JPH04179105A - Plane inductor - Google Patents

Abstract

PURPOSE:To obtain a plane inductor which has a low iron loss and high saturation magnetic flux density and is excellent in power supply efficiency and high- frequency soft magnetic characteristic by specifying the surface roughness of a ferromagnetic substance layer. CONSTITUTION:A Co-group amorphous alloy is electrically precipitated on a polyimide film to a film thickness of 0.1-10mum by a plating method. The composition of the alloy is set at (Co0.94Fe0.06)84P16 and the surface roughness of the alloy is set at 0.5m Ra. In addition, the surface is scratched at angles 30-90 deg. against the exciting direction. While a laser beam, electron beam, etc., as applied as preferable scratching means, no specific restriction is imposed on the shape of the scratches.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a planar inductor, particularly a planar inductor used at high frequencies.

(Prior Art) With the recent technological developments for reducing the size and weight of electronic devices and increasing their performance, there is also a demand for smaller size and higher performance for the functional parts that constitute these devices. For example, inductors used in switching power supplies, which are the power supply source for electronic equipment, include main transformers, saturable cores, and choke coils. A magnetic material with low iron loss and excellent DC superimposition characteristics is desired.

Generally, inductors use a toroidal magnetic core wound with thin plates or a ring magnetic core made of hardened powder.
In the former case, the core needs to be tall for ease of winding, and in the latter case, for reasons such as core strength, which poses a bottleneck to miniaturization.

In response, efforts are being made to miniaturize inductance elements by using planar inductors. A specific example is shown in FIG. FIG. 1(A) is a plan view of a planar inductor,
FIG. 1(B) is a cross-sectional view taken along line A-A' of FIG. 1(A). , lb indicate the locus of the center line in the cross-sectional view of the same spiral conductor coils la, lb. The insulating layers 3a, 3b, 3c are formed of a dielectric material etc. Both spiral conductor coils la,
lb is electrically connected via a through hole 4, and constitutes an inductor between terminals 5a and 5b provided at each end.

However, when considering the application of a planar inductor made of ferrite as a DC/DC converter, for example, it is difficult to realize miniaturization such as reduction in height due to the mechanical strength or saturation magnetic flux density of ferrite.

Therefore, an amorphous alloy ribbon is currently being considered as the ferromagnetic layer in the above technology. This amorphous smooth alloy layer is produced by a liquid quenching method.

However, as in the case of ferrite, for example, DCD
When a planar inductor made of the above amorphous magnetic alloy layer is used as a C converter, there is a problem in that its efficiency is not sufficient compared to the case where an inductor made of current ferrite is used as a DC/DC converter.

(Problems to be Solved by the Invention) As described above, the power supply efficiency of conventional planar inductors using amorphous alloy ribbons was not sufficient compared to those using ferrite.

The present invention was made to solve the above problems, and by making a scratch at an angle of 30 to 90°C with respect to the excitation direction of a ferromagnetic layer with excellent surface properties in a planar inductor, The purpose of this invention is to improve high-frequency soft magnetic properties, to provide a compact magnetic component with excellent magnetic properties, and to provide a highly efficient power supply for electronic devices.

[Structure of the Invention] (Means and Effects for Solving the Problem) As a result of intensive research into planar inductors by the present inventors, it was found that Scratching at an angle of ~90° reduces eddy current loss, resulting in an inductor with low core loss, high saturation magnetic flux density, and excellent high-frequency soft magnetic characteristics. When used in, for example, a DC-DC converter, it has high efficiency. We have discovered that it is possible to achieve

That is, the present invention provides a planar inductor in which both surfaces of a spiral conductor coil are sandwiched between ferromagnetic layers with an insulating layer interposed therebetween, in which the surface roughness of the ferromagnetic layer is Ra of 0.5 μm or less; 30~ with respect to the excitation direction of the ferromagnetic layer
The scratch is made at an angle of 90°, and the ferromagnetic layer is made of a Co-based amorphous alloy having a thickness of 0.1 to 10 μm.

In the present invention, the surface roughness of the ferromagnetic layer is preferably 0.5 μm or less in terms of Ra (center line average roughness).

This is because surface smoothness is important from the viewpoint of magnetic properties when laminating layers, and preferably -4 to 0.3 μm or less, more preferably 0.1 μm or less.

Since this surface roughness also affects soft magnetic properties such as iron loss of the material, it is desirable that the surface roughness falls within the above range.

Also, the angle of the scratch with respect to the excitation direction is 30 to 90
° is preferred. In particular, high frequency iron loss on the plating film can be reduced by making scratches at angles within this range. More preferably, it is 40 to 80 degrees. A specific example is shown in FIG.

As a means for scratching, laser irradiation, electron beam irradiation, etc. are preferable, and the shape of the scratch may be dotted, linear, linear, curved, etc., and there is no particular ilJ shape. The scratched state can be controlled by the irradiation energy beam diameter.

Further, the ferromagnetic layer used in the present invention is preferably made of an amorphous alloy that exhibits excellent magnetic properties at high frequencies, particularly an amorphous alloy based on CO.

In addition, the film thickness of the alloy used in the present invention can be controlled by the electrodeposition time, but from the viewpoint of magnetic properties at high frequencies,
], Oμm range is preferable. 0.1. prr+ below-
This is because when the diameter is 10 -, the proportion occupied by the magnetic material becomes small, so the total magnetic flux becomes a problem, while when the diameter is 10 μm or more, a sufficiently low iron loss cannot be obtained. More preferably, it is 05 to 5 μm.

The amorphous alloy of the present invention that satisfies all of these conditions can be obtained by the plating method. The plating method is also excellent in terms of mass production, and it is preferable to form the conductor coil and the ferromagnetic layer by the plating method.

Next, specific manufacturing conditions of the present invention will be described.

The preferred electrolytic deposition conditions for producing an amorphous alloy in carrying out the present invention are Fe concentration of about 1/100-3 mol/e and Co concentration of about 1/100-3 mol/e. If the metal ion concentration in the plating bath is lower than this concentration range, it will be difficult to form a plating film, and the state of the film formation will also deteriorate.

If this concentration range J: is too high, it becomes difficult for the salts of these metal ions to dissolve in the plating solution.

More preferable conditions include Fe concentration of about 1. /30-1/10mol/4'C
o Concentration: Approximately 1/10-1゜mol/6 is good.

The concentration of phosphorous acid and/or phosphite or hypophosphorous acid and/or hypophosphite is preferably about 1/20 to 5 mol/4'. If the concentration of phosphorous acid or hypophosphorous acid is lower than this range, an amorphous alloy cannot be formed and the state of film formation is also poor. If it is higher than this range, the current efficiency will decrease and the state of film formation will also deteriorate.

More preferable conditions are approximately 1. /1.0~1. /2m
ol/e is good.

Electrodeposition conditions are pH1.0-22 Current density 1-40A/dm ) Tani) Seed 20-80°C is desirable.

When the pH deviates from the above range and becomes 10 or less, hydrogen generation on the working electrode becomes excessive, the current efficiency decreases, and the plating becomes extremely difficult to adhere to. Moreover, when the pH exceeds 2.2, the current efficiency is improved, but the phosphorus content in the alloy decreases, and the alloy becomes amorphous. Telephone, i'L
If the density is lower than the above range, plating will be difficult; if the density is higher than the above range, stress will accumulate in the plating film, and in severe cases, cracks may occur. If the bath temperature is lower than the above range,
It is difficult to form a film with excellent surface smoothness, and if the temperature is higher than the above range, precipitation (precipitate) is likely to form in the plating bath, making it difficult to control the plating bath. pH: 1.6 - 3 - 1.6 Current density: 3 - 20 A/dm - Crystal: 40 - 60°C.The composition of the deposited alloy can be easily adjusted by changing the composition of the electrodeposition bath.

The ferromagnetic layer used in the present invention has the general formula: (Cot-xFex)1oo-A(P+-yYy)AY
: At least one selected from B, C, and Si 0≦X
An amorphous alloy represented by ≦1, 0≦y≦0.50, 10≦A≦25 (at, %) is preferable. More preferably, the general formula: (Coi-a-bFeaMb)1oo-x(Pi-cY
c) xM: Ni, Cr, W, Cu, Zn, Mo, SnY
:At least one selected from B, C, and Si0.
A Co-based amorphous alloy represented by the following formulas: 02≦a≦008 0≦b≦010 0≦C≦0.50 10≦X≦25 (at %) is preferable.

In the above formula, Fe is an element that makes magnetostriction zero, and its content is preferably in the range of 0.02 to 0.08. More preferably, it is in the range of 0.04 to 0.07.

M is an element effective in raising the crystallization temperature of the amorphous alloy and improving soft magnetic properties at high frequencies, but its content is preferably 0.10 or less. More preferably it is 0.08 or less. P and Y are effective elements for amorphization, but especially P is an essential element when using the plating method, and up to 50% of this can be replaced with elements such as B, C, and Si.

Further, it is preferable that the total amount X of P and Y be in the range of -0≦X≦25 in order to promote amorphization.

A more preferable range is ]2≦X≦20.

As a method for producing the above-mentioned amorphous alloy, a film having a desired thickness can be formed on an electrode by electrolytic deposition from a solution containing ions of alloy components. At this time, by setting the surface finish of the electrode to 1.0 μm or less, a film with excellent surface properties can be created.

When laminating amorphous alloys, it is preferable to interpose an insulating layer between the ferromagnetic layer and the conductor coil, but this can be achieved, for example, by selectively using electrolytic plating and electroless plating. Alternatively, an amorphous alloy and an organic polymer film may be alternately laminated, or a predetermined amorphous alloy may be formed on an organic polymer film and then laminated. The organic polymer film is not particularly limited, but polyj-nytylene, polypropylene, polyconistyl, polyimide, etc. are preferred, and polyimide is particularly preferred when heat treatment is required.

Moreover, a long sample can also be obtained by continuously peeling the obtained plating film from the electrode. The thickness of the alloy can be controlled by the electrodeposition conditions (time, current value, etc.).

(Example) The invention will be illustrated by the following examples.

[Example 1 and Comparative Example 1] 5) A Co-based amorphous alloy having a thickness of 21"m was electrodeposited on a polyimide film of 21"m by a plating method. The alloy composition is (Coo94Feo, o6)s4P+6, and the surface roughness is 02zem in Ra.

Similarly, spiral coils of Cu were produced on both sides of the polyimide film by the plating method. A DCDC converter shown in FIG. 2 was manufactured by laminating five layers of amorphous alloy sheets above and below this sheet, and as a result of evaluating the power supply efficiency, an efficiency of 78% was obtained.

For comparison, the plate thickness is 2011 m and the surface a is 11.
When a 5 μm Co-based amorphous alloy ribbon was evaluated with the ferromagnetic layers having the same thickness, the power supply efficiency was 72%.

[Example 2 and Comparative Example 2J 1.
A Co-based amorphous alloy with a film thickness of 5 μm was electrodeposited.

The alloy composition is (Coo94Feo, o6)soP2o, and the surface roughness is Ra: O0]) Yum.

Similarly, spiral coils of Cu were produced on both sides of the polyimide film by the plating method. Five layers of amorphous alloy sheets were stacked above and below this sheet to produce a DCDC converter as shown in FIG. 2, and the power efficiency was evaluated. Incidentally, scratches as shown in FIG. 3 were made in these ferromagnetic layers by laser treatment.

As a result, the efficiency of the DC-DC converter was 79%.

For comparison, a film thickness of 2.5 μm and a surface roughness of R were obtained using the same method.
A Co-based amorphous alloy of the same composition with a diameter of 09 μm was
A DCDC converter having a similar structure was produced by electrodeposition on a μm polyimide film by a plating method. In addition,
These ferromagnetic layers were also scratched by laser treatment as shown in FIG.

When this power supply efficiency was evaluated, it was 73%.

[Effects of the Invention] As described above, according to the present invention, it is possible to obtain a planar inductor with low iron loss, high saturation magnetic flux density, high power efficiency, and excellent high frequency soft magnetic characteristics, and its usefulness is extremely high. be.

[Brief explanation of the drawing]

FIG. 1(A) is a plan view of the planar inductor of the present invention, FIG. 1(B) is a cross-sectional view of the planar inductor of the present invention, and FIG.
The figure is a circuit diagram of a DCDC converter used to evaluate the planar inductor of the present invention, and FIG. 3 is a diagram showing the surface of the planar inductor with scratches. la, lb... Conductor coil 4...
Through poles 2a, 2b... Magnetic layer
5a, 51)..., terminals 3a, 3b,
3c... Insulating layer 6... Magnetic layer m
Goko [)

Claims (1)

[Claims] 1) With an insulating layer on both sides of the spiral conductor coil,
1. A planar inductor sandwiched between ferromagnetic layers, wherein the ferromagnetic layers have a surface roughness of 0.5 μm or less in terms of Ra. 2) The planar inductor according to claim 1, wherein the scratch is made at an angle of 30 to 90 degrees with respect to the excitation direction of the ferromagnetic layer. 3) The planar inductor according to claim 1, wherein the ferromagnetic layer is made of a Co-based amorphous alloy. 4) The planar inductor according to claim 1, wherein the ferromagnetic layer has a thickness of 0.1 to 10 μm.