Thermodynamics Analysis And Fatiguelife Prediction Of Typical Electronic Packages

With the more density, higher performance, downsizing and lower cost of the electronic packaging, the reliabilities of electronic packages induced by vibration and thermal conditions become the focus of people. This dissertation takes the board level packages of ceramic column grid array as study object and investigates the reliabilities of typical electronic packages under vibration and thermal cycle conditions.The work in the subject mainly include: 1) Built three dimensional finite element models of vibration and thermal cycle conditions, and analyzed the stress as well as strain distribution of structures under harmonic excitation and thermal cycle conditions individually; 2) Combined with the modeling results, the fatigue life prediction equation was developed by the principle of high cycle damage; 3) On the basis of accumulative damage theory, the fatigue life prediction of sweep frequency loading was predicted, which meanwhile validated the fatigue life equation fitted before; 4) Based the Coffin-Manson fatigue damage principle and crack growing theory, using the modeling results of the thermal cycle conditions, the thermal fatigue life prediction model was also predicted, and it was validated by comparing with several test data.The results show that the most dangerous location is always on the furthest solder joint from the center of the printed circuit board; When analyzing the vibration conditions, the weakest link is on the volume averaged layer beside the printed circuit board, and the stress in the solder is related to the boundary constraint conditions; The stresses in the solders near the constraint boundary are significantly larger and synchronous with the bending deflection; While dealing with the case of the thermal conditions, the weakest link tends into the volume averaged layer on the substrate side, which is differently from the conclusion from the vibration analysis; Besides, compared with the thickness of the printed circuit board, the thickness of the substrate and the presence of lid have more influence on the thermodynamics distribution, which then seriously affect on the thermal cycle fatigue life. The results from the finite element simulation have been validated to be applicable and reliable by comparing with the test data.The conclusions obtained may provide theoretical guidance for the designation of electronic packages.