JP2001210953A - Wiring board and producing method for the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wiring board and a producing method for the same, with which a breakage hardly occurs on a through hole conductor and reliability is high. SOLUTION: A wiring board 1 is provided with a core substrate 3, composed of the compound materials of inorganic fibers and resins, a principal side resin insulating layer 5 formed on a principal surface 3A and a backside resin insulating layer 7 formed on a rear surface 3B. Between the core substrate 3 and the principal side resin insulating layer 5, a principal side conductor layer 15 is formed and between the core substrate 3 and the principal side resin insulating layer 7, a backside conductor layer 19 is formed. Also a medium thickness through-hole 9 is formed on the core substrate 3 and a medium thick through- hole conductor 11 thicker than the principal side conductor 15 and the backside conductor 19 is formed therein.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wiring board in which a resin insulating layer is laminated on a core board, the wiring board having a through-hole conductor penetrating the core board, and a method of manufacturing the wiring board. The present invention relates to a wiring board whose substrate is made of a composite material of an inorganic fiber such as glass fiber and quartz fiber and a resin, and a method of manufacturing the wiring board.

[0002]

2. Description of the Related Art Conventionally, among wiring boards in which a resin insulating layer is laminated on a core board, the core board is made of a composite material of an inorganic fiber such as glass fiber or quartz fiber and a resin, and penetrates the core board. There is known a structure in which a through-hole conductor is formed. For example, there is a wiring board 101 whose partial enlarged sectional view is shown in FIG. The wiring substrate 101 has a substantially plate-shaped core substrate 103 made of a composite material obtained by impregnating a glass fiber cloth with a resin at the center thereof.
The main surface side resin insulation layer 105 is formed on the upper surface, and the back surface side resin insulation layer 107 is formed on the back surface 103B.

The core substrate 103 includes a main surface 103.
A and a substantially cylindrical through hole 1 penetrating between A and the back surface 103B.
09 are formed in large numbers. Each through-hole 109 has a substantially cylindrical through-hole conductor 1 along its inner peripheral surface.
11 are formed. Further, a through-hole conductor 111 is provided between the core substrate 103 and the main surface side resin insulation layer 105.
A main surface-side conductor layer 113 including a wiring layer, a connection pad, and the like is formed, and a wiring layer connected to the through-hole conductor 111 is also provided between the core substrate 103 and the back surface-side resin insulation layer 107. Back-side conductor layer 11 composed of pads and the like
5 are formed.

The main surface side conductor layer 113 such as a connection pad is provided.
A part of the opening 10 formed in the main-surface-side resin insulating layer 105 for mounting an IC chip or the like on the wiring board 101 is formed.
It is exposed within 5K. Similarly, the connection pads and the like of the back side conductor layer 115 are also exposed in the opening 107K formed in the back side resin insulation layer 107 to connect the wiring board 101 to another board or the like.

[0005]

SUMMARY OF THE INVENTION Such a wiring board 1
In No. 01, since the core substrate 103 is made of a composite material of an inorganic fiber and a resin, the coefficient of thermal expansion in the planar direction of the core substrate 103 is relatively small due to the inorganic fibers, that is, the coefficient of thermal expansion of the conductor layer and the like. It is suppressed to the same degree. Therefore, stress generated in the main-surface-side conductor layer 113 and the rear-surface-side conductor layer 115 due to the difference in the coefficient of thermal expansion between the core substrate 103 and the conductor layer or the like is relatively small.

However, since the coefficient of thermal expansion in the thickness direction of the core substrate 103 is hardly suppressed by the inorganic fibers, the coefficient of thermal expansion becomes a value close to the coefficient of thermal expansion of the resin, and greatly differs from the coefficient of thermal expansion of the conductor layer and the like. . For this reason, the core substrate 10
3 through-hole conductor 11 formed in through-hole 109
In No. 1, stress due to a difference in thermal expansion coefficient is applied in the thickness direction (axial direction), and in a heat cycle test or the like, a problem such as breakage of the through-hole conductor 111 in the through-hole 109 may occur. Poor reliability.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a wiring board and a method of manufacturing the wiring board which are less likely to break in the through-hole conductor and have high reliability.

[0008]

Means for Solving the Problems, Action and Effect The solution is to provide a core substrate having a main surface and a back surface, made of a composite material of inorganic fibers and a resin, and formed on the main surface of the core substrate. At least one main-surface-side resin insulation layer, at least one back-surface-side resin insulation layer formed on the back surface of the core substrate, the core substrate, the main-surface-side resin insulation layer, and the back-side resin Of the insulating layer, at least a through hole penetrating between a plane formed by the main surface and a plane formed by the back surface of the core substrate, a through-hole conductor formed on an inner peripheral surface of the through hole, and the core substrate A main-surface-side conductor layer formed between the main-surface-side resin insulation layers or between the main-surface-side resin insulation layers and connected to the through-hole conductor at the main-surface-side end of the through hole; It is formed between resin insulation layers or between resin insulation layers on the back side. A backside conductor layer connected to the through-hole conductor at the backside end of the through-hole, wherein the thickness of the through-hole conductor is greater than the thicknesses of the main surface-side conductor layer and the backside-side conductor layer It is.

In a wiring board in which the core substrate is made of a composite material of inorganic fibers and a resin, as described above, the coefficient of thermal expansion in the planar direction of the core substrate is relatively small and can be suppressed to the same level as that of the conductor layer and the like. However, the coefficient of thermal expansion in the thickness direction of the core substrate is significantly different from that of the conductor layer and the like. Specifically,
For example, in a core substrate made of FR-4 (a composite material in which glass fiber is impregnated with an epoxy resin), the coefficient of thermal expansion in the planar direction is equal to the coefficient of thermal expansion of a conductor layer (for example, 17.7 p in Cu).
pm (20-300 ° C.)), while the thermal expansion coefficient in the thickness direction is about 50-60.
ppm, which is significantly different from the coefficient of thermal expansion of the conductor layer and the like.

Therefore, relatively small stress is applied to the main-surface-side conductor layer and the back-surface-side conductor layer formed between the core substrate and the resin insulating layer. Also, since the thermal expansion coefficient of the core substrate is low, the thermal expansion coefficient of the resin insulating layer of the main surface side conductor layer and the rear surface side conductor layer formed between the main surface side resin insulation layer and the back surface side resin insulation layer is also low. Is suppressed, so that the stress applied to these conductor layers is also small. On the other hand, through-hole conductors that penetrate only the core substrate and through-hole conductors that penetrate the core substrate and the resin insulation layers formed on the main surface and the back surface of the core substrate also differ from the thermal expansion coefficient of the core substrate. In the case where the resin insulating layer also penetrates, a stress is further applied due to a difference from the coefficient of thermal expansion of the resin insulating layer. For this reason,
In a heat cycle test or the like, problems such as breakage of the through-hole conductor in the through-hole easily occur.

On the other hand, in the present invention, the thickness of the through-hole conductor formed in the thickness direction of the core substrate is made larger than the thickness of the main surface side conductor layer and the back surface side conductor layer formed in the plane direction. I have. For this reason, the stress caused by the difference in the coefficient of thermal expansion between the through-hole conductor and the core substrate and the difference in the coefficient of thermal expansion between the through-hole conductor and the resin insulating layer when the through-hole conductor also penetrates the resin insulating layer. Even if the resulting stress is applied, the breakage of the through-hole conductor is prevented. Therefore,
This wiring board is less likely to break in the through-hole conductor and has high reliability.

Here, the through-hole includes not only a hole that directly penetrates the core substrate but also a hole that penetrates a resin or the like filled in the hole penetrating the core substrate. Even in the through-hole conductor formed in such a filling body, the filling body also expands in accordance with the thermal expansion in the thickness direction of the core substrate, which is caused by a difference in the coefficient of thermal expansion between the core substrate and the through-hole conductor. This is because stress is generated and the through-hole conductor is easily broken. Therefore, by making the thickness of such a through-hole conductor thicker than the thickness of the main-surface-side conductor layer and the back-surface-side conductor layer, breakage of the through-hole conductor can be prevented.

The composite of the inorganic fiber and the resin may be appropriately selected in consideration of the strength and heat resistance of the wiring board, but may be selected from inorganic fiber cloths made of inorganic fibers such as glass fiber and quartz fiber. Inorganic fiber nonwoven fabric, inorganic fiber paper, and the like are impregnated with a resin such as an epoxy resin.

Further, in the above wiring board, it is preferable that the thickness of the through-hole conductor is the thickest in the vicinity of the central portion in the axial direction.

When stress is generated in the through-hole conductor due to a difference in the coefficient of thermal expansion from that of the core substrate, it is found that the most susceptible portion of the through-hole conductor tends to be near the center in the axial direction. ing. On the other hand, in the present invention, the thickness of the through-hole conductor is greatest near the center in the axial direction. In other words, the thickness of the portion that is easily broken by the stress due to the difference in the coefficient of thermal expansion is increased. Therefore, in this wiring board, the breakage of the through-hole conductor is less likely to occur, and the reliability can be further improved.

Another solution is to provide a through hole penetrating between the main surface and the back surface at a predetermined position of a core substrate having a main surface and a back surface and made of a composite material of an inorganic fiber and a resin. Or a substrate main surface at a predetermined position of a substrate comprising the core substrate and at least one main surface side resin insulating layer and at least one back surface resin insulating layer formed on the main surface and the rear surface, respectively. And a through-hole forming step of forming a through-hole penetrating between the substrate and the back surface of the substrate, and forming the first plating layer on the main surface and the back surface, or on the main surface of the substrate and the back surface of the substrate, A plating layer forming step of forming a substantially cylindrical through-hole conductor made of a second plating layer thicker than the first plating layer on the inner peripheral surface of the through hole; and etching the first plating layer to form a predetermined pattern. A conductor layer forming step of forming a conductor layer of It is a method of manufacturing a substrate.

According to the present invention, in the plating layer forming step, the first plating layer is formed on the main surface and the back surface of the core substrate, or on the main surface of the substrate and the back surface of the substrate by a plating technique. At the same time, since a through-hole conductor thicker than the first plating layer is formed on the inner peripheral surface of the through-hole, they can be formed at once. Furthermore, by forming the thickness of the through-hole conductor thicker than the thickness of the conductor layer, the through-hole conductor can be broken even if stress is applied to the through-hole conductor due to a difference in thermal expansion coefficient with the core substrate. Is prevented. Therefore, the through-hole conductor is less likely to break, and a highly reliable wiring board can be manufactured.
Further, in the conductor layer forming step, the first plating layer is etched to form the conductor layer.
Since the plating layer is thinned, the etching is performed efficiently and accurately, so that the pattern accuracy of the conductor layer can be improved.

Here, in the plating layer forming step, besides making the thickness of the second plating layer larger than that of the first plating layer by a plating technique, the following method can be adopted. That is, for example, in the plating step of the plating layer forming step, the first plating layer is formed on the main surface and the back surface of the core substrate, or on the substrate main surface and the back surface of the substrate, and the through hole is formed. A second plating layer is formed on the inner peripheral surface of the substrate. Thereafter, in a polishing step, the first plating layer is polished and removed. Also in this case, in the plating layer forming step, the second plating layer can be made thicker than the first plating layer.

For example, in the plating step of the plating layer forming step, the first plating layer is formed on the main surface and the back surface of the core substrate, or on the main surface of the substrate and the back surface of the substrate. A second plating layer is formed on the inner peripheral surface of the through hole. Thereafter, in an etching roughening step, the plating layer is roughened while being etched using formic acid or the like. When the etching is roughened, the second plating layer in the through-hole is hardly roughened, so that the first plating layer can be selectively thinned.

Further, in the above-described method for manufacturing a wiring board, in the through-hole forming step, a medium-thick through-hole having the largest diameter near the center in the axial direction is formed by a laser.
In the plating layer forming step, a method of manufacturing a wiring board for forming a medium-thick through-hole conductor in which the thickness of the through-hole conductor is largest near the center in the axial direction is preferable.

According to the present invention, in the through hole forming step, the middle through hole having a large diameter near the center in the axial direction is formed. Therefore, in the plating layer forming step, the through hole conductor is formed by a plating technique. A through-hole conductor whose thickness is the thickest near the center in the axial direction can be easily formed. Such a medium-thick through-hole conductor is thicker in a portion that is more likely to be broken by stress due to a difference in the coefficient of thermal expansion from the core substrate, so that the through-hole conductor is more reliably prevented from being broken. Therefore, according to the manufacturing method of the present invention, the through-hole conductor is less likely to break, and a wiring board having higher reliability can be easily manufactured.

[0022]

(Embodiment 1) Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a partially enlarged cross-sectional view of the wiring board 1 of the present embodiment. This wiring board 1 is provided at its center with a core substrate 3 made of a composite material obtained by impregnating a glass fiber cloth (inorganic fiber) with an epoxy resin (resin) and having a substantially plate shape with a thickness of about 800 μm. On the main surface 3A, a main-surface-side resin insulation layer 5 made of epoxy resin or the like having a thickness of about 50 μm is provided.
A backside resin insulation layer 7 made of 0 μm epoxy resin or the like is formed.

The core substrate 3 has a large number of through holes 9 penetrating between the main surface 3A and the back surface 3B. The diameter of the through hole 9 gradually increases from the vicinity of the main surface side end 9A and the rear surface side end 9B toward the vicinity of the central portion 9C in the axial direction, and the through hole 9 has the largest diameter near the center 9C. Thick through holes 9 with diameters near both ends of about 55
μm, and the diameter near the center 9C is about 70 μm.
And, in the inside of this medium-sized through hole 9, Cu
A substantially cylindrical through-hole conductor 11 is formed. This through-hole conductor 11 has a main surface side end 11.
A and the central portion 11C in the axial direction from the vicinity of the rear end portion 11B.
This is a medium-thick through-hole conductor 11 whose thickness gradually increases in the vicinity and becomes thickest in the vicinity of the central portion 11C. The thickness near both ends is about 25 μm each,
The thickness near 1C is about 30 to 35 μm. Note that a resin filler 12 made of epoxy resin or the like is formed in the through-hole conductor 11.

On the main surface 3A of the core substrate 3, that is, between the core substrate 3 and the main surface side resin insulating layer 5, a medium through hole 9 is formed.
Wiring layer 13 and connection pad 14 connected to main surface side end 11A of medium thickness through-hole conductor 11 at main surface side end 9A.
The main surface side conductor layer 15 is formed. Similarly,
On the back surface 3B, that is, also between the core substrate 3 and the back surface side resin insulation layer 7, wiring connecting to the back surface side end portion 11B of the medium-thick through-hole conductor 11 at the back side end portion 9B of the medium through hole 9 Tier 1
A back-side conductor layer 19 composed of 7 and connection pads 18 is formed. Each of the main surface side conductor layer 15 and the back surface side conductor layer 19 is made of Cu and has a thickness of about 20 μm.
It has become. Therefore, the above-described medium-thick through-hole conductor 11 (about 25 to 35 μm in thickness) is thicker than these conductor layers throughout.

A large number of openings 5K are formed in the resin insulating layer 5 on the main surface side.
In order to mount an IC chip (not shown), the connection pad 14 of the main-surface-side conductor layer 15 is exposed. Similarly, a large number of openings 7K are also formed in the backside resin insulating layer 7, and a connection of the backside conductor layer 19 is provided in each of the openings 7K in order to connect the wiring board 1 to another substrate (not shown). Pad 18 is exposed.

In such a wiring board 1, since the core board 3 is made of a composite material of glass fiber cloth and epoxy resin, the thermal expansion coefficient of the core board 3 in the plane direction is about 15 ppm.
And the coefficient of thermal expansion of Cu (about 17.7).
ppm). Therefore, the stress in the plane direction (the left-right direction in the drawing) caused by the difference in the coefficient of thermal expansion between the core substrate 3 and the main surface side conductor layer 15 and the back surface side conductor layer 19 is relatively small. On the other hand, since the coefficient of thermal expansion in the thickness direction of the core substrate 3 is hardly suppressed by the glass fiber cloth, it is about 50 to 60 ppm, which is a value close to the coefficient of thermal expansion of the epoxy resin, and the coefficient of thermal expansion of Cu (about 17. 7 ppm). Accordingly, the medium-thick through-hole conductor 11 formed in the core substrate 3 includes the core substrate 3 and the medium-thick through-hole conductor 1.
A stress is applied in the thickness direction (axial direction) due to the difference in the coefficient of thermal expansion from 1.

However, in the present embodiment, the thickness (about 25 to about 35 μm) of the medium-thick through-hole conductor 11 is larger than the thickness (about 20 μm) of the main surface side conductor layer 15 and the back surface side conductor layer 19. Accordingly, even when a large stress is applied, the breakage of the medium-thickness through-hole conductor 11 is prevented. In particular,
The thickness of the medium-thick through-hole conductor 11 is
In addition, since the thickness of the backside conductor layer 19 is 25% or more of the thickness of the backside conductor layer 19, breakage of the medium-thick through-hole conductor 11 can be more effectively prevented. Further, in the present embodiment, the thickness of the medium-thickness through-hole conductor 11 is the largest near the central portion 11C in the axial direction. In other words, the thickness is increased in a portion that is easily broken by a stress due to a difference in thermal expansion coefficient. Therefore, the medium-thick through-hole conductor 11
Are more difficult to break, and the reliability of the wiring board 1 is high.

Next, a method of manufacturing the wiring board 1 will be described with reference to FIGS. First, FIG.
As shown in (a), the core substrate 3 prepared by a known method, that is, a substantially plate-shaped core substrate 3 made of a composite material in which glass fiber is impregnated with an epoxy resin is prepared.

Next, in the through hole forming step, FIG.
As shown in (b), a predetermined position of the core substrate 3 is pierced by a laser to form a large number of large through holes 9 penetrating between the main surface 3A and the back surface 3B. Specifically, the diameter gradually increases from the vicinity of the main surface side end portion 9A and the back surface side end portion 9B toward the vicinity of the central portion 9C in the axial direction, and the central portion 9
A middle through hole 9 having the largest diameter near C is formed. At this time, the laser conditions and the like may be changed as appropriate according to the material and thickness of the core substrate 3. In this case, a CO ₂ laser is used and the conditions are such that the pulse width is 150 μmsec and the pulse peak is 1 KW. The cycle pulse method has 10 shots. It is preferable to form the through-hole 9 by such laser processing, because the medium-thick through-hole 9 can be formed at once without any special processing.

Next, in the plating layer forming step, FIG.
As shown in (a), the main surface 3A and the back surface 3 of the core substrate 3
B, the first plating layer 21 is formed on the inner peripheral surface of the middle and thick through-holes 9, and the thickness of the first plating layer 21 is gradually increased toward the vicinity of the central portion in the axial direction. The second plating layer 22 having a large thickness, that is, the medium-thick through-hole conductor 11 is formed.

Specifically, first, electroless plating is performed,
Main surface 3A and back surface 3B of core substrate 3 and medium-sized through hole 9
An electroless plating layer is formed on the inner peripheral surface of the substrate. Furthermore, after pretreatment in a pre-dip tank in which a brightener (brightener) is diluted by 50%, electrolytic plating is performed to form an electrolytic plating layer on the electroless plating layer. At this time, the conditions of the electrolytic plating are appropriately selected, and the thickness of the central portion 1 is larger than that of the first plating layer 21.
A medium-thick through-hole conductor 11 having the thickest portion near 1C is formed. Here, the conditions for the electrolytic plating were as follows:
/ L, H ₂ SO ₄ is 180g / l, Cl ^- is 48 mg /
1, the leveler (plating inhibitor) is 0.3 mg / l, and the current density is 1 A / dm ² . As the brightener, a sulfur-containing organic compound such as thiourea or thiocarbamate can be used, and as the leveler, a polyamine or the like can be used.

Thus, the first plating layer 21 and the thicker through-hole conductor 11 having a larger thickness are formed at a time. Further, in the present embodiment, in the through hole forming step, the middle diameter through hole 9 having the largest diameter is formed in the vicinity of the central portion 9C, so that the vicinity of the central portion 11C of the through hole conductor 11 is changed to the main surface side end portion. It can be made thicker than the vicinity of 11A and the back side end 11B.

Next, in a filling body forming step, a resin filling body 12 is formed in the medium-thick through-hole conductor 11 (see FIG. 3B). Specifically, the medium-thick through-hole conductor 1
A resin paste in which an epoxy resin is mixed with an inorganic filler and a curing agent is printed and filled in 1 and heated and semi-cured. Thereafter, excess resin swelling from the main surface 3A and the back surface 3B of the core substrate 3 is polished and removed, and the semi-cured resin is cured by heating to form the resin filler 12.

Next, in the conductor layer forming step, FIG.
As shown in (b), the first plating layer 21 is etched to form the main surface side conductor layer 15 and the rear surface side conductor layer 19 (conductor layer) in a predetermined pattern. Specifically, an etching resist layer having a predetermined pattern is formed on the first plating layer 21 and the like, and the first plating layer 21 exposed from the resist layer is removed by etching, so that the main-surface-side conductor layer 15 and the rear-surface-side The conductor layer 19 is formed. At this time, in the plating layer forming step, the first plating layer 21 is formed into the medium thickness through-hole conductor 11.
Since the thickness is thinner than that, the etching can be performed efficiently and accurately, and the main surface side conductor layer 15 and the back surface side conductor layer 19 with high pattern accuracy can be formed.

Next, in the resin insulating layer forming step, the main surface side resin insulating layer 5 having the opening 5K is formed on the main surface 3A of the core substrate 3, and the back side resin insulating layer having the opening 7K is formed on the back surface 3B. 7 are formed respectively. Specifically, the core substrate 3
A semi-cured main-surface-side resin insulating layer made of epoxy resin or the like and a back-side resin insulating layer are formed on the main surface 3A and the back surface 3B, respectively, using a mask having a predetermined pattern corresponding to the openings 5K and 7K. Exposure and further development. Thereafter, the substrate is further heated and cured to form the main surface side resin insulating layer 5 having the opening 5K and the back surface side resin insulating layer 7 having the opening 7K. Also in this step, the main surface side conductor layer 1
5 and the back side conductor layer 19 are relatively thin,
The unevenness of the main surface 3A and the back surface 3B is reduced, and the surfaces of the main surface side resin insulation layer 5 and the back surface side resin insulation layer 7 can be formed more flat. As described above, the wiring board 1 of the present embodiment shown in FIG. 1 is completed.

(Embodiment 2) Next, a wiring board and a method of manufacturing the wiring board of Embodiment 2 will be described with reference to FIGS. The description of the same parts as in the first embodiment will be omitted or simplified. FIG. 4 is a partially enlarged cross-sectional view of the wiring board 51 of the present embodiment. This wiring board 5
1 is a core substrate 5 similar to the core substrate 3 of the first embodiment.
3 is provided. On the main surface 53A, a main surface side first resin insulation layer 55P made of epoxy resin or the like having a thickness of about 50 μm,
Further, a main-surface-side resin insulating layer 55 composed of two main-surface-side second resin insulating layers 55Q made of epoxy resin or the like having a thickness of about 40 μm and laminated thereon is formed. Also, on the back surface 53B, a back side first resin insulating layer 57P made of an epoxy resin or the like having a thickness of about 50 μm, and a back side second resin made of an epoxy resin or the like having a thickness of about 40 μm laminated thereon. Back side resin insulating layer 5 composed of two layers of insulating layer 57Q
7 are formed.

The core substrate 53 has a main surface 53
A number of outer through holes 59 penetrating between A and the back surface 53B
(Through holes) are formed. This outer through hole 59 is
It has a substantially cylindrical shape with a diameter of about 300 μm, and its inner peripheral surface has
A substantially cylindrical outer through-hole conductor 61 (through-hole conductor) made of Cu having a thickness of about 25 μm is formed.
An outer resin filler 62 made of an epoxy resin or the like is formed in the outer through-hole conductor 61.

The outer resin filler 62 has an outer through hole 5
9 (outer through-hole conductor 61), penetrating between a plane formed by the main surface 53A of the core substrate 53 and a plane formed by the back surface 53B, and further formed on the main surface side first resin insulating layer 55P and the back surface side. An inner through-hole 63 that penetrates also the first resin insulating layer 57P is formed. The inner through-hole 63 gradually extends from the boundary between the core substrate 53 and the main surface side resin insulating layer 55 and the boundary between the core substrate 53 and the back surface side resin insulating layer 57 toward the vicinity of the central portion 63C in the axial direction. The diameter becomes large and becomes the largest in the vicinity of the central portion 63C. In addition, the inner through hole has a shape whose diameter gradually increases from the boundary toward the main surface side end portion 63A and the back surface side end portion 63B.
The diameter at each boundary is about 55 μm, and the central part 63C
The diameter in the vicinity is about 70 μm, and the diameter in the vicinity of the main surface side end 63A and the back surface side end 63B is about 70 μm, respectively.

A substantially cylindrical inner through-hole conductor 65 made of Cu and formed substantially coaxially with the outer through-hole conductor 61 is formed on the inner peripheral surface of the inner and middle through-hole 63. The thickness of the inner through-hole conductor 65 gradually increases from the vicinity of the main surface side end 65A and the rear surface side end 65B toward the vicinity of the central portion 65C in the axial direction, and becomes thickest near the central portion 65C. An inner middle through-hole conductor 65 having the following shape. Main surface side end 65A and back surface side end 65
The thickness in the vicinity of B is about 25 μm, and the thickness in the vicinity of the central portion 65C is about 30 to 35 μm. Note that an inside resin filler 66 made of epoxy resin or the like is formed in the inside medium thickness through-hole conductor 65.

The outer through hole 5 is provided between the core substrate 53 and the main-surface-side resin insulating layer 55 (the main-surface-side first resin insulating layer 55P).
A main surface side core conductor layer 69 (main surface side conductor layer) composed of a wiring layer connected to the main surface side end portion 61A of the outer through-hole conductor 61 is formed at the main surface side end portion 59A. Similarly, the core substrate 53 and the back side resin insulating layer 57 (the back side first
The back-side core conductor layer 7 formed of a wiring layer connected to the back-side end 61B of the outer through-hole conductor 61 at the back-side end 59B of the outer through-hole 59 also between itself and the resin insulating layer 57P).
1 (backside conductor layer) is formed. Both the main surface side core conductor layer 69 and the rear surface side core conductor layer 71
u, and its thickness is about 20 μm. Therefore, the above-mentioned outer through-hole conductor 61 (about 25 μm thick)
m) is thicker than these conductor layers.

Further, between the main-surface-side resin insulation layers 55 (between the main-surface-side first resin insulation layers 55P and the main-surface-side second resin insulation layers 55Q), the main-surface-side inner through hole 63 has At the end 63A,
A main surface side interlayer conductor layer 75 (main surface side conductor layer) including a wiring layer 73 and a connection pad 74 connected to the main surface side end portion 65A of the inner middle through-hole conductor 65 is formed. Similarly, between the back side resin insulation layers 57 (the back side first resin insulation layer 5).
7P and the back side second resin insulating layer 57Q), the wiring layer 7 connected to the back side end 65B of the inner middle through-hole conductor 65 at the back side end 63B of the inner middle through hole 63.
A back-side interlayer conductor layer 79 (back-side conductor layer) including the connection pads 7 and the connection pads 78 is formed. Each of the main surface side interlayer conductor layer 75 and the back surface side interlayer conductor layer 79 is made of Cu and has a thickness of about 20 μm. Therefore, the thickness of the above-mentioned inner middle through-hole conductor 65 (about 25 to
35 μm) is thicker than these conductor layers throughout.

In the main-surface-side first resin insulation layer 55P of the main-surface-side resin insulation layer 55, a main-surface-side via for connecting the main-surface-side core conductor layer 69 and the main-surface-side interlayer conductor layer 75 is provided. Conductor 81
A large number of back side via conductors 83 connecting the back side core conductor layer 71 and the back side interlayer conductor layer 79 are also formed on the back side first resin insulation layer 57P of the back side resin insulation layer 57. ing.

Further, a large number of openings 55K are formed in the second resin insulating layer 55Q on the main surface side of the resin insulating layer 55 on the main surface side, and a connection of the main surface side interlayer conductor layer 75 is formed in each opening 55K. The pad 74 is exposed. Similarly, a large number of openings 57K are formed in the second resin insulating layer 57Q on the back surface of the resin insulating layer 57 on the back surface, and the connection pads 78 of the back surface side interlayer conductor layer 79 are exposed in each opening 57K. ing.

The wiring board 51 has a coefficient of thermal expansion (about 1) in the plane direction of the core board 53, as in the first embodiment.
5 ppm) is about the same as the coefficient of thermal expansion of Cu (about 17.7 ppm). Therefore, the stress in the plane direction caused by the difference in the coefficient of thermal expansion between the core substrate 53 and the main surface side core conductor layer 69 and the back surface side core conductor layer 71 is small. In addition, the core substrate 53 also suppresses the coefficient of thermal expansion of the main surface side resin insulation layer 55 and the back surface side resin insulation layer 57 in the planar direction. Also in the back side interlayer conductor layer 79 between the back side resin insulation layers 57, the stress generated due to the difference in the coefficient of thermal expansion is small.

On the other hand, the coefficient of thermal expansion in the thickness direction of the core substrate 53 (about 50 to 60 ppm) is the same as the coefficient of thermal expansion of Cu (about 17.6 ppm).
7 ppm). Therefore, the outer through-hole conductor 61 penetrating only through the core substrate 53 is provided with the core substrate 5.
Stress in the thickness direction (axial direction) is applied due to the difference between the coefficient of thermal expansion of Cu and the coefficient of thermal expansion of Cu. When the core substrate 53 expands, the outer resin filler 62 is also pulled in the thickness direction. In addition, the main surface side first resin insulation layer 55P and the back surface side first resin insulation layer 55Q also expand in the thickness direction. For this reason, the thickness direction (due to the difference in the coefficient of thermal expansion) also occurs in the inner middle through-hole conductor 65 penetrating the core substrate 53, the main surface side first resin insulation layer 55P, and the back surface side first resin insulation layer 55Q. (Axial direction) stress is applied.

However, in this embodiment, the thickness of the outer through-hole conductor 61 (about 25 μm) and the thickness of the inner middle through-hole conductor 65 (about 25 to 35 μm) are determined by changing the main surface side core conductor layer 69 and the back surface. Side core conductor layer 71, main surface side interlayer conductor layer 75, and back surface side interlayer conductor layer 79 (each about 20 μm)
The through-hole conductors are prevented from breaking even when a large stress is applied. Further, the inner middle through-hole conductor 65 is thickest in the vicinity of the central portion 65C as in the case of the middle through-hole conductor 11 of the first embodiment. 51 is highly reliable.

Next, a method for manufacturing the wiring board 51 will be described with reference to FIGS. First, a core substrate 53 similar to that of the first embodiment is prepared, and in the outer through-hole forming step, as shown in FIG.
The main surface 53A and the back surface 53B
And a large number of outer through holes 59 penetrating therethrough. Since the outer through-hole 59 has a large diameter (about 300 μm), the outer through-hole 59 is drilled with a drill in consideration of work efficiency and the like. Therefore, unlike the through hole 9 of the first embodiment and the inner through hole 63 of the present embodiment, the through hole 9 is a substantially cylindrical through hole.

Next, in a core plating layer forming step, as shown in FIG. 5B, a first core plating layer 85 (first plating layer) is formed on the main surface 53A and the back surface 53B of the core substrate 53.
And the inner peripheral surface of the outer through hole 59 is provided with the first
The second core plating layer 87 (second
An outer through-hole conductor 61 made of a plating layer) is formed. Specifically, the electroless plating and the electrolytic plating may be performed in the same manner as in the plating layer forming step of the first embodiment. As a result, the first core plating layer 85 and the thicker outer through-hole conductor 61 are formed at one time.

Next, in the outer filler forming step, an outer resin filler 62 is formed in the outer through-hole conductor 61 (see FIG. 6A). Specifically, a resin paste in which an epoxy resin is mixed with an inorganic filler and a curing agent is printed and filled in the outer through-hole conductor 61, and the resin paste is heated and semi-cured. After that, excess resin swelling from the main surface 53A and the back surface 53B of the core substrate 53 is polished and removed, and the semi-cured resin is cured by heating to form the outer resin filler 6.
Form 2 The resin paste has a viscosity at 25 ° C. of 2000 Pa · S or less and an elastic modulus of 3.0 to 3.0.
It is preferable to use a paste having a GPa of 8.0 GPa and a volatile content of the paste of 1.0% or less when heated, in terms of good print filling properties and prevention of cracking after curing. Further, the inorganic filler is preferably a spherical filler having a particle size of 0.1 to 10 μm.

Next, in the core conductor layer forming step, the first core plating layer 85 is etched in the same manner as in the conductor layer forming step of the first embodiment, and the main conductor core layer 69 and the rear core core in a predetermined pattern are formed. The conductor layer 71 is formed (FIG. 6
(A)). At that time, in the core plating layer forming step,
Since the first core plating layer 85 is thinner than the outer through-hole conductor 61, the first core plating layer 85 can be efficiently and accurately etched, and the main surface side core conductor layer 69 and the rear surface side core conductor layer 71 having high pattern accuracy are formed. can do.

Next, in the first resin insulating layer forming step,
As shown in FIG. 6A, the main surface side first resin insulating layer 55P having the bottomed hole 55Y on the main surface 53A of the core substrate 53 in the same manner as in the resin insulating layer forming step of the first embodiment.
Are also formed on the back surface 53B, respectively, on the back surface side first resin insulating layer 57P having the bottomed hole 57Y.

Next, in the inner through-hole forming step, FIG.
As shown in (b), a predetermined position of a substrate 89 composed of the core substrate 53, the first resin insulating layer 55P on the main surface side, and the first resin insulating layer 57P on the back surface is pierced by a laser, and the substrate main surface 8 is formed.
A large number of inner middle through holes 63 penetrating between 9A and the back surface 89B of the substrate are formed. Specifically, the central portion 63 is formed under the same laser conditions as in the through-hole forming step of the first embodiment.
The vicinity of C forms the largest inner middle through hole 63. At this time, the main surface side first insulation layer 55P and the back surface side first resin insulation layer 57P are easier to be laser-processed than the core substrate 53. The diameter becomes larger toward the main surface side end portion 63A and the rear surface side end portion 63B. By performing the laser processing in this manner, the inner and middle through-holes 63 can be formed at once without performing special processing.

Next, in the substrate plating layer forming step, as shown in FIG. 7A, a first substrate plating layer 91 (first plating layer) is formed on the substrate main surface 89A and the substrate back surface 89B of the substrate 89. Further, the main surface side via conductor 81 and the back surface side via conductor 83 are formed in the bottomed holes 55Y and 57Y. Along with these, on the inner peripheral surface of the inner middle thick through-hole 63, a second thickness that is thicker than the first substrate plating layer 91 over the entirety and gradually increases toward the vicinity of the central portion in the axial direction. Inner middle thickness through-hole conductor 65 composed of substrate plating layer 93
To form

Specifically, the electroless plating and the electrolytic plating may be performed in the same manner as the plating layer forming step of the first embodiment and the core substrate plating layer forming step of the present embodiment.
As a result, the first substrate plating layer 91, the inner middle through-hole conductor 65 thicker than this, and the via conductor are formed at one time. Also, at this time, in the inside through-hole forming step, since the large diameter inside middle through-hole 63 is formed in the vicinity of the center portion 63C, the vicinity of the center portion 65C of the inside through-hole conductor 65 is changed to the main surface side end portion. The thickness can be easily increased as compared with the vicinity of 65A and the back side end 65B.

Next, in the inner filling body forming step, the inner resin filling body 66 is formed in the inner middle thick through-hole conductor 65 (see FIG. 7B). Specifically, a resin paste in which a metal filler, an inorganic filler, and a curing agent are mixed into an epoxy resin is printed and filled in the inner middle-thick through-hole conductor 65, and the resin paste is heated and semi-cured. Then, the substrate 8
Excess resin that swells from the main surface 89A and the back surface 89B of 9 is polished and removed, and the semi-cured resin is cured by heating to form the outer resin filler 66. In addition, as the resin paste, it is preferable to use a resin paste having a physical property value in the range described in the outer filler forming step. Further, the metal filler is preferably a spherical filler having a particle size of 1.0 to 20 μm. preferable.

Next, in the step of forming the interlayer conductor layer, the first substrate plating layer 91 is etched as shown in FIG. Interlayer conductor layer 75 and backside interlayer conductor layer 79
To form At this time, in the substrate plating layer forming step, the first substrate plating layer 91 is
Since the thickness is smaller than that, the etching can be performed efficiently and accurately, and the main surface side interlayer conductor layer 75 and the back surface side interlayer conductor layer 79 with high pattern accuracy can be formed.

Next, in the second resin insulating layer forming step,
Similarly to the first resin insulating layer forming step, a main surface side second resin insulating layer 55Q having an opening 55K is formed on the substrate main surface 89A of the substrate 89, and a back surface having an opening 57K is formed on the substrate back surface 89B. The second resin insulation layers 57Q are respectively formed. As described above, the wiring board 51 of the present embodiment shown in FIG. 4 is completed.

The present invention has been described with reference to the first and second embodiments.
However, it is needless to say that the present invention is not limited to the first and second embodiments and can be appropriately modified and applied without departing from the gist of the present invention. For example, in the first embodiment, the medium-thick through-hole conductor 11 is formed in the medium-thick through-hole 9, and in the second embodiment,
An inner middle through-hole conductor 65 is formed in the inner middle through hole 63. However, these through holes should be substantially cylindrical through holes, and the through hole conductor should be thick near the center, or these through holes should be approximately cylindrical through holes, and the through hole conductor should have a substantially uniform thickness. It can also be substantially cylindrical. Also in this case, since the thickness of the through-hole conductor is thicker than the conductor layer formed in the plane direction, breakage of the through-hole conductor is prevented.

In the second embodiment, the substantially cylindrical outer through-hole conductor 59 is formed in the substantially cylindrical outer through hole 59.
The outer through-hole 59 has the largest diameter in the vicinity of the center in the axial direction, and the outer through-hole conductor 61 has the thickest outer middle through-hole in the vicinity of the center in the axial direction. It can also be a conductor. In addition, the outer through hole 5
Without changing the shape of 9, the outer through-hole conductor 61 may be an outer middle-thick through-hole conductor having the thickest portion near the center in the axial direction. By forming such a thick through-hole conductor, breakage of the outer through-hole conductor is further prevented, and the reliability of the wiring board is further increased.

In the second embodiment, the thickness of the outer through-hole conductor 61 is made larger than the thickness of the main surface side core conductor layer 69 and the thickness of the rear surface side core conductor layer 71. The thickness is also greater than the thickness of the main surface side interlayer conductive layer 75 and the back surface side interlayer conductive layer 79. However, it is also possible to make only one of the through-hole conductors thicker than the conductor layer. Even in such a case, with respect to the thick through-hole conductor, the through-hole conductor hardly breaks, and the reliability of the wiring board can be increased.

In the second embodiment, the wiring board 51 having the outer through-hole conductors 61 and the inner through-holes 65 coaxial with the outer through-hole conductors 61 is shown. , Core substrate 53, main surface side first resin insulation layer 55P, and back surface side first resin insulation layer 5
The wiring board may be provided with a through-hole conductor penetrating through 7P. Like the inner through-hole conductor 65 of the second embodiment, such a through-hole conductor is less likely to break even when a stress is generated in the axial direction, and the wiring board has high reliability. The wiring board having the through-hole conductor can be manufactured by forming only the first core plating layer 85 (first plating layer) without forming the second core plating layer 87 in the core plating layer forming step. .

[Brief description of the drawings]

FIG. 1 is a partially enlarged cross-sectional view of a wiring board according to a first embodiment.

FIGS. 2A and 2B are diagrams illustrating a method of manufacturing the wiring board according to the first embodiment, wherein FIG. 2A is an explanatory view illustrating a core substrate, and FIG.
FIG. 4 is an explanatory view showing a state in which a through hole is formed.

3A and 3B are diagrams illustrating a method of manufacturing the wiring board according to the first embodiment, in which FIG. 3A is an explanatory diagram illustrating a state in which a plating layer is formed, and FIG. 3B is a state in which a conductor layer having a predetermined pattern is formed; FIG.

FIG. 4 is a partially enlarged cross-sectional view of a wiring board according to a second embodiment.

5A and 5B are diagrams illustrating a method of manufacturing the wiring board according to the second embodiment, wherein FIG. 5A is an explanatory view illustrating a state in which an outer through hole is formed in a core substrate, and FIG. It is explanatory drawing which shows a situation.

6A and 6B are diagrams illustrating a method of manufacturing the wiring board according to the second embodiment, wherein FIG. 6A is an explanatory view illustrating a state in which a first resin insulating layer is formed, and FIG. It is explanatory drawing which shows a mode that it formed.

FIGS. 7A and 7B are diagrams illustrating a method of manufacturing the wiring board according to the second embodiment, wherein FIG. 7A is an explanatory view illustrating a state where a substrate plating layer and a via conductor are formed, and FIG. It is explanatory drawing which shows a mode that the layer was formed.

FIG. 8 is a partially enlarged cross-sectional view of a wiring board according to the related art.

[Explanation of symbols]

1, 51 Wiring board 3, 53 Core board 3A, 53A Main surface (of core substrate) 3B, 53B Back surface (of core substrate) 5, 55 Main surface side resin insulation layer 7, 57 Back surface side resin insulation layer 9 Through hole ( 9C (through-hole conductor) central part 11 through-hole conductor (medium-thick through-hole conductor) 11C (through-hole conductor) central part 15 main-surface-side conductor layer 19 back-side conductor layer 59 outside through-hole 61 outside Through-hole conductor 63 Inner through-hole (inner middle through-hole) 63C (inner through-hole conductor) central portion 65 Inner through-hole conductor (inner middle-thick through-hole conductor) 65C (inner through-hole conductor) central portion 69 Main surface side Core conductor layer 71 Backside core conductor layer 75 Main surface side interlayer conductor layer 79 Backside interlayer conductor layer 89 Substrate 89A Substrate main surface 89B Substrate rear surface

Claims (4)

[Claims] 1. A core substrate having a main surface and a back surface and comprising a composite material of inorganic fibers and a resin, at least one main-surface-side resin insulating layer formed on the main surface of the core substrate. At least one backside resin insulation layer formed on the backside of the core substrate, and at least the main surface of the core substrate among the core substrate, the main surface side resin insulation layer, and the backside resin insulation layer A through-hole penetrating between a plane formed by the rear surface and a plane formed by the back surface; a through-hole conductor formed on the inner peripheral surface of the through-hole; A main surface side conductor layer formed between the resin insulation layers and connected to the through hole conductor at a main surface side end of the through hole; and between the core substrate and the back surface side resin insulation layer, or between the back surface side resin insulation layers. The through-hole conductor is formed at an end on the back side of the through-hole. The back surface side and the conductor layer, with a thickness of the through-hole conductors is thicker wiring board than the thickness of the main surface side conductor layer and the back surface side conductor layer to be connected. 2. The wiring board according to claim 1, wherein the thickness of the through-hole conductor is greatest near a central portion in the axial direction. 3. A core substrate having a main surface and a back surface, comprising a through hole penetrating between the main surface and the back surface at a predetermined position of a core substrate made of a composite material of an inorganic fiber and a resin. Board and
At a predetermined position of the substrate composed of at least one main-surface-side resin insulating layer and at least one back-surface-side resin insulating layer formed on the main surface and the back surface, the substrate penetrates between the main surface of the substrate and the back surface of the substrate. A through-hole forming step of forming a through-hole; forming a first plating layer on the main surface and the back surface, or on the main surface and the back surface of the substrate, and forming the first plating layer on the inner peripheral surface of the through-hole; A plating layer forming step of forming a substantially cylindrical through-hole conductor made of a second plating layer thicker than the first plating layer; and forming a conductor layer of a predetermined pattern by etching the first plating layer. And a method for manufacturing a wiring board. 4. The method for manufacturing a wiring board according to claim 3, wherein in the through hole forming step, a middle diameter through hole having the largest diameter near an axial center is formed by a laser. In the plating layer forming step, a method of manufacturing a wiring board for forming a medium-thick through-hole conductor in which the thickness of the through-hole conductor is largest near a central portion in the axial direction.