WO2018180920A1

WO2018180920A1 - Rolled copper foil

Info

Publication number: WO2018180920A1
Application number: PCT/JP2018/011507
Authority: WO
Inventors: 一貴青島
Original assignee: Ｊｘ金属株式会社
Priority date: 2017-03-30
Filing date: 2018-03-22
Publication date: 2018-10-04
Also published as: JPWO2018180920A1; TW201840869A; KR20190133736A; CN110475883A

Abstract

The purpose of the present invention is to provide rolled copper foil having excellent vibration resistance. This copper foil is rolled copper foil having a thickness of at least 50 µm and no more than 10% non-recrystallized crystal grains.

Description

Rolled copper foil

The present invention relates to a rolled copper foil and the like, and more particularly to a copper foil used for a flexible printed wiring board having excellent vibration resistance.

The flexible printed wiring board (FPC) is obtained by bonding a metal which is a conductive layer and a flexible insulating substrate typified by a resin film. In general, a copper foil is used for the conductive layer, and a rolled copper foil having excellent flexibility is used particularly for applications that require flexibility.

General FPC manufacturing process is as follows. First, the copper foil is bonded to the resin film. For joining, there are a method of imidizing by applying heat treatment to a varnish applied on a copper foil, and a method of laminating a resin film with an adhesive and a copper foil. The copper foil with a resin film joined by these steps is referred to as CCL (copper-clad laminate). Thereafter, wiring is formed by etching to complete the FPC.

Flexibility required for rolled copper foil for FPC has become strict as electronic devices become lighter, shorter, and more functional, and various improvements have been proposed for obtaining rolled copper foil with excellent flex resistance. Yes.

Patent Document 1 discloses a copper foil having a specific softening temperature and a thickness of 50 μm or less. Patent Documents 2 to 3 disclose a rolled copper foil having a thickness of 50 μm to 300 μm that is excellent in vibration resistance in addition to bending resistance.

JP 2000-192172 A JP 2013-167013 A JP 2013-167014 JP

When manufacturing a copper clad laminate, it is necessary to perform heat treatment. At this time, the non-recrystallized portion remaining in the rolled copper foil is reduced. However, when the thickness of the copper foil is constant, the remaining amount of the non-recrystallized portion increases. When the remaining amount of the non-recrystallized portion increases, the frequency of occurrence of cracks during the vibration test increases.

Furthermore, the processing of high temperature (for 1 hour at 400 ° C.) as in Patent Documents 2 to 3 may not be able to be tolerated by the resin of a flexible printed wiring board used in vehicles (eg, polyimide (PI) ), Polyethylene terephthalate (PET), polyethylene naphthalate (PEN)).

In view of the above circumstances, an object of the present invention is to provide a copper foil with few non-recrystallized portions.

As a result of intensive studies by the present inventors, it has been found that impurity elements in copper are likely to precipitate by performing recrystallization annealing and aging precipitation annealing under specific conditions before cold rolling. As a result, it has been found that the purity of copper in the structure is increased and recrystallization is facilitated.

Based on the above findings, the present invention is specified as follows.
(Invention 1)
A copper foil having a thickness of 50 μm or more and an unrecrystallized crystal grain of 10% or less.
(Invention 2)
A copper foil having a thickness of 50 μm or more and a non-recrystallized crystal grain of 10% or less in a metal structure after heating at 180 ° C. for 1 hour.
(Invention 3)
A rolled copper foil according to invention 1 or 2, wherein the semi-softening temperature is 150 ° C or lower.
(Invention 4)
The rolled copper foil according to invention 1 or 2, wherein the semi-softening temperature is 110 to 150 ° C. (invention 5)
A rolled copper foil according to any one of inventions 1 to 4,
Cu concentration is 99.8% by mass or more,
The oxygen concentration is 0.05% by weight or less, and
The total concentration of Ag, Sn, B, Zr, Ti, In and P is 0 to 0.03 mass%,
Copper foil.
(Invention 6)
A flexible copper clad laminate (CCL) comprising the rolled copper foil of any one of inventions 1 to 5.
(Invention 7)
Invention 6 A flexible printed wiring board (FPC) comprising a flexible copper clad laminate.
(Invention 8)
An electronic component comprising the flexible printed wiring board of the seventh invention.
(Invention 9)
A method for producing rolled copper foil,
A step of performing recrystallization annealing at 450 to 800 ° C .;
The method comprising a step of performing aging precipitation annealing at a temperature lower by 150 to 300 ° C. than a temperature of the recrystallization annealing, and a step of performing cold rolling so that the thickness becomes 50 μm or more.
(Invention 10)
It is a manufacturing method of a flexible laminated board, Comprising: This method including the process of laminating | stacking the rolled copper foil obtained by the method of invention 9, and resin.
(Invention 11)
It is a manufacturing method of a flexible printed wiring board, Comprising: The method which includes the process of forming a circuit in the flexible copper clad laminated board obtained by the method of invention 10.

In one aspect, the copper foil of the present invention has an unrecrystallized portion of 10% or less. Thereby, the vibration resistance of a flexible printed wiring board can be improved.

In one aspect, the copper foil of the present invention has an unrecrystallized portion of 10% or less in the metal structure after heating at 180 ° C. for 1 hour. Thereby, the vibration resistance of the flexible printed wiring board manufactured by heat-processing and forming CCL can be improved.

It is a photograph which shows the attachment state of the loop-shaped test piece at the time of performing a vibration test.

Hereinafter, specific embodiments for carrying out the present invention will be described. The following description is intended to facilitate an understanding of the present invention. That is, it is not intended to limit the scope of the present invention.

1. Copper Foil (1) Element In one embodiment, the copper foil may be composed of pure Cu. In another embodiment, the copper foil may contain Cu and other additive elements.

(1-1) Cu
The Cu concentration in the copper foil is not particularly specified, but is preferably 99.8% by mass or more, more preferably 99.85% by mass or more, and 99.9% by mass or more for reasons of ensuring high conductivity. Even more preferably. However, even if the Cu concentration is too high, it leads to an increase in cost, so 99.999 mass% or less is preferable, and 99.995 mass% or less is more preferable.

(1-2) Additive Element The additive element other than Cu may be at least one selected from Ag, Sn, B, Zr, Ti, In, and P. These are preferable from the viewpoint of the flexibility and vibration of the copper foil.

The total concentration of Ag, Sn, B, Zr, Ti, In, and P may be 0.03% by mass or less (more preferably 0.02% by mass or less). If it exceeds 0.03 mass%, the strength is further improved, but there are cases where the conductivity is lowered and the softening temperature is raised. Although it does not specifically limit about a lower limit, 0 mass% or more may be sufficient.

(1-3) Oxygen Since the oxygen concentration in the copper foil leads to an increase in cuprous oxide and leads to the suppression of the development of the cube orientation, it is preferably 0.05% by mass or less, and 0.005% by mass or less. For example, it can be 0.0001 mass% or more and less than 0.01 mass%. As the copper foil satisfying such conditions, for example, oxygen-free copper (OFC) or tough pitch copper specified in JIS-H3510 or JIS-H3100 can be used.

(2) Rolled copper foil The copper foil base material used in the present invention is a rolled copper foil. Rolled copper foil is superior to electrolytic copper foil in that it can cope with an environment in which vibration continuously occurs and has high bending resistance.

For applications such as in-vehicle use where large current flows and heat generation due to energization is particularly disliked, copper foil is relatively easy to secure electric conductivity and heat transmission without disconnection. In such a case, the thickness should preferably be 50 μm or more, and more preferably 70 μm or more. However, if the thickness is excessively large, it may be difficult to remove the conductor layer by etching. Therefore, the thickness is preferably 300 μm or less, and more preferably 150 μm or less.

(3) Semi-softening temperature In one embodiment, the copper foil of the present invention may have a suitable range of softening temperatures. The semi-softening temperature here is defined as follows.

First, the tensile strength (A) after annealing for 60 minutes at various temperatures is measured. Next, the tensile strength (B) after rolling and the tensile strength (C) after annealing at 300 ° C. for 60 minutes and completely softening are measured. Finally, the annealing temperature when the tensile strength (A) after annealing becomes an intermediate value between (B) and (C) is defined as a semi-softening temperature.

In one embodiment, the copper foil of the present invention may have a semi-softening temperature of 150 ° C. or lower, more preferably 110 to 150 ° C. When the temperature is less than 110 ° C., softening at room temperature is likely. If it exceeds 150 ° C., it becomes difficult to soften by heat treatment in the production process of the copper clad laminate.

(4) Amount of unrecrystallized
In one embodiment, the copper foil of the present invention may have an amount of non-recrystallized particles of 10% or less (more preferably 5% or less, 1% or less, or 0%). If it exceeds 10%, the vibration resistance deteriorates. The lower limit value is not particularly defined, but is typically 0% or more.

The amount of unrecrystallized particles can be calculated by the following method. First, a microstructure photograph of a cross section in the rolling direction is taken with a scanning electron microscope (the size of the field of view is not particularly limited, but is typically 100 μm × 200 μm). Next, 100 or more lattice points are written on the photographed photograph, and it is confirmed whether the lattice point is a recrystallized grain or an unrecrystallized part. The two can be identified on the basis of a post-rolling structure (rolling structure) photograph before heating and a structure photograph (completely recrystallized structure) after heating at 300 ° C. × 1 h. And it calculates from the ratio of the number of all the lattice points, and the number of the lattice points of an unrecrystallized part.

(5) Amount of unrecrystallized after heating at 180 ° C. for 1 hour In one embodiment, the copper foil of the present invention has an amount of unrecrystallized particles of 10% or less in a state after being heated at 180 ° C. for 1 hour. (More preferably 5% or less, 1% or less, or 0%) may be used. For example, when the copper foil is shipped as a product, even if the amount of unrecrystallized particles exceeds 10%, the amount of unrecrystallized particles is reduced by heat treatment when forming a copper-clad laminate, The copper foil may finally be 10% or less. As described above, if it exceeds 10%, the vibration resistance deteriorates. The lower limit value is not particularly defined, but is typically 0% or more.

2. Manufacturing method of copper foil The copper foil which concerns on this invention can be manufactured as follows, for example. First, a copper raw material such as electrolytic copper, oxygen-free copper, tough pitch copper or the like is melted, and an alloy element is added as necessary, and then the molten metal is cast to produce an ingot having a thickness of about 100 to 300 mm. Adjustment of the oxygen concentration in the melting step can be performed by techniques known to those skilled in the art, such as carbon sealing of the molten metal and release to the atmosphere. Then, after performing hot rolling, annealing and cold rolling are repeated.

Recrystallization annealing and aging precipitation annealing can be performed before final cold rolling (more preferably, immediately before final cold rolling). Recrystallization annealing is performed under conditions of a high temperature and a short time (for example, in a continuous annealing line). For example, the temperature may be 450 to 800 ° C. (more preferably 550 to 700 ° C.), and the time may be 5 seconds to 300 seconds (more preferably 10 seconds to 200 seconds).

Aging precipitation annealing can be performed at a temperature lower by 150 to 300 ° C. than the recrystallization annealing described above. For example, when the recrystallization annealing is performed at 650 ° C., the aging precipitation annealing may be 350 ° C. to 500 ° C. Further, the aging precipitation annealing time may be 300 times or more of the residence time in the heating furnace in the recrystallization annealing (continuous annealing line) (for example, 5 to 50 h, more preferably 5 to 20 h).

After recrystallization annealing conditions and aging precipitation annealing, final cold rolling is performed. The degree of reduction in the final cold rolling is 90% or more, more preferably 95% or more, and still more preferably 98% or more. And it can finish to the copper foil of the thickness described in said "(2) Rolled copper foil".

3. In one embodiment of the copper-clad laminate , the flexible copper-clad laminate of the present invention includes the copper foil described above. Moreover, the flexible copper clad laminated board of this invention is equipped with the resin layer other than the said copper foil. Several techniques can be employed to provide the resin layer. For example, a method of performing heat treatment by bonding a copper foil and a polyimide resin film using an adhesive made of a thermosetting resin such as epoxy can be used. Or the varnish containing the polyamic acid which is a precursor of a polyimide resin is apply | coated on copper foil, it heat-hardens, and the method of forming a polyimide film on copper foil can be used. When laminating copper foil on both sides, after forming a single-sided copper clad laminate, there are a method of crimping the copper foil layer by hot pressing, and a method of sandwiching a polyimide film between two copper foil layers and crimping by hot pressing. is there. These heat treatments are generally carried out at 125 to 250 ° C. for 60 to 400 minutes. There is also a method of laminating a copper foil and a resin with an adhesive without going through a heat treatment step. Examples of the material for the resin layer include, but are not limited to, polyester, polyimide, polyethylene terephthalate, and polyethylene naphthalate.

As described above, in the manufacturing process of the flexible copper clad laminate (FCCL), the heat treatment is often performed for bonding the insulating substrate and the copper foil. Therefore, the annealing process after the final cold rolling described above is performed by the heat treatment. It can also be combined. The copper foil having the characteristics according to the present invention can be formed by setting the heat treatment during bonding at 150 to 250 ° C. (preferably 180 ° C. or more) for 0.5 to 3 hours (preferably 1 hour or more). Can be simultaneously bonded to the insulating substrate.

Moreover, before laminating | stacking copper foil and a resin layer, a roughening process can be performed with respect to copper foil. Thereby, the adhesive strength of resin and copper foil can be improved. For example, the roughening process can be performed under the following conditions.
Liquid composition: Cu 10-20 g / L, Co 1-10 g / L, Ni 1-15 g / L
pH: 1 to 4
Temperature: 30-50 ° C
Current density (Dk): 20 to 50 A / dm ²
Time: 1-5 seconds

4). Flexible printed wiring board (1) Flexible printed wiring board and method for producing the same In one embodiment, the flexible printed wiring board of the present invention includes the above-described flexible copper-clad laminate. Moreover, it is possible to manufacture a flexible printed wiring board (FPC) by forming a wiring according to a known procedure using the FCCL according to the present invention as a material. For example, apply an etching resist to the copper foil surface of the FCCL only on the necessary part as the conductor pattern, spray the etching solution onto the copper foil surface to remove the unnecessary copper foil, form the conductor pattern, and then peel off the etching resist -The method of removing and exposing a conductor pattern is mentioned. After forming the conductor pattern, it is common to apply a protective coverlay film.

(2) Vibration resistance In one embodiment, the flexible printed wiring board of the present invention can have excellent vibration resistance. For example, the vibration resistance time specified in JIS-D1601 may be 10 hours or more, more preferably 100 hours or more.

(3) Applications Such FPCs are used in electronic and electrical equipment for movable parts in hard disks, mobile phone hinges and sliding parts, printer heads, optical pickups, notebook PCs, etc. This corresponds to FPC. In particular, the FPC according to the present invention is suitable as a vehicle-mounted or automatic machine control FPC that uses a relatively large thickness of copper foil and also requires vibration resistance.

<Manufacture of rolled copper foil>
Ingots having respective compositions shown in Table 1 in which predetermined elements were added to tough pitch copper (TPC) or oxygen-free copper (OFC) were melt cast.
After this was hot rolled, annealing and cold rolling were repeated. Then, immediately before the final cold rolling, recrystallization annealing (60 seconds) and aging precipitation annealing were performed under the conditions described in Table 1. Next, final cold rolling was performed, and the thicknesses shown in Table 1 were adjusted.

<Manufacture of FPC>
One side of each obtained rolled copper foil was subjected to a roughening treatment with electrodeposited copper particles.
-Plating bath composition: Cu 15 g / L, Co 8.5 g / L, Ni 8.6 g / L
-Treatment solution pH: 2.5
・ Processing temperature: 38 ℃
・ Current density: 20 A / dm ²
・ Plating time: 2.0 seconds

Thereafter, a polyimide film having a thickness of 50 μm was laminated on the roughened surface under the condition of hot pressing at a temperature of 180 ° C. for 1 hour to produce a single-sided FCCL. Then, eight circuit etches with a length of 120 mm and a line and space of 0.3 mm / 0.3 mm were formed, and finally, a polyimide coverlay film with a thickness of 50 μm was hot-pressed on both sides at a temperature of 180 ° C. for 1 hour. By laminating, each test piece of FPC having a length of 150 mm and a width of 15 mm was produced.

<Vibration resistance time (h)>
For each of the obtained FPC test pieces, a vibration test was performed based on a JIS-D1601 sweep vibration durability test. Both ends were fixed by a previously described test specimens in a loop of the loop dimensions L = 20 mm, vibration test frequency 5 ~ 170Hz / 5min, amplitude width 0.6 mm, vibration acceleration 45 m / s ^2, at test temperatures -35 ~ 85 ° C. The resistance increase rate of the test piece when a constant current (1.0 mA) was applied to the test piece was recorded, and the time until the resistance increase rate of the test piece reached 20% was measured. The test temperature was maintained at room temperature (25 ° C.) for 60 minutes, then gradually decreased to −30 ° C. over 60 minutes, held at −30 ° C. for 120 minutes, and then increased to 85 ° C. over 1.5 hours. The cycle of holding for 120 minutes and then lowering to room temperature (25 ° C.) over 30 minutes was repeated. The test equipment used was Emic Co., Ltd. F-400BM-E04 fully automatic vibration test equipment and Emic Co., Ltd. temperature and humidity test equipment VC-500BAR (33) M3C3R.
In addition, as shown in FIG. 1, a loop dimension refers to the distance from the fixed location of a test piece to the front-end | tip of a test piece.

The vibration resistance time of vibration resistance was evaluated according to the following criteria.
○: Less than 10 to 100 ×: Less than 10 hours ◎: More than 100 hours

<Measurement of the amount of unrecrystallized>
First, a microstructure photograph of a cross section in the rolling direction was taken with a scanning electron microscope (the size of the field of view is not particularly limited, but is typically 100 μm × 200 μm). Next, 100 or more lattice points were written on the photograph taken, and it was confirmed whether the lattice points were crystal grains or non-recrystallized portions. And it computed from the ratio of the number of all the lattice points, and the number of the lattice points of a non-recrystallized part.

<Measurement of semi-softening temperature>
First, the tensile strength (A) after annealing at various temperatures for 60 minutes was measured. Next, the tensile strength (B) after rolling and the tensile strength (C) after annealing at 300 ° C. for 60 minutes and completely softening were measured. Finally, the annealing temperature when the tensile strength (A) after annealing becomes an intermediate value between (B) and (C) was defined as a semi-softening temperature.

The results are shown in Table 1 below.

From the results of Invention Examples 1 to 9, it was shown that excellent vibration resistance can be obtained when the amount of unrecrystallized is 10% or less. In addition, it was shown that excellent vibration resistance was obtained in a copper foil composed of pure Cu and a copper foil to which any one of Ag, Sn, B, Zr, Ti, In and P was added. In addition, the semi-softening temperature was adjusted to an appropriate range.

Further, in Comparative Example 1, the temperature of aging precipitation annealing was 350 ° C. lower than the recrystallization annealing temperature (that is, not 150 to 300 ° C. lower), so that many unrecrystallized crystals remained. . Therefore, vibration resistance was inferior. Moreover, the semi-softening temperature became high.

In Comparative Examples 2 to 3, the difference in the aging precipitation annealing temperature is less than 150 ° C. compared to the recrystallization annealing temperature (that is, the temperature is not lower by 150 to 300 ° C.). Many remained. Therefore, vibration resistance was inferior. Moreover, the semi-softening temperature became high.

In Comparative Example 4, since aging precipitation annealing was not performed, a large amount of unrecrystallized remained. Therefore, vibration resistance was inferior. Moreover, the semi-softening temperature became high.

In this specification, the description “or” or “or” includes a case where only one of the options is satisfied or a case where all the options are satisfied. For example, in the case of the description “A or B” or “A or B”, it includes both the case where A is satisfied and B is not satisfied, the case where B is satisfied and A is not satisfied, and the case where A is satisfied and B is satisfied I intend to.

The specific embodiment of the present invention has been described above. The said embodiment is only a specific example of this invention, and this invention is not limited to the said embodiment. For example, the technical features disclosed in one of the above embodiments can be provided in other embodiments. Moreover, about a specific method, it is also possible to replace a part process with the order of another process, and you may add an additional process between two specific processes. The scope of the invention is defined by the claims.

Claims

A copper foil having a thickness of 50 μm or more and an unrecrystallized crystal grain of 10% or less.
A copper foil having a thickness of 50 μm or more and a non-recrystallized crystal grain of 10% or less in a metal structure after heating at 180 ° C. for 1 hour.
A rolled copper foil according to claim 1 or 2, wherein the semi-softening temperature is 150 ° C or lower.
The rolled copper foil according to claim 1 or 2, wherein the semi-softening temperature is 110 to 150 ° C.
The rolled copper foil according to any one of claims 1 to 4,
Cu concentration is 99.8% by mass or more,
The oxygen concentration is 0.05% by weight or less, and
The total concentration of Ag, Sn, B, Zr, Ti, In and P is 0 to 0.03 mass%,
Copper foil.
A flexible copper clad laminate (CCL) comprising the rolled copper foil according to any one of claims 1 to 5.
6. A flexible printed wiring board (FPC) comprising a flexible copper clad laminate.
An electronic component comprising the flexible printed wiring board according to claim 7.
A method for producing rolled copper foil,
A step of performing recrystallization annealing at 450 to 800 ° C .;
The method comprising a step of performing aging precipitation annealing at a temperature lower by 150 to 300 ° C. than a temperature of the recrystallization annealing, and a step of performing cold rolling so that the thickness becomes 50 μm or more.
It is a manufacturing method of a flexible copper clad laminated board, Comprising: This method including the process of laminating | stacking the rolled copper foil and resin obtained by the method of Claim 9.
A method for producing a flexible printed wiring board, comprising the step of forming a circuit in the flexible copper-clad laminate obtained by the method according to claim 10.