DE102007012695A1 - Apparatus and method for producing structures in materials using laser beams comprises setting up high speed of rotation of beam and imposing on this oscillating motion so that beam is offset to one side of optical axis - Google Patents

Abstract

Apparatus and method for producing structures in materials using laser beams comprises setting up a high speed of rotation of the beam and imposing on this an oscillating motion so that the beam is offset (S) to one side of the optical axis.

Description

task

The Invention allows the highest possible rotational speed the deflection for the realization of a Laserstrahlfräse at Material processing, especially in applications where the effective laser energy in a narrow circular path with as possible high speed on a workpiece to be distributed. With the described invention, to achieve a Gentle material processing short and ultra-short laser pulses with very high repetition rate on a defined circular path like that be guided on the workpiece to be machined, that at the best possible pulse-to-pulse overlap precise circular cutouts, micro trenches or longitudinal cuts can be realized.

State of the art

The invention presented here describes a method and a device for realizing a rapid circular deflection of optical radiation about the original propagation direction or optical axis. Such a circular deflection can be used when using bundled laser radiation for micromaterial processing of any materials, after which the laser beam ( 1 ) on the workpiece ( 10 ) and is guided over a combination of movements of which at least one movement has a high speed. Such an embodiment in the laser micromachining for the introduction of holes, for the structuring of surfaces or for separating is referred to in this invention as Laserstrahlfräse.

Already known this is from the DE 100 54 853 A1 a method for introducing microbores in mainly metallic materials, in which by means of rotating wedge plates, a beam is placed in tumbling motion about the optical axis. High rotational speeds are excluded in this method by the uneven mass distribution. In addition, the described laser is a system which is equipped with pulse widths in the nanosecond range and moderate repetition rates and, in combination with the slow movement of the tumbling beam, is unsuitable for the processing of brittle materials. In addition, the deflected beam does not run parallel to the optical axis, which means that protection against machining residues can not be achieved without influencing the beam path and the beam quality. This is an essential point in laser micro machining, which influences the quality of the processing result.

Furthermore from the DE 101 05 346 A1 Known is a device for helically cutting holes in workpieces, in which by means of wedge plates, a beam is deflected from the optical axis, which he rotates when turning the wedge plate combination about the optical axis. In addition, here λ½- or λ¼- platelets are brought into rotation to carry the polarization direction with respect to the processing. This system also serves to produce small holes in predominantly metallic materials with high efficiency. However, here too, the parameters necessary for the production of micro trenches such as rotational speed, plane-parallel offset and wavelength independence are not given.

In US 4,461,947 a method is described in which is arranged by means of an eccentrically arranged the optical axis lens by the rotation of the beam in a rotating movement to the optical axis. Again, according to the described embodiments, the problem of unequal mass distribution that does not allow high speeds.

Inventive solution

The solution according to the invention has the advantage that a uniform, rotationally symmetric Mass distribution is present, so that with very high speeds a Distraction of the light beam, which is also parallel in all positions rotated to the optical axis, over the workpiece can be done. Especially when working on brittle Materials such. As glass or ceramic, results from this Type of beam guidance high quality machining, resulting in the good edge quality (minimization of musseling and cracking).

Another advantage of the solution according to the invention is that the beam path is not further changed or disturbed except for the desired beam offset, with the result that the optimum focusing (with converging lens and high-quality laser radiation) is maintained. In particular, the solution according to the invention is not limited by restrictions with regard to the pulse duration or wavelength. It's for everyone Pulse durations from continuous wave (cw) to femtosecond pulses suitable arrangements in the beam path or materials known as a plane-parallel displacement plate ( 3 ) can be used in the described manner. The beam rotation of different wavelengths can also be used with the described principle by suitable selection of materials from UV applications to infrared laser radiation.

One Another significant advantage is that through the targeted Control of the rotational speed and thus the determination a pulse-to-pulse overlap of the laser radiation the workpiece to be machined, the application controlled can be, without entering the parameter field of the laser, z. B. the repetition rate, intervene, which in turn is not only as gentle as possible Machining but also maximizing machining efficiency means.

In the application, it is also advantageous that the beam can also be slightly eccentric to the optics, without this having an effect on the beam offset. Likewise, the focal length can be determined by selecting a suitable focusing optics or their spatial position relative to the plane-parallel plate (FIG. 3 ). It is even possible to use the same focusing optics which were also used before the use of the solution according to the invention.

Another advantage is the possibility of adjusting the beam offset (S) during processing or in a stationary position. This allows, coupled by a motorized XY drive to the device (such as a CNC track unit), a complex, program-based applications of the laser beam milling machine. Thus, also free-form removal tracks with adjustable width can be generated with the device according to the invention. Even with non-rotating offset plate ( 3 ), the beam can be moved in one axis, which allows very narrow micro trenches or a slot-shaped breakthrough or the separation of thin components.

Description of the drawings

One Embodiment of the invention Solution is based on the drawings and in the following Description explained in more detail:

1 shows the physical action principle of the invention with its necessary components and their directions of movement.

2 shows a sectional view of a possible implementation variant with adjusting ring for tilting the plane-parallel plate.

3 shows a perspective view of a machined workpiece with Abtragsspur and hint of the tumbling laser beam

In the 1 schematically outlined device for micromachining of materials has an arrangement based on the physical principle of refraction of light on a plane-parallel plate ( 3 ). The plane-parallel plate ( 3 ) can be rotated, tilted and the distance from the focusing optics ( 2 ) can be changed. This is illustrated by arrows in the drawing.

When passing through the light beam ( 1 ) by a plane-parallel plate ( 3 ), a parallel shift (S) occurs. The size of (S) is determined by the angle of incidence (α) of the incident beam ( 1 ) on the plane-parallel plate ( 3 ), the thickness (d) of the plane-parallel plate ( 3 ) and the refractive index (n) of the plane-parallel plate ( 3 ) certainly. It follows that S = f (α, d, n)

If one adjusts now the standing below the angle of incidence (α) and behind the focussing lens ( 2 ) arranged plane-parallel plate ( 3 ) in rotation, the beam moves centrically around the optical axis due to the parallel offset (S). Depending on the distance or focal length of the lens so the focus diameter can be adapted to the respective working plane and the corresponding processing. By tilting the plane-parallel plate ( 3 ), the angle of incidence (α) is changed, which results in the parallel offset (S) of the radiation. Thus, the diameter of the beam moving centrically around the optical axis is changed.

Another way to influence the plan offset (S) is the thickness (d), and the Bre index (s) of the plane-parallel plate (s) ( 3 ) reached. Hereby a pre-selection of the plan offset (S) can be determined, whereby the tilting of the fine adjustment serves. Due to the arrangement of the moving parts, whereby the optical axis coincides with the mechanical axis, as well as their design, an uneven distribution of the masses eccentric axis avoided, so that a very high rotational speed and thus a very high peripheral speed can be achieved.

In 2 is a sectional view of a possible implementation example shown. Here, the focusing optics is in a version that can be adapted to different variants with the aid of a corresponding tube. The plane-parallel plate ( 3 ) is guided in a second version, which in turn in a barrel sleeve ( 4 ) is stored. The barrel sleeve ( 4 ) in turn is from an externally acting force, in this embodiment, a toothed belt, rotated. Speed limiting acts here only the storage of the barrel sleeve ( 4 ), which is designed in the form of ball bearings. Of course, all other types of bearings are conceivable that allow a much higher speed, for example, with magnetic, sliding or air storage.

With the collar ( 7 ), the plane-parallel plate ( 3 ) both in the dormant state and during the fast rotation tilt, so as to allow a displacement of the beam. To support workpiece machining, the collar ( 7 ) also the possibility to provide a gas connection to create a corresponding (inert gas) atmosphere at the processing station. The protective glass ( 8th ) protects the internal components against soiling and damage due to the residues of machining, without affecting the deflected beam.

3 shows a workpiece ( 10 ), in which a free-form trench ( 11 ) is worn away. Here, the tumbling beam ( 9 ) performs a circular movement about the optical axis and thus carries - like a milling head - material from the workpiece. The efficiency of the removal is very strong by the pulse-to-pulse overlap and thus by the rotational speed of the plane-parallel plate ( 3 ) certainly. Particularly in the case of laser radiation with a high repetition rate or pulse repetition frequency (eg 100,000 pulses per second) extremely gentle speeds (up to 100,000 rpm) are required for gentle machining.

wobei f_r die Anzahl der Laserimpulse pro Sekunde (Repetitionsrate) bestimmt, d_L der wirksame Laserstrahldurchmesser auf dem Werkstück ist und S die Parallelverschiebung nach Gleichung [1] ist. Der Kreisumfang der Strahlablenkung ist gleich 2·π·S.The required speeds in rpm U _r at a given optimum pulse-to-pulse overlap O can be determined according to the following relationship:

wherein f _{r is} the number of laser pulses per second (repetition rate) determined, d _L is the effective laser beam diameter on the work piece and S is the parallel displacement according to Equation [1]. The circumference of the beam deflection is equal to 2 · π · S.

Application Example 1

For gentle and precise micro-removal with short-pulsed laser radiation of a specific pulse duration and wavelength, an optimal pulse-to-pulse overlap of O = 50% is determined or determined to produce a microbore on a material to be machined, ie after the action of the laser pulse on the surface to be machined is to cover the subsequent laser pulses upon impact only about 50% of the area that has irradiated the previous laser pulse. The bundled laser beam has an effective diameter d _L = 100 μm on the material, ie a mean distance of 50 μm should lie between the laser pulses. A circular machining with a radius S = 0.5 mm is determined. If the laser processing is carried out with a repetition rate of f _r = 10 000 laser pulses per second, a required number of revolutions U _r = 10,000 revolutions per minute is obtained according to equation [2].

Application Example 2:

For gentle and precise micro-removal with short-pulsed laser radiation of a specific pulse duration and wavelength, an optimum pulse-to-pulse overlap of O = 70% is determined or determined to produce a precision cut on a material to be machined. The bundled laser beam has an effective diameter d _L = 20 μm on the material. A circular machining with a radius S = 0.1 mm is determined. If the laser processing takes place with a repetition rate of f _r = 10 000 laser pulses per second, the result is a required number of revolutions U _r = 6 000 according to equation [2] U / min.

Application Example 3

During gentle and precise micro-removal with ultra-short pulsed laser radiation of a specific pulse duration and wavelength, an optimum pulse-to-pulse overlap of O = 99% is determined or established for producing a microstructure on a material to be processed. The bundled laser beam has an effective diameter d _L = 5 μm on the material. A circular machining with a radius S = 1 mm is determined. If the laser processing is carried out with a repetition rate of f _r = 100 million laser pulses per second, the result is a required number of revolutions U _r = 50,000 rev / min according to equation [2].

As These calculations show that there are CNC machines available on the market (Machining) with respect to the device resulting circumferential speeds by orders of magnitude away.

1

incident beam

2

focusing lens

3

coplanar plate

4

running sleeve

5

Not used

6

Not used

7

collar

8th

protective glass

9

nutating / rotating beam

10

workpiece

11

Abtragsspur

α

angle of incidence

d

Thickness of ( 3 )

f _r

number the laser pulses per second (repetition rate)

n

refractive index

O

Pulse-to-pulse overlap

S

parallel offset of the beam

U _r

rotation speed the tumble optics at given O

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• DE 10054853 A1 [0003]
• - DE 10105346 A1 [0004]
• US 4461947 [0005]

Claims (14)

Device and method for introducing structures in any materials with laser radiation, characterized in that the laser beam with an extremely high rotational speed, and thus peripheral speed, under a wobbling, or rotational movement laterally offset about the optical axis of the focusing optics moves focused on the workpiece and thus achieve high processing speeds .. Apparatus and method according to claim 1, characterized characterized in that the device is also parallel for several and non-parallel guided laser beams simultaneously can be used. Device and method according to claim 1-2, characterized in that the pulse-to-pulse overlap and / or the rotational speed, and / or the repetition rate of the laser and / or the tilting of the plane-parallel plate ( 3 ) or whose thickness (d) and refractive index (n) can be adjusted. Device and method according to claims 1-3, characterized in that by the tumbling motion of the laser beam around the optical axis in combination with a linear motion Any preselected structuring on the workpiece caused by the creation of trenches by erosion, mold holes by removal or melting, or welding in the micro range. Device and method according to claims 1-4, characterized in that the beam offset with respect the optical axis both during rotation and can be changed in the dormant state. Apparatus and method according to claims 1-5, characterized in that a beam offset of the incident Beam does not affect the parallel offset of the beam. Device and method according to claim 1-6, characterized in that the device by suitable selection of the material of the plane-parallel plate ( 3 ) can be used regardless of the wavelength from the ultraviolet to the near infrared range. Apparatus and method according to claims 1-7, characterized in that the device is independent the pulse duration of the laser radiation can be used. Apparatus and method according to claims 1-8, characterized in that the device also for laser radiation can be used in continuous wave mode. Device and method according to claims 1-9, characterized in that the size of the focus on the workpiece over the use or over the position of the focusing optics can be influenced. Apparatus and method according to claims 1-10, characterized in that the beam path parallel to the optical Axis runs. Device and method according to claims 1-11, characterized in that the parallel offset beam the protective glass can penetrate smoothly. Apparatus and method according to claims 1-12, characterized in that the device has the possibility provides a gas atmosphere in the working plane to create. Method according to claims 1-13, characterized that the edge strength by the combined movement as well as the selected laser parameters (pulse duration between 100 fs and 100 ns, wavelength between 200 and 1100 nm) especially extremely brittle in brittle materials.