Cu Cu METHOD FOR BONDING Cu BALL TO ELECTODE AND METHOD FOR SELECTING Cu BALL

摘要

It provides a Cu ball having excellent alignment properties. In order to suppress the wetting defect of Cu ball at the time of soldering, brightness is prescribed | regulated as an index which determines the film thickness of the oxide film of a ball surface, and brightness is made into 55 or more. In addition, in order to measure lightness accurately, the higher the sphericity of Cu ball | bowl is good, and in order to make a sphericity high, the purity of Cu ball | bowl is made into 99.995% or less. When the brightness is 55 or more, the film thickness of the oxide film formed on the surface of the Cu ball is preferably 8 nm or less.