A new ultrasonic precise bonding method with ultrasound propagation feedback for polymer MEMS

With the advantage of local heating, no foreign materials introduced and high efficiency, etc., ultrasonic bonding was attempted in micro assembly. A new ultrasonic precise bonding method based on ultrasound propagation was proposed. The principle was based on the different propagation efficiencies of ultrasound in the polymer components in different mechanical state. During ultrasonic bonding, local polymer components were heated up and changed from glassy state to viscoelastic state. The propagation of ultrasound though polymer components attenuated, the fusion degree was obtained by detecting the attenuation of ultrasound propagation in real time, which is meaningful for the precise control of ultrasonic bonding. Ultrasonic bonding system was established based on this mechanism. Piezoelectric sensor was fixed in the anvil to detect the ultrasound from horn through polymer components to the bottom. Amplitude attenuation ratio was set as the parameter to control ultrasonic bonding process. Bonding experiments of PMMA (polymethyl methacrylate) micro connectors and substrates were carried out and different fusion degrees were obtained at different parameters. This method is easy to take act at different bonding machine by adjust the amplitude attenuation ratio based on primary experiments and realizes the precise joining of the micro connector with low shape deformation and good appearance in bonding interface, which has significance in micro assembly.

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