Soldering Behavior Study Of Ultrasonic Semi-solid Coating Soldering With Particle Reinforced Filler Metal Based On Conical Horn

The ultrasonic soldering joint strength is low and its performance is poor under the low temperature condition,which can not meet the needs of industrial production.Therefore,whether the ultrasonic soldering method with good technology and good joint performance or the new aluminum alloy soldering filler metal which is an urgent problem to be solved and studied.This study starts from the the design of ultrasonic horn which seeks to promote the wetting of the solders.After that,the influence of ultrasonic parameters on the spread of the solders is studied and the optimal process parameters are obtained to carry out ultrasonic semi-solid coating soldering tests.Finally,the microstructure and mechanical properties of 6061 aluminum alloy soldered joints with Sn-9Zn-x Al₂O₃ alloys are investigated.The effects of different size particles on the microstructure and properties of brazed joints are further investigated.The specific research contents and results are as follows:Firstly,the large amplitude is conducive to the spreading of solder alloys.ANSYS finite element method is used to design the horn.Finally,it is obtained that the horn with diameter of big end is 40 mm,the diameter ofsmall end is 10.4mm,the total length is 142.6mm and the amplitude ratio is7.2.Its stress concentration coefficient is smaller than that of the step horn and it is easy to be processed.Secondly,the ultrasonic coating test is carried out by using a self-assembled ultrasonic soldering device to determine the optimum parameters of ultrasonic assisted semi-solid coating soldering.The distance of the ultrasonic horn and the solder alloys is about 30 mm,which is beneficial to the spreading of the solder alloys.The spreading area of solder becomes larger with the increase of ultrasonic time and ultrasonic power,but it is not infinitely large.The area is no longer increasing,the wetting angle is no longer changed which is in a stable state,when the ultrasonic time is longer than 5s.Especially,when the ultrasonic power is more than 350 W,the increase of the area is reduced,but the amplification of the thickness is still maintained.So it is proved that the atomization effect is bad to the solders.Finally,the parameters of ultrasonic assisted semi-solid coating soldering process: the ultrasonic time is 5s?to ensure full spreading?,the ultrasonic power is 350 W,the temperature is 210?,the frequent is 24 k Hz and the press is 3N.Finally,6061 aluminum alloys are soldered by ultrasonic assisted semi-solid coating soldering with Sn-9Zn alloys,Sn-9Zn-1nm Al₂O₃ alloys and Sn-9Zn-1nm1?m Al₂O₃ alloys.Because the addition of nano size and double size Al₂O₃ particles as the reinforcement are in the soldering seam,the strength of the soldered joint is improved.In addition,the addition of Al₂O₃ particles with different sizes can be used to refine the rich Zn phase and Sn-Zn eutectic structure to improve the diffusion of Al and Zn,but it has a little influence on the intermetallic compound.Then joint fractures of 6061 aluminum alloys soldered by ultrasonic assisted semi-solid coating soldering with Sn-9Zn-x Al₂O₃ solders are studied.It is known that the joint fracture of Sn-9Zn solders is brittle fracture,and the joint fractures of Sn-9Zn solders with Al₂O₃ particles are ductile fracture.Especially,the joint fracture of Sn-9Zn-1nm1?m Al₂O₃ solders is an obvious dimple structure.The microstructure of the fractures is mainly ?-Sn phases,the white and elongated Sn-Zn eutectic phases and a small amount of Zn rich phases.And all fractures occurs in the middle of the joints.According to the above results and analysis,it can be seen that the ultrasonic assisted semi-solid coating soldering has good connection and excellent performance,and the joint strength can reach at least 88 MPa.