JPH09217200A - Anodic oxidation treating device for aluminum or aluminum alloy - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high-speed anodic oxidation device for aluminum or aluminum alloy which does not produce the occurrence of burning. SOLUTION: This device has a function generator D which generates the change quantity of an electrolytic current with lapse of time as an electric signal of voltage or current, etc., to an electricity supplying circuit for connecting an anode 5 connected to a work 4 consisting of the aluminum or aluminum alloy and a cathode 3 existing in the liquid to a power source, a current detector C and an automatic current controller B which regulates the electrolytic current in such a manner as to equal the signals passing a current feedback circuit from the current detector. In such a case, the anode circuit is provided with a current distributing resistor to uniformly distribute the flow rates of the electrolyte so that the electrolyte is uniformly injected onto the surface of the work, which is the anode, from the slit discharge ports 7 of a rotary injection panel 8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method for manufacturing a semiconductor device, comprising:
The present invention relates to an aluminum or aluminum alloy anodic oxidation apparatus capable of forming an anodic oxide film having the above-mentioned thickness at a high speed and greatly reducing an electrolytic treatment time.

[0002]

2. Description of the Related Art In recent years, the thickness of anodic oxide coatings made of aluminum or aluminum alloys on internal combustion engine pistons and semiconductor devices has been reduced from the conventional 20 to 50 μm to 80 μm.
m or more. Various devices are known for anodizing the surface of an object to be treated made of aluminum or an aluminum alloy using an acidic aqueous electrolyte containing sulfuric acid, oxalic acid, chromic acid, and the like. The need to increase the film thickness has been confirmed as a measure to prevent thermal cracks at the top of the piston due to the output and to prevent NOx, but this has not yet been achieved.

[0003] Depending on the material of the object to be processed, the electrolytic anodic oxidation treatment does not take a very long time, for example, 80 minutes or more, to obtain a thick film. In particular, since the time required for the anodizing treatment is longer in the case of processing an AC8A class heat-resistant silicon-containing aluminum alloy workpiece suitable as a material for a piston in an internal combustion engine, for example, the production efficiency in the anodizing process is reduced. Evil is pointed out.

[0004] In order to improve production efficiency and reduce the time of anodizing, the current density during the electrolytic anodizing may be increased, for example, to 10 to 30 A / dm ² or more. This method can be expected to have advantages not only in automation of the production line but also in characteristics of the anodized surface coating and space saving of manufacturing equipment.

However, when the anodic oxidation treatment is performed at 10 to 30 A / d
When performed at densities of m ² or more, local current concentration occurs on the surface being processed due to the generation of Joule heat and oxidative heat which eventually appears as a burning phenomenon, resulting in impaired appearance and unacceptable The production volume of surface anodized products is greatly reduced.

In order to solve the above-mentioned problems in the surface anodic oxidation treatment of an aluminum workpiece, Professor Hoshino of Musashi Institute of Technology has established a unique theory of preventing the burning phenomenon by means of controlling the electrolytic current. −
No. 23196 proposed an improved method of the above processing. According to this theory, the following equation (1) holds between the electrolytic current and the minimum thickness of the anodized surface film where the burning phenomenon occurs. ab = B / √i ... (1) (where, ab is the thickness of the anode surface coating, i is the electrolytic current density, and B is a constant determined by the material being treated, the composition of the electrolytic bath and the electrolytic conditions.) Equations (2) and (3) below: If 0 <t ≦ t ₀ , i = i ₀ (2) And if t ≧ t ₀ , i = i ₀ / [1 + β (t−t ₀ )] ^2/3 (3) (where β = 3Ki ₀ ^3/2 / SB, t is the electrolysis time, t
₀ is the initial electrolysis time, i ₀ is the initial electrolysis current density, i is the electrolysis current density at time t, K is the generation constant of the anodized surface film, B is the burning constant, and S is the safety factor. When) holds, the burning phenomenon is avoided even during high-speed anodizing. This patent publication discloses a function generator that converts a change in electrolytic current into an electric signal of voltage or current, a current detection device, and an automatic current control device that controls the signals from the current detection device to be equal. Discloses an apparatus for performing an anodizing treatment based on JIS.

In this apparatus, if the electrolytic anodic oxidation treatment is performed by gradually decreasing the electrolytic current along the burning curve so as to satisfy the above equations (2) and (3), the problem caused by burning can be avoided. An anodized surface film having a relatively large thickness can be obtained in a short time. For example, when the thickness of the desired anodized surface film is 90 μm, the bath voltage during electrolysis becomes a high voltage exceeding 100 V, and the anodized surface film sometimes generates a low hardness non-uniform layer having a HMV of 200 or less. Is known. The cause of this inconvenient phenomenon is probably that the surface anodic oxidation treatment is performed under the control of the electrolytic current, so that the bath voltage during the electrolysis becomes very high, which results in the formation of a non-uniform structure of the anodized surface film. It is presumed to cause this.

Therefore, as a method of avoiding the formation of a non-uniformly anodized surface film set, in the early stage of electrolysis, the electrolytic current is controlled so that the current density is constant until the bath voltage reaches a certain limit value. Further, once the bath voltage reaches a certain limit value, an anodizing treatment method in which the electrolytic current is continuously reduced so as to maintain the bath voltage at the limit value has been proposed (Japanese Patent Application Laid-Open No. HEI 2 (1990)). -325480). In this method, a uniform anodized film can be obtained by performing electrolysis according to a constant voltage control method (however, in this method, an increase in bath voltage exceeds a preset limit value). The disadvantage is that the electrolysis time required to complete electrolysis is longer than the theoretically expected shortest electrolysis time when the electrolysis current continuously decreases along the burning curve. is there.

When anodizing treatment is performed at a high current density, (a) the electrolysis cannot be continued unless the Joule heat or oxidation heat generated during the electrolysis is uniformly and quickly removed from the target surface. Since the liquid is sprayed onto the processing surface from the plurality of tubular fixed nozzles, the contact state between the electrolytic solution and the processing surface cannot be uniform over the entire surface, and (c) as described above, the liquid is sprayed on the surface. The anodized film formed is glossy due to uneven contact of the electrolytic solution, but the thickness is small on the surface area where the contact between the surface and the electrolytic solution is good. Insufficient removal of heat due to the thermal expansion of the surface area, where direct contact between the surface and the jetted solution is not obtained, is dull and uneven,
The physical strength of the coating is reduced.

[0010]

SUMMARY OF THE INVENTION In view of the foregoing, it is an object of the present invention to provide an aluminum article having a high electrolytic current density at a high electrolytic current density so as to be suitable for industrial production. An object of the present invention is to provide an apparatus for performing high-speed surface anodic oxidation.

[0011]

The object is achieved by a device according to the present invention. That is, the present invention provides an electric supply circuit that connects an anode connected to an object to be processed made of aluminum or an aluminum alloy and a cathode in an electrolytic solution of an electrolytic cell to a power supply, by applying a time-dependent change amount of an electrolytic current to a voltage or a current. In an anodizing apparatus provided with a function generator for generating an electric signal such as an electric current, a current detection device, and an automatic current control device for adjusting an electrolytic current so that a signal passing from the current detection device to a current feedback circuit becomes equal. An aluminum or aluminum alloy anodic oxidation treatment device that is provided with a current distribution resistor to uniformly distribute the flow rate of the electrolytic solution and uniformly spray the electrolyte from the slit discharge port of the rotary spraying plate to the surface of the anode workpiece. I do.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION In the apparatus of the present invention, in order to increase the efficiency and uniformity of removal of heat generated during electrolysis, an electrolytic solution is sprayed from a plurality of rotary spraying plates onto the surface of an object to be processed. The electrolytic current is evenly distributed and the flow of the electrolytic solution is divided. Due to these characteristics, the present invention makes it possible to perform high-speed anodizing of an aluminum workpiece at a high current density, even if the workpiece is a piston of an internal combustion engine or an aluminum alloy die-cast that cannot be electrolytically anodized by conventional methods. Become.

Hereinafter, the device of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic block diagram of an anodizing apparatus of the present invention. FIG. 2-1A shows a conventional fixed injection plate having a tubular nozzle discharge port, and FIG. It is a perspective view of each piston head. FIG. 2-2A is a perspective view of a rotary spray plate having a slit discharge port according to the present invention, and FIG. 2-2B is a perspective view of a piston head after anodizing by the apparatus of the present invention, and FIG. FIG. 4 is a schematic longitudinal sectional view showing a mechanism of rotation of the electrolytic cell and the injection nozzle.

As shown in FIG. 1, an electric supply circuit for connecting the anode 5 and the cathode 3 to a DC power supply A includes an automatic current control device B and a cathode current detection device C connected via a current feedback circuit. The signal generated by the cathode current detection device C is provided to the automatic current control device B. The current from the automatic current controller B is divided by the current distributor and supplied to the anode 5 through the resistor 10, the detector 11, and the circuit breaker 12. The function generator D generates a signal that changes according to a preset condition of the electrolytic current density, and this signal is guided to an automatic current controller through a control circuit, and an input signal from the cathode current detector C is input. The power supply is adjusted by the automatic current control device B such that the input signal from the function generator D matches the input signal from the function generator D.

The electrolytic bath 1 contains an electrolytic solution 2 and a cathode 3, and an object 4 to be anodized is connected to an anode 5 and held in the electrolytic solution 2 so as to be supported by a mask socket 6. An injection plate 8 having a slit discharge port 7 is installed at the bottom of the electrolytic cell 1. The discharge port 7 of the ejection plate is, for example, radially or when the number of slit discharge ports is four, as shown in FIG.
Has a plurality of slit discharge ports arranged in a cross shape as shown in FIG. 1, from which an electrolytic solution is jetted onto the surface of the object to be processed like a jet jet. The arrangement of the slit discharge ports is not limited to the radial arrangement as shown in the figure, but may be another arrangement as long as uniformity of distribution of jet injection is guaranteed. The number of slit outlets arranged radially is 3 to
6 is desirable, and especially 4 is desirable.

The electrolyte 2 is stored in a storage tank F, a pump P, a distribution valve 1
3. Circulate through the circuit connecting the flow meter, electrolytic cell 1 and heat exchanger (not shown). This electrolytic solution is led to the electrolytic cell 1 through the spray plate 8.

The most important feature of the above device is that the spray plate 8 can be rotated by a rotor 9 about a vertical axis. In the experiment of the fixed injection plate shown in FIG. 2-1A, since the injection plate has a plurality of tubular discharge ports 7a and is stationary without rotating, the jet injection of the electrolyte is uniformly applied to the entire surface of the piston head. Since the jet is not jetted and the intensity of the jet jet is strong at the portion facing the nozzle outlet, as shown in FIG. 2-1B, in the portion where the jet is weak, the treated film becomes non-uniform, and sometimes expands and the hardness decreases. And the gloss of the film is reduced. On the other hand, the electrolytic solution in the present invention is shown in FIG.
As shown in FIG. 2, since the liquid is ejected from a plurality of slit outlets of the rotary spraying plate, as shown by oblique lines in FIG. 2-2B, an anodic oxide film was uniformly formed on the entire surface to be treated.

When the slit discharge port of the injection plate is circular or protruding tubular as described above, uniform jet injection cannot be performed on the entire surface. Therefore, in the case of the discharge port of the present invention, each of the discharge ports has an elongated slit shape. Is important. A rotary spray plate with a long slit discharge port can increase the rotation speed to sufficiently remove heat from the surface to be processed.However, if the rotation speed is too high, the strength of the spray increases at the center of rotation, and centrifugation occurs. Because the effect causes the vortex of jet injection,
Should not be too high. At this point the rotation speed is 0.5
It should be between 10 and 10 revolutions / sec, preferably between 0.5 and 5 revolutions / sec. In order to ensure the uniformity of jet injection distribution, as shown in FIG. 2-2A, when the injection plate 8 includes four slit discharge ports 7 arranged in a cross shape,
0.5-3 rotations / second is desirable.

FIG. 3 is an embodiment slightly different from that shown in FIG. 1 and is an explanatory view of a main part of the anodizing apparatus of the present invention including the electrolytic cell 1. In this embodiment, a jacket tank 1A provided with a lid 1B is provided instead of the storage tank F forming a part of the electrolyte circulation circuit of FIG. 1, but as can be seen from the arrow indicating the flow path of the electrolyte. The operation principle of the device is the same. The gap between the object to be treated such as a piston head and the mask socket 6 is tightly sealed by an O-ring packing 16 that determines the surface H of the main body 4 to be anodized so as not to leak liquid. The discharge port 7 of the injection device is rotated by a rotor 9 having four turbine blades 15 and is rotated by energy of a liquid flow.

As can be seen from FIG. 1, the heat exchanger and the pump P
The plurality of anodizing devices shown in FIG. 3 are connected in parallel to one and the same controlled current supply system since the electrolyte coming from the reservoir F through the reservoir is divided into a plurality of partial flows by the distribution valve 13 Are operated at the same time. On the other hand, the total electrolysis current supplied from the automatic current control device B is equally divided by the current distribution control device E, and the divided current is supplied to each anode 5 by monitoring the current in the detection device 11. A circuit breaker (breaker) connected to the current distribution control device E when an abnormality due to burning or other trouble on the workpiece is detected by the detection device during the current flowing to one of the anodes 5. 12 opens the circuit. The signal generated in response to the "open" of the partial circuit is
The current supplied to the special object 4 is input from the current distribution control device E to the current control device B so as to enhance the effect of the current limit control.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to an embodiment.
The twelve electrolyzers 1 are connected in parallel to a single DC power supply A according to FIG. A piston block 4 for an automobile engine made of aluminum alloy AC8A containing 18 to 23% of silicon is inserted into each mask socket 6 of the electrolytic cell 1, and the head surfaces of the 12 piston blocks 4 are simultaneously anodized. Was done. As shown in FIG. 2A, the injection plate 8 of the rotary injection nozzle is provided with four elongated slit discharge ports 7 arranged radially in a cross shape.
An excellent stirring effect of the electrolytic solution and a sufficient and uniform cooling of the surface during the treatment are achieved, so that an anodized surface film of 75 to 100 μm thick can be obtained by anodizing for 1 to 10 minutes. The electrolytic anodic oxidation treatment was performed at a speed of one revolution per second while rotating the injection nozzle. The anodized surface was 0.78 dm ² . Generation constant K of anodized surface film and burning constant B in equations (1) to (3)
Was 0.53 and 450, respectively. Table 1 below
Shows data of current density in A / dm ² , safety factor, anodizing time T (second) and constant current time t in each experiment.

[0022]

[Table 1]

On the other hand, as shown in FIG. 2A, when the anodizing treatment of the piston block is performed using the stationary injection nozzle for the electrolytic solution, it is known that the gloss of the anodized surface is not uniform. And the current density is about 10
Although burning was not confirmed until A / dm ² was reached, no remarkable burning phenomenon occurred until the thickness of the anodized film reached the value shown in Table 1.
As a result, all of the twelve piston blocks could not pass the product inspection due to insufficient surface gloss.

[0024]

According to the present invention, the burning phenomenon associated with a high current density can be prevented, the time required for forming a thick anodic oxide film can be reduced to 1/10 of that of the prior art, and the film characteristics can be significantly improved.
Therefore, it is cheaper for the automation industry and semiconductor device industry,
Contribute to resource conservation and environmental issues by providing better quality products. In particular, in the case of automotive pistons, to prevent thermal cracking, it is necessary to form an anodic oxide film only on the top of the piston.
In the device of the present invention, just insert a special masking,
This can be used repeatedly, which saves masking man-hours and disposable masking material. A rational equipment line becomes possible.

[Brief description of drawings]

FIG. 1 is a schematic block diagram of an anodizing apparatus according to the present invention.

FIGS. 2-1A and 2-1B are perspective views of a conventional static injection spray plate having a tubular nozzle discharge port and a piston head after anodizing treatment, respectively. Fig. 2-2
FIGS. 2A and 2B are perspective views of a rotary spray plate having slit discharge ports according to the present invention and a piston head after anodizing treatment by the device of the present invention.

FIG. 3 is a schematic vertical sectional view showing a rotating mechanism of the electrolytic cell and the injection nozzle of the present invention.

[Explanation of symbols]

1: Electrolyzer A: Power supply 1B: Lid B: Current controller 1A: Jacket C: Current detector 2: Electrolyte D: Function generator 3: Cathode E: Current distribution controller 4: Workpiece F: Storage tank 5 : Anode P: Pump 6: Mask socket 7: Discharge port 8: Injection board 9: Rotor 10: Resistor 11: Detector 12: Circuit breaker 13: Distribution valve 15: Turbine blade 16: O-ring packing

Claims (6)

[Claims] 1. An electric supply circuit for connecting an anode connected to an object to be processed made of aluminum or an aluminum alloy and a cathode in an electrolytic solution of an electrolytic cell to a power supply, the time variation of the electrolytic current being measured by a voltage or a current. A function generator that generates as an electric signal, an anodizing treatment device equipped with an automatic current control device that adjusts an electrolytic current so that signals passing through a current feedback circuit from the current detection device and the current detection device are equalized. Anodizing treatment of aluminum or aluminum alloy characterized by providing a current distribution resistor, uniformly distributing the flow rate of the electrolyte, and uniformly spraying the electrolyte from the slit discharge port of the rotary spraying plate to the surface of the anode workpiece. apparatus. 2. The apparatus according to claim 1, wherein the slit discharge ports of the rotary injection plate are arranged in a cross shape. 3. The apparatus according to claim 1, wherein three to six slit discharge ports of the rotary injection plate are arranged radially. 4. The rotation speed of the rotary injection plate is 0.5 to 10 per second.
The device of claim 1, wherein the device is a rotation. 5. The apparatus according to claim 1, further comprising a current distributor for equally dividing a current from the automatic current controller into partial currents supplied to a plurality of electrolytic cells connected in parallel. The described device. 6. The apparatus according to claim 1, wherein a piston of the internal combustion engine is an object to be processed, and an unmasked top when a dedicated mask is inserted into the piston is a surface to be processed.