric and solder mask), including dimension
al stability (thermal and chemical),::tensile behaviors, and fracture tough
ness have been investigated. Experimental results show that glass transitio
n temperature of materials cured with the manufacturer recommended schedule
did not reach their ultimate, alleged published values, indicating that fu
rther curing is needed. Most HDI materials are brittle at room temperature
with a low strength and low elongation at:failure. It has been found that t
he resistance to crack propagation of HDI materials is much lower than that
of polymer thin films, such as Kapton, widely used in electronic products.
It has also been observed that stress-strain behaviors of partially cured
materials and fully cured materials are very close at room temperature but
very different at higher temperatures, Finite element analyses, however, in
dicate that low fracture toughness of HDI materials will not be major cause
if cracks are observed in the thermal cycling of HDI boards. Rather, it wo
uld be due to combined contribution from low strain-at-failure, strong visc
oelasticity, and low fracture toughness.