JPH11117060A - Metal clad polyimide substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a metal clad polyimide substrate improved in the adhesion property between a polyimide film and a first metallic layer by optimizing the molecular structure of a denatured polyimide layer, in a method for forming the denatured polyimide layer on the surface of the polyimide film by a surface reforming treatment. SOLUTION: This substrate is constituted by forming plural layers of the metallic layers without interposing adhesives on at least one surface of the polyimide film and forming the first metallic layer in contact with the polyimide film among these metallic layers by a dry process plating method. The substrate described above is constituted by forming the denatured polyimide layer having the molecular structure obtd. by adding at least one hydroxyl group to a benzene ring bonded with the carboxyl group formed by ring opening of an imide ring and the nitrogen of the imide ring and/or the nitrogen of a second amide formed by ring opening of the imide group on the surface layer part of the polyimide film in contact with the first metallic layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a printed wiring board,
The present invention relates to a metal-coated polyimide substrate used as a material for electronic components such as a flexible printed board and a TAB tape.

[0002]

2. Description of the Related Art Polyimide resin (hereinafter, simply referred to as "polyimide") has excellent heat resistance, and its mechanical, electrical, and chemical properties are comparable to those of other plastic materials. Polyimide film processed to be very thin is, for example, printed wiring board (PWB),
It is widely used as a material for an insulating substrate of electronic components such as a flexible printed circuit board (FPC) and a tape for automatic tape bonding (TAB tape). Such PWB,
The FPC or TAB tape is obtained by processing a metal-coated polyimide substrate in which one or both surfaces of a polyimide film is mainly coated with a copper foil as a metal conductor layer.

The above-mentioned metal-coated polyimide substrate includes a so-called three-layer substrate in which a polyimide film and a metal foil are bonded via an adhesive layer, and a so-called two-layer substrate in which a metal layer is formed directly on the polyimide film without using an adhesive. There is a two-layer substrate. At present, a two-layer substrate, which has high reliability of a bonding interface and can freely set the thickness of a polyimide film and a metal layer, has attracted attention.

[0004] In such a two-layer substrate, an electroplating method that can easily form a thick metal conductor layer is employed. However, since it is impossible to apply the above-mentioned metal plating directly to the surface of the polyimide film, generally, a dry plating method such as vacuum evaporation, sputtering, ion plating or electroless plating is performed so that electroplating is possible. A method of forming a first metal layer by a wet plating method such as a method, and then forming a second or later conductive metal layer on the outer surface thereof has been adopted.

[0005]

However, when a dry plating method is used to form the first metal layer, the adhesion between the first metal layer and the polyimide film becomes insufficient, and the adhesion between the first metal layer and the polyimide film becomes poor. It was not preferable because it was an important factor related to reliability. Therefore, recently, the surface of the polyimide film before applying the dry plating is plasma, corona discharge,
Or a method of improving the adhesion of metal by dry plating by performing a surface modification treatment using a chemical or the like to alter the molecular structure of the polyimide surface layer portion and forming a so-called altered polyimide layer, Up to now, this method has not been able to form a first metal layer having sufficiently satisfactory adhesion.

The present invention provides a method for forming a deteriorated polyimide layer on the surface of a polyimide film by the above-mentioned surface modification treatment, wherein the molecular structure of the deteriorated polyimide layer is optimized so that the adhesion between the polyimide film and the first metal layer is improved. The first metal layer having a bonding strength of 1.0 kgf / cm or more with a 90 ° peel (peeling in the 90 ° direction) required for PWB, FPC, TAB tape, etc. is coated by dry plating. It is an object of the present invention to provide a metal-coated polyimide substrate adhered thereto.

[0007]

The present inventors have conducted intensive studies on the relationship between the molecular structure of the deteriorated polyimide layer and the adhesion of the first metal layer by dry plating in order to achieve the above object. The inventors succeeded in finding a modified polyimide molecular structure capable of improving the adhesion of the first metal layer, and completed the present invention.

That is, in order to achieve the above object, the present invention provides a method for forming a plurality of metal layers on at least one surface of a polyimide film without using an adhesive, and contacting the polyimide film among the metal layers. In a substrate on which a first metal layer is formed by a dry plating method, a carboxyl group formed by opening of an imide ring and a nitrogen and / or imide of an imide ring are formed on a surface layer of a polyimide film in contact with the first metal layer. A metal-coated polyimide substrate comprising a modified polyimide layer having a molecular structure in which at least one hydroxyl group is added to a benzene ring bonded to the nitrogen of a secondary amide formed by ring opening, and is there.

[0009]

Next, details of the present invention will be described. The polyimide film used as the insulating substrate material in the present invention is not particularly limited, but for example, Kapton HN, VN and EN (trade name of Du Pont-Toray Co., Ltd.), NPI (trade name of Kanefuchi Chemical Co., Ltd.) And a commercially available cured polyimide film such as Upilex S (trade name, manufactured by Ube Industries, Ltd.), which has a basic skeleton represented by the following chemical formula 1.

Embedded image [Where R ₁ is the following chemical formula 2 or 3

Embedded image

Embedded image R ₂ has the following chemical formula 4 or no bonding group

Embedded image It is represented by ]

The modified polyimide layer of the present invention formed on the surface layer by subjecting these commercially available polyimide films to a surface modification treatment is formed by opening an imide ring as exemplified by the following chemical formula 5. Carboxyl group (-COO
H) and at least one hydroxyl group (-OH) is added to the benzene ring bonded to the nitrogen of the imide ring and / or the nitrogen of the secondary amide (N-H) formed by opening of the imide ring. It has a molecular structure. In addition, what was illustrated in Chemical Formula 5 is a case where one hydroxyl group was added,
Those having two or more hydroxyl groups are also included in the scope of the present invention.

Embedded image [Where R ₁ is the following chemical formula 6 or 7

Embedded image

Embedded image R ₂ has the following formula 8 or no bonding group:

Embedded image It is represented by ]

Since the carboxyl group and the hydroxyl group in the deteriorated polyimide layer formed on the surface layer of the polyimide film have a strong bond with the metal atoms of the first metal layer formed by the dry plating method, the first metal layer 90 °
It is estimated that the peel strength was able to provide a high bonding strength of 1.0 kgf / cm or more. In addition, “Polymer Science, A. Polymer Chemistry (J. of Polymer)
r Science: part A Polymer
Chemistry) ", Vol. 30, Nos. 1425-143
On page 1 (1992), a modified polyimide layer in which only a carboxyl group is formed by opening of an imide ring is described, but with such a structure, high adhesion to a metal layer may be obtained. It proved difficult.

Next, a method for specifying the molecular structure of the deteriorated polyimide layer according to the present invention will be described. X-ray photoelectron spectroscopy (XPS) was used to analyze the molecular structure. FIGS. 1A and 2 show the C1s spectra of carbon of the polyimide film (using Kapton VN) before the surface modification treatment and the deteriorated polyimide layer after the surface modification treatment by XPS, respectively.
(A). In addition, the molecular structural formula before the surface modification treatment and the molecular structural formula considered to be changed after the surface modification treatment are shown in FIG. 1B and FIG. 2 (b). Further, Table 1 shows the intensity ratio of the peak area obtained by separating the peaks from the measured spectrum and the intensity ratio obtained by calculation from the molecular structural formula.

[0013]

[Table 1] (%) 測定 Measured value from spectrum From molecular structure Calculated value before processing After processing Before processing Before processing ─────────────────────────────────── Peak α 36.0 31.0 36.4 31.8 Peak β 37.0 28.7 36.4 27.3 Peak χ 11.0 14.4 9.1 13.6 Peak ε-10.5-9 .1 peak δ 16.0 10.3 18.2 13.6 peak φ-5.1-4.5 ───────────

In XPS, the molecular structure can be analyzed by utilizing the fact that the peak position of the C1s spectrum is shifted depending on the chemical state of carbon. That is, 22 carbons in a single molecular structural unit of the polyimide film (Kapton VN) before the surface modification treatment are classified into four according to their chemical states, and the intensity ratio of peak areas obtained by peak separation, It can be seen that the intensity ratio obtained from the molecular structure agrees well as shown in Table 1. In addition, when the polyimide film after the surface modification treatment was analyzed by the same method, the peak area intensity ratio obtained by measurement and the peak area intensity ratio obtained by calculation were similarly calculated in the molecular structure represented by Chemical Formula 2 as shown in Table 1. And the intensity ratio well matched. Further, from the results of semi-quantitative analysis of carbon, nitrogen and oxygen by XPS, as shown in Table 2, it can be seen that the measured values and calculated values in these molecular structures are in good agreement.

[0015]

(Table 2) (at%) 測定 Measured value from spectrum Molecular structure Calculated value from Before processing After processing Before processing After processing ────────────────────────────────── {Carbon 76.6 71.5 75.9 71.0 Nitrogen 6.4 5.7 6.9 6.4 Oxygen 17.0 22.8 17.2 22.6} ──────────────────────────── Note: Semi-quantitative analysis results are based on the relative sensitivity between elements for peak area intensities of carbon, nitrogen, and oxygen. This is a value converted by multiplying the correction coefficient so that the sum of the three elements becomes 100 at%.

The above results and the analysis of fragment ions by a time-of-flight secondary ion mass spectrometer (ToF-SIMS) showed that carboxyl groups (-COOH) on the surface layer of the polyimide film after the surface modification treatment were reduced. When the detection intensity of the hydroxyl group (-OH) increases, the molecular structure of the modified polyimide layer of the present invention, that is, the carboxyl group formed by opening the imide ring and the nitrogen and / or imide ring of the imide ring are opened. Thus, the molecular structure in which at least one hydroxyl group was added to the benzene ring bonded to the nitrogen of the second amide (N—H) formed as described above could be accurately specified.

Although the structural formula of the modified polyimide layer shown in FIG. 2 (b) is different from the structural formula of the above-mentioned chemical formula 5, the carboxyl group formed by opening the imide ring of the present invention ( -COOH) and a hydroxyl group (-OH) added to the benzene ring bonded to the nitrogen of the imide ring and / or the nitrogen of the second amide (N-H) formed by opening the imide ring. This is equivalent to a benzene ring bonded to the nitrogen of the imide ring with a hydroxyl group added, and clearly shows another example of the modified polyimide layer of the present invention.

In the present invention, as a method for forming a deteriorated polyimide layer on the surface of a polyimide film by a surface modification treatment, there are known methods, that is, physical means such as plasma or corona discharge and chemical means such as chemicals. And any one of them is not limited, but the molecular structure of the modified polyimide layer obtained must have the molecular structure of the present invention. For example, even if the same plasma discharge method is adopted, a modified polyimide layer having the molecular structure of the present invention can be formed by oxygen plasma, but a modified polyimide layer having the molecular structure of the present invention can be formed by argon plasma. Cannot be formed. Therefore, when preparing the metal-coated polyimide substrate of the present invention, using the above-described molecular structure specifying means, it is confirmed whether the deteriorated polyimide layer formed by the surface modification treatment has the molecular structure of the present invention. It is necessary to perform the production after performing.

Among the metal species of the first metal layer formed by the dry plating method on the polyimide film after the surface modification treatment, nickel, chromium, and nickel are preferred.
Examples thereof include copper, alloys thereof, and oxides of these metals, but are not particularly limited to these materials. The dry plating may be performed by using a known method such as vacuum deposition, sputtering, or ion plating.

[0020]

EXAMPLES Next, examples of the present invention will be described together with comparative examples performed simultaneously. Example 1: 25 μm-thick polyimide film (Toray
One side of DuPont product name "Kapton 100VN") was exposed to oxygen plasma for several seconds. When the molecular structure of the surface layer was analyzed by XPS, it was found that a carboxyl group formed by opening of the imide ring and a hydroxyl group were added to a benzene ring bonded to nitrogen of the imide ring. 300 angstroms of chromium and 1 copper on the polyimide film after surface modification by sputtering.
A first metal layer was formed by applying a thickness of 000 angstroms, and then copper as a second metal layer was electroplated to a thickness of 35 μm to obtain a metal-coated polyimide substrate. The obtained substrate is subjected to a 90 μm wiring width TAB.
After processing into a tape pattern, it was peeled off in the direction of 90 degrees and the bonding strength was measured. The result was 1.6 kgf / cm, which was a value that could be sufficiently put to practical use.

Comparative Example 1 A metal-coated polyimide substrate was obtained in the same procedure as in Example 1 except that the surface modification treatment was not performed. The obtained substrate was processed into a TAB tape pattern having a wiring width of 90 μm in the same manner as in Example 1, and then peeled in the direction of 90 ° to measure the bonding strength. The result was 190 gf / c.
The value of m was shown. This value is not a value that can be practically used.

Comparative Example 2: A polyimide film having a thickness of 25 μm (manufactured by Toray DuPont, product name “Kapton 100V”)
N ") was exposed to argon plasma for several seconds.
Analysis of the molecular structure of the surface layer by XPS revealed that the imide ring was opened to form a carboxyl group, and that the nitrogen of the imide ring and / or the nitrogen of the second amide formed by opening of the imide ring were not. It did not have a molecular structure in which at least one hydroxyl group was added to the bonded benzene ring. After performing this surface modification treatment, a metal-coated polyimide substrate was obtained in the same procedure as in Example 1. The obtained substrate was processed into a TAB tape pattern having a wiring width of 90 μm in the same manner as in Example 1, and then peeled in the direction of 90 ° to measure the bonding strength. As a result, a value of 400 gf / cm was obtained. It is not a value that can be put to practical use at all.

[0023]

As described above, since the metal-coated polyimide substrate of the present invention has high adhesion between the polyimide film and the metal layer, a highly reliable printed wiring can be obtained by using the metal-coated polyimide substrate of the present invention. Electronic components such as a board (PWB), a flexible printed circuit board (FPC), and a tape for automatic tape bonding (TAB tape) can be obtained.

[Brief description of the drawings]

FIG. 1 is a view showing a state of a polyimide film before a surface modification treatment. FIG. 1 (a) shows C1 of carbon when analyzed by XPS.
FIG. 1B is a diagram showing an s-spectrum, and FIG. 1B is a diagram showing a structural formula before surface modification treatment (the symbols α, β, δ,
Each peak of χ indicates a peak after being separated into individual peaks, and indicates where the peaks belong in the structural formula shown in FIG. 1B by using symbols. ).

FIGS. 2A and 2B show the state of a polyimide film after a surface modification treatment. FIG. 2A shows a carbon C1s spectrum obtained by XPS analysis, and FIG. 2B shows a structural formula after the surface modification treatment. FIG. 2 is a diagram (symbols α, β, δ, ε,
The peaks φ and χ indicate the peaks after being separated into individual peaks, and indicate where the peaks belong to the structural formula shown in FIG. 2B by symbols. is there. Further, the structure in the structural formula indicates a position where the imide ring is opened to generate a carboxyl group, and the structure indicates a position where a hydroxyl group is added to a benzene ring bonded to nitrogen of the imide ring. ).

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takefumi Sami 3-18-5, China, Ichikawa City, Chiba Prefecture Sumitomo Metal Mining Co., Ltd. Central Research Laboratory (72) Inventor Yoshiro Ishii 3-18, China, Ichikawa City, Chiba Prefecture -5 Sumitomo Metal Mining Co., Ltd. Central Research Laboratory (72) Inventor Tadahiro Inamori 125 Takeda Mukaishiro-cho, Fushimi-ku, Kyoto-shi

Claims (1)

[Claims] Claims: 1. At least one surface of a polyimide film,
In a substrate in which a plurality of metal layers are formed without the use of an adhesive, and a first metal layer of the metal layers in contact with the polyimide film is formed by a dry plating method, a polyimide film in contact with the first metal layer is formed. A carboxyl group formed by the opening of the imide ring and at least one hydroxyl group on the benzene ring bonded to the nitrogen of the imide ring and / or the nitrogen of the second amide formed by the opening of the imide ring are formed on the surface layer. A metal-coated polyimide substrate comprising a modified polyimide layer having an added molecular structure.