Light-emitting diode package structure

Abstract

A light-emitting diode (LED) package structure is provided. The LED package structure includes an LED wafer, a wavelength conversion layer, a dielectric layer, a diffuse Bragg reflector layer, conductive elements, and a reflective layer. The LED wafer includes a light-emitting surface and a plurality of side surfaces. The wavelength conversion layer is disposed on the light-emitting surface of the LED wafer and includes a plurality of side surfaces. The dielectric layer covers the side surfaces of the LED wafer, and the diffuse Bragg reflector layer is disposed beneath the LED wafer. The conductive elements are disposed beneath the diffuse Bragg reflector layer and electrically connected to the LED wafer through the diffuse Bragg reflector layer. The reflective layer is disposed on the side surface of the wavelength conversion layer.

Description

Technical Field

[0001] This disclosure relates to light-emitting diode (LED) packaging structures, and more particularly to LED packaging structures including reflective layers. Prior Technology

[0002] Light-emitting devices include light-emitting elements arranged in various ways. However, light-emitting elements may be excited by adjacent light-emitting elements, causing crosstalk between them. This makes it difficult to control the light emitted by the desired light-emitting elements in the device. Additionally, there may be a problem of light leakage due to excessive lateral emission from the light-emitting elements. Summary of the Invention

[0003] The disclosed light-emitting diode (LED) packaging structure includes an LED wafer, a wavelength conversion layer, a dielectric layer, a diffuse Bragg reflector layer, a conductive element, and a reflective layer. The LED wafer includes a light-emitting surface and a plurality of side surfaces. The wavelength conversion layer is disposed on the light-emitting surface of the LED wafer and includes a plurality of side surfaces. The dielectric layer covers the side surfaces of the LED wafer, and the diffuse Bragg reflector layer is disposed beneath the LED wafer. The conductive element is disposed beneath the diffuse Bragg reflector layer and electrically connected to the LED wafer through the diffuse Bragg reflector layer. The reflective layer is disposed on the side surface of the wavelength conversion layer.

[0004] The light-emitting diode (LED) packaging structure disclosed herein can be applied to various types of electronic devices. To make the features and advantages of this disclosure more apparent and understandable, various embodiments are described below in detail with reference to the accompanying drawings. Simple Explanation of the Diagram

[0005] The following detailed description, in conjunction with the accompanying drawings, will provide a better understanding of the views expressed in the disclosed embodiments. It is worth noting that, according to industry standard practice, some features may not be drawn to scale. In fact, for clarity of description, the dimensions of different features may be increased or decreased. Figure 1 is a cross-sectional schematic diagram of the light-emitting diode packaging structure of some embodiments disclosed herein. Figures 2 through 19 are cross-sectional schematic diagrams showing the light-emitting diode packaging structure at various stages of the formation method, representing some embodiments of this disclosure. Figure 20 is a cross-sectional schematic diagram of the light-emitting diode packaging structure of some embodiments disclosed herein. Figure 21 is a cross-sectional schematic diagram of the light-emitting diode packaging structure of some embodiments disclosed herein. Figure 22 is a cross-sectional schematic diagram of the light-emitting diode packaging structure of some embodiments disclosed herein. Figure 23 is a cross-sectional schematic diagram of the light-emitting diode packaging structure of some embodiments disclosed herein. Implementation

[0006] The following provides a detailed description of the packaging structures of various embodiments of this disclosure. It should be understood that the following description provides many different embodiments for implementing different forms of some embodiments of this disclosure. The specific elements and arrangements described below are merely for simple and clear description of some embodiments of this disclosure. Of course, these are only examples and not limitations of this disclosure. Furthermore, similar and / or corresponding element symbols may be used in different embodiments to identify similar and / or corresponding elements for clear description of this disclosure. However, the use of these similar and / or corresponding element symbols is only for simple and clear description of some embodiments of this disclosure and does not represent any relationship between the different embodiments and / or structures discussed.

[0007] It should be understood that relative terms, such as "lower," "bottom," "higher," or "top," may be used in various embodiments to describe the relative relationship of one element to another in the diagram. It is understood that if the device in the diagram is flipped upside down, the element depicted on the "lower" side will become the element on the "higher" side. The embodiments disclosed herein should be understood in conjunction with the drawings, which are also considered part of the disclosure. Furthermore, when a first element is mentioned as being on or over a second element, this may include situations where the first and second elements are in direct contact, or situations where the first and second elements are not in direct contact, i.e., there may be one or more other elements spaced between the first and second elements. However, if the first element is directly on the second element, it indicates that the first and second elements are in direct contact. Furthermore, it should be understood that the ordinal numbers used in the specification and claims, such as "first" and "second," to modify elements are not intended to imply any prior ordinal number for that element (or those elements), nor to indicate the order of one element with another, or the order of manufacturing processes. The use of these ordinal numbers is solely to clearly distinguish one named element from another with the same name. The claims and specification may not use the same terminology; for example, the first element in the specification may be the second element in the claims.

[0008] In this text, the terms "approximately," "about," and "substantially" generally indicate that a given value or range is within 10%, 5%, 3%, 2%, 1%, or 0.5%. The given quantities are approximate; that is, without specific mention of "approximately," "about," or "substantially," these meanings are implied. The phrase "the range is between the first value and the second value" or "the first value ~ the second value" indicates that the range includes the first value, the second value, and other values ​​in between. Furthermore, any two values ​​or directions used for comparison may have a certain degree of error. If the first value equals the second value, it implies an error between the first and second values ​​that may be within approximately 10%, 5%, 3%, 2%, 1%, or 0.5%. If the first direction is perpendicular to the second direction, the angle between the first and second directions can be between 80 and 100 degrees. If the first direction is parallel to the second direction, the angle between the first and second directions can be between 0 and 10 degrees.

[0009] In this disclosure, the directions are not limited to the three axes of a Cartesian coordinate system such as the X, Y, and Z axes, and can be interpreted in a broader sense. For example, the X, Y, and Z axes may be perpendicular to each other, or may represent different directions that are not perpendicular to each other, but are not limited thereto. For ease of explanation, in the following text, the X-axis direction is the first direction D1 (width direction), the Y-axis direction is the second direction D2 (length direction), and the Z-axis direction is the third direction D3 (thickness or depth direction). In some embodiments, the top view described herein is a cross-sectional view of the XY plane, and the cross-sectional view described herein is a cross-sectional view of the XZ plane. In some embodiments, the third direction D3 may be the normal direction of the light-emitting element. In some embodiments, the phrase "a gap between one element and another element" means that the gap exists between the first boundary of one element and the second boundary of another element, and the second boundary may be the boundary closest to the first boundary.

[0010] Referring to Figure 1, which is a cross-sectional schematic diagram of a light-emitting diode (LED) packaging structure according to some embodiments of the present disclosure. As shown in Figure 1, an LED packaging structure 1 includes an LED chip 13, a wavelength conversion layer 90, a dielectric layer 14, a distributed Bragg reflection (DBR) layer 16, a conductive element 70, and a reflective layer 32.

[0011] As shown in Figure 1, in some embodiments, the light-emitting diode wafer 13 includes a light-emitting surface 13A, an electrode surface 13B, a plurality of side surfaces 13C, and an electrode 130. The electrode surface 13B and the light-emitting surface 13A are opposite to each other, and the side surfaces 13C are located between the electrode surface 13B and the light-emitting surface 13A. In some embodiments, the light-emitting diode wafer 13 does not have a growth substrate.

[0012] As shown in Figure 1, in some embodiments, a wavelength conversion layer 90 is disposed on the light-emitting surface 13A of the light-emitting diode chip 13. The wavelength conversion layer 90 includes an upper surface 90T and a plurality of side surfaces 90S. In some embodiments, a third adhesive layer 12C is provided between the wavelength conversion layer 90 and the light-emitting surface 13A of the light-emitting diode chip 13. That is, the wavelength conversion layer 90 can be attached to the light-emitting surface 13A of the light-emitting diode chip 13 by means of the third adhesive layer 12C.

[0013] As shown in Figure 1, in some embodiments, a dielectric layer 14 covers the side surface 13C of the light-emitting diode wafer 13, and the dielectric layer 14 is disposed on the dispersed Bragg reflector layer 16. In some embodiments, the dielectric layer 14 surrounds the side surface 13C of the light-emitting diode wafer 13. In some embodiments, the dispersed Bragg reflector layer 16 is disposed under the light-emitting diode wafer 13, and the electrode surface 13B of the light-emitting diode wafer 13 contacts the dispersed Bragg reflector layer 16.

[0014] As shown in Figure 1, in some embodiments, the conductive element 70 is disposed under the dispersed Bragg reflector layer 16 and is electrically connected to the electrodes 130 of the light-emitting diode chip 13 through the dispersed Bragg reflector layer 16. The conductive element 70 may be a metal pillar.

[0015] As shown in Figure 1, in some embodiments, the reflective layer 32 is disposed on the side surface 90S of the wavelength conversion layer 90. In some embodiments, the reflective layer 32 may be L-shaped and inverse L-shaped.

[0016] As shown in Figure 1, in some embodiments, the light-emitting diode packaging structure 1 further includes a protective layer 50 disposed on the reflective layer 32. In some embodiments, the protective layer 50 has an upper surface 50T, an inner surface 50I, a lower surface 50B, and an outer surface 50A, wherein the reflective layer 32 is disposed on the lower surface 50B and the inner surface 50I of the protective layer 50, and exposes the upper surface 50T and the outer surface 50A of the protective layer 50. The protective layer 50 can protect the reflective layer 32 and prevent the reflective layer 32 from being damaged by external impact.

[0017] As shown in Figure 1, in some embodiments, the light-emitting diode encapsulation structure 1 further includes a filler material layer 40 disposed under the dispersed Bragg reflector layer 16 and surrounding the conductive element 70.

[0018] As shown in Figure 1, the light-emitting diode (LED) package structure 1 further includes a conductive pad 80. In some embodiments, the conductive pad 80 is electrically connected to a conductive element 70. In some embodiments, the conductive pad 80 is made of a conductive material. In some embodiments, the conductive pad 80 is electrically connected to an external circuit outside the LED package structure 1. Therefore, external current can be applied to the LED chip 13 via the conductive pad 80, the conductive element 70, and the electrode 130. In some embodiments, the LED package structure 1 is a cube or cuboid.

[0019] Referring to Figures 2 through 19, which are schematic cross-sectional views of the light-emitting diode packaging structure 1 at various stages of the formation method according to some embodiments of the present disclosure.

[0020] As shown in Figure 2, a first substrate 10 is provided. In some embodiments, the first substrate 10 may be or may include: group III-V compounds, such as gallium nitride (GaN), gallium arsenide (GaAs), gallium phosphide (GaP), aluminum gallium arsenide (AlGaAs), aluminum nitride (AlN), and aluminum gallium nitride (AlGaN); group IV elements or group IV compounds, such as silicon (Si), silicon carbide (SiC), and diamond (C); other suitable materials; or combinations thereof, but this disclosure is not limited thereto. In some embodiments, the first substrate 10 may be or may include glass, quartz, sapphire, ceramic, other suitable materials, or combinations thereof, but this disclosure is not limited thereto. In some embodiments, the first substrate 10 may be or may include polyimide (PI), polycarbonate (PC), polyethylene terephthalate (PET), polypropylene (PP), other suitable materials, or combinations thereof, but this disclosure is not limited thereto. In some embodiments, the first substrate 10 may be or may include a flexible substrate, a rigid substrate, or a combination thereof, but this disclosure is not limited thereto. For example, the first substrate 10 may be a sapphire substrate. In some embodiments, the first substrate 10 may be or may include a light-transmitting substrate, a semi-light-transmitting substrate, or an opaque substrate, but this disclosure is not limited thereto.

[0021] As shown in Figure 2, following the steps described above, a first debond layer 11 is applied to the first substrate 10. In some embodiments, the first debond layer 11 may be or may include laser-release adhesive, UV-release adhesive, thermal-release adhesive, other suitable materials, or combinations thereof, but this disclosure is not limited thereto. In some embodiments, the first debond layer 11 completely covers the upper surface of the first substrate 10, but this disclosure is not limited thereto. In other embodiments, the first debond layer 11 may partially cover the upper surface of the first substrate 10. For example, the first debond layer 11 may partially cover the upper surface of the first substrate 10 corresponding to the position of the light-emitting diode wafer 13 to be subsequently applied.

[0022] As shown in Figure 2, in some embodiments, a plurality of light-emitting diode (LED) chips 13 are arranged side-by-side on a first release layer 11 on a first substrate 10. It is worth noting that, for clarity, Figure 2 only depicts one LED chip 13 on the first release layer 11 of the first substrate 10. In some embodiments, the LED chip 13 may be or may include a thin-film flip-chip LED or a flip-chip LED. A thin-film flip-chip LED is an LED chip 13 without a growth substrate, i.e., the LED chip 13 does not have a growth substrate.

[0023] In some embodiments, light-emitting diode (LED) wafers 13 are first disposed on an adhesive layer of a temporary substrate (not shown), and the adhesive layer and the temporary substrate thereon are removed by a laser transfer process or a similar process, thereby transferring a plurality of LED wafers 13 onto a first release layer 11, but this disclosure is not limited thereto. In some embodiments, the LED wafers 13 may be transferred onto the first release layer 11 by a pick-up process.

[0024] Referring again to Figure 2, in some embodiments, a first adhesive layer 12A may be provided between the light-emitting diode wafer 13 and the first release layer 11. In some embodiments, the first adhesive layer 12A may be first provided on the first release layer 11, and the light-emitting diode wafer 13 may be attached to the first adhesive layer 12A. In some embodiments, alternatively, the first adhesive layer 12A may be first provided on the light-emitting diode wafer 13, and the light-emitting diode wafer 13 may be transferred to the first release layer 11 together with the first adhesive layer 12A.

[0025] In some embodiments, the first adhesive layer 12A may be or may include polyimide (PI), polybenzoxazole (PBO), epoxy resin, transparent silicone resin, other suitable materials or combinations thereof, but this disclosure is not limited thereto.

[0026] Referring again to Figure 2, in some embodiments, the light-emitting diode (LED) chip 13 has a light-emitting surface 13A, an electrode surface 13B, and a plurality of side surfaces 13C. The electrode surface 13B and the light-emitting surface 13A are opposite to each other, and the plurality of side surfaces 13C are located between the electrode surface 13B and the light-emitting surface 13A. Here, the electrode surface 13B refers to the surface of the LED chip 13 itself used to mount the electrode 130, not the surface of the electrode 130. The light-emitting surface 13A is configured to generate a light source. As shown in Figure 2, the light-emitting surface 13A of the LED chip 13 faces the first substrate 10, while the electrode surface 13B faces away from the first substrate 10. That is, the light-emitting surface 13A of the LED chip 13 faces and contacts the first adhesive layer 12A.

[0027] As shown in Figure 3, following the steps described above, a dielectric layer 14 is disposed on the side surface 13C of the light-emitting diode (LED) wafer 13. The dielectric layer 14 directly contacts the side surface 13C of the LED wafer 13 and exposes the electrodes 130 and electrode surfaces 13B of the LED wafer 13; that is, the dielectric layer 14 covers the side surface of the LED wafer. In some embodiments, the dielectric layer 14 continuously and uninterruptedly surrounds the side surface 13C of the LED wafer 13. The dielectric layer 14 may be or may include epoxy resin, polyimide (PI), polybenzoxazole (PBO), silicone, silicon dioxide, or silicon nitride. In some embodiments, the dielectric layer 14 may be an insulating dielectric material.

[0028] As shown in Figure 4, following the steps described above, a dispersed Bragg reflector layer 16 is disposed on the dielectric layer 14, the electrode surface 13B, and the electrode 130, exposing a portion of the surface of the electrode 130. In some embodiments, the dispersed Bragg reflector layer 16 can be patterned to form openings in the dispersed Bragg reflector layer 16, exposing a portion of the surface of the electrode 130. In some embodiments, the dispersed Bragg reflector layer 16 comprises thin films of two or more homogeneous or heterogeneous materials with different refractive indices stacked together. For example, the dispersed Bragg reflector layer 16 may be composed of alternating stacks of silicon dioxide (SiO2) and titanium dioxide (TiO2), alternating stacks of silicon dioxide (SiO2) / alumina (Al2O3) / titanium dioxide (TiO2), or alternating stacks of titanium dioxide (TiO2) / silicon dioxide (SiO2) / tantalum pentoxide (Ta2O5).

[0029] In some embodiments, the dispersed Bragg reflector layer 16 is formed using deposition processes such as vapor deposition, atomic layer deposition (ALD), metal-organic chemical vapor deposition (MOCVD), and subsequent patterning processes.

[0030] As shown in Figure 5, following the steps described above, a plurality of conductive elements 70 are disposed on the dispersed Bragg reflector layer 16, wherein the conductive elements 70 pass through openings in the dispersed Bragg reflector layer 16 and are electrically connected to electrodes 130 on the electrode surface 13B. In some embodiments, the conductive elements 70 are metal pillars. It is worth noting that using conductive elements 70 can significantly increase the thickness and volume of the metal layer, which greatly benefits the heat dissipation, stress relief, current distribution, pressure buffering during subsequent die bonding, and improvement of device lifespan of the light-emitting diode chip 13.

[0031] In some embodiments, the conductive element 70 is formed using methods such as electroplating, vapor deposition, screen printing, and vacuum spraying. In some embodiments, the thickness of the conductive element 70 is between 5 μm and 200 μm. In some embodiments, the conductive element 70 may be or may include a conductive material. For example, the conductive material may include metals, metal compounds, other suitable conductive materials, or combinations thereof, but this disclosure is not limited thereto. For example, the metal may be copper (Cu), tin (Sn), silver (Ag), gold (Au), nickel (Ni), indium (In), platinum (Pt), titanium (Ti), magnesium (Mg), zinc (Zn), germanium (Ge), palladium (Pd), iridium (Ir), titanium (Ti), chromium (Cr), tungsten (W), aluminum (Al), molybdenum (Mo), or alloys thereof. For example, the metal compound may be tantalum nitride (TaN), titanium nitride (TiN), tungsten silicon (WSi₂), indium tin oxide (ITO), etc., but this disclosure is not limited thereto.

[0032] As shown in Figure 6, following the above steps, a filling material layer 40 is disposed on the dispersed Bragg reflector layer 16, wherein the filling material layer 40 surrounds and covers the conductive element 70.

[0033] In some embodiments, the filler layer 40 may be or may include polyimide (PI), epoxy resin, silicone resin, other suitable materials, or combinations thereof, but this disclosure is not limited thereto. In some embodiments, the filler layer 40 may be black by adding black dispersed particles such as carbon black to the filler layer 40 so that the light transmittance of the filler layer 40 is less than 10%.

[0034] In some embodiments, the filler layer 40 includes diffusion particles. In some embodiments, the diffusion particles include silicon dioxide (SiO₂), titanium dioxide (TiO₂), tantalum pentoxide (Ta₂O₅), aluminum oxide (Al₂O₃), boron oxide (BN), or zirconium dioxide (ZrO₂). In some embodiments, the diffusion particles include hollow silicon dioxide (SiO₂) or solid silicon dioxide (SiO₂). In some embodiments, the filler layer 40 contains two or more different sizes of diffusion particles. For example, the filler layer 40 contains two, three, four, or five or more different sizes of diffusion particles. In some embodiments, the diffusion particles may be elongated or spherical. In some embodiments, the filler layer 40 contains two or more spherical diffusion particles with different radii.

[0035] As shown in Figure 7, following the steps described above, a portion of the filler material layer 40 is removed to expose the first surface 70F of the conductive element 70. For example, the filler material layer 40 may be removed by chemical mechanical polishing, etching, other suitable methods, or combinations thereof, but this disclosure is not limited thereto. In some embodiments, after exposing the first surface 70F of the conductive element 70, the first surface 40F of the filler material layer 40 is coplanar with the first surface 70F of the conductive element 70.

[0036] As shown in Figure 8, following the steps above, a conductive pad 80 is disposed on the conductive element 70, and the conductive pad 80 is electrically connected to the conductive element 70. In some embodiments, the upper surface of the conductive pad 80 is not coplanar with the first surface 40F of the filling material layer 40.

[0037] In some embodiments, the conductive pad 80 covers the conductive element 70 and a portion of the filler material layer 40 in the vertical direction. In other words, in a top view, the conductive pad 80 overlaps and directly contacts the conductive element 70, and the ends or peripheries of the conductive pad 80 overlap and directly contact a portion of the filler material layer 40. In some embodiments, the top view area of ​​the conductive pad 80 may be larger than the top view area of ​​the conductive element 70. Thus, in a top view, the conductive pad 80 can completely overlap and directly contact the conductive element 70, and both ends or the entire periphery of the conductive pad 80 overlap and directly contact a portion of the filler material layer 40.

[0038] In some embodiments, the conductive pads 80 may have the same shape. In some embodiments, the conductive pads 80 may have different shapes. In some embodiments, the conductive pads 80 are square. In some embodiments, the conductive pads 80 are square with a triangular notch.

[0039] In some embodiments, the conductive pad 80 may be or may include a conductive material. For example, the conductive material may include metals, metal compounds, other suitable conductive materials, or combinations thereof, but this disclosure is not limited thereto. For example, the metal may be copper (Cu), tin (Sn), platinum (Pt), titanium (Ti), aluminum (Al), molybdenum (Mo), titanium (Ti), magnesium (Mg), palladium (Pd), iridium (Ir), gold (Au), silver (Ag), nickel (Ni), indium (In), chromium (Cr), tungsten (W), zinc (Zn), germanium (Ge), or alloys thereof. In some embodiments, the metal compound may be indium tin oxide (ITO), tantalum nitride (TaN), tungsten silicon silicide (WSi₂), titanium nitride (TiN), etc.

[0040] As shown in Figure 9, following the above steps, the second substrate 20 is first bonded to the conductive element 70 and the conductive pad 80, and the first substrate 10 is flipped over. In some embodiments, the second adhesive layer 12B is disposed on the second substrate 20 and bonded to the conductive element 70 and the conductive pad 80, that is, the conductive pad 80 faces the second adhesive layer 12B and contacts the second adhesive layer 12B.

[0041] In some embodiments, the second substrate 20 may be or may include: group IV elements or group IV compounds, such as silicon (Si), silicon carbide (SiC), diamond (C); group III-V compounds, such as gallium nitride (GaN), gallium arsenide (GaAs), gallium phosphide (GaP), aluminum gallium arsenide (AlGaAs), aluminum nitride (AlN), aluminum gallium nitride (AlGaN); other suitable materials; or combinations thereof, but this disclosure is not limited thereto. In some embodiments, the second substrate 20 may be or may include sapphire, glass, quartz, ceramic, other suitable materials, or combinations thereof, but this disclosure is not limited thereto. In some embodiments, the second substrate 20 may be or may include polyimide (PI), polycarbonate (PC), polyethylene terephthalate (PET), polypropylene (PP), other suitable materials, or combinations thereof, but this disclosure is not limited thereto. In some embodiments, the second substrate 20 may be or may include a flexible substrate, a rigid substrate, or combinations thereof, but this disclosure is not limited thereto. For example, the second substrate 20 may be a sapphire substrate. In some embodiments, the second substrate 20 may be or may include a light-transmitting substrate, a semi-light-transmitting substrate, or an opaque substrate, but this disclosure is not limited thereto.

[0042] In some embodiments, the second adhesive layer 12B may be or may include polyimide (PI), polybenzoxazole (PBO), epoxy resin, transparent silicone resin, other suitable materials or combinations thereof, but this disclosure is not limited thereto.

[0043] As shown in Figure 9, the first substrate 10 is removed. For example, depending on the type of the first release layer 11, the first release layer 11 can be de-adhesive by means of heating, laser, UV light, etc., so as to remove the first substrate 10 thereon.

[0044] As shown in Figure 10, following the steps described above, the first adhesive layer 12A and the first release layer 11 are removed from the light-emitting surface 13A and the dielectric layer 14 of the light-emitting diode chip 13 to expose the light-emitting surface 13A of the light-emitting diode chip 13. For example, the first adhesive layer 12A and the first release layer 11 can be removed by a removal process such as etching, polishing, other suitable methods or combinations thereof.

[0045] Referring again to Figure 10, after removing the first adhesive layer 12A and the first release layer 11, the upper surface 14T of the dielectric layer 14 may be coplanar with the light-emitting surface 13A, but this disclosure is not limited thereto. In some embodiments, the dielectric layer 14 continuously surrounds the side surface 13C of the light-emitting diode wafer 13. Before the aforementioned process of removing the first adhesive layer 12A and the first release layer 11, the dielectric layer 14 prevents the light-emitting diode wafer 13 from falling off. Furthermore, after the process of removing the first adhesive layer 12A and the first release layer 11, the dielectric layer 14 fixes the light-emitting diode wafer 13 in the light-emitting diode package structure 1.

[0046] As shown in Figure 11, following the steps described above, a third adhesive layer 12C is formed on the light-emitting surface 13A of the light-emitting diode wafer 13 and the upper surface 14T of the dielectric layer 14. In some embodiments, the third adhesive layer 12C may be silicone, epoxy resin, polyimide (PI), polybenzoxazole (PBO), other suitable materials, or combinations thereof, but this disclosure is not limited thereto. In some embodiments, the third adhesive layer 12C may be a light-transmitting material.

[0047] Referring to Figure 12, continuing the steps described above, the wavelength conversion layer 90 is disposed on the third adhesive layer 12C. In some embodiments, the wavelength conversion layer 90 may be phosphor-in-glass (PIG), for example, a phosphor is disposed within the glass to avoid thermal quenching of fluorescence, such as phosphor powder. In some embodiments, the wavelength conversion layer 90 may be a phosphor mixture colloid, the colloid being silicone, forming a phosphor sheet. In some embodiments, the wavelength conversion layer 90 is disposed on the third adhesive layer 12C on the light-emitting diode wafer 13 to bond the wavelength conversion layer 90 to the light-emitting diode wafer 13. In some embodiments, the wavelength conversion layer 90 may be placed on the light-emitting surface 13A of the light-emitting diode wafer 13 without the need for bonding using the third adhesive layer 12C (not shown). In some embodiments, the wavelength conversion layer 90 may include a red light conversion material, a blue light conversion material, a green light conversion material, a yellow light conversion material, other suitable light conversion materials, or combinations thereof. In some embodiments, the red light conversion material may include red quantum dots or red phosphors, but this disclosure is not limited thereto. For example, the red light conversion material may include (Sr,Ca)AlSiN3:Eu2+, Ca2Si5N8:Eu2+, Sr(LiAl3N4):Eu2+, manganese-doped red fluoride phosphors, their analogs, or combinations thereof, but this disclosure is not limited thereto. The manganese-doped red fluoride phosphor may include K2GeF6:Mn4+, K2SiF6:Mn4+, K2TiF6:Mn4+, their analogs, or combinations thereof, but this disclosure is not limited thereto. In some embodiments, the blue light conversion material may include blue quantum dots or blue phosphors, but this disclosure is not limited thereto. In some embodiments, the green light conversion material may include green quantum dots or green phosphors, but this disclosure is not limited thereto. For example, green light conversion materials may include lumbrotite (LuAG) phosphors, yttrium aluminum garnet (YAG) phosphors, β-SiAlON phosphors, silicate phosphors, their analogues, or combinations thereof, but this disclosure is not limited thereto. In some embodiments, yellow light conversion materials may include yellow quantum dots or yellow phosphors. For example, yellow light conversion materials may include yttrium aluminum garnet (YAG) phosphors.

[0048] In some embodiments, the light-emitting diode (LED) chip 13 may emit blue light, and the wavelength conversion layer 90 may include a yellow light conversion material. For example, the yellow light conversion material may be yttrium aluminum garnet (YAG) phosphor. Therefore, the light emitted by the LED chip 13 can be white light after passing through the wavelength conversion layer 90. In some embodiments, the LED chip 13 may emit blue light, and the wavelength conversion layer 90 may include a combination of green and red light conversion materials. For example, the wavelength conversion layer 90 may include green silane phosphor and red K₂SiF₆:Mn⁴⁺. Therefore, the light emitted by the LED chip 13 can be white light after passing through the wavelength conversion layer 90. In some embodiments, the wavelength conversion layer 90 may include a combination of green phosphor and two types of red phosphor. For example, the wavelength conversion layer 90 may include green silane phosphor, red K₂SiF₆:Mn⁴⁺, and red (Sr,Ca)AlSiN₃:Eu²⁺. In some embodiments, the wavelength conversion layer 90 may include red quantum dots and green quantum dots.

[0049] As shown in Figure 13, following the steps described above, in some embodiments, a mask layer 21 is disposed on the wavelength conversion layer 90. In some embodiments, the mask layer 21 may be formed by spin coating, other suitable processes, or a combination thereof, but this disclosure is not limited thereto. In some embodiments, the mask layer 21 includes photoresist, but this disclosure is not limited thereto.

[0050] As shown in Figure 14, following the above steps, a cutting process is performed, using the masking layer 21 as a protective layer. The masking layer 21, the wavelength conversion layer 90 beneath it, and the dielectric layer 14 beneath the wavelength conversion layer 90 are cut between one set (e.g., one shown in Figure 13) of light-emitting diode (LED) wafers 13 and another set (not shown) of LED wafers 13, until the dielectric layer 14 is reached. In some embodiments, the cutting process between the two sets of LED wafers 13 can be performed using tools such as cutting tools, lasers, plasma dicing, other suitable methods or tools, or combinations thereof. For example, the cutting tool can be a diamond cutting tool.

[0051] As shown in Figure 15, following the steps described above, a reflective layer 30 is formed on the side surface 90S of the wavelength conversion layer 90 and the upper surface 21T of the masking layer 21. In some embodiments, the reflective layer 30 may be formed by sputtering, electron beam evaporation, electroplating, chemical vapor deposition, resistance heating evaporation, other suitable formation processes, or combinations thereof, but this disclosure is not limited thereto. In some embodiments, the reflective layer 30 may be formed by blanket deposition. In some embodiments, the reflective layer 30 has an upper reflective layer 31 and a reflective layer 32.

[0052] In some embodiments, the reflective layer 30, the upper reflective layer 31, and the reflective layer 32 may include a reflective material. For example, the reflective material may include titanium (Ti), copper (Cu), silver (Ag), aluminum (Al), chromium (Cr), alloys thereof, the likes thereof, or combinations thereof, but this disclosure is not limited thereto. In some embodiments, the reflective layer 30, the upper reflective layer 31, and the reflective layer 32 may include aluminum (Al), or the reflective layer 30, the upper reflective layer 31, and the reflective layer 32 may be aluminum (Al) and substantially exclude copper (Cu). In some embodiments, the reflective layer 30, the upper reflective layer 31, and the reflective layer 32 may include an aluminum-copper alloy (AlCu), wherein the weight of copper in the aluminum-copper alloy accounts for 0.1% to 20% of the total weight of the aluminum-copper alloy. In some embodiments, the aluminum-copper alloy may include 0.1% to 20% copper and 80% to 99.9% aluminum of the total weight of the aluminum-copper alloy. For example, the weight of copper in the aluminum-copper alloy may be 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 10%, 15%, 20% of the total weight of the aluminum-copper alloy, or any value or range of values ​​between the foregoing values, but this disclosure is not limited thereto. For example, the weight of copper in the aluminum-copper alloy may be 0.1% to 0.5% of the total weight of the aluminum-copper alloy. When the weight of copper is too high, the reflectivity of the aluminum-copper alloy is insufficient. In other embodiments, the reflective layer 30, the upper reflective layer 31, and the reflective layer 32 may comprise an aluminum-copper alloy (AlCu), and the number of copper atoms in the aluminum-copper alloy may be 0.1% to 20% of the total number of atoms in the aluminum-copper alloy; or the mass of copper in the aluminum-copper alloy may be 0.1% to 20% of the total mass of the aluminum-copper alloy; or the volume of copper in the aluminum-copper alloy may be 0.1% to 20% of the total volume of the aluminum-copper alloy.

[0053] In some embodiments, the reflective layer 30, the upper reflective layer 31, and the reflective layer 32 may include a dispersed Bragg mirror. In some embodiments, the dispersed Bragg mirror may be formed on the side surface 90S of the wavelength conversion layer 90 using atomic layer deposition (ALD).

[0054] As shown in Figure 16, following the above steps, a removal process is performed to remove the upper reflective layer 31 and the masking layer 21 of the reflective layer 30, forming a reflective layer 32, thus exposing the upper surface 90T of the wavelength conversion layer 90. In some embodiments, the removal process may involve immersing in or rinsing off the photoresist, i.e., the masking layer 21 and the upper reflective layer 31 are removed by the photoresist, leaving the reflective layer 32. In some embodiments, the reflective layer 32 is disposed on the side surface 90S of the wavelength conversion layer 90, the inner surface 14S of the dielectric layer 14, and the second surface 14M of the dielectric layer 14. Accordingly, the reflective layer 32 can improve the luminous efficiency of the light-emitting element 10.

[0055] As shown in Figure 16, in the first direction D1, the reflective layer 32 on the side surface 90S of the wavelength conversion layer 90 may have a thickness t1. In some embodiments, the thickness t1 may be greater than 500 Å. However, this disclosure is not limited thereto. In some embodiments, the thickness t1 may be 0.05 μm to 10 μm. For example, the thickness t1 may be 0.05 μm, 0.08 μm, 0.1 μm, 0.3 μm, 0.7 μm, 1 μm, 3 μm, 5 μm, 7 μm, 9 μm, or 10 μm. In some embodiments, when the thickness t1 of the reflective layer 32 is too thin, it is difficult to effectively reflect the light emitted from the light-emitting diode wafer 13. When the thickness t1 of the reflective layer 32 is too thick, it results in an excessively large volume of the reflective layer 32. In some embodiments, the thickness t1 gradually increases along the second direction D2. In some embodiments, the thickness t1 gradually increases along the second direction D2, that is, it is thinner closer to the dielectric layer 14 and thicker closer to the upper surface 90S of the wavelength conversion layer 90.

[0056] As shown in Figure 16, in some embodiments, after the removal process, the reflective layer 32 can be L-shaped or an inverted L-shaped. The reflective layer 32 can prevent light emitted by the light-emitting diode chip 13 from leaking from the side surface 13C of the light-emitting diode chip 13 to the side surface 90S of the wavelength conversion layer 90. Furthermore, the reflective layer 32 can prevent light emitted by one light-emitting diode chip 13 from interfering with the light-emitting diode chip 13 of another light-emitting diode package structure 1, that is, the reflective layer 32 can prevent crosstalk between the light-emitting diode chips 13 of each light-emitting diode package structure 1.

[0057] Following the steps described above, a protective layer 50 is formed on the reflective layer 32. After forming the protective layer 50 on the upper surface 90T of the wavelength conversion layer 90 and the reflective layer 32, the protective layer 50 on the upper surface 90T of the wavelength conversion layer 90 is then removed. Finally, as shown in Figure 17, the protective layer 50 is disposed on the reflective layer 32. In some embodiments, the upper surface 50T of the protective layer 50, the upper surface 90T of the wavelength conversion layer 90, and the upper surface 32T of the reflective layer 32 are coplanar. In some embodiments, the protective layer 50 is formed by a molding process. In some embodiments, the protective layer 50 may include epoxy resin, polyimide (PI), or silicone resin. In some embodiments, the protective layer 50 may further include fillers. In some embodiments, the diffusing particles include titanium dioxide (TiO₂), tantalum pentoxide (Ta₂O₅), silicon dioxide (SiO₂), boron oxide (BN), aluminum oxide (Al₂O₃), or zirconium dioxide (ZrO₂). In some embodiments, the diffusing particles include hollow silicon dioxide (SiO₂) or solid silicon dioxide (SiO₂). In some embodiments, the protective layer 50 includes two or more different sizes of diffusing particles. For example, the protective layer 50 includes two, three, four, or five or more different sizes of diffusing particles. In some embodiments, the diffusing particles may be spherical or elongated. In some embodiments, the protective layer 50 includes two or more spherical diffusing particles with different radii.

[0058] In some embodiments, the step of forming the protective layer 50 may be omitted. That is, the light-emitting diode package structure 1 may not include the protective layer 50 and can continue with subsequent processes. Omitting the step of forming the protective layer 50 can save manufacturing costs and utilize the reflective layer 32 to avoid crosstalk problems between the light-emitting diode chips 13. In some embodiments, the light-emitting diode package structure 1 may not include the protective layer 50. Viewed from the cross-sectional direction, the reflective layer 32 may be L-shaped, an inverted L-shaped, square, or rectangular.

[0059] Referring to Figure 18, in some embodiments, the second substrate 20 and the second adhesive layer 12B are removed. For example, depending on the type of the second adhesive layer 12B, its adhesiveness can be lost by methods such as heating, UV light, laser, or laser lift-off, thereby removing the second substrate 20. Then, the second adhesive layer 12B can be removed by physical or chemical methods. It is worth noting that the second adhesive layer 12B and the second substrate 20 can also be removed simultaneously in the same step using a suitable process, and are not limited to the methods described above.

[0060] Referring to Figure 19, a set of protective layers 50 (e.g., one shown in Figure 18) of light-emitting diode (LED) wafers 13 and another set (not shown) of LED wafers 13, including the reflective layer 32, the dispersed Bragg reflector layer 16, and the filler material layer 40 beneath it, are individually cut to form a separate LED package structure 1 as shown in Figure 1. In some embodiments, the cutting process between the two sets of LED wafers 13 can be performed using tools such as cutting tools, lasers, plasma dicing, other suitable methods or tools, or combinations thereof. For example, the cutting tool can be a diamond cutting tool. Referring to Figure 19, in some embodiments, the outer surfaces of the LED package structure 1 are coplanar, i.e., the outer surface 50A of the protective layer 50, the outer surface 32A of the reflective layer 32, the outer surface 14A of the dielectric layer 14, the outer surface 16A of the dispersed Bragg reflector layer 16, and the outer surface 40A of the filler material layer 40 are coplanar.

[0061] It is worth mentioning that the cutting depth in Figure 14 can be different. As shown in Figure 20, which is a cross-sectional view of the light-emitting diode packaging structure 2 of some embodiments disclosed herein, the cutting depth can reach the lower surface 90B of the wavelength conversion layer 90. In the second direction D2, the lower surface 32B of the reflective layer 32 is approximately on the same plane as the lower surface 90B of the wavelength conversion layer 90, and the lower surface 50B of the protective layer 50 is slightly higher than the lower surface 90B of the wavelength conversion layer 90. In some embodiments, the light-emitting diode packaging structure 2 may not include the protective layer 50. Viewed from the cross-sectional direction, the reflective layer 32 can be L-shaped, an inverted L-shaped, square, or rectangular.

[0062] As shown in Figure 21, which is a cross-sectional view of the light-emitting diode packaging structure 3 of some embodiments disclosed herein, the cutting depth can be cut from the wavelength conversion layer 90 to the bottom of the third adhesive layer 12C, but not to the dielectric layer 14, that is, to the boundary between the third adhesive layer 12C and the dielectric layer 14. In the second direction D2, the lower surface 32B of the reflective layer 32 and the light-emitting surface 13A of the light-emitting diode chip 13 are approximately on the same plane, and the lower surface 50B of the protective layer 50 is located slightly higher than the light-emitting surface 13A of the light-emitting diode chip 13.

[0063] In some embodiments, the third adhesive layer 12C is not required for bonding; that is, the light-emitting diode package structure 3 may not include the third adhesive layer 12C. The wavelength conversion layer 90 may be placed on the light-emitting surface 13A of the light-emitting diode wafer 13, and the cutting depth may reach the lower surface 90B of the wavelength conversion layer 90. In the second direction D2, the lower surface 32B of the reflective layer 32 is approximately on the same plane as the light-emitting surface 13A of the light-emitting diode wafer 13, and the lower surface 50B of the protective layer 50 is slightly higher than the light-emitting surface 13A of the light-emitting diode wafer 13. In some embodiments, the light-emitting diode package structure 3 may not include the protective layer 50. Viewed from the cross-sectional direction, the reflective layer 32 may be L-shaped, an inverted L-shaped, square, or rectangular.

[0064] As shown in Figure 22, which is a cross-sectional view of the light-emitting diode packaging structure 4 of some embodiments disclosed herein, the cutting depth can be cut from the wavelength conversion layer 90 to the bottom of the dielectric layer 14, but not to the dispersed Bragg reflector layer 16, that is, to the boundary between the dielectric layer 14 and the dispersed Bragg reflector layer 16. The lower surface 32B of the reflector layer 32 is in contact with the upper surface 16T of the dispersed Bragg reflector layer 16. In the second direction D2, the lower surface 50B of the protective layer 50 is slightly higher than the electrode surface 13B of the light-emitting diode wafer 13.

[0065] In some embodiments, the third adhesive layer 12C is not required for bonding; that is, the light-emitting diode package structure 4 may not include the third adhesive layer 12C. The wavelength conversion layer 90 may be placed on the light-emitting surface 13A of the light-emitting diode wafer 13. The cutting depth can be cut from the wavelength conversion layer 90 to the bottom of the dielectric layer 14, but not to the dispersed Bragg reflector layer 16, i.e., cut to the boundary between the dielectric layer 14 and the dispersed Bragg reflector layer 16. The lower surface 32B of the reflective layer 32 contacts the upper surface 16T of the dispersed Bragg reflector layer 16. In the second direction D2, the lower surface 50B of the protective layer 50 is slightly higher than the electrode surface 13B of the light-emitting diode wafer 13. In some embodiments, the light-emitting diode package structure 4 may not include the protective layer 50. Viewed from the cross-sectional direction, the reflective layer 32 may be L-shaped, an inverted L-shaped, square, or rectangular.

[0066] As shown in Figure 23, which is a cross-sectional schematic diagram of the light-emitting diode packaging structure 5 of some embodiments disclosed herein, the cutting depth can extend from the wavelength conversion layer 90 to the lower surface 16B of the dispersed Bragg reflector layer 16, but not to the filling material layer 40, i.e., to the boundary between the dispersed Bragg reflector layer 16 and the filling material layer 40. The lower surface 32B of the reflector layer 32 is in contact with the upper surface 40T of the filling material layer 40. In the second direction D2, the lower surface 50B of the protective layer 50 is slightly higher than the lower surface 16B of the dispersed Bragg reflector layer 16.

[0067] In some embodiments, the third adhesive layer 12C is not required for bonding; that is, the light-emitting diode package structure 5 may not include the third adhesive layer 12C. The wavelength conversion layer 90 may be placed on the light-emitting surface 13A of the light-emitting diode wafer 13. The cutting depth can be from the wavelength conversion layer 90 to the lower surface 16B of the dispersed Bragg reflector layer 16, but not to the filling material layer 40, i.e., to the boundary between the dispersed Bragg reflector layer 16 and the filling material layer 40. The lower surface 32B of the reflective layer 32 contacts the upper surface 40T of the filling material layer 40. In the second direction D2, the lower surface 50B of the protective layer 50 is slightly higher than the lower surface 16B of the dispersed Bragg reflector layer 16. In some embodiments, the light-emitting diode package structure 5 may not include the protective layer 50. Viewed from the cross-sectional direction, the reflective layer 32 may be L-shaped, an inverted L-shaped, square, or rectangular.

[0068] Therefore, any one or more of the light-emitting diode (LED) package structures 1, 2, 3, 4, and 5 can be arbitrarily combined with each other and can be applied to adaptive smart headlamps. Multiple independent LED package structures 1, 2, 3, 4, and 5 are installed inside the adaptive smart headlamp. The reflective layer 32 of each independent LED package structure 1, 2, 3, 4, and 5 can prevent the light emitted by the LED chip 13 of LED package structure 1 from interfering with the LED chip 13 of another LED package structure 1, thus avoiding crosstalk between the LED chips 13 of each independent LED package structure 1, 2, 3, 4, and 5.

[0069] In some embodiments, the adaptive headlamp may include any or more of light-emitting diode (LED) package structures 1, 2, 3, 4, and 5, which may be arbitrarily combined with each other and a circuit board (not shown), but this disclosure is not limited thereto. In some embodiments, the adaptive headlamp may include a processor (not shown) and an image capturing device (not shown). In some embodiments, the processor may be electrically connected to the package structure to perform calculations. In some embodiments, the processor may include a multi-core CPU, a central processing unit (CPU), a graphics processing unit (GPU), the like, or a combination thereof, but this disclosure is not limited thereto. In some embodiments, the image capturing device may include a light detection and ranking (LIDAR), a video recorder, a camera, the like, or a combination thereof, but this disclosure is not limited thereto. In some embodiments, the image capturing device may capture and transmit images to the processor. In some embodiments, the image capturing device may capture road images, pedestrian images, or vehicle images and transmit the road images, pedestrian images, or vehicle images to the processor. In some embodiments, the processor analyzes the captured images to determine whether one or more of the plurality of LED package structures 1 are turned on or off. For example, at least one of the plurality of light-emitting diode (LED) package structures 1 can be turned on or off depending on the environment. In some embodiments, the LED chips 13 of the LED package structure 1 within the adaptive headlamp can all be controlled independently.

[0070] Components in the embodiments disclosed herein may be freely mixed and matched as long as they do not violate the spirit of the invention or conflict with it. Furthermore, the scope of protection of this disclosure is not limited to the processes, machines, manufacturing, material composition, apparatus, methods, and steps described in the specific embodiments of the specification. Any process, machine, manufacturing, material composition, apparatus, method, and step that is currently or will be developed can be understood from the content of this disclosure, and can be used according to this disclosure as long as it can perform substantially the same function or obtain substantially the same result in the embodiments described herein. Therefore, the scope of protection of this disclosure includes the aforementioned processes, machines, manufacturing, material composition, apparatus, methods, and steps. No embodiment or claim of this disclosure needs to achieve all the purposes, advantages, and / or features disclosed herein.

[0071] The above outlines several embodiments to enable those skilled in the art to better understand the viewpoints of the embodiments disclosed herein. Those skilled in the art should understand that they can design or modify other processes and structures based on the embodiments disclosed herein to achieve the same purpose and / or advantages as the embodiments described herein. Those skilled in the art should also understand that such equivalent processes and structures do not depart from the spirit and scope of this disclosure, and that they can make various changes, substitutions, and replacements without departing from the spirit and scope of this disclosure.

[0072] 1,2,3,4,5: Light-emitting diode (LED) packaging structure 10: First substrate 20: Second substrate 11: First peeling layer 12A: First adhesive layer 12B: Second adhesive layer 12C: Third adhesive layer 13: Light Emitting Diode Chip 13A: Light-emitting surface 13B: Electrode surface 13C: Side surface 130: Electrode 14: Dielectric layer 14T, 16T, 21T, 32T, 40T, 50T, 90T: Top surface 14S: Inner surface 14M: Second Surface 14A, 16A: Outer surface 16: Distributed Bragg reflector 21: Masking layer 30, 32: Reflective layer 31: Upper reflective layer 32A, 40A, 50A: Outer surface 40: Filler material layer 50: Protective layer 50I: Inner surface 16B, 32B, 50B, 90B: Lower surface 70: Conductive components 80: Conductive pad 90: Wavelength conversion layer 90S: Side surface 40F, 70F: First surface D1: First Direction D2: Second Direction

Claims

1. A light-emitting diode (LED) packaging structure, comprising: A light-emitting diode chip includes a light-emitting surface, an electrode surface, and a plurality of side surfaces; A wavelength conversion layer is disposed on the light-emitting surface and includes a plurality of side surfaces; a dielectric layer covers the plurality of side surfaces of the light-emitting diode wafer and includes an outermost surface; a reflective layer is disposed on the dielectric layer to cover the plurality of side surfaces of the wavelength conversion layer; a dispersed Bragg reflector layer contains an insulating material and contacts the electrode surface; a conductive element passes through the dispersed Bragg reflector layer to be electrically connected to the light-emitting diode wafer; and a conductive pad is disposed directly below the conductive element.

2. The light-emitting diode packaging structure as described in claim 1, wherein in a cross-sectional view, the reflective layer is L-shaped and disposed on an inner surface of the dielectric layer and a surface of the dielectric layer.

3. The light-emitting diode packaging structure as described in claim 1 further includes a protective layer disposed on the reflective layer.

4. The light-emitting diode packaging structure as described in claim 2 further includes a protective layer having an upper surface, an inner surface, a lower surface and an outer surface, wherein the reflective layer is disposed on the lower surface and the inner surface of the protective layer, exposing the upper surface and the outer surface of the protective layer.

5. The light-emitting diode packaging structure as described in claim 1 further includes an adhesive layer disposed between the wavelength conversion layer and the light-emitting surface of the light-emitting diode chip, wherein the adhesive layer directly contacts the light-emitting surface of the light-emitting diode chip.

6. The light-emitting diode package structure as described in claim 1, wherein the conductive element is a metal pillar.

7. The light-emitting diode packaging structure as described in claim 1 further includes a filler material layer disposed under the dispersed Bragg reflector layer and surrounding the conductive element.

8. The light-emitting diode packaging structure as described in claim 3, wherein the protective layer, the reflective layer, the dielectric layer and the dispersed Bragg reflector layer are coplanar on their outer surfaces.

9. The light-emitting diode packaging structure as described in claim 7, wherein the conductive pad covers the conductive element and a portion of the filler material layer in the vertical direction.

10. The light-emitting diode packaging structure as described in claim 1, wherein the dispersed Bragg reflector layer may be composed of alternating stacks of silicon dioxide and titanium dioxide, alternating stacks of silicon dioxide, aluminum oxide and titanium dioxide, or alternating stacks of titanium dioxide, silicon dioxide and tantalum pentoxide.

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