Fabrication and reliability demonstration of 5μm redistribution layer using low-stress dielectric dry film

Low-stress and low-warpage dielectrics are gaining importance as we move towards large-body Multi-chip Modules (MCMs). This paper demonstrates fabrication of redistribution layer (RDL) with 5 μm linewidth/spacing using a novel low-stress dielectric dry film- PLSF (Panasonic low stress film) as a build-up layer. Microvias formation down to 7 μm diameter has also been demonstrated in this paper. The main feature of PLSF is its low- stress and low-warpage. In this paper, we have studied residual stress characteristics of PLSF and its comparison with the industry-standard dielectric (ISD). The lower tensile modulus of PLSF as compared to ISD results in significantly lower residual stress and warpage on the substrate. Electrical and thermomechanical reliability of RDL with PLSF as build-up layer has also been studied and the results are presented in this paper.