Research On Moistureproof Technology Of Non-hermeticity Flip Chip Devices For Aerospace Application

With the development of microelectronic devices,the power and frequency of electronic devices are getting much higher,so does the electronic packaging technology.Since FPGA(Field Programmable Gate Array)are applied for aerospace electronic devices widely for its lightly weight and smaller volumn,and FPGA products are all adopting Flip-chip technology,so it is high time to study the hermeticity-protection technology for the flip chip devices for its aerospace application.This paper started from the simulation analysis and reliability experiment to study the feasibility of Parylene polymer coating on the flip chip devices,which adopted the Parylene coating technology to improve the strain/stress distribution of solder bumps and protected flip chip devices from the erosion of outer moisture to enhance the long-term reliability of the Non-hermeticity Flip Chip Devices for Aerospace Application.By studying the coating material for the flip chip devices,the Paryene material was selected to study the non-hermeticity and conformal coating technology for the flip chip devices,the technology parameter for Parylene coating was studied to ensure the conformal coating of the whole flip chip devices.The ANSYS structure simulation tool and FEM method are applied to study the influence of chip size and the thickness of Parylene material on the thermal fatigue life of solder bumps;considering to its engineering application,based on the Parylene coating technology,the different thickness of Parylene material were coated on the devices,HAST(Harden accelerated storage test)was carried out to test the electric performance,mechanical properties and moisture-proof performance of the flip chip devices,and the reliability tests such as TC(temperature cycle test),HTS(High temperature storage)were carried to clarify the failure mode of the solder joints under different tests.The main works of this paper are as below:1)Study on the effect of chip size and Parylene coating thickness were carried out by ANSYS simulation technology,the influence of chip size on the thermal fatigue life of solder bump were investigated.It turned out that the thermal fatigue life of solder bump was decreaseing indicial with the increasing of chip size,and Parylene could improve the thermal fatigue life of solder bumps significantly.2)Different thickness of Parylene coating technology were carried out to study the moisture-proof performance of Parylene coating bump,Results showed that Parylene could protect the bump out of erosion by the moisture and improve the shear strength of bump,and bump coating with X um Parylene had showed the best moisture-proof performance.3)The reliability tests such as TC(temperature cycle test),HTS(High temperature storage)were long-term reliability of solder bump with Parylene coating.It turned out that bump coating with X um Parylene had showed the best long-term reliability.