Method for plating through-holes of a circuit board

Abstract

The present application discloses a method for electroplating through holes of a circuit board, which comprises a providing step, a drilling step and a copper plating step. In the providing step, a circuit board is provided. In the drilling step, the circuit board is drilled to form a plurality of through holes corresponding to the circuit board. In the copper plating step, the circuit board is electroplated so that the inner walls of the through holes are respectively formed with a copper plating layer, and the current density during the copper plating step is inversely proportional to the thickness of the copper plating layer.

Description

Technical Field

[0001] This invention relates to an electroplating method, and more particularly to an electroplating method for through holes in a circuit board. Background Technology

[0002] In recent years, with the rapid development of technologies such as artificial intelligence and image recognition, the demand for high density, multifunctionality, and miniaturization has necessitated further reductions in the size of printed circuit boards (PCBs). This undoubtedly increases the difficulty and cost of PCB production. In particular, the copper plating process for through-holes is prone to corner cracking. Therefore, overcoming these defects through improvements in manufacturing processes and structural design has become one of the key challenges facing this industry. Summary of the Invention

[0003] This invention provides an electroplating method for through holes in circuit boards to address the shortcomings of existing technologies, which can effectively improve the defects that may occur in existing circuit board through holes.

[0004] This invention discloses an electroplating method for through-holes in a circuit board, comprising: a providing step: providing a circuit board; a drilling step: drilling holes in the circuit board to form a plurality of through-holes; and a copper plating step: electroplating the circuit board to form a copper plating layer on the inner wall of each of the plurality of through-holes; wherein the current density during the copper plating step is inversely proportional to the thickness of the copper plating layer.

[0005] One of the beneficial effects of the present invention is that the electroplating method for the through holes of the circuit board provided by the present invention can solve the corner cracking problem of the through holes of the circuit board through the technical solution of "the copper plating step: electroplating the circuit board so that the inner walls of the multiple through holes are respectively formed with the copper plating layer; wherein the current density during the copper plating step is inversely proportional to the thickness of the copper plating layer".

[0006] 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

[0007] Figure 1 This is a schematic flowchart of the electroplating method for through holes in a circuit board according to an embodiment of the present invention;

[0008] Figure 2 This is a schematic diagram of experimental data on the number of corner cracks corresponding to the current density during the copper plating step in an embodiment of the present invention.

[0009] Figure 3 This is a schematic diagram of experimental data on the number of corner cracks corresponding to the hole density of the circuit board in an embodiment of the present invention;

[0010] Figure 4 This is a schematic diagram illustrating the action of the grinding brush wheel grinding the copper plating layer according to an embodiment of the present invention;

[0011] Figure 5 This is a schematic diagram illustrating another action of the grinding brush wheel grinding the copper plating layer according to an embodiment of the present invention.

[0012] Symbol Explanation

[0013] S100: Electroplating method for through holes in circuit boards

[0014] S101: Provide steps

[0015] S103: Baking Steps

[0016] S105: Drilling Procedure

[0017] S107: Copper Plating Steps

[0018] S109: Grinding Steps

[0019] 100: Circuit board

[0020] 1: Through hole

[0021] 2: Copper plating layer

[0022] 200: Grinding brush wheel Detailed Implementation

[0023] The following specific embodiments illustrate the implementation of the "electroplation method for through-holes in circuit boards" disclosed in this invention. Those skilled in the art can understand the advantages and effects of this invention from the content disclosed in this specification. This 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 this invention. Furthermore, the accompanying drawings of this invention are merely simple illustrations and are not depictions of actual dimensions, as stated in advance. In addition, if it is indicated below that a specific drawing is referenced or shown as shown in a specific drawing, it is only for emphasis in the following description, and most of the relevant content mentioned appears in that specific drawing, but it does not limit the subsequent description to refer only to that specific drawing. The following embodiments will further describe the relevant technical content of this invention in detail, but the disclosed content is not intended to limit the scope of protection of this invention.

[0024] 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 associated listed items.

[0025] Please see Figures 1 to 5 As shown, this is an embodiment of the present invention. It should be noted that the accompanying drawings and the related quantities and shapes mentioned in this embodiment are only used to specifically illustrate the implementation of the present invention so as to facilitate understanding of the content of the present invention, and are not intended to limit the scope of protection of the present invention.

[0026] like Figure 1 and Figure 5 As shown, this embodiment of the invention provides an electroplating method S100 for through-holes in a circuit board, which sequentially includes: a providing step S101, a baking step S103, a drilling step S105, a copper plating step S107, and a polishing step S109. However, the invention is not limited thereto. For example, in other embodiments of the invention not shown, the electroplating method S100 for through-holes in a circuit board may not include the baking step S103 and the polishing step S109.

[0027] For ease of explanation and understanding, the following steps will be described in sequence: providing step S101, baking step S103, drilling step S105, copper plating step S107, and polishing step S109. Figure 1 and Figure 4 , Figure 5 As shown, in the providing step S101, a circuit board 100 is provided, and the circuit board 100 includes a circuit layer (not shown). In this embodiment, the circuit board 100 is preferably a multi-layer circuit board (Multi-Layer PCB), but the present invention is not limited thereto. For example, in other embodiments of the present invention, the circuit board 100 may also be a single-layer circuit board (Single-Layer PCB) or a double-layer circuit board (Double-Layer PCB).

[0028] Since step S101 is not the main focus of this invention, it will not be described in detail here. The following will begin by describing the baking step S103. Figure 1 As shown, in the baking step S103, the circuit board 100 is baked at a temperature of 120°C to 130°C. This effectively eliminates residual stress from the previous manufacturing process, thereby improving the yield of the circuit board 100 in subsequent steps.

[0029] The baking step S103 has been described here. The drilling step S105 will now be described. Figures 1 to 5 As shown, in the drilling step S105, the circuit board 100 is drilled to form a plurality of through holes 1 (not shown in the figure). Since the drilling step S105 is not the main focus of the improvement of the present invention, it will not be described in detail here.

[0030] The following will begin to describe the copper plating step S107, such as... Figures 1 to 5 As shown, in the copper plating step S107, the circuit board 100 undergoes electroplating, so that a copper plating layer 2 is formed on the inner wall of each of the plurality of through holes 1. The current density during the copper plating step S107 is inversely proportional to the thickness of the copper plating layer 2.

[0031] Furthermore, after the copper plating layer 2 is electroplated onto the plurality of through holes 1 of the circuit board 100, a series of other related manufacturing processes and reflow are usually performed, especially infrared reflow. However, currently, after multiple infrared reflows, corner cracks are prone to occur at the corners of the plurality of through holes 1 after electroplating.

[0032] Therefore, when the copper plating step S107 is performed, if the current density is reduced, for example, if the current density during the copper plating step S107 is limited to between 10 ASF and 20 ASF, the thickness of the copper plating layer 2 at the corners of the multiple through holes 1 (hereinafter referred to as corner copper thickness for ease of explanation) will increase, thus significantly reducing the probability of corner cracks. Specifically, as shown in Table 1 below... Figure 2 As shown, under the condition that multiple through holes 1 have the same hole diameter and the same hole density, the experimental group with a higher current density during the copper plating step S107 usually has a relatively thicker corner copper thickness. For example, compared with experimental group 3.1, experimental group 1.1 with a current density of 10.18 will have a relatively thicker corner copper thickness.

[0033] It should be noted that each experimental group listed in Table 1 underwent a total of 10 experiments, and the corner copper thickness in each group in Table 1 is the average of the corner copper thickness in each of the 10 experiments. This is to avoid misunderstanding.

[0034] Table 1

[0035]

[0036]

[0037] It should be further noted that the thickness of the copper plating layer 2 (corner copper thickness) can also be adjusted by adjusting the hole density of the plurality of through holes 1. Specifically, the thickness of the copper plating layer 2 is inversely proportional to the hole density of the plurality of through holes 1, and in this embodiment, the hole density of the plurality of through holes 1 is between 70 holes / cm². 2 ~210 pieces / cm 2 between.

[0038] Specifically, as shown in Table 1 above and Figure 3 As shown, when the copper plating step S107 is performed, it can be found that under the same conditions, the lower the hole density of the multiple through holes 1, the greater the thickness of the copper at the corners. For example, compared with experimental groups 1.1 to 1.6, the lower the hole density of the multiple through holes 1, the relatively larger the copper thickness at the corners.

[0039] It should be further noted that the thickness of the copper plating layer 2 can also be adjusted by adjusting the apertures of the multiple through holes 1. Specifically, the thickness of the copper plating layer 2 is inversely proportional to the apertures of the multiple through holes 1. As shown in Table 1 above, when the copper plating step S107 is performed, it can be observed that under the same conditions, the smaller the aperture of the multiple through holes 1, the greater the thickness of the copper plating at the corners. For example, comparing experimental group 1.1 with experimental group 2.1, the corner copper thickness of experimental group 1.1, with an aperture size of 7.9 mil, will be relatively larger.

[0040] It should be noted that although the thickness of the copper plating layer 2 at the corners of the plurality of vias 1 has a certain trend relationship with the current density, the aperture, and the aperture density of the plurality of vias 1 during copper plating step S107, it is not without limitations. Specifically, in this embodiment, the opening size of each via 1 is at least 1 times the total thickness of its corresponding copper plating layer 2, while the current density, aperture, and aperture density of the plurality of vias 1 during copper plating step S107 cannot be increased or decreased without limitation, otherwise the openings of the plurality of vias 1 will be closed. In addition, the thickness of the copper plating layer 2 at the corners of the plurality of vias 1 is also limited by the linewidth of the circuit layer; more specifically, the linewidth of the circuit layer is proportional to the thickness of the copper plating layer 2.

[0041] The copper plating step S107 has been described here. The polishing step S109 will now be described. Figure 1As shown, in the grinding step S109, a grinding brush wheel 200 grinds the copper plating layer 2 and cuts the copper plating layer 2 on the opening of each through hole 1. In this embodiment, the grinding brush wheel 200 is preferably a wound grinding brush wheel, and the material of the grinding brush wheel 200 is selected from the group consisting of nylon, ceramic, diamond, and non-woven fabric. The grinding brush wheel 200 is not a bristle-type grinding brush wheel.

[0042] Furthermore, assuming that the grinding brush wheel 200 is a bristle-type grinding brush wheel, when the grinding brush wheel 200 grinds the copper plating layer 2, since the bristles (not shown in the figure) of the bristle-type grinding brush wheel are radial, the bristles are prone to excessively scraping the corner edges of the opening of each through hole 1 due to their excessive length, resulting in a large proportion of cutting of the opening of each through hole 1.

[0043] When the polishing brush wheel 200 is a wound polishing brush wheel, since the wound polishing brush wheel contacts the opening of each through hole 1 almost entirely and has no bristles, the opening of each through hole 1 will not be significantly cut. More specifically, as shown in Table 2 below, it can be observed that, for the same corner copper thickness, the average copper reduction of the wound polishing brush wheel for the copper plating layer 2 is significantly less than that of the bristle-type polishing brush wheel for the copper plating layer 2.

[0044] Table 2

[0045]

[0046] [Beneficial Effects of the Examples]

[0047] One of the beneficial effects of the present invention is that the electroplating method S100 for the through holes of the circuit board provided by the present invention can solve the corner cracking problem of the through holes 1 of the circuit board 100 by means of the technical solution of "the copper plating step S107: electroplating the circuit board 100 to form the copper plating layer 2 on the inner wall of the plurality of through holes 1 respectively; wherein the current density during the copper plating step S107 is inversely proportional to the thickness of the copper plating layer 2".

[0048] Furthermore, the electroplating method S100 for the through holes of the circuit board can reduce the average copper reduction of the copper plating layer 2 by means of the technical means that "the grinding brush 200 is a wound grinding brush, and the material of the grinding brush 200 is selected from the group composed of nylon, ceramic, diamond and non-woven fabric", thereby reducing the probability of corner cracks occurring at the corners of multiple through holes 1.

[0049] The content disclosed above is only a preferred and feasible embodiment of the present invention, and is not intended to limit the claims of the present invention. Therefore, all equivalent technical changes made based on the content of the present invention specification and drawings are included within the protection scope of the present invention.

Claims

1. A method for electroplating through-holes of a circuit board, comprising: a providing step of providing a circuit board; a drilling step of drilling the circuit board to form a plurality of through-holes corresponding to the circuit board; and a copper plating step of electroplating the circuit board to form a copper plating layer on an inner wall of each of the through-holes, wherein a current density during the copper plating step is inversely proportional to a thickness of the copper plating layer, wherein the current density during the copper plating step is between 10 ASF and 20 ASF. Among them, the hole density of multiple said through holes is between 70 / cm 2 ~ 210 / cm 2 between, The baking step is performed before the drilling step.

2. The electroplating method of through-holes of a circuit board according to claim 1, further comprising a baking step of baking the circuit board at a temperature of 120°C to 130°C; wherein, 3. The method of claim 1, further comprising a polishing step of polishing the copper plating layer with a polishing brush wheel and cutting the copper plating layer on an opening of each of the through-holes. The polishing brush wheel is a wrap-around polishing brush wheel, and a material of the polishing brush wheel is selected from a group consisting of nylon, ceramic, diamond, and non-woven fabric.

4. The electroplating method of through-holes of a circuit board as claimed in claim 3, wherein, The polishing brush wheel is not a bristle polishing brush wheel.

5. The electroplating method of through-holes of a circuit board as recited in claim 3, wherein, The thickness of the copper plating layer is inversely proportional to a hole density of the plurality of through-holes.

6. The electroplating method of through-holes of a circuit board as claimed in claim 1, wherein, An opening size of each of the through-holes is at least 1 times a total thickness of the corresponding copper plating layer.

7. The electroplating method of through-holes of a circuit board as claimed in claim 1, wherein, The circuit board includes a circuit layer, and a line width of the circuit layer is proportional to the thickness of the copper plating layer.

8. The electroplating method of through-holes of a circuit board as claimed in claim 1, wherein, ​

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