JP2003049008A - Polyimide film - Google Patents

Abstract

(57) [Problem] To provide a polyimide film which has low water absorption, has a high moisture absorption or dehumidification rate by humidity control, and can reduce the popcorn phenomenon. For a film having a water absorption of 2.2% or less and a dimensional change at the time of moisture absorption or dehumidification at 25 ° C. to reach equilibrium, a film having a thickness of 10 μm or more and less than 30 μm is 3 times.
A polyimide film characterized by being less than 5 hours, less than 5 hours for a film having a thickness of 30 μm or more and less than 60 μm, and less than 10 hours for a film having a thickness of 60 μm or more and less than 100 μm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyimide film which has a low water absorption and a high moisture absorption or dehumidification rate due to humidity control and which can reduce the popcorn phenomenon.

[0002]

2. Description of the Related Art COF (Chip on Flexible Printed Cir)
As semiconductor packages such as cuit) and CSP (Chip size package) become more sophisticated, there are increasing requirements for polyimide films used for them, for example, to reduce dimensional change and curl due to bonding with metal. , And high handling property,
As the physical properties of the polyimide film, the former requires that it has a thermal expansion coefficient similar to that of a metal, and the latter requires that it has a high elastic modulus. And as a polyimide film with such physical properties, "UPILE" manufactured by Ube Industries, Ltd.
X "-S is mentioned and is used in the present market as a film for semiconductor packages.

However, when a polyimide film is used for a semiconductor package, the so-called popcorn phenomenon occurs in which the moisture in the polyimide film explodes due to a rapid rise in temperature during the reflow process during chip mounting. I was holding.

The popcorn phenomenon causes problems such as peeling of a chip or a circuit and short-circuiting of solder terminals, and therefore its improvement is eagerly sought. As a countermeasure, low water absorption of the film can be mentioned. However, since the water absorption is low, the moisture absorption rate and dehumidification rate are slow, and water is stored in the film for a long time. Therefore, this alone does not lead to the improvement of the popcorn phenomenon.

Further, if the moisture absorption rate or dehumidification rate during humidity control is low, it takes a long time for the dimensional change due to the influence of water to saturate, and a large amount of time is required for pre-humidification in each step. Therefore, productivity is also reduced.

[0006]

SUMMARY OF THE INVENTION The present invention has been made as a result of studying to solve the above-mentioned problems in the prior art, and effectively reduces the popcorn phenomenon of the polyimide film during chip mounting. CSP, BGA (Ball G) that has high dimensional accuracy and has a low coefficient of water absorption, a high rate of moisture absorption or dehumidification due to humidity control, and a coefficient of thermal expansion and high elastic modulus similar to those of metals.
For semiconductor packages such as rid Allay), COF, PD
It is intended to provide a polyimide film for high-definition FPC such as P (Plasma Display) and HDD (Hard Disc Driver).

[0007]

To achieve the above object, the polyimide film of the present invention has a water absorption of 2.2.
%, And the time required for the dimensional change to reach equilibrium at the time of moisture absorption or dehumidification at 25 ° C. is 10 μm or more and 30 μm or more.
Films with a thickness of less than μm are less than 3 hours, films with a thickness of 30 μm or more and less than 60 μm are less than 5 hours, thicknesses of 60 μm
It is characterized in that it is less than 10 hours for the film having a thickness of less than 100 μm. Furthermore, it is preferable that the polyimide film of the present invention also has the following conditions (1) to (7). (1) The elastic modulus is 4.5 GPa or more. (2) The coefficient of thermal expansion is 24 ppm / ° C. or less. (3) The polyimide film is made of a polyimide containing both a rigid structure aromatic diamine compound and a flexible structure aromatic diamine compound as an aromatic diamine component. (4) The rigid structure aromatic diamine compound is 10 mol% or more and 90 mol% or less of the wholly aromatic diamine component,
The aromatic diamine compound having a flexible structure is 10 mol% or more and 90 mol% or less of the wholly aromatic diamine component. (5) The aromatic diamine compound having a rigid structure is composed of paraphenylenediamine, and the aromatic compound having a flexible structure is used. Group diamine compound is 4,4'-diaminodiphenyl ether, 3,
It is at least one compound selected from 4'-diaminodiphenyl ether and 4,4'-diaminodiphenylmethane (6) Aromatic aromatic polyimide having pyromellitic acid and two or more benzene rings as aromatic tetracarboxylic acid compounds Being composed of a polyimide containing a group tetracarboxylic acid compound. (7) The pyromellitic acid is 50 mol% or more and 80 mol% or less of the wholly aromatic tetracarboxylic acid component, and the aromatic tetracarboxylic acid compound having two or more benzene rings is the wholly aromatic tetracarboxylic acid. 20 mol% or more and 50 mol% or less of the components. (8) The polyimide film is for a semiconductor package or a high-definition FPC.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The polyimide film of the present invention will be described in detail below.

In order to prevent the popcorn phenomenon from occurring due to a rapid rise in temperature during the reflow process, it is necessary to reduce the residual water content in the polyimide film. That is, the water absorption rate of the film should be kept to 2.2% or less, and It is preferable to set the time until the dimensional change when wet reaches equilibrium within the above range. Furthermore, if the time required for the dimensional change during moisture absorption or dehumidification to reach equilibrium exceeds the above range, it takes a lot of time for pre-humidification in each step, which lowers productivity and is not preferable. .

Further, in order to improve the handling property in the actual process, the elastic modulus is preferably 4.5 GPa or more.

Further, in order to reduce the dimensional change rate and the curl due to the bonding with the metal, the coefficient of thermal expansion is 24.
It is preferably ppm / ° C. or less.

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
An aromatic diamine component consisting of a rigid aromatic diamine compound and a flexible aromatic diamine compound, and a pyromellitic acid and an aromatic tetracarboxylic acid compound having two or more benzene rings. It is preferably obtained by polymerizing an aromatic tetracarboxylic acid component in a solvent.

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 using a cyclization catalyst and a dehydrating agent or thermally cyclized by heat treatment to obtain a polyimide gel film.

Next, fix the end 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.

Examples of the aromatic diamine compound having a rigid structure used in the present invention include the compounds shown below.

[0024]

[Chemical 1]

(In the formula, 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, and X and Y may be the same or different. It may be a substituent.) Among the above-mentioned rigid-structure aromatic diamine compounds, it is particularly preferable to use para-phenylenediamine in terms of increasing the elastic modulus of the obtained polyimide film, handling, and cost. preferable.

Further, examples of the aromatic diamine compound having a flexible structure include the compounds shown below.

[0027]

[Chemical 2]

(Wherein X and Y represent a monovalent substituent selected from hydrogen, a halogen group, a carboxyl group, a lower alkyl group and a lower alkoxy group, and X and Y are the same or different substituents. Group may be used, and 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, diaminodiphenyl ethers are particularly preferably used from the viewpoint of enhancing the moldability of the obtained polyimide film.

Among the aromatic tetracarboxylic acid compounds used in the present invention, examples of pyromellitic acid include pyromellitic acid or its dianhydride, and aromatic tetracarboxylic acid having two or more benzene rings. Examples of the acid compound include 3,3 ′, 4,4′-biphenyltetracarboxylic acid or a dianhydride thereof, and 3,3 ′, 4,4′-benzophenonetetracarboxylic acid or a dianhydride thereof. .

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-closing 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.

In the case of performing the chemical ring closure method, a method of mixing a catalyst and a dehydrating agent in a polyamic acid solution to imidize it and then coating the solution to obtain a polyimide film, and a method of coating the polyamic acid solution 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.
Although the reason is not clear, the former method is preferable because it can increase the water vapor permeability and can shorten the time until the dimensional changes at the time of moisture absorption and dehumidification reach equilibrium.

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 physical treatment such as electrical treatment such as corona treatment or plasma treatment or blast treatment, and further, thermal treatment. The film may be heat relaxed by an annealing treatment to stabilize it.

The polyimide film thus obtained has suitable properties for semiconductor packages.
That is, pre-humidification of each step can be performed in a short time,
It is possible to reduce the water content of the polyimide film at the time of chip mounting to reduce the popcorn phenomenon, and to reduce the dimensional change and curl due to bonding with metal, and to obtain a polyimide film with high handling properties. .

[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, 3,4'-ODA is 3,4'-diaminodiphenyl ether, and PMDA is pyromellitic acid diamine. Anhydride, BPDA represents 3,3′-4,4′-diphenyltetracarboxylic dianhydride, and DMAc represents N, N-dimethylacetamide, respectively.

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) Measurement of the time until the dimensional changes during moisture absorption and dehumidification reach equilibrium. (I) During moisture absorption A film is mounted in the TM7000 furnace at 25 ° C, 90 ° C.
The inside of the TM7000 furnace was humidified by supplying air from the HC-1 type steam generator set to% RH, and the time from the start of humidification until the dimensional change reached equilibrium was measured. (ii) Dehumidification At the time of dehumidification, a film was attached in the TM7000 furnace, and a dry gas was fed from the above apparatus at 25 ° C to dehumidify the TM7000 furnace, and the time from the start of dehumidification until the dimensional change reached equilibrium was measured. (3) Film thickness It was measured using a Lightmatic (Series 318) manufactured by Mitutoyo. (4) Elastic modulus device: RTM-250 is used, tensile speed: 100 mm
It was measured under the condition of / min. (5) Thermal expansion coefficient device: TMA-50 is used, measurement temperature range: 50 to 2
The measurement was carried out under the conditions of 00 ° C. and temperature rising rate: 10 ° C./min. (6) Popcorn Evaluation A three-layer laminated body in which a polyimide film is copper-clad with an adhesive (epoxy type) interposed therebetween is immersed in water at room temperature for 2 days, and then heated at 250 ° C. N was 20 at each level and popcorn was evaluated by the number of pieces in which foaming occurred.

[Example 1] DMAc (239.1 g) was placed in a 500 ml separable flask, and PPD2.
311 g (0.0214 mol) and PMDA 4.569 g
(0.0209 mol) was added and the reaction was carried out at room temperature and atmospheric pressure for 1 hour. Next, 24.254 g (0.1
211 mol) and after stirring until uniform, BP
DA 12.578 g (0.0427 mol) was added and 1
Reacted for hours. Then, here PMDA17.188
g (0.0788 mol) was added, and the mixture was further reacted for 1 hour 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.

Table 1 shows the results of the evaluation of each characteristic of this polyimide film.

Example 2 The procedure of Example 1 was repeated except that the film thickness of the polyimide film was adjusted to 50 μm, and the results of evaluating the physical properties of the resulting polyimide film are also shown in Table 1. .

Example 3 The procedure of Example 1 was repeated except that the film thickness of the polyimide film was adjusted to 75 μm, and the results of evaluation of physical properties of the obtained polyimide film are also shown in Table 1. . [Examples 4 to 8] By the same procedure as in Example 1, the ratios of the aromatic diamine component and the aromatic tetracarboxylic acid component were changed to the ratios shown in Table 1, and polyamic acid solutions were respectively obtained.
The procedure for obtaining a polyimide film from a polyamic acid solution was performed in the same manner as in Example 1, and the film thickness was set as shown in Table 1.
The thickness was adjusted to the value shown in.

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

[0048]

[Table 1]

[Comparative Example 1] "UPILEX" manufactured by Ube Industries, Ltd.
Table 2 shows the results of evaluation of each physical property using -50S.

[Comparative Example 2] "UPILE" manufactured by Ube Industries, Ltd.
Table 2 shows the results of evaluation of each physical property using X ″ -75S.
It was shown to.

[0051]

[Table 2]

[0052]

EFFECTS OF THE INVENTION The polyimide film of the present invention has a water absorption rate of 2.2% or less, and a dimensional change during moisture absorption or dehumidification takes a short time to reach equilibrium, an elastic modulus of 4.5 GPa or more, and a thermal expansion coefficient. Since the coefficient is 24 ppm / ° C or less, it is possible to reduce the water content of the polyimide film at the time of chip mounting to reduce the popcorn phenomenon and further reduce the dimensional change rate and curl due to bonding with a metal. Since it has high handling property, it can be suitably used for semiconductor packages and high-definition FPCs.

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 4F071 AA60 AF10Y AF20Y AF54Y                       AF62Y AH12 BC01                 4J043 QB31 RA34 SA06 SB03 TA14                       TA22 TB03 UA121 UA122                       UA131 UA132 UA141 UA151                       UB011 UB121 UB131 UB151                       UB152 UB221 UB281 UB291                       UB301 UB401 UB402 VA011                       ZA04 ZA32 ZA35 ZA60 ZB47

Claims (9)

[Claims] 1. A film having a water absorption rate of 2.2% or less and reaching a dimensional change during moisture absorption or dehumidification at 25 ° C. is less than 3 hours for a film having a thickness of 10 μm or more and less than 30 μm, A polyimide film having a thickness of 30 μm or more and less than 60 μm for less than 5 hours, and a film having a thickness of 60 μm or more and less than 100 μm for less than 10 hours. 2. The polyimide film according to claim 1, which has an elastic modulus of 4.5 GPa or more. 3. The polyimide film according to claim 1, which has a coefficient of thermal expansion of 24 ppm / ° C. or less. 4. The polyimide film comprises a polyimide containing both a rigid-structure aromatic diamine compound and a flexible-structure aromatic diamine compound as an aromatic diamine component. The polyimide film according to the item. 5. The rigid structure aromatic diamine compound is 10 mol% or more and 90 mol% or less of the wholly aromatic diamine component, and the flexible structure aromatic diamine compound is 10 mol% of the wholly aromatic diamine component. It is 90 mol% or less above, The polyimide film of Claim 4 characterized by the above-mentioned. 6. The aromatic diamine compound having a rigid structure is composed of paraphenylenediamine, and the aromatic diamine compound having a flexible structure is 4,4′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether, 4,4 ′.
-At least one selected from diaminodiphenylmethane
It is a compound of a kind, The polyimide film of Claim 4 or 5 characterized by the above-mentioned. 7. The polyimide film comprises a polyimide containing a pyromellitic acid compound as an aromatic tetracarboxylic acid compound and an aromatic tetracarboxylic acid compound having two or more benzene rings.
The polyimide film according to any one of 1. 8. The pyromellitic acid is 50 mol% or more and 80 mol% or less of the wholly aromatic tetracarboxylic acid component, and the aromatic tetracarboxylic acid compound having two or more benzene rings is wholly aromatic tetracarboxylic acid. 20 mol% or more and 50 mol% or less of a carboxylic acid component are contained, The polyimide film of Claim 7 characterized by the above-mentioned. 9. A high-definition FPC for a semiconductor package
The polyimide film according to claim 1, which is for use.