JP2003335874A - Polyimide film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyimide film suffering from small dimensional changes both at ordinary temperature and at a higher temperature and suitable for a fine pitch circuit board. <P>SOLUTION: The polyimide film has a Young's modulus of at least 4 GPa, a heat shrinkage ratio at 350°C of at most 0.15% and a heat shrinkage ratio at 400°C of at most 0.20%, and preferably has a water absorption of at most 2.5% and a thermal expansion coefficient between 350-400°C of 20-30 ppm/°C. The film is excellent in processability, has high dimensional stability and can reduce dimensional changes in a step at a higher temperature, and therefore is suitably employed for the fine pitch circuit board. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyimide film suitable for a fine pitch circuit substrate, which has a small dimensional change at both room temperature and high temperature.

[0002]

2. Description of the Related Art As flexible printed circuit boards and semiconductor packages have become finer and finer, the requirements for polyimide films used for them have been increasing. For example, reduction of dimensional change and curl due to bonding with metal, and It has high handling properties,
As a physical property of a polyimide film, a film having a coefficient of thermal expansion comparable to that of a metal and a high elastic modulus, and further, a film having a small dimensional change due to water absorption are required, and a polyimide film corresponding thereto has been developed.

For example, JP-A-60-210629, JP-A-64-16832, and JP-A-1-131241 disclose examples of polyimide films using para-phenylenediamine to increase the elastic modulus. Further, JP-A-59-164328 and JP-A-61-1113.
JP-A-59-59 describes an example of a polyimide film using biphenyltetracarboxylic dianhydride in addition to paraphenylenediamine in order to reduce dimensional change due to water absorption while maintaining high elasticity.

By the way, TAB (Tape Automated Bondin)
These polyimide films have been used in applications requiring high dimensional accuracy such as g), but in recent years, for example, C
3 for joining wiring and chip for OF (Chip on Film) applications
A high temperature of 50 to 400 ° C. is directly applied to the polyimide film, and heat shrinkage due to these temperatures is large, which causes a problem that dimensional change is deteriorated. Further, the reliability of the adhesive has been improved and the bonding temperature has been increased accordingly, but when the polyimide film is processed at 350 to 400 ° C., the dimensional change becomes large and it is difficult to meet the demand for fine pitch.

[0005]

The present invention has been made as a result of studying to solve the above-mentioned problems in the prior art, and can reduce the dimensional change during processing at 350 to 400 ° C. It is intended to provide a polyimide film suitable for a fine pitch circuit substrate.

[0006]

In order to achieve the above object, the polyimide film of the present invention has a Young's modulus of 4 GP.
a or more and heat shrinkage at 350 ° C. of 0.15% or less, 4
The heat shrinkage percentage at 00 ° C. is 0.20% or less.

Furthermore, the water absorption is 2.5% or less, and the coefficient of thermal expansion at 350 to 400 ° C. is 20 to 30 pp.
It is preferably m / ° C.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION A polyamic acid solution which is a precursor for obtaining the polyimide film of the present invention will be described.

The polyamic acid solution used in the present invention is preferably composed of paraphenylenediamine and 4,4'-diaminodiphenyl ether as an aromatic diamine component, and pyromellitic dianhydride as an aromatic acid anhydride component. And biphenyltetracarboxylic dianhydride. The molecular weight per unit of polyamic acid molecule is preferably 420 or less. If it exceeds 420, high temperature 350-400 ℃
It is not preferable because the dimensional change and the heat shrinkage become large.
Here, the molecular weight per unit of polyamic acid molecule is
Aromatic diamine component: Aromatic acid anhydride component: The molecular weight when it is 1: 1 and calculated by the following formula.

Molecular weight per unit of polyamic acid molecule = molecular weight of A (aromatic diamine component) × molar ratio of A in the total aromatic diamine component + molecular weight of B (aromatic diamine component) × total aromatic diamine component Molar ratio of B in the mixture + ... + ... + Molecular weight of Z (aromatic acid anhydride component) x molar ratio of Z in the wholly aromatic acid anhydride component + Y (aromatic acid anhydride) Component) molecular weight × molar ratio of Y in the wholly aromatic acid anhydride component + ... + ... The aromatic diamine component used is a rigid structure aromatic diamine component and a flexible structure aromatic diamine component. It is preferable to use it in combination with a diamine component, since it is possible to obtain a film having appropriate flexibility and a small dimensional change. Examples of the rigid structure aromatic diamine component include the compounds shown below.

[0011]

[Chemical 1]

(Wherein X and Y represent a monovalent substituent selected from hydrogen, a halogen group, a carboxyl group, a lower alkyl group and a lower alkoxyl group (having 1 to 3 carbon atoms), and X and Y May be the same substituent or different substituents.) Among the above-mentioned rigid-structure aromatic diamine compounds, in particular in terms of increasing the elastic modulus of the obtained polyimide film, handling and cost, Preference is given to using phenylenediamine.

Examples of the flexible aromatic diamine compound include the compounds shown below.

[0014]

[Chemical 2]

(Where X and Y represent a monovalent substituent selected from hydrogen, a halogen group, a carboxyl group, a lower alkyl group and a lower alkoxyl group (having 1 to 3 carbon atoms),
X and Y may be the same or different substituents. A is -O-, -S-, -CO-, -SO-, -SO.
₂ -, - CH ₂ - represents a divalent linking group, such as. Among the above-mentioned aromatic diamines having a flexible structure, it is preferable to use diaminodiphenyl ethers from the viewpoint of enhancing the moldability of the obtained polyimide film.

As the aromatic acid anhydride component used,
When used in combination with pyromellitic acid and an aromatic tetracarboxylic acid compound having two or more benzene rings,
It is preferable because a film having low water absorption and good dimensional stability at high temperature can be obtained.

Among the aromatic tetracarboxylic acid compounds used in the present invention, examples of pyromellitic acids include pyromellitic acid and dianhydride thereof.
Examples of the aromatic tetracarboxylic acid compound having two or more benzene rings include 3,3 ′, 4,4′-biphenyltetracarboxylic acid or its dianhydride or 3,3 ′, 4,4′-biphenyltetracarboxylic acid.
Although 3 ', 4,4'-benzophenone tetracarboxylic acid or a dianhydride thereof can be mentioned, the former is preferred from the viewpoint of increasing the elastic modulus and low water absorption of the obtained polyimide film.

A polyamic acid solution which is a precursor for obtaining the polyimide film of the present invention will be described.

The polymerization method may be any known method, for example, (1). A method in which the total amount of the aromatic diamine component is first placed in a solvent, and then the aromatic tetracarboxylic acid component is added in an amount equivalent to the total amount of the aromatic diamine component to carry out polymerization.

(2). A method in which the total amount of the aromatic tetracarboxylic acid components is first placed in a solvent, and then the aromatic diamine component is added in an amount equal to that of the aromatic tetracarboxylic acid components to carry out polymerization.

(3). After the aromatic diamine compound having a rigid structure is put into a solvent, the aromatic tetracarboxylic acid compound is mixed with the reaction components at a ratio of 95 to 105 mol% for a time necessary for the reaction, and then the aromatic aromatic compound having a flexible structure is mixed. A method in which a diamine compound is added, and subsequently, an aromatic tetracarboxylic acid compound is added so that the wholly aromatic diamine component and the wholly aromatic tetracarboxylic acid component are approximately equal in amount and polymerized.

(4). After the aromatic tetracarboxylic acid compound is placed in the solvent, the aromatic diamine compound having a rigid structure is mixed with the reaction components at a ratio of 95 to 105 mol% for a time necessary for the reaction, and then the aromatic tetracarboxylic acid compound is mixed. A method in which a compound is added, and subsequently, a flexible aromatic diamine compound is added so that the wholly aromatic diamine component and the wholly aromatic tetracarboxylic acid component are approximately equal in amount and polymerized.

(5). A polyamic acid solution (A) is prepared by reacting an aromatic diamine component having a rigid structure and an aromatic tetracarboxylic acid with each other in a solvent to prepare an excess, and then preparing a polyamic acid solution (A) in another solvent to obtain an aromatic diamine component having a flexible structure. Aromatic tetracarboxylic acids are reacted so that one of them is excessive, and a polyamic acid solution (B) is prepared. A method of mixing the thus obtained polyamic acid solutions (A) and (B) to complete the polymerization. At this time, when the aromatic diamine component is excessive when adjusting the polyamic acid solution (A), the aromatic tetracarboxylic acid component is excessive in the polyamic acid solution (B), and the aromatic tetracarboxylic acid component is excessive in the polyamic acid solution (A). When the acid component is excessive, the polyamic acid solution (B) contains excess aromatic diamine component, and the polyamic acid solutions (A) and (B) are added.
Are mixed so that the wholly aromatic diamine component and the wholly aromatic tetracarboxylic acid component used in these reactions are adjusted to be approximately equal in amount.

The polymerization method is not limited to these, and other known methods may be used.

Next, a method for obtaining a polyimide film from the obtained polyamic acid solution will be described.

First, a polyamic acid solution is chemically cyclized by using a cyclization catalyst and a dehydrating agent or thermally cyclized by heat treatment to obtain a polyimide gel film.

Next, fix the end portion of this gel film,
1.05-1.5 in the vertical direction, 1.05-2.0 in the horizontal direction
It is preferable to stretch at a magnification of. When such biaxial stretching is performed, the mechanical properties of the obtained polyimide film are improved,
Furthermore, the isotropic property is improved, which is preferable.

The running speed is adjusted to adjust the thickness of the polyimide film, and the thickness of the polyimide film is preferably 3 to 250 μm. If it is thinner or thicker than this, the film-forming property of the film is significantly deteriorated, which is not preferable.

As the solvent used in the above polymerization, dimethyl sulfoxide, N, N-dimethylacetamide,
Examples thereof include N, N-diethylacetamide, N, N-dimethylformamide, N, N-diethylformamide, N-methyl-2-pyrrolidone and dimethyl sulfone, and these are preferably used alone or in combination.

The polyamic acid obtained by the above polymerization is adjusted so as to be 10 to 30% by weight in the solvent.

When the obtained polyamic acid is cyclized into a polyimide film, it may be carried out by either a chemical ring-closing method of dehydrating using a dehydrating agent and a catalyst or a thermal ring-closing method of thermally dehydrating. The chemical ring closure method is preferable because the polyimide film obtained has a high elastic modulus, a low thermal expansion coefficient, and chemical etching properties can be imparted.

Examples of the dehydrating agent used in the chemical ring closure method include aliphatic acid anhydrides such as acetic anhydride and aromatic acid anhydrides such as phthalic anhydride. These are used alone or in combination. Is preferred. Further, as the catalyst, heterocyclic tertiary amines such as pyridine, picoline and quinoline, aliphatic tertiary amines such as triethylamine,
Examples thereof include aromatic tertiary amines such as N, N-dimethylaniline, and these are preferably used alone or in combination.

When the chemical ring-closing method is carried out, a catalyst and a dehydrating agent are mixed in a polyamic acid solution to imidize it and then the solution is coated to obtain a polyimide film, and a polyamic acid solution is coated to form a thin film. There is a method of obtaining a polyimide film by immersing it in a mixture of a catalyst and a dehydrating agent and then imidizing it.
The former is preferred because a polyimide film having a uniform thickness can be obtained.

The polyimide film thus obtained is preferably annealed at a temperature of 350 to 400 ° C. By doing so, thermal relaxation of the film occurs and the dimensional change of the polyimide film can be suppressed when used in the process at the same temperature. Specifically, the film is run in a furnace at 350 to 400 ° C. under low tension to perform annealing treatment. The processing time is the time for the film to stay in the furnace, but it is controlled by changing the running speed, and the processing time is preferably 30 seconds to 5 minutes. If the length is shorter than this, heat is not sufficiently transmitted to the film, and if the length is longer than that, the film tends to be overheated and impairs the flatness. The film tension during running is preferably 10 to 50 N / m, and further 2
0 to 30 N / m is preferable. When the tension is lower than this range, the running property of the film is deteriorated, and when the tension is high, the heat shrinkage ratio in the running direction of the obtained film is high, which is not preferable.

An organic filler or an inorganic filler may be mixed with the polyamic acid solution in order to roughen the surface of the obtained polyimide film to give the film slipperiness and improve the process stability.

In order to impart adhesiveness to the obtained polyimide film, the film surface may be subjected to electrical treatment such as corona treatment or plasma treatment or physical treatment such as blast treatment.

The polyimide film thus obtained has a Young's modulus of 4 GPa or more and a water absorption rate of 2.5% or less, 3
The heat shrinkage at 50 ° C is 0.20% or less, the heat shrinkage at 400 ° C is 0.15% or less, and 350 to 4
Since it has characteristics such that the coefficient of thermal expansion at 00 ° C is 20 to 30 ppm / ° C, it has excellent workability, high dimensional stability, and can reduce dimensional changes even in high temperature processes. Suitable for substrates.

[0038]

EXAMPLES The present invention will be specifically described below with reference to examples.

In the examples, PPD is paraphenylenediamine, 4,4'-ODA is 4,4'-diaminodiphenyl ether, PMDA is pyromellitic dianhydride, B
PDA represents 3,3′-4,4′-diphenyltetracarboxylic dianhydride, and DMAc represents N, N-dimethylacetamide.

Each characteristic in the examples was evaluated by the following methods. (1) Water absorption rate: 98%, left in a desiccator under RH atmosphere for 2 days,
The evaluation was made by the weight% increase with respect to the dry weight. (2) Elastic modulus device: RTM-250 is used, pulling speed: 100 mm
It was measured under the condition of / min. (3) Heat shrinkage ratio (a) 350 ° C. The film size (L1) was measured after leaving it in a room adjusted to 25 ° C. and 60% RH for 2 days, and then 350 ° C. 3
After heating for 0 minutes, the film was allowed to stand in a room adjusted to 25 ° C. and 60% RH again for 2 days, and then the film size (L2) was measured and evaluated by the following formula calculation.

Heat shrinkage rate = − (L2-L1) / L1 × 100 (b) 400 ° C. The film size (L1) after standing for 2 days in a room adjusted to 25 ° C. and 60% RH was measured. 400 ℃ 3
After heating for 0 minutes, the film was allowed to stand in a room adjusted to 25 ° C. and 60% RH again for 2 days, and then the film size (L2) was measured and evaluated by the following formula calculation.

Heat shrinkage rate =-(L2-L1) / L1 × 100 (4) Thermal expansion coefficient Equipment: TMA-50 is used, and measurement temperature range: 350-
The measurement was carried out under the conditions of 400 ° C. and temperature rising rate: 10 ° C./min.

Example 1 DMAc (239.1 g) was placed in a 500 ml separable flask, and PPD2.
71 g (0.025 mol), 4,4'-ODA24.4
4 g (0.122 mol), BPDA 6.49 g (0.0
22 mol), PMDA 27.27 g (0.125 mol)
Was added, and the mixture was reacted at room temperature and atmospheric pressure for 1 hour and stirred until it became uniform to obtain a polyamic acid solution.

In this polymerization, the addition molar ratio of each raw material is
It carried out in the ratio shown in Table 1, and adjusted the total solid content weight to 60.9 g. After taking 15 g of this polyamic acid solution and cooling at −5 ° C., the polyamic acid was imidized by mixing 1.5 g of acetic anhydride and 1.6 g of β-picoline.

The polyimide polymer thus obtained was coated on a glass plate and heated at 100 ° C. for 5 minutes to obtain a gel film. The gel film was peeled off from the glass plate, and the ends of the gel film were pinned. Then, it was stretched 1.1 times in the longitudinal direction and 1.3 times in the lateral direction. Then 300
The film was heated and dried at 20 ° C. for 20 minutes and then at 400 ° C. for 5 minutes to obtain a polyimide film having a thickness of 25 μm. 20 N / m of this polyimide film in a furnace set at 370 ° C.
After applying the tension of 1 to perform the annealing treatment for 1 minute, each physical property was evaluated.

Young's modulus: 5.3 GPa Water absorption: 2.4% 350 ° C. heat shrinkage: 0.06% 400 ° C. Heat shrinkage: 0.09% 350-400 ° C. Thermal expansion coefficient: 28.3 ppm / ° C. [ Examples 2 to 4] By the same procedure as in Example 1, the ratios of the aromatic diamine component and the aromatic tetracarboxylic acid component were changed to those shown in Table 1 to obtain polyamic acid solutions, and then the polyamic acid solution was used to remove the polyimide. The operation for obtaining the film was performed in the same manner as in Example 1, and the annealing treatment was performed in the same manner as in Example 1.

Table 1 shows the evaluation results of the physical properties of the obtained polyimide films.

[0048]

[Table 1]

[Comparative Example 1] Preparation of each raw material in the same manner as in Example 1, and after obtaining a polyamic acid solution by the same procedure, the operation of obtaining a polyimide film from the polyamic acid solution was also performed in the same manner as in Example 1. Table 2 shows the results of evaluating the respective physical properties without performing the annealing treatment.

[Comparative Examples 2 and 3] By the same procedure as in Example 1, the ratios of the aromatic diamine component and the aromatic tetracarboxylic acid component were changed to those shown in Table 2 to obtain polyamic acid solutions, and then polyamic acid was obtained. The operation of obtaining the polyimide film from the acid solution was performed in the same manner as in Example 1, and the annealing treatment was performed in the same manner as in Example 1.

Table 2 also shows the evaluation results of the physical properties of the obtained polyimide films.

[0052]

[Table 2]

[0053]

INDUSTRIAL APPLICABILITY The polyimide film of the present invention has a Young's modulus of 4 GPa or more, a water absorption rate of 2.5% or less, a heat shrinkage rate at 350 ° C. of 0.20% or less, and a heat shrinkage rate at 400 ° C. of 0.15. % Or less, and further, the characteristic that the coefficient of thermal expansion at 350 to 400 ° C. is 20 to 30 ppm / ° C. is obtained, so that the workability is excellent, the dimensional stability is high, and the dimensional change is reduced even in the high temperature process. Therefore, it can be suitably used for a fine pitch circuit substrate.

Front page continuation (51) Int.Cl. ⁷ Identification code FI theme code (reference) C08L 79:08 C08L 79:08 ZF term (reference) 4F071 AA60 AA60X AA81 AA81X AF10Y AF61Y AF62Y AG28 AH13 BA02 BB02 BB07 BB12 BC01 4F210 AA40 AC03 AG01 AH36 QA08 QC05 QD01 QG01 QG17 QW06 QW11 QW17 4J043 PA01 PA04 QB05 QB26 QC02 RA05 RA34 SA06 SB03 TA22 TB03 UA121 UA122 UA131 UA132 YA35 YA08 YA08 YA08 YA08 YA02 VA02 XA02 VA06 XA2

Claims (3)

[Claims] 1. A polyimide film having a Young's modulus of 4 GPa or more, a heat shrinkage at 350 ° C. of 0.15% or less, and a heat shrinkage at 400 ° C. of 0.20% or less. 2. The polyimide film according to claim 1, which has a water absorption of 2.5% or less. 3. The coefficient of thermal expansion at 350 to 400 ° C. is 20.
The polyimide film according to claim 2, wherein the polyimide film has a content of -30 ppm / ° C.