Finite element analysis on coarse grained vector machines of residual stresses in plastic IC packages during surface mounting processes

Finite element analyses are utilized on a CRAY T94 to calculate hygrothermally induced anisotropic viscoelastic deformations and stresses in plastic IC packages during surface mounting processes, which is an interdisciplinary coupled hygro-thermo-structure interaction problem. The subroutine for element stiffness calculation is dominated by vector operations and achieves about 432 million floating-point operations per second on a CRAY T94. Computational intensity studies (computational intensity is the ratio of flops to memory references) also indicate that it is an efficient algorithm. As a demonstration example, hygrothermally induced stresses in a lead-on-chip (LOC) thin small outline package (TSOP) during the reflow soldering process preceded by a 168 hours 85°C/85% RH moisture soaking test are analyzed.