Micro-bump bondability design guidelines for high throughput 2.5D & 3D IC assemblies

In this paper, mechanical bonding behaviors of micro-bumps in 2.5D/3D ICs assembly are studied theoretically. Solder force and spring constant of micro-bumps with different bond pad structures are estimated by using Surface Evolver. Deformations of dies with corresponding flattening distances are evaluated based on flexural theory and three-dimensional contact theories. Allowable coplanarity of bond surface or die warpage during both mass reflow and thermal compression bond is developed. Guidelines to ensure successful bond and corresponding structural designs are earned.