JP3196207B2 - Electroplating method for aluminum material - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for electroplating an aluminum-based material, and more particularly, to a method of activating a surface of a substrate made of an aluminum-based material in a plating solution, The present invention relates to a method for electroplating an aluminum-based material for performing desired plating directly without performing a plating process or the like.

[Conventional technology and its problems]

Aluminum-based materials are lightweight, have excellent properties such as high thermal conductivity and high electrical conductivity, and are used in various fields as various components.

In recent years, in order to impart functions such as solderability, corrosion resistance, and abrasion resistance to the aluminum-based material, a plating treatment on the aluminum-based material is often required. However, since aluminum is easily oxidized, when plating is performed, even if a cleaning treatment is performed as a pretreatment, the surface becomes inactive as soon as it comes into contact with the atmosphere, and no plating film is formed in the plating treatment process, The formation was uneven, or the plating film was insufficiently adhered to the substrate, causing blistering, and no practically usable plating film was obtained.

As a method of solving the problem of the prior art, after performing a cleaning treatment of a substrate, zinc, a zinc alloy, and a thin metal film of tin are replaced and deposited by a zincate method, a bondal method, and an Alstan method, respectively. A method has been proposed in which electroplating is carried out via a substrate. However, in these methods, for example, in the case of the zincate method, a double zincate treatment in which zinc substitution treatment is performed twice is necessary in order to form a reliable plating film having strong adhesion, and further, after the zinc substitution, the coating of the film is required. Each method has a problem that the process is complicated, for example, copper cyanide or nickel strike plating is required for base plating in order to prevent dissolution.

Further, as another solution, an intermediate layer is formed by immersing a pair of electrodes insoluble with aluminum in an electrolytic solution and alternately applying positive and negative voltages between the two to activate the aluminum surface. There has been proposed a plating method on aluminum by electrolytic activation, in which a smooth plating excellent in adhesion is directly formed on aluminum without electrolytic bonding (JP-A-62-297492). It is stated that this makes it possible to improve plating adhesion and to perform plating directly on aluminum without using an intermediate layer. However, since this method enables direct plating by special electrolytic activation, a special power supply equipment and a complete set of electrolytic equipment are required, and the equipment is complicated, large-scale, and expensive. Was.

The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems of the prior art, and have conducted various systematic experiments. As a result, the present invention has been accomplished.

[Object of the invention]

An object of the present invention is to provide a method for electrolytic plating on an aluminum-based material which realizes plating with excellent uniformity and adhesion at a simple method and at low cost.

The present inventors have focused on the following with respect to the above-described problems of the related art. That is, first, attention was paid to an electroplating treatment solution as a means for overcoming the above-mentioned problems of the above-described conventional intermediate plating treatment and plating treatment requiring special electrolytic treatment before plating.

Therefore, the surface of the substrate made of an aluminum-based material is activated to an optimal state for plating only by immersion in the electroplating solution, utilizing the activating action of the electroplating solution itself. By omitting the above, the desired plating treatment can be directly performed, and the simplification of plating equipment, improvement of productivity, and improvement of plating quality are realized.

[Description of First Invention] Structure of First Invention In the method for electroplating an aluminum-based material according to the first invention, the surface of a substrate made of an aluminum-based material is immersed in an electroplating solution, and a natural electrode having a constant substrate After the substrate is activated until the potential is reached, the substrate is activated, and then energized to perform electroplating to form a plating film.

Functions and Effects of the First Invention According to the method for electroplating an aluminum-based material of the first invention, a uniform and excellently adhered plating film can be formed on a substrate by a simple method and at low cost.

The mechanism by which the method for electroplating an aluminum-based material of the first invention exerts the above-mentioned effects is not necessarily clear, but is considered as follows.

That is, in the method of the first invention, when the surface of the substrate made of an aluminum-based material is immersed in an electroplating solution controlled under appropriate conditions for a predetermined time, the natural electrode potential of the substrate made of the aluminum-based material changes according to the pH. The predetermined value is obtained, and the plating film forming portion of the substrate is activated to an optimal state for plating. Then, by starting current supply after the substrate has a surface property corresponding to a certain natural electrode potential, direct electroplating of a plating film having a predetermined thickness, uniformity and excellent adhesion is possible. Becomes At this time, since the formation of the plating film is performed by an electrochemical reaction, that is, a reaction using the electrode potential as a parameter, its progress strongly depends on the natural electrode potential of the substrate, and therefore, the direct electroplating becomes possible. Conceivable. Therefore, since the activation step and the electroplating step can be performed continuously in the same electroplating treatment solution, the active surface of the substrate obtained in the activation step does not come into direct contact with air. It is considered that the inactivation (oxidation) of the metal is suppressed, and direct plating with high adhesion can be performed.

[Description of Second Invention] Hereinafter, an invention (hereinafter referred to as a second invention) that is a more specific version of the first invention will be described.

In the second invention, the aluminum-based material is cast,
An aluminum material or an aluminum alloy material manufactured by a method such as rolling, extrusion, or sintering is used. The shape may be any shape such as a block, a plate, a pipe, etc., as long as the surface can be plated.

In addition, when the prepared substrate is in a clean state,
This activation treatment may be applied immediately. However, in the case of a commonly available material or a substrate that has been subjected to secondary machining, a dirt such as an oxide film or oil has adhered. It is preferable to carry out a cleaning treatment for removing such stains before starting the treatment. The cleaning treatment may be performed by a usual method using a normal cleaning treatment liquid such as neutral degreasing without etching or an acid or alkaline cleaning liquid with etching.

Further, in the second aspect of the present invention, since the surface roughening of the substrate surface is not a necessary condition, when surface gloss after plating is required, cleaning by chemical polishing or electrolytic polishing may be performed.

In the present invention, as the electroplating treatment solution, a usual electroplating treatment solution can be used. For example, nickel (Ni) plating is a nickel sulfate solution, nickel sulfamate solution, and copper plating is pyrophosphoric acid. Copper acid liquid, etc.
It does not have to be particularly strong in acidity or alkalinity.

Since the aluminum-based material is chemically active, it easily forms an oxide film, which hinders the plating process.
This high reactivity is the same in the plating solution. That is, the copper sulfate plating solution (pH <1) or the copper cyanide plating solution (pH = 11 to 13) is too acidic or alkaline, so that when immersed in the plating solution, the metal rapidly becomes aluminum. Substitution precipitation occurs on the surface of the system material. When current is applied in such a situation, the plating film is formed for the time being, but the adhesion cannot be expected, for example, peeling already occurs during plating. Therefore, in order to apply the method of the present invention, the pH range of the electroplating solution is preferably 3 to 10. In addition, it is preferable that the range of the pH is about 3 to 6 for an acidic treatment liquid, and that the range of the pH is about 8 to 10 for an alkaline treatment liquid.

In the method for electroplating an aluminum-based material according to the second invention, the surface of the substrate made of the aluminum-based material is immersed in the electroplating solution until the substrate has a surface property corresponding to a constant natural electrode potential. After holding and activating the substrate, electricity is supplied to perform electroplating to form a plating film.

In the electroplating method of the present invention, the most characteristic feature is that the end time of the activation treatment, that is, the time (holding time) at which the substrate surface is sufficiently activated to start energization,
The determination is based on the nobleness of the natural electrode potential of the substrate in the electroplating solution. That is, in the activation treatment, the substrate is kept in a non-energized state until the natural electrode potential of the substrate reaches a predetermined potential value in a predetermined electroplating solution.

Note that the range of the constant natural electrode potential depends on the plating solution.
Considering the plating conditions such as pH and temperature, the plating metal, etc., the range of the natural electrode potential, which is set in advance based on the prior data, etc., to form a plating film with excellent adhesion, should be set. it can.

Depending on the type of the substrate and the composition of the plating solution, even if the activation proceeds during the holding time, there is a case where no remarkable change in the natural electrode potential appears correspondingly. Specifically, it fluctuates within a predetermined potential range where activation is achieved from the beginning when the substrate is immersed in the electroplating treatment solution, and it is difficult to determine the end of the holding time only from the measurement of the electrode. Is the case. In such a case, the relationship between the holding time and the adhesion of the plating film is determined in advance, and an appropriate holding time is set. It can be determined whether or not the plating film has been activated to be easily formed. After the lapse of the time, by energizing and electroplating to form a plating film, high adhesion of the plating film can be secured.

The measurement of the natural electrode potential is performed in the electroplating solution.

The substrate and the saturated calomel electrode (SCE), which have been cleaned as required, are immersed in the electroplating solution, and the natural electrode potential of the substrate is immediately measured with a potentiometer. here,
As the reference electrode, other than the saturated calomel electrode, for example, each electrode of silver chloride, mercury chloride or the like can be used.
When an electrode other than a saturated calomel electrode is used, it can be determined based on whether the value converted based on the saturated calomel electrode satisfies the conditions based on the saturated calomel electrode. Can be set to make the determination.

Since the potential condition that satisfies the sufficient activation depends on the type of the electroplating treatment solution and the cleaning method, it is necessary to determine the relationship between the potential and the adhesion force in advance. The lower the pH of the plating solution, the higher the pH of the alkaline electroplating solution and the higher the temperature of the processing solution, the shorter the time required for activation (holding time). However, the pH of the plating solution
Is related to the physical properties of the resulting film and the stability of the plating solution, and the pH of the plating solution is selected within a range that satisfies the required conditions and characteristics. After being activated in this way, the plating film formed to a desired thickness by starting current supply is firmly adhered to the substrate, and does not cause problems such as peeling in ordinary use. However, in order to further ensure the reliability of the adhesion, it is desirable to perform baking, for example, baking at a temperature of 200 ° C. for about one hour.

Here, copper pyrophosphate 80 g / potassium pyrophosphate 35
Using a copper pyrophosphate electroplating treatment solution consisting of 0 g / pH adjusted to 8.5, degreasing as a cleaning treatment, alkali etching, and desmutting with 30% nitric acid for 30 seconds, sufficient adhesion FIG. 1 shows the natural electrode potential and the holding time of the substrate for obtaining the active surface necessary for showing the strength. In the figure, the shaded portion indicates the range of the natural electrode potential at which a copper film with high adhesion is obtained. Therefore, after immersing the cleaned substrate in a copper pyrophosphate plating solution, the natural electrode potential of the substrate is in the above range, that is, about -0.1.
If the voltage is maintained from 65 volts (V) to about −0.45 V, activation of the substrate surface is sufficiently achieved, and thereafter, when current is supplied, an electrolytic copper plating film having excellent adhesion can be obtained. . Further, in the figure, in order to make it easier to understand the relationship between the electrode potential and the holding time and the temperature of the processing liquid, the processing liquid temperature is indicated by A (indicated by “A” in the figure), B (indicated by “B "
, And C (shown as “C” in the figure). The relationship between the liquid temperatures is A <B <C
It is. As is clear from the figure, the higher the temperature of the processing solution, the sooner the target potential condition is satisfied. For example, in the case of B, it is sufficient that the holding time is 60 seconds or more. The figure shows an example in which nitrate desmutting is performed, and the potential behavior differs depending on the processing method.

Next, using a nickel sulfate electroplating treatment solution consisting of 300 g of nickel sulfate and 40 g of boric acid and adjusting the pH to 4.5, degreasing as a cleaning treatment, alkali etching, and then desmutting with 30% nitric acid for 30 seconds. FIG. 2 shows the natural electrode potential and the holding time of the substrate for obtaining an active surface necessary for exhibiting sufficient adhesion strength. In the figure, the shaded portion is the range of the natural electrode potential at which a nickel film with high adhesion is obtained. Therefore, after immersing the cleaned substrate in the nickel sulfate plating solution, the natural electrode potential of the substrate is in the above range, that is, about -0.70.
By holding it from V to a range of about -0.45 V, activation of the substrate surface is sufficiently achieved.
An electro-nickel plating film having excellent adhesion can be obtained. Further, FIG. 3 shows a difference in electrode potential due to a difference in alloy composition of the base. A simple potential change is observed in the substrate D (indicated as “D” in the figure), and it is understood that a holding time of 120 seconds or more is sufficient. On the other hand, in the case of the substrate E (indicated as “E” in the figure), despite the same pretreatment as the substrate D, after showing a somewhat complicated time change, it settles to around −0.6 V, and the holding time as described above Is difficult to determine only from the natural electrode potential, in such a case,
An appropriate holding time indicating the activated state is set to 60 seconds from the relationship with the adhesion of the formed plating film obtained in advance. In this case, due to the elapse of the holding time (60 seconds),
It can be determined that the activation has been sufficiently performed.

In the method for electroplating an aluminum-based material according to the second aspect of the present invention, the mechanism enabling direct electroplating is not necessarily clear yet, but is considered as follows.

That is, since the treatment liquid is weakly alkaline or weakly acidic, the surface oxide of the aluminum-based material is gradually dissolved by a chemical action and an active surface (metal surface) appears. In such a state, aluminum is eluted due to a difference in ionization tendency, and copper ions or nickel ions in the plating solution are replaced and precipitated. These activation reaction and displacement precipitation reaction are affected by the temperature of the processing solution, the pH, and the composition of the processing solution. The retention time tends to be shorter at higher temperatures as the acidity or alkalinity is stronger. Conventionally, a substitution reaction in a plating solution is considered to be a cause of a decrease in adhesion between a substrate and a plating film, and various measures have been taken to suppress this reaction as much as possible. However, contrary to the conventional idea, focusing on the usefulness of the holding time, by setting the composition of the electroplating solution to an appropriate range where these reactions do not occur rapidly, and by monitoring the electrode potential. By maximizing the activating action of the processing solution while preventing excessive substitutional precipitation, it is possible to form a uniform and excellent adhesion plating film on the substrate in a simple manner and at low cost. It seems to have been.

In the second invention, in addition to the effects of the first invention,
Further, the following effects are obtained.

That is, the surface of the substrate made of an aluminum-based material is
By utilizing the activating action of the electroplating solution itself, it can be activated to an optimal state for plating. In addition, the desired plating process can be directly performed, and simplification of plating equipment, improvement of productivity and The plating quality can be improved.

In addition, the desired plating can be performed directly on the surface of the substrate without subjecting the surface of the substrate made of an aluminum-based material to an intermediate plating process such as zinc substitution plating or the like, and without requiring a special electrolytic device. In addition, special strike plating is not required to prevent elution of the intermediate film, so that equipment costs can be reduced and productivity can be improved. further,
Since the activation and the electroplating are performed in the same bath and are continuous treatments, the activity can be always maintained at a high level, so that uniformity of plating and adhesion can be easily ensured.

〔Example〕

 Hereinafter, embodiments of the present invention will be described.

Example 1 A substrate made of an aluminum-based material (JIS A1100, 50 m long)
m, width 50 mm, thickness 1 mm) was prepared, and one surface of the base was sealed with epoxy resin in advance leaving 10 2 × 2 mm areas, and the exposed portions were prepared as plated portions.

Next, as an electroplating treatment solution, copper prophosphate 80 g /
Two kinds of copper pyrophosphate electroplating treatment solutions were prepared, each of which consisted of potassium pyrophosphate and 350 g / potassium and whose pH was adjusted to 8.5 or 9.5.

Next, the substrate was degreased with a water-soluble degreasing agent for aluminum, etched using an aqueous solution of 50 g / sodium hydroxide, further desmutted with a 30% aqueous nitric acid solution, and cleaned.

Next, the substrate and the saturated calomel electrode were immersed in the electroplating solution to form an electroplating apparatus.

After performing the activation treatment at the treatment liquid temperature, pH and retention time shown in Table 1, current was passed at 5 A / dm ² for 10 minutes to form a copper plating having a thickness of about 10 μm. This copper plating layer was a uniform plating layer having an even surface and a smooth surface. Table 1 shows the natural electrode potential at the end of the holding time by the activation process, that is, immediately before the start of energization. Thereafter, for the purpose of preventing copper erosion by solder, electroless nickel plating was further applied to a thickness of 2 μm, and baking treatment was performed at 200 ° C. for 1 hour.

A performance evaluation test of the obtained plated material was performed by a break test. That is, a tin-plated copper wire of 0.8 mmφ was soldered to the plated portion, and a breaking test was performed using a tensile tester. Whether the adhesion is good or not is determined based on whether the fracture position is inside the solder layer or at the interface between the copper plating and the substrate. Table 1 shows the results obtained by the test.

For comparison, a comparative substrate was subjected to electroplating under the same conditions as in Example 1 except that the holding time of the substrate in the electroplating solution was short, and a similar performance evaluation test was performed. (Sample numbers C1 to C10). The results are shown in Table 2.

As is clear from Tables 1 and 2, the temperature of the processing solution was
At 50 ° C., a plated film having good adhesion was obtained for Sample Nos. 1 and 2, which had a natural electrode potential of more than about −0.65 V. In contrast, sample number C1 in which the natural electrode potential could not exceed about -0.65 V during the holding time
In ~ C4, activation was insufficient, and peeling occurred at the plating interface. When the temperature of the processing solution was 60 ° C., a plating film having good adhesion was obtained for Sample Nos. 3 to 8 satisfying the natural electrode potential, and the substrate surface was activated by increasing the temperature of the processing solution. It can be seen that the holding time required to perform the operation is reduced.

Next, when viewed in terms of the pH of the plating solution, the pH of the
In the case of 8.5, a plated film having good adhesion was obtained for Sample Nos. 1 to 5 in which the natural electrode potential was more than about -0.65 V. On the other hand, in sample numbers C1 to C7 in which the natural electrode potential could not exceed about -0.65 V during the holding time, the activation was insufficient and the peeling at the plating interface occurred.
In addition, when the pH of the processing solution was 9.5, a plating film having good adhesion was obtained for Sample Nos. 5 to 8 satisfying the natural electrode potential, and in the alkaline processing solution, the pH of the processing solution was increased. It can be seen that the holding time required for activating the substrate surface is reduced.

Example 2 An aluminum substrate having the same shape as in Example 1 (JIS A105
0) was prepared and similarly prepared as a sample substrate.

Next, as an electroplating treatment solution, copper pyrophosphate 80 g /
A copper pyrophosphate electroplating treatment solution was prepared, which was made up of 350 g / potassium pyrophosphate and adjusted to pH 8.5.

Next, when the base was subjected to alkali etching in the same manner as in Example 1, the formation of smut was small.
Cleaning was completed.

Next, the substrate and the saturated calomel electrode were immersed in the electroplating solution to form an electroplating apparatus.

After the activation treatment at the treatment solution temperature and the holding time shown in Table 3, current was passed at 5 A / dm ² for 10 minutes to form copper plating with a thickness of about 10 μm. This copper plating layer was a uniform plating layer having an even surface and a smooth surface. Table 2 shows the natural electrode potential at the end of the holding time by this activation process, that is, immediately before the start of energization. Then, in order to prevent copper erosion, a further 2 μm thick electroless nickel plating is applied.
A baking treatment was performed at 0 ° C. × 1 hr.

A performance evaluation test of the obtained plated material was performed in the same manner as in Example 1. Table 3 shows the results obtained by the test.

For comparison, a comparative substrate was subjected to electroplating under the same conditions as in Example 2 except that the holding time of the substrate in the electroplating solution was short, and a similar performance evaluation test was performed. (Sample numbers C11 to C17). The results are shown in Table 2.

As is apparent from Table 3, the substrate of the present example has Naturally, the electrode potential changes slightly more complicatedly than the case where the nitrate desmutting treatment of Example 1 was performed, but the film having a high adhesion exceeded the initial noble potential by about −0.45 V in the base direction. It can be seen that it can be obtained under the following conditions. That is,
When the processing liquid temperature is 50 ° C., sample numbers 9 and 10 correspond to the processing liquid temperature, and when the processing liquid temperature is 60 ° C., sample numbers 11 and 12 correspond thereto.

On the other hand, during the holding time, the natural electrode potential is about -0.45
Sample numbers C11 to C1 that could not cross V in the base direction
In No. 7, the activation was insufficient, and peeling occurred at the plating interface.

Example 3 Seven types of aluminum substrates having the same shape as in Example 1 (99.9%
Al, JIS A 2024, JIS A 3003, JIS A 4343, JIS A 5052, JIS
A 6101, JIS A 7075) was prepared and similarly prepared as a sample substrate.

Next, as an electroplating treatment solution, copper pyrophosphate 80 g /
A copper pyrophosphate electroplating treatment solution was prepared, which was made up of 350 g / potassium pyrophosphate and adjusted to pH 8.5.

Next, after the base was degreased with a water-soluble degreasing agent for aluminum, etching was performed using an aqueous solution of 50 g / sodium hydroxide.
Desmut with a nitric acid aqueous solution and other substrates with a nitric hydrofluoric acid aqueous solution consisting of 4% hydrofluoric acid + 20% nitric acid aqueous solution, respectively.
Cleaning was performed.

Next, the substrate and the saturated calomel electrode were immersed in the electroplating solution to form an electroplating apparatus.

Then, after performing an activation treatment at a treatment solution temperature of 60 ° C. and a holding time shown in Table 3, the mixture was energized at 5 A / dm ² for 10 minutes to about 10 μm.
An m-thick copper plating was formed. This copper plating layer was a uniform plating layer having an even surface and a smooth surface. Table 4 shows the natural electrode potential at the end of the holding time by the activation process, that is, immediately before the start of energization. Thereafter, for the purpose of preventing copper erosion, electroless nickel plating having a thickness of 2 μm was further performed and baking treatment was performed at 200 ° C. for 1 hour.

A performance evaluation test of the obtained plated material was performed in the same manner as in Example 1. Table 4 shows the results obtained by the test.

For comparison, a comparative substrate was subjected to an electroplating process under the same conditions as in Example 3 except that the holding time of the substrate in the electroplating solution was short, and a similar performance evaluation test was performed. (Sample numbers C19 to C23). The results are shown in Table 4.

As is clear from Table 4, the natural electrode potential was about -0.65.
For Sample Nos. 13 to 19 satisfying nobleness than V, plated films with good adhesion were obtained. On the other hand, in sample numbers C18 to C24 in which the natural electrode potential could not exceed about -0.65 V during the holding time, the activation was insufficient, and peeling at the plating interface occurred.

As described above, the composition of the electroplating treatment solution of the present embodiment, that is, the condition of the copper pyrophosphate plating bath having a pH of 8.5, regardless of the type of the substrate, the natural electrode potential in the treatment bath. Is within a predetermined range, i.e., from about -0.65V to about -0.4.
Achieves activation of the substrate surface by holding it in the 5V range It can be seen that an electric copper plating film having excellent adhesion can be obtained by applying a current thereafter.

Example 4 An aluminum substrate having the same shape as in Example 1 (JIS A110
0) was prepared and similarly prepared as a sample substrate.

Next, as an electroplating treatment solution, nickel sulfate 300 g /
And 40 g / boric acid, and two kinds of nickel sulfate electroplating treatment solutions were prepared whose pH was adjusted to 4.5 or 3.5.

Next, the substrate was subjected to degreasing and alkali etching in the same manner as in Example 1, and further desmutted with a 30% nitric acid aqueous solution to perform cleaning.

Next, the substrate and the saturated calomel electrode were immersed in the electroplating solution to form an electroplating apparatus.

Next, after performing an activation treatment at a treatment liquid temperature of 60 ° C. and a pH and a retention time shown in Table 5, a current of 5 A / dm ² was supplied for 10 minutes to form a nickel plating having a thickness of about 10 μm. This nickel plating layer was a uniform plating layer having an even surface and a smooth surface. Table 5 shows the natural electrode potential at the end of the holding time by the activation process, that is, immediately before the start of energization. Thereafter, a baking treatment was performed at 200 ° C. for 1 hour.

A performance evaluation test of the obtained plated material was performed in the same manner as in Example 1. Table 5 shows the results obtained by the test.

For comparison, a comparative substrate was subjected to electroplating under the same conditions as in Example 4 except that the holding time of the substrate in the electroplating solution was short, and a similar performance evaluation test was performed ( Sample numbers C25 to C29). The results are shown in Table 5.

As is evident from Table 5, when the pH of the treatment solution was 4.5, plated films having good adhesion were obtained for Sample Nos. 20 and 22, which had a natural electrode potential of about -0.70 V and satisfied nobleness. On the other hand, during the holding time, the natural electrode potential is about -0.
Over 70V In sample numbers C25 to C27, which could not be performed, activation was insufficient, and peeling at the plating interface occurred.

Next, in the case of the treatment solution having a pH of 3.5, a plating film having good adhesion was obtained for Sample Nos. 24 to 26 satisfying the natural electrode potential, and the substrate surface was activated by lowering the pH of the treatment solution. It can be seen that the holding time required for the conversion is reduced.

Example 5 Seven types of aluminum substrates having the same shape as in Example 1 (99.9%
Al, JIS A 2024, JIS A 3003, JIS A 4343, JIS A 5052, JIS
A 6101, JIS A 7075) was prepared and similarly prepared as a sample substrate.

Next, as an electroplating treatment solution, nickel sulfate 300 g /
And a nickel sulfate electroplating solution prepared from the mixture and boric acid 40 g / and adjusted to pH 4.5.

Next, after the base was degreased with a water-soluble degreasing agent for aluminum, etching was performed using an aqueous solution of 50 g / sodium hydroxide.
Desmut with a nitric acid aqueous solution and other substrates with a nitric hydrofluoric acid aqueous solution consisting of 4% hydrofluoric acid + 20% nitric acid aqueous solution, respectively.
Cleaning was performed.

Next, the substrate and the saturated calomel electrode were immersed in the electroplating solution to form an electroplating apparatus.

Then, after performing an activation treatment at a treatment liquid temperature of 60 ° C. and a holding time shown in Table 6, a current was passed for 10 minutes at 5 A / dm ² to about 10 μm.
An m-thick nickel plating was formed. This nickel plating layer was a uniform plating layer having an even surface and a smooth surface. Table 6 shows the natural electrode potential at the end of the holding time by the activation process, that is, immediately before the start of energization.
Thereafter, a baking treatment was performed at 200 ° C. for 1 hour.

A performance evaluation test of the obtained plated material was performed in the same manner as in Example 1. Table 6 shows the results obtained in the test.

For comparison, a comparative substrate was subjected to electroplating under the same conditions as in Example 5 except that the holding time of the substrate in the electroplating solution was short, and a similar performance evaluation test was performed. (Sample No. C30 ~ C36). The results are shown in Table 6.

As is clear from Table 6, sample No. 2 in which the natural electrode potential was no less than about -0.70 V within the holding time and the holding time was sufficient.
With respect to 7 to 33, plated films having good adhesion were obtained. On the other hand, during the holding time, the natural electrode potential is about -0.
Sample numbers C30, C32, C3 that could not exceed 70V
3. In C36, activation was insufficient, and peeling occurred at the plating interface. Further, as in the example shown by the curve E in FIG. 2, the surface activation is sufficiently advanced in the sample numbers C31, C34, and C35 in which the potential condition is satisfied but the predetermined time has not yet passed. Therefore, peeling occurred similarly. As described above, depending on the type of the base and the composition of the plating solution, when the potential change due to the activation is small and difficult to determine, the activity previously determined from the relationship between the activation time and the adhesion of the plating film is determined. By maintaining a predetermined time for activation, the surface of the substrate can be activated.

In any case, even if the potential change is large or small, the reproducibility is extremely good if the test conditions are constant. Therefore, an appropriate holding time can be set from the relationship between the holding time and the adhesion obtained in advance. It is not necessary to always measure the electrode potential.

[Brief description of the drawings]

FIGS. 1 and 2 are diagrams showing the relationship between the natural electrode potential on the surface of the substrate showing sufficient activation to obtain a good plating film and the holding time in a specific example of the present invention, and FIG. Diagram showing an example using a copper pyrophosphate plating solution, FIG.
The figure is a diagram showing an example using a nickel sulfate plating solution.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) C25D 5/00-7/12

Claims (1)

(57) [Claims] 1. A substrate made of an aluminum-based material is immersed in an electroplating solution, the substrate is activated until the substrate has a constant natural electrode potential, and the substrate is activated. Performing an electroplating method on an aluminum-based material.