JP2667239B2 - Flexible wiring board - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a flexible wiring board having excellent adhesiveness.

[Conventional technology and issues]

2. Description of the Related Art Flexible wiring boards are widely used in electronic devices that enable flexibility, small size, light weight, simplicity, and the like of electronic circuits. This flexible wiring board is obtained by laminating a metal foil and a polyimide film using an adhesive.

However, since the heat resistance of the adhesive layer is significantly inferior to the heat resistance of polyimide, there is a problem that the heat resistance peculiar to polyimide is not utilized in the flexible wiring board by this method, and the heat resistance is poor. In order to solve the above problem, a method of manufacturing a flexible wiring board by forming a polyimide resin layer by directly applying a polyamic acid solution or a polyimide solution previously dehydrated and cured on a metal foil and performing heat treatment has been studied. However, the polyimide resin layer used in the above method has a high coefficient of thermal expansion of the polyimide resin layer as small as the metal foil to suppress the curling phenomenon of the flexible wiring board with the polyimide resin layer on the inside. Since the resin did not easily flow during the bonding and was hardly wet, the adhesion to the metal foil was poor. Therefore, there has been a problem that the adhesiveness between the polyimide resin layer and the metal foil is insufficient, and the metal foil on the polyimide resin is easily peeled off after etching.

[Means for solving the problem]

The present inventors have focused on forming a material that firmly adheres to a metal foil between a polyimide resin and a metal foil in order to solve the above-described problems, and have arrived at the present invention that has been earnestly studied.

That is, in the present invention, the structural formula is (R ₁ is a tetracarboxylic acid residue R ₂ is And a diamine component comprising at least 20% of diaminobenzanilide and the remainder of another aromatic primary diamine, and pyromellitic acid = anhydride or a derivative thereof. Is a flexible wiring board obtained by forming a polyimide resin layer B.

According to the present invention, a flexible wiring board in which the metal foil and the polyimide resin layer are firmly bonded can be obtained.

Such a flexible wiring board is obtained because the polyimide resin layer A that firmly adheres to the metal foil is formed between the polyimide resin layer B and the metal foil.

The flexible wiring board obtained by the present invention has an advantage that the metal foil on the polyimide resin is hardly peeled off after etching because of excellent adhesion between the polyimide resin layer and the metal foil as described above.

The polyimide resin A used in the present invention comprises an acid anhydride and a diamine, and can be obtained by a conventionally known method. As the diamine, 3.3'-diaminodiphenyl ether, 3.4'-diaminodiphenyl ether, 4.4'-diaminodiphenyl ether, 3.3'-
Diaminobenzophenone, 3.4'-diaminobenzophenone, 4.4'-diaminobenzophenone, 3.3'-diaminodiphenylsulfone, 3.4'-diaminodiphenylsulfone, 4.4'-diaminodiphenylsulfone, 3.3'-
Examples thereof include diaminodiphenylmethane, 3.4'-diaminodiphenylmethane and 4.4'-diaminodiphenylmethane, and these diamines can be used alone or in combination. In a range not impairing the properties of the present invention, other than the diamine, P-phenylenediamine, m-phenylenediamine, 4.4'-diaminodiphenylpropane, 4.4'-diaminodiphenylhexafluoropropane, benzidine, 3.3-dichlorobenzidine, 3.3-dimethylbenzidine, 3.3-diethylbenzidine, 3.3-dimethoxybenzidine, 4.4'-bis (4-aminophenoxy) biphenyl, 4.4'-bis [(4-aminophenoxy) phenyl] ether, 4.4'-bis [(4- Aminophenoxy) phenyl] methane, 4.4 '
-Bis [(4-aminophenoxy) phenyl] flufone, 4.4'-bis [(4-aminophenoxy) phenyl] propane, 4.4'-bis [(4-aminophenoxy) phenyl] hexafluoropropane and the like can be used. it can.

As the acid anhydride which is a raw material of the polyimide resin A used in the present invention, pyromellitic dianhydride, 3.3 ′, 4.
4'-benzophenonetetracarboxylic dianhydride, 3.
3 ', 4.4'-biphenyltetracarboxylic dianhydride, 3.
3 ', 4.4'-diphenylsulfonetetracarboxylic dianhydride, 3.3', 4.4'-diphenylmethanetetracarboxylic dianhydride, 3.3 ', 4.4'-diphenylpropanetetracarboxylic dianhydride, 3.3', 4.4'- Diphenylhexafluoropropanetetracarboxylic dianhydride, 1.2.3.4
-Benzenetetracarboxylic dianhydride, 2.3.5.7-naphthalenetetracarboxylic dianhydride, 1.2.5.6-naphthalenetetracarboxylic dianhydride, or derivatives thereof, and the like. Pyromellitic dianhydride, 3.3 ', 4.
4'-biphenyltetracarboxylic dianhydride, 3.3 ', 4.
4'-benzophenonetetracarboxylic dianhydride, 3.
3 ', 4.4'-diphenylsulfonetetracarboxylic acid = anhydride is preferred.

The polyimide resin layer B used in the present invention also comprises an acid anhydride and a diamine, and can be obtained by a conventionally known method.

As the diaminobenzanilide used in the polyimide resin layer B, 3.3'-diaminobenzanilide, 3.4 '
-Diaminobenzanilide, 4.4'-diaminobenzanilide. As the diamine other than diaminobenzanilide, diaminodiphenyl ether, diaminodiphenylmethane, and diaminodiphenylsulfone are preferable, and 4.4'-diaminodiphenylether is most preferable in terms of heat resistance.

In the present invention, it is preferable that 20% or more of the diamine, which is the raw material of the polyimide resin layer B, be diaminobenzanilide. This is because when the diaminobenzanilide is set to 20% or more, the phenomenon of dimensional change in which the substrate shrinks after etching or after overlay is extremely small,
This is because the dimensional stability is excellent.

As long as the properties of the present invention are not impaired, P-phenylenediamine, m-phenylenediamine, 4.4'-diaminodiphenyl sulfide, 3.4'-diaminodiphenyl sulfide, 4.4'-diaminobenzophenone, 3.4'- Diaminobenzophenone, 4.4'-diaminodiphenylpropane, 4.4'-diaminodiphenylhexafluoropropanebenzidine, 3.
3-dichlorobenzidine, 3.3-dimethylbenzidine, 3.
3-diethylbenzidine, 3.3-dimethoxybenzidine,
4.4'-bis (thiaminophenoxy) biphenyl, 4.4 '
-Bis [(4-aminophenoxy) phenyl] ether, 4.4'-bis [(4-aminophenoxy) phenyl] methane, 4.4'-bis [(4-aminophenoxy)
Phenyl] sulfone, 4.4'-bis [(4-aminophenoxy) phenyl] propane, 4.4'-bis [(4-aminophenoxy) phenyl] hexafluoropropane,
Etc. can be used together.

In the present invention, pyromellitic dianhydride or a derivative thereof is preferable as the acid anhydride as a raw material of the polyimide resin layer B. To the extent that the properties of the present invention are not impaired, pyromellitic dianhydride or a derivative thereof may be used as a main component, and another acid anhydride may be added.

For example, 3.3 ', 4.4'-biphenyltetracarboxylic dianhydride, 3.3', 4.4'-benzophenonetetracarboxylic dianhydride, 3.3 ', 4.4'-diphenylsulfonetetracarboxylic dianhydride, 3.3', 4.4 ' -Diphenylmethanetetracarboxylic dianhydride, 3.3 ', 4.4'-diphenylpropanetetracarboxylic dianhydride, 3.3', 4.4'-
Diphenylhexafluoropropanetetracarboxylic dianhydride, 1.2.3.4-benzenetetracarboxylic dianhydride, 2.3.5.7-naphthalenetetracarboxylic dianhydride,
It is also possible to modify with 1.2.5.6-naphthalenetetracarboxylic dianhydride.

The polyimide resin layers A and B in the present invention are obtained by coating and casting a polyimide precursor solution or a polyimide solution that has been previously dehydrated and closed, and heat-treated, and any of these solutions may be used.

The method for producing the polyimide precursor solution and the polyimide solution is not particularly limited.For example, when a polyimide precursor is used, a substantially stoichiometric amount of a tetracarboxylic acid component and a diamine component is used at 0 to 60 ° C. in an organic polar solvent. The reaction is performed in a temperature range for 1 to 24 hours to obtain a polyimide precursor solution.

Examples of the organic polar solvent include N-methyl-2-pyrrolidone, N, N'-dimethylformamide, N, N'-dimethylacetamide, dimethyl sulfoxide, halogenated phenol, 1.3-dimethyl-2-imidazolidinone and the like. These can be used alone or as a mixture.

When a polyimide solution is used, a substantially stoichiometric amount of a tetracarboxylic acid component and a diamine component are similarly mixed in a halogenated phenol-based solvent at a temperature of 80 to 180 ° C. for 1 to 2 times.
The reaction is carried out for 4 hours to make a polyimide solution.

Examples of the halogenated phenol-based solvent include 3-chlorophenol, 4-chlorophenol, 3-bromophenol, 4-bromophenol, 2-chloro-4-hydroxytoluene, and the like. These may be used alone or as a mixture. can do.

The polyimide precursor A or the polyimide solution A for forming the polyimide resin A obtained as described above is applied and cast on a metal foil and subjected to a heat treatment to form a first layer made of the polyimide resin A. At that time, heat treatment, 120 ℃ ~ 2
Heating at 00C may be such that the polyimide resin A does not stick, or heating at 200C to 400C to cure.

Further, a polyimide resin B is formed on the first layer made of the polyimide resin A. The polyimide precursor solution B or the polyimide solution B is applied and cast, and a heat treatment is performed to form a second layer composed of the polyimide resin layer B, thereby manufacturing a flexible wiring board. At this time, the thickness of the polyimide resin A is preferably 50% or less of the total thickness of the polyimide resin A and the polyimide resin B. When the film thickness of the polyimide resin A is 50% or more with respect to the total film thickness, the film characteristics of the polyimide resin A become dominant, curling occurs, the substrate dimensional change becomes large, and it is not practical for a flexible wiring board. .

As the metal foil, copper, aluminum, iron, gold,
Silver, Pd, Ni, Cr, Mo and alloys thereof are exemplified. In the case of using a copper foil, it is preferable to use an electrolytic copper foil, a rolled copper foil, or a surface-treated copper foil for further strengthening the adhesion between the polyimide resin A and the metal foil.

Known means such as a roll coater, a knife coater, a dip coater, and a flow coater can be used as the applying means.

 Hereinafter, the present invention will be described in more detail based on examples.

Example 1 <Synthesis of Polyimide Precursor Solution A> Pyromellitic dianhydride (150 ml / min) was flowed into a flask equipped with a thermometer, a calcium chloride tube, a stirrer, and an N ₂ blow-in port while flowing N ₂ at a rate of 150 ml / min. 104.3 g) (hereinafter abbreviated as PMDA) and 800 g of N-methyl-2-pyrrolidone are added and stirred. Liquid temperature
While maintaining the temperature below 60 ° C, 4.4'-diaminodiphenyl ether (95.7g) (hereinafter abbreviated as DDE) was added, and the mixture was stirred at 60 ° C or less for 5 hours to form a polyimide resin layer A concentration.
A 20% polyimide precursor solution A was obtained.

<Synthesis of Polyimide Precursor Solution B> While flowing 150 ml of N ₂ per minute into a flask equipped with a thermometer, a calcium chloride tube, a stirrer, and an N ₂ blowing port, PMDA
(101.0 g) and 800 g of N-methyl-2-pyrrolidone are added and stirred. 4.4'-Diaminobenzanilide (52.6 g) (hereinafter abbreviated as DABAN) was added while maintaining the liquid temperature at 60 ° C or lower, and then DDE (46.4 g) was added. Then, at 60 ° C or less, 5
20% concentration to form polyimide resin layer B after stirring for hours
The polyimide precursor solution B was obtained.

Next, the polyimide precursor solution A was cast-coated on a 35 μm-thick electrolytic copper foil using a doctor knife,
Heating was performed at 15 ° C. for 15 minutes and at 180 ° C. for 10 minutes to form a 3 μm-thick polyimide resin layer A. Further, the polyimide precursor solution B was similarly cast and applied using a doctor knife, and 100
Heat at 30 ° C for 30 minutes, 200 ° C for 30 minutes, 300 ° C for 60 minutes, thickness 22μ
Thus, a flexible wiring board having a polyimide resin of m was obtained.

[Example 2] DD used for synthesis of the polyimide precursor solution A of Example 1
A flexible wiring board was obtained in the same manner as in Example 1 except that E was changed to 4.4'-diaminobenzophenone (hereinafter abbreviated as DBP).

[Example 3] DD used for synthesis of the polyimide precursor solution A of Example 1
A flexible wiring board was obtained in the same manner as in Example 1 except that E was changed to 4.4'-diaminodiphenyl sulfone (hereinafter abbreviated as DDS).

Example 4 DD used for synthesis of polyimide precursor solution A of Example 1
A flexible wiring board was obtained in the same manner as in Example 1 except that E was changed to 4.4'-diaminodiphenylmethane (hereinafter abbreviated as DDM).

[Example 5] PM used for the synthesis of the polyimide precursor solution A of Example 1
A flexible wiring board was obtained in the same manner as in Example 1 except that DA was changed to 3.3 ', 4.4'-benzophenonetetracarboxylic dianhydride (hereinafter abbreviated as BTDA).

[Example 6] PM used for the synthesis of the polyimide precursor solution A of Example 2
A flexible wiring board was obtained in the same manner as in Example 1 except that DA was changed to 3.3 ', 4.4'-benzophenonetetracarboxylic dianhydride (hereinafter abbreviated as BTDA).

[Example 7] PM used for the synthesis of the polyimide precursor solution A of Example 1
A flexible wiring board was obtained in the same manner as in Example 1 except that DA was changed to 3.3 ', 4.4'-biphenyltetracarboxylic dianhydride (hereinafter abbreviated as S-BPDA).

[Example 8] PM used for the synthesis of the polyimide precursor solution A of Example 2
A flexible wiring board was obtained in the same manner as in Example 1 except that DA was changed to 3.3 ', 4.4'-biphenyltetracarboxylic dianhydride (hereinafter abbreviated as S-BPDA).

[Example 9] PM used for synthesizing the polyimide precursor solution A of Example 1
A flexible wiring board was obtained in the same manner as in Example 1 except that DA was changed to 3.3 ', 4.4'-diphenylsulfonetetracarboxylic dianhydride (hereinafter abbreviated as DSDA).

[Example 10] PM used for the synthesis of the polyimide precursor solution A of Example 2
A flexible wiring board was obtained in the same manner as in Example 1 except that DA was changed to 3.3 ', 4.4'-diphenylsulfonetetracarboxylic dianhydride (hereinafter abbreviated as DSDA).

[Comparative Example 1] The polyimide precursor solution B synthesized in Example 1 was directly
It is cast and applied on a 35μm thick electrolytic copper foil with a doctor knife and heated at 100 ° C for 30 minutes, 200 ° C for 30 minutes, and 300 ° C for 60 minutes,
A flexible wiring board having a polyimide resin layer B having a thickness of 25 μm was obtained.

Example 11 Polyimide resin layer A and polyimide resin layer B of Example 1
Was changed to 5/20 to obtain a flexible wiring board in the same manner as in Example 1.

[Example 12] Polyimide resin layer A and polyimide resin layer B of Example 1
Was changed to 10/15 to obtain a flexible wiring board in the same manner as in Example 1.

[Comparative Example 2] Polyimide resin layer A and polyimide resin layer B of Example 1
Was changed to 15/10, and a flexible wiring board was obtained in the same manner as in Example 1.

[Comparative Example 3] DA used for synthesis of polyimide precursor solution B of Example 1
A flexible wiring board was obtained in the same manner as in Example 1 except that the molar ratio of BAN / DDE was changed to 1/9.

[Example 13] DA used for synthesis of polyimide precursor solution B of Example 1
A flexible wiring board was obtained in the same manner as in Example 1 except that the molar ratio of BAN / DDE was changed to 2/8.

[Example 14] DA used for synthesis of the polyimide precursor solution B of Example 1
A flexible wiring board was obtained in the same manner as in Example 1 except that the molar ratio of BAN / DDE was changed to 7/3.

[Example 15] DA used for synthesis of the polyimide precursor solution B of Example 1
A flexible wiring board was obtained in the same manner as in Example 1 except that the molar ratio of BAN / DDE was changed to 10/0.

Table 1 shows the results of evaluating the characteristics of the flexible wiring boards obtained from the above Examples and Comparative Examples by the following measurement methods.

Adhesive force with copper foil: A 10 mm wide sample was peeled 180 degrees according to JIS C-6481 and measured on an autograph under the condition of a pulling speed of 50 cm.

Curvature radius: After a flexible substrate having a length of 5 cm and a width of 5 cm is allowed to stand on a glass plate such that the polyimide resin layer is on the glass side as shown in FIG. 1, the strain amount δ (cm) and a (cm) are measured. The curvature radius P (cm) was obtained from the following equation, and the degree of curl was evaluated.

Elongation: A sample having a width of 5 mm and a gap between chucks of 20 mm was prepared, and was measured by an autograph at a tension speed of 50 mm / min.

Dimensional change: 10cm x 10cm on the obtained flexible wiring board
Are marked, and the distance between the four points is accurately measured with a length measuring instrument. All the copper was removed by etching to obtain only a film, and the dimensional change was measured by measuring the length between four points in the same manner.

Thermal aging property: After leaving in a constant temperature bath at 200 ° C. for 240 hours, the adhesive strength to the copper foil was measured.

Initial bond strength of 1.0k as characteristic value of flexible wiring board
g / cm or more, radius of curvature 10cm or more, film elongation 15% or more, dimensional change rate -0.10 or less, heat aging 50% of initial adhesive strength
If it is more than 0.36 kg / cm, there is no practical problem.

The polyimide resin layer A shown in the claims of Examples 1 to 10 and Comparative Example 1 in Table 1 was replaced with a copper foil and a polyimide resin layer B.
It is clear that the initial adhesive strength is greatly improved by forming between them.

Also, from Examples 1, 11, 12 and Comparative Example 2, the polyimide resin layer A and the polyimide resin layer B
When the total thickness is 50% or more of the total film thickness, the characteristics of the polyimide resin layer A become dominant, the radius of curvature indicating the curl property of the substrate is large, and the dimensional change rate is large, which causes a practical problem. .

Therefore, it is understood that the thickness of the polyimide resin layer A is preferably 50% or less with respect to the total thickness of the polyimide resin layer A and the polyimide resin layer B.

According to Examples 13 to 15 and Comparative Example 3, the dimensional change rate can be extremely reduced by adding DABAN of 20 mol% or more of the diamine components used in the polyimide resin layer B.

〔The invention's effect〕

As described above, the flexible wiring board of the present invention has a polyimide resin layer that is firmly bonded to the metal foil between the metal foil and the polyimide resin, so that the adhesive strength is improved, and the metal foil after etching is peeled off. It has the advantage of being difficult to perform.

[Brief description of the drawings]

 FIG. 1 is a schematic diagram showing a method of measuring a radius of curvature. (1) Metal foil (2) Polyimide resin layer (3) Glass plate

Claims (4)

(57) [Claims] Claims: 1. A polyimide precursor is applied and cast on a metal foil and heat-treated. (R ₁ is a tetracarboxylic acid residue R ₂ is A diamine component comprising at least 20% of diaminobenzanilide and the remainder comprising another aromatic primary diamine, and pyromellitic acid = anhydride or a derivative thereof. A flexible wiring board, wherein a polyimide resin layer B is formed by subjecting a polyimide precursor to a coating casting heat treatment. (2) R ₁ is The flexible wiring board according to claim 1, which is selected from the group consisting of: 3. The flexible wiring board according to claim 1, wherein the other aromatic primary diamine is diaminodiphenyl ether. 4. The film thickness of the polyimide resin layer A is 50% of the total film thickness of the polyimide resin layer A and the polyimide resin layer B.
The flexible wiring board according to claim 1, wherein: