KR20230157271A - Polyimide film - Google Patents

Abstract

[Problem] To provide a polyimide film with excellent dimensional stability and very suitable for fine pitch circuit boards, especially COF (Chip On Film) wired at a narrow pitch in the film width direction, and a copper clad laminate based on the same. .
[Solution] A polyimide film obtained using an aromatic diamine component including para-phenylene diamine and an acid anhydride component, using TMA-50 manufactured by Shimadzu Works. Measurement temperature range: 50 to 200°C, temperature rise rate: 10°C. The thermal expansion coefficient α _MD in the machine conveyance direction (MD) of the film measured under the conditions of ／min is in the range of 2.0 ppm/℃ or more and less than 10.0 ppm/℃, and the thermal expansion coefficient α _MD in the width direction (TD) is -2.0 ppm. A polyimide film that is in the range of /℃ or higher and 3.5 ppm/℃ or lower and satisfies the relationship of |α _MD |≥|α _TD |×2.0.

Description

Polyimide film {POLYIMIDE FILM}

The present invention relates to a polyimide film that is excellent in dimensional stability and is suitable for fine pitch circuit substrates, especially COF (Chip on Film) wired at a narrow pitch in the film width direction, and a copper clad laminate using the same as a base material. .

As flexible printed circuit boards and semiconductor packages become more detailed, the requirements for polyimide films used in them are increasing, for example, reducing dimensional changes and curls due to contact with metal, and handling. In addition, the physical properties of the polyimide film include a coefficient of thermal expansion comparable to that of metal and a high modulus of elasticity. Furthermore, a film with small dimensional change due to water absorption is required, and a polyimide film is required accordingly. This has been developed.

For example, examples of polyimide films using para-phenylene diamine to increase the elastic modulus are known (Patent Documents 1, 2, and 3). In addition, examples of polyimide films using biphenyl tetracarboxylic dianhydride in addition to para-phenylene diamine are known to reduce dimensional changes due to absorption while maintaining high elasticity (Patent Documents 4 and 5).

Furthermore, in order to suppress dimensional changes during the bonding process with metal, the thermal expansion coefficient in the film's machine conveyance direction (hereinafter referred to as MD) is set to be smaller than the thermal expansion coefficient in the film's width direction (hereinafter referred to as TD) to reduce anisotropy. Examples of polyimide films with polyimide films are known. In general, in the FPC process, a lamination method is adopted in which metal bonding is performed by heating roll-to-roll, and in this process, tension is applied to the MD of the film and elongation occurs, while shrinkage occurs in the TD. The purpose is to offset (patent document 6).

However, recently, in response to the trend toward finer wiring, a two-layer type (copper layer formed directly on a polyimide film) that does not use an adhesive is being adopted as a copper-bonded laminate. There are a method of forming a copper layer by plating on a film, and a method of casting polyamic acid on copper foil and then imidizing it, but since neither of them is a heat compression process like the lamination method, the MD of the film There is no need to make the thermal expansion coefficient smaller than TD, and furthermore, for COF applications, which are the mainstay of the two-layer type, a pattern of wiring with a narrow pitch in the TD of the film is common. Conversely, if the thermal expansion coefficient of TD is large, the chip mounting becomes more stable. The dimensional change between wires increased during bonding, etc., making it difficult to meet the demand for fine pitch. To cope with this, it is ideal to make the thermal expansion coefficient of the film small enough to approximate that of silicon, but since there is a difference in thermal expansion with copper, there is a problem that deformation occurs during the heating process starting from the bonding of chip mounting.

Japanese Patent Publication No. 60-210629 Japanese Patent Publication No. 64-16832 Japanese Patent Publication No. 1-131241 Japanese Patent Publication No. 59-164328 Japanese Patent Publication No. 61-111359 Japanese Patent Publication No. 4-25434

doesn't exist

The present invention was made as a result of examining the problem of solving the problems in the prior art described above, and provides a polyimide film suitable for fine pitch circuit substrates such as COF that can reduce dimensional changes in the film TD, and its base material. The purpose is to provide a copper-clad laminate.

The present invention relates to the following invention.

[1] A polyimide film obtained using an aromatic diamine component including para-phenylene diamine and an acid anhydride component, using TMA-50 manufactured by Shimadzu Corporation, measurement temperature range: 50 to 200°C, temperature rise rate : The thermal expansion coefficient α _MD in the machine conveyance direction (MD) of the film measured under the conditions of 10°C/min is in the range of 2.0 ppm/°C or more and less than 10.0 ppm/°C, and the thermal expansion coefficient α _TD in the width direction (TD) is in the range. A polyimide film characterized in that it satisfies the relationship of |α _MD |≥|α _TD |

[2] The polyimide film described in [1] above, wherein α _MD is in the range of 3.0 ppm/°C or more and 9.5 ppm/°C or less.

[3] The polyimide film according to [1] or [2] above, wherein α _TD is in the range of -1.5 ppm/°C or more and 3.0 ppm/°C or less.

[4] The polyimide film according to any one of [1] to [3] above, wherein the MD and TD of the film have heat shrinkage rates at 200°C of both 0.05% or less.

[5] The polyimide film according to any one of [1] to [4] above, wherein the MD and TD of the film have heat shrinkage rates at 200°C of both 0.03% or less.

[6] The polyimide film according to any one of [1] to [5] above, wherein the film has a tensile modulus of elasticity of 6.0 GPa or more.

[7] The polyimide film according to any one of [1] to [6] above, wherein the film has a water absorption of 3.0% or less.

[8] The polyimide film according to any one of items [1] to [7] above, wherein para-phenylene diamine is at least 31 mol% or more in the total aromatic diamine component.

[9] Furthermore, the above [1]~, characterized in that it contains at least one selected from the group consisting of 4,4'-diamino diphenyl ether and 3,4'-diamino diphenyl ether as an aromatic diamine component. The polyimide film according to any one of [8].

[10] The above [1] to [9], wherein the acid anhydride component is at least one selected from the group consisting of pyromellitic dianhydride and 3,3'-4,4'-diphenyl tetracarboxylic dianhydride. The polyimide film according to any one of the above.

[11] A copper-clad laminate characterized by using the polyimide film described in any one of [1] to [10] above.

[12] A film is produced using an aromatic diamine component including para-phenylene diamine and an acid anhydride component, and the resulting gel film is stretched in the machine conveyance direction at a draw ratio (MDX) of 1.05 to 1.6 times, and stretched in the machine conveyance direction. A method for producing a polyimide film according to any one of items [1] to [10] above, comprising the step of stretching in the width direction at a draw ratio (TDX) of 1.1 to 1.5 times the draw ratio. .

[13] A COF substrate characterized by using the polyimide film described in any one of [1] to [10] above.

The polyimide film of the present invention can effectively suppress the occurrence of dimensional changes in the COF manufacturing process. In addition, the polyimide film of the present invention can be suppressed to a low coefficient of thermal expansion in this direction by advancing the orientation of the film in TD, and further has a low heat shrinkage rate, high elasticity, and high strength.

The polyimide film of the present invention is a polyimide film obtained using an aromatic diamine component containing para-phenylene diamine and an acid anhydride component, using TMA-50 manufactured by Shimadzu Corporation, measurement temperature range: 50 to 200°C, temperature rise Speed: The thermal expansion coefficient α _MD in the machine conveyance direction (MD) of the film measured under the condition of 10°C/min is in the range of 2.0 ppm/°C or more and less than 10.0 ppm/°C, and the thermal expansion coefficient α _TD in the width direction (TD) It is in the range of -2.0 ppm/℃ or more and 3.5 ppm/℃ or less, and is characterized by satisfying the relationship of |α _MD |≥|α _TD |×2.0.

The thermal expansion coefficient α _MD of the polyimide film of the present invention in the machine conveyance direction (MD) is usually in the range of 2.0 ppm/°C to 10.0 ppm/°C, and is more preferably in the range of 3.0 ppm/°C to 9.5 ppm/°C. A range of 3.5 ppm/°C or more and 9.0 ppm/°C or less is more preferable, and a range of 4.0 ppm/°C or more and 8.5 ppm/°C or less is particularly preferable.

The thermal expansion coefficient α _TD in the width direction (TD) of the polyimide film of the present invention is usually in the range of -2.0 ppm/℃ or more and 3.5 ppm/℃ or less, and is particularly suitable for COF, so it is -1.5 ppm/℃ or more. A range of 3.0 ppm/°C or less is more preferable, a range of -1.0 ppm/°C or more and 2.5 ppm/°C or less is even more preferable, and a range of -0.5 ppm/°C or more and 2.0 ppm/°C or less is particularly preferable. If it falls below the above range, the strength (e.g., tensile elongation, etc.) is poor and the obtained film becomes prone to cracking, so it is not preferable. By setting α _TD within the above range and combining it with each component of the present invention, the polyimide film for COF can be used regardless of the partner to which it is bonded (for example, the partner to which the film is bonded is metal (for example, copper)). Since it has excellent dimensional stability (even if it is glass), the influence of dimensional changes on the film side can be suppressed to a small extent, making it possible to design a highly delicate COF circuit board.

The measurement conditions for the thermal expansion coefficients _αMD and _αTD in the present invention are values measured using TMA-50 manufactured by Shimadzu Corporation under the conditions of a measurement temperature range of 50 to 200°C and a temperature rise rate of 10°C/min. am.

The polyimide film _{of the} present invention generally _satisfies the relationship of |α _{MD |} ≥|α _TD | The relationship of 2.5 is satisfied, more preferably, the relationship of |α _MD |≥|α _TD |×2.8 is satisfied, and even more preferably the relationship of |α _MD |≥|α _TD |×3.0 or more is satisfied. Also, although not particularly limited, it is preferable to satisfy the relationship of |α _MD |≤|α _TD |×50.0, and more preferably satisfy the relationship of |α _MD |≤|α _TD | It is further preferable to satisfy the relationship _MD ｜≤｜α _TD ｜×20.0. Since α _MD and α _TD are within the above range and satisfy the relationship of the above equation, conventionally, when the thermal expansion coefficients of the polyimide film and the metal (e.g., copper) to which it is bonded are different, the difference in thermal expansion coefficients results from It has been thought that the problem of thermal stress is large and that dimensional change is a problem when bonding to a metal, but when bonding a polyimide film to a metal (e.g., copper), linear expansion of the metal (e.g., copper) Although the coefficient is different from the linear expansion coefficient of 17 ppm/°C, dimensional stability is not a problem.

The 200°C heat shrinkage rate of the polyimide film of the present invention is preferably 0.05% or less for both MD and TD, and more preferably 0.03% or less for both.

The tensile elastic modulus of the polyimide film of the present invention is preferably 6.0 GPa or more, more preferably 6.5 GPa or more, and even more preferably 6.8 GPa or more. Additionally, it is preferable that both MD and TD are 6.0 GPa or more, both MD and TD are more preferably 6.5 GPa or more, and both MD and TD are still more preferably 6.8 GPa or more.

The water absorption of the polyimide film of the present invention is preferably 3.0% or less, and more preferably 2.8% or less.

The polyimide film of the present invention is not particularly limited, but since the running properties of a film with a TD orientation are good, the tear propagation resistance is preferably 3.0 N/mm or more in both MD and TD, and more preferably 5.0 N/mm or more. do. The tear propagation resistance is a value measured using a light load tear tester similar to the Elmendorf tear method. Since the above measurement value represents the resistance when the film is torn, it indicates that it is difficult to tear considering the entire thickness direction, meaning that the larger the film, the more difficult it is to tear, and the running performance is excellent.

The dimensional change rate of the polyimide film of the present invention is preferably less than 0.01%, and more preferably 0.008% or less.

In producing the polyimide film of the present invention, first, the aromatic diamine component and the acid anhydride component are polymerized in an organic solvent to obtain a polyamic acid solution.

The polyimide film of the present invention contains para-phenylene diamine as the aromatic diamine component. The aromatic diamine component may include substances other than para-phenylene diamine. Specific examples of the aromatic diamine components other than para-phenylene diamine include metaphenylene diamine, benthidine, p-xylenediamine, and 4,4'-. Diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl methane, 4,4'-diaminodiphenyl sulfone, 3,3'-dimethyl -4,4' -diaminodiphenyl methane, 1,5-diamino naphthalene, 3,3'-dimethoxy benzene, 1,4-bis(3 methyl-5 amino phenyl)benzene, and amide-forming derivatives thereof. . These may be used individually, or two or more types may be mixed and used. As the aromatic diamine component, a combination of para-phenylene diamine and 4,4'-diaminodiphenyl ether and/or 3,4'-diaminodiphenyl ether is preferable. Among these, by adjusting the amount of diamine components such as para-phenylene diamine and 3,4'-diaminodiphenyl ether, which are effective in increasing the tensile elastic modulus of the film, the tensile elastic modulus of the resulting polyimide film is set to 6.0 GPa or more. , which is preferable because transportability also improves.

Specific examples of the acid anhydride component include pyromellitic acid, 3,3',4,4'-biphenyl tetracarboxylic acid, 2,3',3,4'-biphenyl tetracarboxylic acid, 3,3', 4,4'-benzophenone tetracarboxylic acid, 2,3,6,7-naphthalene tetracarboxylic acid, 2,2-bis(3,4-dicarboxyphenyl)ether, pyridine-2,3,5,6- Aromatic tetracarboxylic acid anhydride components, such as tetracarboxylic acid and amide-forming derivatives thereof, are included, and pyromellitic dianhydride and 3,3',4,4'-biphenyl tetracarboxylic dianhydride are preferred. These may be used individually, or two or more types may be mixed and used.

Among these, a particularly suitable aromatic diamine component and an acid anhydride component can be combined to form one selected from the group consisting of para-phenylene diamine, 4,4'-diaminodiphenyl ether, and 3,4'-diaminodiphenyl ether. A combination of one or more aromatic diamine components and one or more acid anhydride components selected from the group consisting of pyromellitic dianhydride and 3,3',4,4'-biphenyl tetracarboxylic dianhydride can be mentioned.

The mixing ratio (molar ratio) of para-phenylene diamine in the aromatic diamine component is such that it obtains a thermal expansion coefficient in the above range, provides appropriate strength to the film, and prevents poor running performance, so that among the wholly aromatic diamine components, It is usually at least 31 mol% or more, preferably 33 mol% or more, and more preferably 35 mol% or more.

The mixing ratio (molar ratio) of the acid anhydride component is not particularly limited as long as it does not interfere with the effect of the present invention, but for example, 3,3',4,4'-biphenyltetracarboxylic dianhydride When included, the content of 3,3',4,4'-biphenyl tetracarboxylic dianhydride is preferably 15 mol% or more, more preferably 20 mol% or more, and even more preferably 25 mol% or more.

When the polyimide film, which is the base material, is manufactured from polyamic acid consisting of such an aromatic diamine component and an acid anhydride component, the thermal expansion coefficient of the polyimide film is within the above range in both the machine conveyance direction (MD) and the width direction (TD) of the film. This is desirable because it can be easily adjusted.

In addition, in the present invention, specific examples of the organic solvent used to form the polyamic acid solution include sulfoxide-based solvents such as dimethyl sulfoxide and diethyl sulfoxide, N,N-dimethyl formamide, and N,N-diethyl. Formamide-based solvents such as formamide, acetamide-based solvents such as N,N-dimethyl acetamide, N,N-diethyl acetamide, N-methyl-2-pyrrolidone, N-vinyl-2-pyrroli Pyrrolidone-based solvents such as pork, phenol, o-, m-, or p-cresol, xylenol, halogenated phenol, catechol, etc., or phenol-based solvents such as hexamethyl phosphoramide and γ-butyrolactone. Tonic polar solvents can be used, and it is preferable to use them alone or in a mixture of two or more, but aromatic hydrocarbons such as xylene and toluene can also be used.

The polymerization method may be any known method, for example

(1) First, the entire amount of the aromatic diamine component is placed in a solvent, and then the acid anhydride component is added in an equivalent amount (equal molar) to the entire amount of the aromatic diamine component for polymerization.

(2) First, the entire amount of the acid anhydride component is placed in a solvent, and then the aromatic diamine component is added to an equivalent amount of the acid anhydride component for polymerization.

(3) After placing one aromatic diamine component (a1) in a solvent and mixing for the time necessary for reaction at a ratio such that one acid anhydride component (b1) is 95 to 105 mol% with respect to the reaction components, one aromatic diamine component (a1) is added to the solvent. A method of polymerizing by adding a diamine component (a2) and then adding the other acid anhydride component (b2) so that the total aromatic diamine component and the total acid anhydride component are approximately equivalent.

(4) After placing one acid anhydride component (b1) in a solvent, mixing for the time necessary for the reaction at a ratio such that the aromatic diamine component (a1) on one side is 95 to 105 mol% relative to the reaction component, and then adding the other acid anhydride component (b1) to the solvent. A method of polymerizing by adding an acid anhydride component (b2) and then adding the other aromatic diamine component (a2) so that the total aromatic diamine component and the total acid anhydride component are approximately equivalent.

(5) The polyamic acid solution (A) is adjusted by reacting one aromatic diamine component and the acid anhydride component in a solvent so that either one is in excess, and the other aromatic diamine component and the acid anhydride component are reacted in a different solvent. The polyamic acid solution (B) is adjusted by reacting to excess. A method of mixing the polyamic acid solutions (A) and (B) obtained in this way to complete polymerization. At this time, when adjusting the polyamic acid solution (A), if the aromatic diamine component is excessive, in the polyamic acid solution (B), the acid anhydride component is excessive, and in the polyamic acid solution (A), if the acid anhydride component is excessive, In the polyamic acid solution (B), the aromatic diamine component is added in excess, the polyamic acid solutions (A) and (B) are mixed, and the total aromatic diamine component and the total acid anhydride component used in these reactions are adjusted so that they are approximately equivalent. do. In addition, the polymerization method is not limited to these, and other known methods may be used.

The polyamic acid solution obtained in this way usually contains 5 to 40% by weight of solid content, and preferably contains 10 to 30% by weight of solid content. Additionally, the viscosity is usually 10 to 2000 Pa·s as measured by a Brookfield clay meter, and is preferably 100 to 1000 Pa·s for stable liquid delivery. Additionally, the polyamic acid in the organic solvent solution may be partially imidized.

Next, the manufacturing method of the polyimide film is explained. Methods for forming a polyimide film include casting a polyamic acid solution into a film to obtain a polyimide film by thermally decyclizing and desolvating the polyamic acid solution, and mixing a polyamic acid solution with a cyclization catalyst and a dehydrating agent to chemically decyclize the polyamic acid solution. There is a method of producing a gel film and heating and desolvating it to obtain a polyimide film. The latter method is preferable because the thermal expansion coefficient of the resulting polyimide film can be suppressed low.

In the method of chemical decyclization, the polyamic acid solution described above is first prepared. Additionally, this polyamic acid solution may contain chemically inert organic or inorganic fillers such as titanium oxide, silica, calcium carbonate, calcium phosphate, calcium hydrogen phosphate, and polyimide filler, if necessary. The content of the filler is not particularly limited as long as it does not interfere with the effect of the present invention.

The polyamic acid solution used here may be a polyamic acid solution that has been polymerized in advance, or may be one that has been polymerized sequentially when containing filler particles.

The polyamic acid solution may contain a cyclization catalyst (imidization catalyst), a dehydrating agent, a gelation retardant, etc.

Specific examples of the cyclization catalyst used in the present invention include aliphatic tertiary amines such as trimethylamine and triethylene diamine, aromatic tertiary amines such as dimethyl aniline, and heterocyclic amines such as isoquinoline, pyridine, and beta picoline. Tertiary amines and the like can be mentioned, and heterocyclic tertiary amines are preferable. These may be used individually, or two or more types may be mixed and used.

Specific examples of the dehydrating agent used in the present invention include aliphatic carboxylic anhydrides such as acetic anhydride, propionic anhydride, and butyric acid, and aromatic carboxylic anhydrides such as benzoic anhydride, but acetic anhydride and/or benzoic anhydride are preferred. do. The gelation retardant is not particularly limited, and acetylacetone and the like can be used.

As a method of producing a polyimide film from a polyamic acid solution, a polyamic acid solution containing the above-mentioned cyclization catalyst and the above-described dehydrating agent is formed into a film by being flexible on a support from a clasp with a slit, An example of this is a method of partially deforming the film to form a self-supporting gel film, followed by peeling from the support, heat drying/imidization, and heat treatment.

The above support is a metal rotating drum or endless belt, the temperature of which is controlled by liquid or gas heat and/or radiant heat from an electric heater or the like.

The above gel film is heated to usually 30 to 200 ° C., preferably 40 to 150 ° C., by hydrothermal heat from the support and/or hydrothermal heat from a heat source such as hot air or an electric heater, to undergo a ring-closure reaction, and to release the gel film. By drying volatile components such as organic solvents, it becomes self-supporting and is peeled off from the support.

The gel film peeled from the support described above is not particularly limited, but is preferably stretched in the conveyance direction while regulating the running speed with a rotating roll. Stretching in the conveyance direction is performed at a temperature of 140°C or lower. The stretch ratio (MDX) is usually 1.05 to 1.9 times, preferably 1.1 to 1.6 times, and more preferably 1.1 to 1.5 times. The gel film stretched in the conveyance direction is introduced into a tenter device, has both ends in the width direction held by tenter clips, and is stretched in the width direction while traveling together with the tenter clip. Stretching in the width direction is performed at a temperature of 200°C or higher. The draw ratio (TDX) is usually 1.1 to 1.5 times MDX, and is preferably 1.2 to 1.45 times. By performing this stretching ratio combination on the gel film obtained by the above mixing, it is possible to orient the film TD and obtain a film having the effect of the present invention.

The film dried in the drying zone is heated for 15 seconds to 10 minutes with hot air, an infrared heater, etc. Next, heat treatment is performed from 15 seconds to 20 minutes at a temperature of 250 to 500°C using hot air and/or an electric heater.

In addition, the thickness of the polyimide film is adjusted by adjusting the running speed, and the thickness of the polyimide film is preferably 3 to 250 μm, more preferably 5 to 150 μm, to prevent deterioration of film forming properties.

It is preferable to additionally anneal the polyimide film obtained in this way. By doing so, thermal relaxation of the film occurs and the heat shrinkage rate can be suppressed. The temperature of the annealing treatment is not particularly limited, but is preferably 200°C or more and 500°C or less, more preferably 200°C or more and 370°C or less, and particularly preferably 210°C or more and 350°C or less. In the production method of the polyimide film of the present invention, since the orientation toward the film TD is strong, the heat shrinkage rate in this direction is likely to increase accordingly, but the heat shrinkage rate at 200°C can be suppressed within the above range by thermal relaxation from the annealing treatment. This is desirable because the dimensional accuracy can be further increased. Specifically, it is preferable to carry out the annealing treatment by running the film under low tension in a furnace heated to the above temperature range. The processing time is the time the film stays in the furnace, but it is controlled by changing the running speed, so the processing time is preferably 30 seconds to 5 minutes. If it is shorter than this, heat is not sufficiently transmitted to the film, and if it is longer, it tends to overheat and impairs flatness, which is undesirable. Additionally, the film tension during running is preferably 10 to 50 N/m, and further preferably 20 to 30 N/m. If the tension is lower than this range, the running properties of the film deteriorate, and if the tension is high, the heat shrinkage rate of the obtained film in the running direction increases, which is not preferable.

Additionally, in order to provide adhesiveness to the obtained polyimide film, the film surface may be subject to electrical treatment such as corona treatment or plasma treatment, or physical treatment such as blast treatment, without any particular limitation. The atmospheric pressure in the case of plasma treatment is not particularly limited, but is usually preferably in the range of 13.3 to 1330 kPa, 13.3 to 133 kPa (100 to 1000 Torr), and 80.0 to 120 kPa (600 to 900 Torr). A range of is more preferable.

The atmosphere for plasma treatment contains at least 20 mol% of inert gas, preferably 50 mol% or more, more preferably 80 mol% or more, and most preferably 90 mol% or more. desirable. The above inert gases include He, Ar, Kr, Xe, Ne, Rn, N2 and mixtures of two or more of these. A particularly preferred inert gas is Ar. Additionally, with respect to the above inert gases, oxygen, air, carbon monoxide, carbon dioxide, carbon tetrachloride, chloroform, hydrogen, ammonia, tetrafluoromethane (carbon tetrafluoride), trichlorofluoroethane, trifluoromethane, etc. may be mixed. . Preferred mixed gas combinations used as an atmosphere for the plasma treatment of the present invention include argon/oxygen, argon/ammonia, argon/helium/oxygen, argon/carbon dioxide, argon/nitrogen/carbon dioxide, argon/helium/nitrogen, and argon/helium. /nitrogen/carbon dioxide, argon/helium, helium/air, argon/helium/monosilane, argon/helium/disilane, etc.

The processing power density when performing plasma processing is not particularly limited, but is preferably 200 W·min/m2 or more, more preferably 500 W·min/m2 or more, and most preferably 1000 W·min/m2 or more. . The plasma irradiation time for plasma treatment is preferably 1 second to 10 minutes. By setting the plasma irradiation time within this range, the effect of plasma treatment can be fully exhibited without deterioration of the film. The gas type, gas pressure, and processing density of plasma processing are not limited to the above conditions, and may be performed in the air.

The polyimide film obtained in this way can suppress the coefficient of thermal expansion in this direction to a low level by advancing the orientation of the film toward TD, and also has a low heat shrinkage rate and maintains a high tensile modulus of elasticity, so it has a fine pitch. It is very suitable for circuit boards, especially COF (Chip on Film), which is wired at a narrow pitch on the TD of the film.

Additionally, the copper-clad laminate of the present invention can be obtained by using a polyimide film characterized by any of the above as a base material and forming copper with a thickness of 1 to 10 μm on the polyimide film.

The present invention includes various combinations of the above-mentioned structures within the technical scope of the present invention as long as the effect of the present invention is achieved.

[Example]

Next, the present invention will be described in more detail by way of examples, but the present invention is not limited in any way by these examples, and many modifications may be made within the technical spirit of the present invention as is known in the art. It is possible by a person who has.

Additionally, in the examples, PPD represents para-phenylene diamine, 4,4'-ODA represents 4,4'-diamine diphenyl ether, PMDA represents pyromellitic dianhydride, BPDA represents 3,3', 4,4'-biphenyl tetracarboxylic dianhydride, and DMAc represents N,N-dimethyl acetamide, respectively.

In addition, each characteristic in the examples was evaluated by the following method.

(1)Thermal expansion coefficient

Equipment: TMA-50 (brand name, manufactured by Shimadzu Corporation) was used to measure the temperature under the following conditions: measurement temperature range: 50 to 200°C, temperature rise rate: 10°C/min.

(2) Heating shrinkage rate

The film dimensions (L1) were measured after being left in a room adjusted to 25°C and 60%RH for 2 days, then heated to 200°C for 60 minutes and left again in a room adjusted to 25°C and 60%RH for 2 days. The film dimension (L2) was then measured and evaluated by calculating the formula described below.

Heating shrinkage rate (%) = -{(L2-L1)/L1}×100

(3)Tensile modulus of elasticity

Equipment: RTM-250 (brand name, manufactured by A&D) was used to measure the tensile speed: 100 mm/min.

(4)Dimension change rate

A 10 μm-thick copper layer was formed on the film by electrolytic plating with a copper sulfate plating solution, pattern-etched at a 30 μm pitch (line spacing 15 μm), and copper was wired to the TD, followed by electroless tin plating LT34 manufactured by Shiprepaste. Tin plating was performed and the dimensions at this time were measured (L3). This was placed on a bonding stage at 250°C and the dimensions after bonding to the chip using a bonding tool at 400°C were measured (L4). The rate of dimensional change was obtained using the formula described below.

Dimensional change rate (%) = {(L4-L3)/L3}×100

(5)Tear propagation resistance

A test piece measuring 63.5 mm x 50 mm was prepared from a polyimide film, a length of 12.7 mm was cut into the test piece, and the test piece was measured using a light force cutting tester manufactured by Toyo Seiki in accordance with JIS P8116.

(6)Absorption rate

The film was immersed in distilled water for 48 hours, then taken out, the water on the surface was quickly wiped off, and the sample was cut to a size of approximately 5 mm x 15 mm. After the film was placed on a thermogravimeter, it was measured using a thermogravimetric analyzer TG-50 manufactured by Shimadzu Corporation. The temperature increased to 200°C at a rate of 10°C/min, and the water absorption rate was calculated from the weight change using the formula below.

Water absorption rate (%) ={(weight before heating)｛(weight after heating)｝/(weight after heating)×100

[Example 1]

Add 239.1 g of DMAc to a 500 ml detachable flask, add 5.68 g (0.053 mol) of PPD, 19.56 g (0.097 mol) of 4,4'-ODA, 11.56 g (0.0375 mol) of BPDA, and 22.95 g (0.1132 mol) of PMDA. was added, reacted at room temperature and pressure for 1 hour, and stirred until uniform, to obtain a polyamic acid solution.

15 g was extracted from this polyamic acid solution, cooled to minus 5°C, and then mixed with 1.5 g of acetic anhydride and 1.6 g of β-picorin to obtain a mixed solution.

After the liquid mixture obtained in this way was casted on a rotating drum at 90°C for 30 seconds, the obtained gel film was stretched 1.12 times in the running direction while being heated at 100°C for 5 minutes. Next, both ends in the width direction were held, stretched 1.4 times in the width direction while heated at 270°C for 2 minutes, and then heated at 380°C for 5 minutes to obtain a 38 µm thick polyimide film. This polyimide film was annealed for 1 minute under a tension of 20 N/m in a furnace set at 220°C, and then each characteristic was evaluated.

Thermal expansion coefficient of film MD α _MD : 9.0 ppm/℃

Thermal expansion coefficient α _TD of film TD: 3.0 ppm/℃

Heating shrinkage at 200℃ (MD) : 0.02%

Heating shrinkage at 200℃ (TD): 0.01%

Tensile modulus (MD): 6.5 GPa

Tensile modulus (TD): 8.0 GPa

Tear propagation resistance (MD): 6.7 N/mm

Tear propagation resistance (TD): 5.6 N/mm

Dimensional change rate: 0.006%

Absorption rate: 2.3%

[Examples 2 to 6]

In the same order as in Example 1, polyamic acid solutions were obtained with the aromatic diamine component and the aromatic tetracarboxylic acid component in the ratios shown in Table 1, and then the stretching ratios in the horizontal and vertical directions were performed as shown in Table 1. Each characteristic evaluation of the polyimide film obtained through the same operation was performed, and the results are shown in Table 1.

Example One 2 3 4 5 6

Proportion of each raw material
(molar ratio)
PPD:35
4,4'-ODA:65
BPDA:25
PMDA:75 PPD:40
4,4'-ODA:60
BPDA:25
PMDA:75 PPD:45
4,4'-ODA:55
BPDA:25
PMDA:75 PPD:35
4,4'-ODA:65
BPDA:35
PMDA:65 PPD:40
4,4'-ODA:60
BPDA:35
PMDA:65 PPD:45
4,4'-ODA:55
BPDA:35
PMDA:65

Stretch ratio

MDX

1.12
1.13
1.12
1.10
1.12
1.12
TDX

1.40
1.40
1.40
1.45
1.43
1.40

thermal expansion coefficient
(ppm/℃)
M.D.

9.0
6.5
3.5
9.5

6.6
3.8
TD

3.0
1.5
0.2
3.1
1.6
0.4

Heating shrinkage rate
(%)
M.D.

0.02
0.02
0.01
0.02
0.02
0.01
TD

0.01
0.02
0.01
0.02
0.01

0.01

Tensile modulus
(GPa)
M.D.

6.5

7.3
8.0
6.4
7.0
7.8
TD

8.0
9.0
9.7
7.8
8.8
9.5

Tear propagation resistance
(N/mm)

M.D.

6.7
6.9
7.1
6.7
6.8
7.0
TD

5.6
5.3
5.2
5.3
5.3
5.1
Dimensional change rate (%)

0.006
0.008
0.000
0.006
0.004
0.001
Absorption rate (%)

2.3
2.4
2.5
2.1
2.3
2.5

(Molar ratios in the table represent mole percent in the fully aromatic diamine component and mole percent in the total acid anhydride component, respectively.) Add 239.1 g of DMAc to a 500 ml separable flask, add 4.65 g (0.043 mol) of PPD, Add 21.08 g (0.105 mole) of 4,4'-ODA, 10.91 g (0.031 mole) of BPDA, and 24.26 g (0.111 mole) of PMDA, react for 1 hour at room temperature and pressure, and stir until uniform to form a polyamic acid solution. got it

15 g was taken out from this polyamic acid solution, cooled to minus 5°C, and then mixed with 1.5 g of acetic anhydride and 1.6 g of β-picoline to obtain a mixed solution.

After the mixed liquid obtained in this way was casted on a rotating drum at 90°C for 30 seconds, the obtained gel film was stretched 1.1 times in the running direction while being heated at 100°C for 5 minutes. Next, both ends in the width direction were held, stretched 1.4 times in the width direction while heated at 270°C for 2 minutes, and then heated at 380°C for 5 minutes to obtain a polyimide film with a thickness of 38 μm. This polyimide film was annealed for 1 minute under a tension of 20 N/m in a furnace set at 220°C, and then each characteristic was evaluated.

[Comparative Examples 1 and 2]

In the same order as in Example 1, polyamic acid solutions were obtained with the aromatic diamine component and the aromatic tetracarboxylic acid component in the ratios shown in Table 2, and then the stretching ratios in the horizontal and vertical directions were performed as shown in Table 2 to obtain Example 1. Each characteristic evaluation of the polyimide film obtained through the same operation was performed, and the results are shown in Table 2.

Comparative example One 2
Proportion of each raw material
(molar ratio)
PPD 30
4,4'-ODA 70
BPDA 30
PMDA 70 PPD 20
4,4'-ODA 80
BPDA 30
PMDA 70

Stretch ratio

MDX

1.13
1.20
TDX

1.40
1.40

thermal expansion coefficient
(ppm/℃)
M.D.

12.0
16
TD

4.8
13

Heating shrinkage rate
(%)
M.D.

0.02
0.02
TD

0.01
0.02

Tensile modulus
(GPa)
M.D.

5.7
5.3
TD

7.0
5.8

The front of the tear spread
(N/mm)

M.D.

6.7
7.5
TD

5.6
7.5
Dimensional change rate (%)

0.010
0.025
Absorption rate (%)

2.0
1.7

(Molar ratios in the table represent mole percent in the fully aromatic diamine component and mole percent in the total acid anhydride component, respectively.)

The polyimide film of the present invention can be used very suitably for fine pitch circuit substrates, especially COF (Chip on Film), which is wired at a narrow pitch in the TD of the film.

Claims (13)

A polyimide film obtained using an aromatic diamine component containing para-phenylene diamine and an acid anhydride component, measured using TMA-50 manufactured by Shimadzu Corporation, temperature range: 50 to 200°C, temperature rise rate: 10°C/min. The thermal expansion coefficient α _MD of the film in the machine conveyance direction (MD) measured under the conditions is in the range of 2.0 ppm/℃ to less than 10.0 ppm/℃, and the thermal expansion coefficient α _TD in the width direction (TD) is -1.5 ppm/℃ A polyimide film characterized by being in the range of 2.5 ppm/℃ or less and satisfying the relationship of |α _MD |≥|α _TD |×3.0.
The polyimide film according to claim 1, wherein α _MD is in a range of 3.0 ppm/°C or more and 9.5 ppm/°C or less.
The polyimide film according to claim 1 or 2, wherein α _TD is in a range of -1.0 ppm/°C or more and 2.5 ppm/°C or less.
The polyimide film according to claim 1 or 2, wherein both MD and TD heat shrinkage rates of the film at 200°C are 0.05% or less.
The polyimide film according to claim 1 or 2, wherein both MD and TD heat shrinkage rates of the film at 200°C are 0.03% or less.
The polyimide film according to claim 1 or 2, wherein the film has a tensile modulus of elasticity of 6.0 GPa or more.
The polyimide film according to claim 1 or 2, wherein the film has a water absorption of 3.0% or less.
The polyimide film according to claim 1 or 2, wherein para-phenylene diamine is at least 31 mol% or more in the wholly aromatic diamine component.
The polyethylene according to claim 1 or 2, wherein the aromatic diamine component further contains at least one selected from the group consisting of 4,4'-diamino diphenyl ether and 3,4'-diamino diphenyl ether. mid film.
The polyimide according to claim 1 or 2, wherein the acid anhydride component is at least one selected from the group consisting of pyromellitic dianhydride and 3,3'-4,4'-diphenyl tetracarboxylic dianhydride. film.
A copper-clad laminate using the polyimide film according to claim 1 or 2.
A gel film is produced using an aromatic diamine component including para-phenylene diamine and an acid anhydride component, and the obtained gel film is stretched in the machine conveyance direction at a stretching ratio (MDX) of 1.05 to 1.6 times, and stretched in the machine conveyance direction. The method for producing the polyimide film according to claim 1 or 2, comprising the step of stretching in the width direction at a draw ratio (TDX) of 1.1 to 1.5 times the magnification.
A COF substrate characterized by using the polyimide film according to claim 1 or 2.