The Fatigue Life Calculation Of The Electronic Packaging Structure Under Combined Thermal Stress And Vibration Loading Conditions

With the rapid development of modern military industry science and technology,the reliability verification experiment has become the necessary link to test the function of military products.The environmental stress screening method is widely applied in domestic weapon and equipment field.The main principle of this method is to stimulate the subject,and the internal manufacturing problems will be activated under the action of excitation,and it will show up in the form of failure.However,due to the significant improvement of the manufacturing technology of mechanical and electrical products,the environment stress screening method widely adopted at this stage cannot detect the underlying defects in the products.The single sequential load loading method is one of the main reasons to restrict this method.In order to solve this problem,this paper respectively studied the fatigue life analysis method of typical electronic packaging structures under thermal cycling load,random vibration load,and thermal-vibration coupling load.The main work is introduced as follows:(1)The Anand constitutive equation based on uniform viscous plastic theory is applied in the calculation of fatigue lifetime under the thermal cycling load condition.Firstly,simplified finite element model of the structure of plastic ball grid array packages is established in the design modeler module of Workbench.The corresponding temperature cycling load is applied on model.The time course curve of equivalent plastic strain from the hazardous location in the solder is obtained.And then the fatigue lifetime is calculated by Coffin-Manson equation which is revised by considering the thermal cycling load condition.(2)To calculate the fatigue lifetime under random vibration load condition,the simplified element model of the structure of plastic ball grid array packages is firstly established in the design modeler module of Workbench.The completed model is imported into Ansys classic interface for analysis.Random vibrations under normal temperature,low temperature,and high temperature environment are considered respectively.After applying random vibration load,the strain PSD response curve from solder hazardous location is extracted.Strain time course curve is obtained by the Fourier inverse transform command in Matlab.And then strain distribution range is counted by the application of rain flow counting method.The fatigue lifetime each strain range corresponding to is calculated by the application of Mansion-Coffin equation which is based on strain.The damage value is obtained by the Miner liner fatigue cumulative damage theory.And then the lifetime is obtained.(3)To calculate the fatigue lifetime under thermal-vibration coupling load condition,the damage values under thermal cycling load condition and random vibration load condition in normal temperature,low temperature,and high temperature environment are obtained respectively.The value of fatigue lifetime under thermal-vibration coupling load condition is obtained by the application of the incremental damage calculation method of fatigue lifetime.And the results are analyzed.(4)The above fatigue lifetime calculation methods are applied on certain an electronic packaging structure to calculate the fatigue lifetime of the electronic packaging structure under the loading condition of thermal cycling load,random vibration load,and thermal-vibration coupling load respectively.The research results of this paper can provide some reference for the design scheme of the highly accelerated stress screening test project and the theoretical research on the fatigue lifetime of the structure under thermal-vibration coupling load condition.