A method for manufacturing an electronic component built-in substrate, comprising:
- preparing a first intermediate base material comprising a first core layer;
- preparing a second intermediate base material comprising a second core layer;
- preparing a third intermediate base material comprising a third core layer;
- bonding the first, second and third intermediate base materials such that the first, second and third intermediate base materials form a laminated structure adhered through an adhesive layer formed between the first and second intermediate base materials and an adhesive layer formed between the second and third intermediate base materials;
- forming a first outer side build-up structure on the first core layer on an opposite side with respect to the second core layer such that the first outer side build-up structure comprises a plurality of conductor layers and a plurality of interlayer resin insulating layers;
- and
- forming a second outer side build-up structure on the third core layer on an opposite side with respect to the second core layer such that the second outer side build-up structure comprises a plurality of conductor layers and a plurality of interlayer resin insulating layers,
- wherein the first intermediate base material comprises the first core layer, a first electronic component accommodated in an opening portion of the first core layer, a plurality of conductor layers formed on front and back surfaces of the first core layer respectively, a plurality of interlayer resin insulating layers formed on the front and back surfaces of the first core layer respectively, and a plurality of via conductor structures formed in the interlayer resin insulating layers and connected to a plurality of electrode structures of the first electronic component respectively, the third intermediate base material comprises the third core layer, a second electronic component accommodated in an opening portion of the third core layer, a plurality of conductor layers formed on front and back surfaces of the third core layer respectively, a plurality of interlayer resin insulating layers formed on the front and back surfaces of the third core layer respectively, and a plurality of via conductor structures formed in the interlayer resin insulating layers and connected to a plurality of electrode structures of the second electronic component respectively, and the second core layer has a rigidity which is higher than a rigidity of the first core layer and a rigidity of the third core layer.