抄録
We evaluated viscoelastic characteristic of build-up material, underfill and solder mask material by the dynamic mechanical analysis (DMA), and made master curves of the relaxation modulus. The master curve was approximated by the Prony series, and the shift factor was formulated by the WLF equation. Finite element method (FEM) analyses that considered the viscoelasticity characteristic of an organic material were carried out for stress evaluation of some organic packages at thermal cycling test (TCT). Lifetime was evaluated from the stress and strength degradation behavior by thermal oxidation. The predicted lifetime agreed well with the result of TCT of all the package's. We have confirmed that this method is very effective for the reliability evaluation, and designs for optimized structure of build-up wiring substrate.
