TWI387983B - Planar magnetic device - Google Patents

Description

Planar magnetic component

The present invention relates to a planar magnetic component, and in particular to a coupling reliability between the external electrode and the external electrode.

In recent years, with the prevalence of the use of mobile devices such as mobile devices and notebook computers, the use of small electronic components for internal use has evolved. In particular, the development of a part of the power supply circuit that accounts for a large volume, and the development of small and thin components such as ICs, inductors, and capacitors used here are in progress. Among them, the inductor has the largest occupied volume, and it is the component that is the most demanding in terms of small size and thinness.

In such a case, there is a proposal for a planar magnetic element which is advantageous for thinning (see, for example, Japanese Laid-Open Patent Publication No. 2003-332163, No. 2006-128335).

In the structure in which the upper magnetic body is followed by the adhesive layer, a method of providing the external electrode coupling terminal opening portion on the upper magnetic body side is known, and the adhesive agent will be disclosed in the above-mentioned Japanese Patent Publication No. 2003-332163. The terminal portion is contaminated, and the interface with the external electrode may be mixed in a different phase. For example, in a reliability test such as a current load test, a problem may occur. In order to avoid this, there is a method of providing a through hole in the lower magnetic body side, coupling the coil terminal and the external electrode with a conductive paste, and forming an external electrode on the lower magnetic side. However, since the coupling portion is formed using a conductive paste containing a resin component, there is a difference in material characteristics due to a difference in material characteristics at a coupling position with a coil terminal portion made of a metal, resulting in reliability such as a current load test. Adverse conditions still occur during the test.

On the other hand, the above-mentioned Japanese Patent Laid-Open No. 2006-128335 does not have a detailed description of the relevant coupling portion, but discloses that a through hole (through hole) is provided on the lower magnetic body side, and the coil terminal and the coupling portion are connected. Both are formed of the same substance, and the external electrode is formed by a conductive paste containing a resin component. However, the coupling position of the coupling portion and the external electrode is a heterogeneous material joint, which may result in a defect in the reliability test such as a current load test due to poor material properties.

The present invention is advantageous in solving the above problems, and an object of the invention is to provide a planar magnetic element which can provide sufficient reliability without causing a defect in a reliability test such as a current load test.

Hereinafter, the warp and weft will be described with reference to the present invention.

From the viewpoint of ensuring the coupling reliability from the coil terminals, it is preferable that the heterojunction is not associated with a decrease in reliability, but is formed of the same substance from the coil terminal to the external electrode. Here, the inventors firstly form an integral part of the coupling portion in the step of electrically forming the coil and the coil terminal forming step, and then, the external electrode is electrically coupled to the coupling portion by electrical plating. The matter of formation is considered.

Therefore, the inventors provided a through hole at a position corresponding to the coil terminal on the lower magnetic body side where the coil is formed, and also forms a coupling portion while plating the through hole portion when the coil and the coil terminal are formed.

However, it has been found that the shape of the straight tubular through hole has a non-uniformity in the plating thickness of the through hole, and in particular, it is difficult to form a plating layer on the lower side of the lower magnetic body of the coupling portion with the external electrode. In this state, proper electrical coupling with the external electrodes cannot be obtained.

Therefore, the inventors and the like further review the shape of the through hole. As a result, it was found that a plating layer having a sufficient thickness can be formed on the lower side of the lower magnetic body by forming a through hole into a taper shape. Thereby, the coupling portion can be realized by a coil terminal integrally formed of the same substance that can be well coupled with the external electrode.

Then, in order to be coupled to the formed coupling portion, the external electrode is formed by electroplating from the lower surface side of the lower magnetic body, whereby the coil terminal to the external electrode can be formed of the same substance. That is, a magnetic element that improves the reliability of the coupling portion can be obtained.

Furthermore, in the present invention, since the spiral coil can be formed on the lower magnetic body having the push-through through hole, the shape of the coil is further examined. When an inductor is used in a power supply circuit system, in order to reduce its resistance loss, it is necessary to increase the coil cross-sectional area. In the case of a spiral coil, although the thickness of the coil can be increased, the thickness must be about 40 to 100 μm. Therefore, when a coil formed by optical lithography is formed, the thickness of the resist frame to be a mold frame must be 40 to 100 μm. Therefore, in general, a photoresist is used in an acrylic system which easily penetrates light in the thickness direction during exposure.

However, as shown in FIG. 3, when the coating of the above-mentioned photoresist 14 is performed on the lower magnetic body 2 having the push-like through hole 4 of the present invention, since the gap having the through hole 4 is provided, the light in the upper portion thereof The thickness of the resistor 14 will appear concave. If the exposure is performed in such a state, the scattering of light 13 caused by the depression causes the region which should be shielded from light to be exposed to light. In addition, in the figure, the component code 11 is a glass mask and a 12-type glass mask light-shielding part.

For example, in the case of a negative photoresist, it is necessary to shield the coil wire portion which must be dissolved in the subsequent development step, but as described above, if light scattering occurs due to the through hole, the photoresist is sensitized, thereby causing It remains in the developing step without being dissolved. As a result, the plating growth of this part is hindered, resulting in poor coil breakage and a decrease in the yield of the finished product.

Therefore, the effect of light scattering near the through hole was additionally examined. As a result, it was found that the thickness of the 100 μm thick photoresist having the largest influence on the scattering was not affected by scattering when the coil line portion was separated from the outer periphery of the through hole by 50 μm or more.

The present invention has been completed on the basis of the above findings.

The present invention provides a planar magnetic element comprising: an upper magnetic body; a lower magnetic body; a planar coil disposed on the lower magnetic body and having a coil terminal; and an intermediate magnetic layer including the planar coil wire a mixture of a magnetic powder and a resin between the upper magnetic body and the lower magnetic body, and a layer for fixing the intermediate magnetic layer and the upper magnetic body; and a coupling portion provided in the above The lower magnetic body is integrally formed with the coil terminal by electrical plating, and is provided with a through hole that is pushed out; and an external electrode is formed by being electrically coupled to the coupling portion by electrical plating.

The through hole preferably has a pushing angle θ of 85° or less with respect to a vertical plane of the through hole axis. More preferably, the pushing angle θ is below 80°. The best system is 60°~80°.

Preferably, the planar coil has a coil shape that is at least 50 μm apart from a distance from the outer circumference of the through hole closest to the coil line portion. More preferably, the distance from the outer circumference of the through hole to the coil line portion is 50 to 70 μm.

Preferably, the upper magnetic body is composed of a ferrite sintered plate having a thickness of 30 to 300 μm, and the lower magnetic body is preferably composed of a ferrite-sintered plate having a thickness of 30 to 300 μm.

The above ferrite-sintered plate is preferably a NiZn-based ferrite-sintered plate.

Preferably, the intermediate magnetic layer is composed of a mixture of fermented ferromagnetic powder and a resin binder, and the intermediate magnetic layer preferably has a thickness of 5 to 30 μm.

The above-mentioned adhesive layer is preferably made of an epoxy resin, and the above-mentioned adhesive layer preferably has a thickness of 5 to 20 μm.

The planar coil is preferably a spiral coil or a meander coil.

(effect of the invention)

According to the present invention, a through hole having a push-out is disposed in the lower magnetic body, and when the spiral coil is formed, the coil terminal to the coupling portion are integrally formed of the same substance, and a coupling that is well coupled with the external electrode is formed. The connection portion and the external electrode are formed by coupling the same substance with the coupling portion, so that the coupling reliability can be particularly improved.

Further, by setting the shape of the coil which is separated from the outer circumference of the through hole by 50 μm or more, the yield of the finished product can be further improved.

Hereinafter, the present invention will be specifically described based on the drawings.

Figure 1 is a cross-sectional view showing a planar magnetic member in accordance with the present invention. In the figure, the symbol 1 is a spiral coil, the 2 is a lower magnetic body, the 3 is an intermediate magnetic layer, 4a is a push-through through hole, 5a is an external electrode, 6 is an upper magnetic body, 7 is an upper layer, and 8 is a layer, and 8 is a coil terminal. 9 is a coupling portion formed on the inner circumferential surface of the through hole 4. Further, the pushing angle of the through hole 4a is expressed by θ.

In the present invention, the lower magnetic body 2 formed of the spiral coil 1 is provided with a push-through through hole coupling portion 9 for coupling the coil terminal 8 and the external electrode 5a. Thereby, at the time of the plating step at the time of forming the coil, the spiral coil 1 and the coil terminal 8 can be formed together, and the through-hole coupling portion which is electrically coupled to the external electrode 5a can be integrally formed.

Accordingly, the integral coil including the coupling portion 9 can be integrally formed of the same material, thereby avoiding the deterioration of reliability caused by the joining of the foreign materials.

When the relevant push-out angle θ is, for example, 90° (that is, a straight tubular shape), the plating solution is poor in the plating step during the formation of the spiral coil, and the plating growth on the lower side of the lower magnetic body is hindered. Forming a plating layer necessary for good electrical coupling with the external electrodes.

According to the present invention, by imparting a push-out shape to the through hole, the problem of circulation of the plating solution can be improved, and a plating layer having a sufficient thickness can be formed up to the lower side of the lower magnetic body. In other words, this effect can be obtained by setting the pushing angle θ to less than 90°. In particular, when the pushing angle θ is 80° or less, the thickness of the through hole portion on the upper side of the lower magnetic body is plated and lowered. The side through holes are plated to the same thickness, and the coupling area with the external electrodes is increased, so that it is preferable from the viewpoint of improving the electrical coupling reliability.

Figure 4 shows the results of a survey on the relationship between the relevant push-out angle θ and the plating thickness below the through-hole.

As shown in Fig. 4, as the push-out angle θ gradually decreases from 90°, the plating thickness under the through-hole is gradually increased. If the push-out angle θ is less than 80°, the thickness of the plating is almost the same as the thickness of the plating. Plating layer.

However, if the pushing angle θ is excessively reduced, the opening area of the through hole on the lower magnetic body becomes large, and the area for forming the spiral coil formed on the surface is restricted, thereby causing a decrease in inductance. Therefore, in essence, the lower limit of the push angle θ is preferably set to about 60°.

Then, an external electrode is formed by electroplating on the lower surface side of the lower magnetic body so as to be coupled to the coupling portion, and the same from the coil terminal to the external electrode.

Next, Fig. 2 is a view of the planar magnetic element according to the present invention as seen from above after the upper magnetic body 6, the subsequent layer 7, and the intermediate magnetic layer 3 are removed. In the figure, x means the distance from the outer circumference of the through hole 4 to the coil wire portion 1. In the present invention, by setting the spiral coil wire portion to a coil structure that is away from the outer periphery of the through hole, it is possible to suppress uneven thickness of the photoresist due to the through hole, and further reduce the yield due to poor patterning of the photoresist. occur.

The glass mask of the glass mask that is closest to the through hole shown in FIG. 3 and the distance y from the outer circumference of the through hole are changed in the range of 30 to 60 μm, and the thickness distribution of the photoresist after exposure and development is performed. As shown in Figure 5.

In the region where the light is blocked by the glass mask, there should be no photoresist residue. However, when y=30 μm or 40 μm, the photoresist is present at positions of 30 μm and 40 μm from the outer periphery of the through hole of the light-shielding region. On the other hand, in the case of y = 50 μm and 60 μm, no photoresist exists in the respective light-shielding regions. Therefore, even if the coil wire portion is formed within 50 μm from the outer circumference of the through hole, the photoresist remains in some portions, and the plating growth at this place is hindered, which may cause the coil to be broken.

In this regard, by making the coil wire portion a coil structure that is separated from the outer circumference of the through hole by 50 μm or more, the above-described adverse effects can be avoided, and as a result, the yield of the planar magnetic element can be improved.

In the present invention, the upper/lower magnetic body is more suitably used as a ferrite-sintered plate. The thickness of the ferrite-sintered plate is preferably set to about 30 to 300 μm.

Further, it is preferable to use the NiZn-based ferrite iron which is an insulator.

The intermediate magnetic layer is preferably a mixture of ferrite-based ferromagnetic powder and a resin binder, and in the ferrite-based ferromagnetic resin, the bulk density of the ferro-fermented ferromagnetic powder is preferably set to about 20 to 80 vol%.

The thickness of the intermediate magnetic layer is preferably set to about 5 to 30 μm.

The resin for the subsequent adhesive layer is not particularly limited, but an epoxy resin is particularly preferable.

Further, the thickness of the adhesive layer is preferably about 5 to 20 μm in terms of an average thickness.

The planar coil shape of the planar magnetic element of the present invention may be either a spiral type or a zigzag type, but in order to achieve a larger inductance, a spiral type is preferably used. Further, two or more spiral coils may be arranged in series or in parallel. Further, when two or more electrically insulated coils are disposed, the function of the transformer can be exerted, and the present invention is also effective for such a configuration.

Next, a description will be given of a representative manufacturing method of the present invention, but the manufacturing conditions of the present invention are not limited thereto.

(1) The push-through through hole is formed in advance, and is preferably formed on a NiZn-based (NiCuZn-based) ferrite-iron sintered substrate, and a Cu seed layer having a thickness of about 0.5 μm is formed by sputtering or electroless plating.

(2) A photoresist coating is applied thereon, and the planar coil pattern is exposed and developed to form a photoresist frame. The shape of the associated planar coil is generally a spiral coil.

(3) Cu is deposited by electroplating in the frame. When performing this electroplating, it is important to integrally form an integral coil including a coupling portion with an external electrode.

(4) After the photoresist is peeled off, the unnecessary Cu seed layer is removed by etching.

(5) a paste in which an epoxy resin is mixed into a ferrite-type ferromagnetic powder, and is applied by a screen printing method between the coil wires of the planar coil and the entire surface of the planar coil other than the terminal portion as needed. And heat hardening is performed at about 150 °C.

(6) Next, the resin paste is applied to the entire surface except the terminal portion.

(7) The ferrite-iron sintered substrate is superposed as an upper ferrite layer, and is thermally cured by a resin at about 150 ° C, and the lower magnetic ferrite is sintered to the substrate and the planar coil, and the upper magnetic fertilizer. The granular iron sintered substrate was joined.

(8) The upper and lower magnetic ferrite-sintered substrates can also be used for thinning from the beginning, but when handling is difficult, a thick sintered substrate is used, and at the time of completion of the above (7), The thinning process is performed using, for example, grinding.

(9) On the lower surface of the lower magnetic ferrite-sintered substrate, electrical plating is performed in the order of Cu/Ni/Sn according to the shape of the external electrode to form an external electrode.

[Example 1]

Next, a more specific description will be made using the embodiment for the present invention.

On the sintered ferrite core substrate having a composition of Fe ₂ O ₃ /ZnO/NiO=50/30/20 (mol%) which is a lower magnetic body, shot blasting is applied to the position of the coil terminal portion. A push-through through hole is formed. Further, the pushing angle θ is set to 85°, 80°, and 75°. Next, a seed film at the time of performing electroplating was formed into a Cu film having a thickness of 0.5 μm by a sputtering method. Next, after the photoresist coating was applied to the seed film, a photoresist frame of a 7-turn spiral coil was formed by optical micro-shadow.

Next, after Cu was deposited in the resist frame by electric plating, the resist frame was peeled off, and the plating underlayer between the coils was removed by wet etching to obtain a spiral coil having a thickness of 90 μm. Further, the coil line portion was separated from the outer circumference of the through hole by 50 μm and 75 μm by the pattern of the glass mask used for the optical lithography.

Then, a resin powder granular iron paste (magnetic powder ratio: 70%) containing magnetic powder of Fe ₂ O ₃ /ZnO/CuO/NiO=49/23/12/16 (mol%) was mixed into the resin. Screen printing was performed between the coil and the coil, and thermal hardening was performed at 150 ° C to form an intermediate magnetic layer.

Next, a sintered ferrite plate composed of Fe ₂ O ₃ /ZnO/NiO=50/30/20 (mol%) which is an upper magnetic body was bonded to the intermediate magnetic layer via a thickness of 10 μm. Next, an external electrode in a laminated structure in the order of Cu/Ni/Sn is formed on the lower side of the lower magnetic body to complete the planar magnetic element.

Further, the conventional example 1 is prepared by preparing a planar magnetic element in accordance with the same procedure except that the through-hole coupling portion is not subjected to electroplating but is formed by embedding a conductive paste (see FIG. 6).

Further, the conventional example 2 is prepared in the same manner as in the first embodiment except that a through hole having no push-out is formed in the lower magnetic body (pushing angle = 90°), and an external electrode is formed using a conductive paste. A planar magnetic element was produced in the same manner as described above (see Fig. 7).

Further, Comparative Example 1 was prepared by preparing a planar magnetic member in the same manner as in Example 1 except that a through hole having no push-out was formed in the lower magnetic body (pushing angle = 90°). Refer to Figure 8).

Further, in Comparative Examples 2 and 3, except that the glass mask pattern used for merely changing the optical lithography was changed, and the distance between the coil line portion and the outer circumference of the through hole was set to 0 μm and 25 μm, the rest was as in Example 1. A planar magnetic element was produced in the same manner as described above (see Fig. 9).

The average DC resistance change rate (n number = 20) after the temperature cycle test (-55 ° C / 120 ° C, 1000 times) was measured for each of the planar magnetic elements obtained as described above. Moreover, the yield evaluation measures the DC resistance value and determines whether it is acceptable (n number = 100) and compares it. The reliability and yield evaluation results of the obtained planar magnetic members are shown in Table 1.

From the table, it is known that any of Invention Examples 1 to 4 exhibits a resistance after the temperature cycle test as compared with the conventional examples of Nos. 5 and 6 in which the conductive resin is used as the coupling portion or the external electrode material. The rate of change in value is significantly reduced.

In addition, when the angle θ was extracted, it was found that the comparative example 1 of No. 7 with θ = 90° exhibited a high yield.

In addition, in the case of the temperature cycle test evaluation, in the case of the invention, even when θ is 80° or less (No. 2 to 4), the variation rate of No. 1 of θ=85° is reduced to 1/2 or less. From this phenomenon, it is known that the push angle θ is 80° or less, and the viewpoint of reliability is preferable.

Next, in the case of the invention examples 1 to 4 in which the distance between the outer circumference coil and the coil line portion is 50 μm or more in view of the shape of the coil, a high yield of 90% is obtained, and in comparison, the distance is less than 50 μm. In Examples 2 and 3 (No. 8, 9), the yield was reduced to 50% or less. From this phenomenon, it is understood that the yield can be improved by setting the distance between the outer circumferential coil portions of the through holes to be 50 μm or more.

1. . . Spiral coil

2. . . Lower magnetic body

3. . . Intermediate magnetic layer

4a. . . Push-through through hole

4b. . . Straight tubular through hole

5a. . . External electrode (Cu)

5b. . . External electrode (conductive resin)

6. . . Upper magnetic body

7. . . Next layer

8. . . Coil terminal

9. . . a coupling portion provided in the push-through through hole

10a. . . Coupling portion (conductive resin) provided in the straight tubular through hole

10b. . . Coupling portion (Cu) provided in the straight tubular through hole

11. . . Glass mask

12. . . Glass mask shade

13. . . Scattered light

14. . . Photoresist

θ. . . Push-out angle of the through hole

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a cross-sectional view of a planar magnetic element in accordance with the present invention.

2 is a view of the planar magnetic element in accordance with the present invention, viewed from above, except for the upper magnetic body, the adhesive layer, and the intermediate magnetic layer.

Fig. 3 is a cross-sectional view showing a state in which scattered light is generated in a through hole portion.

Fig. 4 is a graph showing the relationship between the pushing angle θ of the through hole and the plating thickness under the through hole.

Fig. 5 is a graph showing the relationship between the distance x from the outer circumference of the through hole and the thickness of the photoresist after development.

Figure 6 is a cross-sectional view showing an example of a conventional planar magnetic element.

Figure 7 is a cross-sectional view showing an example of a conventional planar magnetic element.

Fig. 8 is a cross-sectional view showing an example of a planar magnetic element of a comparative example.

Fig. 9 is a view of the planar magnetic element of the comparative example as viewed from above except for the upper magnetic body, the adhesive layer, and the intermediate magnetic layer.

1. . . Spiral coil

2. . . Lower magnetic body

3. . . Intermediate magnetic layer

4a. . . Push-through through hole

5a. . . External electrode (Cu)

6. . . Upper magnetic body

7. . . Next layer

8. . . Coil terminal

9. . . a coupling portion provided in the push-through through hole

θ. . . Push-out angle of the through hole

Claims (10)

A planar magnetic element comprising: an upper magnetic body; a lower magnetic body; a planar coil disposed on the lower magnetic body and having a coil terminal; and an intermediate magnetic layer interposed between the lines including the planar coil a mixture of a magnetic powder and a resin between the upper magnetic body and the lower magnetic body; a second layer for fixing the intermediate magnetic layer and the upper magnetic body; and a coupling portion provided on the lower magnetic body Further, it is formed integrally with the coil terminal by electrical plating, and is provided with a through hole having a taper shape, and an external electrode formed by being electrically coupled to the coupling portion by electrical plating. The planar magnetic element according to claim 1, wherein the through hole has a pushing angle θ of 85° or less with respect to a vertical surface of the through hole axis. The planar magnetic component of claim 2, wherein the push angle θ is 60° to 80°. The planar magnetic element according to claim 1, wherein the planar coil has a coil shape having a distance from the outer circumference of the through hole closest to the coil line portion of at least 50 μm or more. The planar magnetic element according to claim 4, wherein a distance from the outer circumference of the through hole closest to the coil line portion is 50 to 70 μm. The planar magnetic component of claim 1, wherein the upper magnetic body is preferably composed of a ferrite sintered plate having a thickness of 30 to 300 μm, and the lower magnetic system is made of a fertilizer having a thickness of 30 to 300 μm. A granular iron sintered plate is formed. The planar magnetic component according to claim 1, wherein the ferrite-sintered plate is a NiZn-based ferrite-sintered plate. The planar magnetic element according to claim 1, wherein the intermediate magnetic layer is composed of a mixture of a ferrite-based ferromagnetic powder and a resin binder, and the intermediate magnetic layer has a thickness of 5 to 30 μm. The planar magnetic element according to claim 1, wherein the adhesive layer is made of an epoxy resin, and the adhesive layer has a thickness of 5 to 20 μm. The planar magnetic component according to claim 1, wherein the planar coil is a spiral coil or a meander coil.