JPH0292482A - Laser boring device - Google Patents

Abstract

PURPOSE:To improve the yield of printed circuit boards by detecting the direct transmitted light from a laser oscillator and the transmitted light of the reflected light from a work surface respectively, computing the ratio of the quantities of the reflected light from the quantities of light of respective sensors and comparing the ratio with a reference value, then controlling the laser light. CONSTITUTION:The laser light 12 outputted from a CO2 laser oscillator 10 is directed by a partial transmission mirror 21 to the work 40, by which the work is irradiated with the laser light 14. This light is reflected as the reflected light 15 of the work and is partly transmitted through a partial reflecting mirror 21. The transmitted light 13 and the reflected light 16 are made into the wavelength components of the CO2 laser light by the effect of the partial reflecting mirror 21 and the quantities of the light are measured by the light quantity sensors 25A, 25B via condenser lenses 23, 24. The ratio of the signals is obtd. by a computing circuit 27 and is compared with the reference value 28 in a comparator circuit 29. A stop command is delivered to a control section 30 of the oscillator when the ratio of the reflected light increases. The visible light region is reflected and the laser light is directly reflected by a copper layer when the laser light arrives at this layer and, therefore, the laser light is stopped when an insulating material 41 is worked.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a COz laser processing device for drilling a hole in a material in which steel is embedded, such as a printed circuit board.

[Conventional technology]

As a known example closest to the present invention, JP-A No. 59-277
In this known example, in order to detect the processing state, a detection light source is installed separately in addition to the processing laser beam, and an optical system is required to separate the reflection of the detection light.

[Problem to be solved by the invention]

The present invention is a composite material such as a printed circuit board in which a copper plate is embedded in an insulator, and the hole is drilled only in the insulator, so that the hole does not penetrate through the buried copper plate and damage to the copper plate is minimized. purpose.

For this purpose, in the above-mentioned known example, a detection beam is irradiated to overlap the processing beam, and the reflected light is detected. However, the laser light source for detection.

Generally, it is several mw to 1w or less, and the detection sensitivity is low.
The reliability is low in terms of signal discrimination against noise, or
It is difficult to realize an optical component that selectively transmits and reflects two wavelengths of processing laser light and detection laser light using a high-power laser for processing, and the optical path etc. are also complicated.

[Means to solve the problem]

In the present invention, drilling is performed using a processing beam.

The light emitted for processing and the reflected light of the same beam from the workpiece are constantly detected and compared, increasing detection sensitivity.

[Effect]

For processing laser light, we installed a sensor that detects a part of the light beam before the processing point and a sensor that detects the wavelength component of the same laser beam reflected from the processing point, and made a relative comparison between the two. Measure the amount of light reflected from the material inside.

Therefore, since a high-output laser for processing is used as the detection light, the detection sensitivity can be increased and the influence of noise etc. can be reduced.

〔Example〕

FIG. 1 shows an embodiment of the present invention. A laser beam 12 output from a COz laser oscillator 10 has spectral characteristics that transmit several percent of 12 wavelength components and do not transmit visible light. The partially transmitting mirror 21 irradiates the workpiece 40 with laser light 14, and the condensing lens 21 irradiates the workpiece 40 with laser light of high energy density. Regarding No. 21, the desired characteristics can be obtained by applying a partial reflection coating to a GaAs material or the like. On the other hand, when the laser beam irradiated onto the workpiece 40 generates reflected light at the processing point, it is reflected toward the partially transmitting mirror 21 as reflected light 15, and when it reaches the partially reflecting mirror 21, it is the same as the laser beam. Part of the wavelength component light is transmitted. Partial reflector 21
Due to the action of C, the transmitted laser light 131 and reflected light 16 are
Oz becomes the wavelength component of the laser beam and passes through the condensing lens 23.2
The amount of light is measured by light amount sensors 25A and 25B via 4. That is, the light amount sensor 25A can measure the amount of light of the output beam of the laser oscillator 10, and the light amount detection sensor 25B can measure the amount of light of the CO2 laser component from the workpiece 40, and the arithmetic circuit 27 calculates the ratio of these signals. The comparison circuit 29 calculates the ratio of reflected light to the incident light, compares it with a preset reference value 28, and issues a stop command to the oscillator control unit 30 when the reflected light ratio becomes large. Send.

On the other hand, the workpiece 40 is a composite material of an insulating layer 41 and a body piece 42 embedded therein, and has a structure often seen in printed circuit boards and the like. In recent printed circuit board technology, there is a need for a non-through drilling technique that allows holes to be drilled into this insulator, but also to maintain an undamaged state without drilling holes in the steel material.

CO2 laser light (input = 10.6 μm), which has a high reflectivity for steel materials, is suitable for this purpose, but when drilling such printed circuit boards, it is necessary to drill dozens of holes in one board. , a reliable drilling technique is required to ensure that the holes reach the copper layer and there is no damage to the copper layer.

FIG. 2 shows the components of reflected light when such a composite material is irradiated with a GO2 laser. While processing the insulating material 41, visible light emission is observed, but when it reaches the copper layer, the laser light is directly reflected due to the high reflectance of copper.

A method of utilizing this characteristic to stop the laser when the laser perforation reaches the copper layer will be described with reference to FIG. When the laser beam 12 is irradiated, the insulating layer 41 is first perforated on the workpiece. At this time, a part of the laser beam 12 passes through the partial reflection mirror 21.
3, and the light amount is always detected by the light amount detection sensor 25A. Furthermore, since the reflected light from the workpiece 40 is mostly in the visible light range while the insulating layer 41 is being processed, the reflected light is blocked by a portion of the mirror of the partial reflecting mirror 21 and is detected by the light amount detection sensor. No output to 25B appears. As the drilling progresses and the hole reaches the copper layer 42, the reflected light 14
．． Most of the 6 μm light is reflected (reflectance of copper, approximately 98
%), the amount of one reflected light 16 is approximately the same as the amount of laser light 13, and appears as the output of the light amount detection sensor 25B. Therefore, by comparing the output value of the circuit 27 with the reference value 28, it is possible to immediately detect that the perforation has reached the copper layer, and the laser oscillator 10 can be stopped to eliminate damage to the copper layer.

In addition, the copper layer is not damaged by emitting more energy than necessary to ensure drilling, improving reliability in microprocessing.

Processing time is reduced.

〔Effect of the invention〕

According to the present invention, it is possible to dramatically improve the yield of printed circuit boards when dozens of holes are formed in the copper layer of a single printed circuit board.

[Brief explanation of drawings]

FIG. 1 is a system diagram of an embodiment of the present invention, FIG. 2 is an explanatory diagram of the wavelength of reflected light from a processed workpiece, and FIG. 3 is an explanatory diagram of the operation of the present invention. 10...Laser oscillator, 12,13.14...Laser light, 15,16...Reflected light, 21...Partial reflecting mirror, 22.23.24...Condensing lens, 25A, 25B
...Light amount detection sensor, 27...Arithmetic circuit, 28...
・Reference value setting circuit, 29... Comparison circuit, 30... Laser control section, 40... Processing work, 41... Insulating layer, 42... Copper Figure 3

Claims (1)

[Claims] 1. A laser oscillator, a reflecting mirror that selectively transmits a part of the laser beam from the laser oscillator, a condensing system that focuses and irradiates the laser beam onto the workpiece, and the reflecting mirror includes: On the other hand, a sensor is provided that captures the direct transmitted light from the laser oscillator and the transmitted light of the reflected light from the workpiece and detects the amount of light,
A laser drilling device characterized in that the laser beam is controlled by calculating a reflected light amount ratio from the light amount of the sensor and comparing it with a reference value. 2. In the laser drilling apparatus according to claim 1, the object to be processed is a composite material of an insulator and a copper piece, a carbon dioxide laser oscillator is used as the laser oscillator, and the laser beam reflected from the copper layer is 1. A laser drilling device, wherein the laser beam is stopped being emitted when the value exceeds a reference value.