Electric lamp and discharge devices – Electrode and shield structures – Indirectly heated cathodes
Reexamination Certificate
1998-09-14
2001-02-06
Patel, Nimeshkumar D. (Department: 2879)
Electric lamp and discharge devices
Electrode and shield structures
Indirectly heated cathodes
C313S446000, C313S449000, C204S242000
Reexamination Certificate
active
06184613
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electrode assembly, a cathode device and a plating apparatus that may be employed in an ideal manner when plating substrates for various types of electronic components, IC wafers or the like.
2. Discussion of the Background
During the plating process of substrates for various types of electronic components, IC wafers or the like, plating must be implemented within a limited planar area on the object that is to be plated, i. e., the substrate or the wafer. During such a process, plating is performed by placing a cathode device in surface contact with the surface of the object to be plated so that the cathode device encloses the area to be plated. Publications that disclose this prior art technology include Japanese Unexamined Patent Publication No. 66698/1992 and Japanese Unexamined Patent Publication No. 125596/1993. In the cathode devices of the known art disclosed in these publications, a cathode or an auxiliary electrode is placed in surface contact with the object to be plated.
Since this type of cathode device is employed to plate an object to be plated that is constituted of a substrate for an electronic component, an IC wafer or the like, it is crucial that the film thickness distribution be improved by achieving consistency in the plating film thickness at the object to be plated over the entire plate forming surface as a means for forming an element having consistent characteristics within the object to be plated.
However, there is still room for improvement in the consistency of the plating film thickness and the film thickness distribution in the prior art technologies including the technology mentioned above.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an electrode assembly and a cathode device and a plating apparatus provided with this electrode assembly, with which the film thickness distribution can be improved by achieving consistency in the plating film thickness within the surface where the plate is formed of the object to be plated.
In order to achieve the object described above, the electrode assembly according to the present invention includes a first cathode member, an insulating member and a second cathode member. The first cathode member is provided with a hole enclosed by a frame portion and a contact surface that comes into contact with an object to be plated at one surface of the frame portion. The insulating member is provided with a hole enclosed by a frame portion, with one surface of the frame portion lying adjacent to another surface of the frame portion of the cathode member and the hole concentric with the hole of the first cathode member. The second cathode member is provided with a hole enclosed by a frame portion, with one surface of the frame portion lying adjacent to another surface of the insulating member and the hole concentric with the hole of the insulating member. The smallest bore diameter of the hole at the second cathode member is larger than the smallest bore diameter of the hole of the insulating member.
The cathode device according to the present invention includes the electrode assembly described above. The plating apparatus according to the present invention includes a plating tank, a cathode device and an anode device. The cathode device is the cathode device according to the present invention described above. The cathode device and the anode device constitute an electric circuit for performing plating through a plating bath solution implemented inside the plating tank.
Plating is implemented as required at a plate forming surface (conductive surface) of the object to be plated whose potential is maintained equal to the potential of the cathode in conformance to the line of electric force traveling from the anode to the cathode through the plating bath solution in the plating apparatus described above.
As explained earlier, the electrode assembly employed in the cathode device according to the present invention includes the first cathode member. Since the first cathode member is provided with a contact surface that comes into contact with the object to be plated at one surface of its frame portion, the plate forming surface (conductive surface) of the object to be plated can be placed in contact with the frame portion of the first cathode member.
The cathode device according to the present invention includes the insulating member and the second cathode member in addition to the first cathode member. The first cathode member, the insulating member and the second cathode member are each provided with a hole enclosed by a frame portion, and they are provided adjacent to each other in that order with their holes concentric with one another. Consequently, the plating bath solution can be placed in contact with the plate forming surface (conductive surface) of the object to be plated through the hole of the second cathode member, the hole of the insulating member and the hole of the first cathode member.
Since the insulating member is provided between the second cathode member and the first cathode member, all the components of the electrode assembly can be held in tight contact with one another by taking advantage of the resiliency and the like of the insulating member. By achieving an appropriate degree of hardness (rigidity) in the insulating member, deformation of the insulating member can be prevented while assuring tight contact achieved through its resiliency.
What characterizes the present invention is that in the structure described above, the smallest bore diameter of the hole of the second cathode member is set larger than the smallest bore diameter of the hole of the insulating member. As a result, the internal circumferential edge of the second cathode member is placed at a position receding toward the outside from the internal circumferential edge of the insulating member by a distance represented by the gap occurring due to the difference between the bore diameters of the two members. This structure achieves consistency in the plating film thickness over the entire plate forming surface of the object to be plated.
In a desirable mode, the insulating member includes a first insulating member and a second insulating member. The first insulating member is constituted of a resilient member and is provided with a hole enclosed by a frame portion. The second insulating member, which is constituted of a material that is harder than the first insulating member, is provided with a hole enclosed by a frame portion and is lying adjacent to the first insulating member. The hole at the second insulating member is placed adjacent to the hole of the first insulating member so that they are concentric with each other. In this desirable mode, sufficient tight—contact force is assured through the resiliency of the first insulating member and, at the same time, incorrect positioning, which may otherwise occur due to resilient deformation of the first insulating member, can be prevented by the presence of the second insulating member.
In the mode described above in which the insulating member includes the first insulating member and the second insulating member, it is desirable to set the smallest bore diameter at the insulating member in conformance to the bore diameter of the hole at the second insulating member, since this will create a gap of stable dimension between the internal circumferential edge of the second cathode member and the internal circumferential edge of the insulating member. However, depending upon the material constituting the first insulating member, the bore diameter of the hole at the first insulating member may instead determine the smallest bore diameter at the insulating member.
In another desirable mode, a structure in which the internal circumferential edge of the first cathode member is covered by the first insulating member may be effectively adopted. In this case, since the first insulating member which is not plated is present between the plate forming surface of the object to be
Inoue Satoshi
Tanaka Toyoaki
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Patel Nimeshkumar D.
TDK Corporation
Williams Joseph
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