JP3169336B2 - Plating method of aluminum die casting - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for plating an aluminum die-cast in which the surface of a pre-treated aluminum die-cast is plated.

[0002]

2. Description of the Related Art Generally, when performing electroless or electrolytic plating on the surface of an aluminum die-cast, pretreatment such as etching is performed in order to enhance the "adhesion" of the plating. In other words, this pretreatment involves dissolving and roughening the surface of the aluminum die-casting with a treatment liquid, and forming the surface on an uneven rough surface. The “adhesiveness” of the plating applied on the uneven rough surface ] Has been improved.

[0003] In such aluminum die-casting plating, "glossiness" and "smoothness" are required in addition to the above-mentioned "adhesion", and among these, for improving the "glossiness" of the plating surface. If the proposal is, for example,
No. 0 discloses this. In the plating method described therein, the surface of an aluminum material is smoothed by buffing, pre-processed, and plated.

[0004]

However, the inventor of the present application has recognized that even if the "glossyness" is improved by the plating method by polishing described in the above-mentioned publication, there is the following problem with respect to "smoothness". I found it. That is, according to the polishing plating method described in the above-mentioned publication, it is possible to improve the "glossiness", but local projections remain on a part of the surface regardless of the degree of polishing. It was found that sufficient "smoothness" could not be obtained only by polishing. The present inventor has studied how this "local projection" is formed, and found that a pure aluminum member occupying most of the aluminum die-casting surface is melted by the pretreatment to become an uneven rough surface. It has been found that impurities such as Si and Cu and other non-soluble components contained in the aluminum die-casting may remain undissolved by the pretreatment, and are formed as “insoluble local projections”. Was.

[0005] Therefore, for example, when the plating surface of aluminum die-casting is opposed to the smooth surface of another member via a very small gap, the “insoluble local projection” formed on the plating surface is formed by the other member. It may collide with the smooth surface side. Therefore, conventionally, a post-process such as a cutting process is generally performed on a plating surface, and a predetermined “smoothness” is obtained only by removing “insoluble local projections” in the subsequent process. I have. Such a post-process is essentially an extra process.

Accordingly, an object of the present invention is to provide a plating method of aluminum die casting which can obtain good and easy gloss and smoothness of a plating surface of aluminum die casting.

[0007]

As described above, the inventor of the present application has found that "insoluble local projections" generated on the plating surface are formed by projecting insoluble impurities such as Si, Cu, etc., contained in the aluminum die cast. Although it was found that it was formed by remaining, the following invention was made as a means for suppressing the formation of the “insoluble local protrusion”.

That is, in order to achieve the above object, an invention according to claim 1 is to provide an irregularly roughened surface after dissolving a surface of an aluminum die-cast by pretreatment to form a roughened surface. In an aluminum die-casting plating method in which electroless or electrolytic plating is performed on an uneven rough surface formed by being dissolved in the pretreatment, and an insoluble formed by not being dissolved in the pretreatment. The pre-processing is performed so that the step between the local projection and the projection is within a predetermined minute amount.

Further, the invention according to claim 2 is that, after the surface of the aluminum die-cast is melted by pretreatment to form a roughened surface having irregularities, the electroless or electrolytically roughened surface is roughened after the pretreatment. In the method of plating aluminum die cast so as to perform plating, the maximum height of the uneven rough surface formed by being melted in the pretreatment, and the insoluble local protrusion formed by not being melted in the pretreatment. Is set within a predetermined minute amount, for example, within 1 μm.

Further, according to the present invention, the surface of the aluminum die-cast is melted by a pretreatment to form a roughened surface having irregularities, and then the electroless or electrolytically roughened surface is roughened after the pretreatment. In an aluminum die-casting plating method for performing plating, an average roughness (Rz) center line of an uneven rough surface formed by being melted in the pre-treatment, and being formed by not being melted in the pre-treatment. The pretreatment is performed so that the step between the insoluble local protrusion and the insoluble local protrusion is within a predetermined minute amount, for example, within 1.55 μm.

Further, the invention according to claim 4 is characterized in that the surface of the aluminum die-cast is melted by pre-treatment to form an uneven rough surface, and then the electro-deformed or rough surface is roughened after the pre-treatment. In the method of plating aluminum die cast so as to perform electrolytic plating, the maximum height based on the center line obtained by averaging the corrugated height of the uneven rough surface formed by being melted in the pretreatment. The pretreatment is performed so that a step between the insoluble local protrusion formed by not being dissolved in the pretreatment and the step is within a predetermined minute amount, for example, 1 μm.

According to the first to fourth aspects of the present invention, the height of the insoluble local projection with respect to the uneven rough surface formed by melting by the pretreatment is controlled within a necessary minute amount. Thus, good smoothness of the plated surface can be obtained.

On the other hand, according to a fifth aspect of the present invention, a predetermined small amount of the step according to the first or second or third or fourth aspect is set to 1 to 1.
The pretreatment is performed so as to be within 55 μm, and the step on the surface after plating is reduced to a very small amount within 1 μm.

According to the fifth aspect of the present invention,
The height of the insoluble local projections with respect to the uneven rough surface formed by melting by the pretreatment is controlled within 1 to 1.55 μm, so that the plating surface can have extremely good smoothness.

In this case, in the invention according to claim 6, the insoluble local protrusion according to claim 1, 2, 3 or 4 is formed by insoluble impurities contained in the aluminum die-cast.

Further, according to the invention of claim 7, according to claim 1,
Alternatively, the pretreatment described in 2 or 3 or 4 is performed as an etching process.

Further, in the invention according to the eighth aspect, the etching treatment according to the seventh aspect is characterized in that hydrofluoric acid and nitric acid are added in a ratio of 1 to 3 to 3: 1.
A step of immersing the surface of the aluminum die-cast in a treatment liquid containing 5 at a rate of 5 to 10 seconds.

According to the eighth aspect of the present invention,
By shortening the time of the etching treatment from the usual time, the height of the insoluble local projections with respect to the uneven rough surface formed by melting in the pretreatment is controlled within a required amount, so that plating is performed. At the same time as the smoothness of the surface is improved, the efficiency of workability is improved.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail. An example of a pretreatment step when plating the surface of an aluminum die-cast will be described. The applied material of the pretreatment step shown in FIG. 1 is ADC-12 or AC4C, and the unevenness state of the base material surface before the pretreatment step is performed is shown in FIGS. ). Since the surface of the base material before this treatment has few irregularities, the "adhesion" of the plating is not good as it is, so that the following pretreatment process is performed.

In the pretreatment step, first, in step 1 in FIG. 1, solvent degreasing is performed. In the solvent degreasing step, a cold liquid or a hot liquid such as trichlene or triethane is used, and the solvent degreasing is performed by performing steam cleaning at a constant temperature for a sufficient time.

In the step 2 after the water washing, an etching treatment with caustic soda is performed first if necessary. In this etching treatment, a 5 to 10% caustic soda solution is used, and the treatment is performed at room temperature for 1 to 5 minutes.

After washing with water, in the next step 3, an etching treatment is performed using a nitric hydrofluoric acid treatment solution comprising hydrofluoric acid and nitric acid. The hydrofluoric acid and nitric acid constituting the nitric hydrofluoric acid treatment solution used in this treatment are mixed at a ratio of 1: 3 to 5; for example, hydrofluoric acid 67% (150 cc / liter), nitric acid 50% (750 cc / liter). Liters). This nitric hydrofluoric acid treatment liquid is used at room temperature, and the surface of the aluminum die-cast is immersed in the nitric hydrofluoric acid treatment liquid for 5 to 10 seconds. As a result, a soluble component such as a pure aluminum component is formed on an uneven rough surface by melting, but impurities such as Si and Cu and other insoluble components are exposed on the surface. Is left undissolved by the nitric hydrofluoric acid etching treatment as described above. Therefore, as the nitric hydrofluoric acid etching process proceeds, the above-mentioned impurities and other non-soluble components remain in the form of local protrusions, thereby forming “insoluble local protrusions”.

Conventionally, the degree of nitric hydrofluoric acid etching, that is, the processing time, is not controlled at all, and the etching is performed for a relatively long time only from the viewpoint of performing the etching sufficiently. I have. When the etching process is performed for a relatively long time, for example, for 15 seconds, as shown in FIG.
As shown in (a), (b), and (c), the dissolution of a soluble component such as a pure aluminum member progresses with the progress of the etching process, and the rough surface 1 having strong irregularities is formed. You. On the other hand, as the dissolution of the soluble component progresses,
The insoluble local projections 2 due to impurities such as i and Cu and other undissolved components are formed higher, and the "insoluble local projections" are formed higher, thereby impairing the "smoothness" of the plating surface. It will be.

On the other hand, in the present embodiment, the processing time is set to a relatively short time such as 5 to 10 seconds as described above, whereby the dissolution of the uneven rough surface is controlled to an appropriate range. The step between the maximum height of the unevenness on the uneven rough surface and the top of the insoluble local projection is a predetermined minute amount, for example, 1
It is controlled to be within μm, so that good “smoothness” can be obtained.

For example, FIGS. 4 (a), (b), and (c)
The surface state after the treatment when the etching treatment with the nitric hydrofluoric acid treatment liquid is set to 10 seconds is shown. In this case, the insoluble local protrusion having a relatively low height with respect to the uneven rough surface 1 is shown. 2, and the step between the maximum height of the unevenness on the uneven rough surface 1 and the top of the insoluble local protrusion 2 is made as small as about 0.3 μm. 5 (a) and 5 (b) showing the surface state after electroless or electrolytic plating.
Has a step within 1 μm.

FIGS. 6 (a), 6 (b) and 6 (c)
The surface state after the treatment when the etching treatment with the nitric hydrofluoric acid treatment liquid is set to 5 seconds is shown. In this case,
An insoluble local protrusion 2 having a lower height is formed on the uneven rough surface 1, and a step between the maximum height of the unevenness on the uneven rough surface 1 and the top of the insoluble local protrusion 2 is about 0.2
It is made in a very small amount of about μm. Further, in FIGS. 7A and 7B showing the surface state after electroless or electrolytic plating, the level difference is only 0.5 μm or less.

In this case, the reference position of the uneven rough surface may be, in addition to the maximum height of the uneven surface described above, the average roughness (Rz) center line of the uneven rough surface, or the wavy shape of the uneven rough surface. The maximum height or the like based on a center line obtained by averaging can be adopted.

Returning to FIG. 1, after such an etching process is completed and washed with water, in the next step 4, zinc substitution is performed. This zinc substitution, for example,
A one-to-one concentration solution is used and is carried out at room temperature for 20-30 seconds. This zinc substitution is performed in the next step 5
Is carried out again in step 6 with the pickling in step. The pickling in the above step 5 is, for example, 67% of nitric acid.
Using a solution (300 cc / liter) at room temperature
Performed over 15 seconds.

When the pre-processing steps from step 1 to step 6 are completed, a predetermined electroless or electrolytic plating is performed in step 7 after washing with water. After completion of the electroless or electrolytic plating, washing is performed, and the drying step is finally performed.

As described above, in the present embodiment, the height of the insoluble local projections with respect to the uneven rough surface formed by melting in the etching step is required by shortening the etching time compared to the normal time. It is controlled within a very small amount, and very good plating surface smoothness can be efficiently performed in a short time.

Although the embodiments of the present invention made by the inventor have been specifically described above, the present invention is not limited to the above-described embodiments, and can be variously modified without departing from the gist thereof. Needless to say.

For example, the etching treatment liquid is not limited to the nitric hydrofluoric acid treatment liquid in the above-described embodiment, and any other treatment liquid can be used.

Further, the present invention is not limited to shortening the time of the etching process as in the above-described embodiment, and may reduce the degree of the pre-processing in the process steps other than the etching process. Good.

[0034]

As described above, according to the present invention, the height of the insoluble local projections with respect to the uneven rough surface formed by melting by the pretreatment is reduced by appropriately reducing the degree of the pretreatment. It is controlled within the required minute amount, and the extremely good electroless or electrolytic plating surface `` smoothness '' is made to improve the efficiency of plating work by simple processing, so that the electroless or aluminum die casting The quality of electrolytic plating can be easily and significantly improved, and post-processes such as cutting can be omitted, so that the reliability and productivity of the electroless or electrolytic plating process for aluminum die casting can be improved.

[Brief description of the drawings]

FIG. 1 is a flowchart showing a pretreatment step according to an embodiment of the present invention.

FIG. 2 is an enlarged diagram illustrating a state of a surface roughness of a base material before a pretreatment process is performed.

FIG. 3 is an enlarged diagram showing a state of surface unevenness when a nitric hydrofluoric acid etching process is performed for 15 seconds.

FIG. 4 is an enlarged diagram showing a state of surface irregularities when a nitric hydrofluoric acid etching process is performed for 10 seconds.

FIG. 5 is an enlarged diagram showing a surface unevenness state after electroless or electrolytic plating is performed on the surface of FIG. 4;

FIG. 6 is an enlarged diagram showing a state of surface irregularities when a nitric hydrofluoric acid etching process is performed for 5 seconds.

FIG. 7 is an enlarged diagram showing a surface unevenness state after electroless or electrolytic plating is performed on the surface of FIG. 6;

[Explanation of symbols]

 1 Rough surface with irregularities 2 Insoluble local protrusion

Claims (8)

(57) [Claims] 1. An aluminum die casting in which the surface of an aluminum die casting is melted by a pretreatment to form a roughened surface having irregularities, and then electroless plating or electrolytic plating is performed on the roughened surface after the pretreatment. In the plating method, the step between the uneven rough surface formed by the component dissolved in the pre-treatment and the insoluble local protrusion formed by the component not dissolved in the pre-treatment is within a predetermined minute amount. A method of plating aluminum die-casting, wherein a pretreatment is performed as follows. 2. An aluminum die casting wherein the surface of the aluminum die casting is melted by a pretreatment to form a roughened surface with irregularities, and then the electroless plating is performed on the roughened surface after the pretreatment. In the plating method, the step between the maximum height of the uneven rough surface formed by the components dissolved in the pre-treatment and the insoluble local protrusions formed by the components not dissolved in the pre-treatment, A method of plating aluminum die-casting, wherein a pre-treatment is performed to keep the amount within a very small amount. 3. An aluminum die casting wherein the surface of the aluminum die casting is melted by a pretreatment to form a roughened surface having irregularities, and then the electroless plating is performed on the roughened surface after the pretreatment. In the plating method, the average roughness (Rz) center line of the uneven rough surface formed by the component dissolved in the pretreatment and the insoluble local protrusion formed by the component not dissolved in the pretreatment. A plating process for aluminum die-casting, wherein the pre-treatment is performed so that the step is within a predetermined minute amount. 4. An aluminum die cast wherein the surface of the aluminum die cast is melted by pretreatment to form a roughened surface having irregularities, and then the electroless plating is performed on the roughened surface having irregularities after the pretreatment. In the plating method of, the maximum height based on the center line obtained by averaging the corrugated height of the uneven rough surface formed by the components dissolved in the pre-treatment, and the components that are not dissolved in the pre-treatment A method of plating aluminum die-casting, wherein a pre-treatment is performed so that a step between the formed insoluble local projection and the formed insoluble local projection is within a predetermined minute amount. 5. A pretreatment is performed so that a predetermined minute amount of the step according to claim 1 or 2 or 3 or 4 is within 1 to 1.55 μm, and a minute amount of the step on the surface after plating is within 1 μm. A method of plating aluminum die-casting, characterized in that: 6. A method for plating an aluminum die cast, wherein the component for forming the insoluble local protrusion according to claim 1, 2, 3 or 4 comprises an insoluble impurity contained in the aluminum die cast. 7. A method for plating aluminum die cast, wherein the pretreatment according to claim 1, 2, 3 or 4 is an etching treatment. 8. An etching process according to claim 7, wherein the surface of the aluminum die-cast is immersed in a processing solution containing hydrofluoric acid and nitric acid at a ratio of 1: 3 to 5 for 5 to 10 seconds. A method of plating aluminum die-casting.