Multilayer three-dimensional circuit substrate, endoscope, and method for manufacturing multilayer three-dimensional circuit substrate

An endoscope comprising:

• an insertion portion configured to be inserted into a subject, and a multilayer three-dimensional circuit substrate provided in a distal end portion of the insertion portion,
• the multilayer three-dimensional circuit substrate comprising:
• a first substrate comprising a first surface, a second surface, a first wiring provided on the first surface, and a second wiring provided on the second surface, a normal of the first surface and a normal of the second surface intersecting with each other on a first plane orthogonal to the first surface and the second surface;
• a first protective metal layer configured to cover a first part of the first wiring, and to be electrically connected to the first wiring;
• a second protective metal layer configured to cover a second part of the second wiring, and to be electrically connected to the second wiring;
• a second substrate comprising a third surface, a fourth surface, a fifth surface, and a sixth surface, a third wiring provided on the third surface, and a fourth wiring provided on the fifth surface, the second substrate being provided on a surface of the first substrate such that the fourth surface faces the first surface and the sixth surface faces the second surface, the second substrate further comprising a first hole and a second hole, the first hole allowing the third surface and the fourth surface to communicate with each other, and exposing a part of the first protective metal layer, the second hole allowing the fifth surface and the sixth surface to communicate with each other, and exposing a part of the second protective metal layer, a normal of the third surface and a normal of the fifth surface intersecting with each other on a second plane orthogonal to the third surface and the fifth surface;
• a first interlayer connecting member provided in the first hole, and configured to electrically connect the first protective metal layer and the third wiring;
• and
• a second interlayer connecting member provided in the second hole, and configured to electrically connect the second protective metal layer and the fourth wiring,
• wherein the first protective metal layer has a lower absorption rate of light in a predetermined wavelength than the first wiring,
• the second protective metal layer has a lower absorption rate of the light in the predetermined wavelength than the second wiring,
• the second substrate is configured such that a thickness between the fifth surface and the sixth surface is thinner than a thickness between the third surface and the fourth surface, and
• a sensor is provided on the fifth surface.

A method for manufacturing a multilayer three-dimensional circuit substrate, the method comprising:

• forming a first wiring on a first surface of a first substrate;
• forming a second wiring on a second surface of the first substrate, a normal of the first surface and a normal of the second surface intersecting with each other, on a first plane orthogonal to the first surface and the second surface;
• forming a first protective metal layer configured to cover a first part of the first wiring, and to be electrically connected to the first wiring;
• forming a second protective metal layer configured to cover a second part of the second wiring, and to be electrically connected to the second wiring;
• providing a second substrate on the first substrate, the second substrate comprising a third surface, fourth surface, a fifth surface, and a sixth surface, a third wiring provided on the third surface, and a fourth wiring provided on the fifth surface, the fourth surface facing the first surface, the sixth surface facing the second surface, a normal of the third surface and a normal of the fifth surface intersecting with each other on a second plane orthogonal to the third surface and the fifth surface;
• forming, by laser, a first hole that allows the third surface and the fourth surface to communicate with each other and exposes a part of the first protective metal layer;
• forming, by the laser, a second hole that allows the fifth surface and the sixth surface to communicate with each other and exposes a part of the second protective metal layer;
• forming a first interlayer connecting member in the first hole, the first interlayer connecting member electrically connecting the first protective metal layer and the third wiring;
• and
• forming a second interlayer connecting member in the second hole, the second interlayer connecting member electrically connecting the second protective metal layer and the fourth wiring,
• wherein the first protective metal layer has a lower absorption rate of light of the laser than the first wiring,
• the second protective metal layer has a lower absorption rate of the light of the laser than the second wiring,
• the second substrate is configured such that a thickness between the fifth surface and the sixth surface is thinner than a thickness between the third surface and the fourth surface, and
• a sensor is provided on the fifth surface.