Electric heating – Metal heating – By arc
Reexamination Certificate
2000-12-13
2002-07-16
Heinrich, Samuel M. (Department: 1725)
Electric heating
Metal heating
By arc
Reexamination Certificate
active
06420676
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method for machining a wiring board with a laser beam for piercing holes such as a through hole, an inner-via hole, and a blind-via hole or the like in a wiring board which is so-called a printed board as well as a device for the same, and more particularly to a method for machining a wiring board with a laser beam for changing the converging characteristic thereof as well as a device for the same.
BACKGROUND OF THE INVENTION
FIG. 14
is a simulated view for explanation of the conventional technology. In
FIG. 14
, designated at the reference numeral
1
is a laser oscillator, at
2
a laser beam oscillated from the laser beam
1
, at
3
a
,
3
b
bend mirrors each for bending the laser beam
2
oscillated from the laser oscillator
1
, at
4
an image transferring mask having an aperture smaller than that of a diameter of the laser beam in a central section thereof, at
5
a galvano-mirror, at
6
a transmission type of optical component such as an f-&thgr; lens, and at
7
a wiring board as an object to be machined.
In
FIG. 14
, a laser beam
2
oscillated from the laser oscillator
1
is bent by the bend mirror
3
a
and goes into the image transferring mask
4
. At this point of time, the laser beam
2
has a diameter larger than the aperture diameter of the image transferring mask
4
and is taken out by a desired amount of energy or as a desired form of beam through the image transferring mask
4
. The laser beam
2
having passed through the image transferring mask
4
is bent by the bend mirror
3
b
, guided to a specified position of the f-&thgr; lens
6
by the galvano-mirror
5
, and also guided to the wiring board
7
, whereby a hole is pierced through the wiring board
7
.
It is well known that a laser beam has a different intensity distribution, as indicated by reference signs &agr;, &bgr;, &ggr; shown in
FIG. 15A
, according to a position after the laser beam is passed through the lens. Namely,
FIG. 15A
shows a laser beam
2
at each of the positions indicated by the reference signs &agr;, &bgr;, &ggr; after the beam is passed through the f-&thgr; lens
6
,
FIG. 15B
shows a beam intensity distribution at each of the positions such as at a position indicated by &agr;, namely a focal position, at a position indicated by &bgr;, and at a position indicated by &ggr; each shown in
FIG. 15A
, and
FIG. 15C
is a view showing a form of a machined hole in the wiring board
7
at each of the positions indicated by &agr;, &bgr;, &ggr; shown in
FIG. 15A
according to each beam intensity.
Generally, in a case where hole-piercing is executed in the wiring board
7
, the wiring board
7
is placed at a position indicated by a in
FIG. 15A
, namely at a focal position. In this case, the intensity distribution of the laser beam
2
is flat as shown in
FIG. 15B
, and as a result, it is possible to machine a hole with a high degree of roundness and is straight in the direction of the board thickness of the wiring board
7
therein as indicated by &agr; in FIG.
15
C.
On the other hand, in a case where the wiring board
7
is placed at a position indicated by &bgr; in
FIG. 15A
, this situation is called a defocusing state, and the laser beam
2
is irradiated to the wiring board
7
as indicated by &bgr; in
FIG. 15B
with the intensity distribution thereof like that by the laser beam
2
with reduced converging characteristic, and for this reason it can be recognized that a tapered hole in which the diameter is large in the upper side of the hole and is small in the lower side thereof is formed, as indicated by &bgr; in FIG.
15
C.
Further, in a case where the wiring board
7
is placed at a position indicated by &ggr; in
FIG. 15A
, the intensity distribution of the beam is like that by r in
FIG. 15B
, and a tapered angle of the machined hole can be increased as indicated by &ggr; in FIG.
15
C. As described above, it is possible to easily change a tapered angle of a machined hole according to increase or decrease of a defocusing rate, so that in recent years, this method has become more and more popular and been used for actual industrial purposes.
In a case where the board is machined in the defocusing state, however, a degree of roundness of a machined hole therein is degraded due to astigmatism in a transmission type of optical components such as an f-&thgr; lens or the like.
It is also difficult to vertically adjust the axis of the laser beam after passing through the f-&thgr; lens to the wiring board in the area covering all inciding positions of the laser beam to the f-&thgr; lens, and for this reason, a positional displacement of a machined hole is generated even if the identical position is tried to be machined in a case of machining the hole at the focal position as well as in a case of machining it in the defocusing state. Accordingly, it is required to correct a positional displacement each time when the defocusing rate is changed, which causes increase of needless works.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a method for machining a wiring board with a laser beam in which the converging characteristic of a laser beam can be changed so that a desired tapered angle can be made in a hole to be machined as well as a device for the same.
A method for machining a wiring board with a laser beam according to the present invention, machines a wiring board by irradiating a laser beam onto a light shielding body provided in a light path between a laser oscillator and a machining lens for shielding a portion of said laser beam, and by introducing a non-shielded portion of said laser beam having passed through said light shielding body to said machining lens.
A device for machining a wiring board with a laser beam according to the present invention, comprises a light shielding body provided in a light path between a laser oscillator and a machining lens for shielding a portion of said laser beam, and a means for introducing a non-shielded portion of said laser beam having passed through said light shielding body to said machining lens.
A device for machining a wiring board with a laser beam according to the present invention, a light shielding body comprises a member which shields a central portion of a laser beam.
A device for machining a wiring board with a laser beam according to the present invention, a light shielding body comprises a member which shields a laser beam in an annular form.
A device for machining a wiring board with a laser beam according to the present invention, a light shielding body comprises a member which can change an area of a laser beam to be shielded.
A device for machining a wiring board with a laser beam according to the present invention, holds a light shielding body by a positioning means movable in the axial direction of a laser beam.
A device for machining a wiring board with a laser beam according to the present invention, comprises a means for changing a diameter of a laser beam inciding into a light shielding body.
A device for machining a wiring board with a laser beam according to the present invention, has the configuration in which a specified area to be shielded, a position of a light shielding body, or a diameter of a laser beam can be adjusted according to an instruction from a control unit.
A device for machining a wiring board with a laser beam according to the present invention, comprises a means for cooling a light shielding body.
A device for machining a wiring board with a laser beam according to the present invention, a light shielding body comprises a laser beam reflecting member with a laser beam damper provided therein.
Other objects and features of this invention will become understood from the following description with reference to the accompanying drawings.
REFERENCES:
patent: 3947093 (1976-03-01), Goshima et al.
patent: 4734550 (1988-03-01), Imamura et al.
patent: 4857698 (1989-08-01), Perun
patent: 5017755 (1991-05-01), Yahagi et al.
patent: RE33947 (1992-06-01), Shinohara
patent: 5119550 (1992-06-01), Baughman
Kurosawa Miki
Matsubara Masato
Sawai Hidekazu
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