Wavelength conversion device and preparation method thereof

Abstract

The present invention relates to a wavelength conversion device and its preparation method. The wavelength conversion device comprises a sequentially stacked luminescent layer, a reflective film, a sintered silver layer, and a substrate. The luminescent layer converts excitation light into emitted light of different wavelengths. The reflective film, coated on the luminescent layer, reflects the emitted light. The sintered silver layer connects the luminescent layer and the substrate and contains flaky silver particles connected to each other via surface contact. The sintered silver layer is formed by sintering a silver paste containing a mixture of nano-spherical silver particles and flaky silver particles. This wavelength conversion device exhibits excellent overall thermal conductivity and high luminous efficiency.

Description

Technical Field

[0001] The present invention relates to the field of lighting and projection technology, and in particular to a wavelength conversion device and a preparation method thereof, as well as a light-emitting device using the wavelength conversion device. Background Art

[0002] With the advancement of display and lighting technologies, conventional LEDs or halogen bulbs are increasingly unable to meet the high-power and high-brightness demands of displays and lighting. Using excitation light from solid-state light sources, such as laser diodes (LDs), to excite wavelength-converting materials, a method for producing visible light of various colors is gaining increasing application in lighting and display applications. This technology offers advantages such as high efficiency, low energy consumption, low cost, and long life, making it an ideal alternative to existing white light or monochromatic light sources.

[0003] In the prior art, when a wavelength conversion device is excited by laser light source irradiation, the continuous laser irradiation makes the working environment of the wavelength conversion device very harsh. In order to withstand the continuous laser irradiation and prevent the large amount of heat generated by the light-emitting layer during the wavelength conversion process from being unable to be eliminated, causing its own temperature to rise rapidly and leading to thermal quenching, the main material of the light-emitting layer has evolved from traditional organic materials to inorganic materials such as glass and ceramics with better thermal conductivity and heat resistance.

[0004] Whether the heat conduction path from the light-emitting layer to the substrate is unobstructed is also a key factor in the overall thermal conductivity and luminous efficiency of the wavelength conversion device. Currently, the connection between the light-emitting layer and the substrate is generally made of a solder layer or a sintered silver layer. The sintered silver layer has better thermal conductivity than the solder layer, but it also has some problems, such as:

[0005] In the process of sintering the organic silver paste to form the sintered silver layer, especially in the 4*4mm 2 In the above large-size packages, the organic solvent in the middle area of ​​the organic silver paste is difficult to evaporate, and the nano-spherical silver particles are prone to shrinking too much and causing large stress during sintering, resulting in problems such as decreased adhesion of the sintered silver layer and easy falling off. At the same time, more pores are formed during the sintering process, which reduces the contact area between the nano-spherical silver particles and reduces the thermal conductivity.

[0006] Therefore, it is necessary to develop a wavelength conversion device with good overall reliability and excellent thermal conductivity and heat dissipation performance. Summary of the Invention

[0007] In response to the defects of the above-mentioned prior art, the present invention provides a wavelength conversion device and a preparation method thereof with high overall reliability, good thermal conductivity and heat dissipation performance, and high luminous efficiency. The wavelength conversion device can be suitable for continuous irradiation of high-power lasers.

[0008] The present invention provides a wavelength conversion device, comprising a luminescent layer, a reflective film, a sintered silver layer and a substrate stacked in sequence; the luminescent layer converts excitation light into outgoing light of different wavelengths; the reflective film is coated on the luminescent layer and is used to reflect the outgoing light emitted from the luminescent layer; the sintered silver layer connects the luminescent layer and the substrate, and the sintered silver layer contains flaky silver particles connected to each other by surface contact.

[0009] In the technical solution of the present invention, nano-spherical silver particles and flaky silver particles are mixed and sintered, where the nano-spherical silver particles melt and combine with the flaky silver particles to form a sintered silver layer. The large-sized flaky silver particles in the sintered silver layer improve shrinkage of the sintered silver paste, reduce sintering stress, and enhance the adhesion of the sintered silver layer. Furthermore, the large-sized flaky silver particles in the sintered silver layer are in surface contact with each other. The large-sized flaky silver particles themselves act as heat conduction channels, and the surface contact heat transfer between them significantly enhances the thermal conductivity of the sintered silver layer.

[0010] Preferably, the thermal conductivity of the sintered silver layer is 80-250 W / (m·K).

[0011] Preferably, the content of the flaky silver particles in the sintered silver layer is 2-20 wt %, preferably 5-15 wt %, more preferably 7-10 wt %.

[0012] Preferably, the light-emitting layer is a light-emitting ceramic layer. The light-emitting layer made of ceramic material has the characteristics of heat resistance and excellent thermal conductivity.

[0013] Preferably, the reflective film is a silver reflective film, which has the characteristics of being dense and having high reflectivity.

[0014] Preferably, a transition layer is provided between the luminescent ceramic layer and the silver reflective film. The transition layer enhances the bonding between the luminescent ceramic layer and the silver reflective film. The transition layer may be an Al2O3 layer or a SiO2 layer. In addition, alternating film layers of high-refractive-index dielectric films and low-refractive-index dielectric films sequentially stacked on the silver reflective film may also be provided between the luminescent ceramic layer and the silver reflective film. For example, a high-refractive-index SiO2 dielectric film and a low-refractive-index TiO2 dielectric film may be provided. The entire film layer may not only increase reflection, but also serve as a transition layer between the silver reflective film and the luminescent ceramic layer, thereby enhancing the bonding between the Ag film and the luminescent ceramic layer.

[0015] Preferably, an anti-diffusion layer is provided between the silver reflective film and the sintered silver layer. The anti-diffusion layer may be a Ni layer, which mainly prevents the diffusion of Ag atoms in the silver reflective film and ensures that the silver reflective film has sufficient reflectivity.

[0016] Preferably, the substrate may be a substrate with high load-bearing capacity and thermal conductivity, such as a metal or ceramic substrate.

[0017] In some embodiments, copper metal has excellent thermal conductivity as a substrate, while ceramic substrates such as AlN or SiC are chosen primarily to mitigate stress caused by the difference in thermal expansion coefficients between the luminescent ceramic layer and the metal substrate during thermal expansion and contraction, thereby enhancing the reliability of the wavelength conversion device. Although ceramic substrates have lower thermal conductivity than copper substrates and exhibit reduced heat dissipation capabilities, their high reliability makes them suitable for a wide range of high-precision light sources.

[0018] The present invention also provides a light-emitting device, comprising an excitation light source and the above-mentioned wavelength conversion device, and the light-emitting device is suitable for the fields of lighting and projection.

[0019] On the other hand, the present invention also provides a method for preparing a wavelength conversion device, which comprises the following steps:

[0020] Step 1: preparing a light-emitting layer and polishing the surface of the light-emitting layer;

[0021] Step 2: forming a reflective film on the polished surface of the light-emitting layer by physical sputtering or evaporation process;

[0022] Step 3: applying a silver paste containing a mixture of nano-spherical silver particles and flake silver particles on one surface of the substrate;

[0023] Step 4: stacking the side of the light-emitting layer coated with the reflective film on the surface of the substrate coated with the silver paste;

[0024] Step 5: Sinter the entire device.

[0025] Preferably, the content of flaky silver particles in the silver paste in step 3 is 2-20 wt %, preferably 5-15 wt %, more preferably 7-10 wt %.

[0026] Preferably, the luminescent layer prepared in step 1 is a luminescent ceramic layer.

[0027] Preferably, in step 2, the reflective film formed on the polished surface of the luminescent ceramic layer by physical sputtering or evaporation is a silver reflective film. Furthermore, before step 2, the process further includes forming a transition layer by physical sputtering or evaporation on the polished surface of the luminescent ceramic layer. The transition layer may be an Al2O3 layer or a SiO2 layer. Furthermore, before step 2, the process further includes forming alternating layers of low-refractive index dielectric films and high-refractive index dielectric films, such as a high-refractive index SiO2 dielectric film and a low-refractive index TiO2 dielectric film, sequentially stacked on the polished surface of the luminescent ceramic layer by physical sputtering or evaporation. Furthermore, after step 2, the process further includes forming an anti-diffusion layer by physical sputtering or evaporation on the silver reflective film. The anti-diffusion layer may be a metal Ni layer.

[0028] Preferably, the substrate in step 3 is a metal substrate or a ceramic substrate. The metal substrate may be a copper metal substrate, and the ceramic substrate may be an AlN or SiC substrate.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] To achieve efficient thermal conductivity and heat dissipation, the wavelength conversion device of the present invention utilizes a sintered silver layer with extremely high thermal conductivity to connect the light-emitting layer and the heat dissipation substrate. This sintered silver layer is formed by mixing and sintering nano-spherical silver particles and large-sized flaky silver particles, then melting the nano-spherical silver particles to combine the large-sized flaky silver particles. The large-sized flaky silver particles in the resulting sintered silver layer mitigate shrinkage of the sintered silver paste, reduce sintering stress, and enhance the adhesion of the sintered silver layer. Furthermore, the large-sized flaky silver particles in the sintered silver layer are in surface contact with each other. The large-sized silver particles themselves act as heat conduction channels, and the surface contact heat transfer between them significantly enhances the thermal conductivity of the sintered silver layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The drawings are only for purposes of illustrating particular embodiments and are not to be considered limiting of the invention.

[0032] Figure 1 Schematic diagram of the structure of the wavelength conversion device according to the first embodiment of the present invention.

[0033] Figure 2 This is a schematic structural diagram of a wavelength conversion device according to a second embodiment of the present invention.

[0034] Figure 3 This is a schematic structural diagram of a wavelength conversion device according to a third embodiment of the present invention.

[0035] Figure 4 Schematic diagram of the structure of the sintered silver layer of the present invention. DETAILED DESCRIPTION

[0036] The embodiments of the present invention are described in detail below with reference to the accompanying drawings and implementation modes.

[0037] As mentioned in the background technology, the current sintered silver is mainly used in small size packages in the device packaging, such as 4*4mm 2 Applications in areas with these dimensions are relatively rare. In large-scale packages, the organic solvent in the middle region of the sintered silver is difficult to evaporate during the sintering process, and the nanosilver particles are prone to shrinking too much during sintering, resulting in high stress, which affects the package performance (such as reduced adhesion). At the same time, more pores are formed in the sintered silver layer, reducing the contact area between the nanosilver particles and lowering thermal conductivity.

[0038] The present invention prepares a sintered silver layer with excellent performance by mixing and sintering nanosilver particles and large-sized flaky silver particles. The sintered silver layer is applied as a thermally conductive adhesive layer between the light-emitting layer and the substrate in the wavelength conversion device, thereby obtaining a wavelength conversion device with high device reliability and good thermal conductivity.

[0039] Please refer to Figure 1 The present invention provides a wavelength conversion device 100, which includes a luminescent layer 101, a reflective film 102, a sintered silver layer 103, and a substrate 104, which are stacked in sequence. The luminescent layer 101 converts excitation light into emitted light of different wavelengths. The reflective film 102 is coated on the luminescent layer 101 and reflects the emitted light from the luminescent layer 101. The sintered silver layer 103 connects the luminescent layer 101 and the substrate 104 and contains flaky silver particles connected to each other by surface contact.

[0040] In the present application, the luminescent layer 101 is typically a luminescent ceramic layer with excellent heat dissipation and heat resistance. The luminescent material, or wavelength conversion material, therein is not particularly limited in composition. For example, it can be one of an aluminate phosphor, a halophosphate phosphor, a garnet-based phosphor, or a quantum dot. In particular, when the wavelength conversion material is a YAG garnet-based phosphor, the luminescent ceramic layer 101 can be a pure YAG luminescent ceramic, or a composite luminescent ceramic obtained by mixing and firing YAG with Al2O3 powder or AlN powder. In a specific embodiment, the luminescent ceramic layer can be formed by encapsulating YAG:Ce phosphor in Al2O3. Preferably, taking into account both luminous efficiency and thermal conductivity, the thickness of the luminescent ceramic layer is approximately 50-250 μm.

[0041] Furthermore, an antireflection film 101a can be disposed on the upper surface of the light-emitting layer 101 facing the incident light. The antireflection film 101a can enhance transmittance and reduce reflection, thereby reducing the reflectivity of the incident excitation light on the upper surface of the light-emitting layer 101 and increasing its transmittance, thereby improving the light extraction efficiency of the light-emitting layer 101. In one embodiment, the thickness of the antireflection film 101a is preferably 0.01 μm to 0.1 μm.

[0042] In the present application, the reflective film 102 coated on the light-emitting layer 101 can be a silver reflective film, which is generally coated on one surface of the light-emitting layer 101 using physical sputtering or evaporation techniques. The obtained silver reflective film has the characteristics of density and high reflectivity. The thickness of the silver reflective film is preferably 10nm to 1um.

[0043] Furthermore, to enhance the bonding between the luminescent ceramic layer and the silver reflective film, a transition layer 101b can be first applied to the luminescent ceramic layer before the silver reflective film is applied. The transition layer 101b can be an Al2O3 layer or a SiO2 layer. Alternatively, alternating layers of low-refractive-index dielectric films and high-refractive-index dielectric films, such as a high-refractive-index SiO2 film and a low-refractive-index TiO2 film, can be provided between the luminescent ceramic layer and the silver reflective film. This layer can both enhance reflection and serve as a transition layer between the silver reflective film and the luminescent ceramic layer, enhancing the bonding between the Ag film and the luminescent ceramic layer. The thickness of the transition layer 101b is approximately 10-200 nm.

[0044] In addition, in order to prevent the diffusion of Ag atoms in the silver reflective film and ensure that the silver reflective film has sufficient reflectivity, an anti-diffusion layer 102a can be plated on the silver reflective film and then connected to the sintered silver layer 103; the anti-diffusion layer 102a can be a metal Ni layer with a thickness of about 10-500nm.

[0045] As for the sintered silver layer 103 of the present application, it is made by sintering nano-spherical silver particles and large-sized flaky silver particles. The curvature radius of the nano-spherical silver particles in all directions is relatively consistent, and it is easy to melt and flow during the sintering process; while the large-sized flaky silver particles are generally rectangular or flat, and their length in the length direction or flat direction is much longer than their length in the thickness direction. They are not easy to melt during the sintering process, which hinders excessive shrinkage of the material; in this way, during the sintering process, the large-sized flaky silver particles support each other, and are melted and bonded by the nano-spherical silver particles, and finally form a sintered silver layer 103 of large-sized flaky silver particles in surface contact with each other, which includes a card bridging structure. The contact area between each flaky silver particle is large, and a better heat conduction network is formed. For example, the sintered silver layer 103 can be a structure in which the flaky silver stacked between layers is bonded by melted silver, such as Figure 4 As shown, 1 represents large-sized flaky silver particles, and 2 represents the silver that melts and connects them.

[0046] The raw silver paste for the sintered silver layer is an organic silver paste mixed with nano-spherical silver particles and large-sized flaky silver particles, containing a small amount of organic solvent. The flaky silver particles are present in an amount of 2-20% by weight, preferably 5-15% by weight, and more preferably 7-10% by weight. The flaky silver particles are micrometer-sized or larger. During the sintering process, due to their larger size, the flaky silver particles have less sintering activity than the nano-spherical silver particles. When sintered at a temperature of 150°C-300°C (preferably 200°C-250°C), they are less likely to participate in the sintering process and nearly maintain their shape. The nano-spherical silver particles are sintered and melted, connecting the flaky silver particles. The content of flaky silver particles in the resulting sintered silver layer remains virtually unchanged. Compared with nano-spherical silver particles alone, the introduction of large-sized flaky silver particles can effectively solve the problems of excessive size shrinkage and high stress of nano-spherical silver particles during sintering, and improve the bonding performance of the sintered silver layer; at the same time, the flaky silver particles are in surface contact, which can greatly improve their thermal conductivity compared to the spherical point contact between nano-spherical silver particles.

[0047] As mentioned above, the amount of large-sized flaky silver particles added to the raw silver paste for the sintered silver layer is a key factor in achieving efficient thermal conductivity and tight adhesion in the resulting sintered silver layer. When the content of flaky silver particles is less than 2 wt%, the relatively small amount of flaky silver particles during the preparation of the sintered silver layer cannot effectively alleviate the excessive size shrinkage of the nanosilver particles during sintering. Furthermore, the resulting sintered silver layer lacks sufficient thermal conductivity channels, resulting in a lack of significant thermal conductivity enhancement. When the content of flaky silver particles is greater than 20 wt%, the flaky silver particles essentially do not participate in the sintering process, resulting in numerous pores between them and poor overall density in the sintered silver layer. When the content of flaky silver particles is between 2 and 20 wt%, preferably 5 to 15 wt%, and more preferably 7 to 10 wt%, the inclusion of flaky silver particles improves the bonding and thermal conductivity of the sintered silver layer. Preferably, the sintered silver layer 103 has a thermal conductivity of 80 to 250 W / (m·K) and a thickness of 2 to 30 μm.

[0048] In the present application, substrate 104 may be a metal substrate or a ceramic substrate having high thermal stability and thermal conductivity. A copper substrate is preferred for its high thermal conductivity, low price, and good strength. When a copper substrate is used, the surface of the copper substrate may be polished and then coated with a protective Au layer by evaporation or sputtering to protect the surface of the copper substrate from oxidation and corrosion. The thickness of the Au protective layer is preferably 0.01 μm to 0.1 μm.

[0049] It should be noted that copper metal has excellent thermal conductivity as substrate 104. The choice of ceramic substrates, such as AlN or SiC, is primarily due to the similar thermal expansion coefficients of the luminescent ceramic layer and the ceramic substrate, resulting in higher reliability for the wavelength conversion device. Although ceramic substrates have lower thermal conductivity than copper substrates and exhibit somewhat reduced heat dissipation capabilities, their high reliability makes them suitable for a wide range of high-precision light sources.

[0050] The present application is further described in detail below in conjunction with the preparation method and the wavelength conversion device obtained in the specific examples. The following examples are only used to further illustrate the present application and should not be understood as limiting the present application.

[0051] Example 1

[0052] like Figure 1 As shown, the wavelength conversion device 100 of this embodiment includes a luminescent ceramic layer 101 formed by Al2O3 encapsulating YAG:Ce phosphor, an Al2O3 transition layer 101b, a silver reflective film 102, a Ni diffusion prevention layer 102a, a sintered silver layer 103, and a gold-plated copper substrate 104, which are stacked in sequence. The specific preparation method of the wavelength conversion device 100 is as follows:

[0053] Step 1: Prepare a light-emitting layer and polish the surface of the light-emitting layer

[0054] After Al2O3 powder, YAG:Ce phosphor particles, MgO powder additive and Y2O3 powder additive are mixed, dried and crushed to obtain a powder, the powder is placed in a graphite mold, sintered into blocks in SPS, and then annealed, cut, ground and polished to obtain a luminescent ceramic layer 101 with a thickness of about 50um to 250um.

[0055] The ceramics processed to a certain thickness are polished on one side, with a polishing accuracy of roughness within 15nm and a mirror-like surface appearance.

[0056] Step 2: Coating of the luminescent ceramic layer

[0057] The luminescent ceramic layer 101 is placed in an electron beam evaporator. After the Al target is volatilized and reacts with O2, an Al2O3 transition layer 101b with a thickness of about 10 to 200 nm is deposited on the polished surface of the luminescent ceramic layer 101.

[0058] The above sample is then taken out and placed in a magnetron sputtering coating machine, and a layer of Ag reflective film 102 is first coated on the Al2O3 transition layer 101b. The film layer is required to be uniformly crystallized without abnormal stacking, and its thickness is about 10nm~1um, which can provide good reflection performance; then, in the magnetron sputtering coating machine, the target head is replaced, and a Ni anti-diffusion layer 102a is coated on the Ag reflective film 102. The Ni layer does not need to be too thick, and its thickness is about 10nm~500nm, which mainly plays the role of preventing the diffusion of Ag atoms.

[0059] The luminescent ceramic layer 101 after coating is cut into 5x5mm 2 size for subsequent bonding.

[0060] Step 3: Preparation of copper substrate

[0061] The copper substrate 104 is processed into an area of ​​20x20mm 2 The substrate is 3mm thick and has several screw holes on the edge of the substrate for fastening with other carrier screws. The surface of the copper substrate 104 is polished and then coated with a layer of Au by evaporation or sputtering with a thickness of about 0.01um to 0.1um.

[0062] Step 4: Sintering and bonding of the coated luminescent ceramic layer and the copper substrate

[0063] A silver paste containing a mixture of nano-spherical silver particles and large-sized flaky silver particles is brushed on the copper substrate 104. The silver paste contains a small amount of organic solvent, and the content of large-sized flaky silver particles is 10wt%. After the silver paste is brushed, one side of the luminescent ceramic layer 101 is covered on the silver paste, and then pressed with a jig, and then heated between 150°C and 300°C, preferably between 200°C and 250°C; at this time, the nano-spherical silver particles melt, but the large-sized flaky silver particles do not melt. After the nano-spherical silver particles melt, they fuse and connect the large flaky silver particles together. The sintered silver layer formed has low stress and good bonding performance. At the same time, there are fewer internal pores, and the large particles of flaky silver contact each other to form a more effective heat conduction channel, and have good thermal conductivity. The thermal conductivity of the sintered silver layer is 250W / (m·k), which has excellent thermal conductivity; the thickness of the sintered silver layer is about 2um to 30um, so that the luminescent ceramic layer 101 and the copper substrate 104 are tightly connected together, and the result is as follows. Figure 1 The wavelength conversion device 100 is shown.

[0064] Example 2

[0065] like Figure 2As shown, the wavelength conversion device 200 of this embodiment is similar to the wavelength conversion device 100 in the first embodiment, and includes an antireflection film 201a, a luminescent ceramic layer 201, an Al2O3 transition layer 201b, a silver reflective film 202, a Ni diffusion prevention layer 202a, a sintered silver layer 203, and an AlN ceramic substrate 204 stacked in sequence. The specific preparation method of the wavelength conversion device 200 is as follows:

[0066] Step 1: Prepare a light-emitting layer and polish both sides of the light-emitting layer

[0067] After Al2O3 powder, YAG:Ce phosphor particles, MgO powder additives and Y2O3 powder additives are mixed, dried and crushed to obtain a powder, which is then placed in a graphite mold and sintered into blocks in an SPS. The blocks are then annealed, cut, ground and polished to obtain a luminescent ceramic layer 201 with a thickness of about 50um to 250um.

[0068] The ceramics processed to a certain thickness are double-sided polished, with a polishing accuracy of roughness within 15nm and a mirror-like surface appearance.

[0069] Step 2: Coating of the luminescent ceramic layer

[0070] The luminescent ceramic layer 201 is placed in an electron beam evaporator. After the Al target is volatilized and reacts with O2, an Al2O3 transition layer 201b with a thickness of about 10 to 200 nm is deposited on one polished surface of the luminescent ceramic layer 201.

[0071] The above sample is then taken out and placed in a magnetron sputtering coating machine, and a layer of Ag reflective film 202 is first coated on the Al2O3 transition layer 201b. The film layer is required to be uniformly crystallized without abnormal stacking, and its thickness is about 10nm~1um, which can provide good reflection performance; then, in the magnetron sputtering coating machine, the target head is replaced, and a layer of Ni anti-diffusion layer 202a is coated on the Ag reflective film 202. The Ni layer does not need to be too thick, and its thickness is about 10nm~500nm, which mainly plays the role of preventing the diffusion of Ag atoms.

[0072] Then, an anti-reflection (AR) film 201a is deposited on the other polished surface of the luminescent ceramic layer 201 (the upper surface of the luminescent ceramic layer 201 in this embodiment) with a thickness of about 0.01-0.1 μm to improve light extraction efficiency.

[0073] The luminescent ceramic layer 101 after coating is cut into 5x5mm 2 size for subsequent bonding.

[0074] Step 3: Preparation of ceramic substrate

[0075] An AlN ceramic substrate with high thermal conductivity is selected, and its thermal conductivity is greater than 100 W / (m·K). In other embodiments, a SiC ceramic substrate may also be selected.

[0076] Process the AlN ceramic substrate into an area of ​​10x10mm 2 , the substrate with a thickness of 1 to 3 mm is ground and polished on the surface, and a copper layer is made on the surface using a copper cladding process, and then a layer of Au is plated on it by evaporation or sputtering. The Au thickness is about 0.01 to 0.1 um.

[0077] Step 4: Sintering and bonding of the coated luminescent ceramic layer and the ceramic substrate

[0078] A silver paste containing a mixture of nano-spherical silver particles and large-sized flaky silver particles is applied to an AlN ceramic substrate 204. The silver paste contains a small amount of organic solvent, and the content of large-sized flaky silver particles is 2-20% by weight. After the silver paste is applied, the silver reflective film 102 is coated on one side of the luminescent ceramic layer 201, which is then pressed with a jig. The luminescent ceramic layer 201 is then heated to a temperature between 150°C and 300°C, preferably between 200°C and 250°C. At this point, the nano-spherical silver particles melt, but the large-sized flaky silver particles do not. The melted nano-spherical silver particles fuse and connect the large flaky silver particles. The resulting sintered silver layer 203 has low stress, good adhesion, and few internal pores. The large flaky silver particles are in surface contact with each other, forming a more efficient heat conduction path, resulting in excellent thermal conductivity. The thermal conductivity of the sintered silver layer 203 is 80-250W / (m·k), which has excellent thermal conductivity. The thickness of the sintered silver layer 203 is about 2um to 30um, so that the luminescent ceramic layer 201 and the AlN ceramic substrate 204 are closely connected together to obtain Figure 2 The wavelength conversion device 200 is shown.

[0079] Compared with Example 1, Example 2 uses an AlN ceramic substrate to replace the copper substrate. Although the thermal conductivity of the AlN ceramic substrate is lower than that of the copper substrate and the heat dissipation capacity is reduced, its thermal expansion coefficient is closer to that of the luminescent ceramic layer. The obtained wavelength conversion device 200 has higher reliability and can be applied to many high-precision light sources.

[0080] Example 3

[0081] like Figure 3 As shown, the wavelength conversion device 300 of this embodiment is similar to the wavelength conversion device 100 in the first embodiment, and includes an antireflection film 301a, a luminescent ceramic layer 301, a high- and low-refractive-index alternating dielectric layer 301b, a silver reflective film 302, a Ni diffusion prevention layer 302a, a sintered silver layer 303, and a gold-plated copper substrate 304. The specific method for preparing the wavelength conversion device 300 is as follows:

[0082] Step 1: Prepare a light-emitting layer and polish both sides of the light-emitting layer

[0083] Al2O3 powder, YAG:Ce phosphor particles, MgO powder additives and Y2O3 powder additives are mixed, dried and crushed to obtain a powder, which is then placed in a graphite mold and sintered into blocks in an SPS. The blocks are then annealed, cut, ground and polished to obtain a luminescent ceramic layer 301 with a thickness of about 50 μm to 250 μm.

[0084] The ceramics processed to a certain thickness are double-sided polished, with a polishing accuracy of roughness within 15nm and a mirror-like surface appearance.

[0085] Step 2: Coating of the luminescent ceramic layer

[0086] The luminescent ceramic layer 301 is placed in an electron beam evaporator, and a film is alternately coated on one of the polished surfaces of the luminescent ceramic layer 301. The alternating film layers are a low-refractive index dielectric film 301b2 and a high-refractive index dielectric film 301b1. The low-refractive index dielectric film and the high-refractive index dielectric film are TiO2 and SiO2, respectively. This alternating dielectric film can be two layers or dozens of layers. In the third embodiment, it is two layers with an overall thickness of about 10nm to 200nm. This alternating high- and low-refractive index dielectric layer 301b can not only increase reflection, but also strengthen the bonding between the silver reflective film 302 and the luminescent ceramic layer 301.

[0087] The above sample is then taken out and placed in a magnetron sputtering coating machine, and a layer of Ag reflective film 302 is first coated on the high and low refractive index alternating coating medium layer 301b. The film layer is required to be uniformly crystallized without abnormal stacking, and its thickness is about 10nm~1um, which can provide good reflection performance; then, in the magnetron sputtering coating machine, the target head is replaced, and a Ni anti-diffusion layer 302a is coated on the Ag reflective film 302. The Ni layer does not need to be too thick, and its thickness is about 10nm~500nm, which mainly plays the role of preventing the diffusion of Ag atoms.

[0088] Then, an anti-reflection (AR) film 301a is deposited on the other polished surface of the luminescent ceramic layer 301 (the upper surface of the luminescent ceramic layer 301 in this embodiment) with a thickness of about 0.01-0.1 μm to improve light extraction efficiency.

[0089] The luminescent ceramic layer 301 after coating is cut into 5x5mm 2 size for subsequent bonding.

[0090] Step 3: Preparation of copper substrate

[0091] Process the copper substrate 304 into an area of ​​20x20mm 2The substrate is 3mm thick, with several screw holes on the edge for fastening with other carrier screws. The surface of the copper substrate 304 is polished and then coated with a layer of Au by evaporation or sputtering, with a thickness of about 0.01um to 0.5um.

[0092] Step 4: Bonding the Luminescent Ceramic Layer to the Copper Substrate

[0093] A silver paste containing a mixture of nano-spherical silver particles and large-sized flaky silver particles is applied to a copper substrate 304. The paste contains a small amount of organic solvent, and the large-sized flaky silver particles account for 2-20% by weight. After the silver paste is applied, one side of the silver-plated reflective film 302 of the luminescent ceramic layer 301 is placed over the silver paste. The layer is then pressed with a jig and heated to a temperature between 150°C and 300°C, preferably between 200°C and 250°C. The nano-spherical silver particles melt, but the large-sized flaky silver particles do not. The melted nano-spherical silver particles fuse and connect the large flaky silver particles. The resulting sintered silver layer 303 has low stress, good adhesion, and few internal pores. The large flaky silver particles are in surface contact, forming a more efficient heat conduction path, resulting in excellent thermal conductivity. The thermal conductivity of the sintered silver layer 303 is 80-250W / (m·k), which has excellent thermal conductivity. The thickness of the sintered silver layer 303 is about 2um to 30um, so that the luminescent ceramic layer 301 and the copper substrate 304 are closely connected together to obtain Figure 3 The wavelength conversion device 300 is shown.

[0094] Example 4

[0095] In this embodiment, except that the content of large-sized flaky silver particles in the sintered silver layer slurry in step 4 is 7 wt %, the remaining steps are the same as those in embodiment 1. The thermal conductivity of the sintered silver layer obtained is 220 W / (m·k).

[0096] Example 5

[0097] In this embodiment, except that the content of large-sized flaky silver particles in the sintered silver layer slurry in step 4 is 15 wt %, the remaining steps are the same as those in embodiment 1. The thermal conductivity of the sintered silver layer obtained is 200 W / (m·K).

[0098] Example 6

[0099] In this embodiment, except that the content of large-sized flaky silver particles in the sintered silver layer slurry in step 4 is 5 wt %, the remaining steps are the same as those in embodiment 1. The thermal conductivity of the sintered silver layer obtained is 150 W / (m·K).

[0100] Example 7

[0101] In this embodiment, the steps are the same as those in Example 1, except that the content of large-sized flaky silver particles in the sintered silver layer slurry in step 4 is 1 wt%. During the sintering process, the area of ​​the silver layer slurry shrinks significantly, and the thermal conductivity of the sintered silver layer is less than 80 W / (m·K).

[0102] Example 8

[0103] In step 4 of this embodiment, when the content of large-sized flaky silver particles in the sintered silver layer slurry is selected to be 22 wt%, gaps exist between the large flaky silver particles during the sintering process, and the overall density is poor, so the sintered silver layer cannot effectively bond to the light-emitting layer and the substrate.

[0104] An embodiment of the present invention further provides a light-emitting device comprising an excitation light source and a wavelength conversion device, wherein the wavelength conversion device may have the structure and functions described in the aforementioned embodiments. The light-emitting device can be used in projection systems, such as liquid crystal displays (LCDs) or digital light processor (DLP) projectors; lighting systems, such as automotive lighting or stage lighting; and the field of 3D display technology.

[0105] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0106] The above description is only an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made by using the contents of the description and drawings of the present invention, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A wavelength conversion device, characterized in that: The invention comprises a light-emitting layer, a reflective film, a sintered silver layer and a substrate which are stacked in sequence; The luminescent layer converts excitation light into emitted light of different wavelengths. The reflective film is coated on the luminescent layer and is used to reflect the emitted light emitted from the luminescent layer. The sintered silver layer connects the luminescent layer and the substrate. The sintered silver layer has a card bridge structure. The card bridge structure includes large-sized flaky silver particles and melted silver. The large-sized flaky silver particles are in surface contact with each other. The melted silver is used to bond the large-sized flaky silver particles together. The content of the flaky silver particles in the sintered silver layer is 2-20 wt %.

2. The wavelength conversion device according to claim 1, wherein: The thermal conductivity of the sintered silver layer is 80-250 W / (m·K).

3. The wavelength conversion device according to claim 1, wherein: The content of flaky silver particles in the sintered silver layer is 5-15 wt %.

4. The wavelength conversion device according to claim 1, wherein: The content of flaky silver particles in the sintered silver layer is 7-10 wt %.

5. The wavelength conversion device according to any one of claims 1 to 4, characterized in that: The luminescent layer is a luminescent ceramic layer.

6. The wavelength conversion device according to claim 5, characterized in that: The reflective film is a silver reflective film.

7. The wavelength conversion device according to claim 6, wherein: A transition layer is provided between the luminescent ceramic layer and the silver reflective film.

8. The wavelength conversion device according to claim 7, wherein: The transition layer is an Al2O3 layer or a SiO2 layer.

9. The wavelength conversion device according to claim 7, wherein: Alternating film layers of high-refractive-index dielectric films and low-refractive-index dielectric films sequentially stacked on the silver reflective film are provided between the luminescent ceramic layer and the silver reflective film.

10. The wavelength conversion device according to claim 6, wherein: An anti-diffusion layer is provided between the silver reflective film and the sintered silver layer.

11. The wavelength conversion device according to any one of claims 1 to 4, characterized in that: The substrate is a metal substrate or a ceramic substrate.

12. A light-emitting device comprising an excitation light source and the wavelength conversion device according to any one of claims 1 to 11.

13. A method for preparing a wavelength conversion device, It is characterized in that The following steps are involved: Step 1: preparing a light-emitting layer and polishing the surface of the light-emitting layer; Step 2: forming a reflective film on the polished surface of the light-emitting layer by physical sputtering or evaporation process; Step 3: applying a silver paste mixed with nano-silver particles and flake silver particles on one surface of the substrate; Step 4: stacking the side of the light-emitting layer coated with the reflective film on the surface of the substrate coated with the silver paste; Step 5: Sintering the entire device to melt the nanosilver particles and bond the flaky silver particles together to form a sintered silver layer. The sintered silver layer connects the light-emitting layer to the substrate. The sintered silver layer has a card-bridge structure, which includes large-sized flaky silver particles and melted silver. The large-sized flaky silver particles are in surface contact with each other, and the melted silver is used to bond the large-sized flaky silver particles. The content of the flaky silver particles in the sintered silver layer is 2-20 wt %.

14. The method for preparing a wavelength conversion device according to claim 13, wherein: In step 3, the content of flaky silver particles in the silver paste is 5-15 wt %.

15. The method for preparing a wavelength conversion device according to claim 13, wherein: In step 3, the content of flaky silver particles in the silver paste is 7-10 wt %.

16. The method for preparing a wavelength conversion device according to any one of claims 13 to 15, characterized in that: The luminescent layer is prepared in step 1 by mixing a ceramic matrix and luminescent material powder, and then pressing and sintering the mixed powder to obtain the luminescent ceramic layer.

17. The method for preparing a wavelength conversion device according to claim 16, wherein: In step 2, the reflective film formed on the polished surface of the luminescent ceramic layer by physical sputtering or evaporation process is a silver reflective film.

18. The method for preparing a wavelength conversion device according to claim 17, wherein: Before step 2, the method further includes forming a transition layer on the polished surface of the luminescent ceramic layer by physical sputtering or evaporation.

19. The method for preparing a wavelength conversion device according to claim 18, wherein: The transition layer is an Al2O3 layer or a SiO2 layer.

20. The method for preparing a wavelength conversion device according to claim 17, wherein: Before step 2, the method further includes forming alternating film layers of low-refractive-index dielectric films and high-refractive-index dielectric films on the polished surface of the luminescent ceramic layer by physical sputtering or evaporation.

21. The method for preparing a wavelength conversion device according to claim 17, wherein: After step 2, the method further includes forming an anti-diffusion layer on the silver reflective film by physical sputtering or evaporation.

22. The method for preparing a wavelength conversion device according to any one of claims 13 to 15, characterized in that: The substrate in step 3 is a metal substrate or a ceramic substrate.

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