The Effect of Different Cu Concentration on the Microstructure and Mechanical Property of Lead –Free Sn-Ag-Cu-Sb Solder

• Main Authors: Tung-Ying Hsieh, 謝東穎
• Other Authors: Shih-Chin Lee
• Format: Others
• Language: zh-TW
• Published: 2006
• Online Access: http://ndltd.ncl.edu.tw/handle/83108420240558085852

碩士 === 國立成功大學 === 材料科學及工程學系碩博士班 === 94 === Abstract In this study, the liquid of tin and copper plate were diffused at 270oC for 100 hours to investigate micro-structures, wettability and mechanical properties of lead-free solder Sn-3.0Ag-0.5Cu-0.2Sb when the concentration of copper was increased. Besides, the tensile test after 160°C for 240 hours thermal treatment was used to understand the different thermal stability between different copper concentrations. The results of structure show that the concentration of copper in tin liquid was increased by rising the diffusion time. When the diffusion time up to 100 hours, the concentration of copper was 0.933 wt%. The increasing of copper will reduce the melt point little and change the temperature difference between solid phase and liquid phase. After 50 hours diffusing, temperature difference between solid and liquid was the largest. No matter in what concentration of copper, it still be the circular eutectic microstructure of Ag3Sn and β-Sn but the grain size was finer and the precipitation of Cu6Sn5 were more and coarse. In wetting behavior, the surface tensile stress of solder-copper interface decreasing by rising copper concentration. The contact angle and wetting time of solder on copper plate decrease too. Summarily, in the study adding copper to the solder can enhance the wettability. On the mechanical properties, when the Cu atoms increasing, hardness and yield strength were improved due to precipitates increasing. After 100 hours diffusing, the yield stress was improved from 29.16 to 35.5 MPa. The rupture forms were the same as non-diffusion specimens and the elongation is not varied. After diffusing for 240 hours at 160oC, the concentration of Cu was increasing, the precipitates became coarse and the yield strength was reduced from 29.16 MPa to 23.62 MPa by 18.8 percent. The yield strength of 100 hours diffused sample was reduced from 35.52MPa to 20.80MPa by 41.4 percent. From the results, when the concentration of Cu increase, the thermal-stable properties were worse. In summary, although the increasing of copper concentration enhance wettability and mechanical properties, thermal stability decreases.The parameters of manufacturer process are very important for lead-free solder. According to the study, if the working environment is on the high temperature, it is the optimum that the copper concentration is lowest in solder. Key words: Sn-Ag-Cu、lead-free solder、wetting behavior