JP2008177516A - Substrate with built-in coil - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a substrate with a built-in coil wherein a high current can flow without a malfunction of a packaged IC caused by heat generated in a plane coil conductor layer. <P>SOLUTION: The present invention relates to a substrate with a built-in coil which comprises a substrate constituted of a pair of insulating layers 1, 1 formed with a wiring layer 6 and a ferrite magnetic layer 2 held between the pair of insulating layers 1, 1 and a plane coil conductor 3 formed within the ferrite magnetic layer 2, wherein a through-conductor 4 for heat conduction is formed in the region inside the plane coil conductor 3 in plane view through the ferrite magnetic layer 2 and the insulating layers 1 from the ferrite magnetic layer 2 to a principal surface of the substrate and a heat radiating conductor layer 5 is formed to which the through-conductor 4 for heat conduction is connected, on the principal surface of the substrate. Since heat generated in the plane coil conductor 3 can be radiated from the heat radiating conductor layer 5 through the through-conductor 4 for heat conduction to the outside, thereby preventing the malfunction of an electronic component such as a packaged IC from being caused by heat generated from the coil. <P>COPYRIGHT: (C)2008,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, the 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. Therefore, it is an object of the present invention to provide a coil-embedded substrate capable of flowing a high current 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. And a heat transfer that penetrates the ferrite magnetic layer and the insulating layer from the ferrite magnetic layer to the main surface of the substrate in a region inside the planar coil conductor in plan view. A through-hole conductor is formed, and a heat-dissipating conductor layer in which the heat-transfer through conductor is connected is formed on the main surface of the substrate.

  The coil-embedded substrate of the present invention is characterized in that, in the above configuration, a plurality of the heat transfer through conductors are arranged along the inside of the planar coil conductor.

  In the coil-embedded substrate of the present invention, in the above configuration, a heat transfer conductor layer connected to the heat transfer through conductor and overlapping the planar coil conductor in plan view is formed on the ferrite magnetic layer. It is characterized by being.

  In the coil-embedded substrate according to the present invention, in the configuration described above, the planar coil conductor is provided in a plurality above and below via the ferrite magnetic layer, and the heat transfer conductor layer is located above and below the plane. It is formed between coil conductors.

  The coil-embedded substrate of the present invention is characterized in that, in the above configuration, the heat transfer conductor layer is formed between the planar coil conductor and the insulating layer.

  The coil-embedded substrate of the present invention is characterized in that, in the above configuration, the heat transfer through conductor has a tubular portion along the inside of the planar coil conductor.

  The coil-embedded substrate according to the present invention is characterized in that, in the above configuration, the heat transfer through conductor has a larger cross-sectional area on the main surface side of the substrate than on the ferrite magnetic layer side. is there.

  According to the coil-embedded substrate of the present invention, the heat transfer through conductor that penetrates the ferrite magnetic layer and the insulating layer from the ferrite magnetic layer to the main surface of the substrate is formed in a region inside the planar coil conductor in plan view. Since the heat-dissipating conductor layer connected to the heat transfer through conductor is formed on the main surface of the substrate, the heat generated in the planar coil conductor is transferred from the heat dissipating conductor layer to the outside through the heat transfer through conductor. It can dissipate heat. As a result, it is possible to prevent an electronic component such as the mounted IC from malfunctioning due to heat generated from the coil.

  Further, according to the coil-embedded substrate of the present invention, in the above configuration, when the plurality of heat transfer through conductors are arranged along the inside of the planar coil conductor, in the area inside the planar coil conductor, Since the through-conductor for heat transfer does not prevent the magnetic flux generated around the planar coil conductor from passing through the area inside the planar coil conductor, the heat generated in the planar coil conductor is transferred without reducing the inductance. Heat can be radiated from the heat radiating conductor layer to the outside through the heat penetration conductor.

  Further, according to the coil-embedded substrate of the present invention, in the above configuration, when the heat transfer conductor layer that is connected to the heat transfer through conductor and overlaps the planar coil conductor in plan view is formed on the ferrite magnetic layer. The heat generated in the planar coil conductor is transferred to the heat transfer conductor layer, which has a large area and easily receives heat, and then is radiated through the heat transfer through conductor to which the heat transfer conductor layer is connected. It is transmitted to the conductor layer, and heat can be radiated to the outside from the main surface of the coil built-in substrate on which the heat radiating conductor layer is formed. Therefore, heat generated in the planar coil conductor can be more efficiently transmitted to the heat transfer through conductor and the heat dissipation conductor layer, so that an electronic component such as an IC mounted on the coil built-in substrate generates heat generated from the plane coil conductor. Therefore, it is possible to more effectively prevent malfunction.

  Further, according to the coil-embedded substrate of the present invention, in the above-described configuration, a plurality of planar coil conductors are provided above and below via the ferrite magnetic layer between the planar coil conductors located above and below the heat transfer conductor layer. When formed, the heat generated from the planar coil conductor is guided to the inside in the thickness direction of the coil-embedded substrate on which the heat transfer conductor layer is formed, and then the heat dissipation conductor layer through the heat transfer through conductor. The heat can be radiated from the main surface of the coil built-in substrate to the outside. Accordingly, heat transfer in the direction of the insulating layer, that is, the direction of the main surface of the coil-embedded substrate on which the electronic component such as IC is mounted can be suppressed, so that the electronic component such as IC mounted on the coil-embedded substrate is a planar coil. It is possible to more effectively prevent malfunction due to heat generated from the conductor.

  According to the coil-embedded substrate of the present invention, in the above configuration, when the heat transfer conductor layer is formed between the planar coil conductor and the insulating layer, the heat transfer path from the planar coil conductor to the insulating layer is reduced. Since the heat transfer conductor layer is arranged on the way, the heat generated by the planar coil conductor is reliably transferred from the heat transfer conductor layer to the heat transfer through conductor and the heat dissipation conductor layer before being transferred to the insulating layer. In addition to the heat transfer conductor layer between the upper and lower flat coil conductors, when formed between the flat coil conductor and the insulating layer, heat transfer to the heat transfer through conductor and the heat dissipation conductor layer Since the path becomes larger, it is possible to further prevent the electronic component such as the mounted IC from malfunctioning due to the heat generated from the coil.

  Furthermore, even if noise is radiated from the planar coil conductor, the heat transfer conductor layer is disposed so as to overlap the planar coil conductor in plan view between the planar coil conductor and the insulating layer on which the wiring layer is formed. Therefore, the heat transfer conductor layer functions as a shield layer and absorbs noise, so that the influence of the emitted noise on the wiring layer can be suppressed, and the mounted IC can be operated more stably. A coil-embedded substrate that can be obtained can be obtained.

  Further, according to the coil-embedded substrate of the present invention, in the above configuration, when the heat transfer through conductor has a tubular portion along the inside of the planar coil conductor, the tubular portion having a large area is more efficiently. It can receive the heat generated in the planar coil conductor and can transmit the heat to the through conductor for heat transfer more efficiently, so that the mounted IC and other electronic components malfunction due to the heat generated from the coil. This can be further prevented.

  Further, according to the coil-embedded substrate of the present invention, in the above configuration, when the cross-sectional area of the heat transfer through conductor is larger on the main surface side of the substrate than on the ferrite magnetic layer side, Since the heat resistance of heat transfer from the ferrite magnetic layer side to the main surface side of the substrate becomes smaller, the heat transferred to the heat transfer through conductor is more efficiently dissipated toward the main surface side of the substrate The heat is transmitted to the conductor layer for heat dissipation to the outside more efficiently through the conductor layer for heat dissipation.

  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 (FIG. 1B is cut along the line BB ′. 1 (b) is a cross-sectional view (transverse cross-sectional view) obtained by cutting FIG. 1 (a) along the line AA ′. In these drawings, 1 is an insulating layer, 2 is a ferrite magnetic layer, 3 is a planar coil conductor, 4 is a through conductor for heat transfer, 5 is a conductor layer for heat dissipation, and 6 is a wiring layer.

  In the example shown in FIG. 1, as the wiring layer 6, a mounting electrode 6 b on which a semiconductor chip such as an IC or a chip component is mounted on the outer surface of the insulating layer 1 and an electrode pad electrically connected to an external electric circuit. 6 d is formed, and an internal wiring layer 6 a 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 through the through conductor 6c.

  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, and the ferrite magnetic layer 2 and the ferrite magnetic layer 2 extending from the ferrite magnetic layer 2 to the main surface of the substrate in a region inside the planar coil conductor 3 in a plan view. The heat transfer through conductor 4 penetrating the insulating layer 1 is formed, and the heat dissipating conductor layer 5 in which the heat transfer through conductor 4 is connected to the main surface of the substrate is formed.

  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 through conductor 4 by such a configuration. As a result, it is possible to prevent an electronic component such as an mounted IC from malfunctioning due to heat generated from the planar coil conductor 3.

  At this time, as shown in FIG. 1, the heat transfer through conductor 4 is spaced so as to provide an area for the magnetic flux generated around the planar coil conductor 3 to pass through the area inside the planar coil conductor 3. Provided and arranged.

  Further, it is preferable that the distance between the heat transfer through conductor 4 and the planar coil conductor 3 is as short as possible because the magnetic flux passage region in the region is not narrowed inside the planar coil conductor 3, but electrical insulation between the two is improved. In consideration, specifically, the distance between the heat transfer through conductor 4 and the planar coil conductor 3 is preferably about 50 μm or more.

  Further, as shown in FIG. 2 similarly to FIG. 1, in the above configuration, it is preferable that the plurality of heat transfer through conductors 4 are arranged along the inner side of the planar coil conductor 3. With this configuration, the heat transfer through conductor 4 does not prevent the magnetic flux generated around the planar coil conductor 3 from passing through the inner region of the planar coil conductor 3 in the inner region of the planar coil conductor 3. Therefore, the heat generated in the planar coil conductor 3 can be radiated from the heat radiation conductor layer 5 to the outside via the heat conduction through conductor 4 without reducing the inductance.

  Even in this case, the heat-transfer through conductors 4 are arranged with an interval through which 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.

  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 through conductor 4 may be disposed at a corner portion in the region inside the planar coil conductor 3. preferable. Since the magnetic flux density at the corner portion is coarser than in other regions, the influence of reducing the magnetic flux passage region by the heat transfer through conductor 4 formed in this portion can be small. Moreover, since the temperature of a corner | angular part tends to become high in the area | region inside the planar coil conductor 3, it can thermally radiate more efficiently.

  In addition, for this reason, as shown in FIG. 2, if the cross-sectional area of the heat transfer through conductor 4 arranged at the corner is larger than that of the other portions, it is more efficient without lowering the inductance. It is preferable because it can dissipate heat.

  The cross-sectional shape of the heat transfer through conductor 4 is not limited to a circle as shown in the drawing, but may be a triangle, a quadrangle, a polygon having more than that, an ellipse or the like, and is not particularly limited. When a plurality of heat transfer through conductors 4 are arranged along the inside of the planar coil conductor 3, the cross sectional shape of the heat transfer through conductor 4 is elongated toward the center of the area inside the planar coil conductor 3. For example, it is preferable to use a rectangle or an ellipse. By adopting such a shape, it is possible to efficiently dissipate heat by increasing the cross-sectional area without narrowing the interval between the heat transfer through conductors 4 and preventing the passage of magnetic flux.

  The coil-embedded substrate according to the present invention includes, for example, a tubular portion 4a in which the heat-transfer through conductor 4 extends along the inner side of the planar coil conductor 3 as shown in FIGS. 3, 5 and 6 in a cross-sectional view similar to FIG. It is preferable to have. Since the tubular portion 4a can receive the heat generated in the planar coil conductor 3 more efficiently and can transmit the heat to the through conductor 4 for heat transfer more efficiently, an electronic component such as an IC is generated from the planar coil conductor 3. It is possible to further prevent malfunctions due to heat that is generated.

  The tubular portion 4 a is a portion that is formed so as to connect the heat transfer through conductors 4 penetrating the ferrite magnetic layer 2 and the insulating layer 1 in the lateral direction and is tubular in plan view. As shown in FIG. 6, it may be formed on one ferrite magnetic layer 2 to form a complete tubular shape. However, as shown in FIGS. 3 and 5, the ferrite magnetic layer 2 is penetrated to increase the thickness. In that case, it may not be completely tubular. When the thickness is increased by penetrating the ferrite magnetic layer 2, it becomes plate-like and the area receiving the heat generated by the planar coil conductor 3 becomes larger, so that heat can be transferred to the heat transfer through conductor 4 more efficiently. it can. In this case, as shown in FIGS. 3 (a) and 5 (a), if it is tubular between the upper and lower planar coil conductors 3 and 3, the passage of magnetic flux may not be hindered.

  Further, since the tubular portion 4a of the heat transfer through conductor 4 is formed at a position close to the planar coil conductor 3, a magnetic flux is generated along the innermost conductor in each of the upper and lower planar coil conductors 3 and 3. It is difficult to generate a magnetic flux around the entire planar coil conductor 3 from the outermost circumference to the innermost circumference (inside the tubular portion 4a) of the upper and lower planar coil conductors 3 and 3. It is possible to suppress the partial saturation of the magnetic flux generated by the concentration of the magnetic flux between the outer periphery and the deterioration of the superposition characteristics.

  FIG. 4 is a view showing an example of an embodiment of a substrate with a built-in coil according to the present invention, and FIG. 4 (a) is a cross-sectional view of the substrate with a built-in coil according to the present invention (FIG. 4B is a cross-sectional view (transverse cross-sectional view) obtained by cutting FIG. 4A along the line AA ′. In these drawings, reference numeral 7 denotes a heat transfer conductor layer.

  As shown in FIG. 4, in the above configuration, a heat transfer conductor layer 7 that is connected to the heat transfer through conductor 4 and overlaps the planar coil conductor 3 in plan view is formed in the ferrite magnetic layer 2. Is preferred. Most of the heat generated in the planar coil conductor 3 is transferred to the heat transfer conductor layer 7 which has a large area and easily receives heat, and then passes through the heat transfer through conductor 4 to which the heat transfer conductor layer 7 is connected. Then, the heat is transmitted to the heat radiating conductor layer 5 and can be radiated to the outside from the main surface of the coil-embedded substrate on which the heat radiating conductor layer 5 is formed. Accordingly, heat transfer in the direction of the insulating layer 1, that is, the main surface direction of the coil-embedded substrate on which the electronic component such as an IC is mounted can be suppressed, so that the electronic component such as the IC mounted on the coil-embedded substrate is flat. It is possible to more effectively prevent malfunction due to heat generated from the coil conductor 3.

  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.

  As shown in FIG. 4, the heat transfer conductor layer 7 is formed between the upper and lower planar coil conductors 3 when a plurality of the planar coil conductors 3 are provided above and below via the ferrite magnetic layer 2. It is preferable that

  In such a configuration, the heat generated from the planar coil conductor 3 is guided to the inside in the thickness direction of the coil-embedded substrate on which the heat transfer conductor layer 7 is formed, and then the heat dissipation conductor layer 5 Heat can be radiated from the main surface of the formed coil-embedded substrate to the outside of the substrate. Accordingly, heat transfer in the direction of the insulating layer 1, that is, the main surface direction of the coil-embedded substrate on which the electronic component such as an IC is mounted can be suppressed, so that the electronic component such as the IC mounted on the coil-embedded substrate is flat. It is possible to more effectively prevent malfunction due to heat generated from the coil conductor 3.

  When the heat transfer conductor layer 7 is formed between the upper and lower planar coil conductors 3 and 3, it is necessary to provide a region through which the magnetic flux generated around the planar coil conductor 3 passes. A region where the heat transfer conductor layer 7 is not provided is required at the center of the planar coil conductor 3 and the outer periphery of the planar coil conductor 3.

  When the heat transfer conductor layer 7 is formed between the planar coil conductors 3 and 3 positioned above and below, at least a part thereof overlaps the planar coil conductor 3 in plan view as shown in FIG. At the same time, it may be connected to the heat transfer through conductor 4, but as shown in FIG. 5 (b), it is preferably provided in a shape that overlaps the entire area where the planar coil conductor 3 is formed in plan view. By adopting such a shape, heat generated in the planar coil conductor 3 can be efficiently received and discharged to the outside, and a magnetic flux passage region can be secured, so that deterioration of the characteristics of the built-in coil is suppressed. be able to. In addition, since the leakage magnetic flux generated between the planar coil conductors 3 provided at the top and bottom can be shielded, the magnetic flux can be prevented from being disturbed, and it is difficult for magnetic saturation to occur when a current is applied, resulting in high superposition. Characteristics can be obtained.

  The heat transfer conductor layer 7 having such a shape has a shape extending from the formation region of the flat coil conductor 3 to the inside and outside in a plan view by a distance from the flat coil conductor 3 to the heat transfer conductor layer 7. Is preferred. Since 90% or more of the heat transfer amount is transferred in the range where the heat from the planar coil conductor 3 is expanded by 45 ° with respect to the direction from the planar coil conductor 3 to the heat transfer conductor layer 7, Most of the heat from the coil conductor 3 toward the heat transfer conductor layer 7 is transferred to the heat transfer conductor layer 7.

  When the heat transfer conductor layer 7 is formed between the flat coil conductors 3 positioned above and below, the distance between the heat transfer conductor layer 7 and the flat coil conductor 3 is such that the heat from the flat coil conductor 3 is more efficiently generated. In order to dissipate heat and to more effectively shield the leakage magnetic flux generated between the conductors of the planar coil conductor 3, it is better to be as small as possible. In a specific example, considering the insulation between the upper and lower planar coil conductors 3, the distance between the heat transfer conductor layer 7 and the planar coil conductor 3 is preferably about 15 μm.

  When the heat transfer conductor layer 7 is formed between the planar coil conductor 3 and the insulating layer 1 as shown in FIG. Since the heat transfer conductor layer 7 is arranged in the middle of the heat transfer path, heat generated in the planar coil conductor 3 is surely transferred to the heat transfer conductor layer 7 before being transferred to the insulating layer 1, which is preferable.

  When the heat transfer conductor layer 7 is formed between the planar coil conductor 3 and the insulating layer 1, the distance between the heat transfer conductor layer 7 and the planar coil conductor 3 is around the planar coil conductor 3. A distance (thickness of the ferrite magnetic layer 2) that is set according to the amount of generated magnetic flux and through which the generated magnetic flux can pass is required. For the same reason, even when the heat transfer conductor layer 7 is not formed between the planar coil conductor 3 and the insulating layer 1, the ferrite magnet having the same thickness is formed between the planar coil conductor 3 and the insulating layer 1. The body layer 2 is formed. This distance varies 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, but for example, the permeability of the ferrite magnetic layer 2 is 500. In that case, it may be 0.1 mm or more.

  In addition to the heat transfer conductor layer 7 between the upper and lower flat coil conductors 3 and 3 as shown in FIG. 7, the heat transfer conductor layer is also provided between the flat coil conductor 3 and the insulating layer 1. 7 is formed, the path for transferring heat to the heat-dissipating conductor layer 5 is increased, so that an electronic component such as an IC that has been mounted malfunctions due to the heat generated in the planar coil conductor 3. Can be prevented.

  Further, when the heat transfer conductor layer 7 is formed between the planar coil conductor 3 and the insulating layer 1, even if noise is radiated from the planar coil conductor 3, the heat transfer conductor layer 7 is flat. Since the coil conductor 3 and the insulating layer 1 on which the wiring layer 6 is formed are arranged so as to overlap with the planar coil conductor 3 in plan view, the heat transfer conductor layer 7 functions as a shield layer and causes noise. Therefore, the influence on the wiring layer 6 due to the radiated noise is suppressed, and a coil-embedded substrate capable of operating the mounted IC more stably can be obtained.

  The heat transfer conductor layer 7 formed between the planar coil conductor 3 and the insulating layer 1 is preferably formed in a shape covering the entire surface as a so-called solid layer as shown in FIGS. As a result, the heat transfer conductor layer 7 is formed so as to cover the entire heat transfer path from the planar coil conductor 3 to the insulating layer 1, and the planar coil conductor 3 that is a noise generation source is also used as the shield conductor layer. Will cover.

  In such a configuration, it is preferable that the heat transfer conductor layer 7 formed between the planar coil conductor 3 and the insulating layers 1 and 1 also serves as a ground conductor layer. In this case, after the heat transfer conductor layer 7 (ground conductor layer) absorbs noise, the potential generated by the noise is released to the outside together with the current flowing through the ground conductor layer, and thus is radiated from the planar coil conductor 3. Therefore, it is possible to obtain a substrate with a built-in coil that can suppress the influence on the wiring layer 6 due to the radiated noise and can operate the mounted IC more stably. . Since the single layer has the functions of the ground conductor layer and the heat transfer conductor layer 7, the mounted IC can be operated more stably than when two layers are separately formed. Thus, a thinner coil-embedded substrate can be obtained.

  As described above, since it is intended to prevent the influence of heat on the electronic components such as the mounted IC and the influence of noise on the wiring layer 6 on which the electronic components are mounted, the mounting of the electronic components such as the IC is performed. It is preferably formed between the insulating layer 1 on the main surface side and the planar coil conductor 3. When electronic components are mounted on both main surfaces of the substrate, they are formed between both planar coil conductors 3 and the insulating layer 1. Needless to say, even if the electronic component is mounted only on one main surface side, it may be formed on both sides in order to improve the efficiency of heat dissipation.

  When the heat transfer conductor layer 7 formed between the planar coil conductor 3 and at least one of the pair of insulating layers 1 and 1 also serves as a ground conductor layer, as shown in FIG. It is preferable to provide an opening 7a in a portion overlapping the planar coil conductor 3 in plan view of the conductor layer 7 (ground conductor layer). As a result, the area of the portion of the ground conductor layer 7 facing the planar coil conductor 3 is reduced, and the capacitance between the planar coil conductor 3 and the ground conductor layer 7 is reduced. Therefore, without increasing the thickness of the substrate, The resonance frequency generated by the inductance and capacitance of the coil can be increased. As a result, since a high inductance value can be obtained even at a higher frequency, the built-in coil can be made smaller, and a small coil-embedded substrate can be obtained.

  The openings 7a provided in the heat transfer conductor layer 7 may have a shape along the planar coil conductor 3 in which all the portions overlapping the planar coil conductor 3 are opened, but are divided and formed as shown in FIG. Preferably it is. A plurality of openings 7a are divided, that is, a plurality of openings 7a are arranged at intervals, so that current flows between the openings 7a and 7a in the ground conductor layer 7 as a planar coil. Since it becomes a path for flowing in a direction intersecting with the opening 7a formed along the conductor 3, an increase in power supply inductance due to the opening 7a and an accompanying increase in power supply noise are suppressed, and the circuit is mounted on the coil built-in substrate. A coil-embedded substrate capable of stably operating an IC at a high frequency can be obtained.

  In order to make such an opening 7a, the size of the opening 7a is preferably slightly larger than that of the planar coil conductor 3, and in consideration of the misalignment of the stack, 0.1 mm with respect to the width of the planar coil conductor 3. What is necessary is just to make it the width | variety large about. Further, the interval between the plurality of openings 7a and 7a need only be 0.1 mm or more in width so that the current path can suppress the increase in power supply inductance and the accompanying increase in power supply noise. The area of the opening 7a may be determined according to the required resonance frequency. Further, the shape is not particularly limited, and may be a polygon, a circle, or the like other than the quadrangle as in the example shown in FIG.

  Further, in the case where the planar coil conductor 3 is formed in a rectangular shape along the outer shape of the rectangular substrate, in order to suppress noise particularly caused by the concentration of the electric field at the corners of the planar coil conductor 3, FIG. As shown, it is preferable that the opening 7 a does not overlap with the corner of the planar coil conductor 3.

  Further, when the corner portion of the planar coil conductor 3 is bent into a curved shape or has a plurality of bent portions, the area of the ground conductor layer facing the planar coil conductor 3 is reduced, and the planar coil conductor is reduced. Since the capacitance between 3 and the grounding conductor layer becomes smaller, inductance values can be obtained up to higher frequencies, and the corners have a shape that makes it difficult for current to concentrate. Can be reduced, which is preferable.

  In the case where the heat transfer conductor layer 7 does not serve as the ground conductor layer, it is needless to say that the ground conductor layer 6e may be provided separately as shown in the cross-sectional view similar to FIG. In this case, since the heat transfer conductor layer 7 formed between the planar coil conductor 3 and the insulating layer 1 prevents the electromagnetic coupling between the ground conductor layer 6e and the planar coil conductor 3, the ground conductor Since the capacitance between the planar coil conductor 3 and the ground conductor layer 4 is reduced without providing the opening 4a in the portion of the layer 6e that overlaps the planar coil conductor 3, the thickness of the built-in coil can be reduced without increasing the thickness of the substrate. The resonance frequency caused by the inductance and capacitance can be increased. Although the ground conductor layer 6e is omitted in FIGS. 1 to 7, the heat transfer conductor layer 7 is not formed as shown in FIGS. 1 to 3, or as shown in FIGS. Necessary even when the heat transfer conductor layer 7 is formed between the planar coil conductors 3 and 3 or when the heat transfer conductor layer 7 does not serve as the ground conductor layer as shown in FIGS. It is formed according to.

  Further, as shown in FIG. 10 to FIG. 12 in the same sectional view as FIG. 1, in the above configuration, the heat transfer through conductor 4 has a cross-sectional area larger than the ferrite magnetic layer 2 side on the main surface side of the substrate (FIG. 10). In the example shown in FIG. 12, it is preferable that the lower surface side of the substrate) is larger. With this configuration, since the heat resistance of heat transfer from the ferrite magnetic layer 2 side to the main surface side of the substrate in the heat transfer through conductor 4 becomes smaller, the heat transferred to the heat transfer through conductor 4 is reduced. The heat is transmitted to the heat radiating conductor layer 5 toward the main surface side of the substrate more efficiently, and the heat is radiated to the outside more efficiently through the heat radiating conductor layer 5.

  The cross-sectional area of the heat transfer through conductor 4 may be increased stepwise as in the examples shown in FIGS. 10 and 11, and as shown in FIG. It may be gradually increased from the magnetic layer 2 to the main surface of the substrate. In the case of increasing stepwise, not only one stage as shown in the example shown in FIG. 10 but also a plurality of stages as shown in the example shown in FIG. The ratio of increasing at is not necessarily constant. In either case, it is possible to more efficiently transfer heat to the main surface side of the substrate by increasing the cross-sectional area on the main surface side of the substrate, but as described above, it spreads by 45 ° with respect to the heat transfer direction. Since 90% or more of the heat transfer amount is transmitted in the range, the shape may be expanded at most 45 ° over the main surface of the substrate. Further, the cross sectional area of the heat transfer through conductor 4 may be increased from any position from the ferrite magnetic layer 2 to the main surface of the substrate, but in order to suppress the decrease in inductance by making the magnetic flux pass as good as possible. For this reason, it is preferable to increase the size in the insulating layer 1, as in the examples shown in FIGS.

Further, the cross-sectional area of the heat transfer through conductor 4 may be made as large as possible in a range not connected to the wiring layer 6 in the insulating layer 1 in order to transfer heat to the main surface side of the substrate more efficiently. As a result, the shape in which the cross-sectional areas are increased into one shape, for example, a plurality of heat-transfer through conductors 4 formed in the ferrite magnetic layer 2 is formed in the insulating layer 1. It is good also as a shape connected to the through-conductor 4 for heat transfer with a large area. In this case, all the heat transfer through conductors 4 formed in the ferrite magnetic layer 2 may be connected to one heat transfer through conductor 4 having a large cross-sectional area formed in the insulating layer 1, The heat dissipating conductor layer 5 may be connected to, for example, two to three heat transfer through conductors 4 having a large cross-sectional area formed in consideration of the arrangement of the wiring layer 6 in the insulating layer 1. As shown in FIG. 12, the heat transfer through conductor 4 is connected to the main surface of the substrate. The size is not particularly limited, and is connected not only to a part of the main surface (lower surface) of the substrate but also to electrode pads 6d formed on the main surface (lower surface) of the substrate as shown in FIG. It may be formed over the entire main surface (lower surface) of the substrate.

  The heat dissipating conductor layer 5 has a sufficient distance from the mounting position of the electronic component on the main surface of the substrate, and heat is not transmitted from the heat transfer through conductor 4 and the heat dissipating conductor layer 5 to the electronic component. Alternatively, it may be formed on the main surface on the electronic component mounting side. Further, when the heat generation of the electronic component mounted on the substrate is larger than the heat generation of the planar coil conductor 3 and the temperature becomes higher, the mounting electrode 6b on which the electronic component is mounted, the heat transfer through conductor 4, and the heat transfer Either the conductive layer 7 for heat dissipation or the conductive layer 5 for heat dissipation may be connected, or an electronic component may be mounted on one of the conductive layers for heat dissipation 5 formed on both main surfaces of the substrate.

  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 it is better to make the thickness thicker than 20 μm.

  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 preferable 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. 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 layer 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 green sheet for the insulating layer 1 or the green sheet for the ferrite magnetic layer 2 is obtained by mixing the insulating powder or the magnetic ferrite powder with an organic binder, an organic solvent, and a dispersant or a plasticizer as necessary, to obtain a slurry. From this, it is produced by applying in a sheet form by a doctor blade method, a rolling method, a calendar roll method, an extrusion molding method, and the like, and drying and molding.

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 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. The substrate with a built-in coil is manufactured by firing the laminate.

  Prior to the formation of the surface wiring pattern and the heat dissipating conductor layer pattern 5 which becomes the heat dissipating conductor layer 5, the heat transfer through conductor 4 is punched or laser-processed into the green sheet for the insulating layer 1 and the green sheet for the ferrite magnetic layer 2. A through-hole is formed by processing or the like, and 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 4 are formed in the same layer, the through hole and the paste may be simultaneously formed.

  In order to increase the cross sectional area of the heat transfer through conductor 4 on the main surface side of the substrate from the ferrite magnetic layer 2 side as in the example shown in FIGS. 10 and 11, it is formed on the green sheet on the main surface side. What is necessary is just to make a through-hole large. In addition, when the cross-sectional area of the heat transfer through conductor 4 is gradually increased from the ferrite magnetic layer 2 to the main surface of the substrate without a step as in the example shown in FIG. It is only necessary to form a through-hole having an inclined inner wall surface such as a taper shape, and this can be achieved by increasing the clearance of the die for punching the green sheet or adjusting the output of the laser.

  When the tubular portion 4a of the heat transfer through conductor 4 does not penetrate the ferrite magnetic layer 2 or the insulating layer 1 as shown in FIG. 6, the green sheet for the ferrite magnetic layer 2 or the ferrite magnetic layer 2 is formed. After forming a pattern to be the heat transfer through conductor 4 on the green sheet for use, the wiring layer 6 is formed on the ferrite magnetic substance layer 2 green sheet or the ferrite magnetic substance layer 2 green sheet so as to overlap the exposed portion. A tubular pattern may be formed in the same manner as the pattern. In the case of a shape penetrating the ferrite magnetic layer 2 and the insulating layer 1 as shown in FIGS. 3 and 5, they may be formed simultaneously in the same manner when the heat-transfer through conductor 4 is formed. If the tubular portion 4a is a perfect tubular shape, a through hole cannot be formed in the green sheet. Therefore, the shape may be divided into a plurality of shapes as shown in FIGS. 3 and 5, and the number and shape of the division are particularly limited. Is not to be done.

  The heat-dissipating conductor layer 5 and the heat-transfer conductor layer 7 are sintered bodies of low-resistance metal powders such as Cu, Ag, Au, Pt, Ag—Pd alloy, and Ag—Pt alloy, like the wiring layer 6. It is made of metallized metal. The conductive layer 7 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 co-firing with them. The heat dissipating conductor layer 5 is made of a conductor paste similar to the conductor paste for 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 by screen printing or gravure printing. It is formed in a predetermined pattern shape on the green sheet for the insulating layer 1 and simultaneously fired together. It may be performed simultaneously with the formation of the mounting electrode 6b and the electrode pad 6d.

  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 7, 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.

  In addition, in order to make the surface of the heat-dissipating conductor layer 5 have an uneven shape, for example, by applying a paste after applying a conductive paste, an uneven shape such as a row of grooves or a number of point-like protrusions or recesses 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. Use a humidified product to facilitate debinding.

  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 the first embodiment, as the coil-embedded substrate of the present invention, as shown in FIG. 7, along the inner periphery of the planar coil conductor 3, there are a total of eight corners in the area inside the planar coil conductor 3 and between them. A heat transfer through conductor 4, and a heat transfer conductor layer 7 between the two planar coil conductors 3, 3 positioned above and below and between the insulating layer 1 on the lower side of the substrate and the ferrite magnetic layer 2, Then, a coil-embedded substrate in which the ground conductor layer 6e is added to the upper and lower insulating layers 1 in the structure in which the heat radiating conductor layer 5 is provided on the lower surface of the substrate, and the surface temperature of the wiring layer 6 formed on the upper surface of the substrate is prepared. 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 and a through hole with a diameter of 240 μm for the heat transfer through conductor 4 were 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. The wiring layer pattern to be the ground conductor layer 6e and the pattern to be the heat transfer conductor layer 7 between the insulating layer 1 and the ferrite magnetic layer 2 were also formed in the same manner on another insulating layer green sheet.

  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 and a through hole with a diameter of 240 μm for the heat transfer through conductor 4 were 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 conductor paste was applied to each of two ferrite magnetic layer green sheets by a screen printing method to a thickness of 30 μm and dried at 70 ° C. for 30 minutes to form a three-turn (three winding) planar coil conductor pattern. . 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, on another green sheet for magnetic ferrite layer, the same conductor paste as the planar coil conductor pattern was applied to a thickness of 30 μm by screen printing, dried at 70 ° C. for 30 minutes, and the heat transfer conductor layer A pattern was formed. The pattern was provided with an opening having a diameter of 250 μm so as not to be connected to the through conductor 6c for connecting the upper and lower planar coil conductor patterns.

  Next, a green sheet for a ferrite magnetic layer formed with a planar coil conductor pattern in order from the bottom, a green sheet for a ferrite magnetic layer formed with a conductor layer pattern for heat transfer, and a ferrite magnetic layer formed with a planar coil conductor pattern A green sheet and a green sheet for a ferrite magnetic layer formed only with a through conductor pattern are stacked, and further, four green sheets for an insulating layer are stacked on top and bottom, respectively, and insulated by thermocompression bonding at a pressure of 5 MPa and a temperature of 50 ° C. The laminated body in which the green sheet for layers is located in the surface layer was produced.

  Next, after cutting the laminate into 12 mm squares, it was heated in air at 500 ° C. for 3 hours to remove organic components, then fired in air at 900 ° C. for 1 hour, A built-in substrate was produced. In the coil-embedded substrate, the ferrite magnetic layer 2 is sandwiched between a pair of insulating layers 1 and 1, and the planar coil conductors 3 are formed in the ferrite magnetic layer 2 so as to overlap each other. 3 is connected to each other by a through conductor 6c, and the other end of the upper planar coil conductor 3 is not electrically connected to the upper ground conductor layer 6e and passes through the upper ground conductor layer 6e. The other end of the lower planar coil conductor 3 is connected to the lower ground conductor layer 6e, and the lower ground conductor layer 6e is connected to the other conductor by the through conductor 6c. The structure was connected to the surface wiring layer. 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 was 0.15 mm. The heat transfer conductor layer 7 has a conductor thickness of 0.02 mm and a shape having an opening of 3.0 mm square in the approximate center of an outer dimension of 6.3 mm square, and the heat transfer through conductor 4 is an innermost planar coil. A conductor having a diameter of 0.2 mm is connected to the conductor layer 7 for heat transfer at a position 0.1 mm away from the conductor 3, and the conductor layer 5 for heat dissipation has a conductor thickness of 0.03 mm and a conductor with an outer dimension of 6 mm square. It was connected to the thermal through conductor 4 and arranged at the center of the lower surface of the substrate.

  On the wiring layer 6 and the heat dissipating conductor layer 5 formed on the outer surface of the coil-embedded substrate, a 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, the heat transfer through conductor 4, the heat dissipating conductor layer 5, and the heat transfer conductor layer as shown in FIG. A substrate with a built-in coil was produced in the same manner as in Example 1 except that the substrate 7 was not provided.

  The coil-embedded substrates of Example 1 and Comparative Example were each mounted on a ceramic substrate using solder. In addition, in the coil-embedded substrate of Example 1, the heat radiating conductor 5 and the connection conductor on the ceramic substrate were also joined by soldering.

  Then, 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 in a state of 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 39 ° C., whereas the temperature on the surface wiring layer of the substrate of the comparative example was 80 ° C. Thereby, it has confirmed that the coil built-in board | substrate of Example 1 was a coil built-in board | substrate which can radiate | emit the heat | fever generate | occur | produced in the planar coil conductor 3 from the main surface of a board | substrate with respect to the comparative example.

(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 A-A 'line | wire. (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 A-A 'line | wire. (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 A-A 'line | wire. (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 A-A 'line | wire. (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 A-A 'line | wire. (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 A-A 'line | wire. (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 A-A 'line | wire. (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 A-A 'line | wire. It is sectional drawing which shows an example of embodiment of the board | substrate with a built-in coil of this invention. (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 A-A 'line | wire. (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 A-A 'line | wire. (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 A-A 'line | wire. 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 through conductor 5 ... Heat-dissipating conductor layer 6 ... Wiring layer 7 ... Heat transfer Conductor layer

Claims (7)

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 through conductor penetrating the ferrite magnetic layer and the insulating layer from the ferrite magnetic layer to the main surface of the substrate is formed in a region inside the planar coil conductor in plan view, A substrate with a built-in coil, wherein a heat-dissipating conductor layer to which the heat-transfer through conductor is connected is formed on the main surface of the substrate. The coil built-in substrate according to claim 1, wherein the plurality of through conductors for heat transfer are arranged along the inside of the planar coil conductor. 3. The coil according to claim 1, wherein a heat transfer conductor layer that is connected to the heat transfer through conductor and overlaps the planar coil conductor in plan view is formed on the ferrite magnetic layer. 4. Built-in board. A plurality of the planar coil conductors are provided above and below via the ferrite magnetic layer therebetween, and the heat transfer conductor layer is formed between the planar coil conductors positioned above and below. Item 4. The coil-embedded substrate according to Item 3. The coil built-in substrate according to claim 3 or 4, wherein the heat transfer conductor layer is formed between the planar coil conductor and the insulating layer. The coil built-in substrate according to any one of claims 2 to 5, wherein the heat transfer through conductor has a tubular portion along an inner side of the planar coil conductor. The coil built-in substrate according to any one of claims 1 to 6, wherein a cross-sectional area of the heat transfer through conductor is larger on the main surface side of the substrate than on the ferrite magnetic layer side.

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