JP3148115B2 - Determination method of additive amount in copper electrorefining - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for determining the amount of an additive in electrolytic copper refining, in which the amount of the additive in the electrolytic copper refining can be easily and reliably determined.

[0002]

2. Description of the Related Art In the electrolytic refining of metals such as copper, it is common practice to add additives such as thiourea, glue, and chloride ions to an electrolytic solution in order to obtain a smooth electrodeposited (electrolytic copper) surface. . Thus, it is said that the additive has an effect of suppressing the progress of electrodeposition at a specific portion by adsorbing on the cathode surface and smoothing the entire surface of the electrodeposit. Therefore, if the amount of the additive is too small, the appearance of the electrolytic copper is deteriorated such as generation of particles and bumps, and conversely, even if the total amount of the additive is excessive, particles may be generated. It is known, and it is important to keep the total amount of addition to a suitable amount. Also, to what extent the amount of each additive such as thiourea, glue, chloride ion should be added,
Known empirically.

[0003]

However, additives are generally very small and are often decomposed in the course of electrolysis, so that each of the additives and the total amount thereof are controlled by the values obtained by performing quantitative analysis. Have difficulty. In addition, in the electrolytic operation, there are many factors other than additives, such as current density, electrolyte composition, liquid temperature, distance between electrode plates and distortion, which affect the electrodeposition condition. Despite the need to make fine adjustments as the temperature changes, it can only be determined empirically, and it is currently difficult to quickly determine the amount of additives and manage the operation for changing electrolysis conditions. There is a problem.

[0004] It is an object of the present invention to provide means for rapidly determining the amount of additive required in electrolytic refining of copper.

[0005]

Means for Solving the Problems The inventors of the present invention have conducted various studies to solve the above-mentioned problems and achieve the above-mentioned object. As a result, the influence of the amount of the additive on the electrodeposition surface roughness is determined by the concentration. Define the additive strength from the approximate formula, determine the combination of additive amounts, and also determine the additive conditions according to the electrolytic conditions from the relational expression between the electrolytic conditions and additive strength, and the resulting appearance evaluation of the copper surface. The inventors have found that the object can be achieved by selecting the amount, and have completed the present invention. That is, in the present invention, in the method for electrolytic refining of copper, the amount of the additive to be added is determined by both the electrodeposit surface roughness (Rz) obtained by the Hull cell test and the roughness variation (σ) due to different current densities. Is determined so as to be minimized by the following two equations (5) and (6).

Formula 5: Rz = −0.187 Ctu−0.053 Cgl
ue-3.115CCl + 4.16

Equation 6 σ = −0.068 Ctu + 0.131 Cgl
ue-14.6CCl + 1.742 (where Ctu is the amount of thiourea added, Cglu is the amount of glue added, and CCl is the chloride ion concentration) In the electrolytic refining of copper, the appearance evaluation of electrolytic copper is described below. It is characterized in that the amount of the additive is determined so as to be equal to or greater than 70 according to Equation 7.

[Formula 7] Appearance = 21.10Ip + 0.397L + 5.1
8 (Cu / Dk) × 1000 + 25.38 (where L is the distance between the electrodes, Ip is the formula [(1 / Rz) ² +
(1 / σ) ² ] The additive strength obtained from ^1/2 , Cu is the concentration of the electrolytic solution, and Dk is the current density.) Further, as an additive, by increasing chloride ions instead of increasing thiourea. It is characterized by increasing additive strength.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION In electrolytic refining, additives are used to smooth the surface of an electrodeposit (copper). Therefore, it is only necessary to add an amount of the additive that minimizes the roughness of the electrodeposit surface on the cathode. However, in actual operation of the electrolytic cell, there are many factors other than the effects of additives, such as changes over time due to energization, suspended matter in the electrolyte, and variations in the solution temperature. It is difficult to measure roughness. In an actual electrolytic cell, current distribution varies due to electrode plate distortion, contact resistance variation, anode dissolution, etc. Additives act to prevent a decrease in uniform electrodeposition due to current distribution variation. There are also things. Therefore, the surface roughness is not only the location of the current density,
It is necessary to evaluate over the variation range of the current density.

However, in actual operation, it is actually difficult to perform tests using all combinations of additives. Therefore, in order to evaluate the surface roughness of the electrodeposit (electrolytic copper) and the variation over the current density range, it is considered desirable to formulate the respective effects and then evaluate each as one item.

In order to easily measure the surface roughness of an electrodeposit, there is a method using a Hull cell test as disclosed in, for example, JP-A-5-72167. This method is characterized in that the electrodeposition states at different current densities and the surface roughness thereof can be easily measured in a short time. Therefore, when the amount of additives is determined by changes in operating conditions or by daily operation management, a known amount of additives is added to the reference electrolyte containing no additives, and the surface roughness is measured by the Hull cell test. Then, the optimum amount of the additive may be determined.

The average value of the 10-point average electrodeposit surface roughness (Rz) and the variation of 10-point surface roughness (σ) at each current density are determined by the combination of the added additives (thiourea, glue, chloride ion). By performing multiple regression, for example, a relational expression between the additive amount and the electrodeposit surface roughness as shown in the following formulas (1) and (2) is obtained. Since the combination of additives that reduces both Rz and σ is the most effective for smoothing the surface of the electrodeposit, the two mathematical formulas are represented by, for example, as shown in mathematical formula (3). By defining it in a mathematical formula that constructs a new constant named
It has been found that the optimum amount of the additive can be determined according to the electrolysis conditions as the electrolysis operation conditions change.

[0010]

[Formula 1] Rz = a ₁ Ctu + a ₂ Cglu + a ₃ CCl + a ₀

Equation 2 σ = b ₁ Ctu + b ₂ Cglu + b ₃ CCl + b ₀

Ip = [(1 / Rz) ² + (1 / σ) ² ] ^1/2 (where Ctu is the amount of thiourea added, Cglu is the amount of glue added, CCl is the chloride ion concentration, a ₀ ~a _3, b
₀ ~b ₃ is a coefficient of each term. )

From the same idea, the relationship between the additive strength and other conditions on electrolysis is also formulated as shown in the following equation (4), whereby the additive required for obtaining a predetermined appearance evaluation of electrolytic copper is obtained. It has been found that the electrolysis conditions such as the composition, the liquid composition, and the current density can be determined.

[0012]

[Formula 4] Appearance = c ₁ Ip + c ₂ L + c ₃ (Cu / Dk)
× 1000 + c ₀ (where L is the distance between the electrodes, Ip is the additive strength, Cu is the concentration of the electrolyte, Dk is the current density, and c _{0 to} c ₃ are the coefficients.)

That is, although the range of the additive amount of each additive is generally known from the experience of the prior art, the respective additive amounts are combined within the range to obtain the additive amount from the above formulas 1, 2, and 3. By determining the strength Ip, it is possible to determine whether or not the addition amount is appropriate. Further, an appearance value is determined using the planned operating conditions and the combination formula 4, and this value is a predetermined value of 70 or more, preferably It can be seen that if the value is 72 or more, it can be the amount of each additive under the operating conditions. Conversely, the additive strength Ip can be determined from Equation 4 using the desired appearance value and the scheduled operating conditions to determine the amount of each additive. Further, the calculated values of the electrodeposit surface roughness (Rz) and its variation (σ), the additive strength (Ip), and the appearance of the surface due to many combinations of the respective additives, together with the operating conditions, are tabulated. If prepared, the amount of each additive to be added under the expected operating conditions can be easily determined by searching the table for the amount of each additive.

In the present invention, the surface roughness can be defined by a test method other than the Hull cell test, for example, by measuring the surface roughness by electrodepositing copper on a stainless steel base plate to 1 mm or less. If so, it can be substituted for the Hull cell test.

[0015]

Next, an embodiment of the present invention will be described. Example 1 (determination of each coefficient of Formulas 1 and 2): As a Hull cell test tank, the width is 83.5 mm, the long side is 127 mm, the short side is 47.6 mm, the depth is 63.5 mm, and the electrolyte volume is 267 m.
1 and a trapezoidal cross section, and rolled copper was used for the anode and cathode. The electrolytic solution has a Cu concentration of 50 g /
1, sulfuric acid 190 m / l, liquid temperature 60 ° C., and additives: thiourea 1.11 mg / l, glue 1.47 mg / l
l is "1 time", the chloride ion concentration is shown in g / l, and the combination shown in Table 1 is added to the electrolytic cell 20 minutes before the energization, and lightly lightened by hand for 1-2 minutes so as to be uniform. Stirred. The current was set to 2 A, and current was supplied for 1 hour without stirring.

After the completion of the power supply, the cathode surface is washed, and a stylus type surface roughness meter (SURFTEST2 manufactured by Mitutoyo) is used.
01 type). The average current density usually is because it is 200~300A / ^{m 2} before and after the measurement considering the variation, it is preferable to measure at a position corresponding to approximately 150~600A / ^{m 2.} In the present embodiment, the 10-point average surface roughness (Rz) defined in JIS B-0601 was used to represent the surface roughness. The results are shown in Table 1 below.

[0017]

[Table 1]

The values shown in Table 1 were obtained for Rz and σ.
Multiple regression of the additive condition, the measured surface roughness value, and the variation were performed, and the coefficients a _{0 to} a ₃ and b _{0 to} b _{3 of} the formulas 1 and 2 were obtained as follows, and the formulas 5 and 6 could be obtained. Was.

Formula 5: Rz = −0.187 Ctu−0.053 Cgl
ue-3.115CCl + 4.16

Equation 6 σ = −0.068 Ctu + 0.131 Cgl
ue-14.6CCl + 1.742 According to the above formula, the additive amount and the surface roughness of the electrodeposit, that is, 1
The relationship between the zero-point average surface roughness (Rz) and the ten-point surface roughness (σ) was expressed by Expressions 5 and 6.

Example 2 (Determining the coefficient of Equation 4): An electrolytic cell (length 3000 × width 1260 × depth 1390 mm) was placed in an electrolytic cell.
Copper refined anode (width 1030 x length 1050 x thickness 38
mm) 26 or 22 and 27 or 23 cathodes (width 1070 x length 1050 x thickness 0.7 mm) were loaded so that the anode-to-anode distance was 105 mm. Since the electrolytic cells are connected in series, the current density is 2
It will be 50 A / m ² or 300 A / m ² . 20 l of an electrolytic solution having a Cu / sulfuric acid concentration under the conditions shown in Table 2 at a temperature of 60 ° C.
/ Min at a flow rate of / min. The amount of the additive (thiourea, glue, chloride ion) shown in Table 2 was supplied to each tank by a metering pump. In addition, the additive strength (Ip) calculated by Formulas 5 and 6 and Formula 3 shown in Example 1 is also shown in Table 2 below. Current density 250A / ^{m 2} is the tank 240 hours, the bath of 300A / ^{m 2} was energized for 200 hours. Thereafter, the cathode was replaced, and the same procedure was repeated for another 240 hours.
The electricity was supplied for 00 hours. Each surface of the cathode was divided into nine parts, and one piece of electrolytic copper was visually evaluated on a scale of five out of five points so as to reach a maximum of 90 points, and the evaluations in the first half and the second half were averaged.

[0020]

[Table 2]

The electrolytic solution Cu concentration (mol
/ L), current density Dk (A / m ² ), additive strength Ip,
The distance L between the anode and cathode in the first half (the first half 33m
m, the latter half of 40.5 mm) and the evaluation of the appearance of the surface of the electrolytic copper obtained as a result of the energization were subjected to multiple regression to obtain Equation 7.

[Formula 7] Appearance = 21.10Ip + 0.397L + 5.1
8 (Cu / Dk) × 1000 + 25.38 Current density Dk for obtaining predetermined appearance evaluation, electrolytic solution Cu
If the electrolysis conditions such as the concentration and the distance L between the electrodes are determined, the surface of the electrolytic copper can be smoothed from the above formulas 5, 6, 3 and formula 7
The addition amount of each additive necessary to obtain a value of 0 or more can be determined, and can be used for operation management such as coping with an operation trouble or determining an addition amount of an additive when changing operation conditions.

Example 3 An electrolytic cell, a cathode and an anode having the same size as in Example 2 were used, and the electrolysis conditions shown in Table 3 were used. Dk is 300 A / m ² , electrolyte Cu concentration is 50 g / l, Cl ion is 50 mg / l, glue is 1
The amount of thiourea was adjusted to 1, 3, and 5 times. The additive strength (Ip) calculated by Formulas 5 and 6 and Formula 3 shown in Example 1 is also shown.

[0023]

[Table 3]

After 240 hours of current supply, each surface of the cathode was divided into nine parts, and one piece of electrolytic copper was visually evaluated on a scale of five out of five points so as to reach a maximum of 90 points. As shown in Table 4, when the Cu concentration is the same, the higher the additive strength due to the change in the amount of thiourea, one of the additives, and the latter half of the interelectrode distance, the better the appearance. Have been.

[0025]

[Table 4]

Example 4: The same equipment as in Example 3 was energized under the conditions shown in Table 5 determined as described above, and the appearance was determined.

[0027]

[Table 5]

As described above, it was recognized that an excellent electrolytic copper surface was obtained using the additive amount determined in accordance with the method of the present invention. As shown in Table 5 for 2-A and 5-A, when the glue, which is one of the additives, was increased by a factor of 1.5, the appearance evaluation of electrolytic copper was rather lowered. , 6 and the effect of Equation 7 in Example 2 could be confirmed again. In addition, No. 2-
As shown by A and 6-A, it was also confirmed that the higher the chloride ion concentration, the better the appearance. No. 7-A, 8-A,
As shown in 9-A, it was confirmed that the appearance improved as the Cu concentration increased with the same addition strength. In addition, No. As shown in 7-A and 10-A, it was confirmed that the same or higher appearance can be maintained even if the amount of thiourea is reduced by the amount of the increase of the chloride ion.

[0029]

According to the present invention, it is possible to easily and surely determine the optimum amount of an additive required in response to a change in operating conditions in copper electrolytic refining, which has traditionally relied on experience, and to achieve a smooth surface. A remarkable effect is obtained, such as obtaining excellent electrolytic copper.

Continuation of front page (56) References JP-A-5-72167 (JP, A) JP-A-6-264278 (JP, A) JP-A-8-178893 (JP, A) JP-A 8-178894 (JP) , A) Actually open Showa 61-155760 (JP, U) Special table Showa 60-500453 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C25C 1/00-7/08

Claims (3)

(57) [Claims] In the method for electrolytically refining copper, the amount of an additive to be added is determined by adjusting both the electrodeposit surface roughness (Rz) obtained by a Hull cell test and the roughness variation (σ) due to different current densities. A method for determining an additive amount of an additive in electrolytic copper refining, wherein the additive amount is determined to be minimized by the following two mathematical expressions. Rz = -0.187Ctu-0.053Cglu-
3.115CCl + 4.16σ = −0.068Ctu + 0.131Cglu-1
4.6 CCl + 1.742 (where Ctu is the amount of thiourea added, Cglu is the amount of glue added, and CCl is the chloride ion concentration) 2. The addition of an additive in electrolytic copper refining according to claim 1, wherein, in the electrolytic copper refining, the amount of the additive is determined so that the appearance evaluation of the electrolytic copper becomes 70 or more by the following formula. How to determine quantity. Appearance = 21.10Ip + 0.397L + 5.18 (Cu
/Dk)×1000+25.38 (where L is the distance between the poles, Ip is the formula [(1 / Rz) ² +
(1 / σ) ² ] The additive strength obtained from ^1/2 , Cu is the electrolyte concentration, and Dk is the current density.) 3. The amount of an additive in copper electrolytic refining according to claim 1, wherein the additive strength is increased by increasing chloride ions instead of increasing thiourea. Decision method.