Thermopile laser power probe and manufacturing method

Abstract

A thermopile laser power probe comprises a laser absorption layer, an insulation substrate, a thermopile layer, an insulation isolation layer and a heat conduction substrate which are sequentially arranged from top to bottom, the thermopile layer is provided with a probe lead, the laser absorption layer is arranged on the front face of the insulation substrate, and the thermopile layer is arranged on the back face of the insulation substrate. The heat conduction substrate and the thermopile layer are separated by an insulation isolation layer. The invention further provides a manufacturing method of the thermopile laser power probe. The position of the thermopile layer is changed, the circular thermopiles arranged in a staggered mode are designed, and meanwhile the sensitivity and the response speed of the thermopile laser power probe are improved.

Description

Technical Field

[0001] The present invention belongs to the field of laser power probes, and relates to a thermopile laser power probe and a manufacturing method thereof, which are used to improve the sensitivity and response speed of the thermopile. Background Art

[0002] Lasers have broad application prospects, especially in the fields related to high-end manufacturing. High-power laser processing has entered the field of electronic devices, and the processing accuracy has reached the micron level, but the processing yield has been halved accordingly. The main reason is that the larger the power of the laser, the more likely it is to drift during use, and this kind of drift is unacceptable in the field of precision processing. Therefore, the technical demand for real-time monitoring and rapid detection of high-power lasers is becoming increasingly urgent.

[0003] The probe is the key core of the laser power detector. Mainstream high-power laser detectors use thermopile probes to sense laser power signals (CN202011578264, CN202023212741). Since the thermal conductivity of thermoelectric materials is generally low, in order to increase the response speed of such probes, researchers use a substrate with high thermal conductivity to share the heat conduction function of the thermopile. The laser absorption layer is on the front side of the substrate, and the thin-film thermopile is on the back side of the substrate (CN202020227804). For probes with a measurement threshold above 10W, a relatively thick substrate is often used to increase the heat flow to ensure the stable operation of the probe. As Figure 1 shown by the old structure of Figure 2 , this is the basic structure of such a probe. The laser absorption layer 1 is on the upper part of the heat-conducting substrate 2 facing the light beam, and the thermopile layer 4 is generally on the lower part of the heat-conducting substrate 2. This configuration ensures sufficient heat dissipation to make the probe stable. However, 正面 the isothermal line distribution of 背面 shows that the temperature difference ΔT between the cold and hot ends on the back side of the heat-conducting substrate 2 is much smaller than the temperature difference ΔT at the same position on the back side of the laser absorption layer 1, and the thicker the heat-conducting substrate, the better the heat dissipation, the smaller the temperature difference, and thus the smaller the sensitivity of the probe.

[0004] To improve the sensitivity, many institutions have proposed to make the thermopile on the side of the cylindrical probe, increasing the temperature difference between the cold end and the hot end (CN201810184299, CN202211594130). However, this method of designing the laser absorption layer and the thermopile layer on both sides of the heat-conducting substrate makes the distance between the heat source and the high-temperature end of the thermopile relatively far, resulting in a response time of up to 9s and a steady-state time exceeding 30s for the probe, which cannot meet the requirements of real-time monitoring of high-power laser processing. This obviously limits the application prospects of the laser probe. Therefore, it is necessary to design and manufacture a power probe that simultaneously has high sensitivity and response speed. Summary of the Invention

[0005] In order to overcome the deficiencies of the prior art, the present invention provides a thermopile laser power probe and a manufacturing method thereof, which changes the position of the thermopile layer, designs a circular thermopile with staggered arrangement, and improves the sensitivity and response speed of the thermopile laser power probe at the same time.

[0006] The technical solution adopted by the present invention to solve its technical problems is as follows:

[0007] A thermopile laser power probe includes a laser absorption layer, an insulating substrate, a thermopile layer, an insulating isolation layer, and a heat-conducting substrate arranged in sequence from top to bottom. The thermopile layer is provided with probe leads. The laser absorption layer is on the front of the insulating substrate, and the thermopile layer is on the back of the insulating substrate. The heat-conducting substrate and the thermopile layer are separated by an insulating isolation layer.

[0008] Furthermore, in the thermopile layer, thermoelectric materials are periodically connected in series with each other and form a disc-shaped thermopile in a circular radial pattern.

[0009] Preferably, the hot ends of the thermopiles use inner diameters arranged in a staggered size.

[0010] The material of the thermopile layer is optionally a high-cost-performance thermoelectric material such as nickel chromium / nickel copper, nickel copper / copper, indium tin oxide / indium oxide, etc. The number of thermocouples in the thermopile is selected as required.

[0011] The thermopile layer is provided with positive and negative pins, and the probe leads are welded to the positive and negative pins with silver material.

[0012] The laser absorption layer uses high-temperature resistant light-absorbing materials such as silicon and silicon carbide and is deposited on the insulating substrate by plasma spraying technology. The thickness of the laser absorption layer is 50-200 microns.

[0013] The material of the insulating substrate layer is optionally one of alumina ceramics, silicon carbide, and glass fiber epoxy resin composite according to the laser power threshold measured by the detector, and the thickness is 300-500 microns.

[0014] The insulating isolation layer is optionally an alumina or silica film, or can also be a heat-conducting silicone grease, and the thickness is 20-100 microns.

[0015] The heat-conducting substrate is in the shape of a flat thick disc.

[0016] The heat-conducting substrate is an anodized aluminum plate with a thickness of 1-10 mm.

[0017] A manufacturing method of a thermopile laser power probe includes the following steps:

[0018] (1) Use an aluminum oxide plate, a silicon carbide plate, or a glass fiber epoxy resin composite plate as the insulating substrate according to the laser power threshold measured by the detector;

[0019] (2) Prepare the laser absorption layer on the front side of the insulating substrate by using the plasma spraying method;

[0020] (3) Prepare the positive and negative electrode materials of the thermopile layer on the back side of the insulating substrate with the laser absorption layer obtained in step (2) by using the magnetron sputtering method;

[0021] (4) Make an anodic aluminum oxide plate from an aluminum plate by using the electrochemical method as the heat conduction substrate;

[0022] (5) Apply thermal conductive silicone, spin-coat alumina or spin-coat silicon oxide according to the level of the laser power threshold measured by the detector, and prepare the insulating isolation layer on the front side of the heat conduction substrate prepared in step (4);

[0023] (6) When preparing the insulating isolation layer in the above step (5), place the insulating substrate prepared in step (3) closely on the insulating isolation layer before the insulating isolation layer is annealed and formed, and then anneal to make the thermopile layer and the insulating isolation layer form good thermal contact;

[0024] (7) Lead out the probe lead for the thermopile layer on the insulating substrate.

[0025] The beneficial effects of the present invention are mainly manifested in: improving the sensitivity and response speed of the thermopile laser power probe. Description of the Drawings

[0026] Figure 1 is the structural diagram of the laser power probe of the prior art.

[0027] Figure 2 is the structural design diagram of the thermopile layer of the prior art.

[0028] Figure 3 is the schematic diagram of the isothermal line distribution when the laser power probe is in a steady state.

[0029] Figure 4 is the structural diagram of the laser power probe of the present invention.

[0030] Figure 5 is the schematic diagram of the structural design of the thermopile layer.

[0031] Figure 6 is the comparison diagram of the laser power response of the probe manufactured by the present invention and the old structure, where (a) represents the old structure and (b) represents the present invention.

[0032] The reference numerals are: 1 laser absorption layer; 2 heat conduction substrate; 3 insulating isolation layer; 4 thermopile layer; 5 insulating protective layer; 6 insulating substrate; 7 probe lead; 8 laser incident direction. Detailed Embodiments

[0033] The present invention will be further described below in conjunction with the accompanying drawings.

[0034] Referring to Figures 1 to 5 , a thermopile laser power probe includes a laser absorption layer 1, an insulating substrate 6, a thermopile layer 4, an insulating isolation layer 3, and a heat-conducting substrate 2 arranged in sequence from top to bottom. The thermopile layer 4 is provided with probe leads 7. The laser absorption layer 1 is on the front of the insulating substrate 6, the thermopile layer 4 is on the back of the insulating substrate 6, and the heat-conducting substrate 2 and the thermopile layer 4 are separated by the insulating isolation layer 3.

[0035] In the present invention, as Figure 3 shown, the radial temperature difference between the laser absorption layer and the heat-conducting substrate is greater than the radial temperature difference at the same position at the lower part of the heat-conducting substrate. Therefore, in the new structure of the present invention as Figure 4 shown, the thermopile layer of the probe is not closely located between the laser absorption layer and the heat-conducting substrate. The laser absorption layer is on the front of the insulating substrate 6, and the thermopile layer is on the back of the insulating substrate. The heat-conducting substrate and the thermopile are separated by the insulating isolation layer 3. Such a design increases the temperature difference between the hot and cold ends of the thermopile, and at the same time, the good heat dissipation of the heat-conducting substrate to the cold end of the thermopile is utilized to make the temperature difference steady-state time shorter.

[0036] Further, in the thermopile layer 4, the thermoelectric materials are periodically connected in series with each other and form a disc-shaped thermopile in a circular radial pattern.

[0037] Preferably, the hot end of the thermopile uses an inner diameter arrangement with staggered sizes.

[0038] To further increase the sensitivity of the probe and make full use of the temperature difference caused by the laser, the present invention uses the thermopile pattern as shown in the new design of Figure 5 . The thermoelectric materials are periodically connected in series with each other and form a disc-shaped thermopile in a circular radial pattern. Compared with the existing design, in the new design, the hot end of the thermopile uses an inner diameter arrangement with staggered sizes, which increases the hot end temperature of some thermocouples and makes full use of the high temperature in the hot end space, further improving the sensitivity of the probe.

[0039] The material of the thermopile layer 4 is optionally a high-cost-effective thermoelectric material such as nickel chromium / nickel copper, nickel copper / copper, indium tin oxide / indium oxide. The number of thermocouples in the thermopile is selected as required.

[0040] The thermopile layer 4 is provided with positive and negative pins, and the probe leads 7 are welded to the positive and negative pins with silver material.

[0041] The laser absorption layer 1 is deposited on the insulating substrate by plasma spraying technology using high-temperature light-absorbing materials such as silicon and silicon carbide, and the thickness of the laser absorption layer is 50 - 200 microns.

[0042] The material of the insulating substrate 2 is optionally one of alumina ceramics, silicon carbide, and fiberglass epoxy composite according to the laser power threshold measured by the detector, and the thickness is 300-500 microns.

[0043] The insulating isolation layer 3 is optionally an alumina or silica film, or can also be thermal conductive silicone grease, and the thickness is 20-100 microns.

[0044] The heat-conducting substrate 2 is in the shape of a flat thick disc.

[0045] The heat-conducting substrate 2 is an anodized aluminum plate with a thickness of 1-10 mm.

[0046] A manufacturing method of a thermopile laser power probe includes the following steps:

[0047] (1) Use an alumina plate, a silicon carbide plate, or a fiberglass epoxy composite plate as the insulating substrate according to the laser power threshold measured by the detector;

[0048] (2) Prepare the laser absorption layer on the front surface of the insulating substrate by plasma spraying;

[0049] (3) Prepare the positive and negative materials of the thermopile layer on the back surface of the insulating substrate with the laser absorption layer obtained in step (2) by magnetron sputtering;

[0050] (4) Use electrochemical method to make an aluminum plate into an anodized aluminum plate as the heat-conducting substrate;

[0051] (5) Apply thermal conductive silica gel, spin-coat alumina, or spin-coat silica according to the laser power threshold measured by the detector, and prepare the insulating isolation layer on the front surface of the heat-conducting substrate prepared in step (4);

[0052] (6) When preparing the insulating isolation layer in the above step (5), place the insulating substrate prepared in step (3) closely on the insulating isolation layer before the insulating isolation layer is annealed and formed, and then anneal to make the thermopile layer and the insulating isolation layer form good thermal contact;

[0053] (7) Lead out the probe lead for the thermopile layer on the insulating substrate.

[0054] In this embodiment, the material of the insulating substrate 6 is optionally one of alumina ceramics, silicon carbide (high power), and fiberglass epoxy composite (low power) according to the laser power threshold measured by the detector, and the thickness is 300-500 microns.

[0055] Using plasma spraying technology, heat-resistant light-absorbing materials such as powdered silicon and silicon carbide are sprayed on the insulating substrate 6 as the laser absorption layer 1. The spraying power is 20 - 80 kW, the spraying time is 15 - 30 s, and the thickness of the laser absorption layer is controlled to be 50 - 200 microns.

[0056] Using magnetron sputtering technology, optional high cost-effective thermoelectric materials such as nickel chromium / nickel copper, nickel copper / copper, indium tin oxide / indium oxide are deposited on the back of the insulating substrate to form the thermopile layer 4. The thermopile pattern is as Figure 4 shown in the new design. The number of thermocouples in the thermopile is selected as needed, optionally 3 to 40 pairs. Thus, the optoelectrothermal conversion unit is fabricated.

[0057] Select an anodized aluminum oxide plate with a thickness of 1 - 10 mm as the heat-conducting substrate 2. For high-power probes, on the front of the heat-conducting substrate 2, alumina and silica films are optionally prepared by multiple repeated spin-coating methods as the insulating isolation layer 3, with a thickness of 20 - 40 microns. For low-power probes, thermal conductive silicone can be applied instead of spin-coating alumina and silica as the insulating isolation layer 2, with the thickness controlled at 40 - 100 microns. For high-power probes, before the spin-coated alumina and silica are annealed and formed, the optoelectrothermal conversion unit prepared in steps (2) - (4) is placed face-down on the insulating isolation layer, and then annealed to form good thermal contact between the optoelectrothermal conversion unit and the insulating isolation layer. For low-power probes, the optoelectrothermal conversion unit can be directly placed on the heat-conducting substrate coated with thermal conductive silicone, and wait for the silicone to cure.

[0058] Example 1: The process of manufacturing a probe with a power threshold of 350 W in this embodiment is as follows:

[0059] 1. Select a silicon carbide ceramic sheet with a thickness of 0.5 mm as the insulating substrate according to the laser power threshold measured by the detector.

[0060] 2. Using plasma spraying technology, silicon powder with a particle size of 45 microns is sprayed onto the silicon carbide ceramic sheet as the laser absorption layer. The spraying power is 50 kW, the spraying time is 30 s, and the thickness of the laser absorption layer is controlled to be 200 microns.

[0061] 3. Using DC magnetron sputtering technology, optional nickel chromium / nickel copper is deposited on the back of the insulating substrate to form the thermopile. The thermopile pattern is as Figure 3 shown in the new design. The number of thermocouples in the thermopile is selected as 34 pairs. The deposition conditions are: base vacuum 8×10 -4 , DC sputtering power 70 W, argon (purity 99.99%) flow rate 50 sccm, sputtering pressure 0.6 Pa, sputtering time 40 minutes.

[0062] 4. Using AC magnetron sputtering technology, a silica film is deposited on the back of the thermopile. The deposition conditions are: base vacuum 8×10-4 , the alternating current sputtering power is 120 W, the flow rate of argon (purity 99.99%) is 50 sccm, the sputtering air pressure is 1 Pa, and the sputtering time is 90 minutes. Thus, the photo-thermoelectric conversion unit is fabricated.

[0063] 5. Select an anodic aluminum oxide plate with a thickness of 10 mm as the heat conduction substrate. Use the spin coating method to prepare an aluminum oxide thin film as the insulating isolation layer. The complete spin coating process includes: spin coating the aluminum oxide precursor solution on the heat conduction substrate at an average rotation speed of 800 revolutions per minute, with each spin coating lasting for 30 s. After spin coating, anneal it at 300 °C under normal pressure with nitrogen protection. The entire spin coating process is repeated 5 times. Before the last annealing, place the photo-thermoelectric conversion unit on the aluminum oxide thin film to be annealed. Then put them together into the annealing furnace at 300 °C under normal pressure with nitrogen protection. The overall thickness of the insulating isolation layer is 40 microns.

[0064] 6. Use a welding machine to weld the lead wires to the positive and negative pins of the thermopile through silver material, and the probe is fabricated.

[0065] Figure 6 (b) shows the laser power response curve of the probe in this embodiment. It can be seen from the figure that its power response time is less than 2 s, and the sensitivity reaches 0.255 mV / W. For the probe with the old structure as a comparison, its structure is as Figure 1 shown. The geometric configurations, material selections of its laser absorption layer 1, heat conduction substrate 2, and insulating isolation layer 3 are the same as those of the new structure probe in this embodiment. The thermopile layer 4 of the old structure probe uses the old design pattern as Figure 2 shown, but the thermoelectric material is the same as that of the new structure probe. The test results show that its power response time is 7 s and the sensitivity is 0.1 mV / W. Therefore, the probe fabricated by the probe design and manufacturing method proposed by the present invention has a significant improvement in the response speed and sensitivity. It can meet the requirements of real-time monitoring in high-power laser processing.

[0066] The content described in the embodiments of this specification is only a list of the implementation forms of the inventive concept and is only for illustrative purposes. The protection scope of the present invention should not be regarded as limited to the specific forms stated in this embodiment. The protection scope of the present invention also extends to equivalent technical means that those of ordinary skill in the art can think of based on the inventive concept of the present invention.

Claims

1. A thermopile laser power probe, characterized in that, The thermopile laser power probe includes a laser absorption layer, an insulating substrate, a thermopile layer, an insulating isolation layer, and a heat-conducting substrate, which are arranged in sequence from top to bottom. The thermopile layer is provided with probe leads. The laser absorption layer is on the front side of the insulating substrate, and the thermopile layer is on the back side of the insulating substrate. The heat-conducting substrate and the thermopile layer are separated by the insulating isolation layer.

2. The thermopile laser power probe according to claim 1, wherein In the thermopile layer, thermoelectric materials are periodically connected in series with each other and form a disc-shaped thermopile in a circular radial pattern.

3. The thermopile laser power probe according to claim 2, characterized in that, The hot ends of the thermopile use an inner diameter arrangement with staggered sizes.

4. A thermopile laser power probe according to any one of claims 1 to 3, characterized in that, The materials of the thermopile layer are nickel chromium / nickel copper, nickel copper / copper, or indium tin oxide / indium oxide.

5. A thermopile laser power probe according to any one of claims 1 to 3, characterized in that, The thermopile layer is provided with positive and negative pins, and the probe leads are welded to the positive and negative pins with silver material.

6. A thermopile laser power probe according to any one of claims 1 to 3, characterized in that, The laser absorption layer is deposited on the insulating substrate using silicon or silicon carbide by plasma spraying technology, and the thickness of the laser absorption layer is 50 - 200 microns.

7. A thermopile laser power probe according to any one of claims 1 to 3, characterized in that, The material of the insulating substrate layer is one of alumina ceramics, silicon carbide, and glass fiber epoxy resin composite, and the thickness is 300 - 500 microns.

8. A thermopile laser power probe according to any one of claims 1 to 3, characterized in that, The insulating isolation layer is an alumina, silica film, or thermal conductive silicone grease, and the thickness is 20 - 100 microns.

9. A thermopile laser power probe according to any one of claims 1 to 3, characterized in that, The heat-conducting substrate is in the shape of a flat thick disc, and the heat-conducting substrate is an anodized aluminum plate with a thickness of 1 - 10 mm.

10. A manufacturing method of the thermopile laser power probe as described in claim 1, characterized in that, The method includes the following steps: (1) Use an aluminum plate, a silicon carbide plate, or a glass fiber epoxy resin composite plate as the insulating substrate according to the high or low laser power threshold measured by the detector; (2) Prepare the laser absorption layer on the front side of the insulating substrate by plasma spraying; (3) Prepare the positive and negative materials of the thermopile layer on the back side of the insulating substrate with the laser absorption layer obtained in step (2) by magnetron sputtering; (4) Use an electrochemical method to make an aluminum plate into an anodized aluminum plate as the heat-conducting substrate; (5) Apply thermal conductive silicone, spin-coat alumina, or spin-coat silica according to the high or low laser power threshold measured by the detector, and prepare the insulating isolation layer on the front side of the heat-conducting substrate prepared in step (4); (6) When preparing the insulating isolation layer in the above step (5), place the insulating substrate prepared in step (3) closely on the insulating isolation layer before the insulating isolation layer is annealed and formed, and then anneal to make the thermopile layer and the insulating isolation layer form good thermal contact; (7) Lead out probe leads for the thermopile layer on the insulating substrate.

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