Investigation of stress relaxation in SAC305 with micro-Raman spectroscopy

Abstract

In the paper, μ-Raman spectroscopy is applied as non-destructive test method to access the creep in chip interconnection materials. To develop the method, a silicon test chip is soldered onto a copper substrate using SAC305 and the strain of the silicon crystal in the top surface of the chip is measured time dependent after assembly by the Raman shift. The in-plane stress in silicon crystal decreased exponentially within several days after soldering. To access the strain in the solder material a finite element model was calibrated based on the experimental data applying the Anand creep model and fitting its parameter. The analysis reveals the applicability of μ-Raman measurement to assess creep within interconnect material in microelectronic assemblies.