KR20120086740A - Copper foil and copper-clad laminate plate using same - Google Patents

Abstract

(Problem) Provided the copper foil excellent in bendability when used for the copper clad laminated board, and the copper clad laminated board using the same.
(Remedy) Thickness 5? It is 30 micrometers and surface roughness (Ra) of 0.1 micrometer of rolling parallel directions, and it is copper foil whose work hardening index after annealing at 350 degreeC for 0.5 hour is 0.3 or more and 0.45 or less.

Description

Copper foil and copper clad laminated board using it {COPPER FOIL AND COPPER-CLAD LAMINATE PLATE USING SAME}

This invention relates to the copper foil used for a flexible printed circuit (FPC: FPC), and the copper clad laminated board which laminated | stacked this copper foil on at least one surface of the resin layer, for example.

As a circuit for driving electronic devices such as digital cameras and mobile phones, a flexible printed circuit (FPC) or a chip of flexible circuit (COF) is used. This FPC and COF are formed by forming a circuit pattern on copper foil using the copper clad laminated board (CCL) which laminated | stacked copper foil on the single side | surface or both surfaces of a resin layer.

In order to downsize and increase the functionality of such electronic apparatuses, a method of folding an FPC into a narrow space in a case is adopted. Moreover, in the case of COF used around a liquid crystal display, in order to thin bezel (so-called "frame"), the copper wiring of COF is folded to the back surface side of a liquid crystal substrate.

However, when FPC and COF are folded, there is a problem that a large deformation load is applied to the copper foil portion, and thus it becomes easy to break.

Then, it is reported that FPC which contains a columnar copper crystal grain and does not fracture | rupture a wiring pattern well is comprised by configuring FPC by the electrolytic copper foil of 5% or more of elongation rate in 25 degreeC (patent document 1).

Japanese Unexamined Patent Publication No. 2007-335541

Conventionally, it is thought that the bending property of the copper foil of CCL has a correlation with the elongation of copper foil, and therefore, as described in the said patent document 1, the electrolytic copper foil with large elongation is used.

By the way, the present inventors found out that the bendability of CCL may not improve even if the rolled copper foil with large elongation is used.

That is, the present invention has been made to solve the above problems, and an object of the present invention is to provide a copper foil excellent in bendability when used in a copper clad laminate and a copper clad laminate using the same.

As a result of various studies, the inventors found that the work hardening index (n value), not the elongation of copper foil, is important as a factor for improving the bendability of CCL.

In order to achieve the above object, the copper foil of the present invention has a thickness of 5? The surface roughness (Ra) in the rolling parallel direction (Ra) is 0.1 µm, and the work hardening index after annealing at 350 ° C. for 0.5 hour is 0.3 or more and 0.45 or less.

It is preferable that the semi-softening temperature of the copper foil of this invention is 150 degrees C or less.

Moreover, it is preferable that the copper foil of this invention consists of oxygen-free copper or tough pitch copper, or contains 500 mass ppm or less of 1 or more types which consist of a group of Ag and Sn in oxygen-free copper or tough pitch copper.

When the total thickness which laminated | stacked the resin layer on the single side | surface of the said copper foil was 50 micrometers or less, and carried out 180 degree close contact bending with the exposed surface of the said copper foil outside using the sample of width 3mm or more and 5mm or less, the said It is preferable that the frequency | count of bending until a copper foil breaks is four or more times.

It is preferable that the total workability at the time of final cold rolling is 85% or more, and rolling is carried out on the following three conditions in the final three passes in the final cold rolling under the following conditions. However, the oil film equivalent before two final passes; 25000 or less, oil film equivalent before one final pass; 30000 or less, oil film equivalent of last pass; 35000 or less Here, when hot-rolling an ingot and manufacturing copper foil through cold rolling, cold rolling and annealing are alternately performed in cold rolling. And the cold rolling performed last after the last annealing is called "final cold rolling."

The copper clad laminated board of this invention laminates | stacks the said copper foil on at least one surface of a resin layer.

According to this invention, when used for the copper clad laminated board, the copper foil excellent in bendability is obtained.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows the method of the sliding bending by an IPC sliding bending apparatus.

Hereinafter, the copper foil which concerns on embodiment of this invention is demonstrated. In addition, in this invention,% shall show the mass% unless there is particular notice.

Copper foil which concerns on embodiment of this invention has thickness 5? The surface roughness (Ra) in the rolling parallel direction (Ra) is 0.1 µm, and the work hardening index after annealing at 350 ° C. for 0.5 hour is 0.3 or more and 0.45 or less.

The work hardening index (n value) is represented by the index n in the case of approximating the relationship of the stress and strain in the plastic strain area more than a yield point by the following formula | equation 1 (Hollomon formula).

[True stress] = [material constant] x [true strain] n (1)

The larger the work hardening index, the less likely the local strain is to break when the strain is applied. In addition, materials having a high work hardening index are excellent in drawing workability and are suitable for press working. And when copper foil is laminated | stacked on the at least single side | surface of a resin layer, and a copper clad laminated board is manufactured, and the bendability of this copper clad laminated board is evaluated, copper foil with a work hardening index of 0.3 or more hardly produces local deformation, and it deforms in the whole bending part. Since it is in charge of, it is thought that the copper foil is not broken well. However, the material whose work hardening index exceeds 0.45 is not suitable for copper clad laminated boards because the strength after annealing is low and handling property deteriorates.

Here, the reason why the work hardening index after annealing at 350 degreeC for 0.5 hour is prescribed | regulated because the heating conditions at the time of manufacturing a copper clad laminated board are this grade. Moreover, when the resin layer of a copper clad laminated board is obtained by apply | coating and hardening a resin composition to copper foil (in the case of 2-layer CCL which does not interpose an adhesive layer between a resin layer and copper foil), resin will harden on the said heating conditions.

Moreover, as a factor which improves the bendability of copper foil, it is thought that the reason why process hardening index (n value) is important rather than elongation of copper foil is as follows.

First, the work hardening index is one of the values which show the work hardening behavior of a material, and as this value is large, a material has the property which is easy to work harden. Here, although the material is locally tightened and broken when subjected to tensile deformation, in the material having a large work hardening coefficient, the joining part is hardened and the tightening part is hardly deformed. Therefore, instead of the fastening part which is hard to deform | transform, the other part starts to deform | transform. By repeating this, the entire material is deformed evenly. On the other hand, since elongation is an index grasped macroscopically without considering such a situation, even if elongation is large, it cannot be said that a work hardening index is large.

Conventionally, as an index of the ease of deformation of the entire material as such, there is an example in which a work hardening index is used in drawing processing of a thick material, but a thin material such as copper foil is subjected to drawing processing or the like. Since it does not, there has been no case where the work hardening index is used as an index. Therefore, in the present invention, when the work hardening index of the copper foil is increased, it was considered that even in 180 degree close bending of the CCL, the entire bent portion is deformed evenly so that it is bent without breaking.

Moreover, it is preferable that the work hardening | curing index after annealing for 0.5 hour at 200 degreeC is also 0.3 or more and 0.45 or less. This is because the lamination temperature at the time of manufacture of 3-layer CCL which laminated | stacked the film and copper foil through the adhesive layer using the film as a resin layer is about 200 degreeC. Since the work hardening index becomes large by recrystallizing copper foil by heating, when the work hardening index is 0.3 or more at 200 degreeC lower than 350 degreeC, the work hardening index of 0.3 or more is obtained also at 350 degreeC. Moreover, in order to fully acquire a recrystallization structure by the said annealing, it is preferable that the semi-softening temperature of copper foil is 150 degrees C or less.

As a method of managing the work hardening index of the copper foil after annealing for 0.5 hour at 350 degreeC to 0.3 or more, making the total workability at the time of final cold rolling into 85% or more is mentioned. Moreover, since it is necessary to obtain a recrystallized structure, it is preferable to manage the semi-softening temperature of copper foil at 150 degrees C or less. In general, the recrystallization temperature is determined by the composition and the degree of workability of the copper foil. In order to set the work hardening index to 0.3 or more, any means may be used.

If the total workability at the time of final cold rolling is less than 85%, the workability is lowered and the softening temperature of the copper foil is increased. Therefore, recrystallization of copper by heating at the time of CCL manufacture becomes insufficient, and work deformation remains and the tendency to bend deteriorates. There is this.

In order to improve the bendability at the time of using copper foil for a copper clad laminated board, it is necessary to consider the influence of surface roughness in addition to the said work hardening index. Here, with regard to the size of the work hardening index, "how much material can be hardened in the future" becomes an important factor. Therefore, in order to make a work hardening index into a large value, it is necessary at the initial stage that a material is not work hardened, that is, a state in which work strain was removed. In the copper foil for CCL, it is necessary to recrystallize copper foil by the heat processing of a CCL manufacturing process.

And since the heat processing conditions of a CCL manufacturing process depend on the property of resin, it is necessary to match the recrystallization temperature of copper foil with heat processing conditions. The recrystallization temperature of copper foil is influenced by composition and workability, and the softening temperature becomes too high in the composition containing a large amount of an additional element. Moreover, even if the composition of copper foil is appropriate, when workability is too high, softening will result in normal temperature, and when workability is too low, softening temperature will become high too much.

In addition to such factors, surface roughness affects bendability as a factor separate from the work hardening index. If the surface roughness is large and there are cutout irregularities on the surface of the material of the copper foil, stress is concentrated at the cutout tip when bent, which causes breakage.

In such a point, the surface roughness Ra of the rolled parallel direction of the copper foil which concerns on embodiment of this invention is 0.1 micrometer or less. This reason is because when surface roughness Ra exceeds 0.1 micrometer, when a copper foil is bent, surface unevenness | corrugation will become a starting point, and a crack (break) will advance easily. Since the indentation called oil pit formed in the copper foil surface by rolling is formed in the groove shape extended in the rolling right angle direction, surface roughness is measured in the rolling parallel direction. Ra is an arithmetic mean roughness measured based on JIS-B 0601.

As a method of adjusting the surface roughness Ra of the rolling parallel direction of copper foil to 0.1 micrometer or less, adjusting the oil film equivalent in the last 3 passes in final cold rolling is mentioned. Specifically, the oil film equivalent before two final passes in final cold rolling; 25000 or less, oil film equivalent before one final pass; 30000 or less, oil film equivalent of last pass; 35000 or less

Further, when the material thickness becomes thin, the oil film equivalent tends to be large, so that the value of the oil film equivalent in the final three passes gradually increases. Therefore, it is necessary to set an appropriate oil film equivalent amount for the last 3 passes each having a different thickness.

In the final cold rolling, if the rolling oil viscosity and the material yield stress are equal in all the passes, the oil film equivalent is proportional to (rolling speed) / (engrave angle). As the thickness of the material becomes thinner, the bite angle becomes smaller, so that the closer to the final pass, the larger the film equivalent is. In addition, in order to maintain productivity, the rolling speed needs to be increased as the material length is closer to the final pass, and accordingly, the oil film equivalent tends to be larger as the material is closer to the final pass.

And if the material surface roughness in the intermediate | middle pass in final cold rolling is coarse, even if the oil film equivalent is suppressed low in a final | pass pass, a material surface cannot fully be smoothed. In this regard, the oil film equivalent in the final three passes in the final cold rolling is managed.

On the other hand, in the final three passes in the final cold rolling, an oil film equivalent before two final passes; 25000 or less, oil film equivalent before one final pass; 30000 or less, oil film equivalent of last pass; If all 35000 or less are not satisfied (when an oil film equivalent exceeds the said value in any one of the last 3 passes), the surface of copper foil will be rough, and the surface roughness Ra of rolling parallel direction will exceed 0.1 micrometer, and the following problems Occurs.

In order to reduce an oil film equivalent, it is preferable to make the rolling workability of a final pass into 25% or more.

In addition, the said oil film equivalent is represented by a following formula. (Oil film equivalent) = {rolled oil viscosity, kinematic viscosity of 40 ° C; cSt) × (rolling speed; m / min)} / {(yield stress of material; kg / mm 2) × (roll bite angle; rad)}

Rolled oil viscosity is 4.0? 8.0 cSt degree, rolling speed 200? 600 m / min, engrave angle of roll is 0.0005? 0.005 rad, preferably 0.001? It can be 0.04 rad.

In the copper foil which concerns on embodiment of this invention, after annealing a copper foil by 350 degreeC x 0.5 hour, when the X-ray diffraction of the rolling surface is performed, the integral value of the intensity | strength of (220) plane and (200) plane, respectively It is preferable that ratio I (220) / I (200) of (I) is 0.11 or less. In this case, it is thought that the ratio of the (220) surface in copper foil becomes high, recrystallization of copper foil advances by annealing of 350 degreeC x 0.5 hour, and a process strain decreases and bending property improves.

Moreover, the total thickness which laminated | stacked the resin layer on the single side | surface of the copper foil which concerns on embodiment of this invention is 50 micrometers or less, and it uses 180-mm-closed contact with the exposed surface of copper foil outside using the sample of width 3mm or more and 5mm or less. When bending is performed, it is preferable that the frequency | count of bending until a copper foil breaks is four or more times.

The sample whose total thickness which laminated | stacked the resin layer on the single side | surface of copper foil is 50 micrometers or less mimics the copper clad laminated board, and the number of bending of the 180 degree close bending will evaluate the bendability of the copper clad laminated board.

As a resin layer, Polyimide; PET (polyethylene terephthalate); Thermosetting resins such as epoxy resins and phenol resins; Although thermoplastic resins, such as saturated polyester resin, can be used, it is not limited to these. Moreover, the varnish (for example, the polyamic-acid solution which is a precursor of a polyimide) which melt | dissolved the components of these resin layers in the solvent is apply | coated to the single side | surface of copper foil, and a solvent is removed by heating, and reaction (for example, imidation reaction) is carried out. You may advance and harden.

The 180-degree close contact bending is performed by folding the sample so that the folded mark is parallel to its own width direction and pressing it by hand pressing. And the presence or absence of the fracture | rupture of the copper foil part of the cross section of a bending part is observed with an optical microscope. If there is no break, the sample after close bending is stretched, stretched flat using a hand press, and then folded again at the same place and pressed by a hand press. In this way, the number of bendings until the copper foil is broken is determined.

It is preferable that the composition of the copper foil which concerns on embodiment of this invention consists of oxygen-free copper or tough pitch copper (both prescribed | regulated by JIS-H3100). The oxygen-free copper or tough pitch copper may contain 500 ppm by mass or less in total of one or more kinds of Ag and Sn. In the copper foil which concerns on embodiment of this invention, when 1 or more types consisting of Ag and Sn group exceed 500 mass ppm in total, recrystallization temperature will become excessively high and recrystallization by heat processing of a CCL manufacturing process will become inadequate. There is a case.

The copper clad laminated board of this invention laminates | stacks said copper foil on at least one surface of the said resin layer. Since the copper foil which concerns on embodiment of this invention is excellent in bendability, the copper clad laminated board using this is also excellent in bendability. For example, the copper clad laminated board of this invention is 90 degrees with a radius of 5 mm or less. It can use suitably for the use which bends 180 degree | times.

Example

Oxygen-free copper or tough pitch copper (JIS H 3100) was melt | dissolved, Ag and Sn were added and cast as needed in Table 1, and the ingot was produced as needed. After the hot rolling of the ingot, cold rolling and annealing were appropriately repeated to prepare copper foil. In order to adjust the softening temperature, the final workability during final cold rolling is 85% or more, and in order to reduce the surface roughness, the final cold work is performed by using a roll whose surface is smooth (Ra ≦ 0.1 μm in the roll axis direction). It rolled and manufactured copper foil. Rolled oil viscosity 4.0? 8.0 cSt, rolling speed 200? 600 m / min, engrave angle of roll 0.003? It adjusted to the range of 0.03 rad, and made all the oil film equivalents in the last 3 passes in final cold rolling into 35000 or less.

<Process Hardening Index>

After the obtained copper foil was atmospherically annealed at 200 ° C for 0.5 hours and 350 ° C for 0.5 hours, a tensile test (based on JIS-Z 2241) was performed to obtain a work hardening index. In addition, since the work hardening index needs to be calculated | required using the uniform elongation and stress after material yields, the value from 2% of elongation to the maximum stress point was used. Then, the true strain obtained from the measured elongation and stress and the approximate logarithmic magnitude of true stress were approximated by the least square method, and the work hardening index was obtained from the slope of the graph. True strain and true stress were obtained by the following equation.

True Strain = ln (1+ [Strain])

[True stress] = (1 + [true strain]) × [stress]

<Semi-softening temperature>

100% of obtained copper foil, respectively. After atmospheric annealing at 400 ° C for 0.5 hour, a tensile test was performed to obtain strength (tensile strength) with respect to heat treatment conditions. The annealing temperature at which the strength TSh after annealing became the average value of the strength TSasroll at the end of rolling (before annealing) and the strength TSanneal in a completely softened state was taken as the semi-softening temperature.

<Number of bending of copper clad laminate>

Next, on the single side | surface of the obtained copper foil, the polyimide layer of thickness about 20 micrometers was formed into a film, and single sided CCL was produced. Specifically, the single side | surface of the obtained copper foil was chemically processed (plated), and it apply | coated so that the precursor varnish (U- varnish A-made by Ube Hungsan) of polyimide resin might be set to 20 micrometers in thickness on this surface. Thereafter, the mixture was dried for 30 minutes in a hot air circulation type high temperature bath set at 130 ° C, gradually heated to 350 ° C over 2000 seconds, cured (imidized), and a resin layer (polyimide layer) was formed to form a single sided CCL. Produced.

180 degree close bending was performed in the following procedures. First, this single-sided CCL is cut to 3.2 mm in width and 30 mm in length so that the longitudinal direction of the test piece is parallel to the rolling direction, and is made as a test piece. Was carried out. And the presence or absence of the fracture | rupture of the copper foil part of a bend part cross section was observed with the optical microscope. If there was no break, the sample after close bending was stretched and stretched flat using a hand press, and then folded again at the same place and pressed by a hand press. In this way, the number of bendings until the copper foil broke was determined.

<Number of sliding bends of copper foil>

Next, the obtained copper foil was cut out at 12.7 mm in width and 200 mm in length so that the longitudinal direction of a test piece may become parallel to a rolling direction, it was set as the test piece, and it heated at 200 degreeC for 30 minutes, and recrystallized. This was measured by the IPC (American Printed Circuit Industry Association) sliding bending apparatus shown in FIG. This apparatus has a structure in which the vibration transmission member 3 is coupled to the oscillation drive body 4, and the test piece 1 is connected to the apparatus at a total of four points of the portion of the screw 2 and the tip of 3 indicated by arrows. It is fixed. When the vibration transmitting member 3 is driven up and down, the intermediate portion of the test piece 1 is bent in a hairpin shape with a predetermined radius of curvature r. In this test, the number of times to break when bending was repeated under the following conditions was calculated | required.

The test was done on condition of curvature radius (r): 2.5 mm, vibration stroke: 25 mm, vibration speed: 1500 times / min.

<I (220) / I (200)>

After air-annealing the obtained copper foil at 350 degreeC x 0.5 hour, the X-ray diffraction of the rolled surface was performed and the integral value (I) of the diffraction peak intensity of the (220) surface and (200) surface, respectively was calculated | required.

The obtained results are shown in Table 1. In addition, in the composition of Table 1, OFC and TPC represent oxygen-free copper and tough pitch copper (JIS H 3100), respectively, and Ag100 ppm TPC shows that 100 mass ppm of Ag was added to tough pitch copper.

As apparent from Table 1, the semi-softening temperature is 150 ° C or less, the surface roughness (Ra) in the rolling parallel direction (Ra) ≤ 0.1 µm, and the work hardening index after annealing at 350 ° C for 0.5 hour is 0.3 or more. In the case of 8, the number of bends at the time of 180 degree close bending was four or more, and it became what was excellent in bendability.

On the other hand, in Comparative Example 3, 6, 7, 8 which made the total workability at the time of final cold rolling less than 85%, the work hardening index after annealing for 0.5 hour at 350 degreeC becomes less than 0.3, and performs 180 degree close bending. The number of bending at the time of doing was less than four, and the bending property deteriorated. In addition, in the case of the comparative example 1, since the addition amount of Sn in copper foil exceeded 500 mass ppm, it is thought that the semi-softening temperature exceeded 150 degreeC and the work hardening index became less than 0.3.

In addition, in the case of Comparative Examples 1, 7 and 8 whose semi-softening temperature exceeded 150 degreeC, the work hardening index after annealing for 0.5 hour at 350 degreeC became less than 0.3, and the number of times of bending when 180 degree close bending was performed It became less than and bendability deteriorated.

As an oil film equivalent in the last 3 passes in final cold rolling, Oil film equivalent before two final passes; An oil film equivalent exceeding 25000 and before one final pass; More than 30000, and an oil film equivalent of the final pass; In the case of the comparative example 2 exceeding 35000, the surface roughness Ra of the rolling parallel direction exceeded 0.1 micrometer, and when the 180 degree close bending was performed, the number of bends became less than 4 times, and bending property deteriorated.

In Comparative Example 4 in which the oil film equivalent before one final pass exceeded 30000 of the oil film equivalents in the last three passes in final cold rolling, the surface roughness Ra in the rolling parallel direction exceeded 0.1 μm, and 180 The number of bending at the time of close contact bending was less than four, and the bendability deteriorated.

Also in the case of the comparative example 5 in which the oil film equivalent before two final passes exceeded 25000 among the oil film equivalents in the last three passes in final cold rolling, the surface roughness Ra of the rolling parallel direction exceeds 0.1 micrometer, The number of bends at the time of 180 degree close bending was less than four, and the bendability was deteriorated.

In addition, Comparative Example 1? Also in the case of 8, the number of times of IPC sliding bending which is a conventional flexibility evaluation is equivalent to each Example, and it turns out that the bending property of a copper clad laminated board cannot be evaluated by a sliding bending test.

Claims (6)

Thickness 5? Copper foil whose surface roughness (Ra) in a rolling parallel direction (Ra) is 0.1 micrometer, and the work hardening index after annealing at 350 degreeC for 0.5 hour is 0.3 or more and 0.45 or less. The method of claim 1,
Copper foil whose semi-softening temperature is 150 degrees C or less. The method according to claim 1 or 2,
Copper foil which consists of oxygen-free copper or tough pitch copper, or contains 500 mass ppm or less in total of 1 or more types which consist of Ag and Sn group in oxygen-free copper or tough pitch copper. The method according to any one of claims 1 to 3,
When the total thickness which laminated | stacked the resin layer on the single side | surface of the said copper foil was 50 micrometers or less, and carried out 180 degree close contact bending with the exposed surface of the said copper foil outside using the sample of width 3mm or more and 5mm or less, the said Copper foil whose bending number of times until a copper foil breaks is four or more times. The method according to any one of claims 1 to 4,
The total workability at the time of final cold rolling is 85% or more, and the copper foil formed by rolling on the oil film equivalent in the last 3 passes in the said final cold rolling on condition of the following.
However, the oil film equivalent before two final passes; 25000 or less, oil film equivalent before one final pass; 30000 or less, oil film equivalent of last pass; 35000 or less The copper clad laminated board formed by laminating | stacking the copper foil in any one of Claims 1-5 on at least one surface of a resin layer.

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