This application claims the benefit of Korean Patent Application No. 10-2011-0003152, filed on Jan. 12, 2011, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.
1. Field
The present disclosure relates to methods and apparatuses for depositing a phosphor, and more particularly, to methods and apparatuses for depositing a phosphor by re-arraying manufactured light-emitting device chips according to their light-emitting characteristics and then by efficiently depositing the phosphor by using a compression molding method.
2. Description of the Related Art
A light-emitting diode (LED) is a semiconductor light-emitting device that converts an electrical signal into light, and is characterized in that the LED has a relatively long lifetime, compared to other light-emitting device, and may be driven at a low voltage. Recently, a lighting apparatus using a white LED having a high brightness replaces lighting apparatuses according to the related art. The white LED may be formed by depositing a phosphor having a red, green, or yellow color on a light-emitting device that emits green color light or ultraviolet (UV) light.
An example of a method of depositing a phosphor on a plurality of LED chips according to the related art is a wafer level coating method. The wafer level coating method involves forming a plurality of LED chips on a wafer and depositing a phosphor on the wafer before an optical characteristic of each LED chip is evaluated.
According to the wafer level coating method, the phosphor is deposited only on the wafer so that its application may be limited to an LED structure in which light is only emitted toward each LED chip.
Also, according to the wafer level coating method, before the plurality of LED chips are bin-sorted based on an optical characteristic evaluation for each of the plurality of LED chips, a phosphor paste is deposited on the wafer whereon the plurality of LED chips that are not bin-sorted are formed. Accordingly, due to an optical characteristic difference between the plurality of LED chips, white chips having irregular optical characteristics are formed, so that a yield rate in an entire process may sharply deteriorate.
Provided are methods of uniformly depositing a phosphor on a side surface and a top surface of each of light-emitting devices by performing compression molding on the light-emitting devices.
Provided are compression molding apparatuses capable of uniformly depositing a phosphor on a side surface and a top surface of each of light-emitting devices.
Additional aspects will be set forth in part in the description which follows and, in part, will be apparent from the description, or may be learned by practice of the presented embodiments.
According to an aspect of the present invention, a method of depositing a phosphor includes the operations of forming a plurality of light-emitting devices on a wafer, evaluating emission characteristics of the plurality of light-emitting devices, and re-arraying and aligning the plurality of light-emitting devices on a carrier substrate according to the emission characteristics; depositing the phosphor on the plurality of re-arrayed light-emitting devices via a compression molding process; and dicing the plurality of re-arrayed light-emitting devices on the carrier substrate.
The operation of evaluating the emission characteristics may include the operations of individually separating the plurality of light-emitting devices formed on the wafer, and evaluating the emission characteristic of each of the plurality of light-emitting devices.
The operation of evaluating the emission characteristics may include the operation of evaluating a light-emission wavelength, brightness, or a response time of each of the plurality of light-emitting devices.
The operation of re-arraying may include the operations of forming an adhesive layer on the carrier substrate, and then re-arraying light-emitting device chips having the same emission characteristic on the adhesive layer.
The adhesive layer may be formed of a photo-sensitive adhesive (PSA).
The operation of depositing the phosphor may include the operations of mounting the carrier substrate in a phosphor depositing apparatus, wherein the plurality of light-emitting devices are re-arrayed on the carrier substrate, and depositing the phosphor on the plurality of light-emitting devices by supplying the phosphor on a region of the carrier substrate, wherein the plurality of light-emitting devices are formed on the region.
The phosphor may be deposited on surfaces of each of the plurality of light-emitting devices, except for an electrode pad of each of the plurality of light-emitting devices.
According to another aspect of the present invention, a phosphor depositing apparatus includes an upper die in which a carrier substrate whereon a plurality of light-emitting devices are arrayed is mounted; a lower die formed to correspond to the upper die; and a molding die formed on a side surface of the lower die.
A pin connected to a spring of each of the plurality of light-emitting devices may be formed on the upper die.
A plurality of vacuum holes may be formed in the upper die.
A plurality of vacuum holes may be formed in the lower die.
A sealing rubber may be formed on the molding die so as to maintain an airtightness by contacting a release film adhered on the upper die, when a molding operation is performed.
The phosphor depositing apparatus may further include a release film contacting the upper die or the lower die.
The release film may be formed of polyvinyl chloride (PVC) or polyethylene terephthalate (PET).
A thickness of the release film may be in the range of several micrometers to several tens of micrometers.
These and/or other aspects will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:
Reference will now be made in detail to embodiments, examples of which are illustrated in the accompanying drawings. In the drawings, the thicknesses of layers and regions are exaggerated for clarity.
Referring to
After the LED chips C are formed on the wafer W, the LED chips C are divided, a characteristic of each of the LED chips C is evaluated, and then the LED chips C are bin sorted according to their characteristics. The characteristics of the LED chips C may be bin-sorted based on a light-emission wavelength, brightness, or a response time, and may be random. For example, based on an emission wavelength of each of the LED chips C formed as illustrated in
After the LED chips C are bin-sorted based on their emission characteristics, LED chips C included in the same group are re-arrayed and aligned on a carrier substrate, e.g., a sapphire substrate or the like. Hereafter, LED chips that are included in the same group according to a bin sort based on emission characteristics of the LED chips are referred to as LED chips having the same characteristic. An interval between the re-arrayed LED chips may be determined in consideration of a thickness of a phosphor to be deposited, and a process of depositing the phosphor and dicing the LED chips. For example, the LED chips may be disposed at an interval of several micrometers to several hundreds of micrometers. A number of pieces of LED chips to be re-arrayed and aligned on one carrier substrate is not limited, and may be random.
After the LED chips having the same characteristic are re-arrayed and aligned on the carrier substrate, a molding process of simultaneously depositing a phosphor on the LED chips is performed. In this manner, when LED chips having the same emission characteristic are aligned on one carrier substrate and then a phosphor is deposited thereon, it is easy to select a phosphor, and as a result, it is possible to control an emission characteristic of an LED package that is a final product, and to improve reliability of the LED package.
After performing the process of depositing the phosphor on the LED chips having the same characteristic, in order to form an LED chip package, a process of dicing the LED chips aligned on the carrier substrate may be performed. Here, in order to facilitate the dicing process, an interval between the LED chips aligned on the carrier substrate may be previously set, in consideration of the dicing process.
Hereinafter, a phosphor deposition process with respect to the LED chips re-arrayed and aligned on the carrier substrate, and a phosphor depositing apparatus used in the phosphor deposition process will be described in detail.
Referring to (a) of
The adhesive layer 302 may be formed of a photo-sensitive adhesive (PSA) and may be formed of a material capable of easily separating the LED chips 303 from the carrier substrate 301. An adhesive component of the adhesive layer 302 may be cured by irradiating ultraviolet (UV) light thereon. However, the adhesive layer 302 is optional, and if the carrier substrate 301 is formed of a material capable of easily fixing the LED chips 303, the adhesive layer 302 may be omitted. The carrier substrate 301 may be formed of a flexible material or a solid plate, and may be formed of one of organic and inorganic materials. Also, the carrier substrate 301 may be formed of a composite material formed by impregnating organic-based polymer or inorganic-based polymer with a glass fiber. The LED chips 303 may include electrode pads formed on their surfaces, and a bump 304 may be formed on each of the electrode pads of the LED chips 303. In the present embodiment, by using the carrier substrate 300 whereon the LED chips 303 are formed, a phosphor is deposited on side surfaces and top surfaces of the LED chips 303.
Referring to (b) of
Referring to (b) of
The release film 306 may be adhered on a surface of the lower die 305a, and may be used to facilitate separation between a phosphor material and the lower die 305a after a phosphor deposition process. The release film 306 may be formed of a material such as polyvinyl chloride (PVC) or polyethylene terephthalate (PET). The phosphor paste 307 may be formed by mixing a resin and one or more phosphor materials according to a predetermined mixture ratio. The resin may include a material having high adherence, heat-resistance, low hygroscopicity, and high transmittance. For example, the resin may include a polymer material, an epoxy resin or a silicon-curable resin. Since the phosphor is cured in the lower die 305a and the upper die 305b, a thermocurable resin may be used. A content of the phosphor is not limited, and may be adjusted according to an optical characteristic of a light-emitting device, and a package level. For example, a weight ratio may be in the range of several percentage to several tens of percentage.
Referring to (c) and (d) of
The LED chips 30 that are separated may be formed as an LED package via an additional package process. As illustrated in (e) of
Referring to (a) of
A material of the adhesive layer 402 may include polyolefin, a photopolymerized acryl-based resin, or a composite material thereof. In a case where a molding temperature is relatively high, a polyimide-based photopolymerized material, an epoxy-based photopolymerized material, a silicone-based photopolymerized material, or a composite material thereof may be used so as to have heat-resistance.
Referring to (b) of
Referring to (b) of
Referring to (c) and (d) of
The LED chips 40 that are separated may be formed as an LED package via an additional package process. As illustrated in (e) of
As described above, a method of depositing a phosphor according to one or more embodiments of the present invention may involve uniformly depositing the phosphor on a surface and a side surface of a light-emitting device, regardless of a shape of the light-emitting device, by performing compression molding. The compression molding according to one or more embodiments of the present invention may vary, and hereinafter, referring to
Referring to (a) of
Referring to (b) of
Referring to (c) of
Referring to (d) of
Referring to (a) of
Referring to (b) of
Referring to (c) of
Referring to (d) of
In the compression molding apparatuses of
The method of depositing a phosphor by performing compression molding according to the one or more embodiments may be applied to not only a carrier substrate whereon light-emitting devices are re-arrayed but also applied to a case in which a light-emitting device chip is bonded to a printed circuit board (PCB).
Referring to
A molding die 106 is formed on a side surface of the lower die 105, and a sealing rubber 107 is formed on the molding die 106 so as to maintain an airtightness by contacting the release film 104 of the upper die 101. While the upper die 101 and the lower die 105 are closely adhered to each other, a phosphor paste 109 may be deposited on exposed regions of the LED chips 100 that are flip-chip boded.
By performing a phosphor deposition process using compression molding, a phosphor may be easily deposited on a side surface and a top surface of each LED chip except for an electrode pad. Also, in a case of a flip-chip structure, a phosphor may be easily deposited around an emission surface. Since LED chips having similar emission characteristic are already re-arrayed, a phosphor paste may be easily selected according to the emission characteristic, so that a white LED having a reliable optical characteristic may be easily manufactured. By performing the method of depositing a phosphor according to the one or more embodiments of the present invention, it is possible to manufacture various LED packages, and to form a desired LED package by individually dicing LED chips on a carrier substrate.
According to the one or more embodiments of the present invention, the compression molding method may involve uniformly depositing a phosphor on top surfaces and side surfaces of light-emitting devices by re-arraying the light-emitting devices having a similar emission characteristic on a carrier substrate and then by depositing the phosphor via a compression molding process. By doing so, it is possible to provide white light-emitting devices having a uniform emission characteristic.
Also, according to the one or more embodiments of the present invention, it is possible to provide the compression molding apparatus capable of uniformly depositing the phosphor on the top surfaces and the side surfaces of the light-emitting devices.
It should be understood that the exemplary embodiments described therein should be considered in a descriptive sense only and not for purposes of limitation. Descriptions of features or aspects within each embodiment should typically be considered as available for other similar features or aspects in other embodiments.
Number | Date | Country | Kind |
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10-2011-0003152 | Jan 2011 | KR | national |