JPS6352113B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an air stirring device for electroless plating solution, and in particular, it prevents air bubbles of air for stirring the plating solution from directly hitting the object to be plated, thereby improving the plating film thickness and The present invention relates to an air stirring device that allows stable precipitation of particulate additives.

Unlike electrolytic plating, electroless plating is a plating method in which a plating material is deposited using a reducing agent contained in a plating solution to form a plating layer on the metal surface. It is applied to the surface treatment of mechanical parts that are subject to high-speed heavy loads that involve sliding and are susceptible to scratch corrosion, such as parts for clutches, and can significantly improve their self-lubricating properties and wear resistance. The reason why such a large characteristic is exhibited is that particulate additives such as ceramics such as oxides, carbides, nitrides, borides, etc. or metals are dispersed and precipitated in the plating material. This fine particle additive is a round fine particle with a diameter of approximately 1 μm, and provides high self-lubricating properties and wear resistance to the metal plated layer.

To perform such electroless plating, fine particle additives such as ceramic particles are mixed and dispersed in a plating solution, and the object to be plated is immersed in the plating solution for a predetermined period of time. and fine particle additives are precipitated to form a plating layer.

However, fine particle additives mixed into the plating solution tend to aggregate extremely easily due to their surface tension.
Therefore, it is technically quite difficult to uniformly disperse this in the plating solution.

Conventionally, for example, in the case of electroless plating of nickel, nickel sulfate (NiSO ₄ ) is mixed with ceramic (SiC) as a fine particle additive, and sodium hypophosphite (NaH ₂ PO ₂ ) is added to form a plating solution, and a dispersant such as a surfactant is mixed with the plating solution to prevent the ceramic (SiC) from agglomerating and dispersed, and air is blown into the plating solution tank to constantly stir. A device was used to

That is, the structure of a conventional plating bath 1 for electroless plating will be explained with reference to FIGS. Diaphragms 2 and 3 are provided, and the plating liquid 4 enters downward from the upper part 1c of the plating tank 1 between the side surfaces 1a and 1b and the respective diaphragms 2 and 3, as shown by arrow A, and is heated. Then, as shown by arrow B, it is mixed into the plating liquid 4 in the plating tank 1 little by little.

Further, as shown in FIG. 2, the bottom 1d of the plating tank 1 is provided with a V-shaped groove 1e, and an air pipe 5 is provided at the bottom of each groove 1e. A large number of air blow-off holes 5a are formed in the longitudinal direction at intervals of 150 degrees, and the air is blown downward as shown by arrow C, blowing up the particulate additives precipitated at the bottom of each groove 1e, and causing air bubbles. 6 and rises as shown by arrow D, stirring the plating solution 4.

However, in the above conventional example, as shown in FIG.
Since the bubbles 6 that have passed through the plating liquid infiltration prevention device 8 gradually expand and come into direct contact with the device, the plating speed is reduced and the precipitation of the particulate additives is inhibited.

The present invention has been made to eliminate the drawbacks of the prior art described above, and its purpose is to provide a plating solution containing particulate additives such as oxides, carbides, nitrides, borides, and metals. In an electroless plating device that uses air bubbles to agitate the plating liquid with air ejected from an air pipe, an air bubble shielding plate is installed to prevent air bubbles from directly hitting the surface of the object to be plated. This also stabilizes the plating film thickness of the object to be plated and the precipitation of the particulate additive, thereby increasing the plating speed and improving work efficiency. That's true.

In short, the present invention provides oxides, carbides, nitrides,
In an electroless plating apparatus that uses a plating solution containing particulate additives such as borides and metals and agitates the plating solution with air jetted from an air pipe, the plating solution is immersed in the plating solution. A bubble shielding plate having a cross-sectional area slightly larger than the maximum cross-sectional area of the plated object is disposed between the plated object and the air pipe, so that air bubbles ejected from the air pipe reach the plated object. It is characterized by being constructed so that it does not come into direct contact with the object.

The present invention will be explained below based on embodiments shown in the drawings. The plating tank 1, diaphragms 2, 3, plating liquid 4, air pipe 5, air blowing hole 5a, object to be plated 7, and required plating area E are the same as the conventional example shown in FIGS. 1 to 3. Similarly, as shown in Figure 4,
A bubble shielding plate 9 is integrated with the plating liquid intrusion prevention device 8.
is arranged between the covered object 7 and the air pipe 5. The maximum cross-sectional area of the bubble shielding plate 9 is set to be slightly larger than the maximum cross-sectional area of the object to be plated 7 (required plating range E) immersed in the plating liquid 4. Preferably, when the object 7 has a circular cross-section, the difference between the maximum radius r ₁ of the object 7 and the radius r ₂ of the bubble shielding plate 9 in the target range E is set as a, and the air bubble shielding When the distance from the top surface 9a of the plate 9 to the liquid level 4a of the plating liquid 4 is b, the dimensions of each part are determined so that the ratio a/b of a and b is 0.1≦a/b≦0.3. Good. This was confirmed through experiments, and a/b was 0.1.
If the size is smaller than that, the bubble shielding plate 9 will not have the ability to block the bubbles 6, and the surface 7 of the object 7 on which the bubbles 6 will be covered.
If a/b exceeds 0.3, the shielding effect of the air bubbles 6 becomes very large, but the effect of stirring the plating liquid 4 by air is lost. It has been found that since the particulate additives near the surface 7a of the plated object 7 aggregate due to the surface tension, the particulate additives do not precipitate sufficiently.

Note that even when the shape of the object 7 to be fitted is not circular in cross section, the same concept may be used.

The present invention is configured as described above, and its operation will be explained below. The air ejected from the air pipe 5 becomes bubbles 6, which gradually expand and rise as shown in FIG. 4, and some of them hit the bubble shielding plate 9 and deviate laterally and rise. , the air bubbles 6 that come into direct contact with the surface 7a of the object 7 to be plated disappear. Moreover, the bubble 6 is on the surface 7a.
Since the plating liquid 4 passes relatively close to the plating liquid 4 and rises, the effect of stirring the plating liquid 4 by the bubbles 6 is not impaired at all. This is best achieved by keeping the ratio a/b in the range of 0.1 to 0.3.

As described above, the plating liquid 4 is sufficiently agitated by air, so that the particulate additives do not aggregate, and the air bubbles 6 do not come into contact with the surface 7a of the object 7 to be plated, so that the particulate additives are mixed together with the plating material. The additives are sufficiently precipitated, the plating film thickness is stabilized, and the plating speed becomes faster.

Since the present invention is constructed and operates as described above, it uses a plating solution containing particulate additives such as oxides, carbides, nitrides, borides, metals, etc., and the plating solution is supplied from an air pipe. In an electroless plating device that is stirred by jetting air,
Since an air bubble shielding plate is installed, air bubbles can be prevented from directly hitting the surface of the plated object, and as a result, the plating film thickness of the plated object and the precipitation of fine particle additives are even and stable. As the plating speed increases, the plating speed increases and work efficiency is improved.

[Brief explanation of the drawing]

Figures 1 to 3 relate to conventional examples, with Figure 1 being a plan view of the plating tank, Figure 2 being a vertical sectional view taken in the direction of the - arrow in Figure 1, and Figure 3 showing the relationship between the plated material and air bubbles. FIG. 4 is a partial vertical cross-sectional view showing the mutual relationship between the object to be fitted, the bubble, and the bubble shielding plate according to the embodiment of the present invention. 4 is plating liquid, 5 is air pipe, 6 is air bubble, 7
9 is a covering plate, and 9 is a bubble shielding plate.

Claims (1)

[Claims] 1. In an electroless plating apparatus using a plating solution containing particulate additives such as oxides, carbides, nitrides, borides, metals, etc., the plating solution is agitated with air jetted from an air pipe. A bubble shielding plate having a cross-sectional area slightly larger than the maximum cross-sectional area of the object to be plated that is immersed in the plating solution is disposed between the object to be plated and the air pipe, and air is blown out from the air pipe. An air agitation device for an electroless plating solution, characterized in that the air agitation device is configured to prevent air bubbles from directly hitting the object to be plated.