TWI683931B - Anode for electrolytic copper plating and electrolytic copper plating device using the same - Google Patents

Abstract

An object of the present invention is to provide an anode for electrolytic copper plating and an electrolytic copper plating apparatus using the same, which can improve plating characteristics such as plating promotion and through hole filling without complicating the structure of the apparatus. To achieve this object, the present invention uses an anode for electrolytic copper plating, which is arranged in an electrolytic treatment tank with an electrolytic copper plating solution stored therein. The electrolytic copper plating solution is an acidic electrolytic copper plating solution containing disulfide. The electronically connected state includes a soluble copper anode and an insoluble anode.

Description

Anode for electrolytic copper plating and electrolytic copper plating device using the same

The invention relates to an anode for electrolytic copper plating and an electrolytic copper plating device using the same.

In the past, when forming a conductor on a printed wiring board, electrolytic copper plating was performed. In the case of electrolytic copper plating, the anode includes a method using a soluble copper anode composed of a copper element and a method using an insoluble anode composed of platinum, titanium, iridium oxide, or the like. In addition, in the electrolytic copper plating solution, additives such as brighteners and leveling agents are added to improve plating characteristics such as plating promotion and through-hole filling.

Here, when electrolytic copper plating is performed, the use of soluble copper anodes has become the mainstream. The reason is that soluble copper anodes have advantages over insoluble anodes in that they can simplify equipment, do not cost maintenance, and the anode itself is cheaper and can be reduced in cost.

However, if a soluble copper anode is used, as the copper electrode chemically dissolves in the copper plating solution, it is generally known that bis(3-sulfopropyl) disulfide added as a brightener in the electrolytic copper plating solution (Hereinafter referred to as "SPS") will be reduced to 3-mercaptopropane-1-sulfonic acid (hereinafter referred to as "MPS"). If this MPS exists in a certain amount or more in the electrolytic copper plating solution, there is a problem that the desired plating characteristics cannot be obtained.

In response to the above problems, as described in Japanese Patent Application (Japanese Patent Laid-Open No. 2004-143478), attempts have been made to increase the dissolved oxygen concentration in the copper plating solution by blowing air into the copper plating solution. Specifically, in the Japanese Patent Application (Japanese Patent Laid-Open No. 2004-143478), a "plating device for acid copper" is disclosed, which is characterized in that: a plating layer tank with overflow tanks in parallel, and a plating solution provided under the plating tank In the acid copper plating device for the jet discharge section, copper anode and special rod for the product to be coated, an air stirring and oxygen stirring device is installed in the overflow tank."

However, in the plating apparatus disclosed in Japanese Patent Application (Japanese Patent Laid-Open No. 2004-143478), it is necessary to separately provide an overflow groove, and the structure of the plating apparatus becomes complicated, so there is a problem that the equipment cost becomes high.

Based on the above reasons, an object of the present invention is to provide an anode for electrolytic copper plating and an electrolytic copper plating apparatus using the same, which can improve plating characteristics such as plating promotion and through hole filling without complicating the structure of the apparatus .

After careful research, the inventor of the present case has achieved the above object by adopting the following method.

The anode for electrolytic copper plating of the present invention is an anode disposed in an electrolytic treatment tank with an electrolytic copper plating solution stored therein, characterized in that the electrolytic copper plating solution is an acidic electrolytic copper plating solution containing disulfide, and the anode The electronically connected state includes a soluble copper anode and an insoluble anode.

Electrolytic copper plating apparatus of the present invention: The electrolytic copper plating apparatus of the present invention is characterized by including the above-mentioned anode for electrolytic copper plating. [Effect of the invention]

According to the anode for electrolytic copper plating and the electrolytic copper plating apparatus of the present invention, it is possible to improve plating characteristics such as plating promotion and through hole filling without complicating the structure of the apparatus.

The anode for electrolytic copper plating of the present invention and the electrolytic copper plating apparatus using the same will be described below using the drawings. FIG. 1 is a schematic cross-sectional view illustrating when the soluble copper anode of the present invention is used in an electrolytic copper plating apparatus.

The electrolytic copper plating apparatus 10 of the present invention includes the anode 1 for electrolytic copper plating of the present invention. The anode 1 for electrolytic copper plating is provided in an electrolytic treatment tank 20 in which an electrolytic copper plating solution 21 is stored. In addition, the electrolytic copper plating solution 21 is an acidic electrolytic copper plating solution containing disulfide (for example, SPS), and the anode 1 includes a soluble copper anode 2 and an insoluble anode 3 in an electronically connected state. These structures will be explained below.

The electrolytic copper plating apparatus 10 of the present invention is an apparatus in which the plated element W is immersed in the electrolytic treatment tank 20 in which the electrolytic copper plating solution 21 is stored, between the plated element (cathode) W and the anode 1 Power is supplied between the electrodes and the treated surface of the plated element W is subjected to electrolytic treatment. Here, the plated element W of the present invention can be used as a printed wiring board or a wafer formed by laminating circuit wiring with an insulating material such as epoxy resin. In addition, as these printed wiring boards or wafers, printed circuit boards or wafers having through holes and/or through holes may be used. The through-holes and/or through-holes are generally such small holes with diameters ranging from 10µm to 1000µm. Through this holes, electrical connections between signal layers are made. According to the electrolytic copper plating apparatus 10 of the present invention, it is possible to perform electrolytic treatment for filling the inside of these through holes and/or through holes with copper. In addition, in the electrolytic copper plating apparatus 10 of the present invention, in order to improve the characteristics such as uniform electro-characteristics, a structure may also be adopted. On the one hand, bubbles are diffused in the electrolytic copper plating solution 21, and on the other hand, it is connected Nozzle 6 ejects high-pressure gas or the like to stir the electrolytic copper plating solution 21.

The electrolytic copper plating solution 21 of the present invention uses an acidic electrolytic copper plating solution containing sulfur dioxide. Generally, the acidic electrolytic copper plating solution 21 is composed of copper sulfate pentahydrate, sulfuric acid, chloride ions, and additives. For example, the composition of the acidic electrolytic copper plating solution 21 can be used within the range of copper sulfate pentahydrate 30 g/L to 250 g/L, sulfuric acid 30 g/L to 250 g/L, and chloride ion 30 mg/L to 75 mg/L. In addition, the temperature of the acidic electrolytic copper plating solution 21 can generally be used within a range of 15°C to 60°C, and more preferably 20°C to 35°C. With the increase in the concentration of copper sulfate pentahydrate or the increase in the concentration of sulfuric acid, the crystals of copper sulfate pentahydrate may sometimes precipitate on the copper anode, so the concentration management of both needs to be paid attention to. Here, the sulfuric acid concentration in the acidic electrolytic copper plating solution 21 is preferably 30 g to 400 g/L. When the sulfuric acid concentration is less than 30 g/L, the conductivity of the acidic electrolytic copper plating solution 21 decreases, and it becomes difficult to energize the acidic electrolytic copper plating solution 21. On the other hand, when the sulfuric acid concentration exceeds 400 g/L, copper sulfate is likely to precipitate in the acidic electrolytic copper plating solution, which has an adverse effect on the coating characteristics.

In the electrolytic copper plating apparatus 10 of the present invention, as described above, the soluble copper anode 2 and the insoluble anode 3 disposed in the electrolytic treatment tank 20 function as the anode 1 by electronic connection. In the case of electrolytic treatment, if an electrolytic copper plating solution 21 containing SPS is used, this SPS will change to MPS. Due to the generation of this MPS, the plating uniformity in the through-hole bath will be reduced or the appearance of the coating will be poor, Problems such as a decrease in the filling rate in the through-hole filling bath or poor plating appearance occur. Here, even when electrolysis is stopped and only the electrolytic copper plating solution 21 is left, it can be confirmed that SPS is reduced near the anode 1 to generate MPS. The production of this MPS is also the reason for the anode sludge composed of MPS-Cu ⁺ composite. This anode sludge will lead to a decrease in plating characteristics such as fillability and uniform plating performance of the through hole. However, the anode 1 for electrolytic copper plating of the present invention includes the soluble anode 2 and the insoluble anode 3 in the electrolytic treatment tank 20 in an electronic connection state, and the insoluble anode 3 can supply oxygen to the electrolytic copper plating solution 21. The oxygen generated from the insoluble anode 3 can oxidize MPS to SPS, suppress the increase in the concentration of MPS in the electrolytic copper plating solution 21, and eliminate the adverse effects of MPS. Therefore, according to the electrolytic copper plating apparatus 10 of the present invention, even if the electrolytic copper plating solution 21 contains SPS as a brightener, the desired plating characteristics can be obtained.

The soluble copper anode 2 constituting the anode 1 for electrolytic copper plating of the present invention is used to maintain the concentration of copper ions consumed in the electrolytic copper plating solution 21 during electrolysis at a predetermined concentration. The shape of the soluble copper anode 2 is not limited, and by adopting a shape with the largest possible surface area, more copper ions can be generated during electrolysis to improve the plating efficiency.

Furthermore, the soluble copper anode 2 of the present invention is preferably composed of a phosphor-containing copper element. By making the soluble copper anode 2 composed of a phosphorus-containing copper element, a compound film called a Cu ₂ P black film can be formed on the surface of the phosphorus-containing copper element during electrolysis to suppress the generation of monovalent copper ions and Effectively suppress the generation of anode sludge and prevent the degradation of plating characteristics. In addition to further suppressing the generation of anode sludge of the phosphorus-containing copper element, the phosphorus content should be between 0.02% and 0.06%. The use of phosphorus-containing copper elements on the soluble copper anode 2 is conducive to the smooth dissolution of copper in electrolysis.

As for the insoluble anode 3 constituting the anode 1 for electrolytic copper plating of the present invention, as long as it is a material that does not elute metal in the electrolytic copper plating solution 21, an anode composed of any material can be used. For example, anodes made of iridium oxide, platinum-plated titanium, platinum, graphite, ferrous salts, lead dioxide, and platinum group element oxide-coated titanium, stainless steel, lead alloy, etc. can be used, but the invention is not limited thereto . In addition, the insoluble anode 3 may be configured by covering the substrate with a coating. In this case, the entire base material may be covered, but only a part of the base material may be covered within the range acting as the insoluble anode 3. At this time, the thickness of the coating is not particularly limited, and from the viewpoint of durability and cost, it is preferably 0.1 µm to 10 µm.

In addition, the shape of the insoluble anode 3 of the present invention is not limited. The insoluble anode 3 is a shape and size that can efficiently produce oxygen without hindering the dissolution of the soluble anode 2 during electrolysis, thereby rapidly oxidizing and reducing MPS present in the electrolytic copper plating solution 21 to SPS, and suppressing MPS It accumulates in this electrolytic copper plating solution 21 to prevent degradation of plating characteristics.

In the anode 1 for electrolytic copper plating of the present invention, from the viewpoint of suppressing the generation of MPS, the area ratio of the surface of the soluble copper anode 2 and the insoluble anode 3 immersed in the electrolytic copper plating solution 21 is preferably 10:1 to 1:10. If the area ratio of the surface of the soluble copper anode 2 and the insoluble anode 3 immersed in the electrolytic copper plating solution 21 is less than 10:1, very little oxygen is generated from the surface of the insoluble anode (eg, iridium oxide element) 3, so the electrolysis cannot be sufficiently suppressed The concentration of MPS in the copper plating solution 21 increases, so that the desired plating characteristics cannot be obtained. In addition, if the area ratio exceeds 1:10, the generation of oxygen from the surface of the insoluble anode (for example, iridium oxide element) 3 increases significantly. Therefore, the additives contained in the electrolytic copper plating solution 21 are oxidatively decomposed to increase the additive consumption the amount. Furthermore, in this case, the copper supplied from the soluble copper anode 2 is insufficient, and in order to maintain the copper concentration in the electrolytic copper plating solution 21 at a predetermined concentration, it is necessary to supply copper from other sources. Here, the area ratio of the surface of the soluble copper anode 2 and the insoluble anode 3 immersed in the electrolytic copper plating solution 21 is 5:1 to 1:5, and the above effect is more easily obtained.

In addition, in the electrolytic copper plating apparatus 10 of the present invention, the applicable cathode current density is preferably within a range where phosphorous-containing copper elements used in electrolytic copper plating of printed wiring boards are generally used. Specifically, the cathode current density is 0.1A/dm ² to 10A/dm ² , preferably 0.5A/dm ² to 6A/dm ² , and more preferably 1A/dm ² to 5A/dm ² . The anode current density can generally be 0.1A/dm ² to 3A/dm ² , preferably 1A/dm ² to 3A/dm ² . The copper concentration in the electrolytic copper plating solution 21 tends to increase when the anode current density is too low, and tends to decrease when the anode current density is too high. Therefore, it is necessary to adjust the anode area according to the cathode current density used.

Here, the effect obtained when the anode 1 for electrolytic copper plating of the present invention is used for electrolysis and electrolysis will be more specifically explained. Generally, during electrolysis and when electrolysis is stopped, the soluble copper anode 2 dissolves according to formula (1) of the following chemical formula 1. In addition, during electrolysis, the cathode generates a reaction represented by formula (2) of the following chemical formula 1, and copper is precipitated. In addition, when the electrolytic copper plating solution 21 contains disulfide, the electrons released when the soluble copper anode 2 dissolves, as shown in formula (3) of the following chemical formula 1, SPS is reduced and MPS is generated . The generated MPS is as shown in formula (4) of the following chemical formula 1, a part of it is oxidized and converted into SPS, but Cu(I) MPS combined with monovalent copper ion is shown as formula (5) of the following chemical formula 1, It becomes MPS.

^{Cu → Cu 2+ + 2e - ...} (1) Cu 2+ + 2e - → Cu ... (2) SPS + 2H + + 2e - → 2MPS ... (3) 4MPS + 2Cu 2+ → 2Cu (I) MPS + SPS ^{+ 4H + ... (4) 2Cu} (I) MPS + H + + e - → 2Cu + 2MPS ... (5) 2H 2 O → 4H + + O 2 + 4e - ... (6) [chemical formula 1]

The formula (1), formula (3) to formula (5) of the above chemical formula 1 show the process of generation of MPS that will cause a decrease in plating characteristics. However, the anode 1 for electrolytic copper plating of the present invention is compatible with soluble copper The anode 2 includes the insoluble anode 3 in the state of being electrically connected, whereby the increase in the MPS concentration in the electrolytic copper plating solution 21 can be suppressed. In other words, during electrolysis, the insoluble anode 3 performs the electronic decomposition of the water in the electrolytic copper plating solution 21 as shown in Formula (6) of the above Chemical Formula 1, and the oxygen generated at this time oxidizes the MPS and converts it to SPS. This can reduce the MPS that has been generated.

The electrolytic copper plating apparatus 10 of the present invention can suppress the increase in the concentration of MPS in the electrolytic copper plating solution 21 by including the above structure. Therefore, according to the anode 1 for electrolytic copper plating of the present invention and the electrolytic copper plating apparatus 10 using the same, even if the electrolytic copper plating solution 21 left for a long period of time is used to start electrolysis, it is difficult to cause a bad appearance of the plating layer. Ideal for maintenance.

The soluble copper anode of the present invention and the storage method of the electrolytic copper plating solution using the same have been described above. The following will show examples of the present invention and explain the present invention in more detail. In addition, the present invention is not limited by these examples.

[Example 1] In Example 1, an experiment was conducted to confirm the effect when using a soluble copper anode and an insoluble anode as an anode for electrolytic copper plating in an electronically connected state.

In this Example 1, first, the Melplate MLB-6001 process (manufactured by Meltex Inc.) was used to remove the slag from the plated element (printed substrate) with a plate thickness of 1.0 mm, a through-hole diameter of 100 μm, and a depth of 80 μm. Next, electroless copper plating was performed by the Melplate CU-390 process (manufactured by Meltex Inc.). Then, this printed board was subjected to acid degreasing, water washing, and sulfuric acid treatment by the Melplate PC-316 process (manufactured by Meltex Inc.), and then electrolytic copper plating was performed under the conditions shown below.

The acidic electrolytic copper plating solution used in Example 1 used a 3L through-hole filling bath, which was added to a plating solution containing copper sulfate pentahydrate 200g/L, concentrated sulfuric acid 100g/L, and chloride ion 50mg/L. Lucent Copper SVF-A (manufactured by Meltex Inc., disulfide series) 0.4mL/L, Lucent Copper SVF-B (manufactured by Meltex Inc., disulfide series) 20mL/L, Lucent Copper SVF-L (Meltex Inc. Manufactured, disulfide system) After 15mL/L adjusted. In addition, the temperature of this acidic electrolytic copper plating solution is set to 25°C.

Then, an anode for electrolytic copper plating was installed in the electrolytic treatment tank in a state of being immersed in the filled through-hole filling bath. The anode for electrolytic copper plating is electronically connected with a soluble copper anode (a phosphor-containing copper plate of 50mm×120nn) and an insoluble anode (a 50mm×120mm iridium oxide coating plate) in an electrolytic treatment bath. In addition, in Example 1, the electrolytic treatment was performed in the electrolytic treatment tank while circulating the plating solution using a pump.

In Example 1, the area ratio of the surface of the soluble copper anode and the insoluble anode immersed in the electrolytic copper plating solution was set to 1:1. In addition, as a cathode, a printed substrate applied with electroless copper plating of 50 mm×130 mm was immersed in an electrolytic copper plating solution. Then, the electrolytic copper plating solution has a current density of 2A/dm ² for 45 minutes under the current conditions of 0AH/L (new bath), 10AH/L, 50AH/L, and 100AH/L. After that, the filling state of the plating layer in the through hole under each condition was observed by the cross-sectional method. FIG. 2 is a cross-sectional photograph showing the filling state of the plating layer in the through hole in Example 1. FIG.

[Example 2] In Example 2, as in Example 1, a test was performed to confirm the effect when the soluble copper anode and the insoluble anode were used as the anode for electrolytic copper plating in an electronically connected state.

In this Example 2, the same plated element as in Example 1 was used. In addition, in Example 2, except that the Lucent Copper SVF-A (0.4 mL/L) was changed to MPS (1 mg/L), the same electrolysis pretreatment conditions and electrolysis treatment conditions as in Example 1 were used. Therefore, the processing conditions adopted in the second embodiment will be omitted here.

In Example 2, regarding the anode for electrolytic copper plating, the area ratios of the soluble copper anode and the insoluble anode immersed in the electrolytic copper plating solution are "10:1", "5:1", "1:1", "1:1 (insoluble anode adopts platinum-plated titanium)", "1:5", "1:10". Then, under the conditions that the amount of electricity of the electrolytic copper plating solution is 0AH/L, 0.5AH/L, 1AH/L, 4AH/L, 10AH/L, as in Example 1, as a cathode, 50 mm× A 130 mm electroless copper-plated printed circuit board was immersed in an electrolytic copper plating solution, and electrolysis was performed at a current density of 2 A/dm ² for 45 minutes. After that, the filling state of the plating layer in the through hole under each condition was observed by the cross-sectional method. In FIG. 3, a cross-sectional photograph showing the filling state of the plating layer in the through hole in Example 2. FIG.

[Comparative Example 1] In Comparative Example 1, a test was performed to confirm the effect when only a soluble copper anode was used as an anode for electrolytic copper plating.

In Comparative Example 1, except that only a soluble copper anode was used as the anode for electrolytic copper plating, the same pre-electrolysis treatment conditions and electrolytic treatment conditions as in Example 1 were used. Therefore, the conditions adopted in Comparative Example 1 are omitted here.

In Comparative Example 1, the same test as in Example 1 was performed. In FIG. 2, in order to be able to be compared with Example 1, a cross-sectional photograph showing the filling state of the plating layer in the through hole in Comparative Example 1 is shown.

[Comparative Example 2] In Comparative Example 2, as in Comparative Example 1, a test was conducted to confirm the effect when only a soluble copper anode was used as an anode for electrolytic copper plating.

In Comparative Example 2, in addition to the point of using only a soluble copper anode as the anode for electrolytic copper plating, and the point of changing Lucent Copper SVF-A (0.4 mL/L) to MPS (1 mg/L), the same examples were used. 1 The same pre-electrolysis treatment conditions and electrolysis treatment conditions. Therefore, the processing conditions adopted in Comparative Example 2 will be omitted here.

In Comparative Example 2, the same test as in Example 2 was performed. In FIG. 3, in order to be able to compare with Example 2, a cross-sectional photograph showing the filling state of the plating layer in the through hole in Comparative Example 2.

According to the results shown in FIG. 2, as the anode disposed in the electrolytic treatment tank storing the electrolytic copper plating solution, if an anode including a soluble copper anode and an insoluble anode in an electronic connection state is used, only an soluble copper is used. The situation of the anode is different, and even if the amount of electricity passed is as large as 100AH/L, there is almost no difference in the filling condition of the through hole, and stable and excellent filling properties can be obtained.

According to the results shown in FIG. 3, it can be seen that, as the anode disposed in the electrolytic treatment tank in which the electrolytic copper plating solution is stored, if an anode including a soluble copper anode and an insoluble anode in an electronic connection state is used, compared with the use of only the dissolved In the case of copper anodes, even if the electrolytic copper plating solution contains 1 mg/L of MPS, the filling property can be restored in a shorter time. In addition, at this time, when the area ratio of the soluble copper anode and the insoluble anode in Example 2 immersed in the electrolytic copper plating solution was "10:1" and the other area ratios were compared, it can be seen that the soluble copper anode The larger the ratio, the more difficult it is to restore the filling property. On the other hand, the smaller the ratio of the soluble copper anode, the less copper is supplied by the soluble copper anode in the electrolytic copper plating solution. To maintain the copper concentration in the electrolytic copper plating solution, it is conceivable that other Source supplies copper. From the above viewpoint, it can be understood that the area ratio of the soluble copper anode and the insoluble anode immersed in the electrolytic copper plating solution is preferably 5:1 to 1:5.

As can be seen from the above, by using the anode for electrolytic copper plating of the present invention and the electrolytic copper plating apparatus using the same, it is possible to improve plating characteristics such as plating promotion and through hole filling without complicating the device structure. It can be understood from this that when the anode for electrolytic copper plating of the present invention is used for electrolytic treatment, the adverse effects caused by the increase in the concentration of MPS in the electrolytic copper plating solution can be effectively eliminated.

[Industrial Applicability] According to the anode for electrolytic copper plating of the present invention and the electrolytic copper plating apparatus using the same, when the acidic electrolytic copper plating solution containing disulfide is used, the increase in the concentration of MPS can be effectively suppressed, Stable to obtain the desired coating characteristics. In addition, by using the anode for electrolytic copper plating of the present invention, the structure of the electrolytic copper plating apparatus can be simplified, and the equipment cost can be reduced. Therefore, the anode for electrolytic copper plating of the present invention and the electrolytic copper plating apparatus using the same are particularly suitable for applying electrolytic plating treatment to printed wiring boards, wafers, etc. having through holes and/or through holes.

1‧‧‧Electrolytic copper plating anode 2‧‧‧Soluble copper anode 3‧‧‧Insoluble anode 5‧‧‧Circulation piping 6‧‧‧Nozzle 10‧‧‧Electrolytic copper plating device 20‧‧‧Electrolytic treatment tank 21 ‧‧‧Electrolytic copper plating solution

[FIG. 1] is a schematic cross-sectional view illustrating when the soluble copper anode of the present invention is used in an electrolytic copper plating apparatus. [FIG. 2] A cross-sectional photograph showing the filled state of the through holes in Example 1 and Comparative Example 1. [FIG. 3] A cross-sectional photograph showing the filled state of the through holes in Example 2 and Comparative Example 2.

1‧‧‧Anode for electrolytic copper plating

2‧‧‧Soluble copper anode

3‧‧‧Insoluble anode

5‧‧‧Circulation piping

6‧‧‧ nozzle

10‧‧‧Electrolytic copper plating device

20‧‧‧Electrolysis treatment tank

21‧‧‧Electrolytic copper plating solution

Claims (4)

An anode for electrolytic copper plating, which is arranged in an electrolytic treatment tank with electrolytic copper plating liquid stored therein, is characterized in that the electrolytic copper plating liquid is an acidic electrolytic copper plating liquid containing disulfide, and the anode includes in an electronic connection state A soluble copper anode and an insoluble anode, wherein the area ratio of the surface of the electrolytic copper plating solution immersed in the soluble copper anode and the insoluble anode is 10:1 to 1:10. An anode for electrolytic copper plating as claimed in item 1 of the patent scope, wherein the area ratio of the surface of the electrolytic copper plating solution immersed in the soluble copper anode and the insoluble anode is 5:1 to 1:5. An electrolytic copper plating device characterized by comprising an anode for electrolytic copper plating as described in item 1 or 2 of the scope of application. An electrolytic copper plating device as claimed in item 3 of the patent scope, wherein the plated element is a printed wiring board or a wafer having through holes and/or through holes, and the inside of the through holes and/or through holes is filled Electrolytic treatment of copper.

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