JPS5952953B2 - 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 drastically. It is necessary to keep properties etc. constant, and for this purpose various automatic control or replenishment devices or methods for electroless plating solution have been proposed (Japanese Patent Laid-Open Nos. 53-44434 and 53-4).
No. 5631, No. 54-8123, etc.). However, electroless plating solutions, such as high-temperature acidic electroless nickel plating solutions, have a short service life, and even with the automatic replenishment method described above,
Or, even if you manually replenish the replenishing solution when necessary, the solution ages in a relatively short period of time, and even if you replenish the metal ion concentration, reducing agent concentration, etc. to the same concentration as at the beginning of bath preparation, the precipitation rate will decrease. compared to the initial stage of bath preparation, and the properties of the glare film have also changed 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 aspect is also not satisfactory. It wasn't something.

The present invention has been made to improve the above-mentioned circumstances, and enables stable continuous plating work over a long period of time, almost eliminates the need for replacing 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. An object of the present invention is to provide an electroless plating control method and apparatus that can be performed reliably and is particularly suitable for implementing electroless nickel plating, electroless cobalt plating, and electroless nickel-cobalt alloy plating. .

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 refractive index of the electroless plating solution, it is possible to reliably detect the degree of aging of the plating solution. When the rate exceeds a predetermined set value, a portion of the plating solution is pumped out and a replenisher corresponding to the pumped-out component is automatically replenished, thereby automatically renewing the plating solution little by little. , discovered that the plating solution can be used continuously for a long period of time, and that the precipitation rate, properties of the precipitate, etc. can be kept almost constant during long-term continuous use, and that the above objectives are achieved. This led to the invention.

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 completion of plating, a filtration machine,
A stirrer, etc.) is included.

The plating tank 1 includes a concentration detector 3, a refractive index 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 refractive index of the plating liquid 2 is measured by the refractive index 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 It is preferable to detect this, and it is preferable to employ a mechanism that converts the plating liquid transmittance at the absorption wavelength of the nickel complex into a voltage.

), 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 is sent from the control device 9 connected to the spectrophotometer 8. A is starting to be emitted. In addition,
By analyzing the nickel content in this manner, the amount of nickel consumed due to plating can be determined, and at the same time, the consumption and amount of the reducing agent, as well as the amount of fluctuation, can be determined at the same time. FIG. 3 shows an example of the refractive index detector 4, in which a bypass pipe 10 is provided in the pipe 6, and the refractive index detector 4 is provided in this bypass pipe 10.

This detector 4 totally reflects incident light L given from a condenser 11 to a prism 12 disposed in a bypass pipe 10 at the plating liquid boundary surface, and sends refracted light LB from the prism 12 to a light receiver 13. This receiver 1
3, the servo motor 11a is operated using the comparison intensifier 14 so as to always keep the same intensity of the critical ray that moves due to changes in the refractive index of the plating liquid 2;
By moving the condenser 11, the angle of the incident light LA is automatically changed and controlled, and the change in angle is detected by the angle detector 11b, and the change in angle is extracted as a change in potential difference. It's becoming like that.

Then, when the refractive index of the plating liquid 2 changes and increases and exceeds a predetermined refractive index setting value, in the case of the detector 4, the potential difference value corresponding to the change in the angle of the incident light LA due to the change in the critical ray position changes. When a predetermined potential difference setting value is reached), a signal B is generated from the control device 15. Although not shown, a cooler is interposed in the pipe 6 on the upstream side of the concentration detector 3, and a bypass pipe 7,
The plating liquid flowing through 10 is cooled to room temperature, and the concentration or refractive index is measured at a substantially constant temperature.

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, with replenishment agent Tanta 17,
Replenishment agent supply pipe whose one end is connected to this tank 17]8
and the solenoid valve 1 interposed in the supply pipe ] 8
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, inhibitor, etc., is opened in response to the consumption of chemicals due to plating. A predetermined amount of a conditioning agent and the like is supplied into the plating tank 1.

In addition, although only one tanker 17 is installed in Figure 1, multiple tanks are installed to store the replenishing nickel salt, reducing agent, adjusting agent, etc. separately. In addition, a supply pipe and a solenoid valve may be provided respectively.

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 15 of the refractive index 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 operates for a predetermined period of time in response to the signal B from the refractive index 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 15 of the refractive index 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 arrange supply pipes and electromagnetic valves in each tank depending on the type of replenisher etc.) Next, the above structure A method of controlling electroless nickel plating using the apparatus will be explained.

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, when 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 the refractive index detector 4 to measure the concentration of the plating solution 2 (or the nickel ion concentration in the case of the concentration detector 3 in FIG. 2). The refractive index of each plating 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 level decreases to 1, a signal A is issued from the control device 9 of this detector 3, and this signal A is sent to the consumable chemical replenishment replenishment mechanism 16.
is applied to the electromagnetic valve 19 to open the valve 19 for a predetermined period of time.

As a result, the replenishment agent in the tank 17 (this replenishment agent mainly consists of the nickel salt consumed by plating, the reducing agent, and the adjusting agent, and if necessary, a small amount of the complexing agent,
Stabilizers, brighteners, etc. are added. In general, nickel salt, reducing agent, ? Preferably, each conditioning agent is housed separately and separately. In this case, complexing agents, stabilizers,
It is preferable that the brightener and the like be mixed with components that do not react with each other among the above three components. ) is added to the plating solution 2 in the plating tank 1 to replenish the nickel ions, reducing agent, etc. consumed by plating, and adjust the ml of the plating solution 2 again. By replenishing the replenisher like this, the plating solution 2
The temperature is kept almost constant, and therefore the plating rate (deposition rate) is kept almost constant.

Furthermore, as reaction products accumulate in the plating solution 2, the refractive index of the plating solution 2 increases, and the refractive index of the plating solution 2 is measured by the refractive index detector 4 shown in FIG. As a result, if the measured value increases beyond a predetermined refractive index setting value, the control device 15 issues a signal B, and this signal B
is applied to the pump 22 of the pumping mechanism 20, and the pump 2
2 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 operation of the pump 22 is stopped, the electromagnetic valve 26 of the pumped consumable drug replenishment replenishment mechanism 23 is opened for a predetermined time, and the replenishment agent in the tank 24 replenishes the components lost due to the pumping. It is mainly a complexing agent, and usually has the same composition as the composition when preparing the plating solution 2,
Or, it consists mainly of a concentrated solution thereof, 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 replenisher corresponding to the pumping out, accumulation of reaction products in the plating liquid 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, the Ni-P alloy composition or the hardness of the plating film when hypophosphite is used as the reducing agent) are also kept substantially 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 the plating speed, etc., and as mentioned above, even if the consumable components due to plating are replenished, the plating speed decreases, and in some cases, the properties of the plating film change. However, according to studies by the present inventors, the accumulation of such reaction products, in other words, the aging of the solution, can be reliably detected by the change in the refractive index of the plating solution 2, and as described above, When the refractive index of the plating liquid 2 exceeds a predetermined refractive index setting value, a part of the plating liquid 2 is drained and replenishment is performed in response to the refractive index detector 4 (mainly replenishment of components lost due to pumping out). ), it is possible to maintain the amount of reaction products in the plating solution 2 almost constant and extend the life of the plating solution 2 almost semi-permanently, at least significantly compared to the conventional method. Moreover, the plating speed, the properties of the plating film, etc. could be maintained almost constant during such long-term continuous use.

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 traditionally been troublesome to manage, is now much easier than electrolytic plating. can be 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 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 to the pipe 6 from the bypass pipe 7 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 manner, other appropriate concentration detection methods, such as potentiometric measurement, can be employed. However, the above-mentioned method of directly measuring the absorbance of the plating solution is the most advantageous since the apparatus does not become complicated and 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, by combining the above-mentioned blind measurement of nickel ion concentration,
Methods such as automatic control of the plating liquid based on the measured values can also be adopted. Furthermore, the method for detecting the refractive index of the plating liquid is not limited to the above-mentioned method, for example, directly sensing a change in the total amount of refracted light with a light receiver, or directly sensing the movement of a critical ray as a change in the amount of light, A method of converting it into electrical output may be adopted. Furthermore, in the above embodiment, the concentration detection and refractive index detection mechanisms were incorporated into the bypass pipe, but such a bypass pipe may not be provided and they may be directly incorporated into the circulation pipe. Although the refractive index is detected in this embodiment, the present invention is not limited to this, and the order of the refractive index detection may be reversed, or the detection may be performed using separate circuits. Although the plating solution is installed outside the tank and the plating liquid is circulated therein, a concentration or refractive index detection mechanism can also be provided inside the plating tank.

Furthermore, as a pumping mechanism, an overflow pipe 27 is provided in the plating tank 1 as shown by the two-dot chain line in FIG. is supplied to the plating liquid 2 in the plating tank 1, and the increased amount of the plating liquid 2 due to the addition of the replenisher is discharged from the overflow pipe 27, thereby pumping out the plating liquid 2. You can also do that.

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,
It detects the amount of consumption due to plating and automatically replenishes the consumable components due to plating accordingly. It also detects the degree of aging of the plating liquid by automatically detecting the refractive index of the electroless plating liquid. Accordingly, a portion of the plating solution can be pumped out and the consumable components caused by this pumping can be automatically replenished.As a result, the solution is automatically renewed in small amounts, so there is no need to replace the solution. The liquid life 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. The implementation is 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. ) and the refractive index was measured.

In this case, the set value of nickel ions is 4 g/l, and if the nickel ion concentration of the plating solution falls below this value,
As a replenisher for the consumable chemicals that generated signal A, use 400 ml of each of replenishment liquids (1), (2), and (3) of the following composition each time.
ml (equivalent to Ni2 + 0.2 g) was added. (In addition,
These replenishment liquids 1, 2, and 3 are stored in three tanks each equipped with a replenishment pipe and an electromagnetic valve, and when signal A is issued, each electromagnetic valve opens simultaneously for a predetermined period of time, aiming to supply the same amount of replenishment liquid. It is now possible to simultaneously supply water into the tank. )Also,
The refractive index setting value is 16.0Brix%, and when the refractive index of the plating liquid exceeds this value, a signal B is generated and 51 pieces of plating liquid are pumped out at a time, and then used as a replenishment agent for pumped out consumable chemicals. A replenishment liquid 451 having the following composition was added (method of the present invention).

For comparison, plating was carried out in the same manner as above, except that the refractive index 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). , only replenishers 1, 2, and 3 were added accordingly.

: 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.
Replenishment Solution (1) In addition, FIG. 4 shows the relationship between the number of turns and the refractive index (Brix%) of the electroless nickel plating solution having the above composition (measurement temperature: 25° C.).

From the results shown in Figure 4, the refractive index of the plating solution increases linearly as the number of turns in electroless nickel plating increases, that is, the degree of aging of the plating solution. It is recognized that the degree of oxidation can be detected reliably.

[Example 2] Electroless cobalt plating with the following composition was heated to 90°C, and the cobalt ion concentration and refractive index were automatically and continuously controlled using a control device as shown in Figures 1 to 3. I took measurements and looked at them.

In this case, the set value of cobalt ions is 4 g/l, and if the cobalt ion concentration of the plating solution falls below this value,
Signal A was emitted, and 2 ml of replenishment liquids 5, 6, and 7 having the following compositions were added each time as replenishers for consumable chemicals.
(These replenishment liquids 5, 6, and 7 are respectively replenishment pipes,
It was housed in three tanks equipped with electromagnetic valves, and when signal A was issued, each electromagnetic valve opened at the same time for a predetermined time so that the same amount of replenishment liquid could be simultaneously supplied into the plating tank. ) Also, if the refractive index setting value is 11.5Brix% and the refractive index of the plating liquid exceeds this value, signal B is emitted and 10 to 50 m1/l of plating liquid is pumped out each time, and then, As a replenishment agent for pumped consumable medicines, replenishment liquid 8 having the following composition was added in an amount equal to the pumped amount (method of the present invention).
. For comparison, plating was carried out in the same manner as above, except that refractive index measurement was not performed and, therefore, the liquid was not pumped out and the replenishment liquid 8 was not replenished (only the cobalt ion concentration was measured, and the 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 refractive index detector of the present invention. FIG. 4 is a graph showing the relationship between the number of turns of electroless nickel plating and the refractive index. 1...Plating tank, 2...Plating liquid, 3
...Concentration detector, 4...Refractive index 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 refractive index of the plating liquid is measured continuously or intermittently, and it is detected that the measured value exceeds a predetermined refractive index 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 refractive index of the plating solution. and a refractive index detector that emits a signal when the measured value exceeds a predetermined refractive index setting value, and a consumable device that automatically replenishes a replenisher corresponding to the amount consumed by plating based on the signal from the concentration detector. A chemical replenishment replenishment mechanism is activated by a signal from the refractive index detector, and automatically pumps out a portion of the plating solution, and automatically supplies 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.