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| Study on ultrasonic assisted low temperature brazing of SAC0307 lead-free solder |
| GAN Gui-sheng1,2，LIU Xin2，CHEN Dong1，XIA Da-quan1，YANG Dong-hua1,2，LIU Cong1 |
| 1Chongqing Municipal Engineering Research Center of Institutions of Higher Education for Special Welding Materials and Technology, Chongqing 402760, China，2Institute of Weapons Technology, Chongqing Electromechanical Vocational Institute, Chongqing 400054, China |
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Abstract The low temperature interconnection of Cu/Cu was realized by SAC0307 lead-free solder. The microstructure and mechanical properties of SAC0307 low silver lead-free solder joint under the combined effect of nano-Ni particles and ultrasonic assistance were studied. The results show that IMC thickness of two kinds of solder interface increases first and then decreases with the increase of ultrasonic time. At low temperature, the solder joint IMC is scallop-like shape, while the composite solder joint IMC is serrated. As the soldering temperature increases, the serrated IMC becomes more significant. With the aid of ultrasonic, when the brazing temperature is 210-230 ℃, the shear strength of the two kinds of solder joints first increases and then decreases with the increase of ultrasonic time, both reaching the highest values at 5 s of ultrasonic time. When the soldering temperature is 240 ℃, the shear strength of the two kinds of solder joints decreases with the increase of ultrasonic time. The shear strength of the two solder joints are the highest at 240 ℃ with no ultrasonic assistance, which is 25.54 MPa and 26.54 MPa, respectively. When the ultrasonic time is 5 s, the shear strength of the solder joint brazed at 220 ℃ is the highest 31.31 MPa, while the shear strength of the composite solder joint brazed at 210 ℃ is the highest 35.26 MPa. When the solder is in solid state, semi-solid state or viscous liquid state, ultrasonic vibration can help solder joint filling and obtain a compact joint with improved mechanical properties. However, if the vibration time is too long, the gas and oxide inclusions in the solder are not easily overflow and will accumulate and grow up, resulting in degradation of mechanical properties.
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Received: 03 September 2017
Published: 25 April 2019
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2019, Vol. 29 
