Technology and compression modeling for thermosonic flip-chip bonding

This thesis research conducted technology development for thermosonic flip-chip bonding and modeling of the compression process involved in bonding. This study resulted in five contributions: (1) a thermosonic flip-chip bonding process was developed and successfully used to assemble fully functional smart pixel arrays with as many as 80 I/O, (2) a new configuration-independent criterion using bond joint interface strain was identified and developed for joint modeling, (3) the strain criterion and modeling were verified by experiment, (4) an optimum joint design aspect ratio was identified by an axisymmetric joint model, and (5) an assembly yield model, originally based on a configuration-dependent deformation criterion, was enhanced using the new strain criterion to help design area arrays of gold joints.; This thesis proposed, and verified, a new configuration-independent criterion that used joint strain across the bond interface to evaluate the potential for joint bond formation. This new criterion is a combined 2-D strain that uses the change in the area of the differential elements on the joint interface, and is stated as{dollar}{dollar}Delta A=vertvarepsilonsb{lcub}rm xx{rcub}+varepsilonsb{lcub}rm yy{rcub}vertgevertvarepsilonsb{lcub}rm xx{rcub}+varepsilonsb{lcub}rm yy{rcub}vertsb{lcub}rm crit{rcub}{dollar}{dollar}Experiments determined a preliminary minimum critical value of joint strain for bonding of 0.016. Single-joint finite element models were developed to use the strain criterion to study the joint interface mechanics for various designs.; Use of the models revealed the existence of an optimum joint design aspect ratio (bump height divided by the diameter) of about 0.3 for axisymmetric joints.; Results from the axisymmetric model studies using the strain criterion were applied to enhance the area array yield model. The formerly used criterion, of the same minimum (15%) deformation for all joint designs, was replaced by minimum deformations determined for each design using the strain criterion. For one set of design aspect ratios, the minimum deformation ranged from 6% to 30%.; This thesis work was conducted for thermosonic flip-chip bonding development, and to determine the effects of joint design on the bond formation. The new area criterion and the compression models can also be applied to wire bonding, TAB, and thermocompression bonding.