KR20130115140A - Rolled copper foil, copper clad laminate, flexible printed wiring board and method of manufacturing the same - Google Patents

Abstract

PURPOSE: A rolled copper foil, a copper-cladding laminated plate, a flexible print wiring board, and a manufacturing method thereof are provided to enable the manufacture of a product having high durability in respect to a curved portion. CONSTITUTION: A method for manufacturing a rolled copper foil includes the following steps of: casting a copper ingot; hot-rolling the copper ingot; cold-rolling and annealing the hot-rolled copper ingot more than once; performing a finish cold-rolling process at a final rolling degree of 96% or greater; performing a finish annealing process at a heating rate of 5 °C/sec or greater and 40 °C/sec or less. [Reference numerals] (AA) Stress; (BB) Transformation

Description

Rolled copper foil, copper clad laminated board, flexible printed wiring board and manufacturing method thereof {ROLLED COPPER FOIL, COPPER CLAD LAMINATE, FLEXIBLE PRINTED WIRING BOARD AND METHOD OF MANUFACTURING THE SAME}

This invention relates to a rolled copper foil, a copper clad laminated board, a flexible printed wiring board, and its manufacturing method.

An electronic device is usually comprised by the some electronic board | substrate, and the flexible printed wiring board (Hereinafter, it may be described as FPC) which electrically connects these electronic boards is formed between electronic boards. The flexible printed wiring board usually includes an insulated substrate and copper wiring formed on the substrate surface. Good flexibility and the like are required for the flexible printed wiring board that connects the electronic substrates.

In particular, in recent years, small electronic apparatuses, such as a mobile telephone, a digital camera, and a video camera, which are equipped with movable parts, such as a folding part, a rotating part, or a slide extraction part, are spread | spreading, and it becomes small size, thin, and high density, and it moves, The flexibility required for the flexible printed wiring board used for the part has become more advanced.

The characteristics required for such a flexible printed wiring board include good bendability typified by MIT bendability, and high cycle bendability typified by IPC bendability, and conventionally, copper foil or copper-resin substrate laminates having such characteristics are It is developed (patent documents 1-2).

For example, in the sliding bending test (IPC), the flexible printed wiring board which bears the number of bending which cannot be practically realistically manufactured with the test apparatus using the test apparatus is also produced.

Japanese Laid-Open Patent Publication No. 2010-100887 Japanese Laid-Open Patent Publication No. 2009-111203

By the way, even in the case of a small electronic device using a flexible printed wiring board that withstands a number of bendings (for example, 100,000 times) that may not be practically possible in the sliding bending test (IPC), for example, a folding cell phone or a sliding cell phone In the real product, the failure that a flexible printed wiring board was broken did not disappear. Even with the use of FPCs that can withstand a large number of bends, this failure still occurs in real products, such as high-density component contact, intervening FPC by other components, and sharp edges. Innumerable causes, such as deterioration of the insulating material due to heat generation and chemical reaction other than the design, have been examined, and measures have been taken.

The present inventors can solve this by improving the copper foil itself of the FPC, rather than determining the cause of these failures on the basis that the failure that the flexible printed wiring board is broken in the actual product has not been eliminated. I thought that it might be, and I decided to advance research and development.

Accordingly, an object of the present invention is to provide a rolled copper foil, a copper clad laminate, and a flexible printed wiring board (FPC) having a higher degree of durability against bending when used in an FPC in an actual product.

In such a situation, the inventors of the present invention provide a flexible printed wiring board that can withstand a bending frequency (for example, 100,000 times) which is not practically possible in a sliding bending test (IPC), and is a product of reality (for example, a folded type). In the case of a mobile phone or a slide-type mobile phone, in consideration of the fact that a breakdown occurs in practice, it has nevertheless been studied in consideration of whether or not such breakage can be avoided by a new improvement of the FPC. .

And the idea that the sliding bending test (IPC) which becomes the standard test method at present does not reflect the actual use environment of a product, rather than the number of bending (per unit time) in a bending test As a result of the reduction and various experimental examinations, it was surprisingly found that the breakage tends to occur due to intermittent bending.

In addition, the present inventors believe that the unexpected phenomenon is caused by the stress relaxation phenomenon of the copper foil, and the stress relaxation phenomenon that is considered to be only a theoretical possibility since the copper foil of the FPC in pursuit of thinning is an actual product. It was found that the resistance to bending under the conditions encountered by the actual product was greatly improved by conducting a study that had a large influence on fracture and that stress relaxation did not occur in the production of copper foil. Reached.

That is, according to the present invention, by manufacturing the copper foil and the FPC so as to satisfy the conditions for reducing the stress relaxation of the copper foil of the FPC, it is possible to improve the durability against intermittent bending and to break the FPC under the conditions encountered in actual products. Can be reduced. Therefore, FPC and copper foil which reduced stress relaxation and improved intermittent bending resistance fall within the scope of the present invention irrespective of the specific means for reducing the stress relaxation.

Therefore, this invention exists in following (1)-.

(1) Intermittent bending resistant copper foil with reduced stress relaxation during bending.

(2) Regarding 0.2% deformation at 25 ° C, the following formula I:

(T ₀ -T ₅ ) / T ₀ ≤ 25 (%) (Formula I)

(Where T ₀ represents initial stress and T ₅ represents stress after 5 hours)

The intermittent flex | flexion resistant copper foil as described in (1) which satisfy | fills the conditions of.

(3) The intermittent flex | flexion resistant copper foil whose length of the grain boundary per 1000 micrometers of observation cross sections is seen from a rolling parallel cross section.

(4) The intermittent bending resistant copper foil of (1) or (2) whose grain boundary length per 1000 micrometers of observation cross sections is seen from a rolling parallel cross section.

(5) The intermittent bending resistant copper foil according to any one of (1) to (4), which has a Young's modulus in the range of 60 to 105 GPa.

(6) The intermittent flex | flexion resistant copper foil in any one of (1)-(5) which is copper foil which copper foil contains copper and an unavoidable impurity.

(7) the copper foil contains copper and inevitable impurities, and further,

Copper foil which consists of 20-500 mass ppm of 1 or more elements chosen from the group which consists of Ag, Sn, In, Ti, Zn, Zr, Fe, P, Ni, Si, Te, Cr, Nb, B, and V in total. , Intermittent bending resistance copper foil in any one of (1)-(5).

(8) The intermittent bending resistance copper foil in any one of (1)-(5) whose copper foil is copper foil which consists of oxygen-free copper or tough pitch copper.

(9) copper foil, in addition to oxygen-free copper or tough pitch copper,

Copper foil formed by adding 20-500 mass ppm of 1 or more elements chosen from the group which consists of Ag, Sn, In, Ti, Zn, Zr, Fe, P, Ni, Si, Te, Cr, Nb, B, and V in total. , Intermittent bending resistance copper foil in any one of (1)-(5).

(10) The intermittent bending-resistant copper foil according to any one of (1) to (9), in which the copper foil is a rolled copper foil.

(11) The intermittent bending-resistant copper foil according to any one of (1) to (10), which is a rolled copper foil obtained by rolling at a workability of 96% or more.

(12) The intermittent bending resistant copper foil in any one of (1)-(11) which is copper foil for flexible printed wiring boards.

(13) The intermittent bending resistant copper foil according to any one of (1) to (11), which is laminated in a flexible printed wiring board.

(14) The intermittent flex | flexion resistant copper foil in any one of (1)-(11) which is copper foil for copper clad laminated boards.

(15) The intermittent bending resistant copper foil according to any one of (1) to (11), which is laminated in a copper clad laminate.

Moreover, this invention is also in following (21)-.

(21) Copper foil which becomes an intermittent bending tolerance copper foil in any one of (1)-(14) after heat processing for 160 seconds at 160-400 degreeC for 1 second.

(22) Copper foil which becomes an intermittent bending tolerance copper foil in any one of (1)-(14) after heat processing for 30 minutes at 200 degreeC, or heat processing for 1 second at 350 degreeC.

(23) The flexible printed wiring board in which the intermittent bending-resistant copper foil in any one of (1)-(10), (11), (12) is laminated | stacked.

(24) The copper clad laminated board by which the intermittent bending resistant copper foil in any one of (1)-(10), (13), (14) is laminated | stacked.

Moreover, this invention is also in following (31)-.

(31) process of casting copper ingots,

Process of hot rolling an ingot of copper,

A process of performing cold rolling and annealing at least once on an ingot of hot rolled copper,

The manufacturing method of the rolled copper foil which includes the process of performing the last cold rolling for letting it be finish thickness.

(32) In the process of performing the final cold rolling for the finish thickness,

The manufacturing method as described in (31) which makes total workability (final rolling workability) in final cold rolling for finishing thickness into 96% or more.

(33) In the step of performing cold rolling and annealing at least once on an ingot of hot rolled copper,

The manufacturing method in any one of (31)-(32) which annealing performed at last is performed at the temperature increase rate of 5 degrees C / sec or more and 40 degrees C / sec or less.

(34) In the step of performing cold rolling and annealing at least once on an ingot of hot rolled copper,

The manufacturing method in any one of (31)-(33) with which cold rolling performed just before annealing performed lastly is performed by 60%-90% of the workability (total workability).

(35) The manufacturing method in any one of (31)-(34) whose ingot of copper is a copper ingot which contains copper and an unavoidable impurity.

(36) the ingot of copper contains copper and unavoidable impurities, and further

Copper containing 20 to 500 mass ppm of one or more elements selected from the group consisting of Ag, Sn, In, Ti, Zn, Zr, Fe, P, Ni, Si, Te, Cr, Nb, B and V in total The manufacturing method in any one of (31)-(35) which is an ingot.

The manufacturing method in any one of (31)-(34) whose ingot of copper is an ingot of copper which consists of oxygen-free copper or tough pitch copper.

(38) Ingot of copper is further added to oxygen-free copper or tough pitch copper,

Of copper formed by adding 20 to 500 mass ppm of one or more elements selected from the group consisting of Ag, Sn, In, Ti, Zn, Zr, Fe, P, Ni, Si, Te, Cr, Nb, B and V in total The manufacturing method in any one of (31)-(34) and (37) which is an ingot.

Moreover, this invention is also in following (41)-.

The manufacturing method of the intermittent flex | flexion resistant copper foil which includes the process of heat-processing the rolled copper foil manufactured by the manufacturing method in any one of (41) (31)-(36) for 1 second-1 hour at 160-400 degreeC. .

(42) Process of laminating | stacking the rolled copper foil manufactured by the manufacturing method in any one of (31)-(36) with a base resin,

The manufacturing method of the intermittent bending tolerance flexible printed wiring board containing the process of heat-processing the rolled copper foil laminated | stacked with base resin at 160-400 degreeC for 1 second for 1 hour.

(43) Process of laminating | stacking the rolled copper foil manufactured by the manufacturing method in any one of (31)-(36) with a base resin,

The manufacturing method of the copper clad laminated board containing the process of heat-processing the base resin and the rolled copper foil laminated | stacked at 160-400 degreeC for 1 second for 1 hour.

Moreover, this invention is also in following (51)-.

Rolled copper foil manufactured by the manufacturing method in any one of (51) (31)-(36).

(52) Intermittent flex | flexion resistant copper foil manufactured by the manufacturing method of (41).

(53) An intermittent bending resistant flexible printed wiring board manufactured by the manufacturing method of (42).

(54) The copper clad laminated board manufactured by the manufacturing method of (43).

According to the present invention, an intermittent bend resistant copper foil can be obtained, and when used for FPC in a real product, a rolled copper foil, a copper clad laminate, and a flexible printed wiring board (FPC) having a higher degree of durability against bending are obtained. Can be. The electronic device using the flexible printed wiring board (FPC) provided with the intermittent bend resistant copper foil according to the present invention is continuous because the FPC serving as the movable part is provided with the bend resistance reflecting the use situation in the actual product. It is excellent in durability and reliability compared with the conventional product which considered only resistance to bending.

1: is explanatory drawing which shows the state of the inner surface and outer surface of the bending of copper foil.
2 is an explanatory diagram illustrating misalignment of the hysteresis loop.
3 is an electron micrograph of a rolled parallel cross section for observation of grain boundaries.

EMBODIMENT OF THE INVENTION Below, this invention is demonstrated in detail with preferable embodiment.

As mentioned above, the flexural evaluation of copper foil was performed by the continuous bending motion conventionally. However, the inventors found out that copper foil breaks with a small number of bending times in intermittent bending compared with continuous bending. And it found out that this change of breaking life originates in the stress relaxation phenomenon of copper foil, and reached | attained this invention.

According to the inventor's examination, when copper foil is bent repeatedly, tensile stress and compressive stress act alternately on the copper foil surface. If the bending is continuous, the tensile / compressive stress acting is the same degree even if the bending is repeated several times. The bending test performed in this state is the bending test conventionally performed. However, in the case of intermittent bends, stress relaxation occurs between the bends and the bends, and the hysteresis loops are shifted to the low stress side. Therefore, when the bends are resumed, the hysteresis loops are displaced, resulting in a large stress amplitude. The inventors have come to the conclusion that this is the cause of shorter life than continuous bending in intermittent bending.

Explanatory drawing explaining this phenomenon is shown in FIG. 1 is a description showing that the outer surface is in a tensioned state and the inner surface is in a compressed state when assuming an inner side and an outer side of the bending of the copper foil and divided into an outer surface (outer surface) and an inner surface (inner surface). It is also. As shown, since the outer surface is in the tensioned state, if this state is maintained, the stress relaxation in the tensioned state occurs soon, and as a result, the hysteresis loop is shifted toward the compression side with respect to the outer surface. On the other hand, as shown in the figure, since the inner surface is in a compressed state, when this state is maintained, stress relaxation occurs in this compressed state, and as a result, the hysteresis loop is shifted toward the tension side with respect to the inner surface. Becomes

Explanatory drawing explaining such a deviation of the hysteresis loop is shown in FIG. 2, the horizontal axis represents deformation and the vertical axis represents stress. In Fig. 2, three hysteresis loops are shown: top, center and bottom. The central hysteresis loop is a hysteresis loop in the case where the bending is performed continuously. If a deviation due to stress relaxation does not occur, the hysteresis loop is originally located as a loop in the center portion. In the continuous bending test conducted conventionally, for example, 100,000 bending tests were performed along this hysteresis loop. So, if the use of the FPC in real-world small electronics would follow this hysteresis loop, the FPC would all be able to withstand, for example, more than 100,000 bends, exhibiting the durability performance expected by each manufacturer. .

The upper hysteresis loop in FIG. 2 is a hysteresis loop after the inner surface side of the copper foil is shifted by the stress relaxation, which is confirmed after the copper foil is bent and stress relaxation occurs with time. The lower hysteresis loop in FIG. 2 is a hysteresis loop after the outer surface side of the copper foil is shifted by the stress relaxation, which is confirmed after the copper foil is bent and stress relaxation occurs with time. Thus, when copper foil is bent and hold | maintained and stress relaxation generate | occur | produces with passage of time, it will have a different hysteresis loop in the outer surface side and inner surface side of the same one copper foil in this way.

Afterwards, when the copper foil is bent to the opposite side, that is, when the outer side is bent to the inner side this time and the inner side to the outer side this time, the hysteresis loop of the upper part of FIG. At the same time, from the lower hysteresis loop to the upper hysteresis loop, a large amplitude exceeding each hysteresis loop is applied to both sides of the copper foil. If the copper foil is then bent to the opposite side again, a large amplitude exceeding each hysteresis loop is again given to both sides of the copper foil, and eventually, if such intermittent bending is continued, the stress relaxation is alternately applied to both sides. To increase the stress and distortion amplitude. The arrow of FIG. 2 shows that such a shift (amplitude) of the hysteresis loop occurs. As the intermittent bend continues, the copper foil is subjected to excessive distortion than the continuous bend to circulate only the central hysteresis loop. As a result, the number of bends that the continuous bend could not be satisfied is not satisfied. , Copper foil will be damaged.

Therefore, the present inventors reached the idea that what should just be improved the stress relaxation characteristic of copper foil in order to avoid such a damage | damage. Accordingly, the present invention improves the intermittent bendability of the copper foil by reducing the stress relaxation or preventing the occurrence of the stress relaxation, and accordingly the copper foil (including the copper foil in the FPC) whose intermittent bendability is improved. Is in. In this specification, although this invention is demonstrated to specific embodiment for improving the intermittent bendability of copper foil, this invention is not limited to the specific embodiment illustrated in this way.

Moreover, this inventor came to the idea that the stress change with respect to deformation amount can be made small by reducing the Young's modulus of copper foil, in order to avoid such a damage. Thereby, even if stress relaxation occurs, increase of stress and distortion amplitude can be suppressed. Therefore, this invention also exists in improving the intermittent bendability of copper foil by reducing the Young's modulus of copper foil, and also the copper foil (including copper foil in FPC) by which the intermittent bendability was improved. Also in this point, in this specification, although this invention is demonstrated to specific embodiment for improving the intermittent bendability of copper foil, this invention is not limited to the specific embodiment illustrated in this way.

[Stress Relief]

The stress relaxation refers to a phenomenon in which the stress loaded on the metal decreases with time under the condition of constant temperature and constant distortion.

Stress relaxation is a phenomenon which occurs microscopically by the movement of the electric potential in a material. Such shift of dislocation is likely to occur at grain boundaries. Therefore, the present inventors have implemented to reduce the length of the grain boundaries of the copper foil as a means for realizing a reduction in stress relaxation, thereby improving the resistance to intermittent bending.

[Grain boundary length]

The length (grain boundary length) of the grain boundary is, for example, a rolled parallel section of the copper foil after annealing at 200 ° C. for 30 minutes using CP (Cross section polisher), and EBSD (JXA8500F manufactured by Electron Back Scattering Diffraction Nippon Electronics Co., Ltd.) Using a step width of 0.5 μm, an acceleration voltage of 15 kV, a WD of 23 mm and a current of 5 × 10 ⁻⁸ A to measure the crystal orientation in the observation range of 1000 μm, with a crystal orientation difference of 15 degrees or more from adjacent measuring points. A case can be considered as a crystal grain, and the grain boundary length contained in an observation range can be measured and calculated | required.

In a preferred embodiment, the length of the grain boundaries per 1000 μm 2 observed in the rolled parallel cross section is, for example, 200 μm or less, preferably 100 μm or less, more preferably 90 μm or less, even more preferably 70 μm. Hereinafter, More preferably, it can be 50 micrometers or less. In view of the reduction in stress relaxation, the smaller the length of the grain boundary, the better. On the other hand, in a preferable embodiment, the length of a grain boundary can be 0.1 micrometer or more, for example, 1.0 micrometer or more, for example, 5.0 micrometers or more. It is preferable that the length of a grain boundary is a value more than this from a viewpoint of the strength of copper foil.

In order to show the length of a grain boundary, an example of the electron microscope photograph of the observed rolling parallel cross section is shown as FIG. 3, the top, middle, and bottom three cross-sectional photographs are shown as photographs of horizontal length. In the cross-sectional photograph of FIG. 3, almost no grain boundary can be confirmed. This sample piece with almost no grain boundary confirmed good intermittent bending resistance (OK). In addition, since the copper foil is very thin, the support is placed on the copper foil to obtain an electron micrograph, and the black portion at the top of the cross-sectional photograph above is the gap between the support and the copper foil, and the white portion immediately below the support. . In the cross-sectional photograph below FIG. 3, a large number of grain boundaries can be confirmed. This sample piece which could confirm a large number of grain boundaries was inferior to intermittent bending tolerance (NG). In the cross-sectional photograph in the middle of FIG. 3, a medium grain boundary can be confirmed. Although this sample piece was superior to the sample of the said cross section picture in intermittent bending tolerance, it was inferior to the sample of the above cross section picture.

[Stress Relaxation Rate]

The stress relaxation rate cuts the copper foil after annealing for 30 minutes at 200 degreeC into the step shape of width 12.7mm using a precision cutter, and uses a tension tester (AGS-X by Shimadzu Corporation), and a distance between chucks. to hold increasing measure the change in the stress at 25 ℃ fixed at 50 ㎜, and a chuck distance of 50.1 ㎜, early and stress T _t obtained after t hours (after 0 hour) the difference between the stress T ₀ and the initial stress T _The thing divided by ₀ {(T ₀ -T _t ) / T ₀ } can be obtained as the stress relaxation ratio (%) after t hours.

In a preferred embodiment, the stress relaxation rate (%) of the intermittent flexure resistant copper foil according to the present invention is represented by the following formula I for a 0.2% strain at 25 ° C when t = 5 hours.

(T ₀ -T ₅ ) / T ₀ ≤ 25 (%) (Formula I)

(Where T ₀ represents initial stress and T ₅ represents stress after 5 hours)

It can be made to satisfy the conditions of, More preferably, it is following formula II:

(T ₀ -T ₅ ) / T ₀ ≤ 20 (%) (Formula II)

The condition can be satisfied. More preferably, the value of (T ₀ -T ₅ ) / T ₀ can be 19% or less.

[Young's modulus]

Young's modulus can be measured, for example using a resonant measuring device (TE-RT by Nippon Techno Plus Co., Ltd.). In a preferred embodiment of the present invention, the Young's modulus of the intermittent bend resistant copper foil is, for example, 60 to 105 GPa, preferably 70 to 105 GPa, more preferably 70 to 100 GPa, still more preferably 70 to 90 ㎬, More preferably, it can be set as the range of 75-85 Hz.

[Furtherance]

The composition of the copper foil of this invention can be used as long as it is a composition which can reduce stress relaxation. For example, pure copper containing copper and unavoidable impurities can be used. In a preferable embodiment, as a composition of copper foil, tough pitch copper standardized by alloy number C1100 of JIS-H3100, or oxygen-free copper standardized by alloy number C1020 of JIS-H3100 can be used as a composition. When the composition is close to pure copper, the electrical conductivity of the copper foil does not decrease, and is suitable for FPC and COF. Usually, the oxygen concentration contained in a rolled copper foil is 0.01-0.05 mass% in the case of tough pitch copper, and 0.001 mass% or less in the case of oxygen-free copper. As the oxygen free copper, oxygen free copper standardized in alloy No. C1011 of JIS-H3510 can also be used.

In a preferable embodiment, as a composition of copper foil, you may contain 500 mass ppm or less of 1 or more types further selected from the group of Ag and Sn with respect to the composition close to the said pure copper. However, it is preferable that Sn content is 300 ppm or less. When the total amount of Ag or Sn added to the rolled copper foil exceeds 500 mass ppm, the conductivity decreases, the recrystallization temperature increases, the growth of the recrystallized grains in the final annealing may be long, and the grain boundary length may be long. Although the minimum of the total addition amount of Ag and Sn is not specifically defined, Usually, it is 20 mass ppm or more in total.

In a preferred embodiment, to copper having a composition close to pure copper, for example to the tough pitch copper or to the oxygen free copper, Ag, Sn, In, Ti, Zn, Zr, Fe, P, Ni, Si, Te 20-500 mass ppm of 1 or more types of elements chosen from the group of Cr, Nb, B, and V may be contained in total.

Further, at least one element selected from the group of Ag, Sn, In, Ti, Zn, Zr, Fe, P, Ni, Si, Te, Cr, Nb, B, and V in copper having a composition close to the pure copper. Is added in an amount of 500 mass ppm or more in total, and for example, a recrystallized grain is grown by applying a heat treatment for 30 minutes or more at a high temperature of 600 ° C. or higher, thereby improving stress relaxation characteristics. However, in this process, in order to manufacture a copper clad laminated board, it is not advantageous at the point which must laminate | stack the soft copper foil after resin and resin.

[Manufacture of Copper Foil]

The manufacturing of the copper foil (intermittent bending-resistant copper foil) which concerns on this invention can be implemented without a restriction | limiting as long as it is a method which can be manufactured as copper foil with reduced stress relaxation as mentioned above. In a preferred embodiment, for example, using a copper (copper alloy) of the composition described above, the step of casting the copper ingot, the step of hot rolling the ingot of copper, cold rolling to the ingot of hot rolled copper Rolled copper foil is manufactured by the manufacturing method including the process of performing annealing 1 time more than once, and the process of performing the last cold rolling to make finishing thickness, and with respect to this rolled copper foil, it is 160 to 400 degreeC for 1 second-1 By performing the process of heat-processing time, it can manufacture as intermittent bending tolerance copper foil. Moreover, you may repeat heat processing in the manufacturing process of the copper clad laminated board which joins copper foil and a resin layer for the heat processing for said 1 second-1 hour at said 160-400 degreeC.

In the process of cold-rolling and annealing at least once in this hot-rolled copper ingot, cold rolling and annealing can be repeated suitably and can be made desired thickness. In a preferred embodiment, in this annealing, the annealing carried out lastly, that is, the annealing performed immediately before the step of performing the final cold rolling for finishing thickness has a temperature increase rate of 5 ° C / sec or more and 40 ° C / sec or less. It is preferable to set it as. When the temperature increase rate is 5 degrees C / sec or less, coarsening of a crystal grain occurs and recrystallization structure becomes nonuniform. On the other hand, when it is 40 degree-C / sec or more, since fine recrystallization grains grow respectively, recrystallization structure becomes nonuniform.

In a preferred embodiment, in the rolling carried out immediately before the annealing carried out at the end, the workability (total workability) is, for example, 90% or less, preferably 89% or less, and more preferably 88% or less. It may be, for example, 60% or more, preferably 65% or more, more preferably 67% or more. By setting it as such a range, a uniform recrystallization structure will arise after the said annealing process, and the rolling structure suitable for a final rolling process can be made. When the total workability of the rolling process performed just before annealing performed last more than 90%, aggregate structure will develop excessively and the crystal grain after an annealing process will be easy to coarsen.

In a preferred embodiment, in the step of performing the final cold rolling for the final thickness, the total workability (final rolling degree) in this final cold rolling is 96% or more, preferably 97% or more, and more. Preferably, it can be 97.5% or more.

In addition, in each rolling process in this invention, it is understood by those skilled in the art that one rolling process may be performed by passing material multiple times through a rolling roll (by several pass). Therefore, in this specification, when the rolling process is performed by such a plurality of passes, the workability of a certain rolling process means the comprehensive workability realized by multiple passes, and is included in the rolling process. In order to make it clear that the workability (one pass workability) of any one pass is not meant, the workability of any rolling process may be described as the total workability.

In a preferable embodiment, the process of heat-processing for 1 second-1 hour at 160-400 degreeC with respect to a rolled copper foil is carried out for 1 second-30 minutes, for example, at 200-400 degreeC for 30 minutes, for example, For example, it can carry out by heat-processing for 1 second at 350 degreeC. In addition, heating time may be shorter than 1 second, for example, 0.1 second-1 second. By this heat processing, the rolled copper foil which received the last cold rolling turns into the intermittent bending tolerance copper foil which concerns on this invention by which stress relaxation was reduced. Although this heat processing may be performed as an independent process with respect to a rolled copper foil, For example, since resin is laminated | stacked in order to manufacture a copper clad laminated board, it heat-processes so that it may become this heat processing condition when thermosetting a film-form resin. In order to manufacture a copper clad laminated board, resin may be laminated | stacked, for example, and when heat-curing a resin material and forming a film layer, you may heat-process so that it may become this heat processing condition.

[Flexible Printed Circuit Board]

The copper foil (intermittent bending tolerance copper foil) of this invention has the outstanding intermittent bending tolerance as mentioned above, and can be used suitably as a conductive wiring part of a flexible printed wiring board. Therefore, this invention also exists in the flexible printed wiring board which laminated | stacked and provided the said copper foil.

In general, a flexible printed wiring board is formed by stacking conductive wirings on insulating resin, and has flexible and flexible properties. Wiring is laminated | stacked on the resin layer of an insulating base material through an adhesive layer as needed. Since the copper foil which concerns on this invention shows the outstanding intermittent bending tolerance in any laminated aspect, if the flexible printed wiring board of this invention laminated | stacked and provided the copper foil which concerns on this invention, various concrete aspects can be taken. . In a preferable embodiment, what adhere | attached the copper foil of this invention to the film-shaped resin layer may be sufficient, for example, and what formed into a film form by coating a resin material on the copper foil of this invention. Resin which can be used for a flexible printed wiring board can be used for a resin layer without a restriction | limiting in particular. In a preferred embodiment, for example, polyimide resins can be used.

The flexible printed wiring board of this invention can be manufactured as follows, for example. On one side of the rolled copper foil, a polyimide precursor mainly composed of polyamic acid is applied, dried and cured, processed into a copper clad laminate of the polyimide resin layer and the copper foil layer, and a predetermined circuit is formed by photolithography. It forms, and can further adhere | attach a polyimide film to the surface of the wiring side by a copper foil layer, and can be set as a flexible printed wiring board. In the said copper clad laminated board, what is necessary is just to make the layer of copper foil become intermittent bending tolerance copper foil, and, for that purpose, as said rolled copper foil, for example, it heats 200 degreeC for 30 minutes by heat processing for formation of a polyimide resin layer. You may receive the process and use the copper foil used as the intermittent bending tolerance copper foil which concerns on this invention. For example, a polyimide film may be adhered to one surface of the rolled copper foil, and processed into a copper clad laminate of the polyimide resin layer and the copper foil layer, followed by subsequent photolithography to give a flexible printed wiring board. . Also in this case, in the said copper clad laminated board, the layer of copper foil should just be an intermittent flex | flexion-resistant copper foil, and for that purpose, it is 200 degreeC 30 by the heat processing for adhesion of a polyimide film as said rolled copper foil, for example. What is necessary is just to receive the heat processing of powder, and to use the copper foil used as the intermittent bending tolerance copper foil which concerns on this invention.

The intermittent bend resistant copper foil according to the present invention and the flexible printed wiring board using the same are preferably used for mobile phones, notebook PCs, wiring members of camera barrels, movable parts of electronic devices such as HDDs, and industrial machines such as automatic processing machines and robot arms. Can be used.

Example

Examples of the present invention will now be described in conjunction with comparative examples, which are provided for a better understanding of the present invention and its advantages and are not intended to be limiting.

[Manufacture of Copper Foil]

Oxygen-free copper (JIS alloy number C1020) (OFC: Oxygen-Free Copper) or tough pitch copper (JIS alloy number C1100) (TPC: Tough-Pitch Copper) is melted and cast as needed to add the elements shown in Table 1. And the ingot of thickness 200mm and width 600mm was produced. After hot rolling the ingot to a thickness of 10 mm, cold rolling and annealing are appropriately repeated, and the workability (final rolling workability) in the final cold rolling for the final thickness is as described in Table 1, respectively. Copper foil was manufactured. The final rolling process and foil thickness at this time are as Table 1 respectively.

Moreover, the total workability of the rolling process performed immediately before the annealing process immediately before final cold rolling, and the temperature increase rate in the annealing process immediately before final cold rolling were made as Table 1, and so on. In addition, "(circle)" of a temperature increase rate means that a temperature increase rate is 5 degrees C / sec or more and 40 degrees C / sec or less. In addition, "x" of the comparative example 7 means what annealed at the temperature increase rate exceeded 40 degree-C / sec.

[evaluation]

The obtained rolled copper foil was annealed at 200 ° C. for 30 minutes, or an FPC for evaluation was created and used for evaluation of Young's modulus, grain boundary length, stress relaxation rate, and flexibility (continuous bending, intermittent bending) to be described later. The obtained result was put together in Table 1 and Table 2. However, about Example 2 and Comparative Example 2, the laminating processing machine which adjusted the roll temperature to 350 degreeC was annealed by lumping together without laminating | stacking a polyimide and a coverlay, and it carried out similarly to the heat processing at the time of producing the evaluation FPC mentioned later. Heat treatment was performed. The heat treatment time at this time was made into 1 second.

[Young's modulus]

Young's modulus was measured using the resonance type measuring instrument (TE-RT by Nippon Techno Plus Co., Ltd.).

[Grain boundary length]

The copper foil after annealing under the above conditions (200 ° C. or 350 ° C.) was rolled out using a CP (Cross section polisher) to give a rolled parallel cross section, and the step width was 0.5 μm using EBSD (JXA8500F manufactured by Electron Back Scattering Diffraction Nippon Electronics Co., Ltd.). The crystal orientation of the observation range of 1000 µm was measured at an acceleration voltage of 15 kV, WD 23 mm, and current 5 × 10 ^-8 A. The case where the crystal orientation difference with an adjacent measuring point is 15 degree or more was regarded as a grain boundary, and the grain boundary length contained in an observation range was measured.

[Stress Relaxation Rate]

The obtained rolled copper foil was cut out into a single step of 12.7 mm in width using a precision cutter, and annealed under the above conditions (200 ° C or 350 ° C), using a tensile tester (AGS-X manufactured by Shimadzu Corporation), The intervertebral distance was fixed at 50 mm. Thereafter, the distance between the chucks was stretched to 50.1 mm (corresponding to 0.2% deformation), and the change in load was measured at 25 ° C. The difference between the stress T _t obtained after t time and the stress T ₀ of the initial stage (after 0 hours) divided by the initial stress T ₀ {(T ₀ -T _t ) / T ₀ } is the stress relaxation rate (%) Obtained as. Table 2 shows the stress relaxation ratio (%) when t = 5 hours.

[Flexibility Evaluation]

The copper foil obtained by the rolling process was thermocompression-bonded (200 degreeC, 30 minutes) with the polyimide film (Nikak Industries Co., Ltd. Nika flex: polyimide thickness 12.5 micrometers, adhesive thickness 15 micrometers), and the copper clad laminated board was obtained. After etching the obtained copper clad laminated board and making it into an FPC with a circuit width of 100 micrometers, a coverlay (Nikka Flex Co., Ltd. make: 12.5 micrometers of polyimide thickness, 15 micrometers of adhesive thickness) was thermocompression-bonded to a circuit surface (200 degreeC, 30 ) To prepare an FPC for evaluation. However, about Example 2 and the comparative example 2, the copper clad laminated board was produced using the lamination processing machine which adjusted the copper foil obtained by rolling process to the said polyimide film and the roll temperature of 350 degreeC, and is similar to the above by FPC. Then, the said coverlay was crimped | bonded to the circuit surface using the laminating machine which adjusted to roll temperature 350 degreeC, and the FPC for evaluation was produced. In addition, the heating time at this time was 1 second in total.

The bending test was carried out at a sliding speed of 120 times per minute, and carried out in a room temperature environment. In order to keep the distortion applied to the copper foil during bending, the bending radius is 1.5 mm when the copper foil thickness is 18 µm, 1.0 mm when the copper foil thickness is 12 µm, and 0.75 mm when the thickness is 9 µm. It was evaluated by the number of times. The sample was energized and breakage was detected by conduction interruption. In continuous bending, when the frequency | count of breaking was less than 100,000 times, it was (circle) and what was (circle) and 300,000 times or more as x, 100,000 times or more and less than 300,000 times. In intermittent bending, 1000 consecutive bendings were performed at intervals of 5 hours, and when the number of breaks was less than 50,000 times, x was 50,000 or more and 100,000 times or less.

According to the present invention, an intermittent bend resistant copper foil can be obtained, and when used for FPC in a real product, a rolled copper foil, a copper clad laminate, and a flexible printed wiring board (FPC) having a higher degree of durability against bending can be obtained. Can be. The electronic device using the flexible printed wiring board (FPC) provided with the intermittent bend resistant copper foil according to the present invention is continuous because the FPC serving as the movable part is provided with the bend resistance reflecting the use situation in the actual product. It is excellent in durability and reliability compared with the conventional product which considered only resistance to bending. The present invention is an industrially useful invention.

Claims (23)

Intermittent bending resistant copper foil with reduced stress relaxation during bending. The method of claim 1,
For 0.2% strain at 25 ° C, the following formula I:
(T ₀ -T ₅ ) / T ₀ ≤ 25 (%) (Formula I)
(Where T ₀ represents initial stress and T ₅ represents stress after 5 hours)
Intermittent bend resistant copper foil that meets the requirements of The intermittent bending resistant copper foil whose grain boundary length per 1000 micrometer <2> of observation cross sections is seen from a rolling parallel cross section. The method of claim 1,
The intermittent bending resistant copper foil whose grain boundary length per 1000 micrometer <2> of observation cross sections is seen from a rolling parallel cross section. The method of claim 1,
An intermittent bend resistant copper foil having a Young's modulus in the range of 60 to 105 GPa. The method of claim 1,
Intermittent flex | flexion resistant copper foil which is copper foil which copper foil contains copper and an unavoidable impurity. The method of claim 1,
Copper foil contains copper and unavoidable impurities, in addition,
Copper foil which consists of 20-500 mass ppm of 1 or more elements chosen from the group which consists of Ag, Sn, In, Ti, Zn, Zr, Fe, P, Ni, Si, Te, Cr, Nb, B, and V in total. Intermittent bend resistant copper foil. The method of claim 1,
Intermittent flex | flexion resistant copper foil whose copper foil is copper foil which consists of oxygen-free copper or tough pitch copper. The method of claim 1,
Copper foil, in addition to oxygen-free copper or tough pitch copper,
Copper foil formed by adding 20-500 mass ppm of 1 or more elements chosen from the group which consists of Ag, Sn, In, Ti, Zn, Zr, Fe, P, Ni, Si, Te, Cr, Nb, B, and V in total. Intermittent bend resistant copper foil. The method of claim 1,
Intermittent flex | flexion resistant copper foil whose copper foil is a rolled copper foil. The method of claim 1,
Intermittent flex | flexion resistant copper foil which is a rolled copper foil in which copper foil is rolled by 96% or more of workability. The method of claim 1,
Intermittent bending resistant copper foil laminated in a flexible printed wiring board. Copper foil which becomes the intermittent flex | flexion resistant copper foil of any one of Claims 1-12 after heat-processing for 1 second-1 hour at 160-400 degreeC.  Copper foil which turns into the intermittent bending tolerance copper foil of any one of Claims 1-12 after heat processing for 30 minutes at 200 degreeC, or heat processing for 1 second at 350 degreeC. The flexible printed wiring board in which the intermittent bending resistant copper foil of any one of Claims 1-12 is laminated | stacked. Process of casting ingots of copper,
Process of hot rolling ingot of copper,
Performing a cold rolling and annealing at least once on an ingot of hot rolled copper,
The manufacturing method of the rolled copper foil which includes the process of performing the last cold rolling for making finish thickness into 96% or more of total workability (final rolling workability). 17. The method of claim 16,
In the step of performing cold rolling and annealing at least once on an ingot of hot rolled copper,
The annealing performed at the last is a manufacturing method performed at the temperature increase rate of 5 degrees C / sec or more and 40 degrees C / sec or less. 17. The method of claim 16,
In the step of performing cold rolling and annealing at least once on an ingot of hot rolled copper,
The manufacturing method in which the cold rolling performed just before annealing performed lastly is performed by 60%-90% of the workability (total workability). 17. The method of claim 16,
The manufacturing method of the copper ingot is a copper ingot containing copper and an unavoidable impurity. 17. The method of claim 16,
The ingot of copper contains copper and unavoidable impurities, and further,
Copper containing 20 to 500 mass ppm of one or more elements selected from the group consisting of Ag, Sn, In, Ti, Zn, Zr, Fe, P, Ni, Si, Te, Cr, Nb, B and V in total Ingot manufacturing method. 17. The method of claim 16,
The ingot of copper is a manufacturing method of the copper ingot which consists of oxygen-free copper or tough pitch copper. 17. The method of claim 16,
Ingot of copper, in addition to oxygen-free copper or tough pitch copper,
Of copper formed by adding 20 to 500 mass ppm of one or more elements selected from the group consisting of Ag, Sn, In, Ti, Zn, Zr, Fe, P, Ni, Si, Te, Cr, Nb, B and V in total Ingot manufacturing method. The manufacturing method of the intermittent flex | flexion resistant copper foil which includes the process of heat-processing the rolled copper foil manufactured by the manufacturing method in any one of Claims 16-22 for 1 second-1 hour at 160-400 degreeC.

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