JP2003318053A - Manufacturing method for flat magnetic element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve forming especially of a plating base film in a method for manufacturing a flat magnetic element by plating copper, etc. <P>SOLUTION: The manufacturing method for a flat magnetic element includes a plating base film formation process where a plating base film is formed on the surface of an insulating resin film, a photolithographic process where a resist frame for forming a plating coil is formed on the plating base film, a process where the resist frame is released after the plating coil is formed, and a process where the plating base film of the released resist frame part is removed by etching and a magnetic material is packed. Before the plating base film formation process, the surface of the insulating resin film is shot-blasted with globular particles. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a flat magnetic element by plating copper or the like, and more particularly to improving the formation of a plating underlayer film, while maintaining a sufficiently high adhesion to an insulating resin film. A plating base film having a surface gloss suitable for photolithographically forming a resist frame having a high aspect ratio cross section is realized.

[0002]

2. Description of the Related Art With the spread of information technology in recent years, the use of portable devices driven by batteries, such as portable telephones and electronic information terminals, is advancing. For these mobile devices,
There has been a demand for further reduction in size, thickness, and weight. Recently, in addition to this, multimedia, broadband, and other communication and display functions have been enhanced, or high-speed processing of large amounts of information including image data has been achieved. Higher functionality is required.

Along with this, the single voltage from the battery is
There has been an increasing demand for a power supply capable of converting each voltage level required by various on-board devices such as U, LCD module, and communication power amplifier. Therefore, it is an important issue to reduce the size and thickness of magnetic elements such as transformers and inductors mounted in a power supply in order to achieve both small size, thickness and weight reduction and high functionality of mobile devices.

Under such circumstances, in order to further miniaturize the magnetic element, a planar magnetic element using a ferrite magnetic film formed by a printing method or a sheet method, that is, a planar magnetic element is disclosed in Japanese Patent Laid-Open No. 2001- No. 244124 is disclosed.
In such a planar magnetic element, a magnetic paste prepared by mixing a ferrite powder with a binder is printed on an Si substrate and fired to form a first ferrite magnetic film, and a flat layer is formed on the smoothing layer formed on the film by a plating method. After the coil was formed, the ferrite powder was further fixed on it by the resin binder.
Magnetic film is formed as a magnetic element.

A conventional method of manufacturing the planar magnetic element shown in FIG. 1 has also been performed. Hereinafter, a representative example of the planar magnetic element manufacturing method will be described with reference to FIGS. First, a paste containing ferrite magnetic powder was formed as a first ferrite magnetic film on the Si substrate 11a by a screen printing method, and subsequently fired at 950 ° C. in the atmosphere. A polyimide resin is applied onto the ferrite magnetic film 11b by spin coating or the like, and then heat-cured to form a polyimide resin film 11c which is an insulating resin film having a thickness of 10 μm, and a plated copper film having a thickness of 0.5 μm serving as a plating base film. Substrate 11 is formed by forming 11d by electroless plating (a).

Here, in the planar magnetic element structure, if the surface of the insulating resin film 11c remains smooth, the plating base film 11d is formed.
Adhesiveness to and is not sufficient, causing manufacturing troubles such as peeling in a later step, which is also a problem from the aspect of reliability of the element. Therefore, efforts are being made to improve the adhesion by various physical or chemical anchor treatments such as shot blasting using polygonal or amorphous particles. The anchor process will be described later.

Next, a photoresist is coated on the plating base film 11d and then exposed by parallel light 5 using a photomask 6 by photolithography to form a resist frame 12 having a desired coil shape (b). . After that, copper plating is deposited (c) inside the resist frame 12 by electroplating, the resist frame 12 is peeled off, and then chemical etching is performed to form a Cu film 11d for undercoating between the coil wires.
Are removed (not shown) to form the planar coil 13 (d). At this time, the coil terminal 16 is also formed.

Next, an epoxy resin 14 containing ferrite magnet powder
Is applied to the space between the planar coils and the upper layer of the planar coil by a screen printing method to be thermally cured to form a second ferrite magnetic film, an external electrode 17 is provided, and the planar magnetic element 10a is completed (e). The thin planar magnetic element 10b may be formed by separating the Si substrate 11a and the first ferrite magnetic film 11b (f). FIG. 3 illustrates a perspective view of the completed planar magnetic element 10b and its AA cross section.

Here, as the physical anchor treatment, for example, there is a method of roughening the surface of the insulating layer by plasma treatment, sputtering treatment, shot blast treatment using polygonal or amorphous particles. There is also a chemical method of dissolving the exposed surface of the soluble particles mixed in the insulating layer with acid or alkali to roughen the surface of the insulating layer. Greatly contributes to

The chemical surface roughening due to the dissolution action of the soluble particles is effective when the insulating layer is sufficiently thick, but pinholes are generated due to the dissolution of the soluble particles in the insulating layer having a size equal to or smaller than that of the soluble particles. Will cause a problem.
Further, even if the insulating layer is thicker than the size of the soluble particles, the soluble particles are not sufficiently dispersed, and the same problem occurs when forming aggregated particles. In particular, JP 2001
A very thin insulating resin film of 0.01 to 10 μm as recommended in Japanese Patent No. 244124 is not suitable.

On the other hand, in the shot blasting which is a physical method, the anchor effect is obtained by sharply scratching the surface of the insulating layer with polygonal or amorphous particles to be shot blasted. Therefore, in the case of a very thin insulating layer, a scratch penetrates and a defect occurs due to infiltration of a chemical solution or the like in the post-treatment. Therefore, the thickness of the applicable insulating resin film is about 5 to 10 μm at the most, even if it is premised on performing mild processing using fine particles.

By the way, other physical methods such as plasma treatment and sputtering treatment can be applied to a thin insulating resin film having a thickness of about 0.01 to 10 μm as compared with the above method. Here, in Japanese Patent Laid-Open No. 2001-244124, in order to improve the adhesion of the base film, it is recommended to further perform heat treatment at 80 to 400 ° C. after forming the base film. However, in these plasma treatment and sputtering treatment,
Although adhesion can be secured when the underlayer film is formed without exposing it to the atmosphere after the treatment, once the substrate is exposed to the atmosphere after the treatment, the activity of the surface is impaired. Adhesion will be significantly reduced. Therefore, an expensive device is required to enable the above process to be continuously performed without opening to the atmosphere.

[0013]

In the above-mentioned structure of the planar magnetic element, if the coil wire width is reduced and the coil height is increased at the same time, it is possible to realize the miniaturization while maintaining the coil cross-sectional area and reduce the coil resistance. Without increasing the thickness, it is possible to suppress the increase in the thickness of the planar magnetic element to a negligible level.

However, a negative photoresist is used on the surface of the plating base film formed on the insulating resin film whose surface has been roughened by shot blasting using polygonal or amorphous particles or dissolving soluble particles. When a resist frame was formed in the shape of a coil with a resist height of more than 70 μm, it was revealed that the resist remained on the soot portion of the resist frame where the underlying film should be exposed, resulting in electrodeposition failure during electroplating. Became. Further, it was found that in the pattern in which the coil wire width is less than 40 μm, the resist residue covers the groove bottom of the resist frame, and the underlying film is not exposed at all.

On the other hand, when the plating base film formed on the insulating resin film subjected to the plasma treatment or the sputtering treatment is used, a normal resist frame can be formed even if the resist height exceeds 70 μm. As a result of detailed investigations and studies on these differences by the present inventors, the surface of the undercoat film subjected to the plasma treatment is almost a mirror surface and has a gloss, so that the parallel light incident on the resist frame in the exposure step of the photolithography is directly corrected. While reflected,
When the insulating resin film is shot blasted using polygonal or amorphous particles, the surface of the base film is not glossy,
It was found that the incident light was diffusely reflected on the surface of the base film, and the portion that should not be exposed to light was exposed and cured. In particular, if the resist height is high, it is necessary to take a long exposure time, and this influence becomes remarkable.

That is, as shown in FIG. 2, when the plating base film 11c is not glossy, the parallel light 5 incident on the resist frame 12 becomes the scattered reflected light 5a, and the eroded portion is not exposed to light. 7 is formed. However, the plasma treatment or the sputtering treatment capable of forming a glossy surface on the plating base film 11c is a very expensive process, and it is difficult to adopt it for manufacturing the planar magnetic element at low cost.

The present invention provides an inexpensive method for manufacturing a planar magnetic element, which forms a resist frame having a high aspect ratio of more than 70 μm while maintaining the adhesion between the insulating resin film and the plating underlayer film. The present invention provides a method of manufacturing a planar magnetic element that is possible. More specifically,
It is intended to provide a method for roughening a surface of an insulating resin film, which makes it possible to obtain a glossy plating base film at low cost.

[0018]

Means for Solving the Problems As a result of intensive studies to achieve the above object, the inventors of the present invention have achieved the above object by subjecting the surface of an insulating resin film to a shot blast treatment using spherical particles. Has been found to be advantageously achieved. It has been found for the first time that by performing shot blasting using spherical particles, glossiness after plating can be maintained and sufficient adhesion strength can be maintained.

That is, according to the present invention, a plating underlayer film forming step of forming a plating underlayer film on the surface of an insulating resin film, a photolithographic step of forming a resist frame for forming a plating coil on the plating underlayer film, and a plating step A method for manufacturing a planar magnetic element, comprising: a step of removing the resist frame after forming a coil; a step of removing the plating base film of the removed resist frame portion by etching and filling a magnetic material, wherein The above problems are solved by a method of manufacturing a planar magnetic element, characterized in that the surface of the insulating resin film is shot-blasted with spherical particles before the formation process.

The present invention has also found that in the above-described method for manufacturing a planar magnetic element, it is preferable that the spherical particles are glass beads.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the method for manufacturing a planar magnetic element of the present invention will be described. In addition, a typical method of manufacturing a planar magnetic element that has been conventionally performed (see FIG.
The description of the same steps and the same members as those of the reference) will be omitted. The present invention is based on the plating base film 11 shown in FIG.
It retains gloss in d, and when roughening the surface of the insulating resin film 11c, the anchor treatment is performed by shot blasting using spherical particles. After the shot blasting, it is preferable to wash with water using an ultrasonic cleaner.

The diameter of the particles used for shot blasting is
The thickness is preferably 10 to 80 μm, more preferably 30 to 50 μm. Examples of the material of the particles include glass, alumina, zirconium and the like.

[0023]

Example A polyimide resin was applied as an insulating resin film on a ferrite sintered plate and then cured. The film thickness of the cured polyimide resin was 3 μm. Next, the particles having the shapes and diameters shown in Table 1 were used to subject the polyimide resin film to shot blasting. The surface roughness Rz of the polyimide resin film after the shot blast treatment was measured. The results are shown in Table 1.

Subsequently, Cu having a thickness of 1 μm was formed as a plating base on this by sputtering. Method 5 specified by JIS Z 8712 for 20 ° specular gloss Gs of plating base surface
It was measured by. In addition, the adhesion strength of the plating base was measured by a JIS H 8504 plating adhesion test. Table 1 shows the measurement results of Gs and adhesion strength. Finally, a photoresist was applied on the plating base to a thickness as shown in Table 1, and a parallel exposure was performed using a photomask by photolithography so that the coil spacing shown in Table 1 was obtained. Then, a resist frame was formed. The obtained resist frame was observed with an optical microscope, and the presence or absence of residue at the bottom of the resist frame groove was investigated. The results are shown in Table 1.

[0025]

[Table 1]

As is clear from Table 1, in the blasting process using irregular particles, the gloss of the plating underlayer is extremely low, the finish of the resist frame is poor, and the resist remains at the groove bottom. On the other hand, in the example of the present invention to which the shot blast treatment using spherical glass is applied,
It can be seen that the gloss is significantly improved, and as a result, the resist frame is also formed normally.

By the way, conventionally, in the shot blasting treatment, spherical glass was used as in the example of the present invention because amorphous particles were used to sharply scratch the surface of the insulating resin film to improve the adhesion. It was thought that sufficient adhesion was not obtained by shot blasting. However, as shown in Table 1, it was found that even in the examples of the present invention using spherical glass, a strong adhesion of 50 N / 25 mm or more can be obtained.

In the present invention, the material of the shot particles is not limited to spherical glass, but zirconia,
Needless to say, the same effect can be obtained with spherical shot particles such as alumina. Although the insulating resin film is formed on the ferrite substrate for simplification of description here, the structure of the planar magnetic element of the present invention is not limited to this. It is also possible to form the first magnetic film on the silicon substrate as disclosed in, and then form the insulating resin film on the first magnetic film. Also, a structure in which an insulating resin is formed on a silicon or alumina substrate may be used. In this case, after manufacturing the planar magnetic element, the silicon or alumina substrate may be peeled off and used.

Furthermore, the present invention is not limited to an insulating smoothing layer having a thickness of 0.01 to 10 μm, and is also effective when a plating underlayer film is formed on an insulating layer having a thickness of 10 μm or more. Also, when irregular particles are used, many particles stuck to the insulating resin film remain even after washing with water using an ultrasonic cleaner, whereas when spherical particles are used, the particles remain extremely. There are few, and the cleanability is also improved.

Further, in this embodiment, as the insulating resin film,
Although the polyimide resin, which is most difficult to secure the adhesion to the base film, is used, the present invention is not limited to this, and an epoxy resin, a polyamide resin, or the like may be used.

[0031]

According to the present invention, the surface of the insulating resin film is blasted by using spherical particles before electroless plating, thereby sufficiently maintaining the adhesion between the insulating resin film and the plating base film. It is possible to obtain a glossy plating underlayer film capable of forming a resist frame of more than 70 μm, and to provide an inexpensive method for manufacturing a planar magnetic element.

[Brief description of drawings]

FIG. 1 is a schematic view illustrating main steps in a method for manufacturing a planar magnetic element.

FIG. 2 is a schematic diagram illustrating a problem at the time of exposure when using conventional shot blasting.

3A is a perspective view of a planar magnetic element manufactured by applying the present invention, and FIG. 3B is a sectional view taken along line AA.

[Explanation of symbols]

1 Magnetic layer 2 Copper plating coil 3 terminals 5 parallel rays 5a scattered reflected light 6 Photo mask 7 Erosion part 10a, 10b Planar magnetic element 11 board 11a Si substrate 11b First ferrite magnetic film 11c Insulating resin film (polyimide film) 11d plating base film (plating copper film) 12 Resist frame 13 plated copper 14 Magnetic material (Epoxy resin containing ferrite magnet powder) 16 coil terminals 17 External electrode

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Kazuhiko Echizen             1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Made in Kawasaki             Technical Research Institute of Iron Co., Ltd. F-term (reference) 5E062 DD01

Claims (2)

[Claims] 1. A plating undercoat film forming step of forming a plating undercoat film on the surface of an insulating resin film, a photolithography step of forming a resist frame for forming a plating coil on the plating undercoat film, and a step of forming the plating coil after the plating coil is formed. A method of manufacturing a planar magnetic element, comprising: a step of removing a resist frame; a step of removing the plating underlayer film of the removed resist frame portion by etching; and a step of filling with a magnetic material, the method comprising: Before, a method of manufacturing a planar magnetic element, characterized in that the surface of the insulating resin film is shot-blasted with spherical particles. 2. The method of manufacturing a planar magnetic element according to claim 1, wherein the spherical particles are glass beads.