JPH0688285A - Electrodeposition method of metal - Google Patents

Abstract

PURPOSE:To make an electrodeposited metal porous and to enable the control of the size of the pores formed therein regardless of the presence or absence of a treatment for making the surface of a work porous in the method for electrodepositing the metal on the work. CONSTITUTION:An anode 7 and a matrix 1 are disposed within an electrocasting cell 5 and a power source is connected therebetween. An electrolyte combining the cation and anion of high ion mobility, for example, hydrobromic acid, is added to an electrolyte 6. Passing of DC current between the two electrodes 7 and 1 to temporarily change the current waveform to AC is intermittently executed at ordinary time. A large amt. of fine bubbles of gaseous hydrogen are generated on the surface of the matrix 1 by the additive. The metal precipitates while extending to enclose these bubbles and the porous mold which is made sufficiently porous is obtd. The large bubbles are removed by the impartation of an electric shock to the metal, by which the sizes of the pores are uniformalized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrodeposition method for electroplating, electroforming, or the like, in which the electrodeposited metal is made porous so as to be porous.

[0002]

2. Description of the Related Art For example, in electroplating, an object to be plated made of metal or having its surface subjected to conductive treatment is placed as a cathode in an electrolytic solution containing metal (for example, nickel) ions, and the metal to be electrodeposited (nickel, for example). ) Is disposed and a direct current is passed between the both electrodes to deposit a metal (nickel) in a thin film on the surface of the object to be plated. Further, the electroforming process uses, for example, a cathode obtained by subjecting the surface of a plastic mold to a conductive treatment, and similarly to electroplating, a surface of a metal is electrodeposited to a predetermined thickness, and then an electrodeposited metal is deposited. The desired product such as a molding die is obtained by peeling it from the mother die.

In such an electrodeposition technique, in recent years, a technique for producing a porous molding die used for vacuum forming a plastic molded product by electroforming has been developed (for example, JP-A-60-152692,
JP-A-61-253392). Unlike the above-mentioned general electrodeposition method, this technique positively generates fine bubbles of hydrogen gas on the surface of a mother die (cathode) having the same outer shape as the molded product and wraps the bubbles. By thus precipitating the metal, it is intended to make the electrodeposited metal porous. FIG. 7 shows a porous molding die 21 obtained by such electrodeposition, and it is possible to manufacture a molding die 21 composed of a porous metal layer having a large number of pores 21a continuous in the thickness direction. It is possible.

In order to manufacture a porous molding die by electroforming as described above, the mother die is subjected to a porosity-treating treatment in which the surface layer of the mother die is in the form of so-called fine spots. An over electric field is generated at the boundary between the conductive portion and the insulating portion to positively generate hydrogen gas. This porosity treatment is carried out by spraying a spray liquid, which is a conductive paint mixed with an insulating lacquer, on the surface of the master mold, or by forming a conductive layer on the surface of the master mold by a silver mirror reaction, and then corroding the conductive layer with silver. The method is applied to remove a part of silver by applying an agent.

[0005]

However, in the conventional technique for producing the porous mold by the electroforming process described above, the conductive portion and the insulating portion are mixed in fine spots on the surface of the mother die. It was essential to carry out the processing for porosity. Therefore, even if it is desired to use it for plating, it is impossible to electrodeposit metal in a porous form if the electrodeposit is a metal (electric conductor). Also, for example, if the electrodeposit is insulative, it is porous. Even if the chemical treatment is performed, once the electroforming (plating) process is interrupted, there is a problem that the electrodeposited metal does not become porous after the process is restarted.

As shown in FIG. 7, even if the pores 21a are extremely fine on the surface of the porous molding die 21, as the electrodeposition progresses and the pores 21a move away from the surface of the mother die, Then, a plurality of bubbles are aggregated to form one large bubble, and the pores 21a gradually increase in size, which causes a problem such as strength.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a method for electrodepositing a metal on an object to be electrodeposited, regardless of whether the surface of the object to be electrodeposited is porous or not. Another object of the present invention is to provide a method for electrodepositing a metal which can sufficiently make the electrodeposited metal porous and can control the size of pores formed.

[0008]

In the method for electrodepositing a metal of the present invention, an anode and an electrodeposit are placed in an electrolytic solution containing metal ions, and an electric current is passed between the anode and the electrodeposit. Thereby, in the method of electrodepositing a metal on the electrodeposited material, while adding an additive comprising an electrolyte in which a cation and anion having high ion mobility are combined to the electrolytic solution,
The feature is that the current is made to flow while intermittently changing the current waveform with respect to the normal current waveform.

[0009]

[Function] In order to make the metal electrodeposited on the electrodeposit to be porous, an infinite number of fine bubbles such as hydrogen gas are generated on the surface of the electrodeposit and the metal is charged while enclosing the bubbles. Just wear it.

According to the metal electrodeposition method of the present invention, the additive consisting of the electrolyte is ionized into cations and anions in the electrolytic solution, and when the energization is started, these ions are respectively cathode and anode. However, due to the high ion mobility of these ions, the reaction of these ions at both electrodes will be carried out rapidly, and a large amount of hydrogen gas will be generated on the surface of the cathode, that is, the electrodeposited material. Become. Therefore, regardless of the presence or absence of the porosity processing,
It becomes possible to generate bubbles necessary for making the electrodeposited metal sufficiently porous.

In this case, as the additive, various kinds of electrolytes can be used as long as they are electrolytes in which cations and anions having high ion mobility are combined, and HCl, HBr, HI are used.
Particularly preferred are hydrohalic acids such as

Even if the bubbles necessary for making the electrodeposited metal porous can always be generated as described above, it is possible that the bubbles remain attached to the surface of the electrodeposited object or the electrodeposited metal layer for a long time. If continued, the number of bubbles will increase too much and they will aggregate into large bubbles.

However, according to the metal electrodeposition method of the present invention, the current is made to flow while intermittently changing the current waveform with respect to the current waveform during normal operation. When the air bubbles that adhered to the surface of the kimono or the electrodeposited metal layer became large, an electrical shock was temporarily applied to the object to be electroplated or the electrodeposited metal layer. The bubbles can be removed by removing them from the electrodeposited object or the electrodeposited metal layer. Then, by returning to normal current waveform energization, fine bubbles can be generated again to be attached to the surface of the electrodeposited object or the electrodeposited metal layer, and by further repeating the electrodeposition of the metal, It becomes possible to control the size of the pores formed in the electrodeposited metal layer.

In this case, the current is normally supplied by direct current, but the current waveform changes include changing from direct current to alternating current, reversing the polarity of direct current, increasing or decreasing the magnitude of current, and passing current. There is a mode of suspending.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. In addition, in the present embodiment, the present invention is applied, for example, when a porous forming die for vacuum forming is manufactured by electroforming.

In order to manufacture a porous molding die by electroforming, as shown in FIG. 2, a mother die 1 as an electrodeposit is used. In this case, the mother die 1 is formed, for example, by laminating an epoxy resin and a reinforcing fiber on the back surface side of the surface layer 2 which has the same concavo-convex shape as the surface of the molded product and has been subjected to the porous treatment. The backing layer 3 is provided. Although not shown in detail, the surface layer 2 includes a conductive portion made of a conductive coating material that is adhered and hardened over the entire surface of the backing layer 3, and an insulating coating material that is adhered and hardened on the surface of the conductive portion in a number of fine spots. And an insulating part.

Although illustration and detailed description are omitted, when manufacturing the mother die 1, a master having the same shape as the molded product is manufactured from a wooden mold or the like, and a silicone resin is cast on the surface of the master. Then, it is cured and released from the mold to produce an inversion mold having a concavo-convex shape opposite to that of the molded product. Then, after spraying the insulating coating material in a mist state by spraying on the inner surface of the reversing mold to cure it, the conductive coating material is sprayed to a predetermined thickness on the entire inner surface of the reversing mold to cure. In this way, the surface layer 2 including the conductive portion and the insulating portion is formed, and then the backing layer 3 is formed on the surface layer 2 and released from the reversal mold together with the surface layer 2. The matrix 1 is obtained.

Next, FIG. 2 schematically shows an electroforming apparatus 4 used in this embodiment, in which the electroforming tank 5 has, for example, nickel sulfamate as a main composition. The electrolytic solution 6 is contained in a state of being maintained at a required pH and temperature. In this case, for example, the concentration of nickel sulfamate is 600 g / l, the pH is 1.5, and the temperature is 35 ° C.

In the electrolytic solution 6, an additive such as hydrobromic acid (HBr), which is an electrolyte in which a cation and an anion having high ion mobility are combined, is used in a required amount (for example, 2 cc / l). ) Has been added.

In this case, as the cations and anions having high ion mobility, those shown in Table 1 below are listed.

[0021]

[Table 1]

As the additive, any combination of cations and anions shown in Table 1 can be used, but hydrogen ion and halogen ion can be combined. Especially preferred are hydrohalic acids such as HCl, HBr, HI and the like. In this case, hydrogen ions have the highest ion mobility as cations, but metal ions can also be used.

In the electroforming tank 5, an anode 7 made of nickel is arranged, the mother die 1 is arranged as a cathode, and a power supply device 8 is connected between the both electrodes 7, 1. Although detailed illustration and description are omitted, this power supply device 8 is a transformer that lowers the voltage of the commercial power supply, a rectifier that converts alternating current to direct current, and switches the current flowing between both poles 7 and 1 between direct current and alternating current. The switch is provided with a timer for causing the switch to perform switching at a predetermined time.

In this case, the power supply device 8 normally causes a direct current to flow between the anode 7 and the matrix 1 (surface layer 2) so that a required current density (for example, 1 A / dm2) is obtained. However, as will be described later, the current waveform is temporarily changed with respect to the DC current waveform. In this embodiment, switching from direct current to alternating current of 50 to 60 cycles is performed, for example, once every hour for several seconds to several tens of seconds.

When performing electroforming, as described above, the anode 7 made of nickel and the mother die 1 as an electrodeposit are placed in the electroforming tank 5 (in the electrolytic solution 6). Then, a power supply device 8 is connected between the both electrodes 7 and 1 to flow a current. In this case, a direct current is normally supplied.

Then, nickel metal is deposited on the surface of the matrix 1 (surface layer 2) by electrolytic reaction to cause electrodeposition. At this time, the additive (hydrogen bromide) added to the electrolytic solution 6 is used. Acid) ionizes hydrogen ions and bromine ions, and by energization, these ions are attracted to the cathode (matrix 1) and the anode 7, respectively. At this time, since the ion mobility of these ions is high, the reaction of these ions on the surface of the matrix 1 and the anode 7 is rapidly performed, and fine bubbles of hydrogen gas are generated on the cathode, that is, the surface of the matrix 1. It will occur innumerably.

Nickel extends while enclosing a large number of fine bubbles adhering to the surface of the mother die 1
As the electrodeposition of nickel progresses, further bubbles adhere to the outside of the master mold 1 so that they continue from the bubbles on the surface of the master mold 1, and nickel is further deposited. It grows so as to wrap the bubbles and precipitates. As a result, nickel is electrodeposited on the surface of the mother die 1 in a porous manner.

In this case, since the surface of the mother die 1 (surface layer 2) is subjected to a porosity treatment in which the conductive portion and the insulating portion are in a so-called minute spot pattern, the boundary between the conductive portion and the insulating portion is formed. In the part, an over-electric field is generated to easily generate bubbles of hydrogen gas and the generation of bubbles will be further promoted, but the treatment for forming porosity is not necessarily required, and by the generation of bubbles by the above-mentioned additive, It is possible to generate sufficient bubbles to make the electrodeposited metal porous.

Thus, the bubbles generated on the surface of the mother die 1 are
Although it is extremely fine, the electrodeposition progresses and the mother die 1
With the distance from the surface to the outside, the number of bubbles becomes too large and a plurality of bubbles aggregate to form one large bubble.
As a result, the pores formed in the electrodeposited metal layer become large.

Therefore, in the present embodiment, the current is made to flow while intermittently changing the current waveform from the normal DC current waveform to AC. As described above, in this embodiment, 50 to 6 from DC.
Switching to 0 cycle AC is performed once an hour for several seconds to several tens of seconds. The current waveform at this time is shown in FIG.

The alternating current at this time is 50 to 6
In addition to 0 cycle AC, low cycle (1.25 to 10 cycles) AC as shown in FIG. 3B, FIG.
It is also possible to employ a double cycle alternating current (100 to 120 cycles) alternating current as shown in FIG. 3, a rectangular wave alternating current as shown in FIG.

As a result, when the bubbles attached to the surface of the mother die 1 or the surface of the electrodeposited metal layer become large, an electric shock is temporarily given, so to speak, and the bubbles are generated. It is also removed from the electrodeposited metal layer and removed. Then, by returning the current to direct current, fine bubbles are again generated and adhered to the surface of the electrodeposited metal layer by the action of the additive, and nickel is electrically charged so as to wrap the bubbles in the same manner as above. It will be worn.

By repeating such an energization pattern, fine bubbles are always generated, and nickel is electrodeposited so as to wrap the fine bubbles. Mother mold 1
When the electrodeposition of a predetermined thickness (for example, 3 mm) is completed, the electroforming process is finished and the electrodeposited nickel layer is released from the mother die 1 to continue in the thickness direction as shown in FIG. It is possible to obtain a porous molding die 9 having a large number of fine pores 9a and having the pores 9a of uniform size. According to the above method, for example, the electroforming process can be interrupted in order to partially mask the electrodeposited metal layer, and after the resumption, bubbles can be newly generated by the action of the additive.

As described above, according to this embodiment, the electrolytic solution 6
By adding an additive composed of an electrolyte in which a cation and an anion having high ion mobility are combined to the above, regardless of the presence or absence of the porousization treatment of the surface of the matrix 1 which was considered to be essential in the past, It is possible to generate bubbles necessary for making the electrodeposited metal porous. Therefore, it is possible to sufficiently make the electrodeposited metal layer porous, and it is possible to suspend and restart the electroforming process, which has been impossible in the past.

Since the current is made to flow while intermittently changing the current waveform to an alternating current with respect to the direct current waveform at the normal time, the bubbles are blown when they become large. By removing it, it became possible to generate fine bubbles again. As a result, unlike the conventional porous molding die 21 in which a plurality of bubbles are aggregated and become larger with the distance from the surface of the matrix to the outside and the pores 21a are gradually enlarged, the size of the bubbles is, in other words, electrodeposition. It is possible to control the size of the pores 9a of the metal layer, and it is possible to obtain a high-quality porous mold 9 that is excellent in mechanical strength and the like.

In the above embodiment, as one mode of changing the current waveform, the direct current is changed to the alternating current.
In addition, a mode in which the DC poles are reversed as shown in FIGS. 4A and 4B and the magnitude of the current as shown in FIGS. 5A, 5B and 5C is increased or decreased. Although not shown, there is a mode in which the flow of current is stopped. The selection of the current waveform and the setting of the energization time and the switching time as described above may be appropriately determined depending on the electrodeposit to be obtained.

In the above embodiment, the case where the porous molding die 9 is manufactured by electroforming is taken as an example, but it goes without saying that the present invention can be applied to electroplating. FIG. 6 shows that a porous electrodeposited metal layer 12 having a number of continuous pores 12a is electrodeposited on the surface of an electrodeposited object 11 made of a thin metal plate by electroplating using the method of the present invention. The porous metal plate 13 obtained by the above is shown. Also in this case, it is possible to form the pores 12a of uniform size in the electrodeposited metal layer 12.

This porous metal plate 13 can be used as an electrode of a battery, for example. This porous metal plate 13 has an extremely large surface area (for example, a flat plate 70 to 8).
Therefore, if used as an electrode, it is possible to increase the voltage, capacity, and size of the battery.

Further, although not shown, a conductive layer is formed on the surface of the electrodeposited object made of an insulating material such as a plastic thin plate by a method such as chemical plating or vapor deposition, and electroplating is performed by the same method. Again, a plastic plate having a porous electrodeposited metal layer on the surface can be obtained. This can be used as a high-quality electromagnetic wave absorber, for example, in an application such as an electromagnetic wave shield.

In addition, the present invention is not limited to the embodiments described above and shown in the drawings, and it is possible to make the electrodeposited metal porous for the materials to be electrodeposited of various materials and shapes. The thickness and shape of the electrodeposited metal layer, and the size and number of pores can be variously changed. The present invention can be variously modified without departing from the scope of the invention, such as nickel, gold, silver, copper, chromium, zinc, tin and the like. is there. Then, the product obtained by using the metal electrodeposition method of the present invention,
In the future, it may be widely used in various fields and applications.

[0041]

As is clear from the above description, according to the metal electrodeposition method of the present invention, an additive composed of an electrolyte in which a cation and an anion having high ion mobility are combined in an electrolytic solution. In addition to the above, the current was made to flow while intermittently changing the current waveform with respect to the current waveform during normal operation. In addition, it is possible to sufficiently make the electrodeposited metal porous and to control the size of the formed pores, which is an excellent practical effect.

[Brief description of drawings]

FIG. 1 shows an embodiment of the present invention and is a partially enlarged vertical sectional view of a porous molding die.

FIG. 2 is a diagram schematically showing an electroforming apparatus.

FIG. 3 is a diagram showing an example of a current waveform when changing from DC to AC.

FIG. 4 is a diagram showing an example of a current waveform when a DC pole is reversed.

FIG. 5 is a diagram showing an example of a current waveform when the magnitude of the current is increased or decreased.

FIG. 6 is a partially enlarged vertical sectional view of a porous metal plate showing another embodiment of the present invention.

FIG. 7 is a view corresponding to FIG. 1 showing a conventional example.

[Explanation of symbols]

In the drawings, 1 is a mold (object to be electrodeposited), 2 is a surface layer, 3 is a backing layer, 4 is an electroforming machine, 5 is an electroforming tank, 6 is an electrolytic solution, 7 is an anode, 8 is a power supply device, 9 is a porous mold, 9a is pores,
Reference numeral 11 indicates an electrodeposited object, 12 indicates an electrodeposited metal layer, and 12a indicates pores.

Claims (1)

[Claims] 1. A method of depositing a metal on an electrodeposited material by placing an anode and an electrodeposited material in an electrolytic solution containing metal ions and applying a current between the anode and the electrodeposited material. In addition, while adding an additive consisting of an electrolyte in which a cation and anion having high ion mobility are combined to the electrolytic solution, intermittently changing the current waveform with respect to the current waveform during normal operation is intermittent. A method for electrodepositing a metal, characterized in that an electric current is made to flow while performing the operation.