Circuit board manufacturing method

Abstract

The present application relates to a kind of circuit board preparation method, the circuit board preparation method includes the following circuit production steps: S1, the copper foil layer on the surface of circuit board is made metal protective layer, metal protective layer at least includes silver protective layer;S2, acid-resistant film is pasted on metal protective layer on the film, then exposure, development, so that the etching area of metal protective layer is exposed from film;S3, metal protective layer is electrolytic etched in acidic or neutral electrolyte, to remove the etching area of metal protective layer;S4, copper foil layer is etched in acid, to remove the area of copper foil layer exposed to film, form conductive circuit;S5, remove film.The preparation method of the present application can effectively solve the problem that silver protective layer is easily dirty and sulfidation yellow in prior art, improve the processing quality and yield of circuit board, and can realize the production of fine circuit.

Description

TECHNICAL FIELD

[0001] The present application relates to a circuit board manufacturing method. BACKGROUND

[0002] In the process of manufacturing circuit board, it is necessary to make a metal protective layer such as an oxidation-resistant layer on the surface of the outer layer circuit (such as the surface of the solder pad exposed to the solder resist layer) in many cases, which usually includes a silver protective layer, typically a combination of a nickel protective layer and a silver protective layer. Among them, electroless nickel silver can ensure the flatness, brightness and high reflectivity of the silver surface, and has obvious advantages for products with high brightness and strict welding flatness requirements.

[0003] Chinese patent document CN113825321A discloses a circuit board manufacturing method, which includes the following circuit manufacturing steps: sequentially forming a seed layer and a copper film layer on a carrier of a circuit board; manufacturing a circuit pattern on the circuit board; filling blue glue in the non-circuit area of the circuit pattern; forming an oxidation-resistant layer on the surface of the circuit pattern in the circuit area, the oxidation-resistant layer being one or more of nickel, tin, gold and silver; removing the filled blue glue to obtain an oxidation-resistant circuit board.

[0004] In the prior art such as the above patent document, when manufacturing the outer layer circuit, the copper circuit is etched first, then the surface of the circuit board which does not need to be made into a metal protective layer is covered with blue glue, and then a metal protective layer including a silver protective layer is electroplated on the copper circuit. However, due to the low bonding force between the blue glue and the circuit board, a gap is easily generated between the edge of the blue glue and the circuit board during production, and the electroplating solution is left, which often causes the surface of the silver protective layer to be dirty or yellowed due to sulfidation. SUMMARY

[0005] The main purpose of the present application is to provide a circuit board manufacturing method to solve the problem of easy dirt and sulfidation yellowing of the silver protective layer on the surface of the circuit in the prior art.

[0006] In order to achieve the above main purpose, the present application provides a circuit board manufacturing method, which includes the following circuit manufacturing steps:

[0007] S1, making a metal protective layer on the copper foil layer on the surface of the circuit board, the metal protective layer including at least a silver protective layer;

[0008] S2, pasting an acid-resistant film on the metal protective layer, and then exposing and developing to expose the etching area of the metal protective layer from the film;

[0009] S3, electrolytic etching the metal protective layer in an acid or neutral electrolyte to remove the etching area of the metal protective layer;

[0010] S4, acid etching the copper foil layer to remove the area of the copper foil layer exposed to the film, forming a conductive circuit;

[0011] S5, removing the film.

[0012] According to one embodiment of the present application, the metal protective layer further comprises a nickel protective layer formed on the surface of the copper foil layer, and the silver protective layer is formed on the nickel protective layer.

[0013] Further, the thickness of the nickel protective layer is 1-10 μm.

[0014] Further, the thickness of the silver protective layer is 1-10 μm.

[0015] Further, the electrolytic etching of the silver protective layer and the nickel protective layer is performed in the same electrolytic system.

[0016] Preferably, the pH of the electrolyte in step S3 is controlled to be 5-7.

[0017] Preferably, the temperature of the electrolyte in step S3 is controlled to be 25-35 °C.

[0018] Preferably, a stainless steel plate is used as the cathode plate in step S3.

[0019] Preferably, the metal protective layer is made by electroplating in step S1.

[0020] Preferably, the circuit board is washed with water after step S3 and before step S4.

[0021] The circuit board preparation method of the present application has the following advantages:

[0022] (1) The metal protective layer is first made on the surface of the copper foil layer of the circuit board, and then the area of the metal protective layer to be etched is removed by electrolytic etching. The silver protective layer is protected by the acid-resistant film during electrolytic etching. Since the film has good adhesion to the silver protective layer, the electrolyte and etching solution will not remain on the circuit board, thus solving the problem of easy contamination and yellowing of the silver protective layer in the prior art, and improving the yield and quality of the product.

[0023] (2) The film has higher pattern precision than the blue resist after exposure and development, which is beneficial to improving the circuit pattern precision and realizing the manufacture of fine circuit.

[0024] In order to more clearly illustrate the purpose, technical scheme and advantages of the present application, the present application will be further described in detail below with reference to the drawings and specific embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 is a flow chart of the circuit board manufacturing method according to an embodiment of the present application;

[0026] Figure 2 is a schematic diagram of the structure of the circuit board after the film exposure and development according to an embodiment of the present application;

[0027] Figure 3 is a schematic diagram of the structure of the circuit board after the electrolytic etching of the metal protection layer according to an embodiment of the present application;

[0028] Figure 4 is a schematic diagram of the structure of the circuit board after the acid etching of the copper foil layer according to an embodiment of the present application.

[0029] It should be noted that different parts of the drawings are not necessarily drawn to scale in order to clearly illustrate the structures to be expressed. Therefore, the content expressed by the drawings does not constitute a limitation on the size and proportion relationship of the parts of the circuit board unless explicitly indicated. DETAILED DESCRIPTION

[0030] In the following description, many specific details are set forth in order to provide a thorough understanding of the present application. However, the present application can be practiced in other manners different from those described herein, and therefore the scope of the present application is not limited to the specific embodiments disclosed below.

[0031] As shown in Figure 1 , the circuit board manufacturing method according to an embodiment of the present application comprises the following circuit manufacturing steps:

[0032] S1, manufacturing a metal protection layer on the copper foil layer on the surface of the circuit board;

[0033] S2, pasting an acid-resistant film on the metal protection layer, and then exposing and developing to expose the to-be-etched area of the metal protection layer from the film;

[0034] S3, electrolytic etching of the metal protection layer in an acid or neutral electrolyte to remove the to-be-etched area of the metal protection layer;

[0035] S4, acid etching of the copper foil layer to remove the area of the copper foil layer exposed to the film, forming a conductive circuit;

[0036] S5, removing the film.

[0037] In an optional embodiment, as Figure 2As shown, the circuit board comprises a copper foil layer 11 formed on the surface of an insulating substrate (e.g. FR-4 substrate), and the metal protective layer comprises a nickel protective layer 12 formed on the copper foil layer 11 and a silver protective layer 13 formed on the nickel protective layer 12. The thickness of the nickel protective layer 12 can be 1 μm to 10 μm, preferably 3 μm to 10 μm, but the present application is not limited thereto; and the thickness of the silver protective layer 13 can be 1 μm to 10 μm, preferably 3 μm to 10 μm, but the present application is not limited thereto.

[0038] In the embodiment of the present application, the circuit board can be sequentially subjected to whole-board electroplating of nickel and silver, so as to form the nickel protective layer 12 on the copper foil layer 11 and the silver protective layer 13 on the nickel protective layer 12. It should be noted that in other alternative embodiments of the present application, the metal protective layer can only comprise the silver protective layer 13 formed directly on the copper foil layer 11.

[0039] Before electrolytic etching of the metal protective layer, the circuit board can be subjected to water washing and drying, as shown in Figure 2 First, an acid-resistant film 14 is attached to the silver protective layer 13, and then the film 14 is subjected to exposure and development, so that the film 14 forms a pattern matching the outer layer circuit, and the etching area of the metal protective layer is exposed from the patterned film 14. Preferably, before attaching the film 14, the circuit board is subjected to water washing and drying.

[0040] In the embodiment of the present application, the nickel protective layer 12 and the silver protective layer 13 are subjected to local electrolytic etching in an acidic or neutral electrolyte, so as to remove the etching area of the nickel protective layer 12 and the silver protective layer 13 exposed to the film 14 (see Figure 3 ). Specifically, during electrolytic etching, the circuit board as an anode plate is electrically connected to the positive pole of a direct current power supply, and a stainless steel plate as a cathode plate is electrically connected to the negative pole of the direct current power supply, and the circuit board and the stainless steel plate are both placed in the acidic or neutral electrolyte and face each other with a distance of about 20 cm. Preferably, the pH of the electrolyte is controlled to be 5 to 7 and the temperature of the electrolyte is controlled to be 25° to 35° during electrolytic etching, so as to achieve a better electrolytic etching effect. The electrolyte used in the present application can be the same as that in the prior art, which will not be described herein.

[0041] In the embodiment of the present application, the electrolytic etching of the silver protective layer 13 and the nickel protective layer 12 is carried out in the same electrolytic system, which is beneficial to improve the production efficiency. In other alternative embodiments of the present application, the electrolytic etching of the silver protective layer 13 and the nickel protective layer 12 can be carried out in different electrolytic systems, respectively.

[0042] Preferably, after electrolytic etching, the circuit board is subjected to water washing. Then, as shown in Figure 4As shown, the copper foil layer 11 is placed in an acid etching solution for chemical etching to etch away the to-be-etched area of the copper foil layer 11 exposed to the film 14, thereby forming a conductive circuit. The etching of the copper foil layer 11 can be the same as the prior art and will not be described herein.

[0043] Finally, the film is removed from the surface of the circuit board, and then the circuit board is washed with water and dried, i.e. the circuit manufacturing step is completed.

[0044] In summary, in the surface circuit manufacturing of the circuit board, the metal protective layer is first manufactured on the surface of the copper foil layer of the circuit board, and then the to-be-etched area of the metal protective layer is removed by electrolytic etching. The silver protective layer is protected by the acid-resistant film during the electrolytic etching. Since the film and the silver protective layer have good bonding force, the electrolyte and the etching solution will not be left on the circuit board, thereby solving the problem of easy contamination and sulfuration and yellowing of the silver protective layer in the prior art, and improving the yield and quality of the product.

[0045] Although the present application is disclosed with specific embodiments as above, any person skilled in the art can make some changes or replacements without departing from the scope of the present application, i.e. any equivalent changes made according to the present application shall be covered by the scope of the present application.

Claims

1. A method of manufacturing a circuit board, characterized by The circuit manufacturing steps include the following steps: S1, manufacturing a metal protection layer on the copper foil layer on the surface of the circuit board, the metal protection layer at least including a silver protection layer; S2, pasting an acid-resistant film on the metal protection layer, then exposing and developing, so that the etching area of the metal protection layer is exposed from the film; S3, electrolytic etching the metal protection layer in an acid or neutral electrolyte to remove the etching area of the metal protection layer; S4, acid etching the copper foil layer to remove the area of the copper foil layer exposed to the film, forming a conductive circuit; S5, removing the film; During the electrolytic etching, the circuit board is used as an anode plate, a stainless steel plate is used as a cathode plate, the pH of the electrolyte is 5-7, and the temperature of the electrolyte is 25-35°.

2. The method of claim 1, wherein: The metal protection layer further includes a nickel protection layer formed on the surface of the copper foil layer, and the silver protection layer is formed on the nickel protection layer.

3. The method of claim 2, wherein: The thickness of the nickel protection layer is 1-10 µm.

4. The method of manufacturing a circuit board according to claim 2, wherein: The thickness of the silver protection layer is 1-10 µm.

5. The method of manufacturing a circuit board according to claim 2, wherein: The electrolytic etching of the silver protection layer and the nickel protection layer is performed in the same electrolytic system.

6. The method of manufacturing a circuit board according to claim 1, wherein: The metal protection layer is manufactured by an electroplating process in step S1.

7. The method of manufacturing a circuit board according to claim 1, wherein: The circuit board is washed with water after step S3 and before step S4.

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