Charles G. Woychik

Solder ball connect (SBC) assemblies under thermal loading: I. deformation measurement via moiré interferometry, and its interpretation

Thermal deformations that result from mismatches of coefficients of thermal expansion (CTE) in Solder Ball Connect (SBC) assemblies were investigated. The CTE mismatches of the materials and the components in the package have both macro and micro effects on the strain distributions in the SBC interconnections. The geometry of the SBC joint also has a strong influence on the solder strains in the SBC package. An experimental technique with high sensitivity and resolution, moire interferometry, was used to obtain whole-field displacements. Thermal strains in SBC packages, especially the strain concentrations in the SBC joints, were then determined from the displacement fields. The experimental results played an important role in failure analysis, structural design optimization, and finite element model verification in the IBM SBC program. The results also show that moire interferometry is a very powerful and effective tool in experimental studies of electronic packaging.

Flip-Chip Die Attach Technology

Wire bonds, tape automated bonding (TAB), and solder-bump, flip-chip connections more popularly referred to as controlled collapsed chip connections or C4 are the three primary chip-to-carrier interconnection technologies currently practiced.

Bonding at Cu-Al interfaces: Relevance to microcircuit packaging

Abstract the nature of bonding interactions at Cu-Al interfaces is investigated both theoretically and experimentally. Extended Huckel-type tight binding calculations were performed on a model for Al binding to a Cu (111) surface. Binding at a three-fold bridge site was most preferred, followed by binding at a two-fold bridge site, followed by binding directly atop a surface Cu atom. Cu-Al interactions at all sites are strongly attractive. These results suggest that the metals should form chemical bonds, even though the interface may be very well defined. Thus, any bonding technique which cleans the surfaces of oxides and allows intimate contact between the metals should produce strong, electrically conductive bonds. Interfacial bonding was probed experimentally by sectioning Cu samples to which Al wire had been ultrasonically bonded. After bonding, the sample was baked in vacuo to accelerate formation of intermetallic phases. The intermetallic phases were observed after only 2 h of annealing at 300°C.

Development of 2.5D and 3D IC Fabrication and Assembly Technologies

2.5D/3D IC assembly is where the traditional foundry and assembly house model breaks down. The greatly reduced feature sizes of microbumps in combination with very large, thin interposers and ICs p...