KR100293307B1 - Stacked ferrite inductor and method for manufacturing the same - Google Patents

Abstract

PURPOSE: A stacked ferrite inductor and method for manufacturing the same is provided to easily estimate an inductance value by changing turns of coil, while maintaining cross section occupied by the coil constant. CONSTITUTION: A stacked ferrite inductor comprises a first ferrite sheet unit having a plurality of first ferrite sheets(51,53,56,58) having via holes(512,532,562) connected to electrode patterns(511,531,561,581); a second ferrite sheet unit having a plurality of second ferrite sheets(52,54,55,57) having via holes(522,542,552,572), wherein the second ferrite sheets having no electrode patterns are inserted between first ferrite sheets; a conductive paste filling the via holes of first and second ferrite sheets so as to interconnect the electrode patterns; and a third ferrite sheet unit having a plurality of third ferrite sheets(1,2) disposed onto and beneath the first ferrite sheet unit, wherein third ferrite sheets have no electrode patterns.

Description

Multilayer Ferrite Inductor and Manufacturing Method Thereof

The present invention relates to a stacked ferrite inductor and a method of manufacturing the same.

An inductor is one of the three passive components that make up an electronic circuit together with a resistor and a condenser. The coil is wound or printed on a ferrite core and electrodes are formed at both ends. It is used as a component of noise elimination or LC resonant circuit.

Inductors can be classified into various types such as stacked type, winding type, thin film type, etc., and stacked type is being widely used.

Next, a structure of a conventional multilayer ferrite inductor will be described with reference to the accompanying drawings.

1 and 2 are exploded perspective views of a conventional multilayer ferrite inductor, in which a plurality of ferrite sheets without electrode patterns are stacked on both sides of a plurality of ferrite sheets having electrode patterns formed thereon. The thickness of all ferrite sheets is about the same here.

First, referring to FIG. 1, first to eighth rectangular ferrite sheets 11, 12, 13, 14, 15, 16, on which electrode patterns 111, 121, 131, 141, 151, 161, 171, and 181 are formed. 17 and 18 are sequentially stacked from the top to the bottom, and a plurality of rectangular ferrite sheets 1 and 2 without electrode patterns are formed above and below.

The electrode patterns 111, 121, 131, 141, 151, 161, 171, and 181 serving as coils are formed linearly along the edges of the sheets 11, 12, 13, 14, 15, 16, 17, and 18. It is formed only around three sides of the four sides of the square, so that the number of coils corresponding to 0.75 is formed when the number of coils is counted. In addition, the electrode patterns 111, 121, 131, 141, 151, which are formed on the first to seventh ferrite sheets 11, 12, 13, 14, 15, 16, and 17 except for the eighth ferrite sheet 18, Via holes 112, 122, 132, 142, 152, 162 and 172 are formed at the ends of the 161 and 171, and conductive pastes are formed in the via holes 112, 122, 132, 142, 152, 162 and 172. Filled, so that the electrode patterns 111, 121, 131, 141, 151, 161, 171, and 181 formed on the sheets 11, 12, 13, 14, 15, 16, 17, and 18 are connected through the conductive paste. . As mentioned above, each sheet 11, 12, 13, 14, 15, 16, 17, 18 has an electrode pattern having a number of turns of 0.75 and the electrode pattern is formed on a total of eight sheets. The number of turns is six.

On the other hand, since the upper ferrite sheet 1 and the lower ferrite sheet 3, in which the electrode pattern is not formed, are each composed of five sheets, the total number of ferrite sheets in FIG. 1 is 18 sheets.

The inductance of such an inductor can be adjusted by reducing or increasing the number of ferrite sheets on which electrode patterns are formed.

FIG. 2 shows a conventional inductor having the same size as the inductor shown in FIG. 1 and having an inductance halved.

Referring to FIG. 2, the first to fourth rectangular ferrite sheets 21, 22, 23, and 24 on which the electrode patterns 211, 221, 231, and 241 are formed in the same shape as in FIG. 1 are sequentially disposed from top to bottom. A plurality of rectangular ferrite sheets 1 and 2, which are stacked and positioned in the center and without an electrode pattern, are formed above and below. In order to make the inductor the same size as in FIG. 1, the ferrite sheets 1 and 2 without the electrode pattern are attached with seven sheets each at the top and bottom.

In FIG. 2, since the electrode pattern of 0.75 turns is formed in 4 sheets in total, the number of turns is three times.

When the inductor is manufactured as shown in FIG. 2, since the number of windings of the coil is half that of the inductor of FIG. 1, the inductance may also be predicted as following the equation.

However, there is a problem in that it is necessary to undergo repeated experiments such as adjusting the number of windings because the expected inductance value does not come out.

The technical problem to be solved by the present invention is to solve this problem, the inductance value can be obtained as expected by changing only the number of turns of the coil without reducing or increasing the overall size of the inductor and the size of the center portion where the electrode pattern is formed. An inductor and a method of manufacturing the same are provided.

1 and 2 are an exploded perspective view of a conventional stacked ferrite inductor,

3 is a cross-sectional view of a conventional stacked ferrite inductor,

4 is a perspective view of a stacked ferrite inductor according to an embodiment of the present invention;

5 and 6 are exploded perspective views of the stacked ferrite inductor according to the first and second embodiments of the present invention,

7 is a cross-sectional view of a stacked ferrite inductor according to an embodiment of the present invention.

8A to 8E are perspective views illustrating a manufacturing procedure of the stacked ferrite inductor according to the exemplary embodiment of the present invention.

In order to achieve the above object, in the present invention, the cross-sectional area occupied by the internal electrode pattern is made constant so that the inductance value can be predicted only by winding the coil in the cross-sectional area.

Two methods can be used to make the cross-sectional area occupied by the internal electrode pattern constant. One of them inserts a ferrite sheet having only via holes and no electrode pattern formed between the ferrite sheets on which the internal electrode patterns are formed, and the other is varying the thickness of the ferrite sheet.

Specifically, in the multilayer ferrite inductor according to the present invention, a plurality of first ferrite sheets having an electrode pattern serving as a coil and having a via hole connected to the electrode pattern are sequentially stacked. A second ferrite sheet having a via hole at a position corresponding to the via hole of the first ferrite sheet and having no electrode pattern is inserted between the first ferrite sheets. The via holes of the first and second ferrite sheets are filled with a conductor so that the electrode patterns are connected to each other. Finally, on both outer sides of the first ferrite sheet, a third ferrite sheet in which neither the electrode pattern nor the via hole is formed is laminated.

In another multilayer ferrite inductor according to the present invention, a first electrode pattern serving as a coil is formed, a first ferrite sheet having a via hole connected to the first electrode pattern, and a second electrode pattern serving as a coil. And a second ferrite sheet having a via hole at a position corresponding to the via hole of the first ferrite sheet, and having a thickness different from that of the first ferrite sheet, are laminated together with the first ferrite sheet. The via holes of the first and second ferrite sheets are filled with a conductor to connect the first and second electrode patterns to each other. Finally, outside the first ferrite sheet and the second ferrite sheet, a third ferrite sheet in which no electrode pattern is formed is laminated.

It is preferable that a ferrite sheet is Ni-Cu-Zn system here.

In order to manufacture such a multilayer ferrite inductor, first, a plurality of first to third Ni-Cu-Zn based ferrite green sheets are manufactured. Here, some of the first green sheets may be different in thickness from other green sheets. Via holes are formed in the first and second green sheets, and internal electrode patterns used as coils are printed on the first green sheets. At least one of the second and third green sheets and the first green sheet are mixed and stacked to form a ferrite inductor. At this time, although the number of windings of the coil is different, the cross-sectional area occupied by the thickness of the ferrite inductor and the internal electrode pattern is made constant.

Then, a multilayer inductor and a method of manufacturing the same according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the same.

In the present invention, in order to manufacture various inductors having predicted inductance values while maintaining the overall thickness of the multilayer inductor, the cross-sectional area or the total thickness occupied by the internal electrode pattern serving as the coil in the inductor is constant. That is, according to the experimental results, if the cross-sectional area occupied by the internal electrode is constant, the inductance as expected can be obtained.

However, as in the prior art, for example, in FIGS. 3A and 3B, which are cross-sectional views of the conventional stacked inductors shown in FIGS. 1 and 2, the overall thickness of the inductor 38 is constant, but the electrode pattern 31 occupies The cross sectional areas 32 and 33 are different.

If the cross-sectional area is changed in this way, it is impossible to obtain as much inductance as desired based on either of the two inductors.

In contrast, the present invention provides a multilayer inductor in which the number of turns is changed while maintaining a constant thickness of the inductor and maintaining a constant cross-sectional area occupied by the electrode pattern. To this end, only via holes are formed between the ferrite sheets on which the electrode patterns are formed, and the ferrite sheets without the electrode patterns are sandwiched, or the thickness of the ferrite sheet itself is increased. In this example, both cases are presented.

4 is a perspective view of a multilayer inductor according to an exemplary embodiment of the present invention, and FIG. 7 is an exploded perspective view of the multilayer inductor according to the first exemplary embodiment of the present invention, taken along line A-A in FIG. 4.

First, referring to FIG. 4, the multilayer ferrite inductor 43 and the external electrode patterns 41 and 42 formed on the outer surface thereof are illustrated. As described later, the external electrode patterns 41 and 42 are internal electrode patterns of the inductor. It is connected to the end of and plays a role of flowing current from the outside.

As shown in Fig. 5, a plurality of ferrite sheets without electrode patterns are laminated on both sides with the center of the eight ferrite sheets in which the ferrite sheet on which the electrode pattern is formed and the ferrite sheet not mixed are placed in the center. Here, the thicknesses of all ferrite sheets are almost the same, and Ni-Cu-Zn-based ferrite sheets are used.

Among the eight central ferrite sheets 51, 52, 53, 54, 55, 56, 57, 58 in the shape of a square, the first, third, sixth, and eighth sheets 51, 53, 56, 58, in turn, from top to bottom, respectively, Linear electrode patterns 511, 531, 561, and 581 serving as a role are formed along the edge of the rectangle. Via holes 512, 532, and 562 are formed at the ends of the electrode patterns 511, 531, and 561 of the remaining sheets 51, 53, and 56 except for the eighth sheet 58 of the four sheets 51, 53, 56, and 58. It is.

In addition, the second, fourth, fifth and seventh sheets 52, 54, 55, 57 have a via hole 512 of the sheet located immediately above each sheet, that is, the first, third, fourth and sixth sheets 51, 53, 54, 56. Also, via holes 522, 542, 552, and 572 are formed at positions corresponding to 532, 542, and 562. The via holes 512, 522, 532, 542, 552, 562, and 572 are filled with a conductive paste to form electrode patterns 551, 531, 561, and the like formed in the sheets 51, 53, 56, and 58. 581 is electrically connected through the conductive paste.

In more detail, one end of the electrode pattern 511 formed on the first sheet 51 extends up to the edge of the sheet 51, and the electrode pattern 511 is therefrom in the clockwise or counterclockwise direction. Proceed along the edge of the) to stop at the position corresponding to the number 0.75 times wound there is a via hole 512. In the second sheet 52, a via hole 522 is drilled at a position corresponding to the via hole 512 of the first sheet 51. One end of the electrode pattern 531 formed on the third sheet 53 is located at a position corresponding to the via holes 512 and 522 of the first and second sheets 51 and 52, and the electrode pattern 531 starts from the first sheet ( Proceed in the same direction as the electrode pattern 511 of 51, and stops at a position corresponding to the number 0.75 wound again, there is a via hole 532 there. Via holes 542 and 552 are formed in the fourth and fifth sheets 54 and 55 at positions corresponding to the via holes 532 of the third sheet 53. One end of the electrode pattern 561 formed on the sixth sheet 56 is located at a position corresponding to the via holes 532, 542, and 552 of the third, fourth, and fifth sheets 53, 54, and 55, and the electrode pattern 561. Starting from here, the process proceeds in the same direction as the electrode patterns 511 and 531 of the first and third sheets 51 and 53, and stops at a position corresponding to the number of turns 0.75, where a via hole 562 is drilled. In the seventh sheet 57, a via hole 572 is drilled at a position corresponding to the via hole 562 of the sixth sheet 56. One end of the electrode pattern 581 formed on the eighth sheet 58 is located at a position corresponding to the via holes 562 and 572 of the sixth and seventh sheets 56 and 57, and the electrode pattern 581 starts first from here. Proceeding in the same direction as the electrode pattern 511 of the sheet 51 stops at a position corresponding to the number of turns 0.75, but proceeds to the edge so that the other end is over the edge. Above the electrode pattern is formed to proceed along the edge of the rectangle except at one end of the electrode pattern 511 of the first sheet 51 and the other end of the eighth sheet 58 to be spaced apart from the edges have. One end of the electrode pattern 511 of the first sheet 51 and the other end of the eighth sheet 58 are connected to the external electrode patterns 41 and 42 as shown in FIG. 4.

In this way, the ends of the electrode patterns 511, 531, 561, and 581 having the number of turns of 0.75 in each of the four sheets 51, 53, 56, and 58 are connected through the conductors, and are formed in the same direction. As a result, the total number is three times.

On the other hand, since the upper ferrite sheet 1 and the lower ferrite sheet 3 on which the electrode pattern is not formed are each five, the total number of ferrite sheets is 18 in FIG.

A cross-sectional view of the inductor thus manufactured is shown in FIG. 7. 7, it can be seen that the thickness of the stacked inductor 78 and the cross-sectional area 72 occupied by the electrode pattern 71 according to the first embodiment of the present invention are the same as those of FIG. 1. The predictable value can be obtained from the inductance obtained from the inductor having the structure as follows. This is also possible by using a ferrite sheet having a different thickness as in the second embodiment of the present invention.

Referring to FIG. 6, which is an exploded perspective view of a multilayer inductor according to a second exemplary embodiment of the present invention, four center ferrite sheets 61, 62, 63, and 64 having electrode patterns 611, 621, 631, and 641 are formed. Except for the lowermost ferrite sheet 64, the thickness is different from the ferrite sheets 1 and 3 in which the electrode pattern is not formed. The first ferrite sheet 61 and the third ferrite sheet 63 located above are usually twice as thick as the ferrite sheets 1 and 3, and the second ferrite sheet 62 is three times as thick. 5, the first, second, and ferrite sheets 51, 52 are combined, and the third, fourth, and fifth ferrite sheets 53, 54, 55 are combined, and the sixth, seventh, ferrite sheets 56, 57 are combined. Same as the structure. The states of the electrode patterns 611, 621, 631, and 641 and the via holes 612, 622, and 632 are the same as in FIG. 5.

Next, a method of manufacturing the multilayer inductor will be described in detail with reference to FIGS. 8A to 8E.

First, as shown in Figure 8a, Ni-Cu-Zn-based low-temperature sintered ferrite powder that can be sintered in the range of 850 ℃-900 ℃ to the organic binder such as polyvinyl butylalcohol (PVB) and DBP (di-butyl) Plasticizers and dispersants such as phthalate and mixed with toluene and ethyl alcohol solvents to make a slurry (slury) state, and the ferrite green sheet (80) is produced by tape casting method After that, it is cut to a certain size and a via hole 81 is formed in the green sheet 80 as shown in Fig. 8B. Here, the ferrite green sheet 80 has the same thickness for the structure shown in FIG. 5 and different thicknesses for the structure shown in FIG. 6.

As shown in FIG. 8C, a conductive paste 82 such as silver paste is filled in the via hole 81 of the green sheet 80, and then, as shown in FIG. 8D, the green sheet 80 is conductive. A thick film is printed on the internal electrode pattern 83 having one end connected to the paste 82. Here, the conductive paste used as the electrode is a metal such as silver, copper, gold, etc., which is capable of simultaneous sintering with Ni-Cu-Zn-based ferrite and has low sheet resistance.

Referring to FIG. 8E, the green sheets on which the via holes 81 and the electrode patterns 83 are formed are arranged in a predetermined order, and ferrite green sheets having no internal electrode patterns are added to the upper and lower layers, respectively, and hot pressed.

The Ni-Cu-Zn-based ferrite green sheet and the conductive paste contain organic materials for maintaining moldability, and these organic materials adversely affect the performance of the inductor. Therefore, in order to remove such organic matter, the ferrite inductor stack 84 is heat treated between 350 ° C and 500 ° C.

Subsequently, co-sintering is performed between 850 ° C and 900 ° C to produce a ferrite inductor sintered body.

Finally, as shown in FIG. 4, the external electrode patterns 41 and 42 are coated with a conductor such as silver connected to the internal electrode pattern on the outside of the ferrite inductor 43, and then fired at 500 ° C. to 600 ° C. Nickel plating is performed on the electrodes 41 and 42, followed by solder plating to complete the ferrite inductor.

As described above, in the present invention, a ferrite inductor having an easy prediction of the inductance value can be manufactured even if only the number of turns of the coil is changed while the cross-sectional area occupied by the coil is kept constant.

Claims (8)

A first ferrite sheet portion in which a plurality of first type ferrite sheets having a via hole connected to the electrode patterns are formed and stacked with an electrode pattern serving as a coil, and the lamination thickness is fixed; Between the first type ferrite sheets of the first ferrite sheet portion having a via thickness in which a plurality of second type ferrite sheets having a via hole at a position corresponding to the via holes of the first type ferrite sheet and the electrode pattern are not formed are fixed. Second ferrite sheet portion interposed in A conductor filling the via holes of the first and second ferrite sheets to connect the electrode patterns to each other; Third ferrite sheet portions, which are respectively located on the upper and lower portions of the first ferrite sheet portion and are laminated with a plurality of third type ferrite sheets having no electrode pattern formed thereon. Stacked Ferrite Inductors Containing ″ In claim 1, The ferrite sheet is a Ni-Cu-Zn-based stacked ferrite inductor. A first ferrite sheet having a first electrode pattern serving as a coil and having a via hole connected to the first electrode pattern, A second electrode pattern serving as a coil is formed and has a via hole at a position corresponding to the via hole of the first ferrite sheet, and is stacked below or on the first ferrite sheet and has a different thickness from the first ferrite sheet. Second ferrite sheet, A conductor filled in the via holes of the first and second ferrite sheets and connecting the first and second electrode patterns to each other; and A third ferrite sheet laminated on and under the laminate of the first ferrite sheet and the second ferrite sheet, wherein the electrode pattern is not formed Multilayer ferrite inductor comprising a. In claim 3, The ferrite sheet is a Ni-Cu-Zn-based stacked ferrite inductor. Manufacturing a plurality of first to third ferrite green sheets, Forming via holes in the first and second green sheets; Printing an internal electrode pattern used as a coil on the first green sheet; Mixing at least one of the second and third green sheets and the first green sheet to form a plurality of ferrite inductors Including; The thickness of the plurality of ferrite inductors and the cross-sectional area occupied by the internal electrode patterns are constant, and the number of windings of the coil is different. Method of manufacturing a multilayer ferrite inductor. In claim 5, At least one of the second green sheets is laminated with the first green sheet, and the thickness of the first green sheet is the same as the thickness of the second green sheet. In claim 5, The thickness of the first green sheet is a stacked ferrite inductor different from the thickness of the third green sheet. The method according to any one of claims 5 to 7, The ferrite green sheet is a Ni-Cu-Zn-based multilayer ferrite inductor.