JPH03280504A - Plane inductor - Google Patents

Abstract

PURPOSE:To enhance the direct current superimposing characteristics by a method wherein the composition of ferromagnetic thin bands or ferromagnetic thin films holding both surfaces of plane conductive coils or laminated body thereof through the intermediary of insulating layers is specified. CONSTITUTION:The intensive magnetic body thin films 5a, 5b holding surface type conductor coils structured of spiral coils 2a, 2b provided on the surface and rear surface of insulating layers 3a, 3b, 3c so as to be connected through the intermediary of a through hole 4 are formed of an amorphous alloy comprising (FexNiyCo1-x-y)1-2Zr2 where 0.6<=x<=0.9, 0<=y<=0.1, 0.08<=z<=0.14.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention (Industrial Application Field) The present invention relates to a planar inductor, and particularly to a planar inductor with improved DC superimposition characteristics.

(Prior Art) Conventionally, a planar inductor is known which has a structure in which both sides of a spiral or zigzag conductor coil are sandwiched between ferromagnetic layers with an insulating layer interposed therebetween. FIG. 1(A) is a plan view showing an example of such a planar inductor, and FIG. 1(B) is a plan view showing an example of such a planar inductor.
is a sectional view taken along line AA' in FIG.

In the figure, 1 is a spiral conductor coil. The spiral conductor coil 1 has spiral coils 2a and 2b provided on both sides of an insulating layer 3b. The spiral coils 2a and 2b are connected through the through holes 4 so that currents in the same direction flow through the spiral coils 2g and 2b.

Here, the solid line and the broken line in FIG. 1(A) indicate the spiral coil 2 on the front side and the back side of the insulating layer 3b, respectively.
It represents the locus of the center of a and 2b. A planar inductor is constructed by sandwiching both surfaces of this spiral conductor coil 1 between ferromagnetic ribbons or ferromagnetic thin films 5a and 5b via insulating layers 3a and 3c. An inductance is formed between the terminals 6a and 6b of the planar inductor configured in this way.

(Problem 1i to be Solved by the Invention) The above-described planar inductor is applied to a choke coil on the output side of a DC-DC converter, for example. In this case, a high frequency current with a superimposed direct current flows through the planar inductor. Therefore, good DC superposition characteristics are required.

However, conventional planar inductors have poor DC superimposition characteristics. This is because the magnetic properties of conventionally used ferromagnetic ribbons are inappropriate. That is, in the case of the planar inductor shown in FIG. 1, magnetic flux flows in the in-plane direction of the ferromagnetic ribbons 5a and 5b on both sides. In order to obtain high inductance, a high magnetic permeability ferromagnetic ribbon is used.

However, when the saturation magnetization of the high permeability ferromagnetic ribbon is low, even if a small direct current magnetic field is superimposed, the magnetic flux density is saturated, the inductance is reduced, and the direct current superposition characteristics are deteriorated. For example, a metal-metalloid amorphous alloy mainly composed of Co is known as a high permeability ferromagnetic material. but,
Although its saturation magnetization is higher than that of ferrite, it is not sufficient, and its DC superimposition characteristics are poor.

Note that even when a Co-based amorphous alloy is used as the ferromagnetic ribbon, the direct current superimposition characteristics can be improved to some extent by laminating these alloys. However, if the amorphous alloy is laminated, the thickness of the planar inductor increases accordingly, making it impossible to reduce the thickness of the planar inductor.

If the DC superimposition characteristics of the planar inductor are poor as described above, the inductance will decrease and control will become difficult, resulting in DC-DC
Converter efficiency decreases. Therefore, it is inappropriate to apply it as it is to a DC-DC converter or the like.

Therefore, in order to improve the DC superimposition characteristics, it is required that the saturation magnetization of the high magnetic permeability ferromagnetic ribbon be high.

The present invention was made to solve the above problems, and an object of the present invention is to provide a planar inductor with good DC superimposition characteristics.

[Invention configuration con (means and action to solve issues) The present invention is a flat -pale coil or a laminated body, a ferromagnetic thin band or a thinner film, or these laminates through an insulating layer. In a planar inductor sandwiched between two ferromagnetic ribbons or a ferromagnetic thin film, the composition is [Fe x N t , Co
, -x-y ko H-Zr2However, 0.6 <x
<0.9, O<y<0.1.

0, Oli<z<0.14.

Here, the planar conductor coil is usually a spiral two-layer conductor coil having a structure in which spiral coils are provided on the front and back surfaces of an insulating layer and each spiral coil is connected by a through hole, as shown in FIG. refers to

Note that the spiral conductor coil may have only one layer of spiral coils as long as there is no problem in taking out the terminal.

Furthermore, when the spiral conductor coils are stacked, the inductance increases, but in this case, it is desirable that only an insulating layer be interposed between the spiral conductor coils, and that no ferromagnetic ribbon be interposed. This is because interposing a ferromagnetic ribbon between spiral conductor coils hardly contributes to increasing inductance, but rather increases the overall thickness of the planar inductor and lowers the inductance per unit volume. .

In addition, the amorphous alloys with the above compositions were used because these alloys are high magnetic permeability materials with high saturation magnetization.
This is because by using these, a planar inductor with good DC superimposition characteristics of inductance can be obtained.

Investigate the efficiency when planar inductors with the same structure made using ferromagnetic ribbons with different saturation magnetization values are applied to, for example, a two-layer non-insulated step-down DC-DCC with an output voltage of 5 V. and becomes as follows.

A Co-based or Fe-based amorphous alloy thin strip (approximately 15 μm thick) is coated on both sides of a spiral conductor coil (approximately 1 mm thick) with an air-core inductance of 54 μH and a coil resistance of 1.8 Ω via a 7 μl-thick polyimide film. A DC-DC converter is manufactured using a planar inductor sandwiched between five-layer laminates. In this case, the saturation magnetization of the amorphous alloy ribbon is 4πM
s, input voltage 15v1 output voltage 5V, output current 0.4
The relationship between efficiency η of the DC-DC converter under the condition A is as shown in FIG.

From FIG. 2, the efficiency η when using an amorphous alloy ribbon of 4 gMs>10 kG has a substantially constant value of about 70%. However, when an amorphous alloy ribbon of 4 gMs<10 kG is used, the direct current superimposition characteristic of the inductance deteriorates, and the efficiency η decreases.

Therefore, in order to obtain high efficiency when applied to a 1 to 2 WIl&Dc-DC converter, the ferromagnetic material must be at least 10k
A high permeability material with a saturation magnetization of G or higher is required.

On the other hand, for example, [F ex (N
1 + Co) r-z ] +-Z rz-based amorphous alloy (0.8 < x < 0.9, 0.08 <
z < 0.14) is known. These amorphous alloys have a saturation magnetization of 10 kG or more. In addition, these amorphous alloys have lower saturation magnetostriction than Fe-based amorphous alloys containing semimetals and having high saturation magnetization. Therefore, in the exterior resin molding step of the planar inductor manufacturing process, the degree of reduction in inductance due to the inverse magnetostrictive effect that occurs due to contractile force during resin curing is reduced.

For example, even if a stress absorbing material such as a polymer film is provided between the magnetic material and the mold resin for stress relaxation to prevent a decrease in inductance due to molding, the thickness of the polymer film can be made thin, which is convenient for making planar inductors thinner.

Regarding saturation magnetostriction, for example, x-0,9, z = 0゜1
, when the Ni content is 0, the saturation magnetization is 4πMs-12
kG, saturation magnetostriction λS-10
, os) a2s i b B12. Saturation magnetostriction 13
smaller than X 10-6.

Moreover, when x=0.6, z -0,1r Ni content is O, saturation magnetization is 16kG, saturation magnetostriction is 25X1
0-6 and containing a semimetal with the same degree of saturation magnetization, such as Fe 78S i 19B
+3+ Saturation magnetization 15.6kG, Saturation magnetostriction 27×10-
smaller than

That is, when comparing compositions having the same saturation magnetization, the metal-metal amorphous alloy used in the present invention is more advantageous than the metal-semimetal alloy in terms of magnetostriction.

However, when Ni is included, the saturation magnetization is smaller or the saturation magnetostriction is larger than when Ni is not included. Therefore, when applied to the planar inductor of the present invention, it is better to have a smaller Ni content.

In addition, these amorphous alloys are thermally stable and less likely to become brittle than systems containing semimetals. Therefore, from these points as well, it is suitable for application to planar inductors. In other words, it can be seen that it is effective to apply the amorphous alloy having the above-mentioned composition to a planar inductor for a DC-DC converter.

Examples of the present invention will be described below.

Example 1 The composition produced by the single roll method is Fe, 2C.

IgZrlo (atomic ratio), an amorphous ribbon (4 gMs -161 (Q, λS
-25

Next, the external dimension is 10 mm and the number of wires is 40. Coil wire width 2
00μm, coil wire thickness 100μl, coil wire pitch 25
0μ city, base film (3b in Figure 1) thickness 25μ
2 square-shaped double-sided spiral coils (1 in Figure 1)
The two layers were stacked and electrically connected in series via a 7 μl thick polyimide film to produce a planar coil with a total number of turns of 80.

Both sides of this planar coil were sandwiched between the above-mentioned ferromagnetic foils with polyimide films (3g and 3C in FIG. 1) having a thickness of 7 μm interposed therebetween to produce a planar inductor.

Example 2 Amorphous alloy (4π
A planar inductor similar to that in Example 1 was manufactured except that Ms -12kQ, λ5-10xlO-') was used.

Example 3 The flat inductor of Example 2 was sandwiched between 50 μl thick polyphenylene sulfide films (pps films) on both sides, and then an exterior mold was applied with epoxy resin to produce a molded flat inductor.

Comparative example 1 (COo, ssF e 'o, obN i 0.04N
b O,02) 75S floB Amorphous alloy with a composition of 1% (4yr Ms -8,8kG.

A planar inductor was produced in the same manner as in Example 1 except that λ5-0) was used.

Comparative example 2 (F e 0.95N b O, 05) 82S i
Amorphous alloy with a composition of 6 B +2 (4πMs −12k
A planar inductor was produced in the same manner as in Example 1, except that G, λs -13X 1O-6) was used.

Comparative Example 3 The same exterior mold as in Example 3 was applied to the planar inductor of Comparative Example 2 to produce a molded planar inductor.

Comparative Example 4 Amorphous alloy (4πMs -12kG, λ5-16x
A planar inductor was produced in the same manner as in Example 1 except that 1O-6) was used.

Next, an exterior mold was applied in the same manner as in Example 3 to produce a molded planar inductor.

50 kHz for the planar inductors of Examples 1 to 3 and the planar inductors of Comparative Examples 1 to 4 thus obtained.
The DC superposition characteristics of the inductance (DC superposition current I DC-0 to 0.4 A) were investigated.

The obtained results are shown in FIGS. 3 to 5.

FIG. 3 is a characteristic diagram comparing the relationship between inductance and DC superimposed current for the planar inductor of Example 1 and the planar inductor of Comparative Example 1 using a high permeability amorphous alloy containing a semimetal. As is clear from the figure, it can be seen that the planar inductor of Example 1 has much better DC superimposed current characteristics than that of Comparative Example 1.

Figure 4 shows the planar inductor of Example 2.3 and Comparative Example 2.
．． Characteristics comparing the relationship between inductance and direct current superimposed current when using a three-plane inductor and using metal-metal type and metal-semimetal type amorphous alloys with the same saturation magnetization from the perspective of the effect of the exterior mold. It is a diagram.

The metal-metal system with small saturation magnetostriction (Example 2, Example 3) is superior to the metal-semimetal system (Comparative Example 2, Comparative Example 3) because the decrease in inductance due to molding is smaller. I understand.

Figure 5 shows the relationship between inductance and DC superimposed current for a metal-metal amorphous alloy with the same saturation magnetization, when Ni is included (Comparative Example 4) and when Ni is not included (Example 3). It is a comparison diagram after molding. It can be seen that Example 3, which does not contain Ni, is far superior to Comparative Example 4, which contains Ni.

[Effects of the Invention] As explained above, according to the present invention, a planar inductor with good DC superimposition characteristics can be obtained, and a planar inductor that can be applied to a DC-DC converter etc. can be easily provided. This makes it possible to make the converter thinner, and its industrial value is extremely large.

[Brief explanation of drawings]

FIG. 1(A) is a plan view showing the configuration of a planar inductor;
The same figure (B) is a sectional view along the line AA' of the same figure (A),
FIG. 2 is a characteristic diagram showing the relationship between the saturation magnetization of the ferromagnetic material constituting the planar inductor according to the present invention and the efficiency of a non-isolated step-down DC-DC converter to which the planar inductor is applied, and FIGS. FIG. 5 is a characteristic diagram showing the relationship between DC superimposed current and inductance in the planar inductors of the example of the present invention and the comparative example. DESCRIPTION OF SYMBOLS 1... Spiral conductor coil, 2a, 2b... Spiral coil, 3a, 3b, 3c... Insulating layer, 4...
...Through hole, 5a, 5b...Ferromagnetic ribbon. (A) 2b b (B) Saturation magnetization (G) Figure V,) Toguhe 8th section

Claims (1)

[Claims] A planar inductor in which both sides of a planar conductor coil or a laminate thereof are sandwiched between ferromagnetic ribbons, ferromagnetic thin films, or laminates thereof with an insulating layer interposed therebetween, comprising: The composition of the ferromagnetic thin film is [Fe_xNi_yCo_1_-_x_-_y]_1_
−_zZr_zHowever, 0.6<x<0.9, 0<y<0
．． 1. A planar inductor characterized in that it is formed of an amorphous alloy having the following relationship: 0.08<z<0.14.