JP2003059744A - Manufacturing method of inductor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of an inductor that can improve a Q factor at a frequency band of GHz or more, and has a small amount of variation in an inductance value. SOLUTION: On a base plate 5 made of thin copper, the opening of an inductor pattern is formed by resist, gold, nickel, and copper plating are made, a substrate material such as a polyimide resin is bonded or applied onto the upper surface for forming a substrate 1, and the base plate 5 is removed. After that, a resist pattern R is removed for forming an inductor 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an inductor used in electronic equipment such as a mobile phone.

[0002]

2. Description of the Related Art In recent years, with the widespread use of wireless communication devices such as mobile phones, there has been an increasing demand for miniaturization, weight reduction and price reduction of these devices. Further, as the amount of information increases, higher frequencies are desired.

Inductors used at frequencies of GHz and above are technologies that require improvement of the material of the dielectric substrate and miniaturization of the conductor pattern in order to obtain better characteristics in the high frequency region.

Regarding the miniaturization of the conductor pattern, the CVD (Chemical Vapor Deposit) used in the semiconductor process is used.
By adopting a thin film technology such as (ion), the conductor pattern can be miniaturized, whereby the length of the inductor can be increased and the target inductance can be obtained. Further, by increasing the film thickness of the conductor pattern, high frequency resistance can be reduced. However, the above-mentioned thin film technology increases the cost, and thus is difficult to use in a general printed circuit board manufacturing process.

FIG. 5 (a) shows a top view of a conventional transfer type inductor, and FIG. 5 (b) shows FIG. 5 (a).
A sectional view taken along line AA ′ of FIG. As shown in FIG. 5, for example, a spiral inductor 20 is formed by being embedded in a substrate 10 made of a polyimide film, and an outer peripheral end of the inductor 20 is connected to a wiring path 40. The peripheral end is connected to the wiring path 40 by a bonding wire 30 made of a gold wire or the like. The conductor pattern forming the inductor 20 is
For example, the line width d1 is formed to be about 20 μm, and the space d2 is
Is formed to have a thickness of about 20 μm.

FIG. 5C is an enlarged sectional view showing details of the inductor 20 shown in FIG. 5B. As shown in FIG. 5C, in the inductor 20, a copper plating film 210 having a film thickness of, for example, about 10 μm to 50 μm is formed from the inside of the substrate 10, and the nickel plating film is formed on the copper plating film 210. 220 is formed to have a film thickness of, for example, about 1 μm to 10 μm, and the gold plating film 230 is formed to have a film thickness of, for example, about 0.1 μm to 3 μm on the nickel plating film 220.

A method of manufacturing the above inductor will be described with reference to FIGS.

First, as shown in FIG. 6A, a base plate on which an inductor is to be formed later is formed, and the thickness thereof is, for example, 5 μm.
A base plate 50 made of copper having a thickness of about 20 μm is prepared.

Next, as shown in FIG. 6B, a resist is spin coated on the base plate 50 by a known technique, and a resist pattern R having an opening C in the inductor formation region is formed by a photolithography technique. Form. The width d1 of the opening C determines the width d1 of the conductor pattern forming the inductor, and the distance d2 of the opening C determines the distance d2 of the conductor pattern forming the inductor. The width d1 is about 20 μm,
The distance d2 is formed to about 20 μm.

Next, as shown in FIG. 6 (c), electroplating is performed using the base plate 50 as an electrode to selectively and sequentially only on the base plate 50 in the openings C of the resist pattern R, a gold plating film. 230, nickel plating film 2
20 、 Copper plating film 210 is deposited to form inductor 2
Form 0.

Next, as shown in FIG. 7D, the resist pattern R is removed by a known release agent.

Next, as shown in FIG. 7E, a polyimide resin is applied so as to cover the base plate 50 and the inductor 20 to form the substrate 10.

Next, as shown in FIG. 7 (f), the inductor 20 embedded in the substrate 10 made of polyimide is obtained by etching the base plate 50 with ferric chloride or the like.
Will be formed. It should be noted that FIG.
It is a cross-sectional view in which the front and back are reversed from the cross-sectional view shown in (b).

[0014]

However, in the inductor formed by the transfer method as described above, since the conductor pattern forming the inductor 20 is embedded in the substrate made of polyimide or the like, the space between the conductor patterns is reduced. However, the Q value was lowered and the satisfactory inductance characteristic could not be obtained in the frequency band of GHz or higher.

Further, when the conductor pattern forming the inductor 20 is formed by projecting on a substrate made of polyimide or the like, conventionally, a resist pattern having an inductor pattern is formed on a copper clad laminate and wet etching is performed. There is also an etching method in which an inductor is formed by patterning a copper film.

However, with the etching method, the influence of side etching cannot be ignored due to the miniaturization of the conductor pattern forming the inductor, the dimensional accuracy of the conductor pattern becomes rough, and the inductance characteristics vary. . Further, in order to reduce the high-frequency resistance of the inductor, when increasing the film thickness of the conductor pattern, it is necessary to etch a thick conductor layer formed in advance, which increases the etching time.
The influence of the side etching becomes large, the dimensional accuracy of the conductor pattern becomes rough, and the variation in the inductance characteristic becomes large.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a method of manufacturing an inductor which can improve the Q value in a frequency band of GHz or higher and which has a small variation in the inductance value. Especially.

[0018]

In order to achieve the above object, a method of manufacturing an inductor according to the present invention is a method of manufacturing an inductor comprising a conductor layer having a predetermined pattern formed on a substrate, the first substrate A step of forming a mask layer having an opening in a formation region of the conductor layer thereon, and a step of forming the conductor layer on the first substrate in the opening,
The method includes a step of providing a second substrate on the mask layer and the conductor layer so as to be fixed to the conductor layer, a step of removing the first substrate, and a step of removing the mask layer.

Preferably, in the step of forming the mask layer, the mask layer having a spiral opening is formed, and in the step of forming the conductor layer, the spiral layer is formed on the first substrate in the opening. Forming the conductor layer of the pattern.

For example, in the step of forming the conductor layer, the conductor layer is formed so as to be thicker than the mask layer and protrude from the surface of the mask layer.

Preferably, in the step of forming the conductor layer, the conductor layer is formed by selectively plating on the first substrate in the opening.

Preferably, the first substrate is made of a conductive material, and in the step of forming the conductor layer, the first substrate is formed.
The conductor layer is formed on the first substrate in the opening by electroplating using the substrate as an electrode.

Preferably, in the step of forming the conductor layer, at least a portion of the conductor layer in contact with the first substrate is formed of a material different from that of the first substrate.

In the step of forming the mask layer, a resist pattern having an opening in the formation region of the conductor layer is formed on the first substrate.

According to the above-described method for manufacturing an inductor of the present invention, a mask layer having an opening in the conductor layer formation region is formed on the first substrate, and the conductor layer is formed on the first substrate in the opening. An inductor including a conductor layer having a predetermined pattern formed on the second substrate by disposing the second substrate on the mask layer and the conductor layer so as to be fixed to the conductor layer and removing the first substrate and the mask layer. Is formed. According to the above manufacturing method, since only the bottom surface of the conductor layer forming the inductor is in contact with the second substrate, the conductor layers between the conductor layers sandwiching the substrate are more likely to be embedded than the case where the inductor is formed by being embedded in the substrate. Capacitance can be reduced, resulting in inductor Q
The value can be improved. In addition, since the etching method is not used when forming the pattern of the conductor layer forming the inductor, there is no disadvantage such as variation in the pattern shape of the conductor layer due to side etching.

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of an inductor manufacturing method of the present invention will be described below with reference to the drawings.

FIG. 1A shows a top view of an inductor formed by the method for manufacturing an inductor according to this embodiment, and FIG. 5B shows a cross section taken along the line AA 'in FIG. 5A. The figure is shown. As shown in FIGS. 1A and 1B, for example, a spiral inductor 2 is formed in a protruding state on a substrate 1 made of a polyimide film. The inductor 2 has a rectangular shape in its cross section, and the conductor pattern forming the inductor 2 has a line width d1 of about 20 μm and an interval d2 of about 20 μm, for example. The outer peripheral edge of the inductor 2 is
It is connected to the wiring path 4, and the inner peripheral end of the inductor 2 is
It is connected to the wiring path 4 by a bonding wire 3 made of a gold wire or the like.

FIG. 1C is an enlarged sectional view showing details of the inductor 2 shown in FIG. 1B. As shown in FIG. 1C, the inductor 2 is formed on the substrate 1 in order from the lower layer.
The copper plating film 21 is formed with a film thickness of, for example, about 10 μm to 50 μm, and the nickel plating film 22 is formed on the copper plating film 21 with a film thickness of, for example, about 1 μm to 10 μm. The gold plating film 23 is formed thereon with a film thickness of, for example, about 0.1 μm to 3 μm. As shown in FIG. 1C, the inductor 2 having a structure in which only the bottom surface of the inductor 2 is bonded to the substrate 10 is formed.

The gold plating film 23 has a function of ensuring good connectivity with the bonding wire 3 made of a gold wire or the like, and the nickel plating film 22 causes copper to diffuse toward the gold plating film 23 when heat is applied. Therefore, it has a function as a barrier metal for preventing this.

Substrate 1 on which the inductor 2 is formed
Can be used by pasting it on a printed wiring board or the like and then connecting the wiring path 4 to the wiring of the printed wiring board, or by providing another circuit integrally on the substrate 1. May be. Further, the substrate 1 also serves as a lead frame base material, and the inductor 2 together with the lead pattern serves as the substrate 1.
The lead frame may be integrally formed on the top, and various usage modes can be adopted.

Next, a method of manufacturing the inductor according to this embodiment will be described with reference to FIGS.

First, as shown in FIG. 2A, a base plate on which an inductor is to be formed later is formed, and the thickness thereof is, for example, 5 μm.
A base plate 5 made of copper having a thickness of about 20 μm is prepared. Since the base plate 5 will be an electrode for depositing a metal on the base plate 5 later by electroplating, it is preferably formed of a metal such as copper. When the metal is deposited on the base plate 5 by electroless plating, the base plate is not limited to the metal, but since the conductor pattern is more beautifully formed by electroplating, the inductor is formed by electroplating. Preferably. When copper is used for the base plate 5, the base plate 5 is removed by etching later. Therefore, it is preferable to form the base plate 5 with high-purity copper in order to eliminate etching residues at this time.

Next, as shown in FIG. 2B, a resist is spin coated on the base plate 5 by a known technique, and a resist pattern R having an opening C in the inductor formation region is formed by a photolithography technique. Form. At this time, in the resist pattern R, an opening is also formed in a region where a wiring path near the inductor is formed. Also,
The width d1 of the opening C determines the width d1 of the conductor pattern forming the inductor, and the interval d2 of the opening C determines the interval d2 of the conductor pattern forming the inductor. For example, the width d1 of the opening C. Is about 20 μm and the distance d2 is about 20 μm. Further, as the function of the resist is improved, it is possible to form the width d1 of the opening C to about 1 μm and the interval d2 to about 1 μm.

Next, as shown in FIG. 2 (c), electroplating is performed using the base plate 5 as an electrode, and 0.1 μm of gold is sequentially deposited only on the base plate 5 in the openings C of the resist pattern R. ˜3 μm is deposited to form a gold plating film 23, nickel is deposited to approximately 1 μm to 10 μm to form a nickel plating film 22, copper is 10 μm to 50 μm.
The copper plating film 21 is formed by depositing about m, and the inductor 2 including the gold plating film 23, the nickel plating film 22 and the copper plating film 21 is formed. Although not shown, at this time, in another region of the resist pattern R, a wiring path 4 made of a gold plating film, a nickel plating film, and a copper plating film is also formed in an opening for forming a wiring path near the inductor. It

Next, as shown in FIG. 3D, a polyimide film is applied so as to cover the inductor 2 and the resist pattern R to form the substrate 1. The material of the substrate 1 is not particularly limited as long as it is a material that has a low dielectric constant and can ensure insulation, and other organic resin compositions such as epoxy resin and BT resin can be used.

Next, as shown in FIG. 3 (e), the base plate 5 is removed by etching with ferric chloride or the like. As a result, the gold plating film 23 and the resist pattern R are exposed. When copper is used for the base plate 5, a gold plating film 23 is formed on the base plate 5 side of the inductor 2.
Since this is formed, the inductor pattern is not etched in the etching process.

Next, as shown in FIG. 3 (f), the resist pattern R is removed by a known release agent, whereby the inductor 2 protruding from the surface of the substrate 1 is formed. Note that FIG. 3F is a cross-sectional view in which the front and back are reversed from the cross-sectional view shown in FIG. 1B. Then, the inner peripheral end of the inductor and the wiring path 4 are connected by a bonding wire 3 such as a gold wire, whereby the structure shown in FIG. 1A is manufactured.

In the method of manufacturing an inductor according to the present embodiment described above, the opening of the inductor pattern is formed by resist on the base plate 5 made of thin copper, and gold plating,
Nickel plating and copper plating are performed, and a substrate material such as polyimide resin is adhered or applied on the upper surface to form the substrate 1, the base plate is removed, and then the resist pattern R is removed to form an inductor. Therefore, since the inductor 2 formed by the above-described manufacturing method has only the bottom surface of the inductor 2 in contact with the substrate 1 made of polyimide or the like, the inductor 2 is more likely to be embedded in the substrate than the inductor 1. The capacitance of 2 can be reduced, and as a result, the Q value of the inductor can be improved in the frequency band of GHz or higher. Actually, assuming that the Q value is about 40 when the inductor is embedded in the substrate made of the conventional polyimide resin, the Q value is 50 in the present invention.
It was confirmed that the value was about the same, and the Q value could be improved by about 20%.

Further, in the method of manufacturing the inductor according to this embodiment, the patterning of the inductor 2 is not performed by etching, but the resist pattern R having the opening C is formed in advance in the inductor pattern forming region, Since the inductor is formed in the opening C by plating, the dimensional accuracy of the pattern of the inductor can be improved and the variation in the inductance characteristic can be reduced.

Further, in order to reduce the high frequency resistance of the inductor, when the film thickness of the conductor pattern is increased, the film thickness of the resist pattern R may be increased.
Since the opening of the resist pattern R can form an opening having a rectangular cross section with higher accuracy than in the conventional etching, it is possible to reduce the deterioration of the dimensional accuracy of the conductor pattern due to the increase of the film thickness, and to reduce the inductance characteristic. Variability is reduced.

In the above example, as shown in FIG. 2C, the metal forming the inductor 2 is deposited in the opening of the resist pattern R so as to be substantially horizontal to the upper surface of the resist pattern R. However, it is also possible to extend the plating time longer than the above conditions and perform the plating so as to protrude from the upper surface of the resist pattern R.

FIG. 4 (b) is a sectional view corresponding to the line AA 'in FIG. 1 (a) when the inductor is formed as described above, and FIG. 4 (c) is shown in FIG. 4 (b). 3 is an enlarged cross-sectional view showing details of the inductor 2 shown in FIG. As shown in FIG. 4, as a result of plating so as to protrude from the upper surface of the resist pattern R, the bottom surface of the inductor 2 is formed by being embedded in the substrate 1 made of polyimide resin or the like. By doing so, even if the pattern line width of the inductor 2 becomes very small in the future and the adhesion area between the bottom surface (copper plating film 21) of the inductor and the substrate 1 becomes small, the board The adhesiveness of the inductor 2 to 1 can be improved, and the strength can be increased.

The inductor of the present invention is not limited to the description of the above embodiment. For example, in this embodiment,
As the inductor material, the one having a three-layer structure of a copper plating film, a nickel plating film, and a gold plating film has been described, but the inductor material is not limited to this, and other materials can be adopted. Further, in the present embodiment, the wiring path 4 connected to the inductor is also formed at the same time as the inductor, but the present invention is not limited to this, and the wiring path 4 may be formed by patterning with copper or the like in another step. Good. Also,
The material of the substrate 1, the material of the base plate 5, the resist material, and the like are not particularly limited, and various materials according to their roles can be used. Besides, various modifications can be made without departing from the scope of the present invention.

[0044]

According to the inductor of the present invention, it is possible to manufacture an inductor having a high Q value and a small variation in the inductance value.

[Brief description of drawings]

1A is a top view of an inductor formed by an inductor manufacturing method according to the present embodiment, FIG. 1B is a cross-sectional view taken along line AA ′ of FIG. 1A, and FIG. FIG.

FIG. 2 is a cross-sectional view after a conductor pattern forming an inductor is embedded in an opening of a resist in the manufacturing process of the inductor manufacturing method according to the present embodiment.

FIG. 3 is a cross-sectional view of a process following the process of FIG. 2 until an inductor is formed.

FIG. 4B is a sectional view of an inductor formed by another method for manufacturing an inductor according to the present embodiment, and FIG. 4C is an enlarged sectional view of the inductor.

5A is a top view of an inductor formed by a method for manufacturing an inductor according to a conventional example, FIG. 5B is a sectional view taken along line AA ′ of FIG. 5A, and FIG. 5C is an enlarged sectional view of the inductor. It is a figure.

FIG. 6 is a cross-sectional view after a conductor pattern forming an inductor is embedded in an opening of a resist in a manufacturing process of a method for manufacturing an inductor according to a conventional example.

FIG. 7 is a cross-sectional view until an inductor is formed in the step following FIG.

[Explanation of symbols]

1 ... Substrate, 2 ... Inductor, 3 ... Bonding wire,
4 ... Wiring path, 5 ... Base plate, 10 ... Substrate, 20 ... Inductor, 21 ... Copper plating film, 22 ... Nickel plating film, 23 ... Gold plating film, 30 ... Bonding wire,
40 ... Wiring path, 50 ... Base plate, 210 ... Copper plating film, 220 ... Nickel plating film, 230 ... Gold plating film, R ... Resist pattern, C ... Opening.

Continued front page    (72) Inventor Hidetoshi Kusano             6-735 Kita-Shinagawa, Shinagawa-ku, Tokyo Soni             -Inside the corporation F-term (reference) 5E062 DD01

Claims (7)

[Claims] 1. A method of manufacturing an inductor comprising a conductor layer having a predetermined pattern formed on a substrate, the method comprising: forming a mask layer having an opening in a formation region of the conductor layer on a first substrate; Forming the conductor layer on the first substrate in the opening; providing a second substrate on the mask layer and the conductor layer so as to be fixed to the conductor layer; and the first substrate And a step of removing the mask layer, a method of manufacturing an inductor. 2. A step of forming a mask layer having a spiral opening in the step of forming the mask layer, and a step of forming a spiral pattern on the first substrate in the opening in the step of forming the conductor layer. The method for manufacturing an inductor according to claim 1, wherein the conductor layer is formed. 3. The method for manufacturing an inductor according to claim 1, wherein in the step of forming the conductor layer, the conductor layer is formed so as to be thicker than the mask layer so as to protrude from a surface of the mask layer. 4. The method of manufacturing an inductor according to claim 1, wherein in the step of forming the conductor layer, the conductor layer is formed by selectively plating on the first substrate in the opening. 5. The first substrate is made of a conductive material, and in the step of forming the conductor layer, the first substrate is used as an electrode by electroplating on the first substrate in the opening, The method for manufacturing an inductor according to claim 4, wherein a conductor layer is formed. 6. In the step of forming the conductor layer, at least a portion of the conductor layer in contact with the first substrate is formed into the first conductor layer.
The inductor manufacturing method according to claim 5, wherein the inductor is formed of a material different from that of the substrate. 7. The method of manufacturing an inductor according to claim 1, wherein in the step of forming the mask layer, a resist pattern having an opening in the formation region of the conductor layer is formed on the first substrate.