Forced-time controlled transient dynamic wire bonding simulation for wire bond process development

Abstract

In wire bond process, wire bond recipe is predefined to wire bonder before the start of wire bonding. This wire bond recipe comprises of single step to multi steps bond force and ultrasonic control depending on type of wire material and bond pad technology to use in wire bonding program [1]. The program always start with wire bondability assessment by manipulate different bond force, ultrasonic power and time to achieve good and reliable bond quality. However, it is not always well understood the fundamental of wire bond mechanism and furthermore it is challenging to quantify the wire bond mechanism with existing measurement equipment and techniques [2]. Hence, numerical simulation technique is still the best tool to re-analyze the wire bond process mechanism and subsequently by using reverse engineering approach to understand and re-evaluate wire bond mechanism. This paper presents an alternative analytic method by using explicit simulation technique with stress sensor correlation to investigate the effect of wire bond recipe to dynamic stress on smashed FAB and bond pad structure during touch down and ultrasonic bonding process. Force-time controlled transient explicit simulation technique was used to define the wire bond recipe and correlated with stress sensor measurement results. ANSYS Ls-dyna explicit simulation software was used in the simulation prediction and stress sensor chip was used to measure stress induced in wire bond process. The results were correlated and used for subsequent wire bond assessment. Preliminary results show simulation prediction has successfully predicted the initial touch down impact on bond pad and the stress distribution and evolution throughout the change of bond force profile. This important information provide valuable understand of wire bond touch down impact and ultrasonic characteristic in wire bond process.