JP2918451B2 - Barrel type electroplating method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a barrel type electroplating method.

[0002]

2. Description of the Related Art Generally, when plating a large number of small articles, a barrel-type electroplating method is used. In the barrel-type electroplating method, an object and a medium are placed in a barrel, and the barrel is immersed in a plating solution in a plating tank. The object to be processed is energized from the attached electrode via a medium to form a plating film on the surface of the object to be processed. The barrel generally has a polygonal cross-sectional shape, but when the cross-sectional shape has a small number of corners such as a triangle or a quadrangle, when the barrel is rotated, the workpiece and the media are not smoothly stirred. , Cracks in the workpiece,
Chipping may occur and yield may deteriorate. Further, when the number of dodecagons or pentagons is increased and the cross-sectional shape becomes close to a circle, the workpiece and the medium are not sufficiently stirred, and the surface condition of the plating film deteriorates. Therefore, the cross-sectional shape of the barrel is pentagonal, hexagonal, and octagonal.
Among them, hexagonal ones are often used.

[0003] The barrel rotates while plating is being performed, so that the object to be processed and the medium are sufficiently stirred inside the barrel. FIG. 1 is a schematic view of the barrel, but the axis of rotation AA of the barrel is off the center of the cross-sectional shape, and the barrel rotates in an eccentric state. Due to the eccentric barrel rotation, the media and the object to be processed in the barrel move left and right while being stirred. The barrel has a number of holes, so that the plating solution can be sufficiently exchanged between the inside and the outside of the barrel while plating, so that the plating solution inside the barrel and the plating solution outside the barrel are the same metal ion. It keeps the concentration. The holes are usually equally spaced and the size must be smaller than the media to prevent the media from jumping out of the barrel during plating.

[0004] The medium is made of a conductive material for conducting electricity from the electrode to the object to be processed, and its shape is usually spherical. The object and the medium are stirred by the rotation of the barrel, and the contact point between the object and the medium does not remain at one place. Therefore, it is possible to form a uniform plating film without leaving traces of contacts on the object after plating. Media size is usually 5-15mm in diameter
Is used. If the media diameter is smaller than 5 mm, the diameter of the barrel must be reduced in order to prevent the media from jumping out of the barrel, but it is difficult to machine a small hole in the barrel. The media diameter is 15mm
When the size is larger, when the medium and the object to be processed are agitated during the rotation of the barrel, the impact force at which the medium hits the object to be processed increases, so that the object to be processed is easily cracked or chipped.

When the object to be processed has a flat shape, when the object is plated by the barrel-type electroplating method, the object to be processed sometimes adheres to the inner wall of the barrel during rotation of the barrel. In such a case, plating cannot be performed on the surface of the workpiece adhered to the barrel, and normal plating cannot be performed. In order to prevent such a state, usually, a large number of pyramid-shaped projections (hereinafter referred to as diamond cuts) are provided on the inner wall of the barrel to prevent sticking of an object to be processed,
The shape is determined by the size of the object. That is, in order to prevent the flat workpiece from sticking to the inner wall of the barrel, the diamond is set so that the area of the plane existing on the inner wall of the barrel is smaller than the area of the largest surface of the flat workpiece. The shape of the cut must be determined.

[0006] Usually, a diamond cut having a quadrangular pyramid shape is adopted, and the diamond cuts are arranged without gaps. FIG. 2 (a)
FIG. 2B is a plan view of the diamond cut, and FIG.
FIG. The distance between the vertices of adjacent diamond cuts is the shortest distance D between the vertices of the diamond cut. This distance is equal to the distance of one side of the bottom surface of the square pyramid forming the diamond cut. The height of the diamond cut is the height of the pyramid. The apex of the diamond cut may be rounded or flat. However, if it is a plane, the area of the plane must not be too large. The vertex of the diamond cut at that time is the center of the plane.

[0007]

However, during the barrel-type electroplating, the media may block the holes during the rotation of the barrel or may fit into the valleys of the diamond cut. If the media closes the hole, the plating solution between the inside and the outside of the barrel becomes difficult to enter and exit, and as the plating proceeds, the metal ion concentration of the plating solution inside the barrel decreases, and as a result, the plating efficiency decreases, Of the surface state of the glass. Further, when the medium closes the holes, the media is aligned according to the arrangement of the holes, and another medium is stacked on the aligned media, so that the movement of the media is deteriorated and the stirring performance is deteriorated. Also, if the media gets into the valleys of the diamond cut, when there is a hole in the valley of the diamond cut, it will be in the same state as when the media has closed the hole, the plating efficiency will decrease, and the surface state will decrease. Cause deterioration.
Furthermore, the media that fit into the valley of diamond cut,
It moves upward with the rotation of the barrel and drops from above due to gravity, which deteriorates the agitation of the object to be processed and the medium, easily causes variations in plating thickness, and deteriorates plating yield. Further, when an object to be processed exists at a place where the medium has dropped, there is a disadvantage that the object to be processed is broken or chipped. In addition, if the medium closes the hole or fits in the diamond-cut valley, the agitation property is deteriorated, and the movement of the medium and the object to be processed, which is caused by the rotation of the barrel, is also hindered. If the left and right movements are not sufficiently performed, the media and the workpiece are stagnated at the corners of the barrel and the plating thickness tends to vary. The present invention is an improvement of the barrel-type electroplating method which has many of these problems. By setting the relationship between the diamond cut, the hole of the barrel and the media to a specific numerical value, the plating efficiency, cracking, chipping, etc. are improved. It is an object of the present invention to provide a barrel-type electroplating method which can prevent the occurrence of the like and the like, has a good yield, and has a small variation in plating film thickness.

[0008]

The inventors of the present invention have made intensive studies to solve the above problems, and found that the media size, the distance between the centers of the holes, and the shape of the diamond cut should satisfy an appropriate relationship. The present invention was completed by establishing various conditions, and the gist of the invention is that a diamond cut is provided on the inner wall of the barrel, and the shortest distance D between the apex of the diamond cut and the center of the hole formed in the barrel are defined. A barrel-type electroplating method, wherein the shortest interval E and the diameter F of the spherical medium satisfy the following relationship. 2 ^1/2 · D <F and D ≠ E.

Hereinafter, the present invention will be described in detail.

The holes and the diamond cuts provided on the inner wall of the barrel are usually arranged at regular intervals. The shortest distance D between the diamond cut vertices is the distance between the vertices of the nearest diamond cut adjacent to the aligned diamond cut vertices. The shortest distance E between the centers of the holes is the distance between the centers of the nearest neighboring holes of the aligned holes. The diameter F of the spherical media is the shortest distance D between the vertices of the diamond cut, 2
When it is smaller than ^1/2 times, the spherical media gets stuck in the valley of the diamond cut. Conversely, F is 2 ^1/2
When the diameter is larger than D, the workpiece and the media during the barrel rotation are sufficiently agitated without the spherical media being stuck in the valley of the diamond cut, preventing cracking and chipping of the workpiece, , The plating yield can be increased. If the shortest distance E between the centers of the holes is different from the shortest distance D between the vertices of the diamond cut, the holes will be opened at various places on the slope of the diamond cut, and many holes will be simultaneously formed by the media. Since the clogging does not occur, the plating solution can be sufficiently exchanged between the inside and the outside of the barrel, and the plating efficiency increases. From the above points, the shortest distance D between the vertices of the diamond cut
, The shortest distance E between the centers of the holes formed in the barrel, and the diameter F of the spherical media must satisfy the above two equations.

[0010]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to examples, but the present invention is not limited to these examples. (Example 1, Comparative Example 1) Using a hexagonal barrel having an inner diameter of 200 mm and a length of 500 mm, a 15 mm ×
15mm x 5mmt size flat Nd-Fe-B permanent magnet
i Plated. Holes with a diameter of 2.5 mm are opened at intervals of 6 mm in this barrel, and square pyramids with a bottom surface of 4 mm x 4 mm and a height of 1.5 mmh are arranged without gaps as diamond cuts. That is, the shortest distance D between the diamond cut vertices is 4 mm, and the shortest distance E between the centers of the holes is 6 mm. A stainless steel ball having a diameter of 6 mmφ as a spherical medium and an Nd-Fe-B-based magnet as an object to be processed were put into the barrel and immersed in a Ni plating solution, and Ni plating was performed until the Ni plating film became 10 μm. . As Comparative Example 1, the same conditions as in Example 1 were used except that the diamond cut was a square pyramid with a height of 3 mmh and a bottom of 7 mm × 7 mm. Plated. Table 1 shows the plating conditions (plating time: required time for Ni plating with a film thickness of 10 μm) and the results (yield such as variation in plating film thickness, cracking, chipping, etc.).

(Example 2, Comparative Example 2) A flat Nd-Fe-B permanent magnet having a size of 10 mm x 10 mm x 6 mmt was plated with Ni using a hexagonal barrel having an inner diameter of 200 mm and a length of 500 mm. . Holes with a diameter of 2 mm are provided in the barrel at intervals of 4 mm, and square pyramids with a bottom of 3 mm x 3 mm and a height of 1.5 mmh are arranged without gaps as diamond cuts. That is,
The shortest distance between diamond cut vertices is 3 mm and the shortest distance between hole centers is 4 mm. A stainless steel ball having a diameter of 5 mm as a medium and an Nd-Fe-B-based magnet as an object to be processed are put into such a barrel, immersed in a Ni plating solution, and plated until the Ni plating film thickness becomes 10 μm. gave. The plating conditions and results are shown in Table 1 as Example 2.
It was also described in. As Comparative Example 2, the same barrel as in Example 2 was used except that holes having a diameter of 2 mm were formed at intervals of 7 mm.
The plating was performed under the same magnets and conditions as described above, and the plating conditions and results are also shown in Table 1.

[0012]

[Table 1]

[0013]

According to the present invention, it is possible to provide a barrel-type electroplating method which has good plating efficiency, has little variation in the plating film, and has few cracks and chips.

[Brief description of the drawings]

FIG. 1 is a side view showing a barrel attached to a plating bath with an eccentric axial direction.

FIG. 2A is a plan view showing a diamond cut according to the present invention;
(B) It is BB sectional drawing.

Claims (1)

(57) [Claims] 1. A have da Iyaka' bets on the inner wall of the barrel, the shortest distance D between the diamond cut vertex, and the shortest distance E between the centers of holes drilled in the barrel, the diameter F of the spherical media, the following formula A barrel-type electroplating method characterized by satisfying the above relationship. 2 ^1/2 · D <F and D ≠ E