Without the progress of drossy laser small processing technique
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source:DDON CNC Machining
The way of input of quantity of heat that region of the blame contact with laser peculiar light beam, bureau changes makes laser makes the optimal choice that delicate spare parts machines high accuracy. Graph a view: Use tone Q Nd: After the silicon chip with YAG large to 250um laser has cut, what remain on material is drossy. A: Of solidify drossy, b: Coarse drossy, c: Small treatment uses careful drossy laser, for example cut, underline, bore, it is to use the pulse laser of high strenth to undertake irradiation to material, make material evaporates, realize material thereby move except. So far, in this technical application, main difficulty depends on machining the material in the process to be formed drossily. These are drossy form, a few it is to be in material surface is caky form, a few collide and form of aeriform element in the course in gas and air. These vapour blast off outwards at first, but finally, major vapour became drossy, dispersed mix around ablation design surface inside quarter chamfer (if pursue 1) . Their transmission speed is as high as every second thousands of meters. Graph sketch map of coping of 2 silicon chip. Ply passes treatment of laser of 355nm ultraviolet ray and high-pressured water cleanness for the silicon chip of 280um. (A) the exterior that the graph showed to treatment project did not use the formation with the drossy circumstance of any cladding to destroy a part and function. It also reduced ablation efficiency, the drossy likelihood that stays because of before one holds off the way that light beam of the laser when scanning the next time spreads. The closest research had shown leather second and flying second laser are machining the advantage on elaborate structure, the data that they process is very clean, because laser is had,this is exceed short pulse width. However, its machine speed to return far the requirement on short of industry. The use of cladding of the water-solubility in reducing drossy methodological chip cut -- already all sorts of advanced technologies are used to in reducing chip cut drossy. Water-solubility bag cladding can is in by deposit workpiece surface, in order to collect drossy grain. The most familiar bag cladding pattern on industry is polyvinyl alcohol (PVA) . Fixature and other black solution also can be used in research and development. After cut, the means of high-pressured water cleanness that can use a level cleans this cladding (if pursue 2) . Graph 3 laser are on the stainless steel with thick 120um the alveolus with great place (right) . The cover of alveolus entry point and exit (left) " with filling " type stiletto -- so called " with filling " type stiletto can avoid to be in laser stiletto burr and drossy formation. Thin cover covers the face in material, to incident laser. This cover can gather the deposit of the vapour in stiletto process and melt. It had the effect of film of attack by surprise, those who held back one part laser is incident. This brings about laser energy to be able to 't make data complete aerification; The quantity of heat that light intensity produces in material bottom melts merely or heated material, this machines character with respect to what affected alveolus. Backward film covers the other one side of material, it is prevented in alveolus provenance drossy with fecal deposit. Graph 3 with the graph 4 gave out by " with filling " the alveolus that type stiletto gets. The air that uses here Q 355 Nm is ultraviolet laser, its pulse energy is as high as 100 MJ. The alveolus that gets on stainless steel and nickel material is very clean. Compare with this photograph, the cover of material coping has very large hole, and have a lot of flaws, burr and drossy. The cover of material bottom also appears a few drossy. Graph the laser that place of 4 use Jiao Ban have fixed light intensity to distributing will have cut -- in a lot of cut application, flat-roofed light intensity distributings more advantageous. Accurate flat-roofed the place that distributings to leave a focus OK and simply not far through be in outside the laser of the predestined relationship is held off will come true. Graph 5 gave out for many times the result surface of scanning cut. The chip with the green pulse large to 280 M laser of the 532 Nm that lamp pump riverside used here has cut. Use these technologies, can reduce the edge effect when melt and burr and drossy formation greatly. Nextpage pursues 5 graphs the 6 water with rapid flow make filmy and auxiliary small treatment -- we had observed through vapour nozzle or liquid film will assist treatment, material surface is more clean. Main problem depends on the discontinuity of the operation. Because water film is destroyed by laser, so lunt broadcast, ground of liquid large area is outward eject, this pollutes focusing lens possibly. According to these experience, diminutive injector type nozzle is used at film of very thin liquid of going from place to place producing in whole irradiation surface. Because film is very thin, flow is very so rapid (be more than 1 M/s) . Prevented plasma of the generation in liquid film and bubble so. And the material of place ablation, and the remains inside cut, be kept clear of by effective ground. Nozzle can be secured to come down, this technology can be used at different laser wavelengh, from 355 to 1064 Nm. Every time the experiment can observe afterwards apparent progress. For instance, we can have bore a hole to the silicon chip with large 280m, scan in laser frequency and dry cut same situation, wet the cut that cuts gain is more clean (if pursue 6) . The cut on copper and aluminium and reticle also got similar result. Graph 7 laser can cause material on silicon chip pervious to light and erupt the phenomenon such as boiling -- because liquid state silicon can be on regular boiling point,this is continue to be heated, and bring about material overheat, material is completely right now transparent to certain wavelengh. Because use accept second,the existence of metastable state silicon is when laser has small treatment, solid - fluid have a common boundary lacks nucleate seat. Overheat silicon material turns transparent liquid dielectric into material from liquid state metal when because of density of the electron in liquid state metal reduce substantially. Of material dielectric constant reduce the refractive index that causes silicon of transparent liquid state to be reduced greatly suddenly. The moves laser of Q solid state pulse parameter that passes pair of 355 Nm undertakes controlling, the material that we observe this laser is caused is transparent phenomenon. Hit completely below the circumstance that we are scanning only wear the silicon chip with large 280m. Normally, such silicon chip needs scanning ability for many times to hit wear, and treatment process will stay in material surface of countless drossy. The mechanism of purify material must use the principle that forms vapour bleb in surface of silicon of overheat liquid state, because of here material won't eject arrives irradiation surface, be in however the bottom of silicon chip (namely the exit of beam of light, if pursue 7) . Namely process of detonation of so called two-phase, this process can bring very high output, the surface after cut is very clean also. Graph a few when here speaks of 8 different techniques are used more easily relatively. To get the small treatment result of high quality, laser user pays close attention to only how choosing appropriate laser and laser parameter is insufficient. The user still must consider a few technologies that here introduces, in order to reduce the occurrence of drossy, recast, burr and fire damage. Author Tuan Anh Mai is the controller of company of small treatment of Canadian KJ laser, the company is located in Canada how to visit Toronto town generally. This company be subordinate to belongs to KJ market to serve a group. His email address is: TUan@kjmarketing.