JPH10303533A - Wiring forming method and double-layer board used for the method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a double-layer wiring board which has excellent tight adhesiveness between its metal wiring and insulating layer at a low cost by a method wherein one of the surfaces of the insulating layer made of organic polymer is roughed by using a metal material sheet and a foundation conductive thin film layer and the metal wiring are successively formed by an additive method. SOLUTION: One of the surfaces of a metal material sheet 110 is subjected to a roughing treatment and an insulating layer 120 made of organic polymer is formed on the roughed surface 110S by a casting method and the metal material sheet 110 is removed by etching. A conductive thin film layer 140 which is to be a foundation for the formation of a wiring is formed over a whole insulating layer surface 120S which is the roughed surface exposed by etching. After plating resist 150 is applied to the conductive thin film layer 140 by an additive method and made up, a metal wiring 160 is formed by an electroplating method. With this constitution, as a glow discharge treatment and a chemical treatment are not used, the metal wiring 160 can be formed on the insulating layer 120 with an excellent adhesiveness at a low cost.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming wiring on a flexible printed circuit board and a substrate used for the method, and more particularly to a method for forming wiring on a two-layer wiring board.

[0002]

2. Description of the Related Art Conventionally, as a wiring board material used for a flexible printed wiring board, as shown in FIG. 5A, a copper layer 511 and an adhesive layer 512 using an epoxy-based moisturizing agent are used. , A three-layer structure composed of a polyimide layer 513
The layer substrate 510 is generally used. However, with the recent demand for higher density, higher speed, multi-functionality, and higher reliability of electronic equipment, a wiring board material that can meet these requirements is required. It has come to be. Under these circumstances, recently, the copper layer 521 without the adhesive layer and the polyimide layer 52 shown in FIG.
The two-layer substrate 520 having a two-layer structure has attracted attention, and the two-layer substrate 520 having no adhesive layer is an HDD (Har
d Disk Drive), FDD (Floppy)
Disk Drive), TAB (TapeAutom)
for example, used bonding).

On the other hand, as a method for manufacturing a two-layer wiring board as a flexible printed wiring board, a first method shown in FIG. 3 and a second method shown in FIG. 4 are generally adopted. In the first method, as shown in FIG. 3, a surface of a roughened copper foil 310 (FIG. 3 (a)) having a roughened surface is coated on a surface 310S on the roughened side with a polyamic polyimide precursor. A two-layer substrate 330 (FIG. 3) provided with a polyimide resin layer 320 by a casting method in which an acid is applied and imidized.
(B)), and a resist pattern 340 for forming a wiring portion on the copper foil 310 is formed (FIG. 3C).
The exposed area of the copper foil 310 is etched and removed to form a wiring section 350 (FIG. 3D), and the resist is removed to obtain a two-layer wiring board 360 (FIG. 3E).
Things. Since the two-layer wiring board obtained by this method uses a material obtained by roughening a copper foil as a raw material, the same adhesive strength between the copper foil 310 and the polyimide resin layer 320 as in the three-layer board can be obtained. The part 350 is made of copper foil 310 as a material.
In this case, it is difficult to miniaturize the wiring because it is formed by a subtractive method.

In the second method, as shown in FIG. 4, a polyimide film 410 is first prepared (FIG. 4A), and a conductive layer is formed on the polyimide film 410 by sputtering, vapor deposition, electroless plating or the like. A metal thin film 420 is directly formed (FIG. 4B), and a plating resist 430 is formed according to the wiring.
After making a plate (FIG. 4C), a region to be a wiring portion is plated with a plating metal layer 440 by electroplating. (FIG. 4
(D)) Then, the plating resist 430 is removed (FIG. 4).
(E)), the exposed metal thin film 420 is removed by etching to obtain a two-layer wiring board 450 (FIG. 4 (f)). In this method, wiring is formed finely by an additive method on a metal thin film serving as a conductive layer on a polyimide film, so that the wiring can be easily miniaturized. It is difficult to improve the adhesion of the metal thin film that becomes the conductor layer.
That is, it is difficult to increase the adhesion of the wiring portion.
This is because it is not possible to easily perform a desired surface roughening by applying a chemical treatment to the surface of the polyimide film. In the second method, a method of chemically modifying a surface layer by an alkali solution treatment such as glow discharge treatment or hydrazine to form a metal thin film having excellent adhesion on a polyimide film may be employed. However, even with these treatments, it was difficult to obtain the same adhesion as a three-layer substrate. Also, the cost was high.

[0005] Separately, a metal thin film to be a conductive layer is directly formed on the entire surface of the polyimide layer by sputtering, vapor deposition, electroless plating or the like, and then a thick metal layer is formed on the entire surface by electroplating or the like. There is also a method of manufacturing a two-layer wiring board in which a wiring part is formed by a subtractive method using a layer. In this method, as in the second method, the polyimide film is roughened and the anchor effect due to the roughening is obtained. Therefore, it is difficult to improve the adhesion of the metal thin film to be the conductor layer, and it is difficult to miniaturize the wiring as in the first method. Here, the additive method means that the wiring portion is made of an insulating layer (or an insulating substrate) by plating or the like.
In addition, a subtractive method is a method in which a wiring region is formed by removing a predetermined region of a conductive layer by etching or the like in a substrate having an insulating layer and a conductive layer. In addition, the two-layer wiring board is the third layer.
As shown in FIG. 4 and FIG. 4, the wiring portion is composed of two layers of an insulating layer such as a polyimide layer and a metal layer, and refers to a wiring board without an adhesive layer.

[0006]

As described above, the conventional two-layer wiring board as a flexible printed wiring board has advantages and disadvantages in the characteristics obtained by its manufacturing method, and has been problematic in terms of quality. For this reason, in a two-layer wiring board as a flexible printed wiring board,
There has been a demand for a device capable of fine wiring and capable of reducing cost while ensuring reliability. The present invention provides a wiring forming method capable of producing a two-layer wiring board as a flexible printed wiring board which enables fine wiring under such circumstances and has excellent adhesion between the wiring and an insulating layer such as polyimide. It is something to offer. At the same time, they seek to achieve this at low cost. Another object of the present invention is to provide a two-layer board used for manufacturing such a two-layer wiring board.

[0007]

According to the present invention, there is provided a wiring forming method for forming wiring on at least one surface of an insulating layer made of an organic polymer, comprising the steps of: (a) forming a rough surface of a sheet-like metal material; Forming an insulating layer made of an organic polymer on the surface subjected to the chemical treatment by casting, (b) etching and removing the sheet-like metal material, and (c) sheet-like metal material of the insulating layer (E) forming an underlying conductive thin film layer for forming a metal wiring on the surface in contact with the substrate by an additive method; (d) forming a metal wiring on the underlying conductive thin film layer by an additive method; And b) etching away the underlying conductive thin film layer other than the metal wiring formation region. Further, the sheet-like metal material in the above is a metal foil. Further, the organic polymer is made of polyimide. In the above-described roughening treatment of the sheet-shaped metal material, the roughened surface has a center line average roughness Ra of JIS B0601 of 0.5 to 2 μm and a ten-point average roughness Rz of 5 to 5 μm.
The thickness is 10 μm. Further, in the above, after the sheet-shaped metal material is removed by etching, the surface of the insulating layer on the side in contact with the sheet-shaped metal material is subjected to a modification treatment, and then the underlying conductive thin film for forming the metal wiring is formed. It is characterized by forming a layer. still,
The term “modification treatment” as used herein refers to a treatment that does not physically change the surface roughness but chemically changes the surface roughness to increase wettability.

The two-layer substrate of the present invention is a substrate for supplying an insulating layer made of an organic polymer whose one surface has been roughened in order to form wiring by an additive method. On the processed surface side, by casting,
An insulating layer made of an organic polymer is provided, and the roughening treatment of the sheet-like metal material is performed on a roughened surface, and the roughening treatment of the sheet-like metal material is performed. Is characterized in that the roughened surface has a center line average roughness Ra of JIS B0601 of 0.5 to 2 μm and a ten-point average roughness Rz of 5 to 10 μm. Further, the sheet-like metal material in the above is a metal foil.

[0009]

According to the wiring forming method of the present invention, by adopting such a structure, the adhesion between the wiring and the insulating layer is excellent, and
It is possible to provide a wiring forming method that enables fine wiring. At the same time, this can be achieved at low cost. Specifically, (a) a step of forming an insulating layer made of an organic polymer by casting on the roughened surface side of a sheet-like metal material, and (b) etching of the sheet-like metal material Removing; (c) forming an underlying conductive thin film layer for forming metal wiring on the surface of the insulating layer in contact with the sheet-shaped metal material by an additive method; and (d) underlying conductive thin film This is achieved by having a step of forming a metal wiring on the layer by the additive method and a step (e) of etching and removing the underlying conductive thin film layer other than the metal wiring. Specifically, by forming an insulating layer made of an organic polymer by casting on the roughened surface side of the sheet-shaped metal material, the side surface of the sheet-shaped metal material of the insulating layer is formed of the metal material. In order to form a metal wiring via a base conductive thin film layer on the roughened surface of the insulating layer, The wiring portion on the layer has good adhesiveness. As a result, in the wiring forming method of the present invention, the wiring portion is formed by using the three-layer substrate shown in FIG. A wiring having an adhesive force can be formed. In addition, when the underlying conductive thin film layer is provided on the insulating layer, a wiring portion having excellent adhesion can be formed without performing a modification treatment on the insulating layer surface. In this case, the manufacturing cost of the wiring substrate is reduced. Can be suppressed. Further, since a metal wiring is formed by an additive method on an insulating layer made of an organic polymer, fine wiring can be achieved. By using a metal foil as the sheet-like metal material, etching is facilitated when the underlying conductive thin film layer other than the metal wiring formation region is removed by etching.
The heat resistance,
It is possible to provide a two-layer wiring board made of copper, polyimide, or the like that does not include an adhesive layer and has excellent flexibility, migration resistance, and bonding properties. The surface roughening treatment of the sheet-like metal material is carried out in such a manner that the roughened surface has a center line average roughness Ra of JIS B0601 of 0.5 to 2 μm and a ten-point average roughness Rz of 5 to 5 μm.
When the thickness is 10 μm, the adhesion of the metal wiring is particularly improved. Furthermore, by etching and removing the sheet-like metal material subjected to the surface treatment of the wiring substrate material, the exposed surface of the organic polymer is modified to form a two-layer structure of copper, polyimide, etc., having a higher wiring adhesion. A wiring board can be provided. Needless to say, a wiring board in which a plurality of the two-layer wiring boards thus manufactured are further stacked can be manufactured.

The two-layer substrate of the present invention having such a structure can be used in the above-described wiring forming method of the present invention, enables fine wiring, and has particularly excellent adhesion between the wiring portion and the insulating layer. In addition, a two-layer wiring board as a flexible printed wiring board can be manufactured.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described with reference to the drawings. FIG. 1 is a process sectional view of a wiring forming method of the present invention.
FIG. 2 shows a two-layer substrate of the present invention. 1 and 2, 110
Is a sheet-like metal material, 110S is a roughened surface, 120
Is an insulating layer (insulating substrate), 120S is an insulating layer surface, 130 is a two-layer substrate, 140 is a conductive thin film layer, 150 is a plating resist, 160 is a metal layer (wiring), and 180 is a wiring substrate.

First, a wiring forming method of the present invention will be described with reference to FIG. First, the surface roughness of one surface of the sheet-shaped metal material 110 is such that the center line average roughness Ra of JIS B0601 is 0.5 to 2 μm and the ten-point average roughness Rz is
A surface roughening process is performed so as to be 0 μm. (Figure 1
(A) As the sheet-like metal material 110, a copper foil may be mentioned.
It is not limited to this. Examples of the surface roughening treatment include electrolytic polishing and the like. Next, in a clean state, the surface 110S on the side of the sheet-shaped metal material 110 on which the surface roughening treatment is performed is
Insulating layer 1 made of organic polymer by casting method
20 is formed in a predetermined thickness, and a sheet-like metal material 110 is formed.
Then, a two-layer substrate 130 including the insulating layer 120 is formed.
(FIG. 1B) Examples of the organic polymer include polyimide and the like. still,
The casting method is also used in the production of a conventional two-layer substrate that does not use an adhesive, and the production conditions are devised in consideration of warpage prevention and the like, but a detailed description is omitted here. Next, the sheet-like metal material 11
0 is removed by etching. (FIG. 1 (c)) Next, the conductive thin film serving as a base for forming wiring is formed on the entire surface of the insulating layer surface 120S having the rough surface shape of the insulating layer 120, which is exposed by etching and removing the sheet-like metal material 110. A layer 140 is formed. (FIG. 1D) Examples of a method for forming the conductive thin film layer 140 include an electroless plating method, a vapor deposition method, and a sputtering method. When forming the underlying conductive thin film layer using a vapor deposition method and a sputtering method,
Even if the surface layer is not modified by a conventionally used glow discharge treatment or treatment with an alkali solution such as hydrazine, the adhesion strength of the wiring that can be practically used can be obtained. Needless to say, in the case where adhesion strength is further required, a base conductive thin film layer may be formed by a vapor deposition method or a sputtering method after performing a glow discharge treatment and an alkali solution treatment. The electroless plating includes, but is not limited to, electroless copper plating.

Next, a plating resist 150 for forming a metal wiring is applied on the conductive thin film layer 140 formed on the insulating layer surface 120S by an additive method, and after plate making (FIG. 1 (e)), it is exposed. A metal layer (wiring) 160 is formed on the conductive thin film layer 140 by electrolytic plating.
(FIG. 1F) As the metal layer (wiring) 160, a copper wiring layer formed by electrolytic copper plating is generally used. Thereafter, the plating resist 150
Is peeled off (FIG. 1 (g)), and the exposed conductive thin film layer 140 is removed by etching to obtain a wiring substrate 180. (Figure 1
(H) As described above, in the wiring forming method of the present invention, the method for forming a metal thin film having excellent adhesion on the insulating layer 120 is as follows.
Since the glow discharge treatment and the chemical treatment are not performed, the cost is relatively low, and the wiring can be formed with the same or higher adhesion as the three-layer substrate.

Incidentally, after FIG. 1 (c), a sheet-like metal material 1 is formed.
The insulating layer 120 exposed by the etching removal of
The insulating layer surface 120S having a rough surface shape is further subjected to a modification treatment for chemically improving the surface wetting property,
As shown in FIG. 1D, the conductive thin film layer 140 may be formed by electroless plating. In this case, further improvement in the adhesion of the wiring portion in the finally obtained wiring board 180 (FIG. 1 (h)) can be expected.

Next, the two-layer substrate of the present invention will be briefly described with reference to FIG. The two-layer substrate of the present invention is a substrate for supplying an insulating layer made of an organic polymer whose one surface is roughened in order to form wiring by an additive method.
As shown in the figure, an insulating layer 120 made of an organic polymer is provided by casting on the roughened surface side 110S of a sheet-shaped metal material 110. Then, the JI of the roughened surface 110S of the sheet-like metal material 111 is obtained.
The center line average roughness Ra of SB0601 is 0.5 to 2 μm
And the ten-point average roughness Rz is 5 to 10 μm. The two-layer substrate 130 is for dissolving and removing the sheet-like metal material 110 and forming a wiring on the surface of the insulating layer 120 on the side where the metal material 110 was located by an additive method, and forms the wiring. The surface of the insulating layer on the side is made of a roughened metal material 1
The surface is roughened in conformity with the surface of No. 10, and the adhesion between the wiring and the insulating layer can be improved.

[0016]

EXAMPLE An example of the wiring forming method according to the present invention will be described with reference to FIG. First, a first embodiment of the wiring forming method of the present invention will be described. In this embodiment, the sheet-shaped metal material 110 is a copper foil having a thickness of 18 μm,
0S is a roughened surface having a center line average roughness Ra of 1.0 μm and a ten-point average roughness Rz of 8 μm. The insulating layer 120 made of an organic polymer is cast on the surface 110S. Was used, which is a commercially available ESPANEX (manufactured by Nippon Steel Chemical Co., Ltd.) wiring substrate. (FIG. 1B) Then, the metal material 110 made of a copper foil was removed by etching with ferric chloride.
(Fig. 1 (c))

Next, a conductive thin film layer 140 to be a sublayer of the wiring was provided on the surface 120S of the insulating layer 120 by electroless plating under the following conditions. First, the surface 120S of the insulating layer 120 made of an organic polymer was cleaned and conditioned to promote adsorption of a catalyst serving as a nucleus for plating deposition, and a catalyst serving as a nucleus for electroless plating deposition was applied. As a method for applying the catalyst, there are a sensitizing activate ink method and a catalyst accelerator method, but in this case, the catalyst accelerator method was used. After applying a catalyst to the surface 120S of the insulating layer 120 made of an organic polymer, electroless copper plating is performed,
A conductive thin film layer 140 having a thickness of 0.2 μm was formed. (Figure 1
(D)) The conditions from the cleaning and conditioning steps to the electroless copper plating step are shown in (Table 1). The chemicals used were all manufactured by Kamibayashi Kogyo Co., Ltd.

Next, a plating resist 150 for forming wiring by plating was plate-made. (FIG. 1 (e)) As the plating resist 150, PMERP-LA900PM manufactured by Tokyo Ohka Kogyo Co., Ltd. was provided by roll coating so as to have a thickness of 12 μm. Thereafter, a metal wiring 160 composed of a 10-μ thick copper-plated wiring was formed on the exposed conductive thin film layer 140 by electrolytic copper plating.
(FIG. 1 (f)) (Table 2) shows the plating solution composition and conditions used in the electrolytic plating. However, Sulcup AC-90M is an additive manufactured by Uemura Koki.

Next, after providing the metal wiring 160 by copper plating, the resist 150 is peeled off (FIG. 1).
(G)) The exposed conductive thin film layer 140 was removed by etching to obtain a flexible printed wiring board 180.
(Fig. 1 (h))

Next, a second embodiment of the wiring forming method of the present invention will be described. In the present embodiment, after removing the sheet-like metal material 110 by etching in the first embodiment (FIG. 1C),
The surface 12 of the insulating layer 120 is formed by using an organic alkali aqueous solution.
1S was chemically modified to improve the wetting property, and then the steps of FIGS. 1D to 1H were performed in the same manner as in Example 1. Table 3 shows the conditions of the reforming treatment with the organic alkali aqueous solution.

[0021]

As described above, the present invention provides a method for forming a wiring of a two-layer wiring board as a flexible printed wiring board, which enables fine wiring and has excellent adhesion between the wiring and the insulating layer. It is possible to achieve this at low cost. Further, it is possible to provide a two-layer board used in such a method for manufacturing a two-layer wiring board. In detail, by using a glow discharge treatment or an alkali solution treatment such as hydrazine, it is possible to obtain the adhesion strength of the wiring that can withstand practical use without chemically modifying the surface of the insulating layer. Become. This is particularly effective when polyimide, which is chemically stable and hardly subjected to surface roughening treatment, is used as the insulating layer. In particular, the organic polymer is polyimide, heat resistance, flexibility, migration resistance,
It is possible to provide a wiring board having a wiring portion composed of two layers of copper and polyimide that does not contain an adhesive layer and has excellent bonding properties. Further, as shown in FIG. 1, a two-layer wiring board having a wiring portion composed of two layers of copper and polyimide having higher wiring adhesion can be provided by the modification treatment.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing steps of a wiring forming method of the present invention.

FIG. 2 is a sectional view of a two-layer substrate of the present invention.

FIG. 3 is a process diagram of a conventional method for manufacturing a two-layer wiring board.

FIG. 4 is a process diagram of a conventional method for manufacturing a two-layer wiring board.

FIG. 5 is a cross-sectional view of a conventional wiring board.

[Explanation of symbols]

 110 Sheet-shaped metal material 110S Roughened surface 120 Insulating layer (insulating substrate) 120S Insulating layer surface 130 Two-layer substrate 140 Conductive thin film layer 150 Plating resist 160 Metal layer (wiring) 180 Wiring substrate 310 Copper foil 310S (of copper foil ) Surface 320 polyimide resin layer 330 two-layer substrate 340 resist pattern 350 wiring part 410 polyimide film 420 metal thin film 430 plating resist 440 plating metal layer 450 wiring substrate 510 three-layer substrate 511 copper layer 512 adhesive layer 513 polyimide layer 520 two-layer substrate 521 Copper layer 523 Polyimide layer

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI H05K 3/38 H05K 3/38 A

Claims (7)

[Claims] 1. A wiring forming method for forming wiring on at least one surface of an insulating layer made of an organic polymer, comprising the steps of: (a) forming an organic material by casting on a surface of a sheet-shaped metal material subjected to a roughening treatment; Forming an insulating layer made of a polymer;
(B) a step of etching and removing the sheet-like metal material;
(C) forming an underlying conductive thin film layer for forming metal wiring on the surface of the insulating layer in contact with the sheet-shaped metal material by an additive method; and (d) forming an underlying conductive film on the underlying conductive thin film layer. Forming a metal wiring by;
(E) etching and removing the underlying conductive thin film layer other than the metal wiring formation region. 2. The sheet-like metal material according to claim 1,
A method for forming a wiring, comprising a metal foil. 3. A method for forming a wiring, wherein the organic polymer according to claim 1 is made of polyimide. 4. The roughening treatment of a sheet-like metal material according to claim 1, wherein the roughened surface is JIS B06.
01, wherein the center line average roughness Ra is 0.5 to 2 μm and the ten-point average roughness Rz is 5 to 10 μm. 5. The metal wiring according to claim 1, wherein after the sheet-shaped metal material is removed by etching, the surface of the insulating layer in contact with the sheet-shaped metal material is subjected to a modification treatment, and then the metal wiring is formed. A method for forming a wiring, comprising forming a base conductive thin film layer to be formed. 6. A substrate for supplying an insulating layer made of an organic polymer whose one surface has been roughened in order to form a wiring by an additive method, and is provided on a surface of a sheet-shaped metal material which has been roughened. An insulating layer made of an organic polymer is provided by casting, and the sheet-shaped metal material is subjected to a surface roughening treatment in which the roughened surface has a center line average roughness Ra of JIS B0601 of 0. 5 to 2 μm, 10-point average roughness Rz
Is 5 to 10 μm. 7. The sheet-like metal material according to claim 6,
A two-layer substrate, which is a metal foil.