Research On Thermal Stress Of Encapsualted Assemblies Of Epoxy Resin Under High And Low Temperature Load

With the rapid development of electronic technology and packaging industry and the continuous improvement of electronic product functions,the requirements for the performance of encapsulated asemblies are also increasing.Epoxy resins are widely used in the electronic packaging industry due to their good dielectric properties,mechanical properties,and cohensive properties.However,epoxy resin has high brittleness and poor thermal shock resistance after curing,which causes problems such as resin cracking and interface debonding due to concentration of internal thermal stress at high and low temperature loads,and will affect the integrity of the encapsulated structure.Damage to the structure.In this paper,the epoxy encapsulated asemblies as the research object,through the means of finite element simulation and experimental mutual verification,carried out the study of the thermal stress of the encapsulated structure composed of two resin systems(resin toughening agent modified epoxy resin called resin system A,silicon micro powder modified epoxy resin called resin system B)under high and low temperature loads,and compared and analyzed the failure of the internal structure of the encapsulated structure.In this case,a group of resin systems with good high and low temperature performance was selected.The main content of this article was as follows:(1)Prepare and test the mechanical properties of the two resin systems at different temperatures,plot the mechanical properties as a function of temperature,analyzed the strengths and weaknesses of the mechanical properties of the two resin systems,and provided material parameters for the finite element simulation.(2)According to the design standards of encapsulated molds,demoulding and airtight optimization design of encapsulated molds met the overall requirements of encapsulated molds.Summarized the heavy and difficult points in the infusion process,and reasonably designed the resin degassing conditions,perfusion vacuum and other infusion processes,solved the problems of bubble residue,leakage irrigation and other issues in the process of the encapsulated structure preparation,and established a standard encapsulated process specification.(3)According to the dimensions of the encapsulated structure and the relative positions of the components,a thermo-mechanical coupling model of the encapsulated structure was established to simulate the distribution of the interface thermal stress at the temperature of-40?~75?.The simulation results showed that: During the warmup phase,the tensile/shear stress at the system A/Kovabie interface(A-interface)and the system B/Kovabie interface(B-interface)are comparable,both in the range of 1.40 MPa ~ 1.90 MPa;During the cooling phase,the A-interface shear Stress up to 2.82 MPa is twice the B-interface.According to the thermal stress distribution of the interface,a suitable cohesive force model was chosen to simulate the interface debonding between the two systems.The results showed that when the temperature reached-40?,the A-interface debonding parameter was as high as 0.9506,indicating that the interface had completely devised the failure.B-interface debonding parameter was only 0.0585,the interface was more secure.In contrast,the B-interface had better stability at high and low temperatures.(4)The thermal stress simulation results of the resin layer showed that the thermal stress of the two resin layers in the heating stage was less than 20 MPa and the resin has no cracking tendency;when the temperature drops to-40?,the equivalent stress at the resin A concentration point was as high as 103 MPa.The allowable strength of the resin was 104.42 MPa,indicating that the resin A had the risk of cracking at low temperatures.(5)The high-low temperature experiments of epoxy encapsualted assemblies were carried out.It was found that after the encapsulated assemblies A experienced high and low temperature loads,a large number of cracks appeared at the interface between the internal insert and the resin bottom,and a slight debonding occurred at the interface.In addition,the simulation results were in agreement with the test results with a average deviation about 28.01%,which verified the accuracy of finite element simulation results.Comprehensive simulation and experimental results showed that the epoxy encapsulated assemblies prepared by system B was more suitable for working conditions with high and low temperature load.In this paper,the epoxy encapsulated structure as the object,established from the raw material performance analysis,mold preparation and process optimization,finite element simulation analysis,high and low temperature experimental verification of the four resin systems encapsulated structure thermal stress failure studies.Through comprehensive simulation and experimental results,the resin system with high stability under high and low temperature environment was selected.In addition,the research ideas and methods in this paper were also applicable to the design and preparation of similar encapsulated structures.