JP3320096B2 - Multilayer inductor and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer inductor and a method for manufacturing the same.

[0002]

2. Description of the Related Art In order to suppress noise in various electronic circuits,
A bead core using a magnetic material such as ferrite or an amorphous magnetic alloy is used as a noise suppressor. There are various types of conventional bead cores, such as toroidal beads having a small magnetic material, a forming type with a wire, and an axial or radial taping type. Some of these are used by directly attaching them to the leads of electronic components or electrically connecting them to circuits, but with the miniaturization of electronic devices and the generalization of applied devices, miniaturization and the same use as general components are used. The need for taping for automatic mounting and leadless for surface mounting is rapidly increasing.

On the other hand, surface mountable multilayer inductors used as ordinary coils and LC composite parts have been put to practical use. The laminated inductor is manufactured by alternately laminating magnetic layers and conductor layers by a thick film technique and then firing.

Japanese Utility Model Publication No. 62-25858 and Japanese Utility Model Publication No. 57-
An air-core type or open-magnetic-path type inductor in which a conductor coil pattern is formed on an insulating substrate described in 78609 or the like has a low impedance and is not suitable for such an application. The path-type multilayer inductor can be used as a bead core for suppressing noise or a noise suppressor.

However, in order to use the laminated inductor as a bead core for suppressing noise, the impedance decreases as the element becomes smaller, and the operating frequency, for example, 5 dB.
In particular, the impedance at a high frequency of about 0 to 1000 MHz becomes insufficient. Also, to increase the impedance,
Increasing the number of laminations (number of turns) lowers the resonance frequency, deteriorating high-frequency characteristics, increases the number of manufacturing steps, increases costs, and is very disadvantageous in mass production.

Conventionally, the laminated inductors are roughly classified into a printed laminated type and a green sheet laminated type.
In the printing lamination type, for example, as described in JP-B-60-50331, a conductor pattern of less than one turn is printed, and a magnetic material is printed so that a part of the conductor pattern is exposed. Are repeatedly laminated and fired.

However, it has been found that, in the printed lamination type, the thickness of the magnetic layer cannot be increased to 0.1 mm or more because the reliability of the conductor connection is reduced, and the impedance at a high frequency above 400 MHz is extremely low. . Further, even if the number of turns is increased to increase the impedance, the resonance frequency shifts to the lower frequency side, and as a result, the high-frequency impedance decreases.

On the other hand, in the green sheet lamination type, as described in, for example, Japanese Patent Application Laid-Open No. 1-151211, a conductor pattern is formed on a magnetic green sheet having a through hole, and a plurality of these are laminated. It is to be fired. In this case, a conductor pattern is formed on each of the plurality of green sheets for each predetermined turn (less than one turn), and the green sheets are laminated and, at the same time, each conductor pattern is conducted by a conductor filled in a through hole formed in each sheet. And a coil having a predetermined number of turns. Then, on each green sheet at the beginning and end of the coil, an end lead portion is formed in a stripe shape connected to the coil end at both opposing edges, and this is exposed at both opposing edges. hand,
A pair of external electrodes is formed on each of these.

Incidentally, it is required that the multilayer inductor for bead cores be reduced in thickness to about 0.8 to 1.5 mm. In such a case, in order to obtain a predetermined impedance, a spiral coil portion is formed on the green sheet, the number of turns per green sheet layer is increased to one or more turns, and the thickness of the green sheet is increased. It is advantageous in mass production to reduce the number of layers.

[0010] In such a case, the thickness after firing is 0.1 mm.
A magnetic sheet thicker than the conventional one, that is, 2 mm or more, is used. Moreover, in such a case, a conductor pattern having a stripe-shaped end lead portion on the entire end portion is printed on a green sheet, laminated and pressed, baked, and thereafter, paste for external electrodes is applied to both ends, When the external electrode is formed by baking, the green sheet is thick, so the wettability with the external electrode paste is not sufficient, the connection between the lead portion and the external electrode is not sufficient, and the DC resistance increases or varies. , Changes over time, and furthermore, poor conduction occurs.

[0011] In the production of a multilayer inductor, a large number of printed patterns of a conductor paste of a coil portion for one layer are formed in an array on a large-area green sheet, and a plurality of the printed patterns are laminated and pressed. Cutting into chips and baking them are preferable for mass production. At this time,
If the laminating position is shifted or the cutting position is shifted, the connection between the external electrode and the end lead portion becomes insufficient, and the possibility of poor conduction or the like increases. Further, the displacement between the patterns due to the lamination displacement also causes a displacement between the conductor in the through hole and the conductor pattern of the green sheet immediately below, which also causes a reduction in yield and a reduction in reliability.

[0012]

SUMMARY OF THE INVENTION It is a main object of the invention of the present application to provide a multilayer inductor having no variation in characteristics and a high production yield and high reliability, and a method of manufacturing the same.

[0013]

This and other objects are achieved by the present invention described in (1) to (4) below. (1) Second and third magnetic sheets are laminated on both main surfaces of the first magnetic sheet, and three layers of magnetic sheets are sintered and integrated, and the first magnetic sheet is Is 0.2
The first magnetic sheet has a thickness of not less than 1 mm, and has a leading end portion on the main surface of the first magnetic sheet on the side of the third magnetic sheet. In the vicinity of the center side end of the first conductor pattern, there is formed a through hole penetrating between both main surfaces of the first magnetic sheet. The hole is filled with a conductor connected to the first conductor pattern, and the main surface of the second magnetic sheet on the side of the first magnetic sheet has an end leading portion. A second conductor pattern is formed spirally from the end to the center, and the second conductor pattern is connected to the conductor filled in the through hole near the center side end. The first and second conductor patterns and the conductor make the conductor approximately 9/4. Down more windings are formed,
A pair of external electrodes connected to end lead-out portions of the first and second conductor patterns are formed;
The second and third magnetic sheets are configured to form a closed magnetic circuit, and the second conductor pattern is directly or indirectly connected to the conductor filled in the through hole. Further, the main surfaces of the first and second magnetic sheets on which the first and second conductor patterns are respectively formed are spaced apart from the first and second conductor patterns, respectively, so that the second and first conductor patterns are separated from each other. Dummy conductor patterns are respectively formed over the entire width at positions facing the end lead-out portions of the conductor patterns, and the first and second conductor patterns 31 and 32 have a width of 50 to 300 μm.
m, a thickness of 5 to 50 μm, a pair of external electrodes connected to end lead portions of the first and second conductor patterns are formed, a thickness of 0.5 to 2 mm, and a planar size of 0.5 to 2 mm. 1. A laminated inductor having a size of 1.3 to 4.8 mm × 0.5 to 3.5 mm and an impedance of 180 Ω or more at a frequency of 300 MHz. (2) The multilayer inductor according to (1), wherein a hole diameter r ₀ of the through hole on the main surface side on which the first conductor pattern is formed is larger than a hole diameter r ₁ on the other main surface side. (3) The above (2) in which r ₀ / r ₁ = 1.2 to 1.7.
Multilayer inductor. (4) First, second and third magnetic green sheets are prepared, a plurality of through holes are formed at predetermined intervals in the first magnetic green sheet, and a conductive paste is printed on the first magnetic green sheet. A pattern is formed, a conductor is filled in the through hole, and a conductor paste is printed on a second magnetic green sheet to form a conductor pattern.
And the third magnetic green sheet are laminated and pressure-bonded, and then formed into chips. At both end portions of the chipped green sheet, the end lead portions of the first and second conductor patterns and the end lead portions are formed. 4. A laminated inductor according to any one of claims 1 to 3, wherein the laminated pattern is exposed by exposing a dummy pattern extending across the entire width in opposition to each other, and then firing to form external electrodes. Manufacturing method.

[0014]

[0015]

[0016]

[0017]

[0018]

[0019]

[Specific Configuration] Hereinafter, a specific configuration of the present invention will be described in detail.

FIGS. 1, 2 and 3 show a preferred embodiment of the multilayer inductor of the present invention. FIG. 1 is a front view of the multilayer inductor, FIG. 2 is a front view showing the internal structure of FIG. 1, and FIG. 3 is an exploded perspective view of FIG.

The laminated inductor 1 has first, second, and third magnetic sheets 21, 22, and 23 having substantially the same thickness as each other.
Are integrated and stacked. That is, in the present invention, the first magnetic sheet 21 has a three-layer structure in which the second magnetic sheet 22 and the third magnetic sheet 23 are laminated on both main surfaces. By using a three-layer structure having substantially the same thickness, only one type of magnetic sheet needs to be prepared, and printing can be performed only on the two-layer magnetic sheets 21 and 22. Will be much easier and mass production will be extremely high. In addition, the sheet thickness per layer, in particular, the first magnetic sheet 21 between the conductor patterns 31 and 32
Can be made sufficiently large, stray capacitance is reduced, and high-frequency characteristics are improved.

The thickness of the chip body 10 is 0.5 to 2 mm, particularly 0.6 to 1.5 mm. The plane size is generally 1.3 to 4.8 mm x 0.5 to 3.5 mm, particularly 1.7 to 4.8 mm.
3.5 mm x 0.9 to 2.8 mm.

For this reason, the thickness of the first magnetic sheet 21 in the chip body 10 can be set to 0.2 mm or more.
If the thickness is smaller than this, the high-frequency characteristics deteriorate. The thickness of the first magnetic material sheet 21 is usually 0.2 to
0.8 mm, especially 0.3 to 0.5 mm.

The second magnetic sheet 22 and the third
The thickness of the magnetic sheet 23 also contributes to the improvement of high frequency characteristics. In order to obtain even better high-frequency characteristics, each of these is preferably 0.2 mm or more, and it is usually preferable that all three layers have a thickness of 0.2 to 0.8 mm.

In such a case, the first magnetic sheet 21
The first and second conductor patterns 31 and 32 are formed on the main surface of the second magnetic sheet 22 on the side of the magnetic sheet 23. In this case, in order to obtain a high impedance with a small number of sheets only on two sheets, the number of turns of the coil on one plane is increased. As described above, forming the coil pattern on the front and back surfaces of the sheet through the through-holes is low in mass productivity and deteriorates the production yield. Therefore, the pattern is formed only on one main surface of the sheet and has a spiral shape.

In the illustrated example, the conductor patterns 31, 32 formed on the first and second magnetic sheets 21, 22 are shown.
Has stripe-shaped end lead portions 310 and 320 provided over the entire main surface end portion on one side end surface side. From the front side of the end drawer portions 310 and 320, the end lead portions 310 and 320 are spirally bent at right angles. It is formed as a stripe-shaped pattern extending toward the central portion of the main surface and reaching pattern ends 315 and 325 at the central portion of the main surface. Then, the pattern ends 315, 325 of the first and second conductor patterns 31, 32
Are electrically connected by the conductor 35 filled in the through hole 4 provided in the first magnetic material sheet 21.

Then, after starting the end lead-out portion 310 of the first conductor pattern 31, the entire pattern is bent four times on the first magnetic material sheet 21 while being bent by 90 °. Next, the second conductor pattern 3 is bent four more times on the second magnetic material sheet 22, and is bent eight times in total to be parallel to the original position.
2 to the end drawer 320. In other words, since the first straight portion 311 starting from the end drawing portion 310 to the position 313 immediately before the straight portion parallel to the first straight portion 311 can be defined as one turn, the pattern is formed on the first magnetic material sheet 21. After one turn, the process moves to the second conductor pattern 32 on the second magnetic material sheet 22 and the position 3
After completing the second turn at 23, the last straight portion 32 parallel to the first straight portion 311 of the first conductor pattern 31
1, the end lead portion 310 of the first conductor pattern
To the end drawer 320 located at the end opposite to. That is, in such a case, the turn is performed for approximately 1/4 of the turn, and is referred to as 9/4 turn. In addition, the term “approximately 1/4 turn” means that one spiral-shaped turn is usually formed from four straight portions, and thus one of the four straight portions contributes to the winding.

By setting the number of windings to approximately 9/4 turn or more, the impedance is improved. In this case, the number of windings can be larger than 9/4 as long as the plane size permits, but in the above-mentioned chip body size, generally, from about 9/4 to about 1/4.
It is possible up to 7/4, in particular up to approximately 13/4. The first
The number of turns of the second conductor pattern and the number of turns of the second conductor pattern are preferably substantially the same as shown in the figure, but they may be different. However, it is preferable that both of them have one or more turns.

Further, the first and second conductor patterns 31 and 33 formed in a spiral shape, as shown in FIG.
It is preferable that the first magnetic sheet 21 is opposed to a substantially vertical position with the first magnetic sheet 21 interposed therebetween. In particular, when the first conductor pattern 31 is vertically projected onto the second conductor pattern 32, it is preferable that 50% of both patterns overlap. This also improves the impedance.

Then, the first and second conductor patterns 3
Preferably, 1 and 32 have a width of about 50 to 300 μm and a thickness of about 5 to 50 μm. The pattern ends 315 and 325 of the first and second conductor patterns 31 and 32 are
It is shaped to have a wide pad having a width of 150 to 400 μm and a length of 150 to 500 μm, and secures connection of the conductor 35 in the through hole 4.

As described above, the through-holes 4 are formed in the magnetic sheet 21 or the like which is thicker than the conventional one, and the conductors 3 are formed in the through-holes 4.
5 and connecting the upper and lower conductor patterns 31, 32, etc., uncertainty of the connection occurs, the filling property of the conductor paste is reduced, and poor conduction, an increase in DC resistance, variation and aging are caused. It can happen. In order to solve such a problem, it is conceivable to first fill the through-hole 4 directly with the conductive paste using a dispenser or the like, but this increases the number of steps and complicates the steps, which is disadvantageous in mass production. is there.

Therefore, in the illustrated example, the hole diameter r ₀ of the through hole 4 on the surface on which the first conductor pattern 31 is formed is changed to the hole diameter r _{1 of the} back surface.
It has a larger diameter. By doing so, the conductor paste can be efficiently filled into the through-holes 4 only by performing printing while sucking from the back surface side of the first magnetic material sheet 21, the mass productivity is improved, and the product yield is improved. It improves and the characteristic variation decreases. Further, the change with time is also reduced.

In such a case, r ₁ is generally 50 to 20.
Preferably, it is about ₀ μm, and r ₀ / r ₁ is about 1.2 to 1.7. If r ₁ is too small, there will be a problem in conduction, while if too large, there will be a problem in filling properties and the wiring density will be adversely affected. When r ₀ / r ₁ decreases, r ₁
The effect of reducing the diameter becomes ineffective, and if the diameter is reduced too much, there is a problem in filling or the wiring density is adversely affected. The state of the diameter reduction from r ₀ to r ₁ may be continuous or stepwise.

In order to obtain the through-hole 4 having such a shape, the shape of the needle for piercing is changed, or when the through-hole 4 is pierced, a laser or the like is used. The sheet may be placed and perforated.

Further, the first and second magnetic sheets 2
Dummy conductor patterns 61 and 65 are formed on the surfaces of the first and second conductor patterns 31 and 32 on which the first and second conductor patterns 31 and 32 are formed. The dummy conductor patterns 61 and 65 are separated from the first and second conductor patterns 31 and 32, and are electrically insulated from the first and second conductor patterns 31 and 32. It is formed in a stripe shape at the end on the side surface side opposite to the unit drawer portions 310 and 320. As a result, the dummy patterns 61 and 65 are different from the magnetic sheets 21 and 22 on which the magnetic patterns 2 and 2 are formed.
The conductor patterns 32 and 31 formed on the first and second conductor patterns 32 and 31 are disposed so as to face end lead portions 320 and 310.

In particular, when a magnetic sheet whose thickness after firing is as thick as 0.2 mm or more, as described above, the conductive paste is printed on the green sheet, laminated and pressed, and fired. And the like are formed in stripes over the entire end portion, and then the external electrode paste is applied to both end portions and baked to form the external electrodes 51 and 55. When the external electrodes 51 and 55 are formed, the contact ratio with the green sheet increases. Insufficient wettability with the electrode paste, poor connection between the lead portion and the external electrode, increased DC resistance, variation, change over time, and poor conduction May be.

In the manufacture of the multilayer inductor, as shown in FIG.
A printed pattern 81 of a conductive paste corresponding to a large number of conductive patterns 31 is formed on FIG. 1 (FIG. 4 (c)), and a plurality of these are laminated and pressed [FIG. 4 (d)], and cut into chips. [FIG. 4 (e)], baking this is preferable for mass production. At this time, if the lamination position is shifted or the cutting position is shifted, the external electrodes 51 and 55 and the end lead-out portion 31 are shifted.
0 and 320 are insufficiently connected, and the possibility of occurrence of conduction failure or the like increases. Further, a shift between the patterns due to the stacking shift also causes a shift between the conductor 35 in the through hole 4 and the second conductive pattern 32, which also causes a reduction in yield and a reduction in reliability.

Therefore, as shown in FIG. 5 (a), for example, when a large number of conductor patterns 81 corresponding to the conductor patterns are simultaneously printed on a large-area green sheet 71, corresponding to the end lead portions 310 and 320. The stripe-shaped pattern 9 to be formed is formed to have a wide width, and in chip formation, if the middle of the pattern 9 is cut along the S line, both ends on the chipped green sheet 710 are formed as shown in FIG. As shown in (b), a pattern 91 corresponding to the dummy conductor patterns 61 and 65 and a pattern 810 corresponding to the end lead portions 310 and 320 are simultaneously formed, and the external conductors 51 and 55 and the end lead portions are formed. 310,
The connection with 320 is ensured. In addition, the dummy conductor patterns 61 and 65 exposed at the end portions improve the wettability of the external electrode paste, thereby improving the yield and reliability.

Further, after cutting into a chip shape after lamination, the patterns 91 and 95 for the dummy conductor patterns 61 and 65 and the patterns 810 and 820 for the end lead portions 310 and 320 are visually exposed. , Normal lamination and cutting can be confirmed [FIG. 6 (a)],
Lamination displacement [FIG. 6 (b)] and cutting displacement [FIG. 6 (c)] can be easily distinguished, and lamination displacement can be corrected. As a result, the yield is improved, and the conduction state can be visually inspected, so that the conduction inspection for each chip after firing becomes unnecessary, which is extremely advantageous in mass production. FIG.
2 shows a different pattern example in forming a dummy conductor pattern by cutting along the S line and the S 'line into chips.

Then, such a chip body 10 is provided with a pair of external electrodes 51 and 55 connected to the first and second conductor patterns, respectively. At this time, the three side surfaces of the formation portions of the end lead portions 310 and 320 are connected to the external electrodes 5.
If it is covered with 1, 55, the connection becomes more reliable, and the moisture resistance and weather resistance due to the influence of moisture are improved, and high reliability is obtained.

As the material of the conductors 31, 32, 35, any conventionally known conductor materials can be used. For example, Ag,
Cu, Pd, an alloy thereof, or the like may be used, and among them, Ag or an Ag alloy is preferable. As the Ag alloy, an Ag-Pd alloy containing 70% by weight or more of Ag is preferable.

The magnetic sheet 21 of the multilayer inductor 1
As the materials 22 and 23, any conventionally known magnetic layer material can be used. For example, various spinel soft ferrites having a spinel structure can be used, but Ni-based ferrites, particularly Ni-Cu-
It is preferable to use Zn ferrite. Ni-Cu-
Since Zn ferrite is a low-temperature firing material and a good insulator, when such a magnetic layer is used, the multilayer inductor of the present invention is suitable for firing at about 900 ° C. or less, and has excellent characteristics. Is obtained. Such a ferrite magnetic green sheet is made of a conductive paste and 800 to
It can be formed by simultaneous firing at a firing temperature of 1000 ° C, especially 850 to 950 ° C.

The materials of the external electrodes 51 and 55 are not particularly limited, and various conductive materials, for example, Ag, N
i, a printed film such as Cu or an alloy thereof such as Ag-Pd, a plated film, a deposited film, an ion plating film,
Either a sputtered film or a laminated film thereof can be used. Among these, those obtained by laminating a plating film of Cu, Ni, and Sn on an Ag or Ag alloy coating film are preferable in terms of solder wettability and aging resistance. The thickness of the external electrodes 51 and 55 is arbitrary, and may be appropriately determined depending on the purpose and application. However, the total thickness is usually about 50 to 200 μm.

The multilayer inductor of the present invention is used for suppressing noise in various electronic circuits. And 50-150
It is effective at a frequency of about 0 MHz, especially about 100 to 1000 MHz. In this case, according to the present invention, an impedance of about 180 to 250Ω can be realized at a frequency of 300 MHz even if the inductor is miniaturized as described above.

Next, a method for manufacturing the multilayer inductor of the present invention will be described. First, a magnetic green sheet, a conductor layer paste, and an external electrode paste are manufactured. The magnetic green sheet, the conductor layer paste, and the external electrode paste may be manufactured by an ordinary method.

For example, to produce a magnetic green sheet, ferrite raw material powder is wet-mixed by a ball mill or the like. The wet-mixed product is usually dried by a spray drier or the like, and then calcined. Usually, this is wet-pulverized by a ball mill or the like until the average particle size becomes about 0.5 to 2 μm, and dried by a spray drier or the like. The obtained mixed ferrite powder, a binder such as ethyl cellulose, acrylic resin, polyvinyl butyral, and polyvinyl alcohol, and a solvent are mixed to form a slurry. In addition, various magnetic particles other than ferrite powder can also be used. Then, according to a known method, a green sheet having a thickness of about 0.2 to 0.8 mm is obtained. The conductor paste and the external electrode paste usually contain conductive particles, a binder, and a solvent.
Such a composition is mixed and kneaded with, for example, a three-roll mill or the like to form a paste (slurry).

Next, as shown in FIG. 4A, first, a magnetic green sheet 71 having a large area is prepared.
As shown in (b), a large number of through holes 4 are provided in this. Then, as shown in FIG. 4C, a large number of conductor paste patterns 81 having a predetermined pattern are formed to obtain the first magnetic green sheets 71.

As shown in FIG. 4D, the second magnetic green sheet 72 produced in the same manner except that the through hole 4 is not formed, and the third magnetic green sheet 72 having no conductive paste pattern are formed. The green sheet 73 is laminated, and then the chip is formed to obtain a chip 100 (FIG. 4E). Then, it is fired.

The sintering conditions and the sintering atmosphere may be appropriately determined according to the material and the like.
The firing time is about 2 to 7 hours at about 50 ° C. The firing atmosphere may be a non-oxidizing atmosphere when Cu, Ni, or the like is used for the conductor layer, and may be in the air when Ag, Pd, or the like is used.

The chip body 10 thus obtained is subjected to end face polishing by, for example, barrel polishing, sand blasting or the like, and the external electrode paste is baked with the external electrode paste.
1, 55 are formed. Then, if necessary, the external electrode 5
Terminal electrodes are formed on the first and the first 55 by plating or the like. Although the multilayer inductor for a three-layered bead core has been described in detail above, the number of layers, the number of turns, and the like can be variously changed.

[0051]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to specific examples of the present invention. Example 1 As ferrite raw materials, NiO, CuO, ZnO, Fe
The powder of ₂ O ₃ was wet-mixed with a ball mill, and then the wet mixture was dried with a spray drier.
The granules were calcined at 0 ° C., pulverized with a ball mill, and dried with a spray drier to obtain an average particle size of 1.
2 μm powder was obtained. Next, this powder was dispersed and mixed with a predetermined amount of polyvinyl butyral in toluene-ethyl alcohol to prepare a Ni-Cu-Zn ferrite slurry, and a 0.4 mm-thick green sheet was obtained.

As shown in FIGS. 4 and 5, 550 chips were obtained from one green sheet by using an Ag-Pd conductor paste and a magnetic green sheet. To No. 1 of the multilayer inductor sample shown in FIGS. In this case, the firing temperature is 920 ° C.
The firing time was 7 hours, and the firing atmosphere was air.

The external electrodes were baked with Ag-Pd paste so as to cover the end lead portions. The dimensions of the obtained laminated inductor were 2.0 mm × 1.25 m × 0.9 mm.

The specifications of each component are as follows. First, second, and third magnetic sheet thickness: 0.4 mm Conductor pattern width: 180 μm Conductor pattern thickness: 10 μm End lead-out part width: 200 μm Dummy conductor pattern width: 200 μm Number of turns: 9/4 Through hole : R ₀ = 220 μm, r ₁ = 150 μm External electrode formation width (length from end face): 0.2 mm

The impedance was measured at different frequencies for these, and the average was determined. In addition, 200-10
The average impedance in the high frequency region at 00 MHz was calculated. Table 1 shows the results.

[0056]

[Table 1]

The DC resistance R _DC of 550 samples
Was less than 3.61%. And the weather resistance was also good.

On the other hand, when no dummy conductor pattern was provided in Sample No. 1, the variation in R _DC increased to 10.9% or more. Further, the diameter of the through-hole is r ₀
= R ₁ = 220 μm, r ₀ = 220 μm, r ₁ = 120
μm, r ₀ / r ₁ = 1.83, or r ₁ = r ₀ = 1
When the thickness was set to 20 μm, the variation in the DC resistance R _DC increased to 9.0% or more in each case.

Example 2 In the sample No. 1 of the example 1, the thickness of the green sheet was 0.35 mm, and three layers of 3.2 × 1.6 × 0.85 mm were used.
No. 4 and 5 were obtained. Number of turns is N
o. 4 made 13/4 turns, and No. 5 made 17/4 turns. The results are also shown in Table 1. Also in this case, the variation of R _DC was 2.4% or less in all cases, and the weather resistance was good.

[0060]

[Effect] There is no variation in characteristics, and the production yield and reliability are good. It is also easy to manufacture.

[Brief description of the drawings]

FIG. 1 is a front view of a multilayer inductor according to the present invention.

FIG. 2 is a partially cutaway front view for explaining the internal structure of FIG. 1;

FIG. 3 is an exploded perspective view of FIG.

FIG. 4 is a perspective view for explaining a method of manufacturing the multilayer inductor in FIG. 1 in the order of steps.

FIG. 5 is a partially enlarged plan view for describing the manufacturing method shown in FIG. 4 in further detail.

FIG. 6 is an enlarged perspective view for describing the manufacturing method shown in FIG. 4 in further detail;

FIG. 7 is a partially enlarged view for explaining the manufacturing method shown in FIG. 4 in further detail;

[Explanation of symbols]

Reference Signs List 1 laminated inductor 10 chip body 100 chip 21 first magnetic sheet 22 second magnetic sheet 23 third magnetic sheet 31 first conductive pattern 32 second conductive pattern 35 conductor 310, 320 Part 35 Conductor 4 Through hole 51, 55 External electrode 61, 65 Dummy conductor pattern 71, 72, 73 Magnetic green sheet 81, 810, 820, 91, 95 Pattern of conductor paste

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-260405 (JP, A) JP-A-2-203796 (JP, A) JP-A-2-208909 (JP, A) JP-A-58-58 67007 (JP, A) JP-A-3-55893 (JP, A) JP-A-2-32594 (JP, A) JP-A-59-189212 (JP, U) JP-A-61-66911 (JP, U)

Claims (4)

(57) [Claims] A first magnetic material sheet on which both second and third magnetic material sheets are laminated, and a three-layer magnetic material sheet which is sintered and integrated; The body sheet has a thickness of 0.2 mm or more, and has a leading end portion on the main surface of the first magnetic sheet on the side of the third magnetic sheet, and spirally extends from the end to the center. A first conductor pattern is formed near the center of the first conductor pattern, and a through-hole penetrating between the two main surfaces of the first magnetic sheet is formed near the center of the first conductor pattern. The through hole is filled with a conductor by being connected to the first conductor pattern. An end portion is formed on a main surface of the second magnetic sheet on the first magnetic sheet side. A second conductor pattern having a lead portion and spirally extending from the end portion toward the center portion; The second conductor pattern, at the center portion side end portion is connected to the filled conductors in the through-hole, by the conductor and the first and second conductor patterns,
A winding of approximately 9/4 turn or more is formed, and a pair of external electrodes connected to end lead portions of the first and second conductor patterns are formed. The second conductor pattern is configured to be directly or indirectly connected to the conductor filled in the through hole. Each of the first and second magnetic sheets
And the main surface on which the second conductor pattern is formed is spaced apart from the first and second conductor patterns, respectively, at positions opposed to the end lead-out portions of the second and first conductor patterns, respectively. The first and second conductor patterns 31 and 32 have a width of 5 mm.
0 to 300 μm, 5 to 50 μm in thickness, a pair of external electrodes connected to the end lead portions of the first and second conductor patterns are formed, and the thickness is 0.5 to 2 mm, flat The size is 1.3-4.8
A laminated inductor with a size of mm x 0.5 to 3.5 mm and an impedance of 180 Ω or more at a frequency of 300 MHz. 2. The hole diameter r ₀ of the through hole on the main surface side on which the first conductor pattern is formed is the hole diameter r ₁ on the other main surface side.
2. The multilayer inductor according to claim 1, which has a diameter larger than that of the multilayer inductor. 3. The multilayer inductor according to claim 2, wherein r ₀ / r ₁ = 1.2 to 1.7. 4. A first, a second, and a third magnetic green sheet are prepared, a plurality of through holes are formed at predetermined intervals in the first magnetic green sheet, and a conductive paste is printed. Forming a conductor pattern, filling the through hole with a conductor, printing a conductor paste on a second magnetic green sheet to form a conductor pattern, and forming a first, second, and third magnetic body. The green sheet is laminated and pressure-bonded and then chipped. At both end portions of the chipped green sheet, end drawing portions of the first and second conductor patterns are separated from each of the end drawing portions. 4. A multilayer inductor which obtains the multilayer inductor according to claim 1 by exposing a dummy pattern over the entire width in opposition to the dummy pattern, followed by firing, and further forming an external electrode. Manufacturing method.