Electric heating – Metal heating – By arc
Reexamination Certificate
1997-09-27
2001-02-06
Evans, Geoffrey S. (Department: 1725)
Electric heating
Metal heating
By arc
C219S121740, C359S629000
Reexamination Certificate
active
06184490
ABSTRACT:
This invention relates to a material irradiation apparatus, and more particularly, to a material irradiation apparatus that produces a processing beam, and to a process for the operation of such material irradiation apparatus.
Such material irradiation apparatus has a beam splitting device that follows the beam source, with which the processing beam is divided into several partial beams. Each partial beam can be deflected by a deflecting device discretely associated with the partial beam, to different places on at least one workpiece to be processed, independently of the other partial beams. The workpiece to be processed is situated on a workpiece movement device that is movable in at least one axis.
DISCUSSION OF RELEVANT PRIOR ART
Irradiation apparatuses for various purposes have been known for a long time, and are known in very varied forms.
In particular, single-beam laser drilling machines are known, which however can only produce one given hole diameter. These apparatuses are relatively slow (one hole at a time) and inflexible (the hole diameter cannot be automatically adjusted, or a larger hole diameter has to be machined out by a trephining process (that is, by the adjoining of many smaller hole diameters).
Multi-spindle guide plate drilling machines on an X-and/or Y-workpiece moving device are also known, the individual drilhng spindles being installed on slides and able to execute separate y-and z-axis movements. A drill change then takes place for individual hole diameters in this mechanical drilling.
A system is known from U.S. Pat. No. 5,268,554 for positioning a laser beam, in which a laser beam is positioned on a workDiece surface. The positioning takes place by means of an adjustable mirror. If it were now desired to work simultaneously at very many places on the workpiece surface, correspondingly many such systems would be required, and mutual spatial interference between them would result Equipment constructed in this manner would also be very complicated.
A system for laser machining is known from Japanese Patent JP 54-102695, in which a predetermined contour is transferred by a laser to another workpiece.
A method for producing a longitudinal strip is known from U.S. Pat. No. 4,670,639, in which a laser beam passes through several splitter mirrors, which respectively deflect the laser beam to different places on the workpiece. The workpiece is then moved in the irradiation axis. The splitter mirrors are set once, and together produce the desired longitudinal strip. This equipment is very inflexible in the disclosed form.
An apparatus for the treatment of workpieces by means of laser energy is known from German Patent DE 20,14,448, in which a laser beam is split by a beam splitter into two separate beams and deflected by deflecting mirrors through a common objective onto a workpiece surface. The use of an objective considerably limits the irradiation surface on the workpiece.
A laser recording equipment is known from U.S. Pat. No. 3,256,524, in which a laser beam is split by beam splitters into several partial beams and is imaged, on a surface to be irradiated, via deflecting rirrors and an objective associated with these.
A laser machining equipment is known from U.S. Pat. No. 4,950,862, in which a laser beam is deflected by means of a mirror through a two iimensional lens array onto a workpiece surface, the workpiece being located on an X-Y table.
A machine for processing many workpiece surfaces with a single laser beam is known from U.S. Pat. No. 4,701,591, the laser beam being divided into several partial beams.
A laser machining equipment is known from U.S. Pat. No. 5,373,137, in which a laser beam is divided by a lens array into many partial beams which are imaged by means of deflecting mirrors and respective discrete optics onto a workpiece surface, where they produce a line pattern.
A laser drilling machine is known from U.S. Pat. Nos. 5,302,798 and 5,113,055, in which deflecting mirrors successively deflect a laser beam through respective discrete objectives onto workpiece surfaces. Machining does not take place in parallel here, but sequentially.
An irradiating device is known from U.S. Pat. No. 5,290,992, in which a laser beam is deflected by beam splitters respectively in different directions in order to be able to machine several workpieces simultaneously.
A single-beam laser drill is known from U.S. Pat. No. 5,063,280, in which the hole production is optimized.
A single beam laser illumination machine is known from U.S. Pat. No. 5,481,407, in which two Fresnel lens arrays assume the task of the objective which is movable in the z-axis; the two arrays are displaced horizontally with respect to each other, in order to obtain the respectively desired focusing of the laser beam.
An irradiating device for the production of three-dimensional objects is known from WO 94/16875, in which a beam is divided into several partial beams, which then fall in common at different places on the object to be produced. No beam shaping takes place here.
The above-described material irradiating equipments of very varied kinds are also particularly used for drilling. In particular, the following possibilities with the laser are available, for the drilling of laminates such as a polyimide foil, 50 &mgr;m thick, which is laminated on both sides with 17 &mgr;m of copper (a starting product in the printed circuit board industry, and today already machined by laser technology), and in which so-called blind holes are to be drilled, passing through the upper copper layer and the polyimide and having the lower copper layer as a floor (see FIG.
1
):
In a first process according to the state of the art, the production of the entry holes in the upper copper layer takes place by a phototechnical-chemical method. The polyimide is then removed by laser drilling of the polyimide through the opened copper with an energy density of, e.g., 0.7 J/cm
2
, which machines the polyimide well but does not attack the copper. The lower copper layer then acts automatically as a stop layer for the laser. The typical laser used here is a pulsed UV laser.
The disadvantage of this process is that apart from the irradiation by means of the laser, additional working processes are required to produce the entry holes in the upper copper layer by the phototechnical-chemical method.
The second process known in the state of the aft is similar to the first; however, a laser is used which is reflected by the copper and thus does not attack the copper. This permits higher energy densities and thus a somewhat more rapid machining of the polyamide. limits are however set (about 2 J/cm
2
) on the increase of the energy density, since otherwise the polyimide is thermally damaged and the hole edges are burnt, and then can no longer be metailized. A typical laser for carying out this process is a pulsed CO
2
laser.
The disadvantage of this process is that additional working processes are required to produce the entry holes in the upper copper layer by the phototechnical-chemical method. Moreover a polynimde coating about 0.7 &mgr;m thick remains on the lower copper floor.
The third known process according to the state of the art uses different lasers for the removal of the copper layer and of the polyimide. For example, a Nd-YAG laser with high energy density (for example, 20 J/cm
2
) is used to drill the upper copper layer, and a UV or CO
2
laser is used to drill the polyimide.
The disadvantage of this process is that two different lasers are required, and the optics used have to be designed for both wavelengths.
In the fourth process known from the state of the art, the machining of the laminate takes place with a LTV laser in such a manner that the upper copper layer is drilled at a high energy density, and the energy density is then reduced by defocusing the beam or by pivoting a filter in, so that the beam does in fact machine the polynimde but does not attack the copper.
This process also has disadvantages. Since lasers are hardly controllable in their energy output, energy is wasted in the machining of t
Carl-Zeiss-Stiftung
Evans Geoffrey S.
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