Abstract: In an electronic device, a heat generating element is connected directly to an electrically-conductive joining material that is the start point of the heat dissipation path on the one surface of the substrate, and the other surface of the substrate is provided by an other surface side insulating layer. An electrically-conductive other surface side electrode connected to an external heat dissipation member is disposed on the surface of the other surface side insulating layer right under the heat generating element. On the other surface side of the substrate, an other surface side inner layer wire that is the end point of the heat dissipation path extends to the other surface side insulating layer and is insulated electrically from the other surface side electrode through the other surface side insulating layer.

Abstract: In a multi-layer substrate, a glass cloth of a build-up layer is deformed toward a land below the land. A thickness of a resin layer of the build-up layer from the glass cloth to a surface adjacent to the land is set to be smaller than a dimension from the glass cloth to a front surface of a core layer. With the above configuration, a progress or an enlargement of a crack can be suppressed from a stage in which the crack is smaller. Therefore, the progress and the enlargement of the crack can be delayed. As a result, even if the crack is generated, an insulating property between the land and an inner layer wire is ensured, and the land and the inner layer wire can be restricted from being short-circuited.

Abstract: In an electronic device, a heat generating element is connected directly to an electrically-conductive joining material that is the start point of the heat dissipation path on the one surface of the substrate, and the other surface of the substrate is provided by an other surface side insulating layer. An electrically-conductive other surface side electrode connected to an external heat dissipation member is disposed on the surface of the other surface side insulating layer right under the heat generating element. On the other surface side of the substrate, an other surface side inner layer wire that is the end point of the heat dissipation path extends to the other surface side insulating layer and is insulated electrically from the other surface side electrode through the other surface side insulating layer.