JP2019029605A - Copper foil for flexible printed board, copper-clad laminate arranged by use thereof, flexible printed board, and electronic device - Google Patents

Abstract

To provide copper foil for a flexible printed board, which is superior in bendability.SOLUTION: The copper foil is copper foil for a flexible printed board, which comprises 99.0 mass% or more of Cu with the balance consisting of inevitable impurities. The copper foil is larger than 75% IACS in conductivity, and KAM value ratio of a copper foil surface given by (Region A of 0-0.875 in KAM value)/(Region B of 0-5 in KAM value) is 0.98 or more.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a copper foil suitable for a wiring member such as a flexible printed circuit board, a copper clad laminate using the copper foil, a flexible wiring board, and an electronic device.

A flexible printed circuit board (flexible wiring board, hereinafter referred to as “FPC”) has flexibility, and is widely used in a bent portion and a movable portion of an electronic circuit. For example, FPCs are used for movable parts of disk-related devices such as HDDs, DVDs, and CD-ROMs, and for folding parts of foldable mobile phones.
The FPC is formed by etching a copper clad laminate (copper-clad laminate, hereinafter referred to as CCL) in which a copper foil and a resin are laminated, and then coating the wiring with a resin layer called a coverlay. The copper foil surface is etched as part of the surface modification step for improving the adhesion between the copper foil and the coverlay before the coverlay is laminated. Further, in order to improve the flexibility by reducing the thickness of the copper foil, thinning etching may be performed.

By the way, along with the downsizing, thinning, and high performance of electronic devices, it is required to mount FPCs in these devices at a high density. The FPC needs to be folded and accommodated, that is, high bendability is required.
On the other hand, copper foils with improved high-cycle flexibility represented by IPC flexibility have been developed (Patent Documents 1 and 2).

JP 2010-100877 A JP 2009-111203 A

However, in order to mount the FPC at a high density as described above, it is necessary to improve the bendability represented by MIT fold resistance, and the conventional copper foil cannot be said to have sufficient improvement in bendability. There's a problem.
The present invention has been made to solve the above-mentioned problems, and aims to provide a copper foil for a flexible printed circuit board excellent in bendability, a copper-clad laminate using the same, a flexible printed circuit board, and an electronic device. To do.

  As a result of various studies, the present inventors have refined the crystal grain size before the final cold rolling of the copper foil to make the accumulation of dislocations uniform in each region of the copper foil during the cold rolling and recrystallization. Later, in any region of the copper foil, it was found that since the strain is released, the KAM value can be reduced and the elongation at break can be improved, and the bendability can be improved. In general, the larger the KAM value, the more intragranular strain is accumulated after recrystallization. In the region where the KAM value is large (the accumulation of intragranular strain is large) and the region where the KAM value is small (the accumulation of intragranular strain is small), Fracture due to different plastic deformation behavior during bending. Therefore, if the region where the KAM value is small is increased, the plastic deformation behavior at the time of bending in the copper foil is equalized, and the bendability is improved.

  That is, the copper foil for a flexible printed board of the present invention is a copper foil composed of 99.0% by mass or more of Cu and the balance unavoidable impurities, the electrical conductivity exceeds 75% IACS, the KAM value of the surface of the copper foil The composition ratio = (region A where the KAM value is 0 to 0.875) / (region B where the KAM value is 0 to 5) is 0.98 or more.

In the copper foil for a flexible printed circuit board of the present invention, when the plate thickness is x [μm], the elongation at break y [%] is expressed by the formula 1: [y = −0.0365 (% · (μm) ⁻² ) x ² +2.1352 It is preferably (% · (μm) ⁻¹ ) x−5.7219 (%)] or more.
The copper foil for flexible printed circuit boards of the present invention is preferably made of tough pitch copper standardized to JIS-H3100 (C1100) or oxygen-free copper of JIS-H3100 (C1020).
In the copper foil for flexible printed circuit boards of the present invention, P is 0.03% by mass or less, Ag is 0.05% by mass or less, Sb is 0.14% by mass or less, Sn is 0.163% by mass or less, Ni is 0.288% by mass or less, Be 0.058% by mass or less, Zn is 0.812% by mass or less, In is 0.429% by mass or less, and Mg is 0.149% by mass or less, each of which is preferably contained alone or in combination.

  The copper foil for a flexible printed circuit board of the present invention is a rolled copper foil, and after annealing at 300 ° C. for 30 minutes (however, the heating rate is 100 ° C./min to 300 ° C./min), the conductivity exceeds 75% IACS, and The composition ratio is preferably 0.98 or more.

  The copper clad laminate of the present invention is formed by laminating the flexible printed circuit board copper foil and a resin layer.

  The flexible printed board of the present invention is formed by forming a circuit on the copper foil in the copper clad laminate.

  The electronic device of the present invention uses the flexible printed circuit board.

  ADVANTAGE OF THE INVENTION According to this invention, the copper foil for flexible printed circuit boards excellent in the bendability is obtained.

It is a figure which shows the relationship between the copper foil thickness and break elongation of an Example and a comparative example. It is a figure which shows the crystal orientation distribution (map) by the EBSD measurement of an Example and a comparative example.

  Hereinafter, embodiments of the copper foil according to the present invention will be described. In the present invention, “%” means “% by mass” unless otherwise specified.

<Composition>
The copper foil according to the present invention comprises 99.0% by mass or more of Cu and the balance of inevitable impurities.
As described above, by miniaturizing the crystal grain size before the final cold rolling of the copper foil, the accumulation of dislocations in each region of the copper foil during the cold rolling is made uniform, and any of the copper foils after recrystallization Even in this region, since the strain is released, the KAM value can be reduced and the elongation at break can be improved at the same time, and the bendability is improved. In general, the larger the KAM value, the more intragranular strain is accumulated after recrystallization. In the region where the KAM value is large (the accumulation of intragranular strain is large) and the region where the KAM value is small (the accumulation of intragranular strain is small), Fracture due to different plastic deformation behavior during bending. Therefore, if the region where the KAM value is small is increased, not only the plastic deformation behavior during bending in the copper foil is equalized, but also the bendability is improved.
However, in the case of the above pure copper-based composition of Cu99.0% by mass, it is difficult to reduce the KAM value after recrystallization of the copper foil, so the initial stage during cold rolling (repeating annealing and cold rolling) By performing recrystallization annealing at the time of initial cold rolling, a large amount of processing strain can be introduced by cold rolling, and after recrystallization, the area with a small KAM value is increased, the elongation at break is increased, and bending is increased. The sex can be further improved.

Moreover, in order to achieve both reduction of KAM value and improvement of elongation at break after recrystallization of copper foil, the crystal grain size before final cold rolling performed after final annealing in the process of repeating cold rolling and annealing is set. The thickness is preferably 10 μm or more and less than 15 μm. When it is 15 μm or more, it is impossible to achieve both reduction in KAM value and improvement in elongation at break, resulting in poor bendability. On the other hand, if it is smaller than 10 μm, the effect of simultaneously reducing the KAM value and improving the elongation at break is saturated.
When the crystal grain size before the final cold rolling is 15 μm or more, the entanglement of dislocations during processing is locally reduced and the accumulation of strain is reduced, so the strain is not released after recrystallization, and the KAM value is reduced. It becomes difficult to improve the elongation at break. When the grain size before final cold rolling is smaller than 10μm, dislocation entanglement during processing occurs in almost all areas of the copper foil, and no further entanglement is possible, reducing the KAM value after recrystallization and breaking The effect of achieving both improvement in elongation is saturated. And rolling cost becomes high. Therefore, the lower limit of the crystal grain size before the final cold rolling is set to 10 μm.

  As a method of refining the crystal grain size before the final cold rolling of the copper foil, the final annealing temperature is set to be higher than 400 ° C. and 500 ° C. or lower, and the cold rolling degree η immediately before the final annealing is 0.91 or higher and 1.6 or lower. Can be mentioned.

Further, as additive elements for reducing the KAM value after recrystallization, P is 0.0005% by mass to 0.03% by mass, Ag is 0.0005% by mass to 0.05% by mass, and Sb is 0.0005% by mass to 0.14% by mass with respect to the above composition. %, Sn from 0.0005% to 0.163%, Ni from 0.0005% to 0.288%, Be from 0.0005% to 0.058%, Zn from 0.0005% to 0.812%, In to 0.0005% The KAM value can be easily reduced by containing not less than 0.4% by mass and not more than 0.429% by mass and Mg in an amount of not less than 0.0005% by mass and not more than 0.149% by mass, either singly or in combination.
P, Ag, Sb, Sn, Ni, Be, Zn, In, and Mg increase the frequency of dislocation entanglement during cold rolling, so both KAM value reduction and fracture elongation improvement can be achieved after recrystallization. Can do. In addition, if recrystallization annealing is performed only once in the initial stage of cold rolling and no subsequent recrystallization annealing is performed, a large amount of processing strain is introduced by increasing the entanglement of dislocations by cold rolling. Thus, the KAM value can be reduced and the elongation at break can be more easily achieved after recrystallization.

  P exceeds 0.03 wt%, Ag exceeds 0.05 wt%, Sb exceeds 0.14 wt%, Sn exceeds 0.163 wt%, Ni exceeds 0.288 wt%, Be exceeds 0.058 wt%, Zn If it exceeds 0.812% by mass, In exceeds 0.429% by mass, or Mg exceeds 0.149% by mass, the conductivity may decrease and may not be suitable as a copper foil for flexible substrates. The upper limit. The lower limit of the content of P, Sb, Sn, Ni, Be, Zn, In, and Mg is not particularly limited. For example, it is industrially difficult to control less than 0.0005% by mass for each element. The lower limit of the amount is preferably 0.0005% by mass.

The copper foil according to the present invention may be composed of tough pitch copper (TPC) standardized to JIS-H3100 (C1100) or oxygen-free copper (OFC) of JIS-H3100 (C1020).
Moreover, it is good also as a composition which contains P with respect to said TPC or OFC.

<Composition ratio of KAM value>
The composition ratio of the KAM value on the surface of the copper foil = (region where the KAM value is 0 to 0.875) / (region where the KAM value is 0 to 5) is 0.98 or more.
The KAM value is an index that quantifies the orientation difference between adjacent measurement points in a crystal grain. When the KAM value is large, the accumulation of intragranular strain is large, and when the KAM value is small, the accumulation of intragranular strain is small. It is in.
The reason for adopting (region A where the KAM value is 0 to 0.875) / (region B where the KAM value is 0 to 5) as the composition ratio of the KAM value is that the region B represents the definition of intragranular strain. In the region A of “0 to 0.875”, the accumulation of intragranular strain is small and it is difficult to become the starting point of cracks during bending, whereas in “region B-region B” (over 0.875 and less than 5), accumulation of intragranular strain is observed. It is because it is easy to become a starting point of the crack at the time of large bending.
When the composition ratio of the KAM value is 0.98 or more, since there are few regions where the accumulation of intragranular strain is large, the starting point of cracks is small and the bendability is improved.

The KAM value is obtained by measuring the surface of the sample with EBSD (electron backscatter diffraction). EBSD can measure the crystal orientation in the vicinity of the sample surface with a resolution on the order of nm, and can calculate the local crystal orientation change (local orientation difference) from the measurement data. From these EBSD data, the boundary where the KAM value (orientation difference) between adjacent measurement points is 0 ° or more and 5 ° or less is regarded as intragranular accumulated strain.
Note that the portion where the KAM value (orientation difference) is greater than 5 ° is a crystal grain boundary, which is different from intragranular strain.

<Elongation at break>
When the plate thickness is x [μm], the elongation at break y [%] is expressed by the formula 1: [y = −0.0365 (% · (μm) ⁻² ) x ² +2.1352 (% · (μm) ⁻¹ ) x− 5.7219 (%)] or more.
The elongation of the copper foil varies depending on the thickness, and the greater the thickness, the greater the elongation. Therefore, the bendability depends on the elongation corresponding to the thickness of the copper foil. For this reason, in order to improve the bendability, it is necessary to define not only the absolute value of the elongation of the copper foil but also the relationship between the elongation and the thickness. The present invention thus focuses on the relationship between elongation and thickness.
FIG. 1 shows the relationship between the thickness and breaking elongation of Examples 1 to 16 and Comparative Examples 1 to 6 described later. As shown in FIG. 1, even if the group of Examples 8-12 has the same thickness rather than the group of Examples 1-7, elongation at break is smaller. Moreover, when it sees with the same thickness, the breaking elongation of all Examples 1-16 is larger than the breaking elongation of the group of a comparative example (comparative examples 1-6).

From this, if it is a region where the elongation at break is larger than that of the comparative example, it is considered that the bending property (the number of MIT foldings) is excellent, and the minimum value (lower limit) at which the elongation at break becomes larger than the comparative example, An approximate quadratic curve passing through each plot of the groups of Examples 8 to 12 having a smaller breaking elongation than the groups of Examples 1 to 7 was obtained by the method of least squares. As a result, the above equation 1 shown by the broken line in FIG. 1 was obtained.
In addition, since Example 1 and 2 overlap and Example 6 and 7 overlap, the number of plots of Examples 1-7 became five instead of seven.

From the above, if the elongation at break y [%] is the region S (see FIG. 1) equal to or greater than Formula 1, the bendability is excellent.
For example, when the copper foil thickness is 12 μm, the elongation at break (%) and bendability (times) are Example 4 (: 35%: 452 times), Example 10 (: 15%: 352 times), and Comparative Example, respectively. 4 (: 12%: 188 times), both Examples 4 and 10 are superior to Comparative Example 4 in bendability, and Example 4 is most excellent.

Incidentally, the formula 2: [y = -0.07625 (% · (μm) -2) x 2 +4.4090 (% · (μm) -1) x-7.5054 (%)] , rather than the group of Examples 8 to 12 It is the result of calculating | requiring the approximate quadratic curve which passes through each plot of Examples 1-7 which is a group with the same thickness and a large breaking elongation by the least square method.
Of course, if the elongation at break is higher, it is preferable to have a higher elongation. Therefore, it goes without saying that those exceeding the value of Formula 2 are also included in the scope of the present invention, but there is a limit to improving the elongation at break even with the same copper foil thickness. As an example of the limit, Equation 2 was obtained. Accordingly, the range S1 (see FIG. 1) of the formula 1 or more and the formula 2 or less can be set as a range for realizing the present invention more reliably, but the present invention is limited to the range of the formula 2 or less. It is not a thing.

When the breaking elongation is less than [y = -0.0365 (% ・ (μm) ^-2 ) x ² +2.1352 (% ・ (μm) ^-1 ) x-5.7219 (%)], the flexible printed circuit board is bent Since the copper foil cannot follow the elongation of the resin and the bendability is poor, it is not suitable for flexible printed circuit board applications.
The breaking elongation y [%] after annealing the copper foil at 300 ° C. for 30 minutes (temperature increase rate: 100 to 300 ° C./min) is also preferably within the above range.

<Tensile strength (TS), elongation at break>
Tensile strength and elongation at break were determined by a tensile test in accordance with IPC-TM650, with a test piece width of 12.7 mm, room temperature (15 to 35 ° C.), a tensile speed of 50.8 mm / min, and a gauge length of 50 mm. Tensile tests were performed in parallel directions.

<Heat treatment at 300 ° C for 30 minutes>
The copper foil which concerns on this invention is used for a flexible printed circuit board, In that case, since CCL which laminated | stacked copper foil and resin performs the heat processing for hardening resin at 200-400 degreeC, a crystal grain is formed by recrystallization. There is a possibility of coarsening.
Therefore, the composition ratio of the KAM value of the copper foil changes before and after being laminated with the resin. Then, the copper foil for flexible printed circuit boards concerning Claim 1 of this application has prescribed | regulated the copper foil of the state which received the hardening heat processing of resin after it became a copper clad laminated body laminated | stacked with resin. In other words, the copper foil is in a state where it has not been subjected to a new heat treatment since it has already undergone a heat treatment.
On the other hand, the copper foil for flexible printed circuit boards according to claim 5 of the present application defines a state when the heat treatment is performed on the copper foil before being laminated with the resin. This heat treatment at 300 ° C. for 30 minutes simulates the temperature condition for curing and heat-treating the resin during CCL lamination. In order to prevent oxidation of the copper foil surface due to the heat treatment, the atmosphere of the heat treatment is preferably a reducing or non-oxidizing atmosphere, for example, a vacuum atmosphere, argon, nitrogen, hydrogen, carbon monoxide, or the like. An atmosphere made of a mixed gas may be used. The heating rate may be between 100 and 300 ° C./min.

The copper foil of this invention can be manufactured as follows, for example. First, after melting and casting a copper ingot, it is hot-rolled, cold-rolled and annealed, preferably by recrystallization annealing at the initial stage of cold-rolling and by performing the above-mentioned final cold-rolling A foil can be produced.
Here, when the crystal grain size before final cold rolling (referring to cold rolling performed after final annealing in the whole process of cold rolling and annealing) is refined to 10 μm or more and less than 15 μm, the composition of KAM value The ratio can be controlled to 0.98 or higher.

<Copper-clad laminate and flexible printed circuit board>
Also, (1) a resin precursor (for example, a polyimide precursor called varnish) is cast on the copper foil of the present invention and polymerized by applying heat, and (2) a thermoplastic adhesive of the same type as the base film is used. By laminating the base film on the copper foil of the present invention, a copper clad laminate (CCL) composed of two layers of the copper foil and the resin base material is obtained. Further, by laminating a base film obtained by applying an adhesive to the copper foil of the present invention, a copper clad laminate (CCL) comprising three layers of a copper foil, a resin base material, and an adhesive layer therebetween is obtained. During the production of these CCLs, the copper foil is heat-treated and recrystallized.
A circuit is formed on these using a photolithographic technique, a circuit is plated as needed, and a cover-lay film is laminated, and a flexible printed circuit board (flexible wiring board) is obtained.

Therefore, the copper clad laminate of the present invention is formed by laminating a copper foil and a resin layer. Moreover, the flexible printed circuit board of this invention forms a circuit in the copper foil of a copper clad laminated body.
Examples of the resin layer include, but are not limited to, PET (polyethylene terephthalate), PI (polyimide), LCP (liquid crystal polymer), and PEN (polyethylene naphthalate). Moreover, you may use these resin films as a resin layer.
As a method of laminating the resin layer and the copper foil, a material for forming the resin layer may be applied to the surface of the copper foil and heated to form a film. Further, a resin film may be used as the resin layer, and the following adhesive may be used between the resin film and the copper foil, or the resin film may be thermocompression bonded to the copper foil without using the adhesive. However, it is preferable to use an adhesive from the viewpoint of not applying excessive heat to the resin film.

  When a film is used as the resin layer, this film may be laminated on the copper foil via an adhesive layer. In this case, it is preferable to use an adhesive having the same component as the film. For example, when a polyimide film is used as the resin layer, it is preferable to use a polyimide-based adhesive for the adhesive layer. In addition, the polyimide adhesive here refers to the adhesive agent containing an imide bond, and polyether imide etc. are also included.

In addition, this invention is not limited to the said embodiment. Moreover, as long as there exists an effect of this invention, the copper alloy in the said embodiment may contain another component. Moreover, an electrolytic copper foil may be used.
For example, the surface of the copper foil may be subjected to a surface treatment by roughening treatment, rust prevention treatment, heat resistance treatment, or a combination thereof.

EXAMPLES Next, although an Example is given and this invention is demonstrated further in detail, this invention is not limited to these. Each element shown in Table 1 was added to electrolytic copper to obtain the composition shown in Table 1, and cast in an Ar atmosphere to obtain an ingot. The oxygen content in the ingot was less than 15 ppm. This ingot was homogenized and annealed at 900 ° C., then hot rolled, then cold rolled, and further annealed once to adjust the crystal grain size to 10 μm or more and less than 15 μm.
Thereafter, the oxide scale generated on the surface was removed, and final cold rolling was performed at a working degree η shown in Table 2 to obtain a foil having a desired final thickness. The obtained foil was heat-treated at 300 ° C. for 30 minutes in an argon atmosphere to obtain a copper foil sample. The copper foil after the heat treatment imitates a state where the heat treatment is performed during the lamination of the CCL.

<A. Evaluation of copper foil sample>
1. Electrical conductivity The electrical conductivity (% IACS) at 25 ° C. was measured for each copper foil sample after the heat treatment by a four-terminal method based on JIS H 0505.
If the conductivity is greater than 75% IACS, the conductivity is good.
2. Tensile strength and elongation at break Each copper foil sample after the above heat treatment was subjected to a tensile test in accordance with IPC-TM650, with a test piece width of 12.7 mm, room temperature (15 to 35 ° C.), tensile speed of 50.8 mm / min, and gauge length of 50 mm. The tensile strength and elongation at break were measured by conducting a tensile test in a direction parallel to the rolling direction of the copper foil.

3. KAM value The surface of each sample after the heat treatment was subjected to EBSD measurement using an EBSD (OIM (Orientation Imaging Microscopy) manufactured by TSL Solutions) apparatus. The measurement voltage was 15 kV, the working distance was 17 mm, and the sample inclination angle was 70 °. The measurement field of view was 25 μm × 25 μm with 5 locations, and the distance between measurements d = 0.2 μm.
The obtained EBSD data was analyzed using the analysis software (OIM analysis 5) attached to the apparatus, and the composition ratio of the KAM value = (KAM value 0 to 0.875) / (KAM value 0 to 5) = was calculated. During the data analysis, data with a CI value (Confidential Index) of 0.05 or less were excluded from the analysis due to low accuracy.
If the composition ratio of the KAM value is 0.98 or more, the accumulation of intragranular strain is small.

4). Copper foil bendability (MIT folding resistance)
About each copper foil sample after the said heat processing, the MIT folding endurance (number of reciprocal bending) was measured based on JISP8115. However, the bending clamp R was 0.38 mm and the load was 250 g.
If the MIT folding endurance number is larger than that of the comparative example having the same thickness, the copper foil has good bendability.
5). Crystal grain size Each sample before the heat treatment and before the final cold rolling (after the final annealing) was observed using a SEM (Scanning Electron Microscope), and the average grain size was determined based on JIS H 0501. However, the twins were measured as if they were separate crystal grains. The measurement region was 400 μm × 400 μm in a cross section parallel to the rolling direction.

  The obtained results are shown in Tables 1 and 2.

  As is clear from Tables 1 and 2, in each Example in which the composition ratio of the KAM value was 0.98 or more, the MIT flexibility was superior to the comparative example having the same thickness.

  On the other hand, as a result of making the final annealing temperature higher than 500 ° C, in the case of Comparative Examples 1 to 6, 9, and 10 in which the crystal grain size before final cold rolling became 15 μm or more, the composition ratio of KAM value was less than 0.98 The MIT flexibility was inferior to each of the examples having the same thickness.

Further, in the case of Comparative Example 7 in which the addition amount of P exceeded 0.03%, the conductivity was 75% or less and the conductivity was inferior.
In Comparative Example 8 where Cu was less than 99.0% by mass, the conductivity was 75% or less and the conductivity was poor.

  FIG. 2 shows crystal orientation distributions (maps) by EBSD measurement of Example 2 (FIG. 2A) and Comparative Example 10 (FIG. 2B). The dark part of FIG. 1 is an area where “KAM value is 0 to 0.875”, and the bright part is an area where “KAM value is more than 0.875 and less than 5”. It can be seen that Example 2 has more dark parts than Comparative Example 10, and the composition ratio of KAM values is higher than that of Comparative Example 10.

Claims (8)

99.0% by mass or more of Cu, the remaining copper foil consisting of inevitable impurities,
Conductivity exceeds 75% IACS,
The composition ratio of the KAM value on the surface of the copper foil = (region A where the KAM value is 0 to 0.875) / (region B where the KAM value is 0 to 5) is 0.98 or more. When the plate thickness is x [μm], the elongation at break y [%] is expressed by the formula 1: [y = −0.0365 (% · (μm) ⁻² ) x ² +2.1352 (% · (μm) ⁻¹ ) x− 5.7219 (%)] or more, The copper foil for flexible printed circuit boards according to claim 1   The copper foil for flexible printed circuit boards of Claim 1 or 2 which consists of tough pitch copper specified to JIS-H3100 (C1100) or oxygen-free copper of JIS-H3100 (C1020).   Furthermore, P is 0.03% by mass or less, Ag is 0.05% by mass or less, Sb is 0.14% by mass or less, Sn is 0.163% by mass or less, Ni is 0.288% by mass or less, Be is 0.058% by mass or less, and Zn is 0.812% by mass or less. Copper foil for flexible printed circuit boards as described in any one of Claims 1-3 formed by containing 0.429 mass% or less of In and 0.149 mass% or less of Mg individually or in 2 types or more, respectively. The copper foil is a rolled copper foil,
The electrical conductivity exceeds 75% IACS and the composition ratio is 0.98 or higher after annealing at 300 ° C for 30 minutes (however, the heating rate is 100 ° C / min to 300 ° C / min). The copper foil for flexible printed circuit boards of description.   The copper clad laminated body formed by laminating | stacking the copper foil for flexible printed circuit boards as described in any one of Claims 1-5, and a resin layer.   The flexible printed board formed by forming a circuit in the said copper foil in the copper clad laminated body of Claim 6.   An electronic apparatus using the flexible printed circuit board according to claim 7.