Electroplating method for improving copper thickness uniformity of circuit board

Abstract

The invention discloses an electroplating method for improving copper thickness uniformity of a circuit board, which comprises the following steps: providing a basic carrier with a copper foil, and preparing deposited copper on the surface of the copper foil; covering the deposited copper with an organic film, and exposing the deposited copper in a to-be-electroplated copper wire region in the circuit open region through photoetching; electroplating copper is prepared on the deposited copper exposed in the circuit open area through electroplating, and the organic film is removed; covering an organic film for the second time, and exposing deposited copper in a to-be-electroplated copper wire area in the circuit dense area through photoetching; and electroplating copper is prepared on the deposited copper exposed in the circuit dense area through electroplating. The circuit board is divided into a circuit open area and a circuit dense area according to the density of circuit design on the circuit board, and the circuit open area and the circuit dense area are electroplated in batches; electroplating parameters are adjusted according to the residual copper rate of the circuit open area and the circuit dense area, the copper thickness uniformity in the whole circuit of the circuit board is improved, and the copper thickness difference of the same circuit board is controlled to be smaller than + / -2 microns.

Description

Technical Field

[0001] The invention relates to the technical field of copper electroplating of circuit boards, and in particular to an electroplating method for improving the uniformity of copper thickness of circuit boards. Background Art

[0002] As the circuit design of high-density circuit boards becomes more and more sophisticated, the requirements for the uniformity of the thickness of the copper wires on high-density circuit boards are getting higher and higher. In the prior art, the production process of the circuit board is as follows: prepare a base carrier with copper foil, make a layer of chemically deposited copper on the base carrier, and then cover the deposited copper with a layer of organic film, remove the organic film on the area where the circuit is to be made by exposure and development, and then electroplate copper in the area where the organic film is removed, and then remove the film from the entire board surface, and finally etch the entire board surface of the circuit board to remove the copper on the base carrier and the chemically deposited copper together.

[0003] However, due to the inconsistent degree of electron accumulation between the open area and the dense area, during the electroplating stage, the copper thickness of the lines in the open area is often greater than that in the dense area, resulting in poor uniformity of copper thickness in the overall circuit of the circuit board product. At the same time, during process operation, the greater the target copper wire thickness, the greater the difference in copper thickness between the open area and the dense area, which may even exceed customer requirements and affect its application in the precision field. Summary of the invention

[0004] In view of the deficiencies in the prior art, the present invention provides an electroplating method for improving the uniformity of copper thickness of a circuit board. According to the density of circuit design on the circuit board, the circuit board is divided into a circuit empty area and a circuit dense area, and the circuit empty area and the circuit dense area are electroplated in batches respectively. The electroplating parameters are adjusted according to the residual copper rates of the circuit empty area and the circuit dense area, so as to improve the uniformity of copper thickness in the overall circuit of the circuit board and avoid the problem of poor copper thickness uniformity of the overall circuit of the circuit board caused by one-time electroplating.

[0005] In order to solve the above technical problems, the present invention provides an electroplating method for improving the uniformity of copper thickness of a circuit board, comprising the following steps:

[0006] S1. providing a base carrier with a copper foil, and preparing a layer of deposited copper on the surface of the copper foil;

[0007] S2, covering the deposited copper with a layer of organic film, and exposing the deposited copper in the copper line area to be electroplated in the circuit empty area by photolithography;

[0008] S3, preparing electroplated copper on the exposed deposited copper in the open area of ​​the circuit by electroplating, and then removing the organic film on the surface of the deposited copper;

[0009] S4, secondary covering with an organic film, covering the deposited copper and the electroplated copper with the organic film, and exposing the deposited copper in the copper line area to be electroplated in the circuit-dense area by photolithography;

[0010] S5. Prepare electroplated copper by electroplating on the exposed deposited copper in the circuit-dense area.

[0011] The present invention divides the circuit board into a circuit empty area and a circuit dense area according to the density of circuit design on the circuit board, and electroplates the circuit empty area and the circuit dense area in batches respectively; adjusts the electroplating parameters according to the residual copper rates of the circuit empty area and the circuit dense area, improves the uniformity of copper thickness in the overall circuit of the circuit board, and controls the copper thickness difference of the same circuit board to be less than ±2μm; avoids the problem of poor copper thickness uniformity of the overall circuit of the circuit board caused by one-time electroplating, and greatly reduces the copper thickness difference in the overall circuit of high copper thickness products and products with large differences in circuit density on the same circuit board.

[0012] Furthermore, the residual copper rate is defined as the area of ​​the copper area to be electroplated / total area, and the circuit board is divided into several unit areas. The unit area with a residual copper rate greater than a preset value is defined as a circuit-intensive area, and the unit area with a residual copper rate less than or equal to the preset value is set as a circuit-free area.

[0013] Furthermore, the preset value of the residual copper rate is 25-35%.

[0014] Furthermore, the current density of the electroplating in the empty area of ​​the circuit / the current density of the electroplating in the dense area of ​​the circuit=the average residual copper rate in the empty area of ​​the circuit / the average residual copper rate in the dense area of ​​the circuit. When other electroplating process parameters remain unchanged, the current density of the two electroplatings is linearly related to the average residual copper rate of the two areas.

[0015] Furthermore, in S1, the deposited copper is prepared by chemical vapor deposition.

[0016] Furthermore, in S2, exposing the deposited copper in the copper wire area to be electroplated in the circuit empty area by photolithography specifically comprises: removing the organic film on the deposited copper in the copper wire area to be electroplated in the circuit empty area by exposure and development.

[0017] Furthermore, in S4, exposing the deposited copper in the copper wire region to be electroplated in the densely-connected area by photolithography specifically comprises: removing the organic film on the deposited copper in the copper wire region to be electroplated in the densely-connected area by exposure and development.

[0018] Furthermore, after S5, a step of removing the organic film is also included.

[0019] Furthermore, after the step of removing the organic film, the method further includes a step of etching and removing the deposited copper.

[0020] Furthermore, the deposited copper removed by etching is the deposited copper not covered by the electroplated copper.

[0021] Beneficial effects of the present invention:

[0022] The method of the present invention divides the circuit board into a circuit empty area and a circuit dense area according to the density of the circuit design on the circuit board, and electroplates the circuit empty area and the circuit dense area in batches respectively; adjusts the electroplating parameters according to the residual copper rates of the circuit empty area and the circuit dense area, improves the uniformity of the copper thickness in the overall circuit of the circuit board, and controls the copper thickness difference of the same circuit board to be less than ±2μm.

[0023] The method of the present invention avoids the problem of poor copper thickness uniformity of the entire circuit of the circuit board caused by one-time electroplating by batch electroplating, and greatly reduces the copper thickness difference in the entire circuit of high copper thickness products and products with greatly different circuit densities on the same circuit board. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solution of the present invention, the drawings required for use in the embodiments are briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0025] Figure 1 This is a process flow chart of an electroplating method for improving the uniformity of copper thickness of a circuit board according to the present invention;

[0026] Figure 2 It is a schematic diagram of the structures of various modules in the electroplating method for improving the uniformity of copper thickness of a circuit board according to the present invention;

[0027] Explanation of the numbers in the figure: 1. copper foil, 2. base carrier, 3. deposited copper, 4. organic film, 5. electroplated copper. DETAILED DESCRIPTION

[0028] The technical solution of the present invention will be described clearly and completely below in conjunction with the specific 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.

[0029] Reference Figure 1 As shown, this embodiment provides an electroplating method for improving the uniformity of copper thickness of a circuit board, comprising the following steps:

[0030] S1, providing a base carrier 2 with a copper foil 1, and preparing a layer of deposited copper 3 on the surface of the copper foil 1;

[0031] S2, covering the deposited copper 3 with a layer of organic film 4, and exposing the deposited copper 3 located in the copper line area to be electroplated in the circuit empty area by photolithography;

[0032] S3, preparing electroplated copper 5 on the exposed deposited copper 3 in the open area of ​​the circuit by electroplating, and then removing the organic film on the surface of the deposited copper 3;

[0033] S4, secondary covering with an organic film 4, covering the deposited copper 3 and the electroplated copper 5 with the organic film 4, and exposing the deposited copper 3 in the copper line area to be electroplated in the circuit-intensive area by photolithography;

[0034] S5, preparing electroplated copper 5 on the exposed deposited copper 3 in the circuit-intensive area by electroplating. The structural schematic diagram of each module in the process flow is as follows: Figure 2 Shown

[0035] Specifically, the residual copper rate is defined as the area of ​​the copper area to be electroplated / total area, and the circuit board is divided into several unit areas. The unit area with a residual copper rate greater than a preset value is defined as a circuit-intensive area, and the unit area with a residual copper rate less than or equal to the preset value is set as a circuit-free area.

[0036] This embodiment divides the circuit board into an open circuit area and a dense circuit area according to the density of circuit designs on the circuit board, and electroplates the open circuit area and the dense circuit area in batches respectively; adjusts the electroplating parameters according to the residual copper rates of the open circuit area and the dense circuit area, improves the uniformity of copper thickness in the overall circuit of the circuit board, and controls the difference in copper thickness of the same circuit board to less than ±2μm; avoids the problem of poor uniformity of copper thickness of the overall circuit of the circuit board caused by one-time electroplating, and greatly reduces the difference in copper thickness in the overall circuit of high copper thickness products and products with large differences in circuit density on the same circuit board.

[0037] As a specific example, the preset value of the residual copper rate is 25-35%; when other electroplating process parameters remain unchanged, the current density of the two electroplatings is linearly related to the average residual copper rate of the two areas: the current density of electroplating in the open area of ​​the line / the current density of electroplating in the densely populated area of ​​the line=the average residual copper rate in the open area of ​​the line / the average residual copper rate in the densely populated area of ​​the line.

[0038] As a preferred embodiment, in S1, the deposited copper 3 is prepared by chemical vapor deposition.

[0039] As a preferred embodiment, in S2, exposing the deposited copper 3 in the copper wire area to be electroplated in the circuit empty area by photolithography specifically comprises: removing the organic film 4 on the deposited copper 3 in the copper wire area to be electroplated in the circuit empty area by exposure and development.

[0040] As a preferred embodiment, in S4, exposing the deposited copper 3 in the copper wire region to be electroplated in the densely-connected area by photolithography specifically comprises: removing the organic film 4 on the deposited copper 3 in the copper wire region to be electroplated in the densely-connected area by exposure and development.

[0041] As a preferred embodiment, after S5, the step of removing the organic film 4 is further included, and after the step of removing the organic film 4, the step of etching and removing the deposited copper 3 is further included, and the deposited copper 3 removed by etching is the deposited copper 3 not covered by the electroplated copper 5.

[0042] In summary, the method of the present invention divides the circuit board into a circuit-free area and a circuit-dense area according to the density of the circuit design on the circuit board, and electroplates the circuit-free area and the circuit-dense area in batches respectively; adjusts the electroplating parameters according to the residual copper rates of the circuit-free area and the circuit-dense area, improves the uniformity of the copper thickness in the overall circuit of the circuit board, and controls the copper thickness difference of the same circuit board to be less than ±2μm; and through batch electroplating, avoids the problem of poor copper thickness uniformity of the overall circuit of the circuit board caused by one-time electroplating, and greatly reduces the copper thickness difference in the overall circuit of high copper thickness products and products with large differences in circuit density on the same circuit board.

[0043] The present invention has been described in detail above in conjunction with specific implementations and exemplary examples, but these descriptions cannot be understood as limiting the present invention. Those skilled in the art understand that, without departing from the spirit and scope of the present invention, a variety of equivalent substitutions, modifications or improvements may be made to the technical solution of the present invention and its implementation methods, all of which fall within the scope of the present invention. The scope of protection of the present invention shall be subject to the attached claims.

Claims

1. An electroplating method for improving the uniformity of copper thickness of a circuit board, characterized in that: The steps include: S1. providing a base carrier with a copper foil, and preparing a layer of deposited copper on the surface of the copper foil; S2, covering the deposited copper with a layer of organic film, and exposing the deposited copper in the copper line area to be electroplated in the circuit empty area by photolithography; S3, preparing electroplated copper on the exposed deposited copper in the open area of ​​the circuit by electroplating, and then removing the organic film on the surface of the deposited copper; S4, secondary covering with an organic film, covering the deposited copper and the electroplated copper with the organic film, and exposing the deposited copper in the copper line area to be electroplated in the circuit-dense area by photolithography; S5. Prepare electroplated copper by electroplating on the exposed deposited copper in the circuit-dense area.

2. The electroplating method for improving the uniformity of copper thickness of a circuit board according to claim 1, characterized in that: Define the residual copper rate = area of ​​copper area to be electroplated / total area, divide the circuit board into several unit areas, define the unit area with a residual copper rate greater than a preset value as a circuit-intensive area, and set the unit area with a residual copper rate less than or equal to the preset value as a circuit-free area.

3. The electroplating method for improving the uniformity of copper thickness of a circuit board as claimed in claim 2, characterized in that: The preset value of the residual copper rate is 25-35%.

4. The electroplating method for improving the uniformity of copper thickness of a circuit board as claimed in claim 2, characterized in that: The current density of electroplating in the open area of ​​the line / the current density of electroplating in the dense area of ​​the line = the average value of the residual copper rate in the open area of ​​the line / the average value of the residual copper rate in the dense area of ​​the line.

5. The electroplating method for improving the uniformity of copper thickness of a circuit board as claimed in claim 1, characterized in that: In S1, the deposited copper is prepared by chemical vapor deposition.

6. The electroplating method for improving the uniformity of copper thickness of a circuit board as claimed in claim 1, characterized in that: In S2, exposing the deposited copper in the copper wire area to be electroplated in the circuit empty area by photolithography specifically comprises: removing the organic film on the deposited copper in the copper wire area to be electroplated in the circuit empty area by exposure and development.

7. The electroplating method for improving the uniformity of copper thickness of a circuit board as claimed in claim 1, characterized in that: In S4, exposing the deposited copper in the copper wire region to be electroplated in the densely-connected area by photolithography specifically comprises: removing the organic film on the deposited copper in the copper wire region to be electroplated in the densely-connected area by exposure and development.

8. The electroplating method for improving the uniformity of copper thickness of a circuit board as claimed in claim 1, characterized in that: After S5, the step of removing the organic film is also included.

9. The electroplating method for improving the uniformity of copper thickness of a circuit board as claimed in claim 8, characterized in that: The step of removing the organic film further includes a step of etching to remove the deposited copper.

10. The electroplating method for improving the uniformity of copper thickness of a circuit board as claimed in claim 9, characterized in that: The deposited copper removed by etching is the deposited copper not covered by the electroplated copper.

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