A method for reducing the consumption of organic additives in pulse plating processes

Abstract

This invention discloses a method for reducing the consumption of organic additives in pulse electroplating processes. Before and / or during pulse electroplating, a non-oxidizing gas is bubbled into the electroplating solution, or a substance that generates the non-oxidizing gas is added, and / or the electroplating solution is degassed. By bubbling a non-oxidizing gas (such as nitrogen) into the electroplating solution or / simultaneously degasing the electroplating solution, the dissolved oxygen content in the electroplating solution can be effectively reduced. This effectively inhibits the oxidative decomposition of additives caused by the oxygen evolution reaction at the anolyte under pulse electroplating conditions, resulting in a very low level of additive consumption when using an anode (especially an insoluble anode), significantly reducing maintenance time and costs.

Description

Technical Field

[0001] This invention belongs to the field of electroplating technology and relates to a method for reducing the consumption of additives, specifically a method for reducing the consumption of organic additives in a pulse electroplating process. Background Technology

[0002] In the copper plating process for printed circuit boards (PCBs), pulse plating technology has gradually become the mainstream process due to its excellent deep plating capability and coating uniformity. Currently, pulse plating processes typically use phosphor bronze balls as soluble anodes, resulting in lower consumption of organic additives. However, phosphor bronze balls present challenges in terms of maintenance, including high time costs and complex manual operation. Therefore, the industry is gradually shifting towards insoluble iridium oxide-coated titanium mesh anodes (i.e., oxygen evolution pulse technology). Driven by the demand for artificial intelligence, oxygen evolution pulse technology is expected to enter industrial applications in 2024-2025. However, this anode triggers a strong oxygen evolution reaction during electroplating, leading to a significant increase in the consumption of organic additives (such as brighteners and leveling agents), typically several times or even ten times that of phosphor bronze ball anodes.

[0003] To reduce the consumption of organic additives in insoluble anode systems, existing technologies mainly explore the following aspects: (1) Physical isolation method: using neutral diaphragm anode boxes to reduce the consumption of additives at the anode end, but the effect is not ideal; (2) Electrochemical redox pair method: introducing Fe 2+ / Fe 3+ Ions (concentration 50ppm~20g / L). Add Fe to the plating bath. 2+ / Fe 3+ Ions can form Fe on the anode surface 2+ / Fe 3+ Redox couples preferentially undergo oxidation reactions over organic additives, thus “sacrificing” the additives; however, this method has a high iron content system, which places higher demands on equipment, and the problem of high additive consumption has not been solved in the plating solution system with low iron content; (3) Chemical inhibition method: Add alcohol compounds (such as US6773573B2) or organic reducing agents (such as those studied by AJ Cobley et al.) to inhibit the decomposition of additives. It can be seen that the existing technical solutions for reducing the amount of organic additives used have not produced satisfactory results; especially for the use of insoluble anodes in pulse electroplating, the improvement measures from the anode side have not yet achieved the expected results. The current consumption level of insoluble titanium mesh affects the stability and product quality of the vertical continuous copper plating process. Some production lines even need to dilute the plating solution every week to maintain stable production, resulting in a significant increase in cost and a decrease in efficiency. Summary of the Invention

[0004] In view of this, the purpose of this invention is to overcome the shortcomings of the prior art and provide a method for reducing the consumption of organic additives in pulse electroplating processes.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is: a method for reducing the consumption of organic additives in a pulse electroplating process, wherein a non-oxidizing gas is bubbled into the electroplating solution or a substance that generates the non-oxidizing gas is added before and / or during the pulse electroplating process, and / or the electroplating solution is degassed.

[0006] Ideally, the dissolved oxygen content in the electroplating solution is reduced to ≤5 mg / L, preferably ≤2 mg / L.

[0007] Ideally, the non-oxidizing gas can be in its liquid or solid state.

[0008] Furthermore, the non-oxidizing gas is a gas that does not contain oxygen or has an oxygen partial pressure ≤10 kPa.

[0009] Furthermore, the degassing treatment of the electroplating solution involves passing the electroplating solution through a degassing membrane and evacuating or introducing a non-oxidizing gas with an oxygen partial pressure ≤10 kPa on the other side of the degassing membrane.

[0010] Furthermore, the non-oxidizing gas is a mixture selected from one or more of nitrogen, argon, carbon dioxide and sulfur dioxide, preferably nitrogen.

[0011] Ideally, the anode used in the pulse electroplating process is an insoluble titanium mesh with an iridium oxide coating.

[0012] Ideally, the pulse electroplating process is carried out in the main electroplating tank, the electroplating solution is placed in the main electroplating tank, and the main electroplating tank is connected to an auxiliary electroplating tank. The non-oxidizing gas is bubbled into the main electroplating tank, the auxiliary electroplating tank, or / and the electroplating solution circulation pipeline connecting the main electroplating tank and the auxiliary electroplating tank, or a substance that generates the non-oxidizing gas is added.

[0013] Furthermore, pipes containing perforated nozzles are arranged in the main electroplating tank, the auxiliary electroplating tank, and / or the circulation pipeline for aeration.

[0014] Furthermore, the non-oxidizing gas is supplied from a gas storage tank or generated on-site.

[0015] Compared with the prior art, the present invention has the following beneficial effects: The method of the present invention for reducing the consumption of organic additives in the pulse electroplating process can effectively reduce the dissolved oxygen content in the electroplating solution by blowing non-oxidizing gas (such as nitrogen) into the electroplating solution or / simultaneously degassing the electroplating solution. This effectively inhibits the oxidative decomposition of additives caused by the oxygen evolution reaction at the anode, so that the additive consumption level when using the anode (especially the insoluble anode) is reduced to a very low level, which can significantly reduce maintenance time and cost. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the pulse electroplating process of the present invention (Example 1). Figure 2 This is a schematic diagram of the pulse electroplating process of the present invention (Comparative Example 2). Detailed Implementation

[0017] The foregoing descriptions and other technical contents, features, and effects of this invention will be clearly presented in the following detailed description of a preferred embodiment with reference to the accompanying drawings. The directional terms used in the following embodiments, such as up, down, left, right, front, or back, are merely for reference to the accompanying drawings. Therefore, the directional terms used are for illustrative purposes and not for limiting the invention.

[0018] The present invention provides a method for reducing the consumption of organic additives in a pulse electroplating process, which involves introducing a non-oxidizing gas into the electroplating solution or adding a substance that generates the non-oxidizing gas before and / or during the pulse electroplating process, and / or degassing the electroplating solution.

[0019] The dissolved oxygen content in the electroplating solution is reduced to ≤5 mg / L, preferably ≤2 mg / L. The non-oxidizing gas can be in liquid or solid state. The non-oxidizing gas is a gas that does not contain oxygen or has an oxygen partial pressure of less than 10 kPa. The atmosphere for the degassing treatment is an atmosphere with an oxygen partial pressure ≤10 kPa. The non-oxidizing gas is a mixture selected from one or more of nitrogen, argon, helium, carbon dioxide, and sulfur dioxide, preferably nitrogen. The degassing treatment of the electroplating solution involves passing the electroplating solution through a degassing membrane and evacuating or introducing a non-oxidizing gas with an oxygen partial pressure ≤10 kPa (or maintaining a non-oxidizing gas atmosphere with an oxygen partial pressure ≤10 kPa) on the other side of the degassing membrane; the degassing membrane usually has two sides, one side through which the electroplating solution passes, and the other side evacuated or introduced with a non-oxidizing gas atmosphere with an oxygen partial pressure ≤10 kPa; here, one side and the other side of the degassing membrane can be the outer and inner sides of the degassing membrane, which can be conventionally distinguished according to the shape of the degassing membrane and the application scenario). The anode used in the pulse electroplating process is an insoluble titanium mesh with an iridium oxide coating.

[0020] The pulse electroplating process is carried out in the main electroplating tank, and the electroplating solution is contained in the main electroplating tank. The main electroplating tank is connected to an auxiliary electroplating tank (i.e., a secondary electroplating tank); the main electroplating tank and the secondary electroplating tank are referred to as the main and secondary tanks, respectively. Figure 1 (As shown); the non-oxidizing gas is bubbled into the main electroplating tank, the auxiliary electroplating tank, and / or the electroplating solution circulation pipeline connecting the main electroplating tank and the auxiliary electroplating tank, or a substance that generates the non-oxidizing gas is added. Pipes containing perforated nozzles are installed in the main electroplating tank, the auxiliary electroplating tank, and / or the circulation pipeline for aeration. The non-oxidizing gas is supplied from a gas storage tank or generated on-site.

[0021] The preferred embodiments of the present invention will now be described in detail. Example 1

[0022] This embodiment provides a method for reducing the consumption of organic additives in a pulse electroplating process, as detailed below: Electroplating solution preparation: sulfuric acid (230 g / L), copper sulfate pentahydrate (75 g / L), chloride ions (70 ppm, added as hydrochloric acid), leveling agent 13 ml / L (Medermay PPR 100 Wetter), brightener 0.5 ml / L (Medermay PPR 100 Replenish), circulation ( Figure 1 (Circulate in the main and auxiliary tanks) for 1-2 hours until completely dissolved, and maintain the temperature at 25±1℃.

[0023] Pulse electroplating process: The electroplating solution is placed in the electroplating tank. The anode is a titanium mesh anode with an insoluble iridium oxide coating (encased in a PP anode box with a polypropylene anode bag and a neutral diaphragm), and the cathode is a PCB board. The anode and cathode are immersed in the electroplating solution for pulse electroplating (pulse electroplating parameters: forward 3ASD, 100 ms, reverse 4.5ASD, 5 ms), and the electroplating time is 1 hour. During the electroplating process, brightener is added at a constant rate (2.0 ml per hour) using a syringe, and the concentration of each component in the electroplating solution is kept stable during the electroplating process, with concentration variations within ±10%. Before electroplating, nitrogen gas (with an oxygen content of <1%, commercially available) is pre-bubbled into the electroplating solution and circulated fully until the dissolved oxygen content in the electroplating solution drops to 5 mg / L. During the electroplating process, a jet pipe is used to spray the electroplating solution onto the cathode PCB board to increase convection (based on the volume of additives added, the additive concentration before and after electroplating measured by cyclic voltammetry (CVS), and the amount of electricity passed, the volume of additives consumed per KAH is approximately 1200-1400 mL). Example 2

[0024] This embodiment provides a method for reducing the consumption of organic additives in a pulse electroplating process. It is basically the same as that in Example 1, except that nitrogen gas is not bubbled in before electroplating, but is continuously bubbled in at 0.2 L / min during the electroplating process. The calculated volume of additive consumed per KAH is approximately 800-1000 mL. If electroplating is continued for 6 hours, it is found that the additive consumption gradually decreases to a stable range of 200-300 mL / KAH as the electroplating time increases. Example 3

[0025] This embodiment provides a method for reducing the consumption of organic additives in a pulse electroplating process. It is basically the same as that in Example 1, except that nitrogen gas (with an oxygen content of <1%, commercially available) is pre-introduced into the electroplating solution before electroplating and circulated fully until the dissolved oxygen content in the electroplating solution drops to 2 mg / L. The calculated volume of additive consumed per KAH is approximately 500-600 mL. Example 4

[0026] This embodiment provides a method for reducing the consumption of organic additives in a pulse electroplating process. It is basically the same as that in Example 1, except that nitrogen gas (with an oxygen content of <1%, commercially available) is pre-introduced into the electroplating solution before electroplating and circulated fully until the dissolved oxygen content in the electroplating solution drops to 1 mg / L. The calculated volume of additive consumed per KAH is approximately 200-300 mL. Example 5

[0027] This embodiment provides a method for reducing the consumption of organic additives in a pulse electroplating process. It is basically the same as that in Embodiment 2, except that the electroplating solution is treated with a degassing membrane assembly during electrolysis (specifically, the electroplating solution flows through the inner tube of the degassing membrane assembly at a rate of 0.5 L / min and then returns to the main electroplating tank. The outer diameter of the degassing module is connected to a vacuum pump (i.e., the degassing membrane assembly has a degassing membrane, the electroplating solution flows through the degassing membrane, and the outer side of the degassing membrane is connected to a vacuum pump). The pressure is -0.99 bar (i.e., 100 kPa). The calculated volume of additives consumed per KAH is 200-300 mL.

[0028] Comparative Example 1 This embodiment provides a method for reducing the consumption of organic additives in a pulse electroplating process. It is basically the same as that in Example 1, except that nitrogen gas is not introduced before electroplating. The calculated consumption is approximately 1600-1800 ml / KAH.

[0029] Comparative Example 2 This embodiment provides a method for reducing the consumption of organic additives in a pulse electroplating process. It is essentially the same as that in Embodiment 2, except that the electroplating solution flows from the main electroplating tank to an auxiliary electroplating tank below or to the side. This process increases the exchange of the plating solution with air, maintaining the dissolved oxygen in the electroplating solution at an atmospheric equilibrium level of 7-9 mg / L. Nitrogen gas is not introduced into the main or auxiliary electroplating tanks before or during electroplating. Figure 2 As shown, the electroplating solution circulates in the main electroplating tank and the auxiliary electroplating tank at this time. The calculated volume of additive consumed per KAH is approximately 1800-2000 mL.

[0030] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for reducing the consumption of organic additives in a pulse electroplating process, characterized in that: Before and / or during pulse electroplating, a non-oxidizing gas is bubbled into the electroplating solution or a substance that generates the non-oxidizing gas is added, and / or the electroplating solution is degassed.

2. The method for reducing the consumption of organic additives in a pulse electroplating process according to claim 1, characterized in that: The dissolved oxygen content in the electroplating solution is reduced to ≤5 mg / L, preferably ≤2 mg / L.

3. The method for reducing the consumption of organic additives in a pulse electroplating process according to claim 1 or 2, characterized in that: The non-oxidizing gas can be in liquid or solid form.

4. The method for reducing the consumption of organic additives in a pulse electroplating process according to claim 1 or 2, characterized in that: The non-oxidizing gas is a gas that does not contain oxygen or has an oxygen partial pressure ≤10 kPa.

5. The method for reducing the consumption of organic additives in a pulse electroplating process according to claim 1 or 2, characterized in that: The electroplating solution is degassed by passing it through a degassing membrane and evacuating or introducing a non-oxidizing gas with an oxygen partial pressure ≤10 kPa on the other side of the membrane.

6. The method for reducing the consumption of organic additives in a pulse electroplating process according to claim 4, characterized in that: The non-oxidizing gas is a mixture selected from one or more of nitrogen, argon, carbon dioxide and sulfur dioxide, preferably nitrogen.

7. The method for reducing the consumption of organic additives in a pulse electroplating process according to claim 1 or 2, characterized in that: The anode used in the pulse electroplating process is an insoluble titanium mesh with an iridium oxide coating.

8. The method for reducing the consumption of organic additives in a pulse electroplating process according to claim 1 or 2, characterized in that: The pulse electroplating process is carried out in the main electroplating tank, the electroplating solution is placed in the main electroplating tank, and the main electroplating tank is connected to an auxiliary electroplating tank. The non-oxidizing gas is bubbled into the main electroplating tank, the auxiliary electroplating tank, or / and the electroplating solution circulation pipeline connecting the main electroplating tank and the auxiliary electroplating tank, or a substance that generates the non-oxidizing gas is added.

9. The method for reducing the consumption of organic additives in a pulse electroplating process according to claim 8, characterized in that: Pipes containing perforated nozzles are installed in the main electroplating tank, the auxiliary electroplating tank, and / or the circulation pipeline for aeration.

10. The method for reducing the consumption of organic additives in a pulse electroplating process according to claim 8 or 9, characterized in that: The non-oxidizing gas is supplied from a gas storage tank or generated on-site.

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