JPS58217700A - Apparatus for replenishing additive of electroplating bath - Google Patents

Abstract

PURPOSE:To make it possible to form a homogenous plating film having a uniform film thickness, by a method wherein the current of a plating bath in a plating tank is detected and the replenishing amount of an additive liquid is controlled in proportion to the detected value. CONSTITUTION:An anode 3 and an object 4 to be plated are set in a plating tank 1 having a plating bath accommodated therein so as to leave a predetermined interval therebetween and respectively connected to a power source 5. On the other hand, an additive 11 in an additive liquid tank 12 is replenished to the plating tank 1 through a pump 22. On the way of the line 6 connecting the anode 3 and the power source 5, a shunt 7 is provided to be connected to a preamplifier 21 which is in turn connected to the pump 2. The preamplifier 21 converts voltage from the shunt 7 to an industrial transmission signal of about D.C. 4-20mA and this signal is sent to the pump 22 to control the operation of the pump 22. By this mechanism, an operation time can be shortened and workability becomes good.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an improvement in an electroplating solution additive replenishing device for replenishing an electroplating solution with additives.

[Technical background of the invention]

As is well known, electroplating solutions are widely used in various fields. Generally, this electroplating solution contains additives or brighteners in addition to main components such as a compound of the metal to be plated and acids and salts that impart conductivity. In order to obtain a plated film with a homogeneous and uniform thickness using this electroplating solution, it is necessary to always maintain the concentration of additives in the plating solution within a predetermined range. However, since the concentration of most additives is difficult to determine by analysis,
Usually, the plating solution is supplemented with an amount of additive based on the amount of electricity (the product of current and time), thereby adjusting the concentration of the additive in the plating solution.

Conventionally, as an electroplating solution additive replenishing device employing the above-mentioned means, one shown in FIG. 1 is known. 1 in the figure is a plating tank containing a plating solution 2 therein. In the plating tank 1, an anode 3 and an object to be plated 4 are set at a predetermined distance from each other, and each of these is connected to a power source 5. A shunt 7 is provided in the middle of the wiring 6 connecting the anode 3 and the power source 5 to convert the current of the plating solution 2 in the plating tank 1 into voltage. An integrating ammeter 8 is connected to the current shunt 7 . This integrating ammeter 8 integrates the converted voltage and converts it into an amount of electricity, and when the amount of electricity reaches a predetermined set value, it sends a signal to operate the timer to be described later, and also integrates the amount of electricity. It has the function of returning the value to zero. A timer 9 with a preset operating time and a constant flow pump 10 with a preset discharge amount are connected to the integrated ammeter 8 in this order. Note that while the timer 9 is operating, the pump 10 is operated by being supplied with current from a power source (not shown). In addition, the pump 1
0 is connected to an additive liquid tank 12 containing an additive 11 therein, and is also connected to the plating tank 1 described above.

Next, the operation of the device having the above-described structure will be explained. When electroplating is performed in the plating tank 1, the current of the plating solution in the plating tank 1 draws a graph as shown in FIG. 2(a). This current is converted into a voltage by a shunt 7, and this voltage is further integrated by an integrating ammeter 8 and converted into an amount of electricity. When the amount of electricity is successively integrated and reaches a preset value at time TI (as shown in FIG. 2(b)), a signal is sent from the integrating ammeter 8 to the timer 9. Note that at time TI, the amount of electricity in the integrating ammeter 8 returns to zero. When such a signal is sent, the timer 9 operates for the set time, and based on the operation of the timer 9, the constant flow pump 1o operates as shown in FIG. The additive 11 in the additive liquid tank 12 is deposited in the plating tank 1 only according to the set time of the timer 9 and the set discharge amount of the pump 10.
Replenish into plating solution 2 inside.

And time T! When the timer 9 stops, the pump 10 also stops, and the same operation as described above is repeated nine times.

[Problems with background technology]

However, in the electroplating solution additive replenishment device having the above-described structure, the amount of additive 1 to be refilled is proportional to the product of the set time of the timer 9 and the set discharge amount of the pump 10. Therefore, the amount of replenishment depends on the accuracy of the timer 9 and the pump 10, and if the accuracy of the timer 9 and the bong 7010 is not sufficient, the concentration of the additive in the plating solution is determined by drawing the graph shown in FIG. This resulted in excess or shortage of the agent, and the plating film on the object to be plated 4 could not be made homogeneous and of uniform thickness.

Also, even if the accuracy of timer 9 or 1-fzo is good,
The additive is not replenished until the amount of electricity on the integrating ammeter 8 reaches the set value, and the additive concentration in the plating solution is low.
On the other hand, when the set value is reached, the additive concentration increases rapidly, causing the additive concentration in the plating solution to fluctuate in a rough manner.
It had the same drawbacks as above.

[Purpose of the invention]

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an electroplating solution additive replenishment device that can always keep the additive concentration in the plating solution constant and form a homogeneous and uniform plating film on the object to be plated. The purpose is to

[Summary of the invention]

The present invention eliminates the timer from the conventional device, and
Instead of an integrated ammeter, it has a structure that uses a control mechanism that includes a flow divider that detects the current of the plating solution and controls the pump discharge amount in proportion to the detected value. Instead of converting the current of the plating solution into an electrical quantity and replenishing the additive into the plating solution based on this electrical quantity, the signal from the control mechanism is sent directly to the pump, and the additive is added to the plating solution based on the detected value from the control mechanism. The main idea is to keep the additive concentration in the plating solution constant by replenishing the plating solution in proportion to -2 and to apply a plating film with a homogeneous and uniform thickness to the object to be plated. .

[Embodiments of the invention]

The present invention will be explained based on FIGS. 3 to 5.

Components that are the same as those of the electroplating solution additive replenishing device shown in FIG.

The electroplating solution additive replenishment device shown in FIG. 3 is different from the device shown in FIG. Variable flow rate pump (manufactured by Metronics Co., Ltd.:
10621-281N-D type ponno) 22 is substituted,
In addition, the preamplifier 21 is directly connected to the variable flow rate pump 22 except for the timer. Note that the preamp f21 converts the voltage from the shunt 7 into a DC voltage of 4 to 20
It includes the function of converting into a mA industrial transmission signal and sending such signal to the pump 22. The operation is substantially the same as that of the apparatus shown in FIG. 1, and the explanation thereof will be omitted.

According to the present invention, a serial f21 is provided in place of the conventional current integration needle υ, and this preamplifier 21 is directly connected to the variable flow rate type bomb f22. There is no change in the additive concentration due to changes in the accuracy of the timer or the amount of electricity of the integrated ammeter, and when the current of the plating solution draws the graph shown in Figure 4 (,), the flow rate of the pump 22 is As shown in Figure (b), a graph proportional to the current of the plating solution is drawn.As a result, a constant amount of additive is always replenished into the plating tank 1, and the additive concentration in the plating solution is as shown in Figure 4 (,). As shown in the figure, the properties were always approximately constant, and a uniform plating film with a uniform thickness could be formed on the object 4 to be plated.

In addition, in the past, Kd had to be obtained by controlling three points: the amount of electricity set by the integrated current needle, the set time of the timer, and the flow rate of the pump, but according to the present invention, the gain of the preamplifier 21 and the flow rate of the den f22 can be controlled. Since a constant additive concentration can be obtained by controlling two points, the operating time for each member can be shortened and workability is improved compared to conventional equipment.

The electroplating solution additive replenishing device according to the present invention is not limited to the one shown in FIG. 3, but may be the one shown in FIG. 5.

That is, compared to the device shown in FIG. 3, a voltage frequency converter (VIP converter) 23 is substituted for the preamplifier, and a pulse-driven metering pump 7' (Ikkki J!! 2 EP- Co., Ltd.) is used as the variable flow rate pump. B15PC-100E type ponno) 24
In addition, the converter 23, the bond f2
It has a structure in which a branching device 25 is provided between the four stations. In such a device, the v/F converter 23 serves to convert the voltage from the shunt 7 into an alternating current signal and send this signal to the frequency divider 25. The frequency divider 25 also serves to convert the signal to a lower frequency. A device having such a structure also has substantially the same effects as the device shown in FIG.

In the above example, when converting the current of the plating solution into the amount of additive replenishment, the conversion was performed via quantities such as voltage, current, frequency, etc. However, this is not limited to this, and other conversion channels may be used. .

〔Effect of the invention〕

As detailed above, according to the present invention, a homogeneous and uniform plating film can be formed on a damaged object, and an electroplating solution additive replenishing device with good workability is provided which can shorten the operation time of each member compared to the conventional method. This is something that can be provided.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram of a conventional electroplating solution additive replenishment device;
Figures 2 (,) to (d) are graphs showing the relationship between time, current of the plating solution, quantity of electricity, flow rate of the pump, and concentration of additives in the plating solution in the apparatus shown in Figure 1; (,
) shows the relationship between time and the current of the plating solution, FIG. d) is a characteristic diagram showing the relationship between time and additive concentration in the plating solution, FIG. 3 is an explanatory diagram of an electroplating solution additive replenishment device which is an embodiment of the present invention, and FIG. ) to (c) show the relationship between time and the current of the plating solution, the flow rate of the pump, and the degree of additive retention in the plating solution in the apparatus shown in Figure 3, and (a) of the same figure shows the relationship between time and the current of the plating solution. Figure 5 (b) shows the relationship between time and pump flow rate, Figure (e) shows the relationship between time and additive concentration in the plating solution, and Figure 5 shows the relationship between time and pump flow rate. FIG. 3 is an explanatory diagram of an electroplating solution additive replenishing device showing another embodiment of the present invention. 1... Plating tank, 2... Plating solution, 7... Divider, 21... 7' Riano, 22... Variable flow rate pump, 23... V/F converter, 24...・Pulse-driven metering pump, 25...frequency divider.

Claims (1)

[Claims] A plating tank is connected to this plating tank via a pump,
It is characterized by comprising an additive liquid tank containing an additive, and a control mechanism that detects the current of the plating solution in the plating tank and controls the discharge amount of the pump in proportion to the detected value. Electroplating solution additive replenishment device.