Fluorescent film sheet and method of manufacturing the same, LED packaging structure and method of manufacturing the same

Abstract

The application provides a fluorescent film piece, a preparation method thereof, an LED packaging structure and a packaging method thereof, wherein the fluorescent film piece emits white light under excitation of a blue light LED chip, the light emission wavelength band of the blue light LED chip is 440nm-460nm, and the fluorescent film piece comprises: a first fluorescent film layer, which is arranged close to the light emission surface side of the blue light LED chip and emits white light under excitation of the blue light LED chip; and a second fluorescent film layer, which is arranged on the surface of the first fluorescent film layer and is a single-color fluorescent powder film layer, wherein the peak wavelength range of the doped single-color fluorescent powder is 470nm-500nm. The first fluorescent film layer capable of meeting the requirements of color temperature and color rendering index and the second fluorescent film layer capable of reducing blue light power are combined together, and the technical problem that some products in the prior art are difficult to reduce blue light damage is overcome through a simple scheme.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor technology, and in particular to a fluorescent film sheet, a preparation method thereof, an LED packaging structure and a packaging method thereof. BACKGROUND

[0002] At present, most of the white light LEDs on the market are obtained by exciting yellow fluorescent powder with blue light emitted by a blue light chip in the 440nm-460nm (nanometer) wave band range. The spectrum of such LEDs has a very high intensity blue spectrum peak, thereby causing "blue light hazard". In order to reduce "blue light hazard", there are two commonly used methods: 1) using double blue light chips, that is, packaging two blue light chips with a wavelength of 450nm±2nm and a wavelength of 480nm±2nm in the same LED lamp bead, such as Chinese patent CN202122089676.0; 2) using a purple light chip to package into an LED lamp bead. The lamp beads packaged by the above two methods usually have a high color rendering index (CRI>90). For LED products with a low color rendering index (CRI<90), especially for LED products with 70<CRI<80, the blue light intensity cannot be reduced by the above two methods.

[0003] To reduce the blue light intensity in LED products with CRI<90 (including 70<CRI<80 mentioned above), the proportion of fluorescent powder can also be adjusted; when this method is applied to LED products with a color temperature of ≤4200K (Kelvin), since more fluorescent powder is added in the fluorescent film sheet, appropriate adjustment of the proportion of fluorescent powder can reduce the intensity of blue light power to a certain extent; but if it is applied to LED products with a color temperature of >4500K, since the amount of fluorescent powder in such products is small, no matter how the proportion of fluorescent powder is adjusted, "blue light hazard" will still occur due to the insufficient amount of fluorescent powder.

[0004] In order to solve the above technical problems, theoretically, the blue light intensity can be further absorbed by adding fluorescent powder with a wavelength close to that of the blue light chip and a peak wavelength between 450nm-500nm in the fluorescent film sheet, but there are several problems when this method is actually used: due to the secondary excitation of the fluorescent powder, the yellow, green and red fluorescent powders originally added therein can easily offset the effect of the wavelength fluorescent powder, thereby failing to achieve the purpose of reducing the blue light intensity of the white light LED. SUMMARY

[0005] In order to overcome the above shortcomings, the present application provides a fluorescent film sheet and a preparation method thereof, an LED packaging structure and a packaging method thereof. A second fluorescent film layer containing monochromatic fluorescent powder with a peak wavelength range of 470nm-500nm is further formed on the surface of the first fluorescent film layer, which is used to absorb and convert blue light and reduce the intensity of blue light.

[0006] The technical scheme provided by the present application is:

[0007] In one aspect, the present application provides a fluorescent film piece, comprising:

[0008] The fluorescent film piece emits white light under the excitation of a blue light LED chip, the light emission band of the blue light LED chip is 440-460 nm, and the fluorescent film piece comprises:

[0009] A first fluorescent film layer is arranged close to the light emitting surface of the blue light LED chip, and the first fluorescent film layer emits white light under the excitation of the blue light LED chip;

[0010] A second fluorescent film layer is arranged on the surface of the first fluorescent film layer, and the second fluorescent film layer is a single-color fluorescent film layer doped with single-color fluorescent powder with a peak wavelength range of 470-500 nm.

[0011] In another aspect, the present application provides an LED packaging structure, comprising:

[0012] A blue light LED chip, the blue light LED chip comprising a light emitting surface, a light emitting side and an electrode surface opposite to the light emitting surface;

[0013] The fluorescent film piece as described above, and the first fluorescent film layer of the fluorescent film piece is arranged close to the light emitting surface of the blue light LED chip.

[0014] In still another aspect, the present application provides a fluorescent film piece preparation method, comprising the following steps:

[0015] Uniformly mix single-color fluorescent powder with a peak wavelength range of 470-500 nm and silica gel, coat the second fluorescent film layer on the surface of the support film, and bake to a semi-cured state;

[0016] Uniformly mix the first fluorescent powder and silica gel, coat the first fluorescent film layer on the surface of the second fluorescent film, and bake to a completely cured state;

[0017] The first fluorescent film layer has a first upper surface and a first lower surface, the second fluorescent film layer has a second upper surface and a second lower surface, the first upper surface of the first fluorescent film layer is in contact with the second lower surface of the second fluorescent film layer, and the surface roughness of the second upper surface of the second fluorescent film layer is less than the surface roughness of the first lower surface of the first fluorescent film.

[0018] In still another aspect, the present application provides a fluorescent film piece preparation method, comprising the following steps:

[0019] Uniformly mix the first fluorescent powder and silica gel, coat the first fluorescent film layer on the surface of the support film, and bake to a semi-cured state;

[0020] Mixing the monochromatic fluorescent powder with peak wavelength range of 470nm-500nm with silica gel uniformly, coating on the surface of the first fluorescent film to form the second fluorescent film layer, and baking to completely solidified state.

[0021] In still another aspect, the application provides a packaging method of LED packaging structure, characterized in that, comprising the following steps:

[0022] Cutting and expanding the whole fluorescent film sheet prepared by the fluorescent film sheet preparation method as described above to obtain the fluorescent film sheet suitable for the light emitting surface of the LED chip;

[0023] Attaching the fluorescent film sheet to the light emitting surface side of the blue light LED chip, and arranging the first fluorescent film layer close to the side of the blue light LED chip.

[0024] The fluorescent film sheet and the preparation method thereof, the LED packaging structure and the packaging method thereof provided by the application can at least bring the following beneficial effects:

[0025] 1. The fluorescent film sheet and the LED packaging structure provided by the application further form a layer of monochromatic fluorescent powder fluorescent film layer with peak wavelength range of 470nm-500nm on the surface of the first fluorescent film layer, which can effectively absorb and convert part of the blue light under the premise of meeting the color temperature and color rendering index requirements of white light, thereby reducing the intensity of the blue light. The fluorescent film sheet provided by the application has double layers of fluorescent film layer, and the two layers of fluorescent film layer are arranged in different structures and do not interfere with each other, so that the roles played by each layer will not be offset, and the fluorescent film sheet has wide applicability and can be applied to any LED with color rendering index and color temperature conditions, and the preparation process is simple, facilitating production and use.

[0026] 2. The application provides two preparation methods of the fluorescent film sheet: one is to form the first fluorescent film layer first, then semi-solidify, and then form the second fluorescent film layer and completely solidify, which is conducive to forming firm bonding between the second fluorescent film layer and the semi-solidified first fluorescent film layer; the other is to form the second fluorescent film layer on the surface of the support film first, then semi-solidify, and then form the first fluorescent film layer on the surface of the second fluorescent film layer and completely solidify, which is not only conducive to forming firm bonding between the first fluorescent film layer and the semi-solidified second fluorescent film layer, but also can make the surface roughness of the second upper surface of the second fluorescent film layer smaller than the surface roughness of the first lower surface of the first fluorescent film, which is conducive to the subsequent process of adsorbing and transferring the second upper surface of the second fluorescent film layer to the light emitting surface of the LED chip by the suction nozzle. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 It is a spectral comparison chart of the fluorescent film sheet in an embodiment of the application;

[0028] Figure 2 A cross-sectional view of an LED package structure according to another embodiment of the present application;

[0029] Figure 3 A cross-sectional view of an LED package structure according to still another embodiment of the present application.

[0030] Reference Signs:

[0031] 10 - phosphor film, 11 - first phosphor film layer, 12 - second phosphor film layer, 20 - blue LED chip, 21 - light emitting upper surface, 22 - light emitting side surface, 23 - electrode side surface, 30 - encapsulation structure. DETAILED DESCRIPTION

[0032] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, specific embodiments of the present application will be described below with reference to the drawings. Obviously, the drawings in the following description 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.

[0033] In one embodiment of the present application, a phosphor film emits white light under the excitation of a blue LED chip, the light emitting wavelength band of the blue LED chip is 440nm-460nm, and the phosphor film comprises: a first phosphor film layer, which is arranged close to the light emitting surface of the blue LED chip and emits white light under the excitation of the blue LED chip; and a second phosphor film layer, which is arranged on the surface of the first phosphor film layer and is a single-color phosphor film layer, and the peak wavelength range of the doped single-color phosphor is 470nm-500nm.

[0034] The phosphor film of the present embodiment is prepared for a blue LED chip with a light emitting wavelength band of 440nm-460nm. For the blue chip of this wavelength band, the light emitted by a single blue chip is excited to white light by the phosphor film provided in the present embodiment, and the blue light power is significantly reduced compared to ordinary white light chips. The phosphor film can absorb the blue light harmful to the human body and convert it into other wavelengths of light that are not harmful to the human body. The blue chip with a light emitting wavelength band of 440nm-460nm can be a vertical structure, a normal structure or a flip-chip structure, and the shape and size of the chip are not limited, which can be circular, square, polygonal or even irregular shape, as long as it can emit light normally. The shape and size of the phosphor film are designed according to the light emitting surface of the LED chip, and the phosphor film covers the light emitting surface of the LED chip.

[0035] The first fluorescent film layer in the fluorescent film sheet is arranged on the surface of the blue light chip light emitting surface, is formed by uniformly mixing the fluorescent powder and silica gel according to a certain mass ratio and then solidifying, emits white light after being excited by the light of the blue light LED chip with a wavelength of 440-460 nm, for example, the yellow fluorescent powder (YAG, yttrium aluminum garnet) generates white light after being excited by blue light. In addition, the chemical composition of the fluorescent powder can be at least one or more of the following: garnet fluorescent powder, oxynitride fluorescent powder, aluminate fluorescent powder, nitride fluorescent powder, sulfide fluorescent powder, KSF fluorescent powder, etc. In actual application, the types and proportions of the fluorescent powder and silica gel in the first fluorescent film layer can be adjusted according to specific conditions to meet different color rendering index and color temperature requirements. For example, for a scene with high color rendering index requirement (CRI>90), the types of fluorescent powder can be appropriately increased, green fluorescent powder and red fluorescent powder can be added to the yellow fluorescent powder, or a mixture of blue fluorescent powder, green fluorescent powder and red fluorescent powder can be used, or even more color fluorescent powders can be mixed to increase the spectral composition of white light and more accurately display the true color of objects. For a scene with low color rendering index requirement, the types of fluorescent powder can be reduced, such as only using yellow fluorescent powder. For a scene with low color temperature requirement (CCT≤4200K), the mass fraction of fluorescent powder in the first fluorescent film layer can be appropriately increased, and for a scene with high color temperature requirement (CCT>4200K), the mass fraction of fluorescent powder in the first fluorescent film layer can be appropriately reduced. In this way, the types and proportions of fluorescent powder are adjusted to meet the requirements of color temperature and color rendering index to meet the quality of white light. Although the white light excited by the first fluorescent film layer can meet the requirements of color temperature and color rendering index, the white light spectrum has a high blue light intensity, which can easily cause blue light damage to the human body. Therefore, the second fluorescent film layer is further arranged on the surface of the first fluorescent film layer.

[0036] The second fluorescent film layer contains monochromatic fluorescent powder with a peak wavelength range of 470-500 nm and silica gel, is formed by uniformly mixing the fluorescent powder and silica gel according to a certain mass ratio and then solidifying, and is arranged on the surface of the first fluorescent film layer away from the light emitting surface of the chip. After the light emitted by the blue light chip is excited to white light by the first fluorescent film layer, the monochromatic fluorescent powder in the second fluorescent film layer further absorbs the blue light harmful to the human body and converts it into greenish light (with a peak wavelength range of 470-500 nm) harmless to the human body, achieving the effect of reducing the intensity of blue light. In the second fluorescent film layer, only monochromatic fluorescent powder with a peak wavelength range of 470-500 nm and silica gel exist. In an example, the mass of the monochromatic fluorescent powder is 50-100% of the mass of the silica gel in the second fluorescent film layer, which has little effect on the color rendering index and color temperature of the excited white light. Figure 1As shown, the abscissa represents the light-emitting wavelength (unit: nm), the ordinate represents the relative light-emitting intensity of each wavelength, the solid line is the spectral curve of the first fluorescent film layer after being excited by the blue light LED chip, and the dashed line is the spectral curve of the double-layer fluorescent film provided by the embodiment after being excited by the blue light LED chip. As can be seen from the figure, the blue light power at 440 nm in the dashed line is obviously lower than that in the solid line, that is, the double-layer fluorescent film provided by the embodiment can effectively reduce the blue light intensity compared with the conventional fluorescent film. Therefore, the fluorescent film provided by the embodiment not only meets the requirements of any color rendering index and color temperature, but also effectively reduces the blue light intensity.

[0037] The fluorescent film is formed with a first fluorescent film layer and a second fluorescent film layer, and the shapes and sizes of the two are usually consistent. The first fluorescent film layer is prepared from fluorescent powder and silica gel, and the second fluorescent film layer is prepared from single-color fluorescent powder doped in silica gel. The first fluorescent film layer has a first upper surface and a first lower surface, and the second fluorescent film layer has a second upper surface and a second lower surface. When the fluorescent film is used on the LED chip, the first fluorescent film layer is located at the lower layer, the first lower surface directly contacts the light-emitting surface of the blue light LED chip, the first upper surface faces upward, the second fluorescent film layer is located at the upper layer, the second lower surface directly contacts the first upper surface of the first fluorescent film layer, and the second upper surface faces upward. The second lower surface of the second fluorescent film layer and the first upper surface of the first fluorescent film layer are located on the same horizontal plane, and are in contact and closely bonded together inside the fluorescent film. For the entire fluorescent film, only the first lower surface of the first fluorescent film layer and the second upper surface of the second fluorescent film layer contact the external environment. The first lower surface of the first fluorescent film layer is bonded together with the light-emitting surface of the blue light LED chip through encapsulation, and the second upper surface of the second fluorescent film layer is used to be acted on by the suction nozzle in encapsulation. Therefore, the surface roughness of the second upper surface plays an important role in the adsorption effect, and the better the flatness of the second upper surface, the more conducive to generating greater adsorption force. In the embodiment, the surface roughness of the second upper surface of the second fluorescent film layer is smaller than that of the first lower surface of the first fluorescent film layer. Therefore, when the suction nozzle acts on the second upper surface, the generated adsorption force can easily lift the fluorescent film from the original release film surface and transfer it to the light-emitting surface of the blue light LED chip. After the adsorption force of the suction nozzle is released, the first lower surface of the first fluorescent film layer with a rougher surface is bonded to the light-emitting surface of the blue light LED chip.

[0038] In addition, another embodiment of the present application is a preparation method of a fluorescent film. Specifically, the preparation process of the fluorescent film is as follows:

[0039] 1. Mix the first phosphor powder and silica gel uniformly, coat on the surface of the support film to form the first phosphor film layer, and bake to semi-cured state. Weigh the first phosphor powder and silica gel according to a certain proportion, and uniformly stir and vacuum degassing. The chemical composition and proportion of the first phosphor powder can be configured according to the color temperature and color rendering index requirements. In an example, the first phosphor powder includes yellow phosphor powder, green phosphor powder and red phosphor powder.

[0040] 2. Place the stirred material on the surface of the support film on the tabletop of the film making machine, set the scraper height, scrape out a first phosphor film layer of a certain thickness (such as 20µm, 50µm, 100µm, 200µm, 300µm, 400µm, 450µm, etc.), and bake the film at a temperature of 130℃ for 0.5h to form; make it in a semi-cured state, that is, lose a certain fluidity but the surface is not completely cured and formed, forming a second phosphor film layer. At this time, the second phosphor film layer is in a semi-cured state, which will not flow like a liquid substance, but also will not be as hard as a completely cured substance. The surface of the substance in this state shows a certain stickiness. Compared with the conditions for completely curing the ordinary phosphor film, the semi-cured state is usually achieved by reducing the baking time or reducing the baking temperature, which is beneficial to the subsequent bonding with the first phosphor film layer, and avoids the influence of re-baking after curing on the properties of the second phosphor film layer, such as changing its chemical properties, causing shrinkage or deformation, etc.

[0041] 3. Weigh the silica gel with a mass of M1 and 50%-100% M1 mass of monochromatic phosphor powder with a peak wavelength range of 470nm-500nm, and uniformly stir and vacuum degassing.

[0042] 4. Place the stirred material on the first support film, set the scraper height, scrape out a second phosphor film layer of a certain thickness (such as 20µm, 50µm, 100µm, 200µm, 300µm, 400µm, 450µm, etc.), and bake the film at a temperature of 150℃ for 1h to completely cure, to obtain a completely cured first phosphor film layer and a second phosphor film layer.

[0043] In addition, in order to make the phosphor powder in the first phosphor film layer and the second phosphor film layer mix more uniformly in the baking and curing process, and avoid sedimentation due to gravity, an anti-settling agent, a uniform light powder or other components can also be added to the first phosphor film layer and the second phosphor film layer, as long as the phosphor film can be normally excited and converted by blue light.

[0044] Before the fluorescent film piece is applied to the blue light chip, it also includes cutting the whole fluorescent film piece according to the shape and size of the light emitting surface of the blue light chip, and transferring the cut fluorescent film piece from the supporting film. In this embodiment, the first fluorescent film layer and the second fluorescent film layer are formed on the surface of the supporting film in turn, and after cutting, when the fluorescent film piece is transferred to the surface of the chip, since the first fluorescent film layer is between the supporting film and the second fluorescent film layer, the fluorescent film piece needs to be turned over to another supporting film, the original supporting film on the bottom surface of the first fluorescent film layer is removed, then the surface of the light emitting surface of the blue light LED chip is pasted to the first fluorescent film layer, and then the blue light LED chip and the fluorescent film piece are turned over to remove the supporting film.

[0045] In another embodiment of the present application, a preparation method of a fluorescent film piece is also provided, which can form the second fluorescent film layer on the surface of the supporting film first and then form the first fluorescent film layer; at this time, when the second fluorescent film layer is prepared, it needs to be baked at a temperature of 130℃ for 0.5h to make it in a semi-cured state; after the first fluorescent film layer is formed on the surface of the second fluorescent film layer, it is baked at a temperature of 150℃ for 1h to make the first fluorescent film layer and the second fluorescent film layer completely cured and formed. Specifically, the preparation process of the fluorescent film piece is as follows:

[0046] S01: The monochromatic fluorescent powder with a peak wavelength range of 470nm-500nm is uniformly mixed with silica gel, coated on the surface of the supporting film to form the second fluorescent film layer, and baked to a semi-cured state. The mass of the monochromatic fluorescent powder is 50%-100% of the mass of the silica gel. The supporting film referred to here plays the role of providing a supporting platform, its surface is smooth and flat and has no adhesion, which is convenient for separating the finally formed fluorescent film piece from the supporting film, and can be a release film, etc. The doctor blade of the film making machine is used to act on the stirred monochromatic fluorescent powder and silica gel to obtain a second fluorescent film layer with a certain thickness on the surface of the supporting film; and finally baked to a semi-cured state (the surface still has adhesion, but has become cohesive and will not flow) under certain conditions. At this time, the second upper surface (i.e. the surface on the bottom) of the second fluorescent film layer is in direct contact with the surface of the bottom supporting film, since the doctor blade exerts a force on the second fluorescent film layer, it is beneficial to form a closer contact between the bottom surface (the second upper surface) and the supporting film, while the surface on the other side (the second lower surface) is free to flow due to the fluidity of the liquid before baking after the doctoring, and the monochromatic fluorescent powder in the functional adhesive layer also causes the roughness of the plane formed by the free flow to be larger.

[0047] S02 the first phosphor powder is uniformly mixed with silica gel, coated on the surface of the second phosphor film layer to form a first phosphor film layer, and baked to a completely cured state. The second phosphor film layer and the support film at the bottom thereof in the previous step are placed on the workbench of the film forming machine (the support film faces downward), the mixture of the first phosphor powder and silica gel is transferred to the surface of the second phosphor film layer, and the doctor blade of the film forming machine is used to act on the mixture to obtain a first phosphor film layer with a certain thickness on the surface of the second phosphor film layer; then the first phosphor film layer is completely cured under certain conditions to obtain a double-layer phosphor film piece. At this time, due to the force of the doctor blade, the first upper surface of the first phosphor film layer (i.e. the bottom of the phosphor gel layer) is tightly attached to the surface of the second phosphor film layer (i.e. the second lower surface) (the first upper surface of the first phosphor film layer and the second lower surface of the second phosphor film layer coincide), and the contact surface (the second upper surface 121) of the second phosphor film layer and the support film is also pressed, which is beneficial to making the second upper surface of the second phosphor film layer more smooth and flat, and further reducing the roughness. The first lower surface of the first phosphor film layer (i.e. the top of the first phosphor film layer) has no external support or platform effect, and the liquid flows freely to form a plane before baking after the glue is scraped, and the first phosphor powder in the first phosphor film layer also causes the roughness of the free-flowing plane to be larger, so the roughness after curing is relatively larger, that is, the surface roughness of the second upper surface of the second phosphor film layer is smaller than the surface roughness of the first lower surface of the first phosphor film.

[0048] In another embodiment of the present application, an LED packaging structure comprises: a blue light LED chip, the blue light LED chip comprising a light emitting upper surface, a light emitting side surface and an electrode surface opposite to the light emitting upper surface; a phosphor film piece as described above, and the first phosphor film layer of the phosphor film piece is close to the light emitting upper surface of the blue light LED chip

[0049] The shape and size of the phosphor film piece are basically consistent with the shape and size of the light emitting upper surface of the LED chip. In order to avoid blue light leakage, the area of the phosphor film layer is usually slightly larger than the light emitting surface of the LED chip, and can completely cover the light emitting upper surface of the LED chip. The cladding structure is formed around the LED chip to reflect the light emitted from the light emitting side surface of the chip. The first phosphor film layer of the phosphor film layer is close to the blue light LED chip, and the second phosphor film layer is relatively far away from the blue light LED chip. The light of the LED chip is emitted from the light emitting surface and enters the first phosphor film layer, is excited to white light meeting the requirements of color temperature and color rendering index, and then the blue light is absorbed by the second phosphor film layer to convert into green light harmless to human body. For example Figure 2As shown, the blue LED chip 20 is a flip chip, the light emitting upper surface 21 is the light emitting surface, the light emitting side surface 22 is the side surface connected with the side of the light emitting surface, and the side opposite to the light emitting surface of the blue LED chip (i.e. the electrode surface) is provided with two chip electrodes (one anode and one cathode), and the electrode side surface 23 is the side surface connected with the chip contact surface of the chip electrodes. The phosphor film 10 is attached to the surface of the light emitting surface of the blue LED chip, and one side of the first phosphor film layer 11 of the phosphor film 10 is close to the blue LED chip, and the other side of the second phosphor film layer 12 is far away from the blue LED chip.

[0050] When the blue LED chip itself is single surface light emitting, such as a vertical structure chip, the package structure can be provided or not, which does not affect the normal use of the LED product. If the package structure is provided, it is beneficial to protect the chip. When the blue LED chip itself is multi-surface light emitting, such as a flip chip, and the final LED product requires single surface light emitting, the package structure can be provided at least around the light emitting side surface of the blue LED chip, and the package structure is doped with high reflectivity particles to reflect the side surface light emitting. For example, Figure 2 As shown, the package structure 30 is a mixture of resin and high reflectivity particles, which is formed around the LED chip, and the light emitted from the LED chip is reflected back by the high reflectivity particles, so that the single LED chip only emits light from the light emitting upper surface of the LED chip to obtain a better light pattern. The high reflectivity 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 titanium oxide is preferred. Since the purpose of forming the first glue layer on the light emitting side surface of the LED chip is to prevent side surface light emitting, the doping proportion of the high reflectivity particles needs to be adjusted according to the actual situation in application, so that the high reflectivity reaches a preset value (such as 80%, 90%, 95%, etc.) or more. In another embodiment, in order to make the light emitting from the side of the chip electrode also form reflection, for example, Figure 3 As shown, in the LED package structure, the package structure 30 is not only formed around the blue LED chip 20, but also formed on the electrode side surface 23 of the blue LED chip, i.e. the package structure is flush with the surface of the chip electrode, which better reflects the light emitting from the non-light emitting surface of the chip. Those skilled in the art can determine whether to provide the package structure and whether to dope the high reflectivity particles in the package structure according to the structural characteristics of the LED chip itself and the requirements of the final product.

[0051] Another embodiment of the present application is a packaging method of an LED package structure, which comprises the following steps:

[0052] The whole fluorescent film sheet prepared by any one of the above fluorescent film sheet preparation methods is cut and expanded to obtain a fluorescent film sheet suitable for the light emitting surface of the LED chip. Since the area of the double-layer film sheet is usually much larger than the area of a single LED chip, it needs to be further cut to a size suitable for the light emitting surface of the LED chip: for a fluorescent film sheet with high hardness (such as a fluorescent film sheet prepared by using phenyl silicone), it needs to be transferred to another adhesive first release film surface for cutting to prevent the fluorescent film sheet from breaking during cutting; for a fluorescent film sheet with low hardness (such as a fluorescent film sheet prepared by using methyl silicone), since it has a certain toughness, it can be cut directly on the support film surface without the need for transfer. The cut whole fluorescent film sheet is transferred to the blue film surface for expansion. Since the blue film has good ductility, as the blue film is expanded, the distance between the small pieces of fluorescent film sheet cut apart on its surface is also gradually increased, preventing mutual adhesion and facilitating subsequent transfer to the surface of the corresponding LED chip.

[0053] The fluorescent film sheet is attached to the light emitting surface side of the blue light LED chip, and the first fluorescent film layer is arranged close to the side of the blue light LED chip. After expansion, the area occupied by the whole fluorescent film sheet is much larger than the table surface of the machine, so it still needs to be further transferred using a release film suitable for the table surface of the machine before it can be used in the production line. The release film can only transfer a part of the fluorescent film sheet at a time, and the fluorescent film sheet transferred at a time can be half or 1 / 4 of the whole fluorescent film sheet, etc., which can be determined according to the actual situation. It should be understood that before the suction transfer is performed, the fluorescent film sheet on the surface of the release film needs to be in a state where the first fluorescent film layer is below and its first lower surface is in contact with the surface of the release film, and the second fluorescent film layer is above and its second upper surface is placed upward; so that the suction nozzle contacts the second upper surface of the second fluorescent film layer from above, and after sucking the fluorescent film sheet, it is transferred to the light emitting surface of the blue light LED chip, so that the first fluorescent film layer in the lower layer is attached to the light emitting surface side of the blue light LED chip. And the release film used at this time should be able to be de-adhesive, which can be a high-temperature bubble film, or a UV film, etc., so that the fluorescent film sheet and the release film are separated when the suction nozzle sucks.

[0054] For the fluorescent film sheet obtained by the method of preparing the second fluorescent film layer first and then preparing the first fluorescent film layer, the surface roughness of the second upper surface of the second fluorescent film layer is relatively smaller than the first lower surface of the first fluorescent film layer, and the sealing effect is better when contacting the suction nozzle, which is conducive to generating a stronger adsorption force, so that the adsorption force is greater than the sum of the weight of the fluorescent film sheet itself and the adhesive force between the fluorescent film sheet and the bottom release film, thereby sucking the fluorescent film sheet from the second release film and transferring it to the light emitting surface of the blue LED chip. In addition, after the pasting of the fluorescent film sheet is completed, the packaging process can also include surrounding the LED chip with white glue to prevent side light emission; and forming a lens on the light emitting surface to focus the light emission angle, etc.; the present embodiment is not limited in this regard.

[0055] It should be noted that the above embodiments can be freely combined as needed. The above is only a preferred embodiment of the present application, and it should be noted that for those skilled in the art, without departing from the principles of the present application, a number of improvements and refinements can also be made, which should be considered within the scope of protection of the present application.

Claims

1. A method for preparing a fluorescent film, characterized in that, Includes the following steps: Monochromatic phosphor with a peak wavelength range of 470nm-500nm is uniformly mixed with silicone, coated on the surface of a support film to form a second fluorescent film layer, and baked to a semi-cured state. The first phosphor is uniformly mixed with silicone, coated onto the surface of the second fluorescent film to form the first fluorescent film, and then baked to a fully cured state. The first fluorescent film layer has a first upper surface and a first lower surface, and the second fluorescent film layer has a second upper surface and a second lower surface. The first upper surface of the first fluorescent film layer is in contact with the second lower surface of the second fluorescent film layer, and the surface roughness of the second upper surface of the second fluorescent film layer is less than the surface roughness of the first lower surface of the first fluorescent film layer. The fluorescent film includes a first fluorescent film layer and a second fluorescent film layer; The second fluorescent film absorbs blue light and converts it into cyan-green light with a peak wavelength range of 470nm-500nm; The mass of the monochromatic phosphor is 50%-100% of the mass of the silica gel.

2. A packaging method for an LED packaging structure, characterized in that, Includes the following steps: The fluorescent film prepared by the fluorescent film preparation method as described in claim 1 is cut and expanded to obtain a fluorescent film that is compatible with the light-emitting surface of the LED chip. The fluorescent film is attached to one side of the light-emitting surface of the blue LED chip, and the first fluorescent film layer is disposed close to the side of the blue LED chip.

3. A fluorescent film, characterized in that, The fluorescent film is prepared by the method described in claim 1. The fluorescent film emits white light when excited by a blue LED chip, wherein the blue LED chip emits light in the wavelength range of 440nm-460nm. The fluorescent film comprises: The first fluorescent film layer is disposed close to the light-emitting surface of the blue LED chip, and the first fluorescent film layer emits white light when excited by the blue LED chip; A second fluorescent film layer is disposed on the surface of the first fluorescent film layer. The second fluorescent film layer is a monochromatic phosphor film layer, and the peak wavelength range of the doped monochromatic phosphor is 470nm-500nm. The second fluorescent film absorbs blue light and converts it into cyan-green light with a peak wavelength range of 470nm-500nm; The second fluorescent film layer is prepared by doping a monochromatic phosphor into silica gel, wherein the mass of the monochromatic phosphor is 50%-100% of the mass of the silica gel. The first fluorescent film layer has a first upper surface and a first lower surface, and the second fluorescent film layer has a second upper surface and a second lower surface. The first upper surface of the first fluorescent film layer is in contact with the second lower surface of the second fluorescent film layer, and the surface roughness of the second upper surface of the second fluorescent film layer is less than the surface roughness of the first lower surface of the first fluorescent film layer.

4. An LED packaging structure, characterized in that, The LED packaging structure includes: A blue LED chip, the blue LED chip including a light-emitting top surface, a light-emitting side surface, and an electrode surface opposite to the light-emitting top surface; The fluorescent film as described in claim 3, wherein the first fluorescent film layer of the fluorescent film is mounted close to the light-emitting surface of the blue LED chip.

5. A method for preparing a fluorescent film, characterized in that, Includes the following steps: The first phosphor is uniformly mixed with silicone, coated on the surface of the support film to form the first fluorescent film layer, and baked to a semi-cured state; Monochromatic phosphor with a peak wavelength range of 470nm-500nm is uniformly mixed with silicone, coated on the surface of the first fluorescent film to form a second fluorescent film layer, and baked to a fully cured state. The second fluorescent film absorbs blue light and converts it into cyan-green light with a peak wavelength range of 470nm-500nm; The mass of the monochromatic phosphor is 50%-100% of the mass of the silica gel.

6. A packaging method for an LED packaging structure, characterized in that, Includes the following steps: The fluorescent film prepared by the fluorescent film preparation method described in claim 5 is cut and expanded to obtain a fluorescent film that is compatible with the light-emitting surface of the LED chip. The fluorescent film is attached to one side of the light-emitting surface of the blue LED chip, and the first fluorescent film layer is disposed close to the side of the blue LED chip.

7. A fluorescent film, characterized in that, The fluorescent film is prepared by the method described in claim 5. The fluorescent film emits white light when excited by a blue LED chip, wherein the blue LED chip emits light in the wavelength range of 440nm-460nm. The fluorescent film comprises: The first fluorescent film layer is disposed close to the light-emitting surface of the blue LED chip, and the first fluorescent film layer emits white light when excited by the blue LED chip; A second fluorescent film layer is disposed on the surface of the first fluorescent film layer. The second fluorescent film layer is a monochromatic phosphor film layer, and the peak wavelength range of the doped monochromatic phosphor is 470nm-500nm. The second fluorescent film absorbs blue light and converts it into cyan-green light with a peak wavelength range of 470nm-500nm; The second fluorescent film layer is prepared by doping a monochromatic phosphor into silica gel, wherein the mass of the monochromatic phosphor is 50%-100% of the mass of the silica gel.

8. An LED packaging structure, characterized in that, The LED packaging structure includes: A blue LED chip, the blue LED chip including a light-emitting top surface, a light-emitting side surface, and an electrode surface opposite to the light-emitting top surface; The fluorescent film as described in claim 7, wherein the first fluorescent film layer of the fluorescent film is mounted close to the light-emitting surface of the blue LED chip.

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