FR2469466A1 - Automatic adjustment of bath compsn. during electroless plating - where analysis appts. is used to control addn. of replenishing solns. and partial drainage of bath - Google Patents

Abstract

Concn. (A) and the consumed amt. (B) of one or more substances in the bath are measured continuously or intermittently. When value (A) reaches a prescribed level, a solenoid valve is automatically opened, so a replenishing soln. (19) contg. consumable constituents is fed from a tank (20) into the bath. Value (B) indicates the ageing of the bath; and when (B) reaches a prescribed level, a pump (28) is started to remove a prescribed vol. of liq. from the bath and then to open another solenoid valve, so another replenishing soln. (29) contg. non-consumable constituents is fed from a tank (30) into the bath. The metal content in the bath is pref. used to derive values (A,B). Accurate bath control over long periods when depositing Ni, Co, Cu, Sn, Au, Ag etc. is obtd.

Description

"Method and apparatus for controlling baths used
for non-electrolytic coatings.

 The present invention relates to a method for the control of baths used for non-electrolytic coatings, such as electroless nickel plating baths and the apparatus used for this purpose, and more particularly to a process for the controlling baths used for non-electrolytic coatings so that a stable coating can be made continuously for a long time, and an apparatus used for this purpose.

 Baths used for nonelectrolyte coatings (hereinafter referred to as "non-electrolyte coating baths") are subject to wide variations in their composition since a metal salt, a reducing agent or other ingredients are quickly consumed during coating. It is therefore necessary to frequently add these consumed ingredients to obtain a constant deposition rate and the thickness and properties of deposits uniform. For this purpose, a large number of methods and apparatus for automatic control or refilling of nonelectrolyte coating baths have been proposed as disclosed in published Japanese Patent Applications Nos. 53-44434, 53-45631 and 54-8123.

 However, non-electrolytic coating baths such as non-electrolytic nickel baths and non-electrolytic copper plating baths have a short effective life. As the non-electrolytic coating is continued for a prolonged period, the by-products of the reaction accumulate in the coating solution. By-products of the reaction, which are believed to be the decomposition products from the coating reaction, adversely affect factors such as deposition rate and deposition properties. With the accumulated reaction byproducts, the refilling of the ingredients consumed by the coating process can not prevent the decrease of the deposition rate and the variations of the composition and the properties of the deposits. Therefore, although the solutions For non-electrolytic coating, either by the above-mentioned automatic refilling methods or by manual close-ins where necessary, the coating baths become old or unusable in a relatively short time. The deposition rate is considerably reduced and the properties of the resulting deposits vary considerably compared to those obtained with the starting coating solution, even when the metal ion and the reducing agent are reloaded in order to raise their concentration to the level they had in the starting coating solution. Under these conditions, the aged bath must be discarded and replaced with a fresh coating solution.

 Even in the case where the above-mentioned automatic control of a non-electrolytic coating bath is used to automatically refill a coating solution, the degree of aging of the bath must always be controlled separately to account for this aging. Therefore, coating baths must be discarded after a relatively short time of use in the prior art non-electrolytic coating processes combined with the above-mentioned automatic control method. The prior coating process is also not satisfactory with respect to bath maintenance.

 Accordingly, it is an object of the present invention to provide a method and apparatus for controlling a non-electrolytic coating bath for performing a continuous, stable, electroless coating for a period of time. extended without the need for renewing the non-electrolyte coating bath, or at least substantially delaying further manufacture of the coating bath in contrast to the prior art processes, and therefore with significant advantages over the production of the coating bath. 'waste disposal.

 It is another object of the present invention to provide a method and apparatus for controlling a non-electrolytic coating bath to maintain substantially uniform and uniform deposition rate and deposit properties during an extended period, and where bath maintenance is easy and accurate.

 Another object of the present invention is to provide a method and apparatus for non-electrolytic coating control suitable in the practice of non-electrolytic coatings of nickel, cobalt, nickel-cobalt alloy, copper, tin, gold, silver and similar metals.

According to an object of the present invention, there is provided a method for controlling a nonelectrolyte coating bath to use this bath for an extended period of time without having to remake it, the method comprising the following steps
continuously or intermittently measuring the concentration of at least one of the consumable ingredients in the non-electrolyte coating bath, and
- automatic addition to the coating bath of a first refill composition consisting essentially of consumable ingredients after detecting that the measured value has reached a predetermined concentration, during this time,
continuous or intermittent measurement of the degree of aging of the non-electrolytic coating bath, and
- Automatic discharge of a predetermined volume of the coating solution and automatic addition to the coating bath of a second refill composition containing the non-consumable ingredients, in an amount corresponding essentially to the amount lost by the unloading, after having detected that the measured value has reached a predetermined degree of aging.

According to another aspect of the present invention, there is provided an apparatus for controlling a non-electrolytic coating bath to allow the bath to be used for an extended period of time without having to remake it, the apparatus comprising
a mechanism for adding a supplement of a first recharge composition and which comprises
means for automatically measuring the concentration of at least one consumable ingredient in the coating bath, non-electrolytic
concentration detecting means provided for generating a first signal when the measured value has reached a predetermined concentration, and
means for automatically adding the first recharge composition consisting essentially of consumable ingredients to the non-electrolyte coating bath after receipt of the first signal, and
a mechanism for discharging a predetermined volume of non-electrolyte coating solution and for adding a supplement to a second charge composition and which comprises
means for measuring the degree of aging of the non-electrolytic coating bath
aging degree detecting means for generating a second signal when the measured value has reached a predetermined degree of aging;
means for discharging a predetermined volume of the coating solution upon receipt of the second signal, and
means for adding to the nonelectrolyte coating bath the second refill composition, containing non-consumable ingredients, in an amount corresponding substantially to the amount lost by the unloading.

 In the present invention, the term "consumable ingredients" refers to ingredients that are consumed during the non-electrolytic coating, for example a metal ion such as a nickel ion and a reducing agent such as sodium hypophosphite, for the non-electrolytic nickel bath, and the term "non-consumable ingredients" denotes the ingredients which are not particularly consumed during the electroless coating, except by the sensor products, for example a chelating agent such as sodium acetate; sodium, sodium citrate, etc.

 In the preferred embodiments of the present invention, the concentration of the non-electrolyte coating bath is measured in terms of the concentration of a metal in the bath, while the degree of aging of the non-electrolyte coating bath is obtained by measuring a physical property, i.e. the density, the electrical conductivity or the refractive index of the nonelectrolyte coating bath, or by measuring the consumed amount of at least one consumable ingredient, for example an ion metallic, in the bath. In the latter case, the consumed amount of consumable ingredient in the bath can be controlled by counting the number of refills of the first refill composition, which in turn is obtained by counting the number of control signals to control the refill. automatic recharge of the first recharge composition.

 Since the concentration of a nonelectrolyte coating bath; for example, the concentration of the metal in the bath is measured to determine the quantity of consumable ingredients consumed during the coating, and that the first makeup composition consisting essentially of the consumable ingredients is automatically refilled in accordance with the measured value, while a physical property, e.g. the density, electrical conductivity or refractive index of the non-electrolyte coating bath or the consumed amount of a consumable ingredient (eg a metal ion) in the bath is measured to determine the degree of of aging of the bath, and that a predetermined volume of the solution is discharged, and that the second refill composition, containing the non-consumable ingredients, corresponding to the discharged quantity is automatically recharged each time the value of the physical property measured has reached a predetermined level, or that the ingr consumable has been consumed in a predetermined amount (i.e., each time the degree of aging has reached a predetermined value), the bath is automatically reloaded substantially eliminating the need to remake a coating bath, or at least substantially extending the effective life of the bath, unlike the processes of the prior art. In addition, since consumable ingredients such as metal ions, reducing agents, etc., are maintained at substantially constant concentrations and the amount of by-products the reaction from the coating process is maintained within a permissible range, the deposition rate and the properties of the deposits obtained are kept constant and uniform. In a different way, it has been found that the bath is maintained under extremely stable conditions for a prolonged period. It is also possible to keep the coating bath at a lower metal concentration than the prior art bath while maintaining the deposition rate at a level substantially the same as in the prior art. These characteristics are also advantageous from the point of view of waste disposal.

 The present invention can be advantageously applied to non-electrolytic coating baths of nickel, cobalt, nickel-cobalt alloy and copper.

The present invention will be better understood and illustrated by the descriptive and nonlimiting examples given below with reference to the accompanying drawings in which:
FIG. 1 is a block diagram showing an embodiment of the non-electrolytic coating device according to the present invention
FIG. 2 is a block diagram of an example of the device for measuring concentration.
FIG. 3 is a block diagram of the portion of the concentration measuring device comprising a spectrophotometer;
FIG. 4 is a block diagram of an example of the control part of the concentration measuring device.
FIG. 5 is a block diagram of an example of the density measuring device;
FIG. 6 is a block diagram of an example of the device for measuring the electrical conductivity;
FIG. 7 is a block diagram of an example of the device for measuring the refractive index
FIG. 8 is a block diagram showing another embodiment of the non-electrolytic coating device according to the present invention
FIG. 9 is a block diagram of the control part of the concentration measuring device used in the installation of FIG. 8
Fig. 10 is a graph showing the relationship between the number of turns and the electrical conductivity of a non-electrolytic coating bath; and
FIG. 11 is a graph showing the relationship between the number of turns and the refractive index of a non-electrolyte coating bath.

 Referring to FIG. 1, one embodiment of the device for controlling a non-electrolytic nickel bath according to the present invention is schematically shown and comprises: a liner bath container-which is provided with accessories necessary including a heating element for heating the non-electrolytic coating bath 2 to the desired temperature, for example a heater or a steam tube, a cooling element for cooling the bath 2 in the vicinity of the ordinary temperature after the coating is completed , a filter, a stirrer and the like, not shown in the figure.

 In connection with the coating bath container 1, the device comprises a concentration measurement / detection system 3 for automatically measuring the concentration of the coating bath and transmitting the signal A when the measured value has reached the concentration level. predetermined, a system 4 for measuring / detecting a physical property for measuring a physical property of the coating bath to determine the degree of aging of the bath and transmit the signal B when the measured value has reached a predetermined level (or a predetermined degree of aging), a pump 5 for the circulation of fluid in the form of a micro-tube pump, for example, and a channel 6 of circulation communicating the container 1, the measuring devices 3 and 4 / detection and the pump 5.

The coating solution 2 in the container 1 is pumped from the inside through the pipe 6 to the measurement / concentration detection system 3 where the concentration of the coating solution 2, for example the nickel concentration, is measured. and then to the physical property measurement / detection system 4 where the chosen physical property of the coating solution 2 is measured before this solution returns to the container 1 on leaving the pipe 6.

 Figures 2 to 4 show an example of the system 3 for measuring / detecting the concentration. As shown in FIG. 2, the duct 6 is provided with a bypass duct 7 which in turn is provided with a spectrophotometer 8 comprising a continuous flow cell 8a. When the coating solution 2 passes through the bypass conduit 7 and then passes through the continuous flow cell 8a of the spectrophotometer 8, the optical transmission rate of the solution is measured to determine the concentration of the metal in the solution. In this respect, it is preferable to measure the absorbance of a metal complex in the coating solution in order to track metal consumption during coating in a more sensitive manner. The optical transmission rate of the coating solution E the absorption wavelength of the metal complex is converted into a voltage signal by means of a suitable transducer. The concentration of the coating solution 2 is controlled in this way.

 The concentration measurement / detection system is described in detail with reference to FIGS. 3 and 4. As shown in FIG. 3, the light L emitted by a light source 9 into the spectrophotometer 8 passes successively through a radiation absorbing filter 10. a wavelength selective filter 11, and a converging lens 12, before passing through the cell 8a through which the coating solution passes continuously. The absorption of light by the coating solution is detected by a photometer 13. Another cell 8b containing the standard solution is mounted adjacent the cell 8a so that the cells can be placed alternately in the path of the light. The measuring cell 8a and the standard cell 8b can be moved in the direction shown by the arrow.

The standard cell 8b can be moved in the path of light to replace the measuring cell 8a when necessary, thereby measuring the absorbance of the standard solution. The spectrophotometer 8 is electrically connected to the control portion 14. As shown in FIG. 4, a weak intensity output signal of the photometer 13 is sent to an input signal 15, amplified and converted into a voltage by an amplifier 16 and indicated by a voltmeter 17 in the form of a voltage corresponding to the absorbance. A comparator 18 compares the output signal of the amplifier 16 with a displayed voltage and gives the signal A at its output 19 when the output signal of the amplifier reaches the displayed value. If the value of the displayed voltage corresponds to Absorbance at a given concentration, at which the metal ion in the coating solution is consumed, then the signal A developing at the outlet 19 means that the concentration of the metal has reached the given value. The signal A is transmitted to a first charging mechanism 20 which comprises a reservoir 21 containing a first charging composition, a supply line 22 connected to the reservoir 21 and opening into the container 1 for a coating bath, and an electromagnetic valve 23 22. Upon receipt of the signal A, the valve 23 is opened for a given time to allow a predetermined amount of the first refill composition to flow into the coating bath container 1 through the conduit. 22.Thus, the given amount of the first recharge composition consisting essentially of the consumable ingredients, for example a metal salt, a reducing agent, a pH controlling agent and other consumable components, is added to the non-electrolytic coating bath. corresponding to the quantity consumed. It should be noted that although there is only one tank 21 depicted in FIG. 1, a plurality of tanks can be used. Each reservoir contains one of the various consumable ingredients (e.g. a metal salt, a reducing agent, a pH regulating agent and other components). Naturally, each tank has its own pipe and its own solenoid valve.

 By analyzing the metal number, for example the nickel index in a non-electrolytic nickel bath, in this way not only the quantity of the metal consumed during the coating is known, but also the amount of reducing agent consumed. and the variation of the pH are known at the same time.

 In the above embodiment, the absorbance of a coating solution is measured directly to determine the concentration of the metal, such as nickel, in the coating solution. However, the method for measuring the concentration of the metal in the coating solution is not limited thereto, and any other suitable means may be used. For example, an indicator reagent or other suitable reagents such as EDTA may be added to the coating solution to produce the development of a corresponding color in the coating solution. The intensity of the color is measured to determine the metal concentration. In this case, however, those parts of the coating solution that have been subjected to concentration measurements can not be returned to Line 6 through the pipe. The coating solution after the measurement must be sent separately to a suitable unit provided for waste disposal. Another example of concentration measurement is to measure the potential difference between the initial portions and the subsequent portions of the solution. However, the above-described method for directly measuring the absorbance of the coating solution is the most important. advantage of the others because it can be achieved by simple equipment and the coating solution subjected to measurement can return to the container 1 for coating bath. In addition # it is also possible to detect changes in the concentration of a coating solution by measuring changes in the pH thereof. In addition, the measurement of the mentioned nickel concentration can be combined with the pH measurement, so that the pH of the coating solution can be automatically and independently controlled according to the measured pH value.

 Figure 5 shows an example of the system 4 for measuring / detecting the physical property. Line 6 is provided with a bypass conduit 24 with which a unit 25 is combined to measure the density of the non-electrolyte coating solution. The density measuring unit 25 comprises a transparent container 26 placed between the bypass pipe 24 and an overflow tube 27 so that the coating solution 2 flows into the container 26 via the Bypass line 24, exceeds its level and overflows from the container 26 to the downstream part of the branch pipe 24 by the tube -27 overflow when the level of the solution exceeds the inlet of the tube 27 overflow. The level of the coating solution is thus kept constant in the container 26.

The container 26 receives a density measuring apparatus 28 in the form of a hydrometer to measure the density of the coating solution. On opposite sides of the transparent container 26 are placed a light source 29 in the form of a light emitting diode and a photoelectric detector 30 in the form of a phototransistor for receiving the light emitted by the source 29. The photodetector 30 is electrically connected to a control portion 31 in which a small current output signal of the photodetector 30 is sent to an output signal 32 and amplified and converted into a voltage by an amplifier 33. A comparator 34 compares this voltage signal with a displayed voltage value which corresponds to the voltage from the photodetector 30 when it receives the total amount of light emitted by the source 29.If the input voltage is not equal to the displayed voltage, the comparator 34 gives the signal B at exit 35.

 When the coating solution 2 passes through the container 26, the hydrometer 28 rises or falls more or less depending on the density of the solution. When the density of the coating solution 2 is relatively low due to a slight aging, and therefore the top of the hydrometer 28 does not intercept the path of the light connecting the light source 29 and the photodetector 30, this photodetector 30 receives all the amount of light emitted by the source 29 so that the signal B is not generated. As the coating solution ages, its density gradually increases and eventually exceeds the predetermined value. The hydrometer 28 rises further and the top of this hydrometer 28 intercepts the path of the light connecting the light source 29 and the photodetector 30. Since the light emitted by the source 29 is partially or totally intercepted by the top of the hydrometer 28 , the photodetector does not receive at all or a part of the light emitted. The intensity transmitted to the unit 32 by the detector 30 is at least reduced and consequently the signal B develops at the output of the comparator 35.

 In order to measure the density of a coating solution, it is also possible to use means for converting the density of the solution into a voltage, charge or graduation connected to a load cell, and the like.

 Figure 6 shows another example of the system 4 for measuring / detecting the physical property. Line 6 is provided with a bypass line 36 having a unit 37 connected thereto for measuring the electrical conductivity of the coating solution. The conductivity measuring unit 37 comprises a cell 38 connected to the bypass line 36. The cell 38 is constituted by a substantially cylindrical tube 38a closed at both ends and 38b input and 38c output elements connected to the opposite sides of the cylindrical tube 38a. The cylindrical tube 38a is provided near its ends with a pair of electrodes 39a and 39b, made of platinum or platinum-coated platinum black, placed at a given distance from each other and connected to an instrument 41 of electrical conductivity measurement, by the conductors 40a and 40b.

The electrical conductivity of the coating solution 2 in the cell 38 can be determined by measuring the resistance between the electrodes 39a and 39b. In this case, the resistance between the electrodes 39a and 39b can be measured as a variation of the intensity by applying a constant voltage between them or as a variation of the voltage by passing a current of intensity constant between these electrodes.

 The above-mentioned conductivity detector 41 is electrically connected to a control section 42 which includes an amplifier 44, a voltmeter 45 and a comparator 46. The output signal of the detector 41 is transmitted in the form of an intensity or a signal. a voltage at the input 43 of the amplifier 44 where it is amplified and converted into a voltage if it is in the form of an intensity. The voltage thus transformed is indicated by the voltmeter 45 in the form of a variation of the voltage corresponding to the variation of the conductivity and is also transmitted to the comparator 46 where it is compared with a displayed voltage. The comparator 46 generates a signal B at its output 47 when the measured voltage reaches the displayed value.

 Figure 7 shows another example of the system 4 for measuring / detecting the physical property. Line 6 is provided with a bypass line 48 having a unit 49 for measuring the refractive index of the coating solution. The unit 49 is constructed in such a way that the incident light LA emitted by a light source 50 having a condenser, in the direction of a prism 51 placed in the bypass line 48, is entirely reflected at the interface between the prism 51 and the coating solution 2, and the resultant reflected light LB is received by a photometer 52. While the photometer 52 measures the critical light, i.e. the position and therefore the intensity of the light that varies depending on the refractive index of the coating solution 2, a comparator / amplifier 53 is used to actuate a servomotor 50A to move the condenser 50 to adjust or adjust the angle of the light incident LA so that the intensity of the critical light, which otherwise may vary depending on the refractive index of the coating solution, is kept constant.

A variation of the angle of the incident light LA is detected as a potential difference by an angular detector 50b.

The angular detector 50b is electrically connected to a control section 54 which comprises an amplifier 56, a voltmeter 57 and a comparator 58. The output signal of the detector 50b is transmitted as a voltage at the input 55 of the amplifier where it is amplified. The amplified voltage is indicated by the voltmeter 57 in the form of a voltage variation corresponding to the variation of the refractive index and is also transmitted to the comparator 58 where it is compared with a predetermined voltage value. The comparator 58 produces the signal B at its output 59 when the measured voltage reaches the predetermined value. The time during which the increase in the refractive index of the coating solution 2 reaches a predetermined value is the time during which the difference potential corresponding to
a variation of the compensation angle of the light in
Cidente LARfor a displacement of the position of the light
critical value reaches a value of potential difference pre-
determined.

Detection of the refractive index of the solution
coating is not limited to the process mentioned
above but it is also possible to get a signal
electrical output by directly measuring a variation
of the total amount of reflected light by means of
of a photometer, or by directly measuring a displacement
critical light in the form of a variation of the
amount of light.

Referring again to Figure 1, the marker 60
means a discharge mechanism that can be triggered at
the reception of the signal B mentioned above. This mechanism
60 of discharge comprises a discharge pipe 61 having a
end in the fluid communicating with the container 1 for coating bath and a control pump 62 disposed on
the tube. Upon receipt of the signal B from the physical property detector system, the pump 62 operates for a specified time to empty a given volume of the coating solution 2 from the container 1. The mark 63 designates a mechanism for the supply of a second refill composition containing the essential ingredients that are removed by the emptying. The recharge mechanism 63 comprises a reservoir 64 containing the second recharge composition, a feed tube 65 having an end connected to the reservoir 64 and an electromagnetic valve 66 placed on the tube 65. The electromagnetic valve 66> which receives the signal B from the physical property detector system 4, opens for a given time after the drain pump 62 has stopped, thereby to add the second refill composition containing the non-consumable ingredients in the container 1 to a volume essentially corresponding to the volume drained. In this respect, the charging mechanism 63 may comprise a plurality of reservoirs provided for each of the ingredients to be refilled and each comprising its supply tube and its valve.

 In FIG. 1, a refrigerant 67 is provided on the measurement pipe 6 for cooling the current of the coating solution which passes therethrough from the container 1 to the vicinity of the ordinary temperature. A filter is also provided on the pipe 6. 68 to filter out very fine insoluble products from the current of the coating solution passing therethrough. The place of the refrigerant 67 on the pipe 6 upstream of the systems 3 and 4 for measuring / detecting the concentration and the physical property makes it possible to measure the concentration and the physical property at the ordinary temperature because the current of the coating solution through the branch lines 7 and 24, 36 or 48 has been cooled to room temperature. In order to prevent these measurements from being temperature dependent, any other means can be used such as, for example, a constant temperature bath or a probe for temperature accompanied by an electrical compensation.

We will now describe how to order a non-electrolytic nickel bath using the device built above-
A part to be coated is first subjected to the pretreatments well known in a conventional manner before the electroless nickel plating is performed by immersing the pretreated part in the coating bath 2 contained in the container 1, heated to the desired temperature, for example 900C.

 In the practice of such a coating, the pump 5 is operated to introduce a portion of the coating solution 2 from the container 1 into the measurement pipe 6. Since the coating solution continuously passes through the systems 3 and 4 for measuring / detecting the concentration and the physical property, the concentration (nickel concentration in the case of the measurement / concentration detection system 3 shown in FIG. Figure 2) and the physical property (density, conductivity or refractive index) of the solution are automatically measured.

 The progress of the coating results in a decrease in the concentration of the coating solution, particularly the concentrations of the nickel ion and the reducing agent (such as sodium hypophosphite) in the solution. In the case where hypophosphite is used as a reducing agent for non-electrolytic nickel plating, the coating solution also shows a decrease in pH. As a result of this decrease in concentration, when the nickel concentration measured by the spectrophotometer 8 reaches a predetermined concentration value in the case of the concentration measurement / detection system 3 shown in FIG. 2, the associated control section 14 The detector system 3 generates the signal A. In a more detailed manner before measuring the absorbance of the actual coating solution, the cell 8b for the standard solution is displaced in the light path to replace the cell 8a. The absorbance of nickel in the standard solution in cell 8b is measured and the absorbance value thus obtained is displayed in comparator 18 as the reference value. Then, the continuous flow cell 8a is moved in the light path.When the nickel concentration of the solution which is expressed in terms of the absorbance of the coating solution measured by the spectrophotometer 8 reaches the value of the predetermined concentration or when the detected voltage decreases to or below the displayed reference value, the comparator 18 transmits the signal A to the electromagnetic valve 23 of the first charging mechanism 20 to open the valve 23 for a predetermined time. Therefore, a certain amount of the first refill composition is fed from the reservoir 21 into the vessel 1 to compensate for those ingredients consumed during the previous coating process, such as the nickel ion and the reducing agent, and to adjust the pH of the coating bath 2. It should be noted that the first refill composition mainly contains those of the consumable ingredients during coating, including the nickel salt, the reducing agent and the pH regulating agent such as the sodium hydroxide. sodium and optionally small amounts of a complexing agent, stabilizer, brightener, etc. It is generally desired to keep the nickel salt, the reducing agent and the pH control agent separate from one another. In this separate storage, each optional agent such as the complexing agent, the stabilizer and the brightener may be preferably blended with the base ingredient to which it is inert.

 By adding the first refill composition in this way, the concentration of the coating bath 2 (the concentration of nickel, reducing agent, etc.) is raised to the initial level so that the coating or deposit rate is maintained substantially constant.

 As the reaction byproducts accumulate in the coating bath (2) the values of the physical properties such as density, conductivity and refractive index of the coating solution vary. The degree of aging of the coating bath can therefore be determined by measuring a physical property, for example the density, the conductivity or the refractive index of the bath. The density, conductivity and refractive index of the solution can be measured by the system shown in Figures 5, 6 and 7, respectively, as described above. When the measured value reaches a predetermined degree of aging (density, conductivity, or refractive index, predetermined), the physical property detector system 4, more specifically the associated control section 31, 42 or 54 transmits a signal B to the mechanism 60 discharge. On receipt of the signal B, the pump 62 starts to operate for a given time to discharge a given volume of the coating solution of the container 1 through the discharge pipe 61. It should be noted that the liquid removed is sent if Desires for a waste treatment system and the essential ingredients contained therein can be recycled once undesired by-products have been removed. When the pump 62 stops, the electromagnetic valve 66 of the second charging mechanism 63 is open for a given time to supply the container 1 with a given volume of the second composition of refilling from the reservoir 64. It should be noted that this second refill composition provides those ingredients which have been removed during the discharge and mainly contains a complexing agent.Generally, one can use a solution having the same composition as the coating bath initially prepared or its concentrate, or that of solutions mainly containing a complexing agent that is rarely consumed during the coating process.

If the ingredients to be recharged such as metal salt and reducing agent tend to react with each other, it is preferable that they be stored separately in different tanks.

 The charging mechanism 60 may be replaced by an overflow tube 69 as indicated by the dotted line in FIG. 1. In this case the signal B is transmitted from the control section 14 to the second mechanism 63. in order to supply a certain volume of the second refill composition in the coating bath placed in the container 1. Excess volume of the coating solution due to the addition of the second refill composition, is removed by the overflow tube 69.

 The removal of a given volume of the coating solution and the refilling of a volume corresponding substantially to the second refill composition prevents the by-products of the reaction from accumulating in the coating bath to a point undesired, thus allowing the amount of these reaction by-products to be controlled within suitable limits. as a result, a reduction in the coating rate due to the accumulation of reaction by-products is avoided. The coating bath is intermittently renewed in a continuous operation for a prolonged period. During prolonged operation of the coating bath, the deposition rate is kept substantially constant and the deposits are maintained substantially uniform in composition and properties. for example, the composition of the Ni-P alloy comprising a hypophosphite reducing agent and the hardness of the deposits. With respect to these, the inventors of the present invention have found that the accumulation of byproducts of the reaction or the degree of aging of the coating bath can be exactly controlled by following the density, conductivity or index of the coating. When the degree of aging of the coating bath reaches a predetermined value or greater, a portion of the coating bath is discharged and a refill composition containing mainly ingredients which are removed by the discharge is recharged. As a result, the amount of by-product of the reaction is kept substantially constant in the coating bath so that the bath is semi-permanently effective or at least the effective life of this bath is remarkably prolonged compared. to the coating processes of the prior art.

For such extended use of the coating baths, the deposition rate, the quality of the deposits and other factors are kept substantially uniform.

 According to the coating method mentioned above, the coating bath is automatically controlled and maintained in an easy but accurate manner. Of particular importance is the ease of maintenance of electroless plating baths which are particularly troublesome to handle compared to conventional electro-deposition. In addition, since the coating bath is always maintained at a substantially constant concentration by the refill, the nickel concentration of the bath can be set lower initially unlike the prior art which requires having an initial nickel concentration to a higher level to compensate for a decrease in the coating or deposition rate due to the decrease in the nickel concentration as the coating progresses. In the beam, the coating bath is gradually renewed automatically at means of the discharge and filling mechanisms 60 and 63, reducing the overload of waste treatment.

 Figure 8 shows another embodiment of the present invention. This embodiment is essentially the same as the first embodiment shown in Figure 1, except that the physical property detector system is omitted.

A counter 70 and a detector 71 replace this system accordingly and are connected to the control section 14 of FIG. 4 as shown in FIG. 9. The counter 70 counts the number of signal commands A serving to instruct the opening of the electromagnetic valve 23 of the first charging mechanism 20. The number of openings of the electromagnetic valve 23 represents the number of refills of the first composition of refills. A detector 71 is also provided which detects whether the number of signal commands
A (i.e., the number of refills of the first refill composition) reaches a predetermined number. At this moment the detector 71 transmits the signal B from its output 72 to the pump 62 of the discharge mechanism 60 to operate the pump 62 for a predetermined time. Since the remaining components and the construction are the same as in FIGS. 4, the same references designate the same parts and the description thereof is omitted.

 In this embodiment, the general operation is substantially the same as in the first embodiment. The counter 70 counts the number of signal commands A sent to the valve 23 of the first charging mechanism 20, that is to say the number of openings of the valve and consequently the number of refills of the first charging composition.

When the detector 71 detects that the counted number reaches a predetermined number, for example every time one or more signals A are generated, the detector 71 transmits the signal B from its output 72 to the pump 62 of the discharge mechanism 60 to put while running the pump 62 for a given time, thereby discharging a given volume of the coating solution 2 of the container 1 through the discharge pipe 61. The following process is the same as in the first embodiment.

 As described above, the by-products of the reaction accumulate in a coating bath as the coating continues for a period of time.

The accumulated reaction by-products adversely affect the coating speed and the quality of the deposits.

These by-products of the reaction consist mainly of the products of the decomposing reducing agent, when the metal ion in the coating bath is reduced to the elemental metal state by the reducing agent, and by the neutralization from this reaction. In this respect, the amount of reducing agent needed to reduce a certain amount of the elemental metal ion is substantially constant and the amount of reaction by-products from this reduction is also substantially constant. The consumption of a given amount of the metal ion or reducing agent results in the formation of a corresponding amount of reaction byproducts. Therefore, the consumed amount of a consumable ingredient in such a coating bath represents the degree of accumulation of by-products of the reaction in the bath. Therefore, by detecting the consumed amount of at least one consumable ingredient in the bath (e.g., the consumed amount of the metal ion or reducing agent, more specifically the consumed amount of the nickel ion or hypophosphite in the case of non-electrolytic nickel plating using the hypophosphite reducing agent, or in some cases, the amount of caustic alkali consumed), the degree of accumulation of reaction by-products, i.e. the degree of aging of the coating bath, can be accurately detected.In this embodiment, the detection of the number of openings of the valve 23 is equivalent to the detection of the number of refills of the first composition of refills which, in turn, is equivalent to detecting the consumed amount of consumable ingredients during coating. Whenever the number of openings of the valve 23 reaches a predetermined value, a given volume of the coating solution 2 is discharged and a substantially corresponding volume of the second refill composition (mainly containing ingredients which will be removed by the discharge ), is reloaded, thereby maintaining the amount of reaction byproducts within suitable limits in the coating bath. As a result, the coating solution is semi-permanently effective or at least the effective life of the coating is remarkably prolonged compared to the prior art process. In addition, the coating speed and the properties of the deposits are maintained substantially uniform during the prolonged operation of the bath.

 Determining the consumed amount of the consumable ingredients is performed by the method of detecting the number of openings of the valve 23 by counting the number of A signal commands in the above embodiment. If a feed pump is used to refill a determined amount of the first fill composition, the consumed amount of the consumable ingredient can be detected by counting the number of feed pump drives. Any other appropriate detection method may be used for a particular way of recharging. In addition, the consumed amount of the consumable ingredient can also be detected by measuring the amount of metal deposited.If the parts to be coated have a substantially equal specific surface area and the necessary coating time or required deposition thickness is equal for each coating cycle, then a equal amount of metal is reduced and deposited, and an equal amount of the metal ion is consumed in each coating cycle. Thus, the detection method can be to count the number of signals generated by a safety circuit breaker whenever a coated part is replaced by a new uncoated part in the coating bath. If the parts to be coated have a surface substantially equal but that the necessary coating time is not always equal, then the amount of deposited metal can be detected by measuring the duration of the coating process, and the consumed amount of the consumable ingredients can be deduced therefrom. After a certain overall duration, the discharge and recharge operations mentioned above can be performed.

 In the above embodiments, the concentration measuring system is incorporated in the bypass line but may be incorporated directly into the flow line by removing the bypass line. Also, the concentration measuring system can be provided inside the coating bath container.

 Although the physical property measuring systems are incorporated in the bypass line to measure the physical properties of the coating bath such as density, conductivity, refractive index in the above embodiments, these systems can be directly incorporated. in the circulation pipeline by removing the bypass line. Although the measurement of the concentration is followed by the measurement of the physical property in the above embodiments, the order of the measurements is not limited to this, but can be reversed. Moreover, concentration and physical property can be measured in different independent circuits. The physical property measuring system can also be provided in the coating bath container.

 In the embodiments mentioned above, the second charging mechanism 63 acts once the drain pump 62 of the discharge mechanism 60 has been stopped. Alternatively, the recharge mechanism 63 may act by controlling the signal B during or before the drain pump 62 operates. The first and second charging mechanisms 20 and 63 are not limited to the embodiments mentioned above. For example, a distribution pump can be used to feed the first or second refill compositions.

 Although the above achievements relate to the control of electroless nickel plating, similar results can be obtained for other non-electrolytic coatings including the non-electrolytic coating of cobalt and cobalt-nickel as well as the non-electrolytic coating. Copper electrolyte using formalin or hypophosphite as a reducing agent.

 The present invention is illustrated by the descriptive and nonlimiting examples hereinafter.

EXAMPLE 1
The coating is carried out in 100 liters of a non-electrolytic nickel bath having the following composition:
Nickel sulphate (NiSO4.6H2O) 18 g / l
(nickel ion)
Sodium hypophosphite (NaH2PO2H2O) 24 g / l
Sodium succinate 16 g / l
Malic acid 18 g / l
Stabilizer (bp2) 0.003 g / l
pH 5.6
Density, 250C 1,051
Electrical conductivity, 250C 36 mm / cm
Refractive index, 250C 7.4% Brix at a temperature of 900C in an apparatus such as that shown in Figures 1 to 5 while the nickel concentration and the bath density are measured automatically and continuously (the measurement of the concentration nickel is made by measuring the optical transmission rate at 670 nm). It is assumed that the displayed amount of the nickel ion is 4 g / liter. At the moment when the measured nickel concentration has decreased to the displayed level (4 g / l) or below, the signal A is generated to add a first composition of refill consisting of three refill solutions I, II and III mentioned below, in amounts equal to 400 ml (equivalent to 0.2 g / liter of
Ni2 +) by addition. These refill solutions I, II and III are contained in three separate tanks each provided with a supply line and an electromagnetic valve. In response to signal A, the valves are simultaneously open for a period of time to feed the coating bath with equal amounts of each of the refill solutions. It is also assumed that the displayed density is 1.221. When the measured density has increased to the displayed level (1,221), or above, the B signal is generated to remove 5 liters of the coating solution each time before 5 liters of a second refill composition consisting of solution IV having the composition below, are fed (process of the present invention).

 For comparison, the above-mentioned coating process is repeated except that the density measurement is not performed and therefore neither the discharge of the coating solution nor the refilling of the second charging solution. IV are performed. That is, only the nickel concentration is measured and solutions I, II and III are added in ratio (comparative method).

 Once the coating is done, a given number of turns, ("one turn" means the consumption of 4 g of nickel ions / liter of coating bath in a continuous operation, and therefore an increase in the number of turns represents the subsequent aging of the bath), the deposition rate and the composition of the deposition of the Ni-P alloy are determined and give the results indicated in Table 1.

1st composition of recharae
Solution I recharge
Nickel sulphate 225 g / l
Stabilizer (Pb2 +) 0.075 g / l
Solution II recharge
Sodium hypophosphite 270 g / l
Solution III recharge
Sodium hydroxide 68 g / l 2nd charging solution (composition) IV
The same ccccosition as the initial coating solution
Sodium succinate 16 g / l
Malic acid 18 g / l
Nickel sulphate 18 g / l
Sodium hypophosphite 24 g / l
Stabilizer (pb2 +) 0.003 g / l
TABLE 1

<tb><SEP> Number <SEP> of <SEP> Speed <SEP> of <SEP> Deposit <SEP> Rate <SEP> of <SEP> P <SEP> in <SEP><SEP> Deposit
<tb><SEP> Ni-P
<tb><SEP> rounds <SEP> (m / <SEP> hour <SEP>(#<SEP><SEP> in <SEP> weight)
<tb><SEP> Present <SEP> Test <SEP> Present <SEP> Test
<tb><SEP> invention <SEP> comparative <SEP> invention <SEP> comparative <SEP>
<tb> 2 <SEP> 20.0 <SEP> 20.0 <SEP> 7.8 <SEP> 7.8
<tb><SEP> 4 <SEP> 20.0 <SEP> 17.0 <SEP> 8.2 <SEP> 8.4
<tb><SEP> 6 <SEP> 200 <SEP> 13.5 <SEP> 8t2 <SEP> 912
<tb><SEP> 8 <SEP> 19.8 <SEP> 10.0 <SEP> 8.2 <SEP> 9.8
<tb><SEP> 10 <SEP> 19.8 <SEP> 8.5 <SEP> 8.2 <SEP> 10.4
<tb><SEP> 12 <SEP> 19.8 <SEP> no <SEP> coated <SEP> 8.2 <SEP>
<tb><SEP> 14 <SEP> 19.6 <SEP> 8.2
<tb><SEP> 16 <SEP> 19.6 <SEP> 8.2
<tb><SEP> 18 <SEP> 19.4 <SEP> 8.2
<tb><SEP> 20 <SEP> 19.4 <SEP> 8.3
<tb><SEP> 22 <SEP> 19.2 <SEP> 8.3
<tb><SEP> 24 <SEP> 19.0 <SEP> 8.3
<tb><SEP> 26 <SEP> 18.8 <SEP> 8.3
<tb> 28 <SEP> 1818 <SEP> 8
<tb><SEP> 30 <SEP> 18.8 <SEP> 8.3
<tb><SEP> 32 <SEP> 18.6 <SEP> 8.3
<tb><SEP> 34 <SEP> 18.6 <SEP> 8.3
<tb><SEP> 36 <SEP> 18.4 <SEP> 8.3
<tb><SEP> 38 <SEP> 18.2 <SEP> 8.4
<tb><SEP> 40 <SEP> 18.0 <SEP> 8.4
<Tb>
EXAMPLE 2
The coating is carried out in a non-electrolytic cobalt bath having the composition below as well as the chemical and physical properties
Cobalt sulphate (CoS04.7H2O) 22.5 g / l
Sodium hypophosphite (NaH2PO2H2O) 22.5 g / l
Sodium tartrate 115.0 g / l
Boric acid 8.4 g / l
Thiourea 0,01 g / i
pH 9.0
Density, 250C 1,036
Electrical conductivity, 250C 26 mm / cm
Refraction module, 25 "C 5.3 g Brix at a temperature of 900 ° C., in a device shown in Figures 1 to 5, while the cobalt concentration and the bath density are measured automatically and continuously. assumes that the displayed amount of the cobalt ion is 4 g / liter.When the measured cobalt concentration has decreased to the displayed amount (4 g / liter) or below, the A signal is generated to add a first charge composition constituted by the three charging solutions V, VI and VII mentioned below in equal amounts of 2 ml per liter of the bath for each addition.These charging solutions V, VI and VII are contained in three reservoirs. Each of them has a supply line and an electromagnetic valve in response to the signal A. The valves are simultaneously open for a given time to supply equal amounts of each of the solutions V, VI and VII. It is also assumed that the density displayed is 1.125. At the moment when the measured density has become equal to or greater than the displayed level (1,125), the B signal is transmitted for the discharge of 10 to 50 ml / liter of the coating bath each time before the corresponding amount of a second composition of recharge consisting of the solution VIII having the composition below, is fed. (Process of the present invention)

 For comparison, the aforementioned coating method is repeated except that density measurement is not performed, and therefore neither the discharge of the coating solution nor the refilling of the second solution. charging VIII are not performed. That is, only the concentration of cobalt is measured and solutions V, VI and VII are added accordingly. (Comparative method)

 Once the coating has been carried out, a given number of turns (by "turn" means the consumption of 4 g of the cobalt ion per liter of coating bath in a continuous coating process), the rate of deposition and the composition of the deposit of the Co-P alloy are determined and give the results mentioned in Table 2.

First recharge position
Solution V recharge
Cobalt sulphate 240 g / l
Thiourea 0.11 g / l
VI recharge solution
Sodium hypophosphite 270 g / l
Solution VII recharge
Sodium hydroxide 68 g / l
Second charging solution VIII
Sodium tartrate 115 g / l
Boric acid 8.4 g / l
TABLE 2

Number <SEP> Speed <SEP> of <SEP> depot <SEP> Content <SEP> in <SEP> P <SEP> in
<tb><SEP> of <SEP> turns <SEP> (m / @ time) <SEP><SEP> Deposit <SEP> Co-P
<tb> (% <SEP> in <SEP> weight)
<tb> present <SEP> test <SEP> present <SEP> test
<tb> invention <SEP> comparative <SEP> invention <SEP> comparative
<tb> 1 <SEP> 14.7 <SEP> 14.5 <SEP> 4.7 <SEP> 4.3
<tb> 2 <SEP> 14.6 <SEP> 14.0 <SEP> 4.7 <SEP> 4.4
<tb> 3 <SEP> 14.0 <SEP> 13.3 <SEP> 4.8 <SEP> 4.8
<tb><SEP> 4 <SEP> 14.0 <SEP> 12.8 <SEP> 4.8 <SEP> 5.2
<tb><SEP> 5 <SEP> 13.7 <SEP> 11.1 <SEP> - <SEP> 5.7
<tb><SEP> 6 <SEP> l3g4 <SEP> 9t1 <SEP> 5.0 <SEP> 5.8 <SEP>
<tb><SEP> 7 <SEP> 13.0 <SEP> 6.3 <SEP> - <SEP><SEP> 6X4 <SEP>
<tb> 8 <SEP> 13.8 <SEP> no <SEP> coated <SEP> 5.4 <SEP>
<tb><SEP> 9 <SEP> 12.7 <SEP>
<tb><SEP> 10 <SEP> 12.2 <SEP> 5.4
<tb><SEP> it <SEP> 1211 <SEP>
<tb><SEP> 12 <SEP> 11.9 <SEP> 5.5
<tb><SEP> 13 <SEP> $ 11, 5 <SEP>
<tb><SEP> 14 <SEP> 11.2 <SEP> 518
<tb><SEP> 15 <SEP> 11.0
<tb><SEP> 16 <SEP> 10p7 <SEP> I <SEP>
<Tb>
EXAMPLE 3
Using 100 liters of the same electroless nickel bath as in Example 1 and apparatus shown in Figures 1 to 4 and 6, the general method of Example 1 is repeated except that the electrical conductivity of the bath is measured at place of density. In this example, the displayed conductivity is assumed to be 50 millimhos (m #) per centimeter. The signal B is transmitted at the moment when the measured conductivity is raised to the displayed value (50 millimhos / cm) or has become higher.

 The results obtained are shown in Table 3 together with the results of a comparative coating process without controlling the conductivity.

TABLE 3

Number <SEP> of <SEP> Speed <SEP> of <SEP> depot <SEP> Content <SEP> in <SEP> P
<tb> rounds <SEP> in <SEP> the <SEP> depot <SEP> Ni-p
<tb><SEP> (in / <SEP> hour) <SEP> (% <SEP> in <SEP> weight)
<tb><SEP> Present <SEP> Trial <SEP> Present <SEP> Trial
<tb><SEP> invention <SEP> comparative <SEP> invention <SEP> comparative
<tb><SEP> 2 <SEP> 20.6 <SEP> 2010 <SEP> 7t8
<tb><SEP> 4 <SEP> 20t0 <SEP> 17 <SEP> 0 <SEP> 8.0 <SEP> 8t4 <SEP>
<tb><SEP> 6 <SEP> 19.8 <SEP> 13.5 <SEP> 8.0 <SEP> 9.2
<tb><SEP> 8 <SEP> 19.8 <SEP> 10.0 <SEP> 8.0 <SEP> 9.8
<tb><SEP> 10 <SEP> 19.8 <SEP> 8t5 <SEP> 8t0 <SEP><SEP> 10.4 <SEP>
<tb><SEP> 12 <SEP> 19.6 <SEP> no <SEP> coated <SEP> 8.0
<tb><SEP> 14 <SEP> 19.6 <SEP> 8.1
<tb><SEP> 16 <SEP> 19.6 <SEP> 8.1
<tb><SEP> 18 <SEP> 19t6 <SEP> 8t1
<tb><SEP> 20 <SEP> 194 <SEP> 8X1 <SEP>
<tb><SEP> 22 <SEP> 19.4 <SEP> 8.2
<tb><SEP> 24 <SEP> 1912 <SEP> 812
<tb><SEP> 26 <SEP> 19.2 <SEP> 8.2
<tb><SEP> 28 <SEP> 19.2 <SEP> 8.2
<tb><SEP> 30 <SEP> 1910 <SEP> 812
<tb><SEP> 32 <SEP> 19.0 <SEP> 8.2
<tb><SEP> 34 <SEP> 19.0 <SEP> 8.2
<tb><SEP> 36 <SEP> 18.8 <SEP> 8.2
<tb><SEP> 38 <SEP> 18.8 <SEP> 8.2
<tb><SEP> 40 <SEP> 18.6 <SEP> 8.3
<Tb>
FIG. 10 is a graph showing the relationship between the number of turns and the electrical conductivity (mm / cm) of the non-electrolytic nickel bath having the composition described above (250C measurement temperature) .The results of FIG. 10 show that the conductivity increases in a linear manner as the number of turns, and hence the degree of aging of the non-electrolytic nickel bath increases. This proves that the degree of aging of a coating bath can be exactly controlled by the measurements of the conductivity of this bath.

EXAMPLE 4
Using the same electroless cobalt bath as in Example 2, and apparatus shown in Figures 1 to 4 and 6, the general method of Example 2 is repeated except that the electrical conductivity of the bath is measured. instead of density. In this example, the displayed conductivity is assumed to be 35 millimhos / cm. The signal B is transmitted at the moment when the measured conductivity has become equal to or greater than the displayed value (35 millimhos / cm).

 The results obtained are shown in Table 4 together with the results of a comparative coating process without conductivity control.

TABLE 4

<tb> Number <SEP> of <SEP> Speed <SEP> of <SEP> depot <SEP>
<tb><SEP> turns <SEP> in <SEP> the <SEP> repository <SEP> Co-p
<tb><SEP> (m / <SEP> hour) <SEP> (% <SEP> in <SEP> weight)
<tb><SEP> Present <SEP> Try <SEP> Present <SEP> Try
<tb><SEP> invention <SEP> comparative <SEP> invention <SEP> comparative
<tb><SEP> 1 <SEP> 14.6 <SEP> 14.5 <SEP> 4.4 <SEP> 4.3
<tb><SEP> 2 <SEP> 14X4 <SEP> 1410 <SEP> 4 <SEP><SEP> t <SEP> 5 <SEP> 4,4 <SEP>
<tb><SEP> 3 <SEP> 14.4 <SEP> 13.3 <SEP> 4.7 <SEP> 4.8
<tb><SEP> 4 <SEP> 14.0 <SEP> 12.8 <SEP> 4.8 <SEP> 5.2
<tb><SEP> 5 <SEP> 13.8 <SEP> 11.1 <SEP> 4.9 <SEP> 5.7
<tb><SEP> 6 <SEP> 13.6 <SEP> 9.1 <SEP> 5.1 <SEP> 5.8
<tb><SEP> 7 <SEP> 13.2 <SEP> 6.3 <SEP> 5.1 <SEP> 6.4
<tb><SEP> 8 <SEP> 13.2 <SEP> no <SEP> coated <SEP> 5t2
<tb><SEP> 9 <SEP> 13.0 <SEP> 5.2
<tb><SEP> 10 <SEP> 12.6 <SEP> 5.4
<tb><SEP> 11 <SEP> 12.4 <SEP> 5.5
<tb><SEP> 12 <SEP> 12r4 <SEP> 5.6
<tb><SEP> 13 <SEP> 1250 <SEP> 5.6 <SEP>
<tb><SEP> 14 <SEP> 11.6 <SEP> 5.7
<tb><SEP> 15 <SEP> 11.4 <SEP> 5.7
<tb><SEP> 16 <SEP> 11.4 <SEP> 5.8
<Tb>
EXAMPLE 5
Using 100 liters of the same electroless nickel bath as in Example 1 and apparatus as shown in Figures 1 and 4 and 7, the general method of Example 1 is repeated except that the refractive index of the bath is measured in place of density. In this example, the displayed refractive index is assumed to be 16% Brix. The signal B is transmitted at the moment when the refractive index measured is equal to or greater than the displayed value (16% in Brix).

 The results obtained are shown in Table 5 together with the results of a comparative coating process without control of the refractive index.

TABLE 5

<SEP> Number <SEP> of <SEP> Content <SEP> in <SEP> P
<tb> Speed <SEP> of <SEP> Deposit
<tb><SEP> in <SEP> the <SEP> depot <SEP> Ni-P
<tb><SEP> rounds <SEP> (m / hour) <SEP> (% <SEP> in <SEP> weight)
<tb><SEP> Present <SEP> Try <SEP> Present <SEP> Try <SEP>
<tb><SEP> invention <SEP> comparative <SEP> invention <SEP> comparative
<tb><SEP> 2 <SEP> 20.5 <SEP> 20.0 <SEP> 7.8 <SEP> 7.8
<tb><SEP> 4 <SEP> 20.0 <SEP> 17.0 <SEP> 8.0 <SEP> 8.4
<tb><SEP> 6 <SEP> 19.8 <SEP> 13.5 <SEP> 8.0 <SEP> 9.2
<tb> 8 <SEP> 19.8 <SEP> 10.0 <SEP> 7.9 <SEP> 9.8
<tb><SEP> 10 <SEP> 19.6 <SEP> 8.5 <SEP> 7.9 <SEP> 10.4
<tb><SEP> 12 <SEP> 19.6 <SEP> no <SEP> coated <SEP> 7.9 <SEP> 14 <SEP> 19.4 <SEP> 7.9
<tb><SEP> 16 <SEP> 19.4 <SEP> 7.9
<tb><SEP> 18 <SEP> 19t4 <SEP>
<tb><SEP> 20 <SEP> 19.2 <SEP> 7.8
<tb><SEP> 22 <SEP> 19.2 <SEP> 7.8
<tb><SEP> 24 <SEP> 1910 <SEP> 718 <SEP>
<tb> 26 <SEP> 19 <SEP> 0 <SEP> 78 <SEP>
<tb><SEP> 28 <SEP> 18.8 <SE> 7.8
<tb><SEP> 30 <SEP> 18.6 <SEP> 7.7
<tb><SEP> 32 <SEP> 18.4 <SEP> 7.7
<tb><SEP> 34 <SEP> 18.4 <SEP> 7.7
<tb><SEP> 36 <SEP> 18 <SEP> 2
<tb><SEP> 38 <SEP> 18 <SEP><SEP> O <SEP> 7t6
<tb><SEP> 40 <SEP> 17d6 <SEP> 7.6
<Tb>
FIG. 11 is a graph showing the relationship between the number of revolutions and the refractive index (% in Brix) of the non-electrolytic nickel bath having the composition described above (measurement temperature 250C). Fig. 11 shows that the refractive index increases in a linear manner as the number of revolutions, and hence the degree of aging of the non-electrolytic nickel bath, increases. This proves that the degree of aging of a coating bath can be exactly controlled by the measurement of its refractive index.

EXAMPLE 6
Using the same non-electrolytic cobalt bath as in Example 2 and apparatus as shown in Figures 1 to 4 and 7, the general method of Example 2 is repeated except that the refractive index of the bath is measured in place of density. In this example, the displayed refractive index is assumed to be 11.5% Brix. The signal B is transmitted at the moment when the refractive index measured has become equal to or greater than the displayed value (11.5 7s in Brix)
The results obtained are shown in Table 6 together with the results of a comparative coating process without control of the refractive index.

TABLE 6

<tb><SEP> Number <SEP> of <SEP> Content <SEP> in <SEP> P
<tb> Speed <SEP> of <SEP> depot <SEP> in <SEP><SEP> depot <SEP> Co-P
<tb> towers
<tb><SEP> (m / hour) <SEP> (% <SEP> in <SEP> weight)
<tb><SEP> Present <SEP> Try <SEP> Present <SEP> Try
<tb><SEP> invention <SEP> comparative <SEP> invention <SEP> comparative
<tb><SEP> 1 <SEP> 14.6 <SEP> 14.5 <SEP> 4.4 <SEP> 4.3
<tb><SEP> 2 <SEP> 14.3 <SEP> 14.0 <SEP> 4.5 <SEP> 4.4
<tb><SEP> 3 <SEP> 14.0 <SEP> 13.3 <SEP> 4.7 <SEP> 4.8
<tb><SEP> 4 <SEP> 13.6 <SEP> 12.8 <SEP> 4.8 <SEP> 5.2
<tb><SEP> 5 <SEP> 13t4 <SEP> 11t1 <SEP> 4X8 <SEP> 5.7 <SEP>
<tb><SEP> 6 <SEP> 13.0 <SEP> 9x1 <SEP> 4t9 <SEP>
<tb><SEP> 7 <SEP> 12.4 <SEP> 6.3 <SEP> 4.9 <SEP> 6.4
<tb><SEP> 8 <SEP> 12 # 4 <SEP><SEP> no <SEP> coated <SEP> 5.0 <SEP>
<tb><SEP> 9 <SEP> 12.2 <SEP> 5.0
<tb><SEP> 10 <SEP> 11.6 <SEP> 5.1
<tb><SEP> 11 <SEP> 11.4 <SEP> 5.2
<tb><SEP> 12 <SEP> 11 <SEP> 0 <SEP> 512 <SEP>
<tb><SEP> 13 <SEP> 11.0 <SEP> 5.3
<tb><SEP> 14 <SEP> 10.6 <SEP> 5.3
<tb><SEP> 15 <SEP> 10.2 <SEP> 5.5
<tb><SEP> 16 <SEP> 9.6 <SEP> 5.5
<Tb>
EXAMPLE 7
Using 100 liters of the same electroless nickel bath as in Example 1 and apparatus as shown in Figures 2, 3, 8 and 9, the general procedure of Example 1 is repeated except that the measurement of In this example, the signal B is transmitted whenever 1 g / l of the nickel ion is consumed or a total amount of the refill solution I reaching 1 g / liter of the nickel ion is recharged.

 The results are shown in Table 7 together with results of a comparative coating process in which neither the coating bath discharge nor the refilling of the second IV refill solution are performed.

TABLE 7

<tb> Number <SEP> of <SEP> Content <SEP> in <SEP> P
<tb><SEP> Speed <SEP> of <SEP> Deposit
<tb><SEP> turns <SEP> in <SEP> the <SEP> depot <SEP> Ni-p
<tb><SEP> (m / <SEP> hour) <SEP> (% <SEP> in <SEP> weight)
<tb><SEP> Present <SEP> Trial <SEP> Present <SEP> Trial
<tb><SEP> invention <SEP> comparative <SEP> invention <SEP> comparative
<tb><SEP> 2 <SEP> 20.5 <SEP> 20.0 <SEP> 7.8 <SEP> 7.8
<tb><SEP> 4 <SEP> 20.0 <SEP> 17.0 <SEP> 8.0 <SEP> 8.4
<tb><SEP> 6 <SEP> 19.8 <SEP> 13.5 <SEP> 8.1 <SEP> 9.2
<tb><SEP> 8 <SEP> 19.7 <SEP> 10.0 <SEP> 8.2 <SEP> 9.8
<tb><SEP> 10 <SEP> 19.5 <SEP> 8.5 <SEP> 8.3 <SEP> 10.4
<tb><SEP> 12 <SEP> 19.3 <SEP> no <SEP> coated <SEP> 8 <SEP> 3 <SEP>
<tb><SEP> 14 <SEP> 19.1 <SEP> 8.4
<tb><SEP> 16 <SEP> 19.0 <SEP> 8.5
<tb><SEP> 18 <SEP> 18.9 <SEP> 8.6
<tb><SEP> 20 <SEP> 18.8 <SEP> 8.5
<tb><SEP> 22 <SEP> 18.6 <SEP> 8.7
<tb><SEP> 24 <SEP> 18.4 <SEP> 8.7
<tb><SEP> 26 <SEP> 18.5 <SEP> 8.8
<tb><SEP> 28 <SEP> 1813 <SEP> 9t0
<tb><SEP> 30 <SEP> 18.0 <SEP> 8.9
<tb><SEP> 32 <SEP> 17.9 <SEP> 9.1
<tb><SEP> 34 <SEP> 1717
<tb><SEP> 36 <SEP> 17.4 <SEP> 9.3
<tb><SEP> 38 <SEP> 17 <SEP> 2 <SEP> 9T5
<tb><SEP> 40 <SEP> 16.7 <SEP> 9.6
<Tb>
EXAMPLE 8
Using the same non-electrolytic cobalt bath as in Example 2 and apparatus as shown in Figures 2, 3, 8 and 9, the general method of Example 2 is repeated except that density measurement In this example, signal B is transmitted whenever 1 g / liter of the cobalt ion is consumed or a total amount of the refill solution up to 1 g / liter of the cobalt ion is recharged.

 The results obtained are shown in Table 8 together with the results of a comparative coating process in which neither the coating bath discharge, nor the recharge of the second charging solution VIII are performed.

TABLRAU 8

<tb><SEP> Content <SEP> in <SEP> P
<tb><SEP> Number of <SEP><SEP> Speed of <SEP> Deposit
<tb> turns <SEP> in <SEP> the <SEP> repository <SEP> Co-p
<tb><SEP> (m / hour) <SEP> (% <SEP> in <SEP> weight)
<tb> Present <SEP> test <SEP> Present <SEP> test
<tb><SEP> invention <SEP> comparative <SEP> invention <SEP> comparative
<tb><SEP> 1 <SEP> 14.7 <SEP> 14.5 <SEP> 4.4 <SEP> 4.3
<tb><SEP> 2 <SEP> 14.4 <SEP> 14.0 <SEP> 4.4 <SEP> 4.4
<tb><SEP> 3 <SEP> 13.8 <SEP> 13.3 <SEP> 4.6 <SEP> 4.8
<tb><SEP> 4 <SEP> 13.3 <SEP> 12.8 <SEP> 4.8 <SEP> 5.2
<tb><SEP> 5 <SEP> 13.0 <SEP> 11.1 <SEP> - <SEP> 5.7
<tb><SEP> 6 <SEP> 12.7 <SEP> 9.1 <SEP> 5.2 <SEP> 5.8
<tb><SEP> 7 <SEP> 12.3 <SEP> 6.3 <SEP> - <SEP> 6.4
<tb><SEP> 8 <SEP> 12.0 <SEP> 3.6 <SEP> 5.5 <SEP> 7.1
<tb><SEP> 9 <SEP> 11.6 <SEP> no <SEP> coated <SEP> - <SEP>
<SEP> 10 <SEP> 11.0 <SEP> 5.7
<tb><SEP> 11 <SEP> 10.4 <SEP>
<SEP> 12 <SEP> 9.8 <SEP> 6.0
<tb><SEP> 13 <SEP> 9.6 <SEP>
<tb><SEP> 14 <SEP> 9.0 <SEP> 6.2
<tb><SEP> 15 <SEP> 8.4 <SEP>
<tb><SEP> 16 <SEP> 7.6 <SEP> 6.4
<Tb>
As can be seen from the results of Tables 1-8, the present invention is advantageous because the effective life of a non-electrolyte coating bath is substantially prolonged compared to the prior art process. In addition, the deposition rate and the physical properties of the deposits are substantially uniform and important, and the coating baths can be kept extremely stable for a prolonged period of time since their metallic value, the reducing agent and other ingredients are maintained at high concentrations. substantially constant and the amount of by-products of the reaction resulting from the coating process is kept within acceptable limits.

Claims (16)

 1. A method for controlling a bath for non-electrolytic coating to use the bath for a prolonged period without having to reconstitute it, characterized in that this process comprises the following stages  measuring continuously or intermittently the concentration of at least one consumable ingredient in the non-electrolytic coating bath; and  automatic addition to the coating bath of a first refill composition consisting essentially of consumable ingredients after detecting that the measured value has reached a predetermined concentration; while continuously measuring, or intermittently, the degree of aging of the non-electrolytic coating bath, and automatically discharging a predetermined volume of the coating solution and automatically adding to the bath for coating a second refill composition containing the non-consumable ingredients in an amount substantially corresponding to the amount removed by the discharge after sensing that the measured value has reached a predetermined degree of aging.  2. A process according to claim 1, characterized in that the concentration of the non-electrolytic coating bath is measured in terms of the concentration of a metal in the bath.  3. A process according to one of claims 1 and 2, characterized in that the degree of aging of the nonelectrolyte coating bath is measured in terms of a physical property selected from density, electrical conductivity and refractive index.  4. A process according to one of claims 1 and 2, characterized in that the degree of aging of the coating bath non-electrolytic is measured by determining the consumed amount of at least one consumable ingredient in the bath.  5. A process according to claim 4, characterized in that the consumable ingredient chosen to measure the consumed amount is a metal ion.  6. A process according to one of claims 4 and 5, characterized in that the consumed amount of the consumable ingredient in the bath is controlled by counting the number of refills of the first refill composition and that the predetermined volume of the coating solution is discharged after detecting that the number of refills has reached a predetermined value.  7. A method according to claim 6, characterized in that the number of refills of the first refill composition is obtained by counting the number of control signals to control the automatic refill of the first refill composition.  8. A process according to any one of claims 1 to 7, characterized in that the bath for non-electrolytic coating is chosen from baths for nickel plating, cobalting, coating of a nickel-cobalt alloy and copper plating, non-electrolytic way.  9. Apparatus for controlling a bath for non-electrolytic coating to use the bath for a prolonged period without having to reconstitute it, characterized in that the apparatus comprises  a mechanism for providing a supplement of a first recharge composition and which comprises  means for automatically measuring the concentration of at least one consumable ingredient in the non-electrolytic coating bath,  concentration detecting means for generating a first signal when the measured value has reached a predetermined concentration, and  means for automatically adding to the non-electrolytic coating bath the first refill composition, consisting essentially of consumable ingredients upon receipt of the first signal; and  a mechanism for discharging a predetermined volume of the coating solution non-electrolytically and providing a supplement of a second charging composition; and that includes  means for measuring the degree of aging of the non-electrolytic coating bath,  means for detecting the degree of aging for generating a second signal when the measured value has reached a predetermined degree of aging;  means for discharging a predetermined volume of the coating solution upon receipt of the second signal, and  means for adding to the non-electrolytic coating bath the second refill composition containing non-consumable ingredients in an amount substantially corresponding to the amount removed by the discharge.  10. Apparatus according to claim 9, characterized in that the means measuring the concentration are designed to determine the absorbance of a metal in the bath for coating electrolessly.  11. Apparatus according to one of claims 9 and 10, characterized in that the means measuring the degree of aging are designed to determine the density of the coating bath non-electrolytic way.  12. Apparatus according to one of claims 9 and 10, characterized in that the means measuring the degree of aging are designed to determine the electrical conductivity of the coating bath by non-electrolytic route.  13. Apparatus according to one of claims 9 and 10, characterized in that the means measuring the degree of aging are designed to determine the refractive index of the nonelectrolyte coating bath.  14. Apparatus according to one of claims 9 and 10, characterized in that the means measuring the degree of aging are designed to determine the consumed amount of at least one consumable ingredient of the coating bath.  15. Apparatus according to claim 14, characterized in that the means for determining the amount consumed is a means for counting the number of refills of the first refill composition.  16. Apparatus according to claim 15, characterized in that the counting means of the number of refills is designed to count the number of control signals for ordering the automatic refill of the first refill composition.