A method for horizontal copper plating uniformity applications

Abstract

The application provides a horizontal copper plating uniformity application method; the method adopts a partitioned anode plate, cancels an anode shielding plate, and has the following advantages: (1) control is more accurate, and the yield of products with higher quality requirements can be improved; (2) greater current can be tolerated, so that products of higher stages can be produced and processed, and process capacity is improved; (3) current distribution can be accurately controlled, current in a high-current area is reduced, current in a low-current area is improved, plating uniformity is improved, and processing cost is reduced; and (4) the anode net adopts a single-layer thickened net design, and cost is reduced. The application adopts the partitioned anode plate, adjusts current output through a segmented process current controller, makes current distribution more accurate, combines the insoluble anode plate, and can meet ideal uniformity indexes. In addition, the grid-shaped insoluble anode and the thickened anode plate coating can tolerate greater current density, and meet the plating uniformity requirements under the condition of large current.

Description

Technical Field

[0001] This invention relates to the field of electronic circuit board manufacturing and processing, specifically to a method for achieving uniformity in horizontal copper plating. Background Technology

[0002] Copper layer uniformity is crucial for signal transmission speed and signal integrity on circuit boards, effectively reducing signal interference. In horizontal electroplating, the current distribution at the anode determines the thickness distribution of the copper layer deposited on the cathode surface; therefore, anode design is a key factor affecting copper plating uniformity. In horizontal electroplating, the following effects lead to uneven plating: edge effect: current tends to concentrate at the edges, resulting in higher current density and thicker plating at the edges; center weakening: current is sparse in the center, resulting in lower current density and thinner plating. In traditional processes, the anode plate is a single piece, and the entire anode is subjected to the same current, making it impossible to correct this inherent uneven current distribution. The plating exhibits a "thick edge, thin center" appearance, resulting in poor uniformity. The only way to passively improve uniformity is to add an anode shield to block the anode, but the effect is limited.

[0003] With the advancement of technology, existing processes can no longer meet the requirements for copper thickness variation. Due to edge effects and varying board sizes, the copper plating variation often exceeds 8 μm, resulting in substandard impedance values ​​after etching, affecting signal transmission integrity; some areas have insufficient linewidth, leading to poor anti-interference capabilities; and burrs exist in edge areas, making it impossible to etch cleanly. This significantly impacts product yield, especially in fields such as 5G, AI server boards, and carrier boards.

[0004] In traditional vertical gantry copper plating lines and VCP plating lines, methods to improve the uniformity of copper plating typically include adding cathode baffles, adding edge strips to clamps, or adding openings to anode baffles. However, the improvement in uniformity is limited, affecting subsequent etching processes. Large variations in copper thickness have a significant impact on subsequent etching processes. Different areas on the same board exhibit varying impedance values, resulting in some areas being poorly etched with burrs, while others are scrapped due to over-etching, causing linewidths to exceed negative tolerances. Furthermore, the utilization rate of copper balls in existing technologies is low. Due to poor plating uniformity, to ensure that the minimum area on the board meets the copper thickness requirements, the overall copper plating thickness must be increased, leading to a significant increase in copper ball consumption, resulting in material waste and increased costs.

[0005] Specifically, a common problem in existing horizontal electroplating is the "dense current at the edges and sparse current in the center." Current tends to concentrate at the edges of the cathode plate, resulting in high current density and a thicker plating layer in the edge region; while the current is sparse in the center of the plate, resulting in low current density and a thinner plating layer. This inherent uneven current distribution means that a single anode cannot simultaneously meet the current regulation needs of different areas, further exacerbating the copper thickness variation and limiting the improvement of plating uniformity.

[0006] In conclusion, a new technical solution is urgently needed to address the problems existing in the current technology. Summary of the Invention

[0007] Based on this, the present invention provides a method for achieving uniformity of horizontal copper plating; the method uses a partitioned anode plate and eliminates the anode shield, which has the following advantages: (1) more precise control, which can improve the yield of products with higher production quality requirements; (2) able to withstand larger currents, thereby producing products at higher stages and improving process capabilities; (3) able to precisely control the current distribution, reduce the current in the high current area and increase the current in the low current area, improve the uniformity of electroplating, and reduce processing costs; (4) the anode mesh adopts a single-layer thickened mesh design, which reduces costs.

[0008] One object of the present invention is to provide a method for achieving uniformity in horizontal copper plating, the method comprising the following steps: S1. Divide the anode plate horizontally into two rectangular regions of the same size. Then, divide each rectangular region diagonally into two triangular regions, resulting in four mutually insulated and isolated independent partitions. The four mutually insulated and isolated independent zones are, from left to right, zone A, zone B, zone C, and zone D; Areas A and C are located in the first horizontal plane; Areas B and D are located in the second horizontal plane; The first horizontal plane and the second horizontal plane are parallel to each other and do not lie in the same plane; in, The division along the diagonal is defined as: division along mutually parallel diagonals; S2. Connect each independent partition to an independent power supply or channel, and control the current output of each partition separately through the independent power supply or channel; S3. Based on the characteristic requirements of different areas on the plate to be plated, segmented current control is performed on the independent partitions to make each independent partition have a differentiated current density. S4. Perform horizontal electroplating on the plate to be plated under the conditions of the differentiated current density.

[0009] Furthermore, the anode plate includes an upper anode plate and a lower anode plate; the upper anode plate is subjected to the above-described treatment to divide it into four mutually insulated and isolated independent zones, and the lower anode plate is subjected to the same treatment.

[0010] Furthermore, the distance between the first horizontal plane and the second horizontal plane in the direction perpendicular to the horizontal plane is 1-5 mm.

[0011] Furthermore, the current density of the four mutually insulated and isolated independent zones is: Zone C > Zone B > Zone A > Zone D.

[0012] Preferably, the current density in region C is 11-19 ASD; the current density in region B is 7-13 ASD; the current density in region A is 5-10 ASD; and the current density in region D is 0.5-1.5 ASD.

[0013] Furthermore, the distance from the lower anode plate to the plate to be plated is 10-15 cm.

[0014] Furthermore, the distance from the upper anode plate to the plate to be plated is 12-17 cm.

[0015] Furthermore, the anode plate is a mesh-shaped insoluble anode with a single-layer thickened mesh design, and the anode plate is thickened with a ruthenium-iridium coating; the thickness of the thickened anode plate is 10-30 μm.

[0016] Furthermore, the set current density for the electroplating process is 1-10 ASD. The set current density refers to the target current density value for the overall electroplating process.

[0017] Furthermore, the independent power supply or channel is implemented through a modular rectifier, with each independent partition connected to an independent output port of the modular rectifier.

[0018] Furthermore, the method for achieving uniformity of horizontal copper plating is applicable to any of the following plating types: DC insoluble anodic plating, pulse insoluble anodic plating, and DC through-hole filling insoluble anodic plating.

[0019] This invention employs a long triangular anode design, with the core principle of using "variable width + oblique boundary + independent current control" to precisely offset edge effects and current unevenness in the conveying direction, ensuring uniform current density on the cathode plate from edge to center and from feed to discharge. Horizontal electroplating (PCB or carrier board) involves continuous transport of long workpieces, resulting in two critical unevennesses in the electric field: Lateral edge effect: The electric field lines are dense on the left and right edges, resulting in dense current and thick coating; the lines are sparse in the middle, resulting in sparse current and thin coating (thick at the edges and thin at the center).

[0020] Differences in conveyor thickness: The current tends to concentrate at the feed end and weakens at the discharge end. Combined with workpiece movement, this results in a thickness difference between the front and back.

[0021] The long triangular partitioning of this invention directly matches these two unevennesses: Wide outer, narrow inner (triangular contour): The outer (edge) anode area is large, and the inner (center) area is small, naturally reducing the edge current density and increasing the center current density, thus compensating for the edge effect. Slanted partition boundary: The partition seam is not parallel to the conveying direction (horizontal direction), avoiding current concentration or interruption at the seam and preventing strip-shaped thickness marks. Long strip extension: The partition is extended along the conveying direction, covering the entire length of the workpiece, compensating for the longitudinal current attenuation from feed to discharge.

[0022] This invention employs a zoned anode control output current control method to precisely control the output current and modularly control the area to compensate for the size of each area, thereby correcting the copper plating thickness. For example, area A has dense holes, so the current in area A can be compensated separately. Area C is in the middle of the board, where the copper thickness in the middle of the plating effect will be less, so the current compensation in area C can be increased. Area D has an edge effect, so the compensation value can be appropriately reduced to reduce the edge effect of plating.

[0023] Dense hole area refers to the area on a PCB board where the number of drilled holes is relatively high. Figure 1 The image shown is a real photograph of the PCB fabrication board; Figure 1 The area indicated by the middle arrow is the area with dense holes.

[0024] The principle behind partitioned anodes is as follows: Essentially, the entire anode is divided into multiple independent, insulated zones. Each zone uses an independent power supply or channel to adjust the current, actively correcting the inherent unevenness of the cathode plate surface, where "the current is denser at the edges and sparser in the center," thereby achieving a uniform coating thickness across the entire surface.

[0025] This invention adopts a single-layer thickened mesh design to reduce costs, and can output current in segments to compensate for dense holes in certain areas, thereby increasing the current density, increasing the copper thickness and reducing the copper thickness difference.

[0026] The present invention has the following beneficial effects: This invention provides a method for achieving uniformity in horizontal copper plating. This method uses a partitioned anode plate and eliminates the anode shield, which has the following advantages: (1) more precise control, which can improve the yield of products with higher production quality requirements; (2) able to withstand larger currents, thereby producing products at higher stages and improving process capabilities; (3) able to precisely control the current distribution, reduce the current in the high current area and increase the current in the low current area, improve the uniformity of electroplating, and reduce processing costs; (4) the anode mesh adopts a single-layer thickened mesh design, which reduces costs.

[0027] This invention employs a partitioned anode plate, enabling segmented current control and flexible adjustment of the current density in each region. The anode plate is divided into four mutually insulated and isolated partitions to prevent cross-conduction and ensure proper current distribution. A segmented current controller regulates the current output, resulting in more precise current distribution. Combined with an insoluble anode plate, this achieves optimal uniformity. Furthermore, the use of a grid-like insoluble anode and a thickened anode plate coating allows for greater current density tolerance, meeting the electroplating uniformity requirements under high current conditions. Attached Figure Description

[0028] Figure 1 The image shown is a real photograph of the PCB fabrication board.

[0029] Figure 2A schematic diagram of a partitioned anode plate according to an embodiment is shown.

[0030] Figure 3 The diagram shows the parameter setting interface for the electroplating equipment.

[0031] Figure 4 A photograph of the copper plating specimen of Example 1 is shown; in, Figure 4 (a) shows a physical image of the copper-plated C-side of Example 1; Figure 4 (b) shows a physical image of the copper-plated S-side of Example 1.

[0032] Figure 5 A photograph of the copper plating specimen from Example 2 is shown. in, Figure 5 (a) shows a physical image of the copper-plated C-side of Example 2; Figure 5 (b) shows a physical image of the copper-plated S-side of Example 2. Detailed Implementation

[0033] To more clearly illustrate the technical solution of the present invention, the following embodiments are provided. Unless otherwise stated, the raw materials, reactions, and post-processing methods appearing in the embodiments are all commercially available raw materials and technical methods well known to those skilled in the art.

[0034] The terms "preferred," "more preferably," and "more suitable" used in this invention refer to embodiments of the invention that provide certain beneficial effects under certain circumstances. However, other embodiments may also be preferred under the same or other circumstances. Furthermore, the description of one or more preferred embodiments does not imply that other embodiments are unavailable, nor is it intended to exclude other embodiments from the scope of this invention.

[0035] It should be understood that, except in any operational instance or otherwise indicated, the amounts or all figures representing ingredients used, for example, in the specification and claims, should be understood to be modified by the term "about" in all cases. Therefore, unless otherwise stated, the numerical parameters set forth in the following specification and appended claims are approximate values ​​varying according to the desired performance to be obtained according to the invention.

[0036] The embodiments of the present invention are implemented in the following manner: A method for achieving uniformity in horizontal copper plating, comprising the following steps: The method for achieving uniform horizontal copper plating includes the following steps: S1. Divide the anode plate horizontally into two rectangular regions of the same size. Then, divide each rectangular region diagonally into two triangular regions, resulting in four mutually insulated and isolated independent partitions. The four mutually insulated and isolated independent zones are, from left to right, zone A, zone B, zone C, and zone D; Areas A and C are located in the first horizontal plane; Areas B and D are located in the second horizontal plane; The first horizontal plane and the second horizontal plane are parallel to each other and do not lie in the same plane; in, The division along the diagonal is defined as: division along mutually parallel diagonals; S2. Connect each independent partition to an independent power supply or channel, and control the current output of each partition separately through the independent power supply or channel; S3. Based on the characteristic requirements of different areas on the plate to be plated, segmented current control is performed on the independent partitions to make each independent partition have a differentiated current density. S4. Perform horizontal electroplating on the plate to be plated under the conditions of the differentiated current density.

[0037] like Figure 2 As shown, the three interior angles of the triangular region in the embodiment are 30°, 60°, and 90°.

[0038] The distance between the first horizontal plane and the second horizontal plane in the direction perpendicular to the horizontal plane is 2 mm.

[0039] The anode plate includes an upper anode plate and a lower anode plate; the upper anode plate is subjected to the above-described treatment to divide it into four mutually insulated and isolated independent zones, and the lower anode plate is subjected to the same treatment.

[0040] The distance from the lower anode plate to the plate to be plated is 10 cm, and the distance from the upper anode plate to the plate to be plated is 12 cm; The anode plate is a grid-shaped insoluble anode (titanium plated with ruthenium-iridium, 10 μm thick); the current density is set to 6-10 ASD; In this embodiment of the invention, the independent power supply or channel is a rectifier; the plate to be plated is a base copper.

[0041] Figure 2 A schematic diagram of a partitioned anode plate according to an embodiment is shown.

[0042] Figure 3The diagram shows the parameter setting interface of the electroplating equipment. The arrows in the diagram indicate examples of current density settings for each zone; the diagram indicates: the current density of surface C (top) corresponds to the current density of the upper anode plate zone, and the current density of surface S (bottom) corresponds to the current density of the lower anode plate zone; the diagram indicates: top, middle 1, middle 2, and bottom correspond to anode plate zones A, B, C, and D, respectively.

[0043] In the bath composition of the example: the brightener AC-900B, the leveling agent AC-900A, and the wetting agent AC-900C are all produced by Zhuhai Songbai Technology Co., Ltd.

[0044] In this embodiment, the C-side of the bottom copper refers to the side of the bottom copper closest to the upper anode plate; the S-side of the bottom copper refers to the side of the bottom copper closest to the lower anode plate.

[0045] Example 1 Example 1 is an example of 20 μm gradient copper plating on a base copper (15 μm, iron-free) with a current density of 6 ASD.

[0046] The composition of the bath solution is shown in Table 1.

[0047] Table 1. Analysis of Bath Solution Components The operating parameters are shown in Table 2.

[0048] Table 2 Operating Parameter Table The base copper is plated with copper according to the above parameters, and then the uniformity of the copper plating is tested.

[0049] The test results are shown in Table 3-5 and Figure 4 As shown.

[0050] Figure 4 A photograph of the copper plating specimen of Example 1 is shown; in, Figure 4 (a) shows a physical image of the copper-plated C-side of Example 1; Figure 4 (b) shows a physical image of the S-side of the copper plating in Example 1. The data in the figure represent the total thickness of the base copper and the copper plating (unit: μm). Subtracting the thickness of the base copper yields the results in Table 3-5.

[0051] Table 3. Test results of copper plating uniformity on C-side with a 20 μm gradient. Table 4. Test results of copper plating uniformity on the S-plane with a 20 μm gradient. Table 5 Uniformity Test Calculation The parameters in Table 5 represent: MAX: Maximum value; MIN: Minimum value; R: Range; AVG: Mean; STP: Standard deviation; COV: Uniformity index; Range R = MAX - MIN; COV = STP / AVG.

[0052] The test results above show that the method of the present invention has good uniformity in copper plating at a gradient of 20 μm.

[0053] Example 2: Example 2 is an example of 30 μm gradient copper plating on a base copper (15 μm, iron-free) with a current density of 8 ASD.

[0054] The composition of the bath solution is shown in Table 6.

[0055] Table 6. Analysis of Bath Solution Components The operating parameters are shown in Table 7.

[0056] Table 7 Operating Parameter Table The base copper is plated with copper according to the above parameters, and then the uniformity of the copper plating is tested.

[0057] The test results are shown in Table 8-10 and Figure 5 As shown.

[0058] Figure 5 A photograph of the copper plating specimen from Example 2 is shown. in, Figure 5 (a) shows a physical image of the copper-plated C-side of Example 2; Figure 5 (b) shows a physical image of the S-side of the copper plating in Example 2. The data in the figure represent the total thickness of the base copper and the copper plating (unit: μm). Subtracting the thickness of the base copper yields the results in Table 8-10.

[0059] Table 8. Test results of copper plating uniformity on C-side with a 30 μm gradient. Table 9. Test results of copper plating uniformity on the S-plane with a 30 μm gradient. Table 10 Uniformity Test Calculation The parameters in Table 10 represent: MAX: Maximum value; MIN: Minimum value; R: Range; AVG: Mean; STP: Standard deviation; COV: Uniformity index; Range R = MAX - MIN; COV = STP / AVG.

[0060] The test results above show that the method of the present invention has good uniformity in copper plating at a gradient of 30 μm.

[0061] Example 3 Example 3 is an example of 30 μm gradient copper plating on a base copper (17 μm, iron-free) with a current density of 10 ASD.

[0062] The composition of the bath solution is shown in Table 11.

[0063] Table 11 Analysis of Bath Solution Components The operating parameters are shown in Table 12.

[0064] Table 12 Operating Parameter Table The base copper is plated with copper according to the above parameters, and then the uniformity of the copper plating is tested.

[0065] The test results are shown in Table 13.

[0066] Table 13 Copper plating uniformity results (base copper 17 μm, the following results do not subtract the base copper thickness). The test results above show that the base copper is 17 μm thick, the thickest copper plating is 49.4 μm thick, the thinnest is 46.4 μm thick, the difference is 3 μm, and the copper plating uniformity is good.

[0067] The test results above show that the method of this invention can improve the uniformity of the coating and save on the processing cost of copper balls. For example, if a minimum copper thickness of 25 μm is required and the tolerance is 3 μm, a copper plating thickness of 28 μm is needed. If the tolerance is 8 μm, a copper plating thickness of 33 μm is required, an additional 5 μm plating. Based on a monthly calculation of 50,000 square meters... 2 8.93 50000 / 1000=4465 kg. If 4465 kg is used less per month, and the copper balls cost 100000 per ton, 446500 yuan can be saved per month, and 5358000 yuan per year.

[0068] This invention can improve production efficiency and save copper plating time. For example, conventional copper plating takes 60 minutes and requires an average copper thickness of 25 μm. With the same current, reducing the range by 5 μm can reduce the copper thickness by 5 μm, saving 20% ​​of the time, improving product quality, enabling the production and processing of higher-stage products, and enhancing process capabilities.

[0069] The method of this invention can achieve a copper plating thickness of 20-30 μm in a single pass. For high-current-density production, a current density of 8 ASD is set, with a 30% increase in current in the middle region and a 15% reduction at the edges to minimize edge effects. A copper thickness of 25 μm can be achieved in just 15 minutes.

[0070] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0071] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for achieving uniformity in horizontal copper plating, characterized in that, The method for achieving uniform horizontal copper plating includes the following steps: S1. Divide the anode plate horizontally into two rectangular regions of the same size. Then, divide each rectangular region diagonally into two triangular regions, resulting in four mutually insulated and isolated independent partitions. The four mutually insulated and isolated independent zones are, from left to right, zone A, zone B, zone C, and zone D; Areas A and C are located in the first horizontal plane; Areas B and D are located in the second horizontal plane; The first horizontal plane and the second horizontal plane are parallel to each other and do not lie in the same plane; in, The diagonal division is defined as: division along mutually parallel diagonals; S2. Connect each independent partition to an independent power supply or channel, and control the current output of each partition separately through the independent power supply or channel; S3. Based on the characteristic requirements of different areas on the plate to be plated, segmented current control is performed on the independent partitions to make each independent partition have a differentiated current density. S4. Perform horizontal electroplating on the plate to be plated under the conditions of the differentiated current density.

2. The method for achieving uniformity of horizontal copper plating according to claim 1, characterized in that, The anode plate includes an upper anode plate and a lower anode plate.

3. The method for achieving uniformity of horizontal copper plating according to claim 1, characterized in that, The distance between the first horizontal plane and the second horizontal plane in the direction perpendicular to the horizontal plane is 1-5 mm.

4. The method for achieving uniformity of horizontal copper plating according to claim 1, characterized in that, The current density of the four mutually insulated and isolated independent zones is: Zone C > Zone B > Zone A > Zone D.

5. The method for achieving uniformity of horizontal copper plating according to claim 2, characterized in that, The distance from the lower anode plate to the plate to be plated is 10-15 cm.

6. The method for achieving uniformity of horizontal copper plating according to claim 2, characterized in that, The distance from the upper anode plate to the plate to be plated is 12-17 cm.

7. The method for achieving uniformity of horizontal copper plating according to claim 1, characterized in that, The anode plate is a grid-shaped insoluble anode with a single-layer thickened mesh design. The anode plate is thickened with a ruthenium-iridium coating. The thickness of the thickened anode plate is 10-30 μm.

8. The method for achieving uniformity of horizontal copper plating according to claim 1, characterized in that, The independent power supply or channel is implemented through a modular rectifier, with each independent partition connected to an independent output port of the modular rectifier.

9. The method for achieving uniformity of horizontal copper plating according to claim 1, characterized in that, The method for achieving uniformity in horizontal copper plating is applicable to any of the following plating types: DC insoluble anodic plating, pulse insoluble anodic plating, and DC through-hole filling insoluble anodic plating.

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