In this case, however, the printing surface 12 c of the conductive paste filler 12 is made flat. [0198] Meanwhile, Ag, Cu, C, Cu coated with Ag and other conductive pastes can be used to form the conductive paste filler 12. [0199] Also, while the conductive paste filler 12 is formed by screen printing as described above, another suitable printing technique is used for this purpose. [0200] Next, th