Optical: systems and elements – Deflection using a moving element – Using a periodically moving element
Reexamination Certificate
2003-02-14
2004-10-12
Cherry, Euncha P. (Department: 2872)
Optical: systems and elements
Deflection using a moving element
Using a periodically moving element
Reexamination Certificate
active
06804035
ABSTRACT:
TECHNICAL FIELD
This invention relates to a machine and in particular to measurement of energy of laser light thereof.
BACKGROUND OF THE INVENTION
As for recent portable information electronic machines, etc., a build-up multi-layer circuit board comprising a plurality of conducting layers and insulating layers deposited on an electronic circuit board is used, whereby the circuitry is made denser and miniaturization of the machine is accomplished. In the build-up multi-layer circuit board, the insulating layer is formed with a large number of conducting holes called bias holes or through holes to bring wiring patterns of the conducting layers with the insulating layer between into conduction, and a machining method using laser light is used as a drilling method to make the conducting holes.
Such a laser beam machine for drilling a circuit board using laser light in a related art has a configuration as shown in FIG.
6
. Laser light
2
emitted from a laser oscillator
1
is reflected by a pair of deflection mirrors, generally galvanometer deflection mirrors
5
(
5
a
and
5
b
) and is gathered through a scanning lens
6
on the surface of a light-applied object, for example, a workpiece
4
.
The galvanometer deflection mirrors (which will be hereinafter described as “deflection mirrors” whenever necessary)
5
are used to change the angle of the laser light
2
incident on the scanning lens
6
, whereby a finite deflection area
7
is provided on the surface of the workpiece
4
. Usually, the deflection mirrors
5
are implemented as two axes of a pair of deflection mirrors
5
a
and
5
b
and thus the deflection area
7
becomes a rectangular shape. Since the deflection mirrors
5
a
and
5
b
of two axes can be freely changed mutually in angle, the laser light
2
can be applied freely to every part in the deflection area
7
. The workpiece
4
is fixed to a two-axis drive table
3
and upon completion of machining one deflection area
7
, the workpiece
4
is moved by a distance equivalent to the length of one side of the deflection area
7
by means of the drive table
3
, whereby the deflection area
7
can be consecutively developed on the surface of the workpiece
4
and the full surface of the workpiece
4
can be machined.
By the way, in laser beam machining, the material component of the workpiece
4
is removed by energy of the laser light
2
for machining. Thus, to perform good machining, the laser light
2
of proper energy needs to be applied. Thus, this kind of laser beam machine is provided with energy measurement means for setting the energy of the laser light
2
actually applied to the workpiece
4
.
FIG. 7
shows an example of laser light energy measurement means provided for the laser beam machine in the related art. An energy measurement section
11
is placed at the tip of an air cylinder
16
, whereby the energy measurement section
11
can be advanced to and retreated from a position opposed to the laser light emission side surface of the scanning lens
6
and only when energy is measured, the energy measurement section
11
is moved to the position opposed to the laser light emission side surface of the scanning lens
6
and energy measurement is conducted. The air cylinder
16
itself is attached and fixed to a column (not shown) to which a machining head is fixed.
The energy measurement means
11
in the related art thus placed is configured so that it can measure only the energy of laser light passing through the center of the scanning lens
6
, namely, the energy of laser light applied to the center of the deflection area
7
.
However, the laser beam machine using the deflection mirrors and the scanning lens machines usually the deflection area measuring about 50 mm square and thus measuring of only the energy of laser light passing through the center of the scanning lens as in the laser beam machine in the related art may be insufficient. The reason will be discussed in detail below:
In laser beam machining, the material component of a workpiece removed by the energy of laser light occurs as machining cuttings. In the laser beam machine using the deflection mirrors and the scanning lens, the machining cuttings are deposited on the laser light emission side surface of the scanning lens, whereby passage of the laser light is hindered and it may be made impossible to apply proper energy to the workpiece. Thus, as shown in
FIG. 8
, in the laser beam machine using the usual deflection mirrors
5
and the scanning lens
6
, dirt prevention means of a dust collection duct
20
, an air curtain
21
, etc., is placed in the proximity of the scanning lens
6
, where by machining cuttings
22
are prevented from being deposited on the laser light emission side surface of the scanning lens
6
.
However, the bore of the laser light emission side surface of the scanning lens
6
used with this kind of laser beam machine has a comparatively large area in the neighborhood of &phgr;100 mm and thus if the above-described dirt prevention means is placed, a partial air flow becomes insufficient or stagnation occurs in the flow, so that a part where dirt prevention becomes incomplete occurs. With the use for a long term, the machining cuttings
22
are gradually deposited on the part and a state in which passage of the laser light
2
is hindered is entered. If the laser light
2
passes through the dirty part of the surface of the scanning lens
6
on which the machining cuttings
22
are deposited, absorption or scattering of the laser light
2
occurs due to the machining cuttings
22
and the energy arriving at the workpiece
4
is decreased and thus nonuniform energy occurs in the deflection area. Particularly with the dirt prevention means as shown in
FIG. 8
, shortage or stagnation of the flow easily occurs in the part near to the marginal portion of the scanning lens
6
in the proximity of the dust collection duct
20
and thus the machining cuttings
22
tend to be easily deposited on the part.
If dirt occurs in the part near to the marginal portion of the scanning lens
6
in such a manner that the machining cuttings
22
are deposited, in the vicinity of the center of the scanning lens
6
, a sufficient flow exists and the above-described dirt prevention means acts effectively and thus deposition of the machining cuttings
22
can be prevented and dirt on the laser light emission side surface of the scanning lens
6
does not occur.
Under such circumstances, if only the energy of the laser light
2
passing through the center of the scanning lens
6
is measured and the energy is set, energy shortage occurs at the position in the deflection area corresponding to the dirty part on which the machining cuttings
22
are deposited, and good machining becomes difficult to perform at the position. Empirically, for example, if machining cuttings of epoxy resin of a component material of a printed wiring board are deposited on a part of the laser light emission side surface of the scanning lens
6
, energy is lowered 20% or more in the part and if machining is performed without being aware of it, a part of the deflection area results in a machining failure. In such a case, it is necessary to remove dirt by cleaning the lower face of the scanning lens
6
in alcohol, etc., so as to make it possible to well machine the whole deflection area. Thus, if nonuniform energy in the deflection area occurs due to deposition of machining cuttings on the laser light emission side surface of the scanning lens
6
, the energy state becomes good if appropriate maintenance of cleaning, etc., is conducted. However, the development degree of dirt varies depending on the machining contents and thus the appropriate maintenance timing cannot be determined. If the maintenance frequency is raised, a problem of hindering productivity also arises.
As described above, in the laser beam machine in the related art, only the energy of the laser light passing through the center of the scanning lens is measured and thus nonuniform energy in the deflection area caused by partial dirt on the l
Cherry Euncha P.
Mitsubishi Denki & Kabushiki Kaisha
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