An ultra-low profile RTF copper foil surface treatment process

Abstract

The application discloses a kind of ultra-low profile RTF copper foil surface treatment processes, comprising the following steps: S1, select the RTF copper foil green foil with roughness Ra≤0.15 μm, roughness Rz≤2.5 μm of smooth surface as base material;S2, the base material in step S1 is sequentially subjected to micro-etching pretreatment, copper tumor layer generation processing, composite heat-resistant layer generation processing, oxidation prevention layer generation processing, coupling layer generation processing;S3, the base material after being treated in step S2 is subjected to drying treatment, and the finished product is obtained after drying.The process in the application adopts micro-etching, tumor, heat resistance, oxidation prevention, organic end-capping treatment process, saves intermediate water washing standing process, can avoid copper foil secondary oxidation, improve the heat resistance, oxidation resistance and resin bonding force of copper foil, the electrolyte used for tumor treatment can form ultra-fine, uniform copper tumor layer on copper foil, realize the ultra-low profile of copper foil.

Description

Technical Field

[0001] This invention relates to the field of RTF copper foil processing technology, and in particular to a surface treatment process for ultra-low profile RTF copper foil. Background Technology

[0002] The development of high-frequency and high-speed PCB technology has put forward core requirements for copper foil used in copper-clad laminates, such as ultra-low profile, low signal transmission loss, and high resin bonding strength. Polyphenylene ether resin has become the mainstream substrate for high-frequency and high-speed copper-clad laminates due to its excellent dielectric properties and simple molding process. However, its interfacial bonding with copper foil has extremely high requirements for the surface morphology of copper foil. Existing surface treatment technologies for RTF copper foil have a series of shortcomings: for example, the copper nodule layer in the nodule treatment has a large particle size and uneven distribution, resulting in a high copper foil profile value, which exacerbates the skin effect during high-frequency signal transmission and leads to large transmission loss. The electrolyte and process parameters in the roughening, heat resistance, and anti-oxidation steps are poorly matched, which easily leads to problems such as copper nodule layer peeling off and insufficient heat resistance. At present, although there are nodule electrolytes and roughening processes for ultra-low profile copper foil, an orderly and complete processing system has not been formed, making it difficult to simultaneously meet the requirements of ultra-low profile and low transmission loss.

[0003] To address these issues, we propose an ultra-low profile RTF copper foil surface treatment process. Summary of the Invention

[0004] The purpose of this invention is to provide an ultra-low profile RTF copper foil surface treatment process to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: A surface treatment process for ultra-low profile RTF copper foil includes the following steps: S1. Select RTF copper foil with a smooth surface roughness Ra≤0.15μm and a rough surface roughness Rz≤2.5μm as the substrate; S2. The substrate in step S1 is subjected to micro-etching pretreatment, copper nodule layer formation treatment, composite heat-resistant layer formation treatment, anti-oxidation layer formation treatment, and coupling layer formation treatment in sequence. S3. The substrate processed in step S2 is dried to obtain the finished product.

[0006] Furthermore, in step S2, the pretreatment for micro-etching uses a sulfuric acid-hydrogen peroxide micro-etching solution. The concentration of H2SO4 in the micro-etching solution is 80~120 g / L, the concentration of H2O2 is 10~30 g / L, the treatment temperature is 25~30℃, the treatment time is 1~3 s, and the micro-etching amount is controlled at 0.5~1.0 g / m³. 2 .

[0007] Furthermore, in step S2, the copper nodule layer formation process employs an electrolyte solution for electroplating. This electrolyte solution consists of CuSO4 at a concentration of 70-100 g / L, H2SO4 at a concentration of 80-130 g / L, sodium stannate at a concentration of 0.02-0.1 g / L, and glucose at a concentration of 2-6 g / L. The electroplating current density is 8-15 A / dm³. 2 The processing time is 3~8s, the electroplating temperature is 25~35℃, and a uniform copper nodule layer with a particle size of 0.5~1.0μm is formed on the smooth surface of the copper foil.

[0008] Furthermore, in step S2, the composite heat-resistant layer formation process involves simultaneously electroplating both the smooth and rough surfaces of the copper foil with a non-magnetic element electroplating solution. The electroplating solution consists of ZnSO4 at a concentration of 50-90 g / L, indium sulfate at a concentration of 0.05-0.2 g / L, and potassium sodium tartrate at a concentration of 80-150 g / L, with a current density of 0.5-1.5 A / dm³. 2 The processing time is 2~5s, forming a zinc-indium composite heat-resistant layer with a thickness of 0.1~0.3μm.

[0009] Furthermore, in step S2, the anti-oxidation layer formation process employs low-concentration chromium plating solution electroplating, wherein the Cr content in the plating solution is... 6 + Concentration of 3~6 g / L, pH value of 3~5, electroplating current density of 2~4 A / dm 2 The processing time is 1~3s, forming a chromium-based anti-oxidation layer with a thickness of 0.05~0.1μm on the surface of the heat-resistant layer.

[0010] Furthermore, in step S2, the coupling layer formation process involves spraying a copper foil surface with an epoxy silane coupling agent solution containing 0.8% to 1.2% by mass, at a spraying amount of 5 to 10 mL / m. 2 The treatment temperature is 25~30℃, which forms an organic coupling layer on the surface of the anti-oxidation layer, thereby improving the interfacial bonding force with the resin.

[0011] Furthermore, in step S3, the drying is a segmented hot air drying process. The first stage of drying is at a temperature of 80~100℃ for 2~3 seconds; the second stage of drying is at a temperature of 120~150℃ for 3~5 seconds, and the moisture content of the finished copper foil is ≤0.05%.

[0012] Furthermore, in step S3, the ultra-low profile RTF copper foil obtained after drying has a smooth surface roughness Rz≤1.2μm and a rough surface roughness Rz≤2.4μm. Under 20GHz conditions, the 18μm copper foil transmission loss is <43dB / m and the 35μm copper foil transmission loss is <38dB / m. The peel strength with polyphenylene ether resin is ≥1.0N / mm, and there is no oxidation discoloration after 1h of heat resistance test at 180℃.

[0013] Compared with the prior art, the beneficial effects of the present invention are: The process in this invention employs micro-etching, nodulation, heat resistance, oxidation prevention, and organic end-capping treatment, eliminating the intermediate water washing and settling process. This avoids secondary oxidation of the copper foil, improves the heat resistance, oxidation prevention, and resin adhesion of the copper foil, and uses an electrolyte for nodulation treatment to form an ultra-fine and uniform copper nodule layer on the copper foil, achieving an ultra-low profile of the copper foil. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the process flow in this invention; Figure 2 This is a schematic diagram of the copper foil structure after processing in this invention.

[0015] In the diagram: 1. Substrate; 2. Copper nodule layer; 3. Composite heat-resistant layer; 4. Anti-oxidation layer; 5. Coupling layer. Detailed Implementation

[0016] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are used only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0017] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] Please see Figure 1 An ultra-low profile RTF copper foil surface treatment process is described below: The following steps are required: S1. Select RTF copper foil with a smooth surface roughness Ra≤0.15μm and a rough surface roughness Rz≤2.5μm as the substrate; S2. The substrate in step S1 is subjected to micro-etching pretreatment, copper nodule layer formation treatment, composite heat-resistant layer formation treatment, anti-oxidation layer formation treatment, and coupling layer formation treatment in sequence. S3. The substrate processed in step S2 is dried to obtain the finished product.

[0020] Furthermore, in step S2, the pretreatment for micro-etching uses a sulfuric acid-hydrogen peroxide micro-etching solution. The concentration of H2SO4 in the micro-etching solution is 80~120 g / L, the concentration of H2O2 is 10~30 g / L, the treatment temperature is 25~30℃, the treatment time is 1~3 s, and the micro-etching amount is controlled at 0.5~1.0 g / m³. 2 .

[0021] Furthermore, in step S2, the copper nodule layer formation process employs an electrolyte solution for electroplating. This electrolyte solution consists of CuSO4 at a concentration of 70-100 g / L, H2SO4 at a concentration of 80-130 g / L, sodium stannate at a concentration of 0.02-0.1 g / L, and glucose at a concentration of 2-6 g / L. The electroplating current density is 8-15 A / dm³. 2 The processing time is 3~8s, the electroplating temperature is 25~35℃, and a uniform copper nodule layer with a particle size of 0.5~1.0μm is formed on the smooth surface of the copper foil.

[0022] Furthermore, in step S2, the composite heat-resistant layer formation process involves simultaneously electroplating both the smooth and rough surfaces of the copper foil with a non-magnetic element electroplating solution. The electroplating solution consists of ZnSO4 at a concentration of 50-90 g / L, indium sulfate at a concentration of 0.05-0.2 g / L, and potassium sodium tartrate at a concentration of 80-150 g / L, with a current density of 0.5-1.5 A / dm³. 2 The processing time is 2~5s, forming a zinc-indium composite heat-resistant layer with a thickness of 0.1~0.3μm.

[0023] Furthermore, in step S2, the anti-oxidation layer formation process employs low-concentration chromium plating solution electroplating, wherein the Cr content in the plating solution is... 6 + Concentration of 3~6 g / L, pH value of 3~5, electroplating current density of 2~4 A / dm 2 The processing time is 1~3s, and a chromium-based anti-oxidation layer with a thickness of 0.05~0.1μm is formed on the surface of the heat-resistant layer.

[0024] Furthermore, in step S2, the coupling layer formation process involves spraying a copper foil surface with an epoxy silane coupling agent solution containing 0.8% to 1.2% by mass, at a spraying amount of 5 to 10 mL / m. 2The processing temperature is 25~30℃, and an organic coupling layer 5 is formed on the surface of the anti-oxidation layer to enhance the interfacial bonding force with the resin.

[0025] Furthermore, in step S3, the drying is a segmented hot air drying process. The first stage of drying is at a temperature of 80~100℃ for 2~3 seconds; the second stage of drying is at a temperature of 120~150℃ for 3~5 seconds, and the moisture content of the finished copper foil is ≤0.05%.

[0026] Furthermore, in step S3, the ultra-low profile RTF copper foil obtained after drying has a smooth surface roughness Rz≤1.2μm and a rough surface roughness Rz≤2.4μm. Under 20GHz conditions, the 18μm copper foil transmission loss is <43dB / m and the 35μm copper foil transmission loss is <38dB / m. The peel strength with polyphenylene ether resin is ≥1.0N / mm, and there is no oxidation discoloration after 1h of heat resistance test at 180℃.

[0027] Example 1 Surface treatment was performed using 18μm RTF copper foil with a smooth surface roughness Ra=0.12μm and a rough surface roughness Rz=2.2μm as the substrate: S1. Micro-etching pretreatment: H2SO4 100g / L, H2O2 20g / L, 28℃, treatment for 2s, micro-etching amount 0.8g / m 2 ; S2. Precision nodule treatment: CuSO4 80g / L, H2SO4 100g / L, sodium stannate 0.05g / L, glucose 4g / L, current density 12A / dm³ 2 Process for 5 seconds at 30°C; S3, Non-magnetic heat-resistant layer electroplating: ZnSO4 70g / L, Indium sulfate 0.1g / L, Potassium sodium tartrate 120g / L, Current density 1.0A / dm³ 2 Processing time: 3 seconds; S4, Low-chromium anti-oxidation treatment: Cr 6 + 4g / L, pH=4, current density 3A / dm³ 2 Processing time: 2 seconds; S5, Silane Organic End-Capping: 1.0% epoxy silane coupling agent solution, spraying amount 8mL / m 2 28℃; S6. Segmented drying: First segment 90℃, 2s; Second segment 130℃, 4s.

[0028] The prepared 18μm ultra-low profile RTF copper foil has a smooth surface Rz=1.0μm and a rough surface Rz=2.3μm. The transmission loss at 20GHz is 41dB / m, the peel strength with polyphenylene ether resin is 1.2N / mm, it can withstand heat at 180℃ for 1h without discoloration, and it can be stored at room temperature for 6 months without oxidation.

[0029] Example 2 Surface treatment was performed using 35μm RTF copper foil with a smooth surface roughness Ra=0.14μm and a rough surface roughness Rz=2.4μm as the substrate: S1. Pretreatment for micro-etching: 90g / L H2SO4, 15g / L H2O2, 26℃, treatment for 1.5s, micro-etching amount 0.6g / m 2 ; S2. Precision tumor treatment: CuSO4 90g / L, H2SO4 120g / L, sodium stannate 0.08g / L, glucose 5g / L, current density 10A / dm³ 2 Processing time: 6 seconds, 32°C; S3, Non-magnetic heat-resistant layer electroplating: ZnSO4 80g / L, Indium sulfate 0.15g / L, Potassium sodium tartrate 100g / L, Current density 1.2A / dm³ 2 Processing time: 4 seconds; S4, Low-chromium anti-oxidation treatment: Cr 6 + 5 g / L, pH=3.5, current density 2.5 A / dm³ 2 Processing time: 1.5 seconds; S5, Silane organic end-capping: 0.9% epoxy silane coupling agent solution, spraying amount 6mL / m 2 27℃; S6. Segmented drying: First segment 85℃, 3s; Second segment 140℃, 3s.

[0030] The prepared 35μm ultra-low profile RTF copper foil has a smooth surface Rz=1.1μm and a rough surface Rz=2.4μm. The transmission loss at 20GHz is 36dB / m, the peel strength with polyphenylene ether resin is 1.1N / mm, it can withstand heat at 180℃ for 1h without discoloration, and it can be stored at room temperature for 6 months without oxidation.

[0031] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0032] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A surface treatment process for ultra-low profile RTF copper foil, characterized in that: Includes the following steps: S1. Select RTF copper foil with a smooth surface roughness Ra≤0.15μm and a rough surface roughness Rz≤2.5μm as the substrate; S2. The substrate in step S1 is subjected to micro-etching pretreatment, copper nodule layer formation treatment, composite heat-resistant layer formation treatment, anti-oxidation layer formation treatment, and coupling layer formation treatment in sequence. S3. The substrate processed in step S2 is dried to obtain the finished product.

2. The ultra-low profile RTF copper foil surface treatment process according to claim 1, characterized in that: In step S2, the pretreatment for micro-etching uses a sulfuric acid-hydrogen peroxide micro-etching solution. The concentration of H2SO4 in the micro-etching solution is 80~120 g / L, the concentration of H2O2 is 10~30 g / L, the treatment temperature is 25~30℃, the treatment time is 1~3 s, and the micro-etching amount is controlled at 0.5~1.0 g / m³. 2 .

3. The ultra-low profile RTF copper foil surface treatment process according to claim 1, characterized in that: In step S2, the copper nodule layer formation process involves electroplating with an electrolyte solution. The electrolyte solution consists of CuSO4 at a concentration of 70-100 g / L, H2SO4 at a concentration of 80-130 g / L, sodium stannate at a concentration of 0.02-0.1 g / L, and glucose at a concentration of 2-6 g / L. The electroplating current density is 8-15 A / dm³. 2 The processing time is 3~8s, the electroplating temperature is 25~35℃, and a uniform copper nodule layer with a particle size of 0.5~1.0μm is formed on the smooth surface of the copper foil.

4. The ultra-low profile RTF copper foil surface treatment process according to claim 1, characterized in that: In step S2, the composite heat-resistant layer formation process involves simultaneously electroplating both the smooth and rough surfaces of the copper foil with a non-magnetic element electroplating solution. The electroplating solution consists of ZnSO4 at a concentration of 50-90 g / L, indium sulfate at a concentration of 0.05-0.2 g / L, and potassium sodium tartrate at a concentration of 80-150 g / L, with a current density of 0.5-1.5 A / dm³. 2 The processing time is 2~5s, forming a zinc-indium composite heat-resistant layer with a thickness of 0.1~0.3μm.

5. The ultra-low profile RTF copper foil surface treatment process according to claim 1, characterized in that: In step S2, the anti-oxidation layer formation process uses a low-concentration chromium plating solution for electroplating, wherein the chromium content in the plating solution is... 6 + Concentration of 3~6 g / L, pH value of 3~5, electroplating current density of 2~4 A / dm 2 The processing time is 1~3s, forming a chromium-based anti-oxidation layer with a thickness of 0.05~0.1μm on the surface of the heat-resistant layer.

6. The ultra-low profile RTF copper foil surface treatment process according to claim 1, characterized in that: In step S2, the coupling layer formation process involves spraying a copper foil surface with an epoxy silane coupling agent solution containing 0.8% to 1.2% by mass, at a spraying amount of 5 to 10 mL / m. 2 The treatment temperature is 25~30℃, which forms an organic coupling layer on the surface of the anti-oxidation layer, thereby improving the interfacial bonding force with the resin.

7. The ultra-low profile RTF copper foil surface treatment process according to claim 1, characterized in that: In step S3, the drying is a segmented hot air drying process. The first stage of drying is at a temperature of 80~100℃ for 2~3 seconds; the second stage of drying is at a temperature of 120~150℃ for 3~5 seconds. The moisture content of the finished copper foil is ≤0.05%.

8. The ultra-low profile RTF copper foil surface treatment process according to claim 1, characterized in that: In step S3, the ultra-low profile RTF copper foil obtained after drying has a smooth surface roughness Rz≤1.2μm and a rough surface roughness Rz≤2.4μm. Under 20GHz conditions, the 18μm copper foil has a transmission loss of <43dB / m and the 35μm copper foil has a transmission loss of <38dB / m. The peel strength with polyphenylene ether resin is ≥1.0N / mm, and there is no oxidation discoloration after 1h of heat resistance test at 180℃.

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