JP2012209383A - Multilayer substrate and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maintain flexibility of a flexible part of a multilayer substrate even when the number of insulation layers of the flexible part increases.SOLUTION: A multilayer substrate 102 includes: a rigid part 51 including a plurality of stacked insulation layers 2; and a flexible part 52 which extends sideways from the rigid part 51 by extending insulating layers 2 of a first group 8 as some of the plurality of insulation layers 2 included in the rigid part 51. The flexible part 52 is flexible as compared with the rigid part 51. The flexible part 52 has a gap 9 inside. The flexible part 52 has a first surface 21 as an inside surface and a second surface 22 as an outside surface by being bent during use. The gap 9 is so arranged as to have larger occupation cubic volume on the side of the first surface 21 with respect to a center surface 23 than on the side of the second surface 22 with respect to the center surface 23.

Description

  The present invention relates to a multilayer substrate and a manufacturing method thereof.

  An example of a multilayer substrate formed by laminating a plurality of insulating layers in which conductor patterns are appropriately arranged is described in Japanese Patent Application Laid-Open No. 8-330683 (Patent Document 1). The printed wiring board shown in this document includes a portion called a first substrate and a second substrate that keeps a hard and flat surface, a portion that connects between the first and second substrates, and a portion that can be bent freely. Is provided.

  A portion that is hard and maintains flatness is called a “rigid portion”, and a portion that can be bent freely is called a “flexible portion”.

  In order to produce a multilayer substrate having both a rigid part and a flexible part by laminating a plurality of insulating layers, the number of insulating layers to be laminated is set to be large for the rigid part and set to be small for the flexible part. Done. An example of such a multilayer substrate is shown in FIG. The multilayer substrate 901 includes both the rigid part 51 and the flexible part 52.

JP-A-8-330683

  In the multilayer substrate 901 shown in FIG. 20, the flexible portion 52 has a thickness corresponding to two layers of the insulating layer 2. On the other hand, when the thickness of each insulating layer is sufficiently thin, a large number of insulating layers are laminated also in the flexible portion 52, for example, like a multilayer substrate 902 shown in FIG.

  On the other hand, when the number of insulating layers of the flexible part increases, the flexibility of the flexible part is lost.

  Therefore, an object of the present invention is to provide a multilayer substrate that can maintain the flexibility of the flexible portion even when the number of insulating layers of the flexible portion is increased, and a method for manufacturing the same.

  To achieve the above object, a multilayer substrate according to the present invention includes a rigid portion including a plurality of stacked insulating layers, and a first group of insulating layers that are a part of the plurality of insulating layers included in the rigid portion. A flexible portion extending laterally from the rigid portion by extending the flexible portion, the flexible portion has a gap inside, and the flexible portion is an inner surface by being bent during use. A first surface and a second surface that is an outer surface, and the void occupies a volume occupied by the void on the first surface side from a center surface in the thickness direction of the flexible portion, It arrange | positions so that it may become larger than the volume which occupies in the said 2nd surface side from the center surface of the thickness direction of a flexible part. By adopting this configuration, since there is a gap inside the flexible part, the flexibility of the flexible part can be maintained even if the number of insulating layers in the flexible part increases. In addition, since a large number of voids are arranged on the side that is compressed when bent, the flexibility of the flexible portion can be maintained even if the number of insulating layers of the flexible portion increases. .

  Preferably, in the above invention, the void is a set of a plurality of void elements. By adopting this configuration, it is possible to disperse the part where the voids function in bending in a wide range, so that smoother and uniform bending can be obtained.

  In the present invention, preferably, the plurality of void elements are arranged such that the number of void elements arranged on the first surface side from the central surface in the thickness direction of the flexible portion is the second above the central surface in the thickness direction of the flexible portion. It arrange | positions so that it may become more than the number of the space | gap elements arrange | positioned at the surface side. By adopting this configuration, it becomes easy to provide a difference in the volume of the gap between the first surface side and the second surface side from the center surface.

  Preferably, in the above invention, the gap is arranged only on the first surface side from the center plane in the thickness direction inside the flexible portion. By adopting this configuration, since all of the voids are arranged on the side where compression occurs when bent, flexibility can be efficiently exhibited.

  Preferably, in the above invention, the gap is provided so as to straddle two or more insulating layers in the thickness direction. By adopting this configuration, it is possible to ensure a large volume of voids or void elements while only occupying a small area in plan view.

  Preferably, in the above invention, the gap has an upper base and a lower base, and at least a part of an outer edge of at least one of the upper base and the lower base is covered with a conductor pattern straddling the inner and outer sides of the outer edge. ing. By adopting this configuration, the covered portion can be prevented from cracking in the insulating layer with the outer edge as a base point during bending.

  Preferably, in the above invention, the gap has an upper base and a lower base, and the entire circumference of at least one outer edge of the upper base and the lower base is covered with a conductor pattern that extends inside and outside of the outer edge. . By adopting this configuration, it is possible to more surely prevent the insulating layer from being cracked from the outer edge as a base point at the time of bending at the bottom.

  In order to achieve the above object, a manufacturing method of a multilayer substrate according to the present invention is a method for manufacturing any one of the above-mentioned multilayer substrates, wherein the rigid portion planned region which is a region to be the rigid portion and the above Preparing a plurality of insulator sheets including a first group of insulator sheets having a flexible portion planned area that is an area to be a flexible part; and at least a part of the first group of insulator sheets Forming a hole to be at least a part of the gap in the flexible region, laminating the plurality of insulator sheets, and crimping the laminated insulator sheets. By adopting this method, it is possible to obtain a multilayer substrate having voids inside the flexible part. The multilayer substrate manufactured in this way has a gap inside the flexible part, so that the flexibility of the flexible part can be maintained even if the number of insulating layers in the flexible part increases.

It is sectional drawing of the multilayer substrate in Embodiment 1 based on this invention. It is sectional drawing of the modification of the multilayer substrate in Embodiment 1 based on this invention. It is sectional drawing of the multilayer substrate in Embodiment 2 based on this invention. It is sectional drawing of the modification of the multilayer substrate in Embodiment 2 based on this invention. It is sectional drawing of the multilayer substrate in Embodiment 3 based on this invention. It is sectional drawing of the multilayer substrate in Embodiment 4 based on this invention. It is sectional drawing of the multilayer substrate in Embodiment 5 based on this invention. It is the elements on larger scale of the multilayer substrate in Embodiment 5 based on this invention. It is sectional drawing of the 1st modification of the multilayer substrate in Embodiment 5 based on this invention. It is sectional drawing of the 2nd modification of the multilayer substrate in Embodiment 5 based on this invention. It is sectional drawing of the 3rd modification of the multilayer substrate in Embodiment 5 based on this invention. It is a flowchart of the manufacturing method of the multilayer substrate in Embodiment 6 based on this invention. It is explanatory drawing of the 1st process of the manufacturing method of the multilayer substrate in Embodiment 6 based on this invention. It is explanatory drawing of the 2nd process of the manufacturing method of the multilayer substrate in Embodiment 6 based on this invention. It is explanatory drawing of the 3rd process of the manufacturing method of the multilayer substrate in Embodiment 6 based on this invention. It is explanatory drawing of the 4th process of the manufacturing method of the multilayer substrate in Embodiment 6 based on this invention. It is explanatory drawing of the 5th process of the manufacturing method of the multilayer substrate in Embodiment 6 based on this invention. It is explanatory drawing of the 6th process of the manufacturing method of the multilayer substrate in Embodiment 6 based on this invention. It is explanatory drawing of the 7th process of the manufacturing method of the multilayer substrate in Embodiment 6 based on this invention. It is sectional drawing of the 1st example of the multilayer substrate based on a prior art. It is sectional drawing of the 2nd example of the multilayer substrate based on a prior art.

(Embodiment 1)
(Constitution)
With reference to FIG. 1, the multilayer substrate in Embodiment 1 based on this invention is demonstrated. In the multilayer substrate 101 according to the present embodiment, a rigid portion 51 including a plurality of stacked insulating layers and a first group 8 insulating layer 2 which is a part of the plurality of insulating layers included in the rigid portion 51 extend. And a flexible portion 52 that extends laterally from the rigid portion 51. The flexible part 52 is more flexible than the rigid part 51. This is because the flexible portion 52 has a smaller number of insulating layers than the rigid portion 51. The multilayer substrate 101 has a gap 9 inside the flexible portion 52.

(Action / Effect)
Since the multilayer substrate 101 in the present embodiment has the gap 9 inside the flexible portion 52, the flexibility of the flexible portion can be maintained even if the number of insulating layers of the flexible portion increases.

  In the example shown in FIG. 1, the gap 9 having a thickness corresponding to one layer is arranged, but the size of the gap 9 is not limited to this. For example, like the multilayer substrate 101e shown in FIG. 2, the gap 9 may have a size extending over a plurality of layers. In the example shown in FIG. 1 and FIG. 2, the gap 9 is arranged at the center in the thickness direction of the flexible portion 52, but may be arranged on either side of the thickness direction. In the example shown in FIGS. 1 and 2, the gap 9 is located at the center in the longitudinal direction, but may be arranged to be biased to either side in the longitudinal direction.

  The material of the insulating layer 2 may be, for example, a thermoplastic resin, but may be other types of resin, and may be other than a resin as long as it is an insulating material. The same applies to the following embodiments.

  In the present embodiment, the gap 9 has been described as a single one, but the gap 9 is preferably a set of a plurality of gap elements. That is, the gap 9 is preferably divided into a plurality of gap elements. This will be described in detail in the second and subsequent embodiments.

(Embodiment 2)
(Constitution)
With reference to FIG. 3, the multilayer substrate in Embodiment 2 based on this invention is demonstrated. It is assumed that multilayer substrate 102 in the present embodiment is bent in the directions of arrows 81a and 81b during use. Also in the following embodiments, the multilayer substrate is bent in the same direction.

  The multilayer substrate 102 has a first surface 21 that is an inner surface and a second surface 22 that is an outer surface by being bent during use. In the gap 9, the volume occupied by the gap 9 on the first surface 21 side from the center plane 23 in the thickness direction of the flexible portion 52 is the volume occupied by the gap 9 on the second surface 22 side from the center plane 23 in the thickness direction of the flexible portion 52. It arrange | positions so that it may become larger.

(Action / Effect)
The multilayer substrate 102 in the present embodiment is bent at the time of use, so that the first surface 21 side is compressed from the central surface 23 in the thickness direction of the flexible portion 52, and the first surface 21 side is compressed from the central surface 23 in the thickness direction of the flexible portion 52. 2 The surface 22 side is in a tensile state. On the other hand, in the present embodiment, the volume occupied by the gap 9 on the first surface 21 side from the central surface 23 in the thickness direction of the flexible portion 52 is larger than that of the central surface 23 in the thickness direction of the flexible portion 52. 2 Since the volume is larger than the volume occupied on the surface 22 side, many voids 9 are arranged on the side that is compressed when bent. As a result, the multilayer substrate 102 is easily bent. Therefore, the flexibility of the flexible part can be maintained even if the number of insulating layers of the flexible part increases.

  As shown in the present embodiment, the gap 9 is preferably a set of a plurality of gap elements. If it is such, since the site | part which a space | gap exhibits a function in the case of a bending can be disperse | distributed to a wide range, since smooth and uniform bending is obtained, it is preferable. In the example shown in FIG. 3, the gap 9 is composed of the two gap elements 31 and 32. However, the gap 9 may be composed of more gap elements.

(Modification)
In the multilayer substrate 102 shown in FIG. 3, each void element is a space having a thickness corresponding to a plurality of layers in the thickness direction. However, like the multilayer substrate 103 shown in FIG. It may have only the thickness.

  Note that, as in the multilayer substrate 102 shown in FIG. 3, it is preferable that the gap 9 is provided so as to straddle two or more insulating layers in the thickness direction. This is because a large volume of voids or void elements can be secured while only occupying a small area in plan view.

(Embodiment 3)
(Constitution)
With reference to FIG. 5, the multilayer substrate 104 in Embodiment 3 based on this invention is demonstrated. In the multilayer substrate 102 shown in FIG. 3 in the second embodiment, each air gap element is arranged so as to straddle the central plane 23. However, in this embodiment, each of the gap elements is arranged like the multilayer substrate 104 shown in FIG. The gap element is arranged at a position where it does not contact the center plane 23. In the multilayer substrate 104, the gap 9 is composed of five gap elements. Each of these five void elements may be of the same volume. Three gap elements are arranged on the first surface 21 side from the center surface in the thickness direction of the flexible portion 52 and two gap elements on the second surface 22 side from the center surface 23 in the thickness direction of the flexible portion 52. Comparing the total volume of the void elements constituting the void 9, the volume occupied by the void 9 on the first surface 21 side from the central surface 23 in the thickness direction of the flexible portion 52 is the center of the void 9 in the thickness direction of the flexible portion 52. It is larger than the volume occupied on the second surface 22 side from the surface 23.

  In the present embodiment, the gap 9 is composed of a plurality of gap elements. As in the present embodiment, in the plurality of gap elements, the number of gap elements arranged on the first surface side from the central surface 23 in the thickness direction of the flexible portion 52 is greater than the central plane in the thickness direction of the flexible portion. It is preferable to arrange so as to be larger than the number of void elements arranged on the second surface side.

(Action / Effect)
In the present embodiment, by making a difference in the number of gap elements, the volume of the gap 9 is clearly made to differ from the center surface 23 on the first surface 21 side and the second surface 22 side. Therefore, it becomes easy to provide a difference in the volume of the gap 9. In the present embodiment, it is possible to make the size and shape of each gap element the same, so that the fabrication becomes easy.

(Embodiment 4)
(Constitution)
With reference to FIG. 6, the multilayer substrate 105 in Embodiment 4 based on this invention is demonstrated. In the multilayer substrate 105, the air gap 9 is disposed only on the first surface 21 side from the central surface 23 in the thickness direction inside the flexible portion 52.

(Action / Effect)
In the present embodiment, even if the total volume of the gaps 9 is small, all of the gaps 9 are arranged on the first surface 21 side from the center plane 23 in the thickness direction, that is, on the side where compression occurs when bent. Therefore, flexibility can be exhibited efficiently. As a result, the flexibility of the flexible part can be maintained even if the number of insulating layers of the flexible part increases.

(Embodiment 5)
(Constitution)
With reference to FIG. 7, the multilayer substrate 106 in Embodiment 5 based on this invention is demonstrated. In the multilayer substrate 106, the gap 9 has an upper base and a lower base, and at least a part of the outer edge of at least one of the upper base and the lower base is covered with a conductor pattern that extends inside and outside of the outer edge. ing. FIG. 8 shows an enlarged view of the vicinity of the gap element 31 in FIG. The conductor patterns 24 and 25 are exposed to the gap 9.

  As shown in FIG. 8, at least a part of the outer edge of the upper base, Z1 part, is covered with a conductor pattern 24. Further, the Z2 portion, which is another part of the outer edge of the upper base, is also covered with the conductor pattern 24. The Z3 portion that is at least a part of the outer edge of the lower bottom is covered with the conductor pattern 25. Further, the Z4 portion, which is another part of the outer edge of the lower bottom, is also covered with the conductor pattern 25.

(Action / Effect)
In this embodiment, at least a part of the outer edge of at least one of the upper and lower bottoms of the gap is covered by the conductor pattern that extends inside and outside of the outer edge, so that the covered part is bent. In this case, it is possible to prevent the insulating layer from cracking from the outer edge.

  FIG. 8 shows an example in which all of the Z1 to Z4 portions are covered with a conductor pattern extending inside and outside the outer edge. In this way, if all of the Z1 to Z4 parts are covered, cracks can be prevented from occurring at any corner, but it is preferable that only a part of the Z1 to Z4 parts extends inside and outside the outer edge. Even if it is the structure covered with, the effect which prevents the crack generation in the said corner | angular is acquired. Here, for convenience of explanation, the four corners visible in the cross-sectional view are extracted to be Z1 to Z4, but the “outer edges” of the upper and lower bases include not only these four corners but also the back side and the near side of the page. Means the entire circumference of the outer edge.

  In the multilayer substrate 106 shown in the present embodiment, the gap 9 has an upper base and a lower base, and the entire circumference of at least one outer edge of the upper base and the lower base extends inside and outside the outer edge. It is covered with a conductor pattern. Thus, if it is covered with the conductor pattern that extends inside and outside of the outer edge over the entire circumference, it is possible to more reliably prevent the insulating layer from cracking from the outer edge as a base point in bending at the bottom. Therefore, it is preferable. The conductor pattern covering the outer edge may be electrically connected to other conductor patterns, or may be a so-called dummy conductor pattern that is not electrically connected to other conductor patterns.

(Modification)
As modifications of the present embodiment, those shown in FIGS. 9 to 11 can be considered. Even in these configurations, it is possible to expect the effect of preventing the occurrence of cracks based on the outer edge of the bottom of the gap during bending.

(Embodiment 6)
(Production method)
With reference to FIGS. 12-19, the manufacturing method of the multilayer substrate in Embodiment 6 based on this invention is demonstrated. FIG. 12 shows a flowchart of the method for manufacturing the multilayer substrate in the present embodiment.

  This manufacturing method is a method for manufacturing the multilayer substrate in each of the above-described embodiments. This manufacturing method includes a plurality of insulator sheets including a first group of insulator sheets having a rigid portion planned area that is a region to be the rigid portion 51 and a flexible portion planned region that is a region to be the flexible portion 52. Step S1 to be prepared, Step S2 of forming a hole to be at least a part of the gap in at least a part of the flexible part region of the first group of insulator sheets, and laminating the plurality of insulator sheets Step S3 and step S4 of pressure-bonding the plurality of laminated insulator sheets. This will be described in detail below.

  First, a resin sheet 12 with a conductive foil as shown in FIG. 13 is prepared as step S1. The resin sheet with conductor foil 12 is a sheet having a structure in which the conductor foil 17 is attached to one surface of the insulating layer 2. The resin sheet with conductor foil 12 corresponds to the insulator sheet in step S1. In step S1, a plurality of insulator sheets are prepared. A part of the plurality of insulator sheets is an insulator sheet that forms a flexible portion after the first group of insulator sheets. The plurality of insulator sheets prepared in step S1 may be formed by cutting out from one resin sheet 12 with a conductive foil, or formed from a plurality of resin sheets 12 with a conductive foil. There may be.

  The insulating layer 2 included in the resin sheet with conductor foil 12 may be a resin layer. The resin layer is made of, for example, LCP (liquid crystal polymer) which is a thermoplastic resin. In addition to LCP, the material of the resin layer that becomes the insulating layer 2 may be PEEK (polyether ether ketone), PEI (polyether imide), PPS (poniphenylene sulfide), PI (polyimide), or the like. . The conductor foil 17 is a 18 μm thick foil made of Cu, for example. The material of the conductor foil 17 may be Ag, Al, SUS, Ni, Au other than Cu, or may be an alloy of two or more different metals selected from these metals. In the present embodiment, the conductor foil 17 has a thickness of 18 μm, but the conductor foil 17 may have a thickness of about 3 to 40 μm. The conductor foil 17 may be any thickness that allows circuit formation.

  As shown in FIG. 14, via holes 11 are formed so as to penetrate the insulating layer 2 by irradiating the surface on the insulating layer 2 side of the resin sheet 12 with conductor foil with a carbon dioxide laser beam. The via hole 11 penetrates the insulating layer 2 but does not penetrate the conductor foil 17. Thereafter, the smear (not shown) of the via hole 11 is removed. Although carbon dioxide laser light is used here to form the via hole 11, other types of laser light may be used. In addition, a method other than laser beam irradiation may be employed to form the via hole 11.

  Next, as shown in FIG. 15, a resist pattern 13 corresponding to a desired circuit pattern is printed on the surface of the conductor foil 17 of the resin sheet 12 with conductor foil by a method such as screen printing.

  Next, etching is performed using the resist pattern 13 as a mask, and as shown in FIG. 16, a portion of the conductor foil 17 that is not covered with the resist pattern 13 is removed. A portion of the conductor foil 17 remaining after this etching is referred to as “conductor pattern 7”. Thereafter, as shown in FIG. 17, the resist pattern 13 is removed. Thus, a desired conductor pattern 7 is obtained on one surface of the resin layer 2.

  Next, as shown in FIG. 18, the via hole 11 is filled with a conductive paste by screen printing or the like. Screen printing is performed from the lower surface in FIG. 17 and 18, for convenience of explanation, the via hole 11 is displayed in a posture in which the via hole 11 faces downward. However, in practice, screen printing may be performed by changing the posture as appropriate. The conductive paste to be filled may be mainly composed of silver as described above, but may instead be composed mainly of copper, for example. This conductive paste forms an alloy layer with the metal that is the material of the conductor pattern 7 at the temperature when the laminated resin layer is thermocompression bonded (hereinafter referred to as “thermocompression temperature”). It is preferable that the metal powder contains an appropriate amount. Since this conductive paste contains copper, that is, Cu as a main component for exerting conductivity, this conductive paste includes at least one of Ag, Cu, and Ni in addition to the main component, and Sn, Bi, Zn. It is preferable that at least one of them is included. Thus, the via conductor 6 is formed.

  Next, as step S2, punching is performed on the insulating layer 2 as shown in FIG. In this punching process, a hole 14 to be at least a part of the gap 9 is formed in at least a part of the flexible part region of the insulating layer 2 as an insulating sheet belonging to the first group. In the example shown in FIG. 19, the hole 14 is a through hole, but is not limited to a through hole. The hole may be a hole that does not penetrate.

  As the insulating sheet belonging to the first group, the insulating layer 2 may be formed with or without the holes 14 formed therein. In the insulating layer 2, the hole 14 is formed only in the insulating layer 2 in which the hole 14 is to be formed according to the design.

  Here, although punching was mentioned as a method of making a hole, you may form a hole by methods other than punching. In order for the conductor pattern to cover the bottom of the hole, the hole is preferably formed by laser processing.

  Although FIG. 12 shows that the process S2 is performed after the process S1, the order is not limited to this. The process so far including the process S2 may be performed first, and the process S1 may be performed thereafter. This is because it may be easier to handle various treatments with a sheet having a large conductor foil than to perform various treatments after cutting out the insulator sheet to the size of the laminate.

  Further, as steps S3 and S4, for example, the multilayer substrate 106 shown in FIG. 7 is obtained by performing lamination and pressure bonding. Other multilayer substrates exemplified in the above-described embodiment can also be manufactured by changing the arrangement of the holes in step S2. The conductor pattern 7 disposed on the lower surface of the multilayer substrate becomes the external electrode 18. The pressure bonding may be performed in two steps, temporary pressure bonding and main pressure bonding.

(Action / Effect)
In this embodiment, since the hole 14 to be at least a part of the gap 9 is formed in at least a part of the flexible part region as the process S2, the flexible part 52 is finally passed through the processes S3 and S4. A multilayer substrate having voids 9 inside can be obtained. Since the multilayer substrate manufactured in this manner has a gap inside the flexible portion, the flexibility of the flexible portion can be maintained even if the number of insulating layers in the flexible portion increases. .

  In each of the above embodiments, only the cross-sectional view is shown when showing the multilayer substrate. However, when viewed in a plan view, the arrangement of the gaps may be one row in the longitudinal direction or a plurality of rows. May be. The voids may be arranged in a zigzag manner in the longitudinal direction.

  In each of the embodiments so far, the multilayer substrate has been described on the premise of a structure having rigid portions at both ends in the longitudinal direction of the flexible portion, that is, a structure in which one flexible portion and two rigid portions are combined. However, the multilayer substrate is not limited to such a structure. For example, the structure which has a rigid part only in the end of a flexible part may be sufficient.

  In addition, the said embodiment disclosed this time is an illustration in all the points, Comprising: It is not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and includes all modifications within the scope and meaning equivalent to the terms of the claims.

  2 Insulating layer, 6 Via conductor, 7 Conductor pattern, 8 First group, 9 Void, 12 Resin sheet with conductor foil, 13 Resist pattern, 14 Hole, 17 Conductor foil (before patterning), 21 First surface, 22 Second surface 23, center plane (in the thickness direction of the flexible portion), 24, 25 conductor pattern (exposed to the void), 31, 32 void element, 51 rigid portion, 52 flexible portion, 81a, 81b arrows, 101, 101e , 102, 103, 104, 105, 106 multilayer substrate, 901, 902 (conventional) multilayer substrate.

Claims (8)

A rigid portion including a plurality of laminated insulating layers;
A flexible portion extending laterally from the rigid portion by extending a first group of insulating layers that are part of the plurality of insulating layers included in the rigid portion;
The flexible part has a gap inside,
The flexible part has a first surface that is an inner surface and a second surface that is an outer surface when the flexible part is bent during use, and the gap is a center of the flexible part in the thickness direction. The multilayer substrate is arranged such that the volume occupied on the first surface side from the surface is larger than the volume occupied on the second surface side by the gap from the central surface in the thickness direction of the flexible part.   The multilayer substrate according to claim 1, wherein the void is a set of a plurality of void elements.   In the plurality of gap elements, the number of gap elements arranged on the first surface side from the central plane in the thickness direction of the flexible part is arranged on the second surface side from the central plane in the thickness direction of the flexible section. The multilayer substrate according to claim 2, wherein the multilayer substrate is disposed so as to be larger than the number of void elements.   The multilayer substrate according to any one of claims 1 to 3, wherein the gap is disposed only on the first surface side from the center plane in the thickness direction inside the flexible portion.   The multilayer substrate according to any one of claims 1 to 4, wherein the void is provided so as to straddle two or more insulating layers in the thickness direction.   The said space | gap has an upper base and a lower bottom, and at least one part of the outer edge of at least one of the said upper base and the said lower base is covered with the conductor pattern which straddles the inside and outside of the said outer edge. To 5. The multilayer substrate according to any one of 5 to 5.   The said space | gap has an upper bottom and a lower bottom, and the perimeter of at least one outer edge of the said upper bottom and the said lower bottom is covered with the conductor pattern which straddles the inside and outside of the said outer edge. A multilayer substrate according to any one of the above. A method for producing a multilayer substrate according to claim 1, comprising:
Preparing a plurality of insulator sheets including a first group of insulator sheets having a rigid portion planned region that is a region to be the rigid portion and a flexible portion planned region that is to be the flexible portion;
Forming a hole to be at least a part of the gap in at least a part of the flexible part region of the first group of insulating sheets;
Laminating the plurality of insulator sheets;
And a step of pressure-bonding the plurality of laminated insulator sheets.

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