JP2013026280A - Wiring board with built-in element, and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inexpensive wiring board with a built-in element having a novel structure where a functional element, e.g., MEMS or an SAW filter, is embedded in a wiring board consisting of at least a pair of wiring layers and an insulation layer interposed therebetween, without degrading the function of the functional surface.SOLUTION: The wiring board with a built-in element comprises a pair of first wiring layer and a second wiring layer arranged to face each other, an insulation layer interposed between the first and second wiring layers, a hollow formation member arranged in the insulation layer and mounted on the first wiring layer, and a functional element housed in the hollow formation member and mounted on the first wiring layer.

Description

  The present invention relates to an element-embedded wiring board having a built-in functional element such as a MEMS (Micro Electro Mechanical Systems) or a surface acoustic wave (SAW) filter, and a method for manufacturing the same.

  In recent years, electronic devices are required to have higher density and higher functionality in the trend toward higher performance and smaller size of electronic devices. From this point of view, even modules with circuit components are required to cope with higher density and higher functionality. In order to meet such demands, at present, a wiring board comprising at least a pair of wiring layers and an insulating layer disposed between the pair of wiring layers is formed, and an electronic component such as a semiconductor component constituting the circuit component is formed. A component built-in wiring board in which components are embedded in an insulating layer of a wiring board and electrically connected to at least one of a pair of wiring layers has been developed and put into practical use.

  However, in the case of a functional element configured such that the element surface is driven (functional surface), such as a MEMS or SAW filter, the functional surface contacts the insulating layer when embedded in the insulating layer of the wiring board as described above. As a result, the function cannot be fully achieved. Therefore, when such a functional element is disposed in the wiring board, a hollow portion is formed in the insulating layer, and the functional element is disposed in the hollow portion so that the functional surface thereof is an insulating layer. The structure which is not directly contacted is adopted (for example, refer to Patent Documents 1 and 2).

  On the other hand, in the technique described in Patent Document 1, since the hollow portion is directly formed in the insulating layer constituting the wiring board, the insulating layer is constituted in the heating and pressing step when manufacturing the wiring board. In some cases, the resin melts and a part of the melted resin comes into contact with the functional surface of the functional element embedded in the insulating layer through the hollow portion, so that the functional element does not function sufficiently. .

  Further, in the technique described in Patent Document 2, a metal film or the like is formed on the inner wall surface of the hollow portion formed in the insulating layer of the wiring board. When the insulating layer is melted in the pressurizing process, the resin constituting the insulating layer causes a displacement of the metal film or the like, and the molten resin flows into the hollow portion as a result of the gap formed. However, the functional element may adhere to the functional surface of the functional element and the functional element may not function sufficiently.

  Further, since the metal film is formed by a sputtering method, the metal film loses its denseness, and the above-described phenomenon occurs remarkably, and moisture absorbed by the insulating layer diffuses into the hollow portion over time, and the functional element There is also a problem that the functional surface is oxidized and corroded, and the function of the functional element deteriorates with time.

International Publication No. 2010/095210 JP 2004-179573 A

  The present invention is a state in which a functional element such as a MEMS or SAW filter does not deteriorate the function of its functional surface in a wiring board comprising at least a pair of wiring layers and an insulating layer disposed between the pair of wiring layers. An object of the present invention is to provide an element-embedded wiring board having a novel structure embedded at a low cost.

In order to achieve the above object, the present invention provides:
A pair of first and second wiring layers disposed opposite to each other;
An insulating layer disposed between the first wiring layer and the second wiring layer;
A hollow forming member disposed in the insulating layer and mounted on the first wiring layer;
A functional element housed in the hollow forming member and mounted on the first wiring layer;
It is related with the wiring board with a built-in element characterized by comprising.

The present invention also provides:
A step of forming a first wiring board in which a functional element is mounted on the first wiring layer and a hollow forming member is mounted so as to accommodate the functional element;
Forming a second wiring board in which a second wiring layer is formed on an insulating layer in which an opening for accommodating the hollow forming member is formed;
Laminating the first wiring board and the second wiring board so that the hollow forming member is accommodated in the opening;
Fluidizing the insulating layer by heating and pressurizing the laminated first wiring substrate and the second wiring substrate, and embedding the hollow forming member in the insulating layer;
It is related with the manufacturing method of the wiring board with a built-in element characterized by comprising.

  According to the present invention, in a wiring board including a pair of first wiring layer and second wiring layer, and an insulating layer disposed between these wiring layers, the first hollow forming component is previously placed in the insulating layer. An element-embedded wiring board is formed so as to be mounted on the wiring layer and mounted on the first wiring layer in a state where the target functional element is accommodated in the hollow forming component.

  Therefore, after the first wiring board and the second wiring board, which are constituent elements of the element-embedded wiring board, are stacked, when the target element-embedded wiring board is manufactured by heating and pressing, When the insulating layer member of the second wiring board, specifically, the insulating layer, specifically, the resin containing reinforcing fibers such as glass fiber is melted and fluidized, is formed. However, the resin does not enter the hollow forming part. As a result, it is possible to prevent the resin, that is, the insulating layer from adhering to the functional surface of the functional element, and to suppress the function of the functional element from being hindered.

  In addition, since the adhesion of the insulating layer to the functional surface of the functional element can be suppressed by a simple operation of mounting the hollow forming part in advance, a metal film or the like is formed by a sputtering method as in the past. Compared to the above, it is possible to suppress the functional deterioration of the functional element at an extremely low cost.

  Further, it is possible to effectively suppress the functional deterioration of the functional element over time due to the oxidative corrosion of the functional surface due to the moisture absorption moisture of the insulating layer that could not be sufficiently suppressed by forming the metal film or the like.

  The “functional element” in the present invention means an element having a so-called functional surface, and examples thereof include, but are not limited to, an element such as a MEMS, SAW filter, or imaging element.

  As described above, according to the present invention, a functional element such as a MEMS or a SAW filter is provided on a functional board in a wiring board including at least a pair of wiring layers and an insulating layer disposed between the pair of wiring layers. It is possible to provide an element-embedded wiring board having a novel structure embedded at a low cost without deteriorating the structure.

It is sectional drawing which shows schematic structure of the wiring board with a built-in element of 1st Embodiment. It is a figure which shows the modification of the hollow formation components of the element built-in wiring board shown in FIG. It is a figure which expands and shows the vicinity of the connection part of the hollow formation components shown in FIG. It is a figure which expands and shows the vicinity of the connection part of the hollow formation components shown in FIG. It is a figure which expands and shows the vicinity of the connection part of the hollow formation components shown in FIG. It is sectional drawing which shows schematic structure of the wiring board with a built-in element of 2nd Embodiment. It is sectional drawing which shows schematic structure of the wiring board with a built-in element of 3rd Embodiment. It is a figure which shows the process drawing in the manufacturing method of the element built-in wiring board of embodiment. Similarly, it is a figure which shows the process figure in the manufacturing method of the element built-in wiring board of embodiment. Similarly, it is a figure which shows the process figure in the manufacturing method of the element built-in wiring board of embodiment. Similarly, it is a figure which shows the process figure in the manufacturing method of the element built-in wiring board of embodiment. Similarly, it is a figure which shows the process figure in the manufacturing method of the element built-in wiring board of embodiment.

  Hereinafter, other features and advantages of the present invention will be described based on embodiments for carrying out the invention.

(First embodiment)
FIG. 1 is a cross-sectional view showing a schematic configuration of the element built-in wiring board of the present embodiment.
As shown in FIG. 1, the element built-in wiring board 10 of the present embodiment has a first wiring layer 11 and a second wiring layer 12, and a first insulating layer 21 is disposed between them. Yes. A box-shaped hollow forming component 41 is disposed in the first insulating layer 21, and the hollow forming component 41 is mounted on the first wiring layer 11. In addition, the functional element 42 is accommodated in the hollow forming component 41 and mounted on the first wiring layer 11. The functional element 42 is electrically connected to the first wiring layer 11 by a wire 43.

  Further, on the outside of the hollow forming component 41, a third insulating layer 21 is electrically insulated between the first wiring layer 11 and the second wiring layer 12 so as to be electrically insulated from the third wiring layer 12. The wiring layer 13 and the fourth wiring layer 14 are provided. Further, a fifth wiring layer 15 is disposed outside (downward) the first wiring layer 11 via a second insulating layer 22, and outside the second wiring layer 12 ( A sixth insulating layer 16 is disposed above the third insulating layer 23 with the third insulating layer 23 interposed therebetween.

  Note that the first wiring layer 11 and the third wiring layer 13 are electrically connected by the first interlayer connector 31, and the third wiring layer 13 and the fourth wiring layer 14 are the second interlayer. The fourth wiring layer 14 and the second wiring layer 12 are electrically connected by a third interlayer connection body 33. The first wiring layer 11 and the fifth wiring layer 15 are electrically connected by the fourth interlayer connector 34, and the second wiring layer 12 and the sixth wiring layer 16 are the fifth interlayer. The connection body 35 is electrically connected. Therefore, the element built-in wiring board 10 of this embodiment constitutes a so-called multilayer wiring board.

  The first wiring layer 11 to the sixth wiring layer 16 may be configured as a wiring pattern by performing predetermined patterning as necessary, or may be configured as a solid pattern.

  Examples of the functional element 42 include, but are not limited to, an element such as a MEMS, SAW filter, or image pickup element.

  In the element built-in wiring board 10 of the present embodiment, the functional element 42 is mounted on the first wiring layer 11 in a state of being accommodated in the hollow forming component 41. Therefore, when the first insulating layer 21 disposed between the first wiring layer 11 and the second wiring layer 12 is formed, a predetermined insulating layer to be the first insulating layer 21, specifically Even when a resin containing reinforcing fibers such as glass fibers is melted and fluidized, which constitutes the insulating layer, the resin does not enter the hollow forming part 41.

  As a result, it is possible to prevent the resin, that is, the insulating layer from adhering to the functional surface 42 </ b> A of the functional element 42, and to suppress the function of the functional element 42 from being inhibited.

  That is, the hollow forming component 41 is provided in advance in the first insulating layer 21 disposed between the first wiring layer 11 and the second wiring layer 12 so as to be mounted on the first wiring layer 11. The functional element 42 is mounted on the first wiring layer 11 while being accommodated in the hollow forming component 41, and the functional surface 42 </ b> A of the functional element 42 is formed on the functional surface 42 </ b> A of the first insulating layer 21 with only a very simple configuration and operation. It is possible to suppress the adhesion of the part, and it is possible to suppress the functional inhibition of the functional element 42.

  Moreover, since it is possible to suppress moisture absorption moisture of the first insulating layer 21 from flowing into the hollow forming component 41, it is possible to suppress oxidative corrosion due to moisture adhering to the functional surface 42A of the functional element 42, It is also possible to suppress functional deterioration of the functional element 42 over time.

  The hollow forming component 41 may be made of a heat-resistant plastic such as polyethersulfone (PES), polyetheretherketone (PEEK), polyamideimide (PAI), polyimide (PI), and polyphenylene sulfide (PPS). it can. Moreover, it can also be comprised from highly conductive metal materials, such as copper and aluminum, for example.

  As in the latter case, when the hollow forming component 41 is made of a highly conductive metal material, moisture absorption in the first insulating layer 21 flows into the hollow forming component 41 as compared with a case where the hollow forming component 41 is made of a heat-resistant plastic. Therefore, it is possible to more effectively suppress the functional deterioration of the functional element 42 over time.

  Further, since the hollow forming component 41 has an electromagnetic wave shielding property, the functionality accommodated in the hollow forming component 41 of the electromagnetic waves flowing from the outside of the hollow forming component 41, that is, from the outside of the element built-in wiring board 10. The influence on the element 42 can be suppressed, and electromagnetic waves emitted from the functional element 42 can be prevented from leaking to the outside of the element built-in wiring board 10 and adversely affecting the external environment.

  Note that the above-described effect by configuring the hollow forming component 41 from a metal material is, for example, after the hollow forming component 41 is configured from a heat-resistant plastic, on the outside or inside thereof, a metal member made of the metal material, so-called film It can also be achieved by forming a body. Furthermore, it can be achieved by adding a scaly metal filler in a high proportion to the heat-resistant plastic.

  For mounting the hollow forming component 41, for example, a thermosetting resin-based adhesive may be provided at the connection portion 41A to be joined. Since the adhesive bonding temperature of such an adhesive is about 150 degrees, the use of such an adhesive can reduce the thermal load on the functional element 42 accommodated in the hollow forming component 41.

  Further, the mounting of the hollow forming component 41 can be performed by arranging solder in the connecting portion 41A and reflowing the solder. In general, since the functional element 42 is mounted on the first wiring layer 11 using solder, the hollow forming component 41 and the functional element 42 are mounted by mounting the hollow forming component 41 using solder. This can be performed in a lump, and the manufacturing process of the element built-in wiring board 10 can be simplified.

  The adhesive and solder are generally disposed on the first wiring layer 11 on the mounting side, but the disposition shape thereof matches the outer diameter shape of the connection portion 41A of the hollow forming component 41. To do so.

  FIG. 2 is a view showing a modification of the hollow forming component 41, and FIGS. 3 to 5 are enlarged views showing the vicinity of the connecting portion 41A of the hollow forming component 41 shown in FIG.

  In FIG. 1, the connecting portion 41 </ b> A of the hollow forming component 41 is configured as a tip portion of the side wall of the hollow forming component 41, so that the area in contact with the adhesive and the solder is the outer periphery of the side wall due to its thickness. It is the difference between the area and the inner peripheral area. However, in FIG. 2, since the connecting portion 41A is formed in a bowl shape, the substantial thickness of the connecting portion 41A has increased, and the contact area with the adhesive or solder 41B as shown in FIG. Will improve. Therefore, the hollow forming component 41 can be firmly mounted on the first wiring layer 11.

  Further, the hook-shaped connecting portion 41A of the hollow forming component 41 can be corrugated as shown in FIG. In this case, since the substantial contact area between the connecting portion 41A and the adhesive or solder 41B can be further improved as compared with the case shown in FIG. 3, the first wiring layer 11 of the hollow forming component 41 is further improved. Can be implemented more firmly.

  Furthermore, the hook-shaped connecting portion 41A of the hollow forming component 41 can be formed in an R shape that is convex inward as shown in FIG. Also in this case, the contact area between the connection portion 41A and the adhesive or solder 41B can be increased, and the hollow forming component 41 can be firmly mounted on the first wiring layer 11.

  Further, the melted insulating layer does not flow into the contact portion between the connecting portion 41A and the adhesive or solder 41B, but flows into the concave portion of the R-shaped hook-shaped connecting portion 41A. Therefore, it is possible to more effectively suppress the molten insulating layer from flowing into the hollow forming component 41 when the element-embedded wiring substrate 10 is manufactured, and to the functional surface 42A of the functional element 42 accommodated therein. The adhesion of the insulating layer can be more completely suppressed, and the functional failure of the functional element 42 can be suppressed.

(Second Embodiment)
FIG. 6 is a cross-sectional view showing a schematic configuration of the element built-in wiring board of the present embodiment. Note that the same reference numerals are used for the same or similar components as those shown in FIGS. 1 to 5 regarding the first embodiment.

  In the element built-in wiring board 50 of the present embodiment, in addition to the functional element 42, the passive element 45 and the active element 46 are accommodated in the hollow forming component 41 mounted on the first wiring layer 11, and the first wiring It differs in that it is mounted on the layer 11. In addition, although the passive element 45 and the active element 46 of this embodiment are flip-chip mounted with respect to the 1st wiring layer 11, the mounting method is not limited to these. Further, as the passive element 45, a resistor or a capacitor can be exemplified, and as the active element 46, an IC chip or the like can be exemplified.

  Since the passive element 45 and the active element 46 do not have a functional surface exposed to the outside like the functional element 42, the function of these elements is hindered even when a molten insulating layer is in contact with these elements. There is no. However, as described in the first embodiment, by forming the hollow forming component 41 from a metal material or adding a film body made of a metal material, the hollow forming component 41 has an electromagnetic shielding property. become.

  Therefore, in such a case, as shown in FIG. 6, the passive element 45 and the active element 46 are accommodated in the hollow forming component 41, so that the passive electromagnetic wave flowing from the outside of the element built-in wiring board 50 is passive. The adverse effect on the element 45 and the active element 46 can be suppressed, and the electromagnetic waves generated by these elements can be prevented from leaking outside the element-embedded wiring substrate 50 and adversely affecting the external environment.

  Further, since the mounting area of the element built-in wiring board 50 can be reduced by incorporating the passive element 45 and the active element 46, the element built-in wiring board 50 can be further downsized.

  Other features and operational effects are the same as those in the first embodiment, and a description thereof will be omitted.

  However, by using a thermosetting resin-based adhesive when mounting the hollow forming component 41, not only the functional element 42 accommodated in the hollow forming component 41 but also the passive element 45 and the active element 46 are subjected to a thermal load. Can be reduced. Further, by using solder, not only the hollow forming component 41 and the functional element 42 but also the passive component 45 and the active element 46 can be mounted together.

(Third embodiment)
FIG. 7 is a cross-sectional view showing a schematic configuration of the element built-in wiring board of the present embodiment. It should be noted that the same reference numerals are used for the components similar or identical to the components shown in FIGS. 1 to 5 relating to the first embodiment and FIG.

  The element built-in wiring board 60 of the present embodiment is shown in the second embodiment in that the hollow forming component 41 has a curved surface in which a portion excluding the connection portion 41A from the box shape has a continuous curved surface. Unlike the element-embedded wiring board 50, the rest is configured in the same manner as the element-embedded wiring board 50 in the second embodiment.

  In the element-embedded wiring board 60 of the present embodiment, the hollow forming component 41 disposed in the first insulating layer 21 does not have an edge portion. Therefore, when the wiring board 60 is manufactured, the first insulation is provided. Even when the insulating layer that constitutes the layer 21, that is, when a resin containing reinforcing fibers such as glass fibers is melted and fluidized as necessary, the resin may concentrate stress on the edge portion of the hollow forming component 41. Absent. Therefore, since the substantial mechanical strength of the hollow molded part 41 is improved, it is possible to avoid the hollow molded part 41 from being damaged by the pressing force due to the flow of the resin.

  Other features and effects are the same as in the second embodiment, and a description thereof will be omitted.

  In this embodiment, the hollow forming component 41 of the element built-in wiring board 50 in the second embodiment is formed in a spherical shape as described above, but the hollow in the element built-in wiring board 10 in the first embodiment is formed. The forming component 41 may be spherical as described above.

(Fourth embodiment)
Next, a method for manufacturing the element built-in wiring board 10 according to the first embodiment will be described. 8-12 is a figure which shows the process drawing in the manufacturing method of this embodiment.

  First, as shown in FIG. 8, the first wiring layer 11 and the fifth wiring layer 15 are formed on both main surfaces of the second insulating layer 22, and the fourth wiring layer penetrating the second insulating layer 22 is formed. A double-sided board that is electrically connected by the interlayer connector 34 is prepared. Next, the functional element 42 is mounted on the first wiring layer 11 of the double-sided board. Next, the hollow forming member 41 is mounted on the first wiring layer 11 so as to accommodate the functional element 42 to form a lower wiring board (first wiring board).

  The hollow forming member 41 is mounted using a thermosetting resin-based adhesive or solder as described above.

  The mounting of the hollow forming member 41 on the first wiring layer 11 is preferably performed in an inert gas atmosphere. Thereby, it is possible to suppress deterioration of functionality due to oxidation or the like of the functional element 42 accommodated in the hollow forming member 41.

  Next, as shown in FIG. 9, the second wiring layer 12 and the sixth wiring layer 16 are formed on both main surfaces of the third insulating layer 23, and are electrically connected by the fifth interlayer connector 35. After forming the wiring board so as to be connected, an insulating layer member that becomes the first insulating layer 21 by performing a heating and pressing step described later on this wiring board, that is, the second wiring layer 12 21P is disposed. Further, the third interlayer connector 33 is formed so as to penetrate the insulating layer member 21P, and the upper wiring board is formed.

  Next, as shown in FIG. 10, the third wiring layer 13 and the fourth wiring layer 14 are similarly formed on both main surfaces of the insulating layer member 21 </ b> P, and are electrically connected by the third interlayer connector 33. After the formed wiring board is formed, the insulating layer member 21P is similarly disposed on the wiring board, that is, the third wiring layer 13, and the first interlayer connection is formed so as to penetrate the insulating layer member 21P. The body 31 is formed, and the intermediate wiring board is formed. An opening 41O for accommodating the hollow forming component 41 is formed at the center of the intermediate wiring board.

  The opening 41O can be formed by, for example, laser processing after the intermediate wiring board is manufactured as described above, or the above-described lamination using the insulating layer member 21P in which the opening 41O is formed in advance. It is also possible to make a body and use the intermediate wiring board.

  The stacked body of the upper wiring board shown in FIG. 9 and the intermediate wiring board shown in FIG. 10 constitutes a second wiring board. However, in this embodiment, since the element-embedded wiring board 10 is configured as a multilayer wiring board, from the viewpoint of simplifying the manufacturing process, as described above, the third wiring layer 13 and the second wiring layer 13 constituting the multilayer wiring board are used. The laminated body including the four wiring layers 14 is separately formed as an intermediate wiring board and separated from the upper wiring board including the second wiring layer 12.

  Further, in the present embodiment, the opening 41O is provided only in the intermediate wiring board by providing the intermediate wiring board, but a part of the upper wiring board, that is, the second wiring layer 12 is left. It can also be formed in a state.

  Next, as shown in FIG. 11, the hollow wiring member 41 mounted on the lower wiring board includes the lower wiring board shown in FIG. 8, the intermediate wiring board shown in FIG. 9, and the upper wiring board shown in FIG. 10. While being accommodated in the formed opening 41O, they are stacked while being aligned with each other.

  Next, as shown in FIG. 12, the laminated body of the obtained wiring board is heated and pressed from above and below to melt the insulating layer member 21P in the intermediate wiring board and the insulating layer member 21P in the upper wiring board. By flowing, the gap between the opening 41O and the hollow forming component 41 is embedded, and the upper wiring board, the intermediate wiring board, and the lower wiring board are closely fixed to each other to obtain the target element built-in wiring board 10.

  The present invention has been described in detail based on the above specific examples. However, the present invention is not limited to the above specific examples, and various modifications and changes can be made without departing from the scope of the present invention.

  For example, in the above-described embodiment, the element-embedded wiring board is configured as a multilayer wiring board having six wiring layers, but the number of wiring layers can be any number as necessary.

  In addition, the element-embedded wiring board does not necessarily have to be formed in a multilayer wiring board configuration, and includes the first wiring layer 11 and the second wiring layer 12, and the first insulating layer disposed between these wiring layers. A single-layer wiring board can also be obtained.

10, 50, 60 Element-embedded wiring board 11 First wiring layer 12 Second wiring layer 13 Third wiring layer 14 Fourth wiring layer 15 Fifth wiring layer 16 Sixth wiring layer 21 First insulation Layer 21P 1st insulating layer member 22 2nd insulating layer 23 3rd insulating layer 31 1st interlayer connection body 32 2nd interlayer connection body 33 3rd interlayer connection body 34 4th interlayer connection body 35 4th Interlayer connection body 5 41 Hollow forming component 42 Functional element 43 Wire 45 Passive component 46 Active component

Claims (8)

A pair of first and second wiring layers disposed opposite to each other;
An insulating layer disposed between the first wiring layer and the second wiring layer;
A hollow forming member disposed in the insulating layer and mounted on the first wiring layer;
A functional element housed in the hollow forming member and mounted on the first wiring layer;
A circuit board with a built-in element, comprising:   The element built-in wiring board according to claim 1, wherein the hollow forming member is mounted on the first wiring layer via a thermosetting resin adhesive.   The element built-in wiring board according to claim 1, wherein the hollow forming member is mounted on the first wiring layer via solder.   The element-embedded wiring board according to claim 1, wherein the hollow forming member includes a metal material or a metal member.   5. The element built-in wiring board according to claim 1, wherein the hollow forming member is formed in a spherical shape having a continuous curved surface of a non-mounting portion.   The element according to claim 1, comprising at least one of an active element and a passive element housed in the hollow forming member and mounted on the first wiring layer. Built-in wiring board. A step of forming a first wiring board in which a functional element is mounted on the first wiring layer and a hollow forming member is mounted so as to accommodate the functional element;
Forming a second wiring board in which a second wiring layer is formed on an insulating layer member in which an opening for accommodating the hollow forming member is formed;
Laminating the first wiring board and the second wiring board so that the hollow forming member is accommodated in the opening;
Insulating layer formed by fluidizing and solidifying the hollow forming member by fluidizing and solidifying the hollow forming member by heating and pressurizing the laminated first wiring board and the second wiring board. A process of embedding in,
A method for manufacturing a wiring board with a built-in element, comprising:   The element built-in wiring according to claim 7, wherein when forming the first wiring board, the hollow forming member is mounted on the first wiring layer in an inert gas atmosphere. A method for manufacturing a substrate.

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