Improvement on yield rate and tact time of anisotropic conductive film in TFTLCD short bar attach process using fuzzy dominant directed graph based multi-objective optimization

This paper proposes a fuzzy-DDG (Dominant Directed Graph) method to solve the multi-objective optimization problem with regard to the ACF (Anisotropic Conductive Film) attach process for TFTLCD. As such, this paper's motivation is to decrease the usage of ACF materials in the ACF attach process. The experimental Taguchi method is used to find the optimal solution for this problem. This paper studies the optimization of yield rate and tact time with respect to the control factors of TFTLCD. In using the Taguchi method, five test cases are discussed: the first involves the optimal yield rate problem; the second, the optimal tact time problem; and the third, solving multiple problems by simultaneously considering yield rate and tact time. In addition, the conventional MPCI (Multiple Performance Characteristics Index) method is used, although it exhibits a less than optimal fuzzy inference structure, and fuzzification as well as defuzzification processes are required; in the fourth and fifth cases, a new fuzzy-DDG method is used to determine the multiple objective problems. Notably, the conventional fuzzy inference structure is not required in this algorithm: only graph-based matrix operations are required. Test results show that the fourth and the fifth cases are more convenient in regard to arithmetical operations, compared to the third case. The fourth case illustrates the problem with the vertex order included only; only crisp potential values are derived. The fifth case illustrates the problem with the vertex S/N ratio values included, and fuzzy potential values derived. Experiment results are provided to verify the validity of the proposed fuzzy-DDG method.