Interposer substrate and circuit module

An interposer substrate comprising:

• a body that includes a first principal surface, a second principal surface, and a third principal surface each of which is perpendicular or substantially perpendicular to a height direction of the body, a distance between the first principal surface and the second principal surface being different from a distance between the first principal surface and the third principal surface in the height direction;
• a first external connection conductor that is provided on the first principal surface to mount the interposer substrate to an external circuit board;
• a second external connection conductor that is provided on the second principal surface to connect the interposer substrate to an external portion;
• a third external connection conductor that is provided on the third principal surface to connect the interposer substrate to an external portion;
• and
• a wiring conductor that is provided in the body and connects the first external connection conductor, and the second external connection conductor and the third external connection conductor;
• wherein
• the wiring conductor includes:
• a flat conductor pattern that has a flat plane perpendicular or substantially perpendicular to the height direction of the body;
• and
• a via conductor that extends in the height direction;
• the first external connection conductor is connected to the second external connection conductor and the third external connection conductor through the flat conductor pattern and the via conductor in the body;
• and
• the first external connection conductor includes a portion that is disposed outside the second external connection conductor and the third external connection conductor in a plan view.