JP2018154549A - Silver oxide, silver oxide cake and manufacturing method of silver oxide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide silver oxide hardly varying a composition or pH of a plating liquid when dissolved in the plating liquid and hardly changing plating properties, a silver oxide cake and a manufacturing method of the silver oxide.SOLUTION: The silver oxide has content of residual acid of 100 mass.ppm or less, and content of Na, K, Ca, Mg, Li of 100 mass.ppm or less as total. The silver oxide cake contains the silver oxide and water. The manufacturing method of the silver oxide has a process for preparing a reaction tank accommodating pure water, a silver salt solution and an alkali solution; and a process for depositing silver oxide particles by adding the silver oxide solution and the alkali solution to the reaction tank with adjusting pH of a mixture of the pure water, the silver salt solution and the alkali solution in the reaction tank to a range of 5.0 to 8.0.SELECTED DRAWING: None

Description

  The present invention relates to a method for producing silver oxide, cake and silver oxide.

  Ag is used as a plating material such as Sn—Ag alloy. In the case where Sn—Ag alloy is electrolytically plated, when Sn is used for the anode, Ag is deposited on the anode surface because Ag is nobler than Sn. In order to avoid the precipitation of Ag, hydrogen is generated on the anode side using an insoluble anode such as Pt, and Sn-Ag alloy is electroplated on the cathode side.

  By the way, in order to continuously produce the Sn—Ag alloy by electrolytic plating, it is necessary to replenish the plating solution with the Sn component and the Ag component and maintain the concentration of Sn and Ag in the plating solution constant. It becomes. As a replenishment method of the Sn component, there are a replenishment method by an Sn anode using an ion exchange membrane, addition of a high concentration solution of Sn, replenishment with stannous oxide, etc., and the simplest and without destroying the composition of the plating solution As a method for replenishment, replenishment of Sn component with stannous oxide has attracted attention. As a method for replenishing the Ag component, a method using a high concentration solution of Ag is used.

On the other hand, silver oxide which is an oxide of Ag is used as a filler for conductive paste because it is reduced by heating at a relatively low temperature to produce Ag.
In Patent Document 1, as a method for producing silver oxide fine particles useful as a filler for conductive paste, an aqueous solution containing a silver salt in an amount of 6 mol / L or less in an aqueous solution adjusted to an alkaline pH of about 12, A method is described in which silver oxide fine particles having small primary particles are precipitated by simultaneously adding an aqueous solution containing an alkali of 1 mol equivalent or more to the silver salt to react.

JP 2012-176892 A

By the way, it is preferable that the compound used as a replenisher for the plating solution is one that dissolves in the plating solution relatively easily and does not change the characteristics of the plating solution even when added to the plating solution in a large amount. However, Ag easily dissolves in inorganic acids such as nitric acid and sulfuric acid, but has a problem that it is difficult to dissolve in sulfonic acid-based organic acids such as methanesulfonic acid that are widely used as anion components of plating solutions. . Further, silver inorganic salts such as silver nitrate and silver sulfate are easily dissolved in the plating solution, but there is a possibility that Ag counter ions (counter ions) such as nitrate ions and sulfate ions are accumulated, and the characteristics of the plating solution may be changed. It was.
In addition, when Ag is replenished by adding a high concentration solution of Ag to the plating bath, moisture and acid components are added simultaneously with Ag. Therefore, it is necessary to remove the solution from the plating bath and adjust the Ag concentration. Ag cannot be replenished. For this reason, it took time for the replenishment of Ag, and the efficiency in the case of continuous plating was poor.

On the other hand, silver oxide is easy to dissolve in sulfonic acid organic acids, and unlike silver inorganic salts such as silver nitrate and silver sulfate, it has the advantage that inorganic salts do not accumulate in the plating solution. Only the Ag component can be continuously replenished without fluctuation, and the efficiency in the case of continuous plating is improved.
However, as described in Patent Document 1, silver oxide fine particles obtained by a method in which an aqueous solution of silver salt and an alkaline aqueous solution are simultaneously added to an aqueous solution adjusted to alkaline are derived from an aqueous solution adjusted to alkaline. Easy to contain impurities. When such silver oxide is used as a replenisher for the Ag component, impurities are accumulated in the plating solution, the pH of the plating solution may fluctuate, and it may be difficult to perform Sn-Ag alloy plating stably over a long period of time. is there.

  The present invention has been made in view of the above-described circumstances, and even when dissolved in a plating solution, the composition and pH of the plating solution are difficult to change, and plating characteristics (for example, the composition variation of plated Ag and An object of the present invention is to provide a silver oxide, a silver oxide cake, and a method for producing silver oxide, which are difficult to change the uniformity of plating height.

In order to solve the above problems, the silver oxide of the present invention has a residual acid content of 100 mass ppm or less and a total content of Na, K, Ca, Mg, Li of 100 mass ppm or less. It is characterized by being.
In the present invention, the residual acid content is defined as follows.
Silver oxide is dissolved in a methanesulfonic acid aqueous solution (methanesulfonic acid concentration: 60% by mass) to prepare a silver-methanesulfonic acid solution, and an anion contained in the silver-methanesulfonic acid solution using an ion chromatogram. The peak (excluding methanesulfonic acid ions contained as a matrix) is detected, and the amount of acid other than methanesulfonic acid contained in silver oxide is determined from the total amount of components corresponding to the detected peak. Next, silver oxide is dissolved in nitric acid to prepare a silver-nitric acid solution, and an ion chromatogram is used to detect the peak of methanesulfonic acid contained in the silver-nitric acid solution. From the detected peak, oxidation is performed. The amount of methanesulfonic acid contained in silver is determined. Then, the total amount of the acid other than methanesulfonic acid contained in the silver oxide and the amount of methanesulfonic acid contained in the silver oxide is defined as the residual acid content.
The silver oxide of the present invention having such a structure has a residual acid content of 100 mass ppm or less and a total content of Na, K, Ca, Mg, Li is 100 mass ppm or less. Therefore, even if a large amount is dissolved in the plating solution, it is difficult to change the composition and pH of the plating solution, and it is difficult to change the plating characteristics.

The silver oxide cake of the present invention is characterized by containing the above-mentioned silver oxide and water.
Since the silver oxide cake of the present invention having such a structure contains the above-mentioned silver oxide, even if it is dissolved in a large amount in the plating solution, it is difficult to change the composition and pH of the plating solution, and it is difficult to change the plating characteristics. . Moreover, since a silver oxide cake contains a water | moisture content, it is hard to disperse | distribute compared with the dry powder, and workability | operativity improves. Furthermore, the silver oxide cake is easy to disperse when introduced into the plating solution, and the dissolution rate of silver oxide in the plating solution is improved.

Here, in the silver oxide cake of this invention, it is preferable that a moisture content exists in the range of 1 mass% or more and 20 mass% or less.
In this case, the dispersibility when introduced into the plating solution is reliably increased, so that the dissolution rate of silver oxide in the plating solution can be further improved.

  The method for producing silver oxide of the present invention includes a step of preparing a reaction vessel containing pure water, a silver salt aqueous solution, and an alkaline aqueous solution, and adding the silver salt aqueous solution and the alkaline aqueous solution to the reaction vessel, The step of adding silver hydroxide particles by adjusting the pH of the mixture of the pure water, the silver salt aqueous solution and the alkaline aqueous solution in the reaction tank so that the pH is within the range of 5.0 or more and 8.0 or less. It is characterized by having.

  According to the silver oxide production method of the present invention having such a configuration, the pH of the mixture of the pure water, the silver salt aqueous solution, and the alkaline aqueous solution is adjusted within the range of 5.0 or more and 8.0 or less. However, since silver oxide particles are precipitated, it is possible to obtain silver oxide with a small amount of acid or alkali. In addition, since trace amounts of metal elements other than silver are unlikely to form and precipitate hydroxides, the purity of the resulting silver oxide is increased.

Here, in the method for producing silver oxide of the present invention, the pH of the aqueous silver salt solution is preferably 3.0 or less.
When pH of silver salt aqueous solution exceeds 3.0, there exists a possibility that a part of silver salt may precipitate in silver salt aqueous solution as silver hydroxide (silver oxide). In this case, since the precipitated silver hydroxide (silver oxide) contains the acid component in the silver salt aqueous solution, the silver oxide particles are precipitated while adjusting the pH of the mixture within the range of 5.0 or more and 8.0 or less. There is a possibility that the residual acid of the silver oxide obtained by increasing the concentration of the silver oxide increases.

  ADVANTAGE OF THE INVENTION According to this invention, even if it melt | dissolves in a plating solution, it is possible to provide the manufacturing method of the silver oxide, silver oxide cake, and silver oxide which are hard to change the composition and pH of the plating solution, and are hard to change a plating characteristic. It becomes.

Below, the manufacturing method of the silver oxide which is embodiment of this invention, a silver oxide cake, and silver oxide is demonstrated.
The silver oxide and silver oxide cake according to the present embodiment are used, for example, as a replenishment material for the Ag component of a plating solution used for the production of Sn—Ag alloy plating.

The silver oxide according to this embodiment has a residual acid content of 100 mass ppm or less and a total content of Na, K, Ca, Mg, Li is 100 mass ppm or less.
Here, the residual acid contained in silver oxide is usually mixed during the production of silver oxide. Examples of acids used in the production of silver oxide include sulfuric acid, nitric acid, alkane sulfonic acid, aryl sulfonic acid, and alkanol sulfonic acid. Such an acid remaining in silver oxide is a residual acid.
On the other hand, Na, K, Ca, Mg and Li contained in silver oxide are usually mixed during the production of silver oxide. In the production of silver oxide, hydroxides, carbonates and hydrogen carbonates of Na, K, Ca, Mg and Li are mainly used. The fact that Na, K, Ca, Mg and Li are contained in silver oxide means that hydroxides, carbonates and hydrogen carbonates of Na, K, Ca, Mg and Li remain in silver oxide. It is shown that.

When silver oxide having a large residual amount of residual acid and Na, K, Ca, Mg, Li is used as a supplement for the Ag component of the plating solution, the residual acid of the plating solution and the metal of Na, K, Ca, Mg, Li The content of the hydroxide, carbonate, and hydrogen carbonate increases, the composition and pH of the plating solution fluctuate, and the plating characteristics may change accordingly.
For this reason, the silver oxide preferably has a residual acid content of 50 mass ppm or less and a total content of Na, K, Ca, Mg, Li of 50 mass ppm or less. More preferably, the amount is 10 mass ppm or less, and the total content of Na, K, Ca, Mg, Li is 10 mass ppm or less.
The lower limit of the residual acid content and the total content of Na, K, Ca, Mg, and Li is not particularly limited, but is preferably 0.1 mass ppm or more. In this case, the effect of preventing aggregation of silver oxide is obtained, and the maintenance of solubility is expected even during long-term storage.

The silver oxide of this embodiment may contain inevitable impurities in addition to the residual acid and Na, K, Ca, Mg, Li. However, in the silver oxide used as a replenishing material for the Ag component of the plating solution, it is preferable that the content of the metal mixed as an impurity is small. For example, it is preferable that the content of Fe, Cr, Ni, Ti, Al, etc., which is easily mixed in the silver oxide production process, is 10 mass ppm or less. When these elements exceed 10 ppm by mass, when silver oxide is repeatedly supplied to the plating solution, it may be concentrated in the plating solution and mixed into the plated product.
Moreover, in order to suppress the occurrence of a soft error in which data in the memory is rewritten by a small amount of α rays emitted from the environment, it is required to reduce the α dose in the solder for joining the semiconductor chip and the substrate. It has been. Therefore, the silver oxide used as a replenisher for the Ag component of the plating solution used to form the solder bump for joining the semiconductor chip and the substrate has a Pb content of 1 mass ppm or less that can cause α rays. Preferably, it is 0.1 mass ppm or less.

The silver oxide cake which concerns on this embodiment contains the above-mentioned silver oxide and water.
Since the silver oxide cake of this embodiment contains the above-mentioned silver oxide, even if it is dissolved in a large amount in the plating solution, it is difficult to change the composition and pH of the plating solution, and it is difficult to change the plating characteristics. Moreover, since a silver oxide cake contains a water | moisture content, it is hard to disperse | distribute compared with the dry powder, and workability | operativity improves. Furthermore, since the silver oxide cake has moisture between the fine particles of silver oxide, it is easy to disperse as fine particles when put into the plating solution. For this reason, time until silver oxide melt | dissolves becomes remarkably short compared with the case where the solid (powder) of silver oxide is thrown in.

  Here, the water content of the silver oxide cake is preferably 1% by mass or more and 20% by mass or less. If the water content is less than 1% by mass, it may be difficult to obtain the above-described effect. When the water content exceeds 20% by mass, the silver oxide cake becomes a slurry and the workability may be reduced. Further, when added to the plating solution, a large amount of water exceeding the amount of water that evaporates during use of the plating solution is introduced into the plating solution, which may change the composition of the plating solution. The water content is more preferably in the range of 5% by mass or more and 20% by mass or less.

  Moreover, the silver oxide cake may contain additives, such as a dispersing agent. The content of the additive is preferably in the range of 0.1 mass ppm to 100 mass ppm with respect to the total amount of the silver oxide slurry. If the amount is less than 0.1 ppm by mass, the effect may be lost. If the amount exceeds 100 ppm by mass, when the silver oxide cake is repeatedly supplied to the plating solution, it may concentrate in the plating solution and adversely affect the plating characteristics. . As the dispersant, for example, fatty acids, fatty acid salts, organic metals, protective colloids and the like can be used. Examples of fatty acids include stearic acid and oleic acid. Examples of the fatty acid salt include sodium stearate and potassium oleate. Examples of the organic metal include magnesium citrate and diethyl zinc. Examples of protective colloids include gelatin and albumin.

Next, a method for producing silver oxide according to this embodiment will be described.
The method for producing silver oxide according to the present embodiment includes a step of preparing a reaction vessel containing pure water, a silver salt aqueous solution, and an alkaline aqueous solution, and adding the silver salt aqueous solution and the alkaline aqueous solution to the reaction vessel. And adding while adjusting the pH of the mixture of the pure water, the aqueous silver salt solution and the aqueous alkaline solution in the reaction tank to be within the range of 5.0 or more and 8.0 or less, thereby precipitating silver oxide particles And a step of causing.

  The silver salt aqueous solution is an aqueous solution in which a silver salt is dissolved in water. Examples of silver salts include silver sulfate, silver nitrate, silver alkane sulfonate (eg silver methane sulfonate, silver ethane sulfonate), silver aryl sulfonate (eg silver benzene sulfonate, silver phenol sulfonate, cresol sulfonic acid) Silver, silver toluene sulfonate), and silver alkanol sulfonate (e.g., silver isethionate). These silver salts may be used individually by 1 type, and may be used in combination of 2 or more type. The silver salt aqueous solution preferably has an Ag concentration of 50 g / L or more from the viewpoint of silver oxide production efficiency. The upper limit of Ag concentration is the saturation concentration of silver salt. The aqueous silver salt solution preferably has a pH of 3.0 or less, more preferably in the range of 1.0 to 3.0, and preferably in the range of 2.0 to 3.0. Particularly preferred. When pH of silver salt aqueous solution exceeds 3.0, there exists a possibility that a part of silver salt may precipitate in silver salt aqueous solution as silver hydroxide (silver oxide). In this case, since the precipitated silver hydroxide (silver oxide) contains an acid component in the silver salt aqueous solution, the residual acid of the obtained silver oxide may increase. On the other hand, when the pH of the aqueous silver salt solution is too low, the amount of the aqueous alkaline solution used in the subsequent step increases and the productivity may decrease.

The alkaline aqueous solution is an aqueous solution in which an alkaline compound is dissolved in water. Examples of alkaline compounds include Na, K, Ca, Mg, Li hydroxides, carbonates, and bicarbonates. These alkaline compounds may be used individually by 1 type, and may be used in combination of 2 or more type.
The alkaline aqueous solution is preferably in the range of 0.5 mol / L or more and 2 mol / L or less as the concentration of the alkaline compound. When the concentration of the alkaline compound is within the above range, when added to a silver salt aqueous solution in a later step, a rapid change in pH can be suppressed while maintaining the production efficiency of silver oxide, and impurities are mixed in. A small amount of high-purity silver oxide can be stably deposited.

  In the present embodiment, the above silver salt aqueous solution and alkaline aqueous solution are added to a reaction vessel in which pure water is accommodated. By adding the silver salt aqueous solution and the alkaline aqueous solution in this manner, silver oxide can be precipitated while suppressing a rapid increase in pH of the mixture of pure water, the silver salt aqueous solution, and the alkaline aqueous solution in the reaction vessel. For this reason, it is suppressed that trace amount metal elements other than silver generate | occur | produce and precipitate a hydroxide, and can precipitate highly purified silver oxide.

In this embodiment, the silver salt aqueous solution and the alkaline aqueous solution are adjusted while adjusting the pH of the mixture of pure water, the silver salt aqueous solution, and the alkaline aqueous solution in the reaction tank to be in the range of 5.0 or more and 8.0 or less. Added. When the pH of the mixture in the reaction vessel is within the above range, the amount of acid and alkali mixed in the precipitated silver oxide can be reduced. If the pH of the mixture in the reaction vessel is less than 5.0, the acid may be easily mixed into the silver oxide produced. On the other hand, when the pH of the silver salt aqueous solution exceeds 8.0, alkali may be easily mixed into the produced silver oxide. Moreover, when the pH of the mixture in the reaction vessel is increased, a trace amount of metal elements other than silver may be likely to form hydroxides and precipitate.
Moreover, in order to make the pH of the entire mixture in the reaction vessel uniform and make it difficult for the pH to locally deviate from the range of 5.0 or more and 8.0 or less, a silver salt aqueous solution and an alkaline aqueous solution are added while stirring. It is preferable. Stirring may be performed within a range of 200 rpm to 2000 rpm using a stirrer.

In order to improve the productivity of silver oxide, the pH of the mixture in the reaction vessel is preferably in the range of 6.0 to 7.5.
On the other hand, the pH of the aqueous silver salt solution is preferably in the range of 5.0 or more and 7.0 or less in order to suppress the metal, particularly Pb, from being mixed in as a hydroxide.
Moreover, it is preferable that the liquid temperature of the mixture in a reaction tank exists in the range of 5 to 50 degreeC. If it is less than 5 degreeC, it becomes difficult to precipitate silver oxide and there exists a possibility that productivity may deteriorate. When it exceeds 50 degreeC, the reactivity of silver salt aqueous solution and alkaline aqueous solution will rise, and there exists a possibility that it may become difficult to make pH in a reaction tank into 5.0 or more and 8.0 or less.

  In addition, the particle diameter of the silver oxide obtained by this embodiment is in the range of 0.01 micrometer or more and 100 micrometers or less normally. If the particle size is less than 0.01 μm, the silver oxide powder may be easily scattered, and the workability during drying / recovery or replenishment to the plating solution may be deteriorated. On the other hand, if the particle diameter exceeds 100 μm, the dissolution rate of silver oxide in the plating solution may be reduced. The particle size of silver oxide is preferably in the range of 0.1 μm to 10 μm.

The silver oxide particles deposited in the mixture in the reaction tank can be recovered by a normal solid-liquid separation method such as decantation, centrifugation, pressure filtration, and vacuum filtration.
The recovered silver oxide is preferably washed thoroughly with water to remove acids and alkalis adhering to the surface. However, when excessive load is applied such as centrifugal separation, pressure filtration, vacuum filtration, etc., silver oxide particles may aggregate and washing may not be performed sufficiently. So, solid-liquid separation is performed by decantation. It is preferable.

  When silver oxide is used as a dry powder, the washed silver oxide is preferably dried at 50 ° C. or lower in order to suppress the self-decomposition of silver oxide.

  The silver oxide of the present embodiment configured as described above has a residual acid content of 100 mass ppm or less and a total content of Na, K, Ca, Mg, Li of 100 mass ppm or less. Therefore, even if a large amount is dissolved in the plating solution, it is difficult to change the composition and pH of the plating solution, and it is difficult to change the plating characteristics.

  Since the silver oxide cake of this embodiment contains the above-mentioned silver oxide and water, even if it is dissolved in a large amount in the plating solution, it is difficult to change the composition and pH of the plating solution, and it is difficult to change the plating characteristics. In addition, since the silver oxide cake contains moisture, it is less likely to scatter compared to the dried powder, and the workability when being added to the plating solution is improved. Furthermore, the silver oxide cake is easy to disperse when introduced into the plating solution, and the dissolution rate of silver oxide in the plating solution is improved. Furthermore, by storing the silver oxide cake in a frozen state, deterioration of the silver oxide due to contact with air can be suppressed over a long period of time. This is considered to be because the contact area between the silver oxide and the air is reduced by covering the surface of the silver oxide with ice (water in the frozen silver oxide cake).

  Furthermore, according to the method for producing silver oxide of the present embodiment, while adjusting the pH of a mixture of pure water, a silver salt aqueous solution, and an alkaline aqueous solution in the reaction vessel to a range of 5.0 or more and 8.0 or less, Since the silver oxide particles are precipitated by adding the salt aqueous solution and the alkaline aqueous solution, it is possible to obtain silver oxide with a small amount of acid or alkali mixed therein. In addition, since trace amounts of metal elements other than silver are unlikely to form and precipitate hydroxides, the purity of the resulting silver oxide is increased.

[Invention Example 1]
Silver nitrate (manufactured by Kanto Chemical Co., Ltd., special grade) was dissolved in pure water to prepare an aqueous silver nitrate solution having an Ag concentration of 100 g / L. Further, sodium hydroxide (manufactured by Kanto Chemical Co., Ltd., special grade) was dissolved in pure water to prepare a sodium hydroxide aqueous solution having a sodium hydroxide concentration of 1 mol / L.

  500 mL of pure water was put into a reaction vessel (HARIO, 1000 mL beaker), a pH meter (HORIBA, double junction type reference electrode) and a stirrer (stirrer: Aswan, stirring bar size: 40 mm, stirring condition: 500 rpm ) Was installed. Next, while stirring pure water in the reaction vessel with a stirrer, the above silver nitrate aqueous solution was dropped as an aqueous silver salt solution, and the above sodium hydroxide aqueous solution was dropped as an alkaline aqueous solution using a dropping pump (manufactured by AS ONE). . The dropping is carried out while dropping a silver nitrate aqueous solution at a rate of 5 mL / min, and adjusting the sodium hydroxide aqueous solution so that the pH in the reaction vessel is within the range of 5.0 or more and 5.5 or less. It was dripped at a speed. The aqueous silver nitrate solution and aqueous sodium hydroxide solution were added dropwise until the amount of the mixture in the reaction tank reached 1000 mL. Moreover, the liquid temperature of the mixture in the reaction tank during dripping was adjusted so that it might become 20 degreeC.

  After completion of the dropwise addition of the aqueous silver nitrate solution and aqueous sodium hydroxide solution, stirring was further continued for 10 minutes to age the precipitated silver oxide particles. After ripening, the stirrer was stopped and the precipitated silver oxide particles were recovered by decantation. The recovered silver oxide particles are redispersed in 200 mL of pure water using a 500 mL beaker, and the decantation washing process is repeated three times. The silver oxide particles after the final decantation are dried at 50 ° C. Of silver oxide was obtained.

[Invention Examples 2-11, Comparative Examples 1-2]
As the silver salt aqueous solution, a silver salt aqueous solution (Ag concentration: 100 g / L) prepared using the silver salt shown in Table 1 below was used. As the alkaline aqueous solution, an alkaline aqueous solution (alkaline compound concentration: 1 mol / L) prepared using an alkaline compound shown in Table 1 below was used. The pH in the reaction vessel was as shown in Table 1 below. Except for the above, silver oxide was obtained in the same manner as Example 1 of the present invention.
In Example 4 of the present invention, when the silver oxide particles after the final decantation were dried, the drying conditions were set to 40 ° C. for 1 hour, and then the whole was uniformly mixed, and the water content became 10% by mass. The silver oxide cake was confirmed.

[Evaluation]
For the silver oxides obtained in Invention Examples 1 to 11 and Comparative Examples 1 and 2, the dissolution rate, residual acid content, total content of Na, K, Ca, Mg, Li, and Pb content were determined by the following methods. It was measured. The results are shown in Table 1.

(Dissolution time)
Weigh 10 g of the sample silver oxide. A 100 mL beaker was charged with 100 g of a 60% by mass methanesulfonic acid aqueous solution, and the aqueous solution was weighed into the aqueous solution while stirring (stirrer: As One, stirring bar size: φ10 mm, stirring condition: 200 rpm). Silver oxide was added. Next, while observing the silver oxide visually, the time from when the silver oxide was added to when the silver oxide was completely dissolved and disappeared was measured. The dissolution rate (g / sec) was calculated from the following formula. The liquid temperature of the methanesulfonic acid aqueous solution at the start of charging was 25 ° C. However, for the silver oxide cake obtained in Invention Example 4, 11.1 g was measured so as to be 10 g equivalent to silver oxide, and the same evaluation was performed.
Dissolution rate (g / sec) = mass of silver oxide (g) / time until silver oxide disappears (second)

(Residual acid content)
In the same manner as the measurement of the dissolution rate, 10 g of silver oxide was dissolved in 100 g of a methanesulfonic acid aqueous solution (methanesulfonic acid concentration: 60% by mass) to prepare a silver-methanesulfonic acid solution. The prepared silver-methanesulfonic acid solution was diluted 100 times with pure water. Then, using an ion chromatogram (Thermo Scientific, ICS-5000 +), the peak of the anion (excluding the methanesulfonate ion included as a matrix) contained in the diluted silver-methanesulfonate solution was detected, From the total amount of components corresponding to the detected peak, the amount (A) of acid other than methanesulfonic acid contained in silver oxide was determined. The conditions of the ion chromatogram are as follows: separation column: AS15, column temperature: 35 ° C., eluent: 38 mM KOH aqueous solution, eluent flow rate: 1.2 mL / min, sample injection amount: 25 μm, detector: electrical conductivity, Suppressor current value: 113 mA.
Next, a silver-nitric acid solution was prepared by dissolving 10 g of silver oxide in 100 g of nitric acid in the same manner as in the measurement of the dissolution rate except that nitric acid was used instead of the methanesulfonic acid aqueous solution.
The prepared silver-nitric acid solution was diluted 100 times with pure water. Next, similarly, using the ion chromatogram, the peak of methanesulfonic acid contained in the diluted silver-nitric acid solution is detected, and the amount (B) of methanesulfonic acid contained in the silver oxide is obtained from the detected peak. It was.
And the total amount ((A) + (B)) of the amount (A) of acid other than methanesulfonic acid contained in silver oxide and the amount (B) of methanesulfonic acid contained in silver oxide is contained in the residual acid. The amount.

(Total content of Na, K, Ca, Mg, Li)
In the same manner as the measurement of the dissolution rate, 10 g of silver oxide was dissolved in 100 g of a methanesulfonic acid aqueous solution (methanesulfonic acid concentration: 60% by mass) to prepare a silver-methanesulfonic acid solution. Next, the contents of Na, K, Ca, Mg, and Li in the prepared silver-methanesulfonic acid solution were measured using an ICP emission spectroscopic analyzer (725-ES manufactured by Agilent Technologies).

(Pb content)
In the same manner as the measurement of the residual acid content, 10 g of silver oxide was dissolved in 100 g of nitric acid to prepare a silver-nitric acid solution. Next, the content of Pb in the prepared silver-nitric acid solution was measured using ICP-MS (manufactured by Agilent Technologies, 7700X).

In the silver oxides of Invention Examples 1 to 11, the residual acid content, the total content of Na, K, Ca, Mg, and Li and the Pb content were low. In particular, the silver oxides of Invention Examples 1 to 4 and 7 to 11 in which the pH of the silver salt aqueous solution when the alkaline aqueous solution was added was 7.0 or less had a low Pb content. In addition, in Invention Example 4 in which silver oxide was in a cake state, the dissolution rate was remarkably increased.
On the other hand, the silver oxide of Comparative Example 1 in which the pH of the silver salt aqueous solution when the alkaline aqueous solution was added was 4.5 or more and 4.9 or less had a high content of residual acid. In addition, the silver oxide of Comparative Example 2 in which the pH of the silver salt aqueous solution at the time of adding the alkaline aqueous solution is 8.1 or more and 8.5 or less has a large content of Na, K, Ca, Mg, Li and a Pb content. became.

Claims (5)

  Silver oxide characterized by having a residual acid content of 100 mass ppm or less and a total content of Na, K, Ca, Mg, Li of 100 mass ppm or less.   A silver oxide cake comprising the silver oxide according to claim 1 and water.   The silver oxide cake according to claim 2, wherein the water content is in the range of 1% by mass or more and 20% by mass or less. Preparing a reaction vessel containing pure water, a silver salt aqueous solution, and an alkaline aqueous solution;
The silver salt aqueous solution and the alkali aqueous solution are placed in the reaction tank, and the pH of the mixture of the pure water, the silver salt aqueous solution, and the alkali aqueous solution in the reaction tank is in the range of 5.0 or more and 8.0 or less. Adding while adjusting so as to precipitate silver oxide particles,
A method for producing silver oxide, comprising:   The method for producing silver oxide according to claim 4, wherein the silver salt aqueous solution has a pH of 3.0 or less.