FIG. 28B is a plan view showing the inner side surface of the upper second housing portion 102 b shown in FIG. 28A. FIG. 28C is a plan view showing an outer side surface of the upper second housing portion 102 b shown in FIG. 28A. [0227] Referring to FIGS. 28A, 28B and 28C, the conductor layer 102 bm made of an electrically conductive material such as magnesium or zinc and including an inverted-U-