JP2008258553A - Substrate with built-in coil - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a substrate with a built-in coil which allows a large current to flow a flat coil conductor, with no mulfunction of a mounted IC which is caused by the heat generated at the flat coil conductor. <P>SOLUTION: The substrate with a built-in coil comprises a substrate comprising a pair of insulating layers 1/1 where a wiring layer 6 is formed and a ferrite magnetics layer 2 pinched by the pair of insulating layers 1/1, and a flat coil conductor 3 formed in the ferrite magnetics layer 2. A heat transfer conductor layer 4 is formed from the outside of the flat coil conductor 3 to the side surface of the substrate, in plan view, and the heat transfer conductor layer 4 is connected to a heat radiation conductor layer 5 formed on the side surface of the substrate. The heat generated at the flat coil conductor 3 can be released to the outside from the heat radiation conductor layer 5 through the heat transfer conductor layer 4. As a result, the electronic components such as a mounted IC is prevented from mulfunctioning by the heat generated from the flat coil conductor 3. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a coil-embedded substrate in which a ferrite magnetic layer in which a coil conductor is embedded is provided inside an insulating layer.

  Conventionally, many electronic devices have been incorporated in electronic devices such as mobile communication devices such as mobile phones, and various electronic devices have been downsized as electronic devices have been rapidly downsized. Thinning is required. As an example of downsizing and thinning of various electronic devices, a ceramic in which an insulating layer made of glass ceramics is laminated on an LC filter that has been conventionally formed by mounting a relatively large chip coil or chip capacitor on a substrate. A coil built-in substrate in which a coil conductor is formed inside the substrate is used.

  However, in an electronic device that requires a relatively high inductance, such as a DC-DC converter used for a cellular phone, a coil is formed in a ceramic substrate that does not have magnetism, and therefore a relatively large inductance of about 100 nH. In order to obtain the above, the number of turns of the coil conductor has to be increased, and there has been a problem that it is impossible to effectively reduce the size and thickness.

  Therefore, in recent years, a ferrite magnetic layer having a high magnetic permeability is formed inside the ceramic substrate, and a coil conductor is embedded in the ferrite magnetic layer, so that the inductance is reduced to 100 nH without increasing the number of turns of the coil. It is practiced to incorporate a coil having a higher inductance and to provide a high-inductance coil-embedded substrate (see, for example, Patent Documents 1 and 2).

Such a coil-embedded substrate is, for example, a pair of insulating layers 11 and 11 having a wiring layer 16 formed thereon and laminated between the insulating layers 11 and 11 as shown in a sectional view in FIG. And a ferrite magnetic layer 12 having a planar coil conductor 13 embedded therein. For the wiring layer 16 and the planar coil conductor 13, it is necessary to use a low resistance metal such as low resistance Cu or Ag in order to suppress electrical loss due to resistance. Such a low resistance metal has a relatively low melting point. For this reason, glass ceramics are used as the insulating layer 11, and Ni—Zn ferrite that can be fired at a low temperature is used as the ferrite magnetic layer 12, which is manufactured by simultaneous firing. The wiring layer 16 has a large area grounding for reducing the inductance component generated between the electrode mounting electrodes from the electrode pads for connecting the coil-embedded substrate to the external substrate and reducing the power supply noise of the mounted IC. A conductor layer is formed. The ground conductor layer relieves stress caused by the difference in firing shrinkage behavior and the difference in thermal expansion coefficient generated between the insulating layer 11 and the ferrite magnetic layer 12, and the insulating layer 11 and the ferrite magnetic layer 12 Is formed between the insulating layer 11 and the ferrite magnetic layer 12 in order to strengthen the bonding with the ferrite magnetic layer 12.
JP-A-6-20839 JP-A-6-21264

  However, in recent years, ICs that supply power from DC-DC converters have been operating at a low voltage, and accordingly, current flowing through the DC-DC converter has been increasing year by year. For this reason, in a substrate with a built-in coil for a DC-DC converter, heat is easily generated even when a low resistance metal is used for the planar coil conductor, and the risk of the IC malfunctioning due to the influence of this heat is increased. It is coming. In order to prevent this problem, it is conceivable to further reduce the resistance by increasing the line width of the planar coil conductor, but this is contrary to the demands for miniaturization and thinning.

  The present invention has been devised in order to solve the above-described conventional problems, and an object thereof is to obtain a high inductance value at a high frequency, for example, a small and low-profile DC-DC converter built-in substrate. In other words, an object of the present invention is to provide a substrate with a built-in coil that allows a large current to flow without causing an IC to malfunction due to heat generated by a planar coil conductor.

  The coil-embedded substrate according to the present invention includes a pair of insulating layers on which a wiring layer is formed and a ferrite magnetic layer sandwiched between the pair of insulating layers, and a planar coil conductor formed in the ferrite magnetic layer. A heat transfer conductor layer formed from the outside of the planar coil conductor to the side surface of the substrate in plan view, and the heat transfer conductor layer formed on the side surface of the substrate. It is characterized by being connected to a heat radiating conductor layer.

  The coil-embedded substrate of the present invention is characterized in that, in the above configuration, the plurality of heat transfer conductor layers adjacent to the outer periphery of the planar coil conductor are disposed along the outer periphery of the planar coil conductor. It is what.

  The coil-embedded substrate according to the present invention is characterized in that, in the above configuration, the heat transfer conductor layer has a shape surrounding the planar coil conductor along the outer periphery.

  The coil-embedded substrate according to the present invention is characterized in that, in the above configuration, the heat transfer conductor layer has a plurality of protrusions whose end portions are close to the outer peripheral portion of the planar coil conductor.

  Further, the coil-embedded substrate according to the present invention is the above-described configuration, wherein the heat transfer conductor layer is formed close to the outer peripheral portion of the planar coil conductor, and is disposed along the outer periphery of the planar coil conductor. It has an opening.

  The coil-embedded substrate according to the present invention is configured such that, in the above configuration, a heat transfer insulating layer having a higher thermal conductivity than the ferrite magnetic layer is connected to the planar coil conductor and the heat transfer conductor layer. It is characterized by being.

  Further, in the coil built-in substrate of the present invention, in the above configuration, the planar coil conductor has a plurality of turns, and the insulating layer for heat transfer is also formed between the planar coil conductors on the outer periphery and the inner periphery adjacent to each other. It is characterized by.

  In the coil-embedded substrate of the present invention, in the above configuration, the planar coil conductor has a plurality of turns, and the insulating layer for heat transfer overlaps the entire area of the planar coil conductor in plan view. It is characterized by being connected to.

  Further, the coil-embedded substrate according to the present invention has the above-described configuration, wherein the planar coil conductor and the heat transfer conductor layer are provided in a plurality above and below via the ferrite magnetic layer, and the heat transfer located above and below. A heat transfer through conductor formed in a direction penetrating the ferrite magnetic layer between them is connected to at least one of the conductor layers for use.

  According to the coil-embedded substrate of the present invention, the heat transfer conductor layer is formed from the outside of the planar coil conductor to the side surface of the substrate in plan view, and the heat transfer conductor layer is formed on the heat dissipation conductor layer formed on the side surface of the substrate. Since it is connected, the heat generated in the planar coil conductor can be radiated to the outside from the heat radiation conductor layer via the heat conduction conductor layer. As a result, it is possible to prevent an electronic component such as an IC mounted from malfunctioning due to heat generated from the planar coil conductor.

  Further, according to the coil-embedded substrate of the present invention, in the above configuration, when a plurality of heat transfer conductor layers close to the outer periphery of the planar coil conductor are arranged along the outer periphery of the planar coil conductor, the planar coil In the region outside the conductor, the heat transfer conductor layer does not prevent the magnetic flux generated around the planar coil conductor from passing through the region outside the planar coil conductor. Heat generated in the conductor can be radiated from the heat radiating conductor layer to the outside through the heat conducting conductor.

  Further, according to the coil-embedded substrate of the present invention, in the above configuration, when the heat transfer conductor layer has a shape surrounding the planar coil conductor along the outer periphery of the planar coil conductor, it occurs in the planar coil conductor. Since heat can be received over the entire outer periphery of the planar coil conductor by the heat transfer conductor layer, heat can be radiated to the outside of the substrate through the heat dissipation conductor layer more efficiently.

  Further, even if noise is radiated from the planar coil conductor, the heat transfer conductor layer has a shape surrounding the planar coil conductor along its outer periphery, so that the heat transfer conductor layer functions as a shield against the planar coil conductor. Therefore, it is possible to obtain a coil-embedded substrate that can suppress the influence of the noise radiated from the planar coil conductor on the wiring layer and can operate the mounted IC more stably. it can.

  Further, according to the coil-embedded substrate of the present invention, in the above configuration, the heat transfer conductor layer having a shape surrounding the planar coil conductor along the outer periphery has a plurality of protrusions whose ends are close to the outer periphery of the planar coil conductor. Since the heat generated from the planar coil conductor can be received more efficiently at the plurality of projections closer to the planar coil conductor, the external can be more efficiently passed through the heat transfer conductor layer and the heat dissipation conductor layer. Can dissipate heat.

  Further, according to the coil-embedded substrate of the present invention, in the above configuration, the heat transfer conductor layer having a shape surrounding the planar coil conductor along the outer periphery is formed close to the outer periphery of the planar coil conductor. In the case of having a plurality of openings arranged along the outer periphery of the coil, heat can be received over the entire outer periphery of the planar coil conductor at a position closer to the planar coil conductor, and the planar coil can be received by the plurality of openings. Since the heat transfer conductor layer does not prevent the magnetic flux generated around the conductor from passing through the area outside the planar coil conductor, heat generated from the planar coil conductor can be more efficiently reduced without reducing inductance. It can dissipate heat to the outside.

  According to the coil-embedded substrate of the present invention, in the above configuration, the heat transfer insulating layer having a higher thermal conductivity than the ferrite magnetic layer is formed connected to the planar coil conductor and the heat transfer conductor layer. In this case, since heat can be transferred from the planar coil conductor to the heat transfer conductor layer by the heat transfer insulating layer having a higher thermal conductivity than the ferrite magnetic layer, the heat generated in the flat coil conductor is transferred to the heat transfer conductor. Heat can be radiated from the heat radiating conductor layer to the outside more efficiently through the layer.

  Further, according to the coil-embedded substrate of the present invention, in the above configuration, when the planar coil conductor has a plurality of turns and a heat transfer insulating layer is also formed between the adjacent outer and inner planar coil conductors. Transmits the heat generated in the planar coil conductor on the inner periphery to the planar coil conductor on the outer periphery via a heat transfer insulating layer formed between the outer and inner planar coil conductors, and further includes the planar coil conductor and the heat transfer conductor. Since heat can be transmitted to the heat radiating conductor layer via the heat transfer insulating layer formed connected to the layer, heat generated in the planar coil conductor can be radiated to the outside more efficiently.

  Furthermore, since there is a heat transfer insulating layer having a lower magnetic permeability than the ferrite magnetic layer between the adjacent outer and inner planar coil conductors, even if the current flowing through the planar coil conductor is large Since magnetic flux does not easily pass between adjacent outer and inner planar coil conductors, leakage flux is less likely to occur between adjacent outer and inner planar coil conductors, thereby suppressing magnetic saturation and superimposition characteristics. Can be suppressed.

  Further, according to the coil-embedded substrate of the present invention, in the above configuration, the planar coil conductor has a plurality of turns, and the heat transfer insulating layer overlaps with the entire area of the planar coil conductor formation region in plan view and is connected to the planar coil conductor. In this case, the heat generated in the planar coil conductor is directly transmitted to the heat transfer insulating layer from the outer periphery to the inner periphery of the planar coil conductor, so the heat generated in the planar coil conductor is more efficient. It is possible to radiate heat from the heat dissipation conductor layer to the outside of the substrate through the heat transfer insulating layer and the heat transfer conductor layer.

  Furthermore, even when a heat transfer insulating layer is not formed between the adjacent outer and inner planar coil conductors, the permeability is higher than that of the ferrite magnetic layer between the outer and inner planar coil conductors adjacent in plan view. Because there is a small heat transfer insulating layer, magnetic flux does not easily pass between the adjacent outer and inner planar coil conductors, so that leakage flux is less likely to occur between the adjacent outer and inner planar coil conductors. Thus, magnetic saturation is suppressed, and deterioration of the superimposition characteristics can be suppressed.

  Further, according to the coil-embedded substrate of the present invention, in the above configuration, a plurality of planar coil conductors and heat transfer conductor layers are provided above and below with a ferrite magnetic layer interposed therebetween, and the heat transfer conductor is positioned above and below. When at least one of the layers is connected to a heat transfer through conductor formed in a direction penetrating the ferrite magnetic layer between them, the heat generated in the planar coil conductor and transferred to the ferrite magnetic layer Is transferred to the heat transfer conductor layer via the heat transfer through conductor, so that heat generated in the planar coil conductor can be more efficiently dissipated from the heat dissipation conductor layer to the outside of the substrate via the heat transfer conductor layer. Can do.

  A coil built-in substrate (hereinafter also referred to as a substrate) of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 is a diagram showing an example of an embodiment of a coil built-in substrate according to the present invention, and FIG. 1A is a cross-sectional view of the coil built-in substrate according to the present invention (a line BB ′ shown in FIG. 1B). FIG. 1B is a cross-sectional view (transverse view) cut along the line AA ′ shown in FIG. In these drawings, 1 is an insulating layer, 2 is a ferrite magnetic layer, 3 is a planar coil conductor, 4 is a heat transfer conductor layer, 5 is a heat dissipation conductor layer, and 6 is a wiring layer.

  In the example shown in FIG. 1, the wiring layer 6 has a mounting electrode 6 b on which an outer surface (upper surface and lower surface of the substrate) of the insulating layer 1 is mounted with a semiconductor chip such as an IC and chip components, and an external electric circuit and an electric circuit. The electrode pads 6d to be connected to each other are formed, and an internal wiring layer 6a is formed inside the insulating layer 1. The internal wiring layer 6a, the mounting electrode 6b, the electrode pad 6d, and the planar coil conductor 3 are connected to each other via a through conductor 6c that penetrates the insulating layer 1 or the ferrite magnetic layer 2.

  The substrate with a built-in coil according to the present invention includes a substrate comprising a pair of insulating layers 1, 1 on which a wiring layer 6 is formed, and a ferrite magnetic layer 2 sandwiched between the pair of insulating layers 1, 1, and a ferrite magnetic layer 2. A coil-embedded substrate having a planar coil conductor 3 formed therein, wherein a heat transfer conductor layer 4 is formed from the outside of the plane coil conductor 3 to the side surface of the substrate in plan view, and the heat transfer conductor layer 4 Is connected to a heat-dissipating conductor layer 5 formed on the side surface of the substrate.

  According to the coil-embedded substrate of the present invention, heat generated in the planar coil conductor 3 can be radiated from the heat-dissipating conductor layer 5 to the outside through the heat-conducting conductor layer 4 by such a configuration. As a result, it is possible to prevent an electronic component such as an IC mounted on the mounting electrode 6b from malfunctioning due to heat generated from the planar coil conductor 3.

  As shown in FIG. 1, in the coil-embedded substrate of the present invention, in the above configuration, a plurality of heat transfer conductor layers 4 close to the outer peripheral portion of the planar coil conductor 3 are arranged along the outer periphery of the planar coil conductor 3. It is preferable. With this configuration, in the region outside the planar coil conductor 3, the heat transfer conductor layer 4 does not prevent the magnetic flux generated around the planar coil conductor 3 from passing through the region outside the planar coil conductor 3. Therefore, the heat generated in the planar coil conductor 3 can be radiated from the radiation conductor layer 5 to the outside via the heat conduction conductor layer 4 without reducing the inductance of the planar coil conductor 3.

  The distance between the heat transfer conductor layer 4 and the planar coil conductor 3 at this time is preferably as close as possible in order to transmit the heat generated in the planar coil conductor 3 to the heat transfer conductor layer 4 more efficiently. Specifically, in consideration of the electrical insulation between them, it is preferably about 15 μm or more.

  Further, the shape of the heat transfer conductor layer 4 is long and narrow from the planar coil conductor 3 to the side surface of the substrate as shown in FIG. 1 in order not to make the magnetic flux passage area of the planar coil conductor 3 as small as possible. However, as shown in the cross-sectional view similar to FIG. 1 in FIG. 2, heat transfer to the heat-dissipating conductor layer 5 is more efficient if the shape becomes wider toward the heat-dissipating conductor layer 5. This is preferable because it is often performed. At this time, since the density of the magnetic flux generated by the planar coil conductor 3 is coarser in the outer peripheral portion than in the substrate in plan view, the magnetic flux passage area is reduced by increasing the width of the heat transfer conductor layer 4. The effect of is small. In this case, it is preferable that the width of the heat transfer conductor layer 4 is widened at an angle of 45 ° on both sides at the maximum, because a sufficient improvement in heat conduction can be obtained while suppressing a decrease in the passage region of the magnetic flux. .

  The larger the width of the heat transfer conductor layer 4 is, the better the heat transfer efficiency to the heat radiating conductor layer is. However, as the width becomes larger, the passage of the magnetic flux is hindered. The heat generated in the planar coil conductor 3 is conducted to the heat radiating conductor layer 5 without lowering the inductance of the planar coil conductor 3, although it varies depending on the frequency and current value of the current flowing through For this purpose, the planar coil conductor 3 in which the sum of the lengths of the heat transfer conductor layer 4 adjacent to the planar coil conductor 3 connects the portions of the heat transfer conductor layer 4 adjacent to the planar coil conductor 3 can be obtained. The length is preferably about 8 to 30% of the length of the surrounding line (the phantom line R shown by a two-dot chain line in FIG. 1).

  When producing the coil-embedded substrate of the present invention, an attempt is made to efficiently and easily produce a large number of coil-embedded substrates in the form of a so-called multi-cavity wiring substrate by arranging a plurality of rectangular coil-embedded substrates vertically and horizontally. In this case, it is preferable that the planar coil conductor 3 is formed in a rectangular shape with the outermost periphery conforming to the shape of the ferrite magnetic layer 2 (outer shape of the substrate) in plan view. By doing so, the length of the planar coil conductor 3 can be formed as long as possible without changing the outer dimensions of the coil-embedded substrate, so that the inductance value proportional to the length of the planar coil conductor 3 is increased. It can be.

  When the planar coil conductor 3 is formed in a rectangular shape along the outer shape of the rectangular substrate in this way, the heat transfer conductor layer 4 is formed in a rectangular shape as shown in FIG. Preferably, the flat coil conductor 3 is formed so as to be drawn from the outside of the corner portion of the planar coil conductor 3 to the heat radiation conductor layer 5 at the corner portion of the rectangular substrate. Since the magnetic flux density at the outer periphery of the corner portion of the planar coil conductor 3 becomes coarse as compared with other regions, the influence of reducing the magnetic flux passage region by the heat transfer conductor layer 4 can be small. For the same reason, only the heat transfer conductor layer 4 arranged at the corner of the rectangular planar coil conductor 3 may be wider than the heat transfer conductor layer 4 arranged at another position. Also in this case, for the reason described above, as shown in FIG. 3, it is more preferable that the width becomes wider toward the heat radiation conductor layer 5 at the corner of the substrate.

  Further, in the coil built-in substrate of the present invention, for example, as shown in a cross-sectional view similar to FIG. 1 in FIG. 4, the heat transfer conductor layer 4 has the planar coil conductor 3 and the outer periphery of the planar coil conductor 3. It is preferable that it is the shape which surrounds along. Thereby, since the heat generated in the planar coil conductor 3 can be received by the heat transfer conductor layer 4 over the entire outer periphery of the planar coil conductor 3, it can be received more efficiently, and the heat radiation conductor layer 5 can be more efficiently received. Heat can be radiated to the outside of the substrate. Further, even if noise is radiated from the planar coil conductor 3, since the heat transfer conductor layer 4 has a shape surrounding the planar coil conductor 3, the heat transfer conductor layer 4 functions as a shield and absorbs noise. Therefore, the influence of the noise radiated from the planar coil conductor 3 on the wiring layer 6 is suppressed, and a coil built-in substrate capable of operating the IC mounted on the mounting electrode 6b more stably is obtained. be able to.

  In this case, the heat transfer conductor layer 4 is arranged with an interval between the planar coil conductor 3 so that magnetic flux can pass. This interval varies depending on the size of the planar coil conductor 3, the frequency and current value of the current flowing through the planar coil conductor 3, or the permeability of the ferrite magnetic layer 2, but for example, the permeability of the ferrite magnetic layer 2 is 500. In that case, it may be 0.1 mm or more.

  Further, the coil-embedded substrate of the present invention has a heat transfer conductor layer 4 in the above-described configuration, for example, as shown in a cross-sectional view similar to FIG. It is preferable to have a plurality of protruding portions 4a. As a result, heat generated from the planar coil conductor 3 can be received more efficiently at the plurality of protrusions 4a closer to the planar coil conductor 3, and therefore more efficient via the heat transfer conductor layer 4 and the heat dissipation conductor layer 5. It can dissipate heat well outside.

  At this time, the distance between the end of the protruding portion 4a of the heat transfer conductor layer 4 and the planar coil conductor 3 is as small as possible in order to transfer the heat generated in the planar coil conductor 3 to the heat transfer conductor layer 4 more efficiently. The closer one is preferable, but in view of the electrical insulation between the two, specifically, it is preferably about 50 μm or more.

  The width of the protruding portion 4a is the length of the portion of the protruding portion 4a adjacent to the planar coil conductor 3 for the same reason as the width of the heat transfer conductor layer 4 when the plurality of heat transfer conductor layers 4 are disposed. The total sum of the lengths is about 8 to 30% of the length of a line (virtual line R of a two-dot chain line shown in FIG. 5) surrounding the planar coil conductor 3 formed by connecting the portions close to the planar coil conductor 3 of the protrusion 4a. Is preferred.

  As shown in a sectional view similar to FIG. 1 in FIG. 6, the protruding portion 4 a has a shape that increases in width toward the heat radiating conductor layer 5. This is preferable because heat transfer to the conductor layer 5 is more efficiently performed. At this time, the density of the magnetic flux by the planar coil conductor 3 is coarser in the outer peripheral portion than in the substrate in plan view, so that the influence on the reduction of the magnetic flux passage region by increasing the width of the protruding portion 4a is small. I'm sorry. In this case, it is preferable that the spread is widened at an angle of 45 ° on both sides at the maximum, since a sufficient improvement in heat conduction can be obtained while suppressing a decrease in the passage region of the magnetic flux.

  Further, when the planar coil conductor 3 is formed in a rectangular shape along the outer shape of the rectangular substrate, the protruding portion 4a of the heat transfer conductor layer 4 is shown in FIG. 7 as a cross-sectional view similar to FIG. In addition, it is preferable that the flat coil conductor 3 formed in a rectangular shape is provided outside the corner portion. Since the magnetic flux density at the outer periphery of the corner portion of the planar coil conductor 3 becomes coarse compared to other regions, the influence of reducing the magnetic flux passage region by the protrusion 4a can be small. For the same reason, only the protrusions 4a outside the corners of the planar coil conductor 3 may be made larger than the protrusions 4a arranged in other parts. Also in this case, for the reason described above, it is more preferable to form the protruding portion 4a so that its width becomes wider toward the heat radiating conductor layer 5 side.

  Further, the coil-embedded substrate of the present invention has a heat transfer conductor layer 4 close to the outer periphery of the planar coil conductor 3 in the above-described configuration, for example, as shown in FIG. 8 and FIG. It is preferable to have a plurality of openings 4 b formed along the outer periphery of the planar coil conductor 3. Thus, heat can be received over the entire outer periphery of the planar coil conductor 3 at a position closer to the planar coil conductor 3, and magnetic flux generated around the planar coil conductor 3 by the plurality of openings 4b is generated by the planar coil conductor 3. Therefore, the heat generated from the planar coil conductor 3 can be radiated to the outside more efficiently without lowering the inductance of the planar coil conductor 3.

  In addition, since the heat transfer conductor layer 4 is located in the vicinity of the planar coil conductor 3, a small magnetic flux is hardly generated along the outermost conductor of the planar coil conductor 3, and from the outermost periphery of the planar coil conductor 3. A large magnetic flux is likely to be generated around the entire planar coil conductor 3 over the innermost circumference, and partial saturation of the magnetic flux generated by the concentration of the magnetic flux between the inner circumference and the outer circumference of the planar coil conductor 3 is suppressed. In addition, it is possible to suppress the deterioration of the superposition characteristics.

  The distance between the heat transfer conductor layer 4 and the planar coil conductor 3 at this time is preferably as close as possible in order to transmit the heat generated in the planar coil conductor 3 to the heat transfer conductor layer 4 more efficiently. Specifically, in view of the electrical insulation between the layers, it is preferably about 50 μm or more.

  The length of the opening 4b in the direction along the outer periphery of the planar coil conductor 3 is the same as the width of the heat transfer conductor layer 4 when the plurality of heat transfer conductor layers 4 are arranged. 4b is a line surrounding the planar coil conductor 3 in which the sum of the lengths on the planar coil conductor 3 side of the opening 4b is connected to the planar coil conductor 3 side of the opening 4b (similar to the virtual line R in FIGS. 1 and 5) ) Is preferably about 70 to 92% of the length.

  The width of the opening 4b of the heat transfer conductor layer 4 (the length in the direction from the planar coil conductor 3 toward the side surface of the substrate) is the dimension of the planar coil conductor 3, the frequency and current value of the current flowing through the planar coil conductor 3, Or, depending on the magnetic permeability of the ferrite magnetic layer 2, for example, when the magnetic permeability of the ferrite magnetic layer 2 is 500, it may be 0.1 mm or more.

  The position of the opening 4b in the heat transfer conductor layer 4 is preferably such that the distance from the inner peripheral end of the heat transfer conductor layer 4 is as small as possible in order not to greatly prevent the passage of magnetic flux. In the case where the conductive layer 4 for heat transfer is formed by printing the conductive paste by screen printing, it is preferably 50 μm or more in consideration of the ease of formation, and the dimensions of the planar coil conductor 3 and the planar coil conductor 3, depending on the frequency and value of the current flowing through the magnetic flux 3, or the magnetic permeability of the ferrite magnetic layer 2, but if there is such a distance, the entire planar coil conductor 3 extends from the outermost circumference to the innermost circumference. Large magnetic flux is likely to be generated around.

  By providing a plurality of openings 4b in the heat transfer conductor layer 4 formed so as to surround the flat coil conductor 3 in the vicinity of the outer periphery of the plane coil conductor 3, a plurality of openings 4b in the heat transfer conductor layer 4 are provided. The portion between the two becomes a heat transfer path for conducting the heat generated in the planar coil conductor 3 from the inner peripheral portion close to the planar coil conductor 3 to the outer peripheral portion to which the heat radiating conductor layer 5 is connected. Therefore, for the same reason as described above, the shape of the opening 4b is changed to parallel parallel sides as shown in FIG. 9B, for example, so that the width of the heat transfer path becomes wider toward the heat radiating conductor layer 5. A shape such as a shape or a trapezoid is preferable. Further, for the same reason as described above, as shown in FIG. 8B, the heat transfer path outside the corner of the rectangular planar coil conductor 3 is enlarged, or the outside of the corner of the planar coil conductor 3 is increased. Alternatively, the four openings 4b may be arranged so as to provide a heat transfer path only.

  The planar coil conductor 3 may be composed of a single layer. However, when a plurality of planar coil conductors 3 are provided on the upper and lower sides as shown in FIG. Can be reduced in size, which is preferable. In such a case, the heat transfer conductor layer 4 is formed on the outer sides of the planar coil conductors 3 and 3 positioned above and below.

  When the planar coil conductor 3 is formed in a rectangular shape along the outer shape of the rectangular substrate, as shown in FIG. 8B or FIG. 9B, the corners of the rectangular planar coil conductor 3 are formed. When the portion is formed into a shape having a plurality of bent portions or a curved shape, the area where the planar coil conductor 3 and the wiring layer 6 such as the ground conductor layer formed in the insulating layer 1 face each other is reduced. By reducing the capacitance between the planar coil conductor 3 and the wiring layer 6, a stable inductance value can be obtained up to a higher frequency, and the corners of the planar coil conductor 3 have a shape in which current is not easily concentrated. This is preferable because the concentration of the electric field is reduced and noise emission from the planar coil conductor 3 can be reduced.

  In addition, the coil-embedded substrate of the present invention has a planar structure in which the heat transfer insulating layer 7 having a thermal conductivity higher than that of the ferrite magnetic layer 2 is planar as shown in FIG. It is preferable to be connected to the coil conductor 3 and the heat transfer conductor layer 4. With such a configuration, heat can be transferred from the flat coil conductor 3 to the heat transfer conductor layer 4 by the heat transfer insulating layer 7 having a higher thermal conductivity than the ferrite magnetic layer. Heat can be radiated from the heat radiating conductor layer 5 to the outside more efficiently through the heat conducting conductor layer 4. Since the heat transfer insulating layer 7 is an insulator, it is directly connected to the planar coil conductor 3, so that the heat generated in the planar coil conductor 3 is efficiently transferred to the heat transfer conductor layer 4 and the heat radiating conductor layer 5. In addition, the magnetic flux generated around the planar coil conductor 3 is not absorbed, so that the passage of the magnetic flux is not greatly hindered and the inductance is not greatly reduced.

  In addition, the coil-embedded substrate of the present invention has an outer periphery in which, as shown in FIG. 11, for example, in the cross-sectional view similar to FIG. It is also preferably formed between the planar coil conductor 3 on the inner periphery. With such a configuration, the heat generated in the inner peripheral planar coil conductor 3 is transmitted to the outer peripheral planar coil conductor 3 via the heat transfer insulating layer 7 formed between the outer peripheral and inner peripheral planar coil conductors 3. Since heat can be transmitted to the heat-dissipating conductor layer 5 through the heat-transfer insulating layer 7 connected to the planar coil conductor 3 and the heat-transfer conductor layer 4, the heat generated in the planar coil conductor 3 can be more efficiently generated. Can be radiated to the outside.

  Further, since the heat transfer insulating layer 7 having a lower magnetic permeability than the ferrite magnetic layer 2 exists between the adjacent outer peripheral and inner peripheral planar coil conductors 3, the current flowing through the planar coil conductor 3 is large. However, since the magnetic flux does not easily pass between the adjacent outer and inner planar coil conductors 3, leakage flux is less likely to occur between the adjacent outer and inner planar coil conductors 3, thereby causing magnetic saturation. Is suppressed, and the deterioration of the superposition characteristics can be suppressed.

  Further, in the coil-embedded substrate of the present invention, for example, as shown in a cross-sectional view similar to FIG. 1 in FIG. The planar coil conductor 3 is preferably connected to the planar coil conductor 3 so as to overlap the entire region where the planar coil conductor 3 is formed. With such a configuration, the heat generated in the planar coil conductor 3 is directly transmitted to the heat transfer insulating layer 7 from the outer periphery to the inner periphery of the planar coil conductor 3. Can be radiated from the heat-dissipating conductor layer 5 to the outside of the substrate through the heat-transfer insulating layer 7 and the heat-transfer conductor layer 4 more efficiently.

  Further, even when the heat transfer insulating layer 7 is not formed between the adjacent outer and inner planar coil conductors 3, the ferrite magnetic layer 2 is compared between the adjacent outer and inner planar coil conductors 3 in plan view. In addition, since the heat transfer insulating layer 7 having a low magnetic permeability exists, it is difficult for the magnetic flux to pass between the adjacent outer peripheral and inner peripheral planar coil conductors 3, and therefore, between the adjacent outer peripheral and inner peripheral planar coil conductors 3. In this case, the leakage magnetic flux is less likely to be generated, whereby the magnetic saturation is suppressed and the deterioration of the superposition characteristic can be suppressed.

  As shown in FIG. 12, the heat transfer insulating layer 7 is connected to the planar coil conductor 3 by overlapping the entire region where the planar coil conductor 3 is formed in plan view, and the adjacent outer periphery and inner periphery of the planar coil conductor 3 It goes without saying that the heat transfer insulating layer 7 may also be formed between the upper and lower planar coil conductors 3. Such a configuration can be easily achieved by applying an insulating layer paste on the planar coil conductor pattern to be the planar coil conductor 3 formed on the green sheet to be the ferrite magnetic layer 2 in the process of manufacturing the coil-embedded substrate. In the subsequent laminating process, it is possible to prevent a gap from being generated between the adjacent outer periphery and inner periphery of the planar coil conductor 3.

  In the case where the heat transfer insulating layer 7 is overlapped over the entire region where the planar coil conductor 3 is formed in plan view and connected to the planar coil conductor 3, a portion overlapping the inner portion of the planar coil conductor 3 or the heat transfer conductor layer 4. In other words, the heat transfer insulating layer 7 may overlap all over the substrate. In this manner, in the process of manufacturing the coil-embedded substrate, for example, when the insulating layer 7 for heat transfer is formed by applying a paste, a screen plate making that matches the pattern shape of the planar coil conductor 3 is prepared. In addition, it is possible to save the time and effort of positioning, and when the green sheet on which the pattern of the planar coil conductor 3 and the pattern of the heat transfer insulating layer 7 are laminated, the pattern of the planar coil conductor 3 and the transmission Since there is no step between the portion where the pattern of the thermal insulating layer 7 is formed and the portion where none is formed, it is possible to prevent the generation of voids inside the green sheet laminate. Can do.

  As shown in FIG. 12, when the heat transfer insulating layer 7 has a relatively large area, a plurality of openings 7a arranged along the outer periphery of the planar coil conductor 3 are formed in the heat transfer insulating layer 7. It is preferable to do. As described above, since the heat transfer insulating layer 7 is not a conductor, the heat transfer insulating layer 7 does not completely obstruct the passage of the magnetic flux, but the plurality of openings 7a surround the planar coil conductor 3. Since the magnetic flux generated in the flat coil conductor 3 more easily passes through the region outside the planar coil conductor 3, it is possible to further suppress the decrease in inductance, and the portion between the plurality of openings 7a generates heat generated in the planar coil conductor 3. Therefore, the heat generated in the planar coil conductor 3 can be radiated to the outside.

  The width of the opening 7a of the insulating layer for heat transfer 7 (the length in the direction from the planar coil conductor 3 toward the side surface of the substrate) is the dimension of the planar coil conductor 3, the frequency and current value of the current flowing through the planar coil conductor 3, Or, depending on the magnetic permeability of the ferrite magnetic layer 2, for example, when the magnetic permeability of the ferrite magnetic layer 2 is 500, it may be 0.1 mm or more. The length of the opening 7a in the direction along the outer periphery of the planar coil conductor 3 is such that the total length of the opening 7a on the planar coil conductor 3 side is 95% or less of the length of the outer periphery of the planar coil conductor 3. Is preferred. If it is larger than this, the heat transfer path from the planar coil conductor 3 of the heat transfer insulating layer 7 to the heat dissipating conductor layer 5 becomes too small, and the heat dissipating efficiency is lowered.

  The position of the opening 7a in the heat transfer insulating layer 7 is preferably such that the distance from the outer periphery of the planar coil conductor 3 is as small as possible so that the passage of the magnetic flux is not greatly hindered. It is preferable to be in contact with the outer periphery of the coil conductor 3. As shown in FIGS. 10 and 11, when the heat transfer insulating layer 7 is connected to the side of the planar coil conductor 3, the heat generated by the planar coil conductor 3 is transmitted over the entire outer periphery of the planar coil conductor 3. Since it is preferable to receive the heat insulating layer 7 from the viewpoint of heat dissipation, it is preferable to provide the opening 7a outside the planar coil conductor 3 by about 50 μm to 200 μm. Further, although it varies depending on the dimensions of the planar coil conductor 3, the frequency and current value of the current flowing through the planar coil conductor 3, or the magnetic permeability of the ferrite magnetic layer 2, this is between the outer periphery of the planar coil conductor 3 and the opening 7a. If there is a certain distance, a large magnetic flux tends to be generated around the entire planar coil conductor 3 from the outermost periphery to the innermost periphery of the planar coil conductor 3.

  When the planar coil conductor 3 is formed in a rectangular shape along the outer shape of the rectangular substrate, as shown in FIG. 12 (b), the corners of the planar coil conductor 3 are formed in a region outside the planar coil conductor 3. It is preferable to form the opening 7a of the heat transfer insulating layer 7 in a region other than the outer side. That is, it is preferable to provide a portion serving as a heat transfer path from the planar coil conductor 3 to the heat transfer conductor layer 4 only outside the corners of the planar coil conductor 3. Since the magnetic flux density at the outer periphery of the corner portion of the planar coil conductor 3 is coarser than that in the other regions, the magnetic flux passing through the heat transfer insulating layer 7 having a lower magnetic permeability than that of the ferrite magnetic layer 2 can be obtained. The impact is small. For the same reason, as shown in FIG. 13 in a cross-sectional view similar to FIG. 1, the width of the heat transfer path arranged at the corner of the rectangular planar coil conductor 3 is larger than the width of the heat transfer path arranged at other positions. You may arrange | position the opening part 7a so that it may become large.

  Also, as shown in FIGS. 12B and 13B, the shape of the opening 7a is such that the heat transfer path from the planar coil conductor 3 to the heat transfer conductor layer 4 in the heat transfer insulating layer 7 dissipates heat. It is preferable that the width is increased toward the conductor layer 5 for heat transfer because heat transfer to the heat transfer conductor layer 4 is more efficiently performed. At this time, since the density of the magnetic flux generated in the planar coil conductor 3 is rougher in the outer peripheral portion than in the substrate in plan view, the magnetic flux passage region is reduced by increasing the width of the heat transfer insulating layer 7. The effect of is small. In this case, it is preferable that the width of the heat transfer insulating layer 7 is widened at an angle of 45 ° on both sides at the maximum, because a sufficient improvement in heat conduction can be obtained while suppressing a decrease in the passage region of the magnetic flux. .

  Further, as shown in FIG. 13, when a plurality of planar coil conductors 3 are provided above and below, the heat transfer insulating layer 7 may be formed between the planar coil conductors 3 positioned above and below. In this way, the heat generated from the planar coil conductor 3 is directly transmitted to the heat transfer insulating layer 7 from the outer periphery to the inner periphery of the planar coil conductor 3 and is also generated in the planar coil conductor 3. After the heat is guided to the inside in the thickness direction of the coil built-in substrate on which the heat transfer insulating layer 7 is formed, heat can be radiated to the outside from the side surface of the coil built-in substrate on which the heat radiating conductor layer 5 is formed. Therefore, the heat generated in the planar coil conductor 3 is more efficiently transmitted to the heat radiating conductor layer 5, and the heat transfer in the direction of the insulating layer 1, that is, the main surface of the coil-embedded substrate on which electronic components such as IC are mounted. Since it can suppress, it can prevent more effectively that electronic components, such as IC mounted in the board | substrate with a built-in coil, malfunction by the heat | fever which generate | occur | produces from the planar coil conductor 3. FIG.

  Further, in the example shown in FIG. 13, the heat transfer insulating layer 7 is formed between the planar coil conductors 3 on the outer periphery and the inner periphery adjacent to each other. Since there is a heat transfer insulating layer 7 having a lower magnetic permeability than the ferrite magnetic layer 2 between the flat coil conductors 3, magnetic flux passes between the adjacent outer peripheral coil conductors 3 and the inner peripheral coil conductors 3. It is difficult to generate a leakage magnetic flux between the adjacent outer peripheral and inner peripheral planar coil conductors 3, thereby suppressing magnetic saturation and suppressing deterioration of the superposition characteristics. Further, similarly, since the leakage magnetic flux is hardly generated between the upper and lower planar coil conductors 3 and 3, magnetic saturation is suppressed, and further deterioration of the superposition characteristic is suppressed.

  In the example shown in FIGS. 10 to 13, the shape of the heat transfer conductor layer 4 is such that the heat transfer insulating layer 7 is formed in the example shown in FIG. Similarly, in the case of the shapes as shown in FIGS. 3 and 5 to 9, the heat transfer insulating layer 7 may be formed by connecting to the planar coil conductor 3 and the heat transfer conductor layer 4.

  14 and 15 are views showing another example of the embodiment of the coil-embedded substrate of the present invention, and (a) of each figure is a sectional view ((b)) of the coil-embedded substrate of the present invention. (B longitudinal section taken along line BB ′), (b) is a sectional view (cross section) cut along line AA ′ shown in (a), and 8 is a through conductor for heat transfer. As shown in FIGS. 14 and 15, when a plurality of planar coil conductors 3 and 3 and heat transfer conductor layers 4 and 4 are provided above and below via the ferrite magnetic layer 2, they are positioned above and below. It is preferable that a heat transfer through conductor 7 formed in a direction penetrating the ferrite magnetic layer 2 therebetween is connected to at least one of the heat transfer conductor layers 4. As a result, the heat generated in the planar coil conductor 3 and transferred to the ferrite magnetic layer 2 is transferred to the heat transfer conductor layers 4 and 4 via the heat transfer through conductor 8 and thus generated in the plane coil conductors 3 and 3. Heat can be radiated from the heat radiating conductor layer 5 to the outside of the substrate through the heat conducting conductor layers 4 and 4 more efficiently.

  Further, since the heat transfer through conductor 8 is formed in the ferrite magnetic layer 2 between the heat transfer conductor layers 4 and 4 (planar coil conductors 3 and 3) positioned above and below, the planar coil conductor 3 and 3 is easily guided to the inner side in the thickness direction of the coil-embedded substrate, and heat is transferred in the direction of the insulating layers 1 and 1, that is, the main surface direction of the coil-embedded substrate on which electronic components such as ICs are mounted. Therefore, it is possible to more effectively prevent an electronic component such as an IC mounted on the coil-embedded substrate from malfunctioning due to heat generated from the planar coil conductors 3 and 3.

  Since the heat transfer through conductor 8 can efficiently transfer the heat generated in the planar coil conductors 3 and 3 to the heat transfer conductor layers 4 and 4 as close as possible to the planar coil conductors 3 and 3 as shown in FIG. As in the example shown in FIG. 15, it is preferable to arrange and connect along the inner periphery of the heat transfer conductor layers 4. The example shown in FIGS. 14 and 15 is an example in which the heat transfer through conductor 8 is added to the example shown in FIG. 8, but the heat transfer conductors like the examples shown in FIGS. 4 to 7 and FIG. In the case where the layers 4 and 4 surround the planar coil conductors 3 and 3, similarly, a plurality of heat transfer through conductors 8 are arranged and connected along the inner circumference of the heat transfer conductor layers 4 and 4. That's fine. When the plurality of heat transfer conductor layers 4 are arranged along the outer periphery of the planar coil conductor 3 as in the examples shown in FIGS. 1 to 3, the heat transferred to the ferrite magnetic layer 2 can be more efficiently performed. In order to transmit to the heat transfer conductor layer 4, not only on the side of each heat transfer conductor layer 4 close to the outer periphery of the planar coil conductor 3, but also on all sides other than the side connected to the heat dissipation conductor layer 5 It is preferable to arrange and connect along.

  Further, the heat transfer through conductor 8 is connected to a position along the outer side and the inner circumference, and not only to one row along the outer side and the inner circumference, but to another position of the heat transfer conductor layer 4. Also good. For example, if the heat transfer conductor layer 4 has a shape surrounding the planar coil conductor 3, the heat transfer through conductors 8 may be arranged in two rows in a so-called staggered arrangement or in more rows. When the heat-dissipating conductor layer 5 side is viewed from the ferrite magnetic layer 2 sandwiched between the upper and lower planar coil conductors 3 and 3, the heat-transfer through conductors 8 can be arranged without gaps, and heat transfer can be performed more efficiently. Heat can be transferred to the heat transfer conductor layer 4 through the through-conductor 8.

  Further, as in the example shown in FIGS. 8 and 9, a plurality of openings in which the heat transfer conductor layer 4 is formed close to the outer periphery of the planar coil conductor 3 and is disposed along the outer periphery of the planar coil conductor 3. When the heat transfer through conductor 8 is arranged and connected along the inner periphery of the shape having the portion 4b (for example, the example shown in FIG. 14), the presence of the heat transfer through conductor 8 Since the magnetic flux generated around each of the planar coil conductors 3 and 3 positioned at the center is prevented from passing between the upper and lower planar coil conductors 3 and 3, the magnetic flux is generated around the entire upper and lower planar coil conductors 3 and 3. Thus, partial saturation of the magnetic flux generated by the concentration of the magnetic flux between the upper and lower planar coil conductors 3 and 3 can be suppressed, and the deterioration of the superposition characteristics can be suppressed.

  In the example shown in FIGS. 14 and 15, the heat transfer through conductor 8 penetrates all of the ferrite magnetic layer 2 between the upper and lower heat transfer conductor layers 4 and 4 and passes through the upper and lower heat transfer conductor layers 4 and 4. 4, it is not always necessary to penetrate through the entire ferrite magnetic layer 2 between the upper and lower heat transfer conductor layers 4, 4, and the upper and lower heat transfer conductor layers 4, 4. As long as it is connected to at least one of the above. For example, when the ferrite magnetic layer 2 between the upper and lower heat transfer conductor layers 4 is composed of three layers, the heat transfer through conductor 8 penetrates only the upper (or lower) two layers and It may be connected only to (or below) the heat transfer conductor layer 4, and only one of the upper and lower layers of the three ferrite magnetic layers 2 penetrates the upper and lower heat transfer conductor layers 4. -It may be connected to 4. 14 and FIG. 15, when the heat transfer through conductor 8 penetrates all of the ferrite magnetic layer 2 between the upper and lower heat transfer conductor layers 4 and 4, the planar coil conductor 3 This is preferable because the area to receive the generated heat becomes larger and the heat transferred to the ferrite magnetic layer 2 can be more efficiently transferred to the heat transfer conductor layer 4 through the heat transfer through conductor 8.

  The cross-sectional shape of the heat transfer through conductor 8 is not limited to a circle as shown in FIG. 14 (b), but may be a triangle, a quadrangle, or more polygons and an ellipse, and is not particularly limited. . The transverse cross-sectional shape of the heat transfer through conductor 8 is preferably an elongated shape along the outer side or inner periphery of the heat transfer conductor layer 4, for example, a rectangle or an ellipse as shown in FIG. By adopting such a shape, the area that receives the heat generated by the planar coil conductor 3 becomes larger, and the heat transferred to the ferrite magnetic layer 2 is transferred through the heat transfer through conductor 8 to the heat transfer conductor layer 4. Can communicate more efficiently.

  Further, as in the example shown in FIG. 15 (a), the heat transfer through conductor 8 is extended to the main surface (lower surface) of the substrate (by forming the 8a portion shown in FIG. 15 (a)). You may connect to the wiring layers 6, such as the electrode layer 6d formed in the conductor layer 5 for thermal radiation extended to the surface (lower surface), and the main surface (lower surface) of a board | substrate. By doing in this way, the heat-transfer path | route to the heat radiating conductor layer 5 increases, and it can thermally radiate more efficiently. In this case, the transverse cross-sectional shape of the heat transfer through conductor 8a located in the ferrite magnetic layer 2 below the lower heat transfer conductor layer 4 is formed on the outer side or inner periphery of the heat transfer conductor layer 4. If the shape is long and narrow, the passage of the magnetic flux generated around the planar coil conductor 3 is obstructed, so that a circle or square having a small width in the direction along the outer edge or inner circumference of the heat transfer conductor layer 4 is formed. Preferably, in order to transfer heat more efficiently in the direction of the main surface of the substrate without obstructing the passage of the magnetic flux, the cross-sectional area is increased by forming an elongated rectangle or ellipse toward the center of the area inside the planar coil conductor 3. Is more preferable. Further, as shown in FIG. 15 (b), the cross sectional area of the heat transfer through conductor 8a is larger on the main surface side of the substrate than on the ferrite magnetic layer 2 side (larger in the lower insulating layer 1). Then, it is preferable because the heat resistance of heat transfer to the main surface (lower surface) side of the substrate in the heat transfer through conductor 8a becomes smaller and heat can be transferred more efficiently.

  Regarding the position of the planar coil conductor 3 in the thickness direction of the substrate in the ferrite magnetic layer 2, the thickness of the ferrite magnetic layer 2 between the planar coil conductor 3 and the insulating layer 1 is generated around the planar coil conductor 3. As long as the magnetic flux to be transmitted has a thickness necessary for passing through the magnetic flux, it is sufficient. Depending on the size of the planar coil conductor 3, the frequency and value of the current flowing through the planar coil conductor 3, or the permeability of the ferrite magnetic layer 2, for example, when the permeability of the ferrite magnetic layer 2 is 500, the plane The thickness of the ferrite magnetic layer 2 between the coil conductor 3 and the insulating layer 1 may be 0.1 mm or more. Further, in the case where a plurality of planar coil conductors 3 are provided above and below, the distance between the upper and lower planar coil conductors 3 and 3 may be any distance that can maintain insulation between the upper and lower planar coil conductors 3. 2 or about 50 μm or more, although it depends on the heat transfer insulating layer 7.

  As shown in FIGS. 1 to 15, the heat dissipation conductor layer 5 is formed on the side surface of the substrate connected to the heat transfer conductor layer 4. When providing a plurality of heat transfer conductor layers 4 close to the outer periphery of the planar coil conductor 3, a plurality of heat transfer conductor layers 4 may be provided corresponding to each of the plurality of heat transfer conductor layers 4 as shown in FIG. However, as shown in FIG. 2B and FIG. 3B, it is preferable that the heat radiation area be increased so that heat can be radiated more efficiently by providing it over the entire circumference of the side surface of the substrate. Further, in this way, even if noise is radiated from the planar coil conductor 3, the radiation conductor layer 5 has a shape surrounding the planar coil conductor 3, so that the radiation conductor layer 5 functions as a shield and noise. Therefore, the influence of the noise radiated from the planar coil conductor 3 on the wiring layer 6 is suppressed, and the IC mounted on the mounting electrode 6b can be operated more stably. A substrate can be obtained. When the heat transfer conductor layer 4 has a shape surrounding the planar coil conductor 3 along the outer periphery, the heat dissipating conductor layer 5 is provided over the entire circumference of the side surface of the substrate and connected to the heat transfer conductor layer 4 over the entire circumference. However, when a wiring layer for connecting the wiring layers 6 formed on the upper and lower insulating layers 1 and 1 is formed on the side surface of the substrate, it is divided into a plurality so as to be insulated from the wiring layers. May be. In this case, the heat transfer conductor layer 4 is not formed up to the side surface in the portion where the wiring layer is formed, but is insulated from the wiring layer.

  Further, the size of the heat-dissipating conductor layer 5 is not particularly limited in the thickness direction of the substrate, and as shown in FIG. 1A, not only the side surface of the ferrite magnetic layer 2 but also FIG. 8A. Thus, it may be formed over the side surface of the insulating layer 1 and further over the main surface (lower surface) of the substrate as shown in FIGS. 3 (a) and 9 (a). From the viewpoint of functioning as a shield for the planar coil conductor 3, for example, it is preferably formed on the entire side surface of the ferrite magnetic layer 2 so as to overlap the planar coil conductor 3 when the substrate is viewed from the side. From the viewpoint of heat dissipation, the larger the area, the more efficiently the heat can be dissipated. In addition, when the insulating layer 1 is formed on the side surface and further on the lower surface of the lower insulating layer 1, the substrate can be bonded to the external circuit board using a bonding material such as solder. By doing so, it is possible to improve the heat radiation efficiency, increase the bonding area with the external circuit board, and improve the bonding strength and mounting reliability, which is preferable.

  Further, the heat dissipation conductor layer 5 can be further improved in heat dissipation by making its thickness thicker than the wiring layer 6 and the planar coil conductor 3. For example, the wiring layer 6 and the planar coil conductor 3 are usually formed with a thickness of about 10 μm, but are thicker, for example, 20 μm or more.

  Furthermore, by increasing the surface roughness of the heat-dissipating conductor layer 5 compared to the mounting electrode 6b and the electrode pad 6d, the surface area can be increased and the heat dissipation can be improved. For example, the surface roughness (arithmetic average roughness: Ra) of the mounting electrode 6b and the electrode pad 6d is usually about 1 to 5 μm, whereas the surface roughness is about 20 μm or more, or higher level. It is good to have an uneven shape.

  The insulating layer 1 is an insulating layer that is co-fired at a temperature of 800 to 1000 ° C. together with the wiring layer 6 formed on the surface and inside, the ferrite magnetic layer 2 formed between the insulating layer 1 and the planar coil conductor 3. From the viewpoint of suppressing the increase in inductance of the wiring layer 6 from a sintered body of body powder, it is preferable to use a nonmagnetic insulator such as nonmagnetic ferrite or glass ceramic. For the insulating layer 1, a green sheet for the insulating layer 1 mainly composed of an insulating powder and an organic binder is manufactured, and the green sheet for the insulating layer 1 is laminated as many as necessary to expand the wiring, and then 800 to 1000 ° C. It is produced by firing at a temperature of

  The thickness of the insulating layer 1 positioned above and below the planar coil conductor 3 varies depending on the dimension of the planar coil conductor 3, the frequency and current value of the current flowing through the planar coil conductor 3, or the magnetic permeability of the ferrite magnetic layer 2, for example. When the magnetic permeability of the ferrite magnetic layer 2 is 500, it may be 0.1 mm or more.

When the insulating layer 1 is made of nonmagnetic ferrite, Zn-based ferrite or Cu-based ferrite may be used. Among them, a Cu—Zn-based ferrite which is a solid solution having a positive spinel structure shown as X—Fe ₂ O ₄ (X is Cu, Zn) is preferable.

In the case of Cu—Zn ferrite, the composition ratio is 1000 ° C. when the sintered body is 50 to 70 mass% Fe ₂ O ₃ , 5 to 20 mass% CuO and 20 to 35 mass% ZnO. High density firing with a sintered density of 5.0 g / cm ³ or more is possible at the following low temperature, and the nonmagnetic ferrite layer after firing is preferable because it is nonmagnetic even in a low temperature range. Fe ₂ O ₃ is the main component of ferrite, and if its proportion is less than 50% by mass, magnetism tends to occur, and if it exceeds 70% by mass, mechanical strength tends to decrease due to a decrease in sintered density. is there. CuO is an important factor for lowering the sintering temperature, and CuO promotes sintering by forming a liquid phase at a low temperature, and the low temperature of 800 to 1000 ° C. without damaging the magnetic properties. Can be fired. Therefore, if the proportion is less than 5% by mass, the sintering density tends to be insufficient and the mechanical strength tends to be insufficient when firing at 800 to 1000 ° C. simultaneously with the wiring layer 6, from 20% by mass. When the amount is large, the Curie temperature rises and magnetism tends to occur in a low temperature region. ZnO is an important element for making nonmagnetic ferrite nonmagnetic. If the ratio is less than 20% by mass, the mechanical strength tends to decrease due to a decrease in sintered density, and if it exceeds 35% by mass. There is a tendency to generate magnetism.

Further, when the insulating layer 1 is made of nonmagnetic ferrite, it may be a nonmagnetic ferrite powder added with a glass having a low softening point and fired at a low temperature. Examples of the glass at this time include SiO ₂ —B ₂ O ₃ system, SiO ₂ —B ₂ O ₃ —Al ₂ O ₃ system, SiO ₂ —B ₂ O ₃ —Al ₂ O ₃ —MO system (however, M Represents Ca, Sr, Mg, Ba or Zn), SiO ₂ —Al ₂ O ₃ —M ¹ O—M ² O system (where M ¹ and M ² are the same or different, and Ca, Sr, Mg, Ba) Or Zn), SiO ₂ —B ₂ O ₃ —Al ₂ O ₃ —M ¹ O—M ² O (where M ¹ and M ² are the same as above), SiO ₂ —B ₂ O ₃ -M ³ ₂ O system (where M ³ represents Li, Na or K), SiO ₂ -B ₂ O ₃ -Al ₂ O ₃ -M ³ ₂ O system (where M ³ is the same as above) ), Pb-based glass, Bi-based glass, and the like, and the softening point of the glass is 600 ° C. or lower. This is desirable because it does not hinder the sintering of ferrite.

When the insulating layer 1 is made of glass ceramics, the insulator powder is made of a sintered body of a mixture of glass powder and filler powder as described above. Examples of filler powder include Al ₂ O ₃ , SiO ₂ , ZrO. ₂ and an alkaline earth metal oxide, a composite oxide of TiO ₂ and an alkaline earth metal oxide, a composite oxide containing at least one selected from Al ₂ O ₃ and SiO ₂ (for example, spinel) , Mullite, cordierite) and the like.

  The wiring layer 6 is made of a metallized metal that is a sintered body of a low-resistance metal powder such as Cu, Ag, Au, Pt, Ag—Pd alloy, and Ag—Pt alloy, and is used as a green sheet for the insulating layer 1. A wiring pattern is formed by printing a conductive paste for the wiring layer 6 and is formed by simultaneous firing with the green sheet for the insulating layer 1.

The ferrite magnetic layer 2 is a sintered body of magnetic ferrite powder such as Ni—Zn ferrite, Mn—Zn ferrite, Mg—Zn ferrite, Ni—Co ferrite, etc., which are ferromagnetic ferrites. Ni—Zn ferrite, which is a solid solution having an inverse spinel structure represented as Fe ₂ O ₄ (X is Cu, Ni, Zn), is preferable for obtaining a sufficiently high magnetic permeability in a high frequency band.

In the case of Ni-Zn ferrite, the composition ratio of the sintered body is 63 to 73% by mass of Fe ₂ O ₃ , 5 to 10% by mass of CuO, 5 to 12% by mass of NiO, and 10 to 10% of ZnO. A mass ratio of 23% by mass is preferable because high-density firing at a sintering density of 5.0 g / cm ³ or higher is possible at a low temperature of 1000 ° C. or lower, and a sufficiently high magnetic permeability can be obtained in a high-frequency band. Fe ₂ O ₃ is the main component of ferrite, and if its proportion is less than 63% by mass, there is a tendency that sufficient magnetic permeability cannot be obtained, and if it exceeds 73% by mass, mechanical strength is reduced due to a decrease in sintered density. There is a tendency to decrease. CuO is an important factor for lowering the sintering temperature, and CuO promotes sintering by forming a liquid phase at a low temperature, and the low temperature of 800 to 1000 ° C. without damaging the magnetic properties. Can be fired. For this reason, if the ratio is less than 5% by mass, the sintering density becomes insufficient when the wiring layer 6 and the planar coil conductor 3 are simultaneously fired at 800 to 1000 ° C., and the mechanical strength tends to be insufficient. If the amount is more than 10% by mass, the ratio of CuFe ₂ O _{4 having} low magnetic properties increases, so that the magnetic properties tend to be impaired. NiO is contained in order to ensure the magnetic permeability in the high frequency region of the ferrite magnetic layer 2. NiFe ₂ O ₄ does not cause the attenuation of the magnetic permeability due to resonance up to the high frequency range, and can maintain the magnetic permeability in the high frequency range at a relatively high value. However, since NiFe ₂ O ₄ has a characteristic that the initial permeability is low, 5 mass If it is less than%, the magnetic permeability in a high frequency region of 10 MHz or more tends to decrease, and if it exceeds 12 mass%, the initial magnetic permeability tends to decrease. ZnO is an important factor for improving the magnetic permeability of the ferrite magnetic layer 2, and if the ferrite composition is less than 10% by mass, the magnetic permeability is lowered, and conversely if it is more than 23% by mass, the magnetic properties are poor. Tend to be.

  The ferrite magnetic layer 2 is produced by using a ferrite magnetic layer 2 green sheet formed by the same method as the insulating layer green sheet used for the insulating layer 1.

  The planar coil conductor 3 is made of a metallized metal layer, which is a sintered body of metal powder, similarly to the wiring layer 6, and the conductor paste for the planar coil conductor 3 is printed on the surface of the ferrite magnetic layer 2 green sheet. Thus, a coil pattern is formed, and a green sheet for the ferrite magnetic layer 2 is further laminated thereon and fired at the same time, thereby being embedded in the ferrite magnetic layer 2. When a plurality of planar coil conductors 3 are stacked one above the other, a plurality of ferrite magnetic layer 2 green sheets on which a coil pattern and a through conductor pattern are formed are stacked, and a ferrite magnetic layer 2 green sheet is further formed. What is necessary is just to laminate.

  The metal powder used for the production of the planar coil conductor 3 is a low-resistance metal powder such as Cu, Ag, Au, Pt, Ag—Pd alloy, and Ag—Pt alloy similar to the wiring layer 6. Thereby, the electrical resistance of the planar coil conductor 3 becomes small, and the heat generation of the planar coil conductor 3 can be suppressed.

  The heat transfer insulating layer 7 is made of a sintered body of insulating powder co-fired at a temperature of 800 to 1000 ° C. together with the insulating layer 1, the ferrite magnetic layer 2, the planar coil conductor 3 and the wiring layer 6. The magnetic conductivity of the ferrite magnetic layer 2 is larger than that of the ferrite magnetic layer 2. As long as the thermal conductivity is higher than that of the ferrite magnetic layer 2, the same one as that of the insulating layer 1 may be used. Since the magnetic conductivity of the ferrite magnetic layer 2 is about 3 W / (m · K) to 4 W / (m · K), the heat conductivity of the heat transfer insulating layer 7 is about 6 W / (m · K) or more. If it is a thing, since the heat | fever generate | occur | produced in the planar coil conductor 3 will become easy to heat-transfer inside the insulating layer 7 for heat transfer, it is preferable.

  The heat transfer insulating layer 7 is produced by manufacturing a green sheet for the heat transfer insulating layer 7 mainly composed of the insulating powder for the heat transfer insulating layer and the organic binder, and on the green sheet for the heat transfer insulating layer 7. A planar coil conductor pattern to be the planar coil conductor 3 is formed on the laminate, laminated on the ferrite magnetic layer 2 green sheet on which the planar coil conductor pattern is formed, or an insulator for the heat transfer insulating layer 7 A paste for heat transfer insulating layer 7 mainly composed of powder, organic binder and solvent is manufactured and connected to or overlapped with the planar coil conductor pattern formed on the green sheet for ferrite magnetic layer 2. In addition, the paste for the heat transfer insulating layer 7 is printed in a predetermined pattern by a printing method such as a screen printing method or a gravure printing method, and the green paper for the insulating layer 1 and the ferrite magnetic layer 2 is printed. It is produced by firing at a temperature of 800 to 1000 ° C. with bets.

The insulator powder for the heat transfer insulating layer 7 may be the same as the glass powder and filler powder used for the insulating layer 1, and examples of the filler powder include AlN, Si ₃ N ₄ , SiC, and BN. The use of ceramic powder is preferable because a higher thermal conductivity can be obtained. As the glass powder, crystallized glass is preferable because it has higher thermal conductivity. When non-oxide ceramics such as AlN are used as the filler, the glass and non-oxide ceramic filler react during firing, and the non-oxide ceramic filler decomposes to generate gas, resulting in a decrease in thermal conductivity. It is preferable to use a rare earth element-containing silicate glass or oxynide glass. The rare earth element-containing silicate glass contains 1 to 30% by mass of RE ₂ O ₃ (rare earth oxide), ₁₀ to 55% by mass of SiO ₂ , ₃ to 35% by mass of Al ₂ O ₃ , ZnO and / or MgO. 5 to 30% by mass, B ₂ O ₃ in an amount of 0 to 25% by mass, and at least one selected from the group of CaO, SrO and BaO in a total amount of 0 to 50% by mass, more Specifically, for example, Y ₂ O ₃ is 14% by mass, SiO ₂ is 22% by mass, Al ₂ O ₃ is 5% by mass, ZnO is 15% by mass, MgO is 5% by mass, and B ₂ O ₃ is 10% by mass. %, Glass containing 29% by mass of SrO (hereinafter referred to as glass A), Y ₂ O ₃ 5% by mass, SiO ₂ 22% by mass, Al ₂ O ₃ 8% by mass, ZnO 2% by mass, MgO 18 _wt%, B 2 _{O 3} of 18 wt%, glass (hereinafter containing SrO 27 mass%, the glass B gutter ), _Nd 2 _{O 3} 10 wt%, a SiO ₂ 30 wt%, the _Al 2 _{O 3} 15 wt%, ZnO of 13% by weight, CaO 15% by mass, the BaO _5% by _weight, the B 2 _{O 3} Examples thereof include glass containing 12% by mass (hereinafter referred to as glass C). The oxinide glass is a glass containing nitrogen. For example, an oxide glass raw material powder mainly composed of SiO ₂ and B ₂ O ₃ is heated in a nitrogen atmosphere at a temperature of 300 ° C. to 800 ° C. for 2 hours. By treating for ˜5 hours, 0.1% by mass or more and 10% by mass or less of nitrogen element can be contained in the glass powder.

As an example of the composition of the heat transfer insulating layer 7, glass A containing 60 mass% and AlN containing 40 mass% can obtain a thermal conductivity of 8.4 W / (m · K) when fired at 900 ° C. A glass A containing 50% by mass and AlN containing 50% by mass can obtain a thermal conductivity of 11.5 W / (m · K) when fired at 900 ° C. A glass A containing 60% by mass and Si ₃ N ₄ containing 40% by mass can obtain a thermal conductivity of 7.2 W / (m · K) when fired at 900 ° C. Glass A containing 60% by mass and AlN and Si ₃ N ₄ each containing 20% by mass can obtain a thermal conductivity of 7.5 W / (m · K) when fired at 900 ° C. A glass B containing 50% by mass and AlN containing 50% by mass can obtain a thermal conductivity of 8.2 W / (m · K) by firing at 950 ° C. A glass B containing 30% by mass and AlN 70% by mass can obtain a thermal conductivity of 14.5 W / (m · K) when fired at 1000 ° C. In addition, glass B containing 50 mass% and Si ₃ N ₄ containing 50 mass% can obtain a thermal conductivity of 7.3 W / (m · K) when fired at 900 ° C. A glass C containing 60% by mass and AlN containing 40% by mass can obtain a thermal conductivity of 7.3 W / (m · K) by firing at 900 ° C. A glass C containing 60% by mass and Si ₃ N ₄ containing 40% by mass can obtain a thermal conductivity of 7.0 W / (m · K) when fired at 900 ° C.

In addition, if carbon or sulfur is present in ceramic fillers such as AlN and Si ₃ N ₄ , gases such as CO, CO ₂ , SO, and SO ₂ are generated during firing, and pores are generated to reduce thermal conductivity. In addition, by forming an oxide layer on the surface of the ceramic filler, the wettability with the glass can be improved and the sinterability can be improved. In order to remove sulfur and produce an oxide film, it is preferable to wash with water having a pH of 5 to 10 for 10 to 30 minutes or boil for 5 to 10 minutes. When ceramic filler and oxynitride glass subjected to such treatment are used, those containing 30% to 60% by weight of AlN powder and 40% to 70% by weight of oxynitride glass are 800 ° C. to A thermal conductivity of about 30 W / (m · K) to 40 W / (m · K) is obtained by firing at 1000 ° C., 30% to 80% by mass of Si ₃ N ₄ powder and 20% of oxynitride glass. In the case of containing 70% by mass to 70% by mass, a thermal conductivity of about 20 W / (m · K) to 30 W / (m · K) can be obtained by firing at 800 ° C. to 1000 ° C.

  The green sheet for insulating layer 1 or the green sheet for ferrite magnetic layer 2 or the green sheet for insulating layer 7 for heat transfer consists of an insulating binder or magnetic ferrite powder, an organic binder, an organic solvent, and a dispersant or plasticizer as required. Etc. are mixed to obtain a slurry, which is then applied by a doctor blade method, a rolling method, a calender roll method, an extrusion molding method, etc., and then dried and molded.

When the insulating layer 1 is made of nonmagnetic ferrite, the insulator powder used for the green sheet for the insulating layer 1 is obtained by mixing and calcining Fe ₂ O ₃ and CuO or ZnO powder at a predetermined ratio. It can be pulverized into raw powder.

The ferromagnetic ferrite powder used for the ferrite magnetic layer 2 green sheet is a ferrite powder prepared by pre-calcining Fe ₂ O ₃ and CuO, ZnO, or NiO, and has an average particle size of 0.1 μm. It is uniform in a range of ˜0.9 μm, and the grain shape is preferably close to a spherical shape. If the average particle size is smaller than 0.1 μm, it is difficult to uniformly disperse the ferrite powder in the production of the ferrite magnetic layer 2 green sheet. If the average particle size is larger than 0.9 μm, the ferrite magnetic layer 2 is used. This is because the sintering temperature of the green sheet tends to increase. Moreover, a uniform sintered state can be obtained because the particle diameter is uniform and nearly spherical. For example, when a small particle size is present in the ferrite powder, the crystal grain growth is reduced only in that portion, and the magnetic permeability of the ferrite magnetic layer 2 obtained after sintering tends to be difficult to stabilize.

  As the organic binder, those conventionally used for ceramic green sheets can be used. For example, acrylic (acrylic acid, methacrylic acid or a homopolymer or copolymer thereof, specifically an acrylic ester. Copolymer, methacrylic acid ester copolymer, acrylic acid ester-methacrylic acid ester copolymer, etc.), polyvinyl butyral, polyvinyl alcohol, acrylic-styrene, polypropylene carbonate, cellulose, etc. Examples thereof include a polymer or a copolymer. In view of decomposability and volatility in the firing step, an acrylic binder is more preferable.

  The organic solvent for the green sheet is not particularly limited as long as the insulator powder or ferrite powder and the organic binder can be well dispersed and mixed, and examples thereof include organic solvents such as toluene, ketones, alcohols, water, and the like. Among these, solvents having a high evaporation coefficient such as toluene, methyl ethyl ketone, and isopropyl alcohol are preferable because the drying step after slurry application can be performed in a short time.

  The slurry for producing the green sheet is obtained by adding 5 to 20 parts by mass of an organic binder and 15 to 50 parts by mass of an organic solvent with respect to 100 parts by mass of the insulator powder or ferrite powder, and mixing them by a mixing means such as a ball mill. It is prepared to have a viscosity of 3 to 100 cps.

  The paste for the heat transfer insulating layer 7 is mixed and kneaded by kneading means such as a ball mill, a three-roll mill, a planetary mixer, etc. after adding an organic binder, an organic solvent, and a dispersant as necessary to the main insulating powder. It is produced by doing.

  As the organic binder of the paste for the heat transfer insulating layer 7, those conventionally used in ceramic green sheets and ceramic pastes can be used. For example, acrylic (acrylic acid, methacrylic acid or esters thereof homopolymers) Or a copolymer, specifically, an acrylic ester copolymer, a methacrylic ester copolymer, an acrylic ester-methacrylic ester copolymer, etc.), polyvinyl butyral, polyvinyl alcohol, acrylic-styrene And homopolymers or copolymers of polypropylene, polypropylene carbonate, cellulose and the like. In view of decomposition and volatility in the baking step, acrylic and alkyd organic binders are more preferable.

  The organic solvent of the paste for the heat transfer insulating layer 7 may be any organic solvent that can disperse and mix the above-described insulator powder and organic binder, and terpineol, butyl carbitol acetate, phthalic acid, etc. are used. Is possible.

  The heat transfer insulating layer 7 paste is kneaded by adding 3 to 15 parts by weight of an organic binder and 10 to 30 parts by weight of an organic solvent to 100 parts by weight of the insulating powder. It is desirable that the viscosity be such that a pattern having a predetermined shape can be satisfactorily formed without causing problems such as bleeding or fading of the paste for 7.

  When the heat transfer insulating layer 7 is formed as in the example shown in FIGS. 10 and 11, for example, heat transfer is performed so that it is connected to the planar coil conductor pattern formed on the ferrite magnetic layer 2 green sheet. The heat transfer insulating layer pattern may be formed by printing the insulating layer 7 paste. Considering misalignment of printing, etc., the transmission is about 100 μm wider than the distance between the planar coil conductor pattern and the heat transfer conductor layer pattern and the distance between the inner circumference and the outer circumference of the planar coil conductor pattern so that the connection is ensured. A thermal insulating layer pattern may be formed.

  When the heat transfer insulating layer 7 is formed as in the example shown in FIG. 12, for example, for the heat transfer insulating layer 7 so as to overlap the planar coil conductor pattern formed on the ferrite magnetic layer 2 green sheet. The paste may be printed to form the heat transfer insulating layer pattern. At this time, in order to form the through conductor 6c for connecting the upper and lower planar coil conductors 3 and 3, a through hole is provided in the heat transfer insulating layer pattern at the time of printing, and a through conductor 6c described later is provided in this through hole. Filled with conductor paste. Further, in order to ensure the connection with the heat transfer conductor layer pattern, a part of the heat transfer conductor layer pattern may be formed to overlap with a width of, for example, about 50 μm or more.

  When the heat transfer insulating layer 7 is formed as in the example shown in FIG. 13, for example, upper and lower planar coil conductor patterns are formed on the ferrite magnetic layer 2 green sheet, and overlap these planar coil conductor patterns. In this way, the heat transfer insulating layer 7 paste may be printed, the surfaces on which the heat transfer insulating layer 7 paste is printed face to face, and aligned to be laminated. At this time, the upper and lower planar coil conductor patterns are mirror images of each other, and a through conductor pattern is formed in the same manner as described above. On the green sheet for the heat transfer insulating layer 7 on which the through conductor patterns for connecting the upper and lower planar coil conductor patterns are formed, the transmission between the inner periphery and the outer periphery of the upper planar coil conductor pattern and the planar coil conductor pattern is performed. The insulating layer pattern for heat is formed and laminated on the green sheet for the ferrite magnetic layer 2 on which the lower planar coil conductor pattern and the insulating layer pattern for heat transfer between the inner periphery and outer periphery of the planar coil conductor pattern are formed. May be.

  When the heat transfer insulating layer 7 is formed of a green sheet, the opening 7a of the heat transfer insulating layer 7 can be provided by punching the green sheet into a predetermined shape using a mold or the like. When forming using the paste for insulating layers 7, the pattern shape at the time of printing should just have the opening part 7a.

  The wiring pattern to be the internal wiring layer 6a, the mounting electrode 6b and the electrode pad 6d of the wiring layer 6 is obtained by printing a conductive paste for the wiring layer 6 on the surface of the green sheet for the insulating layer 1 by a printing method such as a screen printing method or a gravure printing method. Is formed by printing in a predetermined pattern. Prior to the formation of the wiring pattern to be the internal wiring layer 6a, the mounting electrode 6b, and the electrode pad 6d, the wiring pattern to be the through conductor 6c is formed through holes in the green sheet for the insulating layer 1 by punching or laser processing. The through hole is formed by filling the conductive paste for the wiring layer 6 by embedding means such as printing or press filling.

  Similarly, the coil pattern to be the planar coil conductor 3 is formed by printing a conductor paste for the planar coil conductor 3 on the surface of the ferrite magnetic layer 2 green sheet in a predetermined pattern by a printing method such as a screen printing method or a gravure printing method. The wiring pattern serving as the through conductor in the ferrite magnetic layer 2 is also formed in the same manner as the wiring pattern serving as the through conductor 6c. The conductor paste for the planar coil conductor 3 may be the same as the conductor paste for the wiring layer 6.

  The coil pattern to be the planar coil conductor 3 depends on the required inductance value and size, but when formed by printing as described above, the line width and the distance between adjacent outer and inner conductors is about 0.1 mm or more. If it is, it can form easily. In order to increase the number of coil turns in an area as small as possible, the line width may be about 0.1 to 1 mm, and the distance between conductors may be about 0.1 to 0.2 mm.

  Conductor paste for wiring layer 6 and conductor paste for planar coil conductor 3 are kneaded by ball mill, three-roll mill, planetary mixer, etc. by adding organic binder, organic solvent and dispersant as required to the main component metal powder It is produced by mixing and kneading by means.

  As the organic binder for the conductive paste, those conventionally used for the conductive paste can be used. For example, acrylic (a homopolymer or copolymer of acrylic acid, methacrylic acid or esters thereof, specifically acrylic Acid ester copolymer, methacrylate ester copolymer, acrylic ester-methacrylic ester copolymer, etc.), polyvinyl butyral, polyvinyl alcohol, acrylic-styrene, polypropylene carbonate, cellulose, etc. A homopolymer or a copolymer is mentioned. In view of decomposition and volatility in the firing step, acrylic and alkyd organic binders are more preferable.

  The organic solvent for the conductor paste is not particularly limited as long as the above-described metal powder and organic binder can be well dispersed and mixed, and terpineol, butyl carbitol acetate, phthalic acid, and the like can be used.

  The conductor paste for the wiring layer 6 and the conductor paste for the planar coil conductor 3 for forming a wiring pattern to be the internal wiring layer 6a, the mounting electrode 6b and the electrode pad 6d of the wiring layer 6 are based on 100 parts by mass of the metal conductor powder. By adding 3 to 15 parts by weight of organic binder and 10 to 30 parts by weight of organic solvent and kneading, it is possible to form a pattern with a predetermined shape without causing problems such as bleeding or fading of the conductor paste by printing. It is desirable to have a viscosity of.

  The conductive paste for forming the wiring pattern to be the through conductor 6c is for the wiring layer 6 for forming the wiring pattern to be the internal wiring layer 6a, the mounting electrode 6b, and the electrode pad 6d, depending on the amount of the solvent and the amount of the organic binder. The conductive paste and the conductive paste for the planar coil conductor 3 may be adjusted to a paste with relatively low fluidity to facilitate filling into the through-holes and to be heated and cured. Moreover, it is good also as an inorganic component which added the powder of glass or ceramics to the metal conductor powder for adjustment of sintering behavior.

  When the insulating layer 1 is formed of nonmagnetic ferrite, a conductive paste for the wiring layer 6 for forming the wiring layer 6 formed on the outer surface of the insulating layer 1 such as the mounting electrode 6b and the electrode pad 6d is used. It is desirable to add a powder of a divalent metal oxide such as ZnO, CuO, MgO, CoO, NiO, MnO, or FeO. By adding a divalent metal oxide, the wiring layer 6 on the outer surface can be firmly bonded to the insulating layer 1 mainly composed of nonmagnetic ferrite.

  A predetermined number of green sheets for ferrite layer 2 including a coil pattern is disposed above and below a predetermined number of green sheets for insulating layer 1 each having a wiring pattern formed thereon to produce a laminate. A substrate with a built-in coil is produced by firing the laminate.

  Similarly to the wiring layer 6, the heat transfer conductor layer 4 and the heat dissipation conductor layer 5 are sintered bodies of low-resistance metal powders such as Cu, Ag, Au, Pt, Ag—Pd alloy, and Ag—Pt alloy. It is made of metallized metal. The conductive layer 4 for heat transfer is obtained by applying a conductive paste for the wiring layer 6 used for forming the internal wiring layer 6a or the like to the green sheet for the insulating layer 1 or the green sheet for the ferrite magnetic layer 2 by screen printing or gravure printing. It is formed by applying a predetermined pattern shape on the surface and simultaneously firing together. The heat-dissipating conductor layer 5 is formed by forming a laminated body of a green sheet for the insulating layer 1 and a green sheet for the ferrite magnetic layer 2 as described later, and then the insulating layer 1 such as the mounting electrode 6b and the electrode pad 6d. A conductive paste similar to the conductive paste for the wiring layer 6 formed on the outer surface of the substrate is applied in a predetermined pattern shape to the side surface of the laminate by a screen printing method, a gravure printing method, or the like, and simultaneously fired together with these. . In the case of producing in a multi-cavity form, a laminated body in which a hole that does not penetrate or penetrate at the boundary of each substrate is produced, and a conductor paste may be applied to the inner surface of the hole that becomes the side surface of the substrate, It may be divided after filling and co-firing, or may be baked by applying a conductive paste to the exposed side surfaces after firing and dividing the multi-layered laminate.

  In order to make the surface roughness (arithmetic mean roughness: Ra) of the heat-dissipating conductor layer 5 larger than that of the wiring layer 6 (mounting electrode 6b or electrode pad 6d), a metal powder having a large particle size is used for the conductor paste. May be used. For example, a metal paste of about 5 μm is used for the conductor paste used for forming the wiring layer 6, the planar coil conductor 3 or the heat transfer conductor layer 4, whereas the conductor paste used for forming the heat dissipating conductor layer 5 is 10 μm. What is necessary is just to use the metal powder more than a grade.

  Further, in order to make the surface of the heat-dissipating conductor layer 5 have irregularities, for example, by applying a conductive paste and then pressing the mold, the irregularities having a shape such as a row of grooves or a large number of point-like convex portions or concave portions May be formed.

  Prior to the formation of the heat transfer conductor layer pattern to be the heat transfer conductor layer 4, the heat transfer through conductor 8 has a through hole formed in the green sheet for the ferrite magnetic layer 2 by punching, laser processing, or the like. The through hole is filled with a conductive paste for the through conductor 6c by embedding means such as printing or press filling, and is fired at the same time. When the through conductor 6c and the heat transfer through conductor 8 are formed in the same layer, the through hole and the paste may be formed at the same time. Similarly, when extending the heat transfer through conductor 8 to the main surface (lower surface) of the substrate, the insulating layer 1 green is formed prior to the formation of the surface wiring pattern and the heat dissipating conductor layer pattern to be the heat dissipating conductor layer 5. A through hole for the heat transfer through conductor 8a may be formed in the sheet, and the through hole may be filled with a conductive paste.

  In order to increase the cross-sectional area of the heat transfer through conductor 8a on the main surface side of the substrate from the ferrite magnetic layer 2 side, the through holes formed in the green sheet on the main surface side may be made larger. Also, as shown in FIG. 15 (b), when the shape gradually increases from the ferrite magnetic body 2 to the main surface of the substrate without a step, it is sufficient to form through holes with different diameters on the top and bottom, and hit the green sheet. This can be done by increasing the clearance of the mold to be removed or adjusting the output of the laser.

  The method for producing the laminated body includes a method in which heat and pressure are applied to the stacked green sheet for the insulating layer 1 and the green sheet for the ferrite magnetic layer 2 by thermocompression bonding, an organic binder, a plasticizer, a solvent, and the like. A method of applying an adhesive between sheets and thermocompression bonding can be employed. The conditions for heating and pressing during lamination vary depending on the type and amount of the organic binder used, but are generally 30 to 100 ° C. and 2 to 20 MPa.

  The laminate is fired by debinding at a temperature of 300 to 600 ° C. and then firing at a temperature of 800 to 1000 ° C. As the firing atmosphere, when the planar coil conductor 3 and other wirings are made of a material that is difficult to oxidize such as Ag, the firing atmosphere is performed in the air, and when made of a material that is easily oxidized such as Cu, a nitrogen atmosphere is used. A humidified product is used so that it can be easily removed.

  The mounting electrode 6b, the electrode pad 6d, and the heat radiation conductor layer 5 formed on the surface of the coil-embedded substrate after firing are strongly bonded to the semiconductor chip, the chip component, or an external electric circuit by soldering or the like. For this purpose, a nickel layer and a gold layer may be sequentially deposited on the surface by plating.

  In addition, this invention is not limited to the example of the above embodiment, A various change may be added in the range which does not deviate from the summary of this invention. For example, not only the heat transfer conductor layer 4 formed outside on the same plane as the planar coil conductor 3 but also the heat transfer conductor layer in the ferrite magnetic layer 2 positioned above and below the heat transfer conductor layer 4. 4 may be formed to further improve heat dissipation.

  In the first embodiment, as the coil-embedded substrate of the present invention, as shown in FIG. 9, a heat transfer conductor layer 4 is formed close to the outer periphery of the planar coil conductor 3, and along the outer periphery of the planar coil conductor 3. A coil-embedded substrate having a structure in which a grounding conductor layer is provided as an internal wiring layer 6a between the insulating layers 1 and 1 and the ferrite magnetic layer 2 in a configuration having a plurality of openings 4b arranged The surface temperature of the wiring layer 6 formed on the surface of was measured. This will be described in detail below.

First, 630 g of Fe ₂ O ₃ powder, 80 g of CuO powder, and 290 g of ZnO powder were mixed for 24 hours in a 7000 cm ³ ball mill using zirconia balls together with 4000 cm ^{3 of} pure water, and the dried mixed powder was then added to the zirconia crucible. And heated in the air at 730 ° C. for 1 hour to prepare a nonmagnetic ferrite calcined powder. To 100 parts by mass of the calcined nonmagnetic ferrite calcined powder, 10 parts by mass of butyral resin as a binder and 45 parts by mass of IPA (isopropyl alcohol) as an organic solvent are added and mixed by the same ball mill method as above to form a slurry did. Using this slurry, a green sheet for an insulating layer made of nonmagnetic ferrite having a thickness of 100 μm was molded by a doctor blade method.

  A through hole with a diameter of 150 μm for the through conductor 6c was formed in the green sheet for insulating layer by punching with a mold. This through hole was filled with a through conductor paste by screen printing and dried at 70 ° C. for 30 minutes. As a penetrating conductor paste, 100 parts by mass of Ag powder, 10 parts by mass of glass powder as a sintering aid, 12 parts by mass of acrylic resin and 2 parts by mass of α-terpineol as an organic solvent are added, and a stirring deaerator Then, the mixture was sufficiently kneaded with three rolls after being sufficiently mixed.

  Next, a conductive paste is applied to the green sheet for insulating layer by a screen printing method to a thickness of 20 μm in a size of 2 mm square, dried at 70 ° C. for 30 minutes, and a surface wiring layer pattern for temperature measurement and a planar coil conductor 3 An energized surface wiring layer pattern for energizing from the outside was formed.

  As a conductive paste, 100 parts by mass of Ag powder as metal powder and 10 parts by mass of CuO powder as metal oxide, 100 parts by mass of acrylic resin, 12 parts by mass of acrylic resin and 2 parts by mass of α-terpineol as an organic solvent. In addition, after thoroughly mixing with a stirring defoamer, the mixture kneaded sufficiently with three rolls was used.

Next, 700 g of Fe ₂ O ₃ powder, 60 g of CuO powder, 60 g of NiO powder, and 180 g of ZnO powder were used to prepare a ferromagnetic ferrite calcined powder by the same production method as the nonmagnetic ferrite calcined powder. To 100 parts by mass of the calcined magnetic ferrite powder, 10 parts by mass of butyral resin as a binder and 45 parts by mass of IPA as an organic solvent were added, and mixed by the same ball mill method to obtain a slurry. Using this slurry, a green sheet for ferrite magnetic layer having a thickness of 100 μm was molded by a doctor blade method.

  A through hole with a diameter of 150 μm for the through conductor 6c was formed in the ferrite magnetic layer green sheet by punching with a mold. This through hole was filled with a through conductor paste by screen printing, and dried at 70 ° C. for 30 minutes to form a through conductor composition to be a through conductor. As the through conductor paste, the same one as described above was used.

  Subsequently, a conductive paste was applied to each of the two green sheets for the magnetic layer of ferrite by a screen printing method to a thickness of 30 μm, dried at 70 ° C. for 30 minutes, and three turns as shown by the broken line in FIG. 9B. A (3 winding) planar coil conductor pattern and a heat transfer conductor layer pattern were formed. As a conductor paste, 10 parts by mass of an acrylic resin and 1 part by mass of α-terpineol as an organic solvent are added to 100 parts by mass of Ag powder. What was done was used. Also, the same conductor paste is used on the back surface of the ferrite magnetic layer green sheet formed with only one through conductor pattern and the ferrite magnetic layer green sheet formed with one planar coil conductor pattern. A solid pattern was formed.

  Next, a ferrite magnetic layer green sheet having a solid pattern for a ground conductor layer formed on two sheets of a ferrite magnetic layer green sheet on which a planar coil conductor pattern and a heat transfer conductor layer pattern are formed is stacked. Further, four insulating layer green sheets were stacked on the upper and lower sides, respectively, and heat-pressed at a pressure of 5 MPa and a temperature of 50 ° C. to prepare a laminate in which the insulating layer green sheets were positioned on the surface layer.

  Next, after cutting the laminated body into 12 mm square and exposing the conductive layer pattern for heat transfer on the side, the same conductive paste as the surface wiring layer pattern was applied to the thickness of 40 μm on the four sides by screen printing, The film was dried at 70 ° C. for 30 minutes to form a heat dissipation conductor layer pattern. The heat radiating conductor layer pattern was formed on the side surface of the ferrite magnetic layer green sheet and the side surface of the insulating layer green sheet on the side where the surface wiring layer pattern for temperature measurement was not formed.

  Next, this laminate was heated in air at 500 ° C. for 3 hours to remove organic components, and then fired in air at 900 ° C. for 1 hour to produce a coil-embedded substrate. . In the coil-embedded substrate, a ferrite magnetic layer 2 is sandwiched between a pair of insulating layers 1, 1, and planar coil conductors 3 are formed in the ferrite magnetic layer 2 so as to overlap each other. One end portions are connected to each other by a through conductor, and the other end portion of the upper planar coil conductor 3 is not electrically connected to the upper ground conductor layer, and the energizing surface layer is formed by a through conductor penetrating the upper ground conductor layer. Connected to the wiring layer, the other end of the lower planar coil conductor 3 was connected to the lower ground conductor layer, and the lower ground conductor layer was connected to another energizing surface wiring layer by a through conductor. . The coil-embedded substrate has an outer size of 10 mm square and a thickness of 0.8 mm. The planar coil conductor 3 has a conductor thickness of 0.02 mm, a conductor width of 0.3 mm, a rectangular outermost circumference of 6 mm square, and adjacent outer and inner circumferences. The distance between the conductors is 0.15 mm, the conductor layer 4 for heat transfer has a conductor thickness of 0.02 mm, is surrounded by 0.08 mm away from the outermost periphery of the planar coil conductor 3, and has a long side length of 3.0 mm. , 8 openings 4b, which are parallelograms with a height of 0.5 mm and an internal angle of 75 degrees, are arranged at a position 0.12 mm from the inner peripheral edge of the heat transfer conductor layer 4 and are used for heat dissipation. Conductor layer 5 had a conductor thickness of 0.03 mm.

  On the wiring layer 6 formed on the outer surface of the coil built-in substrate, an Ni plating film and an Au plating film were sequentially formed by using an electroless plating method.

Comparative example

  For comparison with Example 1 of the present invention, as a conventional configuration, the sample of Example 1 does not have the heat transfer conductor layer 4 and the heat dissipation conductor layer 5 as shown in FIG. Except for the above, a coil-embedded substrate was produced in the same manner as in Example 1.

  The coil-embedded substrates of Example 1 and Comparative Example were mounted on a ceramic substrate using solder. In the coil-embedded substrate of Example 1, the heat radiation conductor layer 5 on the side surface and the lower surface and the connection conductor on the ceramic substrate were joined by solder.

  A probe is applied to the energizing surface wiring layer on the surface of the substrate that is electrically connected to the planar coil conductor 3 while mounted on the ceramic substrate, and the planar coil is applied by a DC power supply ("PMC18-3A" manufactured by Kikusui Electronics Corporation). A current of 1 A at 5 V was applied to the conductor 3 for 10 seconds, and then the temperature on the surface wiring layer for measuring the temperature of the substrate surface was measured. The temperature was measured using a non-contact type radiation thermometer (Keyence "FT-H10").

  As a result, the temperature on the surface wiring layer of the substrate of Example 1 was 50 ° C., whereas the temperature on the surface wiring layer of the substrate of the comparative example was 80 ° C. Thereby, with respect to the comparative example, the coil-embedded substrate of Example 1 radiates heat generated in the planar coil conductor 3 well from the side surface of the substrate through the heat transfer conductor layer 4 and the heat dissipation conductor layer 5. It was confirmed that the substrate with a built-in coil could be obtained.

(A) is a longitudinal cross-sectional view which shows an example of embodiment of the board | substrate with a built-in coil of this invention, (b) is a cross-sectional view cut | disconnected by the A-A 'line | wire shown to (a). (A) is a longitudinal cross-sectional view which shows an example of embodiment of the board | substrate with a built-in coil of this invention, (b) is a cross-sectional view cut | disconnected by the A-A 'line | wire shown to (a). (A) is a longitudinal cross-sectional view which shows an example of embodiment of the board | substrate with a built-in coil of this invention, (b) is a cross-sectional view cut | disconnected by the A-A 'line | wire shown to (a). (A) is a longitudinal cross-sectional view which shows an example of embodiment of the board | substrate with a built-in coil of this invention, (b) is a cross-sectional view cut | disconnected by the A-A 'line | wire shown to (a). (A) is a longitudinal cross-sectional view which shows an example of embodiment of the board | substrate with a built-in coil of this invention, (b) is a cross-sectional view cut | disconnected by the A-A 'line | wire shown to (a). (A) is a longitudinal cross-sectional view which shows an example of embodiment of the board | substrate with a built-in coil of this invention, (b) is a cross-sectional view cut | disconnected by the A-A 'line | wire shown to (a). (A) is a longitudinal cross-sectional view which shows an example of embodiment of the board | substrate with a built-in coil of this invention, (b) is a cross-sectional view cut | disconnected by the A-A 'line | wire shown to (a). (A) is a longitudinal cross-sectional view which shows an example of embodiment of the board | substrate with a built-in coil of this invention, (b) is a cross-sectional view cut | disconnected by the A-A 'line | wire shown to (a). (A) is a longitudinal cross-sectional view which shows an example of embodiment of the board | substrate with a built-in coil of this invention, (b) is a cross-sectional view cut | disconnected by the A-A 'line | wire shown to (a). (A) is a longitudinal cross-sectional view which shows an example of embodiment of the board | substrate with a built-in coil of this invention, (b) is a cross-sectional view cut | disconnected by the A-A 'line | wire shown to (a). (A) is a longitudinal cross-sectional view which shows an example of embodiment of the board | substrate with a built-in coil of this invention, (b) is a cross-sectional view cut | disconnected by the A-A 'line | wire shown to (a). (A) is a longitudinal cross-sectional view which shows an example of embodiment of the board | substrate with a built-in coil of this invention, (b) is a cross-sectional view cut | disconnected by the A-A 'line | wire shown to (a). (A) is a longitudinal cross-sectional view which shows an example of embodiment of the board | substrate with a built-in coil of this invention, (b) is a cross-sectional view cut | disconnected by the A-A 'line | wire shown to (a). (A) is a longitudinal cross-sectional view which shows an example of embodiment of the board | substrate with a built-in coil of this invention, (b) is a cross-sectional view cut | disconnected by the A-A 'line | wire shown to (a). (A) is a longitudinal cross-sectional view which shows an example of embodiment of the board | substrate with a built-in coil of this invention, (b) is a cross-sectional view cut | disconnected by the A-A 'line | wire shown to (a). It is sectional drawing which shows an example of the conventional board | substrate with a built-in coil.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Insulating layer 2 ... Ferrite magnetic material layer 3 ... Planar coil conductor 4 ... Heat-conducting conductor layer 4a ... Projection part 4b ... Opening part 5 ... Heat-dissipating conductor layer 6. ..Wiring layer 7 ... Insulating layer for heat transfer 8 ... Penetration conductor for heat transfer

Claims (9)

A coil-embedded substrate comprising: a substrate comprising a pair of insulating layers formed with wiring layers; a ferrite magnetic layer sandwiched between the pair of insulating layers; and a planar coil conductor formed in the ferrite magnetic layer. A heat transfer conductor layer is formed from the outer side of the planar coil conductor to the side surface of the substrate in a plan view, and the heat transfer conductor layer is connected to a heat dissipation conductor layer formed on the side surface of the substrate. A coil-embedded substrate characterized by comprising: The coil built-in substrate according to claim 1, wherein the plurality of conductive layers for heat transfer adjacent to an outer peripheral portion of the planar coil conductor are arranged along an outer periphery of the planar coil conductor. The coil built-in substrate according to claim 1, wherein the heat transfer conductor layer surrounds the planar coil conductor along an outer periphery. 4. The coil-embedded substrate according to claim 3, wherein the heat transfer conductor layer has a plurality of protrusions whose end portions are close to the outer periphery of the planar coil conductor. The said heat-transfer conductor layer is formed in the vicinity of the outer periphery of the planar coil conductor, and has a plurality of openings disposed along the outer periphery of the planar coil conductor. Coil built-in substrate. 6. The heat transfer insulating layer having a higher thermal conductivity than the ferrite magnetic layer is formed to be connected to the planar coil conductor and the heat transfer conductor layer. The coil built-in board | substrate in any one. 7. The coil built-in substrate according to claim 6, wherein the planar coil conductor has a plurality of turns, and the heat transfer insulating layer is formed between the planar coil conductors on the outer periphery and the inner periphery adjacent to each other. The planar coil conductor has a plurality of turns, and the insulating layer for heat transfer is connected to the planar coil conductor so as to overlap the entire region of the planar coil conductor in a plan view. The coil built-in substrate according to claim 7. A plurality of the planar coil conductor and the heat transfer conductor layer are provided above and below via the ferrite magnetic layer, and at least one of the heat transfer conductor layers positioned above and below the ferrite between them. The coil built-in substrate according to any one of claims 1 to 8, wherein a heat transfer through conductor formed in a direction penetrating the magnetic layer is connected.

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