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【Rayclass | 锐课堂】Laser Cutting for Sapphire
Date:2019-10-31Source:Original article

蓝宝石晶体的化学成分为氧化铝(Al2O3),蓝宝石材料具有高耐磨性、高硬度和优良的热传导性、电绝缘性、化学性能稳定等优异的物理、化学等特点,被广泛应用于高端智能手机、平板电脑、平板电视等电子显示行业领域。由于蓝宝石是硬脆性材料,传统的机械加工存在易产生裂纹、碎片、分层、崩边、边缘破裂和刀具易磨损等缺陷,又由于蓝宝石化学稳定性较好,使得传统的化学加工方法对其难以加工。

Sapphire is widely used in smart phones, tablet computers, flat panel TVs and other electronic display industries cause the characteristics included abrasive resistance, high hardness, thermal conductivity, electrical insulation, and stable chemical properties. Since sapphire is a hard and brittle material, conventional machining has defects such as cracks, chipping, delamination, edge cracking, and tool wear. 

 

而激光切割技术是一种高速度、高质量的切割方法,对蓝宝石晶片进行切割,不仅具有加工速度快切口质量好并且可以对任意图形进行切割。QCW准连续光纤激光器的稳定性和光束质量较好并且能量密度较大,对硬脆性材料切割相对于Nd∶YAG激光切割有明显的优势,采用QCW准连续光纤激光器结合保护气体对蓝宝石晶片进行切割,热影响区较小,在加工区域表面不会形成波纹,并且加工设备成本低,因此在蓝宝石加工领域被广泛采用。

Laser cutting technology is a high-speed, high-quality cutting method, so sapphire wafers are cut, not only with high processing speed, good cut quality, but also for cutting any pattern. Compared with Nd:YAG laser cutting, QCW fiber laser has better stability and beam quality and higher energy density, which has obvious advantages for hard and brittle material cutting. The QCW fiber laser is combined with the shielding gas to cut the sapphire wafer, the heat-affected zone is small, the surface of the processing area is not corrugated, and the processing equipment is low in cost, so it is widely used in the field of sapphire processing.

 

 

切割蓝宝石操作及注意事项

 

QCW切割蓝宝石原理如图1所示,激光经过光纤传导到准直镜后通过聚焦镜,最终在焦平面获得聚焦光斑后作用于蓝宝石表面实现切割;自动控制系统控制移动平台能在X,Y方向移动。采用QCW准连续光纤激光器切割光学级蓝宝石基片,厚度为0.52mm、直径为5mm。

The principle of cutting sapphire with QCW fiber laser is shown in Figure 1。 The laser is transmitted through the fiber to the collimating mirror and then passed through the focusing mirror。 Finally, the focused spot is obtained in the focal plane and then applied to the sapphire surface for cutting。 Optical grade sapphire substrate is cut by QCW fiber laser with thickness of 0。52mm, diameter of 5mm。

 

应用脉宽为0。15~0。18 ms、波长为1064 nm、光斑直径为15μm、重复频率为0~5 kHz、能量密度变化范围为0~2。4 × 105J/cm²、切割速度变化范围为0~50 mm/s。加工采用氮气作为辅助气体,喷嘴直径为0。5-1 mm。

The application pulse width of 0.15~0.18ms, wavelength of 1064 nm, spot diameter of 15μm, repetition frequency of 0~5 kHz, energy density varies from 0 to 2.4 × 105 J/cm², and the cutting speed varies from 0 to 50 mm/s. The process uses nitrogen as the auxiliary gas and the nozzle diameter is 0.5-1 mm.

 

起刀线位置选择

首先要在蓝宝石切割软件中将起刀线的位置设置好,我们通过改变角度Θ(起刀线与材料边缘的角度)来改变起刀线的位置,如图3所示。并观察和分析起刀线位置对切割质量的影响Θ。依次选取15°、30°、45°、60°、75°和90°进行试验,起刀线的长度为0.3mm。起刀线的位置确定好后,再进行试验。

Firstly, set the position of the cutting line in the sapphire cutting software. We change the angle of the starting line(the angle between the starting line and the edge of the material), as shown in Figure 3. Select the different angles to test, and confirm the position of the line, then test.

 

当激光刚照射到蓝宝石材料表面时,将会发生剧烈的反应。为了消除切割开始时的不利影响,在切割正式的图形前添加的一段切割线,即起刀线,也称为辅助线。起刀线的切入角度也是影响切割质量的重要因素。通过实验发现,当角度为30°或90°时,溅射物长度基本消除。

In order to eliminate the adverse effects at the beginning of the sapphire cutting, a section of the cutting line added before the cutting of the formal pattern is the starting line, also called the auxiliary line. The cutting angle of the cutting line is also an important factor affecting the cutting quality. It has been found through experiments that the sputter length is substantially eliminated when the angle is 30° or 90° .

 

 

切割结果及分析

使用氮气作为辅助气体,喷嘴直径为0。5mm。切割蓝宝石圆孔效果如下图所示:

Nitrogen was used as the auxiliary gas, and the nozzle diameter was 0。5 mm。 The effect of cutting the sapphire round hole is shown in the figure below:

 

从最终的切割样件照片可以看出:

1. 从显微镜上看切割后的蓝宝石边缘光滑、基本无挂渣、无毛刺;

2. 切割面几乎无坡度,锥度在100以内;

3。 蓝宝石正面切割边缘效果较好,崩边尺寸的崩变量较背面崩边尺寸小,背面崩边量也控制在10μm以下。

We can see from the final cut sample photo that:

1。 From the microscope, the sapphire after cutting has a smooth edge, basically no dross, no burr。

公益福彩app2. The cutting surface has almost no slope and the taper are less than 100.

3。 The sapphire front edge cutting effect is better, the collapse size of the chipping size is smaller than the back-surface, and the backside collapse amount is also controlled below 10μm。

 

 

注意事项

影响蓝宝石崩边量的一个很重要的因素为激光能量密度,激光能量密度越大,蓝宝石背面的崩边现象越明显,崩边尺寸越大,所以在保证蓝宝石能被切穿的同时降低激光功率对蓝宝石背面崩边情况有一定改善,但是能量越小在背面存在的挂渣就越严重,且不易清除。若适当增大激光能量可使得蓝宝石背面熔融材料成为粉末状,从而可以改变蓝宝石背面切割效果。

Laser energy density is an important factor affecting the amount of sapphire collapse. The higher the laser energy density, the more obvious the chipping phenomenon on the back of the sapphire and the larger the size of the chipping. Therefore, while ensuring that the sapphire can be cut through, the laser power is reduced to the side of the sapphire, but the smaller the energy, the more serious the slag is on the back surface, and it is difficult to remove. If the laser energy is properly increased, the molten material on the back side of the sapphire can be made into a powder, which can change the cutting effect on the back side of the sapphire.

 

 

影响蓝宝石切割质量的

几个主要因素

 

要获得较好的表面质量等级,必须对激光功率、切割速度等工艺参数进行多次优化处理。下面就说说影响蓝宝石切割质量的几个主要因素。

To obtain a good surface quality grade, it is necessary to optimize the process parameters such as laser power and cutting speed. Here are a few of the main factors that affect the quality of sapphire cutting.

 

(1)激光功率

激光能量是激光切割蓝宝石基片过程中的主要能量来源,激光功率和切割速度决定了输入到蓝宝石基片上的能量,激光功率的大小会对切割产生重要的影响。当切割速度、辅助气体压力等其它工艺参数一定时,切口宽度随着激光功率的增加呈现一种线性正比关系。激光功率过小会出现切不透;增加功率,则切口宽度增加,端面粗糙度增大,激光切割时希望激光功率尽可能大,可以充分发挥激光器的功率优势,提高效率。

Laser energy is the primary source of energy for laser-cut sapphire substrates. Laser power and cutting speed determine the energy input to the sapphire substrate. The amount of laser power has an important effect on the cutting. When other process parameters such as cutting speed and auxiliary gas pressure are constant, the slit width exhibits a linear proportional relationship with the increase of laser power. If the laser power is too small, it will not be cut through; if the power is increased, the slit width will increase and the end surface roughness will increase. The laser power is as large as possible during laser cutting, which can fully utilize the power advantage of the laser and improve efficiency.

 

(2)切割速度

对给定的蓝宝石材料和激光功率,切割速度一般符合于一个经验式,只要在阈值以上,材料的切割速度与激光功率成正比,即增加功率可以提高切割速度。对于切割蓝宝石而言,在其他工艺参数保持不变的情况下,激光切割速度可以有一个相对的调节范围。

切割速度小,切口宽度大,切口粗糙度大;切割速度大,切口宽度和粗糙度小,超过最佳切割速度后粗糙度缓慢增加。切割速度过高,则切口刮渣较多或切不透;切割速度过低,则材料过烧,切口宽度和热影响区较大。要提高切割质量,当其他工艺参数不变时,要优化切割速度。

For sapphire cutting, the cutting speed of the material is proportional to the laser power, that is, increasing the power can increase the cutting speed. The laser cutting speed can have a relative adjustment range while other process parameters remain unchanged.

If the cutting speed is small, the slit width is large and the slit roughness is large. If the cutting speed is large, the slit width and the roughness are small, and the roughness is slowly increased after exceeding the optimal cutting speed. If the cutting speed is too high, the incision scraping slag is more or not permeable; if the cutting speed is too low, the material is over-fired, and the slit width and the heat-affected zone are large. To improve the cutting quality, optimize the cutting speed when other process parameters are unchanged.

 

(3)辅助气体

辅助气体除用于从切割区吹掉熔渣以清除切缝的惰性气体和活性气体外,对蓝宝石材料,使用氮气可以起到抑制切割区过度燃烧的作用。

激光切割对辅助气体的基本要求是气流量要大,以便有充足的氮气与切口材料发生放热反应,并有足够的动力将切口处的熔融材料吹除。高速切割蓝宝石时,增加气体压力可以提高切割速度,防止切口背面产生挂渣。但压力过大,切割面反而变得粗糙。在切割过程中,氮气中含有的杂质对切割质量造成不良影响,因此氮气的纯度要高。

In addition to the auxiliary gas used to blow off the slag from the cutting zone to remove the inert gas and active gas of the slit, the use of nitrogen for the sapphire material can suppress the excessive combustion of the cutting zone.

The basic requirement for laser cutting for assist gas is that the gas flow rate is large so that there is sufficient nitrogen to react exothermically with the slit material and there is sufficient power to blow off the molten material at the slit. When cutting sapphire at high speed, increasing the gas pressure can increase the cutting speed and prevent the slag from being generated on the back of the slit. During the cutting process, the impurities contained in the nitrogen adversely affect the cutting quality, so the purity of the nitrogen is high.

 

 

 

 

 

 

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