| Electronic components continue to develop in the direction of light weight,high performance and high integration.The electronic components adopting flip-chip welding technology have high pin density,good thermal conductivity and excellent electrical performance,and can meet the requirements of extremely harsh environment,high reliability,high air tightness and other conditions.They are widely used in aerospace,national defense and other fields,and have become an important foundation to support the development of future equipment.In this paper,CCGA(Ceramic Column Grid Array)package device is taken as the research object.The failure of its key structures under the conditions of process and temperature cycling is simulated and analyzed,and the reasonable failure physical model is selected for life prediction.First,the packaging process of CCGA package device is simulated,including electroplating copper column,welding bump,filling underfill,filling thermally conductive adhesive,sealing cover plate and welding board level solder column.In the process of packaging,it is found that compared to other process steps,the stress and strain value generated during bump welding are relatively large,largely due to its high reflow temperature.The warpage is the most serious in the two process steps of filling the underfiller and welding the board-level solder column.The corresponding process steps can be optimized to minimize the warpage deformation during the process.Based on the packaging process,the temperature cycling simulation analysis of CCGA package devices is carried out.Using sub-model technology,the failure of the two key structures of copper pillar and board-level solder column in the entire process-service process is analyzed,and a reasonable life model is selected for life prediction.From the analysis results,it is found that after the process is completed,a certain residual stress will be generated.In the process of temperature cycling,the inelastic strain of both structures accumulates with the increase of time,and the stress is released.The predicted life value of the bump is smaller than that of the board-level solder column.It can be seen that the bump is the weakest link of the flip-chip welding device.The life of bump is taken as the life of the whole device,and then the structural parameters and material parameters of the two key structures are optimized respectively.The diameter and height of the bump and the board-level solder column are taken as the design variables of the structural parameter optimization design,and the thermal expansion coefficient of the PCB,LTCC substrate and chip are taken as the design variables of the material parameter optimization design.The results show that the height of bump and the thermal expansion coefficient of LTCC substrate have the greatest influence on the life.The optimal combination of structural parameters is as follows:the diameter of board-level solder column is 500?m,the height of board-level solder column is 2540?m,the diameter of bump is 70?m,and the height of bump is 31?m.The optimal combination of material parameters is as follows:the coefficient of thermal expansion of PCB is 20.0 x10-6/°C,the coefficient of thermal expansion of LTCC is 5.8x10-6/°C and the coefficient of thermal expansion of chip is 3.2 x10-6/°C.In addition,three kinds of finite element models,CCGA(Ceramic Column Grid Array),CBGA(Ceramic Ball Grid Array),and PBGA(Ceramic Ball Grid Array)are established to study the effects of board-level interconnect structure and packaging material on the thermal fatigue life of the device.Board-level interconnect structures adopt solder columns and solder balls,respectively,and packaging materials adopt ceramic and plastic packaging,respectively.From the analysis results,it is found that the value of thermal fatigue life of the CBGA device is the smallest.For ceramic packaging,the form of solder column interconnection is better than that of solder ball interconnection.For solder ball interconnection plastic packaging has greater advantage than ceramic packaging. |
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