Study On Warpage Deformation Of Printed Circuit Boards During Manufacturing And Working Processes

Printed Circuit Boards(PCB)have been widely used as a carrier for information transmission and device interconnection in modern electronic products.Due to the different coefficients of thermal expansion of the component materials and the chemical shrinkage effect of resin,PCBs undergo warpaing and deformation during manufacturing and working processes,which affects the component assembly process and product’s lifespan.Therefore,it is of great significance to investigate the regularity of PCB warpage during the manufacturing and working processes aiming to ensure the quality and reliability of electronic products.Additionally,establishing an effective predictive method for PCB warpage is crucial in the era of informatization.In this work,a combined approach of experimental testing and finite element simulation to study the warping and deformation of PCB was used.Firstly,based on ABAQUS software and its subroutines,as well as the topography testing device,the finite element simulation and experimental verification of PCB from lamination to reflow soldering processes were carried out by using thermal-mechanical sequential coupling method.Next,finite element simulation of the PCB lamination process with different laminated structures was performed to analyze the influence of laminated structures on the warpage and stress of PCB.Subsequently,finite element simulation of the PCB lamination process with different thicknesses of copper foil and different electronic fiberglass woven weft/warp yarn laying directions were carried out to analyze the effect of material composition on the warpage and stress of PCB.Finally,finite element simulation was carried out on the thermal cycle and thermal-oxygen aging of PCB during the working process,and the influence of these two factors on the warpage and stress of PCB was analyzed.The results of the finite element simulation from the lamination to reflow soldering processes of PCB reveled that the PCB’s temperature field is relatively uniform,and the simulated warpage morphology of the PCB was in good agreement with the measured results.Additionally,after demolding and cooling to room temperature,the simulated warpage value of PCB was 727.7 μm,with a relative error of 20%based on the measured warpage value,which proved the model’s reliability.After demolding and cooling to room temperature,the warpage of the PCB increased with a less than 5%growth rate with an increase in Glass Fiber Reinforced Plastic(GFRP)’s thickness.Additionally,the type of prepreg had no significant effect on the warpage of the PCB,but it effected the evolution pattern of Mises stress of GFRP.It was proved that different laminated structures obtained by changing GFRP thickness and the type of prepreg did not significantly affect the warpage value and morphology of PCB.After demolding and cooling to room temperature,an increase in the copper foil thickness(18 μm,35 μm,and 50 μm)led to successive growth in both warpage values and Mises stress of the PCB was observed.The warpage growth rate was found to be approximately 50%in this study.Although the warpage directions of all the three PCBs were the same,there were differences in their morphology,indicating that the thickness of the copper foil significantly affected the warpage value and morphology of the PCB.This was a combined result of the increased chemical shrinkage effect of the wiring layer and the increased rigidity of the PCB,and the demolding deformation of PCB was primarily influenced by the chemical shrinkage of the wiring layer.Further,the study also revealed that the warpage of PCBs with different orientations of fiberglass cloth warp/weft arrangement was similar.The experimental group’s warpage decreased by up to 0.6%compared to the control group,and the morphology of PCBs were similar,indicating that the orientation of fiberglass cloth warp/weft arrangement had a negligible effect on the demolding deformation of PCBs within the scope of this study.The study conducted eight thermal cycles and found that the warpage of the PCB had a positive correlation with temperature.The warpage and Mises stress of the PCB at the highest and lowest temperature gradually decreased with an increase in thermal cycles,indicating a stress relaxation process.Upon returning to room temperature,the PCB’s warpage decreased slightly,but its morphology did not change significantly.Furthermore,a 100-day thermaloxygen aging research revealed that the warpage morphology of PCB did not change noticeably,but the warpage value increased from 1072.7 μm to 1398.2 μm.The elastic modulus of the resin in the surficial resin area and the central axis of the thickness direction of the PCB increased by 26.0%and 1.0%,respectively.And the PCB produced aging shrinkage strain,resulting in an increase in Mises stress.In summary,the finite element simulation of PCB during manufacturing and working processes was reasonably conducted to accurately predict the warping and deformation of PCB at different stages,which is of great significance for the quality and reliability design of electronic products.