Study On The Interface Delamination Behavior And Adhesion Regulation In Film Transfer Printing Technology

Film transfer printing is a technology which is uses viscoelastic stamp to orderly transfer preprocessed films from the donor substrate to the target substrate by means of interface adhesion and finally forms functional devices.It plays an important role in the manufacturing process of flexible inorganic electronic devices.The technology includes two periods of transfer and printing,and both involve the stamp/film interface.The adhesion/delamination characteristics of the interface play a crucial role in the success or failure of the film transfer printing technology.To optimize the existing film transfer printing technology and develop new,efficient transfer methods,it is necessary to predict the adhesion/delamination mechanical behavior of the stamp/film interface,so that theoretical bases for predicting the success or failure of transfer printing can be provided.Furthermore,it is necessary to explore the active regulation strategy of stamp/film interface adhesion to provide a method for solving the transfer failure,so that methods can be provided to solve the failure problem of transfer printing.However,researches about the above two types of problems are still lagging behind.In this thesis,the mechanical behavior and adhesion regulation of stamp/film interface are studied.The main contents are as follows.1.Study on the adhesion/delamination mechanical model of flat stamp/film interface: For the transfer printing problem for silicon film by polydimethylsiloxane flat stamp,the interface mechanical models based on J-integral theory,Virtual Crack Closure Technique(VCCT)and cohesive zone theory(which includes different implementation forms and different constitutive relations)are established.The finite element technique is employed to simulate the adhesion/delamination behavior of the stamp/film interface.The results show that compared with the model based on J-integral theory and VCCT theory,the model based on cohesive zone theory can predict the initiation and propagation of interfacial delamination without presetting initial cracks,and thus it.The model is more suitable for analyzing the adhesion/delamination behavior of the stamp/film interface.Furthermore,under the same traction-separation law,the results of the elementbased cohesive zone model and the surface-based cohesive zone model are basically the same,but the surface-based cohesive zone model is easier to be extended to the analysis of mechanical properties of stamp/film interface in other kinds of film transfer printing technologies.2.Study on the adhesion/delamination mechanical behavior of flat stamp/film interface: Using the selected cohesive zone model to describe the interaction between the flat stamp and film,the effects of unloading velocity,interface constitutive parameters and shear displacement on the maximum adhesion force(that is,pull-off force)of the interface are studied respectively.What’s more,the mechanical behavior testing platform for the transfer printing system interface is established.Experimental studies are conducted and results are compared with theoretical ones.The results show that the pull-off force of the flat stamp/film interface increases with the unloading velocity.High unloading velocity is beneficial to realize the adhesion of the stamp/film interface,while low unloading velocity promotes the interface delamination.The simulation results are consistent with the experimental results.Moreover,the larger the normal strength and fracture energy of the interface,the greater the pull-off force of between the stamp/film interface,and the more difficult the interface delamination to realize;Furthermore,the pull-off force can be effectively reduced through applying shear displacement,and the larger the shear displacement,the smaller the pull-off force.3.Study on the adhesion characteristics of the interface regulated by the microstructure of the stamp surface: For the stamp surface microstructure-assisted film transfer printing technology,a mechanical model of microstructured stamp/film interface is established.The effects of the height,width and area ratio of the grating microstructure on the interface pull-off force under different indentation depth and unloading velocity are investigated.The results show that with the increase of microstructure height,the pull-off force decreases,the adhesion switching ratio based on indentation depth(that is,the ratio of the maximum pull-off force to the minimum pull-off force in the studied indentation depth range)increases,and the adhesion switching ratio based on unloading velocity(that is,the ratio of the maximum pull-off force to the minimum pull-off force in the studied unloading velocity range)increases at first and then decreases.With the increase of microstructure width,the pull-off force decreases at first and then increases,and both the adhesion switching ratio based on indentation depth and that based on unloading velocity increase at first and then decrease.With the increase of microstructure area ratio,the pull-off force decreases at first and then increases,the adhesion switching ratio based on indentation depth increases at first and then decreases,and the adhesion switching ratio based on unloading velocity decreases.4.Study on the adhesion characteristics of the interface regulated by laser: For the laser-assisted film transfer printing technology,an optical-thermal-mechanical coupling model is established to study the effects of laser irradiation time,laser beam power and film thickness on the pull-off force of the stamp/film interface.The results show that the longer the laser irradiation time and the higher the laser beam power,the smaller the pull-off force of the stamp/film interface,and the effect of laser irradiation time on interface adhesion is greater than that of laser beam power.The pull-off force of the stamp/film interface is different for different film thickness,and there exists a film thickness under which the pull-off force is smaller.