Brown-free copper foil and manufacturing method thereof, copper-clad plate and printed circuit board

Abstract

The invention relates to the field of electrolytic copper foil processing and application, and discloses a browning-free copper foil and a manufacturing method thereof, a copper-clad plate and a printed circuit board, and the copper foil is composed of a template copper layer, a high-temperature isolation coating, a browning-free copper layer and a roughening layer from bottom to top. The invention provides a brownification-free copper foil and a manufacturing method thereof, and a copper-clad plate and a printed circuit board manufactured by using the brownification-free copper foil. According to the manufacturing method of the browning-free copper foil, the roughening treatment of the non-treated surface is completed in the copper foil manufacturing stage by using a template method, so that the browning step in the subsequent PCB process is avoided, and the performance of the browning-free copper foil can be adjusted in a large range according to the binding force requirements of different prepregs.

Description

Technical Field

[0001] The present invention relates to the fields of electrolytic copper foil processing and application, and particularly to a copper foil without brownification, a manufacturing method thereof, a copper clad laminate, and a printed circuit board. Background Art

[0002] The main body of a printed circuit board (PCB) is composed of copper foil and a semi-cured sheet substrate laminated. With the continuous improvement of communication technology and computing power, the amount and type of data that a PCB needs to process at the same time are increasing, and the PCB board is developing from the original single-layer board to the multi-layer board direction.

[0003] In the manufacturing process of a printed circuit board (PCB), usually, the processed surfaces of two copper foils after roughening treatment are closely attached to a semi-cured sheet for lamination to form a three-layer structure of copper foil - cured sheet - copper foil. Since the surface of the copper foil has been roughened at this time, the bonding force between the copper foil and the first semi-cured sheet is relatively large. When manufacturing a multi-layer PCB board, two copper clad laminates are required. After the circuit is formed on the surface of the copper clad laminate, a semi-cured sheet is further laminated in the middle for lamination to obtain a multi-layer circuit. However, in the second lamination process, the non-treated surface that has not been roughened is laminated with the semi-cured sheet, and at this time, the bonding force between the copper foil and the substrate is relatively small. At this time, the industry will use the brownification process to treat the non-treated surface.

[0004] The brownification step is an important means to improve the peel strength between the inner core board and the semi-cured sheet. Since the surface of the copper foil shows a brownish-black color after treatment, it is named brownification. In existing mass-produced products, after the processed surface of the copper foil has been laminated with the PP semi-cured sheet, due to its own rigidity and the structure of copper foil - cured sheet - copper foil combination, it is difficult to use the same addition method as the processed surface to prepare copper nodules for roughening treatment. Manufacturers usually use the chemical etching subtraction method to etch downward to form downward blind holes, thereby increasing the surface roughness of the non-treated surface and increasing the bonding force with the semi-cured sheet during the second lamination process. This is the basic principle of brownification. This step is not only complex and costly, but also will cause secondary damage to the etched circuit of the copper foil, and seriously, it will cause problems such as delamination of the PCB oxide surface, incomplete inner layer etching, and plating through holes.

[0005] Brownification treatment is a secondary roughening treatment for copper foil, and it has many defects:

[0006] 1. High-temperature discoloration of the inner brownification film: In a high-temperature environment, the brownification film may change color, which is mainly caused by the oxidation of the brownification layer with the change of temperature, and this will affect the appearance and quality of the product.

[0007] 2. Limited residence time after brownification: The effective time after brownification is limited, usually 24 hours. If the chip placement takes a long time, it is easy to exceed the brownification aging time, resulting in delamination during lamination. This increases the time pressure and quality control difficulty in the production process.

[0008] 3. Rework brownification causes the solder paste to turn black: If it is necessary to rework a brownified PCB board, it may cause the solder paste to turn black. The main reason for the blackening of the solder paste is that tin and its oxides react with the acidic solution of the brownification line, generating stannous oxide (black solid) and stannous sulfate (which oxidizes to light yellow when exposed to air). This will affect the bonding between the solder paste and the semi-cured sheet flow glue, reducing the lamination quality and thus affecting the reliability of the product.

[0009] 4. The lamination quality cannot be guaranteed: Due to possible quality problems during the brownification process, such as discoloration of the brownification film, excessive residence time after brownification, etc., the lamination quality cannot be guaranteed. This will increase the scrap rate and production cost of the product.

[0010] 5. The process complexity increases: The brownification process requires strict control of various parameters, such as temperature, time, solution concentration, etc., to ensure the brownification effect. This increases the process complexity and the skill requirements for operators.

[0011] 6. Cost increases: The brownification process requires the use of specific solutions and equipment, increasing the production cost. At the same time, due to possible quality problems and rework situations during the brownification process, the cost will also increase. Summary of the Invention

[0012] The main purpose of the present invention is to solve the technical problems in the prior art that possible quality problems and rework situations during the brownification process will also lead to an increase in cost. A copper foil without brownification, the copper foil is composed of a template copper layer, a high-temperature isolation coating, a copper layer without brownification, and a roughening layer from bottom to top.

[0013] The surface roughness of the template copper layer is Rz 0.8 - 2.5μm, Rv 0.6 - 1.3μm, Sdr 8.0 - 15%.

[0014] The surface roughness of the side of the copper layer without brownification close to the template copper layer is Rz 0.8 - 2.5μm, Rv 0.6 - 1.3μm, Sdr 8.0 - 15%.

[0015] After laminating the side of the copper layer without brownification close to the template copper layer with a semi-cured sheet, when the surface copper foil is thickened to 35μm, the peel strength ≥ 0.6N / mm; after floating tin at 288°C for 3 times, there is no board separation and board explosion phenomenon, and the peel strength ≥ 0.5N / mm.

[0016] The present invention also relates to a manufacturing method of a copper foil without brownification, comprising the following steps:

[0017] Preparation of the template copper layer, electrolytic treatment of the template copper layer, the sulfuric acid concentration of the electrolyte for the electrolytic treatment is 100 - 120g / L, Cu 2+The concentration is 95 - 100 g / L, the temperature is 50 - 60 °C, and the current density is 30 - 40 A / dm 2 , and a single-sided bright copper foil is obtained;

[0018] The template copper layer is roughened, and electrodeposition treatment is performed on the bright surface of the single-sided bright copper layer. The parameters of the electrodeposition treatment are as follows: the sulfuric acid concentration is 60 - 90 g / L, and the Cu 2+ concentration is 30 - 50 g / L, the temperature is 35 - 45 °C, the current density is 20 - 30 A / dm 2 , and the electrolysis time is 5 - 7 s, obtaining a roughened template copper layer;

[0019] The roughened template copper layer is pickled;

[0020] After pickling, a high-temperature isolation coating is prepared. The adhering liquid of the isolation coating is an aqueous solution of benzotriazole with a concentration of 2 - 4 g / L, the temperature is 30 - 40 °C, the soaking time is 15 - 25 s, and then it is dried by blowing in a blast drying oven at 140 - 160 °C, obtaining a template copper layer with an isolation coating;

[0021] Preparation of a copper layer without brownification. Electroplating treatment is performed on the template copper layer with an isolation coating to obtain a template copper layer with a copper foil layer without brownification. The electroplating treatment parameters are as follows: the sulfuric acid concentration in the electrolyte is 100 - 120 g / L, and the Cu 2+ concentration is 95 - 100 g / L, the temperature is 50 - 60 °C, and the current density is 15 - 25 A / dm 2 ;

[0022] Preparation of a surface roughened layer. The surface of the template copper layer with a copper foil layer without brownification is roughened and cured to obtain a template copper layer with a roughened layer. The sulfuric acid concentration of the roughening solution for roughening treatment is 85 - 95 g / L, and the Cu 2+ concentration is 20 - 30 g / L, and the sulfuric acid concentration of the curing solution for curing treatment is 90 - 100 g / L, and the Cu 2+ concentration is 50 - 60 g / L;

[0023] Surface rust prevention treatment. The template copper layer with a roughened layer is subjected to surface rust prevention treatment to obtain a copper foil without brownification.

[0024] The process of the pickling is as follows: sulfuric acid is used as the treatment liquid, and the two sides of the copper foil are sprayed or soaked for 10 - 30 seconds to remove surface impurities or oxide films. The treatment liquid is sulfuric acid with a concentration of 80 - 90 g / L, and the temperature of the treatment liquid is 35 - 45 °C.

[0025] The process of the surface rust prevention treatment is as follows: First, in an electrolytic solution with a sulfuric acid concentration of 70 - 80 g / L and a cobalt concentration of 5 - 15 g / L, at an electrolytic temperature of 35 - 45 °C and a current density of 10 - 15 A / dm2, electroplate for 5 - 15 s; then, in an electrolytic solution with a sulfuric acid concentration of 80 - 90 g / L and a zinc concentration of 15 - 20 g / L, at an electrolytic temperature of 40 - 50 °C and a current density of 5 - 15 A / dm2, electroplate for 5 - 15 s.

[0026] The present invention also relates to a copper clad laminate, which comprises the copper foil without browning.

[0027] The present invention also relates to a printed circuit board, which comprises the copper foil without browning.

[0028] The present invention also relates to a manufacturing method of a printed circuit board, using the copper foil without browning to manufacture the printed circuit board.

[0029] The present invention has the following beneficial effects:

[0030] The present invention aims to simplify the browning step in the PCB processing and reduce the subsequent processing steps of the copper foil into a circuit board.

[0031] One side of the main body copper foil of the copper foil without browning of the present invention has a roughened copper particle surface prepared by the addition method, and the other side has a recessed roughened surface engraved by the template method. This recessed surface is conducive to increasing its bonding force with the semi-cured sheet substrate, so that the copper foil of the present invention does not require the browning etching treatment step during subsequent processing. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a schematic diagram of the copper foil structure of the present invention;

[0033] Figure 2 It is a schematic diagram of the copper foil circuit etching of the present invention;

[0034] Figure 3 It is an SEM morphology diagram of the non-browning layer.

[0035] Reference Signs:

[0036] 1 - template copper layer; 2 - high-temperature isolation coating; 3 - non-browning copper layer; 4 - roughened layer. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0037] In the description, claims and the above-mentioned drawings of the present invention, the terms "first", "second", "third", "fourth", etc. (if any) are used to distinguish similar objects and do not necessarily describe a specific order or sequence. In addition, the term "comprising" or "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device comprising a series of steps or units need not be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0038] The peel strength between the non-copper nodule roughened surface of the present invention and the semi-cured sheet substrate is mainly provided by the concave roughened surface caused by the peeling of the copper layer from the template. Another key point of the present invention is the separable performance after the copper foil and the semi-cured sheet substrate are laminated. Due to the enhanced thermal diffusion effect of substances at high temperatures, if the isolation layer 2 is not provided, the two copper foils will adhere to each other due to the diffusion effect, resulting in the situation where the copper layer cannot be separated from the template.

[0039] Example 1

[0040] This example provides a copper foil without brownization, which from bottom to top are a template copper layer, a high-temperature isolation coating, an ultra-thin copper layer, and a roughened layer. The preparation method of the copper foil without brownization is as follows:

[0041] a. Preparation of the template copper layer. The template copper layer is prepared through electrolysis equipment. The electrolyte is an aqueous solution of copper sulfate, which contains sulfuric acid with a concentration of 110 g / L and CuSO4·5H2O with a Cu ion concentration of 97 g / L. Electrolysis is carried out in the electrolyte at a temperature of 54 °C with a current density of 36 A / dm for 50 seconds to obtain a single-sided bright copper foil with a thickness of 18 μm. 2+ In the electrolyte at a temperature of 54 °C with a current density of 36 A / dm 2 for 50 seconds to obtain a single-sided bright copper foil with a thickness of 18 μm.

[0042] b. Roughening treatment of the template copper layer. After the single-sided bright copper layer is prepared, a roughened template copper nodule is prepared on its bright surface using an electrodeposition solution containing sulfuric acid with a concentration of 80 g / L and H2SO4·5H2O with a Cu ion concentration of 30 g / L, and copper particles in the shape of ellipsoids are formed on the surface. The electrodeposition temperature is 40 °C, the current density is 25 A / dm 2+ and the electrolysis time is 7 s to finally obtain the template copper layer. 2 for 7 s to finally obtain the template copper layer.

[0043] c. Pickling. After the template copper layer is prepared, the two sides of the copper foil are sprayed and soaked with sulfuric acid as the treatment liquid for 20 seconds to remove surface impurities or oxide films. The treatment liquid is sulfuric acid with a concentration of 85 g / L, and the temperature of the treatment liquid is 40 °C.

[0044] d. Preparation of high-temperature isolation coating. After removing impurities or oxide films on the surface of the copper foil, the copper foil is brought into the isolation coating solution for the preparation of the isolation coating. The isolation coating adsorption solution contains an aqueous solution of benzotriazole with a concentration of 3 g / L, the temperature of the adhesion solution is 35 °C, and the soaking adhesion time is 20 s. After drying by blowing in a blast drying oven at 150 °C, the isolation coating is obtained.

[0045] e. Preparation of the copper layer without brownification. After the isolation coating is air-dried, the copper foil is brought into a solution containing sulfuric acid with a concentration of 110 g / L and Cu 2+ ions with a concentration of 97 g / L of H2SO7·5H2O. Electrolysis is carried out in an electrolyte solution at a temperature of 54 °C with a current density of 20 A / dm 2 for 18 seconds to obtain a main body for use, a copper foil layer without brownification with a thickness of 5.0 μm.

[0046] f. Preparation of the surface roughening layer. After the electroplating of the copper foil layer without brownification is completed, a copper sulfate solution with a sulfuric acid concentration of 90 g / L and a Gu 2+ ion concentration of 25 g / L is used for electroplating the roughening layer. The copper foil is introduced into it, with the copper foil layer without brownification facing the anode plate and the template copper foil layer away from the anode plate. Electroplating is carried out at an average current density of 14 A / dm 2 for 12 s to obtain fine copper nodule particles with a rough surface. Then the copper foil is introduced into a copper sulfate solution with a sulfuric acid concentration of 95 g / L and a Cu 2+ ion concentration of 55 g / L for solidification electroplating, with an electroplating current density of 15 A / dm 2 and an electroplating time of 15 s.

[0047] g. Surface rust prevention treatment. After the roughening process, the copper foil is treated in an electrolyte solution with a sulfuric acid concentration of 75 g / L, a cobalt concentration of 10 g / L, an electrolysis temperature of 40 °C, and a current density of 12 A / dm 2 for 10 s; then in an electrolyte solution with a sulfuric acid concentration of 85 g / L, a zinc concentration of 18 g / L, and an electrolysis temperature of 45 °C, with a current density of 10 A / dm 2 for 10 s. Finally, after spraying and washing with water and drying in an oven, the electrolyte or water stains on the surface of the copper foil are removed.

[0048] The uneven surface of the copper foil with depression and roughening without brownification in this example is measured by an OLS5100 laser confocal microscope. The ten-point height of unevenness Rz is 1.2 μm, the maximum profile valley depth Rv is 0.8 μm, and the interface expansion area ratio Sdr is 9.7%. The copper clad laminate prepared from this copper foil is made into a circuit through steps such as covering with a dry film, exposure, development, and etching. After the dry film is removed, the outer surface of the circuit still retains the depressed roughened structure. At this time, the copper clad laminate can be directly laminated with the semi-cured sheet and a stable bonding force can be obtained.

[0049] The determination method for stable separation force is as follows: 1. After directly laminating the sunken roughened surface with the prepreg, thicken the surface copper foil to 35 μm and then test the peel strength. The peel strength with the prepreg of Fr-4 type ≥ 0.6 N / mm; 2. After tin floating at 288 °C for 3 times, there is no board splitting or board explosion phenomenon, and the peel strength with the prepreg of Fr-4 type ≥ 0.5 N / mm;

[0050] Example 2

[0051] The difference between this Example 2 and Example 1 lies in that during the roughening treatment of the template copper layer in step b, the Cu 2+ ion concentration is 50 g / L and the electrodeposition time is 5 s. The surface roughness Rz of the sunken roughened surface of the copper foil without browning of this sample is 1.4 μm, the maximum profile valley depth Rv is 0.64 μm, and the interface expansion area ratio Sdr is 8.9%. After peeling off the template copper layer of this sample, directly laminate the sunken roughened surface with the prepreg, then thicken the surface copper foil to 35 μm and test the peel strength. The peel strength with the prepreg of Fr-4 type is 0.6 N / mm; 2. After tin floating at 288 °C for 3 times, there is no board splitting or board explosion phenomenon, and the peel strength with the prepreg of Fr-4 type is 0.51 N / mm;

[0052] Example 3

[0053] The difference between this Example 3 and Example 1 lies in that during the roughening treatment of the template copper layer in step b, the Cu 2+ ion concentration is 35 g / L and the electrodeposition time is 5 s. The surface roughness Rz of the sunken roughened surface of the copper foil without browning of this sample is 2.0 μm, the maximum profile valley depth Rv is 0.98 μm, and the interface expansion area ratio Sdr is 13.3%. After peeling off the template copper layer of this sample, directly laminate the sunken roughened surface with the prepreg, then thicken the surface copper foil to 35 μm and test the peel strength. The peel strength with the prepreg of Fr-4 type is 0.64 N / m; 2. After tin floating at 288 °C for 3 times, there is no board splitting or board explosion phenomenon, and the peel strength with the prepreg of Fr-4 type is 0.55 N / mm;

[0054] Comparative Example 1

[0055] The difference between this Comparative Example 1 and Example 1 is that during the production process of the copper foil, the preparation of the roughened copper nodules on the template copper layer in step b is not carried out, which is consistent with the prior art. The surface roughness Rz of the corresponding surface of this sample with the surface without browning is 1.0 μm, and its peel strength with the prepreg of Fr-4 type is 0.22 N / mm; board splitting occurs after tin floating at 288 °C for 3 times.

[0056] Comparative Example 2

[0057] The difference between Comparative Example 2 and Example 1 is that no template layer was used in the copper foil manufacturing process. The roughness Rz of the surface corresponding to the copper foil without brownification is 1.0 μm, and its peel strength with the Fr-4 type prepreg is 0.23 N / m; it delaminated after 3 times of solder dipping at 288°C.

[0058] Comparative Example 3

[0059] The difference between Comparative Example 3 and Example 1 is that no high-temperature isolation layer was prepared during the copper foil manufacturing process. After the copper foil was laminated, the template could not be removed, and the results could not be tested.

[0060] Table 1. Roughness and peel strength of the roughened surface of the copper foil with depressions

[0061]

[0062] A schematic diagram of the copper foil structure without brownification according to the present invention is as Figure 1 shown. A schematic diagram of the copper foil circuit etching according to the present invention is as Figure 2 shown. Before manufacturing the copper foil, a template copper layer is first manufactured. The surface of the template copper layer has spherical copper particles deposited by electroplating. The copper particles are closely attached to the template copper layer. See Figure 3 SEM morphology of the template layer a. Example 1; b. Comparative Example 1. Secondly, an isolation coating capable of providing high-temperature separation performance is attached to the surface of the copper particles. The purpose of this coating is to isolate the template copper layer from the copper layer without brownification. During use, first, the roughened copper nodule particle-treated surface of the copper layer is hot-pressed with the substrate. After the pressing is completed, the template copper layer is peeled off to obtain a copper-clad laminate with a roughened surface showing depressions on the outer surface. The circuit is prepared on the surface of the copper-clad laminate through steps such as covering with a dry film, exposure, development, and etching. After the dry film is removed, the roughened structure with depressions still remains on the outer surface of the circuit. At this time, the copper-clad laminate can be directly pressed with the prepreg, and a stable bonding force can be obtained.

[0063] As described above, the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A copper foil without brownization treatment, characterized in that, The copper foil is composed of a template copper layer, a high-temperature isolation coating, a brownless copper layer, and a roughened layer from bottom to top.

2. The copper foil without browning according to claim 1, characterized in that, The surface roughness of the template copper layer is Rz 0.8 - 2.5 μm, Rv 0.6 - 1.3 μm, and Sdr 8.0 - 15%.

3. The copper foil without brownization according to claim 1, wherein The surface roughness of the side of the brownless copper layer close to the template copper layer is Rz 0.8 - 2.5 μm, Rv 0.6 - 1.3 μm, and Sdr 8.0 - 15%.

4. A copper foil without brownification according to claim 1, characterized in that, After laminating the side of the brownless copper layer close to the template copper layer with a prepreg, when the surface copper foil is thickened to 35 μm, the peel strength ≥ 0.6 N / m; after tin floating at 288°C for 3 times, there is no board separation and board explosion phenomenon, and the peel strength ≥ 0.5 N / m.

5. A manufacturing method of a copper foil without browning, characterized in that, It includes the following steps: Preparation of the template copper layer, electrolytic treatment of the template copper layer, the sulfuric acid concentration of the electrolyte for the electrolytic treatment is 100 - 120 g / L, Cu 2+ concentration is 95 - 100 g / L, temperature is 50 - 60 °C, current density is 30 - 40 A / dm 2 , and a single-sided bright copper foil is obtained; Roughening treatment of the template copper layer, electroplating treatment is carried out on the bright surface of the single-sided bright copper layer, and the parameters of the electroplating treatment are: the concentration of sulfuric acid is 60-90 g / L, and the Cu 2+ concentration is 30-50 g / L, the temperature is 35-45 °C, the current density is 20-30 A / dm 2 , the electrolysis time is 5-7 s, and a roughened template copper layer is obtained; Pickle the roughened template copper layer. After pickling, prepare the high-temperature isolation coating. The adhering liquid of the isolation coating is an aqueous solution of benzotriazole with a concentration of 2 - 4 g / L, the temperature is 30 - 40°C, the soaking time is 15 - 25 s, and then it is dried by blowing in a blast oven at 140 - 160°C to obtain a template copper layer with an isolation coating. Preparation of copper layer without browning: electroplating treatment is carried out on the template copper layer with an isolation coating to obtain a template copper layer with a copper foil layer without browning. The electroplating treatment parameters are as follows: the concentration of sulfuric acid in the electrolyte is 100-120 g / L, and the concentration of Cu 2+ is 95-100 g / L, the temperature is 50-60 °C, and the current density is 15-25 A / dm 2 ; Preparation of the surface roughening layer: roughening treatment and curing treatment are carried out on the surface of the template copper layer with a copper foil layer without brownization to obtain a template copper layer with a roughening layer. The sulfuric acid concentration of the roughening solution for the roughening treatment is 85 - 95 g / L, and the Cu 2+ concentration is 20 - 30 g / L. The sulfuric acid concentration of the curing solution for the curing treatment is 90 - 100 g / L, and the Cu 2+ concentration is 50 - 60 g / L; Surface anti-rust treatment. Perform surface anti-rust treatment on the template copper layer with a roughened layer to obtain a brownless copper foil.

6. The manufacturing method of a copper foil without brownization according to claim 5, characterized in that, The process of the pickling is as follows: Use sulfuric acid as the treatment liquid, spray or soak both sides of the copper foil for 10 - 30 seconds to remove surface impurities or oxide films. The treatment liquid is sulfuric acid with a concentration of 80 - 90 g / L, and the temperature of the treatment liquid is 35 - 45°C.

7. The manufacturing method of a copper foil without brownification according to claim 5, characterized in that, The process of the surface anti-rust treatment is as follows: First, in an electrolytic solution with a sulfuric acid concentration of 70 - 80 g / L and a cobalt concentration of 5 - 15 g / L, at an electrolytic temperature of 35 - 45°C and a current density of 10 - 15 A / dm2, perform electroplating treatment for 5 - 15 s. Then, in an electrolytic solution with a sulfuric acid concentration of 80 - 90 g / L and a zinc concentration of 15 - 20 g / L, at an electrolytic temperature of 40 - 50°C and a current density of 5 - 15 A / dm2, perform electroplating treatment for 5 - 15 s.

8. A copper clad laminate, characterized in that, It has the brownless copper foil described in any one of claims 1 to 4.

9. A printed circuit board, characterized in that, It has the brownless copper foil described in any one of claims 1 to 4.

10. A manufacturing method of a printed circuit board, characterized in that, Use the brownless copper foil described in any one of claims 1 to 4 to manufacture a printed circuit board.

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