JPH10121256A - Electroless plating method and device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the electroless plating method and device by which the film forming rate of electroless plating is increased as compared with the conventional electroless plating technique, and hence the productivity is improved. SOLUTION: In this electroless plating method, an electroless plating bath is kept at >95 deg.C, the atmosphere pressure of the bath is made identical to or higher than the saturated vapor pressure of the bath, and the electroless plating device is provided with an electroless plating tank and a means for heating the bath. In this case, the electroless plating tank 10 is set in a pressure space V, and the tank is formed by a pressure vessel.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for electroless plating, and more particularly to a method for improving the surface of a material in various industrial fields (e.g., abrasion resistance, corrosion resistance, electromagnetic properties, solderability, bonding property). Electroless plating method and apparatus applied to imparting or improving optical properties, heat resistance, design properties, etc.), in particular, a high deposition rate, and suitable as a non-magnetic under plating method for a magnetic disk. It belongs to the technical field of methods.

[0002]

2. Description of the Related Art Electroless plating is a wet type film forming process similar to electroplating, and is used for electronics, home appliances, machinery and precision products, automobiles, bicycles, bicycles, sports and leisure, aerospace, and architecture.・ In the various industrial fields such as civil engineering, the surface of the material is highly functionalized (abrasion resistance, corrosion resistance, electromagnetic characteristics such as magnetic recording, solderability,
Attention has been paid to this as means for imparting or improving bonding properties, optical properties, heat resistance, design properties, and the like, and the frequency of use thereof has been increasing. Along with this increase in use, there is a demand for increasing productivity and increasing plating speed for reducing plating cost as common needs.

In particular, in recent years, in the field of magnetic disks and the like, the pursuit of ease of use, high reliability, and low price of magnetic disks has been pursued. In plating, there is a strong demand for improvement of a plating film such as improvement of impact resistance (reduction of film defects such as pinholes) and an increase in plating speed.

As described above, electroless plating is attracting attention and is used because electroless plating has the following features.
Because there is. In electroplating, metal ions in a solution are reduced and precipitated by electrons supplied from an external power source.In electroless plating, a metal / alloy plating film is deposited by a chemical reaction from a solution in which a metal salt and a reducing agent coexist. is there. Therefore, in the electroless plating, a counter electrode and an external power supply, which are indispensable for the electroplating, are not required, and the film can be formed simply by immersing the material to be plated in the solution. In addition, electroless plating is excellent in principle in terms of throwing power and uniformity of film thickness, and each part is uniformly plated regardless of the shape of the material to be plated. In particular, non-magnetic undercoats for magnetic disks are strictly required to have uniform film thickness, and electroless plating is suitable for ensuring this film thickness uniformity. Electroless plating can also be performed on non-conductive surfaces such as ceramics and plastics.

[0005] However, although electroless plating has such features, the film forming speed is generally lower than that of electroplating. For example, in the case of Ni-P plating, the film forming speed of electroless plating is lower than that of electroplating. Is as small as 1/3 to 1/6 of the film formation rate, which causes a decrease in productivity and a higher cost. Therefore, an improvement in the film formation rate is desired and has been a problem.

Incidentally, many research reports have been made on the electroless plating technique. For example, “Electroless Plating-Fundamentals and Applications-: Electroplating Study Group Edition / Published by Nikkan Kogyo Shimbun (1994)” contains knowledge including the latest results from the principles of electroless plating. References are introduced.

As can be seen from the above, the prior arts proposed to solve the problem of improving the film forming rate of the electroless plating include (A) stirring of a plating bath and (B) control of a plating bath temperature. Alternatively, (C) measures have been taken such as adjusting the pH and the concentration of the reducing agent, and adjusting the composition of the plating bath such as addition of various chemicals (buffers, complexing agents). Note that, in many cases, electroplating can increase the film formation rate more than electroless plating. Therefore, depending on the application (D), use or attempt to use electroplating instead of electroless plating ( Switching to electroplating).

[0008]

However, in the above-mentioned prior arts (A) and (B), there is a problem that the film formation rate of electroless plating is still insufficiently improved as described below.

(A): In the case of plating bath stirring, the limit level is reached by air stirring method or spin plating method (for example, JP-A-64-55386), and there is little room for improvement. The improvement of the plating film formation rate is still insufficient.

(B): The control of the plating bath temperature also
In many cases, the plating temperature is already about 90 ° C., which is the upper limit value of the practical plating bath temperature, which has reached the applicable limit, and the improvement of the film formation rate of electroless plating is still insufficient. That is,
Increasing the plating bath temperature is effective in increasing the deposition rate, but electroless plating is performed at a practical upper limit (90 ° C) of the plating bath temperature from the viewpoint of avoiding mist generation and evaporation of the plating bath. Since the film forming rate is limited by the upper limit (90 ° C.), the improvement of the film forming rate of the electroless plating is still insufficient.

On the other hand, the conventional techniques (C) and (D) have the following problems. That is, the adjustment of the plating bath composition of (C) has a problem that various negative effects (such as shortening of the life of the plating bath and instability) are caused by changing the plating bath composition. Regarding the switch to (D) electroplating, it is often difficult to switch from electroless plating to electroplating because electroplating is poor in throwing power and uniformity of film thickness.

The present invention has been made in view of such circumstances, and an object of the present invention is to solve the problems of the above-mentioned prior art, and to provide a better solution than the above-mentioned prior arts (A) and (B). Another object of the present invention is to provide an electroless plating method and apparatus capable of improving the film forming speed of electroless plating, and thereby improving productivity.

[0013]

To achieve the above object, an electroless plating method and apparatus according to the present invention are described in claims 1 to 3 and 6 and in claims 4 to 6.
The electroless plating apparatus described in 5, 7 or 8, which has the following configuration.

That is, in the electroless plating method according to the first aspect, when performing the electroless plating, the temperature of the electroless plating bath is adjusted.
An electroless plating method characterized in that the temperature is higher than 95 ° C. and the atmospheric pressure of the electroless plating bath is equal to or higher than the saturated vapor pressure of the electroless plating bath (first method).
invention).

According to a second aspect of the present invention, in the electroless plating method according to the first aspect, the electroless plating bath is placed inside a pressure vessel that can withstand the atmospheric pressure of the electroless plating bath. (Second invention). The electroless plating method according to claim 3, wherein the electroless plating bath is placed in a pressure space containing air or gas at the same pressure as the atmospheric pressure of the electroless plating bath. This is an electrolytic plating method (third invention).

According to a fourth aspect of the present invention, in the electroless plating apparatus having an electroless plating bath and a means for heating the electroless plating bath, the electroless plating bath is formed by a pressure vessel. (4th invention). The electroless plating apparatus according to claim 5, wherein in the electroless plating apparatus having an electroless plating tank and a means for heating the electroless plating bath, the electroless plating tank is formed by a container having an opening at an upper part,
An electroless plating apparatus characterized in that the container is disposed in a pressure space (fifth invention).

According to a sixth aspect of the present invention, in the electroless plating method, the evaporation amount of the electroless plating bath is controlled by adjusting a partial pressure of steam in the atmosphere pressure of the electroless plating bath. This is an electroless plating method (sixth invention). The electroless plating apparatus according to claim 7 has a gas introduction pipe for introducing gas into the pressure vessel, and an exhaust pipe for discharging steam in the pressure vessel to outside the pressure vessel. This is an electrolytic plating apparatus (seventh invention). The electroless plating apparatus according to claim 8 has a gas introduction pipe for introducing gas into the pressure space, and an exhaust pipe for discharging steam in the pressure space to outside the pressure space. This is an electrolytic plating apparatus (eighth invention).

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is implemented, for example, as follows. A compressed air cylinder is connected via a pressure regulating valve to a pressure vessel (autoclave or the like) having a heater and a temperature controller. Next, a predetermined electroless plating bath is placed in the pressure vessel, the workpiece is fixed to a workpiece holder that can be remotely operated from outside the pressure vessel, and the lid of the pressure vessel is closed. the pressure P ₀ at the above atmospheric pressure in the pressure vessel by introducing compressed air into the space portion of the pressure vessel from closing the pressure regulating valve. Next, the heater and the temperature controller were operated to raise the temperature of the electroless plating bath in the pressure vessel to 95 ° C.
Adjusted to a temperature T ₁ of the super. Then, the pressure in the pressure vessel becomes elevated P _1.

At this time, the predetermined pressure P ₀ in the pressure vessel at room temperature
Is previously determined pressure, as the pressure P ₁ is saturated vapor pressure P ₂ greater than the pressure of the electroless plating bath at a temperature T ₁ of the pressure vessel at a temperature T ₁ of. Then, the temperature of the electroless plating bath to a temperature T ₁ of the 95 ° C. greater than the saturated vapor pressure P ₂ greater than the pressure of the electroless plating bath atmosphere pressure electroless plating bath of the temperatures T ₁
The P _1. For example, if the saturation vapor pressure P ₂ at 110 ° C. of the electroless plating bath used is 1.7 atm (0.17 MPa), the temperature T ₁ of the electroless plating bath is 110 ° C., and the atmospheric pressure of the electroless plating bath is P ₁ is 2.0 atm (0.20 MPa).

The above electroless plating bath has a temperature exceeding 95 ° C.
Although a T _1, a boiling point T ₁ greater since atmospheric pressure P ₁ is a saturated vapor pressure P ₂ greater than the electroless plating bath of the temperature T _1, therefore, not exhibit boiling phenomenon, mist generation, and There is no problem such as evaporation of the plating bath.

Next, the material to be plated is remotely operated from outside the pressure vessel, and the material to be plated is immersed in an electroless plating bath for electroless plating.

[0022] Thus, not exhibit boiling phenomenon, without causing any trouble of such as evaporation of the mist and the plating bath, can be electrolessly plated with a temperature T ₁ of the 95 ° C. greater,
As a result, the film forming speed of the electroless plating can be improved.

[0023] As can be seen from the preferred embodiment of a present invention, according to the present invention, without causing any trouble of such as evaporation of the mist and the plating bath, can be electrolessly plated with a temperature T ₁ of the 95 ° C. greater Thus, the film formation rate of electroless plating can be improved.

The details will be described below.

Under the atmospheric pressure, the electroless plating bath boils at around 100 ° C. (depending on the atmospheric pressure and the component concentration of the electroless plating bath), so that the conventional method is practical from the viewpoint of avoiding mist generation and evaporation of the plating bath. The upper limit of the typical plating bath temperature is 90 ° C.

[0026] In contrast, in the electroless plating method according to the present invention, as described above, when electroless plating, the temperature of the electroless plating bath while the temperature T ₁ of the 95 ° C. greater than the electroless plating bath since the atmospheric pressure P ₁ of which the saturated vapor pressure P ₂ equal to or higher than the pressure of the electroless plating bath of the temperature T _1, the electroless plating bath is a boiling point of above T _1, therefore, the electroless plating The electroless plating can be performed at a temperature higher than 95 ° C. without causing the boiling phenomenon of the bath and without causing troubles such as generation of mist and evaporation of the plating bath, thereby improving the film forming speed of the electroless plating. That is, the boiling point of the electroless plating bath increases with the atmospheric pressure P ₁ of the electroless plating bath is higher than (P ₂ to the atmospheric pressure P ₁ in the saturated vapor pressure P ₂ greater than the electroless plating bath and also higher), the pressure P ₂ to the boiling point (atmospheric pressure equilibrium to a temperature equal to the boiling point) in the case of P _2, not exhibit boiling phenomenon, without causing any trouble of such as evaporation of the mist and the plating bath , it is possible to increase the temperature T ₁ of the electroless plating bath, therefore, can improve the deposition rate of the electroless plating. At this time, the higher the temperature of the electroless plating bath is, the more the film forming rate is improved, and raising this temperature is extremely effective for improving the film forming rate. Therefore, according to the electroless plating method according to the present invention, without causing problems such as mist generation and evaporation of the plating bath,
It is possible to solve the problems of the prior art, to improve the film formation rate of the electroless plating than in the case of the conventional techniques (A) and (B), and to improve the productivity. Become.

However, the atmospheric pressure of the above electroless plating bath P ₁
A case in which a value equal to P ₂ rather than the saturated vapor pressure P ₂ greater than the electroless plating bath, since the boiling point of the electroless plating bath becomes T _1,
The electroless plating bath exhibits a boiling phenomenon, and a mist generation phenomenon and an evaporation phenomenon of the plating bath occur.These phenomena occur in a system isolated from the outside as described below. Outbreak does not have any trouble. Therefore,
Substantially without causing any trouble of such as evaporation of the mist and the plating bath, can be electrolessly plated with a temperature T ₁ of the 95 ° C. greater, can improve the deposition rate of the thus electroless plating.

That is, in order to make the atmospheric pressure P ₁ of the electroless plating bath equal to the saturated vapor pressure P ₂ of the electroless plating bath, it is basically necessary to control the atmospheric pressure of the electroless plating bath. For this purpose, the electroless plating bath must be placed in a system that is isolated from the outside (in a closed system, that is, in a closed space), for example, in a pressure vessel or pressure space described later. It is. Thus, the electroless plating bath is necessarily in a system that is isolated from the outside. Therefore, even if the electroless plating bath exhibits a boiling phenomenon and a mist generation phenomenon and an evaporation phenomenon of the plating bath occur, since these occur in a system that is shut off from the outside, the mist generation phenomenon and the evaporation phenomenon of the plating bath occur. Outbreak does not have any trouble. Therefore, virtually no hindrance such as mist generation and evaporation of the plating bath occurs,
Can be electrolessly plated with 95 ° C. greater than the temperature T _1, it can improve the deposition rate of the thus electroless plating.

[0029] The temperature of the electroless plating bath in an electroless plating method according to the present invention is to a temperature T ₁ of the 95 ° C. than the
When the temperature is set to 90 ° C. or lower, the film forming speed of the electroless plating is equal to or lower than that of the conventional technologies (A) and (B), and the film forming speed of the electroless plating cannot be improved at all.
If the temperature is super lower than 95 ° C., the film forming speed of the electroless plating is improved as compared with the cases of the prior arts (A) and (B), but the degree of the improvement is small and insufficient.

The saturated vapor pressure of said as the temperature of the electroless plating bath while the temperature T ₁ of the 95 ° C. greater than the temperature T ₁ of the electroless plating bath electroless plating bath temperature T ₁ atmosphere pressure to P ₂ equal to or higher than the pressure P ₁ is a pressure vessel to withstand the atmospheric pressure P ₁ of the electroless plating bath, placed in an electroless plating bath to the interior of the pressure vessel, heated to a temperature T ₁ of (Second invention). Here, when the pressure of the space in the pressure vessel before heating is atmospheric pressure, P ₁ is the degree slightly higher than P ₂ equal to or P _2. Meanwhile, the as in the case of the embodiment of the present invention, when the pressure in the space portion in the pressure vessel prior to heating to the pressure P ₀ above atmospheric pressure, P ₁ is higher than P _2, and P ₁
The difference between P ₂ increases according to P _0.

Alternatively, the electroless plating bath adjusted to the temperature T ₁ may be placed in a pressure space containing air or gas at the same pressure as the atmospheric pressure P ₁ of the electroless plating bath. (Third invention). Here, the pressure space is a space capable of realizing a pressure exceeding atmospheric pressure. Such a pressure space can be realized, for example, by sending compressed air or a gas having a pressure higher than the atmospheric pressure into a pressure chamber or a pressure vessel.

More specifically, the condition according to the third aspect of the present invention is as follows. A container having an opening at the top and containing an electroless plating bath is placed inside a pressure chamber or pressure vessel (pressure space). , Sending compressed air or a gas exceeding atmospheric pressure into the inside,
This can be realized by heating the electroless plating bath to the temperature T ₁ and setting the pressure in the inside (pressure space) to P ₁ .

On the other hand, the electroless plating apparatus according to the present invention
As described above, the present invention is an electroless plating apparatus having an electroless plating bath and a means for heating the electroless plating bath, wherein the electroless plating bath is formed by a pressure vessel (a fourth invention). An electroless plating apparatus having an electroless plating bath and a means for heating the electroless plating bath, wherein the electroless plating bath is formed by a container having an opening at an upper portion, and the container is disposed in a pressure space. (Fifth invention). According to these devices, the second invention, as seen from the descriptive matter of the third invention, any of the apparatus, the temperature of the electroless plating bath as well as to 95 ° C. than the temperature T ₁ of the, temperature T ₁
No atmospheric pressure in the electroplating bath can be a saturated vapor pressure P ₂ equal to or higher than the pressure P ₁ of the electroless plating bath of the temperature T _1, thus, performs an electroless plating method according to the present invention Therefore, the film formation rate of the electroless plating can be improved as compared with the above-mentioned conventional techniques (A) and (B) without any troubles such as generation of mist and evaporation of the plating bath, thereby increasing productivity. Can be improved. Incidentally, in the case where the atmospheric pressure P ₁ of the electroless plating bath to the saturation vapor pressure P ₂ greater than the electroless plating bath, nor exhibit boiling phenomenon of the electroless plating bath.

Here, in the case of using the pressure vessel according to the fourth invention or in the case of the second invention, P ₁ (atmospheric pressure of the electroless plating bath) is set to a value equal to P ₂ (saturated vapor pressure of the electroless plating bath). to it a boiling point of T ₁ next to the electroless plating bath,
Even if the electroless plating bath exhibits a boiling phenomenon and a mist generation phenomenon and a plating bath evaporation phenomenon occur, these occur in the pressure vessel, the pressure vessel is in an equilibrium state, and the mist scatters to the outside of the pressure vessel. (Diffusion) and evaporation of the plating bath (and thus vapor diffusion) do not occur, and no reduction occurs due to evaporation of the plating bath. In itself, there is no trouble at all. Therefore, even when P ₁ = P ₂ ,
Substantially no trouble such as generation of mist and evaporation of the plating bath occurs. However, from the viewpoint of suppressing the occurrence of plating film defects due to bubbles at the time of boiling, P ₁ exceeds P ₂ (that is, P ₁
> P ₂ ), so that the boiling point of the electroless plating bath should be higher than T ₁ so that the electroless plating bath does not boil.

When the apparatus according to the fifth invention is used or in the case of the third invention, when P ₁ = P ₂ , the electroless plating bath exhibits a boiling phenomenon, and a mist generation phenomenon and an evaporation phenomenon of the plating bath occur. Since these occur in the pressure space and do not cause the diffusion of mist to the outside of the pressure space and the diffusion of evaporation vapor from the plating bath, the surface of the inner wall that composes the pressure space and the equipment in the pressure space are subjected to rust prevention treatment in advance. In this way, there is no problem even if mist or vapor adheres to these, so that there is substantially no problem even if mist generation and evaporation of the plating bath occur. However, if the generation of mist and the phenomenon of evaporation of the plating bath do not occur, such a treatment as rust prevention treatment becomes unnecessary, or the treatment is simplified, and the reduction due to the evaporation of the plating bath is suppressed. And it is better to avoid the evaporation phenomenon of the plating bath.
It is desirable that P ₁ > P ₂ . It is also desirable that P ₁ > P ₂ from the viewpoint of suppressing the occurrence of plating film defects due to boiling bubbles.

FIG. 1 shows an example of the electroless plating apparatus according to the fourth invention. In this electroless plating apparatus, a pressure pump 6 is connected to a water tank 5 of the electroless plating bath by a pipe, and a heater 7 having a heater and a temperature controller as a heating means of the electroless plating bath is connected to the pressure pump 6 by a pipe. Then, a pressure vessel (autoclave) 1 having a heater and a temperature controller as an electroless plating tank is connected to the heater 7 by a tube, and a cooler 2, a regenerator 3, and a filter 4 are connected to the pressure vessel 1 in this order. The filter 4 and the water storage tank 5 are connected by pipe connection.
If necessary (especially when P ₁ > P ₂ ), the pressure vessel 1 has a high-pressure gas inlet pipe, and a compressed air cylinder is connected to the inlet pipe via a pressure regulating valve. Is desirable.

According to this electroless plating apparatus, the temperature of the electroless plating bath is set to 95 ° C. in the pressure vessel 1 (plating tank).
While the temperature T ₁ of the super-saturated vapor pressure of the electroless plating bath of the temperature T ₁ of the temperature T ₁ of the atmosphere pressure of the electroless plating bath P ₂
And it can be equal or higher pressure P _1, therefore, may perform the electroless plating method of the present invention. In addition, the plating solution that has become unsuitable for electroless plating is cooled by the cooler 2, the regenerator 3,
It can be sent to the filter 4 and regenerated to obtain a suitable plating solution, and this can be sent from the water storage tank 5 to the heater 7 to a temperature of more than 95 ° C.
After the T _1, by returning the pressure vessel 1 (plating bath), it can be used again. Therefore, the electroless plating method according to the present invention can be performed intermittently (semi-continuously).

FIG. 2 shows an example of the electroless plating apparatus according to the fifth invention. In the present electroless plating apparatus, a heater 9 having a heater and a temperature controller as a means for heating the electroless plating bath is pipe-connected to a water tank 8 for the electroless plating bath. A plating tank 10 formed by a container having an opening is connected to the plating tank 10 via a pump (not shown), and a cooler 11, a regenerator 12, and a filter 13 are connected to the plating tank 10 in this order. The filter 13 and the water storage tank 8 are connected by a pipe via a pump (not shown) to form a pressure space having a gas inlet P and a pressure higher than the atmospheric pressure inside. It is arranged in a pressure chamber (pressure space) V which can be formed, and a compressed air cylinder (not shown) is connected to the gas inlet P of the pressure chamber V via a pressure regulating valve. In addition, the diffusion of evaporation vapor and mist of the plating bath from the water storage tank 8 and the plating tank 10 into the pressure space is suppressed, thereby reducing the influence on the equipment and the like in the pressure space and reducing the evaporation of the plating bath. From the viewpoint of reducing the decrease, it is preferable that the water storage tank 8 and the plating tank 10 be sealed as much as possible by covering the lid as shown in FIG.

According to the present electroless plating apparatus, the electroless plating solution is put into the water tank 8, the material to be plated is placed in the plating tank 10, and compressed air is introduced from the compressed air cylinder into the pressure chamber V. The pressure in the pressure chamber V was adjusted to a predetermined pressure P ₀ equal to or higher than the atmospheric pressure, and then the electroless plating solution was sent from the water storage tank 8 to the heater 9, and adjusted to a temperature T ₁ exceeding 95 ° C. by the heater 9. after, by sending to the plating tank 10, while the temperature of the electroless plating bath to a temperature T ₁ of the 95 ° C. than in the plating bath 10, the temperature T ₁
No atmospheric pressure in the electroplating bath can be a saturated vapor pressure P ₂ equal to or higher than the pressure P ₁ of the electroless plating bath of the temperature T _1, thus, performs an electroless plating method according to the present invention obtain. In addition, the plating solution that has become unsuitable for electroless plating is sent to a cooler 11, a regenerator 12, and a filter 13 to regenerate a suitable plating solution, and then sent from a water storage tank 8 to a heater 9. after the temperature T ₁ of the 95 ° C. greater than Te, by returning to the plating tank 10 may be used again. Therefore, the electroless plating method according to the present invention can be continuously performed.

By the way, since the boiling point of the electroless plating bath tends to be higher as the component concentration of the electroless plating bath is higher, the electroless plating is performed without causing any trouble such as generation of mist and evaporation of the plating bath. electroless plating bath ambient pressure P ₁ becomes lower the required, pressure is reduced to be loaded in turn the pressure vessel and the pressure chambers. Therefore, when applying the present invention, if there is no problem in increasing the component concentration of the electroless plating bath, it is desirable to increase the component concentration as much as possible.

Although the higher the temperature T ₁ of the electroless plating bath, the better the film-forming rate is, the higher the saturation vapor pressure P ₂ of the electroless plating bath at the temperature T ₁ , the higher the pressure P. ₂ and the ambient pressure P ₁ of the necessary electroless plating bath is at least equivalent
, Which increases the pressure applied to the pressure vessels and pressure chambers and increases the costs required for their construction.

On the other hand, the temperature T ₁ is significantly effect on the deposition rate of an electroless plating bath, the temperature T ₁ of the electroless plating bath 95 ° C.
By making it slightly higher, the film forming speed is greatly improved. For example, as will be understood from the examples described later, the film forming rate at 100 ° C. is about twice as high as that at 110 ° C. compared to the film forming rate when the temperature of the electroless plating bath is 90 ° C. which is the conventional upper limit. In the case of, the deposition rate is about 5 times, and in the case of
10 times better.

Therefore, when applying the present invention, the temperature T ₁ of the electroless plating bath and the cost of the it is desirable to set the atmospheric pressure P ₁ and the like. From this point of view, the temperature T ₁ of the electroless plating bath, the saturation vapor pressure P ₂ of the electroless plating bath at the temperature T ₁ is less 95 ° C. Ultra 0.99 ° C. to be in the range of several times the atmospheric pressure It is desirable to do. When the temperature is set to be higher than 95 ° C. and equal to or lower than 150 ° C., the film forming rate is greatly improved in spite of the relatively low cost required for forming the pressure vessel and the pressure space.
When the temperature is set to a nearby temperature, a simple pressure vessel or pressure space is sufficient, and a film deposition rate that is 10 times that of the conventional case of 90 ° C is realized, and when the temperature is set to 100 to 110 ° C. Further, the pressure vessel and the pressure space may be simpler, for example, a pressure cooker, and a film formation rate 2 to 5 times that of the conventional case of 90 ° C. is possible. Incidentally, it is necessary to note that the temperatures T _1, such as not hexa functional deterioration due to decomposition of components of an electroless plating bath, for example, in the case of electroless Ni-P plating, on the Ni-P plating bath Since hypophosphite added as a reducing agent decomposes at a temperature exceeding 140 ° C., from the viewpoint of the high-temperature stability of the reducing agent, the temperature of the plating bath T ₁
The temperature should be more than 95 ° C and 140 ° C or less.

In the present invention, the temperature T ₁ of the electroless plating bath is
It is necessary to exceed 95 ° C., so that the deposition rate of the electroless plating is sufficiently improved and the deposition rate of the electroless plating is improved as compared with the conventional techniques (A) and (B). However, as described above, T ₁ = 100 ° C. compared to the film forming rate when the temperature of the electroless plating bath is 90 ° C. which is the conventional upper limit.
The film forming rate in the case of T ₁ is about double, the film forming rate in the case of T ₁ = 110 ° C. is about 5 times, and the film forming rate in the case of T ₁ = 120 ° C. is about 10 times, and T ₁ ≧ 100 C., the film formation rate is drastically improved to about twice or more. Therefore, in terms of the film formation rate,
Temperature T ₁ of the electroless plating bath is preferably set to 100 ° C. or more, more desirably to 110 ° C. or higher the deposition rate is increased above about 5 times.

[0045] In the electroless plating method according to the present invention, as described above, the temperature of the electroless plating bath while the temperature T ₁ of the 95 ° C. greater than the temperature T ₁ of the atmosphere pressure P ₁ of the electroless plating bath
Electroless is the saturated vapor pressure P ₂ equal to or higher than the pressure of the plating bath, but this time, the control amount of evaporation vapor partial pressure to adjust to the electroless plating bath in the ambient pressure of the electroless plating bath By doing so, it is possible to stabilize the film formation rate and plating quality of electroless plating even when electroless plating is performed for a long period of time (sixth invention). The details will be described below.

Electroless plating is a plating utilizing a metal deposition phenomenon caused by a chemical reaction.
Not only is the metal ion species in the plating bath and the reducing agent involved in the precipitation reaction consumed, but also hydrogen gas is generated and the pH of the plating bath is changed. Therefore, in general, metal salts, reducing agents,
Additives such as complexing agents, buffers, alkalis and acids for pH adjustment are regularly added to the plating bath, thereby stabilizing the components of the plating bath. Here, as an additive, a metal salt such as nickel sulfate, a reducing agent such as hypophosphite or dimethylamine borane, a complexing agent such as acetic acid or citric acid, and a buffering agent such as acetic acid or succinic acid. Ammonia water or the like is used as an alkali for pH adjustment, and dilute sulfuric acid or the like is used as an acid. The type, frequency, and amount of the additives are determined by the type of electroless plating, and the consumption of plating bath components due to chemical reaction, decomposition, evaporation, etc. at the electroless plating bath temperature set in consideration of the desired film formation rate. It is determined according to the amount (fluctuation) and the fluctuation of pH, and the plating bath components are controlled to a concentration range in which an electroless plating film having stable performance can be obtained. The additive is mixed and dissolved in water to form an aqueous additive (hereinafter referred to as a liquid additive),
This is added to the plating bath. This is because, when a liquid additive is used, it is easy to control the addition amount and the like. The concentration of the liquid additive is set so that the amount of the added liquid and the amount of evaporation are balanced.

At this time, in the case of the conventional electroless plating method using a plating bath at 90 ° C. or lower under the open atmosphere, the amount of the plating bath lost by evaporation and the amount of the liquid additive are substantially balanced. In addition, the plating bath components fluctuate slowly due to the low film formation rate, so the frequency of liquid additive addition is low, and therefore, even when electroless plating is performed over a long period of time, the plating bath and its surroundings No special ingenuity is required to maintain the state of the.

On the other hand, in the case of the electroless plating method according to the present invention, since the film forming rate is extremely improved and high, the fluctuation rate of the plating bath components is large, and therefore the addition of the liquid additive per unit time is required. Because the volume of the electroless plating bath is increased and the electroless plating bath is placed in a system (closed space) that is isolated from the outside such as in a pressure vessel or pressure space, the plating bath from the system to the outside of the system When electroless plating is performed over a long period of time, the amount of the plating bath increases with the addition amount of the liquid additive, and eventually the addition of the liquid additive cannot be performed. The components cannot be maintained, and as a result, the deposition rate and plating quality become unstable.

After examining the countermeasures, when the method of adding a powdery agent (additive) in place of the liquid additive or adjusting the concentration of the plating bath component by using a permeable membrane, the plating bath is regenerated. Equipment problems, such as the machine itself becoming complicated and expensive, occurred. In addition, the concentration of hydrogen gas generated by the electroless plating reaction gradually increases in a closed space, and in the case of electroless plating for a long period of time, a safety problem may occur.

On the other hand, by adjusting the vapor partial pressure in the atmosphere pressure of the electroless plating bath to control the evaporation amount of the electroless plating bath, the evaporation amount of the electroless plating bath and the addition of the liquid additive are controlled. Quantity and balance, so
Each time the liquid additive is added, the amount of the plating bath after the addition can be suppressed without any problem, for example, a fixed amount equal to the amount of the plating bath at the start of electroless plating. It was confirmed that it could be. That is, each time the liquid additive is added, the partial pressure of the vapor in the atmosphere pressure of the electroless plating bath is adjusted before the addition of the liquid additive so that the amount of the plating bath after the addition of the liquid additive becomes a problem-free amount. It has been confirmed that the liquid additive can be added without adjusting the amount of the plating bath by adjusting the amount of evaporation of the electroless plating bath and adjusting the amount of the plating bath.

Therefore, when the vapor partial pressure in the atmosphere pressure of the electroless plating bath is adjusted to control the amount of evaporation of the electroless plating bath, even when the electroless plating is performed for a long period of time, the plating bath The required amount of the liquid additive can be added when needed, without inducing a troublesome increase in the amount,
Therefore, the components of the plating bath can be maintained, and the film formation rate and plating quality of electroless plating can be stabilized (sixth invention).

The control of the evaporation amount of the electroless plating bath by adjusting the vapor partial pressure in the atmosphere pressure of the electroless plating bath is as follows.
For example, the following method is used.

A method in which a gas such as compressed air is introduced into the atmosphere of the electroless plating bath and a part of the vapor-containing gas is exhausted from the atmosphere of the electroless plating bath (ie, the vapor-containing gas) (hereinafter referred to as gas (Referred to as the introduction and exhaust method).
Here, the introduction of the gas is to hold the ambient pressure P ₁ of the electroless plating bath to the saturation vapor pressure P ₂ equal to or higher than the pressure of the electroless plating bath. In other words, by merely exhausting the vapor-containing gas, it is possible to lower the vapor partial pressure of the electroless plating bath to increase the amount of evaporation and prevent a troublesome increase in the amount of the plating bath. it is because it becomes impossible to maintain the pressure P ₁ in the saturated vapor pressure P ₂ equal to or higher than the pressure of the electroless plating bath.

As another method, a method of providing a cooled steam collecting plate in an atmosphere of an electroless plating bath to collect steam (hereinafter, referred to as a steam cooling collecting method) is employed.

In the gas introducing / exhausting method, a gas introducing pipe for introducing gas into the pressure vessel of the apparatus according to the fourth invention and an exhaust pipe for discharging vapor in the pressure vessel to the outside of the pressure vessel are provided. A gas introduction pipe for introducing gas into the pressure space of the electroless plating apparatus (seventh invention) or the apparatus according to the fifth invention, and an exhaust pipe for discharging vapor in the pressure space to the outside of the pressure space. It can be performed by using the provided electroless plating apparatus (the eighth invention). The vapor cooling and collecting method can be performed by a device having a cooled vapor collecting plate in a pressure space of the device according to the fifth invention.

FIG. 3 shows an example of the electroless plating apparatus according to the seventh aspect of the present invention. In the present electroless plating apparatus, a heater 23 with a temperature controller, which is a heating means for an electroless plating bath 22, is provided in an electroless plating tank (pressure vessel) 21.
A pipe 25 for introducing compressed air to an atmosphere 24 above the pipe 22 and an exhaust pipe 26 with a pressure regulating valve for exhausting the atmosphere 24 are provided.

Although the liquid additive introduction pipe 27 is provided in the apparatus shown in FIG. 3, the compressed air introduction pipe 25 may be substituted without providing the introduction pipe 27, and the plating tank 21 It is also possible to connect a plating bath regenerator via piping and add the additive in the regenerator.

In a usual electroless plating apparatus, the plating bath may be agitated by air bubbling. However, the present electroless plating apparatus may be provided with a bubbling tube 28 for supplying compressed air as shown in FIG. The compressed air introduced by the bubbling tube 28 rises in the electroless plating bath 22 to reach the atmosphere 24 and has the same effect as the compressed air introduced by the compressed air introduction tube 25, but the amount of bubbling is reduced. Since it is a factor that affects the speed and the amount of compressed air introduced into the bubbling tube 28 should be kept constant, even when the bubbling tube 28 is provided, it is preferable to provide the compressed air introduction tube 25 independently. Is good.

Although a filter is connected in many cases in a normal electroless plating apparatus, a filter may be connected in the present electroless plating apparatus to filter the plating bath 22 by circulation.

According to the present electroless plating apparatus, gas introduction and
By the exhaust method, while maintaining the atmospheric pressure P ₁ of the electroless plating bath to the saturation vapor pressure P ₂ equal to or higher than the pressure of the electroless plating bath, free by adjusting the partial vapor pressure in the atmosphere pressure of the electroless plating bath The evaporation amount of the electrolytic plating bath can be controlled, and the plating bath amount can be adjusted to an appropriate amount. Further, with respect to the problem that hydrogen generated during electroless plating is gradually accumulated in the pressure vessel 21 or the pressure space, it is possible to suppress the amount of accumulated hydrogen to a small amount without any problem.

FIG. 4 shows an example of an electroless plating apparatus to which the above-mentioned vapor cooling collection method is applied. In the present electroless plating apparatus, a heater 33 with a temperature controller, which is a heating means for an electroless plating bath 32, is provided in an electroless plating tank (a container having an opening at the top) 31 in a pressure chamber (pressure space) V. A pipe 35 with a pressure regulating valve for introducing compressed air into an atmosphere 34 above an electroless plating bath 32, and a vapor collecting plate 36 provided on an inner wall of a container 38 forming a pressure chamber V. It is. Cooling water is circulated through the steam collecting plate 36, so that the steam collecting plate 36 can be cooled.

Although the liquid additive introduction pipe 37 is provided in the apparatus shown in FIG. 4, the compressed air introduction pipe 35 may be used instead of connecting the liquid additive introduction pipe 37. It is also possible to connect a plating bath regenerator through a pipe and add the additive in the regenerator. Alternatively, a plating machine may be connected to perform circulating filtration of the plating bath 32.

According to the present electroless plating apparatus, the evaporation amount of the electroless plating bath can be controlled by adjusting the partial pressure of steam in the atmosphere pressure of the electroless plating bath by the steam cooling collection method. Can be adjusted to an appropriate amount. When lowering the partial pressure of the steam under the atmospheric pressure, the cooling water is supplied to the steam collecting plate 36 to lower the surface temperature of the steam collecting plate 36, and when increasing the partial pressure of the steam under the atmospheric pressure, the cooling water is used. The surface temperature of the vapor collecting plate 36 is increased by stopping the cooling by the steam collecting plate 36 or, if necessary, by heating with a preliminary heater. The vapor cooled by the vapor collecting plate 36 becomes a liquid and accumulates at the bottom of the container 38, and is excluded from the system including the electroless plating bath 32 and the atmosphere 34 thereon.

FIG. 8 shows a more specific example of the electroless plating apparatus according to the seventh invention. 8, reference numeral 41 denotes a plating tank outer tank, 42 denotes an opening / closing lid, 44 denotes a clamp, and 45 denotes a packing. Reference numeral 47 denotes a motor, 46 denotes a gear interlocked by the rotation of the motor 47, and 54 denotes a rotating shaft interlocked by the gear 46. A plating target material (not shown) is attached to the rotating shaft 54. Reference numeral 55 denotes a rack including the gear 46, the rotating shaft 54, and the like. Reference numeral 52 denotes a bubbling tube, 51 denotes a heater, and 50 denotes a power supply unit connected to the heater 51. 53 is a plating bath adjusting solution introduction section,
Reference numeral 49 denotes a circulation filter pipe, and a circulation filter (not shown) is connected to the pipe 49. Reference numeral 48 denotes a compressed air introduction unit, 60 denotes an exhaust pipe, and 43 denotes a back pressure valve connected to the exhaust pipe 60.

FIG. 9 shows a more specific example of the electroless plating apparatus according to the eighth invention. In FIG. 9, 58 is a pressure chamber,
56 is a cooling plate provided in the vicinity of the inner wall in the upper part of the pressure chamber 58, 57 is a cooling water pipe for circulating cooling water to the cooling plate 56, 51 is a heater attached to the cooling plate 56, 50 is The energization section connected to the heater 51, 59 is a pressure chamber from the cooling plate 56
The liquid, etc., which has fallen into the concave portion at the bottom of
It shows a drainage pipe for discharging to the outside. The other reference numerals are the same as those in FIG.

[0066]

【Example】

Example 1 Electroless Ni-P plating was performed using the same electroless plating apparatus as in FIGS. 1 and 2 described above. At this time,
As the electroless plating solution, a mixture of a commercially available electroless Ni-P plating agent (P content of the plated film after film formation: 1)
1.5%). Incidentally, those after the preparation, nickel sulfate: 20 g / dm ^3, hypophosphite soda: 20 g / dm ^3, sodium acetate: 10 g / dm ^3, sodium citrate: an aqueous solution containing 10 g / dm ^3. As a material to be plated, an aluminum (Al-4% Mg) alloy plate for a magnetic disk which was subjected to a double zincate treatment was used. The temperature of the electroless Ni-P plating bath and the atmospheric pressure of the electroless plating bath were varied as parameters, and the plating rate was determined from the change in mass before and after plating.

Table 1 shows the results. In the case of the method according to the embodiment of the present invention (Nos. 2 to 6), electroless N
In the case of the comparative example in which the temperature of the IP plating bath was 90 ° C. (No.
The plating speed is extremely high compared to 1). That is, as compared with the film forming rate in the comparative example (No. 1), the film forming rate in the example of the present invention (No. 2 to 6) is set at a temperature of the electroless Ni—P plating bath of 100 ° C. Approximately 2 times at 110 ° C., approximately 5 times at 110 ° C., and approximately 10 times at 120 ° C. In each case, the electroless Ni-P plating could be performed without exhibiting the boiling phenomenon of the electroless Ni-P plating bath and without causing problems such as generation of mist and evaporation of the plating bath.

Example 2 An electroless plating solution prepared by adding copper sulfate based on a commercially available electroless Ni-P plating agent (Ni content of plated film after film formation: 52%, Cu content: 41
%, P content: 7%), and the same material as in Example 1 was used as the material to be plated, and electroless Ni-Cu-P plating was performed using the same electroless plating apparatus as in Example 1. Was done. Then, the plating rate was measured in the same manner as in Example 1.

Table 2 shows the results. According to the method according to the embodiment of the present invention [Temperature of electroless Ni-Cu-P plating bath:
110 ° C, atmospheric pressure of the plating bath: 3 atm (0.3 MPa)]
Is a comparative example (temperature of electroless Ni-Cu-P plating bath: 80
(° C, under atmospheric pressure), the plating rate is 10 times higher and extremely high. In any case, no boiling phenomenon of the plating bath was exhibited, and no troubles such as generation of mist and evaporation of the plating bath occurred.

[0070]

[Table 1]

[0071]

[Table 2]

[0072]

[Table 3]

[0073]

[Table 4]

(Example 3) As an electroless plating solution, a mixture of nickel sulfate, sodium hydroxide, ethylenediamine and the like to which sodium tetrahydroborate was added and blended (B content of plated film after film formation: 5%) was used. An Al alloy (A7075 alloy) plate subjected to double zincate treatment was used as a material to be plated, and electroless Ni-B plating was performed using the same electroless plating apparatus as in Example 1. Then, the plating rate was measured in the same manner as in Example 1.

Table 3 shows the results. In the case of the method according to the embodiment of the present invention [Temperature of electroless Ni-B plating bath: 10
5 ° C, atmospheric pressure of the plating bath: 2 atm (0.2 MPa)]
The plating speed is about 5 times higher than that of the comparative example (temperature of the electroless Ni-B plating bath: 90 ° C. under atmospheric pressure), and is extremely high. In any case, no boiling phenomenon of the plating bath was exhibited, and no troubles such as generation of mist and evaporation of the plating bath occurred.

Example 4 As an example of the present invention, electroless Ni-P plating was performed using the same electroless plating apparatus as in FIGS. At this time, the same electroless plating solution and plating material as in Example 1 were used. Then, the vapor partial pressure in the atmosphere pressure of the electroless plating bath is adjusted to control the evaporation amount of the electroless plating bath, and the liquid additive is periodically added in accordance with the film formation rate experimentally obtained in advance. And electroless Ni-P plating was performed for a total of 7 hours, and changes in the plating bath volume and the pH of the plating bath were investigated.
In addition, a change in the amount of P during plating, which has a significant effect on the electroless Ni-P plating film formation rate and plating performance (performance of the plating film), was investigated. The results are shown in FIGS. 5 and 6 and in the column of Example in Table 4. As the liquid additive, a liquid additive attached to a commercially available electroless Ni-P plating agent was used.

On the other hand, the amount of evaporation of the electroless plating bath was not controlled by adjusting the partial pressure of the vapor in the atmosphere pressure of the electroless plating bath. Ni-P plating was performed, and the same investigation was performed.
The results are shown in FIG. 7 and the column of Comparative Example in Table 4.

In the case of the method according to the comparative example (without controlling the steam partial pressure), as can be seen from FIG. 7, the plating bath volume increases with time and the plating bath pH also increases. In general,
The pH control range of the electroless Ni-P plating bath is the target control value ± 0.
Within 2 hours, the pH exceeded the pH control range 4 hours after the start of plating. In addition, due to the effect of the increase in the pH of the plating bath, as shown in the column of Comparative Example in Table 4, the upward variation in the film forming rate became large, and further, the P amount during plating decreased, and the variation range was also reduced. It is expanding.

On the other hand, in the case of the method according to the embodiment of the present invention, as shown in FIGS. It can be seen that the amount of the plating bath and the pH of the plating bath can be stably maintained by controlling the evaporation amount of the electroless plating bath by adjusting the vapor partial pressure in the atmosphere pressure of the plating bath. Table 4
As shown in the column of Examples, the film formation rate and the P content during plating are stable.

The above results are for electroless Ni-P plating, but similar results were obtained for other electroless plating.

[0081]

According to the present invention, it is possible to perform electroless plating at a temperature higher than 95 ° C. without causing problems such as generation of mist and evaporation of a plating bath. As compared with the method described above, the film formation rate of electroless plating can be remarkably improved, and the productivity can be greatly improved.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an example of an electroless plating apparatus according to the present invention.

FIG. 2 is a diagram illustrating an example of an electroless plating apparatus according to the present invention.

FIG. 3 is a diagram illustrating an example of an electroless plating apparatus according to the present invention.

FIG. 4 is a diagram illustrating an example of an electroless plating apparatus according to the present invention.

FIG. 5 is a diagram showing a relationship between a plating time, a plating bath volume, and a pH according to Example 4.

FIG. 6 is a diagram showing the relationship between plating time, plating bath volume and pH according to Example 4.

FIG. 7 shows a plating time and a plating bath volume according to a comparative example;
It is a figure which shows the relationship with pH.

FIG. 8 is a diagram illustrating an example of an electroless plating apparatus according to the present invention.

FIG. 9 is a diagram illustrating an example of an electroless plating apparatus according to the present invention.

[Explanation of symbols]

1-pressure vessel, 2-cooler, 3-regenerator, 4-filter,
5-water tank, 6-pressure pump, 7-heater, 8-water tank, 9-heater, 10-plating tank, 11-cooler, 12-regenerator, 13- -Filter, 21--Electroless plating tank (pressure vessel), 22
--Electroless plating bath, 23--Heater, 24--Atmosphere, 25--Compressed air inlet, 26--Exhaust, 27--Liquid additive inlet, 28--
Bubbling tube, 31--electroless plating bath, 32--electroless plating bath, 33--heater, 34--atmosphere, 35--compressed air inlet tube, 36
--Vapor collecting plate, 37--Liquid additive introduction pipe, 38--Container, P--
Gas inlet, V--pressure chamber (pressure space), 41--plating tank outer tank, 42--open / close lid, 43--back pressure valve, 44--clamp, 45--packing, 46--gear, 47 --Motor, 48--Compressed air inlet,
49--Circulation filter piping, 50--Electrification section, 51--Heater, 52--Bubbling pipe, 53--Plating bath adjusting solution introduction section, 54--Rotating shaft, 55--Rack, 56--Cooling Board, 57--cooling water piping, 58--
Pressure chamber, 59--drain pipe, 60--exhaust pipe.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Motoharu Sato 1-5-5 Takatsukadai, Nishi-ku, Kobe-shi, Hyogo Kobe Steel, Ltd. Kobe Research Institute

Claims (8)

[Claims] In the electroless plating, the temperature of the electroless plating bath is set to a temperature exceeding 95 ° C., and the atmospheric pressure of the electroless plating bath is set to a pressure equal to or higher than the saturated vapor pressure of the electroless plating bath. An electroless plating method characterized by: 2. The electroless plating method according to claim 1, wherein the electroless plating bath is placed inside a pressure vessel that can withstand the atmospheric pressure of the electroless plating bath. 3. The electroless plating method according to claim 1, wherein the electroless plating bath is placed in a pressure space containing air or gas at the same pressure as the atmospheric pressure of the electroless plating bath. 4. An electroless plating apparatus having an electroless plating tank and a means for heating the electroless plating bath, wherein the electroless plating tank is formed by a pressure vessel. 5. An electroless plating apparatus having an electroless plating bath and a means for heating the electroless plating bath, wherein the electroless plating bath is formed by a container having an opening at an upper part, and the container is formed in a pressure space. An electroless plating apparatus characterized by being arranged. 6. The electroless plating method according to claim 1, wherein an evaporation amount of the electroless plating bath is controlled by adjusting a partial pressure of steam in the atmosphere pressure of the electroless plating bath. 7. The electroless plating apparatus according to claim 4, further comprising a gas introduction pipe for introducing gas into the pressure vessel, and an exhaust pipe for discharging vapor in the pressure vessel to outside the pressure vessel. 8. The electroless plating apparatus according to claim 5, further comprising a gas introduction pipe for introducing a gas into the pressure space, and an exhaust pipe for discharging steam in the pressure space to the outside of the pressure space.