Effects of Bonding Pressure on Quality of SLID Interconnects

摘要

The investigation of the bonding pressure change on the different quality aspects of the solid-liquid interdiffusion(SLID) interconnects is presented. The stacks were produced by a flux-assisted bonding of two Si dies with an area array of square Cu/SnAg bumps on the bottom die and Cu bumps on the top die at approx. 250 °C. The bonding pressure was varied between OMPa, 0.35 MPa, 0.69 MPa, 1.04 MPa, 1.38 MPa, 1.73 MPa, 2.08 MPa, 2.42 MPa. Cross-sections of the stacks were analyzed by optical microscopy and scanning electron microscopy (SEM). Tilt, standoff height (SOH) variation, void fraction, interlayer thickness and Cu_3Sn thickness were measured. It will be shown that increase of the bonding pressure can reduce the void fraction from 35.1 %(OMPa) to 10.7% (2.42MPa) and decrease the interlayer thickness at the same time. Decrease of the interlayer thickness is accompanied by solder squeeze and increase of Cu_3Sn thickness. Shear tests revealed an average shear strength of (81.3 ± 21.5) MPa for the produced samples. The analysis of the fracture surfaces with SEM revealed that the weakest interface is located between Cu_6Sn_5 and Cu_3Sn intermetallic compounds (IMCs) close to the initial Cu bump.