A method for manufacturing a multilayer substrate, comprising:
- a base pattern forming step of forming base patterns on both surfaces of a plurality of resin substrates by patterning copper foil,
- each of the base patterns defining the same plane and having a uniform thickness;
- a plating step of growing a copper-plated film on the base patterns;
- and
- a lamination body forming step of laminating and thermocompression-bonding together the plurality of resin substrates with a bonding layer interposed therebetween to form a lamination body;
- wherein
- the plurality of resin substrates include:
- a first resin substrate including a first surface and a second surface opposite to the first surface;
- a second resin substrate including a third surface facing the second surface and a fourth surface opposite to the third surface;
- a third resin substrate including a fifth surface and a sixth surface opposite to the fifth surface;
- and
- a fourth resin substrate including a seventh surface facing the sixth surface and an eighth surface opposite to the seventh surface;
- the first surface is located closer to a first outermost layer of the lamination body than the second surface is, and the fifth surface is located closer to a second outermost layer of the lamination body than the sixth surface is;
- a first conductor pattern, disposed on the first surface and including a corresponding one of the base patterns and a corresponding one of the plated films, a second conductor pattern, disposed on the second surface and including a corresponding one of the base patterns and a corresponding one of the plated films, a third conductor pattern, disposed on the third surface and including a corresponding one of the base patterns and a corresponding one of the plated films, and a fourth conductor pattern disposed on the fourth surface and including a corresponding one of the base patterns and a corresponding one of the plated films, include overlapping portions when viewed in a lamination direction and are arranged along each other;
- a fifth conductor pattern, disposed on the fifth surface and including a corresponding one of the base patterns and a corresponding one of the plated films, a sixth conductor pattern, disposed on the sixth surface and including a corresponding one of the base patterns and a corresponding one of the plated films, a seventh conductor pattern, disposed on the seventh surface and including a corresponding one of the base patterns and a corresponding one of the plated films, and an eighth conductor pattern, disposed on the eighth surface and including a corresponding one of the base patterns and a corresponding one of the plated films, include overlapping portions when viewed in the lamination direction and are arranged along each other;
- and
- T1<T2, T3<T4, T5<T6, and T7<T8, where T1 denotes a thickness of the first conductor pattern, T2 denotes a thickness of the second conductor pattern, T3 denotes a thickness of the third conductor pattern, T4 denotes a thickness of the fourth conductor pattern, T5 denotes a thickness of the fifth conductor pattern, T6 denotes a thickness of the sixth conductor pattern, T7 denotes a thickness of the seventh conductor pattern, and T8 denotes a thickness of the eighth conductor pattern.