Multilayer coil component and method for manufacturing the same

Abstract

A highly reliable multilayer coil component is provided without forming voids between magnetic ceramic layers and internal conductor layers. According to the multilayer coil component, an internal stress problem is reduced, the direct current resistance is low, and fracture of internal conductors caused by the surge or the like is not likely to occur. An acidic solution is allowed to permeate a magnetic ceramic element from a side surface thereof through a side gap portion which is a region between side portions of the internal conductors and the side surface of the magnetic ceramic element and to reach interfaces between the internal conductors and a magnetic ceramic located therearound. A pore area ratio of the magnetic ceramic of the side gap portion which is located between the side portions of the internal conductors and the side surface of the magnetic ceramic element is set in the range of 6% to 28%.

What is claimed is: 
     
       1. A multilayer coil component comprising:
 a magnetic ceramic element formed from a ceramic laminate having magnetic ceramic layers laminated to each other,   coil-forming internal conductors primarily composed of Ag, the internal conductors being interlayer-connected to each other to form a spiral coil, and   a magnetic ceramic disposed around and between the internal conductors without voids present at interfaces between the internal conductors and the magnetic ceramic located therearound, and   the internal conductors are separated from the magnetic ceramic at the interfaces therebetween.   
     
     
       2. The multilayer coil component according to  claim 1 , further comprising a side gap portion, and wherein each of the internal conductors has a side portion, and in the side gap portion between side portions of the internal conductors and a corresponding side surface of the magnetic ceramic element, a pore area ratio of the magnetic ceramic is in the range of 6% to 20%. 
     
     
       3. The multilayer coil component according to  claim 1 , further comprising a side gap portion,
 wherein a pore area ratio of the magnetic ceramic of the side gap portion is larger than a pore area ratio of an external layer region between an upper surface of the uppermost external layer of the internal conductors in the magnetic ceramic element and an upper surface thereof and a pore area ratio of an external layer region between a lower surface of the lowermost external layer of the internal conductors in the magnetic ceramic element and a lower surface thereof.   
     
     
       4. The multilayer coil component according to  claim 1 , wherein the magnetic ceramic includes NiCuZn ferrite as a primary component and contains 0.1 to 0.5 percent by weight of a zinc borosilicate-based low softening point glass having a softening point of 500° C. to 700° C. 
     
     
       5. The multilayer coil component according to  claim 1 , wherein the magnetic ceramic includes NiCuZn ferrite as a primary component and contains 0.2 to 0.4 percent by weight of a zinc borosilicate-based low softening point glass having a softening point of 500° C. to 700° C. 
     
     
       6. The multilayer coil component according to  claim 1 , wherein the magnetic ceramic includes NiCuZn ferrite as a primary component and contains 0.3 to 1.0 percent by weight of SnO 2  as well as 0.1 to 0.5 percent by weight of a zinc borosilicate-based low softening point glass having a softening point of 500° C. to 700° C. 
     
     
       7. The multilayer coil component according to  claim 1 , wherein the magnetic ceramic includes NiCuZn ferrite as a primary component and contains 0.5 to 0.8 percent by weight of SnO 2  as well as 0.1 to 0.5 percent by weight of a zinc borosilicate-based low softening point glass having a softening point of 500° C. to 700° C. 
     
     
       8. The multilayer coil component according to  claim 2 , wherein the average value of the diameters of pores relating to the pore area ratio of the magnetic ceramic is in the range of 0.1 to 0.6 μm. 
     
     
       9. The multilayer coil component according to  claim 3 , wherein an average value of the diameters of pores relating to the pore area ratio of the magnetic ceramic is in the range of 0.1 to 0.6 μm. 
     
     
       10. The multilayer coil component according to  claim 4 , wherein an average value of the diameters of pores relating to the pore area ratio of the magnetic ceramic is in the range of 0.1 to 0.6 μm. 
     
     
       11. The multilayer coil component according to  claim 5 , wherein an average value of the diameters of pores relating to the pore area ratio of the magnetic ceramic is in the range of 0.1 to 0.6 μm. 
     
     
       12. The multilayer coil component according to  claim 6 , wherein an average value of the diameters of pores relating to the pore area ratio of the magnetic ceramic is in the range of 0.1 to 0.6 μm. 
     
     
       13. The multilayer coil component according to  claim 7 , wherein an average value of the diameters of pores relating to the pore area ratio of the magnetic ceramic is in the range of 0.1 to 0.6 μm. 
     
     
       14. A multilayer coil component comprising:
 a magnetic ceramic element formed from a ceramic laminate having magnetic ceramic layers laminated to each other,   coil-forming internal conductors primarily composed of Ag, the internal conductors being interlayer-connected to each other to form a spiral coil,   external electrodes formed on two side surfaces of the magnetic ceramic element on which two end portions of the spiral coil are exposed,   Ni plating film layers formed on the external electrodes, and   side gap portion,   wherein each of the internal conductors has a side portion, and in the side gap portion between side portions of the internal conductors and a corresponding side surface of the magnetic ceramic element on which the two end portions of the spiral coil are not exposed, a pore area ratio of the magnetic ceramic is in the range of 6% to 20%, and   Ni derived from a Ni plating solution used to form the Ni plating film layers on the external electrodes is present at interfaces between the internal conductors and the magnetic ceramic.    
     
     
       15. The multilayer coil component according to claim 14,
 wherein a pore area ratio of the magnetic ceramic of the side gap portion is larger than a pore area ratio of an external layer region between an upper surface of the uppermost external layer of the internal conductors in the magnetic ceramic element and an upper surface thereof and a pore area ratio of an external layer region between a lower surface of the lowermost external layer of the internal conductors in the magnetic ceramic element and a lower surface thereof.    
     
     
       16. The multilayer coil component according to claim 14, wherein the magnetic ceramic includes NiCuZn ferrite as a primary component and contains 0.1 to 0.5 percent by weight of a zinc borosilicate-based low softening point glass having a softening point of 500° C. to 700° C.  
     
     
       17. The multilayer coil component according to claim 14, wherein the magnetic ceramic includes NiCuZn ferrite as a primary component and contains 0.3 to 1.0 percent by weight of SnO 2  as well as 0.1 to 0.5 percent by weight of a zinc borosilicate-based low softening point glass having a softening point of 500° C. to 700° C.  
     
     
       18. The multilayer coil component according to claim 14, wherein the average value of the diameters of pores relating to the pore area ratio of the magnetic ceramic is in the range of 0.1 to 0.6 μm.