Infrared radiation source and method of manufacturing the same

Abstract

This disclosure discloses an infrared radiation source and its manufacturing method, belonging to the technical field of infrared thermometers and infrared night vision devices for temperature calibration. The infrared radiation source includes: a blackbody surface source; a semiconductor cooler (TEC) disposed opposite to the blackbody surface source, with a metal layer disposed on the side of the TEC facing the blackbody surface source; and a welding layer located between the metal layer and the blackbody surface source. This disclosure, by employing a welding method between the TEC and the blackbody surface source, forms a continuous metal heat conduction channel, allowing heat to be uniformly transferred to the entire blackbody surface source. This effectively solves the problems of uneven local heating, heat conduction attenuation, and unstable temperature rise of the blackbody surface source, while also avoiding the risk of liquid overflowing into the blackbody surface source coating after long-term use.

Description

Technical Field

[0001] This disclosure belongs to the technical field of infrared thermometers and infrared night vision devices for temperature detection and calibration, specifically relating to an infrared radiation source and its manufacturing method. Background Technology

[0002] Currently, the surface of an infrared radiation source (blackbody) is typically coated with a black layer and equipped with heating and cooling mechanisms. For blackbodies in the low-temperature range (-30℃ to 100℃), a semiconductor thermoelectric cooler (TEC) is usually used to control the surface temperature. Thermally conductive silicone grease is filled between the hot and cold ends of the TEC and the contact surface of the copper blackbody as an intermediate heat conduction medium. By filling the tiny gaps at the contact surface with silicone grease and reducing the interfacial thermal resistance, heat transfer between the TEC and the blackbody surface source is achieved, completing a closed-loop temperature control system for surface heating and cooling.

[0003] However, during long-term use, thermal grease is prone to aging, leading to the following problems: 1. Decreased thermal conductivity causes changes in the heating and cooling rates of the blackbody surface source, resulting in unstable heating and cooling rates; 2. After the thermal grease ages, uneven heating occurs in the local area of ​​the blackbody surface source, affecting the temperature uniformity of the blackbody; 3. Thermal grease contains liquid components. After long-term use, the liquid may overflow onto the surface of the blackbody source, affecting the emissivity of the source and further reducing temperature uniformity. Summary of the Invention

[0004] This disclosure aims to at least solve the technical problems existing in the prior art, such as the use of thermal grease for heat conduction between the TEC and the blackbody surface source, the aging of the thermal grease after long-term use leading to a decrease in thermal conductivity, which in turn causes poor temperature uniformity of the blackbody surface source and unstable heating and cooling rates, directly affecting the calibration accuracy and stability of infrared temperature measurement equipment. The disclosure provides an infrared radiation source and its manufacturing method.

[0005] In one aspect, this disclosure provides an infrared radiation source, the infrared radiation source comprising: Blackbody surface source; A semiconductor cooler is disposed opposite to the blackbody surface source, and a metal layer is disposed on the side of the semiconductor cooler facing the blackbody surface source; The welding layer is located between the metal layer and the blackbody surface source.

[0006] Optionally, the metal layer is made of any one of molybdenum, copper, nickel, gold, titanium, and tin; and / or, The thickness of the metal layer is 2-8 μm; and / or, The number of metal layers is 3-8.

[0007] Optionally, the material of the weld layer is any one of indium, indium-based alloys, tin, and tin-based alloys; and / or, The thickness of the weld layer is 10-30 μm.

[0008] Optionally, an electroplated layer is provided on the side of the blackbody surface source facing the welding layer.

[0009] Optionally, the electroplated layer is made of tin, nickel, or copper; and / or, The thickness of the electroplated layer is 2-5 μm.

[0010] In another aspect of this disclosure, a method for producing the infrared radiation source described above is provided, the method comprising: A metal layer is formed on one surface of a semiconductor cooler; A solder layer is formed on the surface of the metal layer, and the solder layer is bonded to the electroplated layer of the blackbody surface source and then welded to form a weld layer between the metal layer and the blackbody surface source.

[0011] Optionally, forming a metal layer on the surface of the semiconductor cooler includes: A metal layer is formed on the surface of a semiconductor cooler by using DPC or DBC processes.

[0012] Optionally, forming a solder layer on the surface of the metal layer includes: A layer of solder paste is screen-printed or a layer of solder sheet is attached to the metal layer surface of the semiconductor cooler to form a solder layer.

[0013] Optionally, the method further includes: An electroplated layer is formed on one surface of the blackbody surface source, and a welding layer is formed between the metal layer and the electroplated layer of the blackbody surface source.

[0014] Optionally, an electroplated layer is formed on one surface of the blackbody surface source, comprising: Tin, nickel, or copper are electroplated onto the surface of the blackbody surface source to form an electroplated layer.

[0015] This disclosure proposes an infrared radiation source and a method for manufacturing the same, which has the following advantages over existing technologies: 1. The metal layer on the TEC surface is fused with the blackbody surface source through a welding layer, with no delamination or gaps at the interface, forming a continuous metal heat conduction channel, which effectively improves the stability of the heating and cooling rate of the blackbody surface source. 2. The metal welding layer is an integrally integrated structure, which allows heat to be evenly transferred to the entire blackbody surface source, improving the temperature uniformity of the surface source and avoiding the problem of decreased thermal conductivity caused by the aging of thermal grease. 3. The metal layer, welding layer, and blackbody surface source are metallurgically fused together, eliminating the risk of liquid overflowing into the blackbody surface source coating after long-term use, thus ensuring long-term stable and reliable operation of the surface source. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure of an infrared radiation source according to a specific embodiment of the present disclosure; Figure 2 This is a schematic diagram of the structure of an infrared radiation source according to another specific embodiment of the present disclosure; Figure 3 This is a flowchart illustrating the method for manufacturing an infrared radiation source according to a specific embodiment of this disclosure. Detailed Implementation

[0017] To enable those skilled in the art to better understand the technical solutions of this disclosure, the disclosure will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain this disclosure and represent a part of the embodiments of this disclosure, not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this disclosure without creative effort are within the protection scope of this disclosure.

[0018] like Figure 1 As shown, one aspect of this disclosure provides an infrared radiation source 100, which includes a blackbody surface source 110 and a semiconductor cooler 120. The semiconductor cooler 120 and the blackbody surface source 110 are disposed opposite to each other, and a metal layer 130 is disposed on the side of the semiconductor cooler 120 facing the blackbody surface source 110. Furthermore, a welding layer 140 is disposed between the metal layer 130 and the blackbody surface source 110.

[0019] In this embodiment, the thermoelectric cooler (TEC) and the blackbody surface source are connected by welding. The heat transfer interface is entirely made of solid metal material and does not contain any silicone oil, solvents or other liquid organic matter. There is no risk of liquid overflowing into the blackbody surface source coating during long-term use. Furthermore, this welding method forms a metallurgical fusion connection between the TEC and the blackbody surface source, which has the characteristics of high thermal conductivity and low thermal resistance. This makes the heating and cooling rate of the blackbody surface source faster, the temperature uniformity better, and the performance more stable and reliable, with a longer service life and no significant performance degradation over several years.

[0020] In some preferred embodiments, the metal layer is made of any one of molybdenum, copper, nickel, gold, titanium, and tin. This metal layer can create a continuous conductive and thermally conductive metal interface on the insulating ceramic substrate of the TEC, improving the thermal conductivity of the TEC end face, while providing a metal substrate for solder wetting and bonding, solving the problem that ceramics cannot be directly brazed, and ensuring a firm adhesion of the solder layer.

[0021] In some other preferred embodiments, the thickness of the metal layer is 3-8 μm. This range ensures a continuous and complete heat conduction path while also adapting to the thermal expansion characteristics of the ceramic substrate, balancing thermal conductivity and structural stability. If the metal layer is too thin, the thermal cross-sectional area is insufficient, resulting in high local thermal resistance. It is also prone to being melted through by the solder at high welding temperatures, leading to localized discontinuities and uneven heat transfer. If the metal layer is too thick, the difference in thermal expansion between the metal layer and the ceramic substrate increases, making it prone to peeling and delamination under repeated high and low temperature shocks, increasing material costs and processing difficulty.

[0022] In some preferred embodiments, the solder layer is made of any one of indium, indium-based alloys, tin, or tin-based alloys. For example, tin-silver-copper solder is preferred. The solder layer fuses the TEC metal layer and the blackbody surface source electroplating layer into one piece, forming a continuous, gapless metal heat-conducting channel, replacing the traditional thermal grease interlayer. Using this solid-state metal connection, which contains no organic liquid components, volatilization, delamination, or seepage will not occur during long-term high and low temperature cycling.

[0023] In some other preferred embodiments, the thickness of the solder layer is 10-30 μm. Solder layers in this range can fully fill the interface gaps to form a continuous and dense heat-conducting channel, taking into account both low thermal resistance and weld bonding strength.

[0024] In other preferred embodiments, such as Figure 2 As shown, an electroplated layer 150 is provided on the side of the blackbody surface source 110 facing the welding layer 140.

[0025] As a further preferred option, the electroplating layer is made of tin, nickel, or copper. For example, a nickel plating layer is preferred to prevent the copper substrate from oxidizing at high temperatures and to prevent the formation of an oxide layer on the copper surface at high welding temperatures. The oxide layer will significantly increase thermal resistance and cause poor soldering. At the same time, it improves the wettability between the copper substrate and the tin-silver-copper solder, allowing the solder to spread fully and reducing solder voids.

[0026] As a further preferred option, the thickness of the electroplated layer is 2-5μm. The plating layer in this range is complete without any missing plating, has low internal stress, and does not increase the interfacial thermal resistance. If the plating layer is too thin, there will be pinholes and missing plating areas, exposing the copper substrate. After high-temperature oxidation, it will produce poor soldering and local thermal conductivity failure. On the other hand, if the plating layer stress is too high, it is easy to crack and peel off during hot and cold cycles. The plating layer has poor thermal conductivity, the overall interfacial thermal resistance increases, and the heating and cooling rate is slowed down.

[0027] like Figure 3 As shown, one aspect of this disclosure provides a method for manufacturing an infrared radiation source, S200, which specifically includes the following steps S210~S220: S210. A metal layer is formed on one surface of a semiconductor cooler.

[0028] In step S210, the side of the TEC that contacts the blackbody surface source is metallized using a direct copper-plated ceramic (DPC) or copper-clad ceramic (DBC) process to form a metal layer on its surface for subsequent welding.

[0029] Specifically, when using the DPC process, a pre-treated semiconductor cooler is placed in a vacuum coating equipment through a combination of vacuum coating, photolithography, and electroplating. The deposition temperature is set to 80–150°C and the coating rate is set to 0.5–2 μm / min to form a copper metal layer.

[0030] Specifically, in the DBC process, high-purity copper foil is selected as the metal substrate and precisely bonded to the pre-treated surface of the semiconductor cooler to be processed. The bonded workpiece is placed in a nitrogen-protected sintering furnace, and the sintering temperature is set to 850–1050℃ for 30–120 minutes. Through a high-temperature metallurgical reaction, the copper foil and the cooler substrate are tightly bonded. After sintering, the workpiece is cooled in the furnace to obtain an integrated copper metal layer with high thermal conductivity and high bonding strength. Of course, other materials can also be sintered at corresponding temperatures to form corresponding metal layers, and no specific limitation is made here.

[0031] S220. A solder layer is formed on the surface of the metal layer, and the solder layer is bonded to the blackbody surface source and then welded to form a weld layer between the metal layer and the blackbody surface source.

[0032] It should be understood that since the blackbody surface source material is generally made of copper, the surface of the blackbody surface source is pretreated before soldering, and the pretreated blackbody surface source is directly bonded to the solder for soldering.

[0033] In step S220, during assembly, a layer of solder paste or a solder sheet is screen-printed on the TEC metal surface, then bonded to the blackbody surface source, and subsequently placed in a soldering oven for soldering according to the temperature profile of the solder used.

[0034] Specifically, when using screen printing for solder paste, a 200-400 mesh stainless steel screen should be selected to evenly print the lead-free tin-based solder paste onto the metal layer surface of the semiconductor cooler. The printing speed should be controlled at 20-50 mm / s, and the printing pressure should be uniform. After printing, a pre-drying treatment at 80-120℃ for 5-15 minutes should be performed to remove the flux solvent in the solder paste, avoid the generation of bubbles during soldering, and form a uniform, flat, and dense solder paste layer.

[0035] Specifically, when using surface mount solder pads, shaped tin-based solder pads can be selected and aligned and bonded to the surface of the metal layer using a precision pick-and-place machine. After placement, slight pressure is applied to fix the pads, ensuring that the solder pads and the metal layer are completely bonded together without gaps or wrinkles, forming a stable solder layer.

[0036] Of course, in other preferred embodiments, the above method further includes: first forming an electroplated layer on one surface of the blackbody source, and then forming a solder layer between the metal layer and the electroplated layer of the blackbody source to increase the soldering effect. That is, a layer of solder paste or a solder pad is screen-printed on the TEC metal surface, then bonded to the electroplated layer of the blackbody source, and subsequently soldered.

[0037] In some preferred embodiments, an electroplated layer is formed on one surface of the blackbody surface source, comprising: Tin, nickel, or copper are electroplated onto the surface of the blackbody surface source to form an electroplated layer.

[0038] Specifically, when electroplating a tin layer, an acidic tin plating system can be used, with an electroplating current density of 1–3 A / dm³. 2 The electroplating temperature is 20-40℃ and the electroplating time is 5-20 minutes. The coating is uniform and bright, which can greatly improve the wettability of solder and reduce the solder void rate.

[0039] Specifically, when electroplating a nickel layer, a neutral nickel plating system can be used, with an electroplating current density of 0.8–2.5 A / dm³. 2 The electroplating temperature is 30-50℃ and the electroplating time is 8-25 minutes. The coating has high hardness and strong oxidation resistance, and can be used as a transition layer to effectively improve the compatibility between the blackbody surface source and the solder.

[0040] Specifically, when electroplating copper layers, an acidic copper plating system can be used, with an electroplating current density of 2–4 A / dm³. 2 The electroplating temperature is 25-45℃, the electroplating time is 3-15min, the coating has excellent thermal conductivity, which can effectively reduce the interface thermal resistance and improve the overall temperature control response speed of the infrared radiation source.

[0041] It should be noted that after welding, the weld void rate between the TEC and the blackbody surface source is tested by ultrasonic testing. A void rate of less than 5% is considered acceptable. After the above steps are completed, structural assembly is performed. For example, blackbody coating is sprayed onto the surface source emitting surface and dried. A temperature sensor is installed on the blackbody surface source, and then the bracket, housing, and other structural components are assembled in sequence. The circuit board and control panel are installed, and after electrical connections are completed, the power is turned on for testing to confirm that the electrical performance is normal. After final confirmation that the assembly, testing, and inspection are qualified, the product is put into storage and ready for shipment.

[0042] This disclosure first performs surface metallization treatment on the contact surface between the TEC and the blackbody, and then welds it together with the blackbody surface source using solder. This metal welding method effectively solves the problems caused by the aging of traditional thermal grease, resulting in faster heating and cooling rates and longer service life. There is no risk of liquid overflowing into the surface source, which significantly improves the performance and reliability of the blackbody radiation source and meets the stringent requirements of high-precision infrared temperature measurement equipment for blackbody radiation sources.

[0043] The method for manufacturing an infrared radiation source will be further explained below with reference to specific embodiments: Example 1 (including metal layer and weld layer) Step 1: Select a ceramic substrate semiconductor cooler, ultrasonically clean it for 15 minutes with a mixture of anhydrous ethanol and acetone to remove surface oil and impurities, then activate it with plasma for 5 minutes, and finally dry it at 100℃ for 20 minutes to ensure that the substrate surface is clean and free of oxidation; set the vacuum deposition temperature to 110℃ and the deposition rate to 0.8μm / min, deposit a copper metal layer on the insulating surface of the semiconductor cooler to prepare a dense copper metal layer with a thickness of 6μm.

[0044] Step 2: Print 20μm tin-silver-copper solder paste on the surface of the metal layer. The printing parameters are 300 mesh screen, printing speed 35mm / s, and pre-drying at 100℃ for 10min. Step 3: After attaching the tin-silver-copper solder paste to the blackbody surface source, apply slight pressure to fix it and complete the encapsulation.

[0045] Step 4: Ultrasonic scanning was used to detect the weld void rate. The measured void rate was 3.2%, which meets the ≤5% qualification standard.

[0046] Step 5: Embed the temperature sensor in the blind hole on the side of the blackbody surface source, fill and fix it with thermally conductive adhesive, then assemble the bracket, housing and other structural components in sequence, install the circuit board and control panel, and after completing the electrical connection, power on and debug to confirm that the electrical performance is normal.

[0047] The infrared radiation source in Example 1 exhibits no delamination or performance degradation after undergoing high and low temperature cycling (-40℃ to 85℃, 100 cycles). After 1000 hours of continuous operation, it shows no interface aging or thermal decay, and its infrared radiation output remains stable.

[0048] Example 2 (including metal layer, electroplated layer and solder layer) Step 1: The semiconductor cooler is pretreated by cleaning, activation and drying. Using the DBC process, 6μm high-purity copper foil is bonded to the surface of the cooler and placed in a nitrogen-protected sintering furnace. The sintering temperature is set to 920℃ and held for 60 minutes. The furnace is then allowed to cool naturally to form a metallurgically bonded copper metal layer on the surface of the cooler. Step 2: Select a 20μm tin-based molded solder sheet, align and mount it using a precision pick-and-place machine, and apply uniform micro-pressure to remove air, ensuring that the solder sheet and the metal layer are bonded together without gaps or wrinkles; Step 3: After polishing, degreasing, and activation pretreatment of the blackbody surface source, a neutral nickel plating system is used, with a current density of 1.5 A / dm². 2 The electroplating temperature was 40℃ and the electroplating time was 15min to prepare a nickel electroplating layer with a thickness of 3μm. After electroplating, the layer was rinsed with pure water, dried with hot air at 75℃ for 10min, and then stored in a vacuum for later use.

[0049] Step 4: After attaching the solder sheet to the nickel plating layer of the blackbody surface source, apply slight pressure to fix it after mounting to complete the encapsulation.

[0050] Step 5: The weld void rate was detected by ultrasonic scanning. The measured void rate was 3.1%, which meets the ≤5% qualification standard.

[0051] Step 6: Embed the temperature sensor in the blind hole on the side of the blackbody surface source, fill and fix it with thermally conductive adhesive, then assemble the bracket, housing and other structural components in sequence, install the circuit board and control panel, and after completing the electrical connection, power on and debug to confirm that the electrical performance is normal.

[0052] After undergoing high and low temperature cycling (-40℃ to 85℃, 100 cycles), the infrared radiation source of this embodiment showed no delamination in structure and no performance degradation. After continuous power-on operation for 1000 hours, there was no interface aging or thermal decay, and the infrared radiation output remained stable.

[0053] Example 3 (including metal layer, electroplated layer and solder layer) Step 1: Pre-treat the semiconductor cooler using the DPC process, setting the deposition temperature to 100℃ and the deposition rate to 1.2μm / min, to prepare a 7μm thick high-purity copper metal layer; Step 2: Use a 250-mesh screen to print solder paste at a printing speed of 40mm / s, dry at 90℃ for 12min, and form a uniform solder layer of 25μm. Step 3: After pretreatment of the blackbody surface source, an acidic copper plating system is used, with a current density of 3A / dm². 2 Electroplating temperature 35℃, electroplating time 8min, to prepare a 4μm thick high thermal conductivity copper plating layer; clean and dry before use.

[0054] Step 4: After attaching the solder layer to the copper plating of the blackbody surface source, apply slight pressure to fix it after mounting to complete the encapsulation.

[0055] Step 5: The weld void rate was detected by ultrasonic scanning. The measured void rate was 3.1%, which meets the ≤5% qualification standard.

[0056] Step 6: Embed the temperature sensor in the blind hole on the side of the blackbody surface source, fill and fix it with thermally conductive adhesive, then assemble the bracket, housing and other structural components in sequence, install the circuit board and control panel, and after completing the electrical connection, power on and debug to confirm that the electrical performance is normal.

[0057] The infrared radiation source in this embodiment 3, after undergoing high and low temperature cycling (-40℃ to 85℃, 100 cycles), showed no delamination in structure and no performance degradation.

[0058] Comparative Example 1 Using the same semiconductor cooler and blackbody surface source substrate as in Example 1 above, without metallization or soldering, only simple cleaning and dust removal of the substrate surface is performed. Commercially available thermal grease is selected and evenly applied manually to the interface between the semiconductor cooler and the blackbody surface source, maintaining the same total thickness as the solder layer, electroplating layer, and metal layer in Example 1. After manual alignment and bonding, slight pressure is applied for fixation, and the mixture is cured at room temperature to complete the infrared radiation source assembly.

[0059] After undergoing 100 high and low temperature cycles from -40℃ to 85℃, the thermal grease in this comparative product showed signs of drying, cracking, shrinkage, and liquid overflow. Its interfacial thermal conductivity was significantly reduced, temperature uniformity deteriorated, and its service life was significantly shortened.

[0060] It is understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of this disclosure, and this disclosure is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and substance of this disclosure, and these modifications and improvements are also considered to be within the scope of protection of this disclosure.

Claims

1. An infrared radiation source, characterized in that, The infrared radiation source includes: Blackbody surface source; A semiconductor cooler is disposed opposite to the blackbody surface source, and a metal layer is disposed on the side of the semiconductor cooler facing the blackbody surface source; The welding layer is located between the metal layer and the blackbody surface source.

2. The infrared radiation source according to claim 1, characterized in that, The metal layer is made of any one of molybdenum, copper, nickel, gold, titanium, and tin; and / or, The thickness of the metal layer is 2-8 μm.

3. The infrared radiation source according to claim 1, characterized in that, The material of the weld layer is any one of indium, indium-based alloys, tin, and tin-based alloys; and / or, The thickness of the weld layer is 10-30 μm.

4. The infrared radiation source according to claim 1, characterized in that, An electroplated layer is provided on the side of the blackbody surface source facing the welding layer.

5. The infrared radiation source according to claim 4, characterized in that, The electroplated layer is made of tin, nickel, or copper; and / or, The thickness of the electroplated layer is 2-5 μm.

6. A method for manufacturing an infrared radiation source as described in any one of claims 1-5, characterized in that, The method includes: A metal layer is formed on one surface of a semiconductor cooler; A solder layer is formed on the surface of the metal layer, and the solder layer is bonded to the blackbody surface source and then soldered to form a solder layer between the metal layer and the blackbody surface source.

7. The method according to claim 6, characterized in that, The process of forming a metal layer on the surface of a semiconductor cooler includes: A metal layer is formed on the surface of a semiconductor cooler by using DPC or DBC processes.

8. The method according to claim 6, characterized in that, A solder layer is formed on the surface of the metal layer, including: A layer of solder paste is screen-printed or a layer of solder sheet is attached to the metal layer surface of the semiconductor cooler to form a solder layer.

9. The method according to claim 6, characterized in that, The method further includes: An electroplated layer is formed on one surface of the blackbody surface source, and a welding layer is formed between the metal layer and the electroplated layer of the blackbody surface source.

10. The method according to claim 9, characterized in that, An electroplated layer is formed on one surface of the blackbody surface source, comprising: Tin, nickel, or copper are electroplated onto the surface of the blackbody surface source to form an electroplated layer.

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