Patent Application
20070286693
The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:
Before describing the embodiment of the present invention, it is to be understood that the terms or words used in this description and the following claims must not be construed to have meanings which are general or can be found in a dictionary. Therefore, considering the notion that an inventor can most properly define the concepts of the terms or words to best explain his or her invention, the terms or words must be understood as having meanings or concepts that conform to the technical spirit of the present invention.
Hereafter, reference will now be made in greater detail to a preferred embodiment of the invention, an example of which is illustrated in the accompanying drawings.
Referring to these drawings, a drill bit 1 in accordance with an embodiment of the present invention is made of an alloy. The drill bit 1 includes a shank part 10, which has the shape of a round bar and a predetermined length, a reamer part 30, which extends from the distal end of the shank part 10 to finish the surface of a hole, and a drill part 20, which extends from the distal end of the reamer part 30 and is formed with helical drilling edges on the outer surface thereof.
In the drill bit 1 having the construction as described above, the shank part 10 and the drill part 20 are structured in the same manner as those of a conventional drill bit for making a hole through a plurality of stacked PCBs.
In the present invention, the reamer part 30 finishes the surface of the hole 2a, which is made by the drill part 20, to improve the roughness thereof, so that the occurrence of the delamination and crack formation resulting from expansion and contraction due to thermal deformation can be minimized.
As can be readily seen from the drawings, the reamer part 30 has 2 to 8 reaming edges 31, which are brought into contact with and finish the surface of the hole 2a. The reaming edges 31 are formed to be spaced apart from one another in the circumferential direction of the drill bit 1 and extend straight in the axial direction of the drill bit 1.
The reamer part 30 configured in this way has a diameter ‘d1’ which is greater than the diameter ‘d0’ of the drill part 20, to finish with high precision the surface of the hole 2a made by the drill part 20. To this end, in the present invention, assuming that the diameter of the hole 2a defined through the PCBs 2 is about 0.1˜0.3 mm, in consideration of the workability of the hole 2a, the diameter of the reamer part 30 is enlarged by 3˜20% in comparison with the drill part 20.
Due to the fact that the reamer part 30 has a diameter greater than that of the drill part 20, when the reamer part 30 is introduced into the hole 2a made by the drill part 20, a shock occurs. In the present invention, in order to prevent this shock, the distal end portion of the reamer part 30 is tapered so that the contact area between the reamer part 30 and the surface of the hole 2a can be gradually increased.
While the taper on the distal end portion of the reamer part 30 can be simply formed through chamfering, it is preferred that the taper be formed to have a gentle inclination angle so as to minimize the shock upon introduction of the reamer part 30 into the hole 2a of the PCBs 2.
The reaming edge 31 can be formed to have a trapezoidal section, as shown in
Hereafter, the operation of the drill bit 1 for a PCB according to the present invention, constructed as mentioned above, will be described with reference to
First, the shank part 10 of the drill bit 1 is mounted to the spindle of a drill machine which can rotate at a high speed greater than 10,000 rpm.
The plurality of stacked PCBs 2 are placed below the distal end portion of the drill bit 1, that is, the drill part 20, and the position on the PCBs 2 at which the hole 2a is to be made is then aligned with the drill part 20 of the drill bit 1.
Thereupon, by actuating the drill machine, as the shank part 10, which is firmly gripped by the spindle of the drill machine, rotates at a high speed, the drill part 20, integrally formed with the shank part 10, also rotates at the high speed and proceeds toward the PCBs 2 to make the hole 2a.
As can be readily seen from the leftmost illustration of
The drill part 20 is driven into the PCBs 2 while the hole 2a is made. When the drill part 20 has been driven into the PCBs 2 a predetermined distance, the reamer part 30, which is formed on the rear end of the drill part 20, is introduced into the hole 2a made by the drill part 20.
Accordingly, the reamer part 30, which is introduced into the hole 2a, finishes the surface of the hole 2a using the rearming edges 31 which has a diameter finely greater than that of the hole 2a to decrease the roughness of the surface of the hole 2a. In this way, it is possible to minimize the occurrence of crack formation and delamination in the hole 2a.
As is apparent from the above description, the drill bit for a PCB according to the present invention, constructed and operated as mentioned above, provides advantages in that, since a drill part formed on the distal end of the drill bit makes a hole through stacked PCBs through a single drilling process, and a reamer part formed next to the drill part finishes the hole, the roughness of the surface of the hole can be significantly decreased.
Thus, even when the PCBs repeatedly undergo expansion and contraction due to thermal deformation occurring in the course of manufacture, delamination and crack formation occurring in the hole in the conventional art can be remarkably reduced. As a result, as the defective percentage decreases, the manufacturing cost can be decreased and the yield can be increased. Further, the reliability of an electronic appliance that adopts the PCB manufactured according to the present invention can be remarkably improved. Therefore, the present invention provides industrial benefit.
Although a preferred embodiment of the present invention has been described for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2006-0052599 | Jun 2006 | KR | national |
