Novel comparative torsional analytical technique to predict mechanical reliability of emerging memory cards and packages

Torsional test is a method widely used to determine the behaviour of materials when subjected to torsional force. Packaged devices ranging from memory modules to cards are subjected to this test to predict its mechanical lifetime reliability. It is however, a challenge to predict an optimum torsion testing condition for new emerging packaged devices, with different package configurations. This paper explores a novel technique to accurately predict the maximum torsional force of various new memory card packages such as micro-secure digital (mu-SD) card profiles and other emerging card types with different die, material and substrate constructions. This technique involves extrapolating torsional results gathered through subjecting various memory packages with known constructions, as well as data correlation of torsional results using various optical and chemical analysis techniques. This facilitates the recommendation of optimum material properties such as mold filler content, as well as the design rules for package construction and material properties of memory cards or packages, to cater for better mechanical reliability. With a novel torsion test setup, a torsional force is applied to different types of memory packages, the authors were able to extrapolate the results from a chart plotting maximum applied torque versus volume of package. Together with chemical and optical characterization tests, we can accurately predict the optimum muSD card torsional force requirements. In addition, results of memory packages with different geometry and criteria to meet torsion test are shared. Results relating to mold compound properties such as flexural storage modulus, which is strongly influenced by filler composition and resin chemistries, contribute to meet torsion test requirements