ScholarWorks@중앙대학교

초록

To enhance the mechanical bonding strength and thermo-mechanical reliability of Sn-58Bi (SB) solder, an SB/Sn-3.0Ag-0.5Cu (SAC) composite solder was developed by mixing SB and SAC alloys. To investigate the effect of the SB-to-SAC mixing ratio on the thermo-mechanical reliability of the composite solder, four types of SB/SAC solders were prepared with different volumetric ratios of SB to SAC solder: 100:0, 50:50, 20:80, and 0:100. A thermal shock test (- 55 to 125 degrees C, 1000 cycles) was conducted to evaluate the thermo-mechanical reliability, while ball shear and microhardness tests were performed to assess changes in mechanical bonding properties after reliability testing. Before thermal shock testing, the SB/SAC composite solders demonstrated improved mechanical bonding properties compared with pure SB or SAC solders, primarily due to the reinforcing effect of uniformly distributed fine Bi-rich precipitates and Ag3Sn and Cu6Sn5 intermetallic particles within the solder joints. Under thermal shock conditions, the SB/SAC composite solders exhibited superior thermo-mechanical reliability relative to the pure solders. This improvement is attributed to the enhanced initial bonding strength obtained through SB and SAC mixing, as well as the suppression of microstructural coarsening and interfacial intermetallic compound (IMC) layer growth and flattening.

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