Reflow Soldering Process And Multiphysics Reliability Analysis Of Complex Components

With the application of various electronic products in more and more fields,their reliability issues have also received more attention.Studies have shown that among the failure causes of electronic products,the interconnection failure of components accounts for 50%,of which temperature and vibration load have a significant impact on the life of components.Reflow soldering is the assembly process of printed board components,and it is also the pre-process of various environmental tests,which has a non-negligible impact on the reliability of components.Domestic random vibration and temperature cycle reliability analysis is often aimed at components or printed board assemblies,while the assembled products of printed board components are widely used in practical engineering.However,there are few reliability analysis and research on the assembled products at present.This thesis takes a PCBA and its assembled products as the object,and simplifies it separately according to the particularity of each process and test process.The deformation and residual stress of the PCBA after reflow soldering are summarized and analyzed,and the fatigue life of the assembled product after reflow soldering under two random vibration conditions,temperature cycle conditions and combined conditions is studied.The main work of this thesis can be summarized as follows:1.Taking the PCBA as the research object,the PCB and components are reasonably simplified,and the reflow soldering simulation analysis is carried out in combination with the vacuum reflow soldering conditions.First,the stress-strain and deformation values at the corners of all key devices are summarized.Then the deformed model after reflow soldering is extracted.Finally,the influence of different restraint methods on reflow soldering is studied.The results show that the residual stress of the component is the largest under the condition of bilateral fixed constraints,and the residual stress is smaller under the fixed constraints of one side and the middle two regions.2.Based on the deformed model of reflow soldering,combined with the structural part and the bolt model,a model with a structural part in the form of an assembled finished product is established.The modal analysis and random vibration analysis were carried out for the belt structure model in the frequency range of 10-2000Hz and the maximum amplitude was0.064g~2/Hz and 0.04g~2/Hz.Combined with the relevant theory,the fatigue life of the model under two random vibration conditions is predicted,and the influence of the bolt preload on the life is studied.The results show that the random vibration fatigue life of the additional structure model under vibration condition 1 is 69h,and the life of vibration condition 2 is8412h;with the increase of bolt preload,the random vibration fatigue life decreases.3.According to the special test conditions of temperature cycle,the simplified way of self-heating non-critical devices is changed,and the thermal cycle additional structure model is established.Anand viscoplastic unified constitutive model is used to describe the viscoplastic properties of solder joints.The temperature cycle test process of the model is simulated in the thermal load range of-55～70℃and under the condition of self-heating of some devices.Through the analysis of the stress-strain response of the solder joints,the temperature cycle fatigue life of the solder joints is predicted and the influence of the structural parts and bolts on life is studied.The results show that the temperature cycle fatigue life of the thermal cycle model with structural parts is 760h.The structural parts and bolts will accelerate the fatigue failure of solder joints and reduce the fatigue life.4.Based on the above random vibration and temperature cycle simulation analysis,the position information of the two dangerous points is obtained,and the combined life prediction of random vibration and temperature cycle is carried out on the printed board assembly structure with structural parts using the linear damage superposition approach.The results show that the location of the danger point is different in different test processes.The combined fatigue life of random vibration and temperature cycle is that the combined life of vibration condition 1 is 69h,and the combined life of vibration condition 2 is 760h.