JP3230417B2 - Plating apparatus and plating method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a multilayer capacitor,
The present invention relates to a plating apparatus and a plating method for performing electroplating on an object to be plated such as a chip-type electronic component such as a cylindrical capacitor, a varistor, and an inductor. Related to plating method.

[0002]

2. Description of the Related Art Conventionally, in a process of manufacturing external electrodes of a chip-type electronic component such as a multilayer capacitor, a method of forming external electrodes made of a metal plating film using an electrolytic plating apparatus has been used. FIG. 1 shows an example of a conventional electrolytic plating apparatus. The plating apparatus 1 has a plating solution container 3 in which a plating solution 2 is stored. The cathode 4 is immersed in the plating solution 2. The cathode 4 is formed of a metal mesh, and is immersed in the plating solution 2 while being suspended by the suspension units 5 and 6. An anode 7 is immersed in the plating solution 2, and electrolytic plating is performed by applying a voltage between the anode 7 and the cathode 4.

FIG. 2 is a structural perspective view of a multilayer ceramic capacitor 8 which is an example of an object to be plated. The multilayer ceramic capacitor 8 has a chip shape having a length L, a width W, and a thickness H, and has both ends of a ceramic sintered body 8a.
External electrodes 8b, 8b made of a metal plating film or the like are formed. The external electrodes 8b, 8b are formed by plating a region having a width e substantially from both end surfaces of the ceramic sintered body 8a. Hereinafter, the region where the plating film for the external electrode is to be formed is referred to as the plated portion 8c.

FIG. 3 is a partial plan structural view of a cathode 4 used in the electrolytic plating apparatus shown in FIG. 1, and FIG.
FIG. 4 is a sectional structural view taken along a cutting line AA in FIG. 3.
The cathode 4 is formed of a metal mesh in which a number of metal wires 4a to 4h having a circular cross section are woven so as to intersect in a direction orthogonal to each other in a mesh shape. The surface of the metal mesh has a shape in which the orthogonal metal wires 4a to 4d and 4e to 4h are wavy. Therefore, the portion to be plated is the portion to be plated 8 of the multilayer ceramic capacitor 8.
If it has a flat surface as shown in FIG.
The metal mesh and the metal mesh are mainly in contact with each other at a raised surface at the intersection of the metal wires. The surface of the metal mesh in contact with the portion to be plated 8c is called a contact portion and will be referred to below. Therefore, in the conventional metal mesh using a metal wire having a circular cross-section, as shown by black circles (for example, 9a to 9d) in FIG.

When the chip-type multilayer ceramic capacitor 8 to be plated is placed on the surface of the cathode 4 as described above, most of the multilayer ceramic capacitor 8 lies on the surface of the mesh, and the plated portion 8c is formed of a metal mesh. The contact portion, for example, 9c is brought into contact with the contact portion, thereby being electrically connected to the cathode 4. As a result, a metal plating film is formed on the surface of the portion to be plated 8b.

[0006]

Conventionally, the metal mesh used for the cathode 4 is appropriately selected from commercially available products based on the roughness of the mesh such that the object to be plated does not fall from the mesh of the mesh. Was used. However,
As chip-type multilayer ceramic capacitors have become smaller, it has become more difficult to obtain a metal mesh having an appropriate coarseness from commercially available products. For this reason, when a metal mesh having a relatively coarse mesh is used for an object to be plated such as a chip-type multilayer ceramic capacitor, a situation occurs in which the object to be plated cannot maintain sufficient contact with the cathode 4. . For example, FIG. 4 shows an example of such a situation. In the metal mesh as described above, the distance S between the metal lines is substantially equal to the distance D between the opposed contact portions 9a and 9b. For this reason, when a coarse metal mesh is used for the cathode 4, that is, a metal mesh whose metal line distance S (contact portion distance D) is larger than the minimum dimension e of the portion to be plated 8 c is used. In this case, as shown in FIG. 4, a state may occur in which one plated portion 8c of the multilayer ceramic capacitor 8 does not contact the cathode 4 at all. In such a state, the plated portion 8c that is not in contact with the cathode 4 is
The formation of the plating film is delayed as compared with the plated portion 8c in contact with the cathode 4, and as a result, both the plated portions 8c,
8c has a variation in the plating film.

The object to be plated is agitated on the cathode 4 by giving vibration to the cathode 4 or the like. There is also a problem that the formation time is prolonged and the plating efficiency is reduced.

It is an object of the present invention to provide a plating apparatus using a metal mesh for a cathode, in which a portion to be plated of an object to be plated is sufficiently brought into contact with the cathode, thereby preventing a variation in plating film thickness. By providing a plating apparatus that can improve the efficiency, and by providing a plating method that maintains a good contact state between a portion to be plated of an object to be plated and a cathode and has a small variation in film thickness and a high plating efficiency. is there.

[0009]

According to the present invention, there is provided a plating apparatus comprising: a plating solution container storing a plating solution; and a plating solution container immersed in the plating solution and having an object to be plated placed thereon. It is a device that comprises a configured cathode and an anode immersed in a plating solution, and forms a plating film on the surface of a portion to be plated of an object to be plated by applying a current between the anode and the cathode in the plating solution. .

The cathode is formed by intersecting a plurality of metal wires, and is formed such that a contact portion on the surface of the metal wire with which the portion to be plated comes into contact is formed around the intersection of the metal wires. It is composed of a mesh-like mesh material. Moreover, the mesh material is formed such that the distance between two adjacent contact portions along the direction in which one metal wire extends is smaller than the minimum dimension of the portion to be plated that contacts the metal wire contact portion. It is characterized by being.

According to another aspect of the present invention, the mesh material forming the cathode has a distance between two contact portions that are farthest among contact portions formed around one mesh. It is characterized in that it is formed so as to be smaller than the minimum dimension of the portion to be plated in contact with the contact portion of the metal wire.

That is, the cathode comprises a plurality of metal wires,
For example, it is made of a mesh material which is intersected in directions orthogonal to each other and woven in a mesh shape. Therefore, the surface of the mesh material on the side on which the object to be plated is placed is formed such that the portion where the metal wires cross each other rises. Therefore, the portion to be plated comes into contact with the metal wire on the surface around the intersection of the metal wires among the surfaces of the mesh-shaped metal wire. For this reason, in order to always maintain the contact between the portion to be plated of the object to be plated and the cathode, the distance between the contact portions scattered is smaller than the minimum size of the portion to be plated. I just need.

In the cathode of the present invention, the surface of the metal wire at the intersection of the metal wires is flattened by polishing or pressing.
A mesh material formed such that the contact portion is flat around the intersection is also included. Further, the mesh shape of the cathode can be formed not only in a square but also in various shapes such as a rectangle and a rhombus.

Further, in the plating method according to the present invention, the cathode on which the object to be plated is placed and the anode are immersed in a plating solution,
This is a method of forming a plating film on a portion to be plated of an object to be plated by applying an electric current between both poles. The contact portion is formed around the intersection of the metal wires and adjacent along the extending direction of one metal wire.
The mesh material is formed so that the distance between the two contact portions is smaller than the minimum dimension of the portion to be plated that contacts the contact portion of the metal wire. Then, an object to be plated is put on the cathode, and a plating film is formed on a portion to be plated of the object to be plated while applying vibration to the object to be plated.

Further, in the plating method according to another aspect of the present invention, the distance between the two most distant contact portions among the contact portions formed around one mesh is used as the mesh material constituting the cathode. It is characterized in that it is formed so as to be smaller than the minimum dimension of the portion to be plated in contact with the contact portion of the metal wire.

In the plating method, a cathode composed of the mesh material of the present invention is used as the cathode, and the plated portion of the object to be plated is always in contact with the cathode. In addition,
As a method of applying vibration to the object to be plated, an arbitrary method such as a method of reciprocating the entire cathode horizontally or vertically using an air cylinder or a method of applying ultrasonic vibration or the like to the plating solution is used. Can be applied.

[0017]

FIG. 5 shows a sectional structure of a plating apparatus according to a first embodiment of the present invention. The plating apparatus 11 has a frame 12 whose upper part is open. A plating solution container 13 is arranged in the frame 12. A plating solution 14 for performing wet plating is stored in the plating solution container 13. The cathode 18 is immersed in the plating solution. The cathode 18 is formed of a metal mesh, and a large number of chip-type electronic components as objects to be plated are mounted on the surface thereof.

The cathode 18 is fixed to lower ends of support members 20, 20 made of an insulating material. Support members 20, 2
The upper end of 0 is fixed to the connecting member 21. Connecting member 2
1 is fixed to the tip of the cylinder rod of the air cylinder 22 and reciprocates in the horizontal direction on the horizontal plane by driving the air cylinder 22. Then, at the time of reciprocating movement, the other end of the connecting member 21 is configured to collide with a stopper 23 provided inside the frame 12. The air cylinder 22, the stopper 23, and the connecting member 21 constitute a vibration unit for giving vibration to the cathode 18.

FIG. 6 is a partial plan structural view of the cathode 18, and FIG. 7 is a sectional structural view taken along a cutting line BB in FIG. The cathode 18 is configured using a metal mesh in which thin conductive metal wires 18a to 18d and 18e to 18h having a circular cross section are alternately woven at equal intervals in a direction orthogonal to each other. The roughness of the metal mesh is formed such that the plated portion 8c of the chip-type multilayer ceramic capacitor 8, which is a plated object, can always contact the cathode 18.

Here, the roughness of the mesh of the metal mesh will be specifically described. As shown in FIG. 6, in the case of a mesh in which metal wires having a circular cross section are alternately woven in the orthogonal direction, the mesh is formed in a square shape, and the contact portions with the object to be plated have metal wires 18a to 18d, 18e to It becomes the surface of the intersection of 18h. This contact portion is indicated by a black circle in the figure,
Some of them are denoted by reference numerals 19a to 19d.

The chip-type multilayer ceramic capacitor 8 to be plated has an appearance as shown in FIG. 2 and has a plated portion 8c on which external electrodes are to be formed.
In general, the width dimension e of the external electrode is set smaller than the width W and the thickness H of the capacitor. Therefore, the plated portion 8c of the chip-type multilayer ceramic capacitor 8 has a rectangular shape in which the width dimension e of the plated portion is the minimum size of the plated portion.

Therefore, in order for the plated portion 8c of the chip-type multilayer ceramic capacitor 8 to be able to come into contact with the metal mesh of the cathode 18, (1) the dimension D between the contact portions of the cathode 18 must be The roughness of the metal mesh may be set so as to be smaller than the minimum dimension e of the plated portion 8c of the ceramic capacitor 8. When the metal mesh uses a metal wire having a circular cross section, the distance D between the contact portions is substantially equal to the distance S between the metal wires. Therefore, the roughness of the square mesh of the metal mesh may be set so that the distance S between the metal lines is smaller than the minimum dimension e of the portion to be plated.

On the other hand, when the mesh of the metal mesh of the cathode 18 is made fine, clogging occurs due to the formation of a plating film on the surface of the metal mesh. If the mesh is clogged, the plating solution may not be sufficiently circulated through the object to be plated on the metal mesh, and the plating process may be delayed or plating may not be possible. Therefore,
Limiting conditions for making the mesh of the metal mesh of the cathode 18 fine include (2) securing a line distance that does not cause clogging of the metal mesh of the cathode.

When a metal mesh whose mesh size is set so as to satisfy the above conditions is used for the cathode 18,
In the chip-type multilayer ceramic capacitor 8 put on the surface of the cathode 18, the plated portion 8c comes into contact with a contact portion on the metal mesh, for example, at least one of 19a to 19d. Therefore, the plated portion 8c and the cathode 1
8 and the plating film is formed on the surface of the portion to be plated quickly and without variation.

A plating test was performed using the metal mesh formed under the above conditions as a cathode. As a plating apparatus, an electrolytic plating apparatus shown in FIG. 5 was used.
In addition, in order to confirm the effect of the metal mesh of the cathode 18, a test was performed without applying vibration to the cathode 18.
The plating bath was a Ni watt bath, and electricity was supplied at ^{2 A} / dm ² for 10 minutes.

A chip-type multilayer ceramic capacitor was used as an object to be plated. Referring to FIG. 2, the size is as follows: length L = 1.6 mm, width W = 0.8 mm, thickness H =
0.8 mm and the width e of the portion to be plated is 0.4 mm.

The metal mesh of the cathode has a square mesh shape, and the distance between lines, that is, the distance between lines (distance between contact portions) S shown in FIG. 7 is 0.26 mm and 0.37 m.
m according to the present invention, and the distance S between lines is 0.4
The plating process was performed using four types of metal meshes of the conventional example of 4 mm and 1.0 mm. Table 1 shows the experimental results.

[0028]

[Table 1]

In Table 1, the plating efficiency indicates the ratio of the parts of the 2000 multilayer ceramic capacitors in which the plating state of the external electrode plating film was good.
The number of times the mesh is clogged indicates the number of times the plating process can be performed until the mesh of the metal mesh of the cathode is clogged by plating and cannot be used. As is apparent from Table 1, the distance S between the metal mesh lines is the minimum dimension e (=
When it was larger than 0.4 mm), the plating efficiency of the component was low, and when the distance between the lines was very large (1.0 mm), the chip component dropped. On the other hand, in the case of the present invention where the distance S between the meshes is smaller than the minimum dimension e of the portion to be plated, it can be seen that the plating efficiency of the component is extremely high. In addition, it can be seen that when the line distance S of the metal mesh is smaller, clogging of the metal mesh is likely to occur. Therefore, it is understood that the distance S between the lines of the metal mesh, that is, the distance D between the contact portions, is preferably smaller than the minimum dimension e of the portion to be plated and closer to the minimum dimension e.

Next, a plating apparatus according to a second embodiment of the present invention will be described. FIG. 8 is a plan structural view of a cathode 30 used in the plating apparatus according to the second embodiment, and FIG. 9 is a cross-sectional structural view taken along a cutting line CC in FIG. The cathode 30 is formed by polishing the surface of a metal mesh having a square mesh shape or flattening the surface using a press or the like, and contacting the plating object (for example, 33a).
To 33d) having a structure with an increased surface area. In the cathode 30 having such a structure, whether or not the portion to be plated and the cathode are in contact with each other depends on the distance D between the flattened contact portions 33a and 33b on the surface of the metal mesh as shown in FIG. Is determined by Accordingly, as in the case shown in FIGS. 6 and 7, the distance between the flattened contact portions D of the cathode 30 is the minimum value of the plated object, for example, the plated portion 8c of the chip-type multilayer ceramic capacitor 8. It is formed so as to be smaller than the dimension e. According to this structure, the plated portion of the multilayer ceramic capacitor, which is a plated object, has one of the contact portions (33a to 33a) on the surface of the metal mesh.
d) is reliably contacted. Moreover, since the contact portion is formed in a plane, the contact area of the portion to be plated with the cathode is increased, and the conduction state is improved. Furthermore, this second
In this embodiment, the distance D between the contact portions is smaller than the distance S between the cathodes. Therefore, if the distance D between the contact portions in the second embodiment is made equal to the distance D between the contact portions (that is, equal to the distance between the metal wires) D in the first embodiment, the distance D becomes smaller than the metal mesh of the first embodiment. A coarse metal mesh can be used.

Here, an experimental example based on the second embodiment will be described. This experiment was performed using the plating apparatus shown in FIG. 5 and using a multilayer ceramic capacitor as an object to be plated. The metal mesh having the structure shown in FIGS. 8 and 9 was used as the cathode of the plating apparatus. The distance D between the contact portions of the metal mesh is four types (0.20, 0.22, 0.37, 0.38 m) smaller than the minimum dimension e (= 0.4 mm) of the portion to be plated of the multilayer ceramic capacitor.
m). The plating conditions were 2 A / dm in a Ni watt bath as in the experimental example in the first embodiment.
⁽²⁾ Energization was performed for 10 minutes to form a Ni film on the external electrode portion of the multilayer ceramic capacitor. Table 2 shows the experimental results.

[0032]

[Table 2]

As can be seen from Table 2, the plating efficiency is such that the distance D between the contact portions is set smaller than the minimum dimension e of the plated portion of the multilayer ceramic capacitor. All of them show high values without being affected. On the other hand, it can be seen that clogging of the mesh occurs with a smaller number of platings as the roughness of the metal mesh becomes finer.

The plating apparatus provided with the cathode using the metal mesh according to the first and second embodiments as described above preferably has a structure provided with a vibration means for applying vibration to the cathode. As such a vibration means, as shown in FIG. 5, a reciprocating vibration is applied horizontally using an air cylinder, or a vibration and an impact are periodically generated by an air cylinder and a stopper provided on the side opposite to the air cylinder. Or a material that further vibrates the cathode vertically. Further, means for applying ultrasonic vibration in the plating solution to slightly vibrate the object to be plated on the cathode may be used.

In the first and second embodiments, an example of a metal mesh suitable for a multilayer ceramic capacitor having a rectangular portion to be plated has been described. Is preferably a metal mesh as described below.

FIG. 10 is a plan view of the cathode 40 used in the plating apparatus according to the third embodiment. As shown in the figure, when the plated portion 42 is square, the plated portion 42 must be in contact with any of the contact portions (19a to 19d) formed at the intersections of the metal wires 40a to 40d and 40e to 40h. A pair of contact portions 4 whose one side length (minimum dimension) e of the plated portion 42 is on a diagonal line of the square mesh
The distance between the metal wires may be determined so as to be larger than the distance D between 1b and 41d. In other words, of these conditions, of the contact portions 41a to 41d existing around one mesh, the contact portions 41a and 41c (41b and 41c) which are furthest apart.
It is sufficient to determine the distance between the metal wires so that the distance D between d) is smaller than the minimum dimension e of the square portion to be plated.

Moreover, such conditions can be applied to a rectangular plated portion. That is, for example, the distance D between the contact portions located on the diagonal line of the square mesh
However, if it is made smaller than the minimum dimension e of the rectangular plated portion, the plated portion and the cathode can always be kept in contact.

Further, such a condition can be similarly applied to a case where the surface of the metal mesh is flattened by polishing or pressing. In the above description, an example was described in which the cathode and the multilayer ceramic capacitor to be plated are in ideal contact with each other as shown in FIG. 6, for example. A ceramic capacitor is placed on the cathode.
Therefore, the multilayer ceramic capacitor is mounted in various forms, such as being inverted, inclined, or leaning on another multilayer ceramic capacitor with respect to the cathode. Therefore, the contact portion of the cathode of the multilayer ceramic capacitor with which the object to be plated comes into contact is not limited to the contact portion as described above, but the conduction state between the multilayer ceramic capacitor and the cathode is changed by plating using the plating apparatus according to the present invention. This can be improved by the method, whereby the variation in the thickness of the plating film can be prevented, and the plating efficiency can be improved.

[0039]

As described above, the plating apparatus according to the present invention uses the mesh material having a mesh shape such that the cathode and the portion to be plated of the plating object are always in contact with each other. And the contact state with the cathode becomes good,
This makes it possible to realize a plating apparatus with less variation in film thickness and excellent plating efficiency.

Further, the plating method of the present invention is configured such that an object to be plated is put on the cathode of the plating apparatus of the above invention, and the plating is performed while applying vibration to the object to be plated. Therefore, the action of agitating the object to be plated due to the vibration is further applied, so that the contact state between the object to be plated and the cathode is favorably maintained. As a result, a plating method with less variation in the thickness of the plating film and excellent plating efficiency is realized.

[Brief description of the drawings]

FIG. 1 is a structural view of a conventional plating apparatus.

FIG. 2 is a perspective view showing the external structure of a chip-type multilayer ceramic capacitor as an example of a plated object.

FIG. 3 is a partial plan structural view of a cathode of a conventional plating apparatus.

FIG. 4 is a sectional structural view taken along a cutting line AA in FIG. 3;

FIG. 5 is a sectional structural view of the plating apparatus of the present invention.

FIG. 6 is a partial plan structural view of a cathode according to the first embodiment of the present invention.

FIG. 7 is a sectional structural view taken along a cutting line BB in FIG. 6;

FIG. 8 is a partial plan structural view of a cathode according to a second embodiment of the present invention.

FIG. 9 is a cross-sectional structural view taken along a cutting line CC in FIG. 8;

FIG. 10 is a partial plan structural view of a cathode according to a third embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 11 ... Plating apparatus 13 ... Plating solution container 14 ... Plating solution 18,30,40 ... Cathode 19a-19d, 33a-33d, 41a-41d ... Contact part 24 ... Anode

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-58-147583 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C25D 17/08 C25D 17/16

Claims (4)

(57) [Claims] 1. A plating solution container storing a plating solution, a cathode immersed in the plating solution and configured to place an object to be plated thereon, A plating apparatus for forming a plating film on the surface of a portion to be plated of the object to be plated by applying a current between the anode and the cathode in the plating solution, comprising: Is formed by crossing a plurality of metal wires, and the contact portion of the surface of the metal wire that contacts the portion to be plated of the object to be plated,
The mesh material is formed of a mesh-like mesh material formed so as to be generated around an intersection of the metal wires, and the mesh material has a distance between two adjacent contact portions along a direction in which one metal wire extends. A plating apparatus, wherein the plating apparatus is formed so as to be smaller than a minimum dimension of the portion to be plated contacting the contact portion of the metal wire. 2. A plating solution container storing a plating solution, a cathode immersed in the plating solution and configured to place an object to be plated thereon, and a cathode in the plating solution. A plating apparatus for forming a plating film on the surface of a portion to be plated of the object to be plated by applying a current between the anode and the cathode in the plating solution, comprising: Is formed by crossing a plurality of metal wires, and the contact portion of the surface of the metal wire that contacts the portion to be plated of the object to be plated,
The mesh member is formed of a mesh-shaped mesh material formed so as to be generated around the intersection of the metal wires, and the mesh material is formed of two of the most distant contact portions among the contact portions formed around one mesh. The plating apparatus is formed so that a distance between them is smaller than a minimum dimension of the portion to be plated that contacts the contact portion of the metal wire. 3. A plating method for forming a plating film on a portion to be plated of an object to be plated by immersing a cathode on which the object to be plated is mounted and an anode in a plating solution and applying a current between both electrodes. The cathode is formed by intersecting a plurality of metal wires, and is formed such that a contact portion of a metal wire surface with which a portion to be plated of an object to be contacted is formed around the intersection of the metal wires. The distance between two contact portions adjacent to each other along the direction in which one metal wire extends is formed to be smaller than the minimum dimension of the portion to be plated that contacts the contact portion of the metal wire. A mesh material having a mesh shape is used, and an object to be plated is put on the cathode, and while applying vibration to the object to be plated, a plating film is formed on a portion to be plated of the object to be plated, Plating method. 4. A plating method for forming a plating film on a portion to be plated of an object to be plated by immersing a cathode on which the object to be plated is mounted and an anode in a plating solution, and applying an electric current between both electrodes. The cathode is formed by intersecting a plurality of metal wires, and is formed such that a contact portion of a metal wire surface with which a portion to be plated of an object to be contacted is formed around the intersection of the metal wires. The distance between the two furthest contact portions among the contact portions formed around one mesh is smaller than the minimum dimension of the portion to be plated that contacts the contact portion of the metal wire. Using a mesh-shaped mesh material formed in the above, the object to be plated is put on the cathode, and while applying vibration to the object to be plated, a plating film is formed on a portion to be plated of the object to be plated. Characteristic plating method.