A base includes a main body and a multilayer metal film disposed on the main body. The multilayer metal film includes a first metal film disposed on the main body, the first metal film having conductivity, second metal film on the first metal film and above the main body, the second metal film having resistance to solder leaching, and a third metal film on the second metal film, the third metal film having wettability. The third metal film includes an inwardly extended portion extending between the second metal film and the main body.