Research On The Factors Affecting The First Bond Of Ultra-Fine Pitch Wire Bonding Process

Wire bonding is the most classical and mature technique for IC package, which plays the most important role in IC package market.As the demand increasing steadily for small volume, high density and high heat-dissipation rate IC, the key parameter of wire bonding----pad pitch has to shrink in accordance. With such understanding, in addition to improvements in wire bonder hardware, it is necessary to develop a steady wire bonding process which satisfies the requirements for fine pitch wire bonding. This dissertation carries out a thorough study on the factors which influence the 1st bond quality in fine pitch wire bonding, and through broad experiment based on orthogonal test on these factors, corresponding results are drawn.Starting from discussing the details on the processes of three main categories of IC interconnection techniques in practice which are wire bonding, TAB, and flip chip, this dissertation analyzes their merits and shortcomings from different viewpoints in I/O density, electrical performance, and costs. It is pointed out that fine pitch wire bonding would still share most part of the market in quite a long future.Many factors would affect wire bonding process. This dissertation analyzes their effects and corresponding affecting routines from aspects of bonder hardware (PRS system, capillary, ultrasound system),bonding parameters and corresponding environments etc. Derived results provide the right selection of the factors in orthogonal test.Every subsystem in the experiment platform are introduced in detail. Factors and respective factor level are decided by 1st bonding quality analysis in addition to pre-experiment results. The experiment is divided into 2 stages since there are so many factors. The 1st stage experiment factor level table and orthogonal table are developed in accordance.The experiment is completed based on orthogonal test program , and the experiment data are analyzed with the help of polar difference analysis method, variance analysis method and main effect plot. All factors are sorted in accordance with influence to the diameter of the first bond , the key variables are identified. Parameter set is optimized to fulfill the requirements of 60um fine pitch wire bonding. Through these results, further studies on the 1st bonding mechanism and corresponding routines would benefit from presented works above.Finally, summary has been given the end of this dissertation, and some advices have been put forward for subsequent research. New aims have been set for future work.