Recently, the metal grid electrode drew attention as a flexible transparent conductive electrode for touch screen panels. In metal grid electrodes, various shapes of grid patterns were used to avoid the moiré phenomenon. In this study, we investigated the effects of the metal grid shapes - such as the honeycomb, diamond, and square - on the flexibility and durability of the metal grid film using an experimental and numerical analysis. The flexibility of the metal grid film was evaluated via the following: bending, cyclic bending fatigue and stretching tests; it was compared with the numerical stress analysis. In the bending test, the resistance of the honeycomb grid sample increased by 10% at a bending radius of 10 mm. On the other hand, the diamond grid showed almost no change in resistance up to a bending radius of 6 mm. When the substrate was stretched to 5%, many cracks appeared on the surface of the honeycomb pattern sample. On the other hand, no cracks were found in the diamond pattern sample. Therefore, the diamond pattern exhibited superior flexibility and durability to the honeycomb pattern. The numerical stress analysis also showed that the honeycomb pattern had the highest stress and the diamond pattern had the lowest stress during bending and stretching, which corresponded with the experimental results.

In 3D integration package using TSV technology, bonding is the core technology for stacking and interconnecting the chips or wafers. During bonding process, however, warpage and high stress are introduced, and will lead to the misalignment problem between two chips being bonded and failure of the chips. In this paper, a finite element approach is used to predict the warpages and stresses during the bonding process. In particular, in-plane deformation which directly affects the bonding misalignment is closely analyzed. Three types of bonding technology, which are Sn-Ag solder bonding, Cu-Cu direct bonding and SiO2 direct bonding, are compared. Numerical analysis indicates that warpage and stress are accumulated and become larger for each bonding step. Inplane deformation is much larger than out-of-plane deformation during bonding process. Cu-Cu bonding shows the largest warpage, while SiO2 direct bonding shows the smallest warpage. For stress, Sn-Ag solder bonding shows the largest stress, while Cu-Cu bonding shows the smallest. The stress is mainly concentrated at the interface between the via hole and silicon chip or via hole and bonding area. Misalignment induced during Cu-Cu and Sn-Ag solder bonding is equal to or larger than the size of via diameter, therefore should be reduced by lowering bonding temperature and proper selection of package materials.

In MEMS (Micro-Electro-Mechanical System), packaging induced stress or stress induced structure deformation becomes increasing concerns since it directly affects the performance of the device. In the decoupled vibratory MEMS gyroscope, the main factor that determines the yield rate is the frequency difference between the sensing and driving modes. The gyroscope, packaged using the anodic bonding at the wafer level and EMC (epoxy molding compound) molding, has a deformation of MEMS structure caused by thermal expansion mismatch. Th is effect results in large distribution in the frequency difference, and thereby a lower yield rate. To improve the yield rate we propose a packaged SiOG (Silicon On Glass) process technology. It uses a silicon wafer and two glass wafers to minimize the wafer warpage. Thus the warpage of the wafer is greatly reduced and the frequency difference is more uniformly distributed. In addition, in order to increase robustness of the structure against deformation caused by EMC molding, a "crab-leg" type spring is replaced with a semi-folded spring. The results show that the frequency shift is greatly reduced after applying the semi-folded spring. Therefore we can achieve a more robust vibratory MEMS gyroscope with a higher yield rate.