JP4809262B2 - Coil built-in board - Google Patents

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 substrate with a built-in coil 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, a planar coil conductor formed in the ferrite magnetic layer, a coil-containing substrate having a large heat transfer insulating layer of the ferrite magnetic layer than the thermal conductivity, it said formed is directly connected to the planar coil conductor from the inside of the substrate toward a side of the substrate, It is connected to a heat radiating conductor layer formed on the side surface of the substrate.

  In the above-described configuration, the coil-embedded substrate of the present invention has a configuration in which the planar coil conductor has a plurality of turns, and the heat transfer insulating layer is also formed between the adjacent outer and inner planar coil conductors. It is a feature.

  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.

  The coil-embedded substrate according to the present invention is characterized in that, in the above configuration, a plurality of the planar coil conductors are provided above and below, and the heat transfer insulating layer is formed between the planar coil conductors positioned above and below. It is what.

  The coil-embedded substrate of the present invention is characterized in that, in the above configuration, the heat transfer insulating layer has a plurality of openings arranged along the outer periphery of the planar coil conductor.

According to the coil-embedded substrate of the present invention, the heat transfer insulating layer having a higher thermal conductivity than the ferrite magnetic layer is directly connected to the planar coil conductor and formed from the inside of the substrate to the side surface of the substrate. Since it is connected to the formed heat radiating conductor layer, heat generated in the planar coil conductor can be radiated from the heat radiating conductor layer to the outside through the heat transfer insulating 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, the planar coil conductor has a plurality of turns, and when the heat transfer insulating layer is formed between the adjacent outer and inner planar coil conductors, Heat generated in the inner peripheral planar coil conductor is transferred to the outer planar coil conductor through the heat transfer insulating layer formed between the outer peripheral and inner peripheral planar coil conductors, and is connected to the planar coil conductor and connected to the side surface of the substrate. Therefore, the 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, since the heat generated in the planar coil conductor is directly transmitted to the insulating layer for heat transfer from the outer periphery to the inner periphery of the planar coil conductor, the heat generated in the planar coil conductor can be radiated more efficiently. The heat can be radiated to the outside of the substrate through the conductive layer.

  Further, according to the coil-embedded substrate of the present invention, in the above configuration, when a plurality of planar coil conductors are provided above and below, and the heat transfer insulating layer is formed between the planar coil conductors positioned above and below, After the heat generated from the planar coil conductor is guided in the thickness direction of the coil-embedded board on which the heat transfer insulating layer is formed, heat is radiated to the outside from the side surface of the coil-embedded board on which the heat radiating conductor layer is formed. Can do. Therefore, the heat transfer in the direction of the insulating layer, that is, the main surface direction of the coil built-in substrate on which the electronic component such as IC is mounted can be suppressed. It is possible to more effectively prevent malfunction due to heat generated from the conductor.

  Furthermore, since a heat transfer insulating layer having a lower magnetic permeability than the ferrite magnetic layer exists between the planar coil conductors adjacent to each other in plan view, the current flowing through the planar coil conductor is large. Even in such a case, it is difficult for magnetic flux to pass between adjacent outer and inner planar coil conductors, so that leakage flux is less likely to occur between adjacent outer and inner planar coil conductors, thereby suppressing magnetic saturation. Thus, it is possible to suppress the deterioration of the superposition characteristics.

  Further, according to the coil-embedded substrate of the present invention, in the above configuration, when the heat transfer insulating layer has a plurality of openings arranged along the outer periphery of the planar coil conductor, the opening of the planar coil conductor Since the magnetic flux generated around easily passes through the region outside the planar coil conductor, the heat generated in the planar coil conductor can be radiated to the outside without reducing the inductance.

  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 substrate with a built-in coil according to the present invention. FIG. 1A is a cross-sectional view of the substrate with a built-in coil according to the present invention cut along the line BB in FIG. FIG. 1B is a cross-sectional view (cross-sectional view) cut along the line AA 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 insulating layer, 5 is a heat radiating 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 and a semiconductor chip such as an IC and chip components are mounted, and an external 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 built-in coil substrate and a flat coil conductor 3 formed within a large heat transfer insulating layer 4 of thermal conductivity than the ferrite magnetic layer 2, the substrate is directly connected to the planar coil conductor 3 It is formed from the inside to the side surface of the substrate and is connected to the heat radiation 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-transfer insulating 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. That is, since the insulating layer 4 for heat transfer is an insulator, it is directly connected to the planar coil conductor 3, so that heat generated in the planar coil conductor 3 can be efficiently transmitted to the radiating conductor layer 5, Since the magnetic flux generated around the flat coil conductor 3 is not absorbed, the passage of the magnetic flux is not greatly disturbed and the inductance is not greatly reduced.

  Further, as shown in FIG. 2 in a sectional view similar to FIG. 1, in the above configuration, the planar coil conductor 3 has a plurality of turns, and the heat transfer insulating layer 4 is adjacent to the adjacent outer and inner planar coil conductors 3. It is preferable that they are also formed. With this 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 4 formed between the outer peripheral and inner peripheral planar coil conductors. 3 can be transferred to the heat-dissipating conductor layer 5 through the heat-transfer insulating layer 4 connected to the side surface of the substrate, so that heat generated in the planar coil conductor 3 can be radiated to the outside more efficiently. Can do.

  Furthermore, since the heat transfer insulating layer 4 having a lower magnetic permeability than the ferrite magnetic layer 2 is present between the adjacent outer and inner 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, as shown in a sectional view similar to FIG. 1 in FIG. 3, in the above configuration, the planar coil conductor 3 has a plurality of windings, and the heat transfer insulating layer 4 has the entire area where the planar coil conductor 3 is formed in plan view. Are preferably connected to the planar coil conductor 3. Since the heat generated in the planar coil conductor 3 is directly transmitted to the heat transfer insulating layer 4 from the outer periphery to the inner periphery of the planar coil conductor 3, the heat generated in the planar coil conductor 3 can be more efficiently radiated. Heat can be radiated to the outside of the substrate through the layer 5.

  Further, even when the heat transfer insulating layer 4 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 4 having a low magnetic permeability exists, it is difficult for 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.

  In the case where the heat transfer insulating layer 4 is connected to the planar coil conductor 3 by overlapping the entire region where the planar coil conductor 3 is formed in plan view, as shown in FIG. The heat transfer insulating layer may be overlapped up to the inner portion of 3, that is, in the entire area of the substrate. In this manner, in the process of manufacturing the coil-embedded substrate, for example, when the insulating layer 4 for heat transfer is formed by applying a paste, a screen engraving adapted to 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 4 are formed is laminated, the pattern of the planar coil conductor 3 and the conductive pattern are transferred. Since there is no step between the portion where the pattern of the thermal insulating layer 4 is formed and the portion where none is formed, it is possible to prevent voids from being generated inside the green sheet laminate. Can do.

  Further, as shown in a sectional view similar to FIG. 1 in FIG. 5, in the above configuration, a plurality of planar coil conductors 3 are provided above and below, and the heat transfer insulating layer 4 is disposed between the planar coil conductors 3 positioned above and below. Preferably it is formed. With this configuration, the inductance of the planar coil conductor 3 can be increased without increasing the size of the coil-embedded substrate in the planar direction, and the heat generated from the planar coil conductor 3 can be transferred from the outer periphery to the inner periphery of the planar coil conductor 3. In addition to being transmitted directly to the heat transfer insulating layer 4 over the entire area, the heat radiating conductor layer 5 was formed after induction in the thickness direction of the coil-embedded substrate on which the heat transfer insulating layer 4 was formed. Heat can be radiated from the side surface of the coil-embedded substrate to the outside. 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, even when the heat transfer insulating layer 4 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. Thus, since the heat transfer insulating layer 4 having a low magnetic permeability exists, the magnetic flux does not easily pass between the adjacent outer peripheral and inner peripheral planar coil conductors 3 and the adjacent outer peripheral and inner peripheral planar coil conductors 3. Leakage magnetic flux is less likely to be generated between them, thereby suppressing magnetic saturation and suppressing deterioration of the superposition characteristics.

  As shown in a sectional view similar to FIG. 1 in FIG. 6, a heat transfer insulating layer 4 is formed both between the adjacent outer periphery and inner periphery of the planar coil conductor 3 and between the upper and lower planar coil conductors 3. Needless to say, it may be.

  Moreover, as shown in FIG. 7 and FIG. 8 with sectional views similar to FIG. 1, in the above configuration, the heat transfer insulating layer 4 has a plurality of openings 4 a arranged along the outer periphery of the planar coil conductor 3. It is preferable to have. Since the heat transfer insulating layer 4 is not a conductor as described above, the heat transfer insulating layer 4 does not completely obstruct the passage of magnetic flux, but the plurality of openings 4a surround the planar coil conductor 3. Since the magnetic flux generated in the flat coil conductor 3 is more likely to pass through the area outside the planar coil conductor 3, it is possible to further suppress the decrease in inductance, and the portion between the plurality of openings 4a generates heat generated in the planar coil conductor 3. Since it becomes a heat transfer path for conducting to the heat radiating conductor layer 5, heat generated in the planar coil conductor 3 can be radiated to the outside.

  The width of the opening 4a of the heat transfer insulating 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. When the width of the opening 4a is equal to the distance from the planar coil conductor 3 to the side surface of the substrate, a plurality of elongated insulating layers 4 for heat transfer as shown in FIG. Is the same as that disposed outside the planar coil conductor 3.

  The length of the opening 4 a in the direction along the outer periphery of the planar coil conductor 3 is such that the sum of the lengths of the opening 4 a on the planar coil conductor 3 side is 95% or less of the outer circumference 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 4 to the heat dissipating conductor layer 5 becomes too small, and the heat dissipating efficiency is lowered.

  The position of the opening 4a in the heat transfer insulating layer 4 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. However, from the viewpoint of heat dissipation, it is preferable that the heat transfer insulating layer 4 receives the heat generated by the planar coil conductor 3 over the entire outer periphery of the planar coil conductor 3, so that 50 μm to 200 μm from the planar coil conductor 3. It is preferable to provide the opening 4a on the outer side. Further, 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 magnetic permeability of the ferrite magnetic layer 2, this is between the outer periphery of the planar coil conductor 3 and the opening 4a. 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 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 outline of the rectangular substrate in this way, the planar coil conductor 3 is formed in a region outside the planar coil conductor 3 as shown in FIG. It is preferable to form the opening 4a of the heat transfer insulating layer 4 in a region other than the outside of the corner. That is, it is preferable to provide a portion serving as a heat transfer path from the planar coil conductor 3 to the heat radiation conductor layer 5 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 other regions, the magnetic flux passing through the heat transfer insulating layer 4 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 FIGS. 7B and 9B, the heat transfer path arranged at the corner of the rectangular planar coil conductor 3 is wider than the heat transfer path arranged at other positions. You may arrange | position the opening part 4a so that may become large.

  As shown in FIGS. 7 and 8, the shape of the opening 4a is such that the heat transfer path from the planar coil conductor 3 to the heat dissipation conductor layer 5 in the heat transfer insulating layer 4 faces the heat dissipation conductor layer 5. A shape that widens the width is preferable because heat transfer to the heat-dissipating conductor layer 5 is more efficiently performed. At this time, since the density of the magnetic flux generated in the planar coil conductor 3 is coarser 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 4. The effect of is small. In this case, it is preferable that the width of the heat transfer insulating 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. .

  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 bent into a curved shape or a shape having a plurality of bent portions, the area where the planar coil conductor 3 and the wiring layer 6 such as the ground conductor layer formed on 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.

  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. 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 may be any distance that can maintain insulation between the upper and lower planar coil conductors 3. Although it depends on the insulating layer 4 for heat transfer, it may be about 50 μm or more.

  As shown in FIGS. 1 to 9, the heat dissipating conductor layer 5 is formed on the side surface of the substrate and connected to the heat transfer insulating layer 4. When providing a plurality of heat transfer insulating layers 4 close to the outer periphery of the planar coil conductor 3, a plurality of heat transfer insulating layers 4 are provided so as to correspond to each of the plurality of heat transfer insulating layers 4 as shown in FIG. However, as shown in FIGS. 1B to 8B, 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 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, the wiring layers may be divided into a plurality so as to be insulated from the wiring layers. The insulating layer 4 for heat transfer in this case is not formed 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 dissipation conductor layer 5 in the thickness direction of the substrate is not particularly limited, and not only the side surfaces of the ferrite magnetic layer 2 as shown in FIGS. 1 (a) to 5 (a), As shown in FIGS. 7 (a) and 9 (a), it is formed on the side surface of the insulating layer 1, and further on the main surface (lower surface) of the substrate as shown in FIGS. 6 (a) and 8 (a). Also good. 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. Further, 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, so that heat is transferred to the external circuit board having a large heat capacity to dissipate heat. 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.

  Moreover, heat dissipation can be further improved by making the thickness of the heat-dissipating conductor layer 5 thicker than that of the wiring layer 6 and the planar coil conductor 3. For this purpose, the thickness of the wiring layer 6 and the planar coil conductor 3 is usually about 10 μm, but is 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

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. For this reason, if the ratio is less than 5% by mass, the sintering density tends to be inadequate when the wiring layer 6 is simultaneously fired at 800 to 1000 ° C., and the mechanical strength tends to be insufficient. If it is more, the Curie temperature rises and magnetism tends to occur in the 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 a low magnetic property increases, so that the magnetic property tends to be easily lost. 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 planar coil conductor pattern is formed, and a green sheet for the ferrite magnetic layer 2 is further laminated 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 green sheets for ferrite magnetic layer 2 on which a planar coil conductor pattern and a through conductor pattern are formed are stacked, and further a green for ferrite magnetic layer 2 What is necessary is just to laminate | stack a sheet | seat.

  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 4 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 4 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 transfer the heat | fever inside the insulating layer 4 for heat transfer, it is preferable.

  The heat transfer insulating layer 4 is manufactured by manufacturing a green sheet for the heat transfer insulating layer 4 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 4 A planar coil conductor pattern to be the planar coil conductor 3 is formed on the laminated body, laminated on the ferrite magnetic layer 2 green sheet on which the planar coil conductor pattern is formed, or an insulating powder for the heat transfer insulating layer. A paste for heat transfer insulating layer 4 mainly composed of an organic binder and a solvent is manufactured and connected to or overlapped with the planar coil conductor pattern formed on the green sheet for ferrite magnetic layer 2 Then, the paste for the heat transfer insulating layer 4 is printed in a predetermined pattern by a printing method such as a screen printing method or a gravure printing method, and the green sheet for the insulating layer 1 and the ferrite magnetic layer 2 is printed. Together it is produced by firing at a temperature of 800 to 1000 ° C..

The insulator powder for the heat transfer insulating layer 4 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 4, a glass A containing 60% by mass and AlN containing 40% by mass can obtain a thermal conductivity of 8.4 W / (m · K) by firing at 900 ° C. The glass A containing 50% by mass and AlN containing 50% by mass has a thermal conductivity of 11.5 W / (m · K) when fired at 900 ° C., and the glass A is 60% by mass and Si ₃ N ₄ is 40%. Those containing 5% by mass have a thermal conductivity of 7.2 W / (m · K) when fired at 900 ° C., and those containing 60% by mass of glass A and 20% by mass of AlN and Si ₃ N ₄ respectively Thermal conductivity of 7.5 W / (m · K) can be obtained by baking at ℃. In addition, glass B containing 50% by mass and AlN 50% by mass has a thermal conductivity of 8.2 W / (m · K) when baked at 950 ° C., glass B being 30% by mass and AlN being 70% by mass. % Containing 1% W / (m · K) is obtained by baking at 1000 ° C, and glass B containing 50% by mass and Si ₃ N ₄ containing 50% by mass is obtained by baking at 900 ° C. A thermal conductivity of 7.3 W / (m · K) is obtained. In addition, the one containing 60% by mass of glass C and 40% by mass of AlN has a thermal conductivity of 7.3 W / (m · K) when fired at 900 ° C., and 60% by mass of glass C and Si ₃ N ₄ In the case of containing 40% by mass, a thermal conductivity of 7.0 W / (m · K) can be obtained by firing at 900 ° C.

In addition, when carbon or sulfur is present in ceramic fillers such as AlN and Si ₃ N ₄ , gases such as CO, CO ₂ , SO, SO ₂ are generated during firing, and pores are generated to reduce the 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, so the carbon and sulfur on the surface of the ceramic filler powder For removal of water and generation of an oxide film, it is preferable to carry out water washing at pH 5 to 10 for 10 minutes to 30 minutes or boiling for 5 minutes 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, the green sheet for ferrite magnetic layer 2, or the green sheet for insulating layer 4 for heat transfer consists of an insulating powder 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 insulating 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 4 is mixed and kneaded by kneading means such as a ball mill, a three-roll mill, a planetary mixer, and the like by 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 4, 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 4 is not particularly limited as long as the above-described insulator powder and the organic binder can be well dispersed and mixed, and terpineol, butyl carbitol acetate, phthalic acid, etc. are used. Is possible.

  The heat transfer insulating layer 4 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 with respect to 100 parts by weight of the insulator 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 4.

  When the heat transfer insulating layer 4 is formed as shown in FIGS. 1, 2, and 9, for example, heat transfer is performed so as to be connected to the planar coil conductor pattern formed on the ferrite magnetic layer 2 green sheet. The insulating layer pattern for heat transfer may be formed by printing the insulating layer 4 paste.

  When forming the heat transfer insulating layer 4 as shown in FIGS. 3 and 4, for example, the paste for the heat transfer insulating layer 4 so as to overlap the planar coil conductor pattern formed on the ferrite magnetic layer 2 green sheet. May be printed to form an insulating layer pattern for heat transfer. 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 this through hole is used for a through conductor 6c described later. Fill the conductor paste.

  When the heat transfer insulating layer 4 is formed as shown in FIG. 5, for example, a ferrite magnetic layer in which a flat coil conductor pattern is formed on a green sheet for the heat transfer insulating layer 4 to form the flat coil conductor pattern. What is necessary is just to laminate | stack on the green sheet for 2 sheets. A through conductor pattern is formed in advance on the green sheet for the heat transfer insulating layer 4. When a through hole is provided in a portion located inside the planar coil conductor 3 in a plan view by punching using a mold or the like as shown in FIG. Easy to pass. When the green sheet for the heat transfer insulating layer 4 is thick and voids are generated during lamination, the green sheet for the heat transfer insulating layer 4 and the green sheet for the ferrite magnetic layer 2 are laminated thereon or below. After that, the through holes may be filled with a ferrite magnetic substance paste. The ferrite magnetic substance paste can be produced using ferrite powder instead of the insulating powder of the heat transfer insulating layer 4 paste.

  When the heat transfer insulating layer 4 is formed as shown in FIGS. 6 to 8, for example, upper and lower planar coil conductor patterns are formed on the ferrite magnetic layer 2 green sheet and overlapped with these planar coil conductor patterns. In this way, the heat transfer insulating layer 4 paste may be printed, the surfaces on which the heat transfer insulating layer 4 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.

  When the heat transfer insulating layer 4 is formed using a green sheet, the opening 4a of the heat transfer insulating layer 4 can be provided by punching the green sheet into a predetermined shape using a mold or the like. When forming using the paste for thermal insulation layers 4, the pattern shape at the time of printing should just have the opening part 4a.

  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 screen printing or gravure printing. 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 planar coil conductor pattern to be the planar coil conductor 3 is also printed 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 that is formed as a through conductor in the ferrite magnetic layer 2 is formed in the same manner as the wiring pattern that forms 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 planar coil conductor 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 0.1 mm. If it is more than about, it can be formed 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 laminate is prepared by arranging a predetermined number of green sheets for insulating layer 1 each having a wiring pattern on top and bottom of a predetermined number of green sheets for ferrite magnetic layer 2 including those on which planar coil conductor patterns are formed. The coiled substrate is manufactured by firing the laminate.

  The heat-dissipating conductor layer 5 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, like the wiring layer 6. . 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-layer 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 powder of about 5 μm is used for the conductor paste used for forming the wiring layer 6 and the planar coil conductor 3, whereas a metal powder of about 10 μm or more is used for the conductor paste used for forming the heat-dissipating conductor layer 5. That's fine.

  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.

  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 insulating layer 4 formed outside on the same plane as the planar coil conductor 3 but also the heat transfer insulating layer in the ferrite magnetic layer 2 positioned above and below the heat transfer insulating layer 4 4 may be formed to further improve heat dissipation.

  In the first embodiment, as the coil-embedded substrate of the present invention, a heat transfer insulating layer 4 as shown in FIG. 6 is disposed between the planar coil conductors 3 positioned above and below, and one planar coil conductor 3 is adjacent to each other. The ground conductor layer is formed as an internal wiring layer 6a between the insulating layers 1 and 1 and the ferrite magnetic layer 2 between the outer periphery and the outer periphery and on the outer periphery of the planar coil conductor 3 so as to be in contact with the planar coil conductor. A substrate with a built-in coil having a structure was prepared, and the surface temperature of the wiring layer 6 formed on the surface of the substrate 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 a screen printing method and dried at 70 ° C. for 30 minutes to form a through conductor composition to be the through conductor 6c. As the through conductor paste, the same one as described above was used.

  Subsequently, a conductor 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 indicated by a broken line in FIG. A (three turns) planar coil conductor pattern was 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. The pattern was such that the upper and lower planar coil conductor patterns are mirror images of each other. Also, a solid pattern for the ground conductor layer was formed on the back surface of the ferrite magnetic layer green sheet on which the planar coil conductor pattern was formed using the same conductor paste.

Next, an insulating layer paste for heat transfer was applied to a thickness of 50 μm by screen printing on the ferrite magnetic layer green sheet on which the planar coil conductor pattern was formed, and dried at 70 ° C. for 30 minutes. An insulating layer pattern for heat transfer as shown in b) was formed. As an insulating layer paste for heat transfer, 100 parts by mass of an insulator powder composed of 60 parts by mass of AlN powder and 40 parts by mass of oxinide glass powder, 10 parts by mass of acrylic resin and 1 mass of α-terpineol as an organic solvent. Then, after thoroughly mixing with a stirring defoaming machine, the mixture was sufficiently kneaded with three rolls. The AlN powder was washed for 30 minutes in a water flow of pH 7, and the oxinide glass powder was obtained by nitriding the SiO ₂ —B ₂ O ₃ glass powder at 600 ° C. for 2 hours in a nitrogen stream. The insulating layer pattern for heat transfer has a through hole with a diameter of 150 μm. The through hole is filled with the same through conductor paste as described above by screen printing and dried at 70 ° C. for 30 minutes. A through conductor pattern for connecting the conductor 3 was formed.

  Next, the ferrite magnetic layer green sheet on which the planar coil conductor pattern and the heat transfer insulating layer pattern are formed is stacked with the heat transfer insulating layer pattern facing each other, and only the through conductor pattern is formed. The green sheets were stacked and thermocompression bonded at a pressure of 5 MPa and a temperature of 50 ° C. to produce a laminate in which the insulating layer green sheet was positioned on the surface layer.

  Next, after cutting the laminated body into 12 mm squares to expose the insulating layer pattern for heat transfer on the side surfaces, the same conductive paste as the surface layer wiring layer pattern was applied on the four side surfaces and the lower surface to a thickness of 40 μm by screen printing. And dried at 70 ° C. for 30 minutes to form a heat-dissipating conductor layer pattern.

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 2 hours 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, and the heat transfer insulating layer 4 has a thickness of 0.03 mm between the planar coil conductors 3 positioned above and below, and between the ferrite magnetic layer 2 on the outer periphery of the planar coil conductor 3. Is formed between adjacent inner and outer peripheries of one planar coil conductor 3, and the heat-dissipating conductor layer 5 has a conductor thickness of 0.03 mm and 2 mm from the outer edge of the substrate on the lower surface. There was a shape surrounding the width.

  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 insulating layer 4 and the heat dissipating conductor layer 5 as shown in FIG. A coil built-in substrate was produced in the same manner as in Example 1 except that.

  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-dissipating conductor 5 on the side surface and the lower surface and the connecting conductor on the ceramic substrate were joined by soldering.

  A probe is applied to the energizing surface wiring layer on the surface of the coil-embedded substrate that is electrically connected to the planar coil conductor 3 while being mounted on the ceramic substrate, and a DC power supply ("PMC18-3A" manufactured by Kikusui Electronics Corporation) is used. A current of 1 A at 5 V was applied to the planar coil 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 60 ° 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 can radiate the heat generated in the planar coil conductor 3 to the outside satisfactorily through the heat transfer insulating layer 4 and the heat radiating conductor layer 5. It was confirmed that it could be a coil built-in substrate.

(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 which cut | disconnected (a) by the AA line. (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 which cut | disconnected (a) by the AA line. (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 which cut | disconnected (a) by the AA line. (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 which cut | disconnected (a) by the AA line. (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 which cut | disconnected (a) by the AA line. (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 which cut | disconnected (a) by the AA line. (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 which cut | disconnected (a) by the AA line. (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 which cut | disconnected (a) by the AA line. (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 which cut | disconnected (a) by the AA line. 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 body layer 3 ... Planar coil conductor 4 ... Heat-transfer insulating layer 4a ... Opening 5 ... Heat-dissipating conductor layer 6 ... Wiring layer

Claims (5)

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. there are large heat transfer insulating layer of thermal conductivity than the magnetic ferrite layer, said formed from the inside of the substrate are directly connected to the flat coil conductor toward a side of the substrate, it is formed on a side surface of the substrate A coil-embedded substrate characterized by being connected to a conductive layer for heat dissipation.   2. The coil-embedded substrate according to claim 1, wherein the planar coil conductor has a plurality of turns, and the heat transfer insulating layer is also formed between adjacent planar coil conductors on the outer periphery and the inner periphery.   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 2.   The said planar coil conductor is provided with two or more up and down, and the said insulating layer for heat transfer is formed between the said planar coil conductors located up and down, The Claim 1 thru | or 3 characterized by the above-mentioned. Coil built-in board.   5. The coil-embedded substrate according to claim 1, wherein the heat transfer insulating layer has a plurality of openings disposed along an outer periphery of the planar coil conductor.

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