JPH03203394A - Manufacture of insulating substrate with thin metallic layer and manufacture of wiring board using insulating substrate manufactured thereby - Google Patents

Abstract

PURPOSE:To stably manufacture high-density wiring by forming a specific thin metallic layer on a copper thin layer formed on a temporary substrate by a vacuum film forming method by specifying the peel-off strength against the temporary substrate and peeling off the temporary substrate after the layers are united with an insulating substrate to a laminated body with the thin metallic layer inside. CONSTITUTION:A thin copper layer 2 is formed on a temporary substrate 1 of stainless steel foil, etc., by a vacuum film forming method by specifying the peel-off strength of the layer 3 to the substrate to <=0.2kgf/cm. A thin film 3 of a metal selected out of chromium, titanium, vanadium, nickel, manganese, molybdenum, and tungsten is formed on the layer 2. Then the substrate 1 is peeled off after the layers 2 and 3 are united with an insulating substrate 4 to a laminated body with the layer 3 inside. Therefore, high-density wiring which is less in undeveloped resists and improved in the adhesive property between the insulating substrate and metallic layers can be manufactured stably.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a method for manufacturing an insulating substrate with a thin metal layer used for manufacturing high-density wiring boards, and a wiring board using the insulating substrate with a thin metal layer. Concerning the manufacturing method.

(Prior technology) Copper-clad laminates used for manufacturing wiring boards include copper foil electrolytically deposited on a rotating stainless steel drum and prepreg made of paper or glass substrate impregnated with thermosetting resin. There are some that are laminated.

Further, as a copper foil-attached film used for manufacturing a flexible wiring board, there is, for example, a film made by thermocompression bonding a polyimide film and a rolled copper foil through an adhesive. In these cases, the thickness of the copper foil is 18 μm, 135 μm, 150 μm.
Medium and thick ones are the mainstream.

Manufacturing methods for wiring boards using copper-clad laminates or films with copper foil as described above include the etched foil method, in which circuit processing is performed by etching copper-clad laminates, etc., and the etched foil method, in which copper foil is used as a resist-forming surface. After processing, there is a semi-additive method in which circuit processing is performed by resist formation, thick plating, resist removal, and quick etching.

The etched foil method has the problem of side etching, making it difficult to form high-density wiring.

The fineness and high density of wiring in the semi-additive method depends on the thickness of the underlying metal layer (copper foil).

That is, the thinner the underlying metal layer to be etched, the higher the etching accuracy. Therefore, when forming high-density wiring, copper-clad laminates using thin copper foil of 5 to 9 μm are used as a base, but aluminum foil (approximately 50 μm thick), which is the carrier of the copper foil, is physically or chemically When removing the aluminum foil, there are problems such as the aluminum foil breaking during peeling due to its lack of mechanical strength, and a large amount of hydrogen gas being generated when removing it by etching with an alkaline etching solution. Furthermore, it is necessary to roughen the copper foil in order to ensure adhesion with the prepreg, and to do so, the thickness must be at least 3 μm, and the wiring width must be 20 μm.
When ultra-high-density wiring on the order of m is targeted, side etching of the wiring becomes a problem.

Other methods for forming a thin base metal layer include electroless plating, vacuum evaporation, and sputtering.

The electroless plating method requires a step of physically or chemically treating the surface of the insulating substrate to make the surface hydrophilic and rough, and also has low adhesion between the generated metal layer and the substrate.

For this reason, a method has been proposed in which electroless plating is applied to the roughened surface of the etched copper foil of a copper-clad laminate to ensure adhesive strength. This has the disadvantage that a large amount of undeveloped material is left behind because it causes diffuse reflection and exposes areas that should not become resists.

Vacuum film forming methods such as vacuum evaporation and sputtering can stably form a metal layer of 1 μm or less even on a smooth substrate. When using a glass cloth, due to the moisture adsorbed to the glass cloth and the solvent remaining in the resin layer, the moisture and solvent gasify under the high vacuum required for vapor deposition and sputtering, and the glass cloth to resin Peeling and voids occur at the interface.

For these reasons, a method has been proposed in which the vapor deposition and sputtering steps are performed separately, and after forming a metal foil layer, it is laminated with an organic base material for a wiring board (Japanese Patent Application Laid-Open No. 114074/1983).

(Problems to be Solved by the Invention) However, even in this method, since the transfer film forming the thin metal layer is roughened, there is a problem of resist development residue during resist formation as described above.

In order to stably form ultra-high-density wiring with a wiring width of about 20 μm using the semi-additive method, (1) the base metal must be as thin as about 1 μm, and (2) the base metal surface must be thin during resist exposure. The diffuse reflection of is as small as possible, (3
) It is necessary that the adhesive strength between the underlying metal and the insulating substrate be strong. The present invention satisfies these factors and provides a method for manufacturing an insulating substrate with a metal foil layer, which makes it possible to stably manufacture a high-density wiring board, and a wiring board using the insulating substrate with a thin metal layer. It provides a manufacturing method.

(Means for solving the problem) The present invention forms a first thin layer of copper on a temporary substrate by a vacuum film forming method so that the peeling strength against the temporary substrate is 0.2 kgf/cm or less. forming a second thin layer of at least one selected from chromium, titanium, vanadium, nickel, manganese, molybdenum and tungsten on the first thin layer of copper by a vacuum deposition method; A process of laminating and integrating with an insulating substrate with the thin layer inside,
An insulating substrate with a metal thin layer is manufactured by a process of peeling off a temporary substrate from a laminate.

Embodiments of the present invention will be described in detail with reference to the drawings.

FIGS. 1(a) to 1(d) are sectional views illustrating an embodiment of the present invention.

1 in FIG. 1(a) is a temporary substrate, for example, the surface roughness is 1.
It is a stainless steel foil (extremely thin stainless steel foil made by Nippon Steel Corporation) with a thickness of 30 μm adjusted to less than μm, and one side of the foil is coated with an electron beam evaporation device (Japan Vacuum Co., Ltd.).
A thin copper layer 2 with a thickness of 5000 Å, followed by a chromium layer 3 with a thickness of 200 Å, were successively formed under the following conditions (FIG. 1(b)).

Copper acceleration voltage 1 Pressure 1 Substrate temperature 2 Film forming rate 1 KV Instead of stainless steel foil, thickness 25-20
A 0 μm polymer film may also be used. Applicable polymer films include polyimide film, Teflon film, polyethylene film, etc., but polyimide film is the most preferable in terms of heat resistance and peelability from copper thin layer (in the case of polyimide film, copper and film Peeling strength between is approximately 0, 1kgf/Cm
).

Peeling strength between temporary substrate and copper thin layer is 0.2kgf/c
m or less. Peeling strength is 02kgf
/cm, it becomes difficult to peel off the temporary substrate from the laminate in a later step.

The peelability between the temporary substrate and the copper thin layer depends on the energy of the copper particles when forming the copper thin layer; if the energy is high, the adhesiveness between the temporary substrate and the copper thin layer improves, resulting in poor peelability. There is a tendency to If the energy of the copper particles is in the range of 1 eV to 50 eV, good releasability is exhibited.

As a film forming method, in addition to the electron beam evaporation method, an evaporation method using a resistance heating method, a sputtering method, an ion cluster beam method, etc. can be applied.

It is desirable to set the thickness of the thin copper layer formed on the stainless steel foil of the temporary substrate in consideration of the wiring width of the fine wiring to be formed afterwards. is preferably 2 μm or less.

Next, with the thin chromium layer inside, the glass cloth-Epokin Prebreg 4 (manufactured by Hitachi Chemical Co., Ltd., product name GEA-67) was used.
-N) for 40 minutes at 170°C and 40 kgf/cm2 (Fig. 1 (c)), the stainless steel foil was peeled off to obtain a glass epoxy substrate with a thin metal layer (Fig. 1 (d)). . In this case, the peel strength between the epoxy substrate and the metal thin layer was approximately 0.8 kgf/cm, which was a good value. Examples of metals that can be used in addition to chromium include titanium, nickel, vanadium, molybdenum, and tungsten. Note that a compound containing at least one of these metals can also be used. For example, when chromium nitride was used, the adhesive strength was about 0.7 kgf/cm.

The two-layer metal thin layer 2.3 formed on the temporary substrate 1 such as stainless steel foil may be adhered to a ceramic substrate or a metal substrate such as aluminum via an acrylic, rubber or thermoplastic resin sheet. Furthermore, the present invention can be applied not only to the fabrication of the surface layer of a multilayer wiring board, but also to the fabrication of the inner layer substrate.

Next, an embodiment of a method for manufacturing a high-density wiring board using the insulating substrate with a thin metal layer of the present invention will be described.

A positive liquid resist TF-20 (Shi
Roll coated with PLAY Co., Ltd. (trade name) on both sides and heated at 80°C.
Prebaking was performed for 20 minutes. Furthermore, using a MAP-1200 large mask alignment exposure machine manufactured by Dainippon Screen Co., Ltd., exposure was performed at 1t500mJ/c through the mask.
Contact exposure was performed at m2. Next, 450 developer manufactured by 5ipley (liquid temperature = 25°C, concentration: 17%)
) for 3 minutes to achieve a minimum line width and space of 20 μm.
After forming a fine resist pattern, a semi-additive method was applied to form a desired wiring pattern.

In this case, since the underlying metal layer is a two-layered layer of chromium and copper, copper is etched in an ammonium persulfate solution (solution temperature: 45°C, concentration: 30 g/l).
For chromium, a mixed solution of potassium ferricyanide and potassium hydroxide (liquid temperature: 50°C, concentration: potassium ferricyanide: 150 g/l, potassium hydroxide: 50 g/l) was used.

(Effects of the Invention) According to the present invention, it becomes possible to form a metal thin layer of 1 μm or less on an insulating substrate for a wiring board with high productivity, and the resist remains undeveloped in the resist pattern forming process, which has been a problem in the past. The adhesion between the substrate and the metal layer was improved. In addition, if the insulating substrate with a thin metal layer according to the present invention is applied to a wiring board, the etching thickness in the wiring forming process is very thin, about 1 μm, so the etching accuracy is significantly improved, and the line width and space can be reduced to 20 μm. can easily form fine wiring.

It is a sectional view explaining a manufacturing process.

(Explanation of symbols) 1. Stainless steel foil (temporary board) 2. Copper thin layer (first metal thin layer) 3. Chromium layer (second metal thin layer) 4. Prepreg

Claims (5)

[Claims] 1. A step of forming a first thin layer of copper on the temporary substrate by a vacuum film forming method so that the peel strength with respect to the temporary substrate is 0.2 kgf/cm or less, and a step of forming at least one kind of second thin layer selected from chromium, titanium, vanadium, nickel, manganese, molybdenum, and tungsten by a film-forming method; and laminating and integrating with an insulating substrate with the second thin layer inside. 1. A method for producing an insulating substrate with a thin metal layer, the method comprising: a step of peeling off a temporary substrate from a laminate. 2. 2. The method for producing an insulating substrate with a thin metal layer according to claim 1, wherein in the vacuum film forming method for forming the first thin layer of copper, the energy range of the copper particles is 1 eV to 50 eV. 3. The temporary substrate is a stainless steel foil with a thickness of 20 to 50 μm or a thickness of 25 to 2 μm with a surface roughness adjusted to 2.0 μm or less.
3. The method for producing an insulating substrate with a metal foil layer according to claim 1 or 2, wherein the insulating substrate is a polymer film with a thickness of 00 μm. 4. The metal thin layer according to claim 1, 2 or 3, wherein the second thin layer on the first thin layer of copper is made of a metal compound containing at least one selected from nickel, chromium, titanium, vanadium, manganese, molybdenum and tungsten. A method for manufacturing a layered insulating substrate. 5. Forming a predetermined resist pattern on the surface of the insulating substrate with a metal thin layer according to claim 1, plating the predetermined portions,
1. A method for manufacturing a wiring board, which comprises etching a first thin layer and a second thin layer of copper after removing a resist pattern.