Process And Reliability Analysis Of CCGA Rework Ang Lead Column Installation

Due to the difference of the number of FPGA gates,the applicable packaging technology of FPGA is not the same.FPGAs with more than 3 million gates commonly use CCGA package.CCGA,as a new type of package,is suitable for larger size and more I/Os.The column grid in the package replaces the ball grid,which greatly eases the failure due to the thermal expansion coefficient mismatch between the alumina ceramic chip carrier and the epoxy resin.But the CCGA assembly process has problems such as difficult soldering process,strict process control,etc.Any control slightly less than strict during the process could easily result in problems such as single solder joint crack,false soldering,excessive porosity,and the device cannot be used normally,the device must be repaired.Domestic research on CCGA column attachment technology and reliability are basically blank.Therefore,it is necessary to conduct in-depth research on the technical reliability of CCGA rework(column attachment).By constructing the finite element analysis model of CCGA solder columns and solder joints,simplifying the finite element analysis model,determining the material characteristic parameters and boundary conditions,the reliability simulation analysis of the model is carried out,and the specific location of fatigue failure is obtained.Using C-M classical equation,the reliability accelerated life prediction of CCGA after rework of column attachment is performed.The simulation results show that the stress of solder columns and solder joints are concentrated on the side near the ceramic package and the maximum stress strain is located at the outermost corner of the package.Using C-M equation,it is predicted that the solder joint fatigue life of reworked CCGA is 427.85 cycles from-55°C to 100°C,meeting the design requirement of high reliability.Through the production of a daisy-chain CCGA sample dedicated for testing,the CCGA rework process is studied and a mature CCGA rework process scheme is created.The design of a special small-volume CCGA column attachment tooling kit is completed,and the patent of the column attachment tooling is applied and granted.The entire design of CCGA rework column attachment process is finally completed and the reworks of column attachment of five samples are finally completed.Through 5 pieces of samples,test analyses such as visual inspection,metallurgical testing,sine random vibration testing,and temperature cycling test reliability.The visual inspection shows that the sample device pin(solder column)perpendicularity is ? 5°,and no appearance or internal defects are found.After rework,the CCGA is well soldered on the printed board.After 200 cycles of temperature tests and mechanical vibration tests,the solder joints do not crack,and the electrical performance tests meet the design requirements.Vibration tests and temperature cycling tests are performed on the samples.It is found that the solder columns and solder joints are failed during the process of 450 temperature cycles.The failure locations are consistent with the prediction of the finite element analysis.The fatigue life is basically consistent with the predicted results.