JPH09137296A - Method for plating electronic parts - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the blossoming phenomenon of cathode, to surely and effectively apply plating and to improve reliability by regulating the size of energization media to be used to a specific range at the time of forming the external electrodes of electronic parts by horizontal rotary barrel plating. SOLUTION: The electronic parts which are the objects to be plated and the energization media are charged onto a horizontal or spiral diaphragm 6 embedded with the cathode 8 in a barrel plating cell 5 and plating is executed while the objects to be plated are moved around the central shaft 7 by the vibration of the diaphragm 6 together with the plating liquid. At this time, the diameter of the energization media is specified to >=0.8 to <=3 times the max. size of the min. projection area of the electronic parts to be plated. Further preferably, the energization media having the diameter of <=0.8 to <=1.3 times the max. size of the min. projection area of the electronic parts are mixed in a proper amt. with the plating liquid to decrease the variations in the plating of the layers. These methods are particularly effectively applicable to the plating of laminated ceramic capacitors.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of plating an electronic component for forming an external electrode of the electronic component.

[0002]

2. Description of the Related Art As a conventional plating method for forming external electrodes of a monolithic ceramic capacitor, an electrolytic barrel plating method as shown in FIG. 5 has been used. That is, in the drum 2 rotatably mounted on the horizontal shaft 1, the electronic component as the object to be plated and the barrel solution 4 consisting of the plating medium and the current-carrying medium having the structure in which the steel ball is solder-plated are stored. The cathode 3 which protrudes downward and is always immersed in the barrel solution 4 is provided on the horizontal shaft 1, and the drum 2 is rotated at a low speed to plate the electronic parts at predetermined positions to form the external electrodes.

However, in this rotary type, the electronic parts which are the objects to be plated are impacted to cause chipping or cracking of the electronic parts, or the electronic parts are soared by surface tension, buoyancy or lift in the plating solution. There was a problem that the plating thickness varied.

For these reasons, recently, the electronic parts to be plated, the energizing medium and the plating solution are stored on a horizontal plate in the plating tank, and the horizontal plate is vibrated to rotate the plate. Have been developed.

[0005]

However, in the above-described horizontal rotary plating method, since a current-carrying medium called a dummy is used, the object to be plated and the current-carrying medium are separated from each other, and sufficient plating cannot be performed. Even if an energizing medium that does not separate from the object to be plated is used, a flowering phenomenon in which the plating grows in a dendritic manner around the cathode 3 provided on the horizontal plate as shown in FIG. 6 occurs depending on the type of plating solution. Significantly lowers the plating efficiency, and the amplitude of the vibration generated by the horizontal plate differs depending on whether it passes through the central part of the plate to be plated or through the peripheral part. There was a problem that variations occurred.

The present invention eliminates the above-mentioned conventional defects, does not cause a flowering phenomenon on the cathode, does not separate the object to be plated from the energizing medium, and has no difference in angular velocity of the object to be plated. It is an object to provide a plating method for parts.

[0007]

In order to solve the above-mentioned problems, a method of plating an electronic component according to the present invention comprises a horizontal plate or a spiral plate in which a cathode is embedded and an electronic component which is to be plated and a substantially spherical shape. When barrel plating is performed on the electronic component while moving the current-carrying medium and the plating liquid around the central axis by the vibration of the horizontal plate or the spiral plate, the diameter of the current-carrying medium is the minimum projected area of the electronic component. Maximum dimension 0.8 ~
This is a method using 1.3 times.

By this method, the plating thickness is uniform and efficient plating can be performed.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention is characterized in that an electronic component which is an object to be plated, an energizing agent, and a plating solution are leveled on a horizontal plate or a spiral plate in which a cathode is embedded. When the electronic component is barrel-plated while being moved around the central axis by the vibration of the plate or the spiral plate, the diameter of the current-carrying medium is 0.8 times or more the maximum size of the minimum projected area of the electronic component. This is a plating method using less than 3 times, and by this method, the current-carrying medium can be surely and uniformly plated without being separated from the object to be plated.

The invention according to claim 2 uses a current-carrying medium as described in claim 1 in which a mixture of 0.8 times or less is used, and a phenomenon in which the plating grows in a dendritic manner on the cathode is observed. It can prevent and improve plating efficiency.

According to a third aspect of the present invention, as a current carrying medium, a mixture of 1.3 times or more of the medium of the first aspect is used, and plating is performed so that the angular velocity of the object to be plated becomes constant. There should be no variation.

According to the invention described in claim 4, the current carrying medium is 0.8 times or less than the one described in claim 1 and 1.3.
By mixing two or more times the amount, the flower bloom phenomenon is prevented and the angular velocity of the object to be plated is kept constant to enable more efficient and uniform plating.

That is, according to the present invention, after plating, the distribution state of the object to be plated and the current carrying medium is investigated, and the current carrying medium having a small diameter is at the bottom of the horizontal plate or the spiral plate, and the large current carrying medium is at the surface or the central axis. In order to confirm this, it was confirmed that only the particles that exist around the object and have the same diameter as the object to be plated are dispersed uniformly in the object to be plated. As a result, it was clarified that there is a relationship shown in (Table 1) between the maximum dimension L of the minimum projected area of the object to be plated and the diameter φ of the current-carrying medium.

[0014]

[Table 1]

It can be said from Table 1 that the diameter φ of the current-carrying medium is 0.8 L or more and 1.3 L or less in order to solve the separation between the plated object and the current-carrying medium.

Next, in order to solve the flowering phenomenon in which the plating grows in a dendritic manner on the peripheral portion of the cathode embedded in the horizontal plate or the spiral plate, the result of the experiment using the classified current carrying medium (Table 2) ) The result shown was obtained.

[0017]

[Table 2]

From the above (Table 2), in order to solve the phenomenon of flower blooming of the cathode, 1.
It can be said that it is effective to use a mixture of 3L or less and less than 0.8L.

Further, in order to solve the phenomenon in which the angular velocity of the object to be plated is different at the center and the peripheral portion of the barrel and the amount of plating is different, the diameter of the current carrying medium is 1. If it is 3 L or more, this energizing agent gathers in the center of the barrel, and it was found that the object to be plated is extruded from the center to the peripheral edge. It is effective to mix and use 1.3 L or more of a current-carrying medium.

Further, in order to eliminate the phenomenon of flower bloom and the inconsistency in the angular velocity of the object to be plated, 0.8L or more and 1.3L or less of the current carrying medium, 0.8L or less and 1.3L or more of the current carrying medium are used. It is effective to mix and use.

Specific embodiments of the present invention will be described below with reference to the drawings. (Embodiment 1) Hereinafter, Embodiment 1 of the present invention will be described with reference to the drawings.

In FIG. 1, reference numeral 5 is a barrel plating tank. A spiral plate 6 is incorporated in the barrel plating tank 5, and a central axis for vibrating the spiral plate 6 is provided at the center of the spiral plate 6. 7 are connected. A cathode 8 is embedded in the spiral plate 6. Further, on the spiral plate 6, 20 cc of the laminated ceramic capacitor as an object to be plated and 140 cc of steel balls plated with solder as a classified current-carrying medium are rotated 100 times in a Ni plating solution, and then the laminated chip capacitor is rotated. Then, it was pulled up from the plating solution and the dispersed state was observed.

The results are shown in (Table 3) to (Table 6).
(Table 3) shows a laminated chip capacitor with a length of 1.0 mm,
It has a width of 0.5 mm and a thickness of 0.5 mm (referred to as a type), and (Table 4) has a length of 1.6 mm, a width of 0.8 mm and a thickness of 0.
8 mm (referred to as b type), (Table 5) is 2.0 mm in length, 1.25 mm in width and 1.0 mm in thickness (referred to as c type), and (Table 6) is in length 3.2 mm, width 1.6
It is the result of an experiment using a film having a thickness of 1.0 mm and a thickness of 1.0 mm (referred to as d type).

[0024]

[Table 3]

[0025]

[Table 4]

[0026]

[Table 5]

[0027]

[Table 6]

In the above (Table 3) to (Table 6), A
~ E are defined as follows.

A: The monolithic ceramic capacitor was observed only near the surface of the current-carrying medium layer, and was not observed at all in the middle and bottom surfaces.

B: Most of the monolithic ceramic capacitors are present in the vicinity of the surface, although they are dispersed almost uniformly over the surface, the middle and the bottom of the current carrying medium layer.

C: Dispersed uniformly over the surface, the middle and the bottom of the current carrying medium layer. D: Almost evenly distributed over the surface, middle and bottom of the current carrying medium layer, but more multilayer ceramic capacitors are present on the bottom.

E: The monolithic ceramic capacitor was observed only near the bottom surface of the conduction medium layer, and was not observed at all on the surface or in the middle.

On the other hand, the maximum dimension of the minimum projected area of each monolithic ceramic capacitor, that is, the target line length L of a rectangle of width × thickness is obtained, and the experimental result of the relation with the diameter φ of the uniformly distributed current-carrying medium is shown in the table. 7).

[0034]

[Table 7]

Although φ / L of the uniformly distributed current-carrying medium is slightly different from this (Table 7), φ / L = 0.80 to 1.
When 30 current-carrying media were prepared, plating was actually performed, and the plating thickness and its variation were evaluated. As a result, there was no difference and the validity of φ / L = 0.80 to 1.30 was confirmed. Further, the same confirmation was performed by solder plating, but the result was exactly the same as that described above.

(Embodiment 2) A type monolithic ceramic capacitor 50 cc, diameter 0.560 mm to 0.930
50 mm of a current carrying medium having a diameter of 0.560 mm and 2 to 40 cc of a current carrying medium having a diameter of less than 0.560 mm were placed in the horizontal rotating barrel shown in FIG. 2 and plated at a rotation speed of 6 rpm.

Further, 30cc of a type monolithic ceramic capacitor, 30cc of current carrying medium having a diameter of 0.560mm to 0.930mm, 100cc of current carrying medium having a diameter of less than 0.560mm are put in the horizontal rotary barrel of FIG. Plating was performed to evaluate the flower bloom phenomenon. The results are shown in (Table 8).

[0038]

[Table 8]

In Table 8 where the flowering phenomenon does not occur, the current-carrying medium 9 having a diameter of less than 0.560 mm is the spiral plate 6.
It sinks above and contacts the cathode 8 embedded in the spiral plate 6, and the entire surface of the spiral plate 6 becomes a cathode, the contact resistance between the multilayer ceramic capacitor and the cathode 8 decreases, and the distribution current to the cathode 8 decreases. Therefore, the adhesion of plating to the cathode 8 is reduced and the flowering phenomenon is eliminated.

A current-carrying medium 9 covering the upper surface of the spiral plate 6.
The minimum amount of is calculated by the following formula. V = 4S · r / 3 where V is the minimum amount (volume) of the current carrying medium covering the upper surface of the spiral plate of the barrel S is the surface area of the upper surface of the spiral plate r is the diameter of the current carrying medium.

In the case of this second embodiment, S = 188 cm
² , the average diameter of the current carrying medium is 0.296mm, that is,
Since r = 0.0296 cm, V becomes 7.4 cm ² (cc). From the results of (Table 8), 0.9 times or less of V, that is, diameter of 0.560 mm or less at 6 cc or more, (diameter of 0.
The flowering phenomenon can be eliminated by using an energizing agent of 80 L or less).

(Third Embodiment) In the third embodiment, 0.
1.3 instead of mixing 80 L or less energizing medium
L or more energizing agents were mixed. Ie 0.9
Table 9 shows the results of plating using 5-85 cc of an energization medium of 30 mm or more. (Table 9) has a diameter of 1.3
The amount of the energizing medium of L or more and the energizing medium 10 are shown in FIG.
Shows the relationship with the thickness gathered around the central axis 7 and the angular velocity ratio of the monolithic ceramic capacitor in the central part to the outer peripheral part.

[0043]

[Table 9]

As is clear from (Table 9), the diameter is 1.
If the amount of the energizing medium of 3 L or more is 15 cc or more, it gathers around the central axis 7, and the energizing medium of 0.8 L or more and 1.3 L or less and the laminated ceramic capacitor are spiral plates 6 having a larger amplitude than the central portion. It can be seen that the angular velocities of the monolithic ceramic capacitors at the outer peripheral portion and the central portion become the same, by chasing them to the outer peripheral portion. This corresponds to 13% of the total amount (volume) of the laminated ceramic capacitor and the current carrying medium, that is, the total amount (volume) of the object to be plated and the current carrying medium.

A combination of the second embodiment and the third embodiment, that is, a current carrying medium having a diameter of 0.8 L or more and 1.3 L or less and a current carrying medium having a diameter of 0.8 L or less and a diameter of 1.
By mixing with 3 L or more energizing agents, as shown in FIG. 4, energizing agents 10 with a large diameter gather around the central axis 7 and energizing agents 9 with a small diameter are deposited on the spiral plate 6. ,
It is possible to perform plating with no flower bloom phenomenon and no difference in the angular velocity of the object to be plated.

Further, in each of the above-mentioned embodiments, the a-type monolithic ceramic capacitor has been described, but it has been confirmed that other types have the same effect. Needless to say, similar effects can be obtained in electronic parts other than the monolithic ceramic capacitor. Also, the same effect can be expected by using a horizontal plate instead of the spiral plate 6.

[0047]

As described above, according to the method of plating an electronic component of the present invention, the electronic component which is the object to be plated and the energizing medium are uniformly dispersed, and reliable and effective plating can be performed. It is possible to significantly improve the sex.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a horizontal rotary barrel plating apparatus showing an embodiment of a plating method for electronic parts of the present invention.

FIG. 2 is a schematic sectional view of a horizontal rotary barrel plating apparatus according to another embodiment.

FIG. 3 is a schematic sectional view of a horizontal rotary barrel plating apparatus according to another embodiment.

FIG. 4 is a schematic sectional view of a horizontal rotary barrel plating apparatus according to another embodiment.

FIG. 5 is a schematic sectional view of a barrel plating apparatus according to a conventional electronic component plating method.

FIG. 6 is an explanatory view showing a state in which plating grows around a cathode by a conventional method.

[Explanation of symbols]

 5 Barrel plating tank 6 Spiral plate 7 Center axis 8 Cathode

Claims (4)

[Claims] 1. A horizontal plate or a spiral plate in which a cathode is embedded moves an electronic component as an object to be plated, an energizing agent, and a plating solution around a central axis by vibration of the horizontal plate or the spiral plate. A method of plating an electronic component, wherein the diameter of the current-carrying medium is 0.8 times or more and 1.3 times or less of the maximum dimension of the minimum projected area of the electronic component when barrel-plating the electronic component. 2. A current carrying agent which is 0.8 times or less of a maximum dimension of a minimum projected area of an electronic component and is mixed with a current carrying agent which is 0.9 times or more a minimum amount for covering a bottom surface of a barrel. Item 2. A method for plating an electronic component according to Item 1. 3. The method of plating an electronic component according to claim 1, wherein a material having 1.3 times or more the maximum dimension of the minimum projected area of the electronic component is mixed and used as the energizing medium. 4. The method of plating an electronic component according to claim 1, wherein a mixture of 0.8 times or less and 1.3 times or more of the maximum dimension of the minimum projected area of the electronic component is used as the energizing medium. .