JP3165617B2 - Multilayer printed wiring board and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rigid, flexible, composite multilayer printed wiring board, and more particularly to a structure for connecting conductive layers of a multilayer printed wiring board and a method of manufacturing the same .

[0002]

2. Description of the Related Art A conventional multilayer printed wiring board is composed of a plurality of conductor layers (conductor patterns) formed by etching or the like, and through holes connecting the respective layers.

A conventional multilayer printed wiring board and its manufacturing process will be described with reference to FIGS. FIG. 6 is a cross-sectional view showing the first half of the manufacturing process of the multilayer printed wiring board, and FIG. 7 is a cross-sectional view showing the structure of the multilayer printed wiring board and the second half of the manufacturing process. This conventional example will be described using a typical four-layered multilayer printed wiring board.

The structure of the multilayer printed wiring board is shown in FIG.
As shown in (c), the outer layer conductor pattern 1 serving as the first layer
, A double-sided core material (inner substrate) 5 having inner layer conductor patterns 3 and 4 serving as second and third layers, and an outer layer conductor pattern 6 serving as fourth layer
A single-sided core material (outer layer substrate) 7 having an adhesive, an adhesive layer (insulating layer) 8 interposed between the single-sided core materials 2, 7 and the double-sided core material 5, and a through hole 9 penetrating therethrough And a copper plating 10 covering the surface of the through hole 9 and the surface of the outer layer conductor patterns 1 and 6.

[0005] The single-sided core members 2 and 7 are made of a base material 2 ',
Outer conductor patterns 1 and 6 are formed on one surface of 7 ', and double-sided core material 5 is formed by inner conductor patterns 3 and 4 formed on the front and back surfaces of base substrate 5'.

The through hole 9 and the metal plating 10 covering the surface thereof constitute a through hole 11 for connecting the conductor patterns 1, 3, 4, and 6.

Hereinafter, a process of manufacturing the multilayer printed wiring board will be described.

First, as shown in FIG. 6 (a), unprocessed continuous copper foils 3 ', 4' serving as an inner layer circuit are formed on a base material 5 '.
6B, a double-sided core material 5 laminated on the front and back surfaces is prepared.
As shown in FIG. 3, the copper foils 3 'and 4' are formed into necessary inner conductor patterns 3 and 4 by etching or the like, and the inner core material 5 is formed.
To form

Next, as shown in FIG. 6C, on the front and back sides of the double-sided core material 5 on which the inner layer conductor patterns 3 and 4 are formed,
Adhesive sheet 8 'and single-sided core materials 2 and 7 in which unprocessed continuous copper foils 1' and 6 'serving as outer layer circuits are laminated on one surface of base materials 2' and 7 'are sequentially laminated. Thereafter, pressure is applied while heating them, and they are laminated as shown in FIG.

In this state, since the inner layer circuit and the outer layer circuit are not connected, as shown in FIG. 7A, a through hole 9 penetrating the entire laminated board 12 including the inner layer circuit is drilled or the like. Then, as shown in FIG. 7B, electroless and electrolytic copper plating 10 is applied to the inner wall surface of the through hole 9 and the entire surface of the copper foils 1 'and 6' of the outer layer. At this stage, the inner layer circuit and the outer layer circuit are electrically connected by the through hole 11.

Finally, as shown in FIG. 7 (c), the outer copper foils 1 ', 6' and the copper plating 10 applied to the surfaces thereof are formed into necessary outer conductor patterns 1, 6 by etching or the like. A four-layer printed wiring board is obtained.

As described above, in the conventional multilayer printed wiring board, the electrical connection between the inner conductor patterns 3 and 4 and the outer conductor patterns 1 and 6 is provided on the inner wall of the through hole 9 by providing the through hole 9. Cross section of inner conductor patterns 3 and 4 corresponding to copper foil thickness and copper plating 1 in through hole 11
It was done through zero.

[0013]

As the technology advances, the components mounted on the multilayer printed wiring board have become multifunctional and smaller, and the wiring density has been increased. In addition, the dimensions of products in which a multilayer printed wiring board is incorporated are also becoming smaller and thinner due to the trend toward light, thin and small. As a result, the multilayer printed wiring board is required to be thinner and finer, and in order to realize this, the copper foil of the outer and inner conductor patterns 1, 3, 4, and 6 is required to be thinner. Incidentally, the copper foil thickness of a general conventional conductor pattern is 35 μm, and it is currently being considered to have a copper foil thickness of 18 μm, and it is considered that the copper foil thickness will be 9 μm in the future. .

However, when the copper foil of the inner conductor patterns 3 and 4 becomes thinner, the inner conductor patterns 3 and 4 in the conventional structure become thinner.
The electrical connection between the outer conductor patterns 1 and 6 is made only through the cross section of the copper foil thickness where the inner conductor patterns 3 and 4 are exposed on the inner wall of the through hole 9 and through the copper plating 10 in the through hole 11. In addition, the connection area tends to decrease, and the connection reliability tends to decrease.

In addition, since the diameter of the through hole 11, specifically, the diameter of the through hole 9 is reduced in order to increase the wiring density, the range of processing conditions for forming a beautiful shape is narrowed. A resin deposit sometimes called smear is likely to be generated on the inner wall of the hole. Incidentally, the hole diameter of a general conventional through-hole 9 is 0.5φ, and a hole diameter of 0.4φ is being studied as the diameter is reduced.

FIG. 8 is a perspective view of a cross section of a through hole for explaining a state in which smear has occurred after drilling. In the figure, 3 and 4 are inner layer conductor patterns, 9 is a through hole, and 13 is a smear.

When the smear 13 occurs on the portion of the inner conductor patterns 3 and 4 exposed on the inner wall of the through hole 9 as shown in FIG.
The connection area between 0 and the inner conductor patterns 3 and 4 is remarkably reduced, and the connection reliability between the two is reduced. In the worst case, the through-hole connection is broken.

SUMMARY OF THE INVENTION In view of the above problems, the present invention provides a multilayer printed wiring board and a method of manufacturing the multilayer printed wiring board, in which the thickness of the inner conductor pattern is reduced and the diameter of the through hole is reduced to prevent disconnection of the through hole connection part. The purpose is to do.

[0019]

According to a first aspect of the present invention, there is provided a multilayer printed wiring board comprising an inner layer base material having an inner layer conductor pattern formed on at least one surface thereof; Printed wiring, comprising: an outer conductor pattern laminated on an insulating layer via an insulating layer; a first through hole penetrating the outer conductor pattern; and a first metal plating covering the surface of the first through hole and the outer conductor pattern. In the substrate, the inner layer substrate has a continuous copper foil laminated on the surface.
A second through hole substantially concentric with the first through hole in the inner layer base material.
After the through hole is formed, the second through hole inner wall surface and the
Electroless and electrolytic plating is applied to the entire copper foil surface on the inner layer base substrate surface.
After the hook is applied and the second metal plating is formed,
Copper foil on the surface of the layer base material and the second copper foil formed on the surface of the copper foil
2 Metal plating forms inner layer conductor pattern by etching
And an insulating layer on the inner conductor pattern on the inner substrate surface.
After the copper foil serving as the outer layer pattern is laminated via the
Copper foil table as inner wall surface of second through hole and outer layer pattern
First metal plating with electroless and electrolytic plating on the entire surface
Is formed, a copper foil serving as the outer layer pattern and the copper foil
The first metal plating formed on the copper foil surface is etched
The outer conductor pattern .

[0020]

According to a second aspect of the present invention, in the multi-layer printed wiring board, the diameter of the through hole for the inner layer formed of the second through hole and the second metal plating covering the surface thereof is made equal to the diameter of the first through hole. It is characterized by having substantially the same diameter.

According to a third aspect of the present invention, in the multi-layer printed wiring board according to the present invention, the diameter of the through hole for connecting the inner layer made of the second through hole and the second metal plating covering the surface thereof is made larger than the diameter of the first through hole. Also has a small diameter. The method for manufacturing a multilayer printed wiring board according to claim 4 of the present invention is characterized in that a continuous copper foil is formed on both sides of the inner layer base material.
A through hole is formed in the inner double-sided core material laminated on the surface, and the through hole is formed.
Copper foil surface on the inner wall surface of the through hole and on the front and back surfaces of the inner layer base material
Electroless and electrolytic copper plating on the whole, the inner layer base
Copper foil on the front and back of the substrate and copper plating formed on the surface of the copper foil
Is formed on the inner conductor pattern by etching,
With a through-hole concentric with the through-hole formed in the core material
Adhesive sheet and continuous copper foil
Through holes formed in the inner layer double-sided core material laminated on the surface
An outer layer core material having concentric through portions,
After sequentially laminating on the inner conductor pattern side of the core material, heat
While applying pressure to form a laminate, the inner layer double-sided core
A through hole formed in the material, a through portion of the adhesive sheet,
Inner wall surface with penetration of outer layer core material and outer layer base substrate
Electroless and electrolytic copper plating on the entire copper foil surface
And forming a copper foil on the surface of the outer layer base material and a surface of the copper foil.
Outer layer conductor pattern by etching the formed copper plating
It is characterized by being formed in.

[0023]

According to the above structure, the present invention has the above-described structure, and therefore , the penetration of the second metal plating surface or the inner layer double-sided core material.
Copper plating formed on the hole inner wall surface of the first inner wall of the through hole also
Is exposed to the through-hole of the laminated plate and becomes a connection part, and the connection area is significantly increased compared to the connection area of the connection part only in the cross section corresponding to the thickness of the inner conductor pattern exposed to the inner wall of the conventional through-hole,
High connection reliability can be obtained even when the thickness of the inner conductor pattern is reduced.

Further, even if a smear occurs in the cross section of the inner conductor pattern, the outer conductor pattern, or the like at the time of forming a hole in the inner base material, the outer base material, or the like, the main connection between the inner conductor pattern and the outer conductor pattern is maintained. , Inner layer conductor pattern surface,
On the inner wall surface of the through-hole of the second metal plating or inner layer double-sided core material
Formed copper plating , first metal plating or inner double-sided core
Through-holes formed in the material, through-holes in the adhesive sheet and outer layer core
Since the copper plating is formed on the inner wall surface with the through portion of the material and is performed through the outer layer conductor pattern surface, the connection reliability is not impaired by the smear.

Further, in the multilayer printed wiring board according to a third aspect of the present invention, the diameter of the through hole for the inner layer formed of the second through hole and the second metal plating covering the surface of the second through hole is smaller than that of the first through hole. Since the diameter is smaller than the hole diameter, the second metal plating covering the surface of the inner conductor pattern is exposed in the first through hole, and the second metal plating is also connected to the first metal plating. Therefore, higher connection reliability can be obtained.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A multilayer printed wiring board according to an embodiment of the present invention and a manufacturing process thereof will be described with reference to FIGS. FIG. 1 is a cross-sectional view showing the structure of the multilayer printed wiring board and the latter half of the manufacturing process, and FIG. 2 is a cross-sectional view showing the first half of the manufacturing process of the multilayer printed wiring board. In the present embodiment, description will be made using a typical multilayer printed wiring board having a four-layer structure.

The structure of the multilayer printed wiring board is shown in FIG.
As shown in (d), the outer layer conductor pattern 2 serving as the first layer
, A double-sided core material (inner substrate) 25 having inner and outer conductor patterns 23 and 24 serving as second and third layers, and an outer conductor pattern serving as a fourth layer Second single-sided core material (outer layer substrate) 27 having 26
And an adhesive layer (insulating layer) 28 interposed between the single-sided core members 22 and 27 and the double-sided core material 25, a first through hole 29 penetrating therethrough, a surface of the first through hole 29, First copper plating 3 covering surfaces of outer conductor patterns 21 and 26
0, wherein the double-sided core material 25 is concentric with the first through-hole 29 and extends through the double-sided core material 25 including the inner-layer conductor patterns 23 and 24. And a second copper plating 32 covering the surface of the second through-hole 31 and the surface of the inner conductor patterns 23 and 24, and the surface of the second copper plating 32 is covered with the first copper plating 30. Consists of a structure.

The single-sided core members 22, 27 have outer conductor patterns 21, 26 formed on one surface of base materials (outer base materials) 22 ', 27', respectively, and include the outer conductor patterns 21, 26. A penetrating portion penetrating the single-sided core members 22 and 27 is formed.

The double-sided core material 25 is provided on the front and back surfaces of a base material (inner layer base material) 25 'with an inner conductor pattern 23,
24, and a second through hole 31 penetrating the double-sided core material 25 including the inner conductor patterns 23 and 24 is formed.
The inner wall surface of the second through hole 31 and the inner conductor pattern 23;
The second copper plating 32 is applied to the surface of the substrate 24. That is, the second through hole 31 and the second copper plating 32 covering the inner wall surface constitute an inner layer connection through hole 33 for connecting the inner conductor patterns 23 and 24 to each other. The single-sided core members 22 and 27 and the double-sided core member 25 are laminated with the central axes of the through-holes of the single-sided core members 22 and 27 and the through-holes 33 for connecting the inner layer of the double-sided core member 25 aligned. One through hole 29 as a printed wiring board is formed, and the surface thereof is covered with a first metal plating 30 to connect the inner conductor patterns 23 and 24 and the outer conductor patterns 21 and 26. That is, the first through-hole 29 and the first copper plating 30 covering the inner wall surface form the inner conductor patterns 23 and 24 and the outer conductor patterns 21 and 24.
26 are formed.

Hereinafter, the manufacturing process of the multilayer printed wiring board will be described.

First, as shown in FIG. 2 (a), a double-sided core material 25 is prepared by laminating unprocessed continuous copper foils 23 'and 24' serving as an inner layer circuit on the front and back surfaces of a base material 25 '. As shown in FIG. 2B, a through hole 31 having a predetermined diameter is formed at a predetermined position of the double-sided core material 25 by a drill or the like.

Next, as shown in FIG. 2 (c), an electric field-free and electric field copper plating 32 is applied to the inner wall surface of the through hole 31 and the entire surface of the copper foils 23 ', 24' to form a through hole 33 for connecting the inner layer. I do. Thereby, the copper foils 23 ', 24'
Are electrically connected.

Next, as shown in FIG.
3 ', 24' and the copper plating 32 formed on the surface thereof are etched to form necessary inner layer conductor patterns 23, 24.
Formed.

Next, as shown in FIG. 1A, the inner-layer connection through-holes 33 and 24 and the inner-layer connection through-holes 33 are formed on the front and back surfaces of the double-sided core material 25, respectively. An adhesive sheet 28 'having a penetrating portion 28a concentric and the same diameter with respect to the through hole 33 at a corresponding position, and unprocessed continuous copper foils 21' and 26 'serving as an outer layer circuit are attached to the base substrate 22. , 27 ′, and single-sided core members 22, 27 having through-holes 22 a, 27 a concentric and of the same diameter with respect to the through-hole 30. While applying pressure, the layers are laminated as shown in FIG. 1B to form one laminated plate 35 having the through holes 29.

In this state, since the inner layer circuit and the outer layer circuit are not connected, as shown in FIG.
9. Electroless and electrolytic copper plating 30 is applied to the inner wall surface and the entire surface of the outer copper foils 21 'and 26'. At this stage, the inner circuit and the outer copper foils 21 ', 26' are electrically connected by the through holes 34.

Finally, as shown in FIG. 1D, the outer copper foils 21 'and 26' and the copper plating 3
0 is a necessary outer layer conductor pattern 21 by etching or the like.
26 to obtain a four-layer printed wiring board.

As described above, according to the multilayer printed wiring board of this embodiment, the through holes 33 (specifically, the second copper plating 32) for connecting the inner layer are exposed on the inner wall of the first through hole 29, and the inner layer circuit is formed. The connection area increases significantly as compared with the connection area of only the cross section corresponding to the thickness of the conventional inner conductor pattern exposed on the inner wall of the through-hole.
High connection reliability can be obtained even when the thickness of the first and the second 26 is reduced.

Also, when the inner layer base material 25 'and the outer layer base materials 22' and 27 'are drilled, the inner layer conductor pattern 2' is formed.
Even if smears occur in the cross sections 3 and 24 and the cross sections of the outer conductor patterns 21 and 26, the main connection between the inner conductor patterns 23 and 24 and the outer conductor patterns 21 and 26 is made as shown in FIG. 23, 24 surface, second copper plating 3
2. Since the first copper plating 30 is performed through the surface of the outer conductor patterns 21 and 26, the connection reliability is not impaired by the smear. In the figure, 36 is a smear.

For this reason, fine patterning of the inner conductor patterns 23 and 24, thinning of the multilayer printed wiring board,
That is, the conductor patterns 21, 23, 24, and 26 are made thinner (especially, copper foil thickness: 18 μm or less), and the diameter of the through holes 34 is reduced (especially, the hole diameters: 0.4 to 0.2 φ), thereby breaking the connection portions of the through holes. Can be prevented.

FIG. 4 is a sectional view showing a multilayer printed wiring board according to another embodiment of the present invention. In the present embodiment, only the points different from the above embodiment will be described.

The multi-layer printed wiring board has an adhesive layer 28
And the penetrating portions 28 of the single-sided core members 22 and 27 as the outer layer substrates
a, 22a, 27a Double-sided core material 2 as inner layer substrate
5 is a structure in which the hole diameter of the through hole 33 for the inner layer connection is larger than the hole diameter of the through hole 33 for the inner layer connection.

Thus, a step is formed in the through hole 34, and the inner conductor patterns 23, 2 of the inner core material 25 are formed.
Since the part of the second copper plating 32 covering the four surfaces is exposed and is electrically connected to the first copper plating 30 together with the second copper plating part in the through hole 33 for the inner layer connection, Higher connection reliability can be obtained as compared with the embodiment.

FIG. 5 is a sectional view showing a multilayer printed wiring board according to still another embodiment of the present invention. This embodiment will be described only with respect to differences from the embodiment shown in FIGS.

The multilayer printed wiring board has a plurality of through holes for connection to the inner layer formed in the double-sided core material 25 which is an inner layer substrate, and a through hole 34 formed at a position corresponding to the through hole for connection to the inner layer. The inner via hole (IVH) 3
A multilayer printed wiring board with 7 can be realized.

Although the above embodiment has been described using a four-layer printed wiring board, the present invention is not limited to the above-described embodiment. For example, the number of inner layers and the number of adhesive layers may be appropriately increased or decreased, or By using a single-sided core material,
The present invention can also be applied to a multilayer printed wiring board having six, six, or more layers.

The outer core material may be a double-sided core material and may have the same structure as the double-sided core material of the above embodiment.

Further, in the above embodiment, only the outer conductor patterns 22, 26 may be used instead of the single-sided core members 22, 27.

[0048]

As described in the foregoing, the present onset Ming, the inner wall surface of the inner connecting through hole provided in advance inner layer board, the through hole for connection to the innerlayer conductor pattern and the outer layer conductor pattern overlaps structure Therefore, the connection area between the inner layer circuit and the through hole is greatly increased, and high connection reliability can be obtained even when the thickness of the inner layer conductor pattern is reduced. Also, even if smears occur in the inner layer conductor pattern cross section, the outer layer conductor pattern cross section, or the like at the time of drilling holes in the inner layer base material, the outer layer base material, etc., the connection reliability between the layers is not impaired.

Therefore, a multilayer printed wiring board corresponding to a fine pattern of the inner layer circuit, a thinner multilayer printed wiring board, and a smaller through hole diameter can be obtained.

Further, in the multilayer printed wiring board according to the third aspect of the present invention, the second metal plating covering the surface of the inner conductor pattern is exposed in the first through hole, so that higher connection reliability is achieved. can get.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a structure of a multilayer printed wiring board according to an embodiment of the present invention and a latter half of a manufacturing process thereof.

FIG. 2 is a cross-sectional view showing a first half of a manufacturing process of the multilayer printed wiring board.

FIG. 3 is a cross-sectional view for explaining a state when smear occurs in the embodiment shown in FIG. 1;

FIG. 4 is a sectional view showing a multilayer printed wiring board according to another embodiment of the present invention.

FIG. 5 is a sectional view showing a multilayer printed wiring board according to still another embodiment of the present invention.

FIG. 6 is a cross-sectional view showing the first half of a conventional multi-layer printed wiring board manufacturing process.

FIG. 7 is a sectional view showing the structure of the multilayer printed wiring board and the latter half of the manufacturing process.

8 is a perspective view for explaining a state when smear occurs in the conventional multilayer printed wiring board shown in FIG. 7;

[Explanation of symbols]

 21, 26 Outer conductor pattern 22, 27 Single-sided core material (outer substrate) 22 ', 27' Outer base material 23, 24 Inner conductor pattern 25 Double-sided core material (inner substrate) 25 'Inner base material 28 Adhesive layer ( Insulating layer) 29 first through hole 30 first metal plating 31 second through hole 32 second metal plating 33 through hole for inner layer connection

Claims (4)

(57) [Claims] 1. An inner layer substrate in which an inner layer conductor pattern is formed on at least one surface of an inner layer base substrate, an outer layer conductor pattern laminated on front and back surfaces of the inner layer substrate via an insulating layer, and penetrates these. In a multilayer printed wiring board comprising: a first through hole; and a first metal plating covering a surface of the first through hole and a surface of the outer layer conductor pattern, the inner layer substrate has a continuous copper foil laminated on a surface thereof. Inner layer
A second through hole substantially concentric with the first through hole is formed in the base material.
After being formed, the inner wall surface of the second through hole and the inner layer base are formed.
Electroless and electrolytic plating on the entire copper foil surface
After forming the second metal plating, the inner layer base is formed.
Copper foil on the base material surface and second gold formed on the copper foil surface
Metal plating is formed on the inner conductor pattern by etching.
And the outer conductor pattern on the inner substrate surface is interposed via an insulating layer.
After the copper foil serving as the layer pattern is laminated, the second penetration
On the inner wall surface of the hole and the entire surface of the copper foil to be the outer layer pattern
Electroless and electrolytic plating applied to form first metal plating
After that, the copper foil to be the outer layer pattern and the copper foil table
The first metal plating formed on the surface is etched to form an outer layer
A multilayer printed wiring board formed on a conductor pattern . 2. A second cover for covering the second through hole and its surface.
The hole diameter of the through hole for inner layer connection consisting of metal plating
2. The multilayer printed wiring board according to claim 1, wherein the diameter of the first through hole is substantially the same as the diameter of the first through hole . 3. A second cover for covering the second through-hole and the surface thereof.
The hole diameter of the through hole for inner layer connection consisting of metal plating
2. The multilayer printed wiring board according to claim 1, wherein the diameter of the first through hole is smaller than the diameter of the first through hole . 4. A continuous copper foil is formed on both sides of an inner layer base material.
A through-hole is formed in an inner-layer double-sided core material laminated on the substrate, and a copper foil on the inner wall surface of the through-hole and the front and back surfaces of the inner-layer base material
Electroless and electrolytic copper plating on the entire surface to form on the copper foil on the front and back surfaces of the inner layer base material and on the surface of the copper foil
Etched copper plating into inner layer conductor pattern
Formed and penetrated concentrically with the through holes formed in the inner layer double-sided core material
Adhesive sheet with a continuous section and a continuous copper foil
Formed on the inner layer double-sided core material laminated on the surface of the material.
A through hole and an outer layer core material having a concentric through portion;
After sequentially laminating on the inner layer conductor pattern side of the layer double-sided core material,
A laminate is formed by applying pressure while heating, and the through holes formed in the inner layer double-sided core material and the adhesive sheet are formed.
Inner wall surfaces of the through portion of the outer core material and the through portion of the outer layer core material;
Electroless and electroless over the entire copper foil surface on the outer layer base substrate surface
Copper plating is applied to form a copper foil on the surface of the outer layer base material and a surface of the copper foil.
Etched copper plating into outer layer conductor pattern by etching
Manufacturing method of multilayer printed wiring board characterized by comprising
Law .