JP4262178B2 - Electric tin plating method - Google Patents

Description

  The present invention relates to an electrotin plating method using an insoluble electrode.

  Electrotin plating in an insoluble electrode system dissolves metal tin while circulating a plating solution in which oxygen is dissolved between a metal tin dissolution vessel and a plating solution circulation vessel. Further, the plating solution is circulated between the plating solution circulation tank and the electrolytic plating tank, and electrotin plating is performed using an insoluble electrode. The insoluble electrode system does not dissolve the anode electrode compared to the soluble electrode system, so the distance between the cathode strip and the anode electrode is constant, the plating quality is uniform, and the frequency of replacing the plating electrode is low. Since it is low, there are advantages such as personnel reduction.

  On the other hand, in the insoluble electrode system, the plating solution concentration is closely related to the gloss of the plated product as well as the current density and the plating solution temperature. Therefore, it is necessary to control the metal ion concentration in the plating solution within a certain range. In particular, in the case of electrotin plating, the metal ion concentration management value is as narrow as about 1/2 compared to electrogalvanization, and it is difficult to control.

Conventionally, as a method of controlling the metal ion concentration of a plating solution, a method of controlling the metal ion concentration by feedback control is known. For example, in Patent Document 1, a reference supply flow rate that compensates for the metal ion consumption result obtained by the product of the actual plating current value and the actual plating time value is obtained, and the target value and the actual value of the metal ion concentration in the plating solution circulation tank are obtained. A technique is disclosed in which a combined supply flow rate that compensates for the difference is used as a supply flow rate of the plating solution to the plating solution circulation tank. In Patent Document 2, the amount of metal ions to be replenished is determined from the difference between the target value and the actual value of the metal ion concentration in the plating solution circulation tank, and a circulation line between the metal tin dissolution tank and the plating solution circulation tank is obtained. Discloses a technique for determining the supply flow rate to the plating solution circulation tank based on the concentration of metal ions in the plating solution supplied to the plating solution circulation tank of the circulation line.
Japanese Patent Publication No.53-24897 Japanese Patent No. 2836670

  However, the metal ion concentration control method for the plating solution circulation tank disclosed in Patent Documents 1 and 2 is controlled only by feedback control. Therefore, a control delay occurs due to the sampling time for measuring the metal ion concentration, the flow control valve operating time, the piping distance from the metal ion concentration measurement point to the plating solution circulation tank, and the like.

  In addition, the method in which the operator predicts the amount of tin ion consumption and adjusts the oxygen blowing amount and the plating solution circulation amount may not allow fine setting changes, and the metal ion concentration cannot be kept within an appropriate range. Needless to say.

  The problem to be solved by the present invention is to provide a method for accurately controlling the tin ion concentration in an electrotin plating method using an insoluble electrode.

  The gist of the present invention is that the flow rate of the plating solution supplied to the plating solution circulation tank is calculated based on the expected consumption rate of tin ions after a predetermined time determined from the production schedule, and this feedforward control flow rate. Is controlled using a feedback control flow rate calculated based on the difference between the actual value and the target value of the tin ion concentration of the plating solution supplied from the plating solution circulation tank to the electrolytic plating tank.

That is, the present invention dissolves metal tin with a plating solution in which oxygen is dissolved in a first plating solution circulation line between the metal tin dissolution vessel and the plating solution circulation vessel, and the plating solution circulation vessel and the electrolytic plating vessel. In the electrotin plating method of electrotin plating using an insoluble electrode in the second plating solution circulation line between the plating solution and the plating solution flow rate supplied to the plating solution circulation tank in the first plating solution circulation line, (1) The tin ion concentration of the plating solution supplied to the plating solution circulation tank in the first plating solution circulation line, the target value of the tin ion concentration of the plating solution supplied from the plating solution circulation tank to the electrolytic plating tank, and the expected consumption of tin ions after a certain time feedforward supply flow rate determined by the speed, (2) plating solution of the plating solution circulating tank from the circulation tank and the tin ion density target value and tin ion concentrations actual value of supplied plating solution into the electrolytic plating bath and tin ions And determining the difference sum of the feedback supply flow rate, determined by the tin ion concentration correction time of the plating solution and a set value of one number of minutes over to correct the target value and the actual value of the degree.

  In the present invention, the predetermined time may be a time from when the tin ion concentration is measured in the first plating solution circulation line until the plating solution having this tin ion concentration is supplied to the plating solution circulation tank.

  According to the electrotin plating method of the present invention, the tin ions are supplied to the plating solution circulation tank according to the expected consumption rate of tin ions (feedforward control), and the plating solution supplied from the plating solution circulation tank to the electrolytic plating tank Since the tin ion is replenished (feedback control) to the plating solution circulation tank so that the tin ion concentration becomes the target value according to the actual value of tin ion concentration, the tin ion concentration in the plating solution circulation tank is stabilized. As a result, even when the plating conditions are changed (plating thickness change, plate width change, etc.), a gloss failure due to the tin ion concentration deviating from the control value does not occur.

  Hereinafter, the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a configuration diagram showing an example of a plating apparatus used in the electrotin plating method of the present invention. As shown in the figure, in the electrotin plating in the insoluble electrode system, the metal tin particles 3 are supplied from the metal tin supply device 2 to the metal tin dissolution tank 1 via the on-off valve 7, and between the plating solution circulation tank 4. Then, while circulating the plating solution, oxygen is blown from the oxygen blowing pipe 11 to dissolve the metal tin particles 3. The dissolved tin ions are supplied from the metal tin dissolution tank 1 to the plating solution circulation tank 4 through the precipitation tank 14 (this circulation line is hereinafter referred to as “first plating solution circulation line 8”).

  On the other hand, while the plating solution is circulated between the electrolytic plating tank 5 and the plating solution circulation vessel 4, the strip 10 is electroplated with the insoluble electrode 9 (this circulation line is referred to as “ 2nd plating solution circulation line 19 "). Also, between the plating solution circulation tank 4 and the electrolytic plating tank 5, between the plating solution circulation tank 4 and the metal tin dissolution tank 1, between the metal tin dissolution tank 1 and the precipitation tank 14, and the precipitation tank 14 and the plating solution. The circulation tank 4 is connected via a pump 6 or an on-off valve 7 to form a plating solution circulation line.

  As described above, in the insoluble electrode system, the plating solution concentration is closely related to the current density and plating solution temperature as well as the gloss of the plated product, so the metal ion concentration in the plating solution must be controlled within a certain range. There is. In particular, in the case of electrotin plating, the metal ion concentration management value is as narrow as about 1/2 compared to electrogalvanization, and it is difficult to control.

Therefore, in the present invention, using the control device 15 that controls the supply amount of tin ions, the production schedule is received from the host computer 16 such as a process computer and the expected consumption rate of tin ions is calculated. And in order to supply the tin ion suitable for a tin ion consumption scheduled speed to the plating solution circulation tank 4, the feedforward control flow rate (F0) is first determined by the following formula (1).
F0 = S / (CA-CB) (1)
here,
F0: Feed forward control flow rate (reference flow rate to the plating solution circulation tank 4 in the first plating circulation line 8) (m ³ / min)
S: Expected consumption rate of tin ions after Td (min) (kg / min)
CA determined by production schedule (tin plating thickness, plate width, plate passing speed): tin ion concentration (kg / m ³ ) of the plating solution supplied to the plating solution circulation tank 4 in the first plating solution circulation line 8
Actual value CB of tin ion concentration meter 12: Tin ion concentration target value (kg / m ³ ) of the plating solution supplied from the plating solution circulation tank 4 in the second plating solution circulation line 19
Td: Time until the plating solution having the concentration measured by the tin ion concentration meter 12 is supplied to the plating solution circulation tank 4 (min)
The above formula (1) expresses that tin ions corresponding to the expected rate of consumption of tin ions are replenished by the difference in tin ion concentration of the plating solution entering and exiting the plating solution circulation tank 4, and CA> CB is there.

Next, in the present invention, the tin ion concentration of the plating solution supplied from the plating solution circulation tank 4 to the electrolytic plating tank 5 in the second plating solution circulation line 19 at the time of calculating the feedforward control flow rate according to the above equation (1). Considering the difference between the actual value and the target value, the correction value of the plating solution supply flow rate to the plating solution circulation tank 4 in the first plating solution circulation line 8, that is, the feedback control flow rate (ΔF) is expressed by the following equations (2) to Determine in (4).
ΔC = CB−C (2)
ΔS = ΔC × V (3)
ΔF = ΔS / CA / t (4)
here,
ΔC: Tin ion concentration correction value (kg / m ³ )
C: Plating solution tin ion concentration (kg / m ³ ) supplied from the plating solution circulation tank 4 in the second plating solution circulation line 19
Actual value ΔS of tin ion concentration meter 18: Tin ion correction amount (kg)
V: Actual amount of plating solution in the plating solution circulation tank 4 (m ³ )
ΔF obtained from the output value of the level meter 13: feedback control flow rate (plating solution circulation tank 4 in the first plating solution circulation line 8
Correction flow rate) (m ³ / min)
t: Correction time (set value for how many minutes the difference between the target value and actual value of tin ion concentration is corrected) (min)

Next, in the present invention, as shown in the following formula (5), the feed forward control flow rate (F0) and the feedback control flow rate (ΔF) to the plating solution circulation tank 4 in the first plating solution circulation line 8 are added, and plating is performed. The plating solution flow rate (F) to be supplied to the liquid circulation tank 4 is determined, and the control device 15 operates the flow rate adjustment valve 17 to set the determined plating solution flow rate (F).
F = F0 + ΔF (5)
here,
F: Supply flow rate (plating solution flow rate) to the plating solution circulation tank 4 in the first plating solution circulation line 8 (m ³ / min)

  As described above, in the present invention, the control device 15 receives the production schedule (tin plating thickness, plate width, plate passing speed) from the host computer 16 such as a process computer, and the control device 15 receives a certain time after the production schedule. Determine the expected consumption rate of tin ions. Then, the plating solution reference flow rate for supplying tin ions to the plating solution circulation tank 4 is determined (feedforward control) according to the expected consumption rate of tin ions, and the plating supplied from the plating solution circulation tank 4 to the electrolytic plating tank 5 is performed. The reference flow rate supplied to the plating solution circulation tank 4 is corrected (feedback control) so that the actual value of tin ion concentration of the solution becomes the target value. For this reason, the operation where the tin ion concentration in the plating solution circulation tank 4 was stabilized became possible. As a result, even when the plating conditions are changed (plating thickness change, plate width change, etc.), a gloss failure due to the tin ion concentration deviating from the control value does not occur.

It is a block diagram which shows the example of the plating apparatus used for the electrotin plating method of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Metal tin dissolution tank 2 Metal tin supply apparatus 3 Metal tin particle 4 Plating solution circulation tank 5 Electrolytic plating tank 6 Pump 7 On-off valve 8 First plating solution circulation line 9 Insoluble electrode 10 Strip 11 Oxygen blowing pipe 12 Tin ion concentration Total 13 Level meter 14 Sedimentation tank 15 Control device 16 Host computer 17 Flow control valve 18 Tin ion concentration meter 19 Second plating solution circulation line

Claims (2)

Metal tin is dissolved in a plating solution in which oxygen is dissolved in a first plating solution circulation line between the metal tin dissolution vessel and the plating solution circulation vessel, and a second between the plating solution circulation vessel and the electrolytic plating vessel. In the electrotin plating method of electrotin plating using an insoluble electrode in the plating solution circulation line,
The plating solution flow rate supplied to the plating solution circulation tank in the first plating solution circulation line is
The tin ion concentration of the plating solution supplied to the plating solution circulation tank in the first plating solution circulation line, the target value of the tin ion concentration of the plating solution supplied from the plating solution circulation tank to the electrolytic plating tank, and the expected consumption of tin ions after a certain time The feedforward supply flow rate determined by the speed,
What is the difference between the target value and actual value of tin ion concentration in the plating solution circulation tank and the target value and actual value of the amount of plating solution and tin ion concentration in the plating solution circulation tank supplied to the electrolytic plating tank from the plating solution circulation tank ? A feedback supply flow rate determined by the tin ion concentration correction time of the plating solution, which is a setting value of whether to correct over a minute ,
The method of electrotin plating, characterized in that it is determined by the sum of   The predetermined time is set to a time until the plating solution having this tin ion concentration is supplied to the plating solution circulation tank after measuring the tin ion concentration in the first plating solution circulation line. 1. The method for electroplating according to 1.

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