with conductive paint prior to the step s 105 in the illustrated embodiment the base substrate 22 is immersed into an electrophoresis tank for receiving an electrophoresis coating under a positive voltage in a range from about 25 to about 100 volts and an electrophoresis time for about 30 to about 180 seconds thereby forming the electrophoresis layer 25 a thickness of the electrophoresis layer 25 is in a range from about 0 5 u03bcm to about 15 u03bcm an electrophoresis paint used in s 105 may be selected from epoxy ester anode electrophoresis paint a pure melt bond anode electrophoresis paint a polybutadiene anode electrophoresis paint a maleic anhydride oil anodic electrophoresis paint in step s 107 a portion of the electrophoresis layer 25 is removed thereby forming a concavity 27 recessed from the electrophoresis layer 25 toward the micro arc oxide layer 24 to form a preformed housing 20 a see fig4 in the illustrated embodiment the concavity 27 is formed by a ray carving process the concavity 27 has a width about 3 mm and a length about 6 mm a bottom of the concavity 27 is the micro arc oxide layer 24 in step s 109 a first metallic layer 2642 is formed on the bottom micro arc oxide layer 24 and positioned within the concavity 27 of the preformed housing 20 a in the illustrated embodiment the first metallic layer 2642 is made of copper material a thickness of.