JP2002353597A - Metal transfer sheet, producing method and wiring circuit board thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a metal transfer sheet, in which a specified pattern can be formed easily at a fine pitch, a metal transfer sheet produced by the producing method, and wiring circuit board in which currently requested fine pitch can be dealt with, using the metal transfer sheet, and high density wiring can be realized. SOLUTION: A peelable metal layer 12 is formed on a metal basic material 11, and then the metal layer 12 and the metal basic material 11 are etched, down to a specified depth of the metal basic material 11 from the metal layer 12 side, thus forming a specified pattern of the metal layer 12. By doing so, since the tapered inclination spreading from the bottom part 18 toward the upper part 19 is make to decrease at the etching part 16 of the metal layer 12, fine pitch patterning can be easily realized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a metal transfer sheet,
The present invention relates to a manufacturing method and a printed circuit board.

[0002]

2. Description of the Related Art Hitherto, wiring circuit boards such as flexible wiring circuit boards have been widely used for electronic devices and electronic components. Usually, a conductor layer is formed as a predetermined wiring circuit pattern on an insulating substrate. Have been.

[0003] Such a printed circuit board is, for example, shown in FIG.
As shown in FIG. 6A, a metal transfer sheet 3 having a releasable metal layer 2 formed on the surface of a base material 1 is prepared, and as shown in FIG. After the metal layer 2 is transferred to the insulating substrate 4 by thermocompression bonding on the insulating substrate 4, the base material 1 is peeled off as shown in FIG. As shown in FIG. 6 (e), a photoresist 5 corresponding to a predetermined pattern is formed on the transferred metal layer 2, and the metal layer 2 is etched using the photoresist 5 as a resist.
As shown in FIG. 2, the metal layer 2 is formed as a predetermined wiring circuit pattern.

[0004]

However, in the method shown in FIG. 6, when the metal layer 2 is etched, as shown in FIG. 7, the side surface 7 of the metal layer 2 around the etched portion 6 is also inclined. Has been etched and etched part 6
Is formed in a tapered shape extending from the bottom 8 to the upper portion 9, so that the line width and the line interval of the wiring circuit pattern cannot be made very narrow. There is a problem that it is not possible to sufficiently cope with fine pitch.

[0005] The present invention has been made to solve such a problem, and the object thereof is to provide:
A method of manufacturing a metal transfer sheet capable of easily forming a predetermined pattern at a fine pitch, a metal transfer sheet obtained by the method, and a metal transfer sheet using the metal transfer sheet. An object of the present invention is to provide a printed circuit board which can cope with a pitch and can achieve high-density wiring.

[0006]

In order to achieve the above object, a method for producing a metal transfer sheet according to the present invention comprises the steps of: forming a peelable metal layer on a metal substrate; Forming a metal layer in a predetermined pattern by etching the metal base from the metal layer side to a predetermined depth of the metal base.

According to such a method of manufacturing a metal transfer sheet, since the metal layer is penetrated in the thickness direction and further etched to a predetermined depth of the metal substrate, the side surface of the metal layer around the etched portion is excessive. To be etched into
The amount can be reduced accordingly. Therefore, in the etched portion of the metal layer, the tapered slope extending from the bottom to the top is reduced, and patterning at a fine pitch can be easily realized.

Further, in the metal transfer sheet of the present invention, a releasable metal layer is formed on a metal base, and the metal layer and the metal base are arranged on the metal base from the metal layer side. The metal layer is formed in a predetermined pattern by being etched to a predetermined depth.

In such a metal transfer sheet, since the etched portion penetrates the metal layer in the thickness direction and is further etched to a predetermined depth of the metal base material, the side surface of the conductor layer around the etched portion is formed. Over-etching is reduced accordingly. Therefore, in the etched portion of the conductor layer, the tapered inclination that spreads from the bottom to the top is small, and patterning at a fine pitch is easily realized.

The printed circuit board according to the present invention is characterized in that the metal layer formed in a predetermined pattern on the metal transfer sheet is transferred.

Since a metal layer that has been patterned at a fine pitch is transferred to this printed circuit board, it is possible to cope with a finer pitch of a printed circuit pattern that has been increasingly required in recent years. Thus, high-density wiring can be achieved.

[0012]

FIG. 1 is a manufacturing process diagram showing one embodiment of a method for manufacturing a metal transfer sheet of the present invention. Hereinafter, an embodiment of a method for manufacturing a metal transfer sheet of the present invention will be described with reference to FIG.

In this method, first, as shown in FIG. 1A, a metal base material 11 is prepared, and a metal base material 11 is placed thereon, as shown in FIG.
As shown in FIG. 5, a peelable metal layer 12 is formed. The metal substrate 11 is not particularly limited as long as it is a metal. For example, copper, nickel, chromium, iron, tin, lead, aluminum, an alloy thereof, or the like is used. Preferably, copper or a copper alloy is used. Further, the metal substrate 11 preferably has a thin sheet shape and a thickness of 5 μm or more and 200 μm or less. If it is less than 5 μm, the strength of the metal layer 12 as a carrier (support) may be insufficient, causing breakage or wrinkles during handling. If it is more than 200 μm, it may be heavy and increase the material cost. There are cases.

The metal layer 12 is not particularly limited as long as it is a metal, but, for example, copper, nickel, chromium, iron, tin, lead, aluminum, an alloy thereof, or the like is used as described above. Note that the metal layer 12 is formed of the metal base material 11.
The material may be the same as that described above, or may be a different material. When this metal layer 12 is used as a wiring circuit pattern of a wiring circuit board, it is preferable to use copper or a copper alloy having good conductivity.

The metal layer 12 has a thickness of
Preferably, it is formed to have a thickness of 0.05 μm or more and 50 μm or less. When it is less than 0.05 μm, when used as a wiring circuit pattern of a wiring circuit board, the film strength as the wiring circuit pattern becomes insufficient, and
If it exceeds 50 μm, it may be difficult to form a fine pattern (for example, a fine wiring circuit pattern having a pitch of 100 μm or less in a subtractive method) in forming a pattern described later.

The surface (transfer surface) of the metal layer 12 is matted (roughened) in order to obtain sufficient adhesion to the adherend to which the metal layer 12 is transferred. Treatment) or fine projections may be formed on the surface (transfer surface).

The formation of the peelable metal layer 12 is as follows.
Although there is no particular limitation, when forming a pattern in the etching step described later, it is necessary to sufficiently adhere to the metal base material 11, but in the transfer step described later, it is easily separated from the metal base material 11. Need to be Therefore, in this method, it is preferable that the interface between the metal base material 11 and the metal layer 12 is subjected to a peeling treatment in order to obtain such adhesion and peelability.

Before the metal layer 12 is formed, for example, the surface of the metal substrate 11 and / or the metal layer 12 is removed.
The surface is modified or oxidized by plasma treatment or corona treatment, or, for example, a peeling layer ( (Not shown).

The release layer is made of, for example, silicon oxide (SiO ₂ ).
And a metal oxide such as titanium oxide (TiO ₂ ), a fluorine compound, a silicone compound, an acrylic compound, and a nitrogen-containing compound such as a triazole. The thickness of the release layer is not particularly limited as long as it can be easily removed in the etching step, but it is usually preferably 0.05 μm or more and 2 μm or less. If it is thinner than this, the effect as a release layer may not be exhibited, and if it is thicker than this,
There are cases where the metal layer 12 cannot be laminated, easily peeled off during formation of the pattern, or the metal layer 12 cannot be etched because it cannot be peeled off in the etching step.

After such a peeling treatment, a metal layer 12 is formed on the metal substrate 11. The metal layer 12 is formed by a known method such as a plating method, a sputter deposition method, and an ion plating method. For example, the metal layer 12 can be formed by plating after sputter deposition.

Next, in this method, the metal layer 12 thus laminated on the metal base material 11 is formed as shown in FIG.
As shown in (g), the substrate is etched into a predetermined pattern by a subtractive method.

That is, in order to etch the metal layer 12 into a predetermined pattern, first, as shown in FIG.
A photoresist 13 is laminated on the metal layer 12. The lamination of the photoresist 13 may be performed, for example, by laminating a dry film resist by a known method. Then
As shown in FIG. 1D, on the photoresist 13,
After disposing a photomask 14 corresponding to a predetermined pattern, a photoresist 13 is
Is exposed, and then the photoresist 13 is developed as shown in FIG. Exposure and development of the photoresist 13 may be performed by a known method, and the photoresist 13 is developed into a predetermined resist pattern by a difference in solubility of a developing solution between an exposed portion and an unexposed portion.

Then, as shown in FIG. 1F, the metal layer 12 is etched. The metal layer 12 may be etched by wet etching using an etchant. Examples of the etchant include sulfuric acid, sulfuric acid-based solution, cupric chloride solution, ferric chloride solution, ammonium persulfate solution, and ammonia-based alkali. A solution or the like is used.

In this method, after the metal layer 12 is etched so as to penetrate the metal layer 12 in the thickness direction, the metal substrate 11 is continuously etched to a predetermined depth. . More specifically, for example, the metal substrate 11 is placed on its surface (metal substrate 11).
From the interface between the metal layer 12 and the metal layer 12 (or the release layer if a release layer is interposed) to the deepest portion thereof (see FIG. 2).
However, etching is performed until the thickness becomes at least 0.1 μm, preferably 0.5 μm or more and 20 μm or less, more preferably 2 μm or more and 5 μm or less. Thereafter, as shown in FIG. 1 (g), the metal transfer sheet 15 is obtained by removing the photoresist 13 by a known method.

In the etching of the metal layer 12, the metal layer 12 and the metal substrate 11 may be etched continuously, but depending on the type of the metal layer 12 and the metal substrate 11, the metal layer 12 may be etched. And the metal substrate 11 may be etched stepwise.

In the etching of the metal layer 12, a protective layer made of an inorganic material or an organic material is laminated on the back surface of the metal substrate 11 in order to prevent the back surface of the metal substrate 11 from being etched. May be.

In the metal transfer sheet 15 thus formed, as shown in FIG. 2, a releasable metal layer 12 is formed as a predetermined pattern on a metal substrate 11 by etching. In the etched portion 16 of the metal layer 12, the metal substrate 11 is etched to a predetermined depth Δd.

That is, in this metal transfer sheet 15,
Since the etched portion 16 penetrates the metal layer 12 in the thickness direction and is further etched to a predetermined depth Δd of the metal base 11, the side surface 17 of the conductor layer 12 around the etched portion 16 is excessively large. Etching is reduced accordingly. Therefore, this etched portion 16
In FIG. 2, the tapered spread from the bottom portion 18 to the upper portion 19 is small, that is, the taper angle θ of the side surface 17 of the metal layer 12 shown in FIG. 2 (the direction in which the interface between the metal base material 11 and the metal layer 12 extends, The angle θ) formed by the direction in which the side surface 17 of the conductor layer 12 extends around the portion 16 is more 90 °.
Is formed so as to be close to Therefore, by forming the metal transfer sheet 15 in this manner, the margin of the etching condition can be set wide, the width of the pattern can be easily controlled, and patterning at a fine pitch can be easily realized. .

The etching condition is a taper angle θ.
Is preferably set to 75 ° or more.
By forming the etched portion 16 at such a taper angle θ, the width of each metal layer 12 formed as a predetermined pattern (the line width Lw (the metal layer 12 Value which is the interface between the metal substrate 11 and the metal substrate 11) is, for example, 5 to 5000 μm,
Preferably, the thickness can be set to 15 to 500 μm, and the distance between the metal layers 12 (the line spacing Ls (the distance between the metal layer 12 and the metal base material 11 when formed as a predetermined wiring circuit pattern) The bottom value which is the interface)) is, for example, 5
5,000 μm, preferably 15-500 μm.

Since the metal transfer sheet 15 can pattern the metal layer 12 at a fine pitch, the metal transfer sheet 15 is preferably used particularly as an application for forming a wiring circuit pattern of a wiring circuit board by transfer. it can.

That is, in order to manufacture a printed circuit board using the metal transfer sheet 15, for example, as shown in FIG.
First, an insulating substrate 20 is prepared as shown in FIG. The insulating substrate 20 is not particularly limited as long as it has electrical insulation properties. For example, a polyester resin, a polyethylene resin, a polystyrene resin, a polycarbonate resin, a polyamide resin, a polyimide resin, a polyurethane resin, A thermoplastic resin or a thermosetting resin such as an ABS resin, an epoxy resin, a fluorine resin, or a silicone resin is used. The insulating substrate 20 has a sheet shape and has a thickness of 5 μm or more from the viewpoint of mechanical properties and electrical insulation.
It is preferably not more than μm.

Next, as shown in FIG. 3B, the metal transfer sheet 15 is brought into close contact with the surface of the insulating substrate 20 while the metal layer 12 formed in a predetermined wiring circuit pattern is in contact with the surface of the insulating substrate 20. Then, the metal layer 12 is transferred to the insulating substrate 20. The transfer of the metal layer 12 is performed by pressing and / or
There is no particular limitation as long as it can be heated, and examples thereof include a hot press, a roll laminating method, a method of uniformly pressurizing in a chamber with air pressure, and a method of using these in combination. The transfer conditions are, for example, a pressure of 0.01 to 10 MPa and a temperature of 20 to 350 ° C.

In such a transfer, in order to prevent voids generated between the transferred metal layer 12 and the insulating substrate 20, the pressure is reduced in advance in a vacuum atmosphere, or
The transfer is preferably performed in a vacuum atmosphere.

Thereafter, as shown in FIG. 3C, if only the metal substrate 11 is peeled off from the insulating substrate 20, the metal layer 1 is removed.
Thus, a wiring circuit board 21 obtained by transferring the wiring circuit pattern of No. 2 to the insulating substrate 20 can be obtained.

Further, as shown in FIG. 4A, such a printed circuit board 21 is provided on the surface of the metal transfer sheet 15 where the metal layer 12 is formed, as shown in FIG.
As shown in FIG. 2, a resin coating liquid 2 such as a molten resin obtained by melting the above resin, a resin solution in which the above resin is dissolved, or a precursor solution in which a precursor of the above resin is dissolved
0p is applied or injection molded in a mold and then
As shown in FIG. 4C, the insulating substrate 20 is formed by drying and curing the same, and then, as shown in FIG. 4D, only the metal substrate 11 is peeled off from the insulating substrate 20. In addition, the metal layer 12 can be transferred to the insulating substrate 20, whereby the wiring circuit board 21 in which the wiring circuit pattern including the metal layer 12 is transferred to the insulating substrate 20 can be obtained.

In the method shown in FIG. 4, after the wiring circuit pattern composed of the metal layer 12 is transferred to the insulating substrate 20, it is necessary to further remove the solvent or cure at a high temperature (for example, if the metal layer 12 is hardened). At the time of transfer, resin coating liquid 20p
In the case where curing is completed after the transfer while leaving the metal substrate in the B-stage state), the metal substrate 11 may be further subjected to a heat treatment in a state where the metal substrate 11 is not peeled off, or after the metal substrate 11 is peeled off.

As described above, when the wiring circuit board 21 is formed by transferring the metal layer 12 having a predetermined wiring circuit pattern onto the insulating substrate 20, the metal layer formed at a fine pitch on the metal transfer sheet 15 is formed. 12 is transferred to the insulating substrate 20 as it is, and the metal layer 1 is easily and reliably transferred to the insulating substrate 20.
2 can be formed with a fine pitch wiring circuit pattern. Therefore, according to such a method,
The wiring circuit board 21 on which the metal layer 12 is formed as a fine-pitch wiring circuit pattern can be manufactured with high production efficiency and at low cost.

Since the obtained wiring circuit board 21 has the metal layer 12 formed of a fine-pitch wiring circuit pattern, it has been responded to the finer pitch of the wiring circuit pattern which has been increasingly required in recent years. High-density wiring can be realized.

Further, such a printed circuit board may be formed as a double-sided printed circuit board as shown in FIG.

That is, in FIG. 5, first, FIG.
As shown in FIG. 5A, an insulating substrate 20 is prepared, and FIG.
As shown in FIG. 5B, a through hole 22 is formed in a predetermined portion of the insulating substrate 20, and then, as shown in FIG. 5C, plating or conductive paste is used in the through hole 22. 5D, the metal transfer sheet 15 is arranged on both sides of the insulating substrate 20 as shown in FIG. 5D, and the conductive path 23 is formed as shown in FIG. A predetermined metal layer 1 formed on a predetermined wiring circuit pattern
2 and the metal transfer sheet 15 is overlapped so as to be in close contact with each other, and
5 is transferred to both sides of the insulating substrate 20, and as shown in FIG. 5 (f), if only the metal base material 11 is peeled off from the insulating substrate 20, a predetermined wiring circuit pattern composed of the metal layer 12 is formed. A double-sided wiring circuit board 24 formed on both sides of the substrate 20 can be obtained.

In this way, if the double-sided wiring circuit board 24 is formed by transferring the metal layer 12 composed of a predetermined wiring circuit pattern to both sides of the insulating substrate 20, the metal transfer sheet 15 is formed at a fine pitch. The wiring circuit pattern made of the metal layer 12 is transferred to both surfaces of the insulating substrate 20 as it is, and a fine-pitch wiring circuit pattern made of the metal layer 12 is easily and reliably formed on both surfaces of the insulating substrate 20. it can. Therefore, a double-sided wiring circuit board 24 capable of realizing high-density wiring is provided.
Can be manufactured with good production efficiency and at low cost.

[0042]

The present invention will be described more specifically with reference to the following Examples and Comparative Examples, but the present invention is not limited to the Examples and Comparative Examples.

Example 1 A 50 μm thick SUS304 foil (metal substrate)
After plasma treatment, a nickel layer and a copper layer each having a thickness of 0.1 μm or less are each sputter-deposited, and further, a copper layer is formed by electrolytic copper plating to a thickness of 10 μm to form a metal layer. did. Thereafter, a photoresist was laminated on the metal layer, and exposed and developed to form a resist pattern having a line width of 20 μm and a line interval of 20 μm (see FIGS. 1A to 1E).

Thereafter, the metal layer was etched with a ferric chloride solution at 40 ° C. for 30 seconds to obtain a line width of 17 μm and a space between lines of 23 μm.
After forming a wiring circuit pattern of μm, the metal transfer sheet was obtained by peeling off the photoresist (FIG. 1).
(See (f) to (g)). In the etching of the metal layer, the SUS304 foil is etched to a depth of 3 μm from the surface, whereby each etched portion is formed so that the taper angle θ is 75 to 90 °. Was.

Next, the obtained metal transfer sheet was coated with a glass epoxy prepreg (EDLIT manufactured by Mitsubishi Gas Chemical Company, Inc.).
E GEPL-150) is superimposed in a state where the metal layer is in contact with the surface, transferred by hot pressing at 180 ° C. and 2 MPa, and then the SUS304 foil is peeled off to form a substantially flat surface. (Fig. 3)
(See (a) to (c)).

Example 2 A printed circuit board was obtained in the same manner as in Example 1, except that the etching time was changed to 40 seconds.

In this printed circuit board, the printed circuit pattern is formed with a line width of 16 μm and a line interval of 24 μm. In the etching, the SUS304 foil is etched to a depth of 5 μm from the surface. Each etched portion has a taper angle θ of 7
It was formed to be 5 to 90 °.

Comparative Example 1 A SUS304 foil (metal substrate) having a thickness of 50 μm was
After plasma treatment, a nickel layer and a copper layer each having a thickness of 0.1 μm or less are sputter-deposited, and further, a copper layer is laminated by electroplating to a thickness of 10 μm to form a metal layer. Thus, a metal transfer sheet was obtained (see FIG. 6A).

Next, the obtained metal transfer sheet was coated with a glass epoxy prepreg (EDLIT manufactured by Mitsubishi Gas Chemical Company, Inc.).
E GEPL-150) was superposed in a state where the metal layer was in contact therewith, hot-pressed and transferred at 180 ° C. and 2 MPa, and then the SUS304 foil was peeled off. Thereafter, a photoresist was laminated on the transferred metal layer, and exposed and developed to form a resist pattern having a line width of 20 μm and a line interval of 20 μm. Thereafter, the metal layer was etched with a ferric chloride solution at 40 ° C. for 30 seconds to form a wiring circuit pattern, and then the photoresist was removed to obtain a wiring circuit board (FIG. 6B). To (e)). In the obtained printed circuit board, the line width of the printed circuit pattern varied from 16 to 22 μm, and the taper angle θ of each etched portion was 60 to 70 °.

Example 3 A 5 μm-thick thin copper layer (metal layer) on which a 2 μm-thick surface projection was formed was laminated on a 35 μm-thick carrier copper foil (metal substrate) via a release layer. A copper foil with a carrier (MT-35 manufactured by Mitsui Mining & Smelting Co., Ltd.) is prepared, a photoresist is laminated on a thin copper layer, and exposed and developed to form a resist pattern having a line width of 20 μm and a line interval of 20 μm. Was formed (see FIGS. 1A to 1E).

Thereafter, the thin copper layer was coated with hydrogen peroxide / 30 ° C.
After etching with a sulfuric acid solution for 60 seconds to form a wiring circuit pattern having a line width of 17 μm and a line interval of 23 μm, the photoresist was removed to obtain a metal transfer sheet (FIGS. 1F to 1G). reference). In the etching of the thin copper layer, the carrier copper foil is etched to a depth of 2 μm from its surface, whereby each etched portion has a taper angle θ of 75 to 90 °. Been formed.

Next, a polyimide precursor solution (biphenyltetracarboxylic dianhydride, p-phenylenediamine and 4,4′-diaminodiphenyl ether, N-methyl-2 of polyamic acid copolymerized with
-Pyrrolidone solution, solid content 20% by weight) and dried at 120 ° C. for 30 minutes to form a polyimide precursor film. Then, by peeling the carrier copper foil, after transferring the thin copper layer having a predetermined wiring circuit pattern to the polyimide precursor film, while fixing the transferred polyimide precursor film, under nitrogen atmosphere, 350 By heating at 1 ° C. for 1 hour to remove the solvent and cure (imidize), a printed circuit board having a substantially flat surface was obtained (see FIGS. 4A to 4D).

Example 4 A printed circuit board was obtained in the same manner as in Example 3, except that the etching time was changed to 80 seconds.

In this printed circuit board, the printed circuit pattern is formed with a line width of 17 μm and a line interval of 23 μm. In etching the thin copper layer, the carrier copper foil is etched to a depth of 4 μm from the surface. Thus, each etched portion is formed such that the taper angle θ is 75 to 90 °.

Comparative Example 2 The same copper foil with a carrier as that of Example 3 (M, manufactured by Mitsui Kinzoku Mining Co., Ltd.)
T-35) was prepared, and the same polyimide precursor solution as in Example 3 was cast on the surface where the thin copper layer was formed, and dried at 120 ° C. for 30 minutes to obtain a polyimide precursor film. Was formed. Then
By peeling the carrier copper foil, after transferring the thin copper layer to the polyimide precursor film, while fixing the transferred polyimide precursor film, under a nitrogen atmosphere,
By heating at 350 ° C. for 1 hour to remove the solvent and cure (imidize), a laminated film in which a thin copper layer was laminated on polyimide was obtained.

Next, a photoresist was laminated on the thin copper layer in the laminated film, exposed and developed to form a resist pattern having a line width of 20 μm and a line interval of 20 μm. Thereafter, the thin copper layer was etched with a hydrogen peroxide / sulfuric acid solution at 30 ° C. for 50 seconds to obtain a line width of 15 μm.
After forming a wiring circuit pattern having a length of 25 μm and a distance of 25 μm, the photoresist was peeled off to obtain a wiring circuit board. In the obtained printed circuit board, the line width of the printed circuit pattern varied from 16 to 22 μm, and the taper angle θ of each etched portion was 60 to 70 °.

Example 5 An insulating film (Pixio BP manufactured by Kanegafuchi Chemical Co., Ltd.) was prepared by laminating a thermoplastic adhesive layer made of polyimide on both surfaces of polyimide having low thermal expansion. Using a YAG laser, a fine through-hole having a diameter of 100 μm was formed in the portion, and the fine through-hole was filled with a solder paste containing tin and gold having a high melting point, and a conduction path was formed in the thickness direction. 5 (a) to (c)).

Next, the same metal transfer film as that of Example 1 was brought into close contact with both sides of the insulating film in a state where the conductive path and the predetermined metal layer of the metal transfer film were positioned so as to face each other. And heat-pressed at 320 ° C. using a heating roll, and then peeled off the SUS304 foil to obtain a double-sided wiring circuit board having a predetermined wiring circuit pattern formed on both sides of the laminated film (FIG. 5). (See (d) to (f)).

[0059]

As described above, according to the method for manufacturing a metal transfer sheet of the present invention, the tapered slope extending from the bottom to the top in the etched portion of the metal layer is reduced, and the metal layer is formed at a fine pitch. Can be easily realized.

Therefore, the metal transfer sheet of the present invention can be easily patterned at a fine pitch. Therefore, the printed circuit board of the present invention obtained by transferring the metal layer formed on this metal transfer sheet is In recent years, it is possible to cope with a finer pitch of a wiring circuit pattern, which is increasingly required in recent years, and it is possible to achieve high-density wiring.

[Brief description of the drawings]

FIG. 1 is a manufacturing process diagram showing one embodiment of a method for manufacturing a metal transfer sheet of the present invention, wherein (a) is a step of preparing a metal substrate, and (b) is a step of preparing a metal substrate. Forming a releasable metal layer, (c) laminating a photoresist on the metal layer, and (d) mounting a photomask on the photoresist and exposing to light. , (E)
Shows a step of developing the photoresist, (f) shows a step of etching the metal layer, and (g) shows a step of removing the photoresist.

FIG. 2 is a cross-sectional view of a main part showing an etched portion of a metal layer obtained by the method of FIG.

3A and 3B are manufacturing process diagrams showing one embodiment of a method of manufacturing a printed circuit board using the metal transfer sheet obtained by the method of FIG. 1, wherein FIG. 3A shows a process of preparing an insulating substrate; (B) shows a step of transferring a metal layer by overlaying a metal transfer sheet on an insulating substrate, and (c) shows a step of peeling a metal substrate from the insulating substrate.

4A and 4B are manufacturing process diagrams showing another embodiment of a method of manufacturing a printed circuit board using the metal transfer sheet obtained by the method of FIG. 1, wherein FIG. (B) is a step of applying a resin coating solution,
(C) a step of drying and curing the resin coating solution,
(D) shows a step of peeling the metal base material from the insulating substrate.

FIG. 5 is a manufacturing process diagram showing one embodiment of a method for manufacturing a double-sided wiring circuit board using the metal transfer sheet obtained by the method of FIG. 1, wherein (a) prepares an insulating substrate; A step of forming a through hole in a predetermined portion of the insulating substrate; a step of forming a conductive path in the through hole; (E) is a step of transferring a metal layer by overlaying a metal transfer sheet in a state where the conductive path and a predetermined metal layer are aligned so as to face each other, and (f) is an insulating step. 4 shows a step of peeling a metal substrate from a substrate.

6A and 6B are manufacturing process diagrams showing a conventional method of manufacturing a printed circuit board, wherein FIG. 6A is a step of preparing a metal transfer sheet, and FIG. Pressure bonding step, (c) is a step of peeling the substrate, (d)
Shows a step of laminating a photoresist on the metal layer and etching the metal layer, and FIG. 3E shows a step of removing the photoresist.

7 is a cross-sectional view of a main part showing an etched portion of a metal layer obtained by the conventional method shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Metal base material 12 Metal layer 15 Metal transfer sheet 16 Etched part 21 Wiring circuit board 24 Double-sided wiring circuit board

Continued on the front page (72) Inventor Kazuo Ouchi 1-2-1 Shimohozumi, Ibaraki-shi, Osaka Nitto Denko Corporation F-term (reference) 2H096 AA30 HA13 HA17 JA04 2H113 AA01 AA06 BA22 BB10 BB22 CA17 DA04 DA47 DA48 DA53 DA56 DA57 DA58 DA62 FA09 5E339 BD07 BD08 BE11 BE13 CD00 CE00 5E343 AA02 BB24 BB38 BB43 BB44 BB71 DD23 DD24 DD25 DD32 DD56 DD63 EE42 EE52 ER52 FF08 FF10 GG08 GG11

Claims (3)

[Claims] A step of forming a releasable metal layer on a metal substrate, wherein the metal layer and the metal substrate are
Forming the metal layer in a predetermined pattern by etching to a predetermined depth of the metal base material. 2. A releasable metal layer is formed on a metal substrate, wherein the metal layer and the metal substrate are
The metal transfer sheet, wherein the metal layer is formed in a predetermined pattern by being etched to a predetermined depth of the metal base material. 3. A printed circuit board, wherein the metal layer formed in a predetermined pattern of the metal transfer sheet according to claim 2 is transferred.