Common mode noise filter and production method therefor

A common mode noise filter comprising:

• a first insulating layer containing glass and inorganic filler, the first insulating layer containing a plurality of first pores dispersed therein;
• a first coil conductor provided in the first insulating layer so as not to be exposed to an upper surface and a lower surface of the first insulating layer;
• a second coil conductor provided in the first insulating layer so as not to be expose to the upper surface and the lower surface of the first insulating layer, the second coil conductor facing the first coil conductor across a part of the first insulating layer;
• a second insulating layer disposed on the upper surface of the first insulating layer, the second insulating layer containing glass and inorganic filler;
• a third insulating layer disposed on the lower surface of the first insulating layer such that the first insulating layer is provided between the second insulating layer and the third insulating layer, the third insulating layer containing glass and inorganic filler;
• a first magnetic oxide layer disposed above an upper surface of the second insulating layer;
• and
• a second magnetic oxide layer disposed below a lower surface of the third insulating layer,
• wherein a total volume of pores contained in the second insulating layer per unit volume and a total volume of pores contained in the third insulating layer per unit volume are smaller than a total volume of the first pores in the first insulating layer per unit volume.

A method of manufacturing a common mode noise filter, comprising:

• providing a first insulating sheet containing glass, inorganic filler, inorganic foaming agent, and organic binder;
• providing a second insulating sheet containing glass, inorganic filler, inorganic foaming agent, and organic binder;
• providing a third insulating sheet containing glass, inorganic filler, inorganic forming agent, and organic binder;
• providing a first magnetic oxide sheet mainly made of magnetic material and containing organic binder;
• preparing a second magnetic oxide sheet mainly made of magnetic material and containing organic binder;
• forming a laminated body which includes
• a first coil conductor disposed on an upper surface of the first insulating sheet,
• the second insulating sheet disposed on the upper surface of the first insulating sheet for covering the first coil conductor,
• a second coil conductor disposed on a lower surface of the first insulating sheet,
• the third insulating layer disposed on the lower surface of the first insulating sheet for covering the second coil conductor,
• the first magnetic oxide sheet disposed above an upper surface of the second insulating sheet, and
• the second magnetic oxide sheet disposed below a lower surface of the third insulating sheet, such that the first insulating sheet, the second insulating sheet, and the third insulating sheet are provided between the first magnetic oxide sheet and the second magnetic oxide sheet,
• obtaining a fired body by firing the laminated body for producing gas from the inorganic foaming agent contained in the first insulating sheet, the inorganic foaming agent contained in the second insulating sheet, and the inorganic foaming agent contained in the third insulating sheet as to form a plurality of pores in each of the first insulating sheet, the second insulating sheet, and the third insulating sheet;
• and
• providing an external terminal electrode on the fired body.

A method of manufacturing a common mode noise filter, comprising:

• providing a first insulating sheet layer, a second insulating sheet layer, and a third insulating sheet layer that contain glass, inorganic filler, inorganic foaming agent, and organic binder and that are configured to be laminated to provide a first insulating sheet;
• providing a second insulating sheet containing glass, inorganic filler, and organic binder;
• providing a third insulating sheet containing glass, inorganic filler, and organic binder;
• providing a first magnetic oxide sheet mainly made of magnetic material and containing organic binder;
• providing a second magnetic oxide sheet mainly made of magnetic material and containing organic binder;
• forming a laminated body which includes
• a first coil conductor disposed on an upper surface of the first insulating-sheet layer.
• the second insulating sheet layer disposed on the upper surface of the first insulating sheet layer to cover the first coil conductor.
• a second coil conductor disposed on a lower surface of the first insulating sheet layer,
• the third insulating sheet layer disposed on the lower surface of the first insulating sheet layer to cover the second coil conductor,
• the second insulating layer disposed on an upper surface of the second insulating-sheet layer,
• the third insulating sheet disposed on a lower surface of the third insulating sheet layer, such that the first insulating sheet layer, the second insulating sheet layer, and the third insulating sheet layer are sandwiched between the second insulating sheet and the third insulating sheet;
• the first magnetic oxide sheet disposed above an upper surface of the second insulating sheet, and
• the second magnetic oxide sheet disposed below a lower surface of the third insulating sheet, such that the first insulating sheet layer, the second insulating sheet layer, and the third insulating sheet layer, the second insulating sheet, and the third insulating sheet are sandwiched between the first magnetic oxide sheet and the second magnetic oxide sheet;
• and
• obtaining a fired body by firing the laminated body to generate gas from the inorganic foaming agent contained in the first insulating sheet layer, the second insulating sheet layer, and the third insulating sheet layer, as to form a plurality of pores in each of the first insulating sheet layer, the second insulating sheet layer, and the third insulating sheet layer;
• and
• providing an external terminal electrode on the fired body.