Abstract: A coil device includes a core containing a magnetic material and a wire disposed in a coil shape around at least a part of the core. 70% or more of a volume of a middle leg portion of the core is located below a venting surface of a heat-dissipating resin. Between a first base portion of the core and one end of the middle leg portion is an air layer. The air layer is located below the venting surface of the heat-dissipating resin.

Abstract: A coil device includes a core containing a magnetic material and a wire disposed in a coil shape around at least a part of the core. The core includes a middle leg portion and a first base portion. The middle leg portion has a winding portion of the wire disposed therearound. The first base portion is disposed apart by a predetermined distance from one end of the middle leg portion along a winding axis of the winding portion. 70% or more, preferably 80% or more, more preferably 90% or more, or still more preferably 95% or more of a volume of the middle leg portion is located below a venting surface of a heat-dissipating resin.

Abstract: A coil device has a core including a magnetic material and a wire disposed in a coil shape around at least a part of the core. 70% or more of a volume of a middle leg portion of the core is located below an atmosphere open surface of a heat dissipation resin. An outer division gap of the core is provided in a middle or an end portion of the outer leg portion, and a partial adhesive portion in which an adhesive is interposed and an air layer in which an adhesive is not interposed are provided in the outer division gap.