Researches on Thermal Stresses at the Interface Edge of a QFP Welded Joint
Abstract：Due to the mismatches of thermomechanical properties among the pin,PCB and solder of a QFP welded joint,singular thermal stresses,which are an inducement of interfacial delamination,will occur at the interface edges of these materials.In order to evaluate the local mechanical behavior of the QFP welded joint,in the paper,singular thermal stresses as well as the corresponding generalized stress intensity factors（GSIFs） at the interface edge of an arbitrary bi-material wedge is determined numerically based on the analytical solu-tion and the FEM.Firstly,A ad hoc FE eigenanalysis method is used to solve the eigensolusions of singular stress fields,i.e.,the singularity stress orders and the angular variations of stresses,and these eigensolusions together with a constant stress term are used to established the expression of the singular thermal stress field at the interface edge.In numerical examples,the effects of elastic modulus,poisson’s ratios and thermal expan-sion coefficients on SIFs at the interface edge of the QFP welded joint are considered,and it is found that the local thermal stress states can be improved by selecting solder with suitable material constants.
Keywords：PCBinterface edgeSIFthermal loading
Publication Date：2011-07-02
Online Publishing Date：2025-08-15(First online date of this platform, not the publication date of the document)
Pages：4( 1-4 )