Theoretical and Experimental Raman Study for Mechanical Stress in Die-attach Process

We measured the stress in Si chip mounted on Cu plate using Raman spectroscopy and compared the results with those calculated by finite element method (FEM). The difference of the stress observed in the vicinity of the chip was about 20 MPa, and the simulated value was smaller than that of the Raman results. We found that the difference occurred owing to the absence of the “filet” structure that was generated from the epoxy adhesive and then we modified the simulation model. The modified FEM results were in good agreement with the measured results. These results indicated that the “filet” structure, which was not a main structure of die bonding, played an important role in the residual stress formation. Feedback using Raman measurements was crucial and we evaluated the stress in electronic devices with high accuracy by combining FEM with Raman microprobe measurements.