Impact of IMC Thickness on Lead-free Solder Joint Reliability under Thermal Aging: Ball Shear Tests vs. Cold Bump Pull Tests

Ball pull test has emerged to be an attractive alternative to the traditional ball shear method for characterizing the attachment strength of solder interconnection. Since it is a relatively new development, so far there is not industrial standard to regulate this testing method. This paper describes firstly the formation and growth of intermetallic compound (IMC) at the interface of Sn-4.0%Ag-0.5%Cu reflow soldered on different types of substrate pad surface finishes (OSP and ENIG). This paper discusses the effect of IMC growth after soldering and thermal aging at 150degC. The attachment strength of solder balls with thermal aging is investigated by ball shear and cold bump pull (CBP) tests. The test results indicate that the CBP test method can reveal the brittle failure of solder joints with a higher sensitivity, especially under the fast pulling speed