LGA Package Device Soldering Process Technology Research

With the development of electronic packaging industry.LGA devices with high power,high integration,miniaturization and high reliability are increasingly used in aerospace products.After using the existing technology to solder the LGA devices.It is found that the voids rate in the solder joints is higher,sometimes more than 15%,which does not meet the standard requirements.The main reason is that the soldering height of this device is relatively low,generally between 50.8?m~76.2?m.And the low height leads to the evaporation of solvent and water vapor in the flux,which is difficult to discharge from solder paste and form void.The void may reduce the thermal conductivity and mechanical strength of the solder,and seriously affect the reliability of the electronic products.In order to meet the high reliability application requirements of aerospace products.This paper improves the soldering process of LGA devices,and carries out theoretical analysis and reliability tests of the improved process.The main content of this paper is to carry out related research on the secondary soldering technology of LGA devices,the process of planting ball,the soldering process of pre-formed soldering pieces and the finite element theory analysis of solder points.First of all,three processes were used to solder LGA devices.By controlling the process parameters and optimizing the process route.The x-ray was used to detect the voids rate of solder joints,and the reliability test of the test circuit board was carried out.The thickness of the alloy layer was observed by metallographic analysis.Then based on the comprehensive factors such as the voids rate,the test cost and the complexity of operation to determine the more appropriate improvement of the process.Finally,the soldering point height before and after process improvement is variable.And Ansys workbench software is used for mechanical simulation analysis.By establishing a finite element model of temperature cycle load.Loading the model to observe the distribution of stress and strain.Locate the dangerous spot,contrast dangerous solder joints under stress value size.Test and verify the reliability of the improved process from theory aspects.Studies have shown that using secondary soldering technology can effectively reduce the voids rate.With simple process,low cost,high reliability.It can replace the existing soldering process to meet the special technological requirements of aerospace electronic products.