TWI519412B - Flexible copper-clad lamination board - Google Patents

Description

Flexible copper clad laminate

The present invention relates to an insulating layer composed of a polyimide resin and a flexible copper clad laminate provided with a copper foil on one or both sides thereof.

In recent years, with the high functionality, miniaturization, and weight reduction of various other electronic devices such as mobile phones, digital cameras, digital cameras, PDAs, car navigators, and hard disks, it is easy to use a line with high degree of freedom and thinness. The printed circuit board is increasing as an example of a rigid substrate used for the substrate material for electronic circuits. Further, there is a demand for a compact printed circuit board which is used for such a device which is gradually increased in size, such as a smaller size, a higher density, a higher thickness, a smaller size, and a higher heat resistance.

In order to cope with such a request, Patent Document 1 and the like disclose that a polyimine resin layer is directly coated on a conductor and formed by multilayering a plurality of polyimine resin layers having different thermal expansion coefficients. This provides a flexible printed circuit board having excellent dimensional stability, adhesion, and flatness after etching, and the like.

In the copper-clad laminate which does not have the adhesive layer used in the flexible printed circuit board, for example, as disclosed in Patent Document 2, Patent Document 3, and Patent Document 4, in order to improve the adhesion to the resin layer, A copper foil having a roughened copper surface is used.

However, in recent years, at the time of refinement of the circuit, residues are liable to occur on the end portions of the circuit after the circuit processing and the polyimide, and it is necessary to remove the residue. In addition, the cleaning of the circuit surface is required in the processing steps before the surface of the copper foil in the electroplating step or the like of the circuit processing. For this purpose, in addition to the acid cleaning of the surface of the copper foil, the surface of the copper foil is polished by a chemical polishing liquid containing copper chemical solution such as hydrogen peroxide/sulfuric acid as a main component. However, in the copper clad laminate produced by using the above-mentioned roughened copper foil, particularly in the flexible printed circuit board obtained by performing circuit processing on the copper clad laminate, if the chemistry is carried out When the polishing is performed, the chemical polishing liquid penetrates into the edge portion of the circuit, and the peeling strength of the circuit is liable to be lowered, and if the circuit is refined, the circuit is lifted due to the peeling of the circuit and the wire is broken, so it is necessary to be improved.

[Patent Document 1] Japanese Patent Publication No. 6-93537

[Patent Document 2] Japanese Patent Laid-Open No. 2-292894

[Patent Document 3] Japanese Patent Laid-Open No. 6-169168

[Patent Document 4] Japanese Patent Laid-Open No. Hei 8-335775

The present invention provides an excellent heat resistance, dimensional stability, and the like, and can meet the requirements of high integration and high density in recent years in the field of electronic equipment, and by improving copper foil and polyaluminum. A method of suppressing circuit peeling during chemical polishing by the subsequent reliability between the amine resin layers.

In order to solve the above problems, it has been found that the surface properties of the copper foil which is in contact with the polyimide layer are controlled to a specific range, and the subsequent reliability between the copper foil and the polyimide layer can be improved. The present invention has been completed.

In other words, the present invention provides a flexible copper-clad laminate which is a copper-clad laminate having a single-sided or double-area layer of a polyimide foil, wherein the copper foil and the polyimide resin are The surface of the copper foil which is in contact with the layer has a surface treatment layer composed of a plurality of treatment layers comprising a layer treated with a decane coupling agent, the surface treatment layer containing copper, cobalt, nickel and zinc, nickel / (nickel + cobalt + zinc) The ratio is 0.23 or more (determined by ICP-AES (Inductively Coupled Plasma-Atomic Emission Spectroscopy), and the zinc content is in the range of 0.2 to 0.6 mg/dm ² , the aforementioned decane coupling The agent treatment layer is formed of a decane coupling agent having an amine group.

The preferred aspect of the flexible copper clad laminate of the present invention is shown below.

1) The decane couplant treatment layer in the surface treatment layer is located at the outermost layer.

2) The polyimine resin layer is composed of a plurality of layers, and the polyimide layer (A) which is in contact with the copper foil is composed of a thermoplastic polyimide resin.

3) Copper foil rolled copper foil (also known as rolled copper foil), the surface roughness (Rz) of the surface treated copper foil which is in contact with the polyimide layer is 0.5 to 2 μm. The scope.

4) The initial adhesion force of the polyimide film layer and the copper foil at a width of 1 mm is 0.6 kN/m or more.

The copper clad laminate resin layer of the present invention and the copper foil are excellent in adhesion strength, heat resistance, flame retardancy, dimensional stability, and the like, and are excellent in fine circuit processability, and do not cause peeling due to chemical polishing. Therefore, when it is used for an electric or electronic component as a flexible printed circuit board, it is applicable to the reliability, and it is especially the use of a fine circuit.

Hereinafter, the present invention will be described in detail.

The flexible copper clad laminate of the present invention is composed of a polyimide film (also referred to as an insulating layer) as an insulating layer and a copper foil. As the copper foil, for example, a conventional production method such as a rolled copper foil or an electrolytic copper foil can be used. The copper foil preferably has a thickness in the range of 6 to 35 μm and more preferably in the range of 9 to 18 μm. If the thickness of the copper foil is less than 6 μm, it is difficult to adjust the tension or the like in the manufacturing steps of the production line such as mass production of the copper clad laminate. On the contrary, if it exceeds 35 μm, the bendability of the copper clad laminate becomes difference.

In order to increase the adhesion to the polyimide layer of the insulating layer, the copper foil used has a surface treatment layer composed of a plurality of processing layers including a decane coupling agent treatment layer. In addition to the decane couplant treatment layer, the treatment layer preferably comprises a roughened layer.

The degree of roughening treatment for forming the roughened layer is preferably in the range of 0.5 to 2 μm in the surface roughness (Rz) and more preferably in the range of 0.5 to 1 μm. Here, the surface roughness (Rz) means a 10-point average roughness defined by JIS B0601 (1994). This roughening treatment causes the metal particles (roughened particles) to adhere to the surface of the copper foil or the like to improve the surface roughness. Thereby, an anchor effect can be generated between the insulating layer and the copper foil to improve the adhesion. If the surface roughness (Rz) is less than 0.5 μm, the anchoring effect on the insulating layer cannot be expected, and the adhesion is low. Further, if the surface roughness (Rz) exceeds 2 μm, the roughened particles are not removed during the etching in the circuit processing, and there is a fear that they are present on the circuit end or the insulating layer as an etching residue. Moreover, this etching residue has a possibility of causing a problem such as so-called short circuit or migration of copper between circuits during fine processing.

The roughened particles used in the roughening treatment may be copper alone or an alloy such as copper + nickel or copper + cobalt + nickel. Further, after the roughened particles are attached, they may be further treated with copper, nickel or nickel + cobalt. However, since the circuit processability is excellent, peeling does not occur due to chemical polishing, and the roughened layer must be entirely made of copper, nickel, or cobalt. When only copper is used in the roughening treatment, it is easily oxidized and easily causes discoloration or the like. Further, when copper or nickel or nickel alone is used, the chemical polishing resistance is enhanced, but it is not easily dissolved in the copper plating solution used in the circuit processing, and there is a fear that etching residues are likely to occur. When copper or cobalt is used or only cobalt is used, acid resistance is deteriorated, and there is a possibility that circuit peeling is likely to occur during chemical polishing.

The copper foil used in the present invention contains 0.2 to 0.6 mg/dm ^{2 of} zinc in the surface treatment layer (preferably in the above roughening treatment layer or on the roughened layer). When the layer containing zinc is provided on the roughened layer, the layer can be formed by a precipitation treatment. In the present invention, it is possible to suppress the peeling of the circuit by chemical polishing while suppressing the oxidation of copper by the zinc treatment. If the content of zinc is less than 0.2 mg/dm ² , the copper foil is embrittled due to discoloration or oxidation of the circuit caused by oxidation, which may easily cause the circuit to be broken. Further, if the content of zinc exceeds 0.6 mg/dm ² , the zinc itself is not resistant to acid, and the peeling of the circuit due to chemical polishing is liable to occur, and disconnection is liable to occur. Meanwhile, the precipitation treatment is not particularly limited as long as it is a means for depositing the above-described metal in a predetermined amount on the surface of the copper foil by electrolytic plating or the like.

In order to further improve the adhesion to the insulating layer, the copper foil used in the present invention has a decane coupling agent treatment layer formed of a decane coupling agent having an amine group. This decane couplant treatment layer is preferably present at the outermost layer of the surface treatment layer. The decane coupling agent having an amine group may, for example, be N-2-(aminoethyl)γ-aminopropyltrimethoxydecane or N-3-(4-(3-aminopropoxy)butoxy Phenyl-3-aminopropyltrimethoxydecane, N-phenyl-3-aminopropyltrimethoxydecane, and the like. These decane coupling agents may be used singly or in combination of two or more. When a plurality of kinds are used, one or more decane coupling agents having an amine group may be contained. Further, chromate treatment may be performed for the purpose of further revealing the adhesion to the insulating layer before the decane coupling agent treatment.

The decane coupling agent treatment method is exemplified by, for example, when the above-mentioned coupling agent is used, first, a predetermined amount of the coupling agent is dissolved in water as a solvent, and then applied to the surface of the copper foil after the metal precipitation treatment described above, and The method of drying. At this time, heat treatment may be performed as needed. Further, as a method of applying a coupling agent dissolved in water to the surface of the copper foil, a conventional method such as a dipping method, a shower method, or a spray method can be used.

Through the above treatment, the surface treatment layer of the entire copper foil contains copper, cobalt, nickel, and zinc. Further, the ratio of nickel/(nickel + cobalt + zinc) must be 0.23 or more, and preferably in the range of 0.24 to 0.3. If the ratio of nickel/(nickel+cobalt+zinc) is less than 0.23, circuit peeling tends to occur at the end of the circuit during chemical polishing. Here, the measurement of copper, cobalt, nickel, and zinc is carried out by ICP-AES measurement, and the measurement is carried out under the conditions described in the examples.

A polyimide layer of a polyimide resin layer as an insulating layer is laminated on the surface of the surface treatment layer provided with the copper foil of the surface treatment layer as described above. The polyimine resin constituting the polyimide resin layer is generally represented by the following formula (1), and substantially a molar component such as a diamine component and an acid dianhydride component can be used, and the organic polar solvent can be used. Manufacturing by conventional methods of polymerization.

In the general formula (1), Ar ₁ has a tetravalent organic group having one or more aromatic rings, and Ar ₂ has a divalent organic group having one or more aromatic rings. Further, the residue of Ar ₁ is an acid dianhydride and the residue of an Ar ₂ -based diamine.

The acid dianhydride may, for example, be an aromatic acid dianhydride represented by O(CO) ₂ -Ar ₁ -(CO) ₂ O. Desirable Ar ₁ is exemplified by a tetravalent organic group shown below.

The acid dianhydride may be used alone or in combination of two or more. Among them, pyromellitic dianhydride (PMDA), 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), 3,3',4,4'-diphenyl are especially used. Among the ketone tetracarboxylic dianhydride (BTDA), 3,3',4,4'-diphenylphosphonium tetracarboxylic dianhydride (DSDA), 4,4'-oxydiphthalic acid dianhydride (ODPA) It is better.

The diamine may, for example, be an aromatic diamine represented by H ₂ N-Ar ₂ —NH ₂ . Desirable Ar ₂ is exemplified by a divalent organic group shown below.

Among these diamines, preferred are, for example, diaminodiphenyl ether (DAPE) and 2,2'-dimethyl-4,4'-diaminobiphenyl (hereinafter referred to as m-TB). ), p-phenylenediamine (p-PDA), 1,3-bis(4-aminophenoxy)benzene (TPE-R), 1,3-bis(3-aminophenoxy)benzene (APB) ), 1,4-bis(4-aminophenoxy)benzene (TPE-Q), 2,2-bis(4-(4-aminophenoxy)phenyl]propane (BAPP).

Examples of the solvent used for the polymerization include dimethylacetamide, N-methylpyrrolidone, 2-butanone, diethylene glycol dimethyl ether, and xylene. For these, 1 can be used. Two or more kinds are used in combination or in combination. Further, the resin viscosity of the polylysine (polyimine precursor) obtained by the polymerization is preferably in the range of 500 cps to 35,000 cps.

The polyimine resin layer of the flexible copper-clad laminate of the present invention may be composed of a single layer or a plurality of layers, in order to make the dimensional stability of the flexible copper-clad laminate, and copper foil Then, the strength is excellent, and it is preferable to form a plurality of layers. When the polyimine resin layer is a plurality of layers, the coefficient of linear expansion (CTE) is 30 × 10 ^-6 (1/K) or less (preferably in the range of 1 to 30 × 10 ^-6 (1/K)) The resin layer having a low coefficient of linear expansion is preferably used as the main polyimide resin layer (B), and a thermoplastic polyimide film layer is preferably provided on one or both sides thereof. The polyimide layer (A) on the side in contact with the copper foil is preferably a thermoplastic polyimide film layer.

Here, the thermoplastic polyimide resin layer means a coefficient of linear expansion (CTE) of more than 30 × 10 ^-6 (1/K) and a glass transition temperature of 330 ° C or lower. The preferred thermoplastic polyimide film has a coefficient of linear expansion of from 30 × 10 ^-6 to 60 × 10 ^-6 (1/K) and a glass transition temperature of from 200 to 330 °C. If the CTE of the main polyimine resin layer (B) is more than 30 × 10 ^-6 / ° C, there is a fear that warpage is intensified when a copper clad laminate is formed, and since dimensional stability is lowered, it is not suitable as product. The thickness of the main polyimide resin layer (B) is preferably 50% or more of the thickness of the wholly polyimine resin layer, preferably 70 to 95%.

The method for forming the polyimide layer of the polyimide resin is not particularly limited, and it is preferably, for example, that the resin solution of poly-proline which is a precursor of the polyimide resin is directly coated on the surface of the surface-treated copper foil. And removing the solvent contained in the resin solution to a certain extent at a temperature of 150 ° C or lower, and then performing heat treatment for about 5 to 40 minutes at a temperature range of 100 to 450 (preferably 250 to 450 ° C) to carry out a solvent. Drying and hydrazine imidization. When the polyimine resin layer is provided in two or more layers, it is preferred to apply and dry the second polyaminic acid resin solution after applying and drying the first polyaminic acid resin solution. After the coating, the third and later polyphosphonic acid resin solution is applied and dried, and then heat-treated at a temperature ranging from 250 to 450 ° C for about 5 to 40 minutes to carry out hydrazine imidization. When the temperature of the heat treatment is less than 100 ° C, the dehydration ring-closure reaction of the polyimine is not sufficiently performed. On the other hand, if it exceeds 450 ° C, the polyimide film and the copper foil may be deteriorated by oxidation or the like.

The thickness of the polyimide layer of the polyimide resin is preferably in the range of 6 to 45 μm, preferably in the range of 9 to 40 μm. When the thickness of the insulating layer is less than 6 μm, there is a fear that wrinkles may occur during transportation during the production of a copper clad laminate or the like. On the other hand, if it exceeds 45 μm, dimensional stability may be unpredictable when manufacturing a copper clad laminate. Or problems such as bending.

The flexible copper-clad laminate of the present invention may of course be a single-sided copper-clad laminate provided with a copper foil on only one side of the polyimide layer, or may be a double-sided layer of the polyimide layer. It has a double-sided copper-clad laminate with copper foil. Furthermore, in order to obtain a double-sided copper-clad laminate, after forming a single-sided copper-clad laminate, it may be formed by pressing the polyimide layer with a face-to-face and press-bonding by hot pressing, or pressing the copper foil to the copper foil. It is obtained by forming a polyimine resin layer on a single-sided copper-clad laminate.

In the flexible copper-clad laminate of the present invention, the initial adhesion force of the polyimide film layer and the copper foil at a first width of 1 mm is preferably 0.6 kN/m or more, more preferably 0.8 to 2.0 kN/m. The initial adhesion force is a value measured by the conditions described in the examples. In order to obtain this initial adhesion, the amount of the specific metal in the surface treatment layer of the copper foil may be in the above range, except that the polyimide layer which is in contact with the copper foil is used as the thermoplastic polyimide resin layer. And reached.

(Example)

Hereinafter, the present invention will be described in more detail based on examples. Further, in the following examples, various evaluations are obtained as follows unless otherwise specified.

[Follow the determination of force]

The adhesive force between the copper foil and the polyimide layer is a flexible copper-clad laminate obtained by forming an insulating layer composed of a polyimide resin on a copper foil, and is processed into a line width of 1 mm. The tensile tester (Strograph M1) manufactured by Toyo Seiki Co., Ltd. was used, and the copper foil was peeled off at 180 ° C to measure.

[Measurement of the amount of metal in the surface treatment layer]

The measurement of the amount of metal of the surface metal layer of the copper foil was carried out by ICP-AES (Optima 4300DV, manufactured by Perkin Elmer Co., Ltd.). In the measurement, a copper foil having a surface-treated layer was used as a sample, and after dissolving 2 g of the sample with nitric acid and hydrochloric acid, the capacity was fixed at 100 mL and diluted 10 times.

[Measurement of Chemical Grinding Resistance]

The chemical polishing resistance was measured by linearly processing a flexible copper-clad laminate into a line width of 1 mm and immersing it in a chemical polishing solution of hydrogen peroxide (2.5 wt% / sulfuric acid 10 wt%) at 40 ° C for 2 minutes. A 200-fold optical microscope confirms the presence or absence of discoloration at the end of the circuit from the side of the insulating layer.

(Synthesis Example 1)

N,N-dimethylacetamide was placed in a reaction vessel equipped with a thermocouple and a stirrer and capable of introducing nitrogen. 2,2'-Dimethyl-4,4'-diaminobiphenyl (m-TB) was dissolved in the vessel while stirring in the reaction vessel. Next, 3,3',4,4'-biphenyltetracarboxylic dianhydride and pyromellitic dianhydride (PMDA) were added. The total amount of the monomers to be charged was 15% by weight, and the molar ratio of each of the acid anhydrides (BPDA: PMDA) was 20:80. Thereafter, stirring was continued for 3 hours to obtain a resin solution a of poly-proline. The solution viscosity of the polyaminic acid resin solution a was 20000 cps. The polyimine obtained from the polyamic acid thus exhibits a low coefficient of linear expansion of 25 × 10 ^-6 (1/K) or less, and has a non-thermoplastic property.

(Synthesis Example 2)

N,N-dimethylacetamide was placed in a reaction vessel equipped with a thermocouple and a stirrer and capable of introducing nitrogen. 2,2-bis[4-(4-aminophenoxy)phenyl]propane was dissolved in the vessel while stirring in the reaction vessel. Next, pyromellitic dianhydride was added so that the total amount of the monomer was 12 wt%. Thereafter, stirring was continued for 3 hours to obtain a resin solution b of poly-proline. The solution viscosity of the polyaminic acid resin solution b was 3000 cps. The polyimine obtained from the polyamic acid thus exhibits a coefficient of linear expansion exceeding 30 × 10 ^-6 (1/K) and has thermoplastic properties.

(Example 1)

A rolled copper foil which was treated as a surface treatment layer and which was treated with an amine group-containing decane coupling agent decane coupling agent and which contained the metal element shown in Table 1 was prepared as a copper foil. This copper foil had a thickness of 18 μm and a surface roughness (Rz) of 0.8 μm. On the copper foil, the resin solution b of the polyamic acid prepared in Synthesis Example 2 and the resin solution a of the polyamic acid prepared in Synthesis Example 1 were sequentially coated and dried, and finally at 300. The heat treatment was carried out at a temperature of ° C or higher for about 10 minutes to obtain a flexible single-sided copper-clad laminate having a thickness of 25 μm of the polyimide layer. Meanwhile, in the polyimide layer, the layer obtained from the resin solution a of the poly-proline was 23 μm, and the layer obtained from the resin solution b of the poly-proline was 2 μm. The initial adhesion force of the 1 mm peeling of the copper clad laminate was 1.0 kN/m. Further, after the sample was chemically polished, discoloration could not be confirmed at the end of the circuit. The results are shown in Table 2.

(Example 2, Comparative Examples 1, 2)

The peeling strength and the chemical polishing resistance were evaluated in the same manner as in Example 1 except that the rolled copper foil shown in Table 1 having a different surface metal amount was used. The results are shown in Table 2.

In Table 1, Ni is the amount of nickel / (the amount of nickel + the amount of cobalt + the amount of zinc).

In the copper clad laminate obtained in Examples 1 and 2, no discoloration was observed at the end of the circuit after the chemical polishing treatment, and it was confirmed that no circuit peeling occurred. On the other hand, in Comparative Examples 1 and 2, it was confirmed that the entire circuit end had discoloration due to circuit peeling.

As described above, the flexible copper-clad laminate obtained in the present invention has high reliability because it does not cause circuit peeling after chemical polishing, and is confirmed to be a material suitable for fine processing.

Claims (4)

A flexible copper-clad laminate, which is a copper-clad laminate having a single-sided or double-area layer of a polyimide layer, wherein the polyimine resin layer has a coefficient of linear expansion (CTE) The polyimine resin layer (B) having a low linear expansion coefficient of 30 × 10 ^-6 (1/K) or less, and a coefficient of linear expansion (CTE) of 30 × 10 ^-6 to 60 × 10 ^-6 (1/ K) and a plurality of layers of a thermoplastic polyimide film (A) having a glass transition temperature in the range of 200 to 330 ° C, wherein the thermoplastic polyimide layer (A) is in contact with the copper foil, and the copper is The foil surface has a surface treatment layer consisting of a plurality of treatment layers comprising a decane coupling agent treatment layer, the surface treatment layer containing copper, cobalt, nickel and zinc, and a nickel/(nickel + cobalt + zinc) ratio of 0.23 to 0.3. (as determined by ICP-AES), and the zinc content is in the range of 0.2 to 0.6 mg/dm ² , and the aforementioned decane coupling agent treatment layer is formed of a decane coupling agent having an amine group. The flexible copper clad laminate according to claim 1, wherein the decane couplant treatment layer in the surface treatment layer is located at the outermost layer. The flexible copper clad laminate according to claim 1 or 2, wherein the copper foil is a rolled copper foil, and the surface of the surface treated copper foil which is in contact with the polyimide layer is rough. The degree (Rz) is in the range of 0.5 to 2 μm. The flexible copper-clad laminate according to the first or second aspect of the invention, wherein the initial force of the polyimide film layer and the copper foil at the initial width of 1 mm is 0.6 kN/m or more.