A deep ultraviolet LED device packaging process

Abstract

The present invention relates to a deep ultraviolet LED device packaging process, which belongs to the field of microelectronic packaging. In the packaging process, a packaging material that can be cured by deep ultraviolet light is filled into the interior of the device to wrap the deep ultraviolet LED chip; then it is cured by deep ultraviolet light to form a packaging lens. Compared with the traditional perfluorinated material packaging process, this process has the characteristics of simple steps, high cost performance, low cost, non-toxic and environmentally friendly. The packaging material has a high deep ultraviolet transmittance and a matching refractive index, and has excellent anti-aging properties. The deep ultraviolet transmittance is still around 90% after 500 hours, and the stability is good. In addition, this process can increase the optical power of 265nm deep ultraviolet LEDs by at least 30%. The packaging process of the present invention can be applied to the packaging of a variety of deep ultraviolet LEDs.

Description

Technical Field

[0001] The present invention belongs to the field of microelectronic packaging, and specifically provides a deep ultraviolet LED device packaging process. Background Art

[0002] Currently, deep-ultraviolet LEDs with a central wavelength shorter than 300nm have low radiant power, particularly those with a wavelength of 265nm, which limits their widespread market adoption. Considering the maturity of the technology, improving the packaging process (including structure and materials) is a viable solution to increasing radiant power.

[0003] Deep ultraviolet light has a short wavelength and high photon energy, which is severely absorbed by many materials and can damage chemical bonds, degrading their performance. Currently, a common solution is to cover the chip with a high-purity quartz lens and then encapsulate it with fluorine-containing materials or resins.

[0004] Fluorine-containing materials have ultra-high chemical bond energies and are resistant to deep-UV photolysis. However, the packaging process for fluorine-containing materials is complex, costly, and yield-reduced. Transmittance in the deep UV region, particularly at 265nm, is low. Furthermore, the materials are unstable, requiring the addition of other components for two- or even multi-component heat curing. This heat curing process can generate internal thermal stress and other issues. Furthermore, fluorine-containing materials are environmentally unfriendly and highly toxic, making them unsuitable for large-scale industrial production. Resin materials for encapsulation are prone to yellowing under UV conditions and exhibit poor stability. Furthermore, they have low transmittance in the deep UV region and a refractive index mismatch, making them incapable of mitigating the severe total internal reflection losses at the sapphire-air interface. Furthermore, conventional encapsulants such as epoxy and silicone are unstable and subject to aging, including yellowing. Furthermore, the packaging process is complex, and aging of the encapsulation material can lead to a rapid decrease in device optical power.

[0005] Therefore, there is an urgent need to improve the packaging process of deep ultraviolet LED devices to improve and solve these problems. Summary of the Invention

[0006] To solve the above problems, the present invention provides a deep ultraviolet LED device packaging process, comprising the following steps:

[0007] (1) Filling a liquid encapsulating material into the deep ultraviolet LED device to be encapsulated to wrap the deep ultraviolet LED chip; the encapsulating material is composed of any one or more structural formulas A, B, and C.

[0008]

[0009] Wherein, n≥1, and n is an integer.

[0010] (2) The packaging material is cured by deep ultraviolet radiation to form a packaging lens.

[0011] By optimizing the packaging materials, the encapsulation silicone oil material selected has multiple Si-O bonds on the main chain. The Si-O bonds have a high bonding energy of 108Kcal / mol, while the deep UV energy is around 102Kcal / mol. This material can support deep UV light in the band between 260-350nm. The Si-H bonds on the side chains are flexible and will form -SiH3 silyl radicals upon deep UV light irradiation. These are highly reactive to oxygen. The more Si-H bonds there are, the greater the oxygen consumption, increasing the degree of cross-linking and thus producing a curing effect. The packaging material can be directly filled into the deep UV LED device cavity through a dispensing process, and then cured using deep UV irradiation to form a lens. The lens is formed simultaneously with the curing of the packaging material. The process is simple and does not require the use of sealants or dam glue.

[0012] Preferably, in step (1), the packaging material is filled into the interior of the device by a constant volume dispensing machine or a mold top machine to improve the packaging efficiency.

[0013] In step (2), the deep ultraviolet light source for curing the packaging material is the deep ultraviolet light emitted by the deep ultraviolet LED chip itself, or external deep ultraviolet light. Preferably, the deep ultraviolet light source for curing the packaging material is the deep ultraviolet light emitted by the deep ultraviolet LED device chip itself.

[0014] Preferably, the refractive index of the package lens formed in step (2) is greater than 1. The refractive index here is the refractive index at 25°C, which can reduce the total reflection problem caused by the mismatch between the refractive index of the blue sapphire of 1.8 and the refractive index of air of 1.0.

[0015] Preferably, the light output power of the deep ultraviolet LED device with the packaging lens formed in step (2) is greater than the light output power of the deep ultraviolet LED device without the packaging lens.

[0016] Further preferably, the shape of the lens can be a flat cup or a convex cup. The curvature of the lens surface can be adjusted by controlling the injection volume.

[0017] Preferably, the deep ultraviolet LED light emission center wavelength is 200-280nm.

[0018] Furthermore, the deep ultraviolet LED has a central wavelength of 265 nm.

[0019] Preferably, this process is applicable to a variety of deep ultraviolet LEDs, and the substrate used for packaging can be a metal (aluminum, copper, etc.), a ceramic (Al2O3, AlN, etc.) substrate, a silicon substrate or an organic flexible substrate; the shape of the reflective cup of the deep ultraviolet LED lamp bead can be round, square, rectangular, or even three-dimensionally stacked.

[0020] Preferably, the rated current of the deep ultraviolet LED device is 10mA-500mA, and the deep ultraviolet LED device can be a single lamp bead or an LED lamp bead matrix.

[0021] The present invention provides a deep ultraviolet LED device packaging process, which eliminates the traditional quartz lens by optimizing the packaging silicone oil material, directly uses a dispensing process to dispense with the packaging, and then utilizes deep ultraviolet irradiation to cure and form a lens. The lens is formed while the packaging material is being cured and packaged. The process is simple and does not require the use of sealants or dam glue. Compared with the traditional perfluorinated material packaging process, this process has the characteristics of simple steps, high cost performance, low cost, and the material used for packaging does not contain fluorine elements, is non-toxic and environmentally friendly. Direct ultraviolet curing is used to replace the traditional two-component heating curing process and the traditional packaging process that requires the addition of a sealant, thereby solving the problems of thermal stress caused by heating and curing in the traditional process, the aging and yellowing of the sealant, and the poor airtightness. In addition, the optical power of the device can be further improved by optimizing materials, conditions, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is a schematic diagram of the packaging sample;

[0023] Figure 2 is a diagram of the optical power of an LED device obtained in an embodiment of the present invention;

[0024] Figure 3 A comparison chart of the optical power of a packaged device obtained by a traditional process and an LED device obtained by an embodiment of the present invention;

[0025] Figure 4 is a topographic image of a 265nm LED PCB according to an embodiment of the present invention;

[0026] Figure 5 FIG. 5 is a schematic diagram of transmittance data of a 265nm LED during a 500-hour aging experiment according to an embodiment of the present invention. DETAILED DESCRIPTION

[0027] The technical solutions in the embodiments of the present invention will be described clearly and completely below with reference to the accompanying drawings in the embodiments of the present invention, but this does not constitute a limitation on the protection scope of the present invention.

[0028] It should be noted that the chemical reagents in the examples of the present invention were all purchased from the market.

[0029] The present invention provides a deep ultraviolet LED device packaging process, comprising the following steps:

[0030] (1) Filling the liquid packaging material into the interior of the device to wrap the deep ultraviolet LED chip; the packaging material is composed of any one or more structural formulas A, B, and C.

[0031]

[0032] Wherein, n≥1, and n is an integer.

[0033] (2) The packaging material is cured by deep ultraviolet radiation to form a packaging lens.

[0034] The main chain of the encapsulated silicone oil material has multiple Si-O bonds, and the Si-O bond has a high bonding energy of 108Kcal / mol, while the deep ultraviolet energy is around 102Kcal / mol. The material can support deep ultraviolet rays in the band between 260-350nm; the Si-H bond on the side chain is flexible and will form -SiH3 silyl radicals after deep ultraviolet irradiation, which is highly reactive to oxygen. The more Si-H bonds there are, the greater the oxygen consumption, which increases the degree of cross-linking, thereby producing a curing effect. The encapsulation material can be composed of a single A, B or C silicone oil material, or it can be composed of A and B, A and C or B and C, or it can be composed of three types of A, B and C. There is no special requirement for the degree of polymerization n of A, B, and C. As long as they meet the liquid state and are easy to encapsulate, in some preferred embodiments, n can be 400, 300, 200, 150, 75, 40, 15, etc.

[0035] The process of the embodiment of the present invention eliminates the traditional quartz lens, and directly fills the liquid UV-curable packaging material into the deep ultraviolet LED device cavity through a dispensing process, and then uses deep ultraviolet irradiation to cure it to form a lens. The lens is formed while the packaging material is being cured. The process is simple and does not require the use of sealants and dam glue. Compared with the traditional process of perfluorinated material packaging, this process has the characteristics of simple steps, high cost performance, low cost, and the material used for packaging does not contain fluorine elements, is non-toxic and environmentally friendly. Direct UV curing is used to replace the traditional two-component heating curing process and the traditional packaging process that requires the addition of sealants, solving the thermal stress problems caused by heating curing in the traditional process, the aging and yellowing of the sealant, the instability, and the poor airtightness. It can also further improve the optical power of the device.

[0036] In an embodiment of the present invention, the packaging material can be filled into the interior of the device through a constant volume dispensing machine or a mold top machine. Specifically, if a constant volume dispensing machine is used to fill the interior of the LED device bowl, the LED device to be packaged can be placed on a stage, and the packaging material enters the interior of the bowl through the needle of the constant volume dispensing machine; or it can also be filled into the interior of the LED bowl by injecting glue through a mold top machine.

[0037] In the embodiment of the present invention, the deep ultraviolet light source for curing the packaging material is the deep ultraviolet light emitted by the deep ultraviolet LED chip itself, or external deep ultraviolet light. Preferably, the deep ultraviolet light source for curing the packaging material is the deep ultraviolet light emitted by the deep ultraviolet LED chip itself.

[0038] Preferably, the refractive index of the package lens formed in step (2) is greater than 1, such as 1.4. The refractive index here is the refractive index at 25°C, which can reduce the total internal reflection problem caused by the mismatch between the refractive index of the blue-bottomed sapphire of 1.8 and the refractive index of air of 1.0.

[0039] Preferably, the light output power of the deep ultraviolet LED device with the packaging lens formed in the step (2) is greater than the light output power of the deep ultraviolet LED device without the packaging lens. The deep ultraviolet LED device without the packaging lens mentioned here can be a deep ultraviolet LED device to be packaged, or a deep ultraviolet LED device using other packaging lenses. Specifically, the increase in the light output power after packaging can be achieved by adjusting the ultraviolet light transmittance of the formed packaging lens, the shape of the lens, etc.

[0040] Preferably, the shape of the lens can be a flat cup or a convex cup, which can be adjusted by controlling the injection volume.

[0041] The deep ultraviolet LED device in the embodiment of the present invention generally has a light emission center wavelength of 200-280 nm, preferably 265 nm.

[0042] The process of the present invention is applicable to a variety of deep-ultraviolet LEDs. The packaging substrate can be metal (aluminum, copper, etc.), ceramic (Al2O3, AlN, etc.), silicon, or an organic flexible substrate. The reflector cup of the deep-ultraviolet LED can be round, square, rectangular, or even three-dimensionally stacked, such as an aluminum-coated stacked silicon reflector LED.

[0043] The deep ultraviolet LED device in the embodiment of the present invention can be a deep ultraviolet LED with a rated current of 10mA-500mA, and can be either a single LED lamp bead or an LED lamp bead matrix.

[0044] Example 1

[0045] (1) Using a constant volume dispensing machine, a UV-curable liquid packaging material is dispensed into the interior of the device, and is sequentially filled to form a flat cup, a slightly convex cup, a relatively convex cup, and a convex cup lens surface. The liquid packaging material is composed of a single silicone oil material with the following structure:

[0046]

[0047] Among them, n=41.

[0048] (2) The obtained sample is powered on and cured by irradiation with 265nm ultraviolet light emitted by the deep ultraviolet LED device itself. The ultraviolet curing process does not require any external interference, heating, or the assistance of colloids such as sealants and dam glue.

[0049] The samples cured by 265nm deep ultraviolet irradiation are as follows Figure 1 As shown in the figure, from left to right, the packaging effects of flat cup, slightly convex cup, relatively convex cup, and convex cup are shown. The refractive index of the packaged lens after curing is 1.4.

[0050] Optical power measurement:

[0051] The 265nm deep ultraviolet LED optical power after the new process was measured and characterized using the Instrument System CAS-140CT. The results are as follows: Figure 2 As shown; further, the optical power of the 265nm LED device before and after packaging of the packaging process of this application is compared, as shown Figure 3 As shown, Figure 3 (a) is the optical power of an unpackaged 265nm LED chip. Figure 3 (b) shows the optical power of the convex cup 265nm LED device packaged in an embodiment of the present invention. By comparison, it can be seen that the packaging process of the present invention can increase the optical power of the device by 30-60%. Figure 4 Schematic diagram of a 265nm LED MCPCB prepared by the packaging process of the present invention.

[0052] Aging test:

[0053] Under the condition of 500mA, 6V power supply, the aging test is carried out under the condition of ensuring that the sample is evenly irradiated. The transmittance is tested every 100 hours. The aging time is 1000 hours. The transmittance of deep ultraviolet materials is tested using a fluorescence spectrometer. The 500-hour transmittance data is as follows: Figure 5 As shown, the measurement results show that the convex cup 265nm LED device encapsulated in the embodiment of the present invention can still achieve a transmittance of about 90% after 500 hours.

Claims

1. A deep ultraviolet LED device packaging process, characterized in that: The steps include: (1) Filling a liquid encapsulating material into the deep ultraviolet LED device to be encapsulated to wrap the deep ultraviolet LED chip; the encapsulating material is composed of any one or more structural formulas A, B, and C. Where n≥1, and n is an integer, (2) The packaging material is cured by deep ultraviolet radiation to form a packaging lens.

2. The deep ultraviolet LED device packaging process according to claim 1, wherein: In the step (1), the packaging material is filled into the interior of the device by a constant volume dispensing machine or a mold top machine.

3. The deep ultraviolet LED device packaging process according to claim 1, wherein: In the step (2), the deep ultraviolet light source used for curing the packaging material is the deep ultraviolet light emitted by the deep ultraviolet LED device chip itself, or the deep ultraviolet light emitted by an external deep ultraviolet LED chip.

4. The deep ultraviolet LED device packaging process according to claim 1, wherein: The refractive index of the packaging lens formed in step (2) is greater than 1.

5. The deep ultraviolet LED device packaging process according to claim 1, wherein: The light output power of the deep ultraviolet LED device with the packaging lens formed in the step (2) is greater than the light output power of the deep ultraviolet LED device without the packaging lens.

6. The deep ultraviolet LED device packaging process according to claim 1, wherein: The shape of the lens is a flat cup or a convex cup, and the curvature of the convex cup is adjusted by the amount of glue injected.

7. The deep ultraviolet LED device packaging process according to claim 1, wherein: The deep ultraviolet LED has a central emission wavelength of 200-280 nm.

8. The deep ultraviolet LED device packaging process according to claim 7, wherein: The deep ultraviolet LED has a central wavelength of 265 nm.

9. The deep ultraviolet LED device packaging process according to claim 1, wherein the substrate of the deep ultraviolet LED is a metal substrate, a ceramic substrate, a silicon substrate or an organic flexible substrate; and the reflective cup of the deep ultraviolet LED is in a circular, square, rectangular or three-dimensional stacked shape. 10 . The deep ultraviolet LED device packaging process according to claim 1 , wherein the rated current of the deep ultraviolet LED is 10 mA-500 mA.

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