An Improved Manufacturing Yield Measure for Gold Bumping Processes With Very Low Nonconformities

Abstract

Nowadays, thinner and slimmer smartphones have been widely applied in daily life. In most portable devices, liquid-crystal display driver integrated circuit (IC) or new touch display driver IC are critical components, in which the gold bumping process is used as an essential interconnection technology and usually outsources to out-sourced assembly and testing factories. In semiconductor packaging manufacturing, due to popular high-definition requirements of display devices, gold bumping processes require very low fraction of nonconformities. For this reason, accurately evaluating the manufacturing yield is very important to guarantee the quality requirements being met. To evaluate the yield of gold bumping processes, the most popular yield index C-pk is widely employed in outsourcing contract arrangements. However, the typical existing nature estimator is a biased estimator and more conservative. In this paper, we provide an unbiased estimator to evaluate the gold bumping manufacturing yield more accurately. Based on the new estimator, we further propose a weighted parametric bootstrap method to obtain a reliable lower confidence bound that is closer to the true manufacturing yield. The new yield assessment can avoid underestimating the gold bumping manufacturing yield and can make more reliable decisions.