Experimental Study Of FAB Formation On EEO Process By Using High Speed Video Record

With the progress of microelectronics manufacturing technology, the integration of chip becomes increasingly high, so the pad pitch is becoming smaller in wire bonding cycle, which leads to a range of issues such as:failure of ball welding, welding short circuit. In Electronic Flame Off(EFO) process, the tail wire melt and Free Air Ball(FAB) forms. The FAB not only affects the quality of the first bonding, but also affects the formation of the feasibility of low wire loop. So it is necessary to study the FAB formation in EFO process, and related studies would be helpful to understand the dynamic FAB formation process. The main work of this paper is to study FAB formation in EFO process, and main contents were as follows:(1) Experimental detection system of FAB formation was designed, high speed video camera was used to record the process of FAB formation, and data acquisition card was used to collected the current and voltage of EFO board. Image processing was used to extract features from image sequence of FAB formation, and the diameter and center of FAB was calculated by RANSAC algorithm.(2) Two phenomenon, the bottom of solid FAB becomes flat at the end of solidification stage and the surface of FAB forms ripple at the beginning of solidification stage were found in FAB formation process. The reasons of ripple and flat ball phenomenon were discussed. Furthermore, the reason of golf ball phenomenon was analyzed by setting up different EFO parameters.(3) Thermal usage was estimated in wire melting stage. The thermal power was produced by the arc between EFO wand and wire tail in wire melting stage.This study will be useful in understanding the FAB formation mechanism and optimizing the EFO parameters.