KR20240017841A - Roughened copper foil, copper clad laminate and printed wiring board - Google Patents

Abstract

When used in a copper clad laminate or a printed wiring board, a roughened copper foil is provided that is excellent in transmission characteristics and circuit linearity and can realize high peel strength. This roughened copper foil has a roughened surface on at least one side. For the roughened surface, Rdc/Rku, which is the ratio of the cut level difference Rdc of the roughness curve to the kurtosis Rku of the roughness curve, is 0.180 μm or less, and the maximum cross-sectional height Wt of the waveform curve is 2.50 μm or more and 10.00 μm or less. Rku and Wt are values measured based on JIS B0601-2013, and Rdc is the cutting level c in the height direction between a load length ratio of 20% and a load length ratio of 80% based on JIS B0601-2013. This is the value obtained as a car.

Description

Roughened copper foil, copper clad laminate and printed wiring board

The present invention relates to roughened copper foil, copper clad laminate, and printed wiring board.

In the manufacturing process of printed wiring boards, copper foil is widely used in the form of a copper clad laminate bonded to an insulating resin substrate. In this regard, in order to prevent peeling of wiring from occurring during the manufacture of printed wiring boards, it is desired that the copper foil and the insulating resin base material have high adhesion. Therefore, in ordinary copper foil for manufacturing printed wiring boards, the joint surface of the copper foil is roughened to form irregularities made of fine copper particles, and these irregularities are dug into the inside of the insulating resin base material by press processing to exert an anchor effect. By doing so, adhesion is improved.

As a copper foil that has undergone such a roughening treatment, for example, in Patent Document 1 (Japanese Patent Application Laid-Open No. 2018-172785), it has a roughening layer on at least one surface of the copper foil and the arithmetic mean of the surface on the roughening layer side. A surface-treated copper foil is disclosed in which the roughness Ra is 0.08 μm or more and 0.20 μm or less, and the glossiness of the TD (width direction) of the surface on the roughening layer side is 70% or less. According to this surface-treated copper foil, it is said that the falling off of the roughened particles provided on the surface of the copper foil is well suppressed, and the generation of wrinkles and stripes at the time of bonding with the insulating substrate is well suppressed.

However, with the recent advancement in functionality of portable electronic devices and the like, signals, whether digital or analog, are becoming higher frequency in order to process large amounts of data at high speeds, and printed wiring boards suitable for high frequency applications are in demand. In such high-frequency printed wiring boards, reduction of transmission loss is required to enable transmission of high-frequency signals without deterioration. A printed wiring board is equipped with copper foil processed into a wiring pattern and an insulating base material. The main transmission losses include conductor loss caused by the copper foil and dielectric loss caused by the insulating base material.

In this regard, a roughened copper foil that aims to reduce transmission loss has been proposed. For example, Patent Document 2 (Japanese Patent Application Laid-Open No. 2015-148011) aims to provide a surface-treated copper foil with low signal transmission loss and a laminated board using the same, and the surface treatment of the copper foil is achieved by surface treatment. Controlling the skewness Rsk to a predetermined range of -0.35 or more and 0.53 or less based on JIS B0601-2001 is disclosed.

Japanese Patent Publication No. 2018-172785 Japanese Patent Publication No. 2015-148011

As described above, in recent years, there has been a demand for improving the transmission characteristics (high frequency characteristics) of printed wiring boards. In order to meet these demands, more fine roughening treatment is being attempted on the bonding surface of copper foil with the insulating resin substrate. That is, in order to reduce the unevenness of the copper foil surface, which is a factor in increasing transmission loss, it is considered to perform micro-roughening treatment on the copper foil surface with a small waveform (for example, the surface of double-sided smooth foil or the electrode surface of electrolytic copper foil). . Furthermore, it is conceivable that the linearity (hereinafter referred to as circuit linearity) of the wiring pattern during circuit formation is improved by using roughened copper foil with a small waveform. However, when processing a copper clad laminate or manufacturing a printed wiring board using such roughened copper foil, the peeling strength between the copper foil and the base material is generally low, and a problem such as poor adhesion reliability may occur.

This time, the present inventors controlled Rdc/Rku, which is the ratio of the cutting level difference Rdc to kurtosis Rku, and the maximum cross-sectional height Wt to a predetermined range on the surface of the roughened copper foil, and produced a copper clad laminate or print using the same. In the wiring board, it was found that transmission characteristics and circuit linearity were excellent, and high peeling strength could be achieved.

Therefore, the purpose of the present invention is to provide a roughened copper foil that is excellent in transmission characteristics and circuit linearity and can realize high peel strength when used in a copper clad laminate or a printed wiring board.

According to the present invention, the following aspects are provided.

[Mode 1]

A roughened copper foil having a roughened surface on at least one side,

The roughened surface has Rdc/Rku, which is the ratio of the cut level difference Rdc of the roughness curve to the kurtosis Rku of the roughness curve, of 0.180 μm or less, and the maximum cross-sectional height Wt of the waveform curve is 2.50 μm or more and 10.00 μm or less,

The Rku is a value measured in accordance with JIS B0601-2013 under the conditions of a magnification of 200 times, a cutoff wavelength of 0.3 μm by the cutoff value λs, and a cutoff wavelength of 5 μm by the cutoff value λc,

The above Rdc is the load length ratio in the illuminance curve measured under the conditions of a magnification of 200 times, a cutoff wavelength of 0.3 μm by the cutoff value λs, and a cutoff wavelength of 5 μm by the cutoff value λc, based on JIS B0601-2013. (Rmr1) is a value obtained as the difference (c(Rmr1)-c(Rmr2)) of the cutting level c in the height direction between 20% and the load length ratio (Rmr2) 80%,

The Wt is a value measured in accordance with JIS B0601-2013 under conditions of a magnification of 20 times, a cutoff wavelength of 5 μm by the cutoff value λc, and no cutoff by the cutoff value λf. The roughened copper foil is a value measured.

[Aspect 2]

The roughened copper foil according to aspect 1, wherein the roughened surface has a maximum cross-sectional height Wt of 2.90 μm or more and 10.00 μm or less.

[Aspect 3]

The roughening-treated surface is the roughening-treated copper foil according to aspect 1 or 2, wherein the cutting level difference Rdc is 0.45 μm or less.

[Aspect 4]

The roughened surface has a maximum peak height Wp of the waveform curve of 1.00 μm or more and 6.00 μm or less, and the Wp is a magnification of 20 times, a cutoff wavelength of 5 μm by a cutoff value λc, and a cutoff value of 5 μm, based on JIS B0601-2013. The roughened copper foil according to any one of aspects 1 to 3, which is a value measured under conditions that do not perform cutoff by value λf.

[Aspect 5]

In the roughened surface, the average height Rc of the roughness curve elements is 0.70 ㎛ or less, and the Rc is at a magnification of 200 times, a cutoff wavelength of 0.3 ㎛ by the cutoff value λs, and a cutoff value λc, in accordance with JIS B0601-2013. The roughened copper foil according to any one of aspects 1 to 4, which is a value measured under conditions of a cutoff wavelength of 5 μm.

[Aspect 6]

The roughened surface has a cut level difference Wdc of the waveform curve of 1.20 μm or more and 3.10 μm or less, and the Wdc is a magnification of 20 times, a cutoff wavelength of 5 μm by a cutoff value λc, and a cutoff value of 5 μm, based on JIS B0601-2013. The difference (c( The roughened copper foil according to any one of aspects 1 to 5, which is a value obtained as Wmr1)-c(Wmr2)).

[Aspect 7]

The roughened surface has a root mean square height Rq of the roughness curve of 0.290 μm or less, and Rq is based on JIS B0601-2013 at a magnification of 200 times, a cutoff wavelength of 0.3 μm by the cutoff value λs, and a cutoff value λc. The roughened copper foil according to any one of aspects 1 to 6, which is a value measured under conditions of a cutoff wavelength of 5 μm.

[Aspect 8]

The roughened copper foil according to any one of aspects 1 to 7, wherein the roughened surface has a kurtosis Rku of 1.30 or more and 8.00 or less.

[Aspect 9]

The roughened copper foil according to any one of aspects 1 to 8, wherein the roughened surface is provided with a rust-prevention layer and/or a silane coupling agent-treated layer.

[Aspect 10]

The roughened copper foil according to any one of aspects 1 to 9, wherein the roughened copper foil is an electrolytic copper foil, and the roughened surface is present on the precipitation surface side of the electrolytic copper foil.

[Aspect 11]

A copper-clad laminate provided with the roughened copper foil according to any one of aspects 1 to 10.

[Aspect 12]

A printed wiring board provided with the roughened copper foil according to any one of aspects 1 to 10.

1 is a diagram for explaining the load curve of the roughness curve determined in accordance with JIS B0601-2013.
Figure 2 is a diagram for explaining the load length ratio Rmr(c) determined based on JIS B0601-2013.
Fig. 3 is a diagram for explaining the cutting level difference Rdc determined based on JIS B0601-2013.
FIG. 4 is a diagram for explaining that the surface irregularities of the roughened copper foil are composed of a roughened particle component and a waveform component.
Figure 5 is a schematic diagram showing an example of the roughened copper foil of the present invention.

Justice

Definitions of terms and parameters used to specify the present invention are shown below.

In this specification, the “load curve of the roughness curve” refers to the ratio of the solid portion that appears when the roughness curve determined based on JIS B0601-2013 is cut at the cutting level c, as shown in FIG. 1, expressed as a function of c. It's a curve. In other words, the load curve of the roughness curve can also be said to be a curve representing the height at which the load length ratio Rmr(c) is 0% to 100%. As shown in FIG. 2, the load length ratio Rmr(c) is a parameter representing the ratio of the load length of the roughness curve element at the cutting level c to the evaluation length determined based on JIS B0601-2013.

In this specification, “cut level difference Rdc of roughness curve”, “cut level difference Rdc” or “Rdc” refers to the load curve of the roughness curve measured in accordance with JIS B0601-2013, as shown in FIG. 3. , is a parameter representing the difference (c(Rmr1)-c(Rmr2)) in the cutting level c in the height direction between two load length ratios Rmr1 and Rmr2 (where Rmr1<Rmr2). In this specification, Rdc is calculated by specifying Rmr1 as 20% and Rmr2 as 80%.

In this specification, "root-mean-square height of roughness curve Rq", "root-mean-square height Rq", or "Rq" refers to the reference length measured in accordance with JIS B0601-2013, Z(x)(Z(x) ) is a parameter representing the root mean square of (representing the height of the illumination curve at an arbitrary position x).

In this specification, “Kurtosis Rku of the roughness curve”, “Kurtosis Rku” or “Rku” refers to the reference length non-dimensionalized by the fourth power of the root mean square height Rq measured in accordance with JIS B0601-2013, Z This parameter represents the 4-squared average of (x). Rku stands for kurtosis, a measure of the sharpness of the surface, and represents the sharpness of the height distribution. Rku=3 means that the height distribution is normal, if Rku>3 means the height distribution is sharp, and if Rku<3 means the height distribution is distorted.

In this specification, “Rdc/Rku” is a parameter indicating the ratio of the cut level difference Rdc to the kurtosis Rku.

In this specification, “average height Rc of roughness curve elements”, “average height Rc” or “Rc” is a parameter representing the average height of roughness curve elements in a reference length measured in accordance with JIS B0601-2013. . A roughness curve element means a set of adjacent peaks and valleys in a roughness curve. The minimum height and minimum length are specified for the peaks and valleys that make up the roughness curve element, and those with a height of 10% or less of the maximum height Rz or a length of 1% or less of the standard length are considered noise, and the valleys that follow before and after are considered noise. It becomes part of the mountain.

In this specification, “maximum cross-sectional height of the waveform curve Wt”, “maximum cross-sectional height Wt” or “Wt” refers to the maximum value of the peak height and trough depth of the waveform curve in the evaluation length measured in accordance with JIS B0601-2013. This is a parameter that represents the sum of the maximum values of .

In this specification, “maximum peak height of the waveform curve Wp”, “maximum peak height Wp” or “Wp” refers to a parameter indicating the maximum value of the peak height of the waveform curve in the reference length measured in accordance with JIS B0601-2013. am.

In this specification, “load curve of waveform curve” is a curve showing the ratio of the solid portion that appears when the waveform curve determined based on JIS B0601-2013 is cut at the cut level c as a function of c. In other words, the load curve of the waveform curve can also be said to be a curve representing the height at which the load length ratio Wmr(c) is 0% to 100%. The load length ratio Wmr(c) is a parameter representing the ratio of the load length of the waveform curve element at the cut level c to the evaluation length determined based on JIS B0601-2013.

In this specification, “waveform curve cut level difference Wdc”, “cut level difference Wdc” or “Wdc” refers to the two load length ratios Wmr1 and This parameter represents the difference (c(Wmr1)-c(Wmr2)) in the cutting level c in the height direction between Wmr2 (where Wmr1<Wmr2). In this specification, Wdc is calculated by specifying Wmr1 as 20% and Wmr2 as 80%.

Rdc, Rq, Rku, Rc, Wt, Wp, and Wdc can be calculated by measuring the surface profile of a predetermined measurement length on the roughened surface using a commercially available laser microscope. In this specification, the illuminance parameters Rdc, Rq, Rku, and Rc are assumed to be measured under the conditions of a magnification of 200 times, a cutoff wavelength of 0.3 μm according to the cutoff value λs, and a cutoff wavelength of 5 μm according to the cutoff value λc. Additionally, the reference length and evaluation length used for calculating the roughness parameters are set to 5 μm and 25 μm, respectively. Meanwhile, the waveform parameters Wt, Wp, and Wdc are measured under the conditions of a magnification of 20 times, a cutoff wavelength of 5 μm according to the cutoff value λc, and no cutoff according to the cutoff value λf. Additionally, the reference length and evaluation length used for calculating waveform parameters are both set to be the same as the measurement length of the roughening process surface. In the examples described later, waveform parameters are measured in an area of 643.973 ㎛ in length x 643.393 ㎛ in width on the roughening surface. However, the reference length and evaluation length in this case are 643.973 in the vertical direction. ㎛, in the horizontal direction it is 643.393 ㎛. Additionally, when both an objective lens and an optical zoom are used in measurement by a laser microscope, the above magnification corresponds to the value obtained by multiplying the magnification of the objective lens by the magnification of the optical zoom. For example, if the objective lens magnification is 100x and the optical zoom magnification is 2x, the magnification is 200x (=100×2). In addition, preferred measurement conditions and analysis conditions of the surface profile by a laser microscope are shown in the Examples described later.

In this specification, the “electrode surface” of the electrolytic copper foil refers to the surface on the side that was in contact with the cathode during manufacture of the electrolytic copper foil.

In this specification, the “precipitation surface” of the electrolytic copper foil refers to the surface on the side where electrolytic copper precipitates during the manufacture of the electrolytic copper foil, that is, the surface on the side that is not in contact with the cathode.

Harmonized copper foil

The copper foil of the present invention is a roughened copper foil. This roughened copper foil has a roughened surface on at least one side. For this roughened surface, Rdc/Rku, which is the ratio of the cut level difference Rdc of the roughness curve to the kurtosis Rku of the roughness curve, is 0.180 μm or less. Additionally, the roughened surface has a maximum cross-sectional height Wt of the waveform curve of 2.50 μm or more and 10.00 μm or less. In this way, on the surface of the roughened copper foil, Rdc/Rku and the maximum cross-sectional height Wt are controlled to a predetermined range, so that in the copper clad laminate or printed wiring board manufactured using this, the transmission characteristics (high frequency characteristics) and circuit linearity are improved. In addition to excellence, high peel strength can be achieved.

It is inherently difficult to achieve both excellent transmission characteristics and high peel strength, and coexistence of excellent circuit linearity and high peel strength. This means that in order to improve the transmission characteristics or circuit linearity, it is required to reduce the irregularities on the surface of the copper foil, while in order to obtain high peel strength, it is required to increase the irregularities on the surface of the copper foil, and these are in a trade-off relationship. Because. Here, as shown in FIG. 4, the irregularities on the surface of the roughened copper foil consist of a "roughened particle component" and a "waveform component" with a longer period than the roughened particle component. Generally, in order to improve transmission characteristics or circuit linearity, it is considered to perform micro-roughening treatment on the surface of copper foil with a small waveform (for example, the surface of double-sided smooth foil or the electrode surface of electrolytic copper foil) to form small roughened particles. However, when a copper clad laminate or a printed wiring board is manufactured using such roughened copper foil, the peeling strength between the copper foil and the base material is generally lowered.

Regarding this problem, the present inventors studied the influence of uneven roughened particles and waveforms on the surface of copper foil on transmission characteristics, circuit linearity, and peeling strength. As a result, contrary to expectations, it was found that the waveform component of the copper foil had little influence on the transmission characteristics, and that the size of the harmonic particles mainly affected the transmission characteristics. In order to improve the transmission characteristics, the present inventors have refined the protrusions (roughened particles) and supplemented the lack of adhesion with the waveform of the copper foil, which has little influence on the transmission characteristics, thereby achieving excellent transmission characteristics and high It was found that peel strength and adhesion reliability are compatible. Additionally, it was found that excellent circuit linearity and high peel strength can be achieved in a good balance by controlling the waveform of the copper foil within a predetermined range. Specifically, by using Rdc/Rku, which is the cutting level difference Rdc divided by the kurtosis Rku, we found that the shape of minute protrusions (harmonic particles) that affect the transmission characteristics can be accurately reflected, and Rdc/Rku It was found that excellent transmission characteristics could be realized by controlling the particle size to 0.180 μm or less. In addition, it was discovered that the maximum cross-sectional height Wt can accurately reflect the waveform component in a wide range of roughened surfaces, and by setting this Wt to 2.50 ㎛ or more and 10.00 ㎛ or less, the circuit linearity is excellent while the copper foil It was also found that high peel strength between copper foil and substrate can be achieved by using waveforms.

The harmonic particle component and waveform component of the copper foil surface that affect transmission characteristics, circuit linearity, or peel strength can be distinguished by using the measurement magnification in a laser microscope and cutoff values λs, λc, and λf. Specifically, by measuring the roughened surface at a high magnification of 200 times, the fine irregularities of the roughened surface that affect the transmission characteristics can be accurately evaluated. Then, by using the roughness curve obtained by measuring the roughened surface under the conditions of a cutoff wavelength of 0.3 μm using the cutoff value λs and a cutoff wavelength of 5 μm using the cutoff value λc, the roughness parameter with the influence of the waveform component cut out can be calculated. You can. Therefore, the roughness parameters in the present invention, namely Rdc, Rku, Rdc/Rku, Rc and Rq, can be said to be parameters that accurately reflect the roughened particle components on the copper foil surface, and by using these indices, the transmission characteristics can be accurately determined. can be evaluated. On the other hand, by measuring the roughened surface at a low magnification of 20 times, the height (waveform) of the entire roughened surface, which affects circuit linearity and adhesion reliability, can be widely evaluated. Then, by using the waveform curve obtained by measuring the roughened surface under conditions of a cutoff wavelength of 5 μm with a cutoff value λc and no cutoff with a cutoff value λf, waveform parameters in which the influence of the roughened particle component is cut can be calculated. You can. Therefore, the waveform parameters in the present invention, namely Wt, Wp, and Wdc, can be said to be parameters that accurately reflect the waveform component on the copper foil surface, and by using these indices, circuit linearity and peeling strength can be accurately evaluated. there is.

The roughened surface of the roughened copper foil has a maximum cross-sectional height Wt of the waveform curve of 2.50 ㎛ or more and 10.00 ㎛ or less, preferably 2.90 ㎛ or more and 10.00 ㎛ or less, more preferably 3.10 ㎛ or more and 9.00 ㎛ or less, even more preferably It is 3.30㎛ or more and 7.00㎛ or less. If Wt is within the above range, excellent circuit linearity and high peel strength can be achieved in a good balance while ensuring excellent transmission characteristics.

The roughened surface of the roughened copper foil has Rdc/Rku of 0.180 μm or less, preferably 0.015 μm or more and 0.150 μm or less, more preferably 0.030 μm or more and 0.110 μm or less, further preferably 0.045 μm or more and 0.080 μm or less. . If Rdc/Rku is within the above range, excellent transmission characteristics can be achieved along with excellent circuit linearity and high peel strength.

The roughened surface of the roughened copper foil preferably has a cut level difference Rdc of the roughness curve of 0.45 μm or less, more preferably 0.04 μm or more and 0.40 μm or less, further preferably 0.08 μm or more and 0.35 μm or less, particularly preferably It is 0.12㎛ or more and 0.30㎛ or less. If Rdc is within the above range, it becomes easy to control Rdc/Rku within the above-mentioned range, and even more excellent transmission characteristics can be realized.

The roughened surface of the roughened copper foil preferably has a kurtosis Rku of 1.30 or more and 8.00 or less, more preferably 1.50 or more and 5.50 or less, further preferably 2.00 or more and 4.50 or less, particularly preferably 2.50 or more and 3.20 or less. . If Rku is within the above range, it becomes easy to control Rdc/Rku within the above-mentioned range, and even more excellent transmission characteristics can be realized.

The roughened surface of the roughened copper foil preferably has a maximum peak height Wp of the waveform curve of 1.00 μm or more and 6.00 μm or less, more preferably 1.20 μm or more and 5.00 μm or less, further preferably 1.30 μm or more and 4.30 μm or less, especially Preferably it is 1.40 ㎛ or more and 3.70 ㎛ or less. If Wp is within the above range, excellent circuit linearity and high peel strength can be achieved in a better balance while ensuring excellent transmission characteristics.

The roughened surface of the roughened copper foil preferably has an average height Rc of the roughness curve elements of 0.70 μm or less, more preferably 0.06 μm or more and 0.60 μm or less, further preferably 0.12 μm or more and 0.50 μm or less, particularly preferably It is 0.18㎛ or more and 0.50㎛ or less. If Rc is within the above range, excellent circuit linearity and high peel strength can be achieved, and even more excellent transmission characteristics can be realized.

The roughened surface of the roughened copper foil preferably has a cut level difference Wdc of the waveform curve of 1.20 μm or more and 3.10 μm or less, more preferably 1.20 μm or more and 2.70 μm or less, further preferably 1.30 μm or more and 2.30 μm or less, especially Preferably it is 1.60㎛ or more and 2.00㎛ or less. If Wdc is within the above range, excellent circuit linearity and high peel strength can be realized in a better balance while ensuring excellent transmission characteristics.

The roughened surface of the roughened copper foil preferably has a root mean square height Rq of the roughness curve of 0.290 μm or less, more preferably 0.030 μm or more and 0.260 μm or less, further preferably 0.060 μm or more and 0.220 μm or less, particularly preferably is 0.090㎛ or more and 0.200㎛ or less. If Rq is within the above range, excellent circuit linearity and high peel strength can be achieved, and even more excellent transmission characteristics can be achieved.

The thickness of the roughened copper foil is not particularly limited, but is preferably 0.1 μm or more and 210 μm or less, more preferably 0.3 μm or more and 105 μm or less, further preferably 7 μm or more and 70 μm or less, particularly preferably 9 μm or more. It is 35㎛ or less. In addition, the roughened copper foil of the present invention is not limited to that obtained by roughening the surface of a normal copper foil, and may be one in which the copper foil surface of the copper foil provided with a carrier is subjected to roughening treatment or fine roughening treatment.

An example of the roughened copper foil of this invention is shown in FIG. 5. As shown in FIG. 5, the roughened copper foil of the present invention forms fine roughened particles by performing roughening treatment under desired low-roughening conditions on the copper foil surface (for example, the precipitation surface of electrolytic copper foil) having a predetermined waveform. By doing so, it can be manufactured preferably. Therefore, according to a preferred aspect of the present invention, the roughened copper foil is an electrolytic copper foil, and the roughened surface exists on the precipitation surface side of the electrolytic copper foil. In addition, the roughened copper foil may have a roughened surface on both sides, or may have a roughened surface only on one side. The roughened surface is typically provided with a plurality of roughened particles, and it is preferable that these plural roughened particles each consist of copper particles. The copper particles may be made of metallic copper or may be made of a copper alloy.

The roughening treatment for forming the roughening surface can be preferably performed by forming roughening particles from copper or a copper alloy on the copper foil. The copper foil before performing the roughening treatment may be unroughened copper foil, or may be one that has undergone preliminary roughening. The surface of the copper foil on which the roughening treatment is performed preferably has a 10-point average roughness Rz of 1.30 μm or more and 10.00 μm or less, as measured in accordance with JIS B0601-1994, and more preferably 1.50 μm or more and 8.00 μm or less. If it is within the above range, it becomes easy to provide the surface profile required for the roughening-treated copper foil of the present invention to the roughening-treated surface.

The roughening treatment is, for example, 10 A/dm2 or more at a temperature of 20°C or more and 40°C or less in a copper sulfate solution containing a copper concentration of 7 g/L or more and 17 g/L or less and a sulfuric acid concentration of 50 g/L or more and 200 g/L or less. It is preferable to perform electrolytic precipitation at 50 A/dm2 or less. This electrolytic deposition is preferably performed for 0.5 seconds or more and 30 seconds or less, more preferably 1 second or more and 30 seconds or less, and even more preferably performed for 1 second or more and 3 seconds or less. However, the roughened copper foil according to the present invention is not limited to the above method, and may be manufactured by any method.

During the above electrolytic precipitation, the following formula:

(In the formula, R _L is the liquid resistance index (mm·L/mol), L is the distance between electrodes (anode-cathode) (mm), and D _C is the charge carrier density (mol/L))

It is preferable to set the liquid resistance index R _L defined by 9.0 mm·L/mol to 20.0 mm·L/mol, and more preferably to 11.0 mm·L/mol to 17.0 mm·L/mol. . By increasing the liquid resistance index R _L in this way, the voltage in the entire system increases, and the voltage during the protrusion formation reaction also increases. As a result of this influencing the protrusion shape, it is possible to preferably form protrusions of a shape suitable for providing the surface profile required for the roughened copper foil of the present invention. Additionally, the charge carrier density D _C can be calculated by summing the product of each ion concentration and valence for all ions present in the plating solution. For example, when using a copper sulfate solution as a plating solution, the charge carrier density D _C is expressed by the following formula:

(In the formula, [H ⁺ ] is the hydrogen ion concentration in the solution (mol/L), [Cu ²⁺ ] is the copper ion concentration in the solution (mol/L), and [SO ₄ ^2- ] is the sulfate ion concentration in the solution (mol/L). mol/L)

It is calculated by

The relationship between the liquid resistance index R _L and voltage is explained as follows. First, according to Ohm's law, the following equation:

(In the formula, V is voltage, ρ is resistivity, L is the distance between poles, I is current, and S is the cross-sectional area between poles)

This is derived. That is, the voltage V is proportional to the resistivity ρ, the interpole distance L, and the current density (=I/S). And, the specific resistance ρ is inversely proportional to the charge carrier density D _C described above. For this reason, when the current density is constant, the voltage also increases by increasing the liquid resistance index (proportional to the interpole distance L and inversely proportional to the charge carrier density D _C ). Therefore, the liquid resistance index can be said to be an index that is correlated with the resistance of the solution.

Depending on desire, the roughened copper foil may be subjected to rust prevention treatment and a rust prevention treatment layer may be formed thereon. It is preferable that the rust prevention treatment includes plating treatment using zinc. The plating treatment using zinc may be either a zinc plating treatment or a zinc alloy plating treatment, and the zinc alloy plating treatment is particularly preferably a zinc-nickel alloy treatment. The zinc-nickel alloy treatment may be a plating treatment containing at least Ni and Zn, and may further contain other elements such as Sn, Cr, Co, and Mo. For example, when the rust prevention layer further contains Mo in addition to Ni and Zn, the treated surface of the roughened copper foil has better adhesion to the resin, chemical resistance, and heat resistance, and is less likely to leave an etching residue.

In zinc-nickel alloy plating, Ni/(Zn+Ni), which is the ratio of the Ni adhesion amount to the total amount of the Zn adhesion amount and the Ni adhesion amount, is preferably 0.3 or more and 0.9 or less as a mass ratio, and more preferably 0.4 or more and 0.9 or less. , more preferably 0.4 or more and 0.8 or less. In addition, the total adhesion amount of Zn and Ni in zinc-nickel alloy plating is preferably 8 mg/m2 or more and 160 mg/m2 or less, more preferably 13 mg/m2 or more and 130 mg/m2 or less, and even more preferably It is more than 19㎎/㎡ and less than 80㎎/㎡. On the other hand, in zinc-nickel-molybdenum alloy plating, Ni/(Zn+Ni+Mo), which is the ratio of the Ni adhesion amount to the total amount of Zn adhesion amount, Ni adhesion amount, and Mo adhesion amount, is preferably 0.20 or more and 0.80 or less as a mass ratio. , more preferably 0.25 or more and 0.75 or less, and even more preferably 0.30 or more and 0.65 or less. In addition, the total adhesion amount of Zn, Ni, and Mo in zinc-nickel-molybdenum alloy plating is preferably 10 mg/m2 or more and 200 mg/m2 or less, more preferably 15 mg/m2 or more and 150 mg/m2 or less, More preferably, it is 20 mg/m2 or more and 90 mg/m2 or less. Each adhesion amount of Zn, Ni, and Mo is determined by dissolving a predetermined area (e.g., 25 cm 2 ) on the roughened surface of the roughened copper foil with acid, and determining the concentration of each element in the obtained solution based on ICP emission spectrometry. It can be calculated through analysis.

It is preferable that the rust prevention treatment further includes chromate treatment, and it is more preferable that this chromate treatment is performed on the surface of the plating containing zinc after the plating treatment using zinc. By doing this, rust prevention can be further improved. A particularly preferable rust prevention treatment is a combination of zinc-nickel alloy plating treatment (or zinc-nickel-molybdenum alloy plating treatment) and subsequent chromate treatment.

If desired, the surface of the roughened copper foil may be subjected to a silane coupling agent treatment and a silane coupling agent treatment layer may be formed. As a result, moisture resistance, chemical resistance, adhesion to adhesives, etc. can be improved. The silane coupling agent treatment layer can be formed by appropriately diluting the silane coupling agent, applying it, and drying it. Examples of silane coupling agents include epoxy functional silane coupling agents such as 4-glycidylbutyltrimethoxysilane and 3-glycidoxypropyltrimethoxysilane, or 3-aminopropyltriethoxysilane, N-(2 -Aminoethyl)-3-aminopropyltrimethoxysilane, N-3-(4-(3-aminopropoxy)butoxy)propyl-3-aminopropyltrimethoxysilane, N-phenyl-3-aminopropyl Amino-functional silane coupling agents such as trimethoxysilane, or mercapto-functional silane coupling agents such as 3-mercaptopropyltrimethoxysilane, or olefin-functional such as vinyltrimethoxysilane and vinylphenyltrimethoxysilane. A functional silane coupling agent, or an acrylic functional silane coupling agent such as 3-methacryloxypropyltrimethoxysilane or 3-acryloxypropyltrimethoxysilane, or an imidazole functional silane coupling agent such as imidazole silane, or and triazine functional silane coupling agents such as triazine silane.

For the above-mentioned reasons, the roughened copper foil is preferably provided with a rust-inhibiting layer and/or a silane coupling agent-treated layer on the roughened surface, and more preferably has both a rust-inhibiting layer and a silane coupling agent-treated layer. When a rust-inhibiting layer and/or a silane coupling agent-treated layer are formed on the roughened surface, the respective values of the roughness parameter and waveform parameter in this specification are the values after the rust-inhibiting layer and/or the silane coupling agent-treated layer are formed. It shall mean the numerical value obtained by measuring the surface of the roughened copper foil. In addition, the rust prevention treatment layer and the silane coupling agent treatment layer may be formed not only on the roughened surface side of the roughened copper foil but also on the side where the roughened surface is not formed.

Copper clad laminate

It is preferable that the roughened copper foil of this invention is used for manufacture of a copper clad laminated board for printed wiring boards. That is, according to a preferred aspect of the present invention, a copper-clad laminated board provided with the above-mentioned roughening-treated copper foil is provided. By using the roughened copper foil of the present invention, both excellent transmission properties and high peel strength can be achieved in a copper-clad laminate. This copper-clad laminate is comprised of the roughened copper foil of this invention, and a resin layer provided in close contact with the roughened surface of this roughened copper foil. The roughened copper foil may be provided on one side of the resin layer, or may be provided on both sides. The resin layer includes a resin, preferably an insulating resin. The resin layer is preferably a prepreg and/or a resin sheet. Prepreg is a general term for composite materials made by impregnating a base material such as a synthetic resin plate, glass plate, woven glass fabric, non-woven glass fabric, or paper with a synthetic resin. Preferred examples of the insulating resin include epoxy resin, cyanate resin, bismaleimide triazine resin (BT resin), polyphenylene ether resin, and phenol resin. Additionally, examples of the insulating resin constituting the resin sheet include insulating resins such as epoxy resin, polyimide resin, and polyester resin. Additionally, the resin layer may contain filler particles made of various inorganic particles such as silica and alumina from the viewpoint of improving insulation properties, etc. The thickness of the resin layer is not particularly limited, but is preferably 1 μm or more and 1000 μm or less, more preferably 2 μm or more and 400 μm or less, and still more preferably 3 μm or more and 200 μm or less. The resin layer may be comprised of multiple layers. A resin layer such as a prepreg and/or a resin sheet may be provided in the roughened copper foil through a primer resin layer previously applied to the surface of the copper foil.

printed wiring board

It is preferable that the roughened copper foil of this invention is used for manufacture of a printed wiring board. That is, according to a preferred aspect of the present invention, a printed wiring board provided with the above-mentioned roughened copper foil is provided. By using the roughened copper foil of the present invention, both excellent transmission characteristics and high peel strength can be achieved in a printed wiring board. The printed wiring board according to this aspect includes a layer structure in which a resin layer and a copper layer are laminated. The copper layer is a layer derived from the roughening-treated copper foil of the present invention. In addition, the resin layer is the same as described above with respect to the copper clad laminate. In any case, the printed wiring board can adopt a known layer configuration. Specific examples of the printed wiring board include a single-sided or double-sided printed wiring board in which the roughened copper foil of the present invention is bonded to one side or both sides of a prepreg to form a cured laminate, and then circuits are formed, and a multilayer printed wiring board obtained by multilayering these is included. . Moreover, other specific examples include a flexible printed wiring board, COF, TAB tape, etc., which form a circuit by forming the roughened copper foil of the present invention on a resin film. In another specific example, a resin-coated copper foil (RCC) is formed by applying the above-described resin layer to the roughened copper foil of the present invention, and the resin layer is laminated on the above-described printed circuit board as an insulating adhesive layer, and then the roughened copper foil is applied to the wiring layer. A build-up wiring board in which circuits are formed in whole or in part by methods such as the modified, semi-additive method (MSAP) or subtractive method, or the roughened copper foil is removed and used in the semi-additive method (SAP). Examples include direct, build-up, on-wafer, etc., which alternately repeat stacking of resin-loaded copper foil and circuit formation on a build-up wiring board on which a circuit is formed, and a semiconductor integrated circuit.

Example

The present invention is explained in more detail by the following examples.

Examples 1 to 11

Manufacture of the roughened copper foil of this invention was performed as follows.

(1) Manufacturing of electrolytic copper foil

As the copper electrolyte, an acidic copper sulfate solution with the composition shown below was used, a titanium electrode was used as the cathode, and DSA (dimensionally stable anode) was used as the anode, with a solution temperature of 45°C and a current density of 55 A/dm2. Electrolysis was performed to obtain an electrolytic copper foil with the thickness shown in Table 1. At this time, as the cathode, an electrode whose surface was polished with a buff of the number shown in Table 1 to adjust the surface roughness was used.

<Composition of sulfuric acid copper sulfate solution>

- Copper concentration: 80g/L

- Sulfuric acid concentration: 300g/L

- Glue concentration: 5mg/L

- Chlorine concentration: 30mg/L

(2) Harmonization processing

Among the electrode surfaces and precipitation surfaces provided in the above-mentioned electrolytic copper foil, roughening treatment was performed on the precipitation surface side for Examples 1 to 6 and 11, and on the electrode surface side for Examples 7 to 10. In addition, 10 points were measured in accordance with JIS B0601-1994 using a contact surface roughness meter on the deposition surface of the electrolytic copper foil used in Examples 1 to 6 and 11, and the electrode surface of the electrolytic copper foil used in Examples 7 to 10. The average illuminance Rz was as shown in Table 1.

For Examples 1 to 8, the roughening process (first roughening process) shown below was performed. This roughening treatment is shown in Table 1 for each example in the copper electrolyte solution for roughening treatment (copper concentration: 7 g/L or more and 17 g/L or less, sulfuric acid concentration: 50 g/L or more and 200 g/L or less, liquid temperature: 30°C). Electrolysis was carried out under the conditions of the liquid resistance index, current density, and time shown, and then washed with water.

For Examples 9 to 11, the first roughening process, second roughening process, and third roughening process shown below were performed in this order.

- The first roughening treatment is the solution shown in Table 1 in the copper electrolytic solution for roughening treatment (copper concentration: 7 g/L or more and 17 g/L or less, sulfuric acid concentration: 50 g/L or more and 200 g/L or less, liquid temperature: 30°C). Electrolysis was performed under the conditions of resistance index, current density, and time, and then washed with water.

- The second roughening treatment was performed by electrolyzing in a copper electrolyte solution for roughening treatment with the same composition as the first roughening treatment under the conditions of the liquid resistance index, current density, and time shown in Table 1, and then washing with water.

- The third roughening treatment is the solution shown in Table 1 in the copper electrolyte solution for roughening treatment (copper concentration: 65 g/L or more and 80 g/L or less, sulfuric acid concentration: 50 g/L or more and 200 g/L or less, liquid temperature: 45°C). Electrolysis was performed under the conditions of resistance index, current density, and time, and then washed with water.

(3) Rust prevention treatment

The rust prevention treatment shown in Table 1 was performed on the electrolytic copper foil after the roughening treatment. As this rust prevention treatment, for Examples 1 and 5 to 8, a pyrophosphate bath was used on the roughened surface of the electrolytic copper foil, and the potassium pyrophosphate concentration was 100 g/L, the zinc concentration was 1 g/L, and the nickel concentration was 2 g/L. Rust prevention treatment A (zinc-nickel-molybdenum-based rust prevention treatment) was performed at L, molybdenum concentration of 1 g/L, liquid temperature of 40°C, and current density of 0.5 A/dm2. Additionally, for the surface of the electrolytic copper foil that has not been subjected to roughening treatment, a pyrophosphate bath is used, with a potassium pyrophosphate concentration of 80 g/L, a zinc concentration of 0.2 g/L, a nickel concentration of 2 g/L, a liquid temperature of 40°C, and a current density of 0.5A. Rust prevention treatment B (zinc-nickel based rust prevention treatment) was performed at /dm2. On the other hand, for Examples 2 to 4 and 9 to 11, rust prevention treatment B was performed on both sides of the electrolytic copper foil under the same conditions as the side on which the roughening treatment of the electrolytic copper foil in Examples 1 and 5 to 8 was not performed.

(4) Chromate treatment

Chromate treatment was performed on both sides of the electrolytic copper foil that had been subjected to the rust prevention treatment, and a chromate layer was formed on the rust prevention treatment layer. This chromate treatment was performed under the conditions of chromic acid concentration of 1 g/L, pH of 11, liquid temperature of 25°C, and current density of 1 A/dm2.

(5) Silane coupling agent treatment

The copper foil to which the chromate treatment was given was washed with water, and then immediately treated with a silane coupling agent, and the silane coupling agent was adsorbed onto the chromate layer of the roughened surface. This silane coupling agent treatment was performed by spraying a solution of the silane coupling agent using pure water as a solvent onto the roughened surface using a shower ring and performing adsorption treatment. As a silane coupling agent, 3-aminopropyltrimethoxysilane was used in Examples 1, 3, 4, and 6 to 8, and 3-glycidoxypropyltrimethoxysilane was used in Examples 2, 5, and 9 to 11. The concentration of the silane coupling agent was all set to 3 g/L. After adsorption of the silane coupling agent, moisture was finally evaporated using a heater to obtain a roughened copper foil of a predetermined thickness.

evaluation

The various evaluations shown below were performed on the manufactured roughened copper foil.

<Surface property parameters of roughened surface>

The roughened surface of the roughened copper foil was measured by surface roughness analysis using a laser microscope (OLS-5000, manufactured by Olympus Corporation) in accordance with JIS B0601-2013. At this time, for the illuminance parameters (Rdc, Rku, Rc, and Rq), the measurement magnification is set to 200 times (100 times objective lens magnification × 2 times optical zoom) as shown in Table 2, and the waveform parameters (Wdc, Wt, and Wp) As shown in Table 3, the measurement was performed at a measurement magnification of 20 times (objective lens magnification of 20 times). Other specific measurement conditions were as shown in Tables 2 and 3. The surface profile of the obtained roughened surface was analyzed according to the conditions shown in Tables 2 and 3, and Rdc, Rku, Rc, Rq, Wdc, Wt, and Wp were calculated. Additionally, based on the obtained values of Rdc and Rku, Rdc/Rku was calculated. The results were as shown in Table 4.

<Measurement of element adhesion amount in rust prevention treatment layer>

An area of 25 cm2 (5 cm The adhesion amount, Ni adhesion amount, and Mo adhesion amount were measured. The results were as shown in Table 4.

<Production of copper clad laminate>

As an insulating substrate, two sheets of prepreg (thickness 100 μm) containing polyphenylene ether, triallyl isocyanurate, and bismaleimide resin as main ingredients were prepared and laminated. The manufactured surface-treated copper foil was laminated on this laminated prepreg so that its roughened surface was in contact with the prepreg, and pressed at 32 kgf/cm2 and 205°C for 120 minutes to produce a 34 cm x 34 cm copper clad laminate. did.

<Circuit linearity>

Circuit linearity was evaluated as follows. First, for Examples 4 to 7, etching was performed on the surface of the copper foil side of the copper clad laminate described above until the thickness of the copper foil reached 12 μm. For Examples 1 to 11, a dry film was affixed to the surface of the copper foil side of the copper clad laminate, exposure and development were performed, and an etching resist was formed. By treating with a copper chloride etching solution, copper was dissolved and removed from between the resists, and three linear circuits each having a circuit width of 300 μm, a circuit height of 12 μm, and a length of 10 cm or 15 cm were formed (6 in total). The linear circuit thus obtained was observed under an optical microscope, and 30 locations per circuit were randomly selected to measure the circuit width. The average value and standard deviation were calculated for the obtained set of 30 circuit width data, and the coefficient of variation (%) for each circuit was calculated by dividing the standard deviation by the average value. The average value of the coefficient of variation in the six circuits was determined and used as the coefficient of variation of the circuit width in each example. The quality of the obtained circuit width variation coefficient was evaluated according to the following criteria. The results were as shown in Table 4.

<Circuit width variation coefficient evaluation criteria>

- Good: Circuit width variation coefficient is 1.50% or less

- Defect: Circuit width variation coefficient exceeds 1.50%

<Peel strength between copper foil and substrate>

In order to evaluate the adhesion between the roughened copper foil and the insulating substrate, the normal peel strength was measured as follows. First, for Examples 4 to 7, etching was performed on the surface of the copper foil side of the copper clad laminate described above until the thickness of the copper foil reached 12 μm. For Examples 1 to 11, circuit formation was performed on a copper clad laminate by an etching method, and a test board with a 3 mm wide straight circuit was manufactured. The linear circuit obtained in this way was peeled from the insulating substrate in accordance with method A (90° peel) of JIS C 5016-1994, and the peeling strength (kgf/cm) was measured. The quality of the obtained peeling strength was evaluated according to the following criteria. The results were as shown in Table 4.

<State peel strength evaluation criteria>

- Good: condition peeling strength of 0.30kgf/cm or more

- Poor: Condition peeling strength is less than 0.30kgf/cm

(c) Transmission characteristics

A high-frequency substrate (MEGTRON6N, manufactured by Panasonic) was prepared as an insulating resin substrate. Roughened copper foil was laminated on both sides of this insulating resin base material so that the roughened surface was in contact with the insulating resin base material, and was laminated using a vacuum press under conditions of a temperature of 190°C and a pressing time of 120 minutes, and an insulating thickness of 136 ㎛ was formed. A copper clad laminate was obtained. After that, etching processing was performed on the copper-clad laminate to obtain a substrate for transmission loss measurement on which microstrip lines were formed so that the characteristic impedance was 50 Ω. For the obtained substrate for transmission loss measurement, the transmission loss (dB/cm) at 28 GHz was measured using a network analyzer (N5225B, manufactured by Keysight Technologies). The quality of the obtained transmission loss was evaluated according to the following criteria. The results were as shown in Table 4.

<Transmission loss evaluation criteria>

- Good: Transmission loss is -0.33dB/cm or more

- Poor: Transmission loss is less than -0.33dB/cm

Claims (12)

A roughened copper foil having a roughened surface on at least one side,
The roughened surface has Rdc/Rku, which is the ratio of the cut level difference Rdc of the roughness curve to the kurtosis Rku of the roughness curve, of 0.180 μm or less, and the maximum cross-sectional height Wt of the waveform curve is 2.50 μm or more and 10.00 μm or less,
The Rku is a value measured in accordance with JIS B0601-2013 under the conditions of a magnification of 200 times, a cutoff wavelength of 0.3 μm by the cutoff value λs, and a cutoff wavelength of 5 μm by the cutoff value λc,
The above Rdc is the load length ratio in the illuminance curve measured under the conditions of a magnification of 200 times, a cutoff wavelength of 0.3 μm by the cutoff value λs, and a cutoff wavelength of 5 μm by the cutoff value λc, based on JIS B0601-2013. (Rmr1) is a value obtained as the difference (c(Rmr1)-c(Rmr2)) of the cutting level c in the height direction between 20% and the load length ratio (Rmr2) 80%,
The Wt is a value measured in accordance with JIS B0601-2013 under conditions of a magnification of 20 times, a cutoff wavelength of 5 μm by the cutoff value λc, and no cutoff by the cutoff value λf. The roughened copper foil is a value measured. According to paragraph 1,
The roughened copper foil has a maximum cross-sectional height Wt of 2.90 μm or more and 10.00 μm or less. According to claim 1 or 2,
The roughened copper foil has a cutting level difference Rdc of 0.45 μm or less. According to claim 1 or 2,
The roughened surface has a maximum peak height Wp of the waveform curve of 1.00 μm or more and 6.00 μm or less, and the Wp is a magnification of 20 times, a cutoff wavelength of 5 μm by a cutoff value λc, and a cutoff value of 5 μm, based on JIS B0601-2013. Roughened copper foil, which is a value measured under the condition of not performing a cutoff by the value λf. According to claim 1 or 2,
In the roughened surface, the average height Rc of the roughness curve elements is 0.70 ㎛ or less, and the Rc is at a magnification of 200 times, a cutoff wavelength of 0.3 ㎛ by the cutoff value λs, and a cutoff value λc, in accordance with JIS B0601-2013. This value is measured under the condition of a cutoff wavelength of 5㎛, roughened copper foil. According to claim 1 or 2,
The roughened surface has a cut level difference Wdc of the waveform curve of 1.20 μm or more and 3.10 μm or less, and the Wdc is a magnification of 20 times, a cutoff wavelength of 5 μm by a cutoff value λc, and a cutoff value of 5 μm, based on JIS B0601-2013. The difference (c( Roughened copper foil whose value is obtained as Wmr1)-c(Wmr2)). According to claim 1 or 2,
The roughened surface has a root mean square height Rq of the roughness curve of 0.290 μm or less, and Rq is based on JIS B0601-2013 at a magnification of 200 times, a cutoff wavelength of 0.3 μm by the cutoff value λs, and a cutoff value λc. The roughened copper foil is a value measured under the condition of a cutoff wavelength of 5㎛. According to claim 1 or 2,
The roughened surface is a roughened copper foil whose kurtosis Rku is 1.30 or more and 8.00 or less. According to claim 1 or 2,
A roughened copper foil comprising a rust prevention treatment layer and/or a silane coupling agent treatment layer on the roughening treatment surface. According to claim 1 or 2,
The roughened copper foil is an electrolytic copper foil, and the roughened copper foil exists on the precipitation surface side of the electrolytic copper foil. A copper-clad laminated board provided with the roughening-treated copper foil according to claim 1 or 2. A printed wiring board provided with the roughened copper foil according to claim 1 or 2.

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