The study of interfacial reaction between SnBi solder and Au substrate

• Main Authors: Zhao-Ming Chen, 陳昭銘
• Other Authors: 黃孟槺
• Format: Others
• Language: zh-TW
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/mbjuaq

碩士 === 國立臺北科技大學 === 化學工程研究所 === 96 === The interfacial reaction between Sn-Bi solder and Au substrate grows Sn-Au intermetallic compound (IMC) mainly. The constituent of IMC depends on the composition (wt%) of Bi in the solder. When the weight percent of Bi is more than eutectic composition (57wt%), AuSn and AuSn2 would be found at interface. When the composition of Bi is 50wt%, a Sn-Au-Bi ternary metastable compound was formed and after longtime aging or the reaction temperature was increased, the ternary compound will become AuSn4. That means AuSn、AuSn2 and AuSn4, three different Sn-Au IMC will be co-existing at the interface. After longtime aging there are some Bi-rich segregation in the intermetallic compound and others which segregate between IMC and solder become a continuous layer. Based on reaction kinetics, we plotted the IMC thickness vs the square root of time and obtained a linear relationship between these two variables by means of linear regression model. The figure shows a straight line, which means that the growth of IMC is controlled by diffusion mechanism. In the figure, we also know that thickness and growth rate constant (k) are increasing with time and temperature for a specific composition of Bi but decreasing with the composition of Bi in the solder under the fixed conditions of temperature and reaction time. Then we substitute the growth rate constant (k) and temperature into Arrhenius equation, we would obtain the reaction activity energy (Q). When the solder is eutectic, the result shows that the reaction activity energy is the lowest and it decreases when the composition of Bi increases.