JP2743185B2 - Circuit board and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a method for manufacturing a metal foil without interposing an adhesive layer.
The present invention relates to a circuit board formed with a thin film of a polyimide resin composition and having excellent productivity and economy, and a method for manufacturing the same.

(Prior Art) A flexible circuit board is composed of a metal foil and a thin insulating layer formed thereon. As the insulating layer, a film of polyimide, polyester, or the like, an epoxy resin-impregnated glass cloth, or the like is used. Epoxy resin impregnated glass cloth has the drawback of poor flexibility and low dielectric properties, and polyester film has the problem of poor heat resistance. Although the polyimide film itself has excellent heat resistance, low dielectric properties, and chemical resistance, it has a disadvantage in that the adhesive properties of the polyimide film to the metal foil are inferior.

Conventionally, the formation of a polyimide film on a metal foil in the manufacture of circuit boards, a polyimide film bonded to the metal foil via an adhesive, a polyamic acid resin of a polyimide precursor applied on the metal foil, 300 ℃ or more And imidization by heat treatment at a high temperature, and heat-bonding a polyimide film on a metal foil at a high temperature of at least 300 ° C. or higher.

However, the circuit board has a disadvantage that the heat resistance of the adhesive is low and the characteristics of the heat resistance of polyimide cannot be sufficiently exhibited. Further, there is a disadvantage that the process becomes complicated with the use of the adhesive. Both of the circuit boards require heat treatment at a high temperature, and thus have the disadvantages of poor productivity and economic efficiency. Further, the circuit board has a disadvantage that the adhesive strength between the formed polyimide film and the metal foil is insufficient depending on the composition of the polyimide precursor, which causes a peeling phenomenon at the time of forming a circuit pattern and causes a defect.

(Problems to be Solved by the Invention) The present invention has been made in order to solve the above-mentioned disadvantages, and has excellent heat resistance, adhesiveness, and high productivity and economy without using an adhesive. An object of the present invention is to provide a circuit board and a method of manufacturing the same.

[Constitution of the Invention] (Means for solving the problem) As a result of intensive studies to achieve the above object, the present inventors have found that a specific polyimide-based material can be directly formed on a metal foil without using an adhesive. It has been found that by forming a thin film of the resin composition, a circuit board having excellent heat resistance and adhesiveness, high productivity and high economic efficiency can be obtained, and the present invention has been completed.

That is, the circuit board of the present invention includes a metal foil and a thin film of a polyimide-based resin composition formed by applying a polyimide-based resin composition solution to the surface of the metal foil. (A) (a) an aromatic tetracarboxylic acid containing 95 mol% or more of 3,3 ', 4,4'-benzophenonetetracarboxylic acid; and (b) a general formula (1) or (2) (Where X is CH ₂ , SO ₂ , C (CH ₃ ) ₂ , C (CF ₃ ) ₂ , O or S
R ⁵ is a benzene nucleus or a cyclohexane nucleus, and R ¹ and R ² are C
The _{H 3, C 2 H 5,} OCH 3 or OC ₂ H _5, and R ^3, R ⁴ is C ₂ H _5, each represent, and R ¹ to R ⁴ is substituted at the ortho position of the amino group either The present invention relates to a method for producing a circuit board according to the present invention, comprising: a polyimide resin obtained by reacting a diamine containing at least 90 mol% of an aromatic diamine represented by After directly applying the polyimide-based resin composition solution to the surface, dried in a tack-free state to obtain a coated metal foil, the coated metal foil is heated in an inert gas to apply a polyimide-based resin to the metal foil surface. It is characterized by forming a composition thin film.

The (A) aromatic tetracarboxylic acid, which is a component of the polyimide resin (A) used in the present invention, has 95% by mole or more thereof.
It is 3,3 ', 4,4'-benzophenonetetracarboxylic acid, and the 3,3', 4,4'-benzophenonetetracarboxylic acid referred to in the present invention includes its anhydride or its alkyl ester. Further, (a) the aromatic tetracarboxylic acid may contain less than 5 mol% of another aromatic tetracarboxylic acid other than 3,3 ', 4,4'-benzophenonetetracarboxylic acid.

90 mol% or more of the aromatic diamine (b) used in the present invention is a diamine represented by the following general formula (1) or (2).

(Where X is CH ₂ , SO ₂ , C (CH ₃ ) ₂ , C (CF ₃ ) ₂ , O or S
R ⁵ is a benzene nucleus or a cyclohexane nucleus, and R ¹ and R ² are C
The _{H 3, C 2 H 5,} OCH 3 or OC ₂ H _5, and R ^3, R ⁴ is C ₂ H _5, each represent, and R ¹ to R ⁴ is substituted at the ortho position of the amino group either (B) Specific compounds of the aromatic diamine include 3,3
3'-dimethyl-5,5'-diethyl-4,4'-diaminodiphenylmethane, 3,3 ', 5,5'-tetraethyl-4,4'-
Diaminodiphenylmethane, 3,3'-dimethyl-4,4'-
Diaminodicyclohexylmethane, 3,3'-dimethoxy-4,4'-diaminodiphenylmethane, 3,3'-diethoxy-4,4'-diaminodiphenylmethane, 3,3'-diethyl-4,4'-diaminodiphenylether, 3 , 3'-Dimethoxy-4,4'-diaminodiphenyl ether, 3,3'-
Dimethyl-4,4'-diaminodiphenylsulfone, 3,3 '
-Diethyl-4,4'-diaminodiphenylsulfone, 3,
3'-dimethoxy-4,4'-diaminodiphenylsulfone, 3,3'-diethoxy-4,4'-diaminodiphenylsulfone, 3,3'-dimethyl-4,4'-diaminodiphenylpropane, 3,3 '-Diethyl-4,4'-diaminodiphenylpropane,3,3'-dimethoxy-4,4'-diaminodiphenylpropane,3,3'-diethoxy-4,4'-diaminodiphenylpropane,3,3'-dimethyl −4,4′-diaminodiphenyl sulfide, 3,3′-diethyl-4,4′-
Diaminodiphenyl sulfide, 3,3'-dimethoxy-4,4'-diaminodiphenyl sulfide, 3,3'-diethoxy-4,4'-diaminodiphenyl sulfide,
4,4'-dimethyl-5,5'-diaminodiphenylhexafluoropropane and the like, and these can be used alone or in combination of two or more. In addition to these aromatic diamines, diamines of less than 10 mol% can be blended.

The reaction between (a) the aromatic tetracarboxylic acid and (b) the aromatic diamine is carried out by adding approximately equimolar addition reaction in an organic solvent at a temperature of 30 ° C or less, preferably 0 ° C or less for 3 to 12 hours. The dehydration cyclization gives a polyimide resin having the following structural formulas (3) and (4).

(Where X is CH ₂ , SO ₂ , C (CH ₃ ) ₂ , C (CF ₃ ) ₂ , O or S
R ⁵ is a benzene nucleus or a cyclohexane nucleus, and R ¹ and R ² are C
The _{H 3, C 2 H 5,} OCH 3 or OC ₂ H _5, and R ^3, R ⁴ is C ₂ H _5, each represent, and R ¹ to R ⁴ is substituted at the ortho position of the amino group either The organic solvent used in this addition polymerization reaction includes
For example, N, N'-dimethylsulfoxide, N, N'-dimethylformamide, N, N'-diethylformamide, N, N
N'-dimethylacetamide, N, N'-diethylacetamide, N-methyl-2-pyrrolidone, hexamethylenephosphamide, etc., can be used alone or in combination of two or more.

As the epoxy resin (B) used in the present invention, for example, 2,2-bis (p-hydroxyphenyl) propane,
2,2-bis (4-hydroxy-3,5-dibromophenyl)
Glycidyl ethers of aromatic polyhydric phenols such as propane, 1,1,2,2-tetrakis (p-hydroxyphenyl) ethane, 4,4'-dihydroxydiphenyl, resorcin, catechol, hydroquinone; phenol novolak, cresol novolak, etc. Glycidyl ether; vinylcyclohexene diepoxide, (3 ', 4'-epoxycyclohexylmethyl) -3,4-epoxycyclohexanecarboxylate, (3', 4'-epoxy-6'-
Methylcyclohexylmethyl) -3,4-epoxy-6
Methylcyclohexanecarboxylate, 3- (3 ',
4'-epoxycyclohexyl) -2,4-dioxaspiro (5,5) -8,9-epoxyundecane, 3- (glycidyloxyethoxyethyl) -2,4-dioxaspiro (5,5)
Alicyclic epoxy resins such as -8,9-epoxyundecane;
Heterocyclic epoxy resins such as triglycidyl isocyanurate and N, N-diglycidyl acid derivative of 5,5-dimethylhydantoin are listed, and these can be used alone or as a mixture of two or more. The polyimide resin composition can be easily obtained by mixing the (A) polyimide resin and the (B) epoxy resin.

The polyimide resin composition used in the present invention may contain at least one additive selected from the group consisting of a curing agent, a curing accelerator, and a filler.

Examples of the curing agent include phthalic anhydride, methylnadic anhydride, 4-methylhexahydrophthalic anhydride, trimellitic anhydride, acid anhydride-based curing agents such as pyromellitic anhydride, hexamethylenediamine, diethylenetriamine,
Tetraethylenepentamine, m-phenylenediamine,
Examples include amine-based curing agents such as diaminophenyl ether and diaminodiphenylmethane, polyamide-based curing agents, imidazole-based curing agents such as 2-ethyl-4-methylimidazole and 2-methylimidazole, and dicyandiamide. Examples of the curing accelerator include a tertiary amine such as benzyldimethylamine, a borate ester, and an organic metal salt. Examples of other additives include diluents, spreaders, softeners and the like. As the solvent, it is necessary to dissolve both the polyimide resin and the epoxy resin, and examples thereof include amide solvents such as N, N-dimethylacetamide and N, N-dimethylformamide, and cyclohexanone and tetrahydrofuran. The mixing ratio of the polyimide resin and the epoxy resin is preferably in the range of 50:50 to 95: 5. Further, the amounts of the curing agent and the curing accelerator may be amounts used as standard with respect to the amount of the epoxy resin.

When coating a metal foil with a solution containing an epoxy resin in a polyimide resin, a solution containing the epoxy resin in the polyimide resin in an amount of 5 to 40% by weight, particularly preferably 10 to 30% by weight, and an intrinsic viscosity (Intrinsic vi
It is preferable to use a solution having a scosity of 0.5 to 6 dl / g, particularly 1 to 4 dl / g, from the viewpoint of the physical properties of the produced polyimide-based thin film and the economy in the coating and drying steps.

As a metal foil to be coated with a resin composition solution containing an epoxy resin in a polyimide, a copper foil or an aluminum foil is generally used, but a conductive metal foil such as a nickel foil can also be used.

The operation of coating a metal foil with a solution in which an epoxy resin is contained in a polyimide resin is preferably performed by cast coating. Specifically, the following method is used. A film of uniform thickness (the thickness is generally adjusted to 30-300 μm) by discharging a solution containing polyimide resin and epoxy resin on the surface of the metal foil from the slit for film formation. Form a layer. As other coating means, other known means such as a roll coater, a knife coater, a comma coater, a doctor blade, and a flow coater can be used.

The resin composition solution coating layer obtained by adding the epoxy resin to the polyimide resin prepared as described above is then heated to remove the solvent. Generally, heating to the required temperature of 100-250 ° C. In these desolvation steps, if the metal foil surface is exposed to a temperature higher than the temperature at which it is oxidized, oxidation of the metal foil surface occurs and the mechanical properties, electrical properties, and adhesion of the metal foil may be easily reduced. Therefore, it is particularly preferable to perform the treatment in an inert gas at a temperature higher than the temperature at which the metal foil surface is oxidized in order to prevent the oxidation of the metal foil surface.

These heating and drying are generally performed in a state where the applied metal foil is spread, but in the case of the present invention, after a solution in which an epoxy resin is contained in a polyimide resin is directly coated on the metal foil, substantially After drying to a tack-free state, the film may be wound into a roll, and the wound material may be heated to completely remove the solvent.

In this manner, a circuit board can be manufactured by forming a thin film of the polyimide-based resin composition directly on the metal foil without using an adhesive layer.

(Operation) The circuit board of the present invention has a thin film of a resin composition containing a polyimide resin and an epoxy resin formed directly on the surface of a metal foil, thereby eliminating defects caused by using an adhesive, thereby improving productivity and economy. It is the one with improved performance.

(Examples) Hereinafter, the present invention will be described specifically with reference to examples, but the present invention is not limited to these examples.

Example 1 After replacing the inside of a three-necked flask with dry nitrogen through the flask, 310 g of 3,3'5,5'-tetraethyl-4,4'-diaminodiphenylmethane was added, and N-methyl-2-pyrrolidone (NMP) was added thereto. 2530 ml was added and dissolved. After dissolution, 0 ° C
Then, 322 g of 3,3 ', 4,4'-benzophenonetetracarboxylic anhydride (BTDA) was added while cooling and stirring. The precursor was reacted by continuing stirring for 6 hours while suppressing the heat generated by the reaction in ice water. Next, 408 ml of acetic anhydride and 40 ml of pyridine, which are dehydrating agents, were added to the reaction solution, and a ring closure reaction was performed for 3 hours while distilling acetic acid at 100 ° C. Thereafter, acetic anhydride / pyridine was distilled off under reduced pressure to imidize.

After the reaction, the reaction solution was poured into a mixed solution of methanol and water to precipitate a polyimide resin. The precipitate was dried to obtain 590 g of a yellow polyimide resin powder (intrinsic viscosity 2.5).
150 g of the obtained polyimide resin powder, 45 g of epoxy resin (Epicoat 828, manufactured by Yuka Shell Epoxy), and 2-
Dissolve 0.2 g of ethyl imidazole in 850 ml of cyclohexanone and use a doctor blade to roll a rolled copper foil (thickness of 35μ).
m) was evenly coated. The coated copper foil was dried by heating at 130 ° C. for 60 minutes, and then heated in a nitrogen atmosphere at 250 ° C. for 60 minutes to obtain a circuit board coated with a 25 μm-thick polyimide-based resin composition thin film. In this case, the surface of the copper foil to be coated may be oxidized or primed.

FIG. 1 shows a cross-sectional view of a circuit board according to the present invention.
A resin composition thin film 2 having a thickness of 25 μm is formed on one surface of a metal foil (copper foil) 1.

Example 2 After replacing the inside of a three-necked flask with dry nitrogen through the flask, 362 g of 4,4'-dimethyl-5,5'-diaminodiphenylhexafluoropropane was added, and N-methyl-
3420 ml of 2-pyrrolidone (NMP) was added and dissolved. After dissolution, the mixture was cooled to 0 ° C and 322 g of 3,3 ', 4,4'-benzophenonetetracarboxylic anhydride (BTDA) was added with stirring.
The precursor was reacted by continuing stirring for 6 hours while suppressing the heat generated by the reaction in ice water. Next, 408 ml of acetic anhydride and 40 ml of pyridine as dehydrating agents were added to the reaction solution, and a ring-closing reaction was performed for 3 hours while distilling acetic acid at 100 ° C. Thereafter, acetic anhydride / pyridine was distilled off under reduced pressure to imidize.

After the reaction, the reaction solution was poured into a mixed solution of methanol and water to precipitate a polyimide resin. The precipitate was dried to obtain 640 g of a yellow polyimide resin powder (intrinsic viscosity 3.44).
150 g of the obtained polyimide resin powder, 45 g of epoxy resin (Epicoat 828, manufactured by Yuka Shell Epoxy), and 2-
Ethyl imidazole (0.2 g) was dissolved in cyclohexanone (850 ml), and uniformly coated on a rolled copper foil (thickness: 35 μm) using a doctor blade. The coated copper foil was dried by heating at 130 ° C. for 60 minutes, and then heated in a nitrogen atmosphere at 250 ° C. for 60 minutes to obtain a circuit board coated with a 25 μm-thick polyimide resin composition thin film.

Example 3 After replacing the inside of the flask with dry nitrogen through a three-necked flask, 282 g of 3,3'-dimethyl-5,5'-diethyl-4,4'-diaminodiphenylmethane was added, and N-methyl-2-pyrrolidone was added thereto. (NMP) 2420 ml was added and dissolved. After dissolution, the mixture was cooled to 0 ° C and 322 g of 3,3 ', 4,4'-benzophenonetetracarboxylic anhydride (BTDA) was added with stirring.
The precursor was reacted by continuing stirring for 6 hours while suppressing the heat generated by the reaction in ice water. Next, 408 ml of acetic anhydride and 40 ml of pyridine, which are dehydrating agents, were added to the reaction solution, and an imide ring closure reaction was performed for 3 hours while distilling acetic acid at 100 ° C.

After the reaction, the reaction solution was poured into a mixed solution of methanol and water to precipitate a polyimide resin. The precipitate was dried to obtain 564 g of a yellow polyimide resin powder (intrinsic viscosity 2.33).
150 g of the obtained polyimide resin powder, 45 g of epoxy resin (Epicoat 828, manufactured by Yuka Shell Epoxy), and 2-
Ethyl imidazole (0.2 g) was dissolved in cyclohexane (850 ml) and uniformly coated on a rolled copper foil (thickness: 35 μm) using a doctor blade. This coated copper foil
After heating and drying at 130 ° C. for 60 minutes, the substrate was heated in a nitrogen atmosphere at 250 ° C. for 60 minutes to obtain a circuit board coated with a 25 μm-thick polyimide-based resin composition thin film.

Comparative Example 1 A commercially available polyimide film having a thickness of 25 μm and the rolled copper foil used in the examples were pressed with an acrylic rubber adhesive at room temperature under a pressure of 0.7 kg / cm ^{2 to} form a circuit board. Obtained.

The adhesive strength between the copper foil and the polyimide-based resin composition thin film or the polyimide film in the circuit boards obtained in these Examples and Comparative Examples was measured in accordance with ASTM-D-1875, and the solder resistance was measured in accordance with JIS-C. Since I went according to −6481,
Table 1 shows the results.

[Effects of the Invention] As is clear from the above description and Table 1, the circuit board of the present invention and the method of the present invention can be used in a specific polyimide resin-based resin directly without interposing an adhesive in a metal foil. Since a thin film of the composition is formed, the composition is excellent in heat resistance and adhesiveness, and has high productivity and economy. Therefore, it is suitable for printed wiring boards, hybrid boards, LSI mounting boards, and the like.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of a circuit board according to the present invention. 1 .... metal foil, 2 .... resin composition thin film.

Claims (2)

(57) [Claims] A metal foil and a thin film of a polyimide resin composition formed by applying a polyimide resin composition solution to the surface of the metal foil, wherein the resin composition comprises: (A) ( a) an aromatic tetracarboxylic acid containing at least 95 mol% of 3,3 ', 4,4'-benzophenonetetracarboxylic acid; and (b) a general formula (1) or (2) (Where X is CH ₂ , SO ₂ , C (CH ₃ ) ₂ , C (CF ₃ ) ₂ , O or S
R ⁵ is a benzene nucleus or a cyclohexane nucleus, and R ¹ and R ² are C
The _{H 3, C 2 H 5,} OCH 3 or OC ₂ H _5, and R ^3, R ⁴ is C ₂ H _5, each represent, and R ¹ to R ⁴ is substituted at the ortho position of the amino group either A circuit board comprising: a polyimide resin obtained by reacting a diamine containing at least 90 mol% of an aromatic diamine represented by the formula: 2. The method according to claim 2, wherein (A) (a) 3,3 ', 4,4'
An aromatic tetracarboxylic acid containing 95 mol% or more of benzophenone tetracarboxylic acid, and (b) a general formula (1) or (2) (Where X is CH ₂ , SO ₂ , C (CH ₃ ) ₂ , C (CF ₃ ) ₂ , O or S
R ⁵ is a benzene nucleus or a cyclohexane nucleus, and R ¹ and R ² are C
The _{H 3, C 2 H 5,} OCH 3 or OC ₂ H _5, and R ^3, R ⁴ is C ₂ H _5, each represent, and R ¹ to R ⁴ is substituted at the ortho position of the amino group either A) A resin composition solution containing a polyimide resin and an epoxy resin (B) obtained by reacting with a diamine containing at least 90 mol% of an aromatic diamine represented by the formula (1) is directly applied, then dried in a tack-free state and applied. Get the metal foil,
A method for manufacturing a circuit board, comprising heating the coated metal foil in an inert gas to form a polyimide resin thin film on the surface of the metal foil.