A method for treating impurities in soft gold electroplating, and a soft gold electroplating process

Abstract

The application provides a soft gold electroplating impurity treatment method and a soft gold electroplating process, which comprises the following steps: performing activated carbon treatment on nickel electroplating solution in a nickel tank; installing a first electrolytic plate and a first filter element in the nickel tank; removing the first electrolytic plate and the first filter element after a first current is applied to a rectifier for a first duration; installing a second electrolytic plate and a second filter element; removing the second electrolytic plate and the second filter element after a second current is applied to the rectifier for a second duration, wherein the second current is greater than the first current, and the second duration is less than the first duration. According to the technical scheme of the embodiment, impurities can be filtered through activated carbon treatment, long-time electrolytic adsorption of impurities can be performed by using the characteristics that a small current has a good gathering effect, short-time electrolytic adsorption of residual impurities can be performed by using the characteristics that a large current has a strong adsorption capacity, impurities in the nickel tank can be effectively reduced, the composition parameters of the soft gold can be optimized, and the yield of the substrate can be improved.

Description

Technical Field

[0001] This invention relates to the field of semiconductor process technology, and in particular to a method for impurity treatment and a soft gold electroplating process. Background Technology

[0002] Soft gold plating is a crucial step in substrate fabrication, capable of depositing nickel-gold onto copper surfaces. Before soft gold plating, the substrate typically undergoes processes such as solder resist or dry film preparation, resulting in the substrate carrying elements like sulfur and chlorine. When the substrate is placed in a nickel bath for heating, these elements precipitate from the substrate into the plating solution. Without proper treatment, this can lead to excessive sulfur-to-nickel or chlorine-to-nickel ratios in the soft gold plating, reducing the subsequent solderability and impacting substrate yield. Summary of the Invention

[0003] The present invention aims to at least solve one of the technical problems existing in the prior art. To this end, the present invention proposes a method and process for impurity treatment in soft gold electroplating, which can treat impurities in the electroplating solution, improve the production quality of soft gold, and increase the yield of substrates.

[0004] In a first aspect, embodiments of the present invention provide a method for impurity treatment in soft gold electroplating, comprising:

[0005] The nickel plating solution in the nickel bath is treated with activated carbon.

[0006] A first electrolytic plate is installed in the rectifier in the nickel tank, and a first filter element is installed in the filter tank of the nickel tank. After applying a first current to the rectifier for a first duration, the first electrolytic plate and the first filter element are removed. The first filter element is used to adsorb sulfur-containing impurities and chlorine-containing impurities.

[0007] A second electrolysis plate is installed in the rectifier, and a second filter element is installed in the filter tank. After applying a second current to the rectifier for a second duration, the second electrolysis plate and the second filter element are removed. The second current is greater than the first current, and the second duration is less than the first duration. The second filter element is used to adsorb sulfur-containing impurities and chlorine-containing impurities.

[0008] According to some embodiments of the present invention, the first current ranges from 2 to 10 amperes, and the first duration ranges from 14 to 24 hours.

[0009] According to some embodiments of the present invention, the second current ranges from 17 to 25 amperes, and the second duration ranges from 1 to 8 hours.

[0010] According to some embodiments of the present invention, the second filter element has a stronger ability to adsorb sulfur-containing impurities and chlorine-containing impurities than the first filter element.

[0011] According to some embodiments of the present invention, both the first electrolytic plate and the second electrolytic plate are bare plates without electronic components.

[0012] According to some embodiments of the present invention, before installing the second electrolytic plate in the rectifier, the method further includes: subjecting the nickel electroplating solution to activated carbon treatment again.

[0013] According to some embodiments of the present invention, after removing the second electrolysis plate and the second filter element, the method further includes:

[0014] Extract the nickel plating solution;

[0015] Clean the nickel bath and the nickel-plated devices in the nickel bath;

[0016] The nickel plating solution is pumped back into the nickel plating tank.

[0017] According to some embodiments of the present invention, after the nickel plating solution is drawn back into the nickel bath, the method further includes:

[0018] A test plate was placed in the nickel bath for soft gold plating.

[0019] The test sulfur-nickel ratio and the test chloride-nickel ratio of the test plate were measured.

[0020] When the tested sulfur-nickel ratio and / or the tested chloride-nickel ratio are greater than the first preset threshold, the activated carbon treatment is repeated on the nickel electroplating solution.

[0021] Alternatively, when the tested sulfur-nickel ratio and / or the tested chloride-nickel ratio are greater than the first preset threshold and less than the second preset threshold, the activated carbon treatment is re-executed on the nickel plating solution, a new first electrolytic plate is re-installed in the rectifier, a new first filter element is installed in the filter tank of the nickel plating bath, the first current is re-applied to the nickel plating solution for the first duration, and then the new first electrolytic plate and the new first filter element are removed.

[0022] Alternatively, when the tested sulfur-nickel ratio and / or the tested chloride-nickel ratio are greater than the second preset threshold, the activated carbon treatment is repeated on the nickel plating solution, a new first electrolytic plate is reinstalled in the rectifier, a new first filter element is installed in the filter tank of the nickel plating bath, the first current is reapplied to the nickel plating solution for the first duration, the new first electrolytic plate and the new first filter element are removed, a new second electrolytic plate is reinstalled in the rectifier, a new second filter element is installed in the filter tank of the nickel plating bath, the second current is reapplied to the nickel plating solution for the second duration, and the new second electrolytic plate and the new second filter element are removed.

[0023] Secondly, embodiments of the present invention also provide a soft gold electroplating process, comprising:

[0024] Impurities in the nickel bath are removed according to the impurity treatment method for soft gold electroplating described in the first aspect;

[0025] The target substrate is placed in the nickel bath for soft gold electroplating.

[0026] According to some embodiments of the present invention, before placing the target substrate into the nickel bath for soft gold plating, the method further includes:

[0027] The target substrate is sequentially leveled, degreased, and micro-etched;

[0028] After the target substrate is acid-washed, it is placed in the nickel bath for pre-plating with gold.

[0029] An embodiment of the present invention includes: treating the nickel plating solution in a nickel bath with activated carbon; installing a first electrolytic plate in a rectifier in the nickel bath, installing a first filter element in a filter tank of the nickel bath, applying a first current to the rectifier for a first duration, and then removing the first electrolytic plate and the first filter element, wherein the first filter element is used to adsorb sulfur-containing impurities and chlorine-containing impurities; installing a second electrolytic plate in the rectifier, installing a second filter element in the filter tank, applying a second current to the rectifier for a second duration, and then removing the second electrolytic plate and the second filter element, wherein the second current is greater than the first current, the second duration is less than the first duration, and the second filter element is used to adsorb sulfur-containing impurities and chlorine-containing impurities. According to the technical solution of this embodiment, after preliminary impurity filtration through activated carbon treatment, the characteristics of good aggregation effect of small current are utilized for long-term electrolysis to adsorb impurities, and the characteristics of strong adsorption capacity of large current are utilized for short-term electrolysis to adsorb the remaining impurities, effectively reducing impurities in the nickel bath, which is beneficial for optimizing the composition parameters of soft gold and improving the yield of the substrate. Attached Figure Description

[0030] Figure 1 This is a flowchart of an impurity treatment method for soft gold electroplating provided in one embodiment of the present invention;

[0031] Figure 2 This is a flowchart of cleaning a nickel bath according to another embodiment of the present invention;

[0032] Figure 3 This is a flowchart for verifying the effect of impurity treatment provided in another embodiment of the present invention;

[0033] Figure 4 This is a flowchart of a soft gold electroplating process provided in another embodiment of the present invention;

[0034] Figure 5This is a flowchart of the pretreatment process for a soft gold electroplating process provided in another embodiment of the present invention. Detailed Implementation

[0035] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0036] In the description of this invention, it should be understood that the orientation descriptions, such as up, down, front, back, left, right, etc., are based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0037] In the description of this invention, "several" means one or more, "multiple" means two or more, "greater than," "less than," and "exceeding" are understood to exclude the stated number, while "above," "below," and "within" are understood to include the stated number. The use of "first" and "second" in the description is merely for distinguishing technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or implicitly indicating the order of the indicated technical features.

[0038] This invention provides a method for impurity treatment and a soft gold electroplating process. The method includes: treating a nickel electroplating solution in a nickel bath with activated carbon; installing a first electrolytic plate in a rectifier in the nickel bath, installing a first filter element in a filter tank of the nickel bath, applying a first current to the rectifier for a first duration, and then removing the first electrolytic plate and the first filter element, wherein the first filter element is used to adsorb sulfur-containing impurities and chlorine-containing impurities; installing a second electrolytic plate in the rectifier, installing a second filter element in the filter tank, applying a second current to the rectifier for a second duration, and then removing the second electrolytic plate and the second filter element, wherein the second current is greater than the first current, the second duration is less than the first duration, and the second filter element is used to adsorb sulfur-containing impurities and chlorine-containing impurities. According to the technical solution of this embodiment, after preliminary impurity filtration through activated carbon treatment, the impurities can be adsorbed by long-term electrolysis using the good aggregation effect of small current, and the remaining impurities can be adsorbed by short-term electrolysis using the strong adsorption capacity of large current. This effectively reduces impurities in the nickel bath, which is beneficial for optimizing the composition parameters of soft gold and improving the yield of the substrate.

[0039] The embodiments of the present invention will be further described below with reference to the accompanying drawings.

[0040] like Figure 1 As shown, Figure 1 This is a flowchart of an impurity treatment method for soft gold electroplating according to an embodiment of the present invention. The method includes, but is not limited to, the following steps:

[0041] S1, The nickel plating solution in the nickel bath is treated with activated carbon;

[0042] S2, a first electrolytic plate is installed in the rectifier in the nickel tank, a first filter element is installed in the filter tank of the nickel tank, a first current is applied to the rectifier and maintained for a first duration, and then the first electrolytic plate and the first filter element are removed, wherein the first filter element is used to adsorb sulfur-containing impurities and chlorine-containing impurities.

[0043] S3, install a second electrolysis plate in the rectifier, install a second filter element in the filter tank, apply a second current to the rectifier and continue for a second duration, then remove the second electrolysis plate and the second filter element, wherein the second current is greater than the first current and the second duration is less than the first duration, and the second filter element is used to adsorb sulfur-containing impurities and chlorine-containing impurities.

[0044] It should be noted that activated carbon treatment of nickel plating solutions in a nickel bath can utilize the adsorption properties of activated carbon to perform preliminary adsorption of sulfur- or chlorine-containing impurities. Activated carbon treatment can be carried out in the nickel bath itself, for example, by placing activated carbon in a carbon treatment tank and then immersing the carbon treatment tank in the plating solution. Alternatively, the nickel plating solution can be pumped to another container for activated carbon treatment before being returned to the nickel bath; for example, the solution can be pumped into a tank equipped with a carbon treatment device, carbonized with activated carbon, and then pumped back into the nickel bath. The specific operation of activated carbon treatment is a technique well-known to those skilled in the art, and the specific form is not limited here; the goal is simply to achieve the effect of preliminary adsorption of impurities.

[0045] It should be noted that the rectifier converts alternating current to direct current after being energized, thus charging the electrolytic plate and causing ions in the electroplating solution to be adsorbed onto it. In this embodiment, the impurities are mainly sulfur-containing and chlorine-containing impurities. Since sulfur and chlorine are both cations, the rectifier can be connected to the negative electrode, allowing the cations to be adsorbed onto the electrolytic plate. To prevent nickel plating on the electrolytic plate, the nickel cake from the nickel bath can be removed, reducing the nickel ion content in the nickel plating solution. As those skilled in the art will know, during the electroplating process, the nickel plating solution is typically circulated under the drive of a circulation device. A filter element can be installed in the filter tank of the nickel bath, allowing the circulating solution to be further filtered at the filter element, improving the impurity removal effect. It should be noted that both the first and second filter elements are capable of adsorbing sulfur-containing and chlorine-containing impurities; this embodiment does not limit the specific type of filter element.

[0046] It should be noted that the number of the first and second electrolytic plates can be adjusted according to the installation availability of the rectifier. For example, if the rectifier is connected to multiple clamping parts, one first or second electrolytic plate can be installed in each clamping part. The more electrolytic plates there are, the more impurities can be adsorbed, thus improving the impurity removal effect. Of course, to further improve the impurity removal effect, multiple electrolytic plates can be distributed at a certain distance to avoid mutual interference of their forces. This embodiment does not limit the specific number of the first and second electrolytic plates.

[0047] For example, taking the first electrolytic plate as an example, the first electrolytic plate is installed in the rectifier, and after the first filter element is installed in the filter tank, the rectifier is powered on. Since the rectifier is connected to the negative electrode, after the electroplating is turned on, the cations in the chemical solution are adsorbed to the first electrolytic plate under the action of the current. During the electroplating process, the chemical solution flows through the filter tank and is filtered at the first filter element to further remove sulfur-containing impurities and chlorine-containing impurities. After the first period of power-on, the power is stopped. At this time, the first electrolytic plate and the first filter element have adsorbed a lot of impurities. After discarding them, the second electrolytic plate and the second filter element are installed to continue filtration.

[0048] In some embodiments, the first current ranges from 2 to 10 amperes, the first duration ranges from 14 to 24 hours, the second current ranges from 17 to 25 amperes, and the second duration ranges from 1 to 8 hours. In this embodiment, the first current is less than the second current, and the first duration is greater than the second duration. When the electrolytic plate is energized, the smaller the current, the better the aggregation effect of sulfur and chloride ions. After preliminary filtration through activated carbon treatment, the impurity content in the nickel plating solution is relatively high. Therefore, after setting up the first electrolytic plate, a smaller first current is applied to the rectifier, so that sulfur and chloride elements can better aggregate on the first electrolytic plate under the action of the small current. Furthermore, a longer energization period is applied to extend the adsorption time, allowing the first electrolytic plate to adsorb more sulfur and chloride elements.

[0049] Understandably, after the first electrolytic plate performs low-current and long-duration impurity adsorption, the impurity content in the nickel plating solution is effectively removed. The first current value is relatively small, resulting in good adsorption effect on impurities near the first electrolytic plate. However, due to the small current and weak adsorption force, the adsorption force may not be sufficient for impurities farther away from the first electrolytic plate. That is, after adsorption by the first electrolytic plate, the more clustered impurities in the nickel plating solution have been removed, and the remaining impurities are usually far away and dispersed. Therefore, the adsorption of the second electrolytic plate does not need to consider too much clustering effect, but rather needs to use a stronger force to adsorb the distant and dispersed impurities. Based on this, in this embodiment, after the adsorption of the first electrolytic plate is completed, the second electrolytic plate is replaced, and a larger current is passed through the rectifier, so that the second electrolytic plate can adsorb the distant impurities with a stronger force. That is, the large current of the second electrolytic plate complements the small current of the first electrolytic plate, ensuring that sulfur-containing and chlorine-containing impurities in the nickel plating solution are better removed.

[0050] In another embodiment, the second filter element has a stronger ability to adsorb sulfur-containing and chlorine-containing impurities than the first filter element.

[0051] It should be noted that during adsorption on the first electrolytic plate, the circulation speed of the nickel plating solution can be relatively slow to ensure a good aggregation effect of impurities. During adsorption on the second electrolytic plate, the circulation speed of the nickel plating solution can be relatively fast to ensure a good adsorption effect on dispersed and distant impurities. Based on this, the second filter element used in this embodiment has a stronger adsorption capacity for sulfur-containing and chlorine-containing impurities than the first filter element. For example, the first filter element uses a conventional filter element to reduce filter element cost, while the second filter element uses a high-efficiency filter element to improve the adsorption effect at high flow rates.

[0052] In another embodiment, both the first electrolytic plate and the second electrolytic plate are bare plates without electronic components.

[0053] It should be noted that impurities have poor adsorption on the surface of electronic devices, and the electrolytic plate is usually discarded after adsorption is completed. The first and second electrolytic plates can be bare plates without electronic devices, which can improve the adsorption effect and adsorption amount of the electrolytic plate, and also reduce the cost of the electrolytic plate.

[0054] In another embodiment, before installing the second electrolytic plate in the rectifier, the method further includes: re-activating the nickel plating solution with activated carbon.

[0055] It should be noted that since activated carbon treatment mainly relies on the adsorption effect of activated carbon without any additional force, the impurities in the nickel plating solution are relatively concentrated after the first activated carbon treatment. When adsorbed by the first electrolytic plate, the force will affect the distribution of sulfur and chlorine elements, causing sulfur-containing and chlorine-containing impurities that were not adsorbed by the first electrolytic plate to disperse in the nickel plating solution. Moreover, the second treatment time is relatively short, and the number of impurities that can be adsorbed is limited. Therefore, in this embodiment, an activated carbon treatment is performed again before adsorption by the second electrolytic plate to further adsorb the impurities in the nickel plating solution that were dispersed by the force of the first electrolysis, thereby improving the efficiency and amount of impurity treatment.

[0056] Additionally, in one embodiment, reference is made to Figure 2 After removing the second electrolysis plate and the second filter element, the method also includes, but is not limited to, the following steps:

[0057] S41, extract the nickel plating solution;

[0058] S42, Cleaning the nickel bath and nickel-plated components in the nickel bath;

[0059] S43, pump the nickel plating solution back into the nickel bath.

[0060] It should be noted that sulfur- and chlorine-containing impurities, after precipitating, will not only remain in the nickel plating solution but may also adhere to the surface of the nickel plating bath and the nickel-plated components. Therefore, after the weak electrolysis through the first and second electrolytic plates, the nickel plating bath and components can be cleaned to remove impurities that cannot be removed by weak electrolysis. The nickel-plated components can be nickel cakes, nickel beads, etc., and no further limitations are specified here.

[0061] It is understandable that nickel baths and nickel-plated devices usually have fewer impurities, and the cleaning process is relatively complex. Therefore, the cleaning cycle can be longer. That is, it is not necessary to clean after each weak electrolysis of the second electrolysis plate. Cleaning can be set to be done once every period of time, such as once a month; or after multiple weak electrolysis cycles, such as once after 5 weak electrolysis cycles. The specific cycle can be adjusted according to actual needs.

[0062] Additionally, in one embodiment, reference is made to Figure 3 The method of pumping the nickel plating solution back into the nickel bath also includes, but is not limited to, the following steps:

[0063] S51, Place the test plate in the nickel bath for soft gold plating;

[0064] S52, test the sulfur-nickel ratio and test the chloride-nickel ratio of the test board;

[0065] S53, when the tested sulfur-nickel ratio and / or the tested chloride-nickel ratio are greater than the first preset threshold, the nickel electroplating solution is re-treated with activated carbon.

[0066] S54, when the tested sulfur-nickel ratio and / or the tested chloride-nickel ratio are greater than the first preset threshold and less than the second preset threshold, the nickel electroplating solution is re-treated with activated carbon, a new first electrolytic plate is re-installed in the rectifier, a new first filter element is installed in the filter tank of the nickel bath, a first current is re-applied to the nickel electroplating solution and maintained for a first duration, and then the new first electrolytic plate and the new first filter element are removed.

[0067] S55, when the tested sulfur-nickel ratio and / or tested chloride-nickel ratio are greater than the second preset threshold, the nickel plating solution is re-treated with activated carbon, a new first electrolytic plate is reinstalled in the rectifier, a new first filter element is installed in the filter tank of the nickel bath, a first current is reapplied to the nickel plating solution and maintained for a first duration, the new first electrolytic plate and the new first filter element are removed, a new second electrolytic plate is reinstalled in the rectifier, a new second filter element is installed in the filter tank of the nickel bath, a second current is reapplied to the nickel plating solution and maintained for a second duration, the new second electrolytic plate and the new second filter element are removed.

[0068] It should be noted that after weak electrolysis through the first and second electrolytic plates, impurities in the nickel plating solution may not be completely removed. In order not to affect the quality of subsequent soft gold production, a test plating can be performed after the weak electrolysis is completed. For example, after soft gold plating on a test plate, the sulfur-nickel ratio and chloride-nickel ratio of the soft gold plated on the test plate can be tested, and the effect of impurity treatment can be judged based on the test sulfur-nickel ratio and test chloride-nickel ratio.

[0069] It should be noted that, based on the description of the above embodiments, the impurity removal effects and principles of activated carbon treatment, weak electrolysis based on the first electrolysis plate, and weak electrolysis based on the second electrolysis plate are different. This embodiment can set three preset thresholds, wherein the first preset threshold is less than the second preset threshold. When the tested sulfur-nickel ratio and / or the tested nickel-chloride ratio is less than the first preset threshold, there are few remaining impurities in the solution, and impurity filtration by activated carbon treatment can meet the sulfur-nickel ratio and nickel-chloride ratio required by the Soft Gold Institute. When the tested sulfur-nickel ratio and / or the tested nickel-chloride ratio is greater than the first preset threshold and less than the second threshold, the remaining impurities in the solution cannot be filtered out by activated carbon treatment alone. Therefore, after completing the activated carbon treatment, a weak electrolysis is performed again based on the first electrolysis plate. For the specific principle, please refer to the description of the above embodiments. If the tested sulfur-nickel ratio and / or the tested nickel-chloride ratio is greater than the second preset threshold, it can be determined that the impurity content in the solution is still high, and the complete process described in the above embodiments can be repeated to clean the sulfur-containing and chlorine-containing impurities again. Of course, after the second cleaning is completed, the sulfur-nickel ratio and / or the chloride-nickel ratio can be tested again to reduce the impact of impurities in the nickel plating solution on the production quality of soft gold during actual production.

[0070] In addition, embodiments of the present invention also provide a soft gold electroplating process, referring to... Figure 4 The soft gold electroplating process includes, but is not limited to, the following steps:

[0071] S61, Remove impurities from the nickel plating bath. The treatment method is the same as the impurity treatment method for soft gold electroplating described above.

[0072] S62, the target substrate is placed in a nickel bath for soft gold plating.

[0073] It should be noted that after impurity treatment according to the method of the above embodiments, the concentration of sulfur-containing and chlorine-containing impurities in the nickel bath and nickel plating solution can be effectively reduced, thereby effectively reducing the sulfur-nickel ratio and chlorine-nickel ratio of the soft gold obtained after soft gold electroplating, and improving production quality and substrate yield.

[0074] Additionally, in one embodiment, reference is made to Figure 5 Before placing the target substrate into the nickel bath for soft gold plating, the following steps are included, but are not limited to:

[0075] S71, the target substrate is sequentially leveled, degreased and micro-etched;

[0076] S72, after acid washing the target substrate, it is placed in a nickel bath for pre-plating gold.

[0077] It should be noted that leveling can refine the crystal structure of the copper surface of the target substrate, making the surface smoother and improving the subsequent electroplating effect. Degreasing can clean the copper surface of the target substrate, improving the metal adhesion during the subsequent electroplating process. Micro-etching can microscopically roughen the copper surface, increasing the metal adhesion area during electroplating and improving the electroplating effect.

[0078] It should be noted that pickling can clean the impurities on the surface of the target substrate to a certain extent, reducing the impurities precipitated into the nickel bath during electroplating, thereby reducing the contamination of the nickel electroplating solution.

[0079] It should be noted that pre-plating can be performed by initially electroplating nickel and gold on the target substrate to form a nickel-gold layer of a certain thickness at the soft gold plating location on the target substrate. Then, electroplating can be performed to the target thickness according to actual needs.

[0080] Other embodiments of this application will readily occur to those skilled in the art upon consideration of the specification and practice of the embodiments disclosed herein. This application is intended to cover any variations, uses, or adaptations of this application that follow the general principles of this application and include common knowledge or customary techniques in the art not disclosed herein.

[0081] It should be understood that this application is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of this application is limited only by the appended claims.

[0082] The above provides a detailed description of the preferred embodiments of the present invention. However, the present invention is not limited to the above embodiments. Those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of the present invention. All such equivalent modifications or substitutions are included within the scope defined by the claims of the present invention.

Claims

1. A method for treating impurities in soft gold electroplating, characterized in that, include: The nickel plating solution in the nickel bath is treated with activated carbon. A first electrolytic plate is installed in the rectifier in the nickel tank, and a first filter element is installed in the filter tank of the nickel tank. After applying a first current to the rectifier for a first duration, the first electrolytic plate and the first filter element are removed. The first filter element is used to adsorb sulfur-containing impurities and chlorine-containing impurities. A second electrolysis plate is installed in the rectifier, and a second filter element is installed in the filter tank. After applying a second current to the rectifier for a second duration, the second electrolysis plate and the second filter element are removed. The second current is greater than the first current, and the second duration is less than the first duration. The second filter element is used to adsorb sulfur-containing impurities and chlorine-containing impurities. The first current ranges from 2 to 10 amperes, and the first duration ranges from 14 to 24 hours; The second current ranges from 17 to 25 amperes, and the second duration ranges from 1 to 8 hours.

2. The method for impurity treatment in soft gold electroplating according to claim 1, characterized in that, The second filter element has a stronger ability to adsorb sulfur-containing and chlorine-containing impurities than the first filter element.

3. The method for impurity treatment in soft gold electroplating according to claim 1, characterized in that, Both the first electrolytic plate and the second electrolytic plate are bare plates without electronic components.

4. The method for impurity treatment in soft gold electroplating according to claim 1, characterized in that, Before installing the second electrolytic plate in the rectifier, the method further includes: subjecting the nickel electroplating solution to activated carbon treatment again.

5. The method for impurity treatment in soft gold electroplating according to claim 1, characterized in that, After removing the second electrolysis plate and the second filter element, the method further includes: Extract the nickel plating solution; Clean the nickel bath and the nickel-plated devices in the nickel bath; The nickel plating solution is pumped back into the nickel plating tank.

6. The method for impurity treatment in soft gold electroplating according to claim 5, characterized in that, After the nickel plating solution is pumped back into the nickel bath, the method further includes: A test plate was placed in the nickel bath for soft gold plating. The test sulfur-nickel ratio and the test chloride-nickel ratio of the test plate were measured. When the tested sulfur-nickel ratio and / or the tested chloride-nickel ratio is less than the first preset threshold, the activated carbon treatment is repeated on the nickel electroplating solution. Alternatively, when the tested sulfur-nickel ratio and / or the tested chloride-nickel ratio are greater than the first preset threshold and less than the second preset threshold, the activated carbon treatment is re-executed on the nickel plating solution, a new first electrolytic plate is re-installed in the rectifier, a new first filter element is installed in the filter tank of the nickel plating bath, the first current is re-applied to the nickel plating solution for the first duration, and then the new first electrolytic plate and the new first filter element are removed. Alternatively, when the tested sulfur-nickel ratio and / or the tested chloride-nickel ratio are greater than the second preset threshold, the activated carbon treatment is repeated on the nickel plating solution, a new first electrolytic plate is reinstalled in the rectifier, a new first filter element is installed in the filter tank of the nickel plating bath, the first current is reapplied to the nickel plating solution for the first duration, the new first electrolytic plate and the new first filter element are removed, a new second electrolytic plate is reinstalled in the rectifier, a new second filter element is installed in the filter tank of the nickel plating bath, the second current is reapplied to the nickel plating solution for the second duration, and the new second electrolytic plate and the new second filter element are removed.

7. A soft gold electroplating process, characterized in that, include: The method for removing impurities from the nickel plating bath according to any one of claims 1 to 6; The target substrate is placed in the nickel bath for soft gold electroplating.

8. The soft gold electroplating process according to claim 7, characterized in that, Before placing the target substrate into the nickel bath for soft gold plating, the method further includes: The target substrate is sequentially leveled, degreased, and micro-etched; After the target substrate is acid-washed, it is placed in the nickel bath for pre-plating with gold.

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