A method for manufacturing an anticorrosion circuit board and a circuit board structure

Abstract

The application relates to a method for preparing an anti-corrosion circuit board, which comprises the following steps: providing a substrate, roughening the surface of the substrate, electroplating a nickel layer on the roughened surface of the substrate, coating, pre-solidifying, masking, exposing and developing a solder resist layer on the substrate in sequence to form a solder resist layer structure with a preset pattern, cleaning the developed substrate, and plating an anti-oxidation layer on the surface of the nickel layer to prevent air oxidation. As a further description of the above technical scheme, the nickel layer is micro-processed before the step of coating, pre-solidifying, masking, exposing and developing the solder resist layer on the substrate in sequence to form the solder resist layer structure with the preset pattern, wherein the surface of the nickel layer is micro-etched to form a micro-rough structure and generate an activated surface rich in hydroxyl groups. The application can solve the undercut and whitening problems of the copper layer substrate by adding a nickel layer on the substrate.

Description

Technical Field

[0001] This invention relates to a semiconductor manufacturing process, and more particularly to a method for preparing a corrosion-resistant circuit board. Background Technology

[0002] The description in this section provides only background information related to the disclosure of this invention and does not constitute prior art.

[0003] In the manufacturing process of WBCSP (Wafer-Scale Chip-Scale Packaging) substrates, a mixture of sulfuric acid and hydrogen peroxide is typically used to clean the surface of the copper pads (Cu Pads) to remove surface residues. However, during this cleaning process, the highly acidic and oxidizing cleaning solution can easily cause excessive erosion of the copper layer at the interface between the copper pads and the solder mask (SR), resulting in corrosion and pitting at the bottom edge of the copper pads, i.e., producing... Figure 7 The undercut phenomenon shown is a problem that disrupts the interface between the solder mask and the copper layer, ultimately leading to reliability issues such as solder mask whitening, poor adhesion, solder bleed-in, and appearance defects.

[0004] Existing technologies often alleviate these problems by reducing the intensity of micro-etching or adding cleaning steps, but neither can fundamentally protect the copper layer, resulting in limited improvement. Therefore, developing a substrate manufacturing solution that can effectively improve the corrosion resistance of solder pads and inhibit solder resist whitening has become an urgent technical challenge for the industry.

[0005] It should be noted that the above description of the technical background is only for the purpose of providing a clear and complete explanation of the technical solutions of the present invention and facilitating understanding by those skilled in the art. It should not be assumed that the above technical solutions are known to those skilled in the art simply because they have been described in the background section of this invention. Summary of the Invention

[0006] The purpose of this invention is to provide a method for manufacturing corrosion-resistant circuit boards, which can fundamentally solve the problems of undercutting and whitening of copper-layer substrates by adding a nickel layer to the substrate.

[0007] To achieve the above objectives, the present invention discloses a method for preparing an anti-corrosion circuit board, the method comprising the following steps: A substrate is provided, and the surface of the substrate is roughened. A nickel layer is formed by electroplating on the surface of the roughened substrate. Solder resist coating, pre-curing, photomask application, exposure and development are performed sequentially on the substrate to form a solder resist structure with a preset pattern. The developed substrate is cleaned, and an antioxidant layer is deposited on the surface of the nickel layer to prevent air oxidation.

[0008] As a further description of the above technical solution, before the step of "sequentially applying solder resist coating, pre-curing, photomask, exposure and development on the substrate to form a solder resist layer structure with a preset pattern", the nickel layer is micro-processed, wherein the surface of the nickel layer is micro-etched to form a micro-rough structure on the surface of the nickel layer and generate an activated surface rich in hydroxyl groups.

[0009] As a further description of the above technical solution, in the micro-processing of the nickel layer, a micro-etching solution composed of sodium persulfate and sulfuric acid is used to micro-etch the nickel layer.

[0010] As a further description of the above technical solution, in the step of "cleaning the developed substrate and depositing an antioxidant layer on the surface of the nickel layer to prevent air oxidation", sulfuric acid and hydrogen peroxide are used to clean the developed substrate, so that a dense nickel oxide layer is formed in situ on the surface of the nickel layer during the cleaning process. The nickel oxide layer is used to prevent the cleaning solution from corroding the substrate.

[0011] As a further description of the above technical solution, after the step of "cleaning the developed substrate with sulfuric acid and hydrogen peroxide, so that a dense nickel oxide layer is formed in situ on the surface of the nickel layer during the cleaning process", the nickel oxide layer is dissolved and removed with sulfuric acid, so that the surface of the nickel layer is re-exposed.

[0012] As a further description of the above technical solution, in the step of "cleaning the developed substrate and plating an antioxidant layer on the surface of the nickel layer to prevent air oxidation", the antioxidant layer is set as a gold plating layer.

[0013] As a further description of the above technical solution, the gold plating layer covers at least all of the exposed surface of the nickel layer in the horizontal direction, and the gold plating layer does not protrude beyond the solder resist layer.

[0014] As a further description of the above technical solution, the thickness of the nickel layer is ten times the thickness of the gold plating layer.

[0015] This invention also discloses a circuit board structure, which is prepared using the corrosion-resistant circuit board preparation method described above, wherein the circuit board structure includes: substrate; A nickel layer covering the surface of the substrate; A solder resist layer partially covers the surface of the nickel layer, and there is an intersection between the solder resist layer and the nickel layer.

[0016] As a further description of the above technical solution, the circuit board structure also includes an anti-oxidation layer, which is configured as a gold plating layer, and the gold plating layer covers the surface of the nickel layer that is not covered by the solder resist layer.

[0017] By employing the above technical solutions, the beneficial effects of the present invention are as follows: The corrosion-resistant circuit board manufacturing method of the present invention solves the problems of undercutting and whitening of copper substrates at the source by adding a nickel layer to the substrate. Specifically, the nickel layer on the surface of the copper substrate can be oxidized to form a passivation layer during the cleaning step using a strong oxidizing acid solution (sulfuric acid and hydrogen peroxide) to protect the underlying substrate, directly blocking the acid from corroding the copper layer below, thus solving the problems of undercutting and whitening of the solder resist layer at the source. Furthermore, the use of an antioxidant layer to protect the nickel layer in this solution further improves the overall structural stability.

[0018] To further understand the features and technical content of the present invention, please refer to the following detailed description and drawings of the present invention. However, the drawings provided are for reference and illustration only and are not intended to limit the present invention. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments or prior art of this specification, the drawings used in the description of the embodiments or prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this specification. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the copper pad roughening step in a method for preparing an anti-corrosion circuit board provided in the embodiments of this specification; Figure 2 This is a schematic diagram of the electroplating nickel layer steps in a method for preparing an anti-corrosion circuit board according to an embodiment of this specification; Figure 3 This is a schematic diagram of the nickel layer micro-etching steps in a method for preparing an anti-corrosion circuit board provided in the embodiments of this specification; Figure 4 This is a schematic diagram of the solder resist coating and exposure forming steps of a corrosion-resistant circuit board manufacturing method provided in the embodiments of this specification; Figure 5 This is a schematic diagram of the cleaning steps in a method for preparing an anti-corrosion circuit board provided in the embodiments of this specification; Figure 6 This is a schematic diagram of the steps involved in plating an anti-oxidation layer in a method for preparing an anti-corrosion circuit board according to an embodiment of this specification; Figure 7 This is a schematic diagram of the undercut phenomenon in proportion; In the picture: 100, bottom tangent point; 200, photomask; 1. Substrate; 11. Prepreg layer; 12. Copper pads; 2. Nickel layer; 21. Micro-etched layer; 3. Solder resist layer; 4. Antioxidant layer. Detailed Implementation

[0021] To enable those skilled in the art to better understand the technical solutions in this specification, the technical solutions in the embodiments of this specification will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this specification, and not all embodiments. Based on the embodiments in this specification, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this specification.

[0022] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can understand the advantages and effects of the present invention from the content disclosed in this specification. The present invention can be implemented or applied through other different specific embodiments, and various details in this specification can also be modified and changed based on different viewpoints and applications without departing from the concept of the present invention. Furthermore, the accompanying drawings of the present invention are for simple illustrative purposes only and are not depictions of actual dimensions; this is stated in advance. The following embodiments will further describe the relevant technical content of the present invention in detail, but the disclosed content is not intended to limit the scope of protection of the present invention.

[0023] It should be understood that while terms such as "first," "second," and "third" may be used in this document to describe various components or signals, these components or signals should not be limited by these terms. These terms are primarily used to distinguish one component from another, or one signal from another. Furthermore, the term "or" as used herein should, as appropriate, include any combination of one or more of the related listed items.

[0024] Please see Figure 1-6 This embodiment provides a method for preparing an anti-corrosion circuit board, which includes the following steps: A substrate 1 is provided, and the surface of the substrate 1 is roughened. A nickel layer 2 is formed by electroplating on the surface of the roughened substrate 1; The solder resist layer 3 is coated, pre-cured, photomasked, exposed and developed sequentially on the substrate 1 to form a solder resist layer 3 structure with a preset pattern. The substrate 1 after development is cleaned, and an antioxidant layer 4 for preventing air oxidation is plated on the surface of the nickel layer 2.

[0025] Based on the above process of the present invention, the substrate 1 actually includes a semi-cured layer 11 and a copper pad 12 on the bottom base. The copper pad 12 is disposed at a local position on the semi-cured layer 11, and the bottom of the copper pad 12 is attached to the semi-cured layer 11.

[0026] In the process of forming a nickel layer 2 by electroplating on the surface of the substrate 1 after the roughening treatment, the nickel layer 2 is actually formed on the copper pads 12 of the substrate 1 and does not involve the semi-cured layer 11. Furthermore, the roughening treatment described above does not involve the semi-cured layer 11.

[0027] Specifically, the roughening treatment of the copper pad 12 refers to roughening the copper layer on the surface of the copper pad 12. Its main purpose is to enhance the bonding force with the nickel layer 2 electroplated in the subsequent steps and ensure stability.

[0028] The above-described process involves sequentially applying a solder resist layer 3, pre-curing, applying a photomask, exposing, and developing it on the substrate 1 to form a solder resist layer 3 structure with a preset pattern. Specifically, firstly, a layer of photosensitive solder resist ink is uniformly coated onto the surface of the substrate 1 using screen printing, roller coating, or curtain coating. Here, the solder resist layer 3 covers at least part of the semi-cured layer 11 and the copper pads 12. Subsequently, the coated substrate 1 is placed in a constant temperature oven for pre-curing treatment to remove some of the solvent from the ink, allowing the solder resist layer 3 to reach a non-sticky semi-cured state. Next, a photomask 200 is placed on top of the solder resist layer 3 according to the preset circuit pattern, and exposure is performed using an ultraviolet light source. During the exposure process, the solder resist material of the solder resist layer 3 corresponding to the light-transmitting area of ​​the photomask 200 undergoes a photopolymerization reaction and hardens, while the opaque area remains uncured. Finally, the exposed substrate 1 is placed in a developing solution for development, and the unexposed solder resist material of the solder resist layer 3 is rinsed and removed, thereby forming a solder resist layer 3 structure with predetermined patterned openings on the surface of the substrate 1 to precisely expose the surface area of ​​the nickel layer 2 to be processed.

[0029] The aforementioned nickel layer 2 is a key structural layer in this application. In existing technologies, a mixture of sulfuric acid and hydrogen peroxide is typically used to clean the surface of the copper pads 12 to remove surface residues. However, with the presence of the nickel layer 2, nickel oxide can be formed on its surface during the cleaning process. Specifically, in the step "cleaning the developed substrate 1 and plating an anti-oxidation layer 4 to prevent air oxidation on the surface of the nickel layer 2," sulfuric acid and hydrogen peroxide are used to clean the developed substrate 1, causing a dense nickel oxide layer to form in situ on the surface of the nickel layer 2 during this cleaning process. This nickel oxide layer prevents the cleaning solution from corroding the substrate 1 during acidic cleaning. Sulfuric acid is then used to dissolve and remove the nickel oxide layer, re-exposing the surface of the nickel layer 2. The nickel oxide layer has good corrosion resistance, effectively preventing acid from corroding the copper pads 12 to the bottom and preventing the formation of oxide layers at the edges where the copper pads 12 intersect with the solder mask layer 3. Figure 7 The bottom tangent point is shown as 100.

[0030] In other words, in the solution of this invention, the undercutting and whitening problems of the copper substrate 1 can be fundamentally solved by adding a nickel layer 2 on the substrate 1. Specifically, the nickel layer 2 on the surface of the copper substrate 1 can be oxidized to form a passivation layer during the cleaning step using a strong oxidizing acid solution (sulfuric acid and hydrogen peroxide) to protect the substrate 1 underneath, directly blocking the acid from corroding the copper layer below, thus fundamentally solving the undercutting and whitening problems of the solder resist layer 3. Furthermore, the use of an antioxidant layer 4 to protect the nickel layer 2 in this solution further improves the overall structural stability.

[0031] Further, before the step of "sequentially applying solder resist layer 3, pre-curing, applying photomask 200, exposing, and developing on the substrate 1 to form a solder resist layer 3 structure with a preset pattern," the nickel layer 2 is micro-processed. This involves micro-etching the surface of the nickel layer 2 to form a micro-rough structure and generate an activated surface rich in hydroxyl groups. Specifically, in the micro-processing of the nickel layer 2, a micro-etching solution composed of sodium persulfate and sulfuric acid is used to micro-etch the nickel layer 2. Sodium persulfate acts as an oxidant under acidic conditions, causing slight and uniform oxidation and dissolution of the nickel layer 2 surface, forming a moderately rough micro-morphology. The addition of sulfuric acid helps dissolve the metal oxides generated during the micro-etching process, maintaining the activated state of the nickel layer 2 surface and generating an activated surface rich in hydroxyl groups, providing excellent chemical bonding sites for the solder resist layer 3. Specifically, as... Figure 3 As shown, after micro-etching, a micro-etched layer 21 can be formed on the entire outer surface of the nickel layer 2.

[0032] Specifically, the aforementioned anti-oxidation layer 4 can be configured as a gold plating layer, where a thin gold film is deposited on the exposed nickel layer 2 surface using an electroplating process to form the gold plating layer. After removing the passivation layer of nickel oxide, gold exhibits extremely high chemical stability and does not oxidize under normal atmospheric conditions. This effectively prevents the nickel layer from being oxidized and discolored by oxygen in the air during storage or use, thereby maintaining the metallic luster and long-term solderability of the solder pad surface.

[0033] Of course, the area and thickness of the gold plating layer can be controlled according to cost considerations. Specifically, the gold plating layer covers at least all of the exposed surface of the nickel layer 2 in the horizontal direction, and the gold plating layer does not protrude beyond the solder resist layer 3, so as to effectively cover the exposed portion of the nickel layer 2. The thickness of the nickel layer 2 is ten times the thickness of the gold plating layer. Taking this embodiment as an example, the thickness of the nickel layer 2 is 1 micrometer, and the thickness of the gold plating layer is correspondingly set at 0.1 micrometers, which can achieve a good protective effect on the nickel layer 2.

[0034] The following also provides a circuit board structure fabricated based on the above-described anti-corrosion circuit board manufacturing method. The circuit board structure includes: a substrate 1; a nickel layer 2 covering the surface of the substrate 1; and a solder resist layer 3 partially covering the surface of the nickel layer 2, wherein the solder resist layer 3 intersects with the nickel layer 2. Specifically, the intersection of the solder resist layer 3 and the nickel layer 2 is located before and after the edge of the semi-cured layer 11 of the nickel layer 2 and the substrate 1. The circuit board structure also includes an anti-oxidation layer 4, which is a gold-plated layer. The gold-plated layer covers the surface of the nickel layer 2 not covered by the solder resist layer 3, thus preventing the nickel layer 2 from being directly exposed to air and oxidized.

[0035] The content disclosed above is only a preferred and feasible embodiment of the present invention, and is not intended to limit the scope of the patent application of the present invention. Therefore, all equivalent technical changes made using the contents of the present invention specification and drawings are included in the scope of the patent application of the present invention.

[0036] The various embodiments in this specification are described in a progressive manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

[0037] Although this application has been described by way of examples, those skilled in the art will know that this application has many modifications and variations without departing from the spirit of this application, and it is intended that the appended embodiments include these modifications and variations without departing from this application.

Claims

1. A method for manufacturing a corrosion-resistant circuit board, characterized in that, The method for preparing the corrosion-resistant circuit board includes the following steps: A substrate is provided, and the surface of the substrate is roughened. A nickel layer is formed by electroplating on the surface of the roughened substrate. Solder resist coating, pre-curing, photomask application, exposure and development are performed sequentially on the substrate to form a solder resist structure with a preset pattern. The developed substrate is cleaned, and an antioxidant layer is deposited on the surface of the nickel layer to prevent air oxidation.

2. The method for preparing an anti-corrosion circuit board according to claim 1, characterized in that: Before the step of "sequentially applying solder resist coating, pre-curing, photomask, exposure and development on the substrate to form a solder resist structure with a preset pattern", the nickel layer is micro-processed, wherein the surface of the nickel layer is micro-etched to form a micro-rough structure on the surface of the nickel layer and generate an activated surface rich in hydroxyl groups.

3. The method for preparing an anti-corrosion circuit board according to claim 2, characterized in that: In the micro-processing of the nickel layer, a micro-etching solution composed of sodium persulfate and sulfuric acid is used to micro-etch the nickel layer.

4. The method for preparing an anti-corrosion circuit board according to claim 1, characterized in that: In the step "cleaning the developed substrate and depositing an antioxidant layer on the surface of the nickel layer to prevent air oxidation", sulfuric acid and hydrogen peroxide are used to clean the developed substrate, so that a dense nickel oxide layer is formed in situ on the surface of the nickel layer during the cleaning process. The nickel oxide layer is used to prevent the cleaning solution from corroding the substrate.

5. The method for preparing an anti-corrosion circuit board according to claim 4, characterized in that: After the step of "cleaning the developed substrate with sulfuric acid and hydrogen peroxide so that a dense nickel oxide layer is formed in situ on the surface of the nickel layer during the cleaning process", the nickel oxide layer is dissolved and removed with sulfuric acid, so that the surface of the nickel layer is re-exposed.

6. The method for preparing an anti-corrosion circuit board according to claim 1, characterized in that: In the step "cleaning the developed substrate and depositing an antioxidant layer on the surface of the nickel layer to prevent air oxidation", the antioxidant layer is set as a gold plating layer.

7. The method for preparing an anti-corrosion circuit board according to claim 6, characterized in that: The gold plating layer covers at least all of the exposed surface of the nickel layer in the horizontal direction, and the gold plating layer does not protrude beyond the solder resist layer.

8. The method for preparing an anti-corrosion circuit board according to claim 7, characterized in that: The thickness of the nickel layer is ten times that of the gold plating layer.

9. A circuit board structure, characterized in that, The circuit board is manufactured using the corrosion-resistant circuit board manufacturing method as described in claim 1, wherein the circuit board structure includes: substrate; A nickel layer covering the surface of the substrate; A solder resist layer partially covers the surface of the nickel layer, and there is an intersection between the solder resist layer and the nickel layer.

10. The circuit board structure according to claim 9, characterized in that: The circuit board structure also includes an anti-oxidation layer, which is configured as a gold plating layer, covering the surface of the nickel layer that is not covered by the solder resist layer.

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