JP2001244380A - Polyimide film for surface mounted area array package - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyimide film for a surface mounted area array package that can maintain a thickness of a film so as to provide a sufficient handling performance for use of the surface mounted area array package, reduce effectively popcorn phenomenon of a polyimide film in mounting a chip, and has low water absorptivity and high-water vapor permeability, and is made of the same material having a high thermal expansion coefficient and excellent elastic modulus as metal. SOLUTION: This polyimide film for the surface mounted area array package is characterized by a water absorptivity of not more than 2.2% and water vapor transmittance of not less than 1.5 g/(m2.24 h).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyimide film used for a surface mount area array package (SMA) which has low water absorption and high water vapor permeability and effectively reduces the popcorn phenomenon.

[0002]

2. Description of the Related Art Net Brain Marketing Report '96 Development status and market search of new generation BGA / CSP packages: Use of ceramics such as alumina as a film for surface mount area array packages defined by Net Brain Co., Ltd. In addition, resin substrates such as glass epoxy and BT resin have been conventionally used. However, these have problems such as difficulty in increasing the number of pins and increase in thickness and size, and it is expected that correspondence to a surface mount area array package in which fine pitch will be advanced in the future will be severe.

On the other hand, by using a polyimide film as a film for a surface mount area array package, it is easy to increase the number of pins and to cope with a fine pitch. However, there are many requirements for polyimide films used for surface mount area array packages, such as minimizing dimensional change and curl due to bonding with metal, and high handling properties. The former is required to have a thermal expansion coefficient comparable to that of metal, and the latter is required to have a high elastic modulus. As a polyimide film having such physical properties, "UPILEX" -S manufactured by Ube Industries, Ltd. is listed, and is used in the current market for surface mounting area array packages.

However, when a polyimide film is used for a surface mount area array package, a sharp high temperature rise in a reflow process at the time of chip mounting causes a problem.
There has been a problem that the water in the polyimide film explodes, which causes a so-called popcorn phenomenon.

The popcorn phenomenon causes problems such as peeling of chips and circuits and short-circuiting of solder terminals. In addition, for surface mount area array packages, those with high handling properties are required, so those with a large film thickness are required.
There was also a problem that the popcorn phenomenon became remarkable as the thickness increased.

[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 is a film capable of imparting sufficient handleability as a surface mount type area array package. While maintaining the thickness, the popcorn phenomenon of the polyimide film at the time of chip mounting can be effectively reduced, and it has low water absorption and high water vapor permeability, and also has the same thermal expansion coefficient and high elastic modulus as metal An object of the present invention is to provide a polyimide film for a surface mount area array package.

[0007]

In order to achieve the above object, a polyimide film for a surface mount area array package of the present invention has a water absorption of 2.2% or less and a water vapor transmission rate of 1.5 g. / (M ² · 24h) or more.

Further, the polyimide film for a surface-mounted area array package of the present invention has the following (1) to
It is preferable that the condition (7) is also satisfied. (1) The film thickness is 30 μm or more. (2) The elastic modulus is 4.5 GPa or more. (3) The coefficient of thermal expansion is 24 ppm / ° C. or less. (4) A polyimide containing both a rigid aromatic diamine compound and a flexible aromatic diamine compound as an aromatic diamine component. (5) the aromatic diamine compound having a rigid structure is 10 mol% or more and 90 mol% or less of the total aromatic diamine component;
The flexible structure aromatic diamine compound is at least 10 mol% and at most 90 mol% of the whole aromatic diamine component. (6) The rigid structure aromatic diamine compound is composed of paraphenylenediamine, The aromatic diamine compound is 4,4′-diaminodiphenyl ether;
Any one of 4'-diaminodiphenyl ether and 4,4'-diaminodiphenylmethane or a mixture thereof. (7) Pyromellitic acids and aromatic tetracarboxylic acid compounds having two or more benzene rings as aromatic tetracarboxylic acid compounds Consisting of polyimide containing (8) The pyromellitic acid is 50 mol% or more and 80 mol% or less of the total aromatic tetracarboxylic acid component, and the aromatic tetracarboxylic acid compound having two or more benzene rings is a wholly aromatic tetracarboxylic acid. 20 mol% or more and 50 mol% or less of the components.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The polyimide film for a surface mount type area array package of the present invention will be described in detail below.

In order to prevent the popcorn phenomenon from occurring due to the rapid high temperature rise in the reflow step, it is necessary to reduce the residual moisture in the polyimide film, that is, the film has a water absorption of 2.2% or less and a water vapor transmission rate of Is 1.
It is preferably at least 5 g / (m ² · 24 h).

Further, in order to improve the handling property in the actual process, it is preferable that the elastic modulus is 4.5 GPa or more and the film thickness is 30 μm or more.

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

First, a polyamic acid solution as a precursor for obtaining such a polyimide film will be described.

The polyamic acid solution used in the present invention comprises:
An aromatic diamine component comprising two kinds of aromatic diamine compounds having a rigid structure and an aromatic diamine compound having a flexible structure, and two or more aromatic tetracarboxylic acid compounds having pyromellitic acids and two or more benzene rings. It is obtained by polymerizing an aromatic tetracarboxylic acid component in a solvent.

The polymerization may be carried out by any known method. For example, (1) First, the whole amount of the aromatic diamine component is put into a solvent, and then the aromatic tetracarboxylic acid component is made equivalent to the whole amount of the aromatic diamine component. A method of adding and polymerizing as much as possible.

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

(3) After the aromatic diamine compound having a rigid structure is placed in a solvent, the aromatic tetracarboxylic acid compound is mixed at a ratio of 95 to 105 mol% with respect to the reaction components for a time necessary for the reaction, and then mixed. A method of adding an aromatic diamine compound having a flexible structure, followed by adding an aromatic tetracarboxylic acid compound so that the total aromatic diamine component and the total aromatic tetracarboxylic acid component are substantially equal in amount, and then polymerizing.

(4) After the aromatic tetracarboxylic acid compound is placed in a solvent, the aromatic diamine compound having a rigid structure is mixed in a ratio of 95 to 105 mol% with respect to the reaction components for a time necessary for the reaction. A method of adding an aromatic tetracarboxylic acid compound, followed by adding a flexible aromatic diamine compound such that the total aromatic diamine component and the total aromatic tetracarboxylic acid component are substantially equal in amount and polymerized.

(5) A polyamic acid solution (A) is prepared by reacting an aromatic diamine component having a rigid structure with an aromatic tetracarboxylic acid in a solvent so that either one of them is in excess, and then preparing a flexible structure in another solvent. (A) by reacting the aromatic diamine component with the aromatic tetracarboxylic acid so that either one becomes excessive. A method in which the polyamic acid solutions (A) and (B) thus obtained are mixed to complete the polymerization. In this case, when the polyamic acid solution (A) is adjusted to have an excess of the aromatic diamine component, the polyamic acid solution (B) contains an excessive amount of the aromatic tetracarboxylic acid component, and the polyamic acid solution (A) contains the aromatic tetracarboxylic acid component. When the acid component is excessive, the aromatic diamine component is excessive in the polyamic acid solution (B), and the polyamic acid solutions (A) and (B)
And the total aromatic diamine component and the total aromatic tetracarboxylic acid component used in these reactions are adjusted so as to be substantially equivalent.

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 polyimide gel film is obtained by chemically cyclizing a polyamic acid solution using a cyclization catalyst and a dehydrating agent or by thermal cyclization by heat treatment.

Next, the end of the gel film is fixed,
1.05 to 1.5 in the vertical direction, 1.05 to 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,
Further, it is preferable because the isotropy is improved.

The examples of the rigid aromatic diamine compound used in the present invention include the following compounds.

[0025]

Embedded image (However, X and Y in the formula 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. Among the rigid aromatic diamine compounds having the rigid structure described above, it is particularly preferable to use paraphenylenediamine from the viewpoints of increasing the elastic modulus of the obtained polyimide film, handling, and cost.

Examples of the flexible aromatic diamine compound include the following compounds.

[0027]

Embedded image (However, X and Y in the formula 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 may be the same or different substituents. A represents -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 particularly preferable to use diaminodiphenyl ethers 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 acids include pyromellitic acid or dianhydride thereof, and aromatic tetracarboxylic acids having two or more benzene rings. Examples of the acid compound include 3,3'-4,4'-biphenyltetracarboxylic acid or its dianhydride and 3,3'-4,4'-benzophenonetetracarboxylic acid or its dianhydride. it can.

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, dimethylsulfone, and the like, and these are preferably used alone or in combination.

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

When the obtained polyamic acid is cyclized into a polyimide film, any of a chemical ring closing method of dehydrating using a dehydrating agent and a catalyst and a thermal ring closing method of thermally dehydrating may be used. It is preferable to perform the chemical ring closure method because the resulting polyimide film has a high modulus of elasticity, a low coefficient of thermal expansion, and a chemical etching property.

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 may be used alone or in combination. Is preferred. Examples of the catalyst include heterocyclic tertiary amines such as pyridine, picoline and quinoline, aliphatic tertiary amines such as triethylamine,
Aromatic tertiary amines such as N, N-dimethylaniline and the like can be mentioned, and it is preferable to use these alone or as a mixture.

When the chemical ring closure method is used, a catalyst and a dehydrating agent are mixed into a polyamic acid solution, imidization is performed, and then the solution is coated to obtain a polyimide film. There is a method of obtaining a polyimide film by immersing in a mixture of a catalyst and a dehydrating agent and imidizing the mixture after the reaction.
Although the reason is not clear, the former method is preferable because the water vapor permeability can be increased. The latter method is not preferable because imidization proceeds unevenly in the surface layer of the film, and as a result, the water vapor permeability is reduced.

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 give the obtained polyimide film an adhesive property, the film surface may be subjected to an electrical treatment such as a corona treatment or a plasma treatment or a physical treatment such as a blast treatment. For stabilization, the film may be thermally relaxed by annealing.

The polyimide film thus obtained has characteristics suitable for a surface mount area array package. In other words, it is possible to reduce the popcorn phenomenon by reducing the water content of the polyimide film at the time of chip mounting, and further reduce the dimensional change and curl due to bonding with metal, and a polyimide film having high handling properties. can get.

[0037]

The present invention will be described below in detail with reference to examples.

In Examples, PPD was paraphenylenediamine, 4,4'-ODA was 4,4'-diaminodiphenyl ether, 3,4'-ODA was 3,4'-diaminodiphenyl ether, and PMDA was pyromellitic acid. Anhydride and BPDA represent 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: Leave in a desiccator under a 98% RH atmosphere for 2 days,
Evaluation was made in terms of% by weight relative to the dry weight. (2) Water vapor permeability Measured at 40 ° C. and 90% RH according to the method B (infrared sensor method) of JIS K7129. (3) Film thickness The film thickness was measured using a lightmatic manufactured by Mitutoyo (Series 318). (4) Elastic modulus Equipment: Using RTM-250, tensile speed: 100 mm
/ Min. (5) Coefficient of thermal expansion Equipment: Use TMA-50, measurement temperature range: 50 to 2
The measurement was performed under the conditions of 00 ° C. and a heating rate of 10 ° C./min. (6) Evaluation of popcorn A three-layer laminate in which a polyimide film was copper-clad with an adhesive (epoxy) was prepared, immersed in water at room temperature for 2 days, and then heated at 250 ° C. For each level, the number of N was 20, and popcorn evaluation was performed based on the number of pieces where foaming occurred. [Example 1] DMA was placed in a 500 ml separable flask.
239.1 g of cPD and 1.552 g of PPD
(0.0144 mol) and 3.068 g (0.0
141 mol) and reacted at normal temperature and normal pressure for 1 hour. Next, 25.862 g of ODA (0.1292
Mol) and stirred until uniform, then BPDA
8.445 g (0.0287 mol) was added and reacted for 1 hour. Then, here, PMDA21.974g
(0.1007 mol) was added, and the mixture was further reacted for 1 hour to obtain a polyamic acid solution.

In this polymerization, the molar ratio of each raw material added was as follows:
The operation was performed at the ratio shown in Table 1, and the total weight of the solid contents was adjusted to 60.9 g. After 15 g of this polyamic acid solution was taken and cooled at minus 5 ° C., 1.5 g of acetic anhydride and 1.6 g of β-picoline were mixed to imidize the polyamic acid.

The thus obtained polyimide polymer 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 end of the gel film was pinned. Then, the film was stretched 1.1 times in the vertical direction and 1.3 times in the horizontal direction. Then 300
The resultant was dried by heating at 20 ° C. for 20 minutes and subsequently at 400 ° C. for 5 minutes to obtain a polyimide film having a thickness of 50 μm.

Table 1 shows the results of evaluation of each characteristic of the polyimide film. [Example 2] The film thickness of the polyimide film was 75 μm.
The procedure was performed in the same manner as in Example 1 except that the value was adjusted to m, and the physical property evaluation results of the obtained polyimide film are also shown in Table 1. [Examples 3 to 8] In the same procedure as in Example 1, the aromatic diamine component and the aromatic tetracarboxylic acid component were changed to the ratios shown in Table 1, and polyamic acid solutions were obtained, respectively.
The procedure for obtaining a polyimide film from the polyamic acid solution was performed in the same manner as in Example 1.
The thickness was adjusted as shown in FIG.

The results of evaluation of the properties of each of the obtained polyimide films are also shown in Tables 1 and 2.

[0044]

[Table 1]

[0045]

[Table 2] [Comparative Example 1] Table 3 shows the results of evaluating each property using "UPILEX" -50S manufactured by Ube Industries, Ltd. [Comparative Example 2] The results of evaluating each property using "UPILEX" -75S manufactured by Ube Industries, Ltd. are shown in Table 3.

[0046]

[Table 3]

[0047]

As described above, the polyimide film of the present invention has a water absorption of 2.2% or less, a water vapor transmission rate of 1.5 g / (m ² · 24 h) or more, and a film thickness of 30 μm. As described above, since the modulus of elasticity is 4.5 GPa or more and the thermal expansion coefficient is 24 ppm / ° C. or less, the popcorn phenomenon can be reduced by reducing the water content of the polyimide film at the time of chip mounting. Since the dimensional change rate and the curl can be reduced and the handling property is high, it can be suitably used for a surface mount area array package.

Claims (9)

[Claims] 1. A polyimide film for a surface-mounted area array package, having a water absorption of 2.2% or less and a water vapor transmission rate of 1.5 g / (m ² · 24 h) or more. 2. The polyimide film for a surface mount area array package according to claim 1, wherein the film thickness is 30 μm or more. 3. The polyimide film for a surface mount area array package according to claim 1, wherein the elastic modulus is 4.5 GPa or more. 4. The polyimide film for a surface mount area array package according to claim 1, wherein the polyimide film has a coefficient of thermal expansion of 24 ppm / ° C. or less. 5. A polyimide comprising both an aromatic diamine compound having a rigid structure and an aromatic diamine compound having a flexible structure as an aromatic diamine component.
5. The polyimide film for a surface-mounted area array package according to any one of items 4 to 4. 6. The aromatic diamine compound having a rigid structure is 10 mol% or more and 90 mol% or less of the total aromatic diamine component, and the aromatic diamine compound having a flexible structure is 10 mol% of the total aromatic diamine component. The polyimide film for a surface mount area array package according to claim 5, wherein the content is 90 mol% or less. 7. The aromatic diamine compound having a rigid structure is composed of paraphenylenediamine, and the aromatic diamine compound having a flexible structure is composed of 4,4′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether, and 4,4 ′.
7. The polyimide film for a surface-mounted area array package according to claim 5, wherein the polyimide film is any one or a mixture of diaminodiphenylmethane. 8. 8. The polyimide according to claim 5, wherein the aromatic tetracarboxylic acid compound is a polyimide containing pyromellitic acids and an aromatic tetracarboxylic acid compound having two or more benzene rings. 4. The polyimide film for a surface mount area array package according to item 1. 9. The method wherein the pyromellitic acid accounts for 50 mol% or more and 80 mol% or less of the total aromatic tetracarboxylic acid component, and the aromatic tetracarboxylic acid compound having two or more benzene rings is a wholly aromatic tetracarboxylic acid compound. The polyimide film for a surface-mounted area array package according to claim 8, wherein the content of the carboxylic acid component is 20 mol% or more and 50 mol% or less.