UVC LED light source with high light extraction efficiency

Abstract

The utility model relates to the technical field of LED packaging, in particular to a UVC LED light source with high light extraction efficiency, which comprises a packaging substrate provided with a metal electrode; a metal electrode is arranged on the packaging substrate, an LED chip is welded on the metal electrode, a light window assembly is further arranged above the packaging substrate, and the periphery of the LED chip is sleeved with the light window assembly; wherein the outer side of the LED chip is coated with an organic oil layer, the upper end of the organic oil layer is in contact with the inner bottom surface of the light window assembly, the interior of a traditional inorganic packaging structure is coated with an organic liquid oily material, and the coated organic liquid oily material forms a trapezoid-like structure with a wide upper part and a narrow lower part, so that the light window assembly can be used for packaging the LED chip. Light emitted from the side face of the deep ultraviolet LED chip can be totally reflected by the organic liquid oil, so that the emitting direction is changed, and the light is emitted upwards.

Description

Technical Field

[0001] The utility model relates to the technical field of LED packaging, in particular to a UVC LED light source with high light extraction efficiency. Background Technique

[0002] As shown in the attached drawings of the specification Figure 1 In the existing UVC LED packaging structure, a chip is arranged on an AlN ceramic bracket, and a lens and a metal shell are welded at high temperature through a solder ring to form a sealed light window, and then the sealed light window is welded to the ceramic bracket through a laser sealing welding technology. This design can solve the airtightness problem caused by poor flatness of the welding layer and poor welding caused by the difference in the thermal expansion coefficients of the welding surface materials when the traditional lens is directly sealed on the ceramic bracket through the solder ring of the lens and the metal shell and the laser sealing welding of the metal shell and the ceramic bracket.

[0003] As Figure 2 shown, the light angle distribution of the current UVC LED chip will show a trend that it is low in the middle and then slowly increases to the maximum when it reaches about 40°, and then rapidly decreases. Combining this light output distribution with the light propagation path of the LED chip-air-lens in the all-inorganic packaging structure described above, there will be more light losses.

[0004] Specifically, the light ray I is emitted vertically or at a very small angle, and basically there is less reflection at the air-lens interface and can be emitted with less loss, but this part accounts for a small proportion; the light ray II is emitted laterally at a larger angle, and this part occupies a larger proportion. This part of the light ray hits the metal shell, and since the reflectivity of the metal shell is very low, most of it is absorbed, so it is difficult to extract this part of the light ray; the light ray III is emitted at a certain angle, and this part accounts for the largest proportion, but due to the large refractive index difference between air and the lens, it will cause a relatively significant Fresnel reflection, and the larger the angle, the stronger the reflection. Therefore, only part of the light ray III-I can be normally emitted, and the reflected III-II will probably be reflected to the bracket and the electrode, and since the reflectivity of the bracket and the electrode is relatively low, absorption will also occur.

[0005] Therefore, although this non-inorganic packaging structure has good reliability, the light output efficiency is relatively low for the current light distribution of deep ultraviolet LED chips. Summary of the Invention

[0006] The purpose of the utility model is to solve the disadvantages such as relatively low light output efficiency of deep ultraviolet LED chips in the prior art, and to propose a UVC LED light source with high light extraction efficiency.

[0007] In order to achieve the above purpose, the utility model adopts the following technical scheme:

[0008] Design a UVC LED light source with high light extraction efficiency, including:

[0009] A packaging substrate configured with metal electrodes;

[0010] An LED chip is soldered on the metal electrode, and a light window assembly is also installed above the packaging substrate, and the light window assembly is sleeved around the periphery of the LED chip;

[0011] Wherein an organic oil layer is coated on the outside of the LED chip, and the upper end of the organic oil layer contacts the inner bottom surface of the light window assembly.

[0012] Further, the light window assembly includes a metal casing and a lens placed in the top opening of the metal casing;

[0013] The outer periphery of the lens and the opening of the metal casing are welded and fixed through a solder ring.

[0014] Further, a sealing metal layer is also formed above the packaging substrate, and the sealing metal layer is formed around the metal electrode and is welded and fixed to the bottom of the metal casing.

[0015] Further, antireflection films are also formed on the upper and lower end faces of the lens.

[0016] Further, a dam structure is also formed on the upper surface of the metal electrode, and the dam structures on the two metal electrodes are symmetrically arranged and block the bottom of the organic oil layer.

[0017] Further, the height of the dam structure is not less than 50um, and the distance between the dam structure and the LED chip is not less than 100um.

[0018] Further, the upper end of the organic oil layer is laterally extruded through the bottom of the lens to form a trapezoidal structure with a larger upper part and a smaller lower part in cross section.

[0019] Further, the packaging substrate is a metal bracket or a ceramic bracket.

[0020] Further, the organic oil layer is an organic fluorine oil layer.

[0021] A UVC LED light source with high light extraction efficiency proposed by the present utility model has the beneficial effects that: in the present utility model, an organic liquid oily material is coated inside a traditional inorganic packaging structure, and by forming a trapezoidal structure with a wider upper part and a narrower lower part for the coated organic liquid oily material, the light emitted from the side of the deep ultraviolet LED chip can be totally reflected by the organic liquid oil to change the emission direction, so as to emit upward. Description of the Drawings

[0022] Figure 1 Schematic diagram of the prior art structure;

[0023] Figure 2 Schematic diagram of the light-emitting angle distribution of the LED chip;

[0024] Figure 3 Schematic diagram of the structure of the present utility model;

[0025] Figure 4 Schematic diagram of the size identification structure of the present utility model;

[0026] Figure 5 Schematic diagram of the side inclination angle α of the organic oil layer of the present utility model;

[0027] In the figure: 1, packaging substrate; 10, metal electrode; 11, sealing metal layer; 12, dam structure; 2, LED chip; 3, light window assembly; 31, metal shell; 32, lens; 33, solder ring; 34, antireflection film; 4, organic oil layer. Detailed implementation manners

[0028] Next, the technical solutions in the embodiments of the present utility model will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present utility model. Obviously, the described embodiments are only a part of the embodiments of the present utility model, rather than all of the embodiments.

[0029] Referring to Figures 3 - 5 One embodiment of the present utility model discloses a UVC LED light source with high light extraction efficiency. Specifically, the UVC LED light source is used to solve the problem of low light extraction efficiency of the current packaging structure;

[0030] It includes a packaging substrate 1 configured with metal electrodes 10. Of course, in this embodiment, two metal electrodes 10 are arranged at intervals to supply power to the positive and negative electrodes of the LED chip 2. The metal electrodes 10 are connected to the back surface of the packaging substrate 1 through metal vias to form electrode pads at the bottom of the packaging substrate 1, forming a back-surface power supply method. In addition, in this embodiment, the packaging substrate 1 is a metal bracket or a ceramic bracket, and in this embodiment, a high thermal conductivity aluminum nitride bracket is preferably used;

[0031] An LED chip 2 is welded on the metal electrode 10. Since small-power UVC LED chips currently mostly use semi-inorganic packaging with lower cost, the LED chip 2 in this embodiment is a medium-high power deep ultraviolet LED chip. A light window assembly 3 is also installed above the packaging substrate 1, and the light window assembly 3 is sleeved around the LED chip 2;

[0032] Wherein, the outside of the LED chip 2 is coated with an organic oil layer 4, and the upper end of the organic oil layer 4 contacts the inner bottom surface of the light window assembly 3.

[0033] In some embodiments, the optical window assembly 3 in the present utility model includes a metal casing 31 and a lens 32 placed within the top opening of the metal casing 31;

[0034] The outer periphery of the lens 32 and the opening of the metal casing 31 are welded and fixed through a solder ring 33. Specifically, in this embodiment, the lens 32 can be ultraviolet-transmitting glass, sapphire, and quartz materials, the solder ring 33 can be glass solders such as silicon oxide and bismuth oxide, and the metal casing 31 generally uses kovar alloy, invar alloy, and super-invar alloy with a relatively low coefficient of thermal expansion.

[0035] Based on the above embodiments, in this embodiment, a sealing metal layer 11 is further formed above the packaging substrate 1. The sealing metal layer 11 provides a welding surface for the subsequent welding of the metal casing 31 and the packaging substrate 1. The sealing metal layer 11 is formed around the metal electrode 10 and is welded and fixed to the bottom of the metal casing 31.

[0036] In addition, in order to reduce interface reflection, antireflection films 34 are further formed on the upper and lower end surfaces of the lens 32 in the present utility model. The antireflection films 34 generally adopt single-layer or multi-layer composites such as aluminum oxide, silicon oxide, calcium fluoride, and magnesium fluoride. It can not only reduce the reflection of incident light, but more importantly, it has better wettability with organic liquid oily materials. In this way, when covering the lens 32, the organic oil layer 4 can quickly spread to form a relatively stable trapezoid-like morphology.

[0037] It should be noted that the upper end of the organic oil layer 4 in this embodiment is laterally extruded through the bottom of the lens 32 to form a trapezoidal structure with a larger upper cross-section and a smaller lower cross-section.

[0038] The organic oil layer 4 forms a trapezoid-like morphology with a wider upper part and a narrower lower part in the packaging device. Under this morphology, the laterally emitted light and the light reflected by the lens can change the propagation direction to upward and be effectively emitted. To achieve this morphology, generally, the organic liquid oil is first coated on the surface of the LED chip 2 to form a convex shape before sealing the optical window assembly 3. Generally, a convex shape is directly formed on the upper surface of the LED chip 2, and then the lens 32 is covered and pressed tightly. At this time, the relatively high convex organic liquid oil will be laterally extruded, thus forming a morphology with a larger lateral dimension at the top than that of the LED chip 2.

[0039] To achieve a better light reflection effect, first, it is necessary to ensure that the organic oil layer 4 forms a certain angle of inclination. By calculating the angle of light emission, we set more optimized parameters, such as Figure 4As shown, where L is the upper dimension of the organic oil layer 4, D is the lower dimension of the organic oil layer 4, H is the height between the lens 32 and the surface of the metal electrode 10, w is the length of the LED chip 2, and h is the height of the LED chip 2. Generally speaking, in order to improve the light output, the height h of the LED chip 2 is relatively close to the height H between the lens 32 and the surface of the metal electrode 10. A larger H will also affect the light extraction of the deep ultraviolet LED chip;

[0040] Referring to Figure 5 , since the light output ratio of the high-power deep ultraviolet LED chip within the 60° light output angle exceeds 90%, it is necessary to ensure that the light within 60° can be reflected out through the side of the fluorinated oil. According to the refractive index of the organic fluorinated oil generally being around 1.3 - 1.4, the total reflection angle at its interface with air is about 50°. Therefore, the inclination angle α of the side of the organic oil layer 4 needs to satisfy ≥ 60 - (90 - 50) = 20°;

[0041] To be more accurate, for the refractive index n of the organic oil layer 4, an inclination angle α can be determined to satisfy ≥ 60 - (90 - arcsin(1 / n)) = arcsin(1 / n) - 30°;

[0042] Since α = arctan((L - D) / 2H), that is, arctan((L - D) / 2H) ≥ arcsin(1 / n) - 30°.

[0043] Furthermore, in this embodiment, a dam structure 12 is also formed on the upper surface of the metal electrode 10. The dam structures 12 on the two metal electrodes 10 are symmetrically arranged and block the bottom of the organic oil layer 4. The two dam structures 12 can form a circle or a square.

[0044] In order to more stably achieve the trapezoidal morphology of the organic liquid oil in terms of structure, we introduced a new structural design in the design of the substrate and the lens. The metal electrode 10 was optimized on the packaging substrate 1, and a dam structure 12 that restricts the diffusion of the fluorinated oil was formed on the metal electrode 10. The height of the dam structure 12 is not less than 50 um, and the distance between the dam structure 12 and the LED chip 2 is not less than 100 um, that is, (D - w) / 2 in the above formula should not be less than 100 um. The design of this minimum distance mainly considers that there will be overflow of gold-tin during eutectic soldering. At the same time, the presence of the dam structure 12 can limit the diffusion of the flux for eutectic soldering and effectively ensure the eutectic soldering effect. Among them, if the dam structure 12 is square, it is the side length, and if it is circular, it is the four corners and the arc.

[0045] Correspondingly, at the corresponding position of the lens, according to the corresponding relationship between L and D described above, we set an anti-reflection film 34 at the corresponding position of the lens 32 to achieve the constraint on the top position of the organic oil layer 4. Moreover, the shape of the anti-reflection film 34 is set corresponding to the topography of the bottom dam structure 12. If the bottom dam structure 12 is circular, the anti-reflection film 34 can also be circular accordingly. Preferably, in this embodiment, the peripheral surfaces of the dam structure 12, the anti-reflection film 34, and the organic oil layer 4 are all set as square structures with arc angles.

[0046] In some embodiments, the organic oil layer 4 is an organic fluorine oil layer.

[0047] In other embodiments, the organic oil layer 4 in the present invention is a mixed layer of organic fluorine oil and organic fluororesin, and the proportion of organic fluorine oil in the mixed volume is 30%-90%.

[0048] That is, in this embodiment, by introducing the organic oil layer 4 into the liquid-solid mixed material, a coating layer that finally stably exists after the solid-liquid mixing is formed; the organic fluorine oil and organic fluororesin are mixed in proportion, and the proportion of organic fluorine oil in the mixed volume is in the range of 30%-90%. Generally, the process flow is to apply glue first, cover the lens 32 and then seal and weld. After sealing and welding, it is cured under the curing conditions of the organic fluororesin. After curing, a stable coating layer in which the cured fluororesin coats the liquid fluorine oil is formed to solve the problem that the traditional fluorine oil coating process cannot be shaped and has a large fluidity, resulting in deformation and failure during use.

[0049] In summary, the present invention coats an organic liquid oily material in the traditional inorganic packaging structure. By forming a trapezoid-like structure that is wider at the top and narrower at the bottom for the coated organic liquid oily material, the light emitted from the side of the deep ultraviolet LED chip 2 can be totally reflected by the organic liquid oil, thereby changing the emission direction and emitting upward.

[0050] As Figure 3 shown, compared with the existing structure, the light I of this packaging structure can be emitted normally;

[0051] As the light II, which is the light with a relatively large proportion of lateral propagation, when it is incident on the interface between the organic liquid and air, since the refractive index of the organic liquid oil is high and the refractive index of air is low, at this time, the light can basically achieve total reflection and change the direction to propagate upward, so as to be incident on the interface between the organic liquid and the lens at a small angle, and thus can be effectively extracted from the lens, improving the light extraction efficiency;

[0052] As the light III, which is the light with the largest proportion and emitted at a certain angle, when it passes through the organic liquid and is incident on the surfaces of the organic oil layer 4 and the lens 32, since the refractive index difference between the organic oil layer 4 and the lens 32 is very small, according to the Fresnel reflection formula, the Schlick approximation of the Fresnel reflection coefficient formula

[0053] F Schlick = F0 + (1 − F0)(1 − cosθ) 5

[0054] It can be seen that as the incident angle θ increases, the reflectivity increases rapidly;

[0055] where F0 = ((n2 - n1) / (n2 + n1)) 2

[0056] It can be seen that as the refractive index difference increases, the reflectivity also increases;

[0057] It can be seen that when the refractive index difference decreases, the reflectivity of the lens surface will be greatly reduced. Therefore, only a small part of the light will be reflected. Specifically, as shown by the light of III-I in the figure, the main light can be extracted normally. Therefore, the extraction efficiency of this part of the light has been significantly improved. So it can be seen that by adding a coating design of an organic oil layer 4 with a trapezoidal shape that is wider at the top and narrower at the bottom, the light that is difficult to extract when exiting at a large angle can be effectively extracted, thereby greatly increasing the radiation power of the deep ultraviolet LED package light source.

[0058] As described above, it is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution of the present invention and its inventive concept, makes equivalent replacements or changes, and should be covered within the protection scope of the present invention.

Claims

1. A UVC LED light source with high light extraction efficiency, characterized in that, Comprising: A packaging substrate (1) configured with a metal electrode (10); An LED chip (2) is soldered on the metal electrode (10), and a light window assembly (3) is further installed above the packaging substrate (1), and the light window assembly (3) is sleeved around the periphery of the LED chip (2); Wherein an organic oil layer (4) is coated on the outer side of the LED chip (2), and the upper end of the organic oil layer (4) contacts the inner bottom surface of the light window assembly (3).

2. The UVC LED light source with high light extraction efficiency according to claim 1, characterized in that: The light window assembly (3) includes a metal shell (31) and a lens (32) placed in the top opening of the metal shell (31); The outer periphery of the lens (32) and the opening of the metal shell (31) are welded and fixed through a solder ring (33).

3. The UVC LED light source with high light extraction efficiency according to claim 2, characterized in that: A sealing metal layer (11) is further formed above the packaging substrate (1), and the sealing metal layer (11) is formed around the metal electrode (10) and is welded and fixed to the bottom of the metal shell (31).

4. The UVC LED light source with high light extraction efficiency according to claim 2, wherein: Anti-reflection films (34) are further formed on the upper and lower end faces of the lens (32).

5. A UVC LED light source with high light extraction efficiency according to claim 1, characterized in that: A dam structure (12) is further formed on the upper surface of the metal electrode (10), and the dam structures (12) on the two metal electrodes (10) are symmetrically arranged and block the bottom of the organic oil layer (4).

6. The UVC LED light source with high light extraction efficiency according to claim 5, characterized in that: The height of the dam structure (12) is not less than 50um, and the distance between the dam structure (12) and the LED chip (2) is not less than 100um.

7. The UVC LED light source with high light extraction efficiency according to claim 2, characterized in that: The upper end of the organic oil layer (4) is laterally extruded through the bottom of the lens (32) to form a trapezoidal structure with a larger upper cross-section and a smaller lower cross-section.

8. A UVC LED light source with high light extraction efficiency according to claim 1, characterized in that: The packaging substrate (1) is a metal bracket or a ceramic bracket.

9. A UVC LED light source with high light extraction efficiency according to any one of claims 1-8, characterized in that: The organic oil layer (4) is an organic fluorine oil layer.

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