Measuring the Manufacturing Yield for Skewed Wire Bonding Processes

In semiconductor manufacturing, the technologies of stacked semiconductor packaging are important miniaturization strategies in which excellent quality is essential for a good reputation. Yield-based index C_pk has been the most popular tool for successful quality improvement activities and quality program implementation in multichip package processes. For in-plant applications, quality practitioners commonly use the nonconformities in parts per million (NCPPM) table of C_pk to obtain manufacturing yields. However, wire bonding processes are often skewed in multichip package factories. In such situations, the NCPPM table of C_pk is inappropriate to be applied directly. In order to reasonably access manufacturing yield for skewed wire bonding processes, we propose a new yield index C_sk. We are the first to modify the index C_sk for various skewed distributions for the consistency of NCPPM mapping between indices C_pk and C_sk. In addition, bootstrap methods are applied to construct lower confidence bounds which are useful to practitioners for making reliable decisions. An approximated unbiased estimator is also provided. For the purpose of illustration, practical applications are presented.