JP3210796B2 - High temperature stretched copper foil for printed circuits - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-temperature stretched copper foil for a printed circuit, and more particularly to a glossy surface of a copper-clad laminate during and after the production process so that the copper foil is not torn. For copper-clad laminates with reduced roughness and smoothness
The present invention relates to high-temperature stretched copper foil for printed circuits.

[0002]

2. Description of the Related Art Copper and copper alloy foils (hereinafter referred to as copper foils)
Has contributed greatly to the development of the electrical and electronics related industries,
In particular, it is indispensable as a printed circuit material. In general, copper foil for printed circuits is laminated and bonded to a base material such as a synthetic resin board and a film under a high temperature and a high pressure with an adhesive or without using an adhesive to produce a copper-clad laminate. After printing a circuit necessary to form a desired circuit, an etching process for removing unnecessary portions is performed. Finally, the required elements are soldered to form various printed circuit boards for electronic devices. The quality requirements for the copper foil for printed circuit boards are different for the surface (roughened surface) bonded to the resin base material and the non-bonded surface (glossy surface), and many methods have been proposed for each.

[0003] As a method for producing a copper-clad laminate, a hot press method or a continuous method has recently been adopted. For example, taking the production of a paper-based phenolic resin copper-clad laminate by a hot press method as an example, a prepreg is produced by synthesizing a phenolic resin, impregnating and drying the phenolic resin on the paper substrate, and finally, A predetermined number of prepregs and copper foils are combined, hot-pressed by a multi-stage press, opened, trimmed, and sent to the next step. In the case of the continuous method, a single-sided copper-clad laminate and a double-sided copper-clad laminate are manufactured. For example, in the case of a paper-based polyester resin copper-clad laminate, the base paper is unwound from a plurality of roll-shaped base papers, individually processed through a paper treatment and a resin impregnation step, and a plurality of resin-impregnated papers are laminated by a roll pair. You. Next, a copper foil that has undergone an adhesive application step, or in the case of one side, a copper foil and a carrier are laminated. The product thickness is controlled in the laminating and laminating steps. Next, the resin is sent to a curing furnace, where a curing reaction of the resin occurs and the resin is cured. After curing, it goes through fixed-size cutting, after-curing, and polishing of the end face, and is further subjected to appearance inspection and characteristic inspection to obtain a product. Rolled raw materials such as base paper, copper foil and carrier are successively connected to new rolls, and continuous operation is performed. The difference between one side and both sides is that in the case of one side,
The carrier film is pulled out from below, and after the resin is cured, the carrier is peeled off and wound up.On the other hand, in the case of both sides, the copper foil is fed out from the bottom through the adhesive application step, and the other steps are also performed on one side. Both sides are equivalent. In addition, a glass-epoxy resin substrate and the like are manufactured in a similar process.

[0004] During the production of a copper-clad laminate, distortion of the inside of the insulating layer due to the movement of the resin such as curing shrinkage and thermal expansion of the resin when the resin-impregnated base material becomes the insulating layer, and the resulting printed circuit board It is known that a copper foil having a high elongation at a high temperature may be used in order to suppress the occurrence of warpage or twist.
For example, according to the description of JP-A-5-243698,
"The metal foil used in the conventional method for continuously manufacturing a metal foil-clad laminate has a low elongation at a high temperature. For example, the elongation at 180 ° C. is about 1 to 8%. Since the material cannot follow the movement of the resin such as curing shrinkage and thermal expansion of the resin when the material becomes an insulating layer, distortion tends to occur inside the insulating layer, and this distortion causes the metal foil-clad laminate to warp or twist. In particular, in metal foil-clad laminates manufactured continuously using long metal foils, the metal foil is always laminated while being stretched during the manufacturing process. And in the case of a double-sided metal foil-clad laminate,
If only one side of the metal foil is removed, warpage and torsion increase due to distortion of the insulating layer. In addition, there is a problem that the dimensional change rate when the metal foil is removed is increased due to the strain inside the insulating layer. The object of the present invention is to provide a metal foil-clad laminate that has less warpage and twist, and that is further excellent in dimensional stability, and a method for producing the same, which is a metal foil-clad laminate manufactured continuously. As 150
It is described that a metal foil having an elongation percentage of 10 to 50% at a temperature of from 200C to 200C is used.

[0005] In the case of copper foil, tension at 180 ° C: tensile strength of 10
２０20 kg / mm ² , elongation: 10-50%, for example, S
A high-temperature and high-strength copper foil called TCS foil (manufactured by Nikko Gould Foil Co., Ltd.) has been obtained.

[0006]

This type of high-temperature, high-strength copper foil is recrystallized by the heat applied during the production of a circuit board.
Hardness decreases. In conventional high-temperature stretched copper foil for printed circuits, after the copper-clad laminate is manufactured, when the circuit board moves due to vibration during loading and transporting, for example, foreign matter such as resin powder generated at the time of cutting is caught and becomes There is a problem that the copper foil is easily torn and thus the copper foil is easily torn. Further, in the case of the double-sided copper-clad laminate, similar tearing of the copper foil was likely to occur even when the hills on the glossy side were caught.

An object of the present invention is to solve the above-mentioned drawbacks. That is, an object of the present invention is to develop a high-temperature stretched copper foil for a printed circuit which can suppress the occurrence of tearing of the copper foil after manufacturing the copper-clad laminate.

[0008]

Means for Solving the Problems In order to solve the above-mentioned drawbacks, the present inventors have conducted intensive studies. As a result, the surface exposed after the production of the copper-clad laminate, that is, the glossy surface side, appears to be smooth at first glance, but still appears to be smooth. Roughness remains on the surface, which causes foreign matter such as resin powder to be caught or crests on the glossy side of the copper foil. By reducing the Ra to 0.15 μm or less, it was found that such catching can be drastically reduced and the occurrence of tearing of the copper foil can be suppressed. In order to reduce the center line average roughness Ra to 0.15 μm or less, it has been found effective to form an extremely thin copper plating layer or zinc plating layer on the glossy surface side. Based on this finding, the present invention provides a 180 ° C. tensile: tensile strength 1
0 to 20 kg / mm ² , elongation: 10 to 50%.
1-20 mg / dm ² copper plating layer or zinc plating layer is formed, and the roughness on the glossy surface side is represented by center line average roughness Ra and Ra: 0.15 μm or less, smoothed luster Characterized by having a surface for copper-clad laminates
Providing a high hot stretch foil for only the printed circuit.

[0009]

The surface roughness of the glossy side of the high-temperature stretched copper foil for a printed circuit is represented by a center line average roughness Ra, and is reduced to 0.15 μm or less. Since the surface laminate has a low surface roughness, even if a foreign substance such as a resin powder enters, it is less likely to be caught, acts like a roller, and is less likely to bite into the copper foil. In addition, the copper foil glossy surface is less likely to be caught by the mountains. Therefore, the occurrence of tearing of the copper foil is suppressed. To reduce roughness on the glossy side of the copper foil for printed circuits, use very thin copper plating on the glossy side
There are methods for forming layers or galvanized layers .

[0010]

DETAILED DESCRIPTION OF THE INVENTION The copper foil used in the present invention is a high-temperature stretched copper foil. High temperature and high temperature copper foil is 180
° C Tensile: Tensile strength 10-20 kg / mm ² , Elongation: 10
ＳＴ50%, for example, STCS foil manufactured by Nikko Gould Foil Co., Ltd.

Although the present invention pertains to the glossy surface of a high-temperature and high-strength copper foil, the roughened surface of the copper foil will be described for reference. Normally, for the purpose of improving the peeling strength of the copper foil after lamination on the surface of the copper foil that adheres to the resin substrate, that is, the roughened surface, for example, copper bumps on the surface of the degreased copper foil. A copper roughening treatment for performing electrodeposition in a shape is performed. Such a bumpy electrodeposition of copper is easily provided by so-called burnt electrodeposition. As an example of the copper roughening treatment, for example, the following conditions can be adopted. [Doaraka processing conditions] _{Cu: 5~50g / l H 2 SO} 4: 10~100g / l As: 0.01~5g / l liquid temperature: room temperature _{~50 ℃ D k: 5~80A / dm} 2 hours : 1 to 30 seconds

After the roughening treatment, thin copper plating is performed as a covering layer for preventing the particles from falling off. For example, the following conditions can be adopted. [Cover thin copper layer plating conditions] _{Cu: 30~100g / l H 2 SO} 4: 10~200g / l liquid temperature: room temperature _{~75 ℃ D k: 5~60A / dm} 2 Time: 1-30 seconds

It is preferable to perform a treatment for forming one or more single metal layers or alloy layers selected from Cu, Cr, Ni, Fe, Co and Zn on the roughened surface. Examples of alloy plating include Cu-Ni, Cu-C
o, Cu-Ni-Co, Cu-Zn and others (for details, see JP-B-56-9028,
4-13971, JP-A-2-292895, JP-A-2-292894, JP-B-51-35711, JP-B-54-6701, etc.). Such a treatment serves as a final property of the copper foil and as a barrier.

On the glossy surface to which the present invention relates, first, a surface roughness reduction treatment for further improving the smoothness of the glossy surface is performed. In order to reduce snagging and suppress the occurrence of tearing of the copper foil, the center line average roughness Ra: 0.15
It is necessary to reduce it to μm or less. This is applied Limi by the performing the copper Me <br/> Kki or galvanized. Examples of conditions for copper plating and zinc plating are given below. [Cu plating conditions] _{Cu: 30~100g / l H 2 SO} 4: 10~200g / l Temperature: room temperature _{~75 ℃ D k: 0.5~60A / dm} 2 Time: 1-30 sec [Zn plating conditions] Zn: 15 to 70 g / l pH: 2.5 to 4.5 g / l Temperature: 40 to 60 ° C. D _k : 0.05 to ^{2 A} / dm ² hours: 1 to 10 seconds The adhesion amount is usually 0.01 to 20 mg. / Dm ² , preferably 0.05 to 10 mg / dm ² , particularly 0.5 to 5 mg / dm ²
dm ² . The pits in the range of 0.1 to 0.3 μm scattered on the original copper foil glossy surface by the copper or zinc plating completely disappear, and the entire surface is covered with fine copper or zinc formed by the plating operation. It was confirmed by a scanning electron microscope (SEM) image at a magnification of 30,000 times.

Thereafter, heat-resistant oxidation treatment is performed as required. Any of the known methods can be used for the heat-resistant oxidation treatment. For example, Zn plating is a typical example. The electrolysis conditions are given. [Zn plating conditions] _{ZnSO 4 · 7H 2 O: 50~350g} / l pH ( sulfate): 2.5 to 4.5 Liquid _{temperature: 40~60 ℃ D k: 0.05~0.4A /} dm 2 hours : 10 to 30 seconds The amount of deposited Zn is generally 15 to 1500 µg / dm ² , preferably 15 to 400 µg / dm ² .

In addition, thermal oxidation resistance (discoloration such as oxidation is prevented under the conditions of 100 ° C. or more × 30 minutes in air, preferably 200 ° C. or more × 30 minutes, particularly preferably 240 ° C. or more × 30 minutes. To increase Zn and Ni, Co,
A Zn alloy plating process made of one or more metals selected from V, W, Mo, Sn, Cr, and the like has been proposed and has achieved results.

For example, taking a Zn-Ni alloy treatment as an example, this is preferably done using a Zn-Ni electrolytic plating bath, preferably with a composition of 50-97 wt% Zn and 3-50 wt% Ni. Zn-Ni alloy layer 100-500μ
It is carried out so as to form a very thin film with an adhesion amount of g / dm ² . If the Ni content is less than 3% by weight, the required improvement in thermal oxidation resistance cannot be obtained. On the other hand, if the Ni content exceeds 50% by weight, the solder wettability deteriorates, and the thermal oxidation resistance also deteriorates. The adhesion amount of the Zn—Ni alloy layer is 100 μg / dm.
^If it is less than ² , improvement in thermal oxidation resistance cannot be obtained. The other 50
If it exceeds 0 μg / dm ² , the conductivity will deteriorate due to the diffusion of Zn or the like. The Zn-Ni alloy layer enhances the thermal oxidation resistance of the glossy surface of the copper foil, and does not impair other properties such as solder wettability and resist adhesion. The amount of adhesion is made thin as described above so that the appearance is not so different from the copper color. The same applies to the Zn—Co alloy treatment.

The composition and conditions of the Zn-Ni plating bath and the Zn-Co plating bath are as follows: [Zn-Ni (or Zn-Co) plating bath conditions] Zn: 5 to 50 g / l Ni (to Co): 1 to 50 g / l pH: 2.5 to 4 Temperature: 30 to 60 ° C Current density: 0.5 to 5 A / dm ² Plating time: 0.1 to 10 seconds

Thereafter, a Cr-based rust-proofing treatment is performed on the heat-resistant oxidation-treated layer or on the glossy surface without the heat-resistant oxidation-treated layer. The Cr-based rust-preventive layer is formed by (1) a single film treatment of chromium oxide, (2) a mixed film treatment of chromium oxide and zinc and / or zinc oxide, or (3) a combination thereof. Rust prevention layer mainly composed of chromium oxide.

Regarding the treatment of a single film of chromium oxide,
Either immersion chromate or electrolytic chromate may be used. When weather resistance is required, electrolytic chromate is preferred. The conditions of immersion chromate or electrolytic chromate follow those established in the art. For example, examples of conditions for immersion chromate and electrolytic chromate treatment are as follows:
(A) Immersion chromate treatment: K ₂ Cr ₂ O ₇ : 0.5 to 1.5 g / l pH: 1.4 to 5.0 Temperature: 20 to 60 ° C. Time: 3 to 10 seconds (B) Electrolytic chromate treatment : K ₂ Cr ₂ O ₇ : 0.2 to 20 g / l (Na ₂ Cr ₂ O ₇ , CrO ₃ ) Acid: phosphoric acid, sulfuric acid, organic acid pH: 1.0 to 3.5 Liquid temperature: 20 to 40 ° C _Dk : 0.1-0.5 A / dm
² hours: 10 to 60 seconds Cr adhesion amount is 50 μg / dm ² or less, preferably 15 μg / dm ² or less.
３０30 μg / dm ² .

[0021] The coating treatment of a mixture of chromium oxide and zinc / zinc oxide means that zinc or zinc oxide and chromium oxide are formed by electroplating using a plating bath containing zinc salt or zinc oxide and chromate. This is a process for coating the anticorrosive layer of the zinc-chromium group mixture thus formed, and is called electrolytic zinc-chromium treatment. As a plating bath, typically, K ₂ Cr ₂ O ₇ ,
At least one of dichromate such as Na ₂ Cr ₂ O ₇ or CrO ₃ and a water-soluble zinc salt such as ZnO, ZnSO
₄ - at least one 7H ₂ O, etc., a mixed aqueous solution of alkali hydroxide is used. Typical plating bath compositions and examples of electrolysis conditions are as follows: (C) Electrolytic zinc / chromium treatment K ₂ Cr ₂ O ₇ (Na ₂ Cr ₂ O ₇ or CrO ₃ ): 2 to 10 g / l NaOH or KOH: 10 to 50 g / l ZnO or _{ZnSO 4 · 7H 2 O: 0.05~10g} / l pH: 7~13 bath temperature: 20 to 80 ° C. current density: 0.05~5A / dm ² Time: 5 30 seconds Anode: Pt-Ti plate, stainless steel plate, etc. Chromium oxide is required to have a coating amount of 15 μg / dm ² or more in terms of chromium, and zinc is required to have a coating amount of 30 μg / dm ² or more. The thickness may be different between the rough side and the gloss side.
Such rust prevention methods are disclosed in JP-B-58-7077, 61-3.
3908, 62-14040 and the like. It is also effective to combine chromium oxide alone and a mixture of chromium oxide and zinc / zinc oxide.

Finally, if necessary, a silane treatment for applying a silane coupling agent to at least the roughened surface on the rust-preventing layer is performed mainly for the purpose of improving the adhesive strength between the copper foil and the resin substrate. The application method may be any of spraying of a silane coupling agent solution, application with a coater, immersion, and pouring. For example, Japanese Patent Publication No. 60-15654 describes that the adhesive strength between a copper foil and a resin substrate is improved by performing a silane coupling agent treatment after performing a chromate treatment on a rough surface side of the copper foil. . Please refer to this for details.

[0023]

The present invention will be described below in more detail with reference to examples and comparative examples. In addition, the evaluation method of the printed circuit board obtained in each Example and Comparative Example is as follows. 1. Surface roughness measurement device: Roughness meter: manufactured by Kosaka; universal surface profiler (SE3)
C) 2. Copper foil tear A substrate of 8 cm × 8 cm and 9 cm × 8 cm is prepared (hereinafter, referred to as substrate A and substrate B, respectively). The substrate A is fixed below, and the substrate B with a string is placed thereon. in addition,
Place a 15 kg weight. Thereafter, the substrate B is pulled 50 mm at a constant speed of 50 mm / sec. At this time, the sum of the number of tears generated on the substrate A and the substrate B (the 8 cm × 8 cm portion that was initially in contact) is measured.

Example 1 A high-temperature, high-temperature stretched copper foil (STCS foil: manufactured by Nikko Gould Foil Co., Ltd.) having a thickness of 18 μm was coated on a glossy surface of Cu: 45 g /
1, electrolysis was performed for 2.2 seconds at a current density of 1 A / dm ² using an electrolyte solution of H ₂ SO ₄ : 100 g / l and a temperature of 40 ° C.
Copper plating having a thickness of about 0.02 μm was performed. Then, on this copper plating, CrO ₃ : 5 g / l, ZnSO ₄ .7H ₂
Electrolysis was carried out for 12 seconds at a current density of 0.6 A / dm ² using an electrolytic zinc / chromium rust preventive liquid of O: 5 g / l, NaOH: 20 g / l, pH = 10, temperature: 60 ° C. Then, the surface roughness of the glossy surface of the copper foil was measured. Further, this copper foil was adhered to a glass-epoxy resin substrate by a heat treatment at 170 ° C. for 20 minutes to obtain a copper-clad laminate. Table 1 shows the results.

Example 2 The copper plating solution of Example 1 was Zn: 20 g / l, pH = 3.
5. Performed in the same manner as in Example 1 except that a sulfuric acid acidic zinc plating solution at a temperature of 40 ° C. was used, the plating conditions were changed to 1.1 seconds at a current density of 1.1 A / dm ² , and rustproof plating was omitted. A sample was prepared and the same evaluation was performed. Table 1 shows the results.

(Comparative Example) The same procedure as in Example 1 was carried out except that the plating step of Example 1 was omitted. Table 1 shows the results.

[0027]

[Table 1]

From Table 1, the roughness of the glossy surface is represented by the center line average roughness R.
It is confirmed that by reducing the Ra to 0.15 μm or less as represented by a, the occurrence of tears can be significantly suppressed.

[0029]

As described above, according to the present invention, there is an advantage that it is possible to suppress the occurrence of tearing of the high-temperature and high-strength copper foil after manufacturing the printed circuit board.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-5-29740 (JP, A) JP-A-5-47852 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H05K 1/09 C22F 1/08 H05K 3/38

Claims (1)

(57) [Claims] 1. 180 ° C. tensile: Tensile strength 10-20 kg
/ Mm ² , elongation: 0.01 to 20 mg on the glossy side of the high-temperature stretched copper foil characterized by 10 to 50%.
/ Dm ^2, a copper plating layer or a zinc plating layer is formed, and the roughness on the glossy surface side is represented by a center line average roughness Ra.
A high-temperature stretched copper foil for printed circuits for copper-clad laminates, characterized by having a smooth glossy surface reduced to 0.15 μm or less.