JP2023168107A - wiring board - Google Patents

Abstract

To provide a wiring board which radiates heat efficiently.SOLUTION: A wiring board 1 of an embodiment includes: a multilayer core substrate 100 having a first surface FS and a second surface SS and including multiple isolating layers and multiple conductor layers; a first lamination part 10 in which a first conductor layer 12, including first conductor pads 12a, is exposed on an outermost layer at the first surface FS side; a second lamination part 20 in which a second conductor layer 22, including second conductor pads 22a, is exposed on an outermost surface of the second surface SS; first via conductors 13a formed in the first lamination part 10; and second via conductors 23a formed in the second lamination part 20. The first conductor pads 12a are component mounting pads. The multilayer core substrate 100 includes multistage heat transfer conductors 17, 27 including multiple laminated metal bodies. The multistage heat transfer conductors 17, 27 are connected to the first conductor pads 12a through the first via conductors 13a and connected to the second conductor pads 22a through the second via conductors 23a.SELECTED DRAWING: Figure 1

Description

The present invention relates to a wiring board.

Patent Document 1 discloses a printed wiring board in which one surface is connected to an IC chip and the other surface is connected to a motherboard. The printed wiring board has a core substrate including a through hole in which a heat dissipation block is accommodated. A conductor layer (conductor pad) connected to the IC chip and a conductor layer (conductor pad) connected to the motherboard are each connected to a heat dissipation block via a via conductor.

Japanese Patent Application Publication No. 2013-135168

The printed wiring board disclosed in Patent Document 1 requires a step for embedding a heat dissipation block in an insulating layer in its manufacture. It is thought that the manufacturing process will become complicated.

The wiring board of the present invention includes a multilayer core board having a first surface and a second surface opposite to the first surface, and including a plurality of insulating layers and a plurality of conductor layers stacked alternately; a first laminated portion formed on the surface and exposing a first conductor layer including a first conductor pad to the outermost surface; and a second layer formed on the second surface and including a second conductor layer including a second conductor pad. a second laminated part exposed on the outermost surface; a first via conductor formed in the first laminated part and connected to the first conductor pad; and a first via conductor formed in the second laminated part and connected to the first conductor pad. and a second via conductor connected to the pad. The first conductor pad is a component mounting pad disposed within a component mounting area, and the multilayer core board further includes a multistage heat transfer conductor including a plurality of laminated metal bodies, and the multilayer core board further includes a multistage heat transfer conductor including a plurality of laminated metal bodies. The thermal conductor is connected to the first conductive pad via the first via conductor and to the second conductive pad via the second via conductor.

According to an embodiment of the present invention, heat absorbed from one of the conductor pads is transferred to the wiring board through a multi-stage heat transfer conductor composed of a plurality of metal bodies that can be manufactured in the same process as forming the via conductor. flows in the stacking direction and is diffused to the other surface of the wiring board. It is believed that a wiring board with excellent heat diffusion efficiency can be provided by a simple method.

FIG. 1 is a cross-sectional view showing an example of a wiring board according to an embodiment of the present invention. 1 is a diagram showing an example of a method for manufacturing a wiring board according to an embodiment of the present invention. 1 is a diagram showing an example of a method for manufacturing a wiring board according to an embodiment of the present invention. 1 is a diagram showing an example of a method for manufacturing a wiring board according to an embodiment of the present invention. 1 is a diagram showing an example of a method for manufacturing a wiring board according to an embodiment of the present invention. 1 is a diagram showing an example of a method for manufacturing a wiring board according to an embodiment of the present invention. 1 is a diagram showing an example of a method for manufacturing a wiring board according to an embodiment of the present invention. 1 is a diagram showing an example of a method for manufacturing a wiring board according to an embodiment of the present invention. FIG. 3 is a cross-sectional view showing an example of a wiring board according to another embodiment of the present invention.

Next, an example of a wiring board that is an embodiment of the present invention will be described with reference to the drawings. Note that the drawings referred to hereinafter are not intended to show exact proportions of each component, but are drawn so that the features of the present invention can be easily understood.

FIG. 1 shows a cross-sectional view of the wiring board 1. As shown in FIG. The wiring board 1 has two main surfaces (surfaces) extending in a direction perpendicular to the thickness direction (planar direction), an F surface FS and an S surface SS on the opposite side to the F surface FS. We are prepared. The wiring board 1 has a multilayer core board 100. The multilayer core board 100 includes an inner conductor layer 100M that is a metal layer extending in a planar direction. In the illustrated example, the inner conductor layer 100M is arranged at the center of the multilayer core substrate 100 in the thickness direction.

The multilayer core substrate 100 includes a first surface 100F and a second surface 100S, which is a surface opposite to the first surface 100F. On the first surface 100F of the multilayer core substrate 100, a first laminated portion 10 including an insulating layer (first insulating layer) 11 and a conductor layer (first conductor layer) 12 formed on the first insulating layer 11 is provided. It is formed. A second laminated portion 20 is formed on the second surface 100S, including an insulating layer (second insulating layer) 21 and a conductor layer (second conductor layer) 22 formed on the second insulating layer 21. . The outermost surface of the first laminated portion 10 constitutes the F-plane FS of the wiring board 1 , and the outermost surface of the second laminated portion 20 constitutes the S-plane SS of the wiring board 1 .

Desired conductor patterns including wiring patterns and/or conductor pads are formed on the first conductor layer 12 and the second conductor layer 22, respectively. In the example wiring board 1 shown in FIG. 1, the first conductor layer 12 includes a plurality of conductor pads (12a, 12b) exposed on the F-plane FS. The conductor pad 12a (first conductor pad) is a component mounting pad. That is, the conductor pad 12a is a conductor pad that can be connected to an external electronic component D1 (for example, a package board) mounted on the wiring board 1 when the wiring board 1 is used, and is a conductor pad that can be connected to an area (for example, a package board) on which the external electronic component D1 is mounted. The first conductor layer 12 is located within the component mounting area (component mounting area). When the wiring board 1 is used, the conductor pad 12a can be electrically connected to the connection pad D1p of the external electronic component D1 via a connection member BD1, such as solder, having appropriate conductivity. That is, the F surface FS may be a component mounting surface on which external electronic components are mounted when the wiring board 1 is used. The conductor pads 12a may be formed in any number and at any position within the component mounting area depending on the wiring pattern of the electronic component D1 mounted on the wiring board 1.

In the illustrated example, the wiring board 1 includes a first conductor layer 12 and a first covering layer 14 formed on the surface of the first insulating layer 11 exposed from the conductor pattern of the first conductor layer 12. The first coating layer 14 is, for example, a solder resist layer. The conductor pads 12a are exposed through the openings 14c provided in the first covering layer 14.

The second conductor layer 22 includes a plurality of conductor pads (22a, 22b) exposed on the S surface SS. The conductor pads 22a and 22b can be connected to, for example, a casing of a mobile terminal when the wiring board 1 is used.

The wiring board 1 in the example of FIG. 1 has a second coating layer, which may be a solder resist layer, for example, formed on the second conductor layer 22 and the surface of the second insulating layer 21 exposed from the conductor pattern of the second conductor layer 22. It is equipped with 24. The conductor pads 22a and 22b are exposed through the openings 24c provided in the second covering layer 24.

In the description of the wiring board, the side far from the inner conductor layer 100M included in the multilayer core board 100 in the thickness direction of the wiring board 1 is referred to as "upper side", "upper", or "outside", or simply "upper", " The side closer to the inner conductor layer 100M is also referred to as the "lower side," "lower side," or "inner side," or simply "lower" or "inner." Furthermore, in the description of each element constituting the wiring board, the surface facing away from the inner conductor layer 100M is also referred to as the "upper surface", and the surface facing the inner conductor layer 100M side is also referred to as the "lower surface". Therefore, for example, in the description of the first laminated part 10 and the second laminated part 20, the side far from the multilayer core substrate 100 is also referred to as "upper side", "upper", "upper layer side", or simply "upper", and The side closer to is also referred to as the "lower side", "lower side", "lower layer side", or simply "lower side".

Via conductors (13a, 13b) penetrating the insulating layer (first insulating layer 11) are formed in the insulating layer (first insulating layer 11) of the first laminated portion 10. The via conductors (13a, 13b) are formed by filling through holes penetrating the first insulating layer 11 with a conductor. The via conductors (13a, 13b) are integrally formed with the conductor layer (first conductor layer 12) above the first insulating layer 11. Via conductor 13a (first via conductor) is connected to conductor pad 12a (first conductor pad). Via conductor 13b is connected to conductor pad 12b.

Via conductors (23a, 23b) penetrating the insulating layer (second insulating layer 21) are formed in the insulating layer (second insulating layer 21) of the second laminated portion 20. The via conductors (23a, 23b) are formed by filling through holes penetrating the second insulating layer 21 with a conductor. The via conductors (23a, 23b) are integrally formed with the conductor layer (second conductor layer 22) above the second insulating layer 21. Via conductor 23a (second via conductor) is connected to conductor pad 22a (second conductor pad). Via conductor 23b is connected to conductor pad 22b.

As shown in FIG. 1, in the wiring board 1 of the embodiment, the multilayer core board 100 includes an inner conductor layer 100M, and insulating layers (a third insulating layer 111, a fourth insulating layer 111, a fourth insulating layer layer 121), a third conductor layer 112 formed on the third insulating layer 111, and a fourth conductor layer 122 formed on the fourth insulating layer 121. The inner conductor layer 100M may be formed of a metal with relatively high thermal conductivity, such as aluminum or copper, for example.

A fifth insulating layer 131 is formed above the third conductor layer 112, and a fifth conductor layer 132 is laminated above the fifth insulating layer 131. The surface of the fifth conductor layer 132 and the upper surface of the fifth insulating layer 131 exposed from the conductor pattern of the fifth conductor layer 132 constitute a first surface 100F of the multilayer core substrate 100. A sixth insulating layer 141 is formed above the fourth conductor layer 122, and a sixth conductor layer 142 is laminated above the sixth insulating layer 141. The surface of the sixth conductor layer 142 and the upper surface of the sixth insulating layer 141 exposed from the conductor pattern of the sixth conductor layer 142 constitute a second surface 100S of the multilayer core substrate 100.

In the wiring board 1 shown in FIG. 1, the multilayer core board 100 has two sets of insulating layers and conductive layers on the inner conductor layer 100M. The number of laminated conductor layers is not limited to this example. The number of laminated layers can be selected as appropriate depending on the desired circuit configuration. Any number of insulating layers and conductive layers may be stacked, for example three or more sets.

The conductor layers (third conductor layer 112, fourth conductor layer 122, fifth conductor layer 132, sixth conductor layer 142) of the multilayer core substrate 100, the first conductor layer 12 included in the first laminated section 10, and The second conductor layer 22 included in the second laminated portion 20 is formed using any material having appropriate conductivity, such as copper or nickel. Preferably, it is formed of a copper foil, an electrolytic copper plating film, an electroless copper plating film, or a combination thereof. In the example shown in FIG. 1, each conductor layer is shown as a single layer, but the first conductor layer 12, the second conductor layer 22, the third conductor layer 112, the fourth conductor layer 122, and the fifth conductor layer 132. , the sixth conductor layer 142 may have a three-layer structure including a metal foil (preferably copper foil), a metal film (preferably an electroless copper plating film), and an electrolytic plating film (preferably an electrolytic copper plating film). .

The insulating layers of the multilayer core substrate 100 (the third insulating layer 111, the fourth insulating layer 121, the fifth insulating layer 131, the sixth insulating layer 141), the first insulating layer 11 included in the first laminated section 10, and The second insulating layer 21 included in the second laminated portion 20 includes any insulating resin such as epoxy resin, BT resin, or phenol resin. Each insulating layer may contain the same insulating resin, or may contain different insulating resins. In the example shown in FIG. 1, the first to sixth insulating layers 11, 21, 111, 121, 131, and 141 include a core material (reinforcing material) that may be formed of glass fiber or aramid fiber. Each insulating layer may contain an inorganic filler (not shown) made of fine particles such as silica (SiO ₂ ), alumina, or mullite. The first coating layer 14 and the second coating layer 24 may be formed using, for example, photosensitive polyimide resin or epoxy resin.

Each of the third insulating layer 111, fourth insulating layer 121, fifth insulating layer 131, and sixth insulating layer 141 of the multilayer core board 100 includes a metal body (heat transfer conductor) that penetrates each insulating layer in the thickness direction. and via conductors are formed. The third insulating layer 111 includes a first heat transfer conductor 115 and a via conductor that penetrate through the third insulating layer 111 and electrically connect the third conductor layer 112 sandwiching the third insulating layer 111 and the inner conductor layer 100M. 113 is formed. Similarly, the fourth insulating layer 121 includes a second heat transfer conductor 125 that penetrates the fourth insulating layer 121 and electrically connects the fourth conductor layer 122 sandwiching the fourth insulating layer 121 and the inner conductor layer 100M. and via conductors 123 are formed. The fifth insulating layer 131 includes a third heat transfer conductor 135 and vias that penetrate through the fifth insulating layer 131 and electrically connect the fifth conductor layer 132 and the third conductor layer 112 sandwiching the fifth insulating layer 131. A conductor 133 is formed. The sixth insulating layer 141 includes a fourth heat transfer conductor 145 and vias that penetrate through the sixth insulating layer 141 and electrically connect the fourth conductor layer 122 and the sixth conductor layer 142 sandwiching the sixth insulating layer 141. A conductor 143 is formed.

Like the via conductors (13a, 13b, 23a and 24b), the first to fourth heat transfer conductors (115, 125, 135 and 145) and via conductors (113, 123, 133 and 143) are connected to each insulating layer. It is formed by filling a through hole that penetrates with a conductor. The first to fourth heat transfer conductors (115, 125, 135, and 145) and via conductors (113, 123, 133, and 143) each penetrate an insulating layer (a third insulating layer 111, a fourth insulating layer 121, It is formed integrally with the upper conductor layer (fifth insulating layer 131 and sixth insulating layer 141). Therefore, for example, the first heat transfer conductor 115, the via conductor 113, and the third conductor layer 112 are formed of the same plating film (electroless plating film and electrolytic plating film) made of, for example, copper or nickel. . The second to fourth heat transfer conductors (125, 135, and 145) and via conductors (123, 133, and 143) are similarly formed of the same plating film as the upper conductor layer.

As shown in FIG. 1, the first to fourth heat transfer conductors (115, 125, 135 and 145) are wider in the plane direction than the via conductors (113, 123, 133 and 143). It has a flat shape. In the example of FIG. 1, the first to fourth heat transfer conductors (115, 125, 135, and 145) and the via conductors (113, 123, 133, and 143) have approximately the same size and approximately the same shape. It is formed.

For example, in the third insulating layer 111, a first through hole 111a for forming the first heat transfer conductor 115 and a second through hole 111b for forming the via conductor 113 are formed. The first through hole 111a and the second through hole 111b may be formed by irradiating the outer surface of the third insulating layer 111 with laser light from above. Due to laser light irradiation, it has a large diameter (width) on the laser light irradiation side, that is, the surface side of the third insulating layer 111, and has a small diameter (width) on the side opposite to the laser light irradiation side (back side). A tapered hole is formed. The second through hole 111b is formed with such a tapered hole. On the other hand, the first through-hole 111a is formed by arranging tapered holes of the same shape side by side and making the tapered holes communicate with each other by partially overlapping adjacent tapered holes. As a result, the first through hole 111a can be formed which is larger in the lateral direction (planar direction) than the second through hole 111b.

As described above, the first through hole 111a and the second through hole 111b are filled with plating to form a filling body made of a conductor (first heat transfer conductor 115 and via conductor 113). Therefore, both the first heat transfer conductor 115 and the via conductor 113 are formed in a tapered shape whose diameter decreases from the outside of the wiring board 1 toward the inner conductor layer 100M. Although the word "diameter reduction" is used for convenience, in this specification, the shape of each heat transfer conductor and each via conductor is not limited, but is simply defined as "diameter reduction". This means that the distance between the two longest points on the outer periphery in the horizontal cross section of is reduced. Further, the length of the first heat transfer conductor 115 in the planar direction is larger than the length of the via conductor 113 in the planar direction. For example, the opening on the surface side of the third insulating layer 111 of the first through hole 111a for the first heat transfer conductor 115 may have a substantially elliptical shape with a long axis in the planar direction. The opening on the surface side of the third insulating layer 111 of the second through hole 111b for the via conductor 113 may have a substantially perfect circular shape. For example, the opening area of the first through hole 111a on the surface side of the third insulating layer 111 is approximately 3 times or more and approximately 20 times or less the opening area of the second through hole 111b on the surface side of the third insulating layer 111. obtain.

The through holes for forming the second to fourth heat transfer conductors (125, 135, and 145) may also be formed in the same manner as the first through hole 111a. As a result, in each insulating layer (the fourth insulating layer 121, the fifth insulating layer 131, and the sixth insulating layer 141) of the multilayer core board 100, similarly to the first heat transfer conductor 115, vias in the same insulating layer The second to fourth heat transfer conductors (125, 135) are larger in the lateral direction than the conductors (123, 133, and 143) and have a tapered shape that decreases in diameter from the outside of the wiring board 1 toward the inner conductor layer 100M. and 145) are formed.

As shown in FIG. 1, the multilayer core substrate 100 includes a multistage heat transfer conductor formed by stacking a plurality of metal bodies (heat transfer conductors). The first heat transfer conductor 115 and the third heat transfer conductor 135 constitute a multistage heat transfer conductor 17. In the example of FIG. 1, the third heat transfer conductor 135 is arranged at a position overlapping the first heat transfer conductor 115 in plan view. Note that "planar view" means viewing the wiring board of the embodiment from a line of sight along its thickness direction. Further, the second heat transfer conductor 125 and the fourth heat transfer conductor 145 constitute a multistage heat transfer conductor 27. In the example of FIG. 1, the fourth heat transfer conductor 145 is arranged at a position overlapping the second heat transfer conductor 125 in plan view.

The multistage heat transfer conductor 17 faces the multistage heat transfer conductor 27 with the inner conductor layer 100M in between. In the multilayer core substrate 100, two metal bodies (the first heat transfer conductor 115 and the third heat transfer conductor 135, and the second heat transfer conductor 125 and the fourth heat transfer conductor 145) are formed on both sides of the inner conductor layer 100M. has been done. Both the multistage heat transfer conductors 17 and 27 are composed of a plurality of metal bodies (heat transfer conductors) each having a tapered shape that decreases in diameter toward the inner conductor layer 100M. The ends of the inner conductor layer 100M with the thermal conductor 27 have substantially the same end surface area and face each other at substantially the same position in the stacking direction. That is, the multilayer core substrate 100 includes a structure in which a multistage heat transfer conductor 17 and a multistage heat transfer conductor 27 are stacked with the inner conductor layer 100M interposed therebetween.

In the wiring board 1 of the embodiment, the multistage heat transfer conductor 17 and the multistage heat transfer conductor 27 are arranged at positions overlapping the component mounting area in a plan view. That is, the electronic component D1 mounted on the wiring board 1 is placed directly above the multistage heat transfer conductor 17 and the multistage heat transfer conductor 27. The multistage heat transfer conductor 17 is connected to a conductor pad 12a (first conductor pad), which is a component mounting pad, via a via conductor 13a (first via conductor). The multistage heat transfer conductor 27 is connected to a conductor pad 22a (second conductor pad) connected to a connection pad of the wiring structure WB via a via conductor 23a (second via conductor).

When using the wiring board 1, the heat generated by the electronic component D1 that can be mounted on the F side FS may cause malfunction of the electronic component if it remains inside the electronic component D1, so it is transferred to the outside of the S side SS via the wiring board 1. It is desirable that heat be dissipated to Therefore, it is desired that the heat generated by the electronic component D1 transmitted to the wiring board 1 be efficiently radiated to the outside of the S surface SS via the conductor pad 12a, which is a component mounting pad. The heat generated by the electronic component D1 should be transmitted to the S surface SS side and also to the entire surface of the wiring board 1 to be efficiently dissipated from the viewpoint of suppressing defects such as warping of the wiring board 1 itself. is desired.

The F side FS, which can be a component mounting surface on which external electronic components are mounted, transfers heat generated from the electronic components D1 to the multilayer core board 100 side via the first conductor layer 12 when the wiring board 1 is used. It can function as an endothermic surface that receives heat in order to transfer it. Further, the heat conducted to the multilayer core board 100 is dissipated within the multilayer core board 100 via the second conductor layer 22, which may be a connection surface with an external structure WB such as a casing of a mobile terminal. Transmit to surface SS.

In this embodiment, the multistage heat transfer conductor 17 is connected to the first insulating layer 11, which is the outermost conductor layer on the F surface FS side of the wiring board 1, via the via conductor 13a formed so as to penetrate the first insulating layer 11. It is connected to the conductor layer 12. Thereby, a heat transfer path is formed from the conductor pad 12a to the multistage heat transfer conductor 17 via the via conductor 13a. The multistage heat transfer conductor 27 is connected to the second conductor layer 22, which is the outermost conductor layer on the S surface SS side of the wiring board 1, via a via conductor 23a formed so as to penetrate the second insulating layer 21. has been done. Thereby, a heat transfer path is formed from the multistage heat transfer conductor 27 to the conductor pad 22a via the via conductor 23a.

That is, in the wiring board 1 of this embodiment, the via conductor 13a, the multistage heat transfer conductor 17 and A heat transfer path is configured via the multistage heat transfer conductor 27 and the via conductor 23a. Through this path, the heat emitted from the electronic component D1 that is transmitted to the F surface FS can be efficiently transmitted to the S surface SS side. As described above, the multistage heat transfer conductor 17 and the multistage heat transfer conductor 27 may be formed in the same process as the method for forming the via conductor 113 and the via conductor 123, respectively. The wiring board 1 with excellent heat diffusivity can be provided without increasing complicated steps. It is also considered easy to arrange the multistage heat transfer conductor 17 and the multistage heat transfer conductor 27 directly below the component mounting area.

In the example of FIG. 1, the multistage heat transfer conductor 17 has a stacked structure of a first heat transfer conductor 115 and a second heat transfer conductor 125, which are two flat conductors. However, the multistage heat transfer conductor 17 and the multistage heat transfer conductor 27 may have a stack structure of three or more heat transfer conductors. That is, when three or more sets of insulating layers and conductor layers are laminated on each side of the inner conductor layer 100M in the multilayer core board 100, a heat transfer conductor is further layered on the multistage heat transfer conductor 17 and the multistage heat transfer conductor 27. A metal body passing through each insulating layer may be formed so as to be stacked. In some cases, heat dissipation can be done more efficiently.

The inner conductor layer 100M has a length larger than the length of the multistage heat transfer conductor 17 and the multistage heat transfer conductor 27 in the planar direction. That is, the inner conductor layer 100M extends to the component mounting area and the area outside of the component mounting area in plan view. In the area outside the component mounting area, the inner conductor layer 100M is connected to the third conductor layer 112 and the fourth conductor layer 122 by via conductors 113 and via conductors 123, respectively. In the example of FIG. 1, the via conductor 123, the via conductor 143, and the via conductor 23b are formed at positions that overlap each other in plan view, forming a so-called stacked via conductor.

In the heat transfer path along the lamination direction from the conductor pad 12a to the conductor pad 22a via the multistage heat transfer conductor 17 and the multistage heat transfer conductor 27, the vicinity of the multistage heat transfer conductor 27 on the S surface SS side of the wiring board 1 There is a risk that heat will remain in the area and local endotherm may occur. In this embodiment, within the wiring board 1, the heat conducted from the multistage heat transfer conductor 17 to the inner layer conductor layer 100M via the conductor pad 12a not only flows in the stacking direction, that is, to the multistage heat transfer conductor 27, It can also be conducted in a planar direction, that is, to an area outside the component mounting area, via the inner conductor layer 100M. The heat conducted in the planar direction flows to the conductor pad 22b through the stacked via conductor composed of the via conductor 123, the via conductor 143, and the via conductor 23b connected to the inner conductor layer 100M, and flows to the conductor pad 22b. It can be transmitted to the surface SS side. It is thought that local accumulation of heat within the multistage heat transfer conductor 27 and in the second conductor layer 22 near the multistage heat transfer conductor 27 is unlikely to occur due to promotion of heat conduction in the planar direction in the inner conductor layer 100M. .

In the example of FIG. 1, the via conductor 113, the via conductor 133, and the via conductor 13b are also formed at positions overlapping each other in a plan view, forming a so-called stacked via conductor. The stacked via conductor composed of the via conductor 123, the via conductor 143, and the via conductor 23b, and the stacked via conductor composed of the via conductor 113, the via conductor 133, and the via conductor 13b are also shown in plan view with the inner conductor layer 100M in between. overlapping.

That is, in this embodiment, the heat emitted from the electronic component D1 is further transferred from the conductor pad 12b connected to the conductor pad 12a in the first conductor layer 12 to the via conductor 113 through the conductor pad 12a which is a component mounting pad. The S surface SS of the wiring board 1 is also can be transmitted to the side. It is considered that heat can be diffused more efficiently from the outermost first conductor layer 12 on the F-plane FS side of the wiring board 1 to the S-plane SS side of the wiring board 1. It is thought that problems caused by heat remaining locally (for example, peeling between components constituting the wiring board 1, warpage of the wiring board 1, etc.) can be suppressed.

Furthermore, for example, the second conductor layer 22 which is the outermost conductor layer on the S surface SS side of the wiring board 1 included in the second laminated part 20 of the wiring board 1 is the first conductor layer included in the first laminated part 10. It may be formed to have a thickness greater than the thickness of the conductor layer 12 and the conductor layers (third conductor layer 112, fourth conductor layer 122, fifth conductor layer 132, sixth conductor layer 142) of the multilayer core substrate 100. . An example of this is shown in FIG. For example, the thickness of the second conductor layer 22 may be about 1.2 times or more and about 2.5 times or less the thickness of other conductor layers, that is, the first conductor layer 12 or the conductor layer of the multilayer core board 100. good. It is thought that local accumulation of heat in the second conductor layer 22 near the multi-stage heat transfer conductor 27 is suppressed, and that backflow of heat from the S surface SS to the F surface FS of the wiring board 1 can also be prevented. . A wiring board 1 can be provided in which heat transmitted to the F-plane FS (specifically, the conductor pad 12a) can be efficiently diffused to the S-plane SS side.

Next, a method for manufacturing a wiring board will be explained with reference to FIGS. 2A to 2G, taking as an example the manufacturing of the wiring board 1 shown in FIG. 1.

As shown in FIG. 2A, a metal layer (inner conductor layer 100M) made of a metal such as copper or aluminum and having a predetermined thickness is prepared. A prepreg having a core material impregnated with, for example, epoxy resin and copper foil are sequentially laminated on both sides of the inner conductor layer 100M and integrated by hot pressing. Due to this integration, the inner conductor layer 100M is sandwiched between the third insulating layer 111 and the fourth insulating layer 121, which are made of hardened prepreg.

Subsequently, as shown in FIG. 2B, the first heat transfer conductor 115 and the second heat transfer conductor 125 and the via conductor 113 and the via conductor 123 shown in FIG. 1 of the third and fourth insulating layers 111 and 121 are A through hole is formed at the position to be formed by laser processing using a carbon dioxide laser or the like. For example, in the third insulating layer 111, a laser beam is irradiated from the surface side of the third insulating layer 111 to form a tapered hole for the second through hole 111b for forming the via conductor 113 (see FIG. 1). At the same time, in order to form the first through hole 111a for forming the first heat transfer conductor 115 (see FIG. 1), the plurality of tapered holes are formed, for example, in two orthogonal directions so that a portion of each taper hole overlaps and communicates with each other. They are formed side by side. Similarly, in the fourth insulating layer 121, through holes for forming the second heat transfer conductor 125 and the via conductor 123 are formed by laser beam irradiation from the surface side of the fourth insulating layer 121.

Next, each through-hole is optionally subjected to a necessary treatment such as desmearing, and then, as shown in FIG. 2C, a metal film is formed on the copper foil and on the inner surface of the through-hole by electroless copper plating or the like. Further, an electroplated film made of copper or the like is formed using a pattern plating method using a plating resist using this metal film as a seed layer. Thereafter, the plating resist used for pattern plating is removed, and the metal film and copper foil exposed by the removal are removed. As a result, third conductor layer 112 and fourth conductor layer 122 including desired conductor patterns are formed. Further, the through holes are filled, and the first heat transfer conductor 115 and the via conductor 113, and the second heat transfer conductor 125 and the via conductor 123 are integrated with the third conductor layer 112 and the fourth conductor layer 122, respectively. It is formed. The first heat transfer conductor 115 and the conductor 113 are formed to connect with the inner conductor layer 100M and the third conductor layer 112. The second heat transfer conductor 125 and the via conductor 123 are formed to connect the inner conductor layer 100M and the fourth conductor layer 122.

Next, as shown in FIG. 2D, the fifth insulating layer 131 covering the third conductor layer 112 and the sixth insulating layer 141 covering the fourth conductor layer 122 heat the copper foil and sheet prepreg. Formed by pressing. Similar to the method for forming the first through hole 111a and the second through hole 111b (see FIG. 2B) in the third insulating layer 111, the through hole and via conductor 133 for forming the third heat transfer conductor 135 in the fifth insulating layer 131 A through hole for formation is formed by irradiating laser light from the surface of the fifth insulating layer 131. A through hole for forming the fourth heat transfer conductor 145 and a through hole for forming the via conductor 143 are formed in the sixth insulating layer 141.

Next, as shown in FIG. 2E, similar to the method for forming the third conductor layer 112 and the fourth conductor layer 122, on the copper foil inside the through hole and on the fifth insulating layer 131 and the sixth insulating layer 141, A metal film layer is formed by electroless copper plating or sputtering, and an electroplated film layer made of copper or the like is formed by a so-called pattern plating method using the metal film layer as a seed layer. After forming the electrolytically plated film layer, the plating resist is removed, and the exposed portion of the metal film layer that is not covered by the electrolytically plated film is removed by etching. As a result, a third heat transfer conductor 135 and a via conductor 133 are formed by the fifth conductor layer 132 on the fifth insulating layer 131, and the metal film layer and electroplated film in the through hole. A fourth heat transfer conductor 145 and a via conductor 143 are formed on the sixth insulating layer 141 by a sixth conductor layer 142, and a metal film layer and an electroplated film in the through hole. The third heat transfer conductor 135 is formed to connect the first heat transfer conductor 115 and the fifth conductor layer 132. The fourth heat transfer conductor 145 is formed to connect the second heat transfer conductor 125 and the sixth conductor layer 142. Formation of the multilayer core substrate 100 having the first surface 100F and the second surface 100S opposite to the first surface 100F as the outermost surface is completed.

Next, as shown in FIG. 2F, the first insulating layer 11 and the first conductor layer 12 are laminated on the upper side of the first surface 100F of the multilayer core substrate 100, and the first conductor layer 12 and the first conductor layer 12 are stacked on the upper side of the first surface 100F of the multilayer core substrate 100. Via conductors 13a and 13b are formed to connect the fifth conductor layer 132, which is an outer conductor layer. The first conductor layer 12 is formed into a pattern including conductor pads 12a and conductor pads 12b. The conductor pad 12a is formed in the component mounting area. Via conductor 13a is formed such that conductor pad 12a is connected to third heat transfer conductor 135 via via conductor 13a. Via conductor 13b is formed such that conductor pad 12b is connected to conductor layer 132 via via conductor 13b.

A second insulating layer 21 and a second conductor layer 22 are laminated on the upper side of the second surface 100S of the multilayer core board 100, and the second conductor layer 22 and the sixth conductor layer, which is the outermost conductor layer of the multilayer core board 100, are laminated. Via conductors 23a and 23b connecting layer 142 are formed. The second conductor layer 22 is formed into a pattern including conductor pads 22a and conductor pads 22b. Via conductor 23a is formed such that conductor pad 22a is connected to fourth heat transfer conductor 145 via via conductor 23a. Via conductor 23b is formed such that conductor pad 22b is connected to sixth conductor layer 142 via via conductor 23b.

Next, as shown in FIG. 2G, a first covering layer 14 and a second covering layer 24, which are, for example, solder resist layers, are formed on the first conductive layer 12 and the second conductive layer 22, respectively. The formation of the first laminated portion 10 on the first surface 100F of the multilayer core substrate 100 and the formation of the second laminated portion 20 on the second surface 100S are completed. The first coating layer 14 is formed, for example, by applying a photosensitive epoxy resin, exposing it to light, and developing it to have an opening 14c that exposes the conductor pads 12a and 12b. The second covering layer 24 is formed to have an opening 24c that exposes the conductor pad 22a and the conductor pad 22b. Manufacturing of the wiring board 1 is completed.

The wiring board of the embodiment is not limited to the structure illustrated in each drawing or the structure and material illustrated in this specification. For example, the wiring board of the embodiment may not include the inner conductor layer 100M as shown in FIG. An example of this is shown in FIG. Note that many components of the wiring board 1a shown in FIG. 3 are the same as those of the wiring board 1 shown in FIG. Omitted.

In the wiring board 1a shown in FIG. 3, the multilayer core board 100a has four conductor layers (in order from the second surface 100S to the first surface 100F: a sixth conductor layer 142a, a fourth conductor layer 122a, a third It has a conductor layer 112a and a fifth conductor layer 132a). Two metal bodies, a metal body 115a and a metal body 135a, each having a tapered shape whose diameter decreases toward the fourth conductor layer 122a are formed in this order on the upper side of the fourth conductor layer 122a. A metal body 27a having a tapered shape whose diameter decreases toward the fourth conductor layer 122a is formed below the fourth conductor layer 122a. That is, in the wiring board 1a, one of the conductor layers included in the multilayer core board 100a corresponds to the inner conductor layer 100M of the wiring board 1.

Further, as shown in FIG. 3, each of the fourth conductor layer 122a and the third conductor layer 112a included in the multilayer core board 100a has a conductor pattern 122b extending to the component mounting area and the area outside thereof in a plan view. and a conductive pattern 112b. In the wiring board 1a, the heat emitted from the electronic component D1 and conducted to the multilayer core board 100 flows along the stacking direction via the metal bodies 135a, 115a, and 27a, and also flows through the conductor pattern 122b and the fourth conductor layer 122a. It can also be conducted through the conductor pattern 112b of the third conductor layer 112 in the planar direction, that is, to an area outside the component mounting area.

In wiring boards 1 and 1a, the first laminated portion and the second laminated portion each have one insulating layer and one conductive layer. However, the number of insulating layers and conductive layers included in the first laminated portion and the second laminated portion of the wiring board is not limited to this, and may be increased or decreased to a desired number of layers. The number of insulating layers and conductive layers included in the multilayer core board of the wiring board can also be increased or decreased to a desired number. Further, a plurality of sets of multistage heat transfer conductors may be formed on the wiring board. Although not shown in FIGS. 1 and 3, the exposed surface of the conductor pad included in the outermost conductor layer of the wiring board is coated with, for example, Ni/Au, Ni/Pd/Au, or Sn. A protective film may be formed, which may be multiple or single metal plating films, or an OSP film. Further, the method for manufacturing the wiring board is not limited to the method described with reference to each drawing, and the conditions, order, etc. may be changed as appropriate. Depending on the structure of the wiring board that is actually manufactured, some steps may be omitted or other steps may be added.

1, 1a Wiring board 10 First laminated portion 20 Second laminated portion 11 First insulating layer 12 First conductor layer 12a Conductor pad (first conductor pad)
12b, 22b conductor pad 13a via conductor (first via conductor)
13b, 23b via conductor 17, 27 multistage heat transfer conductor 21 second insulating layer 22 second conductor layer 22a conductor pad (second conductor pad)
23a Via conductor (second via conductor)
100, 100a Multilayer core board 100M Inner conductor layer 115, 125, 135, 145 Metal body (first to fourth heat transfer conductor)
D1 Electronic component WB Wiring structure

Claims (7)

a multilayer core substrate including a first surface and a second surface opposite to the first surface, and including a plurality of insulating layers and a plurality of conductor layers stacked alternately;
a first laminated portion formed on the first surface and having a first layered portion 12a including a first conductive pad exposed on the outermost surface;
a second laminated portion formed on the second surface and exposing a second conductor layer including a second conductor pad to the outermost surface;
a first via conductor formed in the first laminated portion and connected to the first conductor pad;
a second via conductor formed in the second laminated portion and connected to the second conductor pad;
A wiring board having
The first conductor pad is a component mounting pad arranged within a component mounting area,
The multilayer core substrate further includes a multistage heat transfer conductor including a plurality of laminated metal bodies,
The multi-stage heat transfer conductor is connected to the first conductive pad via the first via conductor and to the second conductive pad via the second via conductor. 2. The wiring board according to claim 1, wherein the multistage heat transfer conductor is connected to a conductor layer of the plurality of conductor layers that extends to the component mounting area and an area outside thereof in a plan view. 2. The wiring board according to claim 1, wherein the multistage heat transfer conductor includes three or more of the metal bodies stacked together. 2. The wiring board according to claim 1, wherein the plurality of metal bodies are arranged at positions that substantially overlap each other in a plan view. The wiring board according to claim 1,
The metal body is formed in a first through hole that penetrates the insulating layer of the multilayer core substrate. The wiring board according to claim 5,
The multilayer core board includes a via conductor formed in a second through hole penetrating the insulating layer of the multilayer core board,
The metal body and the via conductor are formed integrally with a conductor layer formed above them,
The opening area of the first through hole on the surface side of the insulating layer is larger than the opening area of the second through hole on the surface side of the insulating layer. 2. The wiring board according to claim 1, wherein the thickness of the second conductor layer is greater than the thickness of the first conductor layer.

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