KR101089871B1 - Multi layer power inductor - Google Patents

Abstract

The present invention proposes a multilayer power inductor that improves DC overlapping characteristics and increases sintering density and permeability to obtain high inductance even at low stacking length. The stacked power inductor includes a body in which a nonmagnetic layer is stacked between a plurality of magnetic layers, the plurality of magnetic layers including an internal electrode pattern and the internal electrode patterns interconnected to form a coil part; And it is dispersed and formed in the interior of the body, and includes a plurality of dispersed pores having a particle diameter of 0.1 ~ 10㎛.

Description

Multi layer power inductor

The present invention relates to a chip-shaped stacked power inductor, and more particularly, to a chip-shaped stacked power inductor used for power components such as a DC-DC converter.

In a typical power inductor, increasing the current in the coil (inductor) also increases the magnetic force, the magnetic force is no longer increased when the magnetic saturation state is no longer increased magnetic flux density. When magnetic saturation occurs, even if the magnetic field strength (H) is increased, the magnetic flux density (B) hardly increases, so the permeability (B / H) decreases and the inductance also drops sharply.

Self-saturation not only drops the inductance sharply, but also generates heat. Normally, the self-saturation temperature is about 120 ℃ ~ 150 ℃, this temperature is called Curie point, when the temperature reaches this level, the permeability drops sharply.

Thus, a conventional winding type power inductor has air gaps of a predetermined thickness, as shown in FIG. The wound power inductor of FIG. 1 is a double core structure consisting of an inner core 10 (ferrite core) in which the conductive wire 14 is wound a predetermined number of times and an outer core 12 surrounding the inner core 10. An air gap 16 was formed between the two cores 10 and 12. The voids 16 are typically filled with a conductive epoxy. The air gap 16 changes the electrical characteristics of the power inductor according to the magnetic flux density resulting from the conductor 14 (coil). At this time, the magnetic flux density increases as the gap 16 decreases, increasing permeability and increasing inductance. Conversely, the larger the thickness of the cavity 16, the lower the magnetic flux density, so that the permeability is lowered and the inductance is lowered.

In order to slim the conventional winding-type power inductor, voids may be eliminated. However, the above-described effects cannot be expected when the voids are eliminated. Therefore, the height of the inner core 10 may be reduced. However, lowering the height of the inner core 10 has a problem that there is a limit because the mechanical strength of the product is lowered. In particular, in the conventional winding type power inductor, the process of winding the conductor 14 is not only very complicated but also difficult to miniaturize due to many manufacturing difficulties to miniaturize. In addition, the wire-wound power inductor does not become a magnetic shield, so there is a problem of causing magnetic interference in adjacent components.

Conventional wirewound power inductors are inductors with large allowable currents. To this end, ferrite is mainly used as a magnetic material used in the manufacture of a conventional wire-wound power inductor. Ferrite has high permeability and electrical resistance. On the other hand, since the ferrite system has a low saturation magnetic flux density, when used as it is, the inductance due to self saturation is large and the DC overlapping characteristics are deteriorated. The DC superposition characteristic is a magnetic core characteristic for waveforms in which DC is superimposed on the weak AC generated in the process of converting AC input of the power supply to DC. In general, when DC is superimposed on AC, the core permeability decreases in proportion to DC current.At this time, the magnetic permeability of the DC superimposition ratio (μ%) compared to the magnetic permeability of IDC = 0A is not expressed. Evaluate the overlapping characteristics. Typically, the permeability is lowered to increase the DC overlapping characteristics. However, when the permeability is lowered, the number of turns of the power inductor must be increased. For example, if the permeability is reduced to 1/2, the number of turns of the power inductor should be doubled. In this case, the size of the power inductor increases.

The stacked power inductor of FIG. 2 is formed by forming an electrode pattern 20 (inductor pattern) on multiple layers of magnetic sheets and stacking magnetic sheets. The multilayer power inductor of FIG. 2 is advantageous in miniaturization compared to the winding type. In Fig. 2, reference numeral 22 is a via hole, and 24 and 26 are external electrodes.

That is, the stacked power inductor of FIG. 2 has a structure in which an electrode pattern 20 is formed inside a core magnetic material in which a plurality of magnetic layers are stacked and are magnetically saturated at a lower current than a winding power inductor.

As described above, since the coil is surrounded by a magnetic material, the multilayer power inductor generates less magnetic leakage and has a stacked chip structure, which is advantageous in miniaturization and thinning.

However, despite these advantages, stacked power inductors used in power circuits such as DC-DC converters have a disadvantage in that abrupt inductance (ie, deterioration of DC overlapping characteristics) occurs due to magnetic saturation of a magnetic material.

Therefore, at present, various studies have been conducted to prevent such a sudden decrease in inductance, that is, a decrease in DC overlapping characteristics.

SUMMARY OF THE INVENTION The present invention has been proposed to solve the above-mentioned problems, and the object of the present invention is to provide a multilayer power inductor which improves DC overlapping characteristics and increases sintering density and permeability to obtain high inductance even at a low stacking length. have.

In order to achieve the above object, a multilayer power inductor according to a preferred embodiment of the present invention is formed by stacking a nonmagnetic layer between a plurality of magnetic layers, wherein the plurality of magnetic layers include internal electrode patterns and internal electrode patterns. The body is interconnected to form a coil; And dispersed and formed in the body, and include a plurality of dispersed pores having a particle diameter of 0.1 to 10 μm.

The plurality of dispersed voids are formed in the nonmagnetic layer and the plurality of magnetic layer or in the plurality of magnetic layer.

Each of the plurality of magnetic body layers is composed of a sheet shape of a ferrite raw material and a compound ferrite raw material including carbon nanofibers (CNF), and a plurality of dispersed voids are formed by stacking and sintering the plurality of magnetic body layers and nonmagnetic layers. It is formed inside.

Each of the plurality of magnetic body layers is configured in the form of a sheet of a compound ferrite raw material including ferrite raw material and kaolin, and a plurality of dispersed voids are formed inside the body as the plurality of magnetic layer and the nonmagnetic layer are laminated and sintered. Is formed.

The nonmagnetic layer is composed of a sheet-shaped nonmagnetic material.

The nonmagnetic layer includes a sheet of ferrite material and a nonmagnetic internal electrode pattern formed on the sheet of ferrite material.

According to the present invention of such a configuration, the DC overlapping characteristics are improved compared to the existing products.

The effect of voids and high sintered density and permeability make it possible to form high inductance while reducing the number of sheets stacked. As a result, when the same inductance is implemented, a lower DC resistance value is induced to increase the Q-value of the product. This can be expected to improve the efficiency of the DC-DC converter using a power inductor.

In the conventional winding type power inductor, there is a problem in that crosstalk is generated in which a magnetic field affects adjacent components. However, in the present invention, the distributed voids are evenly distributed in the body, thereby suppressing the occurrence of crosstalk. . In addition, when there is no dispersed void, there is a possibility of crosstalk due to leakage of magnetic field in the nonmagnetic layer portion, but by forming a dispersed void, crosstalk due to dispersion of magnetic field is much smaller. .

Hereinafter, a multilayer power inductor according to an exemplary embodiment of the present invention will be described with reference to the accompanying drawings. Prior to the detailed description of the invention, the terms or words used in the specification and claims described below should not be construed as limiting in their usual or dictionary meanings. Configurations shown in the embodiments and drawings described herein are only one of the most preferred embodiments of the present invention and do not represent all of the technical spirit of the present invention, various equivalents that may be substituted for them at the time of the present application It should be understood that there may be variations and variations.

3 is a view for explaining the configuration of a multilayer power inductor according to an embodiment of the present invention. (B) is sectional drawing of the A-A line | wire of (a) of FIG.

The stacked power inductor according to the embodiment of the present invention includes first and second bodies 30 (also referred to as a main body) formed by lamination of a magnetic layer and a nonmagnetic layer and opposite outer surfaces of the body 30. It includes two external terminals (32, 34).

Looking at the inside of the stacked power inductor according to an embodiment of the present invention is as shown in Figure 3 (b). The stacked power inductor of the embodiment of the present invention includes the coil portion 36, the nonmagnetic sheet 38, and the plurality of distributed types, which are formed of internal electrode patterns 36a, 36b, 36c, and 36d interconnected by via holes (not shown). A void 40.

One end 36d of the coil unit 36 is connected to the first external terminal 32, and the other end 36a of the coil unit 36 is connected to the second external terminal 34.

One end of the nonmagnetic sheet 38 is connected to the first external terminal 32, and the other end of the nonmagnetic sheet 38 is connected to the second external terminal 34.

4 is an exploded perspective view illustrating a sheet configuration of a stacked power inductor according to an exemplary embodiment of the present invention. In FIG. 4, the dispersed voids 40 are omitted.

An internal electrode pattern 36a is formed on one surface of the first sheet 52. One end of the inner electrode pattern 36a is exposed to one side of the first sheet 52, and the via hole 42 is formed at the other end of the inner electrode pattern 36a.

An internal electrode pattern 36b is formed on one surface of the second sheet 54. The internal electrode pattern 36b is not exposed to either side of the second sheet 54. Via holes 42 are formed at both ends of the internal electrode pattern 36b.

An internal electrode pattern 36c is formed on one surface of the third sheet 56. The internal electrode pattern 36c is not exposed to either side of the third sheet 56. Via holes 42 are formed at both ends of the internal electrode pattern 36c.

An internal electrode pattern 36d is formed on one surface of the fourth sheet 58. One end of the internal electrode pattern 36d is exposed to one side of the fourth sheet 58.

Reference numeral 50 is a dummy sheet. The dummy sheet 50 is located at the top and bottom and used as a cover layer or a protective layer. The material of the above-described sheets 50, 52, 54, 56, 58 is preferably ferrite.

The nonmagnetic sheet 38 may be made of a material having a low permeability, such as a nonmagnetic ferrite (i.e., a ferrite that is close to the nonmagnetic material in a different composition) or a ceramic. In addition, the nonmagnetic sheet 38 is sufficiently sinterable under the sintering conditions of the body 30, and does not react well with the ferrite and the internal electrode patterns 36a, 36b, 36c, and 36d during sintering, and the plastic shrinkage rate is similar to that of the ferrite. Level is preferred. On the other hand, the nonmagnetic sheet 38 can be manufactured using a dielectric such as BaTiO ₃ or B-Si-Zn-based glass other than nonmagnetic ferrite or ceramic. Via holes 42 are formed in the nonmagnetic sheet 38. The nonmagnetic sheet 38 is an example of the nonmagnetic layer described in the claims of the present invention. The dummy sheet 50 and the first to fourth sheets 52, 54, 56 and 58 are examples of the magnetic layer described in the claims of the present invention.

The nonmagnetic sheet 38 exhibits the same effect as a void (air gap) and can suppress magnetic saturation. In other words, the nonmagnetic sheet 38 exhibits the same effect as the voids (air gaps), thereby preventing magnetic saturation from occurring at low currents, thereby reducing the temperature change and greatly expanding the usable current range of the product. Do it. Preventing magnetic saturation at low current means higher magnetic saturation point, and higher magnetic saturation point results in better DC overlapping characteristics.

Since the inductance and DC overlap characteristics will vary depending on how much of the nonmagnetic sheet 38 occupies, the area occupied by the nonmagnetic sheet 38 may be determined as necessary. This is because the inductance and the DC overlapping characteristics are in a trade-off relationship due to the nonmagnetic layer, and as the number of nonmagnetic layers increases, the inductance decreases, but the DC overlapping characteristics are improved. The nonmagnetic sheet 38 may be referred to as a fixed void as compared to the dispersed void 40.

When the first to fourth sheets 52, 54, 56, 58 and the nonmagnetic sheet 38 are laminated, any one of the via holes 42 of the internal electrode pattern 36b causes the via holes of the internal electrode pattern 36a to be stacked. A contact is made to face the hole 42. The other via hole 42 of the inner electrode pattern 36b is in contact with the via hole 42 of the nonmagnetic sheet 38. On the other hand, the via hole 42 of the nonmagnetic sheet 38 is in contact with one of the via holes 42 of the internal electrode pattern 36c. The other via hole 42 of the inner electrode pattern 36c is in contact with the other end of the inner electrode pattern 36d. In order to connect the inner electrode pattern 36b and the inner electrode pattern 36c adjacent to the nonmagnetic sheet 38, the nonmagnetic sheet 38 is opened to be electrically insulated from the via hole 42 of the sheet 38. Has an area K. For example, when the nonmagnetic sheet 38 is made of ferrite paste, an open area K for insulation is required as shown in FIG. 4 to prevent the portion of the via hole 42 from filling. Of course, even when the ferrite paste is printed on the upper surface of the dummy sheet 50, the bazaar sheet 38 may be implemented. In this case, as shown in FIG. 4 to prevent the via hole 42 from filling up. An open area K for insulation is required. If a non-magnetic green sheet is used, no part for insulation is required since it is a part by via hole punching.

 Internal electrode patterns 36a, 36b, 36c, 36d are formed using Ag paste. The interconnection of the internal electrode patterns 36a, 36b, 36c, and 36d forms a coil shape. The coiled portion 36 is thus referred to as the coil portion 36.

5 is a variation of the nonmagnetic sheet 38 of FIG. In FIG. 4, a nonmagnetic sheet 38 is used. In FIG. 5, a sheet 41 of the same material as the other sheets 50, 52, 54, 56, and 58 is used. A nonmagnetic internal electrode pattern 39 is formed on one surface of the sheet 41 of FIG. 5. The nonmagnetic inner electrode pattern 39 may be made of a material having a low permeability, such as a nonmagnetic ferrite (i.e., a ferrite that is close to the nonmagnetic material in a different composition) or ceramic. On the other hand, the nonmagnetic inner electrode pattern 39 can be manufactured using a dielectric such as BaTiO ₃ or B-Si-Zn-based glass other than nonmagnetic ferrite or ceramic. In the case of FIG. 5, since the sheets 41, 50, 52, 54, 56, and 58 to be laminated are all made of the same material, the peeling problem may be fundamentally solved. In addition, the nonmagnetic internal electrode pattern 39 may be provided through a process similar to the process of printing the internal electrode patterns 36a, 36b, 36c, and 36d. Via holes 42 are formed in the sheet 41. In order to connect the inner electrode pattern 36b and the inner electrode pattern 36c adjacent to the sheet 41, the sheet 41 has an open area to be electrically insulated from the via hole 42 of the sheet 41. For example, when the non-magnetic internal electrode pattern 39 is printed using a ferrite paste, an open area for insulation as shown in FIG. 5 (ie, in FIG. 4) to prevent a portion in which the via hole 42 is filled. Open area K) is required. If a non-magnetic green sheet is used, no part for insulation is required since it is a part by via hole punching. The nonmagnetic internal electrode pattern 39 is sufficiently sinterable under the sintering conditions of the body 30 and upon sintering the sheets 41, 50, 52, 54, 56, 58 and the internal electrode patterns 36a, 36b, 36c, 36d. It does not react well with, and the plastic shrinkage ratio is preferably manufactured using a material having a degree similar to that of the sheets 41, 50, 52, 54, 56, 58. The nonmagnetic inner electrode pattern 39 is another example of the nonmagnetic layer described in the claims of the present invention.

As such, when the non-magnetic sheet 38 or the non-magnetic internal electrode pattern 39 having a predetermined thickness is used, the permeability is lowered to increase the DC overlapping characteristics, but the inductance is lowered as the permeability is lowered to obtain the desired inductance. The number of turns of the power inductor needs to be large. That is, as the thickness of the nonmagnetic sheet 38 or the nonmagnetic inner electrode pattern 39 increases, the permeability decreases, but the number of turns of the power inductor (the number of internal electrode patterns) increases, so that the overall size of the power inductor Becomes large.

Thus, in the embodiment of the present invention, instead of limiting the thickness of the nonmagnetic sheet 38 or the nonmagnetic inner electrode pattern 39 to within a predetermined threshold, a plurality of dispersed voids (air gaps) having a particle size in micro units are provided. 40 is formed to be dispersed inside the body 30. The plurality of dispersed voids 40 assist in the function of the nonmagnetic sheet 38 or the nonmagnetic inner electrode pattern 39. Here, the numerical examples for the predetermined thresholds are not illustrated separately because the thresholds may vary depending on the manufacturing technology know-how of the manufacturer to meet the needs of the orderer. In other words, in the embodiment of the present invention, the thickness of the nonmagnetic sheet 38 or the nonmagnetic inner electrode pattern 39 is limited by limiting the thickness of the nonmagnetic sheet 38 or the nonmagnetic inner electrode pattern 39 to be within a predetermined threshold. Instead of slightly increasing the permeability compared to making the above the predetermined threshold, a plurality of dispersed voids (40 in FIG. 3) are formed inside the body 30. This makes it possible to reduce the overall size of the power inductor by reducing the number of sheets stacked. Further, since a plurality of dispersed voids (40 in FIG. 3) are additionally formed inside the body 30, the self-saturation is further suppressed compared to the absence of the plurality of dispersed voids to further improve the DC overlapping characteristic. If necessary, the plurality of dispersed voids 40 may be formed in the nonmagnetic layer and the plurality of magnetic layer, or may be formed only in the plurality of magnetic layer.

Next, a manufacturing process of the multilayer power inductor according to the exemplary embodiment of the present invention will be described as follows.

1. Slurry Manufacturing

 Ni-Zn-Cu-based low-temperature sintering ferrite powder (ie, raw powder) is prepared at about 55-65 wt% relative to the total wt% of the desired slurry. Polyvinyl butyral (PVB) is used as a binder, but BB (Butyl Benzyl Phthalate) is used as a plasticizer, and a mixed solution of toluene and alcohol is used as a solvent. Then, an additive for producing dispersed voids is prepared. For example, the additive for dispersing voids is prepared by mixing carbon nanofibers (CNF) in powder form of about 0.2 to 1.2 wt% of ferrite and raw material powder of T's FRX series.

Thereafter, the ferrite powder and the dispersion-type pore-forming additives and the solvent are added to the ball mill, and then milled for about 1 hour, the binder and the plasticizer are added to the ball mill, and then mixed for about 10 to 15 hours to prepare a slurry. The numerical values exemplified above are only examples and may vary depending on the manufacturing environment and needs. The prepared slurry is stirred under reduced pressure using a stirring tank for bubble removal to remove bubbles, and then adjusted to a viscosity suitable for sheet forming.

2. Sheet Forming and Processing

 The prepared slurry is manufactured by ferrite green sheet having a desired thickness by a method such as a doctor blade. Drying the ferrite green sheet of the desired thickness completes the forming of the sheet. A via hole 42 of a predetermined diameter is processed by using a punching equipment before printing the internal electrode pattern on the molded sheet. On the other hand, in order to form the nonmagnetic green sheet for obtaining the nonmagnetic sheet 38 of FIG. 4, a material having a low permeability such as a nonmagnetic ferrite (ie, a ferrite close to the nonmagnetic material with a different composition) or a ceramic is used as the raw material powder. The difference is that the use is the same as the above description.

3. Printing and lamination

 Ag paste is used to print the inner electrode pattern on each molded sheet and to fill the via holes 42. Of course, it is not necessary to print the internal electrode pattern on the molded sheet for the nonmagnetic sheet 38. After printing, the dried molded sheet is laminated. For example, as shown in FIG. 4, the molded sheet for the fourth sheet 58 is laminated on the molded sheet for the dummy sheet 50 of the lowermost layer, and the molded sheet for the third sheet 56 is laminated thereon. The molded sheet for the nonmagnetic sheet 38 is laminated on the molded sheet for the third sheet 56, and then the molded sheet for the second sheet 54 is laminated thereon. The molded sheet for the first sheet 52 is laminated on the molded sheet for the second sheet 54, and then the molded sheet for the dummy sheet 50 is laminated thereon. The laminated molded sheet is cut into a desired chip size in consideration of shrinkage ratio and the like.

4. Sintering and Termination

-Chips cut to the desired size are sintered by raising the temperature to several ℃ / min, finally sintered at about 900 ~ 910 ℃ about 2 hours. The melting point of Ag used as the material of the internal electrode pattern is about 960 ° C, and the sintering of the body should sufficiently occur at around 900 ° C lower than this to enable simultaneous firing of the internal electrode pattern and the body. Here, chips cut to a desired size or chips which have been sintered are called bodies. In particular, the carbon nanofibers (CNF) used as part of the additive for forming dispersed pores become CO ₂ at about 800 ° C. during the sintering process and disappear in the body. The missing portion naturally takes the form of voids (40 in FIG. 3). Each void 40 has a particle diameter of about 0.1 to 10 mu m (more preferably, 1 to 3 mu m). For example, in FIG. 3B, a plurality of voids 40 having a larger particle size than the particle diameter of the above-described void 40 are overlapped between the inner electrode pattern 36c and the inner electrode pattern 36d. If located, there is a fear that the internal electrode pattern 36c and the internal electrode pattern 36d are electrically connected. In order to prevent this, it is preferable that the particle diameter of the voids 40 has a numerical value as exemplified above. Of course, if the size of the body 30 is smaller and the upper and lower gaps between the inner electrode patterns are narrower, the particle diameter of the void 40 is also preferably smaller than the above-described value. In such a state, when the sintering temperature of the body is gradually raised and sintered at about 900 to 910 ° C. for about 2 hours, the ferrite of T's FRX series surrounds the outer shell of the pores. Both ends of the body 30 having been sintered are dipped in the terminal paste Ag paste. When dried and then heat treated, first and second external terminals 32 and 34 are formed on both sides of the body 30.

In this manner, the dispersed voids 40 are formed in the body 30 in addition to the fixed voids formed by the nonmagnetic sheet 38. This makes it possible to further suppress the self saturation as compared with the structure without the dispersed void 40, thereby further improving the DC overlapping characteristics. In addition, in the absence of the dispersed void 40, there is a possibility of crosstalk due to leakage of the magnetic field in the nonmagnetic layer portion, but the formation of the dispersed void 40 causes crosstalk due to the dispersion of the magnetic field. The occurrence is much less.

On the other hand, it is also possible to disperse the inside of the body 30 in place of the dispersible pores 40 by using only the ferrites of T's FRX-Z series except tannonano fibers (CNF). In this case, the sintering temperature of ferrite of T company's FRX-Z series is about 920 ~ 940 ℃. If the final sintering temperature of the body is 900 ~ 910 ℃, the ferrite of T company's FRX-Z series is not completely sintered. This causes problems of lowering of sintered density and lowering of permeability.

Therefore, carbon nanofibers (CNF) are raw materials obtained by adding a small amount of dispersed nonmagnetic material to ferrites of T Company's FRX-Z series (i.e., nonmagnetic materials such as Si, Zn, Ni, ferrite, etc.). It is much more efficient to use it as an additive for dispersing voids. This was sufficiently confirmed through experiments.

Applicant tried using kaolin in powder form of about 0.2 to 0.5 wt% of raw material powder instead of carbon nanofibers (CNF). As a result, it was confirmed that even in the case of using kaolin, the DC overlapping characteristics were improved compared to the conventional multilayer power inductors. However, when kaolin is used, the sintering density and permeability are somewhat lower than that of carbon nanofibers (CNF) due to incomplete sintering during the sintering process. When using the kaolin it has had eliminated the decrease in the sintering density by adding a small amount of a sintering aid of Bi ₂ O _3.

The present applicant has checked the change and rate of change of inductance when the current is sequentially applied to the existing products and the product according to the present invention. As a result, experimental data as shown in Table 1 below were obtained.

(Table 1)

division
Comparative product1 Comparative product 2 Comparative product 3 Products of the invention 1 Products of the invention 2 Comparative product1 Comparative product 2 Comparative product 3 Products of the invention 1 Products of the invention 2
90
145
80
114
109
Rate of change
0.0A
2.173
2.21
2.556
2.106
2.078
0.0%
0.0%
0.0%
0.0%
0.0%
0.1 A
2.136
2.217
2.461
2.109
2.066
-1.7%
0.3%
-3.7%
0.2%
-0.6%
0.2 A
2.017
2.038
2.293
2.037
2.031
-7.2%
-7.8%
-10.3%
-3.2%
-2.2%
0.3A
1.860
1.944
2.088
1.920
1.927  -14.4%  -12.0%
-18.3%
-8.8%
-7.3%
0.4A
1.680
1.848
1.791
1.793
1.806  -22.7%
-16.4%
-29.9%
-14.8%
-13.1%
0.5 A
1.497
1.747
1.368
1.664
1.684  -31.1%
-21.0%
-46.5%
-21.0%
-19.0%

In Table 1, the comparative product 1, the comparative product 2, the comparative product 3 are products released by other existing companies, the comparative product 1 is the product of A company, the comparative product 2 is the product of B company, and the comparative product 3 is C It is a product. The product 1 of the present invention and the product 2 of the present invention are the same in terms of construction, but the DC resistance values applied to each other are differentiated.

In Table 1, "90, 145, 80, 114, and 109" are direct current resistance values applied to respective products. In addition, "0.0A, 0.1A, 0.2A, 0.3A, 0.4A, 0.5A" is a current value sequentially applied to each product.

Increasing the current value sequentially with each DC resistance applied to each product causes the inductance of each product to be lowered sequentially. This can be seen by looking at the data in the left part of Table 1. As such, the rate of change of inductance according to the sequential rise in current values for each product can be seen by looking at the data in the right part of Table 1. 6, a graph based on the rate of change of inductance in Table 1 is presented.

As described above, the inductance change rate compared to the applied current can be seen from Table 1 and FIG. 6 that the inductance change rate of the product of the present invention is slower than the existing products. This means that the capacity change according to the applied current is small. If the capacity change according to the applied current is small, it means that the DC overlapping characteristic is improved compared to the existing products.

In addition, the present inventors have checked the sinterability and permeability in the case of using carbon nanofibers (CNF) and kaolin (kaolin) as part of the additives for the production of dispersed voids. As a result of the check, experimental data as shown in Table 2 below were obtained. The experimental data of Table 2 below is a case in which the carbon nanofibers (CNF) of 0 ~ 1.2wt% compared to the ferrite and raw material powder of T Company's FRX series were mixed in a ball mill for about 10 hours and the sintering temperature was set to 905 ° C. Compared to the case where 0 ~ 0.5wt% of kaolin is mixed in ball mill for 15 hours and the sintering temperature is set to 908 ℃ compared to the ferrite and raw powder of FRX series.

(Table 2)

 Additive (wt%)   0   0.1   0.3   0.5   0.7   0.9   1.2

Permeability Carbon Nano Fiber
(CNF)
306
293
279
252
235
217
173 Kaolin
(kaolin)
307
227
129
70
Sintered Density
Carbon Nano Fiber
(CNF)
5.16
5.14
5.11
5.09
5.08
4.99
4.93 Kaolin
(kaolin)
5.2
5.0
4.75
4.5

Figure 7 (a) is a graph of the experimental data for the magnetic permeability of Table 2, Figure 7 (b) is a graph of the experimental data for the sintered density of Table 2. In FIG. 7A, "A" shows a change in permeability when kaolin is used, and "B" shows a change in permeability when carbon nanofibers are used. In FIG. 7B, "A" shows a change in sintered density when using kaolin, and "B" shows a change in sintered density when using carbon nanofibers.

Table 2 and Figure 7 confirms that the use of carbon nanofibers as part of the additives for the production of dispersed voids can increase the permeability and sintered density compared to using kaolin.

In addition, the applicant has checked the change in inductance for each frequency when using kaolin and carbon nanofibers (CNF) as part of the additive for forming the dispersed pores, respectively. As a result of the check, a frequency inductance graph as shown in FIG. 8 was obtained. In FIG. 8, "A" refers to a case in which 0.7 wt% of carbon nanofibers (CNF) are mixed with ferrite and raw material powders of T's FRX series. "B" refers to a case in which 0.5 wt% of carbon nanofibers (CNF) is mixed with ferrite and raw material powder of T's FRX series. "C" refers to a case in which 0.2 wt% of kaolin is mixed with ferrite and raw material powder of T Company's FRX series.

Looking at the arrow K portion of Figure 8, it can be seen that the peak curve of the product added with carbon nanofibers changes more slowly than the peak curve of the product added with kaolin. On the other hand, the inductance curve will change more slowly as the body sinters well.

As described above, the multilayer power inductor according to the exemplary embodiment of the present invention improves the DC overlapping characteristic compared to the conventional products.

The effect of voids and high sintered density and permeability make it possible to form high inductance while reducing the number of sheets stacked. Therefore, when the same inductance is implemented, a lower DC resistance value is induced to increase the Q-value of the product. This can be expected to improve the efficiency of the DC-DC converter using a power inductor.

In the conventional winding type power inductor, there is a problem in that crosstalk is generated in which a magnetic field affects an adjacent component. However, in the stacked power inductor according to the exemplary embodiment of the present invention, distributed voids are evenly distributed in the body, thereby generating crosstalk. It has the effect of suppressing. In addition, in the absence of the dispersed voids, there is a possibility of crosstalk due to the leakage of the magnetic field in the nonmagnetic layer portion, but by forming the dispersed voids, crosstalk due to the dispersion of the magnetic field becomes much less.

On the other hand, the present invention is not limited only to the above-described embodiments and can be carried out by modifications and variations within the scope not departing from the gist of the present invention, the technical idea that such modifications and variations are also within the scope of the claims Must see

1 is a cross-sectional view of a conventional wound power inductor.

2 is a cross-sectional view of a conventional chip type stacked power inductor.

3 is a view for explaining the configuration of a multilayer power inductor according to an embodiment of the present invention.

4 is an exploded perspective view illustrating a sheet configuration of a stacked power inductor according to an exemplary embodiment of the present invention.

FIG. 5 is a diagram illustrating a modification of the nonmagnetic sheet of FIG. 4.

6 is a graph showing the current vs. inductance change rate between the comparative product and the product according to an embodiment of the present invention.

FIG. 7 is a graph comparing sinterability and permeability when used as part of an additive for generating dispersed pores of kaolin and carbon nanofibers (CNF) applied to an embodiment of the present invention.

FIG. 8 is a graph comparing frequency inductance changes of kaolin and carbon nanofibers (CNF) as dispersion materials applied to an embodiment of the present invention.

Claims (7)

A non-magnetic layer stacked between the plurality of magnetic layers, wherein the plurality of magnetic layers include internal electrode patterns, and the internal electrode patterns are interconnected to form a coil part; And It is dispersed and formed in the body, including a plurality of dispersed voids having a particle diameter of 0.1 ~ 10㎛, Each of the plurality of magnetic body layers is configured in the form of a sheet of a compound ferrite raw material including a ferrite raw material and kaolin, And the plurality of dispersed voids are formed inside the body as the plurality of magnetic layers and the nonmagnetic layers are stacked and sintered. The method according to claim 1, And the plurality of distributed voids are formed in the nonmagnetic layer and the plurality of magnetic layer. The method according to claim 1, And the plurality of distributed voids are formed inside the plurality of magnetic layers. The method according to any one of claims 1 to 3, Each of the plurality of magnetic layers is configured in the form of a sheet of a ferrite raw material including a ferrite raw material and carbon nanofibers (CNF), and the plurality of magnetic layers and the non-magnetic layer are laminated and sintered to form the plurality of dispersed types. Multilayer power inductor, characterized in that voids are formed in the body. delete The method according to any one of claims 1 to 3, The nonmagnetic layer is a laminated power inductor, characterized in that consisting of a sheet-like nonmagnetic material. The method according to any one of claims 1 to 3, And the nonmagnetic layer includes a sheet of ferrite and a nonmagnetic internal electrode pattern formed on the sheet of ferrite.

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