Research On Prediction And Optimization Of Junction Temperature Based On Stagger-stacked DDR Module

With the rapidly increase in chip packaging density,traditional packaging technology has been difficult to meet the requirements of packaging.System-in-Package has emerged at the historic moment.System-in-Package is the comprehensive reflection of continuous innovation in packaging technology and architecture,which meets the goals of light,thin,small,high performance and high reliability.Stacked package is a commonly form of System-in-Package.For multi-chips,the heat generated by the chips in each layer will be coupled to each other,which will easily cause the chip to overheat and fail.Therefore,the research on prediction and optimization of the junction temperature of stacked package is significant.For the first time,this thesis takes the stagger-stacked DDR module as the research object and presents a complete set of techniques which can accurately predict the junction temperature of the module.The finite element software Icepak is used to establish the thermal simulation model of the module and the main heat flow path is obtained by simulation.The thermal resistance matrix is used to predict the junction temperature of the module under multiple operating conditions and the error between the calculated value and the simulation value is found to be less than 5%.The thermal resistance network is established based on the specific structure of the module and the components with large thermal resistance are determined.Then,the thesis analyzes the effect of component materials(the material of molding compound,adhesive film and the copper coverage of PCB),structural dimensions(the size of molding compound and die),and component location(the position of the IPD chip in the stacked structure and the chip staggered length)on junction temperature.In addition,the thesis proposes a junction temperature optimization technique based on an improved orthogonal experiment.The orthogonal experiment is used twice continuously to optimize the overall heat dissipation performance of the module.The main and secondary factors affecting the junction temperature of the module are obtained:Thermal conductivity of the molding compound,chip staggered length,thermal conductivity of the adhesive film and the thickness of die.The optimal value of each factor is combined as the optimal design.After simulation,it is found that the optimal design can reduce the junction temperature by 4.74% compared with the initial model.Finally,this thesis compares the thermal performance of cantilever,pyramid,pyramid and cantilever combination package and stagger-stacked package,and then optimizes them by using improved orthogonal experiments.The verification results show that compared with the three traditional stacked packages,the stagger-stacked package has reduced junction temperature by 3.62%,7.95% and 5.63%,respectively.