Generally, a wiring substrate has, on a main surface (front surface) thereof, terminals for connection to semiconductor chips (hereinafter may be referred to as “connection terminals”). In recent years, connection terminals have been provided at high packing density, and the distance (pitch) between adjacent connection terminals has been reduced. Thus, there has been proposed a wiring substrate having an NSMD (non-solder mask defined) structure in which a plurality of connection terminals are arranged in a single opening of a solder resist layer.
However, when a plurality of connection terminals are arranged in a single opening at small pitches, solder applied (through coating) onto the front surface of a connection terminal may flow toward an adjacent connection terminal, and short circuit may occur between these connection terminals. Therefore, there has been proposed a wiring substrate in which an insulating partition wall is provided between adjacent connection terminals so as to prevent flow of solder applied (through coating) on the front surface of a connection terminal toward an adjacent connection terminal (see, for example, Patent Document 1).