What are the classification characteristics of laser processing?

Laser cutting technology is widely used in the processing of metal and nonmetal materials, which can greatly shorten the processing time, reduce the processing cost and improve the quality of the workpiece. Laser cutting is realized by using high power density energy generated after laser focusing. Compared with traditional plate processing methods, laser cutting has the advantages of high cutting quality, high cutting speed, high flexibility (arbitrary shape can be cut) and wide material adaptability.

(1) laser melting cutting

In laser melting cutting, the workpiece is partially melted, and the melted material is ejected by airflow. Because the transfer of materials only occurs in its liquid state, this process is called laser melting cutting.

The laser beam is matched with high-purity inert cutting gas to promote the molten material to leave the incision, and the gas itself does not participate in the cutting.

-Laser melting cutting can achieve higher cutting speed than gasification cutting. The energy required for gasification is usually higher than that required for melting materials. In laser melting and cutting, the laser beam is only partially absorbed.

The maximum cutting speed increases with the increase of laser power, and decreases almost inversely with the increase of plate thickness and material melting temperature. When the laser power is constant, the limiting factors are the air pressure at the notch and the thermal conductivity of the material.

-Laser melting cutting can obtain non-oxidation cutting of iron materials and titanium metals.

—— For steel materials, the laser power density of melting but not gasification is 104W/cm. ~ 105W/cm？ amongst

(2) Laser flame cutting

The difference between laser flame cutting and laser melting cutting is that oxygen is used as cutting gas. With the help of the interaction between oxygen and heated metal, a chemical reaction is generated to further heat the material. For structural steel with the same thickness, the cutting rate obtained by this method is higher than that by melting cutting.

On the other hand, this method may have worse notch quality than melt cutting. In fact, it will produce wider cuts, obvious roughness, increased heat affected zone and worse edge quality.

-Laser flame cutting is not effective in machining precision models and sharp corners (danger of burning sharp corners). Pulsed mode lasers can be used to limit thermal effects.

-The laser power used determines the cutting speed. When the laser power is constant, the limiting factors are the supply of oxygen and the thermal conductivity of the material.

(3) laser gasification cutting

In the process of laser gasification cutting, materials are gasified at the incision, which requires very high laser power.

In order to prevent the material vapor from condensing on the incision wall, the thickness of the material should not greatly exceed the diameter of the laser beam. Therefore, this process is only suitable for applications where it is necessary to avoid excluding molten materials. In fact, this processing is only used in the small application field of iron-based alloys.

This process cannot be used for materials such as wood and some ceramics, which are not in a molten state, so it is impossible to recondense the material vapor. In addition, these materials usually reach a thick incision.

-In laser gasification cutting, the best beam focusing depends on the material thickness and beam quality.

Laser power and vaporization heat have only a certain influence on the optimal focus position.

-The required laser power density is greater than 108W/cm2, depending on the material, cutting depth and beam focus position.

-When the thickness of the plate is constant, assuming there is enough laser power, the maximum cutting speed is limited by the gas injection speed.

2. Laser welding

Laser welding is an important aspect of laser material processing technology application. The welding process belongs to heat conduction type, that is, laser radiation heats the surface of the workpiece, and the surface heat diffuses to the inside through heat conduction. By controlling laser pulse width, energy, peak power and repetition frequency, the workpiece is melted and a specific molten pool is formed. Because of its unique advantages, it has been successfully applied to the welding of tiny parts. Compared with other welding technologies, the main advantages of laser welding are: fast laser welding speed, large depth and small deformation. It can be welded at normal temperature or under special conditions, and the welding equipment is simple.

3. Laser drilling

With the development of electronic products in the direction of portability and miniaturization, the demand for miniaturization of circuit boards is increasing. The key to improve the miniaturization level of circuit board is narrower and narrower line width and smaller micro-vias and blind holes between different levels of circuits. The minimum size of traditional mechanical drilling is only 100μm, which obviously cannot meet the requirements. Instead, it is a new laser micro-through hole processing method. In industry, small holes with a through hole diameter of 30-40μm can be obtained by CO2 laser processing, or about 10μm can be processed by UV laser processing. In the world, the research on laser micro-hole manufacturing and circuit board direct molding has become a hot spot in laser processing application. Compared with other processing methods, laser micro-hole manufacturing and circuit board direct molding have more outstanding advantages and great commercial value.

4. Laser drilling

Pulsed laser can be used for drilling, the pulse width is 0. 1 ~ 1 ms, especially suitable for drilling micro-holes and irregular holes, and the aperture is about 0.005 ~1mm. Laser drilling has been widely used in workpiece processing of watches and instruments such as gem bearings, diamond wire drawing dies and chemical fiber spinnerets. In shipbuilding, automobile manufacturing and other industries, 100 watt to 10000 watt continuous CO2 laser is often used to cut large workpieces, which can not only ensure accurate spatial curve shape, but also have high processing efficiency. Small workpieces are usually cut by medium and low power solid-state lasers or CO2 lasers. In microelectronics, laser is often used to cut silicon wafers or narrow slits, with high speed and small heat affected zone. Laser can be used to carve or mark the workpiece on the assembly line without affecting the speed of the assembly line, and the carved words can be preserved forever.

5, laser fine tuning

To change electrical parameters (such as resistance, capacitance and resonance frequency, etc.). ), medium and small power laser is used to remove some materials of electronic components. Laser trimming has high precision and high speed, which is suitable for mass production. Using similar principle, we can repair the mask of defective integrated circuit, repair the integrated circuit memory, improve the yield and adjust the gyroscope accurately.

6. Laser heat treatment

The material surface can be melted and recrystallized by laser irradiation, and the purpose of quenching or annealing can be achieved by selecting appropriate wavelength and controlling irradiation time and power density. The advantages of laser heat treatment are that the depth of heat treatment can be controlled, the location of heat treatment can be selected and controlled, the workpiece deformation is small, parts with complex shapes can be processed, and the inner walls of blind holes and deep holes can be processed. For example, the life of cylinder piston can be prolonged after laser heat treatment; Laser heat treatment can repair the damage of silicon material caused by ion bombardment.

The application scope of laser processing is still expanding. For example, large-scale integrated circuits made by laser do not need resist, and the process is simple, which can be used for high-precision etching of patterns below 0.5 micron, greatly improving the integration. In addition, new processes such as laser evaporation, laser zone melting and laser deposition are also under development.