Warpage Research And Solutions For Large Panel Level Fan-out Package

Driven by low thickness,low thermal resistance,low cost and high integration,semiconductor components widely used in smart phones,smart watches and wearable products have increasingly higher requirements for packaging technology,materials and processes.As an advanced packaging technology without laminated substrate and wire bonding,large panel level fan-out packaging has smaller thickness,lower cost,shorter interconnection and better electrical performance.In addition,the pitch of the fan-out package Bump Pitch is unlimited,which makes up for the defects of the substrate manufacturing capacity,so it is called the most important package form in "post-Moore era".Combined with TSV technology,it is applied to three-dimensional stacked packaging,with higher integration and a wider range of applications.However,the large panel level fan out package with much larger plastic area than the wafer-level fan out package also encounters the same problem as the wafer-level fan out package warpage deformation.Therefore,it is necessary and significant to study the warpage deformation for the large panel level fan out package,which is the key problem to be solved in this paper.In this paper,the shell element simulation model and solid element simulation model are constructed by combining simulation and experiment.According to the simulation results and the characteristics of the selected simulation unit,the applicability and practicability of two-dimensional and three-dimensional modeling of large panel level fan out package are analyzed.On this basis,the influence of new packaging process,stress relief groove and packaging structure on the warpage deformation of large panel level fan out package is studied,and the solution of warpage of large panel level fan out package is proposed.This paper built two-dimensional and three-dimensional simulation models to study the effect of material thermal expansion coefficient on the warpage of large panel level fan out package,and the thermal stress distribution is also calculated.According to the thermal stress distribution nephogram of the large panel level fan out package,the warpage during the cooling process is explained.The accuracy of two-dimensional and three-dimensional warpage simulation is verified by experimental data,and the optimal simulation modeling type of large panel level fan out package is determined.In order to improve the warpage of large panel level fan out package,a new double-sided plastic packaging process was studied.In this paper,the influence of the new double-sided plastic packaging process on the warpage of large panel level fan out package is illustrated by analyzing the thermal stress distribution nephogram and warpage nephogram.The results show that when the thickness of the secondary plastic package is equal to the height of the primary plastic package,the warpage is 0.45 mm.From the perspective of thermal stress relief,the opening of the stress relief groove can reduce the warpage deformation of the large panel level fan out package to a certain extent.In addition,from the aspect of package geometry,it is concluded that the warpage of large panel level fan out package has a positive correlation with chip size and a negative correlation with chip spacing.