JPH0945531A - Thin laminated coil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a thin laminated coil in which the interlayer distance between double-sided boards constituting a multilayer board is reduced, in which the thickness of the multilayer board can be made thin and the electric and magnetic coupling degree of respective coil patterns can be increased. SOLUTION: Surface coil patterns 7B1, 7C1, rear-surface coil patterns 7B2, 7C2 and dummy patterns 13, 13 which are insulated electrically from the patterns 7B1 to 7C2 are formed on every surface and every rear surface of double-sided boards 6B, 6C. Thereby, a part into which a prepreg 14 creeps can be made thin, and the double-sided boards 6B, 6C can be laminated without a gap even when the thickness B of the prepreg 14 is made small. Then, a multilayer board is made thin, the insulating strength and the bonding strength of the patterns 7B1 to 7C2 are increased, and the electric and magnetic coupling degree of the patterns is increased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin laminated coil in which a multilayer substrate formed by laminating a plurality of double-sided substrates each having a coil pattern is used as a coil.

[0002]

2. Description of the Related Art Generally, an electronic circuit is constructed by mounting a plurality of electronic parts, electric circuit elements, etc. on an insulating substrate, but it is formed separately when the electronic circuit requires an inductance. A method of mounting or connecting the coil on an insulating substrate is used. However, in this case, since the coil itself is bulky, there is a problem that the mounting space when mounted on the board becomes large.

In order to solve this problem, for example, JP-A-48-51250 and JP-A-5-183274 disclose a plurality of double-sided substrates and a conductive thin film on the upper and lower surfaces of each double-sided substrate. There is known a thin laminated coil including a coil pattern formed by the above and an interlayer plate body provided between the double-sided boards for laminating the double-sided boards so that the respective coil patterns overlap each other. There is.

Each of the double-sided boards is a multi-layer board by connecting the coil patterns formed on the upper and lower surfaces thereof through through holes, blind via holes, inner via holes, etc., respectively. Is formed as. Then, the thin laminated coil can be configured as a thin laminated coil which is downsized.

Here, a conventional thin laminated coil is shown in FIGS. 7 to 17.

In the figure, reference numeral 1 denotes a conventional thin laminated coil, which is a multilayer substrate 2 having a substantially square shape.
And a core 3 attached to the multilayer substrate 2.

Here, the multi-layer substrate 2 is formed by stacking a plurality of (for example, five) double-sided substrates 6A, 6B, ..., 6E, which will be described later, to form a multi-layer substrate having a coil pattern of 10 layers. As shown in FIG. 8, the multi-layer substrate 2 has a circular core insertion hole 2A formed in the center thereof and rectangular core insertion grooves 2B, 2B formed on the left and right outer sides, and is formed in the front and rear. Five through holes 2C and 2 each
C, ... Are drilled.

As shown in FIG. 9, the core 3 is composed of a core member 4 having an E-shaped cross section and a core member 5 having an I-shaped cross section. A cylindrical portion 4A to be inserted into the core insertion hole 2A and rectangular prism portions 4B and 4B to be inserted into the core insertion grooves 2B and 2B of the multilayer substrate 2 are formed on both sides.

Reference numerals 6A, 6B, 6C, 6D, and 6E denote first to fifth double-sided boards as shown in FIGS.
The double-sided boards 6A to 6E are each formed of an insulating resin (for example, a glass epoxy material) in a substantially square shape.

7A1, 7B1, 7C1, 7D1, 7E1
Is an upper surface coil pattern formed in the central portion of the upper surfaces of the first to fifth double-sided boards 6A to 6E, 7A2, 7B2, 7C2,
7D2 and 7E2 are the same as the first to fifth double-sided boards 6A to 6
Each of the upper surface coil patterns 7A1 to 7E1 and the lower surface coil patterns 7A2 to 7E2 is a conductive thin film having a film thickness a (see FIG. 14) of, for example, about 70 μm. (For example,
(Copper foil) is formed in a spiral shape.

Further, referring to the first to fifth double-sided boards 6A to 6E, the first double-sided board 6A has, as shown in the plan view of FIG. 11, an upper surface in a clockwise direction around the core insertion hole 2A. A spiral upper coil pattern 7A1 is formed on the lower surface, and a spiral lower coil pattern 7A2 is formed on the lower surface in a counterclockwise direction (clockwise when viewed from the lower surface) around the core insertion hole 2A. ing. The upper coil pattern 7A1 and the lower coil pattern 7A2 are connected in series via the inner via hole 6A1.
The first double-sided board 6A and the fifth double-sided board 6E are the same, and the front and rear sides of the first double-sided board 6A are reversed and used to form the fifth double-sided board 6E.

The second double-sided board 6B is shown in FIG.
As shown in the plan view of FIG. 2, a spiral upper coil pattern 7B1 is formed on the upper surface of the double-sided board 6B so as to reduce the diameter of the periphery of the core insertion hole 2A in the clockwise direction.
A spiral lower surface coil pattern 7B2 is formed so as to reduce the diameter of the circumference thereof in the counterclockwise direction (clockwise when viewed from the lower surface). The upper coil pattern 7B1 and the lower coil pattern 7B2 are connected in series via the inner via hole 6B1. The second double-sided board 6B and the fourth double-sided board 6D are the same, and the second double-sided board 6
A fourth double-sided substrate 6D is obtained by inverting and using the front and rear of B.

Further, the third double-sided board 6C is shown in FIG.
As shown in the plan view of FIG. 3, on the upper surface, a spiral upper surface coil pattern 7 having a diameter reduced in the clockwise direction around the core insertion hole 2A is formed.
C1 is formed, and a spiral lower surface coil pattern 7C2 is formed on the lower surface so as to reduce the diameter around the core insertion hole 2A in the counterclockwise direction (clockwise from the lower surface). The top coil pattern 7C1 and the bottom coil pattern 7C2 are connected in series through the inner via hole 6C1.

Also in the fourth double-sided board 6D, the upper surface coil pattern 7D1 and the lower surface coil pattern 7D2 are connected in series via an inner via hole (not shown), and the upper surface of the fifth double-sided board 6E is also formed. The coil pattern 7E1 and the lower surface coil pattern 7E2 are connected in series via an inner via hole (not shown).

The first to fifth double-sided boards 6A to 6E are also provided.
In the stage before coiling, a large number of double-sided substrates are simultaneously molded from one substrate and then cut.
A, each core insertion groove 2B and each through hole 2C are not formed.

Reference numerals 8A, 8B, 8C and 8D denote thin plate prepregs serving as interlayer plates provided between the first to fifth double-sided boards 6A to 6E, respectively.
D is, for example, about 50-60% of epoxy resin on glass fiber
The thickness b is formed by impregnation. Then, between the double-sided boards 6A and 6B, between 6B and 6C, 6
Between C and 6D, between 6D and 6E prepreg 8A, 8
B, 8C, and 8D are provided, and the double-sided boards 6A to 6E are laminated by the prepregs 8A to 8D by applying heat and pressing. After that, steps such as drilling the entire hole, plating, and etching the outermost layer are performed, and the multilayer substrate 2 shown in FIG.
To form Therefore, the prepregs 8A to 8D are provided between the double-sided boards 6A to 6E facing each other.

Furthermore, 9A is a double-sided substrate 6A which is the outermost layer.
A resist film formed on the upper surface of the double-sided substrate 6E and a resist film 9B formed on the lower surface of the double-sided substrate 6E, respectively, are insulated from external members by the resist films 9A and 9B.

In the thin laminated coil 1 thus constructed, metal pins (not shown) are provided in each through hole 2C, and the metal pins are connected to the upper coil patterns 7A1 to 7E1.
And the lower surface coil patterns 7A2 to 7E2 are respectively connected to generate an inductance required for an electric circuit. For example, when a large inductance is required, a large magnetic field can be generated by connecting the upper coil patterns 7A1 to 7E1 and the lower coil patterns 7A2 to 7E2 in series.

[0019]

In the thin laminated coil 1 according to the prior art described above, the prepregs 8A, 8B, 8C, 8 are provided between the first to fifth double-sided boards 6A to 6E.
Since the multilayer substrate 2 is formed by providing D respectively and laminating the double-sided substrates 6A to 6E, the interlayer distance c is almost determined by the thickness b of the prepreg.

For example, as shown in FIGS. 14 and 15, when the second double-sided board 6B and the third double-sided board 6C are laminated, the prepreg 8B has a film thickness of the lower surface coil pattern 7B2 and the upper surface coil pattern 7C1. a (about 70μ
In consideration of m), it is necessary to select the prepreg 8B so that the epoxy resin in the glass fiber remains even after the epoxy resin leaks to the surroundings when pressed. For this reason, the interlayer distance c of the multilayer substrate 2 has a substantially fixed thickness, and the thickness dimension of the multilayer substrate 2 becomes large.

Further, when the interlayer distance c becomes thicker, the upper surface coil patterns 7A1 to 7E1 and the lower surface coil pattern 7A are formed.
In 2 to 7E2, there is a problem that the degree of mutual electrical and magnetic coupling is lowered.

Here, in order to solve the above-mentioned problem, for example, between the second double-sided board 6B and the third double-sided board 6C, as shown in FIGS. It is conceivable to use a prepreg 8B ′ having a thickness b ′ formed to be thinner than the thickness b of the prepreg 8B in order to reduce the thickness of the prepreg 8B ′. However, in this case, the amount of the epoxy resin contained in the prepreg 8B 'having the thickness b', after pressing, the lower surface coil pattern 7B2 and the double-sided substrate 6
Step with B, top coil pattern 7C1 and double-sided board 6C
It is not possible to completely fill the epoxy resin into every corner such as the stepped portions of and, and there are innumerable voids S, S, ... Between the double-sided boards 6A and 6B. As a result, there is a problem that air enters into each void S and the withstand voltage level is significantly lowered.

Further, the air in these spaces S causes the thin laminated coil 1 to be warmed by the influence of the outside to cause thermal expansion, thereby weakening the adhesive strength and significantly shortening the life of the thin laminated coil 1. There's a problem.

Further, if the epoxy resin with which the void S is impregnated in the prepreg 8B 'is prepared from among the double-sided boards 6A to 6E,
Even if it can be filled between the substrates facing each other, there is a problem that the prepreg 8B 'between the coil patterns 7B2 and 7C1 is made of only glass fiber and the interlayer withstand voltage cannot be secured.

The present invention has been made in view of the above-mentioned problems of the prior art. The present invention reduces the interlayer distance between the double-sided boards to reduce the thickness of the multi-layered board, and also improves the electrical and magnetic properties of the coil pattern. It is an object of the present invention to provide a thin laminated coil capable of increasing a high degree of coupling.

[0026]

In a thin laminated coil according to the present invention, a plurality of double-sided boards, a coil pattern formed of a conductive thin film on the upper and lower surfaces of each double-sided board, and the respective coil patterns overlap each other. As described above, the double-sided board is formed by stacking the double-sided board and the interlayer plate body provided between the double-sided boards.

Then, in order to solve the above-mentioned problems,
The feature of the configuration adopted by the invention of claim 1 is that among the double-sided boards, at least upper and lower surfaces of the double-sided boards facing each other are provided with dummy patterns electrically disconnected from the coil patterns. is there.

According to a second aspect of the present invention, each of the double-sided boards is formed in a rectangular shape, the coil pattern is formed at a central portion of the double-sided board, and the dummy patterns are formed on four sides of the double-sided board. It is located and formed.

In the invention of claim 3, the dummy pattern is formed around the coil pattern.

[0030]

According to the first aspect of the present invention, by providing the dummy patterns on the upper and lower surfaces of the double-sided board, the electrical insulation of which is cut off from the coil pattern, the interlayer board is provided between the double-sided boards. When pressed, the dummy pattern is formed by replacing the portion where the interlayer plate should originally be interposed, and the thickness of the interlayer plate is larger than that of the conventional interlayer plate because the dummy pattern is provided. The thickness can be reduced. In this way, by thinning the portion where the interlayer plate is interposed between the double-sided substrates, the amount of resin filled in the interlayer plate can be reduced, and the dummy pattern acts as a dam to impregnate the interlayer plate. It is possible to prevent resin and the like from leaking to the surroundings. Therefore, it is possible to stack the double-sided boards without gaps while filling the interlayer plate up to the vicinity of the coil pattern of the double-sided board and keeping the interlayer distance between the double-sided boards thin.

Since the coil pattern is formed at the center of the double-sided board and the dummy patterns are formed on the four sides of the double-sided board, the dummy pattern is formed between the double-sided boards. Moreover, the interlayer plates can be laminated without any voids, and external moisture can be prevented from entering from the four sides of the double-sided substrate.

Since the dummy pattern is formed around the coil pattern as in the invention of claim 3, when the dummy pattern and the coil pattern are formed, a conductive thin film is formed on the substrate and the conductive thin film is formed. Each pattern can be easily formed by etching and removing the portion between the dummy pattern and the coil pattern.

[0033]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. In the present embodiment, the first to
The fifth double-sided substrates 6A to 6E, and the upper surface coil patterns 7A1 to 7E1 and the lower surface coil patterns 7A2 to 7E2 formed on the upper and lower surfaces thereof with the same film thickness A as the conventional film thickness a (for example, 70 μm). For configuration,
Since there is no difference from the conventional technique, the double-sided boards 6A to 6E and the upper surface coil pattern 7 are also used in this embodiment.
A1 to 7E1 and bottom coil pattern 7A2 to 7E2
As for the above, the same components as those of the above-described conventional technique are denoted by the same reference numerals, and the description thereof will be omitted.

In the figure, reference numeral 11 denotes a thin laminated coil according to the present embodiment, and the thin laminated coil 11 is roughly composed of a multilayer substrate 12 and a core (not shown), similar to the conventional thin laminated coil 1. Has been done. Here, the multi-layer substrate 12 of this embodiment is a plurality of (for example, five) double-sided substrates 6.
By stacking A, 6B ,.
A multi-layer substrate having a layered coil pattern is formed. As shown in FIG. 2, the multi-layer substrate 12 has a circular core insertion hole 12A formed in the center thereof, and rectangular core insertion grooves 12B, 12B formed on the left and right outer sides. 5 through-holes 1 each on the front and back
2C, 12C, ... Are drilled.

.. show dummy patterns formed on at least the upper and lower surfaces of the facing double-sided boards of the double-sided boards 6A to 6E. The dummy patterns 13 are the upper surface coil patterns 7B1 to 7E1 and the lower surface. These coil patterns 7B1 to 7E are separated from the coil patterns 7A2 to 7D2 and are electrically disconnected.
The same film thickness A as 1, 7A2 to 7D2 (for example, 70 μm)
Of the conductive thin film (copper foil), and the double-sided boards 6A to 6A from around the coil patterns 7A2 to 7E1.
It is formed so as to extend to the four sides of E.

The upper surface of the double-sided substrate 6A is coated with a resist film 9A as in the prior art, and the lower surface of the double-sided substrate 6E is coated with a resist film 9B.

Here, in FIG. 2, the portion of the second double-sided substrate 6B on which the dummy pattern 13 is formed is shown by hatching. The dummy pattern 13 is formed up to the position of the core insertion hole 12A and each core insertion groove 12B, which is the end portion, and the dummy pattern 13 is electrically insulated from the coil patterns 7A1 to 7E2. There is.

That is, the dummy pattern 13 is the longest dummy pattern 1 located between the peripheral dummy pattern 13A located on the four sides of the double-sided substrate 6B and the coil pattern 7B1.
3B and a circular dummy pattern 13C located in the coil pattern 7B1.

Reference numeral 14 denotes a prepreg as an interlayer plate provided between the double-sided boards 6A to 6E.
Is, for example, glass fiber and epoxy resin, for example, 50 to 60
% Impregnated, the double-sided substrates 6A to 6E are laminated by applying heat and pressing. Further, the prepreg 14 has a structure shown in FIGS.
Since the thin prepreg having the same thickness B'as the thickness b'of the prepreg 8B 'shown in FIG. 7 is used, the multilayer substrate 12 can be thin.

Further, as shown in FIG. 2, the dummy pattern 13 is formed by a copper foil so as to cover almost all other portions of the double-sided substrate 6B which are separated from the upper surface coil pattern 7B1. Therefore, the upper surface coil pattern 7B1 is formed. When the patterning is performed by etching, the upper surface coil pattern 7B1 and the dummy pattern 13 can be simultaneously formed by melting the copper foil between the upper surface coil pattern 7B1 and the dummy pattern 13.

The double-sided boards 6A to 6E constituting the multi-layer substrate 12 of the thin laminated coil 11 are formed as described above, and the basic operation of the thin laminated coil 11 is different from that of the prior art. Absent.

Here, as shown in FIGS. 3 and 4 exemplifying the double-sided boards 6B and 6C, the lower surface coil pattern 7B2 is formed.
Since the dummy pattern 13 and the upper coil pattern 7C1 and the dummy pattern 13 are made of copper foil having the same film thickness A, each surface of the double-sided boards 6B and 6C has coil patterns 7B1 to 7C2 and a dummy pattern 13, respectively. The surface is almost flat except for the gap.

Therefore, when the prepreg 14 is sandwiched and laminated between the double-sided substrates 6B and 6C, the prepreg 14 can be made thin because the thickness of the prepreg 14 is such that only substantially flat surfaces are bonded. . Moreover, the portion of the prepreg 14 which is filled with the epoxy resin is only a minute portion between the coil patterns 7B1 to 7C2 and the dummy pattern 13, and the amount of the epoxy resin contained in the prepreg 14 is also small and filled without voids. be able to. Further, since the dummy pattern 13 serves as a barrier for the epoxy resin flowing out from the prepreg 14, the thickness B of the prepreg 14 can be made thin and the interlayer distance C can be made thin.

As a result, when the double-sided substrates 6A to 6E are formed in multiple layers by the prepreg 14, the multi-layer substrate 12 having no void can be formed in an ultrathin shape.

Since the dummy patterns 13 are formed as peripheral dummy patterns 13A on four sides up to the positions of four sides such as the core insertion hole 12A and each core insertion groove 12B, the dummy patterns 13 and the prepreg 14 fix the dummy patterns 13 without gaps. The adhesive strength between the double-sided boards 6B and 6C can be enhanced, and external moisture can be surely prevented from invading from the four sides to prevent the upper surface coil patterns 7B2 and 7C1 from corroding and breaking. The life of the double-sided boards 6B and 6C can be extended.

Next, in order to form patterns on the upper and lower surfaces of the double-sided boards 6B and 6C, after forming copper foils as conductive thin films on the upper and lower surfaces of the double-sided boards 6B and 6C, the upper surface coil pattern 7B1 is formed. , 7C1 and the dummy patterns 13 and 13 and between the lower surface coil patterns 7B2 and 7C2 and the dummy patterns 13 and 13 can be easily formed by etching and melting, and the manufacturing cost of the double-sided boards 6B and 6C can be improved. Can be reduced.

Thus, in this embodiment, among the double-sided boards 6A to 6E constituting the multilayer board 12, at least upper surface coil patterns 7B1 to 7E1 having a film thickness A formed on the upper surfaces of the double-sided boards 6B to 6E facing each other, and the double-sided boards. Substrates 6A-6
Lower surface coil pattern 7A2 of film thickness A formed on the lower surface of D
Dummy patterns 13 having the same film thickness A are respectively formed in the vicinity of .about.7E2. When the double-sided boards 6A to 6E are laminated by the prepreg 14, the double-sided board 6A
Since each dummy pattern 13 is replaced in a portion where the prepreg 14 originally exists between the upper and lower surfaces of 6E to 6E, even if the prepreg 14 is thinned to a thickness B, the prepreg 1
Double-sided boards 6A to 6E depending on the amount of epoxy resin impregnated in 4
It can be fully filled in between.

Further, since the portion filled with the epoxy resin impregnated in the prepreg 14 can be thinned by each dummy pattern 13, the resin can be sufficiently filled even if the resin filling amount is small, and at the same time each dummy pattern is filled. 1
3 serves as a dam, which can prevent the epoxy resin from leaking to the surroundings.
It is possible to stack with high adhesion strength and insulation strength without gaps.

Further, in the multilayer substrate 12 according to the present embodiment, not only the interlayer distance C can be thinly laminated between the double-sided substrates 6A to 6E by the prepreg 14, but also the double-sided substrates 6A to 6E.
The double-sided substrates 6A to 6E can be laminated without gaps between Es.
It is possible to increase the bonding strength between the coil patterns 7A2 and 7B1, 7B2 and 7C1, and 7C2.
And 7D1 and between 7D2 and 7E1 can be increased. As a result, the life of the multilayer substrate 12 can be extended, and the reliability of the thin laminated coil 11 can be improved.

Further, since the interlayer distance C can be reduced while improving the insulating property between the double-sided substrates 6A to 6E, the degree of electrical and magnetic coupling of the coil transformer can be increased, and the thin laminated coil 11 can be obtained. Can be configured as an ultra-thin coil with high inductance.

Further, since each dummy pattern 13 is formed up to four sides such as the core insertion hole 12A and each core insertion groove 12B which are the end portions of the double-sided boards 6A to 6E, the dummy pattern 13 and the prepreg 14 are used. Double-sided board 6A
Stacked without gaps at the four side positions of ~ 6E, double-sided board 6A
It is possible to increase the adhesive strength between 6E and 6E, to reliably prevent external moisture from entering from the four sides, to prevent the coil patterns 7A2 to 7E1 from corroding and breaking due to moisture, and The life can be extended.

On the other hand, since the dummy pattern 13 is formed of a conductive thin film and is electrically insulated from the coil patterns 7A2 to 7E1, the dummy pattern 13 blocks the leakage magnetic field between the coil patterns 7A1 to 7E2. You can Further, when the coil patterns 7A1 to 7E2 generate heat, a heat radiation function can be provided as a heat sink.

The dummy pattern 13 of the above embodiment is used.
The longest dummy pattern 13B is formed between the coil patterns 7B1 as shown in FIG. 2, but the present invention is not limited to this, and the dummy pattern 23 shown in the first modification of FIG. Alternatively, the peripheral dummy pattern 23A and the circular dummy pattern 23C may be formed at two locations.

Further, in the above embodiment, the cylindrical portion 4 of the core 3 is
In order to wind the coil pattern 7B1 around A, the coil pattern 7B1 is wound in a spiral shape, but the present invention is not limited to this, and as shown in the second modification of FIG. In this case, the upper surface coil pattern 7B1 of the double-sided substrate 6B may be formed in a rectangular shape, and the dummy patterns 33 may be formed on four sides around the upper surface coil pattern 7B1. Further, the coil pattern may be formed to be wound at an angle of 1 turn or less.

[0055]

As described above in detail, according to the first aspect of the present invention, by forming a dummy pattern, which is electrically disconnected from the coil pattern, on each of the upper and lower surfaces of the double-sided substrate, each double-sided substrate is formed. When the interlayer board is laminated with the interlayer board provided therebetween, the interlayer board can be thinly formed by the dummy pattern formed in the portion where the interlayer board should originally be interposed. It is possible to reduce the amount of resin to be filled and to prevent the resin impregnated in the interlayer plate body from leaking to the surroundings by blocking the dummy pattern. Therefore, the resin of the interlayer plate can be reliably filled up to the vicinity of the coil pattern of the double-sided board, and the double-sided board can be stacked without a gap while keeping the interlayer distance between the double-sided boards thin, and the insulation strength between the coil patterns can be improved. Along with
The degree of electrical and magnetic coupling between the coil patterns can be increased.

Since the coil pattern is formed at the center of the double-sided substrate and the dummy patterns are formed on the four sides of the double-sided substrate as in the second aspect of the invention, the interlayer plate is provided between the patterns. Since the layers can be laminated by the body without voids, it is possible to prevent external moisture from entering between the substrates from the paper surface of the double-sided substrate, prevent the corrosion of the coil pattern due to the moisture, and prolong the service life.

Since the dummy pattern is formed around the coil pattern as in the third aspect of the invention, when the dummy pattern is formed, a conductive thin film is formed on the upper and lower surfaces of the substrate to form the dummy pattern. By removing the portion between the coil pattern and the coil pattern by etching, each pattern can be easily formed, and the manufacturing cost can be reduced.

[Brief description of drawings]

FIG. 1 is an enlarged vertical sectional view showing a multi-layer substrate that constitutes a thin laminated coil according to an embodiment.

FIG. 2 is a plan view showing a state in which a dummy pattern is formed on a double-sided substrate of a thin laminated coil according to an example, with diagonal lines.

FIG. 3 is a vertical cross-sectional view showing a state before laminating the double-sided substrates.

FIG. 4 is a vertical cross-sectional view showing a state in which double-sided substrates are stacked.

FIG. 5 is a plan view showing a state in which a dummy pattern is formed on a double-sided substrate of a thin laminated coil according to a first modification, as indicated by diagonal lines.

FIG. 6 is a plan view showing a state in which a dummy pattern is formed on a double-sided substrate of a thin laminated coil according to a second modified example, with diagonal lines.

FIG. 7 is a perspective view of a conventional thin laminated coil.

8 is a cross-sectional view as viewed from the direction of arrows VIII-VIII in FIG. 7;

9 is a vertical sectional view as seen from the direction of the arrow IX-IX in FIG. 7.

10 is an enlarged cross-sectional view of the multilayer substrate showing an enlarged portion a in FIG.

FIG. 11 is a plan view showing a coil pattern formed on a first double-sided board.

FIG. 12 is a plan view showing a coil pattern formed on a second double-sided board.

FIG. 13 is a plan view showing a coil pattern formed on a third double-sided board.

FIG. 14 is a vertical cross-sectional view showing a state before laminating the double-sided substrates.

FIG. 15 is a vertical cross-sectional view showing a state in which double-sided substrates are stacked.

FIG. 16 is a vertical cross-sectional view showing a state before laminating the double-sided substrates when the prepreg is thinned.

FIG. 17 is a vertical cross-sectional view showing a state in which double-sided substrates are laminated when the prepreg is thinned.

[Explanation of symbols]

6A, 6B, 6C, 6D, 6E Double-sided substrate 7A1, 7B1, 7C1, 7D1, 7E1 Upper surface coil pattern 7A2, 7B2, 7C2, 7D2, 7E2 Lower surface coil pattern 11 Thin laminated coil 12 Multilayer substrate 13, 23, 33 Dummy pattern 14 Prepreg (interlayer plate)

Claims (3)

[Claims] 1. A plurality of double-sided boards, a coil pattern formed of a conductive thin film on the upper and lower surfaces of each double-sided board, and the double-sided board so that the coil patterns overlap each other. In a thin laminated coil including an interlayer plate body provided between the double-sided boards, a dummy in which a coil pattern is electrically disconnected from at least upper and lower surfaces of the double-sided boards facing each other among the double-sided boards. A thin laminated coil characterized by having a pattern. 2. Each of the double-sided boards is formed in a rectangular shape, the coil pattern is formed in a central portion of the double-sided board, and the dummy patterns are formed in four sides of the double-sided board. The thin laminated coil according to claim 1, wherein 3. The thin laminated coil according to claim 1, wherein the dummy pattern is formed around the coil pattern.