A sapphire surface array microstructure processing device and method

Abstract

The present invention relates to a device and method for processing an array of microstructures on the surface of a sapphire. The processing device includes a fixture; a grinding wheel is provided on one side of the fixture; diamond tips are provided on the circumferential side wall of the grinding wheel; each time the grinding wheel rotates one week, the diamond tips grind the sapphire workpiece once and form a microscopic groove; as the fixture translates, the diamond tips grind at different positions of the sapphire workpiece and form a strip-shaped groove composed of a plurality of microscopic grooves spliced in sequence, and there is an overlap between two adjacent microscopic grooves; the grinding directions of the diamond tips include a first direction and a second direction that are perpendicular to each other, and a plurality of strip-shaped grooves in the first direction and a plurality of strip-shaped grooves in the second direction are respectively arranged side by side in the first direction and the second direction; the plurality of strip-shaped grooves in the first direction and the plurality of strip-shaped grooves in the second direction intersect to form a smooth-surface array microstructure on the surface of the sapphire workpiece. It can limit the generation and propagation of brittle fracture or cracks, reduce the total reflection of light, and improve the light extraction efficiency.

Description

Technical Field

[0001] The present invention belongs to the technical field of sapphire processing, and particularly relates to a device and method for processing an array microstructure on the surface of a sapphire. Background Art

[0002] Sapphire is widely used as a substrate material in many fields, such as optical devices LED, chips, superconducting nanostructure thin films, etc. In order to improve the light extraction efficiency in its optoelectronic applications, the prior art mainly prepares an array microstructure morphology on the surface of sapphire by etching. The sapphire array microstructure obtained by etching can change the propagation direction of light as a substrate, reduce internal total reflection, thereby improving the light extraction efficiency and saving energy consumption. However, at present, no method of mechanical processing is found to grind the surface of sapphire to obtain an ideal sapphire array microstructure morphology as a substrate to improve the light extraction efficiency of LED.

[0003] In the current technology, the processing of sapphire components mainly uses the process chain methods of grinding, lapping, and polishing. Due to the high hardness of sapphire, second only to diamond, and sapphire belonging to typical hard and brittle materials, achieving high-efficiency and low-damage processing has become an obstacle to its application and development. It is extremely difficult to obtain an ideal morphology after mechanical processing, and brittle fracture and cracks are likely to occur during processing. After grinding and polishing, the scratches on the surface of sapphire are heavy and the precision is poor, which is not ideal for improving the light extraction efficiency of LED. Summary of the Invention

[0004] Aiming at the technical problems existing in the prior art, one of the purposes of the present invention is to provide a device for processing an array microstructure on the surface of a sapphire, which can process a morphology with a smooth curved surface and a microscopic array arrangement on the surface of the sapphire, avoid brittle fracture of materials during the processing, reduce the total reflection of light in the sapphire, and improve the light extraction efficiency.

[0005] Aiming at the technical problems existing in the prior art, the second purpose of the present invention is to provide a method for processing an array microstructure on the surface of a sapphire, which can process a morphology with a smooth curved surface and a microscopic array arrangement on the surface of the sapphire, avoid brittle fracture of materials during the processing, reduce the total reflection of light in the sapphire, and improve the light extraction efficiency.

[0006] The purpose of the present invention is achieved by the following technical solutions:

[0007] A device for processing an array microstructure on the surface of a sapphire includes a fixture for fixing a sapphire workpiece, a first driving device, a second driving device, and a control device;

[0008] A grinding wheel is provided on one side of the fixture;

[0009] A diamond indenter is provided on the circumferential side wall of the grinding wheel;

[0010] The first driving device is used to rotate the grinding wheel so that the diamond indenter grinds on the sapphire workpiece once per rotation of the grinding wheel and forms a microgroove.

[0011] The second driving device is used to linearly translate the fixture at a constant speed so that the diamond indenter grinds on different parts of the sapphire workpiece as the fixture translates and forms a strip groove composed of multiple sequentially spliced microgrooves, and there is an overlap between two adjacent microgrooves; wherein, the grinding directions of the diamond indenter on the sapphire workpiece include a first direction and a second direction that are perpendicular to each other, and a plurality of first-direction strip grooves arranged side by side and a plurality of second-direction strip grooves arranged side by side are respectively included in the first direction and the second direction; the plurality of first-direction strip grooves and the plurality of second-direction strip grooves intersect on the surface of the sapphire workpiece to form an array microstructure.

[0012] The control device is used to control the actions of the first driving device and the second driving device.

[0013] Furthermore, a heating device is provided on one side of the fixture, and the heating device is used to heat the sapphire workpiece.

[0014] Furthermore, the heating device is a laser heating platform.

[0015] Furthermore, a pressure sensor is provided on the fixture, and the pressure sensor is connected to the control device and is used to detect the grinding force of the diamond indenter.

[0016] Furthermore, a displacement sensor is provided on one side of the grinding wheel, and the displacement sensor is connected to the control device and is used to detect the grinding depth of the diamond indenter.

[0017] Furthermore, the diamond indenter is a quadrangular pyramid, the tip angle of the indenter is 78.5°, and the arc radius of the tip of the indenter is 1 μm.

[0018] Furthermore, the tangential direction of the grinding wheel is perpendicular to the surface of the sapphire workpiece.

[0019] A method for machining an array microstructure on the surface of a sapphire, using a device for machining an array microstructure on the surface of a sapphire, includes the following steps.

[0020] The first driving device rotates the grinding wheel so that the diamond indenter grinds on the sapphire workpiece fixed by the fixture once per rotation of the grinding wheel and forms a microgroove.

[0021] The second driving device linearly translates the fixture at a constant speed so that the diamond indenter grinds on different parts of the sapphire workpiece as the fixture translates and forms a strip groove composed of multiple sequentially spliced microgrooves.

[0022] A plurality of first-direction strip grooves arranged side by side are obtained by grinding at intervals in the first direction on a sapphire workpiece, and then a plurality of second-direction strip grooves arranged side by side are continuously ground at intervals in the second direction perpendicular to the first direction, so that the plurality of first-direction strip grooves and the plurality of second-direction strip grooves intersect to form an array microstructure on the surface of the sapphire workpiece.

[0023] Furthermore, before the diamond indenter grinds the sapphire workpiece, a heating device is used to preheat the sapphire workpiece to broaden the plastic domain of the sapphire workpiece.

[0024] Furthermore, the grinding force of the diamond indenter is detected by a pressure sensor, and the grinding depth of the diamond indenter is controlled by a displacement sensor. During the grinding process, the tangential direction of the grinding wheel is perpendicular to the sapphire surface.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] Since the diamond indenter grinds the sapphire workpiece once and forms a microscopic groove every time the grinding wheel rotates one week, when the second driving device linearly translates the fixture at a constant speed, the diamond indenter successively grinds out a plurality of microscopic grooves on the sapphire workpiece. Since there is an overlap between two adjacent microscopic grooves, each microscopic groove can be connected to the previous one, and there is no redundant uncut layer between adjacent microscopic grooves, ensuring that the processed microscopic grooves are continuous and uniform, achieving the effect of completely removing the fracture removal zone of the sapphire workpiece material, and being able to limit the generation and expansion of brittle fracture or cracks in the sapphire workpiece material to the greatest extent. A plurality of microscopic grooves can be sequentially connected to form a complete and smooth-surfaced strip groove. By sequentially processing a plurality of strip grooves arranged side by side in the first direction and the second direction respectively, the adjacent strip grooves are arranged at intervals, preventing the overlapping of the residual stress field and the processing stress field between two strip grooves that are relatively close, and thus preventing the transverse crack from spreading to the front and rear microscopic grooves, avoiding brittle fragmentation of the material. A plurality of strip grooves in the first direction and a plurality of strip grooves in the second direction intersect to form an array microstructure on the surface of the sapphire workpiece. Since the processed sapphire surface forms a microscopic array arrangement morphology, and the microstructure morphology can change the propagation direction of light, enabling the light that undergoes total internal reflection inside the chip at an incident critical angle greater than the critical angle to escape from the chip surface, which is equivalent to expanding the escape cone, enabling the photons emitted from the active layer that could not originally escape from the chip surface to escape from the chip surface, and minimizing the total internal reflection of light to the greatest extent, thereby improving the light extraction efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic structural diagram of the processing device according to an embodiment of the present invention.

[0028] Figure 2 It is a schematic structural diagram of a grinding wheel equipped with a diamond indenter.

[0029] Figure 3 Schematic structural diagram of the diamond indenter according to an embodiment of the present invention.

[0030] Figure 4 Schematic diagram of the array morphology microstructure formed after processing the sapphire workpiece.

[0031] Figure 5 Schematic diagram of the light propagation path in a conventional sapphire workpiece.

[0032] Figure 6 Schematic diagram of the light propagation path in the sapphire workpiece with an array arrangement formed after processing.

[0033] In the figure:

[0034] 1 - grinding wheel, 2 - sapphire workpiece, 3 - leveling device, 4 - laser heating platform, 5 - diamond indenter, 6 - pressure sensor, 7 - fixture, 8 - signal amplifier, 9 - dynamic signal analyzer. Specific embodiments

[0035] The present invention will be further described in detail below.

[0036] In this embodiment, a grinding wheel 1 equipped with a diamond indenter 5 is combined with laser-assisted heating to process the sapphire workpiece 2 to form a regular array morphology, so as to achieve the purpose of enhancing light output.

[0037] As Figure 1 shown, a sapphire surface array microstructure processing device includes a fixture 7 for fixing the sapphire workpiece 2, a first driving device, a second driving device, and a control device;

[0038] A grinding wheel 1 is provided on one side of the fixture 7;

[0039] A diamond indenter 5 is provided on the circumferential side wall of the grinding wheel 1;

[0040] The first driving device is used to rotate the grinding wheel 1 so that the diamond indenter 5 grinds on the sapphire workpiece 2 once per rotation of the grinding wheel 1 and forms a microscopic groove;

[0041] The second driving device is used to linearly translate the fixture 7 at a constant speed, so that the diamond indenter 5 grinds at different parts of the sapphire workpiece 2 as the fixture 7 translates and forms a strip-shaped groove composed of a plurality of microscopic grooves spliced in sequence, and there is an overlap between adjacent two microscopic grooves; wherein, the grinding direction of the diamond indenter 5 on the sapphire workpiece 2 includes a first direction and a second direction perpendicular to each other, and a plurality of first-direction strip-shaped grooves arranged side by side and a plurality of second-direction strip-shaped grooves arranged side by side are respectively included in the first direction and the second direction; the plurality of first-direction strip-shaped grooves and the plurality of second-direction strip-shaped grooves intersect to form an array microstructure on the surface of the sapphire workpiece 2;

[0042] The control device is used to control the operation of the first driving device and the second driving device.

[0043] Preferably, the first driving device is a rotating main shaft, and the second driving device is a linear motor.

[0044] Specifically, the processing device includes a grinding wheel 1, a leveling device 3, a laser heating platform 4, a pressure sensor 6, a fixture 7 base, a displacement sensor, a signal amplifier 8, a dynamic signal analyzer 9, a first driving device, a second driving device, and a working platform.

[0045] The sapphire workpiece 2, the leveling device 3, the pressure sensor 6, the fixture 7 base, and the working platform are stacked and installed in sequence from top to bottom, which improves the stiffness of the entire system and the stability during operation.

[0046] At least one diamond indenter 5 is arranged on the grinding wheel 1.

[0047] As Figure 2 shown, preferably, the number of diamond indenters 5 is 6, which are evenly arranged on the circumferential side wall of the grinding wheel 1, so that the grinding wheel 1 can maintain overall balance when rotating.

[0048] As Figure 3 shown, the diamond indenter 5 is a quadrangular pyramid, and the tip angle of the indenter is preferably α = 78.5o, and the arc radius of the tip is preferably r = 1μm. A negative rake angle is beneficial to the processing of brittle materials, so the edge-forward mode of the quadrangular pyramid diamond indenter 5 is selected during grinding to obtain a larger negative rake angle.

[0049] The sapphire crystal has a hexagonal lattice structure and is anisotropic. The physical and chemical properties of sapphire are also different in different lattice directions. In this embodiment, the processing crystal plane of the sapphire workpiece 2 is the C plane, and the C plane has more obvious plasticity relative to other crystal planes.

[0050] After the sapphire workpiece 2 is clamped, the leveling device 3 is used to level it so that the maximum height difference on the upper surface of the sapphire workpiece 2 is within 1 micron. Then, each component is wiped with alcohol and lint-free cloth to ensure that the surface has no oil stains or foreign matters. Finally, a dynamometer is used for auxiliary tool setting in the cutting depth direction. When the diamond indenter 5 just cuts into the sapphire workpiece 2, a peak signal will appear in the cutting force of the dynamometer, and the coordinates at this time are used as the origin.

[0051] The laser heating platform 4 is arranged on one side of the fixture 7 and is used to heat the surface of the sapphire workpiece 2.

[0052] When grinding sapphire, first use the laser head of the laser heating platform 4 to preheat the area to be processed of the sapphire workpiece 2 in advance. When the temperature of the sapphire workpiece 2 reaches a certain threshold, the sapphire material will change from brittle to plastic. Then, use the grinding wheel 1 equipped with the diamond indenter 5 to grind the plastic region of the sapphire. The misaligned arrangement of the grinding wheel 1 and the laser head ensures that they will not collide during processing.

[0053] The grinding wheel 1 is installed on a spindle with a certain rotational speed. The spindle can be steplessly speed-regulated, and the rotational speed range is from 3000 rpm to 28000 rpm. The preferred rotational speed of the spindle during grinding is 3000 rpm. During processing, the grinding force and grinding depth of the diamond indenter 5 are detected or controlled by the pressure sensor 6 and the displacement sensor respectively.

[0054] A method for machining an array of microstructures on the sapphire surface uses a device for machining an array of microstructures on the sapphire surface, including the following steps.

[0055] The first driving device rotates the grinding wheel 1, so that for each rotation of the grinding wheel 1, the diamond indenter 5 grinds once on the sapphire workpiece 2 fixed by the fixture 7 and forms a microscopic groove.

[0056] The second driving device linearly translates the fixture 7 at a constant speed, so that the diamond indenter 5 grinds at different parts of the sapphire workpiece 2 as the fixture 7 translates and forms a strip-shaped groove composed of a plurality of microscopic grooves spliced in sequence, and there is an overlap between two adjacent microscopic grooves.

[0057] On the sapphire workpiece 2, a plurality of strip-shaped grooves arranged side by side are obtained by intermittent grinding in the first direction, and then a plurality of strip-shaped grooves arranged side by side are continuously obtained by intermittent grinding in the second direction perpendicular to the first direction, so that the plurality of strip-shaped grooves in the first direction and the plurality of strip-shaped grooves in the second direction intersect to form an array of microstructures on the surface of the sapphire workpiece 2.

[0058] Furthermore, before the diamond indenter 5 grinds the sapphire workpiece 2, the sapphire workpiece 2 is preheated by a heating device to broaden the plastic region of the sapphire workpiece 2.

[0059] Furthermore, the grinding force of the diamond indenter 5 is detected by the pressure sensor 6, amplified by the signal amplifier 8, and then transmitted to the dynamic signal analyzer 9. The grinding depth of the diamond indenter 5 is controlled by the displacement sensor. During grinding, the tangential direction of the grinding wheel 1 is perpendicular to the sapphire surface.

[0060] Specifically, after the diamond indenter 5 on the grinding wheel 1 completes the tool setting, a microscopic groove with a depth of 300 nm is first ground on the sapphire workpiece 2. With the translation of the fixture 7 carrying the sapphire workpiece 2, the diamond indenter 5 successively grinds out multiple microscopic grooves on the sapphire workpiece 2 and forms a complete strip-shaped groove. There is an overlapping part between adjacent microscopic grooves, aiming to ensure that the multiple processed microscopic grooves are continuous and uniform, and there is no redundant uncut layer between adjacent microscopic grooves. After each transverse machining is completed, the multiple microscopic grooves formed by grinding can be sequentially connected into a complete strip-shaped groove with a smooth curved surface.

[0061] After grinding a strip-shaped groove, the grinding wheel 1 is longitudinally translated by a pitch to control the structure density, and then the next strip-shaped groove is ground in the same way. By repeating this process, multiple strip-shaped grooves arranged side by side in the first direction are obtained.

[0062] The grinding directions include a first direction and a second direction that are perpendicular to each other.

[0063] After grinding in the first direction, multiple strip-shaped grooves arranged side by side in the second direction are ground in the same way. Multiple strip-shaped grooves in the first direction and multiple strip-shaped grooves in the second direction intersect to form an array microstructure on the surface of the sapphire workpiece 2.

[0064] As Figure 4 shown, the morphology of the array microstructure formed after processing has a smooth curved surface and regular shape. By changing the translation speed of the fixture 7 and the size of the grinding depth, the shape of the strip-shaped groove and the tangential angle with the horizontal plane can be adjusted, so as to optimize the light extraction efficiency.

[0065] As Figure 5 shown is a schematic diagram of the light propagation path in the traditional sapphire workpiece 2. As Figure 6 shown is a schematic diagram of the light propagation path in the sapphire workpiece 2 with an array arrangement formed after processing. By comparison, it can be seen that the morphology of the array microstructure can change the direction of light propagation in the LED chip, enabling the light that undergoes total internal reflection in the LED chip due to being greater than the incident critical angle to escape from the surface of the LED chip, thereby improving the light extraction efficiency of the LED chip.

[0066] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. A sapphire surface array microstructure processing device, characterized in that: It includes a fixture for fixing a sapphire workpiece, a first driving device, a second driving device, and a control device; A grinding wheel is provided on one side of the fixture; Diamond tips are provided on the circumferential side wall of the grinding wheel; The first driving device is used to rotate the grinding wheel so that the diamond tip grinds on the sapphire workpiece once per rotation of the grinding wheel and forms a microscopic groove; The second driving device is used to linearly translate the fixture at a constant speed so that the diamond tip grinds on different parts of the sapphire workpiece as the fixture translates and forms a strip groove composed of multiple sequentially spliced microscopic grooves, and there is an overlap between two adjacent microscopic grooves; wherein, the grinding directions of the diamond tip on the sapphire workpiece include a first direction and a second direction that are perpendicular to each other, and multiple first-direction strip grooves arranged side by side and multiple second-direction strip grooves arranged side by side are respectively included in the first direction and the second direction; the multiple first-direction strip grooves and the multiple second-direction strip grooves intersect on the surface of the sapphire workpiece to form an array microstructure; The control device is used to control the actions of the first driving device and the second driving device; A heating device is provided on one side of the fixture, and the heating device is used to heat the sapphire workpiece; A pressure sensor is provided on the fixture, and the pressure sensor is connected to the control device and is used to detect the grinding force of the diamond tip; A displacement sensor is provided on one side of the grinding wheel, and the displacement sensor is connected to the control device and is used to detect the grinding depth of the diamond tip; The diamond tip is a quadrangular pyramid, the tip angle of the tip is 78.5°, and the arc radius of the tip of the tip is 1 μm; The tangential direction of the grinding wheel is perpendicular to the surface of the sapphire workpiece.

2. The processing device for the surface array microstructure of sapphire according to claim 1, wherein: The heating device is a laser heating platform.

3. A method for processing an array of microstructures on a sapphire surface, characterized in that: When using a sapphire surface array microstructure processing device as described in claim 1 or 2, the following steps are included, The first driving device rotates the grinding wheel so that the diamond tip grinds on the sapphire workpiece fixed by the fixture once per rotation of the grinding wheel and forms a microscopic groove; The second driving device linearly translates the fixture at a constant speed so that the diamond tip grinds on different parts of the sapphire workpiece as the fixture translates and forms a strip groove composed of multiple sequentially spliced microscopic grooves, and there is an overlap between two adjacent microscopic grooves; Multiple first-direction strip grooves arranged side by side are obtained by interval grinding on the sapphire workpiece in the first direction, and then multiple second-direction strip grooves arranged side by side are continuously obtained by interval grinding in the second direction perpendicular to the first direction, so that the multiple first-direction strip grooves and the multiple second-direction strip grooves intersect on the surface of the sapphire workpiece to form an array microstructure; Before the diamond tip grinds the sapphire workpiece, the sapphire workpiece is preheated by the heating device to broaden the plastic domain of the sapphire workpiece; The grinding force of the diamond tip is detected by the pressure sensor, and the grinding depth of the diamond tip is controlled by the displacement sensor. During grinding, the tangential direction of the grinding wheel is perpendicular to the sapphire surface.

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