JPH10189344A - Chip inductor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To raise Q value, self-resonance frequency, to make less susceptible to the effect from outside magnetic field at mounting time, and to raise heat- resistance temperature, by allowing a resin dielectrics to comprise, as a monomer, a high polymer material obtained by polymerizing a monomer composition containing fumaric diester. SOLUTION: A resin dielectrics is a fumarate-based polymer obtained by polymerizing a monomer composition containing, at least, fumaric diester as a monomer. The resin is used as an armor resin and a core for an inductance, while a band-like conductor coil is used. Here, relating to the fumarate-based polymer, a dielectric constant is 3 or less while a heat-resistance temperature is 270 deg.C or above. Thus, self-resonance frequency is raised to allow use in a high-frequency region, while a heat-resistance temperature is raised to allow use of such solder as of relatively high melting point.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inductor used in a high frequency band, and more particularly to a surface mount type chip inductor used for a mobile communication device such as a mobile phone.

[0002]

2. Description of the Related Art In recent years, as radio equipment such as a cellular phone has been strongly promoted at higher frequencies and downsizing, it is small, operates up to a high frequency range, has a high Q value, and is surface mountable. Demands for chip inductors are increasing.

For this purpose, a laminated chip inductor as shown in FIG. 11 or a wound chip inductor as shown in FIG. 12 is used.

[0004] The multilayer chip inductor is Ni-Cu-
It comprises a magnetic material 6 such as Zn ferrite, an internal electrode 7 made of Ag or the like, and an external terminal electrode 8. Then, the magnetic paste 61 and the conductive paste 71 having a low-temperature sintering property are combined as shown in FIG.
It is manufactured by repeatedly printing by the method shown in FIG.

The multilayer chip inductor manufactured by the above-described method is very small, has a large inductance, and is excellent in heat resistance.

On the other hand, the wound type chip inductor is obtained by winding a metal wire 10 having a diameter of 0.1 mm or less around a magnetic or dielectric core 9, covering with a resin 11 and attaching a terminal 12,
A large inductance can be obtained.

[0007]

However, since the laminated chip inductor has a low Q value and a low self-resonant frequency, it is not suitable as an inductor in a radio device having a high operating frequency such as a portable telephone. . The Q value of this element is low because the conductor is formed by the sintering method, so that the conductivity is lower than that of the bulk metal, so that the Q value of the conductor is low. Further, the self-resonant frequency is lowered because the stray capacitance between the windings is increased because the relative permittivity of the ceramics supporting the conductor is large (the relative permittivity is about 4 to 5 or more).

On the other hand, a wire-wound chip inductor has a large inductance, but is mounted on a substrate by a reflow soldering method (usually at 230 ° C.) because the softening temperature of the resin used for the exterior is about 180 to 200 ° C. When the temperature rises to the extent, the time required for the exterior of the component to be softened occurs, and it is necessary to be careful in handling at that time. Further, the heat-resistant temperature is about 240 ° C., and solder having a high melting point cannot be used.

Accordingly, the present invention is to provide a chip inductor having a high Q value and a high self-resonance frequency, being hardly affected by an external magnetic field during mounting, and having a high heat-resistant temperature.

[0010]

Such an object can be achieved by the following constitutions (1) to (5).

(1) A chip inductor including a resin-based dielectric, a strip-shaped conductor coil, and an external terminal electrode, wherein the resin-based dielectric includes a monomer composition containing at least a fumaric acid diester as a monomer A chip inductor comprising a polymer material obtained by polymerizing a polymer.

Here, the resin-based dielectric means at least a part including an exterior part and, in some cases, a core part.

(2) The chip inductor according to (1), wherein the resin dielectric has a relative dielectric constant of 3 or less and a heat-resistant temperature of 270 ° C. or more.

Here, the heat-resistant temperature refers to a temperature at which electrical and mechanical properties and the like begin to significantly deteriorate when heated and cooled to room temperature. In other words, it is the temperature at which the resin changes irreversibly.

(3) The chip inductor according to (1) or (2), wherein the strip-shaped conductor coil is formed of a metal conductor material containing copper as a main component.

(4) The chip inductor according to any one of (1) to (3), wherein the band-shaped conductor coil is wound so that a width direction thereof coincides with a radial direction of the coil.

(5) The chip inductor according to any one of (1) to (4), wherein the central axis of the coil is orthogonal to the external terminal electrode surface.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A chip inductor according to the present invention is a chip inductor having a resin-based dielectric, a strip-shaped conductor coil, and an external terminal electrode as described above, wherein the resin-based dielectric is a It is a fumarate-based polymer (fumarate-based resin) obtained by polymerizing a monomer composition containing at least a fumaric acid diester and having a repeating unit derived from the fumaric acid diester.

This fumarate resin is disclosed in Japanese Patent Application No. 8-42.
No. 073 (not disclosed).
It is mainly used as a material for a substrate, and is characterized by low relative dielectric constant and dielectric loss tangent and high heat resistance temperature. The present invention is characterized in that this resin is used as an exterior resin or a core of an inductor, and that a strip-shaped conductor coil is used. And this inductor has a high Q value,
It can be used up to a high frequency of several GHz.

Here, the fumarate resin has a relative dielectric constant of 3 or less, preferably 1 to 3, and a heat-resistant temperature of 270 ° C. or more, preferably 270 ° C. to 350 ° C. By having the above dielectric constant, the self-resonant frequency can be increased, and it can be used in a high frequency range. In addition, when the above-mentioned heat-resistant temperature is used, when mounting on a substrate by the reflow soldering method, the exterior is not softened, and a solder having a relatively high melting point (in recent years, Pb which has an effect of lowering the melting point due to environmental problems and the like). (Which requires the use of solder containing no).

Specifically, for example, di-cyclohexyl fumarate monopolymer, di-isopropyl fumarate /
Di-cyclohexyl fumarate copolymer, di-cyclohexyl fumarate / di-sec-butyl fumarate copolymer, di-isopropyl fumarate / di-sec-butyl fumarate copolymer, di-cyclohexyl fumarate / tert -Butyl vinyl benzoate and the like.

This resin has excellent casting performance and can be cast at room temperature, so that it is easy to manufacture and does not need to be subjected to a high heat treatment unlike a multilayer chip inductor. A low resistance bulk metal can be used.

Here, a strip-shaped conductor wire is used as the conductor wire forming the coil. However, compared with a round wire having the same material and the same cross-sectional area, the conductor wire per unit length can be used without lowering its resistivity. The number of turns can be increased and a larger inductance can be obtained.Moreover, when used at a high frequency, the belt-like shape with a larger surface area per unit length than the round wire with the same cross-sectional area has a higher resistance due to the skin effect. It is because it becomes less.

The material of the strip-shaped conductor wire may be a usual material for a coil, for example, Cu, Au, Ag, Fe, P
t, Sn, Ni, Pb, Al, Co, or an alloy thereof can be used. Among them, an alloy containing Cu as a main component is preferable from the viewpoints of conductivity and cost, and it is particularly preferable to use Cu. This is because the processing temperature of the reflow furnace is usually equal to or higher than the annealing temperature of Cu, and the copper hardened by the stress caused by the machining during winding turns into copper by heating in the reflow furnace (copperization temperature 210 ° C.), and the conductor resistance increases. This is because it can be expected that the Q value further increases and the Q value further increases. This is a characteristic when a bulk metal is used for the conductor, and such an effect cannot be expected in a chip inductor made of a sintered metal.

A method for manufacturing a chip inductor according to the present invention will be described in detail with reference to FIG.

In the first step (FIG. 1A), a predetermined number of turns of the strip-shaped conductor wire 2 are wound around a round bar (core) 1 made of a fumarate-based resin.

Here, in the case of using a strip-shaped conductor wire, the method of winding the coil includes a method of winding so that the wide surface of the strip-shaped conductor wire and the side surface of the round bar (core) are in contact with each other (not shown). A method of winding so that the narrow surface of the wire and the side surface of the round bar (core) 1 are in contact with each other (FIG. 1A), that is, a method of winding such that the width direction of the coil coincides with the radial direction of the coil (the edge (They are wound wise), but the latter winding method, that is, the edge-wise winding is particularly preferable. This is because the number of turns per unit length is the largest, and a small-sized element having a large inductance can be obtained. When winding edgewise, a strip-shaped conductor wire may be wound as described above, or a normal round wire wound in a spiral may be crushed to form a strip.

The surface of the conductive wire is coated with a fumarate resin, preferably the same resin as the resin used as the dielectric, and is insulated so as not to contact with each other.

As a second step (FIG. 1 (b)), the wire end is bent in the winding direction of the coil to provide a lead portion 21, and the round bar (core) 1 is cut to a predetermined length, The wound coil 3 is created.

As a third step (FIG. 1 (c)), the wound coil 3 is placed in a casting, a liquid fumarate resin is poured, and the resin is cured by drying. Here, the fumarate resin used may be the same as or different from the round bar (core) 1.

The liquid fumarate-based resin is a polymer solution obtained by dissolving the fumarate-based resin in a solvent. Here, the solvent that can be used is appropriately selected from, for example, aromatic hydrocarbon solvents such as benzene and toluene, ketone solvents such as methyl ethyl ketone and cyclohexanone, and solvents such as tetrahydrofuran (THF), chloroform, and ethyl acetate. And can be obtained by dissolution.

The concentration is not particularly limited, but it is preferable that the fumarate resin is contained in the range of 5 to 30% by weight in consideration of workability.

The drying temperature is appropriately selected depending on the solvent used, and may be room temperature (about 15 to 30 ° C.) or about 40 to 60 ° C.

In a fourth step (FIG. 1D), the terminal-side surface is polished to expose the wire ends of the lead portion 21, and external terminal electrodes 5 are attached to both ends.

The external terminal electrodes 5 attached to both ends may be formed by bonding a metal conductor film, or may be formed by vacuum evaporation, electroless plating, or the like.

The material of the terminal electrode may be one containing Cu as a main component. The external terminal electrodes may be formed by plating with Ni, Sn, or the like in consideration of solder heat resistance and solder wettability.

Although an example of the manufacturing process has been described above, the present invention is not limited to this. For example, without using the round bar (core) of fumarate-based resin as described above, the edge-wise coil portion is formed by forming. Or a metal plate to be used as the conductor material of the coil is formed by a progressive die or the like, including the edge-wise coil portion and the terminal portion, and then put into a casting to pour the fumarate resin and solidify it. It is.

As shown in FIG. 1 (c), it is preferable that the center axis 3a of the coil has a structure penetrating the external terminal electrode surface 5a to give a degree of freedom when mounting the substrate. This is for the following reason. In the case where the center axis of the coil is perpendicular to the axis that passes between the terminals, such as a multilayer chip inductor, when mounted on a high-frequency circuit board, the center axis of the coil is perpendicular to the board surface when the board is mounted. Therefore, depending on the wiring pattern formed on the substrate and the like, they are mutually affected by the generated magnetic field, and the inductance changes depending on the mounting direction. However, by adopting a structure in which the center axis of the coil penetrates the external terminal electrode surface, when mounted on a high-frequency circuit board, it is hardly affected by a magnetic field generated by a wiring pattern or the like formed on the board, and the mounting direction This is because the inductance can reduce the change.

It is obvious that, as shown in FIG. 2, a structure in which the center axis 3b of the coil is parallel to the external terminal electrode surface 5b is also possible. As described above, it is easily affected by the magnetic field.
It is easy to design below.

[0040]

EXAMPLES Specific examples of the present invention will be described below.

As the resin dielectric material for the chip inductor, fumarate-based resins include di-cyclohexyl fumarate monopolymer, di-isopropyl fumarate / di-cyclohexyl fumarate copolymer, and di-cyclohexyl fumarate / di-fumarate. sec-butyl fumarate copolymer 4
Type used. Table 1 shows the relative dielectric constant, electrostatic tangent, softening temperature and heat-resistant temperature of each.

Here, the relative dielectric constant and the electrostatic tangent were measured by a perturbation method using the resin as a substrate having a size of 12 cm × 2.0 mm × 2.0 mm. The softening temperature was measured using TMA100 (manufactured by Seiko Denshi Kogyo) in accordance with JIS K7126. The heat-resistant temperature was a temperature at which deterioration was observed by immersing in a solder bath set to a predetermined temperature, visually observing appearance, deformation, swelling, cracking, and melting, and measuring electrical and mechanical properties of the device.

[0043]

[Table 1]

(Embodiment 1) A chip inductor according to a first embodiment of the present invention will be described.

The details of the manufacturing method will be described with reference to FIG.

A) A band-shaped conductor wire 2 made of copper having a width of 0.2 mm and a thickness of 35 μm is rounded to a round bar (core) 1 having a diameter of 1.0 mm of a fumarate-based resin (di-cyclohexyl fumarate monopolymer). 8 turns (the figure is wound 5 times for easy viewing). The strip-shaped conductor wire 2 made of copper
Is coated with a fumarate-based resin (di-cyclohexyl fumarate monopolymer) to a thickness of about 100 μm and is insulated so as not to contact each other. At this time, the coil is spirally wound with the resin concentration being about 15 to 30% by weight to give the resin flexibility.

B) A wire end is bent in the winding direction of the coil to provide a lead portion 21, and the round bar (core) 1 is cut into a length of 2.5 mm to form a coil 3 wound.

C) The wound coil 3 is put into a casting mold, a solution of a fumarate resin (di-cyclohexyl fumarate monopolymer) is poured, dried at room temperature, and the cured resin is removed from the mold. Here, toluene was used as a solvent for the polymer solution, and the resin concentration was about 15% by weight.

D) The terminal side surface is polished and the lead terminal portion 2 is polished.
1 are exposed, and external terminal electrodes 4 made of copper foil are attached to both ends.

The thus-produced substantially rectangular parallelepiped (vertical,
Impedance frequency characteristics of the chip inductor according to the present invention (width, height 2.5 × 2.0 × 1.8 mm) (FIG. 3)
And the self-resonant frequency (FIG. 5) were measured. For comparison, the same inductance (33 nH) as that of the chip inductor according to the present invention was used as a conventional chip inductor.
(100 MHz)), and the same using the diallyl phthalate resin having a relative dielectric constant of about 4 to 5 and a softening temperature of 180 to 200 ° C., the impedance frequency characteristic (FIG. 4) and the self resonance Frequency (Fig. 6)
Was measured.

As a result of the element constant measurement, the Q value (100 MHz) of the chip inductor according to the present invention was 32, and the Q value (100 MHz) of the conventional inductor having the same inductance and the same shape and dimensions as the chip inductor according to the present invention.
The value was 33% higher than 24.

The self-resonant frequency of the chip inductor according to the present invention is 3.0 GHz or more, and the self-resonant frequency of the conventional inductor having the same inductance and the same shape and dimensions as the chip inductor according to the present invention is 1.8 GHz.
A value higher than that by 60% or more was shown.

(Embodiment 2) Next, a chip inductor according to a second embodiment of the present invention will be described.

The second chip inductor was manufactured by the same manufacturing method and dimensions as in Example 1 except that the number of turns of the coil was four. As a comparative example, the same inductance as the chip inductor of the second embodiment (12 nH (10 nH
0 MHz)) and have the same shape and dimensions, and a relative dielectric constant of 4 to 5
The measurement was also performed on a material using a diallyl phthalate-based resin having a softening temperature of about 180 ° C to 200 ° C.

As for the evaluation, the impedance frequency characteristic (FIG. 7) and the self-resonant frequency (FIG. 9) of the chip inductor of the second embodiment were measured in the same manner as in the first embodiment. 8) and the self-resonant frequency (FIG. 10) were measured.

As a result of the element constant measurement, the Q value (100 MHz) of the chip inductor according to the present invention was 33, and the Q value (100 MHz) of the conventional inductor having the same inductance and the same shape and dimensions as the chip inductor according to the present invention.
It was 70% higher than 19.

The self-resonant frequency of the chip inductor according to the present invention is 6.7 GHz or more, and the self-resonant frequency of the conventional inductor having the same inductance and the same shape and size as the chip inductor according to the present invention is 3.2 GHz.
The value was much higher than twice or more.

In conventional chip inductors, the spacing between layers and lines is structurally determined. Even when the constant required for a chip inductor having the same structure is small, the spacing between layers and lines is the same and only the number of turns is small. Although the number of turns is often small, in this embodiment, when the number of turns is the same and the number of turns is small, the distance between layers can be easily widened, so that the line capacitance per unit number of turns can be reduced. This is because the self-resonant frequency can be dramatically increased.

In the examples, various characteristics were shown only when an inductor element was prepared using a di-cyclohexyl fumarate monopolymer. However, di-isopropyl fumarate / di-cyclohexyl fumarate copolymer, Similarly, when the di-cyclohexyl fumarate / di-sec-butyl fumarate copolymer was used, a high Q value and a high self-resonant frequency were also exhibited.

[0060]

The chip inductor according to the present invention has a high self-resonant frequency since a fumarate resin is used as a dielectric material, and can be used up to a high frequency. The heat resistance temperature of the resin is higher than that of the conventional resin, and it can be applied to a reflow furnace treatment using a solder having a relatively high melting point. This resin has excellent casting performance and is easy to manufacture because it can be cast at room temperature, and does not need to be subjected to high heat treatment unlike a multilayer chip inductor, and has low resistance to the internal conductor forming the coil. The Q value is high because bulk metal can be used. At the same time, according to the resin molding, almost no distortion or peeling of the element occurs, which is common in ceramic sintered elements.

Furthermore, since the number of turns per unit length can be increased by winding the coil edgewise, a small inductor having a large inductance can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing a manufacturing process according to the present invention.

FIG. 2 is a transparent perspective view of a chip inductor according to the present invention.

FIG. 3 is a diagram illustrating impedance frequency characteristics of the chip inductor according to the first embodiment.

FIG. 4 is a diagram illustrating impedance frequency characteristics of a comparative example (33 nH) with respect to the first embodiment.

FIG. 5 is a diagram showing a self-resonant frequency of the chip inductor according to the first embodiment.

FIG. 6 is a diagram showing a self-resonant frequency of a comparative example (33 nH) with respect to the first embodiment.

FIG. 7 is a diagram illustrating impedance frequency characteristics of a chip inductor according to a second embodiment.

FIG. 8 is a diagram illustrating impedance frequency characteristics of a comparative example (12 nH) with respect to the second embodiment.

FIG. 9 is a diagram illustrating a self-resonant frequency of the chip inductor according to the second embodiment.

FIG. 10 is a diagram showing a self-resonant frequency of a comparative example (12 nH) with respect to the second embodiment.

FIG. 11 is a transparent perspective view of the multilayer chip inductor.

FIG. 12 is a transparent perspective view of a wire-wound inductor.

FIG. 13 is a diagram showing a lamination process of the multilayer chip inductor.

[Explanation of symbols]

 1; round bar (core) 2; strip-shaped conductor wire 3; wound coil 3a, 3b; center axis of coil 4, 11; exterior resin 5, 8, 12; Magnetic material 61; magnetic material paste 7; internal electrode 71; conductor paste 9; core 10;

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshiyuki Yasukawa 1-13-1 Nihonbashi, Chuo-ku, Tokyo Inside TDK Corporation

Claims (5)

[Claims] 1. A chip inductor having a resin-based dielectric, a strip-shaped conductor coil, and an external terminal electrode, wherein the resin-based dielectric is obtained by polymerizing a monomer composition containing at least a fumaric acid diester as a monomer. A chip inductor comprising a polymer material obtained by the above method. 2. The chip inductor according to claim 1, wherein said resin-based dielectric has a relative dielectric constant of 3 or less and a heat-resistant temperature of 270 ° C. or more. 3. The chip inductor according to claim 1, wherein said strip-shaped conductor coil is formed of a metal conductor material containing copper as a main component. 4. The chip inductor according to claim 1, wherein the band-shaped conductor coil is wound so that a width direction thereof coincides with a radial direction of the coil. 5. The chip inductor according to claim 1, wherein a center axis of the coil is orthogonal to an external terminal electrode surface.