JP2005206915A - Copper foil for printed circuited board, and its production method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide copper foil for a two layer flexible board obtained by a casting method using a pyromellitic acid type polyimide precursor as the raw material, in which the ten point average roughness Rz of the copper foil face adhered to polyimide is ≤1.5 μm, and 90° normal peeling strength with polyimide is ≥1.0 kN/m, and to provide its production method. <P>SOLUTION: In the copper foil for a two layer flexible board, at least either side of the copper foil is provided with a fine cilia-shaped copper roughening treatment layer or a nickel and/or antimony-containing cilia-shaped copper alloy roughening treatment layer with a roughening particle length of 0.01 to 0.5 μm, also, the surface of the roughening treatment layer is provided with an alloy barrier layer composed of a tungsten or molybdenum-containing nickel-phosphorus layer, and also, the surface of the barrier layer is provided with a chromate film layer. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a copper foil for printed wiring boards and a method for producing the same, and more specifically, a fine ciliary copper roughening treatment having a roughened particle length of 0.01 to 0.5 μm on at least one surface of the copper foil or A ciliary copper alloy containing nickel and / or antimony is subjected to a roughening treatment, and an alloy barrier layer comprising a nickel-phosphorus layer containing tungsten or molybdenum is further provided on the roughening treatment layer, and further on the barrier layer. By applying a chromate film layer, the 10-point average roughness Rz of the copper foil treated surface can be reduced to 1.5 μm or less. Further, using the copper foil with the above surface treatment, casting with pyromellitic acid type polyimide as a raw material In addition to the copper foil for two-layer flexible substrate, the 90 ° normal peel strength with polyimide is 1.0 kN / m or more in the two-layer flexible substrate prepared by the method, and its manufacturing method It is.

  Printed wiring boards are widely used in various electrical devices that require high-density wiring, such as personal computers and mobile phones, but the recent development speed in this field is much faster than other industrial fields. The quality required for printed wiring boards is also increasing.

  A printed wiring board is roughly classified into a rigid substrate and a flexible substrate. Rigid board is a non-flexible printed wiring board that uses a copper-clad laminate made of paper or glass cloth hardened with thermosetting resin, and is fixed in a housing such as a computer or personal computer. Most printed wiring boards are rigid boards.

On the other hand, the flexible substrate is a printed wiring board in which a conductor pattern is formed on a flexible insulating film such as polyimide or polyester, and is used for a movable part, a place where flexibility is required, or a place where it is stored in a folded state. . This flexible substrate often uses a polyimide film having a high elastic modulus, heat resistance and chemical resistance, and excellent dimensional stability.
Its form consists of a polyimide film (12-125 μm) / adhesive layer (10-25 μm) / three-layer flexible substrate made of copper foil (18,35 μm) and a polyimide film (12-125 μm) / copper layer (3-18 μm) There is a two-layer flexible substrate.

There are still more three-layer flexible boards in the market, but with the recent progress of high performance, multi-functionality, small size, light weight, and portability of electronic information devices, ICs are becoming more highly integrated, faster, COF (Chip On Flexible Printed Circuit) is becoming mainstream as an LCD driver circuit board. In COF mounting, IC is directly mounted on a flexible board after circuit pattern formation, and heat resistance, dimensional stability, etc. are indispensable conditions. In particular, with regard to heat resistance, the mounting temperature has risen with the increasing frequency of use of lead-free solder in consideration of environmental problems in recent years, and higher heat resistance is required than before.

  On the other hand, the conventional three-layer flexible substrate has a problem that the heat resistance is not sufficient due to the presence of the adhesive layer. As mentioned earlier, the two-layer flexible substrate can be less than half the thickness of the three-layer flexible substrate, and is suitable for electronic information equipment applications that are rapidly becoming smaller, thinner and more portable. Under such market conditions, the flexible substrate is shifting from the three-layer flexible substrate to the two-layer flexible substrate, and it can be said that the two-layer flexible substrate is growing as a completely different market according to the viewpoint.

As a manufacturing method of the two-layer flexible substrate, there are a sputtering / copper plating method, a laminating method, and a casting method.
The sputtering / copper plating method is a method of forming a thin conductive layer by sputtering copper or a different metal after performing several kinds of pretreatments on a polyimide film, and further forming a copper layer by a wet electrolytic plating method. Since the conductor is formed by plating without using a copper foil, the flexibility of the conductor thickness is high. The laminating method is a method in which a polyimide film having adhesiveness and a copper foil are heat-pressed, and the used copper foil is generally 12, 18, 35 μm.

The casting method is a method in which polyimide varnish, which is a polyimide precursor, is applied onto a copper foil and heat-treated to form a polyimide. The two-layer flexible substrate has advantages and disadvantages in each method, but the following two points are particularly important in the copper foil properties required for the laminating method and the casting method using copper foil.
(1) Having sufficient peeling strength with the polyimide film.
(2) Ultra low roughness.

  As a general method for satisfying the required characteristic (1), there is a roughening treatment to an untreated copper foil obtained by cathodic electrolysis from sulfuric acid and a copper sulfate bath. Roughening treatment means that at least one surface of an untreated copper foil is catholyzed in sulfuric acid and a copper sulfate aqueous solution at a critical current density or higher to deposit copper protrusions, and copper or a copper alloy is further deposited on the layer. Cover plating is applied. As a result, the mechanical anchoring effect is enhanced and the peel strength is significantly increased.

  However, the problem solved by this roughening treatment is only the above-mentioned copper foil required characteristic (1), and conversely (2) is not satisfactory because the copper foil surface roughness increases. In recent years, the circuit pitch of flexible printed wiring boards has been rapidly reduced, and it is not uncommon for ultra-high thin flexible printed wiring boards to have a requirement of 40 μm or less.

  In addition, the linearity of the circuit is important for personal computers and the like because the electrical signal is becoming high frequency and the skin effect that current flows only on the circuit surface appears in the GHz order. Furthermore, the transparency of the polyimide film after etching is also important in order to eliminate optical positioning from the back surface and misalignment during thermocompression mounting when mounting a chip such as a semiconductor after circuit formation. All of these required characteristics can be achieved by ultra-low roughness of the copper foil surface. Thus, it can be seen that (1) and (2) are very difficult to achieve at the same time because of their conflicting characteristics.

As a method for solving these problems, for example, a copper foil surface treatment method suitable for a copper foil for a flexible substrate includes a cobalt plating layer or cobalt and a roughening treatment by plating made of copper-cobalt-nickel on the surface of the copper foil. After forming a plating layer made of nickel, a method of forming a single coating of chromium oxide or a treatment of chromium oxide with zinc and / or zinc oxide (see Patent Document 1), or copper- After roughening treatment by cobalt-nickel alloy plating, a cobalt-nickel alloy plating layer is formed, and after further zinc-nickel alloy plating is formed, chromium oxide single coating treatment or chromium oxide and zinc and / or zinc A method of forming an oxide treatment has been proposed (see Patent Document 2).
This method has a drawback that it is soluble in an alkaline etching solution having selective etching properties and has a low roughness, but the normal peel strength is not sufficient.

  In addition, as a method for obtaining sufficient normal peel strength, a method of electrolysis around an limiting current density in an acidic copper electrolytic bath containing arsenic, antimony, bismuth, selenium, tellurium (see Patent Document 3 and Patent Document 4) In addition, there has been proposed a method of electrolyzing around an upper limit current density in an acidic copper electrolytic bath containing one or two of chromium or tungsten (see Patent Document 5). This method is an effective means to obtain the normal peel strength because the rough surface of the copper foil is rough and the anchoring effect is high, but on the other hand, the roughness of the rough surface increases and is required for the current ultra-fine wire flexible substrate. It is not suitable for the fine line.

Furthermore, when the roughness of the copper foil rough surface is high as in the present method, the polyimide film surface after etching has the disadvantage that the transparency is extremely deteriorated because the shape of the copper foil surface is transferred as it is.
Japanese Patent Laid-Open No. 4-96395 Japanese Patent Laid-Open No. 9-87889 Japanese Patent Publication No.53-39327 Japanese Examined Patent Publication No. 54-38053 Japanese Patent No. 2717911

The present invention receives a particularly strong demand as a copper foil for a two-layer flexible board manufactured by a method using the above-described copper foil.
(1) Having sufficient peeling strength with the polyimide film.
(2) Ultra low roughness.
The copper foil surface that adheres to the polyimide in the two-layer flexible substrate created by the casting method using the pyromellitic acid type polyimide precursor as a raw material. Provided is a copper foil for a two-layer flexible substrate having a 10-point average roughness Rz of 1.5 μm or less, and having a 90 ° normal peel strength of 1.0 kN / m or more and a method for producing the same. Is an issue.

  As a result of studying various copper foil treatment methods for solving the problems (1) and (2) above as a copper foil for a two-layer flexible substrate, the roughened particle length is 0.01 to at least on one surface of the copper foil. A fine ciliary copper roughening treatment of 0.5 μm or a ciliary copper alloy roughening treatment containing nickel and / or antimony is applied, and a nickel-phosphorous layer containing tungsten or molybdenum is formed on the roughening treatment. By applying an alloy barrier layer and applying a chromate film layer on the barrier layer, the 10-point average roughness Rz of the copper foil treated surface can be reduced to 1.5 μm or less, and the copper subjected to the surface treatment of the present invention is further provided. Obtained knowledge that 90 ° normal peel strength with polyimide can be increased to 1.0 kN / m or more in a two-layer flexible substrate prepared by casting method using pyromellitic acid type polyimide precursor as a raw material using foil It was.

  The effect of the present invention is to obtain a copper foil that can ensure a sufficient peel strength from the polyimide film by performing the above surface treatment and can draw a super fine line pattern because of its ultra low roughness. It is done. Its application is suitable as a copper foil for a two-layer flexible substrate, which requires ultra-fine wire pattern, circuit linearity, sufficient normal peel strength, and high transparency for the polyimide film after etching.

The present invention is described in detail below.
In the present invention, the target surface-treated copper foil cannot be obtained even if any of the surface treatments described in detail below is lacking.

  First of all, the copper foil used for flexible substrates is the untreated copper foil used, but the rolled copper foil is common, but with the recent rise of the flexible substrate market, the electrolytic treatment has the same characteristics as the rolled copper foil. Copper foil is also being developed. For this reason, it is not necessary to limit to a rolled copper foil, and any copper foil may be used.

[Ciliary copper roughening layer or ciliary copper alloy roughening layer containing nickel and / or antimony]
The ciliated copper roughening layer or the ciliary copper alloy roughening layer containing nickel and / or antimony is a first surface treatment layer formed on the surface of the untreated copper foil and is formed by a plating method using a water-soluble electrolysis method. Is. By applying this treatment layer, the coatability with the polyimide precursor is improved, and the 90 ° normal peel strength after the formation of the polyimide film is improved.

  In addition, this treatment is a fine ciliary roughening treatment layer, and as mentioned earlier, unlike general roughening treatment methods, it is possible to suppress the increase in roughness of the surface extremely low, high etching accuracy, There is also an advantage that the polyimide film after etching can have high transparency. In addition, there is also an advantage that the adhesiveness to the copper foil is high and there is little powder omission that is generally said.

  When the particle length of the cilia-like roughening treatment of the present invention is in the range of 0.01 to 0.5 μm, it is good in all properties, but outside this range, if less than 0.01 μm, the coatability with the polyimide precursor is Depending on the amount of precipitation of the alloy barrier layer comprising a nickel-phosphorus layer containing tungsten or molybdenum after the deterioration, there may be a problem that sufficient 90 ° normal peel strength cannot be obtained. On the other hand, when the thickness exceeds 0.5 μm, the roughness of the rough surface increases, and as a result, the etching accuracy may be deteriorated and the transparency of the polyimide film after etching may be deteriorated.

  The appearance color tone of this treatment layer is brown to black, and the color of the copper foil can be controlled by a combination of metal elements. In the case of copper single roughening treatment, brown-brown color is exhibited, the copper-nickel alloy roughening treatment layer is gray-black, the copper-antimony alloy roughening treatment layer is black, and the copper-nickel-antimony 3 The base alloy roughening layer exhibits gray to black.

As an electrolytic bath and electrolytic conditions for applying the roughening treatment layer, for example, the following conditions are preferable.
Copper sulfate pentahydrate 10-100g / L (particularly preferably 30-70g / L)
Nickel sulfate hexahydrate 0-100 g / L (particularly preferably 10-70 g / L)
Potassium antimonyl tartrate 0-10 g / L (particularly preferably 1-5 g / L)
Diethylenetriaminepentaacetic acid pentasodium (hereinafter DTPA · 5Na)
10 to 300 g / L (particularly preferably 40 to 100 g / L)
pH 2.5-13.0 (particularly preferably 3.5-6.0)
The pH adjustment is using sulfuric acid and sodium hydroxide current density 0.5~10.0A / dm ² (particularly preferably 1.0~4.0A / dm ²⁾
Electricity 10 ~ 400A ・ sec / dm ² (particularly preferably 20 ~ 150A ・ sec / dm ² )
Liquid temperature 20-70 ° C (preferably 20-50 ° C)
Anode copper

The metal ion supply source is not limited to sulfate, acetate, citrate and the like. The concentration of DTPA · 5Na is suitably 10 to 300 g / L. Outside this range, when the concentration is 10 g / L or less, it is difficult to obtain a sufficient refining effect and coarse particles become coarse.
If it is 300 g / L or more, the current efficiency is lowered, the amount of precipitation in the roughening treatment is extremely reduced, and the voltage is further increased, which is not economical. Further, even when this treatment is performed using an aminocarboxylate having a molecular structure similar to that of diethylenetriaminepentaacetate, it is not possible to obtain roughened particles having stickiness.

In addition, the amount of electricity is 10 to 400 A · sec / dm ^{2, and} in this range, it depends on the amount of precipitation of the alloy barrier layer consisting of a nickel-phosphorous layer containing tungsten or molybdenum as the second treatment layer, but with polyimide. 90 ° normal peel strength is high, and ultra-low roughness is achieved. On the other hand, when the amount of electricity is less than 10 A · sec / dm ² , the wettability with polyimide deteriorates and the 90 ° normal peel strength decreases. On the other hand, when it exceeds 400 A · sec / dm ² , problems such as poor adhesion to the copper foil, increased powder fall, and increased roughness of the rough surface occur.

[Alloy barrier layer made of nickel-phosphorus layer containing tungsten or molybdenum]
The alloy barrier layer comprising a nickel-phosphorus layer containing tungsten or molybdenum is a ciliary copper roughening layer or a second surface treatment layer performed after a ciliary copper alloy roughening layer containing nickel and / or antimony. It is formed by a plating method using a water-soluble electrolysis method. By applying this treatment layer, the 90 ° normal peel strength after polyimide film formation is remarkably high due to the synergistic effect with the ciliary copper roughening treatment layer or the ciliary copper alloy roughening treatment layer containing nickel and / or antimony. To improve. Although the detailed mechanism by which the 90 ° normal peel strength is significantly improved is not known, the same phenomenon can be confirmed not only in the alloy barrier layer but also in the nickel single layer, and it is assumed that the compatibility between nickel and polyimide is good. The

  On the other hand, the nickel single layer is soluble in the ferric chloride and cupric chloride etchants often used in circuit formation, but is insoluble in the alkaline etchant often used in pattern plating. In addition, it has a serious drawback that an etching residue (stain) that impairs electrical insulation is generated. When considering the narrowing of circuits in recent years, it is an indispensable condition that a fine pattern can be drawn with ferric chloride or cupric chloride, but alkali etching is also an indispensable condition due to various types of resists.

  On the other hand, an alloy barrier layer composed of a nickel-phosphorus layer containing tungsten or molybdenum has sufficient 90 ° normal peel strength, and at the same time, depending on the content of each element, it is soluble in an alkaline etchant and nickel alone There is an advantage that it is more versatile than the layer.

The good content of each element in this alloy barrier is the following conditions in weight percent (wt%).
60wt% ≤nickel≤99wt% (including nickel in the first layer)
1wt% ≤ phosphorus ≤ 20wt%
0.1wt% ≦ tungsten ≦ 20wt% or 0.1wt% ≦ molybdenum ≦ 20wt%
More preferably
80wt% ≦ nickel ≦ 95wt% (including nickel in the first layer)
3wt% ≤ phosphorus ≤ 17wt%
0.4wt% ≤ tungsten ≤ 15wt% or 0.4wt% ≤ molybdenum ≤ 20wt%

Also, precipitation of the alloy barrier layer is also important range of 40 to 500 mg / m ² are preferred, more preferably from 50 to 300 mg / m ^2. When the precipitation amount of this alloy barrier layer is less than 40 mg / m ² , the effectiveness of this alloy barrier cannot be fully exhibited, and a sufficient value may not be obtained in the 90 ° normal peel strength. On the other hand, when it exceeds 500 mg / m ² , problems such as copper purity lowering, high cost and uneconomical, and long etching time during circuit formation may occur.

As an electrolytic bath for applying the alloy barrier layer and electrolytic conditions, for example, the following conditions are preferable.
In the case of a nickel-phosphorus layer containing tungsten, nickel sulfate hexahydrate 10 to 100 g / L (particularly preferably 20 to 50 g / L)
Sodium tungstate dihydrate 0.1-20 g / L (particularly preferably 0.5-10 g / L)
Sodium hypophosphite monohydrate 0.1-10 g / L (particularly preferably 0.5-5 g / L)
Sodium acetate trihydrate 2-20g / L (particularly preferably 3-15g / L)
pH 3.0-5.5 (particularly preferably 3.5-5.0)
Use sulfuric acid to adjust pH Current density 0.1 to 10.0 A / dm ² (particularly preferably 0.5 to 5.0 A / dm ² )
Amount of electricity 1.0 to 30.0 A · sec / dm ² (particularly preferably 2.0 to 20.0 A · sec / dm ² )
Liquid temperature 20-50 ° C (particularly preferably 25-40 ° C)
Anode platinum

In the case of molybdenum-containing nickel-phosphorus layer Nickel sulfate hexahydrate 10 to 100 g / L (particularly preferably 20 to 50 g / L)
Disodium molybdate dihydrate 1 to 200 g / L (particularly preferably 10 to 100 g / L)
Sodium hypophosphite monohydrate 1-70 g / L (particularly preferably 5-40 g / L)
Trisodium citrate dihydrate 10-100 g / L (particularly preferably 20-70 g / L)
pH 9.0-12.0 (particularly preferably 10.0-11.0)
Use ammonia water to adjust pH Current density 0.1 to 10.0 A / dm ² (particularly preferably 0.5 to 5.0 A / dm ² )
Amount of electricity 1.0 to 30.0 A · sec / dm ² (particularly preferably 2.0 to 20.0 A · sec / dm ² )
Liquid temperature 20-50 ° C (particularly preferably 25-40 ° C)
Anode platinum

  As the supply source of nickel, phosphorus, tungsten and molybdenum ions, the following can be used. However, it is not limited to this. Nickel sulfate, nickel ammonium sulfate, nickel chloride, nickel acetate and the like can be used as a nickel ion supply source. As a source of phosphorus ions, sodium phosphite, sodium hypophosphite, nickel phosphite and the like can be used. As a supply source of tungsten ions, sodium tungstate, potassium tungstate, ammonium tungstate, or the like can be used. As a supply source of molybdenum ions, sodium molybdate, potassium molybdate, ammonium molybdate and the like can be used. Moreover, you may add sodium sulfate as provision of electroconductivity.

  The pH varies in the appropriate range when tungsten or molybdenum is used for the alloy barrier layer, but the pH is preferably about 3.0 to 5.5 when tungsten is used, and about 9.0 to 12.0 when molybdenum is used. In this pH range, the simultaneous precipitation of the three elements, the barrier properties, and the workability are all good, but this is not limited to the above conditions. In addition, the electrolytic solution for forming the tungsten-containing nickel-phosphorous layer employs an acetic acid bath as a pH buffering agent. However, unlike the chelate bath, nickel can be easily removed by a neutralization coagulation precipitation method when performing waste liquid work. Is possible and is very advantageous for environmental measures.

[Chromate film layer]
The chromate coating layer contains a ciliary copper roughening layer which is the first surface treatment layer or a ciliary copper alloy roughening layer containing nickel and / or antimony, and then a second surface treatment layer of tungsten or molybdenum. This is a third surface treatment layer formed after the alloy barrier layer made of a nickel-phosphorus layer is formed, and is formed by plating by a water-soluble electrolysis method or immersion in an aqueous solution. By applying this chromate film layer, various properties are improved. For example, the oxidation resistance is improved, and the normal peel strength is increased in order to improve the adhesion to the substrate.

  Moreover, the bath for forming this chromate film layer may be a known bath, and any material having hexavalent chromium such as chromic acid, sodium dichromate, potassium dichromate, etc. may be used. The chromic acid solution may be alkaline or acidic. Each of the above two types of chromic acid solution has advantages and disadvantages, and may be properly used depending on the purpose of use. However, when an alkaline chromic acid solution is used, the chromate film layer has a slightly lower corrosion resistance than the acidic chromic acid solution. Although there is a disadvantage that the adhesion to the bonding substrate is slightly inferior, the above-mentioned problem does not occur even if the chromate film layer is applied with the alkaline chromic acid solution on the surface treatment of the present invention.

  In addition, an alkaline zinc chromate solution containing zinc ions and hexavalent chromium ions described in Japanese Patent Publication No. 58-15950 may be used as the alkaline chromic acid solution. Oxidation resistance can be improved as compared with the chromate film layer. Of course, even if an acidic chromic acid solution is used, the same result can be obtained without any problem.

Examples of the electrolytic bath and electrolysis conditions for applying the chromate film layer include the following conditions.
Sodium dichromate 10g / L
Bath temperature 30 ℃
pH 4.2
Current density 0.5A / dm ²
Electrolysis time 5 seconds Anode Platinum

Examples of the present invention and comparative examples will be described below.
(Examples 1 to 26)

The rolling oil was removed by immersing a previously prepared 35 μm untreated rolled copper foil having a surface roughness of Rz 0.72 μm (10-point average roughness) in a hydrocarbon-based organic solvent for 60 seconds. After washing with water, perform electrolysis at a current density of 5 A / dm ² for 6 seconds using a copper plate as the cathode and the above-mentioned untreated rolled copper foil as the anode in a 100 g / L sulfuric acid solution. Made.

  After washing with water, a ciliary copper roughening layer or a ciliary copper alloy roughening treatment containing nickel and / or antimony, which becomes the first surface treatment layer of the present invention, using a copper plate as an anode for Examples 1 to 26, The bath was formed at the constant bath temperature of 40 ° C. and the electrolytic bath composition and electrolytic conditions shown in Table 1. In addition, DTPA * 5Na density | concentration in this bath is constant in Examples 1-26, and is 60 g / L.

  After washing with water, an alloy barrier layer composed of a nickel-phosphorus layer containing tungsten or molybdenum as the second surface treatment layer of the present invention was used, and platinum was used as the anode for Examples 1 to 26, and the bath temperature was kept at 30 ° C. Formation was performed with the electrolytic bath composition and electrolytic conditions shown in 1. In Examples 1 to 4, 8 to 12, 15 to 18, and 21 to 24 when forming a tungsten-containing nickel-phosphorus layer, an acetic acid bath is used, but the concentration of sodium acetate trihydrate in the electrolytic bath is constant. It is 10g / L. Further, Examples 5 to 7, 13, 14, 19, 20, 25, and 26 when forming a molybdenum-containing nickel-phosphorous layer use a citric acid bath, but the concentration of trisodium citrate dihydrate in the electrolytic bath Is a constant condition and is 50 g / L.

After washing with water, a chromate film layer serving as the third surface treatment layer of the present invention was formed with the electrolytic bath composition and electrolysis conditions shown below for Examples 1 to 26.
Sodium dichromate 10g / L
Bath temperature 30 ℃
pH 4.2
Current density 0.5A / dm ²
Electrolysis time 5 seconds Anode Platinum

  Table 2 shows the results of quantifying the precipitation amount for each element on the surface of the rolled copper foil subjected to the surface treatment of the present invention consisting of three layers. In addition, about Examples 8-14 and 21-26 which used nickel for the cilia-like roughening processing layer used as the 1st surface treatment layer, from the nickel-phosphorus layer containing tungsten or molybdenum used as the 2nd layer surface treatment layer The total amount of precipitation with nickel deposited from the alloy barrier layer.

  Next, a pyromellitic acid type polyimide precursor was applied to the rolled copper foil with a clearance of 350 μm using a bar coater. This polyimide precursor was obtained by collecting N, N-dimethylacetamide in a separable flask, dissolving pyromellitic anhydride and 4,4′-diaminodiphenyl ether with stirring, and performing a polymerization reaction by stirring.

  Next, the copper foil after coating the polyimide precursor was vaporized at 130 ° C for 10 minutes and 200 ° C for 4 minutes with a drier in the atmosphere, and then heat-cured at 360 ° C for 2 minutes with an inert drier. A two-layer flexible substrate was produced. The thickness of the polyimide film at this time was 32 to 37 μm.

Comparative example

(Comparative Example 1)
Surface treatment was performed in the same manner as in Examples 1 to 26 except that ciliary roughening treatment, which was the first treatment layer of the present invention, was not performed, and a two-layer flexible substrate was produced in the same manner. In this comparative example, the electrolytic bath composition and electrolysis conditions of the alloy barrier layer composed of the tungsten-containing nickel-phosphorous layer that is the first treatment layer in this comparative example are shown in Table 1, and the quantitative results of the amount of each element deposited on the surface of the rolled copper foil are shown. It is shown in Table 2.
(Comparative Examples 2 to 5)

Surface treatment was carried out in the same manner as in Examples 1 to 26 except that an alloy barrier layer comprising a nickel-phosphorus layer containing tungsten or molybdenum as the second treatment layer of the present invention was not used. A layer flexible substrate was prepared. The electrolytic bath composition and electrolysis conditions of the ciliary copper roughening layer or the ciliary copper alloy roughening layer containing nickel and / or antimony, which are the first treatment layer in this comparative example, are shown in Table 1, and rolled. Table 2 shows the quantitative results of the amount of each element deposited on the treated copper foil surface.
(Comparative Example 6)

Surface treatment was performed in the same manner as in Examples 1 to 26 except that a single nickel layer was used instead of an alloy barrier layer comprising a nickel-phosphorus layer containing tungsten or molybdenum as the second treatment layer of the present invention. A two-layer flexible substrate was produced by the same method. In this comparative example, a ciliary copper roughening layer or a ciliary copper alloy roughening layer containing nickel and / or antimony, which is the first layer in this comparative example, the electrolytic bath composition, electrolysis conditions, and the second layer Table 1 shows the electrolytic bath composition and electrolysis conditions of the nickel single layer, and Table 2 shows the quantitative results of the amount of each element deposited on the surface of the rolled copper foil.
(Comparative Example 7)

The rolling oil was removed by immersing a previously prepared 35 μm untreated rolled copper foil having a surface roughness of Rz 0.72 μm (10-point average roughness) in a hydrocarbon-based organic solvent for 60 seconds. After washing with water, perform electrolysis at a current density of 5 A / dm ² for 6 seconds using a copper plate as the cathode and the above-mentioned untreated rolled copper foil as the anode in a 100 g / L sulfuric acid solution. Made.

After washing with water, cathodic electrolysis was performed using an electrolytic bath having the following bath composition, and surface roughening was performed.
Copper sulfate pentahydrate 70g / L
Sulfuric acid 100g / L
Liquid temperature 35 ℃
Current density 20A / dm ²
Electrolysis time 5 seconds Anode Platinum

Next, cathodic electrolysis was performed using an electrolytic bath having the following bath composition, and cover plating was applied to the surface roughening treatment.
Copper sulfate pentahydrate 250g / L
Sulfuric acid 100g / L
Liquid temperature 45 ℃
Current density 10A / dm ²
Electrolysis time 30 seconds Anode Platinum

Next, rust prevention treatment was performed using an electrolytic solution having the following bath composition.
Sodium dichromate 10g / L
Bath temperature 30 ℃
pH 4.2
Current density 0.5A / dm ²
Electrolysis time 5 seconds Anode Platinum A two-layer flexible substrate was produced from the rolled copper foil obtained as described above in the same manner as in Examples 1 to 26.

  Table 3 shows the results of evaluating the 90 ° normal peel strength, the roughened surface roughness (Rz: 10-point average roughness), and the alkali etching property of the two-layer flexible substrate obtained as described above. In addition, the evaluation method of each test is shown below.

90 ° normal peel strength
Measured according to JIS C 5016 method.
After forming a circuit with a copper width of 1 mm by etching cupric chloride on a 2 mm thick vinyl chloride plate
The two-layer flexible substrate was fixed with double-sided tape, and the peel strength at 90 ° was measured at a speed of 50 mm every time using a tensile tester.

Roughening surface roughness (Rz: 10-point average roughness)
Measured according to the method of JIS B 0601.

Alkali etchability Alkaetch used by Yamatoya Corporation.
A 2-layer flexible substrate is immersed in 1L of Alkaetch maintained at 47-50 ° C and held for 10 minutes while stirring with a magnetic stirrer. Thereafter, it was washed with water and dried, and the etching residue was visually confirmed.
Evaluation: ○ No etching residue is observed.
X A strong etching residue is observed.

  As shown in Table 3, the two-layer flexible substrate produced using the copper foil having the surface-treated layer of the present invention has good adhesion to polyimide, and the 90 ° normal peel strength is 1.0 kN / m or more, It can be seen that the ten-point average roughness Rz of the copper foil roughening-treated surface is 1.5 μm or less and is soluble in an alkaline etching solution. Further, as can be seen from the electron micrograph of the copper foil surface treatment shape of the present invention of FIG. 2 attached, since the roughened particles are extremely fine, the polyimide film surface to which the copper foil surface shape is transferred is extremely high after etching. It turns out that it can have transparency.

  On the other hand, Comparative Examples 1 to 5 in which one or more kinds of the surface treatment method of the present invention were not performed are suitable for use in a two-layer flexible substrate where the 90 ° normal peel strength is as low as 0.40 kN / m or less and the demand for the ultrafine wire pattern is high. I understand that there is no. Further, as for Comparative Example 6, the 90 ° normal peel strength is a sufficiently high value at the Example level, but there is a defect that etching residue is generated in the alkali etching test and is less versatile than the surface treatment method of the present invention. I understand that there is.

In addition, it can be seen that Comparative Example 7 has a 90 ° normal peel strength higher than that of the Example, but is not suitable for a two-layer flexible substrate application where the roughness of the rough surface is high and a super fine line pattern is required. Furthermore, as can be seen from the attached copper foil surface treatment shape electron micrograph of FIG. 3, the roughened particle diameter is much larger than the roughened treatment diameter of the present invention. It is expected that the transparency after etching will be worsened and will hinder the manufacturing process of the two-layer flexible substrate.

  By using a copper foil prepared using the surface treatment method of the present invention, a two-layer flexible substrate can be prepared to ensure sufficient peel strength from the polyimide, and the ultra-low roughness can be used to draw an ultra-fine line pattern. The copper foil which becomes possible is obtained. Further, in the future, it is considered that it can sufficiently cope with a two-layer flexible substrate that is expected to have a finer pitch between circuit pitches.

This invention surface treatment copper foil cross-sectional schematic diagram Copper foil surface treatment shape electron micrograph of the present invention (Example 2) Conventional copper foil surface treatment shape electron micrograph (Comparative Example 7)

Explanation of symbols

1-copper foil 2-ciliary copper roughening layer or containing nickel and / or antimony
Ciliated copper alloy roughening layer 3-nickel-phosphorus layer containing tungsten or molybdenum 4-chromate film layer

Claims (8)

  A fine cilia-like roughened layer on at least one surface of the copper foil, and an alloy barrier layer comprising a nickel-phosphorus layer containing tungsten or molybdenum on the roughened layer; and A copper foil for a two-layer flexible substrate, comprising a chromate film layer on the alloy barrier layer.   2. The copper foil for a two-layer flexible substrate according to claim 1, wherein the fine cilia-like roughened layer is copper.   2. The copper foil for a two-layer flexible substrate according to claim 1, wherein the fine ciliary roughening layer is a copper alloy containing nickel and / or antimony.   4. The copper foil for a two-layer flexible substrate according to claim 1, wherein the fine ciliary roughening treatment has a particle length of 0.01 to 0.5 [mu] m.   The copper foil for a two-layer flexible substrate according to any one of claims 1 to 4, wherein the ten-point average roughness Rz of the copper foil surface bonded to polyimide is 1.5 µm or less.   A fine ciliary roughening treatment layer is applied to at least one surface of the copper foil, and an alloy barrier layer comprising a nickel-phosphorus layer containing tungsten or molybdenum is provided on the roughening treatment layer; and the alloy A method for producing a copper foil for a two-layer flexible substrate, comprising applying a chromate film layer on the barrier layer.   7. The method for producing a copper foil for a two-layer flexible substrate according to claim 6, wherein the electrolytic solution for applying the fine ciliary roughening treatment layer is an electrolytic bath containing diethylenetriaminepentaacetate and copper. 7. The copper foil for a two-layer flexible substrate according to claim 6, wherein the electrolytic solution for applying the fine ciliary roughening layer is an electrolytic bath containing diethylenetriaminepentaacetate and nickel and / or antimony and copper. Production method.

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