White light LED device

Abstract

According to the white light LED device provided by the utility model, the light homogenizing layer containing the light reflecting particles is formed on the surface of the light conversion layer, and light rays emitted from the light conversion layer enter the light homogenizing layer and then are fully reflected and scattered, so that the light rays are more uniformly distributed in all directions, the color temperature difference at all positions can be effectively reduced, and the light color uniformity of the whole LED device is improved; in addition, the light emitting uniformity and brightness of the LED device can be adjusted by adjusting the thickness of the light equalizing layer and the mass fraction of the light reflecting particles.

Description

TECHNICAL FIELD

[0001] The utility model relates to a semiconductor technical field especially a white light LED device. BACKGROUND

[0002] The white light LED device implementation method at home and abroad mainly is the scheme implementation of "blue light LED chip + fluorescent powder layer", wherein the fluorescent powder layer is obtained by "yellow / green / red fluorescent powder + silica gel" mixing, and is "coated" on the light emitting surface of the blue light chip through certain process technical means, and the white light LED device made in this way can meet the demand of most white light illumination application scenes. However, for the electronic digital imaging application scenes such as camera shooting, photographing and machine vision with higher requirements for "spatial light color uniformity", there are still deficiencies. For example, the white light LED device has "light spot color unevenness" in Chinese patents CN201611083244 (a LED packaging structure and a preparation method thereof) and CN201922429405 (a white light LED chip). SUMMARY

[0003] In order to overcome the above deficiencies, the utility model provides a white light LED device, which effectively solves the problem of insufficient light color uniformity of the existing LED device.

[0004] The technical scheme provided by the utility model is as follows:

[0005] A white light LED device comprises:

[0006] A packaging substrate, the surface of which is formed with a conductive circuit;

[0007] An inverted LED chip, which is fixed on the conductive circuit on the surface of the packaging substrate;

[0008] A light conversion layer, which is formed on the light emitting upper surface of the inverted LED chip;

[0009] An even light layer, which is formed on the surface of the light conversion layer;

[0010] A reflective glue layer, which is arranged around the light emitting side surface of the inverted LED chip;

[0011] An optical lens, which is formed on the surface of the packaging substrate and covers the inverted LED chip, the light conversion layer and the even light layer.

[0012] Further preferably, the even light layer is prepared by doping light reflecting particles in silica gel, and the silica gel has a refractive index greater than 1.4 and a Shore hardness greater than 40D.

[0013] Further preferably, the reflectivity of the light-reflecting particles to visible light is greater than 97%, and the light-reflecting particles are one or more of TiO2, SiO2, ZnO, Al2O3, BaSO4, and BaCO4.

[0014] Further preferably, the thickness of the light-uniform layer is 20 µm-100 µm, and the particle size of the doped light-reflecting particles is 1 µm-20 µm.

[0015] Further preferably, the mass fraction content of the light-reflecting particles in the light-uniform layer is 0.1%-75%.

[0016] Further preferably, the area of the light-uniform layer is greater than or equal to the light-conversion layer.

[0017] Further preferably, the lower surface of the optical lens covers the surface of the reflective adhesive layer around the LED chip, and the surfaces of the light-conversion layer and the light-uniform layer.

[0018] Further preferably, the upper surface of the optical lens is one of a hemisphere, a square, an ellipse, and a cone.

[0019] The white light LED device provided by the present application forms a light-uniform layer containing light-reflecting particles on the surface of the light-conversion layer, and the light emitted from the light-conversion layer is fully reflected and scattered after entering the light-uniform layer, so that the light is more uniformly distributed in all directions, the color temperature difference at different positions can be effectively reduced, and the light color uniformity of the entire LED device is improved; in addition, the light-emitting uniformity and brightness of the LED device can be adjusted by adjusting the thickness of the light-uniform layer and the mass fraction of the light-reflecting particles. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 Fig. 1 is a structural schematic diagram of a white light LED device according to an embodiment of the present application;

[0021] Figure 2 Fig. 2 is a schematic diagram of a detection track according to an embodiment of the present application;

[0022] Figure 3 Fig. 3 is a spatial light intensity distribution curve and a spatial color temperature distribution curve of an LED device A;

[0023] Figure 4 Fig. 4 is a spatial light intensity distribution curve and a spatial color temperature distribution curve of an LED device B;

[0024] Figure 5 Fig. 5 is a spatial light intensity distribution curve and a spatial color temperature distribution curve of an LED device C.

[0025] REFERENCE SIGNS:

[0026] 10 - white LED device, 11 - ceramic substrate, 12 - flip blue LED chip, 13 - reflective glue layer, 14 - light conversion layer, 15 - light uniform layer, 16 - optical lens, 20 - light detector, 30 - XYZ coordinate axis, C21 is a detection trajectory in the direction of 0°-180°, C22 is a detection trajectory in the direction of 90°-270°. DETAILED DESCRIPTION

[0027] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the specific embodiments of the present application will be described below with reference to the drawings. Obviously, the drawings described below are only some embodiments of the present application, and for those skilled in the art, other drawings can be obtained from these drawings without creative labor, and other embodiments can also be obtained.

[0028] In one embodiment of the present application, a white LED device comprises: a packaging substrate, a conductive circuit is formed on the surface thereof; a flip LED chip is fixed on the conductive circuit on the surface of the packaging substrate; a light conversion layer is formed on the light emitting upper surface of the flip LED chip; a light uniform layer is formed on the surface of the light conversion layer; a reflective glue layer is arranged around the light emitting side of the flip LED chip; and an optical lens is formed on the surface of the packaging substrate, covering the flip LED chip, the light conversion layer and the light uniform layer.

[0029] The packaging substrate is used to provide support, and can be made of ceramic substrate, PCT, EMC, SMC and the like, as long as a conductive circuit is formed on the surface thereof and can be correspondingly welded and fixed with the electrode of the flip LED chip. The flip LED chip usually adopts a blue chip, and the light conversion layer with yellow light emits white light. Other color LED chips and other color light conversion layers can also be used in cooperation, as long as the light emitted by the LED chip is excited and mixed by the light conversion layer to form white light. The present embodiment does not limit this.

[0030] The light conversion layer is prepared by mixing silica gel and fluorescent powder, and the composition of the internal fluorescent powder material can be at least one or more of: garnet fluorescent body, nitroxide fluorescent body, aluminate fluorescent body, nitride fluorescent body, sulfide fluorescent body, KSF fluorescent body, etc. Different materials can be mixed in the light conversion layer according to different application scenarios. The thickness of the light conversion layer is 40μm-90μm, which covers the light emitting upper surface of the flip LED chip, and the area is greater than or equal to the light emitting upper surface, and the shape and size are adapted to the light emitting upper surface of the LED chip, i.e. it can be the same as the light emitting upper surface of the LED chip, or it can be larger than the light emitting upper surface. After the light conversion layer is attached to the light emitting upper surface of the LED chip, the edge position slightly exceeds; in other embodiments, the area of the light conversion layer can also be slightly smaller than the light emitting upper surface of the LED chip.

[0031] The light uniform layer is prepared by mixing silica gel and light reflection particles, and has an area greater than or equal to that of the light conversion layer, and can fully cover the surface of the light conversion layer. The white light emitted from the light conversion layer is fully reflected and scattered in the light uniform layer, and then emitted to the outside. The silica gel can be single-component silica gel or double-component silica gel, and generally requires a refractive index greater than 1.4 and a Shore hardness greater than 40D. In order to better combine with the light conversion layer, the silica gel can be selected to be the same type as the light conversion layer, or other types of silica gel can be selected, which is not limited in the embodiment. The light reflection particles are white powder substances with certain reflection performance, and the reflectivity of visible light is greater than 97%, such as one or more of TiO2, SiO2, ZnO, Al2O3, BaSO4, and BaCO4, which are uniformly distributed in the light uniform layer. In order to fully reflect and scatter the white light emitted from the surface of the light conversion layer, the particle size of the light reflection particles is limited to 1-20 μm, and the mass fraction in the light uniform layer is 0.1%-75%, that is, the mass of the light reflection particles / the total mass of the light uniform layer is 0.1%-75%, that is, regardless of the number of light reflection particles in the light uniform layer, the ratio of the total mass of the light reflection particles to the total mass of the light uniform layer is 0.1%-75%. The concentration cannot be too high or too low. When the concentration is too low, it cannot fully reflect and scatter the light, and cannot effectively improve the light color uniformity. When the concentration is too high, the light brightness is reduced, the light efficiency is affected, and the light uniform layer is also difficult to prepare. In addition, the thickness of the light uniform layer also affects the light color uniformity and light brightness, and is generally 20-100 μm. When the thickness is too thin, the light cannot be fully reflected and scattered, and when the thickness is too thick, the brightness is reduced. Generally, the total thickness of the light conversion layer and the light uniform layer is less than 200 μm. Therefore, in actual application, the thickness of the light uniform layer and the content of the light reflection particles inside are comprehensively adjusted according to the required light color uniformity and brightness of the LED device, to ensure that the optical parameter conditions required by the device are met.

[0032] In the preparation process of the light conversion layer and the uniform light layer, the whole surface light conversion layer and the uniform light layer can be prepared synchronously, then patterned and cut together and attached to the surface of the LED chip, or the light conversion layer can be formed first and then patterned and attached to the surface of the LED chip, and then the uniform light layer is further formed and attached. Before the preparation of the light conversion layer and the uniform light layer, the LED chip is fixed and welded on the surface of the packaging substrate, and a reflective glue layer is formed around the LED chip for reflecting the light emitted from the side surface of the LED chip to the upper surface of the light conversion layer. The upper surface of the reflective glue layer is not higher than the upper surface of the LED chip, and is generally prepared by mixing silicone and light reflective particles, or by mixing resin and light reflective particles. The resin can be a thermosetting resin such as epoxy resin, thermosetting polyimide resin, phenolic resin, urea resin, melamine resin, unsaturated polyester resin, diallyl phthalate resin, thermosetting polyurethane resin, etc., and is preferably a thermosetting silicone resin or an epoxy resin. The light reflective particles are generally white inorganic pigments such as titanium oxide, zinc oxide, zirconium oxide, lead white (lead carbonate), calcium carbonate, kaolin (kaolinite), clay minerals, etc., and are preferably titanium oxide, which is doped in the resin at a suitable concentration to make the reflective glue layer as a whole have a high reflectivity, such as 85% or more, 90% or more, etc. In other embodiments, the thickness of the reflective glue layer can be further extended to cover the side walls of the light conversion layer and the side walls of the uniform light layer.

[0033] After the light conversion layer and the uniform light layer are attached, an optical lens is formed on the top of the LED device, the LED chip with the attached film is put into a molding machine for one-time optical lens molding, and then is baked in an oven at 150°C for 2H (hours). Finally, the Dissco cutting machine is used for cutting to obtain a single white light LED device. The optical lens is made of transparent materials such as glass, silicone, etc., and is directly molded on the surface of the packaging substrate. The lower surface of the optical lens covers the entire LED chip, the light conversion layer and the uniform light layer, and can also cover the surface of the reflective glue layer around the LED chip, i.e. the area of the lower surface of the optical lens can basically cover the area of the packaging substrate in the single LED device, fully collecting and utilizing the light generated by the single LED device, and forming a whole with the LED chip; the upper surface of the optical lens can be hemispherical, square, elliptical, conical, etc., to gather stray light and adjust the emission angle of the light to the outside.

[0034] In an example, as shown in FIG. 1, the LED chip 1 is fixed and welded on the surface of the packaging substrate 2, and the reflective glue layer 3 is formed around the LED chip 1. The light conversion layer 4 is formed on the upper surface of the LED chip 1, and the uniform light layer 5 is formed on the light conversion layer 4. The optical lens 6 is formed on the top of the LED device. Figure 1As shown, the white LED devices are all 3535 ceramic white light products, using 38 mil flip-chip blue LED chip 12 soldered on the surface of the ceramic substrate 11, the chip around the set of reflective glue layer 13, and in the light-emitting surface mounted light conversion layer 14 and light uniform layer 15, while in the top configuration hemispherical optical lens 16, the lower surface of the optical lens covered in the LED chip around the reflective glue layer 13 surface and light conversion layer 14 and light uniform layer 15 surface, making full use of the area occupied by a single white LED device package substrate, comprehensive collection of internal LED chip generated light.

[0035] For the relationship between the light reflection particles in the light uniform layer and the light color uniformity, three white LED devices with the same structure except for the light uniform layer were prepared, and the basic structure and Figure 1 As shown, the structure of the LED chip light-emitting surface is as follows:

[0036] The LED device A is mounted with a common yellow light conversion layer on the light-emitting surface, which cooperates with the blue LED chip to emit white light; the LED device B is mounted with a common yellow light conversion layer and a light uniform layer containing TiO2 on the light-emitting surface, the light uniform layer only doped with TiO2 particles without other light reflection particles, the concentration of TiO2 particles is 1.0%, and the thickness is 80 μm; the LED device C is mounted with a common yellow light conversion layer and a light uniform layer containing TiO2 on the light-emitting surface, the light uniform layer only doped with TiO2 particles without other light reflection particles, the concentration of TiO2 particles is 1.5%, and the thickness is also 80 μm. The particle concentration referred to here is the mass fraction of TiO2 in the light uniform layer.

[0037] The following tests were performed, and the weighted average color temperature of each was calculated for comparison: after lighting the LED device, a stereoscopic detection method was used, as shown in Figure 2 The bottom center of the packaging substrate of the white LED device 10 under test was taken as the origin to construct a three-dimensional space "Cartesian" coordinate system (i.e. XYZ coordinate axis 30), with a 0°-180° direction detection track and a 90°-270° direction detection track, on each detection track, the light detector 20 moved along the detection track, and the optical characteristic parameter was tested every 1°, i.e. there were 181 detection points uniformly distributed on each detection track. Finally, the data collected was calculated by the following formula:

[0038] The weighted average color temperature is:

[0039]

[0040] Where c is the number of detection trajectories, c(0-180°) is the detection trajectory corresponding to the 0-180° direction of the plane where the LED device is located, and c(90°-270°) is the detection trajectory corresponding to the 90°-270° direction of the plane where the LED device is located; I i The light intensity value detected by CCT at observation angle i, with the LED device as the origin, in the corresponding detection trajectory. i The color temperature value detected by the i-angle of observation with the LED device as the origin in the corresponding detection trajectory.

[0041] Spatial color temperature difference Wherein, CCT0 is the center color temperature.

[0042] The spatial color temperature difference ΔCCT for LED devices A, B, and C was calculated separately, and the results are shown in the table below:

[0043]

[0044] Simultaneously, based on the collected data, spatial luminous intensity distribution curves and spatial color temperature distribution curves were plotted for each LED device, such as... Figures 3-5 As shown, each figure displays the data collected on two detection trajectories (C0 / 180 represents the detection trajectory in the 0°-180° direction, and C90 / 270 represents the detection trajectory in the 90°-270° direction), visually demonstrating the distribution of light intensity and color temperature.

[0045] The specific details are as follows:

[0046] For LED device A: its structure is a combination of a regular LED chip and a light conversion layer. When the emitted light is transmitted through a white background, it appears as an abnormal light spot with a "white center and yellow outer ring," and the color difference is observable to the human eye. Its spatial light intensity distribution curve and spatial color temperature distribution curve are shown below. Figure 3 As shown in the diagram (left side is the light intensity distribution diagram, right side is the color temperature distribution diagram), it can be seen from the light intensity distribution curve that the spatial light intensity distribution of LED device A is similar to a "Lambertian matrix distribution". That is, the light intensity value I0 is the largest in the direction perpendicular to the light-emitting surface of the device; the light intensity value I in the direction deviating from the normal angle by the largest "±90°" is... -90 / I90The minimum. As can be seen from the color temperature distribution curve, the color temperature distribution curve fluctuates greatly, indicating that the color temperature values detected by the light detector at different observation angles in space are different and the difference is large: for example, in the C0 / 180 direction, the maximum central color temperature value of 3153K is detected at the “0°” observation angle, the color temperature value of 2827K is detected at the “-90°” observation angle, and the color temperature value of 2868K is detected at the “74°” observation angle; in the C90 / 270 direction, the maximum central color temperature value of 3153K is detected at the “0°” observation angle, the color temperature value of 2723K is detected at the “-90°” observation angle, and the color temperature value of 2492K is detected at the “90°” observation angle. The final calculation result is that the central color temperature CCT0=3153K, the weighted average color temperature =2989K, and the spatial color temperature difference calculation result is △CCT=|3153K-2989K|=164K. The light color uniformity is poor, which is consistent with the result perceived by the human eye.

[0047] For LED device B: its structure is a combination of LED chip plus light conversion layer and a light uniform layer containing TiO2 particles formed on the surface of the light conversion layer. When the transmitted light is transmitted on a white background plate, the human eye cannot observe color difference. The spatial light intensity distribution curve and the spatial color temperature distribution curve are as shown in Figure 4 The spatial light intensity distribution curve of device B is also similar to the “Lambertian distribution”, and the light intensity value I0 perpendicular to the light emitting surface of the device is the maximum; the light intensity value I -90 / I90 The minimum. As can be seen from the color temperature distribution curve, the color temperature distribution curve fluctuates greatly, indicating that the color temperature values detected by the light detector at different observation angles in space are different and the difference is large: for example, in the C0 / 180 direction, the maximum central color temperature value of 3153K is detected at the “0°” observation angle, the color temperature value of 2827K is detected at the “-90°” observation angle, and the color temperature value of 2868K is detected at the “74°” observation angle; in the C90 / 270 direction, the maximum central color temperature value of 3153K is detected at the “0°” observation angle, the color temperature value of 2723K is detected at the “-90°” observation angle, and the color temperature value of 2492K is detected at the “90°” observation angle. The final calculation result is that the central color temperature CCT0=3153K, the weighted average color temperature =2989K, and the spatial color temperature difference calculation result is △CCT=|3153K-2989K|=164K. The light color uniformity is poor, which is consistent with the result perceived by the human eye.

[0048] For LED device C: its structure is a combination of LED chip plus light conversion layer, and a light uniform layer containing TiO2 particles is formed on the surface of the light conversion layer, and the concentration of TiO2 particles in the light uniform layer is higher than that of device B. When the transmitted light is transmitted on a white background plate, the human eye cannot observe chromatic aberration. Its spatial light intensity distribution curve and spatial color temperature distribution curve are as shown in Figure 5 The light intensity distribution curve shows that the spatial light intensity distribution of device C is also similar to "Lambertian distribution", and the light intensity value I0 is maximum perpendicular to the light emitting surface of the device; the light intensity value I -90 / I90 is minimum at the maximum "±90°" direction deviating from the angle. From the color temperature distribution curve, it can be seen that the color temperature distribution curve is smooth and almost undulating, which shows that the color temperature values detected by the light detector at different observation angles of device C are different, but the difference is very small: for example, in the direction of C0 / 180, the maximum central color temperature value detected at the observation angle of "0°" is "3022K", the color temperature value detected at the observation angle of "-80°" is "2793K", and the color temperature value detected at the observation angle of "80°" is "2773K"; in the direction of C90 / 270, the maximum central color temperature value detected at the observation angle of "0°" is "3022K", the color temperature value detected at the observation angle of "-80°" is "2761K", and the color temperature value detected at the observation angle of "80°" is "2709K". The final calculation results are central color temperature CCT0=3022K, weighted average color temperature =3003K, and the spatial color temperature difference calculation result is △CCT=|3022K-3003K|=19K. The light color uniformity is very good, which is consistent with the result perceived by the human eye. Compared with LED device B, the spatial color temperature difference is further reduced by 29K, which shows that the larger the mass fraction of light reflecting particles in the light uniform layer, the better the light color uniformity.

[0049] From the above test results, it can be easily known that the white light LED device with the light uniform layer on the surface of the light conversion layer in the utility model has a significantly reduced spatial color temperature difference compared with the traditional LED device without the light uniform layer, and can effectively improve the light color uniformity; and as the mass fraction of light reflecting particles in the light uniform layer increases, the light color uniformity improvement effect of the LED device will be better. Generally, after the light uniform layer is formed on the surface of the light conversion layer, the spatial color temperature difference of the white light LED device calculated by the above method is less than 100K, at this time, the human eye cannot observe chromatic aberration, and the overall light emission of the white light LED device is uniform and good. In practical applications, the thickness, mass fraction of light reflecting particles and other parameters of the light uniform layer can be adjusted according to the application scene, so that the spatial color temperature difference of the LED device is less than the required threshold value, such as less than 50K, less than 100K, etc., and generally not more than 200K. The smaller the spatial color temperature value, the better the light color uniformity.

[0050] It should be noted that the above embodiments can be freely combined according to needs. The above is only the preferred embodiment of the present application, it should be pointed out that, for those skilled in the technical field, without departing from the principles of the present application, can make a number of improvements and refinements, these improvements and refinements should also be considered as the protection scope of the present application.

Claims

1. A white light LED device, characterized by, The application relates to a flip-chip LED package, which comprises: a packaging substrate, the surface of which is formed with a conductive circuit; a flip-chip LED chip, which is fixed on the conductive circuit on the surface of the packaging substrate; a light conversion layer, which is formed on the light-emitting upper surface of the flip-chip LED chip; a light-uniform layer, which is formed on the surface of the light conversion layer; a reflective glue layer, which is arranged around the light-emitting side surface of the flip-chip LED chip; an optical lens, which is formed on the surface of the packaging substrate and covers the flip-chip LED chip, the light conversion layer and the light-uniform layer.

2. The white LED device as described in claim 1, characterized in that, The light-uniform layer is prepared by doping light-reflective particles in silica gel, the refractive index of the silica gel is greater than 1.4, and the Shore hardness is greater than 40D.

3. The white LED device as described in claim 2, characterized in that, The reflectivity of the light-reflective particles to visible light is greater than 97%.

4. The white LED device as described in claim 2, characterized in that, The thickness of the light-uniform layer is 20-100 mu m, and the particle size of the doped light-reflective particles is 1-20 mu m.

5. The white LED device according to any one of claims 1 to 4, wherein the phosphor layer is formed on the surface of the LED chip. The area of the light-uniform layer is greater than or equal to that of the light conversion layer.

6. The white LED device of any of claims 1-4, wherein the phosphor is a mixture of a red phosphor and a blue phosphor. The lower surface of the optical lens covers the surface of the reflective glue layer around the flip-chip LED chip, the surface of the light conversion layer and the surface of the light-uniform layer.

7. The white LED device of any of claims 1-4, wherein the phosphor is a mixture of a red phosphor and a blue phosphor. The upper surface of the optical lens is one of a semispherical shape, a square shape, an elliptical shape and a conical shape.

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