Fatigue Characteristics Of Three-dimensional Microsystem Structures Under Electro-thermal Coupling

The development of integrated circuit packaging technology tends to be more and more three-dimensional integration,so the integration density of chips can be rapidly increased.However,people’s demand for chips will only make the size of the chip smaller.Even if the power consumption remains unchanged,the problems of thermal effects and electrothermal effects will only become more prominent.Under the high-density integrated module,multiple heat sources will strengthen the thermal coupling effect and generate high heat flux density points,and high temperature will cause the performance of components to degrade or even fail.Therefore,in order to promote the development of chip 3D integration technology,researchers must consider how to improve the reliability of 3D microsystems.This paper takes multi-layer stacked chips as the research object,and uses Ansys finite element software to simulate and analyze the fatigue characteristics under the thermalmechanical coupling field and the electrothermal-mechanical coupling field.At the same time,the influence of temperature on the structure of the three-dimensional microsystem in the thermal cycle is studied by changing the values of the highest temperature and the lowest temperature in the thermal cycle,and the influence of the current density on the structure of the three-dimensional microsystem under the combined action of electric heat is studied by changing the applied current density.Finally,the impact on the three-dimensional microsystem structure is studied by changing the solder joint material,spacing and chip length,and the number of stacked layers.It was found that under the thermal-mechanical coupling field,the deformation at the edge of the top chip of the 3D microsystem structure is the largest,and the most dangerous solder joints are located at the edge of the bottom chip.The equivalent stress and equivalent plastic strain at the most dangerous solder joints are the largest during the entire thermal cycle,and the simulation found that low temperature is the key factor for the plastic strain of the most dangerous solder joints.The results show that increasing the maximum temperature value and decreasing the minimum temperature value in the temperature cycle will reduce the fatigue life of the three-dimensional microsystem structure.The deformation of the three-dimensional microsystem structure under the action of the electric-thermal-mechanical coupling field,the equivalent stress of the most dangerous solder joints,and the simulation results under the action of the equivalent plastic strain and the thermal-mechanical coupling field are similar.The addition of current will reduce the impact of the three-dimensional microsystem structure at low temperature,thereby increasing its fatigue life,and the lifetime of the three-dimensional microsystem structure gradually increases with increasing current density.