Ultra fine pitch 20 micron 2N second bond improvement with new capillary surface morphology

Abstract

Wire bonding of 20micron 2N wire using conventional pink capillary for ultra Fine Pitch package results in high stoppages of short tail which causes machine to stop, higher yield loss and reduced equipment efficiency and stability. The objective of present study is to improve the 2nd bond quality and stability for reducing the stoppages caused by the short tail. The new design, called as Fortus capillaries have granular tip surface morphology that improves mechanical interlocking, relative displacement between capillary's tip and wire, and also improve the energy transfer efficiency at wire-lead inter layer surface. Statistical analysis comparisons and internal physical inspection were done through SEM image at 0 hour, 96 hours and 192 hours after High Temperature Storage (HTS) and 500 and 1000x Thermal cycle. Cross section analysis was also done to study the Inter Metallic Compound (IMC) formation between wire and lead plating. The Fortus pink capillary effectiveness in reducing short tail was proven in actual production during 5000 unit wire bond process operation with 75% improvement of machine stoppages and resulting in significant improvement of production yield up to 99.5%. This new granular tip capillary also gave about 100% improvement compared to the conventional capillaries life ©2008 IEEE.