Protection method for pyrophosphate copper plating of aluminum substrate

Abstract

The invention discloses a protection method for pyrophosphate copper plating of an aluminum substrate, which relates to the technical field of metal-based copper-clad plate processing, and comprises the following steps of: firstly, performing mechanical drilling according to requirements, pasting a layer of high-temperature adhesive tape on the aluminum substrate surface for protection after removing surface burrs left by drilling, and performing browning treatment on the copper foil layer surface; a layer of high-temperature adhesive tape is attached to the plate face of the copper foil layer, windowing is conducted through laser, holes needing to be pre-plated are exposed, and then copper pre-plating is conducted on the protected aluminum substrate; before copper pre-plating, in order to improve the binding force between the aluminum substrate and a copper plating layer, the aluminum substrate needs to be subjected to zinc immersion and chemical nickel treatment twice, in the process, a high-temperature adhesive tape plays a first protection role and protects the plate surface of a copper foil layer from reacting, and then an organic oxidation film and CuO on the surface of a brownification layer play a second protection role and can completely block permeation of zinc and nickel layers, so that the bonding force between the aluminum substrate and the copper plating layer is improved. And the copper foil layer plate surface is effectively protected from being subjected to nickel melting in the machining process, so that an ideal copper surface state is obtained.

Description

Technical Field

[0001] The invention relates to the technical field of metal-based copper-clad plate processing, and in particular to a protection method for pyrophosphate copper plating of an aluminum substrate. Background Art

[0002] Aluminum substrates are widely used in LED packaging and communication products due to their efficient heat dissipation characteristics. Generally, single-sided aluminum substrates are composed of three layers, namely the circuit layer (copper foil), the insulating layer (dielectric) and the aluminum base layer. When the insulating layer dielectric contains polytetrafluoroethylene, the aluminum substrate needs to be metallized after drilling during the processing and manufacturing process to achieve the conduction of the upper and lower layer signals. Because the aluminum base part of the hole wall reacts with the alkaline copper plating solution, it is necessary to pre-plate a thin layer of copper on the surface of the aluminum base hole wall after drilling to protect the aluminum base part from being dissolved by the reaction in the alkaline environment such as subsequent copper plating. Then, the part containing polytetrafluoroethylene dielectric is plasma modified to enhance the bonding strength between the dielectric and copper. Finally, the aluminum substrate is subjected to copper plating and electroplating thickening. During the pre-copper plating process of the aluminum substrate, the copper surface needs to be protected to prevent nickel from penetrating during the process, which causes the subsequent nickel layer to cover the copper surface and fail to etch the required pattern.

[0003] The traditional protection method is to directly stick a layer of high-temperature tape on the copper surface during pyrophosphate copper plating, then open a window in the tape to expose the hole part, and then pre-plating. However, in this process, the high-temperature tape at the hole mouth is often prone to bubbling and floating when the bath liquid is above 80°C due to bonding problems, resulting in nickel exposure at the hole mouth and part of the copper surface area after pre-copper plating. Due to the high hardness of the nickel layer, it is very difficult to remove it later. At present, it can only be removed by grinding, and the copper surface is easily exposed to the medium during the operation, affecting the reliability of product processing. Summary of the invention

[0004] The object of the present invention is to provide a protection method for pyrophosphate copper plating of aluminum substrates to solve the following technical problems:

[0005] How to prevent nickel infiltration on the copper foil layer of aluminum substrate during pyrophosphate copper plating?

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] A method for protecting an aluminum substrate from pyrophosphate copper plating, wherein the aluminum substrate comprises an aluminum base layer, an insulating layer and a copper foil layer stacked in sequence, and the method is performed in the following steps:

[0008] S1: Mechanically drill holes on the aluminum substrate according to design requirements;

[0009] S2: After mechanical drilling, deburr the aluminum base plate surface to level the burrs left by mechanical drilling at the hole mouth;

[0010] S3: After deburring, a layer of high temperature tape is attached to the aluminum substrate surface for protection to prevent the aluminum substrate surface from reacting with the browning solution during the subsequent browning process;

[0011] S4: After attaching a layer of high temperature tape on the aluminum base plate surface, the copper foil layer of the aluminum base plate is subjected to browning treatment to form a browning layer. Under the action of the browning treatment, a rough organic oxide film + CuO is formed on the surface of the browning layer;

[0012] S5: After the browning treatment, a layer of high temperature tape is pasted on the browning layer, and the bubbles between the high temperature tape and the browning layer are discharged to make the high temperature tape and the browning layer more closely bonded;

[0013] S6: After pasting a layer of high temperature tape on the browning layer, a window is opened between the aluminum base plate surface and the high temperature tape on the browning layer to expose the drilled hole;

[0014] S7: After opening the window, the aluminum substrate is pre-plated with pyrophosphate copper;

[0015] S8: After the copper is pre-plated, the high temperature tape on the browning layer and the browning layer on the copper foil layer are removed in sequence;

[0016] S9: After removing the high-temperature tape and the browning layer in turn, the aluminum substrate is electroplated with copper throughout the board to prevent the pre-plated copper in the hole from being resistant to the attack of the chemical solution during the subsequent copper micro-etching process;

[0017] S10: After the entire board is electroplated with copper, the surface of the aluminum substrate is subjected to plasma modification treatment, thereby increasing the surface activity of the dielectric part in the holes of the aluminum substrate;

[0018] S11: After the plasma modification treatment, the aluminum substrate is subjected to hole metallization treatment, and copper is plated in the holes to meet the design requirements.

[0019] In a further embodiment of the present invention, the insulating layer contains polytetrafluoroethylene.

[0020] In a further embodiment of the present invention: in step S2, the aluminum base plate surface is deburred by a deburring machine, and the horizontal line speed of the deburring machine is 2500±500 mm / min and the pressure is 0.3±0.1 MPa.

[0021] In a further embodiment of the present invention: in step S3 and step S5, the thickness of the high temperature tape is 50-100 um.

[0022] In a further embodiment of the present invention: in step S4, the treatment liquid components used in the browning treatment include browning stock solution, Ar grade hydrogen peroxide and sulfuric acid; wherein each 1L of treatment liquid contains 90-110mL of browning stock solution, 30-40mL of Ar grade hydrogen peroxide and 115-135mL of sulfuric acid.

[0023] In a further embodiment of the present invention, the browning stock solution is BondFilm Part APlus.

[0024] In a further embodiment of the present invention: in step S5, bubbles between the high temperature tape and the copper foil layer surface are removed by a laminator.

[0025] In a further embodiment of the present invention: in step S6, the window opening method is: using a laser to perform laser window opening;

[0026] Furthermore, the laser is an ultraviolet laser, and the cutting power during laser window opening is 33%, the frequency is 1000KHz, the marking speed is 1200mm / s, the marking delay is 500us, the jump speed is 3000mm / s, and the jump delay is 500us; when the laser is turned on / off, the cutting parameters should be adjusted accordingly as the laser energy fluctuates during cutting; the number of cutting times is 4-8 times, and during the cutting process, the flatness of the honeycomb pad is checked to maintain a precise and consistent focal depth, ultimately ensuring the uniformity of the cutting.

[0027] In a further embodiment of the present invention, the pre-copper plating step includes: degreasing, etching, primary zinc immersion, nitric acid stripping, secondary zinc immersion, chemical nickel, and pyrophosphate copper plating.

[0028] In a further embodiment of the present invention: in step S8, the brown layer is removed by a deburring machine with a brush, and the horizontal line speed of the deburring machine is 2500±500 mm / min and the pressure is 0.3±0.1 MPa.

[0029] Beneficial effects of the present invention:

[0030] The present invention prepares an aluminum substrate to be processed, mechanically drills holes on it as required, removes burrs on the board surface left by the drilling, and then affixes a layer of high-temperature tape to the aluminum base board surface for protection, and performs browning treatment on the copper foil layer board surface, and a layer of high-temperature tape is affixed to the copper foil layer board surface and a window is opened by laser to expose the holes to be pre-plated, and then the protected aluminum substrate is pre-plated with copper; before pre-plating with copper, in order to improve the bonding strength between the aluminum substrate and the copper-plated layer, the aluminum substrate needs to be subjected to zinc immersion + chemical nickel treatment twice, in which the high-temperature tape plays a first-layer protective role, protecting the copper foil layer board surface from being reacted, and then the organic oxide film + CuO on the surface of the browning layer plays a second-layer protective role, which can completely block the infiltration of zinc and nickel layers, and effectively protect the copper foil layer board surface from being nickel-plated during the processing; after the pre-plating is completed, the copper surface tape and the browning layer are removed, and an ideal copper surface state can be obtained, which lays a good foundation for subsequent copper electroplating and pattern production, fundamentally ensures product quality, and reduces processing difficulty. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The present invention will be further described below in conjunction with the accompanying drawings.

[0032] Figure 1 It is a flow chart of the protection method of pyrophosphate copper plating on aluminum substrate of the present invention;

[0033] Figure 2 It is a schematic diagram of the principle of the protection method of pyrophosphate copper plating on an aluminum substrate of the present invention;

[0034] Figure 3 It is a schematic diagram of the copper foil layer board surface after the browning layer is brushed off in one embodiment of the present invention. DETAILED DESCRIPTION

[0035] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0036] See also Figure 1-2 As shown, the present invention is a protection method for pyrophosphate copper plating of an aluminum substrate, wherein the aluminum substrate is composed of an aluminum base layer, an insulating layer and a copper foil layer stacked in sequence, wherein the insulating layer contains polytetrafluoroethylene material; the method is performed in the following steps:

[0037] Step 1: Select an aluminum substrate of Rogers RT6010, with a size of 300×300mm, an aluminum base layer thickness of 1.5mm, and an insulating layer dielectric thickness of 0.508mm; mechanically drill the aluminum substrate according to the design requirements. The design requirements here are: drill 200 holes with a diameter of 0.3mm on the aluminum substrate.

[0038] Step 2: After mechanical drilling, the aluminum substrate is placed with the aluminum base plate facing up, and the aluminum base plate surface is smoothed using a deburring machine (Shenzhen Tianhua Machinery Equipment Co., Ltd., model 19DB25DN01). The horizontal line speed of the deburring machine is 2800 mm / min, and the pressure is 0.3 MPa. After completion, the burrs left by the mechanical drilling at the hole mouth are smoothed.

[0039] Step 3: After deburring, a layer of high temperature tape is attached to the aluminum base plate for protection. The high temperature tape is a 50um thick high temperature tape produced by 3M China Co., Ltd.

[0040] Step 4: First, prepare the browning treatment solution by evenly mixing 100 mL of browning stock solution, 35 mL of Ar-grade hydrogen peroxide, 125 mL of sulfuric acid, and 740 mL of water. The browning stock solution is BondFilm Part A Plus produced by Antmei.

[0041] Next, the aluminum substrate was treated with browning using the 20BR15DNAA05 browning line produced by Dongguan Universe Circuit Board Company. The horizontal line speed of the browning line was 1.5m / min, so that the copper foil layer of the aluminum substrate reacted with the browning treatment liquid to form a browning layer, and a rough organic oxide film + CuO was formed on the surface of the browning layer. In this process, since the aluminum-based surface was affixed with high-temperature tape in advance, the aluminum-based surface would not react with the browning solution under the barrier of the high-temperature tape.

[0042] Step 5: After the browning treatment, a layer of high temperature tape is pasted on the browning layer. The high temperature tape is also a 50um thick high temperature tape produced by 3M China Co., Ltd. Then use the CST-M25E laminating machine produced by Zhisheng Technology to press twice, with a line speed of 1.0m / min and a pressure of 4kg / cm 2 , the temperature is 110℃, so as to discharge the bubbles between the high temperature tape and the browning layer, so that the high temperature tape and the browning layer are more closely combined;

[0043] Step 6: After sticking a layer of high-temperature tape on the browning layer, use the H5 laser equipment produced by Dezhong Laser Company to emit ultraviolet laser to align the drilling position to open the window; the cutting power of the laser is 33%, the frequency is 1000KHz, the marking speed is 1200mm / s, the marking delay is 500us, the jump speed is 3000mm / s, and the jump delay is 500us; when the laser is switched on and off, the cutting parameters should be adjusted accordingly as the laser energy fluctuates during cutting; the number of cuts is 4, and the flatness of the honeycomb pad is checked during the cutting process to maintain a precise and consistent depth of focus, ultimately ensuring the uniformity of the cutting; thereby exposing the drill hole.

[0044] Step 7: After the window is opened, the aluminum substrate is first degreased, etched, zinc-impregnated once, stripped with nitric acid, zinc-impregnated twice, and chemically nickel-impregnated, and finally pre-plated with pyrophosphate copper; conventional process methods in the prior art are used here, so they will not be described in detail here.

[0045] Step 8: After pre-copper plating, tear off the high-temperature tape on the brown layer, and then use a deburring machine to grind off the brown layer on the copper foil layer surface at a horizontal line speed of 2800mm / min and a pressure of 0.3Mpa; observe the copper foil layer surface, such as Figure 3 As shown, the copper foil layer has uniform copper foil coverage and no nickel plating occurs.

[0046] Step 9: After removing the high-temperature tape and the browning layer in turn, use the GN2021-06-2197 electroplating line produced by Huizhou Xinhuamei Company to electroplate copper with sulfate. The concentration of sulfuric acid is 120ml / L, the concentration of copper sulfate is 45g / L, the electroplating time is 30 minutes, and the current density is 1.2A / dm2 , to prevent the pre-plated copper in the hole from being resistant to the attack of chemical solution during the subsequent copper micro-etching process;

[0047] Step 10: After the whole board is electroplated with copper, the surface of the aluminum substrate is treated with plasma modification using the model GH-10M produced by Kunshan Guohua Company, with a N2 flow rate of 1000sccm, a H2 flow rate of 300sccm, an RF power of 8000W, and a treatment time of 30min, thereby improving the surface activity of the dielectric part in the holes of the aluminum substrate;

[0048] Step 11: After plasma modification, the aluminum substrate is treated with HFSEL-2201 copper deposition wire produced by Kunshan Broadcom Machinery for hole metallization. The copper ion concentration is 2.4g / L, the sodium hydroxide concentration is 12g / L, the formaldehyde content is 4.5g / L, and the EDTA concentration is 26g / L. A copper layer with a thickness of 0.8um is deposited on the dielectric surface in the hole, and then copper is plated for 100 minutes using an electroplating wire to meet the design requirements.

[0049] In the description of the present invention, it should be understood that the terms "upper", "lower", "left", "right", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, and a specific direction structure and operation, and therefore, cannot be understood as a limitation on the present invention. In addition, "first" and "second" are only for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0050] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", etc. should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0051] The above is a detailed description of an embodiment of the present invention, but the content is only a preferred embodiment of the present invention and cannot be considered to limit the scope of implementation of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the patent coverage of the present invention.

Claims

1. A method for protecting an aluminum substrate from pyrophosphate copper plating, wherein the aluminum substrate comprises an aluminum base layer, an insulating layer and a copper foil layer stacked in sequence, characterized in that: Follow the steps below: S1: Mechanically drill holes on the aluminum substrate according to design requirements; S2: Deburring the aluminum base plate surface; S3: Paste a layer of high temperature tape on the aluminum base plate; S4: performing browning treatment on the copper foil layer surface of the aluminum substrate to form a browning layer; S5: stick a layer of high temperature tape on the browning layer, and remove the bubbles between the high temperature tape and the browning layer; S6: Open windows on the aluminum base plate surface and the high temperature tape on the browning layer to expose the drilling holes; S7: Pre-plating the aluminum substrate with pyrophosphate copper; S8: removing the high temperature tape on the browning layer and the browning layer on the copper foil layer in sequence; S9: electroplating copper on the entire aluminum substrate; S10: performing plasma modification treatment on the surface of the aluminum substrate; S11: performing hole metallization processing on the aluminum substrate.

2. The method for protecting aluminum substrate from pyrophosphate copper plating according to claim 1, characterized in that: The insulating layer contains polytetrafluoroethylene.

3. The method for protecting aluminum substrate from pyrophosphate copper plating according to claim 1, characterized in that: In step S2, the aluminum base plate surface is deburred by a deburring machine, and the horizontal line speed of the deburring machine is 2500±500mm / min and the pressure is 0.3±0.1Mpa.

4. The method for protecting aluminum substrate from pyrophosphate copper plating according to claim 1, characterized in that: In step S3 and step S5, the thickness of the high temperature tape is 50-100 um.

5. The method for protecting aluminum substrate from pyrophosphate copper plating according to claim 1, characterized in that: In step S4, the treatment liquid components used in the browning treatment include browning stock solution, Ar grade hydrogen peroxide and sulfuric acid; wherein each 1L of treatment liquid contains 90-110mL of browning stock solution, 30-40mL of Ar grade hydrogen peroxide and 115-135mL of sulfuric acid.

6. The method for protecting aluminum substrate from pyrophosphate copper plating according to claim 5, characterized in that: The browning stock solution is BondFilm Part A Plus.

7. The method for protecting aluminum substrate from pyrophosphate copper plating according to claim 1, characterized in that: In step S5, air bubbles between the high temperature tape and the copper foil layer surface are removed by a laminator.

8. The method for protecting aluminum substrate from pyrophosphate copper plating according to claim 1, characterized in that: In step S6, the window opening method is: using a laser to perform laser window opening.

9. The method for protecting aluminum substrate from pyrophosphate copper plating according to claim 1, characterized in that: The steps of pre-copper plating include: degreasing, etching, primary zinc immersion, nitric acid stripping, secondary zinc immersion, chemical nickel, and pyrophosphate copper plating.

10. The method for protecting aluminum substrate from pyrophosphate copper plating according to claim 1, characterized in that: In step S8, the browning layer is removed by a deburring machine with a brush, and the horizontal line speed of the deburring machine is 2500±500 mm / min and the pressure is 0.3±0.1 MPa.

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