KR20040100945A - A coil substrate and a coil device of surface-mounted type - Google Patents

Abstract

PURPOSE: A coil substrate and a surface mount type coil element are provided to manufacture the coil substrate using less number of operations by using a conductive material having a high inductance and a low resistance. CONSTITUTION: A coil substrate includes an insulating substrate(11) and a coil conductive material(20). The coil conductive material is formed by using an electric coating layer on at least one surface of the insulating substrate. A spacing between adjacent conductive materials is less than 20 m. The insulating substrate includes a through hole(12) in a center thereof. The coil conductive material is formed in a spiral shape on both sides of the insulating substrate around the through hole. The coil conductive materials on upper and lower surfaces of the insulating substrate is connected with each other via the through holes.

Description

Coil Substrate and Surface-Mount Coil Device {A COIL SUBSTRATE AND A COIL DEVICE OF SURFACE-MOUNTED TYPE}

The present invention relates to a coil substrate and a surface-mounted coil element widely used in electrical appliances such as consumer equipment and industrial equipment, and more specifically, using a printed circuit circuit technology and a semiconductor circuit wiring technology with a small number of processes. The present invention also relates to a coil substrate and a surface-mounted coil element suitable for use in the frequency range of 10 kHz to 20 MHz, which can be constructed at low cost.

Conventionally, this type of surface mount coil element is widely used in electrical appliances such as consumer equipment and industrial equipment. Among them, small portable devices need to obtain a plurality of voltages from a single power supply to drive each device according to the enhancement of functions, and surface-mount coil devices are also used for such power supply applications. As a request for use in such small portable devices, electrical insulation, reliability, miniaturization, and low cost have been emphasized. Therefore, a surface coil structure applying printed circuit board technology and semiconductor circuit technology has been proposed. 7-142254, Japanese Patent Laid-Open No. 11-26239, Japanese Patent Laid-Open No. 9-153406, Japanese Patent Laid-Open No. 11-204361, Japanese Laid-Open Patent Publication No. 2002-353056, Japanese Laid-Open Patent Publication 2002- Publication 203732)

Coils constructed by these techniques form coil patterns on insulated substrates by application of printed circuit circuit technology and semiconductor circuit technology. In particular, in miniaturization, the electrical characteristics and product dimensions are uneven in comparison with the conventional winding type structures. There are advantages such as low cost due to low mass production.

However, in order to achieve such a small and thin coil element, high integration (high density) of the coil conductor is required, but there is a limit to high integration in the conventional coil structure. For example, in the conventional example of Japanese Patent Laid-Open No. 11-204361, there are problems as described below.

In other words, the pattern of the base conductor layer (sheet layer) is first formed, and then the resist and the base conductor layer are removed by etching to form a pattern having a shape of a cross-section, but the width of the conductor regardless of the aspect ratio of the gap between conductor portions is formed. When it is 20 micrometers or less, it is difficult to remove a resist and a base conductor layer. In the etching of the ground conductor layer, the pattern becomes thinner and the pattern root portion becomes thinner, which causes problems such as pattern peeling from the base substrate due to an increase in DC resistance and a decrease in adhesion.

In addition, in applications such as a power supply in which a large current flows through a coil conductor, a gap is formed in a magnetic core such as ferrite, but the gap is required to be highly precise and free from nonuniformity.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is an embodiment of a coil substrate and a surface mounted coil element according to the present invention, and is a perspective view before external terminal electrode formation showing a central portion in cross section.

2 is an embodiment of the present invention, a perspective view before forming the external terminal electrode showing the end structure.

Figure 3 is an embodiment of the present invention, a perspective view showing the appearance after external terminal electrode formation.

4 is an exploded perspective view of the core structure used in the embodiment.

5 is a plan view of the coil substrate used in the embodiment.

6 is a manufacturing process diagram of the coil substrate.

※ Explanation of symbols about main part of drawing ※

1: core structure 2: T-type ferrite core

3,6: Flat part 4: Mid leg part

5: U-shaped ferrite core 7: outer leg

8: microgap 10: coil substrate

11: insulation plate 12: perforation

15: front and back conductor portion 20: coil conductor

21: lead-out electrode portion 30: the base conductor layer

31: resist 32: electroplating layer

33: protective resin layer 35: adhesive

40: external terminal electrode

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and a first object thereof is to provide a coil substrate and a surface-mounted coil device having a high inductance, a low resistance coil conductor, and a low number of processes. Is in.

The second object of the present invention consists of a combination of small, high precision and low cost magnetic core, has a high precision gap in the inner side, and the outer side has a core structure of the closed structure and the non-uniformity in high inductance. To provide a low-resistance, surface-mounted coil device.

Other objects and novel features of the present invention will become apparent in the following Examples.

In order to achieve the above object, the coil substrate according to the present invention has a structure in which a coil conductor is formed on at least one surface of an insulating plate, and the coil conductor has a conductor portion formed of an electroplating layer, and also removes lead-out electrode portions and front and back conductor portions. The gap between conductor parts adjacent to each other is characterized in that 20 µm or less.

In the coil substrate according to the present invention of claim 2, the insulation plate has a perforation in the center of the invention, and the coil conductor is formed in a spiral shape on the front and back surfaces of the insulation plate around the perforation, and the insulation plate front and rear surfaces are formed through front and back conductor portions. Coil conductors are connected to each other.

The nose leaf substrate according to the invention of claim 3 is characterized in that the aspect ratio of the coil conductor is 0.2 to 5 according to claim 1 or 2.

The coil substrate according to the invention of claim 4 is characterized in that the insulating plate is impregnated with resin in glass cross in claim 1, 2 or 3.

The coil substrate according to the invention of claim 5 of the present invention is characterized in that the coil conductor has a DC resistance of 0.01 to 10 ohms according to claim 1,2,3 or 4.

The surface-mounted coil element according to the present invention of claim 6 includes a core structure which is made to face a first magnetic core and a second magnetic core, and has a closed outer portion and a central leg at both ends thereof;

A coil substrate in which spiral coil conductors are formed on the front and back surfaces of the insulating plate having perforations in the center, and the spiral coil conductors of the front and back surfaces are connected to each other via the front and back conductor portions;

An external electrode connected to the coil conductor,

The coil substrate may be disposed inside the core structure in the state where the center leg part enters the through hole, and the first and second magnetic cores may have a gap in a part of the center leg part.

In the surface-mounted coil device according to the invention of claim 7, the first ferrite core has a central leg portion, the second ferrite core has outer leg portions at both ends, and the front end surface of the outer leg portion is the first end. It is characterized by facing the ferrite core.

The surface-mounted coil element according to the invention of claim 8 of the present invention is characterized in that the gap is 0.1 to 100 µm according to claim 6 or 7.

Best Mode for Carrying Out the Invention Embodiments of a coil substrate and a surface mounted coil element according to the present invention will be described with reference to the drawings.

1 to 3 show an embodiment of a coil substrate and a surface mounted coil element according to the present invention, FIG. 4 shows a core structure used in the embodiment, FIG. 5 shows a coil substrate, and FIG. 6 shows a coil substrate. The manufacturing process of the coil conductor to form is shown.

In these drawings, the surface-mounted coil element includes a core structure 1, a coil substrate 10 disposed therein, and a lead end of coil conductors 20 formed on both surfaces of the coil substrate 10 connected thereto. An external terminal electrode 40 is provided. As shown in FIG. 3, the external terminal electrodes 40 are formed at the both ends of the core structure 1 in a c-shaped cross section.

As shown in FIG. 4, the core structure 1 includes a T-type ferrite core 2 and a U-shaped ferrite core 5 as magnetic cores. The T-type ferrite core 2 has a center leg portion (footnote convex portion) 4 formed at the center of the plate portion 3, and the U-shaped ferrite core 5 has outer leg portions at both ends of the plate portion 6. (7) formed, and the outer shell which became substantially closed by facing the distal end surface of the c-shaped ferrite core 5 and the outer leg portion 7 to the flat plate portion 3 of the T-type ferrite core 2 The part (flat plate part 3, 6 and the outer leg part 7) is comprised, and the center leg part 4 is arrange | positioned inside the outer part.

By making the center leg part 4 slightly shorter than the outer leg part 7, the microgap 8 can be formed between the front end surface of the center leg part 4, and the flat plate part 6 here. The gap 8 is used to prevent self-saturation of the ferrite cores 2 and 5 by the current flowing through the coil conductor 20 of the coil substrate 10. The external dimension of the core structure 1 is very small (one side). Since it is a rectangular parallelepiped of several mm or less), the gap 8 becomes like this. Preferably it is 0.1-100 micrometers, More preferably, it is set to 0.1-50 micrometers. In addition, it is difficult for the gap 8 to be less than 0.1 mu m in terms of core processing accuracy, and when it exceeds 100 mu m, the gap becomes large and the inductance of the coil tends to decrease.

The formation of the T-type ferrite core 2 and the U-shaped ferrite core 5 is performed by grinding a ferrite substrate having a predetermined thickness into a high precision slicer using a grindstone such as a diamond wheel grindstone, and a center leg portion 4. And left by the outer leg 7 to grind the thickness of the unnecessary portion thinly.

The ferrite substrate for constructing the ferrite cores (2) and (5) comprises at least one main component containing iron oxide and nickel oxide and an additive comprising one or two or more kinds of bismuth oxide, vernadium oxide, chlorine oxide and boron oxide. And a first subcomponent composed of silicon oxide and a second subcomponent composed of one or two or more of magnesium oxide, calcium oxide, verium oxide, and strontium oxide. %, A 1st component, and a 2nd component are 0.1-10.0 weight%, respectively. An example of the composition (weight%) of a preferable main component is shown below.

Fe ₂ O ₃ : 66%

CuO: 3%

ZnO: 20%

NiO: 11%

The coil substrate 10 is formed by forming a spiral coil conductor 20 on the front and back surfaces of the insulating plate 11 having the perforations 12 at the center, and the front and back conducting portions 15 formed at the periphery of the perforations 12 ( For example, the coil conductors 20 (the circumferential direction of the coil conductors on the rear surface side in FIG. 5 in the front and back sides in FIG. 5) are connected to each other via conductor holes. The coil conductors 20 on the front and back sides are respectively connected to the lead end electrode portions 21 at one end and the other end of the insulating plate.

The coil conductor 20 is constructed in the order of FIG. First, a base conductor layer (sheet layer) 30 is formed by electroless plating on the front and back surfaces of the insulating plate 11, as shown in FIG. 6 (a), and an electrodeposition film 31 is deposited thereon. A selective plating mask resist corresponding to the coil conductor formation pattern is formed by the photolithography method. Then, the electroplating layer 32 for coil conductors is electrodeposited by the electroplating method selectively on the portion where the base conductor layer 30 is exposed by using the pot resist 31 as a plating mask. However, in the process of Fig. 6A, the thickness of the electroplating layer 32 for coil conductors is still small.

Next, as shown in Fig. 6 (b), the pot resist 31 as the plating mask is removed, and then the underlying conductor layer 30 other than the portion where the electroplating layer 32 for coil conductor is formed is etched and removed.

Thereafter, as shown in FIG. 6 (c), the electroplating layer 32 for coil conductors is further grown by electrodeposition by an electroplating method without a selective plating mask. Thereby, the conductor part of sufficient thickness which consists of the electroplating layer 32 is obtained, and the electroplating layer 32 can be grown and formed at high density until the clearance gap G between adjacent conductor parts is 15 micrometers or less.

After the coil conductor 20 is formed on both sides of the insulating plate 11 by the completion of the formation of the electroplating layer 32 for the coil conductor, the protective resin layer (solder resist) 33 is formed as shown in FIG. The coil substrate 10 is completed by printing on the front and back surfaces of (11) and covering and protecting the coil conductor 20 with the protective resin layer 33.

The coil substrate 10 is a coil conductor 20 in which the electroplating layer 32 is grown and formed at a high density until a gap G between adjacent conductor parts of the electroplating layer 32 for coil conductors is 15 µm or less. ) And the aspect ratio (height / width of the conductor part) of the coil conductor 20 can be set as high as about 0.2 to 5, so that the DC resistance can be reduced to about 0.01 to 10 ohms. It is possible to apply to the coil element for power supply with large current of 20). In addition, setting the DC resistance to less than 0.01 ohms is difficult to realize in a small coil element, and when it exceeds 10 ohms, heat generation due to the current of the coil conductor 20 becomes a problem. If the aspect ratio is less than 0.2, the DC resistance of the coil conductor 20 becomes large, and if the aspect ratio exceeds 5, it is not preferable because problems such as an increase in electroplating time and an uneven increase in the formation of the coil conductor 20 occur.

After constructing the coil substrate 10 as described above, as shown in FIG. 1, the central substrate 4 of the T-type ferrite core 2 enters the through-hole 12 on the coil substrate 10 side, and thus the coil substrate 10 is formed. ) Is placed inside the T-type ferrite core 2 and the U-shaped ferrite core 5, and the T-type ferrite core 2 and the U-shaped ferrite core 5 are mutually bonded with an adhesive 35 such as an epoxy resin. Adhesively integrated as the core structure 1 in the facing state.

Thereafter, the pair of external terminal electrodes 40 are surrounded by a c-shape so as to surround both ends of the core structure 1 including the exposed portion of the lead-out electrode portion 21 of the coil substrate 10 of FIG. Form. The external terminal electrode 40 is constructed by sequentially forming Cr and Cu conductor layers with a mask sputter, and then forming an electroplating layer in the order of Cu, Ni, and Sn by barrel plating. Thereby, the external terminal electrode 40 connected to the said lead-out electrode part 21 (in other words, connected to the coil conductor 20) is obtained.

In the process of Fig. 6, the insulating plate 11 is preferably impregnated with resin such as glass cross BT redin, polyimide, epoxy aramid, and the like in order to have sufficient strength in a thin shape. In addition, the dielectric constant of the resin is selected to 7 or less in order to avoid the increase of the floating capacity. Ceramic may also be used as the insulating plate 11, but in this case, in order to avoid an increase in floating capacity, a dielectric constant of 7 or less is selected.

In addition, although Cu is used as the metal material of the base conductor layer 30 and Cu is also used as the metal material of the electroplating layer 32 for coil conductors, it is possible to adopt Ag or Ni in view of permittivity and cost. .

In addition, the external terminal electrode 40 may be formed by applying and curing a conductive paste such as Ag or Cu.

In addition, when a core structure having a closed outer shell and a center leg at both ends is formed by grinding a ferrite substrate by a high precision slicer, the T-shaped ferrite core (2) and the c-shaped ferrite can be reduced in mass production. The core structure of the embodiment in which the core 5 is combined is more preferable, but the core structure is not necessarily limited to this structure.

According to this first embodiment, the following effects can be obtained.

(1) The coil conductors 20 of the coil substrate 10 are patterned on both sides of the insulating plate 11 by electroplating, and the coil conductors 20 can be formed at a high density (conductive portions adjacent to each other). Since the clearance gap G can be 15 micrometers or less, the DC resistance of the coil conductor 20 can be reduced. As a result, it is possible to form a high aspect ratio coil conductor 20 with excellent electrical reliability.

(2) The T-shaped ferrite cores (2) and the U-shaped ferrite cores (5) of the core structure (1) are ground to a high-precision slicer using a grindstone such as a diamond wheel grinding wheel, and the ferrite substrate having a predetermined thickness is formed. 4) or by leaving the outer leg part 7 thin and grinding unnecessary thicknesses, and by combining these cores, the structure can be realized with gaps 8 and closed with high precision and less unevenness between products. .

(3) Compact, low-profile surface-mounted coil elements can be constructed with high precision by low cost processing, the coil conductor 20 has low resistance, and the core structure 1 has high precision gap. (8) can be suitably used as a coil element for power supply (for example, a boost coil element) of 10 kHz to 20 MHz.

(Example)

Hereinafter, the coil substrate and the surface mounted coil device according to the present invention will be described in detail by way of examples.

Electroless Cu film with a thickness of 0.1 to 1 µm is coated on the upper and lower surfaces of a glass cross substrate having a thickness of 60 µm (through which the glass cross is impregnated with BT reddin) processed through holes for conducting the conductor hole and the center leg. It plated and used as the base conductor layer. And then forming the pattern of the spiral where the coil conductor by the port lithography by forming a photosensitive electrodeposition resist on the both surfaces of the substrate and go's cross in a current density of 15A / dm ² or less subjected to electroplating for about 20 minutes height 35㎛, A Cu conductor pattern having a width of 35 µm was formed. After stripping the mask resist for selective plating, the underlying conductor layer was etched and subjected to second electroplating with a predetermined current profile to form a Cu conductor pattern having a height of 75 µm and a width of 65 µm. Cu was blackened on this surface, and the surface was coated with a solder ink resist to prepare a wafer (collective assembly of coil substrates) in which coil conductors of spiral patterns were aligned. In addition, the unnecessary part in the assembly to a ferrite board | substrate was cut out into slit shape using the high precision slicer.

Next, a diamond wheel grinding wheel was used to form a ferrite substrate with a thickness of 0.77 mm, one convex pattern to form a T-type ferrite core and the other concave pattern to form a U-shaped ferrite core, respectively, by a high precision slicer. did.

The assembly of coil substrates having these coiled spiral coil conductors and the aggregates of T-type and U-shaped ferrite cores were bonded while pressing in an atmosphere of 150 ° C. using an epoxy adhesive. The T-type ferrite core backplate portion of the bonded substrate was ground to a thickness of 0.77 mm with a high precision slicer, and then chipped with a dicer to fabricate each device.

After that, since the external terminal electrode serving as the user terminal for circuit connection is formed, after the parallel polishing, the Cu (drawing electrode electrode part) on the terminal surface is cleaned by both weight treatment and dry treatment, and Cr is masked by the mask sputtering method. And Cu were formed into a film continuously. By carrying out parallel plating of Cu, Ni, and Sn, a surface-mounted coil device having a product size of 3 mm X 2.6 mm X 0.8 mm in height could be constructed.

In the same manner, a surface-mounted coil element having a product size of 4 mm x 4 mm x 1 mm in height could be constructed.

As mentioned above, although the Example and Example of this invention were described, this invention is not limited to this, It will be clear to those skilled in the art that various deformation | transformation and a change are possible in the range of the claim.

As described above, according to the present invention, it is possible to realize a coil substrate and a surface-mounted coil element having a high inductance, a low resistance coil conductor, and being operable with a small number of processes.

In addition, it is made of a combination of small size, high precision and low cost magnetic core, and has a high precision gap inside, and uses the core structure of the outer structure to close the inductance to reduce the inductance non-uniformity to increase the inductance can do.

Claims (10)

Insulation board, A coil substrate having a coil conductor formed by an electroplating layer on at least one surface of an insulating substrate, and having a gap between adjacent conductors of 20 m or less. The method of claim 1, It has a hole in the central portion of the insulating substrate, the coil conductor is formed in a spiral (spiral) on both front and back sides of the insulating substrate around the hole and the coil conductors on the front and back surfaces of the insulating substrate through the hole is connected to each other. Coil substrates. The method of claim 1, Coil substrate, characterized in that the aspect ratio of the coil conductor is 0.2 to 5. The method of claim 1, The insulating substrate is a coil substrate, characterized in that the resin is impregnated with glass cross. The method of claim 1, The coil substrate, characterized in that the DC resistance of the coil conductor is 0.01 ~ 10 ohms. A core structure which is made to face the first magnetic core and the second magnetic core and has closed outer and central legs at both ends thereof; A coil substrate having an insulated field substrate having perforations in the center, a spiral coil conductor formed on the front and back surfaces thereof and connected to each other through the perforations; An external electrode connected to the spiral coil conductor, The coil substrate is disposed inside the core structure in a state where the center leg part enters the through hole, and the first and second magnetic cores have a gap in a part of the center leg part. . The method of claim 6, The spiral coil conductor is a surface-mounted coil element, characterized in that the gap between the adjacent portions to each other 20㎛ or less. The method of claim 6, And a first magnetic core having a center leg portion, a second magnetic core having an outer leg portion at an end portion, and a distal end surface of the outer leg portion abuts against the first magnetic core. The method of claim 6, Surface-mount coil device, characterized in that the gap is 0.1 ~ 100㎛. Forming a ground conductor layer on at least one side of the insulating substrate, Patterning a resist layer on the underlying conductor layer, Using the patterned resist layer as a mask, a coil conductor layer is selectively formed on the portion exposed by the base conductor layer. Removing a resist layer and a ground conductor layer other than the portion where the coil conductor layer is formed, And forming the coil conductor layer until the gap between the conductors adjacent to each other is 20 µm or less.