Analysis and Optimization of Fine-Pitch Gold Wire Ball Bonding Thermosonic Parameters

One of the main characteristics of semiconductors' history is their scale reduction, effectively shortening the distances between I/O electrical pads. Gold wire ball bonding is a standard in semiconductor packaging and the optimization of its parameters is essential. This study employed the use of three key parameters as input and two measurements as output in a 5-level Full Factorial Design of Experiments, later extrapolated to a 9-level mathematical model for detailed analysis. A fitness function was developed to find the best overall results based on the inputs, as the two outputs are proportional but inversely desired (as the shear resistance desirably increases, so increases the bond diameter, undesirably). This function returned bonds with 40.27μm in diameter on a 48 μm wide pad and 15.43 gf in shear resistance from a 20.32 μm (0.8 mils) wire, both desirable. Potassium Hidroxide etching was later performed to validate the physical implications from the method's best results, where all the desired intermetallic characteristics were found.