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New Laser Technology for Fragile Materials

Le 27 November 2017, 09:40 dans Humeurs 0

Cost, quality, yield are the key success factors for the semiconductor and photovoltaic manufacturing industries. Among them, an important processing method is cutting, because the need to use different cutting process to separate the wafer into a die or the solar cell into a half-cell. However, the conventional mechanical or laser-based cutting techniques have more or less disadvantages such as particle formation due to material removal or material damage at the cutting edge.

red laser pointer

In this case, TLS-Dicing becomes a fast, clean, easy-to-use and reliable method for separating semiconductor materials such as silicon (Si), silicon carbide (SiC), germanium (Ge) and gallium arsenide (GaAs) Cost-effective alternative solution. Depending on the application, starting with the initial scribing process, the material is then high power laser heated according to carefully calculated energies. The material is heated and expanded, the pressure in the heated zone rises, and the tensile stress around the heated zone also increases. Immediately after laser heating, a very small amount of deionized water is sprayed for cooling (less than 10 ml / min). This will create a second cooling zone near the first zone, causing a tangential tensile stress mode. Tensile stresses generated in the superposed area of the two stress modes cause the material to crack and guide the crack tip through the material.

Compared with traditional cutting technology, the heat laser beam separation technology shows many advantages, such as fast separation speed, very smooth side wall, no cracks and micro-cracks, excellent bending strength and no tool wear and material consumption Low cost of ownership. The process uses two laser sources: a Gaussian beam short pulse scribing laser (532 nm or near-infrared wavelength laser) for initial scribing and another cutting green laser pointer. Cutting lasers enable 200W continuous wave laser and near infrared wavelengths. Thermal laser beam separation technology is a non-cutting cutting process, the process itself produces almost no particles.

Traditional cutting techniques have some drawbacks in terms of processing speed and cutting quality. For example, mechanical sawing feeds slowly, blades wear large, and costly. In addition, sawing tends to cause chipping on the edge of the wafer and delamination. In contrast, laser ablation produces a significant heat-affected zone, resulting in poor edge quality and the formation of micro-cracks. At the same time, the laser ablation rate is very low, requiring multiple ablations to complete the singulation of a single wafer. Compared with the above processing methods, the heat laser beam separation technology is a one-time process that can complete the thickness of the SiC wafer 300mm / s separation. In addition, the metal structure on the front-end cut tracks, the polyimide on the wafer, and the backside metal are both successfully separated without delamination or thermal effects.

In general, thermal burning laser pointer separation is an entirely new and efficient way to segment brittle semiconductor materials used in the semiconductor and photovoltaics industries. It offers the advantages of high yield, low cost, and high quality partitioning, often with a single separation. The feed rate of this process is between 300 mm / s and 500 mm / s, depending on the application.

Research on Laser Cooling Solid Materials

Le 22 November 2017, 05:03 dans DIY 0

Laser cooling refers to the use of a beam or beam of specific laser irradiation material, the interaction between the laser and the material, the temperature of the object becomes low. However, it can be seen from the daily life experience, the object can absorb light energy and heat, such as we all love the sun on the beach, in the summer sun on the road to a barefoot and so on. Compared with the sun, laser power density is higher, high power laser can even melting the material, so you can use laser machining, cutting, manufacturing laser weapons and so on.

If someone says that the laser can be used to cool, maybe people will feel a little counterintuitive. But in fact, scientists have not only realized the cooling of rare atomic gas by laser, but also realized the solid material refrigeration by laser in recent years. So how does the laser cool the material? To explain this problem, we need to understand what temperature is. In a simple way, heat is the manifestation of the atomic motion in the material, and the degree of heat and cold represents the intensity of the atomic motion of the material. Take water molecules for example: the higher the temperature, the faster the movement of water molecules, the greater the magnitude of free movement. When the water temperature is higher than the boiling point, the water will boil, a large number of water molecules out of the water, gas and water; the lower the temperature is, the slower the molecular motion, the motion amplitude is small, when the water temperature is below the freezing point of water, ice, can only be around the center position of vibration. Under the concept of quantum mechanics, the energy of this thermal vibration is quantized into phonons.

Laser cooling of solids, also known as Optical Refrigeration, was first proposed by German physicist Peter Pringsheim back in 1929. The basic principle is that when a laser-cooled material is irradiated with monochromatic light of a specific wavelength, the material absorbs low-energy red laser photons (long-wavelength photons) and simultaneously emits the same number of high-energy photons by spontaneous radiation (Short wavelength photons) - this process is called upconversion fluorescence or anti-Stokes fluorescence. According to the law of conservation of energy, the emitted high-energy photons need to take away a part of the energy from the material, which can be the thermal vibration (phonon) of the material. When a phonon in a substance is absorbed and phonon energy is taken away by photons emitted and there is no other additional heating mechanism, the temperature of the substance drops. After this theory was put forward, there has been a historical controversy over whether this process violates the second law of thermodynamics.

red laser pointer

Eventually, Landau gave the definition of optical radiation entropy in 1946, and solved thermodynamically the physics of photoluminescence mechanism. Optical radiation entropy represents the degree of order of the radiation photons. The more monochromatic the radiation photons, the narrower the frequency distribution is. Therefore, the radiation entropy is smaller. On the contrary, the wider the radiation spectrum, the greater the radiation entropy. According to the second law of thermodynamics, if the temperature of a substance is to be decreased, the entropy of the substance needs to be reduced. In the process of laser cooling, the low entropy laser works on the material and changes into a high entropy spontaneous emission photon so as to satisfy the total The entropy of the system increases this basic law.

This principle was first used for cooling atoms and thin gas, when irradiated with a green laser pointer beam energy is slightly less than that of a gas atom atom transition energy required (e.g. rubidium gas) when the velocity of atomic motion and the opposite direction of the laser atom than the other direction to feel the energy of the laser will be higher, therefore these atoms the scattered photons and high energy absorption of low-energy laser photons, which is widely known as the Doppler effect. In this process, the scattered photons take away the excess energy so that the velocity of the atoms in this direction decreases, so that the temperature of the atomic gas can be reduced to very close to the absolute zero degree. The laser cooling of atomic gas is carried out at extremely low temperature of Na Kevin (nK).

In fact, the cooled material can be a single atom or molecule, or a solid composed of a large number of atoms, including short-range ordered glass (rare earth ion doping), and long-range ordered semiconductors (without intentional doping). Laser cooling of solid is very similar with the atomic laser cooling, the fundamental difference is that between the solid in a large number of atoms interact to form atomic chain, atoms are fixed in the crystal lattice, photon absorption kinetic energy is no longer isolated atom, but a large number of atomic collective vibration. In the form of lattice vibration (phonon), thermal energy can provide additional energy and momentum needed for fluorescence upconversion. Compared with laser cooling atoms, the conditions of laser cooling solid are more stringent: the external quantum efficiency of upconversion fluorescence is close to 100%.

Solid laser cooling recent breakthrough in 2013, research group for the first time that the burning laser pointer can make the semiconductor cooling from room temperature to -20 degrees, the mechanism of laser cooling in different rare earth metal doped glass cooling mechanism before, the first use of free electronic band in the laser cooling. In addition, compared with rare earth materials, semiconductor materials are easier to be compatible and integrated with existing industrial systems, and lower limit temperatures can be achieved theoretically.

Industrial Laser Materials Processing

Le 30 October 2017, 09:00 dans Sorties 0

Metal foil cutting is based on the design of the battery, a roll of metal foil along the long side cut into thin strips. Applicable to this part is the infrared pulse laser, high-speed high-quality cutting electrode plating. If the cutting width and quality have more precise requirements, you can also consider the pulse green and ultraviolet light. Metal foil cutting links refer to the design of the battery, the elongated strip of the anode film and cathode film cut into the desired shape. Depending on the battery design and whether the foil is fully coated, you can select or adjust the beam to cut the coating or cut only the foil. The green laser pointer used in this section is the same as the aluminum foil slit.

The best way to cut the round hole is to 1: 1, that is, the ratio of aperture and plate thickness is 1: 1. Of course, this ratio, that is, the larger the pore size, cut out the high quality circle Hole is easier. Otherwise, when the fiber laser cutting machine energy is insufficient, the cutting hole easy to break point off point and round hole is not round the phenomenon. Round hole sometimes elliptical or irregular phenomenon This is related to the X Y axis motion does not match, and lead to X Y axis movement does not match the direct cause is the servo motor parameter adjustment is not appropriate. So the quality of cutting round hole, the servo motor also has certain requirements.

red laser pointer

Conventional fiber lasers use fiber-coupled technology to couple multiple beam outputs together, resulting in lower brightness of the output laser. The new generation of fiber lasers uses an innovative architecture that combines the pump diodes and drivers into separate pump modules. The gain fiber is mounted in a configurable gain module that can output more than 8kW of laser power. The gain module is based on the novel main oscillator / power amplifier (MOPA) design, enabling high-brightness most powerful laser output. In addition, the Ennie laser also uses a reliable integrated backlash isolator to protect all modules from the impact of backlit light, can be high anti-material full power, uninterrupted, stable processing. These two technological innovations play a vital role in RLS applications.

As we all know, graphene can be used to manufacture a variety of electronic, optoelectronic devices, more scientists predicted that graphene will "completely change the 21st century", it is possible to set off a sweeping global disruptive new technology and new industrial revolution. It is understood that this time through laser writing to upgrade the existing graphene technology, the process is similar to the use of laser beam "hammer" metal forged into three-dimensional form. Finally, through the experiment and computer simulation, we can observe the authenticity and mechanism of the two-dimensional structure of graphene carbon atoms to three-dimensional shape.

In 2016, China's industrial laser materials processing equipment market was about $ 3.8 billion, with an average annual compound growth rate (CAGR) of 12.51% over the past five years. The growth rate in 2017 is expected to be about 22%, the value will reach 4.6 billion US dollars. From this point of view, the global market for materials processing in 2016, the total market volume of about 12.6 billion US dollars, while the Chinese market reached the global laser materials processing equipment system revenue of one-third. Global burning laser materials processing system popular markets include smart phone manufacturing, aluminum deep processing of metal sheet cutting, electric vehicle batteries and display and so on.

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