Copper foil with ultralow profile and high peel strength as well as preparation method and application of copper foil

Abstract

The invention relates to the technical field of copper foil processing, in particular to an ultralow-profile high-peel-strength copper foil and a preparation method and application thereof. A preparation method of a copper foil with ultralow profile and high peel strength comprises the following steps: (1) performing primary surface treatment on a raw material foil in a primary treatment solution, and performing strong polarization treatment on the copper foil by adopting high current density to form fine and compact copper nodules on the surface of the copper foil so as to obtain a primary treatment copper foil; and (2) carrying out secondary surface treatment on the primary treated copper foil in a secondary treatment solution, and consolidating copper nodules formed by the primary surface treatment through surface low-current smooth plating so that the copper nodules are not easy to fall off, thereby obtaining the copper foil with ultralow profile and high peel strength. The copper foil prepared by the method has ultra-low profile and relatively high peel strength.

Description

Technical Field

[0001] This invention relates to the field of copper foil processing technology, and in particular to a copper foil with ultra-low profile and high peel strength, its preparation method, and its application. Background Technology

[0002] With the continuous development of communication technology, 5G communication offers significant improvements over 4G communication in terms of transmission speed and data latency, requiring the use of high-frequency communication bands from 3.5GHz to 30GHz. However, during high-frequency signal transmission, due to the uneven distribution of electromagnetic fields on the conductor surface, the electromagnetic intensity near the conductor surface is higher, causing current to concentrate on the conductor surface and producing the "skin effect." When a signal propagates on a rough surface structure, the alternating electromagnetic waves interact with the uneven, rough surface, resulting in scattering and absorption, causing energy loss. Therefore, copper foil, as a key conductive material in printed circuit boards (PCBs), must reduce its surface roughness to minimize signal loss caused by the "skin effect" in order to meet the requirements of 5G communication and high-performance electronic products for transmitting high-frequency signals. Developing low-size copper nodules is an effective way to reduce the surface roughness of copper foil.

[0003] Furthermore, as surface roughness decreases, the adhesion between the copper foil and the substrate also decreases. Therefore, how to prepare a copper foil with ultra-low profile and high peel strength is an urgent problem to be solved.

[0004] Application number CN200410028463.5 discloses an electrolytic copper foil, which uses copper as the main component and is formed by electrolysis using an electrolyte containing at least one organic compound other than a thiol compound and chloride ions. A portion of its surface has an uneven surface with a roughness of 2-4 μm, composed of nodular protrusions. Furthermore, the electrolytic copper foil of this invention is an untreated copper foil with a surface roughness of 2-4 μm on the bonding surface to a resin substrate, where a specified current is applied for a specified time in an electrolyte to roughen the bonding surface. Ultimately, a copper foil with a smaller surface roughness than the roughened copper foil and high adhesion strength to a certain substrate can be formed. While this electrolytic copper foil has a smaller surface roughness, it still cannot meet the requirements for a low profile.

[0005] CN116497407A discloses a method for preparing copper foil, comprising the following steps: (1) electrodepositing an electroplating solution to obtain raw copper foil; (2) placing the raw copper foil into a micro-roughening solution for micro-roughening to obtain micro-roughened copper foil; and (3) placing the micro-roughened copper foil into a curing solution for curing to obtain cured copper foil. Specifically, on the surface of the micro-roughened copper foil, 10-20 spherical copper nodules are distributed per square micrometer, with an average spacing of 10-20 nm between adjacent spherical copper nodules; the spherical copper nodules include small spherical copper nodules and large spherical copper nodules, with the small spherical copper nodules having an average diameter of 150-250 nm and the large spherical copper nodules having an average diameter of 260-500 nm. The copper foil provided by this invention has low profile characteristics, but it has not yet reached the standard for ultra-low profile characteristics and still cannot meet the requirements for ultra-low profile copper foil with high peel strength. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing low-sized copper nodules on the surface of ultra-low profile copper foil and its application, so as to solve the problem that existing surface treatment processes cannot produce ultra-low profile copper foil with both high peel strength and low roughness.

[0007] To achieve the above objectives, a first aspect of the present invention provides a method for preparing copper foil with ultra-low profile and high peel strength, wherein the method includes the following steps: (1) The raw material foil is subjected to a first surface treatment in a primary treatment solution, and a primary treatment copper foil is obtained by using a high current density. The combination of low copper ions and high sulfuric acid forms a high overpotential, which promotes the nucleation of fine copper nodules and inhibits crystal growth, laying the foundation for ultra-low profile.

[0008] (2) The copper foil that was treated once is subjected to a second surface treatment in a secondary treatment solution, and a low current density is used to obtain the second-treated copper foil. The high copper ion concentration and medium sulfuric acid form a lower overpotential, which promotes uniform growth of copper nodules, fills the micro-defects of the first treatment, and optimizes the surface morphology. In particular, the slow deposition at a low current density smooths the tip of the copper nodules, reduces sharp structures, and lowers signal loss.

[0009] (3) Anti-oxidation treatment, which is a routine operation, forms a passivation film to prevent oxidation.

[0010] (4) Silane coupling agent coating is used to finally prepare copper foil with ultra-low profile and high peel strength. Silane coupling agent coating is a routine operation to improve peel strength.

[0011] The primary treatment solution includes a copper ion concentration of 5–60 g / L and a sulfuric acid concentration of 40–350 g / L; the secondary treatment solution includes a copper ion concentration of 30–120 g / L and a sulfuric acid concentration of 80–300 g / L; in the first surface treatment, the current density is 20–160 A / dm³. 2The electroplating time is 0.1–5 s, and the plating bath temperature is 15–50 °C; in the second surface treatment, the current density is 1–20 A / dm³. 2 The electroplating time is 1–10 seconds, and the plating bath temperature is 30–60°C. This invention promotes deposition and inhibits copper nodule growth through low current density, without the use of additives, resulting in cost savings and a simplified process.

[0012] Furthermore, the primary treatment solution comprises a copper ion concentration of 45–60 g / L and a sulfuric acid concentration of 40–45 g / L. Optimized parameters balance the nucleation rate and copper nodule size, avoiding excessive coarsening or uneven deposition.

[0013] Furthermore, the secondary treatment solution comprises a copper ion concentration of 100–120 g / L and a sulfuric acid concentration of 250–280 g / L. Optimizing parameters to lower the upper limit of copper ion concentration inhibits secondary growth of copper nodules and maintains an ultra-low profile.

[0014] Furthermore, in the first surface treatment, the current density is 60–120 A / dm². 2 The electroplating time is 0.1 to 2 seconds, and the plating solution temperature is 35 to 45°C.

[0015] Furthermore, in the second surface treatment, the current density is 5–7 A / dm². 2 The electroplating time is 2-5 seconds, and the plating solution temperature is 40-45℃.

[0016] This invention also provides a copper foil prepared by the above method. The copper nodule size of the copper foil is 50 nm to 200 nm; the non-contact line roughness SRz of the copper nodule size is 0.5 to 1 μm; the interface expansion area ratio Sdr of the copper foil is 10% to 15%; and the peel strength between the rough surface of the copper foil and the thermosetting resin is 0.4 to 0.6 N / mm. The nanoscale roughness increases the interface expansion area ratio, forming micromechanical interlocking and improving peel strength. The ultra-low profile reduces skin effect loss in high-frequency signal transmission, and the high peel strength meets the reliability requirements of high-density interconnect boards, preventing delamination after lamination.

[0017] Furthermore, the copper foil has a copper nodule size of 100–150 nm; the copper nodule size has a non-contact line roughness SRz of 0.5–0.75 μm; the copper foil has an interface expansion area ratio Sdr of 10%–12%; and the peel strength between the rough surface of the copper foil and the thermosetting resin is 0.5–0.6 N / mm.

[0018] Finally, this invention provides the application of the copper foil prepared by the above method in printed circuit boards.

[0019] By adopting the above technical solution, the present invention achieves the following beneficial technical effects: 1) This invention provides a method for preparing ultra-low profile high peel strength copper foil. It uses an electroplating solution without any additives. By adjusting the copper ion concentration, sulfuric acid concentration, current density, electroplating time, and plating solution temperature in the electroplating solution, the size of copper nodules on the copper foil surface is reduced, thereby reducing the surface roughness of the copper foil. At the same time, the high current density treatment results in densely distributed copper nodules on the surface of the copper foil, which reduces the surface roughness while maintaining high peel strength, meeting the application requirements of copper foil under high frequency and high speed conditions.

[0020] 2) The copper foil surface provided by the present invention has low-sized copper nodules, with the copper nodule size below 200nm, which effectively reduces the roughness value of the copper foil and reduces the loss of transmitted electronic signals caused by the skin effect. 3) The copper foil provided by this invention is particularly suitable for high-frequency, high-speed fine printed circuit boards. The small copper nodules can reduce burrs in the etched circuits and will not cause connection between circuits due to large copper nodules. It can avoid short circuits and can meet the wiring requirements of fine printed circuits and the transmission requirements of high-frequency, high-speed copper foil printed circuits above 10GHz. 4) The method for preparing ultra-low profile high peel copper foil provided by the present invention has simple plating solution composition, simple operation, low cost, and is suitable for industrial promotion. Attached Figure Description

[0021] Figure 1 This is an electron microscope image of the copper foil treated surface in Example 1, with a shooting angle of 0° and a magnification of 20K. Figure 2 This is an electron microscope image of the copper foil treated surface in Example 1, taken at a 45° angle and a magnification of 10K. Figure 3 This is an electron microscope image of the copper foil treated surface in Example 2, with a shooting angle of 0° and a magnification of 20K. Figure 4 This is an electron microscope image of the copper foil treated surface in Example 2, taken at a 45° angle and a magnification of 10K. Figure 5 This is an electron microscope image of the copper foil treated surface in Example 3, with a shooting angle of 0° and a magnification of 20K. Figure 6 This is an electron microscope image of the copper foil treated surface in Example 3, taken at a 45° angle and a magnification of 10K. Figure 7 The image shows the electron microscope morphology of the copper foil treated surface in Comparative Example 1, with a shooting angle of 0° and a magnification of 20K. Figure 8 The image shown is an electron microscope image of the copper foil treated surface in Comparative Example 1, with a shooting angle of 45° and a magnification of 10K. Figure 9The image shows the electron microscope morphology of the copper foil treated surface in Comparative Example 2, with a shooting angle of 0° and a magnification of 20K. Figure 10 The image shown is an electron microscope (EM) image of the copper foil treated surface in Comparative Example 2, taken at a 45° angle and a magnification of 10K. Detailed Implementation

[0022] The invention can be further understood through the specific embodiments and comparative embodiments given below. However, they are not intended to limit the invention.

[0023] Unless otherwise specified, the raw materials used in the embodiments and comparative examples of this invention can all be purchased commercially.

[0024] Example 1 As one embodiment of the present invention, see Figure 1 and Figure 2 The present invention provides a method for preparing low-size copper nodules on the surface of ultra-low profile copper foil, comprising the following steps: (1) The raw material foil is subjected to a first surface treatment in a primary processing solution. A high current density is used to strongly polarize the copper foil, so that fine and dense copper nodules are formed on the surface of the copper foil, thus obtaining a primary processed copper foil; wherein, in the first surface treatment, the current density is 60A / dm 2 The electroplating time is 3 seconds, and the solution temperature for each treatment is 25°C. The solution for each treatment includes copper ion concentration of 10 g / L and sulfuric acid concentration of 130 g / L. (2) The copper foil that has undergone primary treatment is subjected to a second surface treatment in a secondary treatment solution. The copper nodules formed in the first surface treatment are consolidated by a low-current smoothing plating process, making them less prone to peeling off, thus obtaining the copper foil product. In the second surface treatment, the current density is 5A / dm³. 2 The electroplating time is 3 seconds, and the secondary treatment solution temperature is 45℃. The secondary treatment solution includes copper ion concentration of 50 g / L and sulfuric acid concentration of 100 g / L.

[0025] (3) Anti-oxidation treatment; (4) Silane coupling agent coating was used to finally prepare copper foil with ultra-low profile and high peel strength.

[0026] Example 2 Unlike Example 1, in step (1), the copper ion concentration was adjusted to 5 g / L, while the rest was the same as in Example 1. See [link to example]. Figure 3 and Figure 4 .

[0027] Example 3 Unlike Example 2, in step (1), the copper ion concentration was adjusted to 15 g / L, while the rest was the same as in Example 2. See [link to example]. Figure 5 and Figure 6 .

[0028] Example 4 Unlike Example 1, in step (1), the sulfuric acid concentration is adjusted to 60 g / L, and the rest is the same as in Example 2.

[0029] Example 5 Unlike Example 4, in step (1), the sulfuric acid concentration is adjusted to 100 g / L, while the rest is the same as in Example 4.

[0030] Example 6 Unlike Example 5, in step (1), the sulfuric acid concentration was adjusted to 200 g / L and the current density was adjusted to 40 AA / dm³. 2 Everything else is the same as in Example 5.

[0031] Example 7 Unlike Example 6, in step (1), the sulfuric acid concentration was adjusted to 350 g / L and the current density was adjusted to 80 AA / dm³. 2 Everything else is the same as in Example 6.

[0032] Example 8 Unlike Example 5, in step (1), the electroplating time is adjusted to 5 seconds, while the rest is the same as in Example 5.

[0033] Example 9 Unlike Example 8, in step (1), the electroplating time is adjusted to 8s, while the rest is the same as in Example 8.

[0034] Example 10 Unlike Example 5, in step (2), the copper ion concentration is adjusted to 55 g / L, while the rest is the same as in Example 5.

[0035] Example 11 Unlike Example 10, in step (2), the copper ion concentration is adjusted to 60 g / L, while the rest is the same as in Example 10.

[0036] Example 12 Unlike Example 10, in step (2), the current density is adjusted to 3 AA / dm. 2 Everything else is the same as in Example 10.

[0037] Example 13 Unlike Example 12, in step (2), the current density is adjusted to 8 AA / dm. 2 Everything else is the same as in Example 12.

[0038] Example 14 Unlike Example 10, in step (2), the electroplating time is adjusted to 5 seconds, while the rest is the same as in Example 10.

[0039] Example 15 Unlike Example 14, in step (2), the electroplating time is adjusted to 8s, while the rest is the same as in Example 14.

[0040] Example 16 Unlike Example 1, in step (1), the copper ion concentration was adjusted to 45 g / L and the current density was adjusted to 100 AA / dm³. 2 Everything else is the same as in Example 1.

[0041] Example 17 Unlike Example 1, in step (1), the copper ion concentration was adjusted to 50 g / L and the current density was adjusted to 140 AA / dm³. 2 Everything else is the same as in Example 1.

[0042] Example 18 Unlike Example 1, in step (1), the copper ion concentration was adjusted to 60 g / L and the current density was adjusted to 160 AA / dm³. 2 Everything else is the same as in Example 1.

[0043] Example 19 Unlike Example 1, in step (2), the copper ion concentration is adjusted to 100 g / L, while the rest is the same as in Example 1.

[0044] Example 20 Unlike Example 19, in step (2), the copper ion concentration is adjusted to 110 g / L, while the rest is the same as in Example 19.

[0045] Example 21 Unlike Example 1, in step (2), the copper ion concentration is adjusted to 120 g / L, while the rest is the same as in Example 1.

[0046] Example 22 Unlike Example 1, in step (2), the current density is adjusted to 6A / dm², while the rest is the same as in Example 1.

[0047] Example 23 Unlike Example 1, in step (2), the current density is adjusted to 7A / dm², while the rest is the same as in Example 1.

[0048] Comparative Example 1 Unlike Example 1, in step (1), the current density is adjusted to 20 AA / dm. 2 Everything else is the same as in Example 1, see [link to example]. Figure 7 and Figure 8 .

[0049] Comparative Example 2 Unlike Example 1, in step (1), the current density is adjusted to 20 AA / dm. 2 The electroplating time was adjusted to 8 seconds; everything else remained the same as in Example 1. See [link to example]. Figure 9 and Figure 10 .

[0050] Performance testing: In this invention, the roughness test is conducted according to the test method JIS-B-0601-2001, using an Olympus OLS-5000 microscope to test the linear roughness SRz value and the interface expansion area ratio Sdr of the copper foil treated surface, and the average value is taken from three points.

[0051] In this invention, the peel strength of the copper foil is determined according to the test method GB / T29847-2013. Specifically, the copper foil sample is pressed with a polyphenylene ether resin substrate using a press machine, and then the peel strength is measured using a tensile testing machine.

[0052] In this invention, the copper powder shedding test of copper foil is conducted according to test method GB / T29847-2013. A 25g weight is used to press down the filter paper, and the filter paper is dragged along the "U" shape on the surface of the copper foil. The presence of copper powder on the filter paper is observed under an optical microscope at 100x.

[0053] The size of the copper nodule described in this invention was measured using a scanning electron microscope.

[0054] The test results are shown in Table 1.

[0055] Table 1 Copper nodule size / nm SRz / μm Sdr / % PPO substrate peel strength (N / mm) Does it contain copper powder? Example 1 91-193 0.648 13.082 0.439 no Example 2 64-148 0.593 13.838 0.431 no Example 3 85-189 0.589 13.733 0.427 no Example 4 130-197 0.697 10.984 0.425 no Example 5 100-182 0.694 14.571 0.473 no Example 6 93-194 0.724 14.567 0.472 no Example 7 89-162 0.702 13.246 0.448 no Example 8 94-193 0.576 14.691 0.477 no Example 9 81-200 0.648 13.333 0.423 no Example 10 60-182 0.674 14.085 0.417 no Example 11 79-196 0.62 12.791 0.467 no Example 12 83-167 0.663 12.976 0.427 no Example 13 100-193 0.663 14.958 0.486 no Example 14 74-174 0.699 14.405 0.501 no Example 15 85-183 0.71 13.414 0.586 no Example 16 88-156 0.521 10.314 0.462 no Example 17 92-161 0.537 10.714 0.471 no Example 18 95-163 0.549 11.000 0.485 no Example 19 78-152 0.593 14.246 0.512 no Example 20 80-158 0.601 14.617 0.528 no Example 21 82-160 0.618 15.185 0.541 no Comparative Example 1 192-317 0.863 13.762 0.234 yes Comparative Example 2 201-347 0.97 13.106 0.387 no Table 1 shows that the copper foils of Examples 1-21 meet the requirements of copper nodules of 50-200 nm, SRz of 0.5-1 µm, Sdr of 10-15%, peel strength ≥0.4 N / mm, and no copper powder.

[0056] In Examples 1, 2, and 3, only the copper ion concentration in step (1) was changed. The copper nodule size, non-contact roughness SRz, and interface expansion area ratio Sdr all decreased as the copper ion concentration in step (1) decreased. At the same time, the copper powder shedding situation improved as the copper ion concentration in step (1) decreased.

[0057] Electron micrographs clearly show that the copper nodules in the product obtained in Example 1 are similar in size to those in Example 2, but the copper nodules in the product obtained in Example 1 are more densely distributed and grow better.

[0058] At a suitable copper ion concentration of 10 g / L in step (1), compared with Examples 1, 4 and 5, the sulfuric acid concentration in step (1) was changed. In Example 1, the copper nodule size was lower due to the sulfuric acid concentration of 130 g / L.

[0059] By fixing the copper ion concentration at 10 g / L and the sulfuric acid concentration at 130 g / L in step (1), and comparing Examples 5, 6, 7 and Examples 5, 8, 9, it can be concluded that high current density and short electroplating time are more conducive to the formation of low-sized copper nodules.

[0060] Comparative Example 1 reduced the current density of a single treatment and found that reducing the current density did not reduce the copper nodule size. Furthermore, due to the low current density and fewer deposited copper nodules, the copper foil peel strength decreased significantly. Comparative Example 2 extended the electroplating time based on Comparative Example 1, which solved the problems of the number of copper nodules and peel strength, but at the same time increased the size of the copper nodules.

[0061] With step (1) fixed as suitable conditions, the copper ion concentration in step (2) was changed as in Examples 5, 10, and 11. By comparing the data in Table 1, it can be found that increasing the copper ion concentration in step (2) improves the copper powder shedding situation.

[0062] At a suitable copper ion concentration of 55 g / L in step (2), by adjusting the current density and electroplating time, it can be observed that increasing the current density and extending the electroplating time are beneficial to improving the copper powder shedding, but will cause the copper nodule size to increase.

[0063] In summary, this invention provides a method for preparing ultra-low profile, high peel strength copper foil. It employs an additive-free electroplating solution and reduces the size of copper nodules on the copper foil surface by adjusting the copper ion concentration, sulfuric acid concentration, current density, electroplating time, and solution temperature. The nodule size is below 200 nm, thereby reducing the surface roughness of the copper foil. Simultaneously, the high current density treatment results in a dense distribution of copper nodules on the copper foil surface, maintaining high peel strength while reducing surface roughness, meeting the requirements for high-frequency and high-speed applications. Furthermore, the plating solution of this invention has a simple composition, is easy to operate, and has low cost, making it suitable for industrial application.

[0064] The specific embodiments described herein are merely illustrative of the spirit of the invention. Those skilled in the art to which this invention pertains may make various modifications or additions to the described specific embodiments or use similar methods to replace them, without departing from the spirit of the invention or exceeding the scope defined by the appended claims.

Claims

1. A method for producing a copper foil having an ultra-low profile and a high peel strength, characterized by, The method comprises the following steps: (1) first surface treatment of raw material foil in a first treatment solution, using high current density to obtain a first treated copper foil; (2) second surface treatment of the first treated copper foil in a second treatment solution, using low current density to obtain a second treated copper foil; (3) anti-oxidation treatment; (4) silane coupling agent coating, finally preparing a copper foil with ultra-low profile and high peel strength; The primary treatment solution comprises copper ions at a concentration of 5-60 g / L and sulfuric acid at a concentration of 40-350 g / L; the secondary treatment solution comprises copper ions at a concentration of 30-120 g / L and sulfuric acid at a concentration of 80-300 g / L; in the first surface treatment, the current density is 20-160 A / dm 2 , the plating time is 0.1-5 s, and the plating solution temperature is 15-50℃; in the second surface treatment, the current density is 1-20 A / dm 2 , the plating time is 1-10 s, and the plating solution temperature is 30-60℃.

2. The method of claim 1, wherein the copper foil has a peel strength of 0.1 g / 25 mm or more and a thickness of 5 μm or less. The first treatment solution comprises copper ion concentration of 45-60 g / L and sulfuric acid concentration of 40-45 g / L.

3. The method of claim 1, wherein the copper foil has a peel strength of 0.1 g / 25 mm or more and a thickness of 5 μm or less. The second treatment solution comprises copper ion concentration of 100-120 g / L and sulfuric acid concentration of 250-280 g / L.

4. The method of claim 1, wherein the copper foil has a peel strength of 0.1 g / 25 mm or more and a thickness of 5 μm or less. In the first surface treatment, the current density is 60-120 A / dm 2 , the plating time is 0.1-2 s, and the plating solution temperature is 35-45°C.

5. The method of claim 1, wherein the copper foil has a peel strength of 0.1 g / 25 mm or more and a thickness of 5 μm or less. In the second surface treatment, the current density is 5-7 A / dm 2 , the plating time is 2-5 s, and the plating solution temperature is 40-45 °C.

6. An ultra-low profile high peel strength copper foil, characterized by, The copper foil prepared by the method of any one of claims 1-5 has copper tumor size of 50-200 nm, non-contact line roughness SRz of 0.5-1 μm, interface expansion area ratio Sdr of 10-15%, and peel strength between the rough surface and thermosetting resin of 0.4-0.6 N / mm.

7. The ultra-low profile, high peel strength copper foil according to claim 6, wherein, The copper foil prepared by the method of any one of claims 1-5 has copper tumor size of 100-150 nm, non-contact line roughness SRz of 0.5-0.75 μm, interface expansion area ratio Sdr of 10-12%, and peel strength between the rough surface and thermosetting resin of 0.5-0.6 N / mm.

8. Use of the copper foil with ultra-low profile and high peel strength according to claim 6 or 7 in printed circuit boards.

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