TWI582271B - Sn alloy plating apparatus and method - Google Patents

Description

Sn alloy plating device and method Field of invention

The present invention relates to a Sn alloy plating apparatus and method for forming a film on a surface of a substrate. The plating film is made of an alloy of Sn and a metal more noble than Sn, for example, lead-free and Sn solderable. -Ag alloy.

Background of the invention

An alloy of Sn (tin) and a metal more noble than Sn, for example, a Sn-Ag alloy which is an alloy of Sn and Ag (silver) is plated on the surface of the substrate to form a film formed of a Sn-Ag alloy. Lead-free solder bumps are known. The Sn-Ag alloy plating is performed by applying a voltage between an anode and a substrate surface which are mutually immersed in a Sn-Ag alloy plating solution having Sn ions and Ag ions, and a Sn-Ag alloy is plated. The film is formed on the surface of the substrate. As for the alloy of Sn and a metal more noble than Sn, in addition to the Sn-Ag alloy, for example, there is a Sn-Cu alloy which is an alloy of Sn and copper (Cu), and Sn- which is an alloy of Sn and Bi (铋). Bi alloy, etc.

The plating of such an alloy of Sn with a metal more noble than Sn is often the use of an insoluble anode as the anode. This is because if a soluble anode (Sn anode) made of Sn is used as the anode, the metal which is more expensive than Sn is deposited on the surface of the Sn anode, and the concentration of the metal component is destabilized. The problem of contaminating plating solution.

Regarding the Sn alloy plating method using a soluble anode (Sn anode) made of Sn material, there is proposed a method in which an anode chamber in which an Sn anode is disposed is isolated from a plating bath through an anion exchange membrane, and is insulated from the plating tank. The Sn plating solution, the acid or a salt thereof is accommodated in the room, and the Sn alloy plating solution is accommodated in the plating tank, and the Sn ion in the anode chamber is transferred to the Sn alloy plating solution in the plating tank by the transfer pump (refer to Japan) Japanese Patent No. 4,441,725); plating a plated object placed in a plating tank in a state in which a Sn anode is formed in a plating tank by an anode bag or a box formed of a cation exchange membrane (refer to Japanese Patent) Japanese Patent No. 3368860).

Further, there is proposed a Sn-Ag alloy plating method in which an auxiliary groove is provided which is attached to a plating bath and which separates the cathode chamber from the anode chamber by a separator or a partition wall so as not to cause a deterioration factor to diffuse to the cathode chamber. In the auxiliary tank, the Sn ions are supplied to the plating solution (anolyte) in the anode chamber (refer to Japanese Laid-Open Patent Publication No. Hei 11-21692).

Summary of invention

The present inventors have found that an electrolyte solution (anolyte) containing Sn ions and an acid or a salt thereof is deposited in an anode chamber by an anion exchange membrane as described in Japanese Patent No. 4441725. In the method of disposing the Sn anode and dissolving the Sn ions and transferring the Sn ions toward the cathode side, in order to stably dissolve the Sn ions in the anolyte in the anode chamber, it is important to manage the acid concentration of the anolyte in the anode chamber. . another In addition, the method described in Japanese Patent No. 4441725 is to provide a replenishing device such as a pump and a replenishing path in order to transfer Sn ions, and thus the structure of the device is complicated.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a Sn alloy plating apparatus and method for appropriately and accurately managing Sn ions of an anolyte supplied to a Sn alloy plating solution together with Sn ions. The concentration and the concentration of the acid which forms a complex with the divalent Sn ions make it easier to manage the Sn alloy plating solution, and the apparatus can be simplified.

The Sn alloy plating apparatus has an anion exchange membrane for isolating the inside of the plating tank into a cathode chamber and an anode chamber, wherein the cathode chamber is a Sn alloy plating solution, and the substrate serving as a cathode is immersed in the Sn alloy plating solution. The anode chamber is an anolyte that retains an acid containing Sn ions and a complex with a divalent Sn ion, and an Sn anode is immersed in the anode liquid; and the electrolyte supply line includes the foregoing The acid electrolyte is supplied to the anode chamber, and the electrolyte supply line is such that the Sn concentration of the anolyte in the anode chamber is equal to or greater than a predetermined value and the concentration of the acid is not lower than an allowable value. The electrolyte solution is supplied to the chamber, and the anode liquid in the anode chamber which is increased by the supply of the electrolyte solution is supplied to the Sn alloy plating solution.

Thereby, the concentration of the Sn ions in the anolyte and the concentration of the acid forming the complex with the divalent Sn ions are appropriately and correctly managed, and the anolyte having a high Sn ion concentration and a stable presence of the divalent Sn ions is supplied to the Sn. The alloy plating solution can stably supply Sn ions to the Sn alloy plating solution.

In a suitable aspect, the electrolyte supply line is supplied to the Sn alloy plating solution by allowing the anolyte which is supplied by supplying the electrolyte solution to the anode chamber to overflow the anode chamber.

Thereby, the anolyte having a high Sn ion concentration and a stable presence of the divalent Sn ions can be supplied to the Sn alloy plating solution without requiring power.

In a suitable aspect, the Sn alloy plating apparatus further comprises: an overflow tank for depositing a plating solution overflowing from the cathode chamber; and a plating liquid circulation line for causing the Sn alloy plating solution in the overflow tank Return to the aforementioned cathode chamber and circulate it.

Thereby, the Sn alloy plating solution in the cathode chamber can be circulated through the plating liquid circulation line and stirred.

In a suitable aspect, the Sn alloy plating apparatus further has a pure water supply line for supplying pure water to the inside of the anode chamber.

Thereby, the concentration of the acid in the anode liquid in the anode chamber can be adjusted by controlling the amount of the liquid supplied to the anode chamber through the pure water supply line or the electrolyte supplied to the anode chamber through the electrolyte supply line. To the right range.

In a suitable aspect, the Sn alloy plating apparatus further has an acid concentration measuring device for measuring the concentration of the aforementioned acid in the anolyte in the anode chamber.

In a suitable aspect, the dialysis cell is further provided with a portion of the Sn alloy plating solution removed from the cathode chamber, and at least a portion of the acid is removed from the Sn alloy plating solution and returned to the cathode chamber.

Thereby, when the concentration of the aforementioned acid of the Sn alloy plating solution becomes excessive, At least a portion of the acid may be removed from the Sn alloy plating solution through a dialysis bath to adjust the acid to a suitable range.

In a suitable aspect, the Sn alloy plating apparatus further has an N ₂ gas supply line for supplying nitrogen gas to the anode liquid in the anode chamber to foam the anode liquid.

Thereby, the anolyte in the anode chamber is sufficiently stirred with nitrogen gas to uniformly distribute the Sn ions or the acid in the anolyte in the anode chamber, and the oxidation of the Sn ions in the anolyte can be prevented.

In a suitable aspect, there is an auxiliary electrolytic cell having an auxiliary anode chamber and an auxiliary cathode chamber separated by an anion exchange membrane, and is assisted in anodic liquid which has been immersed in the auxiliary anode chamber. Applying a voltage between the Sn anode and the auxiliary cathode of the catholyte immersed in the auxiliary cathode chamber to increase the Sn ion concentration of the anolyte in the auxiliary anode chamber, and replenishing the anolyte in the auxiliary anode chamber to the Sn alloy Plating solution.

Thereby, for example, when the Sn ions in the entire system are insufficient, the insufficient Sn ions can be supplemented by the anolyte in the anode chamber in which the Sn ion concentration is increased.

The Sn alloy plating method is prepared by preparing a plating bath in which an inner portion is separated into a cathode chamber and an anode chamber by an anion exchange membrane; a Sn alloy plating solution is accommodated inside the cathode chamber, and a substrate is disposed and immersed in the Sn alloy. a plating solution; an anolyte containing Sn ions and an acid forming a complex compound with divalent Sn ions is housed inside the anode chamber, and an Sn anode made of Sn is placed and immersed in the anolyte; The Sn of the anolyte in the anode chamber When the sub-concentration is equal to or greater than a predetermined value and the concentration of the acid is not lower than the allowable value, the electrolyte is supplied into the anode chamber, and the anode liquid in the anode chamber which is increased by the supply of the electrolyte is supplied to the Sn alloy plating. The liquid is applied with a voltage between the cathode and the Sn anode, and Sn alloy plating is performed on the surface of the substrate.

In a suitable aspect, the anolyte which is increased by supplying the electrolyte solution to the anode chamber overflows the anode chamber and is supplied to the Sn alloy plating solution.

In a suitable aspect, the Sn alloy plating solution in the cathode chamber is circulated.

In a suitable aspect, the amount of the electrolyte or pure water supplied to the anode chamber is controlled based on the concentration of the acid in the anode liquid in the anode chamber.

In a suitable aspect, the concentration of the acid in the anolyte is determined by the concentration of the acid in the initial anolyte, the amount of electrolysis and current efficiency at the anode of the Sn, the supply of the electrolyte, and the passage. The penetration rate of the acid which moves from the cathode chamber to the anode chamber by the anion exchange membrane is determined.

In a suitable aspect, a portion of the Sn alloy plating solution is removed from the cathode chamber and at least a portion of the acid is removed from the Sn alloy plating solution and returned to the cathode chamber.

In a suitable aspect, nitrogen is supplied to the anolyte in the anode chamber to foam the anolyte.

In a suitable aspect, the auxiliary Sn anode, which has been immersed in the anolyte of the auxiliary anode chamber of the auxiliary electrolytic cell, is immersed in the yin Applying a voltage between the ion exchange membrane and the auxiliary cathode of the catholyte in the auxiliary cathode chamber isolated from the auxiliary anode chamber to increase the Sn ion concentration of the anode liquid in the auxiliary anode chamber, and replenishing the anode liquid in the auxiliary anode chamber to The aforementioned Sn alloy plating solution.

According to the invention, the electrolysis containing the acid is supplied to the anode chamber such that the Sn ion concentration of the anolyte in the anode chamber is equal to or greater than a predetermined value and the concentration of the acid which forms a complex with the divalent Sn ions is not lower than the allowable value. The liquid can appropriately and correctly manage the concentration of the Sn ions of the anolyte and the concentration of the aforementioned acid. Further, the anolyte in the anode chamber which is increased by the supply of the electrolytic solution is supplied to the Sn alloy plating solution, and the anolyte having a high Sn ion concentration and a stable presence of the divalent Sn ions can be supplied to the Sn alloy plating solution. The Sn alloy plating solution can be stably supplied with Sn ions.

10‧‧‧Anode tank

10a‧‧‧ next door

10b‧‧‧ overflow gap

10c‧‧‧Rectangular gap

10d‧‧‧ openings

10e‧‧‧ next door

12‧‧‧Cathode chamber

14‧‧‧Anode chamber

16‧‧‧ plating tank

16a‧‧‧ plating tank

16b‧‧‧ plating tank

18‧‧‧ plating solution supply

20‧‧‧ plating solution supply line

22‧‧‧Substrate holder

23‧‧‧Anolyte supply line

24‧‧‧ electrolyte supply line

24a‧‧‧ electrolyte supply port

26‧‧‧pure water supply pipeline

26a‧‧‧pure water supply port

28‧‧‧Draining line

30‧‧‧Anode holder

32‧‧‧Sn anode

33‧‧‧N ₂ gas supply line

33a‧‧‧Spray outlet

34‧‧‧ plating power supply

36‧‧‧ overflow trough

38‧‧‧ pump

40‧‧‧ heat exchanger

42‧‧‧Filter

44‧‧‧ flowmeter

46‧‧‧ plating liquid circulation pipeline

50‧‧‧Adjustment board

50a‧‧‧Central hole

52‧‧‧Agitator

54‧‧‧ anion exchange membrane

60‧‧‧ anion exchange membrane

62‧‧‧dialysis tank

64‧‧‧ plating solution supply tube

66‧‧‧ plating solution discharge pipe

68‧‧‧ plating solution dialysis pipeline

70‧‧‧pure water supply pipeline

72‧‧‧Pure water discharge pipeline

74‧‧‧Sn ion concentration analyzer

76‧‧‧Methanesulfonic acid concentration tester

80‧‧‧Control Department

82‧‧‧ Liquid level detection sensor

84‧‧‧ floating body

86‧‧‧ movable

100‧‧‧Auxiliary electrolytic cell

102‧‧‧cathode tank

102a‧‧‧ next door

104‧‧‧Anode chamber

106‧‧‧Cathode chamber

108‧‧‧ anion exchange membrane

110‧‧‧Anolyte supply line

112‧‧‧ electrolyte supply line

114‧‧‧Sn ion replenishment pipeline

116‧‧‧Anode holder

118‧‧‧Sn anode

120‧‧‧ pump

122‧‧‧ Catholyte supply line

124‧‧‧Draining line

126‧‧‧Cathode holder

128‧‧‧ cathode

130‧‧‧Auxiliary power supply

154‧‧‧1st holding member

154a‧‧‧through hole

156‧‧‧Chain

158‧‧‧2nd holding member

160‧‧‧ base

162‧‧‧ Seal holder

164‧‧‧Shacking the ring

164a‧‧‧ convex

164b‧‧‧Protruding

165‧‧‧ spacers

166‧‧‧Substrate side sealing member

168‧‧‧Retainer side sealing member

169a‧‧‧fasteners

169b‧‧‧fasteners

170a‧‧‧1st retaining ring

170b‧‧‧2nd retaining ring

172‧‧‧ pressed plate

174‧‧‧ positioner

180‧‧‧Support surface

182‧‧‧ Highlighting the strip

184‧‧‧ recess

186‧‧‧Electrical conductor

188‧‧‧Electrical contacts

189‧‧‧fasteners

190‧‧‧Retainer hanger

200‧‧‧anode cover

202‧‧‧ Cover member

204‧‧‧Electrical shield

204a‧‧‧ openings

206‧‧‧ board

208‧‧‧Cylinder

210‧‧‧Gas Supply Department

220‧‧‧ inner slot

230‧‧‧ anolyte circulation line

232‧‧‧ pump

234‧‧‧Methanesulfonic acid concentration tester

240‧‧‧ pump

242‧‧‧Connected pipeline

250‧‧‧ plating tank

252‧‧‧storage tank

254‧‧‧Anolyte supply line

256‧‧‧Anode liquid recovery pipeline

258a‧‧‧ pump

258b‧‧‧ pump

260a‧‧‧Switching valve

260b‧‧‧Switching valve

262‧‧‧heater

A‧‧‧Anolyte

B‧‧‧ Catholyte

E‧‧‧ anolyte

H‧‧‧ liquid level

Q‧‧‧ plating solution

W‧‧‧Substrate

Fig. 1 is a schematic view showing a Sn alloy plating apparatus according to an embodiment of the present invention.

2 is a perspective view showing an anode tank.

Fig. 3 is a cross-sectional view showing an important part of another example in which the anolyte in the anode is overflowed.

Fig. 4 is a perspective view showing an important part of another example in which the anolyte in the anode is overflowed.

Fig. 5 is a perspective view showing the outline of the substrate holder shown in Fig. 1.

Figure 6 is a plan view of the substrate holder shown in Figure 1.

Figure 7 is a right side view of the substrate holder shown in Figure 1.

Fig. 8 is an enlarged view of a portion A of Fig. 7;

Fig. 9 is an enlarged view of an important part showing a state in which plating is being performed by a Sn alloy plating apparatus.

Fig. 10 is a graph showing a comparison between the Sn ion concentration of the anolyte in the anode chamber and the actually measured Sn ion concentration by the amount of electrolysis.

Fig. 11 is a schematic view showing another plating tank.

Fig. 12 is a schematic view showing a Sn alloy plating apparatus according to another embodiment of the present invention.

Fig. 13 is a schematic view showing a Sn alloy plating apparatus according to still another embodiment of the present invention.

Fig. 14 is a schematic view showing a Sn alloy plating apparatus according to still another embodiment of the present invention.

Fig. 15 is a schematic view showing a Sn alloy plating apparatus according to still another embodiment of the present invention.

Form for implementing the invention

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following examples, the same or equivalent components are denoted by the same reference numerals, and the description thereof will be omitted.

In the following example, Ag (silver) is used as the metal of Sn (tin), and a plating film made of a Sn-Ag alloy is formed on the surface of the substrate. Further, methanesulfonic acid is used as the acid which forms a complex with the divalent Sn ion. Therefore, the Sn-Ag alloy plating solution used as the plating solution contains tin methanesulfonate as Sn ions (Sn ²⁺ ) in the plating solution, and contains silver methanesulfonate as Ag ions (Ag). ⁺ ). Silver alkane sulfonate can also be used as the Ag ion (Ag ⁺ ).

Fig. 1 is a schematic view showing a Sn alloy plating apparatus according to an embodiment of the present invention. As shown in FIG. 1, the Sn alloy plating apparatus has a plating tank 16 which divides the inside into the inside of the cathode chamber 12 and the anode tank 10 by disposing the box-shaped anode tank 10 therein. The anode chamber 14 is.

The cathode chamber 12 is connected to the plating liquid supply line 20 extending from the plating liquid supply source 18 by the overflow tank 36 described below to hold the Sn-Ag alloy plating liquid (hereinafter simply referred to as a plating liquid). The way of Q. The substrate W that serves as a cathode during plating is detachably held by the substrate holder 22 and immersed in the plating solution Q to be placed at a predetermined position inside the cathode chamber 12.

On the other hand, the anode chamber 14 is connected to the anolyte supply line 23, the electrolyte supply line 24, the pure water supply line 26, and the drain line 28, respectively, so as to hold the anolyte E therein. The Sn anode 32, which is made of Sn and held by the anode holder 30, is immersed in the anolyte E and placed at a predetermined position inside the anode chamber 14. Further, an N ₂ gas supply line 33 for supplying nitrogen gas to the anolyte E to foam the anolyte E is disposed at the bottom of the anode chamber 14.

In this example, a solution containing methanesulfonic acid and Sn ions which form a complex with a divalent Sn ion and containing no Ag ions is used as the anolyte E. One part of the methanesulfonic acid ion in the anolyte E surrounds the periphery of the Sn ion to form a complex with the divalent Sn ion, and the other part is present in the anolyte E as a free acid. Incidentally, in the present specification, the methanesulfonic acid concentration means the acid concentration as a free acid unless otherwise specified. Because the anolyte E does not contain Since Ag ions are contained, even if the Sn anode 32 is immersed in the anolyte E, no Ag reacts with the Sn anode 32 to replace the surface of the Sn anode 32. Further, an aqueous solution containing methanesulfonic acid (aqueous methanesulfonic acid) is used as the electrolytic solution supplied to the anode chamber 14 through the electrolytic solution supply line 24.

At the time of the plating treatment, the Sn anode 32 is connected to the positive electrode of the plating power source 34, and a conductive layer (not shown) such as a sheet layer formed on the surface of the substrate W is connected to the negative electrode of the plating power source 34. Thereby, a plating film made of a Sn-Ag alloy is formed on the surface of the conductive layer. The plated film is used, for example, for lead-free solder bumps.

The plating tank 16 is provided with an overflow tank 36 which is adjacent to the cathode chamber 12 and overflows the plating liquid Q at the upper end of the cathode chamber 12. The bottom of the overflow tank 36 is connected to one end of a plating liquid circulation line 46 in which a pump 38, a heat exchanger (temperature adjuster) 40, a filter 42, and a flow meter 44 are disposed, and the plating liquid circulation line 46 is The other end is connected to the bottom of the cathode chamber 12. Further, the top of the overflow tank 36 is connected to the plating liquid supply line 20 extending from the plating liquid supply source 18.

Inside the cathode chamber 12, a regulation plate 50 is disposed between the substrate holder 22 and the Sn anode 32 disposed therein to adjust the potential distribution in the cathode chamber 12. In this example, the adjustment plate 50 is made of a dielectric material of vinyl chloride, and has a central hole 50a having a size that sufficiently restricts the diffusion of an electric field. The lower end of the adjustment plate 50 is the bottom plate that reaches the cathode chamber 12.

An agitator 52 is disposed inside the cathode chamber 12, and the agitator 52 is located between the substrate holder 22 disposed in the cathode chamber 12 and the adjustment plate 50. The stirrer which extends in the vertical direction and reciprocates in parallel with the substrate W as a stirring agent for stirring the plating liquid Q between the substrate holder 22 and the adjustment plate 50. A sufficient metal ion can be supplied to the surface of the substrate W evenly by stirring the plating solution Q in the cathode chamber 12 with a stirrer (stirring) 52 during plating.

The inside of the partition wall 10a which divides the inside of the plating tank 16 into the cathode chamber 12 and the anode chamber 10 of the anode chamber 14 is provided with an anion exchange membrane 54 through which the cathode chamber 12 and the anode chamber 14 are passed through an anion exchange membrane. 54 and isolated. The anion exchange membrane 54 is, for example, AAV manufactured by AGC Engineering Co., Ltd., and an arbitrary number of anion exchange membranes 54 are placed in the partition wall 10a in accordance with the amount of penetration of water molecules containing methanesulfonic acid. The number and arrangement of the anion exchange membranes 54 can be arbitrarily adjusted in accordance with the required membrane area or the amount of penetration of water molecules to be described later. The anion exchange membrane 54 is water-tightly inserted into the partition wall 10a by an O-ring or the like so that the plating liquid Q in the cathode chamber 12 does not move to the anode chamber 14.

The partition wall 10a and the anion exchange membrane 54 are positioned between the Sn anode 32 and the substrate W. The partition wall 10a functions as a weir to block the anolyte E in the anode chamber 14 and allows the anolyte E overflowing the upper end of the partition wall 10a to flow into the cathode chamber 12. That is, in the anode chamber 14, the anode liquid E is blocked by the partition wall (overflow weir) 10a while maintaining the predetermined liquid level H (refer to FIG. 9). If the liquid level H is exceeded, the excess amount is exceeded. The anolyte E overflows the upper end of the partition wall 10a and flows into the anode chamber 14.

The plating liquid circulation line 46 is connected to the plating liquid supply pipe 64 which is provided downstream of the flow meter 44 and supplies the plating liquid Q to the dialysis tank 62 in which the anion exchange membrane 60 is housed, and is plated from the dialysis tank 62. Liquid discharge pipe 66 It is connected to the top of the overflow tank 36. The plating solution supply pipe 64 and the plating liquid discharge pipe 66 are connected to the plating liquid circulation line 46, and constitute a plating liquid dialysis line for taking out one part of the plating liquid Q from the plating liquid circulation line 46 and circulating it. 68. The dialysis tank 62 is connected to a pure water supply line 70 that supplies pure water to the inside thereof, and a pure water discharge line 72 that discharges the inside pure water to the outside.

The plating solution Q flowing in the plating solution dialysis line 68 is supplied into the dialysis tank 62, and is removed by dialysis using the anion exchange membrane 60 to remove at least a portion of the methanesulfonic acid as a free acid. Overflow slot 36. The methanesulfonic acid removed from the plating solution Q by the dialysis is diffused into the pure water supplied into the dialysis tank 62 through the pure water supply line 70, and is discharged to the outside from the pure water discharge line 72.

As the anion exchange membrane 60, for example, a DSV manufactured by AGC Engineering Co., Ltd. is used. An arbitrary number of anion exchange membranes 60 are placed in the dialysis tank 62 in accordance with the amount of penetration of the plating solution (removal amount of methanesulfonic acid).

Incidentally, although this example removes at least a portion of the methanesulfonic acid as a free acid in the plating solution Q by using the dialysis bath 62 to the diffusion dialysis method, it may be used by electrodialysis or The free acid removal tank of the ion exchange resin method removes at least a portion of the methanesulfonic acid as a free acid in the plating solution Q.

The plating liquid circulation line 46 is provided with a Sn ion concentration measuring device 74 for measuring the Sn ion concentration of the plating solution Q flowing in the plating liquid circulation line 46, and measuring the plating flowing in the plating liquid circulation line 46. The methanesulfonic acid concentration measuring device 76 of the methanesulfonic acid concentration of the dressing solution Q. In the plating solution supply source 18 and control The portion 80 inputs the output from the Sn ion concentration measuring device 74 and the methanesulfonic acid concentration measuring device 76 (i.e., the concentration measurement value).

FIG. 2 is a perspective view showing the anode tank 10. As shown in Fig. 2, a relief notch 10b that serves as an outlet for the anolyte E that overflows the anode chamber 14 is provided at a position in the upper direction of the upper end of the partition wall 10a functioning as a weir. The liquid level H of the anolyte E held in the anode chamber 14 is determined by the position of the lower end of the overflow notch 10b (refer to Fig. 9).

The electrolyte supply line 24 extends downward along the side of the anode tank 10. An electrolyte supply port 24a for supplying an electrolytic solution (aqueous methanesulfonic acid solution) to the anode chamber 14 is formed at the lower end of the electrolyte supply line 24. The electrolyte supply port 24a opens to the bottom of the anode tank 10 and opens in the horizontal direction. The pure water supply line 26 also extends downward along the side of the anode tank 10. A pure water supply port 26a for supplying pure water to the anode chamber 14 is formed at the lower end of the pure water supply line 26. The pure water supply port 26a opens to the bottom of the anode tank 10 and opens in the horizontal direction. Incidentally, the electrolyte supply port 24a and the pure water supply port 26a may be opened downward. Then, the electrolyte supply port 24a, the pure water supply port 26a, and the overflow notch 10b of the partition wall 10a are arranged diagonally to each other on the horizontal projection surface of the anode cell 10. Thereby, pure water is supplied to the anode chamber 14 through the pure water supply line 26, or when the electrolyte is supplied to the anode chamber 14 through the electrolyte supply line 24, the anolyte E containing the Sn ions is supplied with the pure water. After the electrolyte is sufficiently stirred, it overflows into the overflow notch 10b and is supplied to the cathode chamber 12.

The N ₂ gas supply line 33 extends downward along the side of the anode tank 10 to reach the bottom of the anode tank 10, and extends almost the entire length of the anode tank 10 in the longitudinal direction. Then, the anode liquid E is foamed by discharging nitrogen gas from the discharge port 33a provided in the N ₂ gas supply line 33. The anolyte E in the anode chamber 14 is sufficiently stirred with nitrogen. Thereby, in the anolyte E in the anode chamber 14, the Sn ions or the methanesulfonic acid are promoted to be evenly distributed, and the oxidation of the Sn ions in the anolyte E is prevented. Therefore, the foaming of the anolyte E caused by nitrogen gas is preferably carried out from the bottom of the anode chamber 14.

Incidentally, it is preferable to stop the supply of nitrogen gas before supplying pure water or an electrolyte to the anode chamber 14, without performing foaming of the anolyte E caused by nitrogen in the supply of pure water or electrolyte. Thereby, the anolyte E which is sufficiently diffused by the Sn ions can be prevented from being excessively diluted by the supplied pure water or the electrolytic solution, and supplied to the cathode chamber 12.

A liquid level detecting sensor 82 is disposed above the anode chamber 14, and the liquid level detecting sensor 82 detects the cause of the anolyte E in the anode chamber 14 by detecting the liquid level of the anolyte E in the anode chamber 14. The amount of liquid caused by evaporation is reduced. Thereby, when the amount of liquid caused by evaporation of the anolyte E is detected, pure water is supplied from the pure water supply line 26 to the anolyte E in the anode chamber 14, and the anolyte E in the anode chamber 14 is made. The liquid level of the liquid is always fixed. Further, the supply amount of Sn ions to the cathode chamber 12 can be managed by the supply amount of pure water or electrolyte to the anode chamber 14.

Incidentally, the anolyte E in the anode chamber 14 may be overflowed to the cathode chamber 12 by mechanical means. For example, as shown in FIG. 3, the anolyte E in which the floating body 84 floats in the anode chamber 14 and the anolyte E of the volume of the floating body 84 are made by sinking the floating body 84 into the anolyte E. It overflows to the cathode chamber 12. In this case, since the water is not introduced with the supply of pure water or electrolyte, Therefore, the anolyte E is not diluted, and the anolyte E is supplied to the cathode chamber 12.

Further, as shown in FIG. 4, a movable dam 86 that can be moved up and down can be provided inside the rectangular cutout 10c provided at the upper end of the partition wall 10a functioning as a weir. In the example shown in Fig. 4, the movable cymbal 86 is lowered to supply the anolyte E of the height to the cathode chamber 12. Also in this case, the anolyte E can be prevented from being diluted and supplied to the cathode chamber 12.

When the Sn ions of the entire system are insufficient, it is necessary to supply the plating solution Q with Sn ions. Regarding the method of supplying the Sn ions, a method of adding a high-concentration Sn replenishing liquid to the plating solution Q can be employed, but a high-concentration Sn replenishing liquid is generally expensive and high in cost. Therefore, in this example, in addition to the plating tank 16, an auxiliary electrolytic cell 100 for supplying Sn ions is provided.

A box-shaped cathode tank 102 is disposed inside the auxiliary electrolytic cell 100. The inside of the auxiliary electrolytic cell 100 is a cathode chamber (auxiliary cathode chamber) 106 which is divided into an anode chamber (auxiliary anode chamber) 104 and an anode chamber 102. Further, an anion exchange membrane 108 is placed inside the partition wall 102a on the anode chamber side of the cathode chamber 102 in which the anode chamber 104 and the cathode chamber 106 are divided. The auxiliary electrolytic cell 100 is isolated into an anode chamber 104 and a cathode chamber 106 by an anion exchange membrane 108.

The anode chamber 104 is connected to the anolyte supply line 110 and the electrolyte supply line 112, and the anolyte supply line 110 supplies the anolyte A containing Sn ions and methanesulfonic acid and containing no Ag ions, and the electrolyte supply line 112 is supplied with An electrolyte solution of an aqueous solution of sulfonic acid (aqueous methanesulfonic acid). Inside the anode chamber 104, the Sn anode (auxiliary Sn anode) 118 held by the anode holder 116 is immersed in the anolyte A and disposed. Furthermore, the anode chamber 104 is connected One end of the Sn ion supply line 114, and the other end of the Sn ion supply line 114 is connected to the upper end of the overflow tank 36 of the plating tank 16. A pump 120 is provided in the Sn ion supply line 114.

The cathode chamber 106 is connected to the catholyte supply line 122 and the drain line 124. The catholyte supply line 122 supplies the catholyte B formed by an aqueous solution containing methanesulfonic acid (an aqueous methanesulfonic acid solution), and the drain line 124 is a catholyte. B is discharged; inside the cathode chamber 106, a cathode (auxiliary cathode) 128 made of, for example, SUS held by the cathode holder 126 is immersed in the catholyte B. The partition wall 102a and the anion exchange membrane 108 described above are located between the Sn anode 118 and the cathode 128.

The auxiliary electrolytic cell 100 first supplies the anolyte A containing a high concentration (for example, 220 g/L to 350 g/L) of Sn ions and methanesulfonic acid and no Ag ions to the anode chamber 104 through the anolyte supply line 110. The Sn anode 118 is immersed in the anolyte A. Further, the catholyte B made of the methanesulfonic acid aqueous solution is supplied into the cathode chamber 106 through the catholyte supply line 122, and the cathode 128 is immersed in the catholyte B.

In this state, the positive electrode of the auxiliary power source 130 is connected to the Sn anode 118 and the negative electrode is connected to the cathode 128 to start electrolysis. After the start of electrolysis as described above, the Sn ions are dissolved from the Sn anode 118 and the Sn ion concentration of the anolyte A is increased. Since the anode chamber 104 and the cathode chamber 106 are isolated by the anion exchange membrane 108, the Sn ions do not move into the cathode chamber 106, and the cathode 128 is not plated. In addition, since the anolyte A does not contain Ag ions, Ag does not replace the surface of the Sn anode 118. The Sn ions contained in the anolyte A are supplied from the anolyte supply line 110 before the start of the operation, and are started from the Sn anode 118 after the start of the operation. Dissolved and supplied.

Then, the anolyte A reaching a predetermined concentration is supplied from the pump 120 and supplied to the overflow tank 36 of the plating tank 16 through the Sn ion supply line 114. Since the supply of the anolyte A in the anode chamber 104 is reduced by the supply of the overflow tank 36 to the anolyte A, the electrolyte which compensates for the amount is supplied from the electrolyte supply line 112 to the anode chamber 104. Since the concentration of Sn ions in the anolyte A is high, the amount of liquid discharged from the entire system can be suppressed, which is advantageous.

The mesylate ions contained in the catholyte B of the cathode chamber 106 are moved into the anode chamber 104 through the anion exchange membrane 108. Therefore, the conductivity of the catholyte B of the cathode chamber 106 is lowered with time. Then, the catholyte B is supplied to the cathode chamber 106 through the catholyte supply line 122 connected to the cathode chamber 106. The catholyte B in the cathode chamber 106 is discharged to the outside through the drain line 124 so that the supplied catholyte B does not overflow.

As shown in FIG. 5 to FIG. 8 , the substrate holder 22 has a first holding member 154 having a rectangular flat shape, and a second holding member 158 that is opened and closed by the hinge 156 and is attached to the first holding member 154 . In another configuration example, the second holding member 158 may be disposed at a position facing the first holding member 154, and the second holding member 158 may be advanced to the first holding member 154 or may be separated from the first holding member 154. The second holding member 158 is opened and closed.

The first holding member 154 is made of, for example, vinyl chloride. The second holding member 158 has a base portion 160 and an annular seal holder 162. The seal holder 162 is, for example, made of vinyl chloride and has a good sliding property with the press ring 164 described below. An annular substrate-side sealing member 166 that protrudes inwardly is attached to the upper portion of the seal holder 162 (refer to FIGS. 7 and 8). The substrate side sealing member 166 is at When the substrate holder 22 holds the substrate W, the outer peripheral portion of the surface of the substrate W is pressure-bonded to seal the gap between the second holding member 158 and the substrate W. An annular holder-side sealing member 168 is attached to a surface of the seal holder 162 that faces the first holding member 154 (see FIGS. 7 and 8). The holder-side sealing member 168 presses the first holding member 154 while the substrate holder 22 holds the substrate W, and seals the gap between the first holding member 154 and the second holding member 158. The holder side sealing member 168 is located on the outer side of the substrate side sealing member 166.

As shown in FIG. 8, the substrate-side sealing member 166 is sandwiched between the seal holder 162 and the first fixed ring 170a, and is attached to the seal holder 162. The first fixing ring 170a is attached to the seal holder 162 via a fastener 169a such as a screw. The holder side sealing member 168 is sandwiched between the seal holder 162 and the second fixed ring 170b and attached to the seal holder 162. The second fixing ring 170b is attached to the seal holder 162 via a fastener 169b such as a screw.

A stepped portion is provided on the outer peripheral portion of the seal holder 162, and the press ring 164 is rotatably attached to the stepped portion through the spacer 165. The pressing ring 164 is attached without being detachable by a pressing plate 172 (refer to FIG. 6) which is attached to the side of the seal holder 162 so as to protrude outward. The pressure ring 164 is made of a material having good corrosion resistance to an acid or a base and having sufficient rigidity. For example, the crush ring 164 is composed of titanium. The spacer 165 is constructed of a material having a low coefficient of friction, such as PTFE, so that the pressing ring 164 can smoothly rotate.

On the outer side of the pressing ring 164, a plurality of positioners 174 are disposed at equal intervals along the circumferential direction of the pressing ring 164. The positioners 174 are fixed to the first holding member 154. Each of the positioners 174 has an inverted L shape, and the inverted L-shaped shape has a protruding portion that protrudes inward. Pressing the ring 164 The outer peripheral surface is provided with a plurality of protrusions 164b that protrude outward. The projections 164b are disposed at positions corresponding to the positions of the positioners 174. The lower surface of the inner projection of the retainer 174 and the upper surface of the projection 164b of the retaining ring 164 are tapered surfaces that are inclined in opposite directions along the direction of rotation of the retaining ring 164. The plurality of portions (for example, three portions) of the pressing ring 164 in the circumferential direction are provided with convex portions 164a that protrude upward. Thereby, the pressing portion 164 can be rotated by pushing the rotation pin (not shown) to push the convex portion 164a from the side.

In a state where the second holding member 158 is opened, the substrate W is inserted into the central portion of the first holding member 154, and the second holding member 158 is closed by the hinge 156. The pressing ring 164 is rotated clockwise to slide the projection 164b of the pressing ring 164 into the inner portion of the inner portion of the retainer 174, whereby the perforating is provided on the tapered surface of the retaining ring 164 and the retainer 174, respectively. The first holding member 154 and the second holding member 158 are locked to each other, and the second holding member 158 is locked. Further, the pressing ring 164 is rotated counterclockwise to remove the projection 164b that presses the ring 164 from the retainer 174, whereby the locking of the second holding member 158 is released.

When the second holding member 158 is locked, the lower protruding portion of the substrate-side sealing member 166 is pressed against the outer peripheral portion of the surface of the substrate W. The substrate-side sealing member 166 is pressed against the substrate W on average, thereby sealing the gap between the outer peripheral portion of the surface of the substrate W and the second holding member 158. Similarly, when the second holding member 158 is locked, the lower protruding portion of the holder-side sealing member 168 is pressed against the surface of the first holding member 154. The holder-side sealing member 168 is pressed against the first holding member 154 on average, thereby sealing the gap between the first holding member 154 and the second holding member 158.

A pair of slightly T-shaped seals are provided at the end of the first holding member 154. Holder hanger 190. An annular protruding strip portion 182 having almost the same size as the size of the substrate W is formed on the upper surface of the first holding member 154. The protruding strip portion 182 has an annular support surface 180 that abuts against the peripheral edge portion of the substrate W and supports the substrate W. A recess 184 is provided at a predetermined position along the circumferential direction of the protruding strip portion 182.

As shown in FIG. 6, a plurality of (12 shown) conductors (electrical contacts) 186 are disposed in the recesses 184, respectively. The conductors 186 are connected to a plurality of wires extending from connection terminals (not shown) provided on the holder hanger 190. When the substrate W is placed on the support surface 180 of the first holding member 154, the end portion of the conductor 186 is in elastic contact with the lower portion of the electrical contact 188 shown in FIG.

The electrical contact 188 electrically connected to the conductor 186 is fixed to the seal holder 162 of the second holding member 158 by a fastener 189 such as a screw. The electrical contact 188 is formed in the shape of a leaf spring. The electric contact 188 has a contact portion that protrudes inward in a leaf spring shape outside the substrate-side sealing member 166. The electric contact 188 has a spring property derived from the elastic force at the contact portion, and is easily bent. When the substrate W is held by the first holding member 154 and the second holding member 158, the contact portion of the electric contact 188 elastically contacts the outer peripheral surface of the substrate W supported on the support surface 180 of the first holding member 154.

The opening and closing of the second holding member 158 is performed by the weight of the cylinder (not shown) and the second holding member 158 itself. In other words, the first holding member 154 is provided with a through hole 154a, and the sealing holder 162 of the second holding member 158 is pushed upward by the piston rod of the cylinder (not shown) through the through hole 154a. The second holding member 158 is opened, and the second holding is maintained by contracting the piston rod Member 158 is closed by its own weight.

Next, the operation of the plating apparatus of this embodiment will be described. The pump 38 is driven to circulate and agitate the plating solution Q in the cathode chamber 12 through the plating liquid circulation line 46. In this state, the substrate W held by the substrate holder 22 is immersed in the plating solution Q in the cathode chamber 12 and placed at a predetermined position. On the other hand, the inside of the anode chamber 14 is filled with the initial anolyte E, and the Sn anode 32 is immersed in the anolyte E.

In this state, the Sn anode 32 is connected to the positive electrode of the plating power source 34, and a conductive layer such as a sheet layer formed on the surface of the substrate W is connected to the negative electrode of the plating power source 34, and plating treatment is started on the surface of the substrate W. At the time of the plating, the agitator (stirring) 52 is reciprocated parallel to the substrate W as needed to agitate the plating solution Q in the cathode chamber 12. At the same time, the anolyte E in the anode chamber 14 is bubbled by nitrogen gas through the N ₂ gas supply line 33.

When the plating treatment is performed in this manner, as shown in FIG. 9, Sn ions are eluted from the Sn anode 32 into the anode liquid E in the anode chamber 14. Since the elution of Sn ions occurs every time the plating treatment is performed, the Sn ion concentration of the anolyte E in the anode chamber 14 gradually increases. Further, when the electrolytic solution is supplied into the anode chamber 14 from the electrolytic solution supply line 24 or the pure water is supplied from the pure water supply line 26 into the anode chamber 14, the anolyte E in the anode chamber 14 is increased. If the liquid level of the anolyte E in the anode chamber 14 rises above the predetermined liquid level H by ΔH, the anolyte E overflows with the rise amount ΔH of the liquid level in the anode chamber 14 The overflow of the partition wall 10a flows into the cathode chamber 12 by the notch 10b (refer to Fig. 2). Thereby, a part of the Sn ions in the anode chamber 14 is supplied into the cathode chamber 12, and the Sn ions consumed by the plating to the substrate W can be replenished. When the anolyte E is supplied to the plating solution Q as described above, since the amount of the plating solution Q is increased, the plating liquid Q equal to the amount of the anolyte E supplied into the cathode chamber 12 is discharged in advance.

Incidentally, if an electric field is formed between the Sn anode 32 and the substrate W as the cathode, the methanesulfonic acid in the cathode chamber 12 passes through the anion exchange membrane 54 together with the water molecules and flows into the anode chamber 14. Thereby, the anolyte E in the anode chamber 14 is also increased, and the anolyte E exceeding the predetermined liquid level H is overflowed into the partition chamber 10a and flows into the cathode chamber 12. Thus, the Sn ions in the anode chamber 14 can be supplied to the cathode chamber 12.

Here, the inventors have confirmed by experiments that in order to stabilize the Sn ions dissolved from the Sn anode, the concentration of methanesulfonic acid as a free acid in the anode chamber 14 is important. In the experiment, the anolyte made of the methanesulfonic acid aqueous solution was allowed to enter the anode chamber so that the concentration of methanesulfonic acid became 100 g/L, and electrolysis was started. In this case, if electrolysis is continued, the anolyte in the anode chamber is turbid. This means that the Sn ions are not stably present as divalent ions in the anolyte, and are precipitated as metal Sn or tetravalent Sn ions.

On the other hand, when electrolysis was started at a concentration of 140 g/L of methanesulfonic acid, even if electrolysis was continued, the anolyte in the anode chamber was not turbid, and the concentration of Sn ions in the anolyte was dissolved at a price of Sn. The calculated values below are consistent. That is, this means that since the methanesulfonic acid ion is sufficiently present, the divalent Sn ion is surrounded by the methanesulfonic acid ion to form a complex and stably exist. Therefore, it is known that the methanesulfonic acid concentration of the anolyte must be a concentration at which the Sn ions are suitably present as divalent ions.

As described above, pure water can be supplied from the pure water supply line 26 to In the anode chamber 14, the anolyte E in the anode chamber 14 overflows into the cathode chamber 12, and Sn ions are supplied to the cathode chamber 12. In this example, an electrolyte supply line 24 for supplying an electrolytic solution (aqueous methanesulfonic acid solution) to the anode chamber 14 is provided. This is because of the following reasons.

When pure water is supplied from the pure water supply line 26 to the anode chamber 14 to overflow the anolyte E in the anode chamber 14, the methanesulfonic acid in the anode chamber 14 flows into the cathode chamber 12, and the anolyte in the anode chamber 14 The methanesulfonic acid concentration of E is lowered. Further, methanesulfonic acid in the cathode chamber 12 is moved from the cathode chamber 12 to the anode chamber 14 through the anion exchange membrane 54 by forming an electric field between the Sn anode 32 and the substrate W as a cathode. Although the conditions are considered, the mobility of the methanesulfonic acid is not 100%, and it is 50% to 90% because of the loss. In this case, in the anode chamber 14, the ratio of the methanesulfonic acid moving through the anion exchange membrane 54 to the anode chamber 14 to the molar concentration of the Sn ions dissolved from the Sn anode 32 is deviated by 1:2. As a result, the methanesulfonic acid concentration in the anolyte E in the anode chamber 14 is lowered. Thus, as described above, there is a possibility that the Sn ions in the anode chamber 14 are destabilized.

Therefore, it is necessary to supply the electrolyte containing methanesulfonic acid from the electrolyte supply line 24 to the anode chamber 14 so that the methanesulfonic acid concentration of the anolyte E in the anode chamber 14 is not lower than the allowable value.

In order to operate the plating apparatus efficiently, it is preferable that the anolyte E is supplied to the cathode chamber 12 by overflow in a state where the Sn ion concentration of the anolyte E in the anode chamber 14 is as high as possible. This is because if the anolyte E is supplied to the cathode chamber 12 in a state where the Sn ion concentration is low, the supply of the anolyte E from the anode chamber 14 required to supply a certain amount of Sn ions to the cathode chamber 12 is required. Since the amount (the amount of overflow) is increased, the amount of the plating solution Q which becomes the waste liquid from the circulation system including the cathode chamber 12 is increased, which is uneconomical.

Specifically, the Sn ion concentration in the anolyte E of the anode chamber 14 is generally managed in the range of 80 g/L to 500 g/L, and is preferably managed in the range of 200 g/L to 400 g/L, and is preferably managed at 220 g/ Range of L~350g/L. The Sn ion concentration in the anolyte E is determined by the Sn ion concentration in the anolyte E newly charged in the anode chamber 14 before the start of the operation and the Sn ion concentration converted from the amount of electrolysis in the Sn anode 32 after the start of the operation. Out. In order to manage the Sn ion concentration of the entire plating bath, the Sn ion concentration of the anolyte E is very important.

The Sn ion concentration in the Sn-Ag plating solution Q is usually 50 g/L to 80 g/L. In the case where the amount of reduction of the Sn ion concentration in the cathode chamber 12 is supplemented by the anolyte E containing the Sn ions in the anode chamber 14, the anode of the cathode chamber 12 is supplied with the higher the Sn ion concentration of the anode liquid E of the anode chamber 14 The volume of liquid E can be less. Usually, the amount of the plating solution Q of the cathode chamber 12 is reduced by evaporation or the like. If the anolyte E of the anode chamber 14 that has been replenished is equal to or greater than the decrement component, the amount of excess liquid above the decrement component may eventually need to be a waste liquid from the plating solution Q of the cathode chamber 12. However, the concentration of Sn ions in the anolyte E does not increase above the saturation concentration of tin methanesulfonate. Further, in order to stably store the Sn ions, it is necessary to make the concentration of the Sn ions of the anolyte E below the saturation concentration.

The pure water supply line 26 is not only used to supplement the moisture evaporation component in the anode chamber 14, but the anode liquid in the anode chamber 14 can be made in the case where the concentration of the sulfonic acid of the anolyte E in the anode chamber 14 is sufficiently high. The E overflows to supply the Sn ions into the cathode chamber 12. Further, the pure water supply line 26 can adjust the concentration of the components in the anode chamber 14 by supplying pure water into the anode chamber 14 use.

Next, an operation example of the Sn alloy plating apparatus shown in Fig. 1 will be described.

Before the start of the operation of the Sn alloy plating apparatus, first, an anolyte E containing a high concentration of Sn ions (for example, 220 g/L to 350 g/L) and methanesulfonic acid is supplied to the anode chamber 14 through the anolyte supply line 23. The anode chamber 14 is filled with the anolyte E. This is because, as described above, it is advantageous to reduce the amount of the plating solution Q to the amount of the waste liquid by supplying the anode liquid E of the anode chamber 14 to the cathode chamber 12 in a state where the Sn ion concentration is high, and it is advantageous; When the operation is started in a state where the Sn ion concentration of the liquid E is low, it is necessary to wait for the concentration of the Sn ion of the anolyte E to become a high concentration, which is disadvantageous.

As described above, the pump 38 is driven, and the substrate W held by the substrate holder 22 is immersed in the cathode chamber 12 while the plating solution Q in the cathode chamber 12 is circulated and stirred by the plating liquid circulation line 46. The plating solution Q is disposed at a predetermined position.

In this state, the Sn anode 32 is connected to the positive electrode of the plating power source 34, and a conductive layer such as a sheet layer formed on the surface of the substrate W is connected to the negative electrode of the plating power source 34, and plating treatment is started on the surface of the substrate W. At the time of this plating, the stirrer (stirring) 52 is reciprocated parallel to the substrate W as needed, and the plating liquid Q in the cathode chamber 12 is stirred. At the same time, nitrogen gas is supplied to the anode liquid E in the anode chamber 14 through the N ₂ gas supply line 33 to cause the anode liquid E to foam.

While the plating is performed in this manner, the Sn ion concentration of the plating solution Q is measured by the Sn ion concentration measuring device 74, and the measurement result is sent to the control unit 80 by a signal (measured value). In this example, the control unit 80 is the estimated anode chamber 14 The methanesulfonic acid concentration of the anolyte E is determined based on the estimated value, and one or a combination of the electrolyte supplied from the electrolyte supply line 24 to the anode chamber 14 and the pure water supplied from the pure water supply line 26. That is, the electrolyte containing methanesulfonic acid is directed from the electrolyte supply line 24 toward the anode chamber 14 in such a manner that the concentration of the amic acid E as the free acid methanesulfonic acid is not lower than the lower limit value. supply. When the concentration of methanesulfonic acid in the anode chamber 14 is sufficiently high, it is necessary to supply pure water to the anode chamber 14 from the pure water supply line 26 when the Sn ions are supplied to the cathode chamber 12. The anolyte E of the anode chamber 14 is a plating solution Q that overflows to the cathode chamber 12 to supply Sn ions to the cathode chamber 12.

The concentration of methanesulfonic acid as the free acid in the anolyte E in the anode chamber 14 is controlled to be 30 g/L or more, whereby a high concentration of Sn ions of, for example, 220 g/L to 350 g/L can be stably used as a divalent ion. presence. When the concentration of methanesulfonic acid in the anolyte E is high, the methanesulfonic acid concentration of the plating solution Q in the cathode chamber 12 is also increased by the supply of the anolyte E. As will be described later, the uniformity of the film thickness of the plating is deteriorated. Therefore, the methanesulfonic acid concentration of the plating solution Q is predetermined to be higher than the demand in consideration of the actual operation state of the apparatus.

The concentration of methanesulfonic acid as a free acid in the plating solution Q in the cathode chamber 12 is varied by the amount of electrolysis and current efficiency of the Sn anode 32, the supply amount of the overflow of the anolyte E, and the circulation of the plating solution. The amount of drain out of line 46 and the rate of methanesulfonic acid penetration of anion exchange membrane 54. When the methanesulfonic acid concentration of the plating solution Q in the cathode chamber 12 exceeds about 250 g/L, the film thickness uniformity of the substrate plating tends to be deteriorated. Then, when the methanesulfonic acid concentration measuring device 76 detects that the methanesulfonic acid concentration of the plating solution Q in the cathode chamber 12 exceeds the upper limit value, the plating solution Q flows through and removes the methanesulfonic acid from the plating solution Q. Dialysis tank 62 The solution of the methanesulfonic acid-removed plating solution Q is returned to the overflow tank 36 in the liquid dialysis line 68. Thereby, the methanesulfonic acid concentration of the plating solution Q used for plating can be adjusted to, for example, a preferred range of 60 to 250 g/L, and more preferably 90 to 150 g/L.

The concentration of methanesulfonic acid as a free acid in the anolyte E during operation of the Sn alloy plating apparatus may be managed based on the estimated value of the methanesulfonic acid concentration of the anolyte E in the anode chamber 14. The estimated value of the methanesulfonic acid concentration is the methanesulfonic acid concentration of the initial anolyte E, the electrolysis amount and current efficiency at the Sn anode 32, the supply amount of the electrolyte from the electrolyte supply line 24, and the supply line from the pure water. The supply amount of 26 pure water and the transmittance of methanesulfonic acid which passes through the anion exchange membrane 54 and moved from the cathode chamber 12 to the anode chamber 14 are theoretically or experimentally determined. The concentration of Sn ions and methanesulfonic acid in the anode chamber 14 can be estimated from the Sn ion dissolution amount curve of the electrolysis amount accompanying the plating treatment and the anion exchange membrane permeability of the acid.

As described above, before the start of the operation of the Sn alloy plating apparatus, first, the anode liquid E containing a high concentration of Sn ions (for example, 220 g/L to 350 g/L) and methanesulfonic acid is held in the anode chamber 14. Then, in the operation of the Sn alloy plating apparatus, when the Sn ion concentration of the anolyte E in the anode chamber 14 estimated by the amount of electrolysis of the Sn anode, the electrolysis efficiency, or the like reaches a predetermined threshold (for example, 300 g/L), electrolysis is performed. The liquid supply line 24 supplies the electrolytic solution to the anode chamber 14 and overflows the anolyte E to supply the Sn ions to the cathode chamber 12.

Although the supply of methanesulfonic acid causes the Sn ion concentration of the anolyte E in the anode chamber 14 to become low, after that, the Sn ion concentration becomes high again after the plating treatment is continued, and then reaches the threshold. In the meantime, the Sn ion of the plating solution Q is due to It is consumed for the plating of the substrate W. If the substrate W and the Sn anode 32 have the same electrolysis efficiency and no Sn ions are discharged outside the system, the Sn ions are eluted from the Sn anode 32 in the same amount as the Sn ions consumed in the plating of the substrate W. Therefore, the amount of Sn ions in the entire system is constant. However, if the Sn ion concentration of the anolyte E of the anode chamber 14 becomes high, the electrolysis efficiency is lowered. Therefore, the amount of Sn ions supplied by the dissolution of the Sn anode 32 becomes smaller than the amount of Sn ions consumed in the plating, and the Sn ions of the entire system are gradually insufficient.

Fig. 10 is a graph showing the comparison of the Sn ion concentration of the anolyte in the theoretical anode chamber 14 converted from the amount of electrolysis with the actually measured Sn ion concentration. As can be seen from Fig. 10, the electrolysis efficiency is almost 100% until the Sn ion concentration of the anolyte E in the anode chamber 14 is about 130 g/L, and if the Sn ion concentration exceeds about 150 g/L, the electrolysis efficiency is gradually lowered. The Sn ion concentration was 300 g/L, and the electrolysis efficiency was about 80%. That is, if the Sn ion concentration of the anolyte E is to be managed at a high concentration of, for example, 220 g/L to 350 g/L, the system as a whole may have 10% to 20% of Sn ions insufficient. In addition, when the anode liquid E of the anode chamber 14 is introduced into the cathode chamber 12 by overflow, the plating solution Q containing the Sn ions is discharged from the cathode chamber 12 or the overflow tank 36 in advance, so that the entire system is Sn ions. The amount is gradually insufficient.

Therefore, in this example, the auxiliary electrolytic cell 100 is provided in order to supplement the insufficient Sn ions of the entire system. Simultaneously or appropriately with the start of operation of the Sn alloy plating apparatus, the electrolysis of the auxiliary electrolytic cell 100 is started. The pump 120 is driven based on the Sn ion concentration measured by the Sn ion concentration measuring device 74, and the anolyte A in the anode chamber 104 having a high Sn ion concentration is supplied to the overflow tank 36 of the plating tank 16. Thereby, it can be supplemented by the Sn ion supply from the auxiliary electrolytic cell 100. The difference between the electrolysis efficiency of the plating of the substrate W and the electrolysis efficiency of the Sn anode 32 in the anode chamber 14 is insufficient, and the Sn ions are insufficient due to the liquid discharge from the plating tank 16.

When the Sn alloy plating apparatus is operated for a long period of time, the concentration of Sn ions and methanesulfonic acid in the anolyte E in the anode chamber 14 may deviate from the predetermined concentration. In this case, the concentration of Sn ions and methanesulfonic acid in the plating solution Q is measured by the Sn ion concentration measuring device 74 and the methanesulfonic acid concentration measuring device 76, and the change is recorded, and if the concentration becomes more than the concentration assumed by the operating conditions, The tendency to be higher or lower, in the case of Sn ions, is to change the dissolution efficiency used for the concentration prediction, and in the case of methanesulfonic acid, the transmittance of the film is changed, and the concentration management of Sn ions and methanesulfonic acid is continued.

Incidentally, the supply of the anolyte E containing the high-concentration Sn ions in the anode chamber 14 to the cathode chamber 12 or the overflow tank 36 is performed by means of piping for overflowing by means of a pump. Better. The reason is as follows.

When the anolyte containing a high concentration of Sn ions is retained in the thin tube for a long time, even if the wall of the tube is an insulating material, metal adhesion (abnormal precipitation) occurs on the surface. Then, once the metal adhesion starts, there is a tendency for the metal to grow in succession on the surface. In addition, if the liquid is continuously supplied from the anode chamber to the cathode chamber in order to keep the anolyte in the tube always flowing, the total amount of liquid in the cathode chamber is increased, and it is necessary to always make the plating liquid Q having the same amount as the liquid to be supplied. Waste liquid.

On the other hand, when the supply of the anolyte is performed by overflow, the risk of metal adhesion is small. Due to the anolyte E in the anode chamber 14 It is always stirred by the bubbling of nitrogen gas, so that metal adhesion on the inner wall surface of the anode chamber 14 can be avoided. In addition, in the case where the methanesulfonic acid accompanying electrolysis overflows with the movement of the water molecules accompanying it, since the amount of overflow at that time is the volume of water passing through the anion exchange membrane and the methanesulfonic acid itself, in the cathode chamber 12 In the middle, the increase or decrease is equal to zero, because the overall capacity of the plating solution does not change, so there is no need to drain.

Fig. 11 is a view showing the outline of another plating tank 16a. An anode holder 30 that holds the disk-shaped Sn anode 32 is housed inside the anode chamber 14 of the plating tank 16a. The annular anode cover 200, which is limited in the field in which the Sn anode 32 is in contact with the anolyte E, is attached to the front surface of the anode holder 30 in close contact with the outer peripheral portion of the Sn anode 32. An opening 10d is provided in the partition wall 10a on the cathode chamber side of the anode tank 10, and an anion exchange membrane 54 is attached along the edge of the opening 10d. The anion exchange membrane 54 is interposed between the cover member 202 and the partition wall 10a which are limited to the side where the anion exchange membrane 54 is in contact with the plating solution Q. As described above, by sealing the gap by sandwiching the anion exchange film 54 between the partition wall 10a and the cover member 202, leakage between the cathode chamber 12 and the anode chamber 14 can be prevented.

The anion exchange membrane 54 and the opening 10d are, for example, quadrangular, and the cover member 202 is formed of a ring having a substantially square shape. The opening size of the opening portion 10d and the cover member 202 is preferably the same as or larger than the inner diameter of the anode cover 200. In order to suppress the overall resistance between the anode and the cathode, the area of the anion exchange membrane 54 which is in contact with the anolyte E or the plating solution Q is preferably larger than the area of the Sn anode 32 which is in contact with the anolyte E.

Furthermore, an electric field shielding plate 204 is disposed on the front surface of the cover member 202, The electric field shielding plate 204 is a circular opening portion 204a having a shape similar to that of the cover member 202 and having a similar shape to the substrate W. The diameter of the opening portion 204a of the electric field shielding plate 204 is set to be smaller than the opening size of the cover member 202. By providing the electric field shielding plate 204 at a position in the vicinity of the Sn anode 32 in the cathode chamber 12, even when the thickness of the sheet formed on the substrate is reduced and the film thickness at the outer periphery of the substrate is increased, the film can be made. Thick distribution average. In order to control the film thickness distribution, the electric field shielding plate 204 preferably has a mechanism for changing the opening area. The diameter of the opening portion 204a of the electric field shielding plate 204 is set to be equal to or smaller than the diameter of the central hole 50a of the adjustment plate 50 positioned between the substrate W and the Sn anode 32. In this example, the object in which the cylindrical body 208 is attached to the plate body 206 is used as the adjustment plate 50.

When the anolyte E in the anode chamber 14 overflows and is supplied to the cathode chamber 12, excess water is supplied in addition to the Sn ions, and the amount of the plating solution Q in the cathode chamber 12 and the overflow tank 36 increases. When the amount of the plating solution Q exceeds a predetermined amount, the liquid must be drained and the cost is increased. In order to avoid this, in this example, a gas supply unit 210 that promotes evaporation of moisture is provided on the upper portion of the plating tank 16a. With the gas supply unit 210, the amount of evaporation of moisture from the cathode chamber 12 can be made equal to the amount of the anolyte E supplied from the anode chamber 14, and the concentration of the plating solution Q of the cathode chamber 12 can be stably maintained. Reduce or decrease the amount of liquid discharged.

Further, in order to further reduce the amount of liquid discharged, a dewatering device capable of removing water may be provided in the plating liquid circulation line 46, and the plating solution Q may be passed through the dewatering device.

Fig. 12 is a schematic view showing a Sn alloy plating apparatus according to another embodiment of the present invention. The difference between this example and the example shown in Figure 1 is: overflow slot A plating groove 16b is formed around the inner groove 220 integral with the anode groove 10, and the partition wall 10e adjacent to the overflow groove 36 of the anode groove 10 functions as a weir to block the anolyte in the anode chamber 14. E, and the anolyte E overflowing the upper end of the partition wall 10e flows into the overflow tank 36. That is, in the anode chamber 14, the anode liquid E is blocked by the partition wall (overflow weir) 10e while maintaining the predetermined liquid level H (refer to FIG. 9). If the liquid level H is exceeded, the excess amount is exceeded. The anolyte E overflows the upper end of the partition wall 10e and flows into the overflow groove 36 around the plating tank 16b. The Sn ions supplied to the overflow tank 36 are supplied to the cathode chamber 12 via the plating liquid circulation line 46.

Fig. 13 is a schematic view showing a Sn alloy plating apparatus according to another embodiment of the present invention. This example differs from the example shown in FIG. 1 in that an anolyte circulation line 230 for withdrawing a portion of the anolyte in the anode chamber 14 from the bottom of the anode tank 10 and returning to the upper portion of the anode tank 10 is provided. The anolyte circulation line 230 is provided with a pump 232 and a methanesulfonic acid concentration measuring device 234.

According to this example, the pump 232 can be driven to circulate the anolyte E in the anode chamber 14 through the anolyte circulation line 230, and the methanesulfonic acid of the anolyte E can be measured frequently or periodically by the methanesulfonic acid concentration measuring device 234. Acid concentration.

Fig. 14 is a schematic view showing a Sn alloy plating apparatus according to another embodiment of the present invention. This example differs from the example shown in FIG. 1 in that the drain line 28 of the plating tank 16 shown in FIG. 1 and the electrolyte supply line 112 of the auxiliary electrolytic tank 100 are connected by a connecting line 242 provided with a pump 240. In addition, a Sn ion supply line 114 extending from the anode chamber 104 of the auxiliary electrolytic cell 100 is connected to the upper portion of the anode chamber 14 of the plating tank 16.

According to this example, the anolyte E in the anode chamber 14 of the plating tank 16 can be used as an electrolyte supplied to the anode chamber 104 of the auxiliary electrolytic cell 100, and the Sn ion concentration in the anode chamber 104 of the auxiliary electrolytic cell 100 can be used. The high anolyte A is returned to the anode chamber 14 of the plating tank 16. It can also be used to replenish insufficient Sn ions.

Fig. 15 is a schematic view showing a Sn alloy plating apparatus according to still another embodiment of the present invention having a plurality of plating grooves. As shown in FIG. 15, the Sn alloy plating apparatus has a plurality of plating tanks 250 having the same configuration as the plating tank 16 shown in FIG. 1, and a single storage tank 252. Further, the anode chamber and the storage tank 252 of each plating tank 250 are connected to the anolyte supply line 254 and the anolyte recovery line 256, respectively. One pump 258a is provided in the anolyte supply line 254. The anolyte supply line 254 is branched on the downstream side of the pump 258a and extends toward each of the plating tanks 250, and a switching valve 260a is provided in each branching portion. A pump 258b is also provided in the anolyte recovery line 256. The anolyte recovery line 256 is branched on the upstream side of the pump 258b and extends toward each plating tank 250, and a switching valve 260b is provided in each branching portion.

In order to increase the temperature of the anolyte to improve the electrolysis efficiency, a heater 262 for heating the anolyte is provided inside the storage tank 252. The anolyte is exemplified by a temperature range of 26 ° C to 40 ° C.

According to this example, the anodic liquid in the anode chamber of each plating bath 250 can be made to have the same Sn ion concentration and methanesulfonic acid concentration in the anode chamber of each plating bath 250 by circulating the anolyte between the anode chamber of each plating bath 250 and the storage tank 252. Thereby, it is possible to avoid the trouble that the plating bath 250 individually manages the Sn ion concentration of the anolyte and the methanesulfonic acid concentration.

In this example, there are two pumps 258a, 258b, by switching valve 260a, Switching 260b, the anolyte is circulated between the sump 252 and the anode chamber of one plating bath 250. Thereby, liquid management of the anode chamber of each plating tank 250 becomes easy. Incidentally, a pump for circulating the anolyte may be provided between the anode chamber of each plating tank 250 and the storage tank 252, and the anode liquid may be circulated independently of the anode chambers of the other plating tanks 250.

Furthermore, as described above, it is also possible to cope with the shortage of Sn ions caused by the difference between the electrolytic efficiency of plating on the substrate and the electrolytic efficiency of the Sn anode in the anode chamber, and the shortage of Sn ions caused by liquid discharge from the plating bath. The problem occurs that the entire system has insufficient Sn ions, and the storage tank 252 is provided with an auxiliary electrolytic cell having the same configuration as the auxiliary electrolytic cell 100 shown in Fig. 1 to supplement the insufficient Sn ions.

In addition, a configuration may be adopted in which the Sn alloy plating apparatus integrally has one outer tank (overflow tank) and a plurality of cathode chambers, and in each cathode chamber, the anode liquid is taken from the cathode chamber by the outer tank by a pump. The supply underneath is returned to the outer tank by overflowing; thereby, liquid management of the cathode chamber becomes easy.

Although the embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiments, and various embodiments can be implemented without departing from the scope of the technical idea.

10‧‧‧Anode tank

10a‧‧‧ next door

12‧‧‧Cathode chamber

14‧‧‧Anode chamber

16‧‧‧ plating tank

18‧‧‧ plating solution supply

20‧‧‧ plating solution supply line

22‧‧‧Substrate holder

23‧‧‧Anolyte supply line

24‧‧‧ electrolyte supply line

26‧‧‧pure water supply pipeline

28‧‧‧Draining line

30‧‧‧Anode holder

32‧‧‧Sn anode

33‧‧‧N ₂ gas supply line

34‧‧‧ plating power supply

36‧‧‧ overflow trough

38‧‧‧ pump

40‧‧‧ heat exchanger

42‧‧‧Filter

44‧‧‧ flowmeter

46‧‧‧ plating liquid circulation pipeline

50‧‧‧Adjustment board

50a‧‧‧Central hole

52‧‧‧Agitator

54‧‧‧ anion exchange membrane

60‧‧‧ anion exchange membrane

62‧‧‧dialysis tank

64‧‧‧ plating solution supply tube

66‧‧‧ plating solution discharge pipe

68‧‧‧ plating solution dialysis pipeline

70‧‧‧pure water supply pipeline

72‧‧‧Pure water discharge pipeline

74‧‧‧Sn ion concentration analyzer

76‧‧‧Methanesulfonic acid concentration tester

80‧‧‧Control Department

100‧‧‧Auxiliary electrolytic cell

102‧‧‧cathode tank

102a‧‧‧ next door

104‧‧‧Anode chamber

106‧‧‧Cathode chamber

108‧‧‧ anion exchange membrane

110‧‧‧Anolyte supply line

112‧‧‧ electrolyte supply line

114‧‧‧Sn ion replenishment pipeline

116‧‧‧Anode holder

118‧‧‧Sn anode

120‧‧‧ pump

122‧‧‧ Catholyte supply line

124‧‧‧Draining line

126‧‧‧Cathode holder

128‧‧‧ cathode

130‧‧‧Auxiliary power supply

A‧‧‧Anolyte

B‧‧‧ Catholyte

E‧‧‧ anolyte

Q‧‧‧ plating solution

W‧‧‧Substrate

Claims (19)

A Sn alloy plating apparatus for electrodepositing an alloy of Sn and a metal more noble than Sn on a surface of a substrate; the apparatus is characterized by having an anion exchange membrane for isolating the inside of the plating tank into a cathode chamber and an anode chamber; The cathode chamber is a Sn alloy plating solution, and the substrate serving as a cathode is immersed in the Sn alloy plating solution; the anode chamber is an anolyte for holding an acid containing Sn ions and forming a complex with the divalent Sn ions. a Sn anode as a material is immersed in the anolyte; and an electrolyte supply line supplies an electrolyte containing the acid to the anode chamber; and the electrolyte supply line is a Sn ion in the anolyte of the anode chamber. The electrolyte solution is supplied to the anode chamber so that the concentration is equal to or higher than a predetermined value and the concentration of the acid is not lower than the allowable value, and the anode liquid in the anode chamber which is increased by the supply of the electrolyte is supplied to the Sn alloy plating. Apply fluid. The Sn alloy plating apparatus according to claim 1, wherein the electrolyte supply line is supplied to the Sn alloy plating solution by allowing the anolyte which is supplied by supplying the electrolyte solution to the anode chamber to overflow the anode chamber. The Sn alloy plating apparatus of claim 1, further comprising: an overflow tank for depositing a plating solution overflowing from the cathode chamber; and a plating liquid circulation line for returning the Sn alloy plating solution in the overflow tank The aforementioned cathode chamber is circulated. The Sn alloy plating apparatus of claim 1, which further has an anode chamber facing the foregoing The pure water supply line for supplying pure water inside. The Sn alloy plating apparatus of claim 1, further comprising an acid concentration measuring device for measuring the concentration of the acid in the anolyte in the anode chamber. The Sn alloy plating apparatus of claim 1, further comprising a dialysis bath for taking out a portion of the Sn alloy plating solution from the cathode chamber, and removing at least a portion of the acid from the Sn alloy plating solution and returning it to the cathode room. The Sn alloy plating apparatus according to claim 1, further comprising an N ₂ gas supply line for supplying nitrogen gas to the anode liquid in the anode chamber to foam the anode liquid. The Sn alloy plating apparatus of claim 1, which has an auxiliary electrolytic cell having an auxiliary anode chamber and an auxiliary cathode chamber separated by an anion exchange membrane, and is an anolyte which has been immersed in the auxiliary anode chamber Applying a voltage between the auxiliary Sn anode and the auxiliary cathode immersed in the cathode liquid in the auxiliary cathode chamber to increase the Sn ion concentration of the anode liquid in the auxiliary anode chamber, and replenishing the anode liquid in the auxiliary anode chamber to The aforementioned Sn alloy plating solution. The Sn alloy plating apparatus according to claim 1, further comprising a partition wall, wherein the partition wall is provided with an anion exchange membrane for blocking the anolyte in the anode chamber; and the electrolyte solution is supplied to the electrolyte supply line through the electrolyte supply line The anolyte in the anode chamber is increased in the anode chamber, and the anolyte is overflowed from the upper end of the partition wall to be supplied to the Sn alloy plating solution. A Sn alloy plating method is an alloy for making Sn and a metal more noble than Sn Deposited on the surface of the substrate; the method is characterized in that: a plating bath that has been internally separated into an anode chamber and an anode chamber by an anion exchange membrane; a Sn alloy plating solution is accommodated in the cathode chamber, and the substrate is immersed in the substrate a Sn alloy plating solution; an anolyte containing Sn ions and an acid forming a complex compound with divalent Sn ions is housed inside the anode chamber, and a Sn anode made of Sn is placed and immersed in the anolyte; The electrolyte solution is supplied to the anode chamber so that the concentration of Sn ions in the anode chamber in the anode chamber is equal to or higher than a predetermined value, and the concentration of the acid is not lower than the allowable value. The anolyte in the anode chamber is supplied to the Sn alloy plating solution, and a voltage is applied between the cathode and the Sn anode to perform Sn alloy plating on the surface of the substrate. The Sn alloy plating method according to claim 10, wherein the anolyte which is increased by supplying the electrolyte solution to the anode chamber overflows the anode chamber, and is supplied to the Sn alloy plating solution. The Sn alloy plating method of claim 10, which circulates the Sn alloy plating solution in the cathode chamber. The Sn alloy plating method according to claim 10, wherein the supply amount of the electrolyte or pure water to the anode chamber is controlled based on a concentration of the acid in the anode liquid in the anode chamber. The Sn alloy plating method of claim 10, wherein the concentration of the acid in the anolyte is from the concentration of the acid in the initial anolyte, before The amount of electrolysis and current efficiency of the Sn anode, the amount of supply of the electrolyte, and the transmittance of the acid moving from the cathode chamber to the anode chamber through the anion exchange membrane were determined. The Sn alloy plating method of claim 10, wherein a portion of the Sn alloy plating solution is taken out from the cathode chamber, and at least a portion of the acid is removed from the Sn alloy plating solution and returned to the cathode chamber. The Sn alloy plating method according to claim 10, wherein the anode liquid is bubbled by supplying nitrogen gas to the anode liquid in the anode chamber. The Sn alloy plating method of claim 10, which is an auxiliary Sn anode which has been immersed in an anolyte in an auxiliary anode chamber of the auxiliary electrolytic cell, and which has been immersed in the anion exchange membrane and is separated from the auxiliary anode chamber A voltage is applied between the auxiliary cathodes of the catholyte in the auxiliary cathode chamber to increase the Sn ion concentration in the anode liquid in the auxiliary anode chamber, and the anode liquid in the auxiliary anode chamber is supplied to the Sn alloy plating solution. The Sn alloy plating method of claim 10, wherein the anode liquid in the anode chamber is blocked by a partition wall containing an anion exchange membrane; and the anode in the anode chamber is increased by supplying an electrolyte solution to the anode chamber The liquid is supplied to the Sn alloy plating solution by overflowing the anolyte from the upper end of the partition wall. A Sn alloy plating apparatus for electrodepositing an alloy of Sn and a metal more noble than Sn on a surface of a substrate; the apparatus is characterized by having an anion exchange membrane for isolating the inside of the inner tank into a cathode chamber and an anode chamber; The chamber is provided with a Sn alloy plating solution inside, and the substrate to be a cathode is immersed in the Sn alloy plating solution; the anode chamber is Holding an anolyte containing Sn ions and an acid forming a complex with the divalent Sn ions, and arranging the Sn anode made of Sn as the anolyte; and the overflow groove surrounds the inner groove; a partition wall adjacent to the overflow tank for blocking an anolyte in the anode chamber; a plating liquid circulation line connected to the overflow tank and the cathode chamber, and supplying Sn ions supplied to the overflow tank to the cathode And an electrolyte supply line for supplying an electrolyte containing the acid to the anode chamber; and further, the Sn ion concentration of the anolyte in the anode chamber is greater than a predetermined value and the concentration of the acid is not lower than an allowable value. In the above-described electrolyte solution supply line, the electrolyte solution is supplied into the anode chamber, and the anode liquid in the anode chamber which is increased by the supply of the electrolyte solution overflows from the upper end of the partition wall and flows into the overflow tank, and the foregoing The anolyte is supplied to the Sn alloy plating solution in the overflow tank.