JPH02107685A - Bonding resin composition - Google Patents

Abstract

PURPOSE:To obtain the subject composition capable of providing a polyimide film copper film laminated body excellent in initial adhesive strength and solder heat resistance by adding a spiroacetal derivative to a thermoplastic copolymer resin containing ethylene/vinyl acetate as main monomers. CONSTITUTION:The objective composition obtained by adding a spiroacetal derivative having plural unsaturated bonds in the molecule and, as necessary, an organic peroxide to a thermoplastic copolymer containing ethylene and vinyl acetate as main recurring units. The above-mentioned composition is used for bonding a copper foil of a flexible printed circuit board to either a polyimide film or an overlaying film.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention particularly relates to an adhesive resin composition used for adhesion between a copper foil and a polyimide film of a flexible printed circuit board, or for adhesion between a flexible printed circuit board and an overlay film. .

(Conventional technology) In recent years, as electronic devices have become lighter, smaller, and more sophisticated,
Instead of ordinary insulated wires, circuit boards with metal foil wiring formed on the board are used in consumer electronic equipment such as television receivers and audio equipment, electronic equipment such as measuring instruments and computers, automobiles, etc. It has come to be widely used for various types of aircraft wiring.

The circuit boards used for such applications are often flexible printed circuit boards made of a film made of a polymeric material and copper foil.
The board is manufactured by a method in which a wiring pattern is formed on the surface of the copper foil by chemical etching or the like, leaving only the necessary portions.

Currently, this flexible printed circuit board is produced by laminating copper foil and flexible insulating film such as polyethylene terephthalate film or polyimide film using film adhesive, or by laminating copper foil or flexible insulating film on top of copper foil or flexible insulating film. It is manufactured by applying an adhesive and heat-bonding it under pressure, or by heat-bonding epoxy-impregnated glass cloth (prepreg) to copper foil under pressure.

Furthermore, when mounting wiring and electronic components, automatic soldering is often a process that requires high performance in terms of solder heat resistance, heat aging resistance, electrical insulation, chemical resistance, tear strength, etc. In particular, with regard to heat resistance properties such as solder heat resistance, not only the heat resistance of the flexible insulating film but also the adhesive layer with the copper foil is required to have a high degree of heat resistance.

Regarding the heat resistance of flexible insulating films, polyethylene terephthalate film is inexpensive but has poor heat resistance, and problems such as softening of the film, blistering, and separation from the copper foil may occur during the soldering process. . Furthermore, epoxy-impregnated glass cloth has disadvantages such as discoloration during the soldering process, difficulty in manufacturing extremely thin and flexible products, and high cost.

From this point of view, polyimide films are currently most commonly used as flexible insulating films, and from the same point of view polyimide films are also most often used as overlay films for flexible printed circuit boards.

In order to bond the copper foil and polyimide film of flexible printed store boards or the flexible printed circuit board and overlay film, an adhesive that adheres to both the copper foil and the polyimide film is required. Fluorine-based resins such as fluorinated ethylene copolymers (such as "Teflon FFP" manufactured by DuPont), epoxy-novolanok-based resins (manufactured by Dow Chemical Company!!!
DEN 438, etc.), Nitrile-phenolic resins (DC282, manufactured by Koningen Corporation, etc.), nitrile-phenolic resins (Plastilok 605, manufactured by BF Gutdrich, etc.), polyester resins (USM Bostic 7] 51 → -F Scodur 1, etc.),
Acrylic resins (Hiker 2679χ6 manufactured by BF Gutdrich, Hovlenx LC40 manufactured by Rohm and Haas, Nycal 370 manufactured by U, C, C) are known (Industrial Materials, Vol. 21, No. 10). No. 28
Page, published 1981).

When using the adhesive described in F, the initial adhesive strength between polyimide film and copper foil is 1.0 kg/cm or more, except for systems using silicone resin adhesive, and For example, even when immersed in a solder bath at 290°C for 10 seconds, no blistering or peeling of the polyimide film or copper foil was observed, and the film also has excellent heat resistance.

However, many of the above adhesives require high temperatures and long periods of time for bonding (for example, in the case of epoxy novolanol resin, 180 to 200 degrees are required to complete the curing reaction of the adhesive). It is necessary to heat and press the bond for 30 to 60 minutes at a high temperature of There is a problem that the adhesion process becomes rate-limiting, which hinders productivity improvement.

On the other hand, when using a hexafluorinated propylene-tetrafluorinated ethylene copolymer as an adhesive, a film of hexafluorinated propylene-tetrafluorinated ethylene copolymer is sandwiched between a polyimide film and a copper foil. Bonding can be done simply by thermocompression bonding at ~320°C, and bonding can be done in a short time, making it suitable for continuous production of flexible printed 11s boards. However, since the processing temperature is higher, copper foil There are problems such as partial oxidation of oxidation.

In addition to the adhesive used for polyimide film and copper foil, various other adhesives such as epoxy resin-polyamine adhesives and polyurethane adhesives such as polyol-isocyanate adhesives are being investigated, but the curing reaction of the adhesive is In order to complete the bonding process, the bonding process requires a hatching process, as in the above case, since high temperatures and a long period of time are required. It is also known to shorten the curing time by adding catalysts, etc., but completing curing in a short time causes problems such as curing distortion remaining in the adhesive and curling of the resulting flexible printed circuit board. This may occur.

On the other hand, true melt adhesives are known as adhesives that can bond not only copper foils and polyimide films but also adherends at relatively low temperatures and in a short time.

True-melt adhesives are solid adhesives that are based on thermoplastic resins and are mixed with plasticizers, tackifiers, antioxidants, etc. as necessary.

When applied to adhesives, hot melt adhesive is melted with an applicator, applied to the adherend, and pressed.

True melt adhesives have the advantage of being able to complete adhesion instantly because they solidify when cooled.

Known types of true melt adhesives include ethylene homopolymers and copolymers, styrene bronze copolymers (thermoplastic rubber), polyamides, nylons, and butyl rubbers, and tackifiers include rosin and copolymers. Its ester derivatives, hydrogenated rosin and its ester derivatives, petroleum-based hydrocarbon resins, etc. are used as plasticizers, and paraffin waxes are used as antioxidants, hindered phenols, phosphites, etc. ing.

The application of this hot melt adhesive to the adhesion of polyimide films and copper foils can be easily inferred; for example, ethylene-vinyl acetate copolymer-based real-melt adhesives and ethylene-ethyl acrylate-based real-melt adhesives can be used as melt adhesives. If it is applied to a polyimide film to a thickness of about 30 microns and pressed with copper foil for 1 minute at 100 to 170°C,
It is possible to bond copper foil and polyimide film, in this case,
It was possible to easily form a material having an initial adhesive strength of 1 kg/c+a or more.

However, the polyimide film-copper foil laminate formed using the above hot melt adhesive has a problem in that the polyimide film and the copper foil completely peel off when immersed in a solder bath at 280° C. for 5 seconds, for example.

[Problems to be Solved by the Invention] As explained above, many adhesives for copper foil and polyimide film with good adhesive strength and soldering heat resistance are known and used. Since curing of the agent requires high temperature and a long time, the bonding process is a batch process, resulting in poor productivity.

On the other hand, when a true melt adhesive is used, it can be bonded for a short time and has a good initial adhesive strength, but it has poor solder heat resistance, so it can be bonded for a short time and has a high initial adhesive strength. Moreover, at present, almost no adhesives are known that have excellent solder heat resistance.

[Means for Solving the Problems] As a result of the inventors' intensive investigation into the above-mentioned problems,
An adhesive resin composition made by adding a spiroacetal derivative having multiple unsaturated bonding bones in the molecule to a thermoplastic copolymer resin whose main repeating units are ethylene and vinyl acetate is used as an adhesive for polyimide film and copper foil. The inventors have discovered that a polyimide film foil laminate with excellent initial adhesion and solder heat resistance can be obtained by using the polyimide foil laminate as a polyimide film, and based on this knowledge, the present invention has been completed.

Specifically, a resin composition made by adding a spiroacetal derivative having a plurality of unsaturated bonding bones in the molecule to a thermoplastic copolymer resin whose main repeating units are ethylene and vinyl acetate was deposited on a polyimide film. A resin composition layer is formed by heating and melting and coating, or by dissolving the resin composition in a solvent to form a solution, coating and drying the solution, and then applying copper foil to the resin composition layer. 1
By thermocompression bonding for 1 to 10 minutes at a temperature of 00"C to 180°C, preferably by irradiating ionizing radiation from the surface of the polyimide film, a polyimide film with excellent initial adhesive strength and excellent solder heat resistance can be produced. A foil laminate is obtained.

At this time, it is possible to complete the adhesion by thermocompression alone, but in this case, it is preferable to add a crosslinking agent such as an organic peroxide that generates active species such as free radicals to the adhesive resin when heated. It may be added to the composition in advance.

In addition, a cobalt curing accelerator such as a cobalt organic acid salt may be used together with the organic peroxide crosslinking agent.

The above ionizing radiation includes α rays, β rays (electron beams), T
Rays, X-rays, ultraviolet rays, etc. can be used, but from the standpoint of industrial use, it is preferable to use β-rays (electron vA) and ultraviolet rays.

In addition, when performing photocuring such as ultraviolet irradiation, a photosensitizer such as a benzoin type or a benzophenone type may be included in the composition.

As the organic peroxide crosslinking agent, benzoyl peroxide, lauroyl peroxide, dicumyl peroxide, etc. can be used, but dicumyl peroxide is preferable for high temperature application.

Thermoplastic copolymer resins containing ethylene and vinyl acetate as main repeating units include copolymers of ethylene and vinyl acetate, as well as copolymers containing other olefin compounds (for example, vinyl chloride, (meth)). Acrylic acid and/or its ester, maleic acid, maleic anhydride, etc.) copolymerized or graft copolymerized, or
Partially or completely saponified products of the ethylene-vinyl acetate copolymer are included.

Preferred examples of the thermoplastic copolymer resin include ethylene-vinyl acetate copolymer, ethylene-vinyl acetate-maleic anhydride copolymer, partially saponified ethylene-vinyl acetate copolymer, and ethylene-vinyl acetate-maleic anhydride copolymer. Examples include acid graft copolymers.

Further, the vinyl acetate content of the copolymer resin does not need to be particularly limited, but is preferably 10 to 45%.

The melt flow rate of the copolymer resin is not particularly limited, but is preferably 1 to 200.

In addition, mel[flow rate is ASTM-01238-5
It is measured by treating f(7).

In addition, spiroacetal derivatives having multiple unsaturated bones in the molecule include mixtures of compounds produced by the reaction of polyhydric alcohols such as pentaerythritol with unsaturated aldehydes such as acrolein, and compounds produced by the reaction of polyhydric alcohols such as pentaerythritol with unsaturated aldehydes such as acrolein. It includes various derivatives such as prepolymers derived from the above, and modified products obtained by reacting the above-mentioned produced compounds with hydroxyl group-containing compounds and carboxyl group-containing compounds.

Preferred examples of the spiroacetal derivatives include monoallylidene pentaerythritol, diallylidene pentaerythritol, diallylidene dipentaerythritol, or mixtures thereof, monoallylidene pentaerythritol, diallylidene bentaerythritol, and diallylidene dipentaerythritol. Specific examples include oligomers or oligomer mixtures, monoallylidene pentaerythritol, diallylidene pentaerythritol, acrylic modified products of diallylidene dipentaerythritol, or unsaturated polyester modified products, and these compounds include , U.S. Patent Cylinder 2.998,
The mixture may be a mixture formed by adding and reacting a sulfur-containing compound as disclosed in No. 427 (1961), or a mixture formed by adding and reacting a polyvalent thiol compound.

Incidentally, spirane resin is known as a typical spiroacetal derivative (Journal of Japan Adhesive Association Vol. 13. No. 9. (1977), P. 7-20).
).

The mixing ratio of the thermoplastic copolymer resin whose main repeating units are ethylene and vinyl acetate and the spiroacetal derivative having a plurality of unsaturated bonding bones in the molecule is not particularly limited, but the desirable range is ethylene and vinyl acetate. The weight ratio of thermoplastic copolymer resin having vinyl acetate as a main repeating unit to spiroacetal derivative having a plurality of unsaturated bonding bones in the molecule is in the range of 90/10 to 30/70.

In the present invention, in order to make the adhesive particularly suitable for use as a hot melt adhesive, modifiers such as various waxes and tackifiers may be blended, or other known hot melt adhesives may be used in combination. It's okay.

Furthermore, various additives such as plasticizers and antioxidants can be added as appropriate.

The adhesive resin composition of the present invention is applicable to applications where ethylene-vinyl acetate-based true melt adhesives are used, and is particularly suitable as an adhesive for polyimide film-copper foil laminates.

[Effect]

In the present invention, when only a thermoplastic copolymer resin whose main repeating units are ethylene and vinyl acetate is used as an adhesive between a polyimide film and a copper foil, a polyimide film-copper foil laminate with excellent initial adhesive strength can be obtained. However, it is not possible to obtain a product with excellent soldering heat resistance. Furthermore, when only a spiroacetal derivative having multiple unsaturated bonds in the molecule is used as an adhesive between a polyimide film and copper foil, a polyimide film-copper foil laminate with excellent initial adhesion can be obtained. do not have.

Only when a mixture of a thermoplastic copolymer resin whose main repeating units are ethylene and vinyl acetate and a spiroacetal derivative having multiple unsaturated bonds in the molecule is used as an adhesive between polyimide film and copper foil. , a polyimide film with excellent initial adhesion and soldering heat resistance.
This has the unique effect of producing a copper foil laminate.

Furthermore, according to the present invention, it is possible to significantly reduce the time required for bonding, which has been a problem with conventional adhesives.
For example, when completing the bonding by electron beam irradiation, even if the thermocompression bonding process is included, the bonding process will be 1/2 to 1/10th of the conventional bonding process.
It can be completed with 100 to 150° temperature of thermocompression bonding.
The temperature can be lowered to C, and it is possible to improve workability and productivity.

〔Example〕

As the polyimide film, Kapton 100) 1 (trade name) manufactured by DuPont Toshiki was used, with a thickness of 25 microns, and as the copper foil, an electrolytic copper foil with a thickness of 35 microns was used. Further, as a spiroacetal derivative having a plurality of unsaturated bonds in the molecule, Subilanque resin (trade name) manufactured by Showa Kobunshi ■ was used.

In the molecule with a thermoplastic copolymer resin whose main repeating units are ethylene and vinyl acetate? 3! A mixture of spiroacetal derivatives having several unsaturated bonds was mixed using a roll mixer, and then coated onto a polyimide film to a thickness of 35 microns using a hot applicator and solidified by cooling to form an adhesive layer. .

Copper foil was brought into close contact with this adhesive layer and bonded using a heat press at 150'C, and then the adhesion was completed by irradiation with ionizing radiation. For those that were irradiated with an electron beam at an accelerating voltage of 400 kV, the surface of the polyimide film was irradiated. .

Evaluation after adhesion was performed by peeling test (reinforcing plate type) and observation of the sample after being immersed in a solder bath (solder bath temperature: 280°C, immersion time = 30 seconds).

Examples are summarized in Table 1 and comparative examples are summarized in Table 2 below.

As is clear from the experimental results shown in Tables 1 and 2 above, a copolymer containing ethylene and vinyl acetate as main repeating units (hereinafter abbreviated as copolymer resin) and multiple unsaturations in the molecule An adhesive resin composition blended with a spiroacetal derivative containing connective bones (hereinafter abbreviated as spiroacetal derivative) has the following properties when used as a hot melt adhesive for producing a polyimide film-copper foil laminate:
Compared to using them alone, the initial adhesion strength is significantly superior on average for both the polyimide film side and the copper foil side, and the laminate is not immersed in a solder bath, which is a problem when applied to printed circuit boards. It has excellent heat resistance with no peeling or swelling, and compared to the results of heat resistance that are completely inferior when used alone, it shows an outstanding effect.

[Effects of the Invention] According to the present invention, a polyimide film-copper foil laminate can be bonded to a polyimide film and copper foil in a short time, and is excellent in both initial adhesion strength and soldering heat resistance. Since it can be obtained, it can be applied to flexible printed circuit boards, adhesion of polyimide film overlays to flexible printed circuit boards, etc., and has great utility value.

Claims (2)

[Claims] (1) An adhesive resin composition obtained by adding a spiroacetal derivative having a plurality of unsaturated bonds in the molecule to a thermoplastic copolymer resin whose main repeating units are ethylene and vinyl acetate. (2) An adhesive resin composition obtained by adding a spiroacetal derivative having multiple unsaturated bonds in the molecule and an organic peroxide to a thermoplastic copolymer whose main repeating units are ethylene and vinyl acetate. .