KR102466340B1 - Polyimide film - Google Patents

Abstract

[Problem] To provide a novel polyimide film that can be used for double-sided copper clad laminates and the like.
[Solution] In the first aspect, in the polyimide film containing inorganic particles, the ratio of protrusions having a height of 0.8 μm or more on one side (a) of the film is A number/100 cm 2 and the other side (b) of the film ), when the ratio of projections having a height of 0.8 μm or more is set to B/100 cm 2 , both A and B are set to 10 or less. In the second aspect, in the polyimide film containing inorganic particles, the absolute value of the difference between A and B may be 2 or more.

Description

Polyimide film {Polyimide film}

The present invention relates to a polyimide film.

With the miniaturization, weight reduction, and high functionality of electronic devices, printed wiring boards for mounting electronic components such as ICs and LSIs require higher-density wiring in a small space. To cope with this, COF ( Chip On Film) method has been developed and put into practical use. In recent years, the trend has been particularly remarkable in the mounting of ICs that drive displays such as liquid crystal TVs, notebook PCs, and smartphones, and finer detailing for realizing higher-density mounting along with higher-quality displays, thinner and higher-functionality of mobile devices. Improvements are being made in mounting methods such as wiring and double-sided COFs in which wiring is provided on both sides.

For the copper clad laminate used for COF, a two-layer type that can respond to miniaturization of wiring and directly forms a copper layer on a polyimide film without using an adhesive is employed. For this, there is a method of forming a copper layer on a film by a sputter plating method and a method of imidizing after casting polyamic acid on a copper foil, but the sputter plating method, which is easy to thin the copper layer and is advantageous for fine wiring, The two-layer copper-clad laminate is becoming mainstream.

In the formation of the fine wiring of the COF substrate, a photoresist layer is provided on the surface of the copper layer of the copper clad laminate, the photoresist layer is exposed and developed to form a desired pattern, and the pattern is used as a masking material. A method of etching (subtractive method) is used. However, with this method, it is difficult to make the wiring pitch smaller (for example, smaller than 25 μm (eg, line width 12 μm, space width 13 μm)), making it difficult to cope with some cutting-edge models.

Recently, as a method to replace this, a base metal layer is formed on the surface of an insulating substrate, a photoresist layer is provided on the surface of the base metal layer, a desired pattern is formed on the photoresist layer, and the exposed base metal layer is conductive. A method of electrolytically depositing metal to form a wiring pattern (semi-additive method) is attracting attention. According to this method, a small (for example, 20 μm or less) wiring pitch can be formed, and further high-density mounting is possible.

In these technological trends, the demand for characteristics and quality of polyimide films used in two-layer copper-clad laminates is also becoming more sophisticated. For example, COFs are compactly bent and mounted on electronic devices after being mounted with ICs or panels. However, as the wiring is miniaturized, cracks are easily generated in the wiring, so crack resistance is also required. In order to cope with these, for example, a base metal layer made of a nickel alloy without an adhesive is formed on the surface of a polyimide film, and wiring of a laminated structure having a copper layer on the surface of the base metal layer is formed by a semi-additive method. In the manufacturing method of a flexible wiring board, the proposal which stipulates the crystal orientation of a copper layer is made (patent document 1).

Patent Document 1: Japanese Unexamined Patent Publication No. 2014-159608

An object of the present invention is to provide a novel polyimide film.

As described above, although various studies have been conducted on COF, according to the present inventors, it has been found that there is room for further examination and improvement. For example, in a double-sided COF in which wiring is provided on both sides, the bending angle of the wiring on the inner surface of the bend is smaller than that of the wiring on the outer surface, and cracking of the wiring is more likely to occur along with miniaturization of the wiring. In order to respond to this, as in Patent Document 1, it is not sufficient to improve the copper layer, and it is considered that improvement is necessary also in the polyimide film.

In addition, as fine wiring progresses, the demand for quality of the surface of the copper layer and the surface of the polyimide film also increases, and finer foreign matter and defects than before affect the yield of wiring formation. Furthermore, in the case of using a copper clad laminate used for wiring formation by the semi-additive method, the thickness of the copper layer is one-third or less (1 to 3 µm) compared to the copper clad laminate used in the conventional subtractive method. Since there are many, higher quality is requested|required of the surface of a polyimide film.

From this point of view, the present inventors attempted various examinations, but it was difficult to achieve sufficient performance. For example, attempts have been made to smooth the surface of a polyimide film, but simply performing such an attempt deteriorates the slipperiness between films and degrades handling, as well as defects and defects during film transport or winding. Wrinkles tend to occur, and the quality of the surface of the film is rather deteriorated.

In the meantime, as a result of intensive research, the inventors of the present invention focused on both sides of the film in a polyimide film containing inorganic particles and adjusted the ratio of protrusions on both sides, thereby obtaining a polyimide film with excellent handling properties. However, the inventors discovered that a polyimide film suitable for a double-sided COF or the like can be obtained, and the present invention was completed by repeating further studies.

That is, the present invention relates to the following inventions and the like.

[1] In a polyimide film containing inorganic particles, the ratio of protrusions having a height of 0.8 μm or more on one side (a) of the film is A number/100 cm 2 , and the height on the other side (b) of the film is 0.8 μm. A polyimide film in which both A and B are 10 or less (for example, a polyimide film for double-sided COF) when the ratio of the above projections is B/100 cm 2 .

[2] In a polyimide film containing inorganic particles, the ratio of protrusions having a height of 0.8 μm or more on one side (a) of the film is A number/100 cm 2 , and the height on the other side (b) of the film is 0.8 μm. A polyimide film (for example, a polyimide film for double-sided COF) in which the absolute value of the difference between A and B is 2 or more when the ratio of the above projections is B/100 cm 2 .

[3] The polyimide film according to [1] or [2], wherein A and/or B are two or more.

[4] In any one of [1] to [3], wherein the surface roughness (Ra) is 0.01 to 0.05 µm and the surface roughness (Rz) is 0.05 to 0.6 µm on both sides of surface (a) and surface (b). The polyimide film described.

[5] The polyimide film according to any one of [1] to [4], wherein the coefficient of thermal expansion in the MD direction is 4 to 10 ppm/°C and the coefficient of thermal expansion in the TD direction is 0 to 8 ppm/°C.

[6] The polyimide film according to any one of [1] to [5], which satisfies a tensile modulus of 5 to 10 GPa and/or a loop stiffness of 10 to 75 mN/cm.

[7] The polyimide film according to any one of [1] to [6], which is composed of a polyimide containing an aromatic diamine component containing para-phenylenediamine and an acid anhydride component as a polymerization component.

[8] The polyimide film according to any one of [1] to [7], wherein the inorganic particles have an average particle diameter of 0.05 to 0.5 µm.

[9] A metal laminate (especially a double-sided copper clad laminate) using the polyimide film according to any one of [1] to [8].

[10] The metal laminate according to [9] having a copper thickness of 1 to 3 μm (particularly double-sided copper clad laminate).

[11] A substrate for double-sided COF using the metal laminate described in [9] or [10] (particularly, a double-sided copper clad laminate).

[12] A method of manufacturing a double-sided COF substrate by a semi-additive method using the metal laminate described in [9] or [10] (particularly, a double-sided copper clad laminate).

In this invention, a novel polyimide film can be provided. In particular, in this invention, the polyimide film excellent in balance, such as dimensional stability, flexibility, and the surface smoothness in both sides of a film, can also be provided.

Such a polyimide film is suitable for COF (Chip On Film), for example. In particular, for the purpose of high-density packaging, it can be suitably used for fine-pitch circuit boards such as double-sided COFs and semiconductor packages provided with wiring on both sides.

1 is a cross-sectional view of a copper clad laminate using a polyimide film as a substrate.
2 is a cross-sectional view and a surface view of a COF substrate for dimensional evaluation in which a copper wiring circuit pattern is formed on a polyimide film.
Fig. 3 is a diagram showing a cycle of bending the COF substrate for dimensional evaluation and returning it to its original state.
4 is a cross-sectional view after glass is pressed onto a COF substrate for dimensional evaluation.

[Polyimide film]

In the polyimide film of the present invention, the ratio of specific projections is adjusted on both sides of the film.

First, in the first aspect, in the polyimide film, the ratio of projections having a height of 0.8 μm or more on one side (a) of the film is A number / 100 cm 2 (A number per 100 cm 2), and the other side of the film (b ), when the ratio of projections having a height of 0.8 μm or more is B / 100 cm 2 (B per 100 cm 2 ), A and B are each 20 or less (for example, 18 or less), preferably is 15 or less (eg, 12 or less), more preferably 10 or less (eg, 9 or less, 8 or less).

Further, the lower limit values of the proportions A and B of the projections are not particularly limited, but may be, for example, 0 or finite values (eg, 1 or 2).

In this way, defects such as pinholes are easily suppressed efficiently by suppressing the ratio of specific protrusions on both sides of the film. Therefore, such a film is easy to improve the yield and is suitable as a film or the like for providing a metal layer such as copper on both surfaces. In addition, according to the study of the present inventors, it seems that, among the protrusions, the correlation between protrusions of 0.8 μm or more and defects such as pinholes is unexpectedly high.

In the second aspect of the present invention, in the polyimide film, the absolute value of the difference between A and B is 1 or more, preferably 2 or more (for example, 3 or more). The upper limit of the absolute value of the difference between A and B is not particularly limited, but may be, for example, 30, 25, 20, 18, 16, 14, 12, 10, 9, 8, 7, 6 or the like.

In this way, by providing a specific ratio of projections on both sides of the film, it is easy to ensure sufficient slipperiness between the planes (a) and (b) of the film, so when winding in a roll shape at the time of film production, etc. , it is easy to efficiently obtain a film with excellent handleability. In addition, with respect to such excellent handleability, the film is less likely to be scratched or wrinkled, and it is easy to efficiently form wiring on the film (it is easy to form wiring in high yield).

The polyimide film of the present invention may satisfy at least one aspect of the first aspect and the second aspect, and may more preferably satisfy both aspects.

Further, in the first aspect and/or the second aspect, at least one of A and B (A and/or B) is a finite value [for example, one or more, preferably two or more (for example, , 2 to 10, 2 to 8, 3 to 7, etc.] may be used. By daring to form protrusions on at least one surface, it is easy to obtain a film excellent in balance such as good wiring formation and handleability.

The polyimide film of the present invention may have a predetermined surface roughness. For example, the Ra (centre line average roughness) of the polyimide film may be, for example, about 0.01 to 0.05 µm or 0.01 to 0.04 µm. Further, Rz (10-point average roughness) of the polyimide film may be 0.05 to 0.6 µm, preferably 0.1 to 0.5 µm.

In addition, such a surface roughness may be satisfied in either one of surface (a) and surface (b) of a film, and may be satisfied in surface (a) and surface (b).

According to a polyimide film having such a surface roughness (particularly, a polyimide film that satisfies the combination of such a surface roughness and the first and/or second aspects), omissions (pinholes) of copper layers and the like are less likely to occur, and yield easy to improve In addition, since it is easy to ensure sufficient slip properties of the film when processing the film or preparing the copper clad laminate, etc., it is easy to suppress the occurrence of defective conveyance or the occurrence of defects on the surface of the film that reduce the yield, making it possible to obtain a good film. easy to get

The polyimide film of the present invention may have a specific coefficient of thermal expansion. For example, the coefficient of thermal expansion of the polyimide film is 4 to 10 ppm/°C, preferably 3.5 to 9 ppm/°C, and more preferably 3 to 9 ppm in the MD direction (machine transport direction, longitudinal direction, and flow direction). It may be about 8 ppm/°C, or it may be about 0 to 8 ppm/°C, preferably 0 to 6 ppm/°C, and even more preferably about 0.5 to 5 ppm/°C in the TD direction (width direction, transverse direction, right angle direction). .

By setting the coefficient of thermal expansion within this range, bonding defects are less likely to occur during mounting with a semiconductor or glass panel, and it is easy to make the film more suitable for use in fine pitch circuit boards and semiconductor packages.

The tensile modulus of elasticity of the polyimide film of the present invention is preferably 5 GPa or more (eg, 5 to 10 GPa), and more preferably 6 to 8 GPa in MD and 7 to 10 GPa in TD. Such a tensile modulus may be satisfied in the MD direction and/or the TD direction of the film, and particularly may be satisfied in both the MD direction and the TD direction.

The loop stiffness of the polyimide film of the present invention is preferably 10 to 75 mN/cm, and more preferably 10 to 65 mN/cm.

The polyimide film of the present invention usually contains inorganic particles (or fillers). It does not specifically limit as such an inorganic particle, For example, a titanium oxide, a silica, a calcium carbonate, a calcium phosphate, calcium hydrogen phosphate, etc. are mentioned.

The average particle size of the inorganic particles may be, for example, 0.01 to 5 μm, preferably 0.02 to 2 μm (eg, 0.03 to 1 μm), and more preferably about 0.05 to 0.5 μm. In addition, the average particle diameter of the inorganic particles is, for example, in the state of a slurry dispersed in DMAc (N, N-dimethylacetamide), the particle size measured by a laser diffraction / confusion type particle size distribution analyzer LA-920 manufactured by Horiba Manufacturing Co., Ltd. In the distribution, the median diameter is defined as the average particle diameter.

The content of the inorganic particles is not particularly limited as long as the effect of the present invention is not hindered, but is, for example, 0.05% by mass or more, preferably 0.1 to 1.5% by mass, and more preferably 0.3% by mass relative to the polyimide film. -1.0 mass % may be sufficient.

(Method of manufacturing polyimide and polyimide film)

The polyimide film (or the polyimide or polyamic acid constituting the polyimide film) usually contains an aromatic diamine component and an acid anhydride component (tetracarboxylic acid component) as polymerization components. Further, the polymerization component may contain other polymerization components as long as the main components are an aromatic diamine component and an acid anhydride component. Although not particularly limited when producing a polyimide film, first, a polyamic acid (polyamic acid) solution is obtained by polymerizing an aromatic diamine component and an acid anhydride component in an organic solvent.

The polyimide film of the present invention may particularly preferably contain para-phenylenediamine as an aromatic diamine component. In this way, by using the aromatic diamine component containing para-phenylenediamine, it is easy to efficiently obtain a polyimide film having the above characteristics and physical properties. The aromatic diamine component may also contain things other than para-phenylenediamine. Specific examples of the aromatic diamine components other than para-phenylenediamine include meta-phenylenediamine, benzidine, para-xylenediamine, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4, 4'-diaminodiphenylmethane, 4,4'-diaminodiphenylsulfone, 3,3'-dimethyl-4,4'-diaminodiphenylmethane, 1,5-diaminonaphthalene, 3,3' -dimethoxybenzidine, 1,4-bis(3-methyl-5-aminophenyl)benzene, and amide-forming derivatives thereof. These may be used individually by 1 type, and may mix and use 2 or more types. As the aromatic diamine component, a combination of p-phenylenediamine, 4,4'-diaminodiphenyl ether and/or 3,4'-diaminodiphenyl ether is preferable. Among these, it is preferable to adjust the amount of the diamine component of paraphenylenediamine and 3,4'-diaminodiphenyl ether, which have the effect of increasing the tensile modulus of elasticity of the film, to make the obtained polyimide film have a tensile modulus of elasticity of 5 GPa or more, Since transportability also improves, it is preferable.

Specific examples of the acid anhydride component include pyromellitic acid, 3,3',4,4'-diphenyltetracarboxylic acid, 2,3',3,4'-diphenyltetracarboxylic acid, 3,3',4,4 '-benzophenonetetracarboxylic acid, 2, 3, 6, 7-naphthalenetetracarboxylic acid, 2, 2-bis (3, 4-dicarboxyphenyl) ether, pyridine-2, 3, 5, 6-tetracarboxylic acid and their amides aromatic tetracarboxylic acid anhydride components such as formation derivatives are exemplified, and pyromellitic dianhydride and 3,3',4,4'-diphenyltetracarboxylic acid dianhydride are preferable. These may be used individually by 1 type, and may mix and use 2 or more types.

Among these, as a particularly preferable combination of an aromatic diamine component and an acid anhydride component, 1 selected from the group consisting of para-phenylenediamine, 4,4'-diaminodiphenyl ether and 3,4'-diaminodiphenyl ether and combinations of at least one aromatic diamine component and at least one acid anhydride component selected from the group consisting of pyromellitic dianhydride and 3,3',4,4'-diphenyltetracarboxylic dianhydride.

The blending ratio of para-phenylenediamine in the aromatic diamine component is to obtain a thermal expansion coefficient within the above range, to give the film appropriate strength, to prevent poor runability, etc. With respect to the total amount of the aromatic diamine component, It can also be selected from the range of 15 mol% or more (for example, 18 mol% or more), usually 20 mol% or more (for example, 25 mol% or more), preferably 30 mol% or more (for example, 31 mol% or more, 32 mol% or more), preferably 33 mol% or more, and more preferably 35 mol% or more. The upper limit of the ratio of paraphenylenediamine in the aromatic diamine component may be, for example, 100 mol%, and particularly less than 100 mol% [for example, 99 mol%, 95 mol%, 90 mol%, 80 mol% %, 70 mol%, 60 mol% or less (for example, 60 mol%, 55 mol%, 52 mol%, 50 mol%, 48 mol%, 45 mol%, etc.)]. Typically, the ratio of 4,4'-diaminodiphenyl ether and/or 3,4'-diaminodiphenyl ether (particularly 4,4'-diaminodiphenyl ether) in the aromatic diamine component is 20 to 85 mol% (for example, 22 to 82 mol%), 25 to 80 mol% (for example, 30 to 78 mol%), 35 to 75 mol% (for example, 30 to 78 mol%) with respect to the aromatic diamine component total amount , 38 to 72 mol%), 40 to 70 mol% (for example, 45 to 70 mol%), 50 to 68 mol%, etc. may be sufficient. The blending ratio (molar ratio) of the acid anhydride component is not particularly limited as long as the effects of the present invention are not hindered, but examples include 3,3',4,4'-diphenyltetracarboxylic dianhydride. In this case, the content of 3,3',4,4'-diphenyltetracarboxylic dianhydride is preferably 15 mol% or more (for example, 18 mol% or more), and 20 mol%, based on the total amount of the acid anhydride component. The above is more preferable, and 25 mol% or more is still more preferable. The upper limit of the ratio of 3,3',4,4'-diphenyltetracarboxylic dianhydride in the acid anhydride component may be 100 mol%, particularly less than 100 mol% (for example, 99 mol% or 95 mol%). , 90 mol%, 85 mol%, 80 mol%, 70 mol%, 60 mol%, 50 mol%, 45 mol%, 42 mol%, 40 mol%, 38 mol%, 35 mol%, 33 mol%, etc.) It is also good. Typically, the ratio of 3,3',4,4'-diphenyltetracarboxylic dianhydride in the acid anhydride component is 15 to 85 mol% (for example, 18 to 70 mol%) with respect to the total amount of the acid anhydride component. %), 18 to 60 mol% (for example, 18 to 50 mol%), or 20 to 40 mol% may be sufficient. When the acid anhydride component contains pyromellitic dianhydride, the ratio of pyromellitic dianhydride is, for example, 15 mol% or more (for example, 20 mol% or more) with respect to the entire acid anhydride component, preferably may be 25 mol% or more (eg, 30 mol% or more), more preferably 35 mol% or more (eg, 40 mol% or more), or 45 mol% or more (eg, 48 mol% or more) % or more, 50 mol% or more, 55 mol% or more, 58 mol% or more, 60 mol% or more, 62 mol% or more). The upper limit of the ratio of pyromellitic dianhydride in the acid anhydride component is particularly limited. may be, for example, 100 mol%, particularly less than 100 mol% (eg, 95 mol%, 90 mol%, 85 mol%, 80 mol%, 82 mol%, 75 mol%, 72 mol% etc.) may also be used. Typically, the ratio of pyromellitic dianhydride in the acid anhydride component is 10 to 95 mol% (for example, 12 to 90 mol%), 15 to 85 mol% (for example, 15 to 85 mol%) with respect to the total amount of the acid anhydride component. For example, 20 to 82 mol%), 30 to 85 mol% (eg, 40 to 82 mol%), 50 to 80 mol% (eg, 60 to 80 mol%) or the like may be sufficient. By using the polyamic acid composed of the aromatic diamine component and the acid anhydride component as the raw material (precursor) of the polyimide film, the thermal expansion coefficient of the polyimide film is set within the above range in both the machine conveyance direction (MD) and the transverse direction (TD) of the film. It can be easily adjusted, which is preferable.

Further, in the present invention, specific examples of the organic solvent used for forming the polyamic acid solution include, for example, sulfoxide-based solvents such as dimethyl sulfoxide and diethyl sulfoxide, N, N-dimethylformamide, N, Formamide solvents such as N-diethylformamide, acetamide solvents such as N,N-dimethylacetamide and N,N-diethylacetamide, N-methyl-2-pyrrolidone, N-vinyl- Pyrrolidone-based solvents such as 2-pyrrolidone, phenolic solvents such as phenol, o-, m-, or p-cresol, xylenol, halogenated phenols, catechol, or hexamethylphosphoramide, γ-butylol and aprotic polar solvents such as lactone, and it is preferable to use these alone or as a mixture of two or more, but aromatic hydrocarbons such as xylene and toluene can also be used.

The polymerization method can be carried out by any known method, for example

(1) A method of polymerization by first putting the entire amount of the aromatic diamine component into a solvent, and then adding an acid anhydride component so as to have an equivalent (equimolar) weight to the entire amount of the aromatic diamine component.

(2) A method of polymerization by first putting the entire amount of the acid anhydride component in a solvent, and then adding an aromatic diamine component so as to have an equivalent weight with the acid anhydride component.

(3) After putting a part of the aromatic diamine component (a1) in a solvent, mixing the part of the acid anhydride component (b1) in a ratio of 95 to 105 mol% with respect to the reaction component for the time necessary for the reaction, A method of polymerizing by adding an aromatic diamine component (a2) and subsequently adding another part of the acid anhydride component (b2) so that the wholly aromatic diamine component and all the acid anhydride components are substantially equivalent.

(4) After adding part of the acid anhydride component (b1) to the solvent, mixing the part of the aromatic diamine component (a1) in a ratio of 95 to 105 mol% with respect to the reaction components for the time necessary for the reaction, A method of polymerization by adding an acid anhydride component (b2), and subsequently adding another part of the aromatic diamine component (a2) so that the wholly aromatic diamine component and all the acid anhydride components are substantially equivalent.

(5) A polyamic acid solution (A) is prepared by reacting a part of the aromatic diamine component and an acid anhydride component in a solvent so that either one is excessive, and another part of the aromatic diamine component and the acid anhydride component are mixed in a different solvent. The polyamic acid solution (B) is adjusted by reacting so that the side becomes excessive. A method of mixing each of the polyamic acid solutions (A) and (B) thus obtained to complete the polymerization. At this time, when the aromatic diamine component is excessive when preparing the polyamic acid solution (A), the acid anhydride component is excessive in the polyamic acid solution (B), and the acid anhydride component is excessive in the polyamic acid solution (A), In the mix acid solution (B), the aromatic diamine component is excessive, and the polyamic acid solution (A) and the polyamic acid solution (B) are mixed and adjusted so that the total aromatic diamine component and all acid anhydride components used in these reactions are almost equivalent. In addition, the polymerization method is not limited to these, and other well-known methods can also be used.

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

Next, the manufacturing method of a polyimide film is demonstrated. As a method for forming a polyimide film, a polyimide film is obtained by casting a polyamic acid solution into a film shape and subjecting it to thermal decyclization and desolvation to obtain a polyimide film, and mixing a cyclization catalyst and a dehydrating agent with the polyamic acid solution and chemically decyclizing to gel Although a method of obtaining a polyimide film by preparing a film and desolvating it by heating is exemplified, the latter is preferable because the coefficient of thermal expansion of the obtained polyimide film can be suppressed low.

In the chemical decyclization method, first, the polyamic acid solution is prepared. Moreover, in this invention, you can also make this polyamic-acid solution contain the above inorganic particle normally.

The polyamic acid solution used here may be a polyamic acid solution previously polymerized, or may be sequentially polymerized when containing inorganic particles.

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

As the cyclization catalyst, amines such as aliphatic tertiary amines (such as trimethylamine and triethylenediamine), aromatic tertiary amines (such as dimethyl annealing lyne), and heterocyclic tertiary amines (such as isoquinoline) , pyridine, β-picoline, etc.) and the like. These may be used individually by 1 type, and may mix and use 2 or more types.

Examples of the dehydrating agent include acid anhydrides such as aliphatic carboxylic acid anhydrides (eg, acetic anhydride, propionic acid anhydride, butyric anhydride, etc.), aromatic carboxylic acid anhydrides (eg, benzoic acid anhydride, etc.). These may be used individually by 1 type, and may mix and use 2 or more types. It does not specifically limit as a gelation retardant, Acetylacetone etc. can be used.

As a method for producing a polyimide film from a polyamic acid solution, a polyamic acid solution (particularly, a polyamic acid solution containing a cyclization catalyst and a dehydrating agent) is casted on a support to form a film, and imidation is partially progressed on the support. After making it into a gel film having self-supporting properties, it is separated from the support, heat-dried/imidized, and heat-treated.

Examples of the support include a metal rotary drum and an endless belt, but are not particularly limited as long as they are made of a uniform material and the surface roughness can be controlled and managed.

The gel film is heated at a temperature of usually 20 to 200° C., preferably 40 to 150° C., by hydrothermal from a support and/or by hydrothermal heat from a heat source such as hot air or an electric heater to cause a ring closure reaction, and volatile components such as advantageous organic solvents. By drying, it becomes self-supporting and peels off from the support.

The gel film peeled from the support may be subjected to stretching. As the stretching treatment, the device and method are not limited as long as it is possible to combine stretching in the conveying direction (MD) and stretching in the width direction (TD) at a predetermined magnification. The draw ratio for producing the film having the effect of the present invention is usually 1.05 to 1.9 times in MD at a temperature of 200 ° C. or higher, preferably 1.1 to 1.6 times, and even more preferably 1.1 to 1.5 times. good night. In TD, the magnification of MD is usually 1.1 to 1.5 times that of X, preferably 1.2 to 1.45 times.

The film may be subjected to heat treatment at a temperature of 250 to 500° C. for 15 seconds to 30 minutes using hot air and/or an electric heater.

It is preferable to adjust the solid content concentration, viscosity, and amount of the polymer flexible to the support so that the thickness of the film is 5 to 75 μm, preferably 10 to 50 μm, and more preferably 20 to 40 μm.

It is preferable to further annealing the polyimide film obtained in this way. By doing so, thermal relaxation of the film occurs and the heat shrinkage rate can be suppressed to a small level. The temperature of the annealing treatment is not particularly limited, but is preferably 200°C or higher and 500°C or lower, more preferably 200°C or higher and 370°C or lower, and particularly preferably 210°C or higher and 350°C or lower. Since the heat shrinkage rate at 200 degreeC can be suppressed within the said range by the thermal relaxation from annealing process, it is preferable that dimensional accuracy is further improved.

Further, in order to impart adhesion to the obtained polyimide film, the surface of the film may be subjected to an electrical treatment such as corona treatment or plasma treatment or a physical treatment such as blast treatment. can be carried out. The ambient pressure in the case of plasma treatment is not particularly limited, but is usually in the range of 13.3 to 1330 kPa, preferably in the range of 13.3 to 133 kPa (100 to 1000 Torr), and more preferably in the range of 80.0 to 120 kPa (600 to 900 Torr). do.

The circumference where the plasma treatment is performed contains at least 20 mol% of an inert gas, preferably 50 mol% or more of an inert gas, more preferably 80 mol% or more, and 90 mol% or more of an inert gas most desirable The inert gas includes He, Ar, Kr, Xe, Ne, Rn, N ₂ and a mixture of two or more of these. A particularly preferred inert gas is Ar. Furthermore, oxygen, air, carbon monoxide, carbon dioxide, carbon tetrachloride, chloroform, hydrogen, ammonia, tetrafluoromethane (carbon tetrafluoride), trichlorofluoroethane, trifluoromethane, etc. may be mixed with the inert gas. . Preferred combinations of mixed gases used as ambient for the plasma treatment of the present invention are argon/oxygen, argon/ammonia, argon/helium/oxygen, argon/carbon dioxide, argon/nitrogen/carbon dioxide, argon/helium/nitrogen, argon/helium. /nitrogen/carbon dioxide, argon/helium, helium/air, argon/helium/monosilane, argon/helium/disilane, and the like.

The processing power density when performing the plasma treatment is not particularly limited, but is preferably 200 W min/m 2 or more, more preferably 500 W min/m 2 or more, and most preferably 1000 W min/m 2 or more. The plasma irradiation time for performing the plasma treatment is preferably 1 second to 10 minutes. By setting the plasma irradiation time within this range, the effect of the plasma treatment can be sufficiently exhibited without deterioration of the film. The gas type, gas pressure, and processing density of the plasma treatment are not limited to the above conditions, and may be performed in the atmosphere.

Further, the polyimide film of the present invention has specific characteristics and physical properties (ratio of specific projections, etc.) as described above, but these aspects can be adjusted by appropriately selecting the above conditions and the like. For example, the ratio of specific protrusions on both sides of the film can be adjusted by selecting the average particle diameter or addition amount of inorganic particles added to the polyamic acid solution. In addition, since this projection ratio may be affected by the viscosity of the polyamic acid solution, the surface roughness of the support on which the polyamic acid solution is cast, and the stretch ratio of the film after peeling from the support, the projection ratio can be further adjusted by selecting these. may be That is, in the present invention, it is possible to adjust the projection ratio on both sides of the film by adjusting the average particle diameter of the inorganic particles, the added amount, the viscosity of the polyamic acid solution, the surface roughness of the support, the stretch ratio of the film, and the like within a predetermined range. that made it

Since the polyimide film obtained in this way is excellent in dimensional stability, surface smoothness, flexibility, etc., as described later, a COF (Chip On Film) wired at a narrow pitch in the width direction of the film, especially for high-density packaging Thus, it can be suitably used for fine pitch circuit boards such as double-sided COFs provided with wiring on both sides and semiconductor packages.

[Copper Foil Laminate]

The present invention also includes a copper clad laminate using (equipped with) the polyimide film of the present invention described above. In such a copper clad laminate, a copper layer is formed on at least one surface of the polyimide film, and in particular, a copper layer is formed on both surfaces of the polyimide film. The manufacturing method of such a copper clad laminate is not specifically limited, A conventionally well-known manufacturing method may be used. For example, a method in which a layer containing copper as a main component is laminated by an electroplating method on a metal layer containing nickel chromium as a main component formed by a sputtering method on at least one surface (particularly both surfaces) of a polyimide film is common. . In the copper clad laminate of the present invention, for example, a nickel chromium alloy layer is provided on both sides of a polyimide film, and copper having a predetermined thickness (eg, 1 to 3 μm in thickness) is formed thereon by the plating method described above. can be obtained by doing

Further, the present invention includes a substrate for double-sided COF using (equipped with) the copper-clad laminate of the present invention described above. The substrate for double-sided COF may be one in which a wiring circuit is provided on a copper-clad laminate. The manufacturing method of such a double-sided COF board|substrate is not specifically limited, A well-known method can be used, In particular, it can also manufacture by a semiadditive process. As a more specific method, after patterning the wiring circuit using the photolithography method, peeling off the resistor layer where the wiring is to be formed, forming wiring on the exposed thin copper layer by electrolytic copper plating, and then forming the resistor layer, A method of removing the thin copper layer and the base metal layer, forming 0.1 to 0.5 μm of tin on the wiring by an electroless tin plating method, and then laminating a solder resist on a necessary portion.

The present invention includes various combinations of the above configurations within the technical scope of the present invention as long as there is an effect of the present invention.

[Example]

Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited in any way by these examples.

Further, in the Examples, PPD represents para-phenylenediamine, 4,4'-ODA represents 4,4'-diaminodiphenyl ether, PMDA represents pyromellitic dianhydride, and BPDA represents 3,3 ',4,4'-diphenyltetracarboxylic acid dianhydride, and DMAc represents N,N-dimethylacetamide, respectively.

[Example 1]

(Creation of polyimide film)

PPD (molecular weight: 108.14), 4,4'-ODA (molecular weight: 200.24), BPDA (molecular weight: 294.22), and PMDA (molecular weight: 218.12) were prepared at a molar ratio of 35/65/30/70 and prepared as a 20% by weight solution in DMAc. Polymerization was performed to obtain a 3500 poise polyamic acid solution. To this was added 0.5% by weight of DMAc slurry of silica with an average particle diameter of 0.1 µm per weight of resin, and stirred sufficiently to disperse. Subsequently, a polyester film (Lumira X43: manufactured by Toray, Ra 0.2 μm) having a thickness of 125 μm was placed on the glass substrate to serve as a support, and a polyamic acid solution was placed on the support, followed by casting with an applicator. Next, after immersing this in a mixed solution of acetic anhydride and β-picoline for 10 minutes to cause an imidation reaction, the polyimide gel film is peeled off from the polyester film, and the gel film is manually stretched in the direction of the applicator (hereinafter referred to as MD). After stretching 1.15 times and 1.40 times in the vertical direction (hereinafter referred to as TD), it was fixed to a support frame. Thereafter, after heating and drying at 300°C for 20 minutes and subsequently at 400°C for 5 minutes, it was removed from the support frame to obtain a polyimide film having a thickness of 35 µm.

About this film, each of the following characteristics was evaluated, and the result was shown in Table 1.

(1) Surface roughness

It was measured according to JIS B0601-1982 using a surface roughness measuring instrument SE-3500 (manufactured by Kosaka Laboratories).

(2) Number of surface asperities

Using a laser microscope VK-9710 (manufactured by Keyence Corporation), projections on the surface of the film were observed in a field of view of 100 cm 2 , the height was measured, and the number of projections of 0.8 μm or more was counted.

In addition, observation was performed by enlarging the measurement site 10 times with an objective lens (at a magnification of 200 times on a monitor). All of the observed projections had a width of 15 μm or more (there was no projection with a width of less than 15 μm), and when the projection had a plurality of projections, the height of the highest projection was determined as the height of the projection.

(3) Coefficient of thermal expansion

Measurement was performed using TMA-60 (manufactured by Shimadzu Corporation) under conditions of a measurement temperature range of 50 to 200°C and a temperature increase rate of 10°C/min.

(4) Tensile modulus

Using RTM-250 (manufactured by A&D Day), it was measured under conditions of tensile speed: 100 mm/min.

(5) Loop stiffness

Using a loop stiffness tester DA (manufactured by Toyo Seiki Seisakusho), the measurement was performed under the conditions of a sample width of 20 mm, a loop length of 50 mm, and a compression distance of 20 mm.

(6) Film handling

The support surface and the non-support surface of the sample were overlapped and fixed to a slip tester (manufactured by Technonis), and the static friction coefficient and the dynamic friction coefficient were measured at a load of 200 g and a measurement speed of 120 mm/min. The results are shown in Table 1.

(Creation of double-sided copper clad laminate)

After forming a nickel chromium layer (Ni:Cr = 80:20 m, thickness: 25 nm) and a copper layer (thickness: 100 nm) by the spatter method on the support surface of the polyimide film obtained above, similarly nickel on the non-support surface. A chromium layer and a copper layer were formed. Subsequently, a copper layer having a thickness of 2 μm was formed on both sides by electrolytic plating using a copper sulfate plating solution.

The following items were evaluated about the obtained double-sided copper-clad laminate (FIG. 1). The results are listed in Table 1.

(7) Number of pinholes

After protecting the support surface of the double-sided copper clad laminate with a cover film, an etching treatment was performed using a ferric chloride solution to remove the copper layer and nickel chromium layer on the non-support surface. Subsequently, in a dark room, a fluorescent lamp backlight was illuminated from the polyimide surface (non-support surface), and the number of light (pinholes) leaking to the copper surface (support surface) side was counted by eye in a field of view of 100 cm 2 . The number of pinholes on the non-support surface was also evaluated in the same manner.

(Creation of board for evaluation COF)

With respect to the sample obtained above from which the copper layer and nickel chromium layer of the non-support surface of the double-sided copper-clad laminate were removed, the copper surface (support surface) was mixed with a solution obtained by diluting Sulfap ACL-067 manufactured by Kamimura Kogyo Co., Ltd. with water at 15%, After degreasing by impregnation at 30°C for 30 seconds, the photoresist was laminated to a dry thickness of 15 µm, and the pattern for evaluation (line width 20 µm, space width 20 µm) shown in Fig. 2 was exposed and developed. Thereafter, according to a conventional method, a copper plating layer having a thickness of 8 μm was formed by a semi-additive method, and a substrate for COF for evaluation was created. For the obtained substrate for COF, the following items were evaluated, and the results are shown in Table 1.

(8) Flexibility

The conductor side of the COF board was bent inward as shown in Fig. 3, and a load of 1.0 kgf was applied for 10 seconds, and then the COF board was opened and returned to its original state. This was made into one cycle, and it was repeated 5 times to 30 times, and during that time, the place where the conductor was bent was observed under a microscope, and the number of times until the conductor broke was measured.

(9) Dimensional stability

The COF substrate for evaluation obtained above was bonded to an adherend (glass) using an anisotropic conductive film (ACF: product name, Anisorum C5311 manufactured by Hitachi Kasei) under conditions of 180°C×10 seconds and 5 MPa (FIG. 4).

The external dimensions of the circuit pattern 30 sample for evaluation were measured before crimping (L3) and after crimping (L4), and the standard deviation of elongation calculated by the following formula was measured.

Elongation (%)={(L4-L3)/L3}×100

[Example 2]

A polyimide film having a thickness of 38 μm was obtained in the same procedure as in Example 1, except that the gel film was stretched 1.25 times in MD and 1.40 times in TD.

[Example 3]

A polyimide film having a thickness of 35 µm was obtained in the same procedure as in Example 1, except that a silica DMAc slurry having an average particle diameter of 0.4 µm was used.

[Example 4]

A polyimide film having a thickness of 25 μm was obtained in the same procedure as in Example 3, except that the gel film was stretched 1.15 times in MD and 1.35 times in TD.

[Example 5]

PPD, 4,4'-ODA, BPDA, PMDA were prepared at a molar ratio of 20/80/35/65 and silica having an average particle diameter of 0.4 µm was used in the same procedure as in Example 2, except that silica having a thickness of 38 µm was prepared. A polyimide film was obtained.

[Example 6]

A polyimide film having a thickness of 38 μm was obtained in the same procedure as in Example 3, except that PPD, 4,4′-ODA, BPDA, and PMDA were adjusted to a molar ratio of 30/70/25/75.

[Example 7]

A polyimide film having a thickness of 25 µm was obtained in the same procedure as in Example 5, except that calcium hydrogen phosphate having an average particle diameter of 1.0 µm was used.

[Example 8]

A polyamic acid solution was prepared by adding PPD and BPDA at a molar ratio of 1:1, to which was added 0.5% by weight of DMAc slurry of silica having an average particle diameter of 0.1 µm per weight of resin. Then, a polyimide film having a thickness of 38 μm was obtained in the same procedure as in Example 4, except that a polyester film (Lumira S10: manufactured by Toray, Ra 0.05 μm) having a thickness of 125 μm was used as the support.

[Example 9]

A polyimide film having a thickness of 35 μm was obtained in the same procedure as in Example 3, except that PPD, 4,4′-ODA, BPDA, and PMDA were adjusted to a molar ratio of 40/60/25/75.

[Example 10]

A polyimide film having a thickness of 35 µm was obtained in the same procedure as in Example 3, except that PPD, 4,4'-ODA, BPDA, and PMDA were adjusted to a molar ratio of 45/55/35/65.

The characteristics of the polyimide films obtained in Examples 2 to 8, the double-sided copper-clad laminate produced in the same procedure as in Example 1 using them, and the COF substrate for evaluation were evaluated in the same manner as in Example 1, and the results are shown in Table 1. showed

From the results of the table above, it can be said that the polyimide films of Examples are excellent in surface smoothness, dimensional stability, flexibility, and the like. Further, since the balance of surface smoothness on both sides of the film was excellent, it was confirmed that the film had good handleability and was a film capable of maintaining high productivity.

The polyimide film of the present invention is excellent in dimensional stability, flexibility, and the like. Further, in the present invention, a film having high surface quality on both surfaces can be obtained. Therefore, such a polyimide film of the present invention can be suitably used for fine pitch circuit boards such as double-sided COFs and semiconductor packages provided with wiring on both sides for the purpose of high-density packaging.

Claims (12)

In a polyimide film containing inorganic particles, the ratio of projections with a height of 0.8 μm or more on one side (a) of the film is A / 100 cm 2 , and the ratio of projections with a height of 0.8 μm or more on the other side (b) of the film A polyimide film for double-sided COF, wherein when the ratio is B/100 cm2, both A and B are 10 or less, and the absolute value of the difference between A and B is 2 or more.
The polyimide film according to claim 1, wherein the absolute value of the difference between A and B is 3 or more.
The polyimide film according to claim 1 or 2, wherein A and/or B are two or more.
The polyimide film according to claim 1 or 2, wherein the surface roughness (Ra) is 0.01 to 0.05 μm and the surface roughness (Rz) is 0.05 to 0.6 μm on both surfaces of the surface (a) and the surface (b).
The polyimide film according to claim 1 or 2, wherein the coefficient of thermal expansion in the MD direction is 4 to 10 ppm/°C and the coefficient of thermal expansion in the TD direction is 0 to 8 ppm/°C.
The polyimide film according to claim 1 or 2, which satisfies a tensile modulus of 5 to 10 GPa and/or a loop stiffness of 10 to 75 mN/cm.
The polyimide film according to claim 1 or 2, which is composed of a polyimide containing an aromatic diamine component containing para-phenylenediamine and an acid anhydride component as polymerization components.
The polyimide film according to claim 1 or 2, wherein the inorganic particles have an average particle diameter of 0.05 to 0.5 μm.
A double-sided copper clad laminate using the polyimide film according to claim 1 or 2.
The double-sided copper clad laminate according to claim 9, wherein the copper thickness is 1 to 3 μm.
A double-sided COF substrate using the double-sided copper clad laminate according to claim 9.
A method for manufacturing a double-sided COF substrate by a semi-additive method using the double-sided copper clad laminate according to claim 10.

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