13th International Conference on Fracture June 16–21, 2013, Beijing, China -8- 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 100 144 196 256 324 400 ≥484 Bond yield Bonding area (μm2 ) array‐shaped anchor single anchor Figure 10. Correlation between bond yield and bonding area 4.2 Comparison of torsional bonding strength Figure 11 shows a SEM photograph of torsional bonding strength testing devices. To avoid footing effect in DRIE process, protecting metal layer is deposited on glass wafer (Fig. 11(a)). As a result, the actual size of the beam (41.7μm), shown in Fig. 12, is almost the designed size (43μm). Figure 11. SEM photograph of torsional bonding strength testing devices Torsional fracture tests were carried out for both array-shaped anchor and single anchor. Based on the fractured displacements from the fracture tests, the torsional bonding strength is obtained by FEA. Figure 13 shows the correlation between torsional bonding strength and bonding area. The strength of array-shaped anchor is stronger than that of single anchor. And one reason is that the average bonding quality of array-shaped anchor is better than that of single anchor, which can be seen in section 4.1. Another reason is expressed below. There is a low-stress region in the middle of
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