JPH02299786A - Method for controlling dot interval at time of starting laser beam marking - Google Patents

Abstract

PURPOSE:To realize uniform laser beam marking by eliminating (n) pieces of pulses given by a formula at the time of starting laser beam marking. CONSTITUTION:In a single stroke writing type laser beam machine to scan a laser beam two-dimensionally by two galvanometers, when the marking command speed, the time till the galvanometers start to move after receiving a command and a pulse interval are denoted by V, td and B, respectively, (n) pieces of pulses given by the formula, n = (td,V)/B are eliminated at the time of starting laser beam marking. Namely, when the laser beam moving speed V and the pulse interval B are determined, the pulse irradiation in the state with the galvanometers stopped can be avoided by calculating n from the formula and instructing it to software for controlling the machine.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention scans laser light two-dimensionally using two galvanometers with relatively large response delays. The present invention relates to a method of controlling laser light in a single-stroke laser processing machine, and particularly to a method of controlling dot spacing at the start of laser marking.

[Conventional technology]

Conventionally, in this type of laser processing machine, the emission of laser light and the start of movement of the galvanometer are performed at the same time, and the time from when the galvanometer receives a command until it actually moves (Fig. 2 ta) and the acceleration of the galvanometer are time in (t
Ignore a).

Laser pulses were emitted at equal time intervals assuming that the galvanometer was moving at a constant velocity.

[Problem to be solved by the invention]

In the conventional dot spacing control method described above, the pulse oscillation and the movement of the galvanometer are performed at independent times, so in the area until the galvanometer actually reaches the command speed, the dots are denser than the setting. You will be hit by

When performing laser processing on the surface of a soft synthetic resin material such as a semiconductor package, if you hit the same spot twice, the depth will be twice as deep as once.
The appearance of the machining pattern is not only bad, but there is also the risk of destroying the inside of the workpiece.For this reason, the required machining depth often allowed for an error of only a few microns.

The present invention aims to solve the above-mentioned problems of the conventional methods, and provides a complete method for controlling the dot spacing at the start of laser marking, which can realize uniform processing.

[Means to solve all problems]

According to the present invention, in the one-stroke type laser processing machine that scans two-dimensionally using two galvanometers with two laser bases as described above, the time from receiving the marking command speed kv+ command until the galvanometer starts moving is i td.
, when the pulse interval is 'lf,B.

A dot spacing control method for laser marking and marking is obtained, which is characterized in that n pulses given by are removed at the start of laser marking.

〔Example〕

Next, one embodiment of the present invention will be explained with reference to all the drawings.

Figure 1 shows the command waveforms sent to the galvanometer of a laser processing machine and the response curves showing all the actual movements of the galvanometer. Vertical axis is total speed, horizontal axis is time, 1
indicates the command value, and 2 indicates the response value. It can be seen that the response value is shifted to the right by td compared to the command value. This td
is the response delay that is the problem, and during this time the galvanometer actually stops moving and is struck too many pulses (n) and the pulse interval (B).

When the marking command speed (laser beam movement speed) is set to V, the pulse control section assumes that the movement distance is tdXv and irradiates pulses at intervals of B, which actually results in n overshoots. It is.

Therefore, once the laser beam movement speed V and pulse interval B, which are the conditions for processing the workpiece more beautifully, have been determined, ni is calculated from equation (1).

By instructing the device control software, pulse irradiation with the galvanometer stopped can be avoided.

For example, speed 100 mm/see, td = 0
．． 8 m-5ec.

If the pulse interval is 40 μm, the number n of pulses to be deleted in Equation (1) is 2. That is, in this case, it is sufficient to delete two pulses at the start of laser marking.

Returning to FIG. 1 again, the acceleration section ta of the response value also shifts to the right by the command value td. Laser beam emission control is required in this section.

In this section, the interval between the marked dots is constant: the emission time Δt2 is calculated and controlled.

The formula for calculating eight is shown below. Let a be acceleration +' as a natural number.

The units of B and a are μm and m/B2, respectively.

Similar to td, a used here is a value specific to a galvanometer or the like, and therefore a value that should be determined through experiments.

For example, a=4900 (m/5ec2), B=2
When calculating the case of 1=2 as 00 (μm), the time required between the 1st pulse and the 2nd pulse (Δt) is 0.11
8meθC. If 1=4, the time (Δt) required between the 3rd pulse and the 4th pulse is 0077I
It is n88C. If equations (1) and (2) are incorporated into the software for metal forming pulse control, uniform processing can be achieved for all markings.

〔Effect of the invention〕

As explained above, in the present invention, the number of pulses to be irradiated at the start of laser marking is determined in consideration of the characteristics td of the galvanometer, the processing conditions speed V, and pulse interval B. There is an effect that uniform processing can be realized regardless of the conditions.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing the relationship between a command value and a response value of a galvanometer according to the present invention, and FIG. 2 is a diagram showing a relationship between a command value and a response value of a conventional galvanometer. Explanation of symbols: 1 is the command value, 2 is the response value, 5 is the movement value (
4 is the acceleration interval ta, 5 is the command value, 6 is the response value, 7 is the movement delay time td, and 8 is the acceleration interval ta.

Claims (1)

[Claims] (1) Use two galvanometers with a relatively large delay in response to movement commands to irradiate the pulsed laser beam.
In a single-stroke type laser processing method that performs laser marking by scanning dimensionally, the marking command speed is defined as td, the time from receiving the command until the galvanometer starts moving is td, and the pulse interval is B. When, n=
- A dot spacing control method at the start of laser marking, characterized in that n pulses given by td·v/B are removed at the start of laser marking.