Influence of Cylindrical Cells Surface Cleaning by Means of Laser Ablation on Wedge Wire Bonding Process

Abstract

Wire bonding is a method of connecting two or more surfaces by the means of a thin wire which is ultrasonically bonded to those surfaces and provides an electrical connection. While this method is well established in the microelectronics industry its popularity is rising in the area of cylindrical lithium-ion battery pack manufacturing. Previous studies have shown that even in experimental conditions this process might be unstable which was indicated by the high standard deviation of the bonds shear test results. This might have been related to contamination of the interface area between the joined materials. The aim of this study was to determine the impact of surface laser cleaning on the properties of the wire-bonded joint. The results have shown that laser cleaning with 40% power of the 30 W ATMS4060 laser marker helps to reduce the standard deviation of the shear test results from 16.1% for the uncleaned sample down to 2.6% and greatly reduces the number of oxides within the interface area of the bond cross section. Cleaning with 80% of the laser power did not have a further impact on shear test results and almost completely eliminated oxides from the bonded materials interface.