Reliability prediction of area array solder joints

Packages for high pin counts using the ball grid array technology or its miniaturized version, the chip scale package, inherently require reliability concepts as an integral part of their development. This is especially true for the latter packages, if they are combined with the flip chip technology. Accordingly, thermal fatigue of the solder balls is frequently investigated by means of the finite element method. Various modeling assumptions and simplifications are common to restrict the calculation effort. Some of them, like geometric modeling assumptions, assumptions concerning the homogeneity of the cyclic temperature fields, simplified creep characterization of solder, and the related application of Manson-Coffin failure criteria, are discussed in the paper. The packages chosen for detailed analyses are a PBGA 272 and a FC-CSP 230.