JPH08231717A - Flexible circuit substrate - Google Patents

Abstract

PURPOSE: To obtain a flexible circuit substrate material, comprising a thermal oxidation-resistant polyimide film and a metallic thin film, excellent in high- temperature durability in adhesion of the film to the thin film and further flexibility, etc., and useful as semiconductor IC chips, etc. CONSTITUTION: This flexible printed circuit substrate comprises (A) a thermal oxidation-resistant polyimide film, comprising preferably (i) an aromatic diamine and (ii) an aromatic acid dianhydride and having carbonyl and an ether in the chemical structure and (B) a metallic thin film having preferably 10-3000nm, more preferably 100-500nm thickness. Furthermore, the thin film of the component (B) is preferably a copper film and a copper layer is preferably formed on at least one surface of the film of the component (A) preferably by a sputtering method. The component (A) preferably has a recurring unit of formula I (X and Y are each 0 or CO; X is not equal to Y), preferably e.g. a recurring unit of formula II.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a material for a flexible circuit board composed of a polyimide film and a metal thin film, and more particularly to a material for a flexible board which has excellent adhesiveness between the metal thin film and the polyimide film at high temperature.

[0002]

2. Description of the Related Art A flexible circuit board having a metal film formed on an insulating polymer film has a film thickness of about 10 μm.
The above-mentioned metal film and polymer film may be joined with an adhesive, but the thermal properties of the adhesive are inferior to the performance of the polymer film and the thickness of the metal film is 10 μm.
Since it is thick as described above, there are problems that it cannot be applied to high-density wiring in the semiconductor industry, that dimensional stability is poor, and that the product has a warp, because it is difficult to perform fine processing of several tens of μm. In order to solve this, a technique of forming a metal film without an adhesive has been studied. This is a method of forming a circuit pattern after forming a metal thin film by a thin film forming method such as vacuum deposition and sputtering. In this material, since the metal thin film is as thin as 1 μm or less, fine processing with a width of several tens of μm is easy.

That is, this is a technique for forming a finely processed conductor by further depositing and growing a metal by electrolytic plating or the like based on the circuit pattern formed as described above. Note that the latter technique is a technique that enables high-density wiring in the semiconductor industry, but there has been a problem of a decrease in adhesive force in a post process such as a circuit forming process and an electrolytic plating process. In JP-A-02-98994, a chromium layer having a thickness of 0.01 to 5 μm is formed by sputtering, and in JP-A-62-181488, it is 5-1000.
nm nickel layer or nickel-chromium layer by vapor deposition, JP-A-62-62551 discloses a chromium layer by vapor deposition, and JP-B-57-18357 discloses nickel, cobalt, zirconium, Techniques such as forming a metal layer of palladium or the like by an ion plating method and forming a nickel or nickel-containing alloy layer by an inoplating method have been already proposed in Japanese Patent Publication No. 57-18356.

However, although these known techniques have been partially successful, they are still unsatisfactory in performance as materials for enabling high-density wiring in the semiconductor industry, which is a hindrance to practical use. Was there. That is,
The problem of the metal layer peeling from the polyimide film was partially solved in the circuit pattern formation process using lithography technology and the electrolytic plating process of laminating the metal layer on the formation pattern for lowering the conduction resistance and improving the mechanical strength. However, sufficient performance could not be achieved in the heat resistance, which is the original characteristic of the flexible circuit board composed of the metal layer / polyimide film. For example, 15 in the air
There has been a problem that the adhesiveness between the metal layer and the polyimide film is remarkably lowered only by keeping the temperature at about 0 ° C. for 24 hours.

[0005]

Therefore, the inventors of the present invention have made a diligent investigation into the cause of the decrease in adhesiveness and found that the reactive gas passing through the polyimide film affects the adhesiveness. It has been found that a decrease in adhesiveness can be prevented by providing a gas barrier layer for blocking passing gas (Japanese Patent Laid-Open No. 06-2.
9634). As a result, it has been possible to obtain a flexible circuit board material composed of a metal layer / polyimide film that can be put to practical use in the semiconductor industry having the harsh process as described above. As a specific example, as a gas barrier layer, a substantially silicon oxide layer is formed on one surface of a polyimide film by plasma chemical vapor deposition (P-CVD) using tetramethyldisiloxane and oxygen as raw materials. A method of forming a ~ 300 nm thickness has been disclosed. It has been found that such a method dramatically improves the gas barrier property of the film, and thus also suppresses the deterioration of high temperature strength. However, a new problem was encountered in that some samples obtained by subjecting such a film to secondary processing such as bending and cutting show a decrease in adhesiveness when subjected to a heating test.

[0006]

The present inventors believe that the reactive gas that permeates through the polyimide film reacts with the metal layer in contact with the polyimide surface to partially generate a metal oxide. It was presumed that the thing is the main cause of peeling, but it was found that the polyimide layer in contact with the metal layer was also oxidized by the metal layer as a catalyst, and if the polyimide is a structure that is difficult to oxidize, from the metal polyimide film It has been found that the peeling off of is completely suppressed.

That is, the present invention is (1) a flexible circuit board material comprising a heat-resistant oxidation resistant polyimide film and a metal thin film, and (2) a heat-resistant oxidation resistant polyimide film comprising an aromatic diamine and an aromatic acid diamine. A polyimide synthesized from an anhydride, which is a flexible circuit board material according to (1) having a carbonyl group and an ether group in its chemical structure, and (3) on at least one surface of a heat-resistant oxidation-resistant polyimide film. Copper layer is formed on (1)
Alternatively, the flexible circuit board material according to (2), and (4) the copper layer formed on at least one surface of the heat-resistant oxidation-resistant polyimide film is formed by a sputtering method (1) to (3). The flexible circuit board material according to any one of (1) to (5), and (5) the general formula (1)

[0008]

Embedded image The flexible circuit board material according to any one of (1) to (4), which is formed by using the heat-resistant oxidation-resistant polyimide having the repeating unit shown in (6) and (2).
[Chemical 9]

[0009]

[Chemical 9] The flexible circuit board material according to (5), which is formed by using a heat-resistant oxidation-resistant polyimide having a repeating unit represented by the formula (7), and also has a formula (7) (3)

[0010]

[Chemical 10] A flexible circuit board material according to (5), which is formed by using a heat-resistant oxidation-resistant polyimide having a repeating unit represented by the formula (8), formula (4)

[0011]

[Chemical 11] A flexible circuit board material according to (5), which is formed by using a heat-resistant oxidation-resistant polyimide having a repeating unit represented by the formula (5)

[0012]

[Chemical 12] The flexible circuit board material according to (5), which is formed by using the heat-resistant oxidation-resistant polyimide having the repeating unit represented by the formula (10), and also has the formula (10) (6)

[0013]

[Chemical 13] The flexible circuit board material according to (5), which is formed by using the heat-resistant oxidation-resistant polyimide having the repeating unit represented by the formula (11), and also has the formula (11) (7)

[0014]

Embedded image The flexible circuit board material according to (5), which is formed by using the heat-resistant oxidation-resistant polyimide having the repeating unit shown in FIG.

The term "heat-resistant oxidation resistant polyimide film" as used herein refers to a film in which an ether group serving as an electron donor and a carbonyl group serving as an electron acceptor are present in the repeating unit of the polyimide molecule and thus have an electron balance.
This ether group and carbonyl group are Charge Transfer Com
By forming a plex (CT-complex), it is considered that it has heat-resistant oxidation resistance (Japanese Patent Laid-Open No. 05-279477).
S.Tamai et.al., Int, SAMPE Tech.Conf, Vol.26,365 (199
4), BV Kotov, Polym . Sci. USSR, 19, 711 (1977).).

First, referring to the attached drawings, FIG.
3 to 3 show one embodiment of the material for a flexible circuit board of the present invention, 1 is an oxidation resistant polyimide film, 2 and 2'are metal thin films, 3 is a circuit metal film such as a circuit copper film. Is shown.

The present invention will be described below with reference to these drawings. That is, the present invention is basically a heat resistant oxidation resistant polyimide film 1 shown in FIG. 1 and a flexible circuit board material in which a metal thin film 2 is formed on the main surface of the polyimide film.

The flexible circuit board material in the present invention is not limited to the one in which the metal thin film 2 is laminated on one surface of the heat resistant oxidation resistant polyimide film 1 as described above, but the metal thin film 2 ', the heat resistant oxidation resistance as shown in FIG. It goes without saying that a multilayer thin film laminated on both surfaces such as the polyimide film 1 and the metal thin film 2 is also included. It goes without saying that the metal thin films 2 and 2'may be made of different metals.

Copper is generally used as the metal for 2 or 2 ', but aluminum, silver, gold and the like can be used, but the metal is not limited thereto. Further, as shown in FIGS. 2 and 3, a circuit metal film 3, for example, a circuit copper film may be further formed on the metal thin film 2 to form a multilayer metal thin film.

The thickness of such a metal layer is preferably 10 to 3000 nm, more preferably 100 to 500 nm, as long as it can maintain the adhesion to the polyimide layer. If the film thickness is too thin, there may be a part where the metal is laminated and a part where the metal is not laminated, that is, there is a problem in the uniformity of the metal thin film, and if it is too thick, it takes time to form the metal thin film layer. However, it is not preferable in terms of production efficiency.

For forming the metal thin film, not only a dry forming method such as a vacuum deposition method, an ion plating method, a sputtering method and a CVD method but also a wet thin film forming method such as an immersion method and a printing method can be used. . The sputtering method, which is excellent in the adhesiveness of the thin film and the controllability of the thin film, is a particularly preferable method. There is no particular limitation on the sputtering method. It is understood by those skilled in the art that a target is appropriately selected and used according to the thin film to be formed. The sputtering method is also not limited, and methods such as DC magnetron sputtering, high frequency magnetron sputtering, and ion beam sputtering are effectively used.

The case of using copper for the metal thin film layer will be described in more detail. A copper thin film is formed on the main surface of the heat resistant oxidation resistant polyimide by the DC magnetron sputtering method using argon gas.

The copper thin film is a material for forming a circuit, which can be easily understood by those skilled in the art. More specifically, the copper thin film is preferably made of copper having a purity of 99.99% or more. The copper thin film is more preferably formed to a film thickness of 100 nm or more, but the present invention is a flexible circuit board, and a circuit is usually formed through a plating step and a soldering step rather than being used as it is. In consideration of these subsequent steps, the film thickness is preferably 200 nm or more in order to facilitate circuit processing.

The thickness of the heat-resistant oxidation-resistant polyimide film is not particularly limited, but is usually 25 μm to 125 μm.
A polyimide film having a film thickness of is appropriately selected and used according to the application. The heat-resistant oxidation-resistant polyimide film is a polyimide synthesized from an aromatic diamine and an aromatic dianhydride, in which a carbonyl group and an ether group are present in the polyimide repeating structure, and the electron transfer is well balanced. Used.

As a concrete example, for example, 3,
3'-diaminobenzophenone (3,3'-diaminobenzophe
none) and 3,3 ', 4,4'-diphenylether tetracarboxylic dianhydride (3,3', 4,4'-diphenylether tetr
Polyimide of repeating unit shown in Formula (1) synthesized from acarboxylic dianhydride, or 3,3'-
Diaminodiphenyl ether (3,3'-diaminodiphenylet
her) and 3,3 ', 4,4'-benzophenone tetracarboxylic dianhydride (3,3', 4,4'-benzophenone tetracarb
The polyimide of the repeating unit represented by the formula (2) synthesized from oxy dianhydride, and the ones represented by the formulas (3) to (7) can be mentioned, but the invention is not limited thereto. These polyimides are used after being formed into a film by a casting method, for example.

[0026]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to the following examples. Example 1 A polyimide film of a repeating unit represented by the formula (2) having a film thickness of 50.0 μm was used, and the surface of the polyimide film was treated with oxygen glow discharge on one surface of the polyimide film, and then copper was used as a target. , Thickness 250n by DC magnetron sputtering method with argon gas
m copper thin film layer was formed. Next, the thickness of the copper film for the circuit is reduced to 2 by subjecting the copper thin film to electrolytic plating of copper.
It was set to 0 μm. When the adhesive strength of the circuit copper film obtained by such a method to the polyimide film was measured, the average strength in normal state was 0.8 kg / cm on average. This was put in an oven at 150 ° C. and kept for 10 days, and then the adhesive strength was measured in the same manner. As a result, the average adhesive strength was 1.2 kg / cm, and the adhesive strength increased by 50.0% to 1.0 kg / cm. It was confirmed that the high adhesive strength was exceeded. On the other hand, before being placed in an oven at 150 ° C., the film was wrapped around a stainless steel rod having a diameter of 10 mm, 5 times each on the front and back sides, a total of 10 times, and then placed in an oven at 150 ° C. and held for 10 days.
Similarly, when the adhesive strength was measured, the average was 1.2 kg / cm.
Even in this case, it was confirmed that the adhesive strength increased by 50.0% and the high adhesive strength exceeding 1.0 kg / cm was maintained.

Example 2 A polyimide film of repeating unit represented by the formula (3) having a film thickness of 50.0 μm was used, and the surface of the polyimide film was treated by glow discharge of oxygen on one surface of the polyimide film. As a target, a 250 nm-thick copper thin film layer was formed by a DC magnetron sputtering method using argon gas. Next, the thickness of the circuit copper film was set to 20 μm by electrolytically plating copper on the copper thin film. When the adhesive strength of the circuit copper film obtained by such a method to the polyimide film was measured, the average strength was 0.9 kg / cm on average. This was placed in an oven at 150 ° C. and kept for 10 days, and then the adhesive strength was measured in the same manner, averaging 1.1 kg /
cm, the adhesive force increased by 22.2%, 1.0 kg /
It was confirmed that a high adhesive force exceeding cm was maintained. On the other hand, before putting the film in an oven at 150 ° C., put the film on a stainless steel rod having a diameter of 10 mm, 5 times each on the front and back.
After wrapping it 0 times, put it in an oven at 150 ° C for 10
After holding for a day, the adhesive strength was similarly measured and found to be 1.1 kg / cm on average, and in this case as well, the adhesive strength increased by 22.2%, and the high adhesive strength exceeding 1.0 kg / cm was maintained. Confirmed to do.

(Example 3) A polyimide film having a film thickness of 50.0 µm, which is a repeating unit represented by the formula (4), was used. On one surface of the polyimide film, the surface of the polyimide film was treated by glow discharge of oxygen, and then copper was used. As a target, a 250 nm-thick copper thin film layer was formed by a DC magnetron sputtering method using argon gas. Next, the thickness of the circuit copper film was set to 20 μm by electrolytically plating copper on the copper thin film. When the adhesive strength of the circuit copper film obtained by such a method to the polyimide film was measured, the average strength was 0.9 kg / cm on average. This was placed in an oven at 150 ° C. and kept for 10 days, and then the adhesive strength was measured in the same manner, averaging 1.2 kg /
cm, the adhesive force increased by 25.0%, 1.0 kg /
It was confirmed that a high adhesive force exceeding cm was maintained. On the other hand, before putting the film in an oven at 150 ° C., put the film on a stainless steel rod having a diameter of 10 mm, 5 times each on the front and back.
After wrapping it 0 times, put it in an oven at 150 ° C for 10
After keeping for a day, the adhesive strength was measured in the same manner, averaging 1.2 kg / cm, and even in this case, the adhesive strength increased by 25.0%, and the high adhesive strength exceeding 1.0 kg / cm was maintained. Confirmed to do.

Example 4 A polyimide film of a repeating unit represented by the formula (5) having a film thickness of 50.0 μm was used, and the surface of the polyimide film was treated with glow discharge of oxygen on one surface of the polyimide film, followed by copper. As a target, a 250 nm-thick copper thin film layer was formed by a DC magnetron sputtering method using argon gas. Next, the thickness of the circuit copper film was set to 20 μm by electrolytically plating copper on the copper thin film. When the adhesive strength of the copper film for a circuit obtained by such a method to the polyimide film was measured, the average strength in normal state was 1.0 kg / cm on average. This was placed in an oven at 150 ° C. and kept for 10 days, and the adhesive strength was measured in the same manner.
cm, the adhesive force increased by 23.1%, 1.0 kg /
It was confirmed that a high adhesive force exceeding cm was maintained. On the other hand, before putting the film in an oven at 150 ° C., put the film on a stainless steel rod having a diameter of 10 mm, 5 times each on the front and back.
After wrapping it 0 times, put it in an oven at 150 ° C for 10
When the adhesive strength was measured in the same manner after being kept for a day, the average was 1.3 kg / cm, and in this case also, the adhesive strength increased by 23.1%, and the high adhesive strength exceeding 1.0 kg / cm was maintained. Confirmed to do.

(Example 5) A polyimide film having a film thickness of 50.0 µm, which is a repeating unit represented by the formula (6), was used. On one surface of the polyimide film, the surface of the polyimide film was treated by glow discharge of oxygen. As a target, a 250 nm-thick copper thin film layer was formed by a DC magnetron sputtering method using argon gas. Next, the thickness of the circuit copper film was set to 20 μm by electrolytically plating copper on the copper thin film. When the adhesive strength of the copper film for a circuit obtained by such a method to the polyimide film was measured, the average strength in normal state was 0.7 kg / cm on average. This was placed in an oven at 150 ° C. and kept for 10 days, and then the adhesive strength was measured in the same manner, averaging 1.1 kg /
cm, the adhesive force increased by 36.4%, 1.0 kg /
It was confirmed that a high adhesive force exceeding cm was maintained. On the other hand, before putting the film in an oven at 150 ° C., put the film on a stainless steel rod having a diameter of 10 mm, 5 times each on the front and back.
After wrapping it 0 times, put it in an oven at 150 ° C for 10
After holding for a day, the adhesive strength was measured in the same manner and found to be 1.1 kg / cm on average, and in this case also, the adhesive strength increased by 36.4%, and the high adhesive strength exceeding 1.0 kg / cm was maintained. Confirmed to do.

Example 6 A polyimide film having a repeating unit represented by the formula (7) having a film thickness of 50.0 μm was used, and the surface of the polyimide film was treated by glow discharge of oxygen on one surface of the polyimide film, followed by copper. As a target, a 250 nm-thick copper thin film layer was formed by a DC magnetron sputtering method using argon gas. Next, the thickness of the circuit copper film was set to 20 μm by electrolytically plating copper on the copper thin film. When the adhesive strength of the copper film for a circuit obtained by such a method to the polyimide film was measured, the average strength in normal state was 0.7 kg / cm on average. This was placed in an oven at 150 ° C. and kept for 10 days, and then the adhesive strength was measured in the same manner, averaging 1.2 kg /
cm, the adhesive force increased by 41.7%, 1.0 kg /
It was confirmed that a high adhesive force exceeding cm was maintained. On the other hand, before putting the film in an oven at 150 ° C., put the film on a stainless steel rod having a diameter of 10 mm, 5 times each on the front and back.
After wrapping it 0 times, put it in an oven at 150 ° C for 10
After holding for a day, the adhesive strength was measured in the same manner and found to be 1.2 kg / cm on average, and even in this case, the adhesive strength increased by 41.7%, and the high adhesive strength exceeding 1.0 kg / cm was maintained. Confirmed to do.

(Comparative Example 1) A Kapton film (manufactured by DuPont) having a film thickness of 50.8 μm was used. On one side of this, the surface of the polyimide film was treated by glow discharge of oxygen, and then copper was used as a target for argon. A 250 nm-thick copper thin film layer was formed by a gas DC magnetron sputtering method. Next, the thickness of the circuit copper film is reduced to 20 μm by electrolytically plating copper on the copper thin film.
And When the adhesive strength of the circuit copper film obtained by such a method to the polyimide film was measured, the average strength in normal state was 1.2 kg / cm. This was put in an oven at 150 ° C. and kept for 10 days, and then the adhesive strength was measured in the same manner. As a result, the decrease was remarkable, and it was 0.01 kg / cm or less.

[0033]

As is apparent from the above Examples and Comparative Examples, the present invention not only sufficiently satisfies the thermal oxidation resistance for realizing the high integration of the semiconductor IC chip, but also the film. The present invention provides a technique for a material for a flexible circuit board, which exhibits excellent characteristics in terms of flexibility, which makes the most of the characteristics described above, and is an extremely useful invention for the semiconductor industry.

[Brief description of drawings]

FIG. 1 is a layer structure of an embodiment of a material for a flexible circuit board of the present invention.

FIG. 2 is a layer structure of an embodiment of the material for a flexible circuit board of the present invention.

FIG. 3 is a layer structure of one embodiment of the material for a flexible circuit board of the present invention.

[Explanation of symbols]

 1 Oxidation-resistant polyimide film 2 Metal thin film 2'Metal thin film 3 Metal film for circuits such as copper film for circuits

 ─────────────────────────────────────────────────── (72) Inventor Yoshinori Ashida 1190 Kasama-cho, Sakae-ku, Yokohama-shi, Kanagawa Mitsui Toatsu Chemical Co., Ltd. (72) Nobuhiro Fukuda 1190 Kasama-cho, Sakae-ku, Yokohama, Kanagawa Mitsui Toatsu Kagaku (72) Inventor Shoji Tamai, 1190 Kasama-cho, Sakae-ku, Yokohama-shi, Kanagawa Mitsui Toatsu Chemical Co., Ltd. (72) Wataru Yamashita 1190, Kasama-cho, Sakae-ku, Yokohama-shi, Kanagawa Mitsui Toatsu Chem., Ltd. ( 72) Inventor Akihiro Yamaguchi 1190 Kasama-cho, Sakae-ku, Yokohama-shi, Kanagawa Mitsui Toatsu Chemical Co., Ltd.

Claims (11)

[Claims] 1. A flexible circuit board material comprising a heat resistant oxidation resistant polyimide film and a metal thin film. 2. The flexible circuit board according to claim 1, wherein the heat-resistant oxidation-resistant polyimide film is a polyimide synthesized from aromatic diamine and aromatic dianhydride, and has a carbonyl group and an ether group in its chemical structure. material. 3. The flexible circuit board material according to claim 1, wherein a copper layer is formed on at least one surface of the heat resistant oxidation resistant polyimide film. 4. The flexible circuit board material according to claim 1, wherein the copper layer formed on at least one surface of the heat resistant oxidation resistant polyimide film is formed by a sputtering method. 5. The general formula (1) [Chemical formula 1] The flexible circuit board material according to any one of claims 1 to 4, wherein the flexible circuit board material is formed by using a heat-resistant oxidation-resistant polyimide having a repeating unit shown in. 6. Formula (2) [Chemical Formula 2] [Chemical Formula 2] The flexible circuit board material according to claim 5, wherein the flexible circuit board material is formed by using a heat-resistant oxidation resistant polyimide having a repeating unit represented by. 7. Formula (3) [Chemical Formula 3] [Chemical Formula 3] The flexible circuit board material according to claim 5, wherein the flexible circuit board material is formed by using a heat-resistant oxidation resistant polyimide having a repeating unit represented by. 8. Formula (4) [Chemical Formula 4] [Chemical Formula 4] The flexible circuit board material according to claim 5, wherein the flexible circuit board material is formed by using a heat-resistant oxidation resistant polyimide having a repeating unit represented by. 9. Formula (5) [Chemical Formula 5] [Chemical Formula 5] The flexible circuit board material according to claim 5, wherein the flexible circuit board material is formed by using a heat-resistant oxidation resistant polyimide having a repeating unit represented by. 10. Formula (6) [Chemical Formula 6] [Chemical Formula 6] The flexible circuit board material according to claim 5, wherein the flexible circuit board material is formed by using a heat-resistant oxidation resistant polyimide having a repeating unit represented by. 11. Formula (7) [Chemical Formula 7] [Chemical Formula 7] The flexible circuit board material according to claim 5, wherein the flexible circuit board material is formed by using a heat-resistant oxidation resistant polyimide having a repeating unit represented by.