Study Of Ultrasound Propagation Regulation In Ultrasonic Bonding Process Of Polymer

With the widespread applications of ultrasonic bounding technology in the field of polymer micro component,it is important to put forward higher requirements on the accuracy for the bonding because the structure sizes of micro device become smaller.Polymer ultrasonic bonding is the process of interface fusion,where the property status changes of the polymer directly reflect the degree of interface fusion.While ultrasonic propagation efficiency is a parameter that is able to reflect the changes of property status of the polymer from moment to moment.The ultrasonic propagation efficiency as the control parameter in the bonding process can indirectly realize the energy input control of ultrasonic energy,so that it is able to realize accurate control of interface fusion quality and improve precision of the bonding.To understand this parameter of ultrasonic propagation efficiency,the ultrasound propagation in the ultrasonic bonding was studied in this paper.The study results can improve accurate usage performance and reduce the complexity and blindness of this parameter in the actual bonding process,which provides theoretical guidance for the process of ultrasonic precise bonding for polymer micro devices.With respect to the control parameter of ultrasonic propagation efficiency,the article firstly carries out finite element simulation of the ultrasonic propagation in the process of ultrasonic bonding,establishing the finite element model of ultrasonic bonding tool horn,micro components and anvil.According to the viscoelastic constitutive relation of polymer material,ultrasonic bonding is simulated under different temperature and amplitude respectively.Afterwards contact force is calculated on every contact surface,propagation law is concluded that ultrasonic propagation efficiency decreases with the temperature increase of the micro components and increases with the increase of ultrasonic wave amplitude by studying the relationship between the contact force and temperature as well as amplitude.The regulation has theoretical guidance meaning to the application of the law of ultrasonic propagation efficiency.Secondly,for simulating dynamic pressure curve of polymer micro devices under the action of high frequency ultrasound in the actual bonding process,the bonding model with thermal expansion was established in the finite element simulation.The relative complete vibration curve was got through inducting vibration outputs between contact surfaces in different temperature models.In order to investigate the law of ultrasonic propagation in the progress of bonding,the precise 60 kHz ultrasonic bonding equipment which is of high frequency,low amplitude and low power is established with respect to bonding of the PMMA micro connector.The destruction of ultrasonic power to the micro components can be reduced by low amplitude and the sound intensity of low amplitude ultrasonic energy can be compensated by high frequency.The precise ultrasonic bonding system is designed and produced which is a collection of ultrasonic,drive,sensor,leveling,control.In order to detect the change of propagation efficiency during bonding,vibration acceleration of micro component base bottom surface is detected by the piezoelectric ceramic acceleration sensor and high frequency dynamic pressure during the ultrasonic vibration is detected by the piezoelectric dynamic pressure sensor.In order to further analyze the ultrasonic propagation law in polymer ultrasonic bonding,the precise ultrasonic experimental platform of different pressure and different amplitude is detected by piezoelectric ceramic acceleration sensor and piezoelectric dynamic pressure sensor.With the experimental platform under the situation of no-load,the output curve of actual vibration with the change of pressure and ultrasonic amplitude is drew,which can provide reference to the selection of pressure and amplitude in utilizing the welding machine to bond.The micro polymer PMMA connector and base layer in the ultrasonic packaging of different amplitude is detected by piezoelectric dynamic pressure sensor.The typical dynamic pressure change trend of thermoplastic polymer micro components is obtained under the action of ultrasonic wave.What's more,the trend curve of this experiment is consistent the curve of dynamic pressure trend gained through simulating to ultrasonic bonding of micro polymer components with thermal expansion,which verify the correctness of the simulation curve of the dynamic force in ultrasonic bonding.