TW201524277A - Copper foil for a printed wiring board - Google Patents

Abstract

The copper foil for a printed wiring board, the copper foil being copper or an alloy of copper and having a thickness of no more than 18[mu]m, is characterized by the following: a temperature Tmax, at which a gradient (S) of tensile strength represented by formula (1) becomes largest, is 150 DEG C-370 DEG C in a range of no more than 400 DEG C; in such a case, a gradient (Smax) is at least 0.8; and the tensile strength after heat treatment for one hour at Tmax is 80% or less of normal strength. Formula (1): S=(Ts(T-50)-Ts(T))/50 Here, Ts(T) is the tensile strength after heat treatment for one hour at T DEG C.

Description

Copper foil for printed circuit boards

The present invention relates to a copper foil for a printed circuit board.

A flexible printed circuit board (FPC) is printed on a copper foil surface of FCCL by bonding polyimide and copper foil to form FCCL (Flexible Copper Clad Laminates). The resist coating process is performed by etching and removing an unnecessary copper foil (etching process). Further, if necessary, the copper foil can be made thinner by soft etching, and the product can be formed by the hole drilling process, the hole-fill plating, or the like by using a drill.

The manufacturing method of FCCL includes two types, namely, a casting method and a lamination method.

The casting method is applied to a copper foil as a support by coating a polyimide precursor, poly-proline, and drying at a temperature of about 130 ° C to volatilize the solvent, repeating the processes a plurality of times, and uniformly spreading the surface of the copper foil. The polyamic acid is applied to the ground and heat-treated at a high temperature of 300 ° C or higher at a curing temperature of the polyimide, so that the copper foil and the polyimide are adhered.

The lamination method is performed by pressing a copper foil on a polyimide film having a thermoplastic polyimide layer as an adhesive layer by roll lamination, and heat-treating at a curing temperature, thereby making the copper foil and the poly The amine film is adhered.

In recent years, from the viewpoint of reducing costs and ensuring manufacturing stability, a series of processes are continuously processed while winding a rolled copper foil. (Roll to Roll) manufacturing has gradually become mainstream. When the FCCL is produced by a roll-to-roll casting method, the copper foil is subjected to a plurality of polyamic acid coating processes and a drying process in a state where tension is applied thereto, and then heated at a high temperature using a hardening furnace.

At this time, a mechanical external force such as a roll tension and a thermal change caused by the drying process are applied to the copper foil. Due to the mechanical external force and heating, the copper foil in the production line may wrinkle and break.

In particular, in the roll-to-roll process, if the mechanical properties of the copper foil are the same, the thinner the thickness, the more likely wrinkles and breakage occur. On the other hand, as the pattern is refined and the thickness of the circuit is thinned, the soft etching is also simplified, so that the thickness of the copper foil used in the flexible printed circuit board tends to be thin. At present, the thickness of the copper foil used in FCCL or FPC is mainly 18 μm or less, and the thinner one having a thickness of 9 μm or 6 μm is gradually used.

Moreover, with the popularity of thin displays and smart phones, the level of folding required for circuit boards is high, and it is required to have a fixed bending property as an FPC substrate. Further, in a drive unit similar to a foldable mobile phone, a higher flexibility is required in applications requiring repeated bending.

In this way, the copper foil for FPC is required to have a thin foil of 18 μm or less, and is not broken or wrinkled during roll-to-roll conveyance, and can be sufficiently softened after being heat-treated at a polyimine hardening temperature. High bending performance and flexibility.

At present, only flexibility is required for FPC use, so a copper foil having a very low strength when heated at a temperature of 300 ° C or higher is used. For example, Patent Document 1 discloses a copper foil having a low strength of 270 MPa or less after heat treatment at 300 °C. However, the copper foil of the invention is in a normal state The lower strength is also lower than 350 MPa, which is liable to cause breakage and wrinkles during roll-to-roll handling.

On the other hand, in the use of a negative electrode current collector or the like as a lithium ion battery, it is also possible to use a copper foil having a high strength in a normal state of roll-to-roll transportation. For example, Patent Document 2 discloses a method for producing an electrolytic copper foil having a strength of 450 MPa or more in a normal state. However, the copper foil produced by the invention is softened by heating at a temperature lower than the pre-drying temperature of about 130 degrees, and the strength is lowered, so that it is not suitable for the roll-to-roll manufacturing of the casting method.

Further, Patent Document 3 discloses a copper foil having a tensile strength of 650 MPa or more in a normal state and a high strength and thermal stability of 450 MPa or more after heating at 300 °C. However, since it is excellent in thermal stability at 300 ° C, it cannot be sufficiently softened at the curing temperature of polyimine, and it cannot satisfy the high flexibility required for FPC use.

[Prior Art Literature]

[Patent Literature]

Patent Document 1: Japanese Patent No. 4712759 (Japanese Patent Laid-Open Publication No. 2008-013847)

Patent Document 2: Japanese Patent No. 4349690 (Japanese Patent Laid-Open Publication No. 2001-11684)

Patent Document 3: Japanese Patent Laid-Open Publication No. 2013-28848

Patent Document 4: Japanese Patent Laid-Open No. Hei 9-306504

Patent Document 5: Japanese Patent Laid-Open Publication No. 2013-28848

The present invention provides a copper foil which is a thin foil having a thickness of 18 μm or less which is required for a copper foil for a printed circuit board (hereinafter referred to as a printed circuit board) such as FCCL or FPC, and which does not cause breakage or wrinkle during roll-to-roll conveyance. The pleats are sufficiently softened by heat treatment at a polypyrimidine hardening temperature to exhibit high bending properties and flexibility.

The copper foil for a printed circuit board of the present invention is characterized in that it is a copper foil for a printed circuit board having a thickness of 18 μm or less composed of copper or an alloy containing copper, and is in a field of a heat treatment temperature of 400 ° C or less, (1) The temperature Tmax at which the slope S of the tensile strength is maximum is 150° C. or more and 370° C. or less. At this time, the slope S is 0.8 or more, and the tensile strength after heat treatment for 1 hour at the temperature Tmax is 80% or less of the normal state.

S=(Ts(T-50)-Ts(T))/50 (1)

Among them, Ts (T) is a tensile strength at room temperature after heat treatment at T ° C for 1 hour.

Further, in the field of the heat treatment temperature of 400 ° C or lower, the temperature Tmax at which the slope S of the tensile strength expressed by the above formula (1) is maximum is preferably 180 ° C or more and 310 ° C or less.

Further, in the field of the heat treatment temperature of 400 ° C or lower, the tensile strength is preferably 70% of the normal state after the heat treatment for 1 hour at the temperature Tmax at which the slope S of the tensile strength expressed by the above formula (1) is maximum.

The normal tensile strength of the copper foil for a printed circuit board of the present invention is preferably 500 MPa or more and 750 MPa or less.

Further, after the copper foil for a printed wiring board of the present invention is heat-treated at a heat treatment temperature of 300 ° C for 1 hour, the tensile strength is preferably 450 MPa or less.

The copper foil for a printed circuit board of the present invention is preferably an electrolytic copper foil.

The copper foil for a printed circuit board of the present invention is preferably provided on at least the surface of the copper foil to which the film is adhered, and a roughened particle layer is provided as needed, and a metal for heat resistance, chemical resistance, and rust prevention is provided thereon. Surface treatment layer.

The above metal surface treatment layer is preferably bismuth (Si), chromium (Cr), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), molybdenum (Mo), tin (Sn Or at least one of the alloys is disposed on the surface of the copper foil or the roughened particle layer.

The copper foil of the present invention is a copper foil for FCCL or FPC, and even if it is a thin foil having a thickness of 18 μm or less, it does not break or wrinkle during roll-to-roll conveyance, and is heat-treated at a polyimine hardening temperature. It can fully soften and exhibit high bending performance and flexibility of copper foil.

Fig. 1 is a graph showing the relationship between the tensile strength of copper foil and the heating temperature.

The form of copper foil:

The copper foil has a thickness of 18 μm or less. When the thickness of the copper foil for a printed circuit board is 18 μm or less and the thickness is 18 μm or more, there is no wrinkle problem in the roll-to-roll conveyance.

In order to ensure that the roll-to-roll is handled without wrinkles and breakage, a copper-clad laminate is formed (thin The film) exhibits excellent flexibility, and it is desirable that the heat softening temperature of the copper foil exists between the pre-drying temperature and the hardening temperature of the polyimide. The pre-drying temperature of the polyimine is generally about 130 °C. However, in general, the copper foil has softened at this temperature, so it is necessary to increase the softening temperature. On the other hand, the curing temperature of the polyimide is 300 ° C or more and 400 ° C or less, and it is desirable to soften the copper foil at this temperature.

That is, the copper foil is required to be softened at 130 ° C and softened in the range of 130 ° C or more and 400 ° C or less. Based on the above premise, the inventors of the present invention have found that in the graph of FIG. 1 showing the relationship between the heating temperature and the tensile strength, the slope S of the tensile strength expressed by the formula (1) is 0.8 or more, and the maximum time is When the temperature Tmax is 150 ° C or more and 370 ° C or less, a copper foil satisfying the above preconditions can be obtained. In addition, it has been found that when the temperature Tmax at which the slope S of the tensile strength expressed by the formula (1) is maximum is 180° C. or higher and 310° C. or lower, a wider pre-drying and curing temperature can be obtained.

S=(Ts(T-50)-Ts(T))/50 (1)

Among them, Ts (T) is a tensile strength after heat treatment at T ° C for 1 hour.

In the graph of Fig. 1 showing the relationship between the heating temperature and the tensile strength, the slope S of the tensile strength expressed by the formula (1) is 0.8 or more because the copper foil of 0.8 or less has no clear softening. The temperature and the tensile strength after heating are not lowered, so that the flexibility is not improved, and the high flexibility required for the copper foil for printed circuit boards cannot be satisfied.

If the slope S of the tensile strength expressed by the formula (1) at the temperature T is 0.8 or more and the tensile strength is 80% or less after the heat treatment for 1 hour at the temperature T, the copper is heated at the polyimine hardening temperature. The strength of the foil is sufficiently reduced, It meets the minimum bending performance and flexibility required for the original flexible substrate application. The tensile strength after the heat treatment at the temperature T for 1 hour is more preferably 70% or less. Due to the improved bending performance and flexibility, it is also possible to cope with the need for repeated bending, such as the active portion of a folding mobile phone.

Normally, it is called normal state after it is manufactured at atmospheric pressure of 20 ° C or more and 50 ° C or less and stored for one week or more, and the product which has not been subjected to heat treatment in advance is measured at normal temperature (= room temperature, about 25 ° C) and atmospheric pressure. The tensile strength is preferably 500 MPa or more, and if it is less than 500 MPa, the tensile strength and the wrinkles are likely to occur when the tension of the polyimine adhesive line is high. Further, the normal tensile strength is preferably 750 MPa or less. Since there is a trade-off relationship between the strength and the elongation of the copper foil, if the strength is higher than 750 MPa, the elongation is small, and the fracture is liable to occur.

The tensile strength after heat treatment at 300 ° C for 1 hour is preferably 450 MPa or less. As described above, the hardening temperature of polyimine is at least 300 ° C, and if the tensile strength at this temperature is 450 MPa or less, the minimum bending property and flexibility can be satisfied regardless of the polyimide used. .

(Manufacturing method of electrolytic copper foil)

In the present invention, the copper foil which satisfies the above characteristics is not limited as to a method for producing an electrolytic copper foil or a rolled copper foil.

Hereinafter, an electrolytic copper foil produced using an electrolytic solution containing sulfuric acid and copper sulfate as a main component will be described in detail.

Electrolytic copper foil is known to control normal strength and thermal stability by using an organic additive in the electrolyte. A nitrogen-containing water-soluble polymer such as glue or polyethylene glycol is added to the copper foil, whereby the copper crystal grains can be made finer and the strength under normal conditions can be improved. In addition, chloride ions have an auxiliary water-soluble polymer intake The role of copper foil. However, it does not have the effect of preventing recrystallization upon heating, so the strength is lowered at a softening temperature of copper, that is, at a temperature of about 120 ° C, and the chlorine-containing copper foil recrystallizes at normal temperature, and the time lapses after manufacture. The decrease in strength is the so-called "normal temperature softening" problem.

On the other hand, when a thiourea-like additive has a structure in which one sulfur (chemical formula 1) and two nitrogens and carbon are coordinated, the structure of [S=] can be obtained by colocalization of electrons. In the electrodeposition environment of copper, the [S=] preferentially adsorbs on the copper surface, and the absorption into the grain boundary can pin the movement of the grain interface, thereby having the effect of hindering recrystallization during heating. However, the decomposition temperature of the thiourea additive is about 130 to 160 ° C. When used for this type of application, the heating will be decomposed at a temperature higher than the above temperature, and the pinning effect will be impaired, which will occur to the same extent as pure copper. soften.

Therefore, the inventors of the present invention have intensively studied to use the organic additive A and the organic additive B, and to manufacture a copper foil using an electrolyte having a chlorine concentration lower than that of the conventional electrolytic solution, thereby successfully producing an electrolytic copper foil which satisfies the above characteristics. Wherein the organic additive A has a sulfur and two nitrogens coordinated to carbon and forms a heterocyclic ring, for example, a structure of (Chemical Formula 2) or a structure of (Chemical Formula 3), and the organic additive B is a nitrogen-containing compound such as polyethylene glycol or the like. Water soluble polymer.

The incorporation of the organic additive A into the grain boundary can exert a pinning effect and hinder recrystallization upon heating. That is, the organic additive A has a structure in which sulfur and two nitrogens are coordinated to carbon, and a heterocyclic ring is formed, so that the decomposition temperature is high, and even if heated at a high temperature, a pinning effect can be exerted. By using this effect and the effect of the organic additive B to increase the strength under normal conditions, and by suppressing the recrystallization under normal conditions with a chlorine concentration lower than the existing concentration, the characteristic heating at 150 to 370 ° C in the present invention can be achieved. soften.

Surface treatment form:

In the present embodiment, if necessary, a roughened particle layer is provided on at least the surface of the copper foil to which the film is adhered, and a metal surface treatment layer is further provided thereon. In addition, the formation of the roughened particle layer does not need to be set by a special method, and the usual The roughened particle layer formation (roughening treatment) method is carried out.

About roughening

An example of a roughening treatment method for providing a roughened particle layer on a copper foil for improving the adhesion between the copper foil and the polyimide film is described in the order of roughening plating treatment 1 → roughening plating treatment 2 The method.

Rough plating treatment 1

Copper sulfate: 20~160g/L

Sulfuric acid concentration: 30~200g/L

Fe: 0.1~10g/L

Mo: 0.1~5.0g/L

Liquid temperature: 20~60°C

Current density: 10~60A/dm ²

Rough plating treatment 2

Copper sulfate: 80~360g/L

Sulfuric acid concentration: 30~150g/L

Liquid temperature: 20~65°C

Current density: 5~65A/dm ²

In the present embodiment, a metal surface treatment layer for heat resistance, chemical resistance, and rust prevention is provided on the surface of the roughened particle layer or the surface of the copper foil on which the roughened particle layer is not provided.

Regarding the metal surface treatment layer, at least one or more metals may be plated depending on the type and use of the polyimide pigment applied to the copper foil. Examples of the metal include chromium (Cr), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), molybdenum (Mo), tin (Sn) monomers or the like. Alloys, hydrates, etc. Following An example of an electroplating bath and plating conditions for carrying the above metals.

Nickel plating bath

Ni 10~100g/L

H ₃ BO ₃ 1~50g/L

PO ₂ 0~10g/L

Bath temperature 10~70°C

Current density 1~50A/dm ²

Processing time 1 second ~ 2 minutes

pH 2.0~4.0

Ni-Mo plating bath

Ni 10~100g/L

Mo 1~30g/L

Trisodium citrate dihydrate 30~200g/L

Bath temperature 10~70°C

Current density 1~50A/dm ²

Processing time 1 second ~ 2 minutes

pH 1.0~4.0

Mo-Co plating bath

Mo 1~20g/L

Co 1~10g/L

Trisodium citrate dihydrate 30~200g/L

Bath temperature 10~70°C

Current density 1~50A/dm ²

Processing time 1 second ~ 2 minutes

Zinc plating bath

Zn 1~30g/L

NaOH 10~300g/L

Bath temperature 5~60°C

Current density 0.1~10A/dm ²

Processing time 1 second ~ 2 minutes

Chrome plating bath

Cr 0.5~40g/L

Bath temperature 20~70°C

Current density 0.1~10A/dm ²

Processing time 1 second ~ 2 minutes

Below pH 3.0

Preferably, the decane is coated on the surface after the plating treatment of the metals. The coated decane may, for example, be an amine group, a vinyl group, an epoxy group or the like which is usually used.

Printed circuit board form:

It is not particularly limited, and for example, a lamination method or a casting method can be used.

Example

Hereinafter, the present invention will be described in further detail based on examples, but the present invention is not limited thereto.

Example

(Manufacture of copper foil)

In Examples 1 to 8, the surface of titanium was polished using #2000 abrasive paper, and a cathode made of ground titanium was used, and the electrolyte described below was used, and the bath temperature was 30 to 75 ° C, and the current density was 30 to 100 A/dm ^{2 .} Electric current was applied to produce an electrolytic copper foil having a thickness shown in Table 1.

(electrolyte composition)

The composition described in Table 1 was added to the basic bath with copper sulfate 200-500 g/L and sulfuric acid 20-200 g/L as the basic bath composition to prepare an electrolyte solution. In addition, the organic additive A uses an additive having the structure of the chemical formula 2, represented by 2-mercapto-5-benzimidazolesulfonic acid, and a structure having the chemical formula 3, and 3(5-fluorenyl-1H-tetrazolyl)benzene. The sulfonate is a representative additive, but it has been confirmed that as long as it is an organic additive in which one sulfur and two nitrogens are coordinated to carbon and a hetero ring is formed, the same effect can be obtained by using an organic additive other than the above.

In Examples 1 to 4 and 6 to 8, the copper foil produced was directly subjected to metal surface treatment. On the other hand, in Example 5, the copper foil to be produced was subjected to a roughening particle layer in accordance with the following roughening treatment method, and a metal surface treatment layer was applied to the roughened particle layer. The roughening treatment is carried out in the order of roughening plating treatment 1 → roughening plating treatment 2.

Rough plating treatment 1

Copper sulfate: 90g/L

Sulfuric acid concentration: 150g/L

Fe: 3g/L

Mo: 0.3g/L

Liquid temperature: 25 ° C

Current density: 40A/dm ²

Rough plating treatment 2

Copper sulfate: 240g/L

Sulfuric acid concentration: 120g/L

Liquid temperature: 50 ° C

Current density: 10A/dm ²

Example 9 is a rolled copper alloy foil produced by a casting or rolling method. The raw materials of copper, chromium (Cr), tin (Sn), and zinc (Zn) are melted in a high-frequency furnace, and then cast at a cooling rate of 0.5 to 150 ° C / sec to obtain an ingot. The ingot contains 0.3% by mass of chromium, 0.3% by mass of tin, and 0.1% by mass of zinc, and the remainder is a substance formed by copper and unavoidable impurities.

Then, the obtained ingot was subjected to homogenization heat treatment at a temperature of 1000 ° C for 8 hours, and then directly hot rolled at 600 to 1050 ° C. Among them, the hot rolling temperature range of 600 to 1050 ° C is the temperature range from the start to the end of hot rolling. The processing rate is 85~97%.

Further, it is cooled at a cooling rate of 30 ° C / sec at a cooling rate of at least 600 ° C to 200 ° C, and is subjected to intermediate cold rolling at a processing rate of 80 to 99.8%, and aging at 300 ° C to 540 ° C for 4 hours. After heat treatment, final cold rolling was performed at a processing ratio of 86% to prepare a rolled copper alloy foil having a foil thickness of 12 μm.

Comparative example

In Comparative Examples 1 to 3, the surface of titanium was polished using #2000 polishing paper, and the cathode composed of the polished titanium was used, and the electrolytic solution and electrolytic conditions described in Table 2 were used.

In addition, Comparative Example 1 is a copper foil produced in Example 1 of Patent Document 2 (Japanese Patent No. 4349690, Japanese Patent Laid-Open No. 2001-11684), and Comparative Example 2 is based on Patent Document 4 (Japanese Patent Laid-Open) A copper foil produced in Example 1 of the Japanese Patent Publication No. 9-306504, and a copper foil produced in Example 1 of the Patent Document 5 (Japanese Patent Laid-Open Publication No. 2013-28848).

Comparative Example 4 is a commercially available Cu-0.015-0.03Zr rolled copper alloy foil (trade name: HCL (registered trademark)-02Z, manufactured by Hitachi Cable Co., Ltd.) having a thickness of 12 μm.

(surface treatment)

The copper foil produced based on Examples 1 to 4, 6 to 8 and Comparative Examples 1 to 3, and the roughened layer of the copper foil produced in Example 5 were sequentially deposited in the order of nickel, zinc, and chromium. Metal plating followed by coating of commercially available epoxy decane. The coating conditions of each metal plating and decane are as follows.

Nickel plating

Ni 40g/L

H ₃ BO ₃ 5g/L

Bath temperature 20 ° C

Current density 0.2A/dm ²

Processing time 10 seconds

pH 3.6

Zinc plating

Zn 2.5g/L

NaOH 40g/L

Bath temperature 20 ° C

Current density 0.3A/dm ²

Processing time 5 seconds

Chrome plating

Cr 5g/L

Bath temperature 30 ° C

Current density 5A/dm ²

Processing time 5 seconds

Epoxy decane coating

Reagent name S510 (manufactured by Chisso Co., Ltd.)

Concentration 0.25wt%

Processing time 2 seconds

(assessment)

The copper foil of each of the examples and the comparative examples was heat-treated at normal temperature to 400 ° C for 10 hours, and the tensile strength at each temperature was measured, and the slope S represented by the formula (1) at each temperature was calculated. The temperature Tmax when S is the maximum value. The tensile strength was measured based on JIS Z2241-1880.

Further, the rolled copper foils of Example 9 and Comparative Example 4 were subjected to a tensile test in a direction of 45° with respect to the rolling direction, and the tensile strength was measured.

The tensile strength ratio is calculated by dividing the tensile strength value at the time of heat treatment by the temperature T by the normal tensile strength value. The results are shown in Table 3. In addition, the tensile strength at 300 ° C is used as a reference value, and is also shown in Table 3.

The conveyance test was carried out by heat treatment at 200 ° C for 1 hour while applying a tension of 0.1 N/mm or 0.3 N/mm to determine the presence or absence of wrinkles. The copper foil which is wrinkled under the tension of 0.1 N/mm cannot be used for the roll-to-roll method, so it is judged as ×; wrinkles are not generated under the tension of 0.1 N/mm, and the copper foil which is wrinkled under the tension of 0.3 N/mm can be carried out. Roll-to-roll handling, so judged as ○; 0.3N/mm There is no wrinkled copper foil under the force, and it can be transported even if the line speed is increased, so it is judged as ◎. The judgment results are shown in Table 3.

In the bending test, the surface of the copper foil was bonded to a polyimide film of 50 μm thickness (UPILEX-VT manufactured by Ube Industries, Ltd.), and the whole was clamped with two smooth stainless steel plates, using a 20 torr vacuum press to 300 The film was thermocompression bonded at ° C or 370 ° C under a pressure of 2 kg/cm ² for 10 minutes, and then thermocompression bonded at a pressure of 50 kg/cm ² for 5 minutes to prepare a film-formed copper foil (circuit board), and subjected to an MIT test. The curvature (R) at this time was measured at 0.8 (mm) and a load of 500 g. Regarding the evaluation results of the bending test, the number of times before the break in the MIT test is less than 200 times is judged as × (failed), and 200 times or more and less than 450 times are regarded as satisfying the bending performance required for the flexible printed circuit board, and it is judged When it was ○ (passed), it was judged as ◎ by considering 450 times or more as being able to withstand repeated bending and having excellent flexibility. The evaluation results are shown in Table 3.

According to Table 3, the slant represented by the formula (1) in all the examples The rate Smax Smax is 0.8 or more, and the temperature Tmax when S is the maximum value is 150° C. or more and 370° C. or less, and the tensile strength is 80% or less of the normal state (25° C.) after heat treatment for 1 hour at Tmax. Both the test and the bending test show the performance that can withstand the actual application.

In particular, in Example 4, all items were within the preferred range, so both the carrying test and the bending test showed particularly excellent results. Further, in Example 5, a metal surface treatment layer was provided on the roughened particle layer, but the conveyance test and the number of times of bending were not inferior to those of the other examples, and the provision of the roughened layer did not greatly affect the conveyance test and the number of bending.

The slope Smax of the tensile strengths of Examples 1 and 8 is low, and the normal tensile strength of Example 6 is less than 500 MPa, and there is a tendency to easily wrinkle when the line speed is increased. If the line speed is set to a lower value, There is no problem. The normal tensile strength of Examples 3 and 7 exceeds 750 MPa, so the flexibility at 300 ° C does not meet the standard, but the bending test results are acceptable when heated at 370 ° C. Therefore, when the temperature of the polyimine hardening process is high temperature can use.

In the second embodiment, the tensile strength ratio of Tmax to normal is more than 70%, and the portability and the flexibility at 300 ° C are slightly inferior, but the performance can still withstand practical use.

In Example 4 using an electrolytic copper foil with respect to Example 9 using a rolled copper foil, the conveyance test and the number of bending times all showed excellent results.

In Comparative Example 1, the Tmax was low, so wrinkles were generated in the conveyance test.

In Comparative Example 2, Smax was small and was 0.8 or less, and wrinkles were generated in the conveyance test. When the Smax is small, the copper foil has no clear softening point, which is a typical characteristic of a foil which is softened at room temperature. Normal temperature softened copper foil under application of tension Easy to produce wrinkles.

The tensile strength ratio of Comparative Example 3 exceeded 80%. Such a foil hardly softens during the hardening process of the polyimide, and is broken in advance in the bending test.

In Comparative Example 4, the Tmax was high, so that it did not sufficiently soften during the hardening process of the polyimide, and it was broken in advance in the bending test.

As described above, the copper foil of the present invention is a thin foil having a thickness of 18 μm or less which is required for a copper foil for a printed circuit board such as FCCL or FPC, and does not cause breakage or wrinkles during roll-to-roll conveyance, and is hardened by polyimine. When the temperature is heat-treated, it can be sufficiently softened to exhibit high bending performance and flexibility, and it can exhibit excellent effects as a copper foil for a printed circuit board.

Claims (10)

A copper foil for a printed circuit board, which is a copper foil for a printed circuit board having a thickness of 18 μm or less and composed of copper or an alloy containing copper. The tensile strength represented by the formula (1) is in a field of a heat treatment temperature of 400 ° C or less. When the slope S of the intensity S is maximum, the temperature Tmax is 150° C. or more and 370° C. or less. At this time, the slope Smax is 0.8 MPa/° C. or more, and the tensile strength after the heat treatment for 1 hour is 80% or less of the normal state; S=( Ts(T-50)-Ts(T))/50 (1) wherein Ts(T) is a tensile strength after heat treatment at T ° C for 1 hour. The copper foil for a printed circuit board according to the first aspect of the invention, wherein the slope S maximum value Smax calculated by the above formula (1) is 1.8 or more in a field of a heat treatment temperature of 400 ° C or lower. The copper foil for a printed circuit board according to the second aspect of the invention, wherein, in the field of the heat treatment temperature of 400 ° C or less, the temperature Tmax at which the slope S of the tensile strength expressed by the above formula (1) is maximum is 180 ° C. Above, below 310 °C. The copper foil for a printed circuit board according to any one of claims 1 to 3, wherein the slope S of the tensile strength expressed by the above formula (1) is the largest in the field of the heat treatment temperature of 400 ° C or less. When the temperature Tmax was heat-treated for 1 hour, the tensile strength was 70% or less of the normal state. The copper foil for a printed circuit board according to any one of claims 1 to 4, wherein the normal tensile strength is 500 MPa or more. Copper for printed circuit boards according to any one of claims 1 to 5 The foil is characterized in that the normal tensile strength is 750 MPa or less. The copper foil for a printed circuit board according to any one of claims 1 to 6, wherein the tensile strength after the heat treatment at 300 ° C for 1 hour is 450 MPa or less. The copper foil for a printed circuit board according to any one of claims 1 to 7, wherein the copper foil is an electrolytic copper foil. The copper foil for a printed circuit board according to any one of the first to eighth aspects of the present invention, characterized in that the roughened particle layer is provided on at least the surface of the copper foil for the printed circuit board. The copper foil for a printed circuit board according to any one of the first to ninth aspects of the present invention, characterized in that the surface of at least the adhesive film of the copper foil for the printed circuit board is provided with bismuth (Si) or chromium ( At least one metal surface treatment layer of Cr), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), molybdenum (Mo), tin (Sn) or the like .