| 摘要 |
<p>According to the present invention, an insulating substrate (1) having a through-hole (2) is injection molded. The top part of the through-hole (2) is formed into a conical space (21), and the bottom part is formed into a cylindrical space (23). The vertex angle of the cone shape is formed to 60 to 120 degrees, and the opening diameter in the top end of the through-hole (2) is formed to 10 to 100 µm. On the front and back surfaces of the insulating substrate (1) and the inside surfaces of the through-hole, electrolytic copper plating layers (32-52) are stacked respectively on electroless plating layers (31-51), forming electroconductive layers (3-6). The peripheral edge of an opening (22) in the top end of the through-hole (2) has a high electric current density because of an acute angle, and electrolytic copper plating solution easily enters and circulates from the bottom end of the through-hole; therefore, an electrolytic copper plating layer can be formed quickly on the peripheral edge of this opening, and the top end of the through-hole can be closed up in a short amount of time, making the surface flat.</p> |
