JP2019021877A - Wiring board and planar transformer - Google Patents

Abstract

To provide a wiring board capable of increasing a diameter of a connection conductor, and suppressing occurrence of a defect in an insulation layer and generation of a void in the connection conductor.SOLUTION: A wiring board comprises: at least one insulation layer having a surface and a rear surface; a first wiring layer arranged on a surface side of the at least one insulation layer; a second wiring layer arranged on a rear surface side of the insulation layer in which the first wiring layer is arranged; and a connection conductor electrically connecting the first wiring layer and the second wiring layer. The insulation layer includes a through hole penetrating this insulation layer in a thickness direction. The connection conductor includes metallic grains arranged in the through hole, and a junction part joining the grains, the first wiring layer, and the second wiring layer.SELECTED DRAWING: Figure 2

Description

  The present disclosure relates to a wiring board and a planar transformer.

  As a method for manufacturing a multilayer wiring board in which a plurality of insulating layers and a plurality of wiring layers are alternately stacked, a method of forming a wiring layer by printing a metal paste on the insulating layer and baking it is known (Patent Document). 1). In this method, vias, which are connection conductors for conducting a plurality of wiring layers, are also formed by firing a metal paste.

JP-A-6-204039

  In the multilayer wiring board described above, in order to reduce electrical resistance, it is sometimes required to increase the diameter of the connecting conductor in conjunction with increasing the thickness of the wiring layer. However, when a large-diameter connection conductor is formed by the method described above, stress is generated during firing due to the difference in thermal expansion coefficient between the connection conductor forming material and the insulating layer, and defects such as cracks are generated in the insulating layer. It's easy to do. In addition, voids (so-called voids) are generated inside the connection conductor, which may make it difficult to form the connection conductor.

  One aspect of the present disclosure aims to provide a wiring board capable of suppressing generation of defects in an insulating layer and generation of voids in the connection conductor while increasing the diameter of the connection conductor.

  One embodiment of the present disclosure includes at least one insulating layer having a front surface and a back surface, a first wiring layer disposed on a front surface side of the at least one insulating layer, and a back surface side of the insulating layer on which the first wiring layer is disposed And a connection conductor that electrically connects the first wiring layer and the second wiring layer to each other. The insulating layer has a through hole penetrating the insulating layer in the thickness direction. The connection conductor includes a metal particle disposed in the through hole, and a joint that joins the particle, the first wiring layer, and the second wiring layer.

  According to such a structure, generation | occurrence | production of the void in a connection conductor is suppressed by using the connection conductor which joined the metal particle | grains with the wiring layer by the junction part. Further, since there is no need to fire the connection conductor, the stress due to the difference in thermal expansion coefficient between the insulating layer and the connection conductor is suppressed, and the stress at the time of joining the joint is also buffered by the granules. Therefore, the occurrence of defects such as cracks and breakage in the insulating layer is also suppressed. Therefore, it is easy to increase the diameter of the connection conductor.

  In one aspect of the present disclosure, in the connection conductor, the total volume of the particles may be smaller than the total volume of the joint portion. According to such a structure, since the joint strength by a junction part increases, the connection reliability of a connection conductor can be improved.

  In one aspect of the present disclosure, the particles may not be fixed to the inner wall of the insulating layer that forms the through hole. According to such a configuration, since the particles are not fixed to the insulating layer by the joint portion, the connecting conductor including the particles and the insulating layer are individually displaced. Generation of stress due to a difference in thermal expansion coefficient can be suppressed.

  In one aspect of the present disclosure, at least one of the first wiring layer and the second wiring layer includes a non-fixed region that is not fixed to the adjacent insulating layer and a fixed region that is fixed to the adjacent insulating layer. May be. Alternatively, the first wiring layer and the second wiring layer may not be fixed to the adjacent insulating layer. According to such a configuration, when the wiring layer and the insulating layer expand or contract due to a temperature change, a non-fixed region where the difference in deformation amount between the wiring layer and the insulating layer due to the difference in thermal expansion coefficient is not fixed to the insulating layer. Can be absorbed by. Therefore, the stress generated between the insulating layer and the wiring layer is reduced, and defects such as cracks in the insulating layer are suppressed.

In one aspect of the present disclosure, the first wiring layer and the second wiring layer may contain copper as a main component. According to such a configuration, a highly reliable wiring board having high electrical conductivity and high thermal conductivity can be obtained at low cost.
In one aspect of the present disclosure, the material of the granules may be the same as the main component of the first wiring layer and the second wiring layer. According to such a configuration, since the thermal expansion coefficients of the particles and the wiring layer are the same, the stress generated between the connection conductor and the wiring layer when the temperature changes can be reduced.

  In one embodiment of the present disclosure, the insulating layer may include ceramic as a main component. According to such a configuration, since the flatness of the insulating layer is improved, wirings can be arranged in the insulating layer with high density. Furthermore, high insulation can also be obtained.

It is a typical sectional view of a wiring board of an embodiment. It is a typical partial expanded sectional view of the connection conductor vicinity in the wiring board of FIG. It is a flowchart which shows the manufacturing method of the wiring board of FIG. It is typical sectional drawing of the wiring board in embodiment different from FIG.

Hereinafter, embodiments to which the present disclosure is applied will be described with reference to the drawings.
[1. First Embodiment]
[1-1. Wiring board]
A wiring board 1 shown in FIG. 1 includes a plurality of insulating layers (first insulating layer 2 and second insulating layer 3) and a plurality of wiring layers (first wiring layer 4, second wiring layer 5, and third wiring layer 6). ), A plurality of connection conductors 7 for connecting a plurality of wiring layers, and a plurality of wiring layer fixing members 9.

  In the present embodiment, a multilayered wiring board 1 including two insulating layers and three wiring layers will be described as an example of the present disclosure. The number of insulating layers and wiring layers in the wiring board of the present disclosure is as follows. It is not limited to.

  The wiring board 1 is used for applications such as a transformer (that is, a transformer), an insulated gate bipolar transistor (IGBT), a light emitting diode (LED) lighting device, a power transistor, and a motor, depending on the design of the wiring layer pattern. The wiring board 1 can be particularly suitably used for high voltage and large current applications.

<Insulating layer>
The first insulating layer 2 and the second insulating layer 3 each have a front surface and a back surface. The first insulating layer 2 and the second insulating layer 3 are mainly composed of ceramic. The “main component” means a component contained in an amount of 80% by mass or more.

  Examples of the ceramic constituting the first insulating layer 2 and the second insulating layer 3 include alumina, beryllia, aluminum nitride, boron nitride, silicon nitride, silicon carbide, LTCC (Low Temperature Co-fired Ceramic), and the like. These ceramics can be used alone or in combination of two or more.

  The first insulating layer 2 has a first wiring layer 4 adjacent to the front surface side and a second wiring layer 5 adjacent to the back surface side. The second insulating layer 3 is arranged on the surface side of the first insulating layer 2 via the first wiring layer 4, and the third wiring layer 6 adjacent to the surface side is arranged.

  The first insulating layer 2 and the second insulating layer 3 have at least one through-hole 2A, 3A that penetrates the first insulating layer 2 and the second insulating layer 3 in the thickness direction, respectively. The through holes 2A and 3A are via holes in which vias for electrically connecting so-called wiring layers are formed. In the present embodiment, the through hole 2A of the first insulating layer 2 and the through hole 3A of the second insulating layer 3 are provided at the same position as viewed from the thickness direction of the insulating layers 2 and 3 (that is, in plan view). Have the same diameter.

<Wiring layer>
The 1st wiring layer 4, the 2nd wiring layer 5, and the 3rd wiring layer 6 have electroconductivity, and contain a metal as a main component. Examples of the metal include copper, aluminum, silver, gold, platinum, nickel, titanium, chromium, molybdenum, tungsten, and alloys thereof. Among these, copper is preferable from the viewpoints of cost, conductivity, thermal conductivity, and strength. Therefore, a copper foil or a copper plate can be suitably used as each wiring layer 4, 5, 6.

  The first wiring layer 4 is disposed on the surface side of the first insulating layer 2. The first wiring layer 4 has a fixed region A that is fixed to the adjacent first insulating layer 2 and a non-fixed region B that is not fixed to the adjacent first insulating layer 2. The first wiring layer 4 is an internal wiring layer disposed between the two insulating layers 2 and 3.

  The second wiring layer 5 is disposed on the back side of the first insulating layer 2. The third wiring layer 6 is disposed on the surface side of the second insulating layer 3. Similar to the first wiring layer 4, the second wiring layer 5 and the third wiring layer 6 include a fixed region A that is fixed to the adjacent insulating layer and a non-fixed region B that is not fixed to the adjacent insulating layer. Have. Details of the fixed area A and the non-fixed area B will be described later.

<Connection conductor>
The plurality of connection conductors 7 are disposed in the through hole 2 </ b> A of the first insulating layer 2 and in the through hole 3 </ b> A of the second insulating layer 3. The connection conductor 7 is a so-called via that electrically connects the first wiring layer 4 and the second wiring layer 5 or the third wiring layer 6. The connection conductor 7 is joined to the first wiring layer 4 and the second wiring layer 5 or the third wiring layer 6.

  As shown in FIG. 2, the connection conductor 7 includes metal particles 7 </ b> A and a joint portion 7 </ b> B. Below, although the connection conductor 7 arrange | positioned in the through-hole 2A of the 1st insulating layer 2 is demonstrated, the following description is the same also about the connection conductor 7 arrange | positioned in the through-hole 3A of the 2nd insulating layer 3. It is.

  The particle body 7A is an aggregate of metal individual particles. The granule 7A is disposed in the through hole 2A. The granule 7A electrically connects the first wiring layer 4 and the second wiring layer 5 through the joint 7B.

  The material of the granule 7A is not particularly limited, and the same metal that can be used for the first wiring layer 4 and the second wiring layer 5 can be used. However, the material of the granule 7A is preferably the same as the main components of the first wiring layer 4 and the second wiring layer 5. Thereby, the stress which generate | occur | produces between the connection conductor 7 and the wiring layers 4 and 5 at the time of a temperature change can be reduced.

  The shape of each particle constituting the particle body 7A is not particularly limited, and may be a sphere, a polyhedron, or the like. Further, it is not necessary that all the grains have the same shape, and the grain body 7A may include grains having different sizes and shapes.

  The maximum width of the granular material 7A is, for example, ½ or less, preferably 1/10 or less of the diameter of the through hole 2A. Further, the lower limit of the maximum width of the granule 7A is, for example, 1/100 of the diameter of the through hole 2A.

  The granule 7A is held in the through hole 2A by the joint 7B. Within the through-hole 2A, the grains 7A may be in contact with each other. The granular body 7A may include a grain protruding from the joint 7B or a grain that comes into contact with the first wiring layer 4 or the second wiring layer 5.

  The joint portion 7B has conductivity, and electrically connects the granule 7A to the first wiring layer 4 and the second wiring layer 5. The joint portion 7B is made of, for example, a metal brazing material such as silver-copper alloy or a solder material such as tin-silver-copper alloy.

  As shown in FIG. 2, the joint portion 7 </ b> B is joined to the outer surface of each grain of the granule 7 </ b> A and to the first wiring layer 4 and the second wiring layer 5. That is, the joint portion 7B joins the particles 7A to the first wiring layer 4 and the second wiring layer 5.

  Further, the bonding portion 7B is not bonded to the first insulating layer 2. That is, the granular material 7A is not fixed to the inner wall of the first insulating layer 2 constituting the through hole 2A. Further, a gap exists between the connection conductor 7 and the inner wall of the first insulating layer 2 constituting the through hole 2A.

  In one connection conductor 7, the total volume of the granules 7A is smaller than the total volume of the joint 7B. Therefore, from the viewpoint of connection reliability, it is preferable that the particles 7A be dispersed in the joint 7B.

  The lower limit of the ratio of the total volume of the particles 7A to the volume of one connection conductor 7 (that is, the sum of the total volume of the particles 7A and the total volume of the joint 7B) is preferably 30%, more preferably 50%. preferable. On the other hand, the upper limit of the ratio is preferably 95% and more preferably 75%. When the said ratio is too small, there exists a possibility that the frame | skeleton of the connection conductor 7 may become small and formation of the connection conductor 7 may become difficult. On the other hand, if the ratio is too large, the bonding strength by the bonding portion 7B is lowered, and the connection reliability may be insufficient.

<Wiring layer fixing member>
As shown in FIG. 1, the plurality of wiring layer fixing members 9 are provided between the first wiring layer 4, the second wiring layer 5, or the third wiring layer 6 and the first insulating layer 2 or the second insulating layer 3. Each is arranged.

  The plurality of wiring layer fixing members 9 are made of, for example, a metal brazing material or a solder material similar to the joint portion 7B of the connection conductor 7. The first wiring layer 4 is fixed to the adjacent first insulating layer 2 and second insulating layer 3 by a plurality of wiring layer fixing members 9.

<Fixed area and non-fixed area>
As described above, each of the plurality of wiring layers 4, 5, 6 has the fixed region A and the non-fixed region B. In the present embodiment, the fixed area A and the non-fixed area B of each wiring layer 4, 5, 6 are arranged at the same position in plan view. Hereinafter, each region will be described using the first wiring layer 4, but the following description is the same for the other wiring layers.

  The fixed region A is a region where the first wiring layer 4 is fixed to the first insulating layer 2. Specifically, as shown in FIG. 1, in the first wiring layer 4, regions where a plurality of wiring layer fixing members 9 are joined constitute fixing regions A, respectively. The planar shape of the fixed region A is not particularly limited.

  A region where the plurality of wiring layer fixing members 9 are not joined is included in the non-fixed region B. In the present embodiment, since each connection conductor 7 is not bonded to each insulating layer 2, 3, the connection portion of each wiring layer 4, 5, 6 with the connection conductor 7 is included in the non-fixed region B.

  The maximum distance from the center of gravity of the fixed region A to the outer edge viewed from the thickness direction of the first wiring layer 4 is preferably 7 mm or less, and more preferably 5 mm or less. If the maximum distance is too large, cracks and breakage due to the difference in thermal expansion coefficient between the insulating layer and the wiring layer may occur in the first insulating layer 2 and the second insulating layer 3.

  Note that the “maximum distance from the center of gravity of the fixed region to the outer edge” is the length of the longest stretched line segment from the center of gravity of the fixed region to the outer edge of the fixed region (hereinafter also referred to as a stretched line segment). Means. When a non-fixed area is included in the fixed area (for example, when the fixed area is circular), first, a virtual center of gravity including the non-fixed area included in the fixed area is determined, and the above-described stretched line segment is obtained. To do. Next, the part which passes through a non-fixed area | region among the acquired said extending line segments is excluded from the length. That is, the length of the stretched line segment is the length of only the portion included in the fixed region.

  In the present embodiment, in the non-fixed region B, the wiring layers 4, 5, 6 are separated from the first insulating layer 2 or the second insulating layer 3, but the wiring layers 4, 5, 6 are The first insulating layer 2 or the second insulating layer 3 may be in contact. That is, in the non-fixed region B, as shown in each drawing, the wiring layer and the insulating layer may be in contact with each other as long as the wiring layer and the insulating layer can be individually displaced in the plane direction. .

[1-2. Wiring board manufacturing method]
Next, a method for manufacturing the wiring board 1 will be described.
The wiring substrate 1 is obtained by a manufacturing method including the through-hole forming step S1, the grain arranging step S2, the layer arranging step S3, and the joining step S4 shown in FIG.

<Through hole formation process>
In this step, a plurality of insulating layers are formed, and through holes that penetrate these insulating layers in the thickness direction are formed in these insulating layers.

  In this step, first, an unsintered ceramic is formed into a ceramic substrate. Specifically, first, ceramic powder, an organic binder, a solvent, and additives such as a plasticizer are mixed to obtain a slurry. Next, this slurry is formed into a sheet by a known method, whereby a substrate-like unsintered ceramic (so-called ceramic green sheet) is obtained.

  Through holes 2A and 3A are provided by drilling or the like in the obtained ceramic green sheet. Thereafter, the ceramic green sheet is sintered. Thereby, ceramic insulating layers 2 and 3 are formed.

<Granule arrangement process>
In this step, the granules 7A and the joints 7B are disposed in the through holes 2A and 3A. Specifically, for example, a paste prepared by mixing a particle 7A and a metal brazing material or solder material constituting the joint 7B with a solvent is disposed in each of the through holes 2A and 3A by a dispenser or the like. In addition, you may arrange | position the particle body 7A and the junction part 7B which were mutually joined shown in FIG. 2 in each through-hole 2A, 3A. Further, for each of the plurality of solid particles included in the particle 7A, the particle 7A having a surface coated with a joint 7B such as a metal brazing material may be disposed in each of the through holes 2A and 3A. .

<Layer arrangement process>
In this step, the insulating layers 2 and 3 on which the grains 7A and the joints 7B are arranged and the wiring layers 4, 5, and 6 are alternately overlapped.

  That is, in this step, the first wiring layer 4 is disposed on the front surface side of the first insulating layer 2, and the second wiring layer 5 is disposed on the back surface side of the first insulating layer 2. The second insulating layer 3 is disposed on the surface side of the first wiring layer 4, and the third wiring layer 6 is disposed on the surface side of the second insulating layer 3. Further, a plurality of wiring layer fixing members 9 are arranged between the layers.

  In addition, you may perform layer arrangement | positioning process S3 before the granule arrangement | positioning process S2. Moreover, you may perform granule arrangement | positioning process S2 and layer arrangement | positioning process S3 simultaneously. For example, after the second wiring layer 5 is disposed on the back surface side of the first insulating layer 2, the particles 7 </ b> A and the joint 7 </ b> B are disposed in the through hole 2 </ b> A. You may arrange | position on the surface side of.

<Joint process>
In this step, the bonding portion 7B is melted and solidified, and the particles 7A are bonded to the first wiring layer 4 and the second wiring layer 5.

  Specifically, the laminated body which laminated | stacked each layer obtained by layer arrangement | positioning process S3 is heated. Thereby, the connection conductor 7 is formed, and the plurality of insulating layers 2, 3 and the plurality of wiring layers 4, 5, 6 are joined by the wiring layer fixing member 9.

  The wiring layer fixing member 9 can be made of the same metal brazing material as that of the joint 7B. The wiring layer fixing member 9 and the insulating layers 2 and 3 can be fixed easily by forming a metallized layer (not shown) in a range that becomes the fixing region A of the insulating layers 2 and 3.

  Moreover, in the above-mentioned joining process, the joining part 7B is melted and solidified, but the inner wall of the insulating layer 2 constituting the through hole 2A and the granule 7A are not fixed by the joining part 7B. This is because the metal layer is not formed on the inner wall surface of the insulating layer 2 constituting the through-hole 2A, thereby preventing the joint portion 7B from spreading out.

[1-3. effect]
According to the embodiment detailed above, the following effects can be obtained.
(1a) By using the connection conductor 7 in which the metal particles 7A are bonded to the wiring layers 4, 5, and 6 by the bonding portion 7B, the particles 7A serve as a skeleton in the connection conductor 7, so that the connection conductor The generation of voids in 7 is suppressed. Further, since it is not necessary to form the connection conductor 7 simultaneously or separately with the insulating layer in a state where the connection conductor 7 is disposed in the through holes 2A and 3A in the insulating layers 2 and 3, the insulating layer 2 and 3 and the connection conductor 7 are restrained from the stress caused by the difference in thermal expansion coefficient, and the stress at the time of joining the joint 7B is also buffered by the granule 7A. Therefore, the occurrence of defects such as cracks and breakage in the insulating layers 2 and 3 is also suppressed. Therefore, it is easy to increase the diameter of the connection conductor 7, and the wiring board 1 can be provided as an excellent quality transformer corresponding to a high voltage and a large current.

  (1b) In the connection conductor 7, the total volume of the granules 7A is smaller than the total volume of the joint 7B. Therefore, the joining strength by the joining part 7B is increased, and the connection reliability of the connecting conductor 7 can be improved.

  (1c) Since the particles 7A are not fixed to the inner walls of the insulating layers 2 and 3 constituting the through holes 2A and 3A by the joint portion 7B, the connection conductor 7 including the particles 7A and the insulating layers 2 and 3 are Each can be displaced individually. Therefore, the generation of stress due to the difference in thermal expansion coefficient between the connection conductor 7 and the insulating layers 2 and 3 can be suppressed.

  (1e) Since the wiring layers 4, 5, and 6 have the non-fixed region B, the wiring layers 4, 5, and 6 are expanded when the wiring layers 4, 5, and 6 and the insulating layers 2 and 3 expand or contract due to temperature changes. The difference in deformation amount between the wiring layers 4, 5, 6 and the insulating layers 2 and 3 due to the difference in thermal expansion coefficient between the insulating layers 2 and 3 is absorbed by the non-fixed region B that is not fixed to the insulating layers 2 and 3. it can. Therefore, the stress generated between the insulating layers 2 and 3 and the wiring layers 4, 5 and 6 is reduced, and defects such as cracks in the insulating layers 2 and 3 are suppressed.

Therefore, for example, alumina (thermal expansion coefficient 7.6 × 10 ⁻⁶ m / K) is used as the main component of the insulating layer, and copper (thermal) having high electrical conductivity and high thermal conductivity as the main component of the wiring layer. An expansion coefficient of 17 × 10 ⁻⁶ m / K) can be used.

  (1f) Since the first insulating layer 2 and the second insulating layer 3 are mainly composed of ceramic, the flatness of the insulating layers 2 and 3 is improved. Therefore, wirings can be arranged at high density in each of the insulating layers 2 and 3. Furthermore, high insulation can also be obtained. Thereby, even when a relatively large current is passed through the wiring layers 4, 5, 6, reliable electrical insulation between the wiring layers 4, 5, 6 is possible.

[2. Second Embodiment]
[2-1. Wiring board]
4 includes a plurality of insulating layers (first insulating layer 2, second insulating layer 3, third insulating layer 22, fourth insulating layer 23, and fifth insulating layer 24) and a plurality of wirings. The layers (first wiring layer 4, second wiring layer 5, third wiring layer 6, fourth wiring layer 25, fifth wiring layer 26, and sixth wiring layer 27) and a plurality of wiring layers are electrically connected. A plurality of connecting conductors 7 and a plurality of insulating layer fixing members 10.

The plurality of insulating layers 2 and 3, the wiring layers 4, 5 and 6, and the plurality of connection conductors 7 are the same as those of the wiring substrate 1 of FIG.
The third insulating layer 22, the fourth insulating layer 23, and the fifth insulating layer 24 have the same configuration as the first insulating layer 2. The third insulating layer 22 is disposed on the surface side of the first insulating layer 2. The fourth insulating layer 23 and the fifth insulating layer 24 are arranged on the back surface side of the second insulating layer 3 in this order.

<Wiring layer>
The fourth wiring layer 25 is disposed between the fourth insulating layer 23 and the fifth insulating layer 24. The fifth wiring layer 26 is disposed on the surface side of the third insulating layer 22. The sixth wiring layer 27 is disposed on the back side of the fifth insulating layer 24.

  The fifth wiring layer 26 and the sixth wiring layer 27 include terminals 26A, 26B, 27A, and 27B that are electrically connected to the outside, respectively. These terminals 26A, 26B, 27A, 27B are entirely fixed to the insulating layer. These terminals 26A, 26B, 27A, and 27B have a relatively small area and may be bonded to the insulating layer because the stress caused by the difference in coefficient of thermal expansion is small even when the terminal 26A, 26B, 27A, and 27B are fixed to the insulating layer as a whole. However, since the terminals 26A, 26B, 27A, and 27B are only required to be connected to the wiring layer by the connection conductor 7, the terminal 26A, 26B, 27A, and 27B are fixed to the insulating layer because it is not necessary to consider the stress caused by the difference in thermal expansion coefficient. It is better not to.

  In the present embodiment, the first wiring layer 4, the second wiring layer 5, the third wiring layer 6, and the fourth wiring layer 25 are respectively connected to the main wiring layers 4A, 5A, 6A, and 25A, and the main wiring layer. 4A, 5A, 6A, 25A and sub-wiring layers 4B, 5B, 6B, 25B separated from each other.

  The main wiring layers 4A, 5A, 6A, and 25A are wiring layers on which wiring patterns such as coils are formed. Since the main wiring layers 4A, 5A, 6A, and 25A have a relatively large area, they have a non-fixed region B shown in FIG.

  The sub wiring layers 4B, 5B, 6B, and 25B are wiring layers for connecting the main wiring layers in the thickness direction. For example, the sub wiring layer 4B of the first wiring layer 4 electrically connects the main wiring layer 5A of the second wiring layer 5 and the main wiring layer 6A of the third wiring layer 6 via the connection conductor 7. Yes.

  Similar to the terminals 26A, 26B, 27A, and 27B, the sub-wiring layers 4B, 5B, 6B, and 25B have a relatively small area, and the maximum distance from the center of gravity to the outer edge in plan view is 7 mm or less. Therefore, the sub-wiring layers 4B, 5B, 6B, and 25B do not include the non-fixed region B, and the whole in a plan view may be fixed to the front-side or back-side insulating layer. In this case, the sub wiring layers 4B, 5B, 6B, and 25B include only the fixed region A.

<Insulating layer fixing member>
The insulating layer fixing member 10 is a member that joins and fixes adjacent insulating layers (for example, the first insulating layer 2 and the second insulating layer 3) in the thickness direction. The insulating layer fixing member 10 is disposed between the insulating layers. Each insulating layer fixing member 10 is disposed so as to surround the first wiring layer 4, the second wiring layer 5, the third wiring layer 6, or the fourth wiring layer 25 as viewed from the thickness direction.

Each insulating layer fixing member 10 has two metallized layers 10A and a joint portion 10B.
The two metallized layers 10A are arranged on the back surface of one insulating layer (for example, the first insulating layer 2) and the front surface of the other insulating layer (for example, the second insulating layer 3) of the two insulating layers to be joined. Yes.

The joint portion 10B is disposed between the two metallized layers 10A and joins the two metallized layers 10A in the thickness direction.
The material of the metallized layer 10A can be mainly composed of tungsten or molybdenum, for example. The material of the joint 10B can be the same as that of the joint 7B of the connection conductor 7.

  The plurality of insulating layer fixing members 10 may include an insulating layer fixing member 10 formed of a resin adhesive such as an epoxy resin or a silicone resin. Alternatively, the insulating layer fixing member 10 may be formed using a paste containing ceramic. When resin or ceramic is used, the metallized layer 10A may not be formed.

  Further, in order to seal and fix each insulating layer, in addition to the insulating layer fixing member 10 provided between the insulating layers, an insulating layer that collectively covers the side portions of the wiring board across the plurality of insulating layers A fixing member 10 may be provided. Further, instead of disposing the insulating layer fixing member 10 between the insulating layers, only the insulating layer fixing member 10 that covers the side portions of the wiring board across the plurality of insulating layers may be provided.

[2-2. effect]
According to the embodiment detailed above, the following effects can be obtained.
(2a) Since the plurality of wiring layers 4, 5, 6 and 25 are sealed by the plurality of insulating layer fixing members 10, the wiring layers 4, 5, 6 and 25 are oxidized and wiring layers are caused by moisture in the air. The short circuit is suppressed. As a result, the reliability of the wiring board 1 can be improved.

[3. Other Embodiments]
As mentioned above, although embodiment of this indication was described, it cannot be overemphasized that this indication can take various forms, without being limited to the above-mentioned embodiment.

  (3a) In the wiring substrate 1 of the above embodiment, the wiring layer fixing member 9 is not necessarily provided between the wiring layer and the insulating layer. That is, each wiring layer may have only the non-fixed region B without the fixed region A.

  (3b) In the wiring board 1 of the above embodiment, the fixed area A and the non-fixed area B of each wiring layer may be arranged at different positions in plan view. That is, the wiring layer fixing member 9 may be arranged at a different position in each layer.

  (3c) In the wiring substrate 1 of the above embodiment, the granular material 7A may be in contact with the inner walls of the insulating layers 2 and 3 constituting the through holes 2A and 3A. Moreover, the granular material 7A may be joined to the inner walls of the insulating layers 2 and 3 constituting the through holes 2A and 3A by the joint portion 7B.

  (3d) In the wiring boards 1 and 21 of the above embodiment, the total volume of the particles 7A in the connection conductor 7 may be larger than the total volume of the joint 7B.

  (3e) In the wiring boards 1 and 21 of the above embodiment, the material of each insulating layer is not limited to ceramic. For example, each insulating layer may contain resin, glass, or the like as a main component.

  (3f) In the wiring substrate 1 of the above embodiment, an adhesive may be used as the wiring layer fixing member 9. As the adhesive in this case, a resin adhesive such as an epoxy resin or a silicone resin can be selected.

  (3g) In the wiring substrate 21 of the above embodiment, the sub-wiring layers 4B, 5B, 6B, and 25B may have both the fixed area A and the non-fixed area B, respectively. Further, the sub wiring layers 4B, 5B, 6B, and 25B may have only the non-fixed region B.

  (3h) The wiring boards 1 and 21 of the above embodiment can form a planar transformer. That is, the first wiring layer and the second wiring layer may each have a coil-shaped wiring pattern at the outer edge of the insulating layer. Further, a core insertion hole penetrating the inside of the winding wiring pattern formed in a coil shape may be formed in the central portion of the insulating layer. For example, a magnetic core such as ferrite is inserted into the core insertion hole.

  (3i) In the wiring substrates 1 and 21 of the above embodiment, each insulating layer and each wiring layer are shown to have the same thickness, but the thickness of each insulating layer is different from the thickness of the wiring layer. May be. Further, the occupied area of each wiring layer may be different.

  (3j) The functions of one component in the above embodiment may be distributed as a plurality of components, or the functions of a plurality of components may be integrated into one component. Moreover, you may abbreviate | omit a part of structure of the said embodiment. In addition, at least a part of the configuration of the above embodiment may be added to or replaced with the configuration of the other embodiment. In addition, all the aspects included in the technical idea specified from the wording described in the claims are embodiments of the present disclosure.

DESCRIPTION OF SYMBOLS 1 ... Wiring board, 2 ... 1st insulating layer, 2A ... Through-hole, 3 ... 2nd insulating layer,
3A ... through hole, 4 ... first wiring layer, 4A ... main wiring layer, 4B ... sub wiring layer, 5 ... second wiring layer,
5A ... main wiring layer, 5B ... sub wiring layer, 6 ... third wiring layer, 6A ... main wiring layer,
6B ... Sub-wiring layer, 7 ... Connection conductor, 7A ... Granule, 7B ... Junction, 9 ... Wiring layer fixing member,
10 ... Insulating layer fixing member, 10A ... Metallized layer, 10B ... Joining part,
21 ... Wiring board, 22, 23, 24 ... Insulating layer, 25, 26, 27 ... Wiring layer,
25A ... main wiring layer, 25B ... sub wiring layer, 26A, 26B, 27A, 27B ... terminals.

Claims (9)

At least one insulating layer having a front surface and a back surface;
A first wiring layer disposed on a surface side of the at least one insulating layer;
A second wiring layer disposed on the back side of the insulating layer on which the first wiring layer is disposed;
A connection conductor for electrically connecting the first wiring layer and the second wiring layer;
With
The insulating layer has a through-hole penetrating the insulating layer in the thickness direction,
The connection conductor is
Metal particles disposed in the through hole; and
A bonding portion for bonding the particles, the first wiring layer and the second wiring layer;
Having a wiring board.   The wiring board according to claim 1, wherein in the connection conductor, a total volume of the particles is smaller than a total volume of the joint portion.   The wiring board according to claim 1, wherein the granules are not fixed to an inner wall of the insulating layer that constitutes the through hole.   2. The at least one of the first wiring layer and the second wiring layer has a non-fixed region that is not fixed to the adjacent insulating layer and a fixed region that is fixed to the adjacent insulating layer. The wiring board according to claim 3.   4. The wiring board according to claim 1, wherein the first wiring layer and the second wiring layer are not fixed to the adjacent insulating layer. 5.   The wiring board according to claim 1, wherein the first wiring layer and the second wiring layer are mainly composed of copper.   The wiring board according to claim 1, wherein a material of the grain is the same as a main component of the first wiring layer and the second wiring layer.   The wiring board according to claim 1, wherein the insulating layer is mainly composed of ceramic.   A planar transformer using the wiring board according to any one of claims 1 to 8.