CN112118672A

CN112118672A - Advanced reverse electrolytic copper foil with long island-shaped microstructure and copper foil substrate using same

Info

Publication number: CN112118672A
Application number: CN202010566817.0A
Authority: CN
Inventors: 宋云兴; 李思贤; 许纮玮; 高羣祐
Original assignee: Jinju Development Co ltd
Current assignee: Jinju Development Co ltd
Priority date: 2019-06-19
Filing date: 2020-06-19
Publication date: 2020-12-22
Anticipated expiration: 2040-06-19
Also published as: TWM608774U; TWI736325B; CN112118669A; TW202100813A; CN112118672B; CN112118669B; TW202102722A; TWI776168B

Abstract

The invention discloses a stepped reverse electrolytic copper foil with a long island-shaped microstructure and a copper foil substrate using the same. The advanced reverse electrolytic copper foil includes a micro-roughened surface having a plurality of copper crystals, a plurality of copper whiskers, and a plurality of copper crystal clusters which are non-uniformly distributed and form a long island-like pattern. Therefore, the advanced reverse electrolytic copper foil has good bonding force with a resin matrix composite, can improve signal integrity and reduce signal transmission loss, and meets the requirement of 5G application.

Description

Advanced reverse electrolytic copper foil with long island-shaped microstructure and copper foil substrate using same

Technical Field

The present invention relates to an electrolytic copper foil, and more particularly, to a step-reversed electrolytic copper foil having a long island-like microstructure, and a copper foil substrate using the same.

Background

With the development of the information and electronics industries, high frequency, high speed signal transmission has become a part of modern circuit design and manufacture. In order to meet the requirement of electronic products for high-frequency high-speed signal transmission, a Copper Clad Laminate (CCL) is required to prevent excessive insertion loss (insertion loss) of high-frequency signals during transmission so as to have good Signal Integrity (SI). Among them, the insertion loss expression of the copper foil in the copper foil substrate has a high correlation with the roughness of the surface-treated surface thereof because a Skin effect (Skin effect) is generated at the time of high-frequency high-speed signal transmission: a phenomenon in which the current distribution inside the conductor is not uniform. Along with the gradual increase of the distance from the surface of the conductor, the current density in the conductor is exponentially decreased, namely, the current in the conductor is concentrated on the surface of the conductor, so that the smaller the surface area of the surface treatment surface of the conductor is, the more the high-frequency and high-speed signal transmission is facilitated; however, the greater the surface area, the more favorable the peel strength, which conflicts with signal integrity, and further, the flatter the surface topography of the copper foil, the better the signal integrity, while the greater the surface area of the copper foil, the better the peel strength. Therefore, there is a need in the art to develop a copper foil substrate that can achieve both signal integrity and peel strength.

Disclosure of Invention

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a step-reversed electrodeposited copper foil having a long island-like microstructure, which can be applied to a high-frequency and high-speed 5G field, and can maintain characteristics required for a target application, for example, a peel strength (peel strength) of the electrodeposited copper foil. The invention also provides a copper foil substrate using the advanced reverse electrolytic copper foil, which can be used as a high-frequency high-speed substrate.

In order to solve the above technical problems, one of the technical solutions of the present invention is to provide an advanced reverse electrolytic copper foil having a long island-like microstructure, which includes a micro-roughened surface. The micro-roughened surface has a plurality of copper crystals in a non-uniform distribution, wherein different numbers of the copper crystals are stacked together to form respective copper whiskers, and different numbers of the copper whiskers are agglomerated together to form respective clusters of copper crystals. Under observation by a scanning electron microscope at an inclination angle of 35 degrees and a magnification of 10,000 times, the micro-roughened surface has the following structural features: (1) at least ten first smooth regions of 250nm length and 250nm width; (2) at least one second smooth region having a length of 500nm and a width of 500 nm; (3) at least one long island-shaped microstructure with the length of more than 1,500nm, wherein at least three copper crystals and/or copper whiskers exist in the long island-shaped microstructure; and (4) at least two strip-shaped copper-free regions with a length of 1,000nm or more.

In order to solve the above technical problem, another technical solution of the present invention is to provide a copper foil substrate, which includes a substrate and a step-reverse electrolytic copper foil, wherein the step-reverse electrolytic copper foil is disposed on the substrate and has a micro-roughened surface bonded to a surface of the substrate. The micro-roughened surface has a plurality of copper crystals in a non-uniform distribution, wherein different numbers of the copper crystals are stacked together to form respective copper whiskers, and different numbers of the copper whiskers are agglomerated together to form respective clusters of copper crystals. Under observation by a scanning electron microscope at an inclination angle of 35 degrees and a magnification of 10,000 times, the micro-roughened surface has the following structural features: (1) at least ten first smooth regions of 250nm length and 250nm width; (2) at least one second smooth region having a length of 500nm and a width of 500 nm; (3) at least one long island-shaped microstructure with the length of more than 1,500nm, wherein at least three copper crystals and/or copper whiskers exist in the long island-shaped microstructure; and (4) at least two strip-shaped copper-free regions with a length of 1,000nm or more.

In an embodiment of the invention, the copper crystal is not present in both the first smooth region and the second smooth region.

In an embodiment of the invention, each of the copper whiskers has a top copper crystal.

In an embodiment of the present invention, the top copper crystals are in a shape of cone, rod and/or sphere.

In one embodiment of the present invention, the micro-roughened surface has a surface roughness (Rz jis94) of less than 2.1 μm.

In an embodiment of the invention, the micro-roughened surface further includes a plurality of peaks and a plurality of grooves between the plurality of peaks, and the plurality of copper crystals, the plurality of copper whiskers and the plurality of copper crystal clusters are formed on the plurality of peaks correspondingly.

In an embodiment of the invention, each of the grooves has a U-shaped or V-shaped cross-sectional profile.

One of the advantages of the invention is that the advanced reverse copper foil of the invention can have a plurality of copper crystals in non-uniform distribution through the 'micro-roughening treatment surface, and has at least ten first smooth regions with the length of 250nm and the width of 250nm, at least one second smooth region with the length of 500nm and the width of 500nm, and at least one long island-shaped microstructure with the length of 1,500nm or more, and the long island-shaped microstructure has at least three copper crystals and/or copper whiskers', so as to reduce insertion loss (insertion loss) on the premise of not damaging peeling strength, improve signal integrity, adapt to high frequency and high speed of signal transmission, and meet the requirement of 5G application.

For a better understanding of the features and technical content of the present invention, reference should be made to the following detailed description of the invention and accompanying drawings, which are provided for purposes of illustration and description only and are not intended to limit the invention.

Drawings

Fig. 1 is a schematic structural view of a copper foil substrate according to the present invention.

Fig. 2 is an enlarged schematic view of section II of fig. 1.

Fig. 3 is an enlarged schematic view of a portion III of fig. 2.

FIG. 4 is a schematic view showing the structure of a continuous electrolytic apparatus for producing an advanced reverse electrolytic copper foil having a long island-like microstructure according to the present invention.

Fig. 5 is a scanning electron micrograph image at 1000 times magnification showing the surface topography of the advanced reverse electrodeposited copper foil with a long island-like microstructure of the present invention.

Fig. 6 is a scanning electron micrograph image obtained by observation at a magnification of 3000 times, which shows the surface morphology of the advanced reverse electrolytic copper foil having a long island-like microstructure according to the present invention.

Fig. 7 is a scanning electron micrograph image obtained by observation at a magnification of 10000 times, which shows the surface morphology of the advanced reverse electrolytic copper foil having a long island-like microstructure according to the present invention.

FIG. 8 is a scanning electron micrograph image showing the surface topography of a conventional RTF-3 copper foil.

FIG. 9 is a scanning electron micrograph image showing the surface topography of a conventional MLS-G copper foil.

Wherein the reference numerals are as follows:

c: copper foil substrate

1: substrate

2: advanced electrolytic copper foil

20: micro-roughened surface

20 a: first smooth area

20 b: second smooth region

20 c: long island microstructure

20 d: line-shaped copper-free area

21: copper crystal

211: top copper crystallization

W: copper whisker

G: copper crystal mass

22: convex peak

23: groove

3: continuous electrolysis apparatus

31: feed roll

32: material collecting roller

33: electrolytic cell

331: electrode for electrochemical cell

34: electrolytic roller group

35: auxiliary roller set

Detailed Description

The following description will be made of embodiments of the present invention relating to a "advanced reverse electrolytic copper foil and a copper foil substrate using the same" with reference to specific examples, and those skilled in the art will understand the advantages and effects of the present invention from the disclosure of the present specification. The invention is capable of other and different embodiments and its several details are capable of modifications and various changes in detail, all without departing from the spirit and scope of the present invention. The drawings of the present invention are for illustrative purposes only and are not intended to be drawn to scale. The following embodiments will further explain the related art of the present invention in detail, but the disclosure is not intended to limit the scope of the present invention. In addition, the term "or" as used herein should be taken to include any one or combination of more of the associated listed items as the case may be.

Referring to fig. 1 to 3, the present invention provides a copper foil substrate C, which includes a substrate 1 and at least one advanced reverse electrolytic copper foil 2 disposed on the substrate 1. In the present embodiment, the number of the advanced reverse electrolytic copper foils 2 is two, each having an uneven micro-roughened surface 20 bonded to the surface of the substrate 1, but the present invention is not limited thereto. In other embodiments, the copper foil substrate C may include only one stepped reverse electrolytic copper foil 2.

In order to reduce the insertion loss (insertion loss), the substrate 1 may be formed of a material having a low loss factor (Df); the Df of the substrate 1 at a frequency of 10 gigahertz (GHz) may be less than or equal to 0.015, preferably less than or equal to 0.010, and more preferably less than or equal to 0.005.

Further, the substrate 1 is formed of a resin-based composite material (i.e., prepreg) in which a base material is impregnated with a synthetic resin and then cured. Specific examples of the base material include phenolic cotton paper, resin fiber cloth, resin fiber nonwoven fabric, glass plate, glass woven fabric, or glass nonwoven fabric; specific examples of the synthetic resin include epoxy resin, polyester resin, polyimide resin, cyanate resin, bismaleimide triazine resin, polyphenylene ether resin, or phenol resin, and the synthetic resin may form a single layer or a multilayer structure. The resin-based composite material may be a medium-loss, low-loss, very low-loss, or ultra-low-loss material, and the above terms are well known to those skilled in the art, and specifically, the following commercially available products may be mentioned: EM890, EM890(K), EM891(K), EM528, EM526, IT170GRA1, IT958G, IT968G, IT150DA, S7040G, S7439G, S6GX, TU863(+), TU883(a, SP), MEGTRON 4, MEGTRON 6, MEGTRON 7, and MEGTRON 8. However, the above-mentioned examples are only one possible embodiment and are not intended to limit the present invention.

Referring to fig. 2 and 3, the micro-roughened surface 20 of the advanced reverse electrolytic copper foil 2 is formed by an electrodeposited copper micro-roughening treatment; it is worth mentioning that the micro-roughened surface 20 has a plurality of copper crystals 21, a plurality of copper whiskers W, and a plurality of copper crystal grains G, which are non-uniformly distributed, i.e., non-uniformly deposited on the surface of the copper foil. Each copper whisker W is formed by stacking two or more copper crystals 21 and different numbers of copper crystals 21 are stacked together to form the respective copper whisker W, wherein each copper whisker W has a top copper crystal 211 in a conical, rod or sphere shape, preferably a sphere shape. Each copper crystal group G is formed by agglomerating two or more copper whiskers W, and different numbers of copper whiskers W are agglomerated together to form respective copper crystal groups G.

In some embodiments, the plurality of copper whiskers W can have an average height of less than 3 microns, preferably less than 1.8 microns, and more preferably less than 1.0 micron; in addition, the average height of the plurality of copper crystallized groups G may be less than 3.5 microns, preferably less than 1.8 microns, and more preferably less than 1.0 micron. In some embodiments, each copper whisker W may comprise at most 25 copper crystals 21, preferably at most 12 copper crystals 21, more preferably at most 10 copper crystals 21, and particularly preferably at most 8 copper crystals 21. In some embodiments, the plurality of copper crystals 21 may have an average outer diameter of less than 0.5 microns, preferably from 0.05 to 0.5 microns, and more preferably from 0.1 to 0.4 microns.

It is worth mentioning that unlike the existing electrolytic copper foil, in which a plurality of copper crystals are uniformly distributed on the surface of the copper foil, only a few portions are aggregated together; the surface of the advanced reverse electrolytic copper foil 2 of the present invention has a plurality of copper crystal whiskers W formed from different numbers of copper crystals 21 and a plurality of copper crystal clusters G formed from different numbers of copper crystal whiskers W, in addition to a plurality of copper crystals 21 having non-uniform distribution, so that the surface morphology of the copper foil has significant unevenness. Thus, the advanced reverse electrolytic copper foil 2 of the present invention can improve signal integrity and suppress insertion loss (insertion loss) while maintaining good peel strength, thereby being suitable for high frequency and high speed signal transmission. Further, the surface roughness (Rz jis) of the micro-roughened surface 20 is 2.1 μm or less, which contributes to the reduction of the line width and the line pitch.

As shown in fig. 3, the micro-roughened surface 20 further includes a plurality of peaks 22 and a plurality of grooves 23 between the peaks 22, and a plurality of copper crystals 21, a plurality of copper whiskers W and a plurality of copper crystal clusters G are formed on the plurality of peaks 22. Wherein each groove 23 has a U-shaped or V-shaped cross-sectional profile. When the advanced electrolytic copper foil 2 of the present invention is laminated to a resin-based composite material, the micro-roughened surface 20 can receive more resin materials to increase the bonding force between the copper foil and the substrate.

[ preparation examples ]

Referring to fig. 2 in conjunction with fig. 4, the method of manufacturing the advanced reverse electrolytic copper foil 2 according to the present invention may be obtained by performing an electroplating copper micro-roughening treatment on a dark side (mate side) of a raw foil, wherein a micro-roughened surface 20 is formed on a bright side after the electroplating copper micro-roughening treatment. The electrolytic copper micro-roughening treatment can be carried out by using known equipment such as: a continuous electrolysis plant or a batch electrolysis plant and is realized at a production speed of 5m/min to 20m/min, a production temperature of 20 ℃ to 60 ℃ and a predetermined current density. It should be noted that, the dark side of the green foil may be scratched by using a steel brush to form the non-directional and long island-shaped groove, but not limited thereto. In some embodiments, the bright side (shiny side) of the green foil may be subjected to an electro-coppering micro-roughening treatment to form the micro-roughened surface 20. The conditions of the electrolytic copper micro-roughening treatment are shown in Table 1.

Referring to fig. 4, in the present embodiment, the processing equipment used is a continuous electrolytic equipment 3, which includes a feeding roller 31, a receiving roller 32, a plurality of electrolytic cells 33, a plurality of electrolytic roller sets 34 and a plurality of auxiliary roller sets 35; a plurality of electrolytic cells 33 are arranged between the feeding roller 31 and the receiving roller 32 for containing copper-containing plating solutions with the same or different formulas, and each electrolytic cell 33 is provided with a group of electrodes 331 (such as platinum electrodes); the plurality of electrolytic roller sets 34 are respectively arranged above the plurality of electrolytic cells 33, the plurality of auxiliary roller sets 35 are respectively arranged in the plurality of electrolytic cells 33, and the plurality of electrolytic roller sets 34 and the plurality of auxiliary roller sets 35 can drive the raw foil to sequentially pass through the plating solution in the plurality of electrolytic cells 33 at a certain speed; the electrode 331 in each electrolytic cell 33 and the corresponding electrolytic roller set 34 are electrically connected to an external power source (not shown) for electrolyzing the corresponding plating solution to add the desired effect on the copper foil.

In practice, the copper-containing electroplating solution contains copper ions, acid, and metal additives. The source of copper ions may be copper sulfate, copper nitrate, or a combination thereof. Specific examples of the acid include sulfuric acid, nitric acid, or a combination thereof. Specific examples of the metal additive include cobalt, iron, zinc, or a combination thereof. In addition, the copper-containing plating solution may further contain known additives as required, for example: gelatin, organonitrogen compounds, Hydroxyethylcellulose (HEC), polyethylene glycol (polyethylene glycol), PEG), Sodium 3-mercapto-1-propanesulfonate (MPS), Sodium polydithiodipropanesulfonate (Bis- (Sodium sulfopropyl) -disulphide, SPS), or thiourea-based compounds. However, the above examples are only one possible embodiment and are not intended to limit the present invention.

It is worth mentioning that the above mentioned electroplated copper micro-roughening treatment can be used not only for the production of reversal copper foil, but also for the production of High Temperature ductile (HTE) copper foil or Very Low roughness (VLP) copper foil.

[ Performance evaluation 1]

Example 1 is a step-reversed electrodeposited copper foil with a long island-like microstructure (hereinafter referred to as "long island-like microstructure copper foil" or "ULVLP copper foil" for convenience of explanation) according to the present invention, which is obtained by the foregoing electrolytic copper micro-roughening treatment, and the preparation conditions at each stage are shown in table 1 below, and the surface morphology of the copper foil is shown in fig. 5, 6 and 7. FIGS. 5, 6 and 7 are all obtained by photographing at an inclination angle of 35 degrees using a Hitachi S-3400N Scanning Electron Microscope (SEM); fig. 5 is an SEM image at a magnification of 1,000 times, fig. 6 is an SEM image at a magnification of 3,000 times, and fig. 7 is an SEM image at a magnification of 10,000 times.

As can be seen from fig. 5 and 6, in the reversed copper foil of example 1, a plurality of copper crystals 21, copper whiskers W, and copper crystal clusters G form a pattern of long islands with undulation. Further, as can be seen from fig. 7, the micro-roughened surface of the long island-like microstructured copper foil of example 1 had the following structural features: (1) at least ten first smooth regions 20a having a length of 250nm and a width of 250nm, the first smooth regions 20a having an area corresponding to 250nm × 250 nm; (2) at least one second smooth region 20b having a length of 500nm and a width of 500nm, the area of the second smooth region 20b corresponding to 500nm × 500 nm; (3) at least one long island-shaped microstructure 20c having a length of 1,500nm or more, and at least three copper crystals and/or copper whiskers are present in the long island-shaped microstructure 20 c; and (4) at least two line-shaped copper-free regions 20d having a length of 1,000nm or more. The structural features (1) and (2) contribute to a reduction in the surface area of the copper foil.

The structural features are all the results obtained by observing the surface morphology of the copper foil with a scanning electron microscope (SEM, model: Hitachi S-3400N) at an inclination angle of 35 degrees and at an appropriate magnification (10,000 times if no particular reference is made), which illuminates the surface corresponding to the surfaceThe volume size is about 12.7 μm × 9.46 μm, close to 120 μm²(ii) a The terms "first smooth region 20 a" and "second smooth region 20 b" refer to regions where no copper crystals are present under observation by SEM; the term "long island microstructure 20 c" means a structure having a nearly island-like or peninsular outline shape under SEM observation, in which a plurality of smooth regions are present around the structure; the term "line-shaped copper-free region 20 d" refers to a region (which may be linear or non-linear) having no copper crystal and a width of 1/3 or less of the length, for example, 1/10, 1/100 or 1/1000, which may be linear or non-linear and may have a uniform or non-uniform width.

The insertion loss (insertion loss) values of the ULVLP copper foil of example 1 and various types of prepregs were made into a copper foil substrate, and the results are shown in table 2 below.

TABLE 2

[ test example 1]

The ULVLP copper foils of examples 1 and 2, the reverse electrolytic copper foil (model: RG311, hereinafter referred to as RG311 copper foil) according to Taiwan patent application No. 107133827, and the reverse electrolytic copper foil (model: RTF-3, hereinafter referred to as RTF-3 copper foil) manufactured by C were respectively bonded to a medium loss (Mid-loss) prepreg (model: IT170GRA1) manufactured by I, and cured to form respective single-layer copper foil substrates. Wherein the surface roughness (Rz jis94) of the RG311 copper foil is less than 2.3 microns. The surface morphology of RTF-3 copper foil is shown in FIG. 8, which was photographed at an inclination angle of 35 degrees and a magnification of 10000 times using a scanning electron microscope (model: Hitachi S-3400N), wherein copper crystals are clearly uniformly distributed on the surface of the copper foil. The peel strength of all single-layer copper foil substrates satisfied the application requirements, and signal integrity was tested at 3mils Core (1oz), 10mils PP, and 4.5mils Trace Width using the Delta L test method proposed by Intel corporation, the results of which are shown in Table 3 below.

TABLE 3 Signal integrity test

As can be seen from the test results of table 3, the insertion loss of the ULVLP copper foil is reduced by about 16% to 21% compared to that of the RTF-3 copper foil and by about 5% to 10% compared to that of the RG311 copper foil at a frequency of 8 GHz; at a frequency of 16GHz, the insertion loss of ULVLP copper foil is reduced by about 20% to 24% compared to that of RTF-3 copper foil and by about 6% to 10% compared to that of RG311 copper foil. Therefore, ULVLP copper foil has better signal integrity than RTF-3 copper foil and RG311 copper foil.

[ test example 2]

The ULVLP copper foils of examples 1 and 2, the reverse electrolytic copper foil (model: RG311, hereinafter referred to as RG311 copper foil) according to Taiwan patent application No. 107133827, and the reverse electrolytic copper foil (model: RTF-3, hereinafter referred to as RTF-3 copper foil) manufactured by C were respectively bonded to a Low-loss prepreg (model: IT958G) manufactured by I, and cured to form respective single-layer copper foil substrates. Wherein the surface roughness (Rz jis94) of the RG311 copper foil is less than 2.3 microns. The surface morphology of the RTF-3 copper foil is shown in FIG. 8, which was photographed at an inclination angle of 35 degrees and a magnification of 10,000 times using a scanning electron microscope (model: Hitachi S-3400N), wherein copper crystals are clearly uniformly distributed on the surface of the copper foil. The peel strength of all single-layer copper foil substrates satisfied the application requirements, and signal integrity was tested at 3mils Core (1oz), 10mils PP, and 4.5mils Trace Width using the Delta L test method proposed by Intel corporation, the results of which are shown in Table 4 below.

TABLE 4 Signal integrity test

As can be seen from the test results in table 4,

at a frequency of 8GHz, the insertion loss of the ULVLP copper foil is reduced by about 15.80-20.53% compared with that of RTF-3 copper foil and by about 3-9% compared with that of RG311 copper foil; at a frequency of 16GHz, the insertion loss of ULVLP copper foil is reduced by about 18% to 23% compared to that of RTF-3 copper foil, and by about RG311 copper foil? Is there a . Therefore, ULVLP copper foil has better signal integrity than RTF-3 copper foil and RG311 copper foil.

[ test example 3]

The ULVLP copper foils of examples 1 and 2, the reversed electrolytic copper foil (model: RG311, hereinafter referred to as RG311) according to Taiwan patent application No. 107133827, and the electrolytic copper foil (model: HS1-M2-VSP, hereinafter referred to as HS1-M2-VSP copper foil) manufactured by M were laminated and cured using an Ultra Low-loss prepreg (model: IT968) manufactured by I, respectively, to form respective single-layer copper foil substrates. Wherein the surface roughness (Rz jis94) of the RG311 is less than 2.3 μm. The peel strength of all single-layer copper foil substrates satisfied the application requirements, and signal integrity was tested at 3mils Core (1oz), 10mils PP, and 4.5mils Trace Width using the Delta L test method proposed by Intel corporation, the results of which are shown in Table 5 below.

TABLE 5 Signal integrity test

From the test results of table 5, it can be seen that the insertion loss of ULVLP copper foil is reduced by about 16.04% to 19.73% compared to that of HS1-M2-VSP copper foil and by about 5% to 10% compared to that of RG311 copper foil at a frequency of 8 GHz; at a frequency of 16GHz, the insertion loss of the ULVLP copper foil is reduced by about 16-21% compared with that of the HS1-M2-VSP copper foil and by about 5-10% compared with that of RG 311. Therefore, ULVLP copper foil has better signal integrity compared to RG311 copper foil and HS1-M2-VSP copper foil.

[ advantageous effects of the embodiments ]

One of the advantages of the invention is that the advanced reversal copper foil with long island-shaped microstructure of the invention can have a plurality of copper crystals in non-uniform distribution through the ' micro-roughening processing surface, and has at least ten first smooth regions with the length of 250nm and the width of 250nm, at least one second smooth region with the length of 500nm and the width of 500nm, and at least one long island-shaped microstructure with the length of 1,500nm or more ', and the long island-shaped microstructure has at least three copper crystals and/or copper whiskers ', so as to reduce insertion loss (insertition loss) on the premise of not damaging peeling strength, improve signal integrity, adapt to high frequency and high speed of signal transmission, and meet the requirement of 5G application.

It should be noted that the present invention adopts a technical means abandoned due to the "technical prejudice" to some extent, even if the surface of the copper foil has a certain unevenness, and the technical means directly produces the beneficial technical effects of maintaining good peel strength and further optimizing the electrical characteristics.

The disclosure is only a preferred embodiment of the invention and should not be taken as limiting the scope of the invention, which is defined by the appended claims.

Claims

1. A step reversal electrolytic copper foil with a long island-shaped microstructure is characterized by comprising a micro-roughened surface, wherein the micro-roughened surface is provided with a plurality of copper crystals in non-uniform distribution;

wherein different numbers of said copper crystals are stacked together to form respective copper whiskers, and different numbers of said copper whiskers are agglomerated together to form respective clusters of copper crystals;

wherein the micro-roughened surface has at least ten first smooth regions of 250nm in length and 250nm in width, at least one second smooth region of 500nm in length and 500nm in width, and at least one long island-like microstructure of 1,500nm or more in length, as observed with a scanning electron microscope at an inclination angle of 35 degrees and a magnification of 10,000 times.

2. The advanced reverse electrolytic copper foil having a long island like microstructure according to claim 1, wherein the copper crystal is not present in both the first smooth region and the second smooth region.

3. The advanced reverse electrolytic copper foil having a long island like microstructure according to claim 1, wherein at least three of the copper crystals and/or the copper whiskers are present in the long island like microstructure under observation by a scanning electron microscope at an inclination angle of 35 degrees and a magnification of 10,000 times.

4. The advanced reverse electrolytic copper foil having a long island microstructure according to claim 1, wherein each of the copper whiskers has a top copper crystal.

5. The advanced reverse electrolytic copper foil having a long island structure according to claim 4, wherein a plurality of the top copper crystals are in a cone shape, a rod shape and/or a spherical shape.

6. The advanced reverse electrolytic copper foil having a long island microstructure according to claim 1, wherein the micro-roughened surface further has at least two linear copper-free regions having a length of 1,000nm or more.

7. The advanced reverse electrolytic copper foil having a long island like microstructure according to claim 1, wherein the surface roughness (Rz jis94) of the micro-roughened surface is less than 2.1 μm.

8. The advanced reverse electrolytic copper foil having a long island-like microstructure according to claim 1, wherein the micro-roughened surface further comprises a plurality of peaks and a plurality of grooves between the plurality of peaks, and a plurality of the copper crystals, a plurality of the copper whiskers, and a plurality of the copper crystal agglomerates are formed on the plurality of peaks in correspondence.

9. The advanced reverse electrolytic copper foil with a long island microstructure according to claim 1, wherein each of the grooves has a U-shaped or V-shaped cross-sectional profile.

10. A copper foil substrate, comprising:

a substrate; and

a step-reversed electrolytic copper foil disposed on the substrate and having a micro-roughened surface bonded to a surface of the substrate, wherein the micro-roughened surface has a plurality of copper crystals in a non-uniform distribution;

11. The copper foil substrate of claim 10, wherein the copper crystals are not present in both the first smooth region and the second smooth region.

12. The copper foil substrate according to claim 10, wherein at least three of the copper crystals and/or the copper whiskers are present in the island-like microstructure under observation with a scanning electron microscope at an inclination angle of 35 degrees and a magnification of 1,000 times.

13. The copper foil substrate of claim 10, wherein each of said copper whiskers has a top copper crystal.

14. The copper foil substrate of claim 13, wherein the plurality of top copper crystals are in the shape of a cone, a rod and/or a sphere.

15. The copper foil substrate according to claim 10, wherein the micro-roughened surface further has at least two linear copper-free regions having a length of 1,000nm or more.

16. The copper foil substrate according to claim 10, wherein the micro-roughened surface has a surface roughness (Rz jis94) of less than 2.1 μm.

17. The copper foil substrate according to claim 10, wherein said micro-roughened surface further comprises a plurality of peaks and a plurality of grooves between said plurality of peaks, and wherein a plurality of said copper crystals, a plurality of said copper whiskers and a plurality of said copper crystal agglomerates are formed on said plurality of peaks in correspondence therewith.

18. The copper foil substrate of claim 17, wherein each of said recesses has a U-shaped or V-shaped cross-sectional profile.