US 12,136,510 B2
Coil device
Satoshi Sugimoto, Tokyo (JP); Kyohei Tonoyama, Tokyo (JP); Miyuki Asai, Tokyo (JP); and Takamasa Iwasaki, Tokyo (JP)
Assigned to TDK CORPORATION, Tokyo (JP)
Filed by TDK CORPORATION, Tokyo (JP)
Filed on Apr. 14, 2021, as Appl. No. 17/230,332.
Claims priority of application No. 2020-072410 (JP), filed on Apr. 14, 2020.
Prior Publication US 2021/0319944 A1, Oct. 14, 2021
Int. Cl. H01F 27/255 (2006.01); H01F 27/28 (2006.01); H01F 27/32 (2006.01); H01F 41/02 (2006.01)
CPC H01F 27/255 (2013.01) [H01F 27/2823 (2013.01); H01F 27/32 (2013.01); H01F 41/0246 (2013.01)] 9 Claims
OG exemplary drawing
 
1. A coil device comprising:
an element body including a magnetic powder and a resin, and
a coil part embedded in the element body and having a wound wire around which an insulation coating layer is formed, wherein
the element body includes a resin rich layer surrounding the insulation coating layer and an outer area with a smaller weight ratio of elements constituting the resin in comparison to the resin rich layer surrounding the resin rich layer,
the resin rich layer is formed along a shape of an outer circumference of the coil part, and has a predetermined thickness on an outer surface of the insulation coating layer of the wire,
a thickness of the resin rich layer is 50 to 150 μm,
the insulation coating layer is located on the outer circumference of the coil part along the shape of the outer circumference of the coil part, and
the outer area extends along the shape of the outer circumference of the coil part so as to surround the outer circumference of the coil part,
the magnetic powder includes a first magnetic powder and a second magnetic powder having a smaller particle size than a particle size of the first magnetic powder,
the resin rich layer includes the first magnetic powder and the second magnetic powder,
a particle size of the first magnetic powder is 20 to 50 μm,
a particle size of the second magnetic powder is 5 to 10 μm,
an amount of the second magnetic powder is larger than an amount of the first magnetic powder at a position close to the coil part in the resin rich layer, and
in the resin rich layer, the amount of the second magnetic powder increases at a position closer to the coil part and the amount of the first magnetic powder increases at a position away from the coil part.