SU1750900A1 - Method of laser drilling and drilling device - Google Patents

Abstract

Use: in automated equipment for laser drilling of large-diameter holes with continuous material sampling, in particular in the dielectric layers of printed circuit boards. SUMMARY OF THE INVENTION: A radiation spot, rotating around a circle, at the same time discretely moves radially after each rotation period by a predetermined feed amount, and the linear velocity of movement remains constant. The device consists of a laser, control system, coordinate table, deflector, deflector drive. In addition, a computing device was introduced into the machine, consisting of a decoder, a divider, a generator with a programmable frequency, two amplifiers with a programmable gain, and a block of synchronization of the gate 2 with a pf-ly, 1 silt

Description

The invention relates to mechanical engineering and can be used in automated equipment for laser drilling of blind holes of large diameters with continuous material sampling, in particular, in the dielectric layers of printed circuit boards.

A laser machine, selected as a prototype, is known, comprising a laser, a shutter, a control system, an optical system with a deflector and deflector drives for deflecting the beam along two mutually perpendicular axes, a deflector control device, a coordinate table with displacement drives along two axes.

However, this method and machine are characterized by insufficient technological capabilities in terms of drilling blind holes of large diameters with a continuous sample of material.

The aim of the invention is the expansion of technological capabilities in terms of ensuring the drilling of deaf holes of large diameters with a continuous sample of material.

This goal is achieved in that according to the method of laser drilling of holes, which consists in supplying focused radiation to the surface of the workpiece and rotating the laser beam in such a way that the irradiation pattern on the surface of the workpiece rotates circumferentially relative to the center of the hole being formed, in addition, the irradiation spot is additionally moves along the radius of the formed hole from the center to the extreme position at which the radius of the hole is equal to the specified value or from the extreme n Proposition to the center of the hole.

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vi

This goal is also achieved by the fact that a laser processing machine comprising a laser, a shutter, a control system, an optical system with a deflector and deflector drives for deflecting the beam along two mutually perpendicular axes, a device for matching oscillation amplitudes, adders whose inputs are connected to the drives the deflector, and the coordinate table with two-axis movement drives, is additionally equipped with a computing device consisting of a block for calculating the maximum values of the amplitudes of the scan nodes; yn angles varying amplitudes scanning period for scanning the current calculating block scanning angles, wherein the input of a computing device associated with the control system, and the output - to the inputs of the adders.

The method is implemented as follows

The workpiece is installed on the desktop of the machine. The automatic processing mode is activated. The table moves the position to the desired position. At the Start command, focused radiation is delivered to the workpiece being processed. In this case, the radiation spot on the surface of the workpiece is rotated relative to the center of the hole being formed. At the beginning of the machining process, the spot can be either in the center of the hole being formed and then, rotated, gradually moving along the radius to the extreme position at which the hole radius is equal to the specified value, or in the extreme position and then gradually moving toward the center of the hole. The speed of the spot moving along the radius is selected from the condition of providing the required hole parameters. Rotation of the irradiation spot with simultaneous displacement along the radius provides for drilling a blind hole to the required depth with a continuous sample of material.

Example. The workpiece is installed on the desktop of the machine. Include automatic processing mode. The table moves the workpiece to the desired position. At the command of the control system (SU), the deflector is set to its original position. The shutter opens and the laser radiation enters a given point on the surface of the workpiece and at the same time the deflector begins to move the irradiation spot on the surface of the workpiece around a circle with a radius r equal to the radius of the focal spot. After a 360 ° rotation, the shutter blocks the radiation and the deflector takes next position. Then the shutter opens and the radiation is rotated by a deflector along the following path (a circle with radius R + h, where h is the value of the feed pitch).

Then the cycle is repeated until the hole radius reaches the specified value R.

In another embodiment of the hole drilling method, first, the radiation is rotated so that a circle with a radius R is described, and each subsequent drilling step shifts the radiation spot by h to the center of the hole until the rotation radius is equal to the value of. At each step the angular rotational speed is varied by varying the scan frequency of the deflector so that the linear velocity V const. The practical implementation of the method was carried out with the formation of a COG-laser type ILGN-802 deaf holes f, 1 mm in a one-sided (foil) copper layer of polyimide 90 µm thick. The feed pitch was 200 µm, with an irradiation spot diameter of 250 µm. A smaller value of the displacement step with respect to the spot radius provided for the repeated irradiation of zones with respect to which the linear velocity of the spot movement is greater (i.e., more distant from the center of rotation). In addition, the copper substrate in some limits did not allow the depth of the hole to depend on the magnitude of the exposure. The linear velocity of the center of the irradiation spot was 7.5 m / min. The shutter time is 2 ms (specially developed by the Novosibirsk Electrotechnical Institute). The hole was formed before the copper layer. The edges of the holes had a slope of 70 °. The material from the orifice zone was partially evaporated and blown out with compressed air. The final cleaning of the holes was carried out by an ultrasonic installation of the type UZU-0.25 with distilled water. The laser power was 30 W and remained unchanged during processing. The irradiation of the workpiece by the radiation of this laser defocused in a tree, 2 mm did not provide the required holes.

The machine contains a laser 1; shutter 2; deflector 3; consisting of a swivel mirror 4 with sensors 5 and 6 and position. coils 7-10 electromagnets rotation of the mirror 4; a two-channel deflector drive 11, consisting of a comparison device 12 and 13, regulators 14 and 15, and current amplifiers 16-19, the outputs of which are connected to coils 7-10; a computing device 20, consisting of a decoder 21, a divider 22 of a programmable frequency generator 23, amplifiers 24 and 25 with a programmable gain factor, a gate synchronization unit 26; machine control systems 27; a driver 28 controlling a desk 29; the focusing lens 30. On the desktop 29, the workpiece 31 is machined. - The machine works as follows. The control system 27, through the actuator 28, displays the work table 29 with the workpiece 31 placed on it in the required position. In this case, the shutter 2 overlaps the radiation of the laser 1. The control system 27 opens the shutter 2 and then sends to the decoder 21 a code corresponding to the initial (But) processing, and to the divisor 22-value of the linear speed V of processing. At the same time, the code corresponding to the value of R0 is input to the divider 22 input. From the input of the divider to the input of the generator 23 with a programmable frequency receives the code corresponding to the value of V / R0. From the output of the generator 23 to the inputs of amplifiers 24 and 25 with a programmable gain, signals are received that determine the frequency of scanning of the mirror 4 and are shifted by an angle of 90 °. The signal from the output of the decoder 21 sets the required gain of the amplifiers 24 and 25, which determines the angle of rotation of the mirror 4. As a result, from the output of the computing device 20 to the input of the deflector drive 11, signals are received from two channels

 slrbЈ t,

Ki

 cos t,

where R) is the drilling radius at the lth step;

p. here Pmax - maximum radius

drilling,

h is the feed rate (increases or decreases the drilling radius by one step).

These signals are respectively supplied to the inputs of the device 12 and 13 for comparison, which also receives signals from position sensors 5 and 6. The error signals from the outputs of the devices 12 and 13 are fed respectively to the controllers 14 and 15, which convert them into corresponding sinusoidal voltages, which, through current amplifiers 16-19, excite coils 7-10 of electromagnets and, under their influence, mirror 4 simultaneously performs oscillatory movements along the X, Y coordinates, which cause the radiation to move around the circle. In this case, signals from sensors 5 and b are sent to comparison devices 12 and 13 and to synchronization unit 26

gate 2. At a certain ratio of the phases of the sensors 5 and 6 of the block 26, it issues a signal to the control system 27, which commands the shutter to close. The Fazopos ratio of the signals of the sensors 5 and 6, in which the block 26 generates a signal to the control system 27, is determined such that the closure of the shutter 2 occurs simultaneously with the passage of the spot of radiation around the circumference by 360 °. The system 27 then gives the next signal to open the gate 2 and outputs the next value RI to the decoder 21. The cycle repeats until the value RI reaches the desired value R - the radius of the hole (if the initial radius RO was equal to the radius of the spot radiation the surface of the workpiece) or the radius of the spot radiation (if the initial radius was equal to the desired radius of the hole). In the first case, control system 27 yields R values with positive increments of h, equal to the cutting step, and in the second, with negative ones. After the completion of the process of forming the aperture, the control system 27 moves the table 29 to another position and the cycle repeats.

Claims (2)

Claim 1. Laser drilling method of holes, which consists in delivering focused radiation to the surface of the product and rotating the laser beam around the circumference relative to the center of the hole being formed, characterized in that, in order to expand the technological capabilities, the hole area is divided into n concentric circles, the radii of the two nearest circles differ by a step size, not more than the diameter of the focused radiation, then, starting either from the center or from the outer radius of the hole and sequentially moving the laser beam in concentric circles, maintaining a constant linear velocity of movement of the focused radiation on each of the concentric circles. 2. A device for laser drilling of holes, comprising a laser, a shutter, a control system, an optical system with a deflector containing a mirror and position sensors, a drive of the deflector for deflecting the beam along two mutually perpendicular axes and a coordinate table with displacement drives along two axes, characterized in that it is provided with a computing device consisting of a decoder, a divider, a programmable frequency generator, two programmable gain amplifiers and a gate synchronization unit, the first inputs of the decoder and the divider are connected to the first output of the control system, the second input of the decoder to the second output of the control system, the third output of which is connected to the gate input, the generator input with a programmable frequency is connected to the output of the divider, and the outputs to the first inputs of amplifiers programmable gain, the second inputs of which are connected to the outputs of the decoder, and the outputs - to the deflector drives, the input of the synchronization unit of the shutter is connected to the outputs of the position sensors of the deflector mirrors, and the output one with control input.