JP2007214348A - Magnetic induction element and manufacturing method thereof - Google Patents

Abstract

[Objective] To provide a thin film magnetic induction element in which a through hole is formed in a thick magnetic insulating substrate at a low cost and a method for manufacturing the same.
The magnetic induction element includes a first coil conductor formed on a first main surface (front surface) of a magnetic insulating substrate and a bottom portion of a groove formed on a second main surface (back surface). The second coil conductor 5 to be formed, the connection conductor 3 formed to electrically connect the end of the first coil conductor 4 and the end of the second coil conductor 5, and the connection conductor 3 are formed. For this purpose, it is constituted by a through hole 23 opened in the magnetic insulating substrate 1. A solenoidal coil conductor is formed by the first coil conductor 4, the second coil conductor 5, and the connection conductor 3, and a protective film 16 is coated on the surface. By forming the groove 21 and digging a hole from one direction in a thin portion of the magnetic insulating substrate 1 to form a through hole, the through hole can be formed in the thick magnetic insulating substrate at low cost.
[Selection] Figure 1

Description

  The present invention relates to a magnetic induction element such as a thin inductor and a transformer, and a manufacturing method thereof.

  In recent years, various electronic devices have been reduced in size and weight, and there has been a demand for lower power consumption. Accordingly, there is an increasing demand for a small switching power supply as a power supply mounted on an electronic device. In switching power supplies used for small portable devices such as notebook personal computers and mobile phones, thin CRTs, flat panel displays, etc., there is a strong demand for miniaturization and thinning. In particular, in various portable electronic devices, a battery is used as a power source, and a power conversion device such as a DC-DC converter is built in, and a reduction in size and thickness is required. However, in conventional switching power supplies, magnetic components such as transformers and inductors, which are main components, occupy a large volume.

  Various efforts have been made to reduce the size and thickness of the device, and Patent Document 1 describes a thinned inductor (thin film magnetic induction element). FIG. 4 is a configuration diagram of the inductor. FIG. 4A is a plan view of the main part, FIG. 4B is a cross-sectional view of the main part taken along line XX of FIG. ) Is an enlarged view of a portion B in FIG. As shown in FIG. 4, this element has a structure in which a magnetic conductor generated by a coil is in the substrate plane by forming a through hole in the magnetic insulating substrate 1 and winding a coil conductor. A coil conductor 4 is formed on the first main surface of the magnetic insulating substrate 1, and a coil conductor 5 is formed on the second main surface. The conductors 4 and 5 are electrically connected by the connection conductor 3 formed in the through hole 23. Thus, a solenoidal coil is formed. Along with miniaturization, the size of the thin-film magnetic induction element 1 is reduced to a side length L of 3.5 mm (square) and a thickness of 525 μm, and the diameter of the through hole 23 is as small as about 130 μmφ on the surface. It has become a thing.

  Such a through hole 23 is processed by sandblasting, laser processing, electric discharge processing, ultrasonic processing, or the like. As a method of processing a large number of through holes with high productivity, there is sandblasting. In this method, the diameter of the hole is reduced as processing from the surface of the magnetic insulating substrate 1 to the back. For example, as shown in FIG. 5, when a hole 31 having a diameter D3 of 150 .mu.m is formed on the surface of a ferrite flat plate, which is a magnetic insulating substrate 1 having a thickness M of 500 .mu.m, by sandblasting, the center (depth of the magnetic insulating substrate 1). N is 250 μm), the diameter D4 of the bottom of the hole is about 80 μm, the size is reduced to about 2/3, and the side wall of the hole 31 is tapered. Even when trying to dig deeper, the sandblast particles from the bottom 33 bounce off and cannot be dug.

Here, although the sandblasting is shown, the taper 32 is attached to the hole 31 in this way also in other processing methods. Therefore, it is inevitable that the through hole 3 has a constricted central portion. In the figure, 6a and 6b are terminal electrodes, 2 is a connecting conductor for connecting the terminal electrodes 6a and 6b, 16 is a protective film, and 16a is an opening.
JP 2004-274004 A

  If the thickness of the magnetic insulating substrate 1 is increased in order to reduce the size of the thin film magnetic induction element (reduction of the occupied area) or to improve the performance of the thin film magnetic induction element, the through holes 3 are formed by processing. Since the hole has a taper, the hole diameter gradually decreases in the depth direction of the magnetic insulating substrate 1, and it becomes difficult to form the through hole 3 in the thick magnetic insulating substrate 1. Further, as shown in FIG. 4, when the holes are dug from both surfaces of the magnetic insulating substrate 1, the manufacturing cost is increased.

  An object of the present invention is to solve the above-described problems and provide a thin film magnetic induction element in which a through hole is formed in a thick magnetic insulating substrate at low cost and a method for manufacturing the same.

      In order to achieve the above object, the first conductor formed on the first main surface of the magnetic insulating substrate, the second conductor formed on the second main surface of the magnetic insulating substrate, and the magnetic insulating substrate are penetrated. In a thin magnetic induction element having a coil conductor formed by connecting a connection conductor formed in each through hole, the thickness of the magnetic insulating substrate at the location where the through hole is provided is selectively reduced. .

  The coil conductor may be a solenoidal coil conductor.

  The magnetic insulating substrate may be a ferrite substrate or a dust core.

  A first conductor formed on the first main surface of the magnetic insulating substrate; a second conductor formed on the second main surface of the magnetic insulating substrate; and a through-hole penetrating the magnetic insulating substrate. In the method of manufacturing a thin magnetic induction element having a coil conductor formed by connecting each of the connection conductors, a step of forming a groove in the magnetic insulating substrate so as to include the planned location for forming the connection conductor; The manufacturing method which has the process of forming a through-hole in this, the process of forming the said connection conductor in this through-hole, and the process of forming the conductor connected to this connection conductor on both surfaces of the said magnetic insulation board | substrate And

  Moreover, it is good to set it as the manufacturing method in which the said through-hole is formed by sandblasting.

  The diameter of the through hole may be a manufacturing method in which the diameter decreases from one surface of the magnetic insulating substrate to the other surface (tapered).

  According to the present invention, when the through hole is formed in the thick magnetic insulating substrate, the magnetic insulating substrate is selectively thinned by digging the magnetic insulating substrate in advance so as to include the portion where the through hole is to be formed. By digging a hole from the direction to form the through hole, the through hole can be formed even with a thick magnetic insulating substrate.

  Further, by digging a hole from one direction, the manufacturing cost can be reduced as compared with the conventional case of digging a hole from both directions.

  Thus, since a thick magnetic insulating substrate can be used, even if the magnetic induction element is reduced in size (occupied area is reduced), coil characteristics equivalent to those of the prior art can be obtained. In addition, when the size of the magnetic insulating substrate is the same as the conventional size, the thickness of the magnetic insulating substrate can be increased, so that the coil characteristics can be improved.

  The best mode for carrying out the invention will be described in the following examples.

  FIGS. 1A and 1B are configuration diagrams of an inductor which is a magnetic induction element according to a first embodiment of the present invention. FIG. 1A is a plan view of an essential part, and FIG. 1B is an XX of FIG. The principal part sectional drawing cut | disconnected by the line | wire, the figure (c) is an enlarged view of the A section of the figure (b). In addition, the same code | symbol was attached | subjected to the same site | part as FIG.

  This magnetic induction element is formed on the first coil conductor 4 formed on the first main surface (front surface) of the magnetic insulating substrate 1 and on the bottom portion 22 of the groove 21 formed on the second main surface (back surface). Two coil conductors 5, a connection conductor 3 formed to electrically connect the end of the first coil conductor 4 and the end of the second coil conductor 5, and magnetic insulation to form the connection conductor 3 It consists of a through hole 23 opened in the substrate 1. A solenoidal coil conductor is formed by the first coil conductor 4, the second coil conductor 5, and the connection conductor 3, and a protective film 16 is coated on the surface.

  The magnetic insulating substrate 1 is, for example, a ferrite substrate. When the length L1 of the magnetic insulating substrate 1 is 3.0 mm, the horizontal length L2 is 3.5 mm, and the thickness H is 600 μm, the depth T of the groove 21 is 350 μm, and the groove 21 is formed. The thickness W of the magnetic insulating substrate 1 at the formed position is set to 250 μm. Since the through hole 23 is formed by digging a hole having a surface diameter D1 of 150 μm from only one direction, a taper 24 is formed on the side wall of the through hole 23, and the diameter D2 of the bottom surface of the through hole 23 is 80 μm. .

  In the figure, 6a and 6b are terminal electrodes formed on the outer periphery of the magnetic insulating substrate 1, 2 is a connecting conductor for connecting the terminal electrodes 6a and 6b, and 16a is an opening formed in the protective film 16.

  In this way, the through holes 23 can be formed even in the thick magnetic insulating substrate 1 by partially forming the grooves 21 to thin the magnetic insulating substrate 1 and forming the through holes 23 in this thin portion from one direction. Moreover, since the through-hole 23 can be formed in one direction, manufacturing cost can be reduced.

  2 is a cross-sectional view of the main part taken along line YY of FIG. A groove 21 is formed only around the through hole 3.

  FIG. 3 shows a method of manufacturing the magnetic induction element of FIG. 1, and FIGS. As the magnetic insulating substrate 1, a Ni—Zn ferrite substrate having a thickness H of 600 μm was used. The thickness H of the magnetic insulating substrate 1 is determined from necessary inductance, coil current value, and magnetic properties (such as magnetic permeability) of the substrate, and is not limited to this thickness.

  First, the thickness of the magnetic insulating substrate 1 is reduced by digging the grooves 21 so that the magnetic insulating substrate 1, which is a ferrite substrate having a thickness of 600 μm, includes a portion where the through hole 23 is to be formed. The groove 21 is formed in a band shape, and the thickness of the thinned magnetic insulating substrate 1 is W.

  As the groove 21 processing, there is sand blasting or mechanical processing by a dicer or the like. In this embodiment, the sand blasting method is used ((a) in the figure).

  Next, the through hole 23 is formed in the magnetic insulating substrate 1 by digging a hole in one direction from the first main surface by the sandblast method. The diameter D1 of the surface of the through-hole 23 is 150 μm, and the diameter D2 of the bottom portion 22 is 80 μm ((b) in the figure). Here, the planar shape of the groove 21 and the planar shape of the through-hole 23 were processed using a resist as a mask to shield sandblast particles. Therefore, it can have an arbitrary planar shape such as a square in addition to a circle.

  The resist pattern for the groove 21 was 2.5 mm × 0.3 mm, and the resist pattern for the through hole 23 was 150 μmφ. The sandblasting conditions were sprayed from one direction, the particle size of the spray particles SiC was about 20 μm, the spray amount was 100 mg / min, and the spray pressure was 0.2 MPa. Groove 21 processing had a processing time of 2 hours, and the groove depth was about 350 μm. At this time, the thickness W of the magnetic insulating substrate at the location where the groove is formed is 250 μm. The through hole 23 was processed by setting the processing time to 2 hours, and the minimum hole diameter (bottom diameter D2) was about 80 μm. For comparison, a prototype without groove processing was also performed, but the hole did not penetrate.

  Next, a Ti film and a Cu film (not shown) are formed on the magnetic insulating substrate 1 by sputtering to form a conductive plating seed layer (not shown). Each film thickness is 0.1 μm for the Ti film and 0.2 μm for the Cu film. Next, the pattern of the 1st, 2nd coil conductors 4 and 5 which are going to be formed in the 1st main surface and the 2nd main surface is formed with a resist. A Cu film is formed on the openings of the resist pattern by electrolytic plating. At this time, a Cu film is also formed on the through hole 23 by plating, and the connection conductor 3 is also formed at the same time. Next, a Ni film having a thickness of 2 μm and an Au film having a thickness of 1 μm are continuously formed on the Cu film by electrolytic plating. Next, by removing unnecessary resist and sheet layers, a solenoidal coil conductor composed of the first and second coil conductors 4 and 5 and the connection conductor 3 is formed. Although the thicknesses of the first and second coil conductors 4 and 5 are each 37 μm, they are exaggerated in FIG. 2 ((c) in FIG. 2).

  Table 1 shows the DC superposition characteristics of the inductance values of the products of the present invention. Here, the vertical length L1 of the magnetic insulating substrate 1 was 3.0 mm, the horizontal length L2 was 3.5 mm, and the thickness H was 600 μm. The distance d between the connecting conductors 3 that becomes the solenoid coil width is 1.5 mm, and the permeability μ of the ferrite substrate is 100. The number of coil turns is 11 turns. The measurement frequency was 2 MHz.

  Table 2 shows the DC superposition characteristics of the inductance values of the conventional magnetic induction element. The material is the same as that of the product of the invention, but the dimensions are different. That is, in the conventional magnetic induction element whose characteristics are shown in Table 2, the vertical length L1 and the horizontal length L2 are 3.5 mm (square), the thickness H is 525 μm, and the distance d between the connection conductors 3 is 1. The number of turns of the coil is 75 mm.

  Table 3 shows the DC superposition characteristics of the inductance value of the magnetic induction element, which is 600 μm, which is the same as that of the present invention, by increasing the thickness of the conventional magnetic induction element for comparison. The use of the comparative product is the same as in Table 2 except for the thickness H.

  As shown in Table 1, although the inductance value decreased with the application of the DC superposition current, the same value as 2 μH of the conventional magnetic induction element could be obtained at 200 mA. That is, L1 of the conventional magnetic induction element can be shortened by 0.5 mm (the area can be reduced by about 15%).

このデータは表２の従来のＬ＝３．５ｍｍ（正方形）、厚さ＝５２５μｍ、ｄ＝１．７５ｍｍ、ターン数＝１１と、ほぼ同じであった。

This data was almost the same as the conventional L = 3.5 mm (square), thickness = 525 μm, d = 1.75 mm, and number of turns = 11 in Table 2.

当然、Ｌ１＝Ｌ２＝３．５ｍｍ(正方形)、厚さ＝６００μｍ、ｄ＝１．７５、ターン数＝１１にすると、表３の比較品に示すように従来より厚くした分コイル特性を改善できる。

Naturally, when L1 = L2 = 3.5 mm (square), thickness = 600 μm, d = 1.75, and number of turns = 11, the coil characteristics can be improved by increasing the thickness as shown in the comparative product of Table 3. .

尚、溝２１は一面（ここでは第２主面）から形成したが、両面（第１、第２主面）から形成して、磁性絶縁基板１の厚さ薄くし、一方の溝の底面から一方向に穴をあけて貫通させて、貫通孔２３を形成しても構わない。また、磁性絶縁基板１として、フェライト基板の場合で説明したが磁性粉末を絶縁処理してから圧粉成形した圧粉磁芯であっても構わない。

Although the groove 21 is formed from one surface (here, the second main surface), it is formed from both surfaces (the first and second main surfaces), the thickness of the magnetic insulating substrate 1 is reduced, and from the bottom surface of one of the grooves. The through hole 23 may be formed by making a hole in one direction to penetrate. The magnetic insulating substrate 1 has been described as a ferrite substrate, but may be a dust core obtained by subjecting magnetic powder to insulation treatment and then compacted.

BRIEF DESCRIPTION OF THE DRAWINGS It is a block diagram of the inductor which is a magnetic induction element of 1st Example of this invention, (a) is a principal part top view, (b) is principal part sectional drawing cut | disconnected by the XX line of (a), ( c) Enlarged view of part A of (b) Sectional drawing of the principal part cut | disconnected by the YY line of FIG. 1. It is a manufacturing method of the magnetic induction element of FIG. 1, (a) to (c) is a main part manufacturing process sectional view showing in order of processes. It is a block diagram of the inductor which is the conventional magnetic induction element, (a) is a principal part top view, (b) is principal part sectional drawing cut | disconnected by the XX line of (a), (c) is (b). Enlarged view of part B of Diagram showing a state where holes are dug from one direction by sandblasting on a thick magnetic insulating substrate

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Magnetic insulating board 2, 3 Connection conductor 4 1st coil conductor 5 2nd coil conductor 6a, 6b Terminal electrode
16 Protective film 16a Opening 21 Groove 22 Bottom 23 Through-hole 24 Taper D1 Surface diameter D2 Bottom diameter
H Thickness of magnetic insulating substrate
W Thin part thickness
T depth of groove

Claims (6)

A first conductor formed on the first main surface of the magnetic insulating substrate, a second conductor formed on the second main surface of the magnetic insulating substrate, and a connection conductor formed in a through-hole penetrating the magnetic insulating substrate A thin magnetic induction element having coil conductors connected to each other, wherein the thickness of the magnetic insulating substrate at the portion where the through hole is provided is selectively reduced. The magnetic induction element according to claim 1, wherein the coil conductor is a solenoidal coil conductor. 3. The magnetic induction element according to claim 1, wherein the magnetic insulating substrate is a ferrite substrate or a dust core. A first conductor formed on the first main surface of the magnetic insulating substrate, a second conductor formed on the second main surface of the magnetic insulating substrate, and a connection conductor formed in a through-hole penetrating the magnetic insulating substrate In the method of manufacturing a thin magnetic induction element having coil conductors connected to each other, a step of forming a groove in the magnetic insulating substrate so as to include a portion where the connection conductor is to be formed; A step of forming a hole; a step of forming the connection conductor in the through hole; and a step of forming a coil conductor by forming conductors connected to the connection conductor on both surfaces of the magnetic insulating substrate. A method for manufacturing a magnetic induction element. The method of manufacturing a magnetic induction element according to claim 4, wherein the through hole is formed by sandblasting. 6. The method of manufacturing a magnetic induction element according to claim 5, wherein the diameter of the through hole decreases from one surface of the magnetic insulating substrate toward the other surface.

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