1. Field of the Invention
The present invention relates to a spool holder structure for a wire bonder which holds a spool around which a wire is wound.
2. Prior Art
Wire bonders form a ball by the discharge of a discharge electrode on the tip end of a wire that passes through a capillary. In this case, it is necessary that the initial end of the wire, which is wound on a spool, be grounded.
The structure described in Japanese Utility Model Registration No. 2550162 may be cited as a conventional example of a grounding structure for the initial end of a wire. This structure includes a contact plate which is fastened to a motor attachment plate so that the contact plate is pressed against the holder shaft of the spool holder by an elastic force. The contact plate has two contact parts, and one end of each contact part is a fixed part while the other end is free or not fixed. These two contact parts are formed so as to press against both side of the holder shaft so that the free ends of the contact parts are oriented in the direction of rotation of the holder shaft.
In the above-described prior art, the contact parts are pressed against the holder shaft by an elastic force. Accordingly, the portions of the contact parts that contact the holder shaft become worn by friction. Thus, there are problems in terms of durability.
The object of the present invention is to provide a spool holder structure for a wire bonder that can extend the useful life of the spool holder structure.
The above object is accomplished by a unique structure of the present invention for a spool holder structure equipped with a spool holder that holds a spool around which a wire is wound, a holder fastening shaft consisting of an insulating material that is fastened to the inner circumference of the holder shaft of the spool holder, and a motor that has an output shaft fastened to the holder fastening shaft; and in the present invention, the holder shaft is rotatably supported via a conductive bearing that is fastened to an attachment plate, and the conductive bearing is grounded.
The above object is further accomplished by another unique structure of the present invention for a spool holder structure equipped with a spool holder that holds a spool around which a wire is wound, a holder fastening shaft consisting of an insulating material that is fastened to the inner circumference of the holder shaft of the spool holder, a motor that has an output shaft fastened to the holder fastening shaft, and an attachment plate to which the motor is mounted; and in the present invention, the inner race of a conductive bearing is fastened to the outer circumference of the holder shaft, the outer race of the conductive bearing is fastened to the attachment plate via a bearing holder, and the bearing holder is grounded.
In the above structures, it is preferable that the motor is grounded.