Bond pad effects on the shear strength of copper wire bonds

Abstract

Wire bond evaluation is crucial in determining its quality. With the increase in use of copper wire bonds, this becomes even more important due to its nature to induce defects such as pad cracking. Bond shear testing is a widely used method to assess wire bond quality. Standards for evaluating wirebonds by shear test are in place (JEDEC, ASTM, IEC, etc.) however, they do not prescribe factors that affect results, making it difficult to compare the quality of bonds made in different conditions. Bond pad thickness is a major factor, studied in detail in this work. It is shown from a design of experiment and through finite element analysis, that bond pad thickness affects the bond shear strength value, while the IMC % coverage and shear mode are not dependent on pad thickness.