Rationally designing the trace of wire bonder head for large-span-ratio wire bonding in 3D stacked packaging

The increasing miniaturization of functional devices drives the microelectronic industry to pursuit large-span-ratio and high-density wire bonding packaging technology as it can facilely interconnect various chips at a low cost. The design method of wire bonder head trace is urgently needed in the Post Moore Era. Herein, a rational design strategy of wire bonder head trace was proposed. By solving the geometric mapping equations derived from the geometrical evolution of the wire loop, the wire bonder head trace can be easily designed to fit the desired loop profile. The explicit finite element model was also developed to verify the designed wire bonder head trace and disclose the dynamic evolution of strain/stress on wire loops simultaneously. Furthermore, by using orthogonal experimental design, the trace height was found to be the most critical geometric factor influencing loop profiles. The proposed strategy was illustrated to design wire bonder head traces with which large span-ratio loops (>5) with the finest reported gold wire (sub- $10~\mu \text{m}$ ) were successfully formed. The mechanical strength tests showed the wire loops were superior to loops with other larger wire. The proposed strategy significantly improves the efficiency of design reliable wire bonder head trace for high-density packaging and will have broad application prospects in microelectronic industry.