Optimizing the fine-pitch copper wire bonding process with multiple quality characteristics using a grey-fuzzy Taguchi method

• A grey-fuzzy Taguchi method is proposed to optimize the fine-pitch Cu wire bonding.
• The multiple responses are transformed into a synthetic index prior to optimization.
• We examine significant factors affect the fine-pitch Cu wire bonding process.
• The results help in cost saving and yield improvement for the subject company.

This paper presents an application of the grey-fuzzy Taguchi method to derive the optimum parameters for the fine-pitch copper (Cu) wire bonding process with multiple quality characteristics. Cu wire has become an important replacement material without the high manufacturing cost of gold for wire bonding processes in integrated circuit (IC) packaging. However, it sometimes fails to take advantage of the Cu material properties due to an insufficient understanding of the relationship between process inputs and outputs of the fine-pitch Cu wire bonding. To assure the accomplishment of cost savings without losing yield, the proposed grey-fuzzy Taguchi method is utilized with an L18 (21 × 37) experimental design and grey relational analysis (GRA) to evaluate the degree of relationship between process inputs and responses, followed by transforming the multiple quality characteristics into a single performance index using a fuzzy inference system. Finally, the process parameters are optimized by the Taguchi method. The proposed optimization methodology provides superior optimization performance compared to the grey-Taguchi method and the parameter setting used in mass production in terms of the conformation experiments.