Inductor with an electrode structure

Abstract

A method to form an electrical component, comprising: overlaying a conductive and adhesive layer on a body and covering a first portion of a terminal part of a conductive element, wherein a second portion of the terminal part of the conductive element is not covered by the conductive and adhesive layer; and overlaying at least one metal layer on the conductive and adhesive layer and covering the second portion of the terminal part of the conductive element, wherein the at least one metal layer is electrically connected to the second portion of the terminal part of the conductive element for electrically connecting with an external circuit.

Claims

1. A method to form an electrical component, comprising: providing a body, wherein a conductive element is disposed in the body, wherein a terminal part of the conductive element is exposed outside of the body with said terminal part exposed outside of the body being entirely disposed on a bottom surface of the body; overlaying a conductive and adhesive layer on the body and covering a first portion of the terminal part of the conductive element, wherein a second portion of the terminal part of the conductive element is not covered by the conductive and adhesive layer; and overlaying at least one metal layer on the conductive and adhesive layer and covering the second portion of the terminal part of the conductive element with a portion of the conductive and adhesive layer being located between the at least one metal layer and the first portion of the terminal part of the conductive element and in contact with the at least one metal layer and the first portion of the terminal part of the conductive element, wherein the at least one metal layer is in contact with and electrically connected to the second portion of the terminal part disposed on the bottom surface of the body for electrically connecting with an external circuit.

2. The method of claim 1, further comprising disposing an additional metal layer on the body to encapsulate the terminal part of the conductive element, wherein the conductive and adhesive layer overlays on a top surface of the additional metal layer.

3. The method of claim 1, wherein the at least one metal layer comprises a first metal layer and a second metal layer, wherein the first metal layer overlays on the conductive and adhesive layer and the second portion of the terminal part of the conductive element; and the second metal layer overlays on the first metal layer for electrically connecting with an external circuit.

4. The method of claim 3, wherein the conductive and adhesive layer is made by mixing Ag powder with epoxy resin, the first metal layer is made of Ni and the second metal layer is made of Sn.

5. The method of claim 3, wherein the conductive and adhesive layer is made by mixing the Ag powder with epoxy resin, the first metal layer is made of Cu and the second metal layer is made of Sn.

6. The method of claim 3, wherein the first metal layer and the second metal layer are made by electroplating.

7. The method of claim 1, wherein the conductive and adhesive layer overlays on the first portion and a third portion of the terminal part of the conductive element, wherein the second portion is located between the first portion and the third portion.

8. The method of claim 1, wherein a third portion of the terminal part of the conductive element is covered by the conductive and adhesive, wherein the second portion of the terminal part of the conductive element is located between the first portion and the third portion of the terminal part of the conductive element.

9. The method of claim 1, wherein a recess is formed on a top surface of the body, wherein the terminal part of the conductive element is disposed in the recess.

10. The method of claim 1, wherein the electrical component is an inductor.

11. The method of claim 1, wherein the electrical component is a choke.

12. The method of claim 1, wherein the electrical component is an inductor and the conductive element is a coil, and the coil is disposed in the body with the terminal part of the coil disposed in a recess on a surface of the body.

13. The method of claim 1, wherein the electrical component is an inductor and the conductive element is a coil, wherein the body is a magnetic body and the coil is disposed in the magnetic body with the terminal part of the coil disposed in a recess on the bottom surface of the magnetic body, wherein the magnetic body comprises a T-core having a pillar, wherein the coil surrounds the pillar and the terminal part of the coil disposed in a recess on the bottom surface of the magnetic body via a side surface of the T-core.

14. A method to form an inductor, comprising: providing a magnetic body, wherein a coil is disposed in the magnetic body, wherein a terminal part of the coil is exposed outside of the magnetic body with said terminal part exposed outside of the magnetic body being entirely disposed on a bottom surface of the magnetic body; overlaying a conductive and adhesive layer on the magnetic body and a first portion of the terminal part of the coil, wherein a second portion of the terminal part of the coil is not overlaid by the conductive and adhesive layer; and overlaying at least one metal layer on the conductive and adhesive layer and the second portion of the terminal part of the coil with a portion of the conductive and adhesive layer being located between the at least one metal layer and the first portion of the terminal part of the coil and in contact with the at least one metal layer and the first portion of the terminal part of the coil, wherein the at least one metal layer is in contact with and electrically connected to the second portion of the terminal part disposed on the bottom surface of the magnetic body for electrically connecting with an external circuit.

15. The method of claim 14, wherein the magnetic body comprises a T-core having a pillar, wherein the coil surrounds the pillar and the terminal part of the coil disposed in a first recess on a bottom surface of the magnetic body via a side surface of the T-core.

16. The method of claim 14, wherein the magnetic body comprises a T-core having a pillar and a plate connected to the pillar, wherein the coil surrounds the pillar and the terminal part of the coil is disposed in a recess on the plate.

17. A method to form an inductor, comprising: forming a magnetic body, wherein a recess is formed in the magnetic body, wherein a coil formed by an insulated conductive wire is disposed in the magnetic body, wherein a terminal part of the insulated conductive wire is placed on a bottom surface of the recess, wherein a first portion of the terminal part of the insulated conductive wire is embedded inside the recess, wherein an internal conductor of a second portion of the terminal part of the insulated conductive wire is exposed from the magnetic body; and forming an electrode structure on the magnetic body, wherein the terminal part comprises a first area and a second area of a cross-section surface of a first end of the insulated conductive wire, wherein said first area of the cross-section surface is in contact with the magnetic body and not in contact with the electrode structure and said second area of the cross-section surface is in contact with the electrode structure and not in contact with the magnetic body, and wherein at least one portion of the electrode structure is disposed over the bottom surface of the recess and in contact with the internal conductor of the second portion of the terminal part of the insulated conductive wire for connecting with an external circuit.

18. The method of claim 17, wherein the electrode structure comprises a conductive and adhesive layer overlaying on the magnetic body and covering a first part of the second portion of the terminal part of the insulated conductive wire, wherein a second part of the second portion of the terminal part of the insulated conductive wire is not covered by the conductive and adhesive layer.

19. The method of claim 17, the electrode structure further comprises a first metal layer overlaid on the second portion of the terminal part of the insulated conductive wire, wherein the electrode structure comprises a conductive and adhesive layer overlaying on said first metal layer and covering a first part of the first metal layer, wherein a second part of the first metal layer is not covered by the conductive and adhesive layer.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The foregoing aspects and many of the accompanying advantages of this invention will become more readily appreciated as the same becomes better understood by reference to the following detailed description when taken in conjunction with the accompanying drawings, wherein:

(2) FIG. 1A-1E illustrate a cross-sectional view of an electrode structure of an electrical component according to an embodiment of the present invention

(3) FIG. 2A-2B illustrate a cross-sectional view of an electrode structure of an inductor, or a choke.

(4) FIG. 3A-3G illustrate a top view of an electrode structure of an inductor or a choke in different ways according to an embodiment of the present invention.

(5) FIG. 4 illustrates a manufacturing process of the inductor or choke.

DETAILED DESCRIPTION OF THE INVENTION

(6) The detailed explanation of the present invention is described as following. The described preferred embodiments are presented for purposes of illustrations and description, and they are not intended to limit the scope of the present invention.

(7) The following embodiments disclose an electrical component, the electrical component, comprising: a body; a conductive element, disposed in the body, wherein at least one portion of a first terminal part of the conductive element is exposed outside of the body; a conductive and adhesive layer, overlaying on the body and covering a first portion of the terminal part of the conductive element, wherein a second portion of the terminal part of the conductive element is not covered by the conductive and adhesive layer; and at least one metal layer, overlaying on the conductive and adhesive layer and covering the second portion of the terminal part of the conductive element, wherein the at least one metal layers is electrically connected to the second portion of the terminal part of the conductive element for electrically connecting with an external circuit.

(8) Please refer to FIG. 1A, which illustrates a cross-sectional view of an electrode structure of an electrical component according to an embodiment of the present invention. The electrode structure can be used to electrically connect terminals of conductive elements of the electrical component with an external circuit such as a printed circuit board (PCB). In one embodiment, the electrical component comprises: a main body 10 and a conductive element having a terminal part 40, wherein at least one portion of the terminal part 40 is exposed outside of the body; a conductive and adhesive layer 30, overlaying on the main body 10 and a first portion 40a and a third portion 40c of the terminal part 40, wherein a second portion 40b of the terminal part 40 of the conductive element are not overlaid by the conductive and adhesive layer 30; a first metal layer 20, overlaying on the conductive and adhesive layer 30, the first portion 40a and the third portion 40c of the terminal part 40 of the conductive element, wherein the first metal layer 20 is electrically connected to the second portion 40b of the terminal part of the conductive element for electrically connecting with an external circuit.

(9) In one embodiment, the conductive and adhesive layer 30 is made of polymer material mixed with a conductive material, such as Ag powder mixed with epoxy resin. In one embodiment, the first metal layer 20 comprises Sn. The conductive material is not limited to the Ag powder, it can be Cu powder or any other suitable conductive metal or alloy. In one embodiment, the first metal layer comprises Sn.

(10) In one embodiment, the first metal layer 20 overlays on the conductive and adhesive layer 30 through a thick film process such as electroplating.

(11) In one embodiment, the first metal layer 20 overlays on the conductive and adhesive layer 30 through a CVD process.

(12) In one embodiment, the first metal layer 20 overlays on the conductive and adhesive layer 30 through a PVD process.

(13) Please refer to FIG. 1B, which illustrates a cross-sectional view of an electrode structure of an electrical component according to an embodiment of the present invention. The electrode structure can be used to electrically connect terminals of conductive elements of the electrical component with an external circuit such as a printed circuit board (PCB). In one embodiment, the electrical component comprises: a main body 10, a conductive element having a terminal part 40, wherein at least one portion of the terminal part 40 is exposed outside of the body; a conductive and adhesive layer 30, overlaying on the main body 10 and a first portion 40a and a third portion 40c of the terminal part 40, wherein a second portion 40b of the terminal part 40 of the conductive element are not overlaid by the conductive and adhesive layer 30; a first metal layer 20, overlaying on the conductive and adhesive layer 30, the first portion 40a and the third portion 40c of the terminal part 40 of the conductive element; a second metal layer 60, overlaying on the first metal layer 30, wherein the first metal layer 30 and the second metal layer 60 are electrically connected to the second portion 40b of the terminal part 40 of the conductive element for electrically connecting with an external circuit.

(14) In one embodiment, the conductive and adhesive layer 30 is made of polymer material mixed with a conductive material, such as Ag powder mixed with epoxy resin. The conductive material is not limited to the Ag powder, it can be Cu powder or any other suitable conductive metal or alloy.

(15) In one embodiment, the first metal layer 20 is made of Ni or Cu or other suitable metal and the second metal layer 60 is made of Sn.

(16) In one embodiment, the first metal layer 20 overlays on the conductive and adhesive layer 30 through a thick film process such as electroplating.

(17) In one embodiment, the first metal layer 20 and the second metal layer 60 are made through a CVD process.

(18) In one embodiment, the first metal layer 20 and the second metal layer 60 are made through a PVD process.

(19) Please refer to FIG. 1C, which illustrates a cross-sectional view of an electrode structure of an electrical component according to an embodiment of the present invention. The electrode structure can be used to electrically connect terminals of conductive elements of the electrical component with an external circuit such as a printed circuit board (PCB). In one embodiment, the electrical component comprises: a main body 10, a conductive element having a terminal part 40, wherein at least one portion of the terminal part 40 is exposed outside of the body; a conductive and adhesive layer 30, overlaying on the main body 10 and a first portion 40a of the terminal part 40, wherein a second portion 40b and a third portion 40c of the terminal part 40 of the conductive element are not overlaid by the conductive and adhesive layer 30; a first metal layer 20, overlaying on the conductive and adhesive layer 30 and the first portion 40a of the terminal part 40 of the conductive element, wherein the first metal layer 20 is electrically connected to the second portion 40b and the third portion 40c of the terminal part 40 of the conductive element for electrically connecting with an external circuit.

(20) In one embodiment, the conductive and adhesive layer 30 is made of polymer material mixed with a conductive material, such as Ag powder mixed with epoxy resin. The conductive material is not limited to the Ag powder, it can be Cu powder or any other suitable conductive metal or alloy.

(21) In one embodiment, the first metal layer 20 comprises Sn; the first metal layer 20 overlays on the conductive and adhesive layer 30 through a thick film process such as electroplating.

(22) In one embodiment, the first metal layer 20 overlays on the conductive and adhesive layer 30 through a CVD process.

(23) In one embodiment, the first metal layer 20 overlays on the conductive and adhesive layer 30 through a PVD process.

(24) Please refer to FIG. 1D, which illustrates a cross-sectional view of an electrode structure of an electrical component according to an embodiment of the present invention. The electrode structure can be used to electrically connect terminals of conductive elements of the electrical component with an external circuit such as a printed circuit board (PCB). In one embodiment, the electrical component comprises: a main body 10, a conductive element having a terminal part 40, wherein at least one portion of the terminal part 40 is exposed outside of the body; a conductive and adhesive layer 30, overlaying on the main body 10 and a first portion 40a of the terminal part 40, wherein a second portion 40b and a third portion 40c of the terminal part 40 of the conductive element are not overlaid by the conductive and adhesive layer; a first metal layer 20, overlaying on the conductive and adhesive layer and the first portion 40a of the terminal part 40 of the conductive element; a second metal layer 60, overlaying on the first metal layer 20, wherein the first metal layer 20 and the second metal layer 60 are electrically connected to the second portion 40b and the third portion 40c of the terminal part 40 of the conductive element for electrically connecting with an external circuit.

(25) In one embodiment, the conductive and adhesive layer 30 is made by mixing the Ag with epoxy resin, the first metal layer 20 is made of Ni and the second metal layer 60 is made of Sn.

(26) In one embodiment, the conductive and adhesive layer 30 is made by mixing the Ag with epoxy resin, the first metal layer 20 is made of Cu and the second metal layer 60 is made of Sn.

(27) In one embodiment, the first metal layer overlays on the conductive and adhesive layer through a thick film process such as electroplating.

(28) In one embodiment, the first metal layer overlays on the conductive and adhesive layer through a CVD process.

(29) In one embodiment, the first metal layer overlays on the conductive and adhesive layer through a PVD process.

(30) Please refer to FIG. 1E, which illustrates a cross-sectional view of an electrode structure of an electrical component according to an embodiment of the present invention. The electrode structure can be used to electrically connect terminals of conductive elements of the electrical component with an external circuit such as a printed circuit board (PCB). In one embodiment, the electrical component comprises: a main body 10, a conductive element having a terminal part 40, wherein at least one portion of the terminal part 40 is exposed outside of the body; a third metal layer 45 overlays on the terminal part 40; a conductive and adhesive layer 30, overlaying on the main body 10 and the third metal layer 45, wherein a first portion 40a and a third portion 40c of the terminal part 40 is covered by the conductive and adhesive layer 30, and a second portion 40b of the terminal part 40 of the conductive element are not covered by the conductive and adhesive layer 30; a first metal layer 20, overlaying on the conductive and adhesive layer 30 and the third metal layer 45; a second metal layer 60, overlaying on the first metal layer 20, wherein the first metal layer 20 and the second metal layer 60 are electrically connected to the second portion 40b of the terminal part 40 of the conductive element for electrically connecting with an external circuit. In one embodiment, the third metal layer 45 encapsulates the entire terminal part 40 of the conductive element.

(31) In one embodiment, the third metal layer 45 overlays on the terminal part 40 is made of Cu or Ni.

(32) In one embodiment, the conductive and adhesive layer 30 is made of polymer material mixed with conductive material, such as Ag powder mixed with epoxy resin, the first metal layer 20 is made of Ni and the second metal layer 60 is made of Sn. The conductive material is not limited to the Ag powder, it can be Cu powder or any other suitable conductive metal or alloy.

(33) In one embodiment, the first metal layer 20 is made of Cu and the second metal layer 60 is made of Sn.

(34) In one embodiment, the first metal layer 20 overlays on the conductive and adhesive layer 30 through a thick film process such as electroplating.

(35) In one embodiment, the first metal layer 20 and the second metal layer 60 are made through a CVD process.

(36) In one embodiment, the first metal layer 20 and the second metal layer 60 are made through a PVD process.

(37) The electrode structure as shown in FIG. 1A-1E can be applied to many different products including an inductor or a choke, which will be described hereafter.

(38) Please refer to FIG. 2A, which illustrates a cross-sectional view of an electrode structure of an electrical component according to an embodiment of the present invention. The electrical component comprises: a T-core 70, a coil 50 having a first terminal part 40, wherein the first terminal part 40 of the coil 50 is disposed in a first recess 90a on the top surface of the T-core 70 via a side surface 91 of the T-core; a conductive and adhesive layer 30, overlaying on the main body 10 and a first portion 40a and a third portion 40c of the first terminal part 40, wherein a second portion 40b of the first terminal part 40 are not overlaid by the conductive and adhesive layer; a first metal layer 20, overlaying on the conductive and adhesive layer 30, the first portion 40a and the third portion 40c of the first terminal part 40 of the conductive element; a second metal layer 60, overlaying on the first metal layer 20, wherein the first metal layer 20 and the second metal layer 60 are electrically connected to the second portion 40b of the first terminal part 40 of the conductive element for electrically connecting with an external circuit. As shown in FIG. 2A, a first area of an axial surface 40v of the first terminal part 40 is encapsulated by the main body 10 and not in contact with the electrode structure, and a second area of the axial surface 40u of the first terminal part 40 is in contact with the electrode structure.

(39) Likewise, the electrode structure on the first terminal part 40 can be applied to the second terminal part 80 of the coil 50. As shown in FIG. 2B, the second terminal part 80 of the coil 50 disposed in a second recess 90b on the top surface of the T-core 70 via the side surface 91 of the T-core; a conductive and adhesive layer 30, overlaying on the top surface of the T-core 70 and a first portion 40e and a third portion 40g of the second terminal part 80, wherein a second portion 40f of the second terminal part 80 of the coil 50 are not overlaid by the conductive and adhesive layer 30; a first metal layer 20, overlaying on the conductive and adhesive layer 30, the first portion 40e and the third portion 40g of the second terminal part 80 of the coil 50; a second metal layer 60, overlaying on the first metal layer 20, wherein the first metal layer 20 and the second metal layer 60 are electrically connected to the second portion 40b of the first terminal part 40 of the conductive element for electrically connecting with an external circuit.

(40) In one embodiment, the magnetic body comprises a T-core having a pillar and a plate connected to the pillar, wherein the plate has a first hole at a first corner of the plate, wherein the coil surrounds the pillar and the first terminal part of the coil disposed in a recess on the top surface of the body via the first hole of the top plate. The top plate has a second hole at a second corner of the top plate, wherein a second terminal part of the coil disposed in a second recess on the top surface of the body via the second hole of the top plate.

(41) The coil can be formed by an enameled wire, and the insulating material of the enameled wire encapsulating the internal conductor can be removed by a laser, for example, to expose the internal conductor for electrically connecting the terminal 40 with the metal layer. The shape of the enameled wire can be round or flat or other suitable shapes. In one embodiment, the round or flat wire can surround the pillar of the T-core by a machine automatically.

(42) In one embodiment, the conductive and adhesive layer 30 is made of polymer material mixed with a conductive material, such as Ag powder mixed with epoxy resin. Please note that the conductive material is not limited to the Ag powder, it can be Cu powder or any other suitable conductive metal or alloy.

(43) In one embodiment, the first metal layer 20 is made of Ni and the second metal layer 60 is made of Sn. In one embodiment, the first metal layer 20 is made of Cu and the second metal layer 60 is made of Sn.

(44) In one embodiment, the first metal layer 20 overlays on the conductive and adhesive layer 30 through a thick film process such as electroplating.

(45) In one embodiment, the first metal layer 20 and the second metal layer 60 are made through a CVD process.

(46) In one embodiment, the first metal layer 20 and the second metal layer 60 are made through a PVD process.

(47) Please refer to FIG. 3A-3G which illustrate a top view of an electrode structure of an inductor or a choke in terms of the positions of the conductive and adhesive material such as Ag glue 303, relative to the exposed portions of the first terminal part 301 and a second terminal part 302 of the coil.

(48) As shown in FIG. 3A, which shows a view of the first terminal part 301 and a second terminal part 302 of the coil disposed on the bottom surface of the choke before overlaying the conductive and adhesive on the magnetic body 300.

(49) As shown in FIG. 3B, the first terminal part 301 and a second terminal part 302 of the coil are disposed on the bottom surface of the choke, and the conductive and adhesive material, such as Ag glue 303, is disposed on the magnetic body 300 such that exposed portions 304, 305 of the first terminal part 301 and exposed portions 306, 307 of the first terminal part 302 are not covered by the Ag glue 303, so that the first metal layer, such as a metal layer made of Ni, can be overlaid on the bottom surface of the choke to contact the exposed portions 304, 305, 306, 307 of the terminal parts 301, 302, wherein the second metal layer, such as a metal layer made of Sn, can be overlaid on the bottom surface of the choke to contact the first metal layer Ni so as to form the electrode structure of the choke.

(50) As shown in FIG. 3C, the first terminal part 301 and a second terminal part 302 of the coil are disposed on the bottom surface of the choke, and the conductive and adhesive material, such as Ag glue 303, is disposed on the magnetic body 300 such that the exposed portions 314 of the first terminal part 301 and the exposed portion 315 of the first terminal part 302 are not covered by the Ag glue 303, so that the first metal layer, such as a metal layer made of Ni, can be overlaid on the bottom surface of the choke to contact the exposed portions 314, 315 of the terminal parts 301, 302, wherein the second metal layer, such as a metal layer made of Sn, can be overlaid on the bottom surface of the choke to contact the first metal layer Ni so as to form the electrode structure of the choke.

(51) As shown in FIG. 3D, the first terminal part 301 and a second terminal part 302 of the coil are disposed on the bottom surface of the choke, and the conductive and adhesive material, such as Ag glue 303, is disposed on the magnetic body 300 such that the exposed portions 324 of the first terminal part 301 and the exposed portion 325 of the second terminal part 302 are not covered by the Ag glue 303, so that the first metal layer, such as a metal layer made of Ni, can be overlaid on the bottom surface of the choke to contact the exposed portions 324, 325 of the terminal parts 301, 302, wherein the second metal layer, such as a metal layer made of Sn, can be overlaid on the bottom surface of the choke to contact the first metal layer Ni so as to form the electrode structure of the choke.

(52) As shown in FIG. 3E, the first terminal part 301 and a second terminal part 302 of the coil are disposed on the bottom surface of the choke, and the conductive and adhesive material, such as Ag glue 303, is disposed on the magnetic body 300 such that exposed portions 334, 335 of the first terminal part 301 and exposed portions 336, 337 of the second terminal part 302 are not covered by the Ag glue 303, so that the first metal layer, such as a metal layer made of Ni, can be overlaid on the bottom surface of the choke to contact the exposed portions 334, 335, 336, 337 of the terminal parts 301, 302, wherein the second metal layer, such as a metal layer made of Sn, can be overlaid on the bottom surface of the choke to contact the first metal layer Ni so as to form the electrode structure of the choke.

(53) As shown in FIG. 3F, the first terminal part 301 and a second terminal part 302 of the coil are disposed on the bottom surface of the choke, and the conductive and adhesive material, such as Ag glue 303, is disposed on the magnetic body 300 such that the exposed portions 344 of the first terminal part 301 and the exposed portion 345 of the second terminal part 302 are not covered by the Ag glue 303, so that the first metal layer, such as a metal layer made of Ni, can be overlaid on the bottom surface of the choke to contact the exposed portions 344, 345 of the terminal parts 301, 302, wherein the second metal layer, such as a metal layer made of Sn, can be overlaid on the bottom surface of the choke to contact the first metal layer Ni so as to form the electrode structure of the choke.

(54) As shown in FIG. 3G the first terminal part 301 and a second terminal part 302 of the coil are disposed on the bottom surface of the choke, and the conductive and adhesive material, such as Ag glue 303, is disposed on the magnetic body 300 such that the exposed portions 354 of the first terminal part 301 and the exposed portion 355 of the second terminal part 302 are not covered by the Ag glue 303, so that the first metal layer, such as a metal layer made of Ni, can be overlaid on the bottom surface of the choke to contact the exposed portions 354, 355 of the terminal parts 301, 302, wherein the second metal layer, such as a metal layer made of Sn, can be overlaid on the bottom surface of the choke to contact the first metal layer Ni so as to form the electrode structure of the choke.

(55) Please note that FIG. 3A-3G only show examples of the shape of the electrode structure, the present invention is not limited to the shape of the electrode structure.

(56) Please refer to FIG. 4, which shows a manufacturing process for making an inductor such as a choke. In step 501, forming a T-core; in step 502, winding a coil on a pillar of a magnetic core. In one embodiment, the coil is made by a flat or a round wire, but it is not limited to. In one embodiment, the round or flat wire can surround the pillar of the T-core by a machine automatically; in step 503, disposing a first end and a second end of a coil on a surface of the magnetic core; in step 504, encapsulating the coil with magnetic material by a molding process so as to form a magnetic body; in step 505, removing off the insulating layer of the coil so that two ends of the coil are respectively exposed on the molding body; in step 506, forming a conductive and adhesive layer, such as Ag glue, on the magnetic body covering a portion of each end of the coil; and in step 507, forming a Ni metal layer on the magnetic body covering the Ag glue and the exposed portion of each end of the coil and forming a Sn metal layer on Ni metal layer so as to form the electrodes of the choke. In one embodiment, step 504, comprising surrounds the coil on a pillar of a T-core, then filling the magnetic powders to encapsulate the pillar and the coil so as to form a magnetic body.

(57) In one embodiment, the length of the pillar of the T-core is relatively short for better shielding and high density for increasing the permeability of the choke. The coil can be formed by an enameled wire, and the insulating material of the enameled wire encapsulating the internal conductor can be removed by laser. The shape of the enameled wire can be round or flat or other suitable shapes. However, the DCR of the flat wire is less than that of the round wire. In one embodiment, the round or flat wire can surround the pillar of the T-core by a machine automatically.

(58) The electrodes of this invention are formed without using a lead frame, so that the choke can be made smaller and thinner. Ag paste comprises polymer conductive paste, such as Ag powder mixed with resin, which comprises metal powder for conducting electricity and adhesive material overlaying across the surface of the magnetic body and the ending parts of the coil for fixing the ending parts of the coil on the magnetic body. The conductive material is not limited to the Ag powder, it can be Cu powder or any other suitable conductive metal or alloy.

(59) Furthermore, the terminal parts of the coil are placed outside of the areas for winding the coil to increase the winding space. The terminal parts of the coil can be embedded in a recess on the top surface of the magnetic body. In addition, the T-core can have recesses on the corners for passing the terminal parts, so that the terminal parts of the coil can be fixed firmly. By doing so, there is no soldering required inside the magnetic body for connecting the terminal parts of the coil of the choke to the outside electrodes at all.

(60) There are two conductive paths in the electrode structure, the first one is through the stack of layers: Cu/Ag paste/Ni/Sn, the second one is through the stack of layers: Cu/Ni/Sn. By doing so, Ag paste can fix the terminal part, Cu, to the magnetic body, and metal bonding can be formed between each two adjacent metal layer in the second conductive path Cu/Ni/Sn, which is less susceptible to the variations of temperature or moisture. As a result, the DCR of the choke can be maintained at a substantially fixed value.

(61) The above disclosure is related to the detailed technical contents and inventive features thereof. People skilled in the art may proceed with a variety of modifications and replacements based on the disclosures and suggestions of the invention as described without departing from the characteristics thereof. Nevertheless, although such modifications and replacements are not fully disclosed in the above descriptions, they have substantially been covered in the following claims as appended.