Ultrasonic Welding Process And Quality Analysis Of Thermoplastic Plate For Packaging

Ultrasonic welding of thermoplastic composite is widely used in the connection and assembly of manufacturing industry.For all kinds of industrial production,the connection effect of components is crucial to meet the functionality,serviceability and stability of the final products.Compared with other welding methods,ultrasonic welding has the advantages of speed and energy saving,and it has the potential to realize high-speed industrial welding process for welding devices in certain sizes.Ultrasonic welding can also be used in the packaging of non-glass packaged solar cell modules.Solar cells need to be exposed outdoors for a long time,and their related products are increasingly chasing the features of portability and lightweight.Therefore,thermoplastic and highly transparent polymers are often used as packaging substrates in production,and they are stilled fixed by packaging glue in the packaging process,In order to solve the stability problem of the packaging life of the battery devices,In this paper,ultrasonic welding technology is introduced into the packaging of photovoltaic devices to improve the reliability of packaging and the service life of solar devices.In view of the packaging of solar cell modules,the method of ultrasonic bonding is firstly proposed.A variety of thermoplastic substrates,such as crystalline plastics PP and PET,amorphous plastics ABS and PVC were selected as the representatives to design the process parameters by orthogonal experiment.The effects of ultrasonic parameters such as ultrasonic time,ultrasonic amplitude and ultrasonic pressure on the bonding strength of different types of polymer plastics were studied to determine the optimal process parameters.Secondly,the ultra-depth of field microscopy system was used to analyze the microstructure of the bonding interface and the cross-linking degree between molecules at the bonding interface was analyzed by infrared spectroscopy.The results show that only polymer plastics with similar physical properties and chemical composition can produce excellent welding joints.Ultrasonic energy is determined by ultrasonic time and amplitude,Too low output of ultrasonic energy leads to the local connection of welding parts,so that the discontinuous welding interface fails to form an effective connection;Too high output of ultrasonic energy leads to the local melting of plastic and large specimen deformation,resulting in penetration of welding and perforation at the interface.The welding pressure ensures the close contact of the specimen interface,and too low pressure will lead to poor interface contact and low connection strength,while too high pressure will collapse the welding parts.The ultrasonic time of crystalline plastic welding is 3 s,the ultrasonic amplitude is 30～40 μm,the ultrasonic time of noncrystalline plastic welding is0.5～1.5 s,and the ultrasonic amplitude is 20～40 μm.Under the suitable combination of welding parameters,the maximum shear strength between crystalline PP,PET and PP-PET materials shall be 7.17 MPa,6.40 MPa and 7.52 MPa,and the maximum welding strength between noncrystalline ABS,PVC and ABS-PVC materials is 14.85 MPa,13.12 MPa and 12.43 MPa.This project designs and builds a microwave nondestructive testing platform,uses the microwave vector network analyzer,takes the upper and lower surface of the polymer plastic as the detection object,and uses the microwave scanning method to detect the uncombined defects of the welding interface.The interaction with the specimen and the material makes the different reflection coefficients between the poorly combined parts and the fully combined parts,thus causing different echo loss to the microwave transmission.The study results show that the following: At the point frequency at 14.68 GHz,the echo loss value of the defectfree part of the polymer plastic after welding is between-10 db～-11 db;The echo loss value of the defect site is within the range of-5 db～-8 db.By comparing the microwave energy reflected at different interfaces,the reliable echo loss characteristic values are extracted for imaging to realize the rapid positioning and determination of the unconnected defects of plastic plates,thus realizing the nondestructive detection and analysis of the binding quality of the packaging interface.There is a good agreement between the obtained microwave test results and the destructive test results.