JPS6213067B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a heat-resistant resin-coated metal clad plate or foil by forming an electrically insulating film directly on a metal plate or foil without using an electrically insulating film or fibrous base material. It is something. Recently, there has been a growing demand for simpler, smaller, higher reliability, and higher performance mounting methods for communication equipment, consumer equipment, computer equipment, and audio equipment, and similar demands are also being made for the printed wiring boards used inside these equipment. is strongly desired. Therefore, among printed wiring boards, flexible printed wiring boards, which are lightweight and compact and can be bent to form three-dimensional wiring, meet these requirements and have recently been used as printed wiring boards for a wide range of equipment. Such flexible printed wiring boards have conventionally been made by bonding electrically insulating films such as polyester resin films, polyimide resin films, fluororesin films, etc. to metal foils via adhesives, or by bonding them with metal foils using adhesives, or by using glass cloth, glass nonwoven fabrics, etc. A so-called flexible copper-clad board has been used, which is obtained by bonding a prepreg, which is a fibrous base material impregnated with a heat-resistant resin such as a polyimide resin or an epoxy resin, to a metal foil. However, in the case of film-based materials, in addition to the properties of the film itself, the properties of the adhesive used have a large influence on the performance. When a film is used as a base, the properties of the film, such as heat resistance, are diminished by the adhesive, and the original properties of the film are not utilized. Also, those using resin-impregnated fibrous substrates without adhesives cannot be used in applications that require severe bending because they will break. There is also a method of bonding plastic film or resin powder to metal foil by heat fusion without using an adhesive, but films or powders that have a high degree of heat resistance can themselves be heat-fused at a high melting point. It is difficult to bond, requires special treatment, and requires extremely high-temperature crimping equipment, making it difficult to manufacture industrially and also resulting in very high costs. On the other hand, if an insulating resin could be wet-coated on the metal foil surface and dried to form a film, and the film itself could be used as an insulating layer and support for flexible printed circuits, it would be possible to use the above-mentioned conventional materials. In comparison, since no adhesive is used, the properties of the resin itself can be utilized as they are in the printed wiring board. The process of crimping with metal foil becomes unnecessary, increasing productivity. The thickness of the insulating layer and support can be freely controlled, making it possible to manufacture ultra-thin substrates. Continuous manufacturing becomes easier. These advantages make it an extremely attractive material industrially. The solution casting method has long been known as a manufacturing method for such materials. For example, varnishes made of resins such as epoxy, urethane, and alkyd are applied to the surface of metal foil, dried, and then a coating film is formed on the surface of the metal foil. It is known that it can be done. However, when such resins are applied to flexible printed circuit boards for the purpose described above, the film obtained by coating and drying often lacks mechanical strength and cannot be used as a support film for flexible printed circuits. It cannot withstand the mechanical stress during the subsequent printed board processing process and use. Thermoplastic resins, which are easy to form into films using the usual solution casting method, have drawbacks such as insufficient heat resistance during processing and mounting as flexible printed circuits. Recently, in order to compensate for these drawbacks, a method has been described in which a flexible printed circuit board is manufactured by a solution casting method using a heat-resistant resin having a heterocycle such as polyimide, polyamideimide, polyesterimide, etc. as the resin. When such a resin is used, it has excellent heat resistance, but because it has few polar groups, it lacks adhesion to metal foil, and when the resin is applied onto the metal foil surface and hardened by drying, Curing shrinkage occurs, and the substrate curls significantly toward the opposite side of the metal foil, that is, the resin film side, making it unsuitable for practical use as a printed wiring board. This tendency is such that the curl becomes larger as a polymer resin is used. Furthermore, if a polymeric resin is not used, the molecular bonding will be weak, resulting in poor film forming properties, resulting in weak mechanical strength and brittleness. Therefore, as a method to compensate for these drawbacks and take advantage of the properties of heat-resistant resins, the present inventors have already proposed reacting a heat-resistant resin that forms a heterocycle with a thermosetting resin such as an epoxy resin or a phenoxy resin. Through this method, we have been able to provide a well-balanced product that provides good film forming properties, adhesion to metal foil, and curling, all of which are necessary for printed wiring boards to support the board. However, this method Since it is a three-dimensional reaction using a thermosetting resin, it inevitably lacks flexibility and is also brittle and easily torn when notched. The present invention also overcomes this drawback. That is, the present invention utilizes the properties of the substrate resin without using adhesives, and provides a new printed wiring board that has extremely excellent practical properties such as adhesiveness, film flexibility, mechanical strength, and no curling. It provides materials. That is, the present invention is characterized in that a film obtained by reacting a heat-resistant resin forming a heterocycle with a resin having high elasticity is used for a flexible printed wiring board. A heat-resistant resin having a heterocycle alone has excellent heat resistance as described above, but has poor adhesion to metal foil because it has few polar groups. Also, curls and wrinkles occur due to shrinkage during curing. In addition, these drawbacks can be solved by reacting with a thermosetting resin, but as mentioned above, since it is a product of a three-dimensional reaction of a thermosetting resin, it impairs flexibility and Moreover, the tear strength decreases. Therefore, as a result of intensive research to take advantage of the heat resistance of this resin and compensate for these drawbacks, we were able to solve all of these drawbacks at once by reacting a resin with high elasticity. The resin reacted with a highly elastic resin increases the number of polar groups that the highly elastic resin has, so it has strong adhesion to metal foil that cannot be obtained with a heat-resistant resin alone. Make it. Furthermore, if only a linear polymeric heat-resistant resin is used, it will shrink significantly during curing, and the obtained metal clad plate will have curls, wrinkles, etc. However, by reacting the heat-resistant rubber of the present invention, the rubber will shrink during curing. Crosslinking occurs due to its own vulcanization, three-dimensionality occurs, and curing shrinkage can be suppressed, and surprisingly, almost no wrinkles, curls, etc. were generated in the experimental examples. Another feature is that the use of rubber improves elasticity, as is well known.
The cured product is highly flexible, so even if the cured product is made into a film, the tear strength etc. will not decrease and the film will be strong. In terms of film forming properties, it has been found that the use of a polymeric resin is faster and the mechanical strength of the resulting film is stronger when a polymeric resin is used than a low molecular weight resin. This is due to the difference in intermolecular bonding strength between the process of polymerizing the resin, which is performed in a dynamic state by stirring under heating, and in a method in which it is performed in a static state under heating.
Obviously, it will be stronger. In the present invention, the step of synthesizing the resin corresponds to the step of casting it on metal foil. By the way, the present inventors have discovered that a film with strong mechanical strength can be obtained by using a resin that has been polymerized in advance to be cast on the metal foil. As mentioned above, if a linear polymer made only of heat-resistant resin is used, the shrinkage due to curing will be greater, but in the present invention, by plasticizing the film by reaction with heat-resistant rubber, , succeeded in suppressing this. As described above, by using the resin of the present invention, it is possible to solve the major drawbacks of the resin, such as adhesive strength, curls, wrinkles, etc., while taking advantage of the resin's heat resistance. We were able to obtain a highly practical product with flexibility. The metal plates or foils used in the present invention are ordinary metal foils or plates thereof having good conductivity, such as copper foil, aluminum foil, nichrome foil, nickel foil, titanium foil, etc. The thickness is preferably 1 to 150μ, and if necessary, gold,
Surface plating with nickel, solder, etc. may also be applied. Further, in order to further improve the adhesive strength, the surface of the metal foil may be mechanically roughened by polishing or the like, or treated with a chemical agent such as a chromic acid-sulfuric acid solution. Heat-resistant resins having a heterocycle include polyimide, polyamideimide, polyesterimide, polyesteramideimide, polyvidantoin, polyimidazopyrrolone, polybenzimidazole,
Polyparabanic acid, polyparapanic acid, polychiazole, polybenzothiazole, polyquinoxaline, polyoxadiazole, etc., and copolymers thereof have a heterocyclic ring.
Heat-resistant resins without heterocycles include fluororesins and silicone resins, but polymerized resins have almost no polar groups and are difficult to react with other resins. When resin is used, it lacks adhesion to metal foil, and even as a metal clad plate, curls, wrinkles, etc. occur, making it impractical.
The heat-resistant resin used in the present application has a molecular weight of about 5,000 or more. The upper limit of the molecular weight of the heat-resistant resin is not particularly limited, but is preferably about 5000 to
200,000, more preferably about 8,000 to 100,000. This is because, as mentioned above, those with a high molecular weight have excellent film-forming properties, and in particular those with a molecular weight of about 5,000 or more have excellent mechanical strength such as tensile strength of the obtained film. If it is less than about 5,000, the film becomes brittle and is insufficient as a support for a printed wiring board. Examples of highly elastic resins include butadiene-styrene copolymers, butadiene-acrylonitrile copolymers, chloroprene polymers, acrylic acid ester polymers, alkylsiloxane condensates without double bonds in the main chain, and vinylidene fluoride. -Trifluoroethylene copolymer, vinylidene fluoride-hexafluoride propylene copolymer, chlorosulfonated polyethylene, alkylene-sulfide polymer, ethylene-propylene copolymer, propylene oxide polymer, epichlorohydrin polymer, epichlorohydrin- Ethylene oxide copolymers and the like can be used. These resins have a Mooney viscosity of 150
Use the following: Those with a Mooney viscosity of 150 or more are difficult to dissolve in solvents and require a large amount of solvent to dissolve, resulting in poor productivity. Furthermore, it has very poor compatibility with heat-resistant resins, and ordinary mixing does not result in uniformity, making it impractical. Furthermore, these resins are those in which the ratio of unsaturated atoms to carbon atoms forming the main chain is 40% or less. If it exceeds 40%, the ratio of double bonds in the main chain increases, and the bonds between molecules adjacent to the double bonds are weak, so thermal decomposition is likely to occur at high temperatures, resulting in a loss of heat resistance. Furthermore, when oxygen is present, the double bond itself is oxidized, and at high temperatures this oxidative deterioration occurs rapidly, resulting in a decrease in heat resistance. Among the above resins with high elasticity, acrylonitrile with an acrylonitrile content of 25% by weight or more
Preferably, a butadiene copolymer is used. In general, those with double bonds in their main chains are susceptible to thermal deterioration due to oxidation, but the acrylonitrile used in this application has an acrylonitrile content of 25% by weight or more.
Butadiene copolymer is usually called high nitrile rubber and has excellent heat resistance, so it prevents a decrease in heat resistance due to deterioration of the butadiene component. Furthermore, as the acrylonitrile content increases, the number of polar groups such as CN- groups increases, providing strong adhesiveness and increasing flexibility. In addition to these, small amounts of vulcanizing agents such as sulfur, metal oxides, peroxides, and vulcanization accelerators such as aldehyde-ammonia, aldehyde-amines, guanidine, thiourea, thiazole, etc. may also be added. Flexibility agents such as polyester, polyester, antioxidants such as diphenylamine and butylphenol, talc, clay, mica, feldspar powder,
Fillers such as quartz powder and magnesium oxide, colorants such as carbon black and ferrocyanine blue,
Small amounts of flame retardants such as tributyl phosphate, tetrabromodiphenylmethane, antimony trioxide, and barium metaborate may also be added, allowing for special uses as printed wiring boards. can be applied. The blending ratio of each resin described above is preferably 0.1 to 40 parts by weight of the resin having high elasticity, more preferably 100 parts by weight of the heat-resistant resin having a heterocycle, to 100 parts by weight of the heat-resistant resin having a heterocycle. On the other hand,
It is a mixture of 1 to 30 parts by weight of a highly elastic resin. More preferably, these resins are not only mixed together, but also before being cast onto the metal foil surface.
It is best to use one that has been heated and stirred at a temperature of 15°C to 150°C for 30 minutes to 10 hours. The resin mixed and reacted within this range has excellent film-forming properties, and at the same time, the resulting film has even better mechanical strength as a support for a printed wiring board. It also has excellent adhesive properties and does not cause curls, wrinkles, etc. in appearance. Furthermore, since no adhesive is used, the performance of the heat-resistant resin can be utilized as is, and it has superior mechanical properties, chemical properties, and physical properties at high temperatures compared to those using conventional adhesives. Become. In particular, the extremely low thermal deterioration of adhesive strength is an epoch-making feature that greatly expands the range of applications in which this printed wiring board can be mounted on various devices. Resin with high elasticity
If it is less than 0.1 part by weight, it will shrink when cured.
Curls and wrinkles occur, which is a serious drawback for printed wiring boards. Moreover, if it exceeds 40 parts by weight, it will not mix well with the heat-resistant resin and will be difficult to form uniformly, resulting in poor film forming properties. The resin composition of the present invention can be prepared using a suitable organic solvent such as dimethylacetamide, dimethylformamide,
Dimethyl sulfoxide, N-methylpyrrolidone, γ-butyllactone, caprolactam, pyridine, piperidine, phenol, cresol, dichloromethane, dioxane, tetrahydrofuran, toluene, xylene, solvent naphtha, ketones, alcohols, etc., or a mixture thereof dissolves in An example of a method for manufacturing printed wiring board substrates is to dissolve a resin composition in a solvent to a concentration of 3 to 70%, and cast it onto a metal foil surface to a uniform thickness in the range of 0.5 to 300μ. Apply, then in the dryer 50-450
The resin film is formed by drying at a temperature of 25°C for 2 minutes to 25 hours in two or more steps if necessary. Coating or casting equipment includes roll coaters, doctor blades,
A Gisa, a wheeler, a flow coater, etc. are used, and infrared rays, steam, high frequency, or a combination thereof are used for drying. It can be used not only for various flexible printed circuit boards, but also as a film by removing metal. For example, flexible printed boards for cameras, calculators, calculators, measuring instruments, etc., flexible flat cables, flexible sheet heaters, memory devices, bus bars, etc.
It can be used in a wide range of fields such as transducers, motor coils, capacitors, magnetic tapes, overcoat films for printed circuit boards, and various diaphragms for audio equipment. This will be explained in more detail below with reference to Examples. Example 1 100 parts by weight of a polyimide resin with a molecular weight of 12,000 obtained by polycondensing 2 moles of pyromellitic anhydride and 1 mole of diaminodiphenylmethane in N-methylpyrrolidone and the unsaturated atoms relative to the carbon atoms forming the main chain. 40% acrylonitrile with a proportion of 20%
20 parts by weight of acrylonitrile-butadiene copolymer with a Mooney viscosity of 80 and 0.2 parts by weight of sulfur as a vulcanizing agent were reacted at 80°C for 5 hours to form a heat-resistant resin with an intrinsic viscosity of 2.0 at 25°C. Obtained. This resin was mixed and diluted with a mixed solvent of N-methylpyrrolidone and xylene to a concentration of 30% by weight, and then coated on a 35μ thick copper foil using a coating machine for approximately 30 minutes.
Apply μ. This was dried at 250°C for 30 minutes to form a film and a flexible copper clad board was made. Table 1 shows the performance of this copper clad board as a printed wiring board and the performance of a film obtained by etching the copper foil with a 40° Baumé ferric chloride solution. Example 2 100 parts by weight of a polyamideimide resin with a molecular weight of 21,000 obtained by addition polymerizing 2 moles of trimellitic anhydride and 3 moles of diphenylmethane diisocyanate in N-methylpyrrolidone and Mooney viscosity.
15 parts by weight of epichlorohydrin polymer No. 60 and 0.15 parts by weight of dicumyl peroxide as a vulcanizing agent were added and reacted at 100°C for 1 hour to obtain a heat-resistant resin having an intrinsic viscosity of 1.9 at 25°C. This resin was mixed and diluted with N-methylpyrrolidone to a concentration of 15% by weight.
Apply approximately 20μ on 35μ copper foil. This is heated to 150℃.
After drying for 10 minutes at 220°C, a film was formed by further drying at 220°C for 60 minutes to produce a flexible copper clad board. Table 1 shows the performance of this copper clad board as a printed wiring board and the performance of a film obtained by etching it in the same manner as in Example 1. Example 3 100 parts by weight of a polyesterimide with a molecular weight of 30,000 obtained by reacting 1 mole of diaminodiphenyl ether with an adduct obtained by reacting 1 mole of trimellitic anhydride and 1 mole of hydroquinone diacetate in cresol and Mooney viscosity 10 parts by weight of a copolymer of vinylidene fluoride and ethylene trifluoride of No. 80 and 0.1 part by weight of hexamethylene diamine as a vulcanizing agent were added and mixed to give an intrinsic viscosity of 1.8 at 25°C.
A heat-resistant resin was obtained. Mix and dilute this resin with dimethylformamide to a concentration of 40% by weight, and apply about 50μ of this onto a 20μ thick aluminum foil using a coating machine. this
After drying at 100°C for 60 minutes, it was further dried at 150°C for 120 minutes to form a film and produce a flexible aluminum veneer. Table 1 shows the performance of this aluminum clad board as a printed wiring board and the performance of a film obtained by etching it in the same manner as in Example 1. Example 4 Copper cladding was made in the same manner as in Example 1 using 100 parts by weight of the polyimide resin used in Example 1, 30 parts by weight of the acrylonitrile-butadiene copolymer used in Example 1, and 0.3 parts by weight of sulfur. The board and its film were made. This performance is shown in Table 1. Example 5 Copper was prepared in the same manner as in Example 2 using 100 parts by weight of the polyamide-imide resin used in Example 2, 3 parts by weight of the epichlorohydrin polymer used in Example 2, and 0.03 parts by weight of dicumyl peroxide. Manufactured veneer boards and their films. This performance is shown in Table 1. Comparative Example 1 Using a polyimide resin with a molecular weight of 3200 obtained in the same manner as in Example 1, the acrylonitrile-butadiene copolymer and vulcanizing agent used in Example 1, flexible copper was prepared in the same manner as in Example 1. A veneer and its film were obtained. Its performance is shown in Table 1. Comparative Example 2 Using 100 parts by weight of the same polyamide-imide resin as in Example 2, 60 parts by weight of the epichlorohydrin polymer used in Example 2, and 0.6 parts by weight of dicumyl peroxide, a flexible resin was prepared in the same manner as in Example 2. A copper clad board and its film were obtained. Its performance is shown in Table 1. Comparative Example 3 A flexible copper-clad board and a film thereof were obtained in the same manner as in Example 1 using only the polyimide resin used in Example 1 as the resin. The performance is shown in Table 1 in accordance with Example 1. Comparative Example 4 A flexible copper-clad board and a film thereof were obtained in the same manner as in Example 2 using only the polyamide resin used in Example 2 as the resin. The performance is shown in Table 1 in accordance with Example 2. Comparative Example 5 40 parts by weight of bisphenol A type epoxy resin (Epicoat-#828 manufactured by Ciel), 30 parts by weight of maleic anhydride, and 30 parts by weight of acrylonitrile-butadiene copolymer were mixed and dissolved in acetone to a concentration of 40% by weight. The resulting solution is applied to a thickness of about 30μ on a 25μ thick polyimide film (Kapton H, manufactured by DuPont). After drying at 130°C for 5 minutes, a 35μ thick copper foil was passed between rolls and bonded under heat to form a copper clad board.
Further, the adhesive was completely cured by after-baking at 130°C for 10 hours. Table 1 shows the performance of this copper-clad board as a printed wiring board and the performance of an adhesive-backed film obtained by etching it in the same manner as in Example 1. Comparative example 6 Silicone resin (Shin-Etsu Chemical KR#271)
A copper clad board and its film were made in the same manner as in Example 1 using 100 parts by weight of the acrylonitrile-butadiene copolymer used in Example 1 and 0.2 parts by weight of sulfur as a vulcanizing agent. . This performance is shown in Table 1. Comparative Example 7 100 parts by weight of the polyimide resin used in Example 1 was combined with an acrylonitrile-butadiene copolymer having a Mooney viscosity of 80 and containing 40% by weight of acrylonitrile in which the ratio of unsaturated atoms to the carbon atoms forming the main chain was 60%. A copper clad board and its film were produced in the same manner as in Example 1 using 0.2 parts by weight of sulfur as the sulfur agent. This performance is shown in Table 1.

【table】

[Table] As shown in Table 1, the metal clad boards (Examples 1 to 5) obtained by the method of the present invention have well-balanced quality that fully meets each of the required performances as a printed wiring board. are doing. Compared to the conventional method using adhesive (Comparative Example 5), this method has not only electrical insulation but also approximately twice the peel strength. ) This is an epoch-making product that can be used with sufficient reliability in applications where printed wiring boards often had accidents such as peeling of circuit lines. This is a big advantage now that the line is becoming more common. Furthermore, the present invention not only has a very small dimensional change rate, but also almost no warping such as wrinkles or curls, which are important properties for printed wiring boards. This feature is an important factor when processing metal clad plates into printed wiring boards, and is expected to significantly improve yield. Furthermore, the film itself has strong mechanical strength and flexibility, and maintains sufficient strength and flexibility as a support for a printed wiring board. In particular, those using the high molecular weight resin of the present invention (Examples 1 to 5) have higher strength. Since it can be made as a single film at a low cost, it can be applied to motor coils, capacitors, magnetic tapes, etc. The one using a heat-resistant resin with a molecular weight smaller than that of the present application (Comparative Example 1) has significantly lower mechanical strengths such as tensile strength and tear strength, and is weak as a support for printed boards, and is not practical as a single film. Do not serve. In addition, those in which a resin having high elasticity is not reacted with a heat-resistant resin (Comparative Examples 3 to 4) have a markedly reduced peel strength and large warpage, and their practical use as printed wiring boards is extremely limited. It can only be used within a certain range,
Compared to conventional film-based products, it has fewer advantages and has the disadvantage of warping. Moreover, when the blending amount is larger than that in the present application (Comparative Example 2), the mixture with the heat-resistant resin is poor and it becomes difficult to form a uniform film, resulting in poor film forming properties and, as a result, the mechanical strength of the film is reduced. Furthermore, in the case of using a highly elastic resin in which the ratio of unsaturated atoms to the carbon atoms forming the main chain is 40% or more (Comparative Example 7), the ratio of double bonds in the main chain is low as described above. As the amount increases, heat resistance is poor, and in particular, thermal deterioration of peel strength is significantly lower than the initial value. In addition, if a resin containing a heterocyclic ring is not used (Comparative Example 6), as mentioned above, adhesiveness is lacking, and curls, wrinkles, etc. occur even when used as a metal clad plate. I can't. As mentioned above, the material made of metal plate or foil/heat-resistant resin film obtained by the present invention can be used not only as a flexible printed wiring board but also in conventional applications.
It expands new fields of application and provides excellent balanced performance in heat resistance, electrical insulation, flexibility, film strength, non-directionality, dimensional stability, adhesion, etc. There is very little deterioration in electrical insulation properties, dielectric properties, and adhesive strength when using electricity, and ultra-thin films of about 1 to 10μ can be made, and they can be made industrially at low cost. It is an extremely useful material for practical purposes.

Claims (1)

[Claims] 1. A heat-resistant resin having a heterocycle with a molecular weight of 5,000 or more and a main chain in which the ratio of unsaturated carbon atoms to carbon atoms is 40% or less and a Mooney viscosity of 150
A method for manufacturing a resin-coated metal clad plate, which comprises applying the following organic solvent solution containing a resin having high elasticity to one or both sides of a metal plate or foil and drying it to form a resin film on the metal surface. 2. A resin-coated metal clad plate according to claim 1, in which an acrylonitrile-butadiene copolymer having an acrylonitrile content of 25% by weight or more or a copolymer having no double bond in the main chain is used as the resin having high elasticity. manufacturing method. 3 0.1 to 40 parts by weight of a heat-resistant resin having a heterocycle with a molecular weight of 5000 or more and a resin having high elasticity
3. A method for manufacturing a resin-coated metal clad plate according to claim 1 or 2, characterized in that a resin consisting of parts by weight is used.