FIG. 27B is a plan view showing the inner side surface of the upper second housing portion 102 b shown in FIG. 27A. FIG. 27C is a plan view showing an outer side surface of the upper second housing portion 102 b shown in FIG. 27A. [0225] Referring to FIGS. 27A, 27B and 27C, the conductor layer 102 bm made of an electrically conductive material such as magnesium or zinc and including a rectangular