Fang Hongyuan

New general double ellipsoid heat source model

Abstract Based on the tridimensional Gauss distribution of power density, a general double ellipsoid welding heat source model has been developed. This model not only consists of all the characteristics of a double ellipsoid model, but also can deal with the situation where, under an external disturbance, the arcs backbone is not perpendicular to the work surface. This general double ellipsoid model is validated by measured results of the temperature field during twin wire welding. Using the non-linear finite element software Marc, the temperature field during twin wire welding was calculated using both the double ellipsoid heat source and the general double ellipsoid heat source. The thermal cycling curves and the weld pool cross-section obtained by the general double ellipsoid heat source tally well with the experimental results.

The research on the resistance of electromigration of different connection form

For the purpose to start the requirement on the mechanical and the electromigration reliabilities, this paper take the study on the electromigration on Cu Column Grid Array(CuCGA) and Ball Grid Array(BGA). In order to eliminate the influence by the heat migration, the study build and simulate the two models which contain the distribution of current density and temperature of the two connection form by using the software MSC.MARC. Then design the one integrated circuit to fulfill the current density which is more than 104A/cm2. And take the experiment that the current density is 1.21×103A/cm2, the electric time is 0h,50h, 100h,150h,200h respectively. Take and observe the metallographic diagram at last. The result shows that the peak value on current density and temperature appear at the joint interface between pad and solder. The peak value of current density and temperature of CuCGA is higher than BGAs since the average current density on pad is same. While the average current density keeps 1.21×103 A/cm2, the resistance on electromigration of CuCGA joints is weaker than the BGAs joints.