CN111031663B

CN111031663B - Copper foil substrate

Info

Publication number: CN111031663B
Application number: CN201811173307.6A
Authority: CN
Inventors: 宋云兴; 高羣祐; 吴宗宪
Original assignee: Jinju Development Co ltd
Current assignee: Jinju Development Co ltd
Priority date: 2018-10-09
Filing date: 2018-10-09
Publication date: 2023-05-05
Anticipated expiration: 2038-10-09
Also published as: CN111031663A

Abstract

The invention discloses a micro-rough electrolytic copper foil and a copper foil substrate. The micro-roughened electrolytic copper foil includes a micro-roughened surface. The micro-rough surface is provided with a plurality of convex peaks, a plurality of grooves and a plurality of micro-crystal clusters. The grooves have a U-shaped cross-sectional profile and/or a V-shaped cross-sectional profile, the grooves having an average width of 0.1 to 4 microns and an average depth of less than or equal to 1.5 microns. The microcrystalline clusters are located at the top of the convex peak. Each microcrystal cluster is composed of a plurality of microcrystal stacks having an average diameter of less than or equal to 0.5 microns. The microroughened surface of the microroughened electrolytic copper foil has an Rlr value of less than 1.3. The micro-rough surface and the substrate have good bonding force and good insertion loss, and can effectively inhibit signal loss.

Description

Copper foil substrate

Technical Field

The present invention relates to a copper foil, and more particularly, to an electrolytic copper foil and a copper foil substrate having the same.

Background

With the development of information and electronics industry, high frequency and high speed signal transmission has become a ring of modern circuit design and manufacture. In order to meet the high-frequency and high-speed signal transmission requirement of the electronic product, the adopted copper foil substrate needs to have good insertion loss (insertion loss) performance at high frequency so as to prevent the high-frequency signal from generating excessive loss during transmission. The insertion loss of the copper foil substrate is highly correlated with its surface roughness. When the surface roughness is reduced, the insertion loss is better represented, otherwise, the insertion loss is not represented. However, the roughness is reduced, and the peeling strength between the copper foil and the substrate is reduced, so that the yield of the rear end product is affected. Therefore, it has been an object of the present invention to maintain the peel strength at the industrial level and provide a good performance of the insertion loss.

Disclosure of Invention

The invention aims to solve the technical problem of providing a micro-rough electrolytic copper foil aiming at the defects of the prior art.

In order to solve the technical problems, one technical scheme adopted by the invention is to provide a micro-rough electrolytic copper foil. The micro-roughened electrolytic copper foil comprises a micro-roughened surface. The micro-rough surface is provided with a plurality of convex peaks, a plurality of grooves and a plurality of micro-crystal clusters. The grooves have a U-shaped cross-sectional profile and/or a V-shaped cross-sectional profile, the grooves have an average width of 0.1 to 4 microns, and the grooves have an average depth of less than or equal to 1.5 microns. The microcrystalline clusters are located at the tops of the peaks. Each of the micro-crystalline clusters is composed of a plurality of stacks of micro-crystals having an average diameter of less than or equal to 0.5 microns. The Rlr value of the micro-roughened surface of the micro-roughened electrolytic copper foil is lower than 1.3.

Preferably, each of the micro-crystalline clusters is composed of a plurality of stacks of micro-crystals having an average diameter of less than or equal to 0.5 microns and an average height of each of the micro-crystalline clusters of less than or equal to 2 microns.

Preferably, each of the micro-crystalline clusters is composed of a plurality of stacks of micro-crystals having an average diameter of less than or equal to 0.5 microns and an average height of less than or equal to 1.3 microns. A plurality of the microcrystals constitute a bifurcated crystal mass.

Preferably, the microroughened surface of the microroughened electrolytic copper foil has an Rlr value of less than 1.26.

In order to solve the above technical problems, one of the technical solutions adopted in the present invention is to provide a copper foil substrate, which includes a base material and a micro-roughened electrolytic copper foil. The micro-rough electrolytic copper foil comprises a micro-rough surface attached to the base material, wherein a plurality of convex peaks, a plurality of grooves and a plurality of micro-crystallization clusters are formed on the micro-rough surface, the average width of the grooves is 0.1-4 microns, the average depth of the grooves is less than or equal to 1.5 microns, the micro-crystallization clusters are positioned at the tops of the convex peaks, and the average height of the micro-crystallization clusters is less than or equal to 2 microns. The Insertion Loss (Insertion Loss) of the copper foil substrate at 20GHz is between 0 and-1.5 db/in. The peel strength between the micro-roughened electrolytic copper foil and the substrate is greater than 4.3lb/in.

Preferably, the insertion loss of the copper foil substrate at 16GHz is between 0 and-1.2 db/in.

Preferably, the insertion loss of the copper foil substrate at 8GHz is between 0 and-0.65 db/in, and the insertion loss of the copper foil substrate at 12.89GHz is between 0 and-1.0 db/in.

Preferably, the insertion loss of the copper foil substrate at 8GHz is between 0 and-0.63 db/in, the insertion loss of the copper foil substrate at 12.89GHz is between 0 and-0.97 db/in, the insertion loss of the copper foil substrate at 16GHz is between 0 and-1.15 db/in, and the insertion loss of the copper foil substrate at 20GHz is between 0 and-1.45 db/in.

Preferably, the micro-crystalline clusters have an average maximum width of less than or equal to 5 microns; part of the microcrystal clusters are formed with a bifurcation structure; each of the micro-crystalline clusters has an average height of less than or equal to 1.8 microns; each of the microcrystal clusters is composed of a plurality of microcrystal stacks, and the average diameter of the microcrystals is less than or equal to 0.5 micron; the Rlr value of the micro-roughened surface of the micro-roughened electrolytic copper foil is lower than 1.26.

Preferably, the Dk value of the substrate at 10GHz frequency is less than or equal to 4 and Df value at 10GHz frequency is less than or equal to 0.020, more preferably, the Dk value of the substrate 11 at 10GHz frequency is less than or equal to 3.8 and Df value at 10GHz frequency is less than or equal to 0.015.

One of the advantages of the invention is that the micro-rough surface has good bonding force with the substrate, and has good insertion loss performance, and can effectively inhibit the loss during signal transmission.

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

Drawings

Fig. 1 is a schematic side view illustrating one embodiment 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 a schematic view illustrating a production facility of micro-roughened electrolytic copper foil.

FIG. 4 is a scanning electron microscope image showing the surface morphology of the micro-roughened electrolytic copper foil of example 1.

FIG. 5 is a scanning electron microscope image showing the cross-sectional shape of a micro-roughened electrolytic copper foil of example 1.

Fig. 6 is a scanning electron microscope image showing the surface morphology of the copper foil of comparative example 3.

Fig. 7 is a scanning electron microscope image showing the cross-sectional shape of the copper foil of comparative example 3.

Detailed Description

The following specific examples are given to illustrate the embodiments of the present invention disclosed herein with respect to "micro-roughened electrolytic copper foil and copper foil substrate", and those skilled in the art will appreciate the advantages and effects of the present invention from the disclosure herein. The invention is capable of other and different embodiments and its several details are capable of modifications and various other uses and applications, all of which are obvious from the description, without departing from the spirit of the invention. The drawings of the present invention are merely schematic illustrations, and are not intended to be drawn to actual dimensions. The following embodiments will further illustrate the related art content of the present invention in detail, but the disclosure is not intended to limit the scope of the present invention.

Referring to FIG. 1, the copper foil substrate 1 of the present invention comprises a substrate 11 and two micro-roughened electrolytic copper foils 12. The micro-roughened electrolytic copper foil 12 is bonded to opposite sides of the base material 11. It should be noted that the copper foil substrate 1 may also include only one micro-roughened electrolytic copper foil 12.

The substrate 11 preferably has a low Dk value and a low Df value to suppress an insertion loss (insertion loss). Preferably, the Dk value of the substrate 11 at 10GHz frequency is less than or equal to 4 and Df value at 10GHz frequency is less than or equal to 0.020, more preferably, the Dk value of the substrate 11 at 10GHz frequency is less than or equal to 3.8 and Df value at 10GHz frequency is less than or equal to 0.015.

The base material 11 may be a composite material obtained by impregnating a prepreg with a synthetic resin and then curing the resin. The prepreg sheet can be exemplified by: phenolic tissue paper, resin fiber cloth, resin fiber non-woven cloth, glass plate, glass woven cloth, or glass non-woven cloth. The synthetic resin may be exemplified by: epoxy resin, polyester resin, polyimide resin, cyanate resin, bismaleimide triazine resin, polyphenylene ether resin, or phenol resin. The synthetic resin layer may be a single layer or a plurality of layers, and is not limited. The substrate 11 may be selected from, but is not limited to, EM891, IT958G, IT DA, S7439G, MEGTRON, MEGTRON 6, or MEGTRON 7.

Referring to fig. 1 and 2, the micro-roughened electrolytic copper foil 12 is obtained by roughening the surface of a copper foil by electrolytic process. The electrolytic roughening treatment may treat either surface of the copper foil, and therefore the micro-roughened electrolytic copper foil 12 has a micro-roughened surface 121 on at least one side. In one embodiment of the present invention, a reverse copper foil (Reverse Treated copper Foil, RTF) is used as a green foil, and then a roughening treatment is further performed on the glossy surface thereof to obtain a micro-roughened electrolytic copper foil 12.

The micro-roughened surface 121 is used for adhering to the substrate 11 and comprises a plurality of peaks 122, a plurality of grooves 123 and a plurality of micro-crystalline clusters 124. Two adjacent peaks 122 define a recess 123. The grooves 123 have a U-shaped cross-sectional profile and/or a V-shaped cross-sectional profile, and the grooves 123 have an average depth of less than or equal to 1.5 microns, preferably less than or equal to 1.3 microns, and more preferably less than or equal to 1 micron. The grooves 123 have an average width of 0.1 to 4 microns.

The average height of the microcrystal clusters 124 is less than or equal to 2 microns, preferably less than or equal to 1.8 microns, and more preferably less than or equal to 1.6 microns. The aforementioned average height refers to the distance from the top of the microcrystalline clusters 124 to the top of the peaks 122. The average maximum width of the microcrystalline clusters 124 is less than or equal to 5 microns, preferably less than or equal to 3 microns. Each of the microcrystal clusters 124 is formed by a stack of a plurality of microcrystals 125, and the average diameter of the microcrystals 125 is less than or equal to 0.5 microns, preferably 0.05 to 0.5 microns, and more preferably 0.1 to 0.4 microns. The average stack number of the microcrystals 125 of each microcrystal cluster 124 in its own height direction is 15 or less, preferably 13 or less, more preferably 10 or less, still more preferably 8 or less. When stacked in the microcrystal clusters 124, the microcrystals 125 may be stacked in a tower-like structure or may extend outward to form a bifurcated structure, thereby forming a bifurcated crystal cluster M.

The arrangement of the micro-crystalline clusters 124 is not necessarily the same, and may be disordered, may be arranged substantially along the same direction, or may be arranged in a plurality of micro-crystalline clusters 124 in a row and have the same extension direction portion in each row.

The average height of the micro-roughened surface 121 of the micro-roughened electrolytic copper foil 12 is preferably greater than 0.5 micrometers, more preferably greater than 1.5 micrometers, still more preferably greater than 2.0 micrometers. When the average roughness Rz of the micro rough surface 121 is in the above range, good bonding force with the substrate 11 is exhibited, that is, when the average roughness Rz is increased, the bonding force with the substrate 11 is effectively increased, so that the Peel strength (Peel strength) is effectively increased. Preferably, the peel strength between the microroughened electrodeposited copper foil 12 and the substrate 11 is greater than 4.3lb/in, preferably greater than 4.5lb/in, more preferably greater than 4.7lb/in, for a 1oz copper foil substrate 1. Since the adhesive coated on the micro-roughened surface is permeated into the bottom of the grooves 123 and the micro-crystalline clusters 124 when adhered to the substrate 11, the peel strength can be effectively improved after the adhesion to the substrate 11.

By the form of the micro-roughened surface 121, the micro-roughened electrolytic copper foil 12 and the substrate 11 can have sufficient peel strength, and can also effectively suppress the loss at the time of signal transmission. The microrough surface 121 has an Rlr value of less than 1.3, preferably less than 1.26, more preferably less than 1.23, still more preferably less than 1.2. The Rlr value refers to the ratio of the developed length, i.e., the ratio of the surface profile length of the object to be measured in a unit length. The higher the value, the more rugged the surface and when the value is equal to 1, the more flat the surface. Rlr satisfies the relationship rlr= Rlo/L. Wherein Rlo is the measured contour length, and L is the measured distance.

When the Rlr value of the micro-roughened electrolytic copper foil 12 is lower than 1.3, the copper foil substrate 1 (for example, IT170gra1+rg 311) has a better insertion loss performance. The insertion loss of the copper foil substrate 1 at 8GHz is 0 to-0.65 db/in, more preferably 0 to-0.63 db/in, still more preferably 0 to-0.60 db/in, still more preferably 0 to-0.57 db/in. The insertion loss of the copper foil substrate 1 at 12.89GHz is 0 to-1.0 db/in, preferably 0 to-0.97 db/in, more preferably 0 to-0.94 db/in, still more preferably 0 to-0.90 db/in. The insertion loss of the copper foil substrate 1 at 16GHz is 0 to-1.2 db/in, more preferably 0 to-1.15 db/in, still more preferably 0 to-1.1 db/in. The insertion loss of the copper foil substrate 1 at 20GHz is 0 to-1.5 db/in, preferably 0 to-1.45 db/in, more preferably 0 to-1.4 db/in, still more preferably 0 to-1.36 db/in, still more preferably 0 to-1.34 db/in. The micro-roughened electrolytic copper foil 12 of the invention can effectively inhibit the loss during signal transmission from 4GHz to 20 GHz.

[ method for producing micro-roughened electrolytic copper foil ]

The micro-roughened electrolytic copper foil 12 is produced by immersing a green foil in a copper-containing plating solution and then subjecting the copper foil to electrolytic roughening treatment for a predetermined period of time. In the embodiment of the present invention, a reverse copper foil (RTF) is used as a green foil, and the roughened surface is subjected to electrolytic roughening treatment. The electrolytic roughening treatment may be performed using any well known apparatus, for example: continuous electrolysis apparatus, or batch electrolysis apparatus.

The copper-containing plating solution contains copper ions, acid and metal additives. The copper ion source may be exemplified by copper sulfate, copper nitrate, or a combination thereof. The acid may be exemplified by sulfuric acid, nitric acid, or a combination thereof. The metal additive may be, for example, cobalt, iron, zinc, or a combination thereof. Furthermore, the copper-containing plating solution may further be added with well-known additives such as: gelatin, organic nitride, hydroxyethyl cellulose (hydroxyethyl cellulose; HEC), polyethylene glycol (Poly (ethylene glycol), PEG), sodium 3-mercapto-1-propane sulfonate (Sodium 3-mercaptopropanesulphonate, MPS), sodium polydithio-dipropyl sulfonate (Bis- (Sodium sulfopropyl) -disulfide, SPS), or thiourea-based compounds, but are not limited thereto.

The number of roughening treatments is at least two, and the composition of the copper-containing plating solution in each roughening treatment may be the same or different. In one embodiment of the present invention, two sets of copper-containing plating solutions are alternately roughened, and the copper ion concentration of the first set of copper-containing plating solution is preferably 10 to 30g/l, the acid concentration is preferably 70 to 100g/l, and the addition amount of the metal additive is preferably 150 to 300mg/l. The copper ion concentration of the second group of copper-containing plating solutions is preferably 70 to 100g/l, the acid concentration is preferably 30 to 60g/l, and the addition amount of the metal additive is preferably 15 to 100mg/l.

Electrolytic power supply methodA constant voltage, a constant current, a pulse type waveform, or a saw type waveform is used, but not limited thereto. In one embodiment of the present invention, the roughening treatment is performed by first using a first copper-containing plating solution to a constant current of 25 to 40A/dm ² Treating, and then using a second group of copper-containing plating solution to make constant current 20-30A/dm ² And (5) processing. Preferably, the first set of copper-containing plating solutions is used for constant current of 30 to 56A/dm ² Treating the second copper-containing plating solution with a constant current of 23 to 26A/dm ² And (5) processing. It should be noted that the constant current can also be supplied in a pulse-type waveform or a saw-type waveform. In addition, if the power supply is to be performed with a constant voltage, it is necessary to ensure that the voltage value applied in each stage of the roughening treatment falls within the above-described range.

When the number of roughening treatments is three or more, the roughening treatments can be performed by alternately using the first and second sets of copper-containing plating solutions. The current value is controlled to be between 1 and 60A/dm ² . In one embodiment of the present invention, the third and fourth roughening treatments respectively employ a first copper-containing plating solution and a second copper-containing plating solution, and the current values are respectively controlled to be 1 to 8A/dm ² 40 to 60A/dm ² . The current value of the roughening treatment after the fifth time is controlled to be less than or equal to 5A/dm ² . It should be noted that the constant current can also be supplied in a pulse-type waveform or a saw-type waveform. In addition, if power is supplied with a constant voltage, it is necessary to ensure that the voltage value applied in each stage of roughening treatment falls within the aforementioned range.

It should be noted that the arrangement of the micro-crystal clusters 124 of the micro-roughened surface 121 and the extending direction of the grooves 123 can be controlled by the flow field of the copper-containing plating solution. When a flow field is not applied or turbulence is formed, the micro-crystallization clusters 124 can be arranged in a disordered way; when the flow field is controlled to flow in a specific direction on the surface of the copper foil, a structure is formed which is arranged in the same direction. However, the arrangement of the micro-crystallization clusters 124 and the extending direction of the grooves 123 are not limited thereto, and the non-oriented grooves 123 may be formed by scraping with a steel brush, and the manufacturer can adjust the arrangement in any known manner.

In one preferred embodiment of the present invention, the roughening treatment is performed using a multi-tank and multi-electrolytic roll continuous electrolytic apparatus. Wherein, each groove alternately accommodates a first group of copper-containing plating solution and a second group of copper-containing plating solution. The power supply method adopts constant current. The production speed is controlled to be 5 to 20m/min. The production temperature is controlled between 20 and 60 ℃.

It should be noted that the micro-roughened electrolytic copper foil manufacturing method described above can also be used for processing high Wen Yanzhan copper foil (High Temperature Elongation, HTE) or Very Low roughness copper foil (VLP).

The respective layer structures and the manufacturing methods of the copper foil substrate 1 have been described above, and examples 1 to 3 will be exemplified below, and the advantages of the present invention will be described in comparison with comparative examples 1 to 4.

Example 1

Referring to fig. 3, the micro-roughened electrolytic copper foil is roughened by using a continuous electrolytic device 2. The continuous electrolysis apparatus 2 comprises a feed roll 21, a collection roll 22, six grooves 23 between the feed roll 21 and the collection roll 22, six sets of electrolysis rolls 24 each disposed above the grooves 23, and six sets of auxiliary rolls 25 each disposed within the grooves 23. A set of platinum electrodes 231 is provided in each of the slots 23. Each electrolytic roll set 24 includes two electrolytic rolls 241. Each auxiliary roller group 25 includes two auxiliary rollers 251. The platinum electrode 231 and the corresponding electrolytic roller set 24 in each tank 23 are electrically connected to the anode and the cathode of the external power supply, respectively.

In this example 1, an inverted copper foil (RTF) was used as a green foil, which was purchased from gold development limited (model RG 311). The raw foil is wound on the material conveying roller 21, sequentially wound on the electrolysis roller set 24 and the auxiliary roller set 25, and then wound on the material collecting roller 22. The copper-containing plating solution composition and plating conditions in each of the tanks 23 are shown in Table 1, wherein the source of copper ions is copper sulfate. The ultra-low roughness copper foil is roughened from the first to sixth grooves in order at a production speed of 10m/min to obtain a micro-roughened electrolytic copper foil having a roughness Rz (JIS 94) of 2.5 μm or less. And then, bonding two micro-rough electrolytic copper foils with one substrate IT170GRA1 to finish the manufacturing.

In example 1, the surface and cross-sectional structure were observed by a scanning electron microscope, and are shown in fig. 4 and 5, respectively.

The peel strength of the micro-roughened electrolytic copper foil of this example 1 was measured according to the IPC-TM-650.4.6.8 test method after the micro-roughened surface was coated with a copper silane coupling agent and bonded to the substrate IT170GRA1 for curing. The test results are shown in Table 2.

The Rlr value of the micro-roughened electrolytic copper foil of this example 1 was measured by a shape measuring laser microscope (manufacturer: keyence, model: VK-X100). The test results are shown in Table 2.

The insertion loss of the Micro-roughened electrolytic copper foil of this example 1 was tested by using the method of Micro-strip line (characteristic impedance 50Ω), and detected at frequencies of 4GHz, 8GHz, 12.89GHz, 16GHz, and 20GHz, respectively. The test results are shown in Table 2.

Example 2 and 3

The raw foil, the electrolytic device and the copper-containing plating solution were the same in composition as in example 1, and the plating conditions were as shown in Table 1, and the production speed was 10m/min. And then, bonding two micro-rough electrolytic copper foils with one substrate IT170GRA1 to finish the manufacturing. The measurement was carried out in the same manner as in example 1, and the test results are shown in Table 2.

Comparative examples 1 and 2

Comparative example 3

The surface and cross-sectional structure of the inverted copper foil (model: MLS-G, hereinafter referred to as MLS-G copper foil) produced by Mitsui metal was observed by a scanning electron microscope, and is shown in FIGS. 6 and 7, respectively. After two pieces of MLS-G copper foil were bonded to one piece of substrate IT170GRA1, the peel strength, rlr, and insertion loss were measured, and the test results are shown in Table 2.

Comparative example 4

The surface and cross-sectional structure of the copper foil were observed by a scanning electron microscope using a reversed copper foil (model: RTF3, hereinafter referred to as RTF3 copper foil) produced by vinca group. After two RTF3 copper foils were bonded to one substrate IT170GRA1, the peel strength, rlr, and insertion loss were measured and the test results are shown in Table 2.

TABLE 1

TABLE 2

Referring to fig. 4 and 5, the micro-roughened surface of embodiment 1 has a plurality of grooves extending in the up-down direction, and the extending directions of the grooves are substantially parallel. The grooves have a width of about 0.1 to 4 microns and a depth of less than or equal to 0.8 microns. At the convex peaks between the grooves, obvious micro-crystal clusters are formed. The height of the micro-crystal clusters is less than or equal to 2 microns, and each micro-crystal cluster is formed by stacking a plurality of micro-crystals with the particle size of 0.1-0.4 microns.

Referring to fig. 6 and 7, the surface of the mls-G copper foil is uniformly coated with a plurality of crystals having a particle size of more than 3 μm, and a few of the micro-crystals are aggregated with each other. From the sectional view, it is known that the microcrystals are distributed on the surface at intervals from each other and are not concentrated at specific positions.

Referring to Table 2, examples 1 to 3 exhibited peel strengths of at least 4.75lb/in, at least 18% greater than industry standard 4 lb/in. Therefore, the micro-rough electrolytic copper foil has good bonding force with the base material, is favorable for the subsequent process and maintains the product yield.

Regarding the performance of the insertion loss, the insertion loss between the frequencies of 8GHz to 20GHz in examples 1 to 3 was superior to that in comparative examples 1 to 4. It is worth mentioning that the signal loss of the copper foil substrate at high frequency can be obviously inhibited by controlling the surface morphology of the micro-rough surface and adjusting the Rlr value to be less than or equal to 1.3. In addition, the lower the Rlr value, the more effective the signal loss can be reduced.

From the above, the microrough electrolytic copper foil of the present invention further optimizes the performance of the insertion loss while maintaining good peel strength, and can effectively suppress the signal loss.

The foregoing disclosure is only a preferred embodiment of the present invention and is not intended to limit the scope of the claims, so that all equivalent technical changes made by the application of the present invention and the accompanying drawings are included in the scope of the claims.

Claims

1. The copper foil substrate is characterized by comprising:

a substrate; and

a micro-roughened electrolytic copper foil, which comprises a micro-roughened surface attached to the substrate, wherein the micro-roughened surface is formed with a plurality of peaks, a plurality of grooves and a plurality of micro-crystalline clusters, the grooves have U-shaped cross-sectional profile and/or V-shaped cross-sectional profile, the average width of the grooves is 0.1-4 microns, the average depth of the grooves is less than or equal to 1.5 microns, the micro-crystalline clusters are positioned on the tops of the peaks, each micro-crystalline cluster is composed of a plurality of micro-crystalline stacks with the average diameter of less than or equal to 0.5 microns, and the average height of each micro-crystalline cluster is less than or equal to 2 microns;

wherein, the insertion loss of the copper foil substrate at 20GHz is between 0db/in and-1.5 db/in;

wherein the peel strength between the micro-roughened electrolytic copper foil and the substrate is greater than 4.3lb/in.

2. The copper foil substrate according to claim 1, wherein the insertion loss of the copper foil substrate at 16GHz is between 0 and-1.2 db/in.

3. The copper foil substrate according to claim 2, wherein the insertion loss of the copper foil substrate at 8GHz is 0 to-0.65 db/in, and the insertion loss of the copper foil substrate at 12.89GHz is 0 to-1.0 db/in.

4. The copper foil substrate according to claim 3, wherein the insertion loss of the copper foil substrate at 8GHz is 0 to-0.63 db/in, the insertion loss of the copper foil substrate at 12.89GHz is 0 to-0.97 db/in, the insertion loss of the copper foil substrate at 16GHz is 0 to-1.15 db/in, and the insertion loss of the copper foil substrate at 20GHz is 0 to-1.45 db/in.

5. The copper foil substrate according to claim 1, wherein the average maximum width of the micro-crystalline clusters is less than or equal to 5 microns; a plurality of the microcrystal clusters form a bifurcated crystal cluster; each of the micro-crystalline clusters has an average height of less than or equal to 1.8 microns; each of the microcrystal clusters is composed of a plurality of microcrystal stacks, and the average diameter of the microcrystals is less than or equal to 0.5 micron; the Rlr value of the micro-roughened surface of the micro-roughened electrolytic copper foil is lower than 1.26.

6. The copper foil substrate according to claim 1, wherein the substrate has a Dk value of less than or equal to 4.0 at 10GHz frequency and a Df value of less than or equal to 0.015 at 10GHz frequency.