| To satisfy the requirement that flexible electronic devices can withstand certain loads such as tension,bending and twisting during service,a multi-layer heterogeneous structure is used to protect some non-stretchable semiconductor components during the packaging process.However,due to the mismatch between the polymer material of the encapsulation layer and the semiconductor device materials such as chips,many interface failure problems occur,and the geometry and material properties of the encapsulation layer both affect the reliability of the interface.In addition,the material of the adhesive layer connecting the chip and the encapsulation layer is easy to cause the degradation of the material performance and the degradation of the interface adhesive force due to exposure to the load of the humid and hot environment,which ultimately leads to the failure of the interface layer.Therefore,in view of the above problems,this thesis comprehensively considers the factors.Combined with the experimental method,energy method,finite element numerical simulation and other angles to research the reason of the change of the bonding strength of the interface under different influence mechanisms and the fracture mechanism.The following is a summary of the work of this article:(1)To study the effect of hygrothermal degradation on the adhesive layer,two dumbbell-shaped samples of the commonly used electronic packaging adhesive layer material were made in this thesis:epoxy resin and conductive adhesive filled with different proportions of silver nanoparticles.According to the JEDEC hygrothermal environment test standard,the weighing method is used to calibrate the hygroscopic weight under different hygrothermal environments such as 45~oC/85%RH?65~oC/85%RH?85~oC/85%RH under different time periods,and obtain the corresponding weight.It is found that whether the temperature or humidity is increased will increase the rate and concentration of moisture absorption,especially under 85 ~oC/85%RH environment,the rate and concentration of moisture reach 1.534×10-5m~2/s and 35 kg/m~3,respectively.And for conductive adhesives filled with different proportions of silver particles of 0-50%,the moisture absorption rate and concentration are first increased by 24%and 21%due to the effect of pores,but with the filling amount exceeding 10%,the moisture absorption concentration is reduced due to the amount of epoxy resin decreased by 14%.In addition,the degree of degradation of the corresponding elastic modulus,tensile strength and other mechanical properties under different moisture concentrations under uniform moisture distribution was measured,and it was found that with the increase of the degree of moisture absorption,the elastic modulus and tensile strength will show degradation The phenomenon did not decrease by as much as 33%and 21%respectively.At the same time,for the conductive adhesive filled beyond 10%concentration of silver particles,as the epoxy resin content is reduced,the moisture absorption concentration will also be reduced and the degradation effect will be weakened,especially for the addition of 50%——the elastic modulus was only reduced by 7%.(2)To study the degradation mechanism of the multi-layer heterogeneous packaging structure on the interface bonding strength in hygrothermal environment,the elastic modulus and thickness of the multi-layer composite film packaging layer,as well as the effects on the bonding strength under different moisture absorption concentrations were considered.In this thesis,the designed peeling device and the film-based structure are used to control the fracture mode to study the effect of normal and tangential peeling on the bonding force under different factors.Furthermore,from the perspective of energy,the mechanism of the influence of the competition between the geometric dimensions and material properties of the encapsulation layer and the hygrothermal degradation on the peel force is further explained.It is found that the moisture degradation effect mainly affects the critical fracture energy of the interface and the elastic modulus of the film.The latter has a more obvious effect on the multilayer composite film.At the same time,the elastic modulus and thickness of the film mainly affect the strain energy of the film during peeling and eventually cause a change in peeling force.In addition,based on the mechanism of moisture diffusion,the relationship between the peel force and the degradation time and fracture position under the non-uniform moisture distribution state is established,which found that the less time treated by moisture and less peel angle,the more difference in the peel force in the different displacement.(3)Based on the peeling process simulated by the cohesion model,the degraded secondary model is used to obtain the cohesion parameters under different operating conditions according to the corresponding energy release rates at different moisture concentrations.Moreover,the simulation data is compared with the force-displacement curves of different environments obtained in the experiment to verify that the thin single-layer film's hygrothermal degradation effect affects the fracture energy of the interface more.In addition,using the corresponding cohesion parameters under different moisture concentrations to simulate the size effect and material properties of the composite film encapsulation layer,and comparing the experimental results,it is found that the adhesion to the multilayer composite film structure is mainly caused by the interface fracture energy and the elasticity of the film.The degree of degradation of the modulus is determined jointly.Moreover,it has a greater influence on the hydrophilic film.(4)The design and preparation of another packaging layer material and structure,which is analysized using the method in this thesis,confirm accuracy and wide application in flexible electronic packaging.Provide a method for flexible electronic package design in the face of hygrothermal reliability. |
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