Warpage Analysis And Optimization Of Large Size Fan-Out Panel Level Package(FOPLP)

Electronic devices are evolving towards smaller,lighter,and more highly integrated designs with lower costs.This requires minimizing costs and enhancing production efficiency and integration while ensuring high yield rates.The fan-out panel-level packaging technology is meeting the market demands.Moreover,the manufacturing process of fan-out panel-level packaging is almost identical to that of wafer-level fan-out packaging.In recent years,a clear trend has emerged in the market’s mainstream fan-out wafer-level packaging towards the adoption of fan-out panel-level packaging with higher wafer utilization efficiency.However,in the production and application of this technology,the significant obstacle on the development path of fan-out panel-level packaging is the warpage deformation caused by the mismatch between the shrinkage of the epoxy molding compound(EMC)during the curing and cooling stage and the coefficient of thermal expansion(CTE)of various packaging materials.As the size of the board continues to increase,the issue of package warpage becomes increasingly prominent.Therefore,it is important to simulate and optimize the warpage of FOPLP before production and processing.This paper is based on the RDL-First process and proposes a research method for the warpage of FOPLP.Finite element simulation is used to analyze and predict the warpage deformation of FOPLP,investigate the influencing mechanisms,and further reduce and optimize the warpage deformation of FOPLP.An orthogonal experimental design is adopted to optimize the packaging structure.The primary research contents of this article are as follows:(1)We aim to investigate the material properties of the carrier board,encapsulant,and the copper volume fraction on the RDL layer,as well as the relationship between the solidification shrinkage of FOPLP and the warpage,to optimize and improve the warpage.With the increase of Young’s modulus of the carrier board and packaging materials in the semiconductor industry,the deformation resistance of the packaging body is improved and the maximum warpage value is reduced.When the thermal expansion coefficients of the substrate,the encapsulant material match,the warpage of the entire package will reach its minimum value.When the proportion of copper volume in the RDL layer increases,the thermal conductivity and coefficient of thermal expansion of the RDL layer also increase,resulting in an overall increase in the warpage value.When considering the mutual influence of material properties,it is found that the thermal expansion coefficient has the greatest influence on warping,followed by the Young’s modulus and the volume fraction of copper in the RDL layer.(2)Study the relationship between the properties of the carrier board material,the encapsulant material,the volume ratio of copper on the RDL layer,and the warpage of FOPLP during the curing and shrinkage process,and then optimize and improve the warpage.With the increase of the Young’s modulus of the carrier board and the encapsulating material,the deformation resistance of the package body is improved,and the maximum warpage value decreases.When the thermal expansion coefficient of the carrier board matches that of the encapsulant material,the warpage of the entire package will be minimized.As the proportion of copper volume in the RDL layer increases,the thermal conductivity and coefficient of thermal expansion of the RDL layer also increase,leading to an increase in the overall warpage value.When considering the mutual influence of material properties,it is found that the coefficient of thermal expansion has the greatest impact on warpage,followed by the Young’s modulus and the volume fraction of copper in the RDL layer.(3)In the context of packaging structure,the warpage of FOPLP in the plastic encapsulation cooling solidification process is analyzed from three aspects: material thickness,encapsulation ratio,and stress relief groove.Then,an orthogonal experimental design is used to analyze and optimize the packaging structure.The research results indicate that as the thickness of the carrier board and chip increases,the maximum warpage of the package decreases.However,an increase in the thickness of the encapsulant material leads to an increase in the maximum warpage of the package.Furthermore,from the perspective of package ratio analysis,it has been observed that there is a negative correlation between the package ratio and the warpage values of FOPLP.The stress release slot can also have a positive effect on the warpage of FOPLP,and increasing the slot depth,slot width,and density can all reduce the maximum warpage of FOPLP.