JPH02206541A - Manufacture of metal foil-clad film for electron radiation curing type flexible printed-wiring board - Google Patents

Abstract

PURPOSE:To reduce the warpage of wiring-board by a method wherein electroconductive metal foil and base material film are laminated to each other through an adhesive layer, which is made of flexible polymer having unsaturated double bond in molecule, and, after that, the adhesive layer is cured. CONSTITUTION:Electroconductive metal foil and base material film are laminated to each other through an adhesive layer, which is made of flexible polymer having unsaturated double bond in molecule, and, after that, the adhesive layer is cured by irradiation with electron rays in order to produce metal foil-clad film electron radiation curing type flexible printed-wiring board. As the electroconductive metal foil, copper foil, silver foil, gold foil, aluminum foil and the like are mentioned and the foil having a thickness of 100mum or less is preferable. The flexible polymer having unsaturated double bond in molecule contains diene copolymer ingredient such as butadiene rubber, isoprene rubber or the like in molecule and preferably has a weight average molecular weight of 50,000-1000,000.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for manufacturing an electron beam-curable film with metal foil for use in flexible printed wiring boards.

3. Flexible film with unsaturated double bonds in the molecule [Conventional technology] Film with metal foil for flexible printed wiring boards:
Conventionally, to explain the case of polyimide film with W4 foil as an example, an adhesive composition is prepared by blending appropriate amounts of thermally crosslinkable epoxy resin and phenol resin with various rubber-based, urethane-based, and acrylic-based base resins. It has been obtained by diluting this in a solvent, coating it on a polyimide film, drying the solvent, laminating it with copper foil, and curing it by heating.

[Problem to be solved by the invention]

In recent years, the density of flexible printed wiring boards has increased,
Demand for multi-layering is increasing. However, conventional manufacturing methods require an adhesive curing process at high temperatures, resulting in large dimensional changes due to thermal expansion and contraction of the base film. Furthermore, a typical heat curing process requires a large amount of time for curing, resulting in poor production efficiency. Furthermore, when a low molecular weight monomer or oligomer is used as an adhesive composition, polymerization shrinkage is large, which causes warping and twisting of the wiring board. The present invention has been made in view of the above points, and is an electron beam curing metal for flexible printed wiring boards that can produce flexible wiring boards with small dimensional changes, warping, and twisting of the base film with high production efficiency. The present invention aims to provide a method for producing a film with foil.

[Means to solve the problem]

The present invention solves the above-mentioned problems by bonding a metal foil and a film through an adhesive whose main component is a flexible polymer having a specific electron beam-reactive group, and curing the film by irradiating it with an electron beam. This is what I did.

That is, the present invention is characterized by laminating a conductive metal and a base film using a flexible polymer having an unsaturated double bond in the molecule as an adhesive layer, and then curing the adhesive layer by irradiating it with an electron beam. The present invention relates to a method for manufacturing an electron beam-curable film with metal foil for flexible printed wiring boards.

Next, the adhesive components used in the present invention will be explained in detail. In the present invention, the flexible polymer having an unsaturated double bond in the molecule refers to a polymer containing a rubbery diene copolymer component such as butadiene or isoprene in the molecule. In addition to these copolymerized components, it is copolymerized with styrene to provide strength and heat resistance, acrylonidonyl to improve adhesion to metals, and other acrylic esters to adjust the glass transition temperature. There may be. Specific examples of these polymers include polybutadiene, poly-acrylonitrile-butadiene, and polyacrylonitrile-butadiene.
Examples include isoprene, polystyrene-butadiene, polystyrene-isoprene, polystyrene-butadiene-styrene, and polystyrene-isoprene-styrene. These may be used alone or in a blend. In order for these polymers to be sufficiently cured by electron beams and have heat resistance, the butadiene or isoprene component is preferably 20% by weight or more, and 40 to 1% by weight.
00% by weight is more preferable.

Further, in order for the adhesive to maintain sufficient adhesive strength, it is desirable that the molecular weight is 50,000 or more, but if the molecular weight exceeds 1,000,000, the dispersibility in organic solvents will deteriorate, which is undesirable.

When used as an adhesive, diluting solvents for the polymer include MEK, toluene, ethyl acetate, Hensen, THF,
A material with excellent compatibility and dispersibility can be selected from carbon tetrachloride, hexane, etc. The drying temperature of the solvent, which has a large effect on dimensional stability, is determined by the boiling point of the solvent used and the temperature dependence of the heating shrinkage rate, but it is usually 200°C or less,
More preferably, the temperature is 0°C or lower. Further, in order to maintain the stability of unsaturated double bonds, the adhesive used in the present invention may contain a polymerization inhibitor such as hydroquinone or benzoquinone or an antioxidant.

Next, examples of the conductive metal foil used in the present invention include copper foil, silver, gold, and aluminum foil, but copper foil is superior in terms of electrical conductivity and price, and its thickness is
100 due to the constraints of flexible printed wiring board applications.
It is desirable that the thickness be less than μm.

Further, since the material is desired to have flexibility, rolled copper foil is more desirable than electrolytic copper foil, and its surface may be nickel-plated to improve wettability of the adhesive. As the base film used in the present invention, heat-resistant plastic films such as polyimide films, polyamide films, and polyester films are suitably used.

In particular, polyimide film is excellent. Its thickness is 12°5 to 125° due to bending resistance, strength, electron beam transparency, etc.
μm is preferred, and 25 to 50 μm is more suitable.

Further, the surface may be subjected to sandblasting treatment if necessary.

Next, the dose of an electron beam irradiation device for curing the adhesive of the present invention can generally be used in the range of 0.5 to 100 Mrad, and more preferably 1.0 to 50 Mrad. If the dose is less than 0.5 Mrad, sufficient crosslinking may not be obtained, and if it exceeds 100 Mrad, the polymer begins to degrade. Note that during electron beam irradiation, care must be taken to prevent active radicals from being deactivated by oxygen. In order to avoid this, it is preferable to vacuum defoam the adhesive in advance, apply it to the base film, dry the solvent, and then immediately laminate the copper foil to avoid entraining air bubbles.

In the present invention, the adhesive is usually dissolved in a solvent, applied to copper foil, and after drying the solvent, laminated with a base film, and cured by irradiating the adhesive layer with an electron beam. At this time, heat aging may be performed after lamination depending on the case.

On the other hand, electron beam irradiation methods generally use low energy (300
(KeV or lower) Since the adhesive can be cured by electron beams, it is preferable to irradiate from the base film side. but,
In some cases, the adhesive may be cured by irradiating an electron beam with high energy (IMeV or more) from the copper foil side. Therefore, when using this high-energy electron beam, it can be applied to double-sided metal foil films and multilayer metal foil films.

[Effect]

Although the reason why the effects of the present invention are produced is not necessarily clear, the mechanism that causes the dimensional change is considered as follows. Conventional thermosetting adhesives have internal distortion due to the thermal history of raising the temperature to the curing temperature and then cooling it to room temperature, and the distortion is released during the copper foil etching process, causing dimensional changes.

Therefore, in the present invention using electron beam reaction, it is thought that dimensional changes are small because the adhesive can be cured without undergoing high-temperature thermal history. In addition, the degree of polymerization shrinkage of the adhesive, which causes warping and twisting of the substrate, depends on the number of reaction points.
When a low Tg rubber prepolymer is used as a starting material like the adhesive of the present invention, there are fewer reaction points, and
It is presumed that the internal strain relaxation mechanism caused by the flow is working, keeping warpage and twisting to a minimum.

〔Example〕

Next, the present invention will be explained in detail in Examples, but the present invention is not limited thereto.

Example 1 Poly-acrylonitrile-butadiene polymer (manufactured by Nippon Zeon ■, trade name N1pol DN401, butadiene component 82 wt%, weight average molecular weight approximately 500,000) was dissolved in MEK
After making a 15 wt % solution, hydroquinone monomethyl ether was added to 1.5 wt% of the polymer weight. ．． 000p
pm. Spread this solution on a polyimide film (manufactured by Toshi DuPont, trade name: Kapton 100H1).
The surface was sandblasted, and the coating was coated to a solid content of 40 μm (thickness: 25 μm), and dried in a drying oven at 100° C. for 10 minutes. Thereafter, lamination was performed while degassing with rolled copper foil (manufactured by Nikko Gould ■, surface nickel treated, thickness 35 μm) while being careful not to introduce air bubbles.

This polyimide film with copper foil was irradiated with an electron beam of 10 Mrad from the film side. For this sample (
Table 1 shows the results of the following tests: 1) Dimensional change, (2) Warping/twisting, (3) Beer strength, and (4) Solder heat resistance.

Example 2 Poly-styrene-butadiene polymer (manufactured by Japan Synthetic Rubber, trade name JS) was used instead of the polymer used in Example 1.
Using R-1013N (butadiene component: 60 wt%, weight average molecular weight: about 500,000) as an adhesive, a polyimide film with copper foil similar to that in Example 1 was prepared and each test was conducted.

Example 3 Polystyrene was used instead of the polymer used in Example 1.
Isoprene-styrene polymer (manufactured by Japan Synthetic Rubber ■, trade name JSR-3IS-5,000, weight average molecular weight approximately 50
A copper foil-covered polyimide film similar to that in Example 1 was prepared using 1,000 yen) as an adhesive and subjected to each test.

Example 4 A poly-acrylonitrile butadiene polymer containing 67 wt% of butadiene component (manufactured by Nippon Zeon ■, trade name N1po11032, weight average molecular weight approximately 500,000) was used as an adhesive instead of the polymer used in Example 1, and the experiment was carried out. A copper foil-covered polyimide film similar to that in Example 1 was prepared and subjected to each test.

Example 5 Instead of the polymer used in Example 1, a polyacrylonitrile-butadiene polymer with a butadiene component of 58 wt% (manufactured by Nippon Zeon ■, trade name N1pol DNI) was used.
Using OI (weight average molecular weight: approximately 500,000) as an adhesive, a polyimide film with a copper foil similar to that in Example 1 was prepared and subjected to each test.

Comparative Example 1 Acrylic polymer (manufactured by Teikoku Kagaku Sangyo ■, trade name WS-O23, ethyl acrylate/butyl acrylate/acrylonitrile =
20/65/15 (expressed as wt%) and a weight average molecular weight of about 200,000 was made into a 23wt% toluene solution to prepare a polyimide film with copper foil similar to that in Example 1, and each test was conducted.

Comparative Example 2 Instead of the polymer used in Example 1, poly-acrylonitrile and butadiene polymer (N1pol manufactured by Nippon Zeon ■) were used so that the butadiene component was 15 wt%.
Using DNIOI (weight average molecular weight: approximately 500,000) as an adhesive, a polyimide film with a copper foil similar to that in Example 1 was prepared and each test was conducted.

Example 6 The drying temperature of the adhesive solution used in Example 1 was set to 100°C.
to 150°C, a polyimide film with copper foil similar to that in Example 1 was prepared, and each test was conducted.

Example 7 The electron beam irradiation dose was changed from 10 Mrad to 40 Mrad, and a polyimide film with copper foil similar to that in Example 1 was prepared and various tests were conducted.

Example 8.9.10 In the process of creating a polyimide film with copper foil in Example 1, the coating order was changed and the adhesive was first applied to the foil for one period, and then a polyimide film was laminated. ,
An electron beam of 10 Mrad was irradiated from the film side (Example 8). The coating order is the same! A high energy electron beam of 2 MeV was irradiated at 10 Mr ad from the i1 foil side (Example 9). After coating the polyimide film, copper foil was laminated, and immediately after that, heat aging was newly added at 100° C. for 10 minutes (Example 10). Various tests were conducted on these polyimide films with copper foil.

The tests in the above Examples and Comparative Examples were conducted as follows.

Dimensional Change Rate All the copper in the polyimide film with copper foil was removed by etching, and the dimensional changes in the polyimide film before and after etching were measured using a three-dimensional dimension measuring device.

Warpage/Twisting After all the copper of the polyimide film with copper foil was removed by etching, the state of warpage/twisting of the polyimide film was observed with the naked eye. The degree is determined in three stages: large, medium, and small.

The beer-strength polyimide film with copper foil was stored in a constant temperature and humidity chamber at 40° C. and 190% RH for 96 hours, and the peel strength of the copper foil was immediately measured. Peeling angle: 180° Peeling speed: 50 mm/
ffl1n.

A polyimide film with solder heat-resistant copper foil was treated in a constant temperature and humidity bath at 40° C. and 190% RH for 96 hours, and immediately after that, it was immersed in a solder bath for 1 minute to observe the presence or absence of abnormalities.

The value is the maximum temperature at which no abnormality occurs.

〔Effect of the invention〕

The manufacturing method of the present invention has excellent production efficiency, and the wiring board obtained using the metal foil-attached film for electron beam-curable flexible printed wiring boards manufactured by the present invention has small dimensional changes, and It does not warp or twist, and has excellent basic properties such as beer strength and solder heat resistance.

Claims (5)

[Claims] 1. An electronic method characterized by laminating a conductive metal foil and a base film using a flexible polymer having an unsaturated double bond in the molecule as an adhesive layer, and then irradiating the adhesive layer with an electron beam to cure the adhesive layer. A method for producing a film with metal foil for line-curing flexible printed wiring boards. 2. 2. The metal foil-attached film for an electron beam-curable flexible printed wiring board according to claim 1, wherein the flexible polymer having an unsaturated double bond in the molecule contains a butadiene or isoprene component in a range of 20 to 100% by weight. Production method. 3. The metal for electron beam curable flexible printed wiring boards according to claim 1 or 2, wherein the flexible polymer having an unsaturated double bond in its molecule has a weight average molecular weight within the range of 50,000 to 1,000,000. A method for producing a film with foil. 4. 2. The method for producing a film with metal foil for an electron beam-curable flexible printed wiring board according to claim 1, wherein the conductive metal foil is a copper foil. 5. Claim 1 wherein the base film is a polyimide film.
The method for producing a metal foil-attached film for an electron beam-curable flexible printed wiring board as described above.