ABSTRACT:In this study, a new unified creep constitutive relation axld a modified energy-based fatigue model have been established respectively to describe the creep flow and predict the fatigue life of Sn-Pb solders. It is found that the relation successfully elucidates the creep mechanism related to current constitutive relations. The model can be used to describe the temperature and frequency dependent low cycle fatigue behavior of the solder. The relation and the model axe further employed in part II to develop the numerical simulation approach for the long-term reliability assessment of the plastic ball grid array (BGA) assembly.

No abstract

In the present study, a facility, i.e., a mechanical deflection system (MDS), was established and applied to assess the long-term reliability of the solder joints in plastic ball grid array (BGA) assembly. It was found that the MDS not only quickly assesses the long-term reliability of solder joints within days, but can also mimic similar failure mechanisms in accelerated thermal cycling (ATC) tests. Based on the MDS and ATC reliability experiments, the acceleration factors (AF) were obtained for different reliability testing conditions. Furthermore, by using the creep constitutive relation and fatigue life model developed in part I, a numerical approach was established for the purpose of virtual life prediction of solder joints. The simulation results were found to be in good agreement with the test results from the MDS. As a result, a new reliability assessment methodology was established as an alternative to ATC for the evaluation of long-term reliability of plastic BGA assembly.

Deformation measurement of mechanical-electrical devices is important for their reliability evaluation. However, with the development of fabrication technology, sizes of mechanical-electrical devices are reduced to micro or even nano-scale. Correspondingly, testing resolution of the required metrology techniques must be improved to the same or even higher level. The commonly used characterization facility with nano-scale resolution is STWAFWSEM etc. In this paper, some metrology technologies based on these facilities for nano-scale deformation measurement, e.g. AFWSEM moire and AFMiSEM digital speckle correlation are introduced, including their principles, advantages and disadvantages. Their applications in the deformationistrain measurement of MEMS and IC packages will be highlighted.