Research On Reliability Of Flip-chip Solder Joints

With the rapid development of modern microelectronics packaging technology,the processing size of semiconductors is getting smaller and smaller,the size of wafers is getting larger and larger,and the number of I/O ports of chips in integrated circuits is also increasing,corresponding to this,micro Electronic packaging technology is also increasingly inclined to high precision,high stability,and low cost.In all electronic packaging chip interconnection technologies,flip chip bonding(FCB)technology benefits from high packaging density and excellent high frequency performance,which has made great progress in microelectronic packaging technology and is becoming a modern micro The main interconnection technology of electronic packaging.But at the same time,flip-chip welding technology has also caused a lot of problems in the packaging failure.Therefore,the reliability of flip-chip solder interconnection solder joints has become an extremely critical issue in microelectronics packaging technology.Under the condition of thermal cycling,not only the plastic behavior and creep behavior of the solder joint should be considered separately,but also the factors that affect the plasticity and the creep behavior of the solder joint are analyzed together.Therefore,if only theoretically,it is impossible to accurately Analyze the stress and strain distribution.In this paper,finite element software ANSYS is mainly used to simulate the reliability of flip-chip solder joints and the results of stress and strain distribution of solder joints are given.In the simulation process,using different material models will have a big impact on the final simulation results of the finite element software ANSYS.In this paper,after comparing a series of welding point materials viscoplastic constitutive model,we decided to use Anand constitutive model.The Anand model has been widely used in solder joint stress analysis,and the model has been embedded in ANYSY software,so using this model to observe the performance of flip-chip solder joints is quite useful.The stress and strain distribution of solder joint under thermal cycling conditions is more reasonable under this model.Using this model,we can try to use the nonlinear finite element method to solve the general viscoplastic problem.The process of solving this problem is analyzed in detail here.At the same time,the viscoplastic mechanical properties of the flip-chip solder joints under the Anand constitutive model were analyzed using the finite element method,and the stress-strain distribution characteristics of the solder joints under thermal cycling conditions were obtained.The maximum stress strain value of the solder joints appeared.At the contact point between the solder joint and the chip edge,the stress under the solder joint is less than the stress applied above it;during the entire thermal cycle,the place where the stress strain changes significantly is always at the edge solder joint.The solder joint is The change of stress and strain during temperature change is significant,and the change of stress and strain is lighter during the process of temperature stabilization.Based on the above analysis,using the relevant experience to modify the calculation equation,we can calculate and predict the thermal fatigue life of flip-chip solder joints more accurately.