Preparation method of low-profile HTE copper foil for mini LED

Abstract

The invention relates to a preparation method of a low-profile HTE copper foil for a mini LED. The preparation method comprises the following steps: (1) electrolyzing a raw foil under the action of a composite additive to prepare a compact copper layer; (2) feeding the compact copper layer into a surface treatment section, and performing acid pickling, coarsening, curing and water washing to form a low-profile roughened structure, wherein a coarsening additive is added into a coarsening solution; (3) electroplating non-copper metal anti-oxidation layers on the two surfaces of the copper foil subjected to surface treatment; and (4) the copper foil electroplated with the anti-oxidation layer is coated with a silane coupling agent in a roller coating mode, and the low-profile HTE copper foil for the mini LED is obtained. The method has the capacity of continuous batch production, and the problem of layering and bubbling in outer layer pressing of the PCB for the mini LED is greatly solved while spontaneous heating of the copper foil is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrolytic copper foil, and in particular relates to a method for preparing a low-profile HTE copper foil for miniLED. Background Art

[0002] In the field of electronic display technology, miniLED, a new display technology, is widely used in electronic devices such as televisions, monitors, and laptops due to its high brightness and high contrast. Electrolytic copper foil is a key material used in miniLED manufacturing. Electrolytic copper foil is produced through an electrolysis process and exhibits excellent electrical conductivity and mechanical properties. Existing technologies typically use low-profile HTE (High Temperature Extrusion) electrolytic copper foil as a material for miniLED manufacturing. This type of copper foil has a low roughness, typically less than 6 microns, and offers excellent thermal stability. Furthermore, heat treatment minimizes the grain size change in the copper foil's crystal structure, ensuring minimal degradation of the photosensitive element (PS) during post-lamination high-temperature baking. While existing low-profile HTE electrolytic copper foil can meet the manufacturing requirements of miniLEDs to a certain extent, it still has some challenges and limitations. First, while low-profile HTE electrolytic copper foil has a low roughness, it can still contain tiny surface defects and pores. These defects and pores can cause problems during subsequent processing and manufacturing, impacting product quality and performance. Secondly, although the grain size of the existing copper foil does not change much after heat treatment, some changes may still occur, which may affect the conductivity and mechanical properties of the copper foil. Finally, although the attenuation of the existing copper foil during the high-temperature PS baking process is relatively small, it may still have some attenuation, which will affect the brightness and contrast of the miniLED. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a method for preparing low-profile HTE copper foil for miniLED. The method has the ability of continuous batch production, which greatly improves the problem of delamination and blistering during the lamination of the outer layer of the PCB board for miniLED while reducing the self-heating of the copper foil.

[0004] The present invention provides a method for preparing a low-profile HTE copper foil for miniLED, comprising the following steps:

[0005] (1) preparing a dense copper layer by electrolyzing raw foil under the action of a composite additive; wherein the composite additive is composed of a leveling agent and a brightener;

[0006] (2) sending the dense copper layer to a surface treatment section to form a low-profile roughened structure through pickling, roughening, curing, and water washing steps, wherein a roughening additive is added to the roughening solution;

[0007] (3) electroplating a non-copper metal anti-oxidation layer on both sides of the surface-treated copper foil;

[0008] (4) Roll-coat the copper foil after electroplating the anti-oxidation layer with a silane coupling agent to obtain a low-profile HTE copper foil for miniLED.

[0009] Preferably, the leveling agent (or moving agent) in step (1) is one or more of collagen, saccharin sodium, polyethylene glycol, polyethyleneimine, aminosulfonic acid, ammonium iminodiacetate, polyetheramine, and polyetheramide; the brightener is one or more of sodium sulfite, butynediol, sodium p-toluenesulfonate, and sodium azoaromatic benzyl quaternary ammonium; the mass ratio of the leveling agent to the brightener is 1-5:1-5; and the total concentration of the composite additive is 40-60 mg / L.

[0010] Preferably, the thickness of the green foil in step (1) is 9 μm-35 μm; the green foil type is one of double-sided electrolytic copper foil and ultra-low profile electrolytic green foil.

[0011] Preferably, the roughening additive in step (2) is a combination of sodium mercaptoimidazolepropanesulfonate, polyethyleneimine, tetrahydrothiazolidinethione and 1-propynyl glycerol ether, sodium molybdate, sodium tungstate, and polyvinyl alcohol, the mass ratio of the two is 1:1, and the total concentration is 10-30 mg / L.

[0012] Preferably, the microstructure of the low-profile roughened structure in step (2) is one or more of the following: needle-like, round-grained, long-grained, whisker-like, and clustered.

[0013] Preferably, the current process parameters used in the roughening step (2) are: the current density at the liquid inlet is 20-23A / dm 2 , the intermediate current density is 25-27A / dm 2 , the current density at the liquid outlet is 15-17A / dm 2 .

[0014] Preferably, the curing process parameters used in step (2) are: the current density at the liquid inlet is 13-15A / dm 2 , the intermediate current density is 17-19A / dm 2 , the current density at the liquid outlet is 11-13A / dm 2 .

[0015] Preferably, the non-copper metal used in the non-copper metal anti-oxidation layer in step (3) includes one or two of chromium, zinc, tin, molybdenum, cobalt, tungsten and nickel, and has a thickness of 5 to 500 nm.

[0016] Preferably, the silane coupling agent in step (4) is a mixed solution of epoxysilane, aminosilane, acrylic silane and chromium oxide, the mass ratio of the two is 3:1, and the total concentration of the silane coupling agent is 1-3wt%.

[0017] The dense copper layer electroplated in this invention, using a specific composite additive, exhibits excellent dimensional stability, and its crystal structure remains stable even after high-temperature treatment. Furthermore, the roughening additive creates a uniform, low-roughness roughened surface structure on the copper foil, resulting in a large specific surface area. The silane coupling agent's formulation is optimized to ensure good thermal stability after lamination with the prepreg, and minimizes PS degradation after high-temperature baking.

[0018] Beneficial effects

[0019] (1) Improved Surface Quality: The low-profile HTE electrolytic copper foil of the present invention has a roughness of less than 5 microns and fewer surface defects and pores. Compared to existing technologies, the improved surface quality of the copper foil of the present invention reduces the problems caused by defects and pores during subsequent processing and manufacturing, thereby improving product quality and performance.

[0020] (2) Optimized Crystal Structure: The low-profile HTE electrolytic copper foil of the present invention maintains minimal changes in grain size after heat treatment. Compared to existing technologies, the copper foil of the present invention achieves more stable conductivity and mechanical properties during heat treatment due to optimized crystal structure, thereby improving product reliability and durability.

[0021] (3) Reduced PS attenuation: The low-profile HTE electrolytic copper foil of the present invention has less PS attenuation after high-temperature baking. Compared with the prior art, the copper foil of the present invention improves the brightness and contrast of the miniLED and enhances the display effect due to the reduced attenuation after high-temperature baking.

[0022] (4) Improved Thermal Stability: The low-profile HTE electrolytic copper foil of the present invention has excellent thermal stability. Compared to existing technologies, the improved thermal stability of the copper foil of the present invention in high-temperature environments extends the product's service life and reduces maintenance and replacement costs.

[0023] (5) Wide application: The low-profile HTE electrolytic copper foil of the present invention is not only suitable for the manufacture of miniLEDs due to its excellent performance and thermal stability, but can also be widely used in other electronic devices such as televisions, monitors, laptops, etc., and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is the EBSD test image of the low-profile HTE copper foil prepared in Example 1. DETAILED DESCRIPTION

[0025] Below in conjunction with specific embodiment, further set forth the present invention.Should be understood that these embodiments are only used to illustrate the present invention and are not used in limiting the scope of the present invention.In addition, should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall equally within the scope limited by the appended claims of the application.

[0026] Example 1

[0027] 1. Electrolytic foil to prepare dense copper layer: Use electrolytic machine to prepare low roughness dense copper layer with specification of 12μm. Electrolytic process parameters are controlled in the following range: electrolyte Cu 2+ Concentration: 110g / L; H2SO4 concentration: 120g / L; Cl - Concentration: 15-25 mg / L; current density: 70-80 A / dm 2 During the electrolysis process, a composite additive consisting of sodium saccharin, polyethylene glycol, and sodium p-toluenesulfonate was used in a mass ratio of 2:1:1, with a total additive concentration of 50 mg / L. The resulting dense, low-roughness copper layer had a measured thickness of 11.7 μm, a tensile strength of 411 MPa, and an elongation of 7.6%. The roughness Rz of the smooth surface was 1.1 μm, and that of the matte surface was 1.2 μm. Compared to conventional HTE copper foil electrolysis, this copper foil exhibits a lower matte surface roughness.

[0028] 2. Surface treatment to form a low-profile roughened structure: The roughened structure is prepared on a dense copper layer by pickling, roughening, curing, and water washing.

[0029] 2.1 Pickling: The low-roughness copper foil obtained in the first step is put into the pickling tank for pickling to remove the oxide layer on the surface of the copper foil; the pickling process parameters are controlled within the following ranges: H2SO4 concentration of the pickling solution: 110g / L; temperature: 25-30℃.

[0030] 2.2 Roughening treatment: The rough surface of the copper foil after washing away the oxide layer is roughened. By applying electric current, copper nodules are plated on the foil surface. The microstructure of the copper nodules after treatment is needle-like, forming a copper foil with preliminary roughening treatment. The roughening process parameters are controlled within the following ranges: the H2SO4 concentration of the roughening solution is 110g / L; the Cu 2+Concentration: 15-25g / L; the roughening additive is a mixed additive of sodium molybdate and sodium tungstate, with a mass ratio of 1:1; the total concentration of the roughening additive is 10mg / L. Temperature: 25-30℃; Flow rate: 5-8m 3 / h; the current density at the liquid inlet is 23A / dm 2 , the intermediate current density is 26A / dm 2 , the current density at the liquid outlet is 16A / dm 2 After the roughening treatment, the foil surface will be washed with water. The purpose is to reduce the contamination of the subsequent bath solution by the electrolyte adsorbed on the surface of the copper foil.

[0031] 2.3 Curing treatment: The copper foil obtained in the previous step is further roughened and passed through the curing tank. The copper foil surface is smoothed by applying current to improve the roughness of the copper nodules. At the same time, the needle-shaped copper structure after the roughening treatment is fixed to prevent the copper nodules on the copper foil surface from falling off. The curing process parameters are controlled in the following range: Curing liquid Cu 2+ Concentration: 55-60g / L; H2SO4 concentration: 100±10g / L; Temperature: 50-55℃; Flow rate: 6-10m 3 / h; the current density at the liquid inlet is 14A / dm 2 , the intermediate current density is 18A / dm 2 , the current density at the liquid outlet is 12A / dm 2 The thickness of the copper foil increases after curing. The thickness of the roughened layer can be controlled by the roughening and curing current. A loose structure copper layer grows on the basis of the dense copper layer, with a thickness of about 0.5μm. The copper foil is washed with water. The foil surface of the cured copper foil is washed with water and a metal anti-oxidation layer is electroplated.

[0032] 3. Electroplating a metal anti-oxidation layer: Electrochemically deposit a metal layer on the roughened copper layer of the roughened copper foil, ultimately forming an anti-oxidation layer covering the loose copper layer to slow down the oxidation of the copper foil. The anti-oxidation layer is electroplated with nickel, zinc, and chromium. The electroplating process parameters are as follows: nickel ion concentration: 1.22g / L; temperature: 33°C; pH: 11; flow rate: 7m 3 / h; the current density at the liquid inlet is 10A / dm 2 , the current density at the liquid outlet is 7A / dm 2 Zinc ion concentration: 1.0 g / L; temperature: 33°C, pH: 10.5; flow rate: 7 m 3 / h; the current density at the liquid inlet is 10A / dm 2 , the intermediate current density is 15A / dm 2 , the current density at the liquid outlet is 7A / dm 2 Chromium ion concentration: 1.0 g / L; temperature: 33°C; pH: 9.8; flow rate: 7 m 3 / h; the current density at the liquid inlet is 10A / dm 2 , the intermediate current density is 15A / dm 2 , the current density at the liquid outlet is 7A / dm 2 .

[0033] 4. After the anti-oxidation layer is electroplated, it is washed and silane-coated. A layer of hydrolyzed silane coupling agent (a mixture of aminosilane and chromium oxide, with a mass ratio of 3:1 and a concentration of 1.2 wt%) is roller-coated on the barrier layer. After coating, it is oven-dried at 120°C to obtain the low-profile HTE copper foil.

[0034] Example 2

[0035] The difference from Example 1 is that the additives for the electrolytic foil are replaced with a mixture of collagen, sodium p-toluenesulfonate, and sodium azoaromatic benzyl quaternary ammonium in a mass ratio of 1:2:1, with a total concentration of 40 mg / L. Otherwise, the preparation method is the same as in Example 1.

[0036] Example 3

[0037] The difference from Example 1 is that the additives for the electrolytic foil are replaced with a mixture of polyethyleneimine, aminosulfonic acid, and sodium p-toluenesulfonate in a mass ratio of 1:2:1, with a total concentration of 60 mg / L. Otherwise, the preparation method is the same as that of Example 1.

[0038] Example 4

[0039] The difference from Example 1 is that during the roughening step, the roughening additives are replaced from sodium molybdate and sodium tungstate to sodium tungstate and polyvinyl alcohol, with a mass ratio of 1:2 and a total concentration of 20 mg / L. Other than that, the preparation method is the same as that of Example 1.

[0040] Example 5

[0041] The difference from Example 1 is that during the roughening step, the roughening additives are replaced from sodium molybdate and sodium tungstate with sodium mercaptoimidazolepropanesulfonate and sodium tungstate, with a mixing ratio of 1:1 and a total concentration of 30 mg / L. Other than that, the preparation method is consistent with that of Example 1.

[0042] Example 6

[0043] The difference from Example 1 is that the alkaline electroplating process is replaced by an acidic electroplating process during the electroplating treatment of the anti-oxidation layer. Other than that, the preparation method is consistent with that of Example 1.

[0044] Example 7

[0045] The difference from Example 1 is that during the silane coating process, aminosilane is replaced with acrylic silane, and the silane concentration is 1.0 wt %. Other than that, the preparation method is the same as that of Example 1.

[0046] Performance evaluation method and result analysis

[0047] 1. Copper foil tensile strength and elongation test method: Refer to "GB / T 5230-1995 Electrolytic copper foil tensile strength, elastic modulus, and elongation at break test" for tensile strength and copper foil elongation tests. The test results are the average of three test data.

[0048] 2. Surface roughness test method: According to the test method GB / T29847-2013, use the Japanese Mitutoyo portable roughness meter SJ-210 to test the roughness Rz value of the copper foil treated surface, and take the average value of the roughness values at three points.

[0049] 3. SDR test method: Obtain SDR data on the copper foil surface using the confocal laser OLS5000 in surface scanning mode at 50x magnification (X50) using the ISO 25178-2012 method. Three measurements were taken and the average was calculated.

[0050] 4. Peel strength test method: Refer to IPC-TM-6502.4.8 standard, press SI13UR sheet for peel strength test, test normal state and tin immersion 15min peel strength, test three times and take the average value.

[0051] 5. Grain structure and size test: EBSD analysis of copper foil slices was performed using a Zeiss scanning electron microscope to compare the grain size and changes in normal state and after high-temperature annealing.

[0052] The following table shows the performance test results:

[0053]

[0054]

[0055] Performance test results analysis:

[0056] 1. Comparison of Example 1 with Example 2 and Example 3: Example 1 has fine grains, which provide better etching performance during the subsequent etching process, facilitating the fabrication of fine circuits. Furthermore, the grain size change in Example 1 before and after annealing is only 1%, demonstrating excellent thermal stability. The grains in Examples 2 and 3 are blocky and columnar, respectively, and the grain size change before and after annealing is significant, reaching 16% to 20%. Their processability is inferior to that of Example 1. Preferably, the dense copper layer used in Example 1 is selected for subsequent processing.

[0057] 2. Comparing Example 1 with Examples 4 and 5: Example 1 has a matte surface roughness of 4.9 microns and an SDR of 46%. Examples 4 and 5 use different roughening additives, resulting in a higher roughness and SDR than Example 1. Excessive roughness can increase the risk of copper teeth piercing the PP sheet and causing adhesive overflow during processing, while a high SDR can degrade electrical performance and increase heat generation. The roughening additive used in Example 1 is preferably used as a roughening additive for low-profile HTE copper foil for miniLEDs.

[0058] 3. Comparison between Example 1 and Example 6: The normal peeling resistance of the alkaline electroplating barrier layer in Example 1 is close to the normal peeling resistance of the acidic electroplating barrier layer in Example 6, but the peeling strength of Example 6 after tin immersion for 15 minutes is 0.79 N / mm, which is higher than 0.76 N / mm in Example 1. The anti-aging performance of the sample prepared by the acidic electroplating barrier layer process used in Example 6 is better than that of the alkaline electroplating barrier layer process in Example 1; preferably, the acidic electroplating barrier layer process is the best process for barrier layer electroplating of low-profile HTE copper foil for miniLED.

[0059] 4. Comparison between Example 1 and Example 7: In Example 7, the silane is replaced by acrylic silane instead of amino silane. The normal peel strength and peel strength after tin immersion treatment on SI13UR resin are both better than those of Example 1. This shows that different types of silanes have certain differences in reliability due to differences in parameters such as different resin materials and glue content of the board. Preferably, acrylic silane is the best silane treatment agent on SI13UR resin.

[0060] In summary, due to the advanced nature of the present invention, it can be widely used in application fields such as electronic display technology, precision manufacturing technology, and new material manufacturing technology. First, in the field of electronic display technology, miniLED, as a new display technology, is widely used in electronic devices such as televisions, monitors, and laptops due to its high brightness and high contrast. The low-profile HTE electrolytic copper foil provided by the present invention has low roughness and excellent thermal stability, which can meet the manufacturing requirements of miniLED, improve the brightness and contrast of miniLED, and thus enhance the display effect of electronic devices. Secondly, in the field of precision manufacturing technology, the low-profile HTE electrolytic copper foil provided by the present invention has a smooth surface and few defects and pores, which can reduce the occurrence of problems in subsequent processing and manufacturing processes and improve product quality and performance. In addition, through heat treatment, the crystal structure grain size of the copper foil does not change much, thereby ensuring that the PS attenuation of the copper foil after high-temperature baking after lamination is small, which is of great significance for quality control in the precision manufacturing process. Finally, in the field of new material manufacturing technology, the low-profile HTE electrolytic copper foil provided by the present invention has a simple manufacturing process, low cost, and good conductivity and mechanical properties, which has broad market demand. At the same time, due to its excellent thermal stability, it can maintain good performance in high-temperature environments, which is of great significance for electronic and mechanical equipment that need to operate in such environments. Overall, the present invention has broad application prospects and large market demand, and is expected to play an important role in the fields of electronic display technology, precision manufacturing technology, and new material manufacturing technology.

Claims

1. A method for preparing a low-profile HTE copper foil for miniLED, comprising the following steps: (1) preparing a dense copper layer by electrolyzing raw foil under the action of a composite additive; wherein, The composite additive is composed of a leveling agent and a brightener; (2) sending the dense copper layer to a surface treatment section to form a low-profile roughened structure through pickling, roughening, curing, and water washing steps, wherein a roughening additive is added to the roughening solution; (3) electroplating a non-copper metal anti-oxidation layer on both sides of the surface-treated copper foil; (4) Roll-coat the copper foil after electroplating the anti-oxidation layer with a silane coupling agent to obtain a low-profile HTE copper foil for miniLED.

2. The preparation method according to claim 1, wherein: The leveling agent in step (1) is one or more of collagen, saccharin sodium, polyethylene glycol, polyethyleneimine, aminosulfonic acid, ammonium iminodiacetate, polyetheramine, and polyetheramide; the brightener is one or more of sodium sulfite, butynediol, sodium p-toluenesulfonate, and sodium azoaromatic benzyl quaternary ammonium; the mass ratio of the leveling agent to the brightener is 1-5:1-5; and the total concentration of the composite additive is 40-60 mg / L.

3. The preparation method according to claim 1, wherein: The thickness of the green foil in step (1) is 9 μm-35 μm; the green foil type is one of double-sided electrolytic copper foil and ultra-low profile electrolytic green foil.

4. The preparation method according to claim 1, wherein: The roughening additives in step (2) are two compositions of sodium mercaptoimidazolepropanesulfonate, polyethyleneimine, tetrahydrothiazolidinethione and 1-propynyl glycerol ether, sodium molybdate, sodium tungstate and polyvinyl alcohol, with a mass ratio of 1:1 and a total concentration of 10-30 mg / L.

5. The preparation method according to claim 1, wherein: The microstructure of the low-profile roughened structure in step (2) is one or more of needle-like, round-grained, long-grained, whisker-like, and clustered.

6. The preparation method according to claim 1, wherein: The current process parameters used in the roughening step (2) are: the current density at the liquid inlet is 20-23A / dm 2 , the intermediate current density is 25-27A / dm 2 , the current density at the liquid outlet is 15-17A / dm 2 .

7. The preparation method according to claim 1, wherein: The curing process parameters used in step (2) are: the current density at the liquid inlet is 13-15A / dm 2 , the intermediate current density is 17-19A / dm 2 , the current density at the liquid outlet is 11-13A / dm 2 .

8. The preparation method according to claim 1, wherein: The non-copper metal anti-oxidation layer in step (3) includes one or two of chromium, zinc, tin, molybdenum, cobalt, tungsten and nickel, and has a thickness of 5 to 500 nm.

9. The preparation method according to claim 1, wherein: The silane coupling agent in step (4) is a mixed solution of epoxy silane, amino silane, acrylic silane and chromium oxide, the mass ratio of the two is 3:1, and the total concentration of the silane coupling agent is 1-3wt%.

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