JPS5952952B2 - Electroless plating control method and device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for controlling electroless plating such as electroless nickel plating, and a control device used for this electroless plating.
More specifically, the present invention relates to an electroless plating control method and an apparatus therefor that make it possible to stably perform continuous plating work over a long period of time.

When using an electroless plating solution, metal salts, reducing agents, etc. are consumed in a short period of time, and the composition of the solution fluctuates dramatically. Therefore, it is necessary to frequently replenish the consumable chemicals to improve the deposition rate, properties of the plating film, etc. It is necessary to keep the value constant, and for this purpose various automatic electroless plating solution control or replenishment devices or methods have been proposed (Japanese Patent Laid-Open Nos. 53-44434 and 53-456).
No. 31, No. 54-8123, etc.). However, electroless plating solutions, such as high-temperature acidic electroless nickel plating solutions, have a short lifespan, and whether by the automatic replenishment method described above or by manually replenishing the replenishment solution when necessary, The solution ages in a relatively short period of time, and even if you replenish metal ion concentration, reducing agent concentration, etc. to the same concentration as at the beginning of bath preparation, the precipitation rate will decrease significantly compared to the initial period of bath preparation, and the film will not form again. The properties of the will also change considerably.

In this case, the liquid must be discarded and a new bath prepared. For this reason, even if the above-mentioned automatic control method for electroless plating solution is adopted to automatically replenish the replenishment solution, the degree of aging of the solution must be constantly monitored and appropriate countermeasures should be taken. Therefore, in the conventional electroless plating method, even if the automatic control method described above is adopted, the plating solution must be disposed of in a relatively short period of time, and the management thereof is not sufficiently satisfactory. It wasn't something.

The present invention was made to improve the situation in the first half, and it enables stable continuous plating work over a long period of time, almost eliminates the need to rebuild the liquid, and is at least better than the conventional method. It is possible to significantly delay the period for rebuilding the liquid, which is advantageous in terms of waste liquid and wastewater treatment, and it is also possible to maintain the deposition rate, properties of the plating film, etc. almost constant over a long period of time, making liquid management simple and easy. The purpose of the present invention is to provide an electroless plating control method and apparatus that can perform electroless plating reliably and is particularly suitable for electroless nickel plating, electroless cobalt plating, and electroless nickel-cobalt alloy plating. do.

That is, as a result of various studies conducted by the present inventors in order to solve the conventional drawbacks, the amount of chemical consumption due to plating can be detected by measuring the concentration of the electroless plating solution, and the amount of chemical consumption due to plating can be detected according to the measured value. By automatically replenishing components consumed by plating and at the same time measuring the conductivity of the electroless plating solution, it is possible to reliably detect the degree of aging of the plating solution. When the plating liquid exceeds a predetermined set value, the plating liquid is automatically renewed little by little by pumping out the negative part of the plating liquid and automatically replenishing the replenishing agent corresponding to this pumped-out component. It was discovered that the plating solution can be used continuously for a long period of time, and that the precipitation rate, properties of the precipitates, etc. can be kept almost constant during long-term continuous use, and the above objects are achieved, and the present invention has been made. This is what we have come to do.

Hereinafter, one embodiment of the present invention will be described with reference to the drawings. Fig. 1 shows an example of equipment used for electroless nickel plating, and 1 in the figure is a plating tank. A heating device for heating the electroless nickel plating solution 2 such as a pipe to a predetermined temperature, a cooling device for cooling the plating solution 2 to around room temperature after plating, a filtration machine,
A stirrer, etc.) is included.

The plating tank 1 includes a concentration detector 3, a conductivity detector 4,
and one end of a circulation pipe 6 interposed with the pump 5 communicates with each other,
Due to the operation of the pump 5, the plating liquid 2 in the plating tank 1 flows into the pipe 6 from one end of the pipe 6.
After the concentration of the plating liquid 2 (for example, nickel ion concentration) is measured by the concentration detector 3 while flowing through the pipe, and the conductivity of the plating liquid 2 is measured by the conductivity detector 4, the The plating liquid 2 is returned into the plating tank 1 from the other end of the plating tank 6.

FIG. 2 shows an example of the concentration detector 3. In this example, a bypass pipe 7 is disposed in the pipe 6, and a spectrophotometer 8 equipped with a flow type cell 8a is installed in the bypass pipe 7. By measuring the light transmittance of the plating solution 2 as it flows through the bypass pipe 7 and through the flow-through cell 8a of the spectrophotometer 8, The amount of nickel ions in the plating solution is measured (in the case of acidic electroless nickel plating using hypophosphite as the reducing agent, the absorbance of the nickel complex in the plating solution is detected in order to sensitively detect metal consumption due to plating). It is preferable to use a mechanism that converts the plating liquid transmittance at the absorption wavelength of the nickel complex into voltage.

), so that the concentration of the plating solution 2 is detected, and when the amount of nickel ions falls below a predetermined concentration setting value, a signal A is sent from the control device 9 communicated to the spectrophotometer 8. is beginning to be emitted. By analyzing the nickel content in this way, it is possible to determine the amount of nickel consumed due to plating, as well as the amount of consumption of the reducing agent. The amount of variation can also be known at the same time. FIG. 3 shows an example of the conductivity detector 4, in which a bypass pipe 10 is provided in the pipe 6, a conductivity measuring cell 11 is interposed in the bypass pipe 10, and the cell 11 is electrically connected. degree measuring instrument 1
2 and the control device 13.

The cell 11 has a structure in which a liquid inflow pipe 11b and a liquid outflow pipe 11C are connected to the sides of a substantially cylindrical body 11a with both end faces closed, and the vicinity of both end faces of the cylindrical body 11a are plated with platinum or platinum black. Polar plates 14a and 14b made of platinum or the like are arranged with a predetermined distance apart, and these polar plates 14a and
, 14b are connected to the conductivity measuring device 12 via conducting wires 15a, 15b, respectively. Then, when the conductivity of the plating liquid 2 in the cell 11 is measured by detecting the resistance between the bipolar plates 14a and 14b, and the measured conductivity value increases to a predetermined conductivity setting value or more, A signal B is emitted from a control device 13 connected to the measuring instrument 12. In this case, the bipolar plates 14a, 14b
The resistance between the two polar plates 14a and 14b can be changed, for example, by applying a constant potential between the two polar plates 14a and 14b, or by changing the current between the two polar plates 14a and 14b.
By flowing a constant current between a and 14b, it can be detected as a voltage fluctuation. Although not shown, a cooler is installed in the pipe 6 on the upstream side of the concentration detector 3, and the plating liquid flowing through the bypass pipes 7 and 10 is cooled to room temperature and kept at a substantially constant temperature. Concentration or conductivity measurements are being made.

In addition, in order to prevent the influence of temperature in these measurements, other methods such as using a constant temperature bath, providing a temperature measuring probe, and performing electrical compensation can also be adopted. 16
is a replenishment agent replenishment mechanism for consumable chemicals, which includes a replenishment tank 17;
Replenishment agent supply pipe 18 whose one end is connected to this tank 17
and the electromagnetic valve 1 interposed in this supply pipe 18.
9, an electromagnetic valve 19 is opened for a predetermined period of time in response to a signal A from the control device 9 of the concentration detector 3, and a predetermined replenisher, such as nickel salt, reducing agent, or A predetermined amount of a conditioning agent and the like is supplied into the plating tank 1.

In addition, although only one tank 17 is installed in FIG. 1, in order to store the nickel salt, cyclic agent, inhibitor, etc. for replenishment separately, multiple tanks are installed accordingly. It is also possible to install a supply pipe and a solenoid valve for each.

Reference numeral 20 denotes a pumping mechanism, which has a pumping pipe 21 whose one end communicates with the inside of the plating tank 1, and which is interposed in the pumping pipe 21 and is operated for a predetermined period of time by a signal B from the control device 13 of the conductivity detector 4. It consists of a control pump 22 that sucks up a predetermined amount of plating liquid 2 from the plating tank 1. The pump 22 is operated for a predetermined period of time in response to the signal B from the conductivity detector 4, and the pump 22 sucks up a predetermined amount of plating liquid from the plating tank 1. 2 is now being discharged.

Furthermore, 23 is a replenishment replenishment mechanism for pumped consumable chemicals, which includes a replenishment tank 24, a replenishment supply pipe 25 connected to this tank 24 at one end, and an electromagnetic valve interposed in this supply pipe 25. 26, this electromagnetic valve 26
receives the signal B from the control device 13 of the conductivity detector 4,
After the pump 22 stops operating, it is opened for a predetermined period of time, and a predetermined amount of replenisher for the pumped consumable chemicals is supplied into the plating tank 1 in response to the pumping of the plating liquid 2. (In the case of this replenishment mechanism 23 as well, it is also possible to install a plurality of tanks and install supply pipes and electromagnetic valves in each tank depending on the type of replenishment agent, etc.) Next, the apparatus with the above configuration We will explain how to control electroless nickel plating using this method.

First, in electroless nickel plating, the object to be plated is subjected to a predetermined pretreatment and then heated to a predetermined temperature, for example, 90°C.
This is done by immersing the plate in a plating solution 2 in a plating tank 1 which has been heated to . On the other hand, while carrying out such plating, the pump 5 is operated to drain the plating liquid 2 in the plating tank 1.
A part of the plating solution is introduced into the pipe 6 and guided to the concentration detector 3 and conductivity detector 4 to measure the concentration of the plating solution 2 (the nickel ion concentration if the concentration detector 3 in Fig. 2 is followed) and the target value. The electrical conductivity of the soaking liquid 2 is measured. As the plating progresses, the concentration of the plating solution 2 in the plating tank 1, especially the nickel ion concentration and the concentration of the reducing agent (for example, sodium hypophosphite) decreases, and the hypophosphite is used as the reducing agent. In the case of electroless nickel plating solution, use plating solution 2. However, such a concentration change occurs, and for example, if the concentration detector 3 shown in FIG. When the temperature decreases to 1, the control device 9 of the detector 3 issues a signal A, which is applied to the electromagnetic valve 19 of the consumable chemical replenishment mechanism 16, which opens the valve 19 for a predetermined period of time. As a result, the replenishment agent in the tank 17 mainly consists of the nickel salt consumed by plating, the reducing agent, and the ml adjuster, and if necessary, a small amount of the complexing agent, stabilizer, and brightening agent. etc. are added. In general, it is preferable that the nickel salt, reducing agent, and conditioner be stored separately. In this case, it is preferable that the complexing agent, stabilizer, brightener, etc. be mixed with components that do not react with each other among the above three components. ) for a predetermined amount of plating tank 1
It is added to the plating solution 2 inside to replenish the Nitsugel ions, reducing agent, etc. that were consumed during plating, and then replenish the plating solution 2. is adjusted. By replenishing the replenisher like this, the plating solution 2
The concentration of is kept almost constant, and therefore the plating rate (deposition rate) is kept almost constant.

Further, as reaction products accumulate in the plating solution 2, the conductivity of the plating solution 2 increases, and the conductivity of the plating solution 2 is measured by the conductivity detector 4 shown in FIG. As a result, if the measured value increases to a predetermined conductivity setting value or more, the control device 13 issues a signal B, and this signal B is given to the pump 22 of the pumping mechanism 20.
is operated for a predetermined period of time, and a predetermined amount of the plating liquid 2 in the plating tank 1 is discharged through the pumping pipe 21.

It is desirable to send the waste liquid to a waste liquid treatment device, and after removing by-products, the active ingredient may be reused.
). When the pump 22 stops operating, the electromagnetic valve 26 of the pumped consumable drug replenishment mechanism 23 opens for a predetermined period of time.
The replenisher in the tank 24 is used to replenish the components lost due to the pumping out, and is mainly a complexing agent, usually having the same composition as the plating solution 2 at the time of preparation, or a complexing agent. It mainly consists of a concentrate or a complexing agent that is hardly consumed by plating. Note that if the components to be replenished are likely to react with each other, such as a metal salt and a reducing agent, it is preferable to separate and store these components. ) is supplied to the plating liquid 2 in the plating tank 1. Therefore, by pumping out the plating liquid 2 and replenishing the replenishment agent corresponding to the pumping out,
Accumulation of reaction products in the plating solution 2 is prevented, and the amount of reaction products is controlled to be approximately constant. This prevents the plating speed from decreasing due to the accumulation of reaction products, and the plating solution 2 is constantly refreshed even after long-term continuous use, so the plating speed remains constant even after long-term use. The properties of the plating film (for example, if hypophosphite is used as the reducing agent, the Ni-P alloy composition,
Also, the hardness of the plating film, etc.) is also kept more or less constant.
To explain this point in more detail, if plating is carried out for a long time, reaction products (mainly considered to be decomposition products of the reducing agent and neutralized salts of the plating reaction) may be present in the plating solution 2. ) accumulates, and this reaction product affects plating speed, etc.
As mentioned above, replenishing the components consumed by plating will reduce the plating speed and may also cause changes in the properties of the plating film, but according to the studies of the present inventors, this Accumulation of such reaction products, in other words aging of the solution, can be reliably detected by changes in the electrical conductivity of the plating solution 2, and as described above, the electrical conductivity of the plating solution 2 has exceeded the predetermined electrical conductivity setting value. In this case, by discharging a part of the plating liquid 2 and replenishing it in response to the conductivity detector 4 (mainly replenishing the components lost due to pumping out),
The amount of reaction products in the plating solution 2 can be maintained almost constant, the life of the plating solution 2 can be made almost semi-permanent, and the life of the solution can be significantly extended, at least compared to conventional methods.
Furthermore, during such long-term continuous use, the plating speed, properties of the plating film, etc. could be maintained almost constant.

Furthermore, according to the above-mentioned plating method, the plating solution 2 is easily and reliably automatically controlled and managed, and electroless plating, which has conventionally been troublesome to manage, is much easier than electroless plating. Can be easily managed.

Furthermore, as mentioned above, since the concentration of the plating solution 2 is always maintained at a nearly constant value by replenishment, the nickel concentration before plating is adjusted to compensate for the decrease in the precipitation rate due to the decrease in the nickel concentration due to the progress of plating. The nickel concentration of the plating solution 2 can be lowered without requiring any operations to keep the nickel concentration high, and since the plating solution is automatically renewed little by little by the pumping mechanism 20, wastewater,
The burden of waste liquid treatment is drastically reduced. In the above example, the method of directly measuring the absorbance of the plating solution as described above was adopted as a method for measuring the amount of nickel ions in the plating solution 2, but the method is not limited to this. E.D.T.
It is also possible to adopt a method in which a suitable reagent or test agent such as A is added to develop a predetermined color, and the amount of nickel ions is measured based on the degree of color development.

However, in this case, the plating solution after concentration measurement cannot be returned from the bypass pipe 7 to the pipe 6 as shown in FIG. 2, and must be separately sent to a waste solution treatment facility for disposal. Furthermore, in addition to measuring the absorbance of the plating solution in this way, other appropriate concentration detection methods, such as potentiometric measurement, can be adopted. However, the above-mentioned method of directly measuring the absorbance of the plating solution However, the equipment does not become complicated,
This method is most advantageous in that the measured plating solution can be returned to the plating tank 1. It is also possible to detect the concentration of the plating solution by measuring the concentration. Furthermore, it is also possible to adopt a method in which the measurement of the nickel ion concentration and the concentration measurement described above are combined, and the concentration of the plating solution is automatically controlled based on the measured value. Furthermore, in the above embodiment, concentration detection,
Although the conductivity detection mechanism is incorporated into the bypass pipe, it is also possible to directly incorporate the conductivity detection mechanism into the circulation pipe without providing such a bypass pipe, and conductivity detection may be performed after concentration detection. , of course, it is not limited to this,
The order may be reversed or the detection may be performed using separate circuits.Also, as described above, the detector may be installed outside the plating tank and the plating solution may be circulated through it. A concentration or conductivity detection mechanism may also be provided within the plating tank.

Furthermore, as a pumping mechanism, an overflow tube 27 is provided in the plating tank 1 as shown by the two-dot chain line in FIG. A configuration in which a replenisher is supplied to the plating solution 2 in the plating tank 1, and the increased amount of the plating solution 2 due to the addition of the replenisher is discharged from the overflow pipe 28, thereby pumping out the plating solution 2. It is also possible to do this.

Furthermore, although the above embodiment describes the control of electroless nickel plating, electroless cobalt plating, electroless cobalt-nickel alloy plating, etc. can be similarly controlled, and other configurations may depart from the gist of the present invention. You may make various changes as long as you do not. As explained above, according to the present invention,
By automatically detecting the concentration of electroless plating solution,
By detecting the amount of consumption due to plating and automatically replenishing the consumable components due to plating and plating accordingly, by automatically detecting the conductivity of the electroless plating solution, the degree of aging of the plating solution can be adjusted. It is possible to detect this and automatically pump out a portion of the plating solution and replenish the consumable components caused by this pumping out. There is almost no need for changing, and the longevity of the liquid can be significantly extended, at least compared to conventional methods.

In addition, the metal content, reducing agent, etc. in the plating solution are maintained at a nearly constant concentration, and the amount of reaction products caused by plating is maintained within limits, so the deposition rate and physical properties of the deposited film are almost constant. This makes it possible to maintain highly stable bath conditions for a long period of time, and also to manage the plating solution at a lower metal concentration than before while maintaining almost the same deposition rate as before, which improves waste liquid and wastewater treatment. It is also advantageous. Examples are shown below.

Electroless nickel plated 1001 was heated to 90°C, and the nickel ion concentration (670 nm light transmittance) was automatically and continuously measured using a control device as shown in Figures 1 to 3. (The conductivity was measured by the following methods) and the conductivity was measured.

In this case, the set value of nickel ions is 4 g, and when the nickel ion concentration of the plating solution falls below this value, signal A is generated and a replenishment solution with the following composition], 2, 3 is used as a replenishment agent for consumable chemicals. 400m1 (Ni2
+0.2g equivalent) was added. (In addition, these replenishment liquids), 2 and 3 are 3 equipped with a replenishment pipe and a solenoid valve, respectively.
When the signal A is issued, each electromagnetic valve is simultaneously opened for a predetermined period of time so that the same amount of replenishment liquid can be simultaneously supplied into the plating tank. ) Also, if the conductivity setting value is 50m'C5/Cm, and the conductivity of the plating liquid exceeds this value, signal B is generated and 51 plating liquids are pumped out at a time, and then the consumable chemicals are pumped out. Replenishment liquid (4) 51 having the following composition was added as a replenisher (method of the present invention). For comparison, plating was carried out in the same manner as above, except that the conductivity was not measured and therefore the liquid was not pumped out and the replenishing liquid 4 was not replenished (only the nickel ion concentration was measured and the plating was carried out accordingly). Only replenishment liquids 1, 2, and 3 were added.

: comparative law). Deposition rate and Ni-P alloy composition are determined every predetermined number of turns (one turn means when 4g of nickel ions are consumed per plating solution 11 when plating is performed continuously). was investigated, and the results shown in Table 1 were obtained.
Incidentally, FIG. 4 shows the relationship between the number of turns and the electrical conductivity (millimo) of the electroless nickel plating solution having the above composition (measurement temperature: 25° C.).

According to the results shown in Figure 4, the electrical conductivity of the plating solution increases linearly as the number of turns of the electroless nickel plating solution increases, that is, the degree of aging of the plating solution. It is recognized that the degree of aging can be reliably detected.

[Example 2] Using a control device as shown in the composition shown in FIG. 3, plating was carried out while automatically and continuously measuring the cobalt ion concentration and conductivity.

In this case, the cobalt ion setting value is 4g/1, and if the cobalt ion concentration of the plating solution falls below this value,
Signal A was issued, and replenishment solutions 5, 6, and 7 having the following compositions were added at 2 ml/l each time as replenishers for consumable chemicals. (These replenishment liquids 5, 6, and 7 are stored in three tanks each equipped with a replenishment pipe and a solenoid valve, and when signal A is issued, each solenoid valve opens at the same time for a predetermined period of time to replenish the same amount.) In addition, the conductivity setting value is set to 35 m0/Cm, and when the conductivity of the plating liquid exceeds this value, signal B is generated and 10 m0/Cm is output per time. After pumping out ~50m1/1 of the plating solution, use replenishment solution 8 with the following composition as a replenishment agent for the pumped out consumable chemicals.
was added in the same amount as the amount pumped out (method of the present invention).
For comparison, plating was carried out in the same manner as above, except that the conductivity was not measured and therefore the liquid was not pumped out and the replenishing liquid 8 was not replenished (only the cobalt ion concentration was measured and the plating was carried out accordingly). Only replenishment liquids 5, 6, and 7 were added.

: comparative law). Deposition rate and CO-P alloy composition are determined every predetermined number of turns (one turn means when 4g of cobalt ions are consumed per plating solution 11 when plating is performed continuously). was investigated, and the results shown in Table 2 were obtained.

[Brief explanation of the drawing]

FIG. 1 is a plot diagram showing an example of the present invention, FIG. 2 is a plot diagram showing an example of the concentration detector of the present invention, and FIG. 3 is a plot diagram showing an example of the conductivity detector of the present invention. FIG. 4 is a graph showing the relationship between the number of turns in electroless nickel plating and the electrical conductivity. 1...Plating tank, 2...Plating liquid, 3
... Concentration detector, 4 ... Conductivity detector, 5 ... Pump, 6 ... Circulation pipe,
16... Replenishment mechanism for consumable chemicals, 20...
... Pumping mechanism, 23... Pumping out replenishment mechanism for consumable chemicals, A, B... Signal.

Claims (1)

[Claims] 1. If the concentration of the electroless plating solution is measured continuously or intermittently and it is detected that the measured value has fallen below a predetermined concentration setting value due to consumption due to plating, When the replenisher corresponding to the consumed amount is automatically replenished, and the conductivity of the plating liquid is measured continuously or intermittently, and it is detected that the measured value exceeds a predetermined conductivity setting value. , automatically pumping out a portion of the plating solution, and
An electroless plating control method characterized by automatically replenishing a replenisher corresponding to the component lost due to pumping. 2. The method according to claim 1, wherein the electroless plating solution is an electroless nickel plating solution, an electroless cobalt plating solution, or an electroless nickel-cobalt alloy plating solution. 3. A concentration detector that automatically measures the concentration of the electroless plating solution and issues a signal when the measured value falls below a predetermined concentration setting value, and a concentration detector that automatically measures the electrical conductivity of the plating solution. and a conductivity detector that issues a signal when the measured value exceeds a predetermined conductivity setting value, and a consumable device that automatically replenishes a replenisher corresponding to the amount of consumable material due to plating based on the signal from the concentration detector. The chemical replenishment replenishment mechanism is activated by a signal from the conductivity detector, and automatically pumps out a portion of the plating solution, and automatically dispenses a replenishment agent corresponding to the components lost due to this pumping out. 1. An electroless plating liquid control device comprising: a pumping mechanism for replenishing the liquid, and a pumping mechanism for replenishing consumable chemicals.