JP2003078247A - Wiring board and method of manufacturing the same - Google Patents

Abstract

(57) [Summary] [PROBLEMS] In a stacked via structure, an electrical connection area is large, and the density of wiring conductors cannot be increased. A first wiring conductor having a first wiring conductor formed on an upper surface thereof is provided.
A second wiring conductor 2b having an insulating resin layer 1a and a second wiring conductor 2b formed on the upper surface;
The insulating resin layer 1b and the third insulating resin layer 1c are sequentially laminated so that a part of the first and second wiring conductors 2a and 2b are vertically overlapped. The first through hole 3a penetrating through the second insulating resin layer 1b and the second wiring conductor 2b, and has a cross section that is located immediately above the first through hole 3a and through the first through hole 3a that penetrates through the third insulating resin layer 1c. A large second through hole 3b is formed, and a metal thin film 4 is formed from the inner walls of the first and second through holes 3a and 3b to the upper surface of the third insulating resin layer 1c.
A wiring board to which a wiring conductor 2a, a second wiring conductor 2b, and a third wiring conductor 2c formed of a metal thin film 4 formed on an upper surface of a third insulating resin layer 1c are connected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wiring board used for mounting electronic parts such as semiconductor elements and a method for manufacturing the same.

[0002]

2. Description of the Related Art Generally, current electronic devices are required to be small, thin, lightweight, high-performance, high-performance, high-quality and highly reliable as represented by mobile communication devices. Electronic devices mounted on various electronic devices are also required to be small and have high density. Therefore, wiring boards that make up electronic devices are also required to be small, thin, and have multiple terminals. To achieve this, the widths of wiring conductors such as signal conductors are made narrower and the intervals between them are reduced. High-density wiring is achieved by multilayering wiring conductors.

A wiring board manufactured by adopting a build-up method is known as a wiring board capable of such high-density wiring. Build-up wiring board is, for example, a core insulation layer surface cured by impregnating a reinforcing material such as glass cloth or aramid non-woven fabric with a thermosetting resin typified by an epoxy resin having heat resistance and chemical resistance. After the wiring conductor has been deposited, a resin varnish made of thermosetting resin such as epoxy resin is applied and cured by heating to form an insulating resin layer. ~ 20
After forming a through hole of about 0 μm, the inner wall of the through hole and the surface of the insulating resin layer are chemically roughened with a roughening solution such as potassium permanganate solution, and then the surface of the insulating resin layer and the through hole are penetrated by using a semi-additive method. It is manufactured by depositing a copper conductor film on the inner wall of the hole to form a wiring conductor and a through conductor, and forming an insulating resin layer and a through conductor / wiring conductor thereon a plurality of times.

Recently, in order to further increase the density of the build-up wiring board, the width and spacing of the wiring conductors have been reduced, and the diameter of the through holes has been reduced to reduce the spacing. Further, a wiring board having a stacked via structure in which through conductors are arranged in the vertical direction has been put into practical use.

As a wiring board having such a stacked via structure, Japanese Unexamined Patent Publication No. 2001-156450 discloses a planar board, a wiring circuit formed on the surface of the board, and a wiring board including the wiring circuit. The first part that penetrates to the wiring circuit
A first insulating resin layer having a via hole formed therein, a first via formed in the first via hole, and a second via hole formed on the first insulating resin layer and partially penetrating to the bottom surface of the first via are formed. A second insulating resin layer and a second via formed in the second via hole, and the second via hole has a space between the inner peripheral side surface of the first via and the outer peripheral side surface of the second via,
A build-up multilayer printed wiring board having a size such that at least the inner bottom surface of the first via and the outer side surface of the second via contact each other has been proposed.

[0006]

[Problems to be Solved by the Invention]
In the build-up multilayer printed wiring board described in Japanese Patent Publication No. 01-156450, the second via is formed inside the first via, so the diameter of the opening of the first via hole is increased in order to increase the density of the wiring circuit. If the value is decreased, the connection area between the bottom surface of the second via and the first via becomes smaller, and the temperature cycle test (TC
In a thermal fatigue resistance test such as T), the thermal stress due to the difference in thermal expansion between the insulating resin layer and the via is concentrated in the connection portion between the two, resulting in disconnection failure, which results in higher density of the wiring board. In addition, when a plurality of insulating resin layers are laminated, the diameter of the opening portion of the first via hole becomes considerably large according to the number of laminated layers, and the wiring board becomes large. Had.

In the method of manufacturing the build-up multilayer printed wiring board described above, the second insulating resin layer must be formed after forming the first via, and then the second via hole and the second via must be formed. Therefore, there is a problem that the manufacturing process becomes complicated.

The present invention has been completed in view of the above problems of the prior art, and an object thereof is a stacked via structure in which through conductors are vertically arrayed, in which electrical connection is necessary and sufficient and a wiring conductor An object of the present invention is to provide a wiring board which can achieve high density and has high connection reliability, and a manufacturing method thereof.

[0009]

A wiring board according to the present invention comprises a first insulating resin layer having a first wiring conductor formed on an upper surface thereof and a second insulating resin layer having a second wiring conductor formed on an upper surface thereof. The first insulating layer and the third insulating resin layer are sequentially laminated so that the first and second wiring conductors partially overlap with each other, and
A first through hole penetrating the second insulating resin layer and the second insulating resin layer located on the wiring conductor, and a third insulating resin layer penetrating immediately above the first through hole. A second through hole having a cross section larger than that of the first through hole is formed, and a metal thin film is formed from the inner walls of the first and second through holes to the upper surface of the third insulating resin layer to form the first through hole. The wiring conductor, the second wiring conductor, and the third wiring conductor formed of a metal thin film formed on the upper surface of the third insulating resin layer are connected to each other.

Further, the wiring board of the present invention is characterized in that, in the above structure, the diameter of the cross section of the first through hole is 0.2 to 0.9 times the diameter of the cross section of the second through hole. is there.

According to the method of manufacturing a wiring board of the present invention, the step of forming the first wiring conductor on the upper surface of the first insulating resin layer and the second step on the first insulating resin layer and the first wiring conductor are performed. Laminating the insulating resin layer, forming a second wiring conductor having an opening located above the first wiring conductor on the second insulating resin layer, the second insulating resin layer, and A step of laminating a third insulating resin layer on the second wiring conductor, and forming a first through hole having a cross section of substantially the same shape as the opening of the second wiring conductor in the second insulating resin layer. At the same time, a step of forming a second through hole having a cross section larger than the cross section of the first through hole located immediately above the first through hole in the third insulating resin layer, the first through hole and the second through hole A metal thin film from the inner wall of the third insulating resin layer to the upper surface of the third insulating resin layer, and the metal thin film is applied to the upper surface of the third insulating resin layer. That the first to third wiring conductors to form a third wiring conductor is characterized in that it comprises the step of connecting a metal thin film.

According to the wiring board of the present invention, the first through hole is formed on the first wiring conductor so that the first wiring conductor is exposed in the first through hole and the first through hole is formed. A second through hole having a larger cross section than the first through hole is formed immediately above to expose the second wiring conductor in the second through hole, and
A metal thin film is formed from the inner walls of the first and second through holes to the upper surface of the third insulating resin layer to expose the exposed portion of the first wiring conductor, the exposed portion of the second wiring conductor, and the third insulation. Since the third wiring conductor formed of the metal thin film formed on the upper surface of the resin layer is connected, the bonding area between the first and second wiring conductors and the metal thin film becomes large, and as a result,
The first and second wiring conductors can be firmly connected to the third wiring conductor, and the connection reliability is excellent even if the first through holes are miniaturized in order to increase the density of the wiring board. It can be a wiring board.

Further, according to the wiring board of the present invention, the diameter of the cross section of the first through hole is 0.2 times the diameter of the cross section of the second through hole.
Since it is set to 0.9 times, the area of the second wiring conductor exposed in the second through hole becomes sufficiently large, and the bonding between the metal thin film formed in the through hole and the second wiring conductor is strengthened. It can be anything. Further, even when a plurality of through holes are formed in the upper and lower sides to form a stacked via, the diameter of the cross section of the through hole formed at the top is smaller than the diameter of the cross section of the through hole formed at the bottom. It does not become very large, and as a result, the wiring board does not become large.

According to the method for manufacturing a wiring board of the present invention, after the second insulating resin layer and the third insulating resin layer are laminated on the first insulating resin layer, the second resin insulating layer and the third insulating resin layer are formed. Since the first through hole and the second through hole are formed in the insulating resin layer, the process does not become complicated and the process can be simplified. In addition, an opening is formed in the second wiring conductor on the second resin insulating layer, and the first through hole having a cross section of substantially the same shape as the opening of the second wiring conductor is formed in the second resin insulating layer. Therefore, it is not necessary to penetrate the wiring conductor when forming the through hole in the insulating resin layer by the laser, and as a result, the laser processing conditions may be set only to the conditions for processing the insulating resin layer. The process can be shortened.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a wiring board of the present invention will be described in detail with reference to the accompanying drawings. 1 is a sectional view showing an example of an embodiment of a wiring board of the present invention, and FIG.
It is a principal part expanded sectional view of FIG. In these figures, 1
Is an insulating resin layer, 2 is a wiring conductor, 3 is a through hole, 4 is a metal thin film, and these mainly constitute the wiring board 5 of the present invention. In this example, an example is shown in which the second insulating resin layer 1b and the third insulating resin layer 1c are laminated on the upper and lower surfaces of the first insulating resin layer 1a serving as the core.

The first insulating resin layer 1a serving as a core has a function as a support for the insulating resin layers 1b and 1c and a function of imparting strength to the wiring board 5, and has a thickness of 0.3.
It has a plate shape of about 1.5 mm. Such a first insulating resin layer 1a is formed, for example, by impregnating a glass cloth in which glass fibers are woven vertically and horizontally with a thermosetting resin such as an epoxy resin or a bismaleimide triazine resin and having a diameter of 0.1 from the upper surface to the lower surface. It has a plurality of through holes 11 of about 1.0 mm. Then, the first wiring conductor 2a is provided on the upper and lower surfaces thereof, and the copper plating film 12 is provided on the inner wall of each through hole 11.
And the first wiring conductors 2a on the upper and lower surfaces are electrically connected via the copper plating film 12 formed on the inner wall of the through hole 11.

The first insulating resin layer 1a as described above has a thickness of 3 to 50 on the entire upper and lower surfaces of the uncured insulating resin layer sheet.
After the copper foil having a thickness of μm is applied and the copper foil is cured and then etched to form a predetermined pattern, the first wiring conductor 2a is formed, and after the sheet is thermally cured, The through hole 11 is formed by drilling from the upper surface to the lower surface, and the copper plating film 12 is formed by depositing copper plating having a thickness of about 3 to 50 μm on the inner wall of the through hole 11 by plating.
Is formed. The first wiring conductor 2a may be integrally formed with the copper plating film 12 by a plating method when the copper plating film 12 is formed on the inner wall of the through hole 11.

Further, in the first insulating resin layer 1a, resin columns 13 made of a thermosetting resin such as epoxy resin or bismaleimide triazine resin are filled in the through holes 11. The resin column 13 is for closing the through hole 11 so that the second and third insulating resin layers 1b and 1c can be formed immediately above and below the through hole 11, and the uncured paste-like heat is applied. Through hole for curable resin
It is formed by filling the inside of 11 by a screen printing method, thermally curing it, and polishing the upper and lower surfaces thereof to be substantially flat. Then, the second and third insulating resin layers 1b and 1c are formed on the upper and lower surfaces of the first insulating resin layer 1a including the resin columns 13.
Are stacked.

Second and third insulating resin layers 1b and 1c
Each has a thickness of about 20 to 60 μm, a thermosetting resin such as epoxy resin or modified polyphenylene ether resin, and a particle size of 0.01 to 2 μm and a content of 10 to 50% by weight such as silica, alumina, aluminum nitride, etc. It consists of an inorganic insulating filler.

Second and third insulating resin layers 1b and 1c
Is for providing an insulating space for high-density wiring of the second and third wiring conductors 2b and 2c, and penetrates the second wiring conductor 2b and the third wiring conductor 2c. High-density wiring can be three-dimensionally formed by electrically connecting via the metal thin film 4 formed on the inner wall of the hole 3. Such second and third insulating resin layers 1b
The layer 1c is formed by sequentially stacking uncured thermosetting resin films having a thickness of about 20 to 60 μm on the upper and lower surfaces of the first insulating resin layer 1a and thermally curing the films. The second wiring conductor 2b is the second insulating resin layer 1
After forming b, the thickness is 3 to 50 so that the first wiring conductor 2a and the second wiring conductor 2b partially overlap with the surface thereof.
It is formed by depositing a copper plating film of about μm in a predetermined pattern by a conventionally known pattern forming method such as a semi-additive method or a subtractive method. The third wiring conductor 2c has a thickness of about 3 to 50 μm at the same time when the metal thin film 4 is formed on the inner peripheral wall of the through hole 3 described later on the surface of the third insulating resin layer 1c. It is formed by depositing a copper plating film in a predetermined pattern by a conventionally known pattern forming method such as a semi-additive method or a subtractive method.

The second through hole 3a is formed in the second insulating resin layer 1b, and the second through hole 3 is formed in the third insulating resin layer 1c.
b is formed. The first through hole 3a is located on the first wiring conductor 2a, and the second insulating resin layer 1b and the second insulating resin layer 1b are provided.
Of the first wiring conductor 2a while penetrating the wiring conductor 2b of
Is formed so as to be exposed in the first through hole 3a, and the second through hole 3b has a cross section larger than that of the first through hole 3a and is located immediately above the first through hole 3a. Third
Of the second wiring conductor 2 while penetrating the insulating resin layer 1c of
It is formed so that b is exposed in the second through hole 3b.

The opening diameter of the first through hole 3a is 20 to 100.
The opening diameter of the second through hole 3b is about 50 to 250 μm.
m, and the second and third insulating resin layers 1b and 1c
After stacking, by using a well-known carbon dioxide gas laser, UV-YAG laser, excimer laser, etc.,
The second through hole 3b is formed so as to be located immediately above the first through hole 3a.

Furthermore, the first and second through holes 3a.3
On the inner wall of b, a metal thin film 4 for electrically connecting the upper and lower wiring conductors 2 is adhered and formed. After forming the first and second through holes 3a and 3b by a laser, the metal thin film 4 is coated with a copper plating film having a thickness of about 3 to 50 μm by a conventionally known plating method to form the first and second through holes 3a and 3a. It is formed by depositing and depositing on the inner wall of 3b. The portion of the metal thin film 4 formed on the surface of the third insulating resin layer 1c becomes the above-mentioned third wiring conductor 2c.

The wiring conductor 2 and the metal thin film 4 serve as a conductive path for connecting each electrode of an electronic component (not shown) such as a semiconductor element to be mounted to an external electric circuit board (not shown). It is preferable that the wiring conductor 2 and the metal thin film 4 have a function, and the thickness of the wiring conductor 2 and the metal thin film 4 is about 3 to 50 μm, and that the wiring conductor 2 and the insulating resin layer 1 have a thickness of 3 μm or more from the viewpoint of transmitting a high-speed signal. It is preferably 50 μm or less from the viewpoint of preventing peeling due to the difference in thermal expansion.

In the wiring board 5 of the present invention, as described above, the first through hole 3a is formed on the first wiring conductor 2a.
To expose the first wiring conductor 2a in the first through hole 3a, and to form a second through hole 3b larger than the cross section of the first through hole 3a immediately above the first through hole 3a. Then, the second wiring conductor 2b is exposed in the second through hole 3b, and the metal thin film 4 is formed from the inner walls of the first and second through holes 3a and 3b to the upper surface of the third insulating resin layer 1c. A third wiring conductor 2c formed by the exposed portion of the first wiring conductor 2a, the exposed portion of the second wiring conductor 2b, and the metal thin film 4 formed on the upper surface of the third insulating resin layer 1c.
It is preferable to connect and. This is also important.

According to the wiring board 5 of the present invention, the first wiring conductor 2a is exposed in the first through hole 3a and the second wiring conductor 2b is exposed in the second through hole 3b. , The metal thin film 4 is formed from the inner walls of the first and second through holes 3a and 3b to the upper surface of the third insulating resin layer 1c to form the exposed portion of the first wiring conductor 2a and the second wiring conductor 2b. Since the exposed portion is connected to the third wiring conductor 2c formed of the metal thin film 4 formed on the upper surface of the third insulating resin layer 1c, the first and second wiring conductors 2a.
The bonding area between b and the metal thin film 4 becomes large, and as a result, the first and second wiring conductors 2a and 2b and the third wiring conductor 2c can be firmly connected to each other, and the wiring board 5 can be made high. Even if the first through holes 3a are miniaturized in order to increase the density, the wiring board 5 having excellent connection reliability can be obtained.

In the wiring board 5 of the present invention, it is preferable that the diameter of the cross section of the first through hole 3a is 0.2 to 0.9 times the diameter of the cross section of the second through hole 3b.

According to the wiring board of the present invention, the diameter of the cross section of the first through hole 3a is less than the diameter of the cross section of the second through hole 3b.
Since it is set to 2 to 0.9 times, the area of the second wiring conductor 2b exposed in the second through hole 3b becomes sufficiently large, and the metal thin film 4 and the second wiring conductor formed in the through hole 3 become large. 2b
It is possible to strengthen the bond with the. Further, even when a plurality of through holes 3 are vertically formed to form a stacked via, the diameter of the cross section of the through hole 3 formed at the top is the diameter of the cross section of the through hole 3 formed at the bottom. However, the size of the wiring board 5 does not increase as a result. When the diameter of the cross section of the first through hole 3a is less than 0.2 times the diameter of the cross section of the second through hole 3b, the area of the second wiring conductor 2b exposed in the second through hole 3b becomes smaller. It becomes small, the bonding strength between the second wiring conductor 2b and the metal thin film 4 becomes insufficient, and in the thermal fatigue resistance test such as the temperature cycle test (TCT), the insulating resin layer 1, the second wiring conductor 2b and the metal. The thermal stress due to the difference in thermal expansion from the thin film 4 causes the second wiring conductor 2b.
Tends to concentrate on the connection between the metal thin film 4 and the metal thin film 4, and if it exceeds 0.9 times, when a plurality of through holes 3 are stacked vertically, the through hole 3 formed on the top of The diameter of the cross section becomes large, and the wiring board 5 tends to be large. Therefore, it is preferable that the diameter of the cross section of the first through hole 3a is 0.2 to 0.9 times the diameter of the cross section of the second through hole 3b.

Further, when forming the second wiring conductor 2b formed on the surface of the second insulating resin layer 2b, an opening may be formed in advance to the size of the first through hole 3a. preferable. An opening having the size of the first through hole 3a is formed in the second wiring conductor 2b, and the first through hole 3a is formed so that the opening has a cross section of the first through hole 3a. As a result, the opening serves as a mask when forming the first through hole 3a, and the first through hole 3a can be formed with high positional accuracy. Further, since it is not necessary to penetrate the first wiring conductor 2a when forming the first and second through holes 3a and 3b with a laser, the processing conditions of the laser are set to the second and third insulating resin layers. The conditions for processing 1b and 1c may be set, and as a result, the process can be shortened.

Thus, according to the wiring board 5 of the present invention,
Conductor bumps 6 such as solder are attached to the connection pads formed of a part of the third wiring conductors 2c formed on the upper surface of the wiring board 5 having the above-described configuration.
A third element formed on the lower surface of the wiring board 5 while electrically connecting an electronic component (not shown) such as a semiconductor element via the
By forming the conductive bumps 6 such as solder on the connection pads formed by a part of the wiring conductor 2c, it is possible to obtain an integrated circuit device having high density and excellent insulation reliability.

The present invention is not limited to the above-mentioned example of the embodiment, and various modifications can be made without departing from the gist of the present invention. For example, in the above-mentioned embodiment, Although the first insulating resin layer 1a is illustrated as the core body, the first insulating resin layer 1a may be formed of the same material as the second and third insulating resin layers 1b and 1c. In addition, in the above-described embodiment, the second and third insulating resin layers 1b and 1c are respectively formed on the upper and lower surfaces of the first insulating resin layer 1a which is the core.
Although an example in which the
Alternatively, the third insulating resin layers 1b and 1c may be laminated.
Furthermore, four or more insulating resin layers 1 may be laminated and three or more through holes 3 may be vertically stacked. Further, in the above-described embodiment, the example in which the through holes 11 and the through conductors 12 are formed in the first insulating resin layer 1a serving as the core is shown, but these may be formed as needed. Further, a solder resist layer 7 may be formed on the surface of the outermost insulating resin layer 1 in order to improve heat resistance during solder reflow.

Next, a method for manufacturing a wiring board according to the present invention will be described by taking the case of manufacturing the above wiring board as an example. Note that FIG. 3 is a partial cross-sectional view of each step for explaining the method of manufacturing the wiring board of the present invention.

First, as shown in the sectional view of FIG.
An insulating resin layer 1a to be a core is prepared, and a first wiring conductor 2a is adhered and formed on the upper surface thereof. Insulating resin layer 1
The thickness a is about 0.3 to 1.5 mm, and is formed by drying a sheet obtained by impregnating a glass cloth in which glass fibers are woven lengthwise and widthwise with a thermosetting resin such as an epoxy resin or a bismaleimide triazine resin. In addition, the first wiring conductor 2a is formed by applying a copper foil having a thickness of 3 to 50 μm to the surface of the uncured sheet that will be the insulating resin layer 1a, and etching the copper foil into a predetermined pattern after curing the sheet. It is formed by processing.

In this example, the insulating resin layer 1a has a plurality of through holes 11 each having a diameter of about 0.1 to 1.0 mm from its upper surface to its lower surface. And through hole 11
A copper plating film for electrically connecting the first wiring conductors 2a formed on the upper and lower surfaces of the insulating resin layer 1a to the inner wall of the
12 are deposited by using a well-known plating method. In addition, the inside of the through hole 11 is filled with a resin column 13 made of a thermosetting resin such as an epoxy resin or a bismaleimide triazine resin so that the insulating resin layer 1b can be formed immediately above and below the through hole 11. ing. Such a resin column 13 is obtained by filling an uncured paste-like thermosetting resin into the through hole 11 by a screen printing method, heat-curing the resin, and polishing the upper and lower surfaces thereof to be substantially flat. It is formed. The first wiring conductor 2a may be integrally formed with the copper plating film 12 by a plating method when the copper plating film 12 is formed on the inner wall of the through hole 11.

Next, as shown in the sectional view of FIG.
The second insulating resin layer 1b is laminated on the first insulating resin layer 1a and the first wiring conductor 2a. Second insulating resin layer 1
b is for providing an insulating space for wiring the wiring conductors 2 at a high density, and the wiring conductors 2 in the upper layer and the wiring conductors 2 in the lower layer, which will be described later, are attached to the inner walls of the through holes 3. High-density wiring can be three-dimensionally formed by electrically connecting via the formed metal thin film 4. Such a second insulating resin layer 1b has a thickness of about 20 to 60 μm,
For example, a thermosetting resin such as an epoxy resin or a modified polyphenylene ether resin and a particle size of 0.01 to 2 μm and a content of 10
First, an uncured film consisting of -50% by weight of silica or an inorganic insulating filler such as alumina or aluminum nitride
It is formed by laminating on the insulating resin layer 1a and the first wiring conductor 2a, and thermosetting the same.

Then, as shown in a sectional view in FIG. 3C, a second wiring conductor 2b having an opening K located on the first wiring conductor 2a is formed on the second insulating resin layer 1b. To form. The second wiring conductor 2b is immersed in a roughening liquid such as an aqueous solution of permanganate for 15 minutes at 60 ° C. to roughen the surface of the second insulating resin layer 1b, and then in an aqueous solution of a palladium catalyst for electroless plating. The surface of the second insulating resin layer 2b is immersed in an electroless plating solution containing copper sulfate, Rossell salt, formalin, EDTA sodium salt, stabilizer, etc. for about 30 minutes. And depositing an electroless copper plating layer having a thickness of about 1 to 2 μm, and then depositing a plating resistant resin layer on the upper surface of the electroless copper plating layer and arranging it on the first wiring conductor 2a by exposure and development. An opening for depositing an electrolytic copper plating layer is formed on the pattern shape of the second wiring conductor 2b having an opening K, and further, an electrolysis comprising sulfuric acid, copper sulfate pentahydrate, chlorine, a brightener, etc. Apply a current of several A / dm ² to the copper plating solution. While depositing an electrolytic copper plating layer in the opening by immersing for several hours, finally, the electroless copper plating layer exposed by peeling the plating resistant resin layer with sodium hydroxide and peeling the plating resistant resin layer It is formed into a thickness of about 3 to 50 μm by etching away with a sulfuric acid-based aqueous solution.

In the method for manufacturing a wiring board of the present invention, it is important to form the second wiring conductor 2b so as to have the opening K located on the first wiring conductor 2a. The second wiring conductor 2b is formed so as to have an opening K located on the first wiring conductor 2a, and the first through hole is formed so that the opening K has a cross section of the first through hole 3a. 3a
By forming the first through hole 3a, the opening K serves as a mask when forming the first through hole 3a.
Can be formed with high positional accuracy. Further, since it is not necessary to penetrate the first wiring conductor 2a when forming the first and second through holes 3a and 3b with a laser, the processing conditions of the laser are set to the second and third insulating resin layers. 1b ・ 1
It suffices to set conditions for processing c, and as a result, the process can be shortened.

Next, as shown in the sectional view of FIG.
The third insulating resin layer 1c is laminated on the second insulating resin layer 1b and the second wiring conductor 2b. Third insulating resin layer 1
Similarly to the second insulating resin layer 1b, c is for providing an insulating space for wiring the wiring conductors 2 at high density, and has the same composition, thickness, and thickness as those of the second insulating resin layer 1b. Second insulating resin layer 1b and second wiring conductor 2b
Stacked on top of.

Then, as shown in the sectional view of FIG. 3 (e), the first through-hole of the second insulating resin layer 1b has a cross section of substantially the same shape as the opening K of the second wiring conductor 2b. 3a is formed, and a second through hole 3b having a larger cross section than the cross section of the first through hole 3a located immediately above the first through hole 3a is formed in the third insulating resin layer 1c. This is important in the method of manufacturing a wiring board of the present invention.

The first through hole 3a has an opening diameter of 20 to 10
The opening diameter of the second through-hole 3b is about 0 to about 50 μm to 250 μm.
μm, the second through hole 3b is the first through hole 3a
Is formed immediately above. Such through holes 3a and 3b
Is a well-known carbon dioxide gas laser or UV-YAG laser.
By processing using an excimer laser or the like, both are formed so as to overlap with each other.

According to the method of manufacturing a wiring board of the present invention, the second through hole having a larger cross section than the cross section of the first through hole 3a located immediately above the first through hole 3a is formed in the third insulating resin layer 1c. Since the hole 3b is formed, the first and second through holes 3a and 3b can be simultaneously formed by using the laser after the insulating resin layer 1 is laminated, so that the process is not complicated and the process can be simplified. . In addition, the first through hole 3a
Since the opening K of the second wiring conductor 2b can be used as a mask for forming the through hole 3a when forming the first wiring conductor, the positional accuracy of the first through hole 3a in the opening K of the second wiring conductor 2b can be improved. Can be well formed. Further, an opening K is formed in the second wiring conductor 2b on the second resin insulating layer 1b, and a cross section of the same shape as the opening K of the second wiring conductor 2b is formed in the second resin insulating layer 1b. Since the first through-hole 3a is formed, it is not necessary to penetrate the wiring conductor 2 when forming the through-hole 3 in the insulating resin layer 1 with a laser, and as a result, the processing conditions by the laser can be changed. The process can be shortened by setting only the conditions for processing.

When the diameter of the cross section of the first through hole 3a is set to 0.2 to 0.9 times the diameter of the cross section of the second through hole 3b, the second wiring conductor exposed in the second through hole 3b is formed. 2b
The area is sufficiently wide, and the metal thin film 4 formed in the through hole 3 and the second wiring conductor 2b can be joined firmly. Further, even when a plurality of through holes 3 are vertically formed to form a stacked via, the diameter of the cross section of the through hole 3 formed at the top is the diameter of the cross section of the through hole 3 formed at the bottom. However, the size of the wiring board 5 does not increase as a result.

Finally, as shown in the sectional view of FIG. 3 (f), the metal thin film 4 extends from the inner walls of the first through hole 3a and the second through hole 3b to the upper surface of the third insulating resin layer 1c.
The metal thin film 4 on the upper surface of the third insulating resin layer 1c.
By forming the third wiring conductor 2c consisting of and connecting the first to third wiring conductors 2a, 2b, 2c with the metal thin film 4, the wiring substrate of the present invention as shown in FIG. 1 is completed. .

The metal thin film 4 is composed of the wiring conductors 2 located above and below.
A function as a conductive path for electrically connecting each other and connecting each electrode of an electronic component (not shown) such as a semiconductor element mounted on the wiring board 5 to an external electric circuit board (not shown) And a part thereof is formed on the upper surface of the third insulating resin layer 1c to form the third wiring conductor 2c.

The metal thin film 4 preferably has a thickness of about 3 to 50 μm. From the viewpoint of transmitting a high-speed signal, the thickness of the metal thin film 4 is 3 μm or more. The thickness is preferably 50 μm or less from the viewpoint of preventing peeling due to peeling.

Such a metal thin film 4 has the first and second
After forming the through holes 3a and 3b of the third insulating resin layer 1
c The surface and the inner walls of the first and second through holes 3a and 3b are immersed in a roughening solution such as an aqueous solution of permanganate for 15 minutes at 60 ° C. for roughening, and then the same as the second wiring conductor 2b described above. Of the third insulating resin layer 1c
On the surface and the inner walls of the first and second through holes 3a and 3b,
It is deposited to a thickness of 3 to 50 μm.

Thus, according to the method for manufacturing a wiring board of the present invention, the first insulating resin layer 1a is formed on the second insulating resin layer 1b.
And the third insulating resin layer 1c are laminated, and the first through hole 3a and the second through hole 3b are formed in the second resin insulating layer 1b and the third insulating resin layer 1c, respectively. Does not become complicated and the process can be simplified. Further, an opening K is formed in the second wiring conductor 2b on the second resin insulating layer 1b, and a cross section of the same shape as the opening K of the second wiring conductor 2b is formed in the second resin insulating layer 1b. By forming the first through hole 3a of the insulating resin layer 1 by laser
It is not necessary to penetrate the wiring conductor 2 when forming the through hole 3 in the through hole 3, and as a result, it is sufficient to set the processing conditions by the laser only to the conditions for processing the insulating resin layer 1, and the process can be shortened. .

[0048]

According to the wiring board of the present invention, the first wiring conductor is formed into the first wiring conductor by forming the first through hole on the first wiring conductor.
Of the first through hole and a second through hole larger than the cross section of the first through hole is formed immediately above the first through hole to expose the second wiring conductor in the second through hole. Then, a metal thin film is formed from the inner walls of the first and second through holes to the upper surface of the third insulating resin layer to form an exposed portion of the first wiring conductor, an exposed portion of the second wiring conductor, and an exposed portion of the second wiring conductor. Since the third wiring conductor made of a metal thin film formed on the upper surface of the third insulating resin layer is connected, the bonding strength between the first and second wiring conductors and the metal thin film can be made sufficient. As a result, the first and second wiring conductors can be firmly connected to the third wiring conductor, and the connection can be made even if the first through holes are miniaturized in order to increase the density of the wiring board. The wiring board can be highly reliable.

According to the wiring board of the present invention, the diameter of the cross section of the first through hole is set to 0.2 times the diameter of the cross section of the second through hole.
Since it is set to ~ 0.9 times, the area of the second wiring conductor exposed in the second through hole is sufficiently wide, and the bonding between the metal thin film formed in the through hole and the second wiring conductor is made firm. It can be anything. Further, even when a plurality of through holes are formed in the upper and lower sides to form a stacked via, the diameter of the cross section of the through hole formed at the top is smaller than the diameter of the cross section of the through hole formed at the bottom. It does not become very large, and as a result, the wiring board does not become large.

According to the method of manufacturing a wiring board of the present invention, after the second insulating resin layer and the third insulating resin layer are laminated on the first insulating resin layer, the second resin insulating layer and the third insulating resin layer are formed. Since the first through hole and the second through hole are formed in the insulating resin layer, the process does not become complicated and the process can be simplified. In addition, an opening is formed in the second wiring conductor on the second resin insulating layer, and the first through hole having a cross section of substantially the same shape as the opening of the second wiring conductor is formed in the second resin insulating layer. Therefore, it is not necessary to penetrate the wiring conductor when forming the through hole in the insulating resin layer by the laser, and as a result, the laser processing conditions may be set only to the conditions for processing the insulating resin layer. The process can be shortened.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an example of an embodiment of a wiring board of the present invention.

FIG. 2 is an enlarged cross-sectional view of a main part of the wiring board shown in FIG.

3A to 3F are partial cross-sectional views of respective steps for explaining the method for manufacturing a wiring board of the present invention.

[Explanation of symbols]

1 ... Insulating layer 1a ... 1st insulating resin layer 1b ... 2nd insulating resin layer 1c ... ...... Third insulating resin layer 2 ...... Wiring conductor 2a ・ ・ ・ ・ ・ ・ ・ ・ First wiring conductor 2b ・ ・ ・ ・ ・ ・ ・ ・2 wiring conductor 2c ... 3rd wiring conductor 3 ... through-hole 3a ... 1st through-hole 3b ...・ ・ ・ ・ Second through-hole 4 ・ ・ ・ ・ ・ ・ ・ ・ Metal thin film 4a ・ ・ ・ ・ ・ ・ Metal thin film 4b formed in the first through-hole・ ・ ・ Metal thin film 5 formed in the second through hole ・ ・ ・ Wiring board K ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Opening

Claims (3)

[Claims] 1. A first wiring conductor having a first wiring conductor formed on an upper surface thereof.
Second insulating resin layer and second wiring conductor formed on the upper surface
The insulating resin layer and the third insulating resin layer are sequentially laminated so that a part of the first and second wiring conductors are vertically overlapped with each other, and the insulating resin layer is located on the first wiring conductor. A first through-hole penetrating the second insulating resin layer and the second wiring conductor, and the first through-hole penetrating the third insulating resin layer located immediately above the first through-hole. A second through hole having a larger cross section than that of the first and second through holes, and a metal thin film is formed from the inner walls of the first and second through holes to the upper surface of the third insulating resin layer. A wiring board, wherein the second wiring conductor and the third wiring conductor formed of the metal thin film formed on the upper surface of the third insulating resin layer are connected to each other. 2. The wiring board according to claim 1, wherein the diameter of the cross section of the first through hole is 0.2 to 0.9 times the diameter of the cross section of the second through hole. 3. A step of forming a first wiring conductor on an upper surface of a first insulating resin layer, and a second insulating resin layer laminated on the first insulating resin layer and the first wiring conductor. And a step of forming a second wiring conductor having an opening located above the first wiring conductor on the second insulating resin layer, the second insulating resin layer and the second insulating resin layer. Laminating a third insulating resin layer on the wiring conductor of step (1), and forming a first through hole having a cross section of substantially the same shape as the opening of the second wiring conductor in the second insulating resin layer. At the same time, the first insulating layer located on the third insulating resin layer is located directly above the first through hole.
Forming a second through hole having a cross section larger than the cross section of the through hole; and applying a metal thin film from the inner walls of the first through hole and the second through hole to the upper surface of the third insulating resin layer. To form a third wiring conductor formed of the metal thin film on the upper surface of the third insulating resin layer, and
Through the step of connecting the third wiring conductor with the metal thin film, the method for manufacturing a wiring board.