Transceiver smd package for gas laser sensing and transceiver assembly

Abstract

The present application relates to the technical field of gas sensor, and proposes a kind of transceiver SMD package and transceiver assembly for gas laser sensing, comprising: substrate, with insulating base material, first metal electrode and second metal electrode, the first metal electrode and the second metal electrode are arranged on the insulating base material;Laser chip, one side is arranged on the first metal electrode, and the other side is connected to the second metal electrode by metal wire;Light-transmitting plastic cover plate, cover on the laser chip;Optical antireflection film, cover on the surface of light-transmitting plastic cover plate, for increasing the light transmittance of light-transmitting plastic cover plate, the present application adopts SMD structure to package laser chip, can be directly adapted to standard surface assembly technology production line, surface plating optical antireflection film, improve manufacturing consistency, optical antireflection film can compensate the partial absorption of light-transmitting plastic cover plate in infrared wave band, improve light energy utilization, improve signal-to-noise ratio, applicable to domestic low-power consumption scene.

Description

Technical Field

[0001] This invention relates to the field of gas sensor technology, and more particularly to a transceiver SMD package and transceiver assembly for gas laser sensing. Background Technology

[0002] Semiconductor laser absorption spectroscopy (TDLAS) is an optical measurement method that uses the principle of selective absorption of laser energy by gas molecules to form an absorption spectrum in order to measure gas concentration. The working principle is as follows: a semiconductor laser emits a laser beam of a specific wavelength. When the laser beam passes through the gas being measured, the attenuation of the laser intensity is a function of the concentration of the gas. Therefore, by measuring the attenuation of the laser intensity, the concentration of the gas being measured can be analyzed and obtained.

[0003] In existing technologies, laser transceivers used for gas sensing mostly employ TO-can metal packaging structures. Publication number CN104568831B describes a photoelectric gas sensor and detection device that encapsulates the laser source and detector within the same device, incorporating a housing and a gas absorption cell structure. By designing multiple reflection optical paths to increase the optical path and improve the signal-to-noise ratio, miniaturization of the device is achieved. However, this solution still primarily uses traditional packaging processes. TO-can packaging suffers from drawbacks such as high cost, large device size, high investment in production equipment, and complex processes, hindering the widespread adoption of laser gas sensing technology in the consumer market. Furthermore, directly applying SMD (surface mount) plastic packaging technology to mid- and far-infrared laser gas sensing transceivers will face technical challenges such as severe signal attenuation due to insufficient infrared transmittance and a decreased signal-to-noise ratio.

[0004] Therefore, an SMD package and transceiver assembly for gas laser sensing are proposed to solve the technical problem of insufficient transmittance of ordinary epoxy resin encapsulation materials in the mid- and far-infrared bands, so as to facilitate the popularization and promotion of laser gas sensing equipment. Summary of the Invention

[0005] In view of this, the present invention proposes a transceiver SMD package and transceiver assembly for gas laser sensing, which solves the technical problem of insufficient transmittance of ordinary epoxy resin encapsulation materials in the mid- and far-infrared bands, so as to facilitate the popularization and promotion of laser gas sensing equipment.

[0006] This invention proposes a transceiver SMD package for gas laser sensing, comprising: The substrate has an insulating substrate, a first metal electrode, and a second metal electrode, wherein the first metal electrode and the second metal electrode are disposed on the insulating substrate. The laser chip has one side disposed on the first metal electrode and the other side connected to the second metal electrode via a metal wire; A light-transmitting plastic cover plate is placed over the laser chip; An optical antireflective film is applied to the surface of the light-transmitting plastic cover to increase the light transmittance of the cover.

[0007] Based on the above technical solution, preferably, the laser chip is a side-emitting laser chip; The transceiver SMD package also includes a 45° reflective mirror, which is disposed in the light output path of the side-emitting laser chip to allow the laser to penetrate the light-transmitting plastic cover plate perpendicularly.

[0008] Based on the above technical solution, preferably, it also includes a heating resistor, which is attached to the first metal electrode and electrically connected to the laser chip.

[0009] Based on the above technical solution, preferably, a thermistor is also provided on the substrate at the position corresponding to the laser chip, and the heating resistor, the thermistor and the external temperature control circuit form a closed-loop feedback loop.

[0010] Based on the above technical solution, preferably, the material of the optical antireflection film is silicon nitride and / or silicon dioxide, and the thickness of the optical antireflection film is 0.2 to 0.3 times the wavelength of the emitted light.

[0011] Based on the above technical solution, preferably, the light-transmitting plastic cover is made of epoxy resin with added light-transmitting modified filler; the mass fraction of the light-transmitting modified filler in the epoxy resin is 2% to 5%.

[0012] Based on the above technical solution, preferably, the light-transmitting modified filler is an infrared absorbing material in red dye or titanium dioxide nanoparticles, and the surface roughness of the light-transmitting plastic cover is less than 0.1 μm.

[0013] Based on the above technical solution, preferably, a sealed cavity is formed between the light-transmitting plastic cover and the substrate, and the sealed cavity is filled with nitrogen or kept in a vacuum state.

[0014] Based on the above technical solution, preferably, the laser wavelength generated by the laser chip is in the range of 1650nm~2600nm.

[0015] On the other hand, the present invention also provides a gas laser sensing transceiver assembly, comprising: a base and two aforementioned transceiver SMD packages, wherein the two transceiver SMD packages are horizontally spaced on the base and maintain a spacing of 3 to 6 cm.

[0016] The present invention provides an SMD package and transceiver assembly for gas laser sensing, which have the following advantages compared with the prior art: 1. It adopts an SMD structure instead of the traditional TO-can packaging, which can be directly adapted to standard surface mount technology production lines, significantly reducing manufacturing costs and equipment investment; and it is coated with an optical anti-reflection film on the surface to improve manufacturing consistency. The optical anti-reflection film can compensate for part of the absorption of light-transmitting plastic cover in the infrared band, improve light energy utilization, and improve the signal-to-noise ratio, making it suitable for low-power home scenarios. 2. The heating resistor is closely integrated with the laser chip to reduce the thermal resistance between them. When the ambient temperature is too low or a stable emission wavelength is required, the heating resistor is energized and generates heat, keeping the laser chip at the set temperature. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the structure of a transceiver SMD package for gas laser sensing according to the present invention; Figure 2 This is another structural diagram of a transceiver SMD package for gas laser sensing according to the present invention; Figure 3 This is a structural diagram of a transceiver assembly for gas laser sensing according to the present invention.

[0019] Explanation of reference numerals in the attached drawings: 1. Substrate; 11. Insulating substrate; 12. First metal electrode; 13. Second metal electrode; 101. 45° reflective mirror; 2. Laser chip; 3. Transparent plastic cover plate; 4. Optical antireflective film; 5. Heating resistor; 6. Base. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0021] In the description of the embodiments of the present invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of the present invention based on the specific circumstances.

[0022] In the description of the embodiments of the present invention, it should be noted that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of the present invention.

[0023] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0024] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0025] The following disclosure provides numerous different embodiments or examples for implementing various structures of the invention. To simplify the disclosure, specific examples of components and arrangements are described below. These are merely examples and are not intended to limit the invention. Furthermore, reference numerals and / or letters may be repeated in different examples. Such repetition is for simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed. Additionally, examples of various specific processes and materials are provided in this invention; however, those skilled in the art will recognize the applicability of other processes and / or the use of other materials.

[0026] The technical solution was explained. The existing solution still mainly uses traditional packaging technology. The TO-can packaging solution has shortcomings such as high cost, large device size, large investment in production equipment and complex process, which restricts the popularization and promotion of laser gas sensing technology in the home market. However, if SMD plastic packaging technology is directly transplanted to mid- and far-infrared laser gas sensing transceivers, it will face technical problems such as severe signal attenuation and reduced signal-to-noise ratio due to insufficient infrared transmittance.

[0027] In view of this, such as Figure 1 As shown, the present invention provides a transceiver SMD package for gas laser sensing.

[0028] The substrate 1 is composed of an insulating substrate 11 and a first metal electrode 12 and a second metal electrode 13 disposed thereon. The insulating substrate 11 can be selected from an epoxy glass cloth laminate, a ceramic substrate or a thermosetting resin substrate. The first metal electrode 12 and the second metal electrode 13 are intermittently disposed on different sides of the insulating substrate 11. The first metal electrode 12 and the second metal electrode 13 can be designed as standard SMD pads for surface mounting.

[0029] Laser chip 2 is a vertical-cavity surface-emitting laser (VCSEL) chip. The back side of laser chip 2 is attached to the first metal electrode 12 using conductive silver paste or eutectic solder, and the front side of laser chip 2 is bonded to the second metal electrode 13 via metal wires to achieve electrical connection. The wavelength range emitted by laser chip 2 covers the mid-far infrared range of 1650nm to 2600nm, and is suitable for the absorption peaks of methane, carbon monoxide, or carbon dioxide.

[0030] The light-transparent plastic cover plate 3 is made by injection molding or mold forming process and covers and encapsulates the laser chip 2.

[0031] An optical antireflective film 4 is deposited on the upper surface of a light-transmitting plastic cover plate 3 through physical vapor deposition or plasma-enhanced chemical vapor deposition processes, thereby increasing the light transmittance of the light-transmitting plastic cover plate 3.

[0032] Using an SMD structure instead of the traditional TO-can packaging, it can be directly adapted to standard surface mount technology production lines, significantly reducing manufacturing costs and equipment investment; and it is coated with an optical anti-reflection film 4 on the surface to improve manufacturing consistency. The optical anti-reflection film 4 can compensate for part of the absorption of light-transmitting plastic cover in the infrared band, improve light energy utilization, and enhance the signal-to-noise ratio, making it suitable for low-power home scenarios.

[0033] It is important to note that in order to promote the use of laser gas sensors in home environments with lower profit margins and to automate mass production using surface mount technology, while maintaining low light loss and high transmittance of the translucent plastic cover in the mid- and far-infrared bands, the investment cost of production equipment and the material cost can be effectively reduced.

[0034] like Figure 1 As shown, laser chip 2 is a side-emitting laser chip, and the laser is mid- to far-infrared light with a wavelength range of 1650nm to 2600nm. The transceiver SMD package also includes a 45° reflective mirror 101, which is disposed on the light output path of the side-emitting laser chip to allow the laser to penetrate the light-transmitting plastic cover plate 3 vertically.

[0035] The 45° reflective mirror 101 can be implemented as an independent microprism, using single-crystal silicon as the substrate material, adhered to the substrate 1 and located in the light output path of the laser chip 2; and a highly reflective metal layer is deposited; the horizontal laser beam emitted by the laser chip 2 is reflected by the 45° reflective mirror 101 and turned into a vertical direction, penetrating the light-transmitting plastic cover plate 3 vertically; the setting of the 45° reflective mirror 101 can solve the problem that traditional edge-emitting laser chips are difficult to align with the optical path of the external gas chamber in a flat SMD package.

[0036] like Figure 2 As shown, in another embodiment of the present invention, the laser chip 2 can also be replaced with a planar laser chip (VCSEL), and the wavelength range of the laser is also 1650nm~2600nm. In this case, the 45° reflecting mirror 101 is not required, but the heating resistor temperature control and hermetically sealed packaging structure can still be retained, and the laser beam emitted by the laser chip 2 can penetrate the light-transmitting plastic cover plate 3.

[0037] like Figure 1 As shown, the aforementioned transceiver SMD package for gas laser sensing also includes a heating resistor 5, which is attached to the first metal electrode 12 and electrically connected to the laser chip 2. The heating resistor 5 and the laser chip 2 are connected in series via internal wires and jointly led out to the second metal electrode 13 or an additional separate temperature control electrode.

[0038] The heating resistor 5 is closely integrated with the laser chip 2 to reduce the overall size between them. When the ambient temperature is too low or a stable emission wavelength is required, the heating resistor 5 is energized and heats up, maintaining the laser chip 2 at the set temperature. The power and resistance of the heating resistor 5 are pre-designed according to home use scenarios.

[0039] The optical antireflective coating 4 is made of silicon nitride and / or silicon dioxide. The thickness of the optical antireflective coating 4 is 0.2 to 0.3 times the wavelength of the emitted light. The optical antireflective coating 4 can reduce the infrared reflectivity of the transparent plastic cover plate 3. For a single-layer optical antireflective coating 4, the optimal physical thickness is approximately λ / 4 (i.e., 0.25λ). For example, when λ = 1650 nm, the corresponding physical thickness is approximately 412.5 nm.

[0040] The optical antireflective coating 4 can be deposited by electron beam evaporation or magnetron sputtering. After the transparent plastic cover plate 3 is formed and cleaned, the coating temperature is lower than the glass transition temperature of the plastic substrate to avoid thermal deformation.

[0041] A transition layer is composited between the light-transmitting plastic cover plate 3 and the optical antireflective film 4. The composition of the light-transmitting plastic cover plate 3 and the optical antireflective film 4 effectively transitions from the organic / inorganic interface. The introduction of the transition layer ensures that the refractive index of the film interface changes continuously without abrupt changes. The transition layer can be made of a fluorinated polymer with low infrared absorption, such as PVDF-HFP, a copolymer of vinylidene fluoride and hexafluoropropylene. It is added between the light-transmitting plastic cover plate 3 and the optical antireflective film 4 using a dip-coating or spray-coating process.

[0042] The light-transmitting plastic cover 3 is made of epoxy resin with added light-transmitting modified filler; the mass fraction of the light-transmitting modified filler in the epoxy resin is 2% to 5%.

[0043] While maintaining the low cost and ease of molding of plastic encapsulation, the light transmittance of the light-transmitting plastic cover plate to infrared light is maintained at over 85% through the action of light-transmitting modified filler, significantly improving the mid- and far-infrared transmittance; the modified formula has simple components, does not increase the complexity of the process, and is compatible with existing SMD molding processes.

[0044] The light-transmitting modified filler is an infrared absorbing material in red dye or titanium dioxide nanoparticles, and the surface roughness of the light-transmitting plastic cover plate 3 is less than 0.1 μm.

[0045] Red dye fillers can correct the "depression" caused by intrinsic absorption in the mid-infrared band of plastics, making the transmission spectrum more stable and enhancing wavelength locking reliability; titanium dioxide nanoparticles can improve the overall light transmission performance of plastic substrates through scattering mechanism and refractive index matching; a surface roughness of less than 0.1μm ensures the uniformity and adhesion of the antireflective coating when coating the antireflective film, avoiding light energy loss caused by scattering.

[0046] A thermistor is also provided on the substrate 1 at the position corresponding to the laser chip 2. The heating resistor 5, the thermistor, and the external temperature control circuit form a closed-loop feedback circuit.

[0047] A thermistor collects the temperature near the laser chip 2 in real time. The temperature control circuit reads the temperature value and compares it with the target set value. If the actual temperature is too low, the driving current or duty cycle of the heating resistor 5 is increased to raise the temperature until it stabilizes near the target value. If the temperature is too high, heating is stopped or the current is reduced. This circuit performs PID adjustment periodically. The plastic SMD package itself has poor thermal conductivity and is easily affected by ambient temperature fluctuations. The closed-loop temperature control can actively stabilize the operating temperature of the laser chip and ensure that the emission wavelength is aligned with the gas absorption peak.

[0048] A sealed cavity is formed between the light-transmitting plastic cover plate 3 and the substrate 1. The sealed cavity is filled with dry nitrogen or kept in a vacuum. Plastic resin materials have a certain water vapor permeability, and long-term exposure to high humidity environments may lead to corrosion of the laser chip's metal electrodes or performance drift. Hermetically sealed nitrogen filling or vacuum encapsulation can significantly delay this aging process.

[0049] The working principle of the transceiver SMD package for gas laser sensing is as follows: The laser chip 2 stably emits 1650nm~2600nm mid-far infrared laser under the adjustment of the heating resistor 5 and the thermistor; if it is a side-emitting chip, the laser is deflected to a vertical direction by the 45° reflecting mirror 101; if it is a VCSEL chip, it is emitted directly vertically. After the laser passes through the light-transmitting plastic cover plate 3 coated with optical anti-reflection film 4, it enters the opposite package on the base (6) and passes through the gas to be measured. There is a detection gap of 3~6cm between the two SMD packages. The methane or carbon monoxide gas to be measured selectively absorbs the laser of a specific wavelength. The photoelectric chip in the receiving package converts the attenuated light signal into an electrical signal. The external circuit analyzes the change in light intensity, thereby retrieving the gas concentration.

[0050] like Figure 3 As shown, the present invention also provides a gas laser sensing transceiver assembly comprising: a base 6 and two aforementioned transceiver SMD packages, wherein the two transceiver SMD packages are horizontally spaced on the base 6 and maintain a spacing of 3 to 6 cm.

[0051] The horizontal gap between the two transceiver SMD packages forms an open gas absorption cell. The gas to be measured can enter this gap through natural diffusion or driven by a micro-fan. The mid-to-far-infrared laser (wavelength between 1650nm and 2600nm) emitted by the laser emitter passes through the gas in this gap and is received by the photoelectric receiving chip at the receiver. Integrating two SMD packages on the base 6 constitutes a low-cost, calibration-free gas detection component with optimized signal-to-noise ratio.

[0052] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A transceiver SMD package for gas laser sensing, characterized in that, include: The substrate (1) has an insulating substrate (11), a first metal electrode (12) and a second metal electrode (13), wherein the first metal electrode (12) and the second metal electrode (13) are disposed on the insulating substrate (11); The laser chip (2) is disposed on one side of the first metal electrode (12) and connected to the second metal electrode (12) through a metal wire on the other side. A light-transmitting plastic cover plate (3) is placed over the laser chip (2); An optical antireflective film (4) is applied to the surface of the light-transmitting plastic cover plate (3) to increase the light transmittance of the light-transmitting plastic cover plate (3).

2. The transceiver SMD package for gas laser sensing as described in claim 1, characterized in that, The laser chip (2) is a side-emitting laser chip; The transceiver SMD package also includes a 45° reflective mirror (101), which is disposed on the light output path of the side-emitting laser chip to allow the laser to penetrate the light-transmitting plastic cover plate (3) vertically.

3. The transceiver SMD package for gas laser sensing as described in claim 2, characterized in that, It also includes a heating resistor (5), which is attached to the first metal electrode (12) and electrically connected to the laser chip (2).

4. The transceiver SMD package for gas laser sensing as described in claim 3, characterized in that, A thermistor is also provided on the substrate (1) at the position corresponding to the laser chip (2). The heating resistor (5), the thermistor, and the external temperature control circuit form a closed-loop feedback circuit.

5. The transceiver SMD package for gas laser sensing as described in claim 1, characterized in that, The material of the optical antireflective film (4) is silicon nitride and / or silicon dioxide, and the thickness of the optical antireflective film (4) is 0.2 to 0.3 times the wavelength of the emitted light.

6. The transceiver SMD package for gas laser sensing as described in claim 1, characterized in that, The light-transmitting plastic cover (3) is made of epoxy resin with added light-transmitting modified filler; the mass fraction of the light-transmitting modified filler in the epoxy resin is 2% to 5%.

7. The transceiver SMD package for gas laser sensing as described in claim 6, characterized in that, The light-transmitting modified filler is an infrared absorbing material in red dye or titanium dioxide nanoparticles, and the surface roughness of the light-transmitting plastic cover (3) is less than 0.1 μm.

8. The transceiver SMD package for gas laser sensing as described in claim 1, characterized in that, A sealed cavity is formed between the light-transmitting plastic cover plate (3) and the substrate (1), and the sealed cavity is filled with nitrogen or kept in a vacuum state.

9. The transceiver SMD package for gas laser sensing as described in claim 1, characterized in that, The laser wavelength range generated by the laser chip (2) is 1650nm~2600nm.

10. A gas laser sensing transceiver assembly, characterized in that, include: The base (6) and two transceiver SMD packages as described in any one of claims 1 to 9 are arranged horizontally at intervals on the base (6) and maintain a distance of 3 to 6 cm.

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