LED PACKAGE AND METHOD FOR FABRICATING THE SAME
An LED package is disclosed herein. The disclosed LED package comprises a base having an LED chip mounted thereon, an encapsulation member formed by a light-transmittable resin to encapsulate the LED chip, and a housing formed to expose a top portion of the encapsulation member and to encompass a side surface of the encapsulation member, wherein the encapsulation member is formed by a transfer molding process using a mold to have a predetermined shape. Further, the housing may be light-transmittable.
This application is the National Stage of International Application No. PCT/KR2008/007103, filed Dec. 2, 2008, and claims priority from and the benefit of Korean Patent Application No. 10-2007-0126436, filed on Dec. 6, 2007, which are both hereby incorporated by reference for all purposes as if fully set forth herein.
BACKGROUND OF THE INVENTION1. Field of the Invention
The present invention relates to a light emitting diode (LED) package and a method of fabricating the same, and more particularly, to an improvement of an LED package, which includes a light-transmittable encapsulation member for encapsulating an LED chip and a housing configured to surround the encapsulation member.
2. Discussion of the Background
An LED is a semiconductor light emitting device in which a current is supplied thereto and electrons and holes may be recombined in p-n semiconductor junctions to emit light. Conventionally, the LED is fabricated as a package structure including an LED chip, and the light emitting device configured as described above may be generally referred to as an “LED package.”
Generally, the LED package includes a base which is mounted with the LED chip and is provided with electric terminals, and a light-transmittable encapsulation member which is configured to protect the LED chip. A lead frame or a printed circuit board (PCB) has been prevailingly used as the base which is mounted with the LED chip. Depending on what is used as the base, the LED package may also be classified into a lead frame type LED package and a PCB type LED package. Further, an additional component such as a heat sink may also be used as the base which is mounted with the LED chip.
The lead frame type LED package includes a housing for defining a cavity in which the encapsulation member is formed. Such a housing generally serves to reflect light in order to narrow a viewing angle, i.e., in order to collect light, so that the housing has been referred to as a reflector. In the LED package as described above, the housing is formed of an opaque resin material by an ejection molding process and then a liquefied light-transmittable resin is injected into the cavity of the housing in a dotting manner to thereby form the encapsulation member.
It is conventionally difficult to design and fabricate the LED package with a viewing angle of light variably changed. This is because the design for the light viewing angle of the housing primarily depends on the shape for the reflection surface of the housing (in particular, the angle for the reflection surface). Further, since there is a large difference between the molding method of the housing and the molding method of the encapsulation member, it is difficult to consecutively fabricate the LED package and the fabrication process for the LED package is cumbersome and complicated.
According to the technique in which a liquefied resin is injected into the cavity of the ejection-molded housing in a dotting manner to form the encapsulation member, the encapsulation member is configured to have an undesired, upwardly convex shape due to the surface tension exerted on the liquefied resin. The shape of the encapsulation member deteriorates various performances of the LED package in the optical aspect. For example, if the LED package fabricated as described above is employed in a back light, the convex portion of the encapsulation member faces a light guide plate, thereby generating a hot spot phenomenon, i.e., a phenomenon in which there exists a point-shaped region excessively brighter than other regions. At this time, it is noted that such a convex shape of the encapsulation member as described above is different from that of the convex lens that is designed as required to control the viewing angle of light. On the other hand, if the amount of the liquefied resin injected into the cavity is reduced, there is generated an undesired, concave shape to thereby decrease the light emitting efficiency of the LED package.
SUMMARY OF THE INVENTIONAccordingly, an object of the present invention is to provide an LED package and a method for fabricating the same, in which an encapsulation member for encapsulating an LED chip within a housing is easily designed to have a shape as required.
Another object of the present invention is to provide an LED package and a method for fabricating the same, in which a housing is formed of a light-transmittable material which may control the transparency and the viewing angle, so that controlling the transparency of the housing may enlarge a design range for the viewing angle of light.
A further object of the present invention is to provide an LED package and a method for fabricating the same, in which a housing is formed by a method which is identical to or similar with a process for forming an encapsulation member, thereby being capable of fabricating the LED package in a consecutive and simple manner.
An LED package according to an aspect of the present invention comprises a base having an LED chip mounted thereon, an encapsulation member formed by a light-transmittable resin to encapsulate the LED chip, and a housing formed to expose a top portion of the encapsulation member and to encompass a side surface of the encapsulation member, wherein the encapsulation member is formed by a molding process using a mold to have a top surface of a desired shape. At this time, the top portion of the encapsulation member may be formed in the shape of a plane or lens. Here, it is preferable that the molding process using a mold be a transfer molding process.
Preferably, the housing may be formed by a transfer molding process before or after the encapsulation member is formed. Further, the housing is light-transmittable. More preferably, the housing may be a semitransparent housing, which includes a diffuser for adjusting the transparency of the housing and is used as a reflector.
An LED package according to another aspect of the present invention comprises a base having an LED chip mounted thereon, an encapsulation member formed by a light-transmittable resin to encapsulate the LED chip, and a housing formed to expose a top portion of the encapsulation member and to encompass a side surface of the encapsulation member, wherein the housing is light-transmittable. At this time, the housing and the encapsulation member are preferably formed by a transfer molding process.
A method for fabricating an LED package according to an aspect of the present invention comprises the steps of mounting an LED chip on a base, forming a housing for supporting the base, and forming an light-transmittable encapsulation member for encapsulating the LED chip, the housing encompassing a side surface of the encapsulation member, wherein the step of forming the encapsulation member comprises the step of molding the encapsulation member using a mold so that the encapsulation member has a predetermined, desired top surface. Preferably, the molding process is a transfer molding process.
A method for fabricating an LED package according to another aspect of the present invention comprises the steps of: mounting an LED chip on a base, forming a light-transmittable encapsulation member for encapsulating the LED chip and supporting the base, and forming a housing for encompassing a side surface of the encapsulation member, wherein the step of forming the encapsulation member comprises the step of molding the encapsulation member using a mold. Preferably, the molding process is a transfer molding process.
In the step of forming the housing, a mixing ratio of the diffuser is preferably adjusted to adjust a viewing angle.
Further, if the transfer molding is repeated twice or more in the step of forming the housing as described above, a structure in which a plurality of the housings are laminated with each other is made. The transfer molding is referred to as multiple transfer molding. Further, if the transfer molding is repeated twice or more in the step of forming the encapsulation member as described above, a structure in which a plurality of the encapsulation members are laminated with each other is made. The transfer molding is referred to as multiple transfer molding.
According to an embodiment of the present invention, a control range of a light viewing angle of an LED package is enlarged, and the LED package can be easily designed to have the desired light viewing angle. Further, it is possible to solve various problems which may be caused by a shape of an encapsulation member, such as a hot spot phenomenon, in which a contact portion between a light guide plate and the encapsulation member of the LED package is excessively bright when the LED package is used as a backlight, or the degradation of the light emitting efficiency caused by the concave shape of the encapsulation member. Further, according to an embodiment of the present invention, since the encapsulation member and the housing are formed by a transfer molding process, a molding equipment may be used as it is while a mold may be replaced with another to form both the encapsulation member and the housing, which is more economical than the prior art. Furthermore, unlike the prior art in which the encapsulation member is separately formed in a dotting manner, only one mold having a plurality of spaces for forming an encapsulation member is used, and the liquefied resin is filled in the spaces at a time and then is rapidly cured according to one embodiment of the present invention. Thus, a plurality of LED packages can be quickly fabricated, thereby largely enhancing the productivity of LED packages.
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The following embodiments are provided only for illustrative purposes so that those skilled in the art can fully understand the spirit of the present invention. Therefore, the present invention is not limited to the following embodiments but may be implemented in other forms. In the drawings, the widths, lengths, thicknesses and the like of elements may be exaggerated for convenience of illustration. Like reference numerals indicate like elements throughout the specification and drawings.
Referring to
The LED chip 2 is die-attached onto a top surface of the first lead terminal 12 of the lead frame 10, and the LED chip 2 on the first lead terminal 12 is electrically connected to the second lead terminal 14 via a bonding wire.
Further, the LED package 1 of this embodiment includes the housing 20 and the encapsulation member 30. The encapsulation member 30 is formed of a light-transmittable material and encapsulates the LED chip 2 to protect the LED chip 2 and the like. The housing 20 may function as a reflector and is configured to encompass a side surface of the encapsulation member 30 and to expose a top portion of the encapsulation member 30. In this embodiment, the housing 20 serves to support the lead frame 10, i.e., the first lead terminal 12 and the second lead terminal 14.
As will be described in detail below, the encapsulation member 30 and the housing 20 are formed by a transfer molding process. In this embodiment, the housing 20 is formed of an epoxy molding compound (EMC) by the transfer molding process in order to support the lead frame 10 before the encapsulation member 30 is formed. At this time, a bottom surface of the housing 20 is substantially flush with that of the lead frame 10, so that the first and second lead terminals 12 and 14 of the lead frame 10 may be exposed to the outside in the neighborhood of the bottom surface of the housing 20 even without a bending process.
In order to function as the reflector, the housing 20 is formed of the EMC into which a white, milky and/or light gray diffuser 21 (as shown in
Referring back to
It is preferable that the encapsulation member 30 is formed by a molding process using a mold, particularly, by a transfer molding process, wherein the molding process using a mold allows the shape of a top surface 31, through which the light is primarily emitted, to be formed as desired. For example, the transfer molding makes it possible to form the encapsulation member 30 having a planar top surface 31. When a liquefied resin is injected into the cavity of the housing 20 to form the encapsulation member 30, the surface tension makes it impossible to obtain the planar shape as desired above. However, it is noted that the present invention does not completely exclude the injection of the liquefied resin into the cavity in a dotting manner.
A phosphor which is excited by light having a specific wavelength to emit light having a different wavelength may be contained in the encapsulation member 30.
The shape of the encapsulation member 30 is not limited to the planar shape, but various encapsulation members 30 having hemispherically convex or concave lens shapes or various lens shapes having Fresnel patterns may be formed by a molding process using a mold, such as a transfer molding process. Fresnel pattern contributes to enlarging the viewing angle of its corresponding lens.
Meanwhile, instead of the lead frame 10 as described in the previous embodiment, another base on which the LED chip 2 is mounted may be used. For example, in the LED package 1 shown in
Although it has been described above that the housing 20 is first transfer-molded and the encapsulation member 30 is then transfer-molded as described above, it may be considered that the encapsulation member 30 is first transfer-molded and the housing 20 is then transfer-molded. It is easy to separately transfer-mold the housing 20 and the encapsulation member 30 regardless of their sequential order particularly when the housing 20 and the encapsulation member 30 are formed of thermosetting plastic such as epoxy or silicone. This is because a portion to be formed first is not influenced by the melting temperature of the other portion to be formed later. Further, it may be considered that a housing 20 having a cavity is formed by a transfer molding process and then a liquefied resin is injected into the cavity in a dotting manner to form the encapsulation member 30.
If the transfer molding process is used, it is possible to make an integrated housing 20 in which a plurality of partial housings are laminated by repeating the transfer molding twice or more in order to form the integrated housing 20. Further, if the transfer molding process is used, it is possible to make an integrated encapsulation member 30 in which a plurality of partial encapsulation members are laminated by repeating the transfer molding twice or more. The transfer molding process repeated twice or more as described above is referred to as multiple transfer molding.
Now, various embodiments of a method for fabricating the LED package as described above will be described.
First, as shown in
Then, as shown in
Then, as shown in
Referring to
Referring to
Although the processes shown in
First, the lead frame 10 which comprises the first and second lead terminals 12 and 14 is prepared as shown in
Then, as shown in
Then, as shown in
If the resin is injected through the injection hole I and the groove 202 and then the injected resin is cured, the encapsulation member 30 is formed in the cavity 201. The upper shape of the encapsulation member 30 is defined by the mold M4. For example, if the mold M4 having a planar surface for closing the cavity 201 is used, the encapsulation member 30 whose top surface is plane is formed. Depending on the surface shape of the mold M4 for closing the encapsulation member 30, lenses having various shapes, i.e., a spherical lens, a Fresnel lens or other shaped lens, may be formed. Patterns, roughness and/or unevenness on a surface of the lens may be regular or irregular.
Although not drawn, upper and lower molds for receiving and supporting a housing or an LED package including the housing 20 and a mold M4 used for the molding may be used to molding the encapsulation member while the upper and lower molds and the mold M4 are assembled as a set.
The present invention is not limited to the aforementioned embodiments but may be applied to all kinds of LED packages having an encapsulation member and a housing, for example, a side view type LED package, a PCB type or chip LED package, a lamp type LED package or a high-flux type LED package as well as a top type LED package.
Claims
1. An LED A light emitting diode (LED) package, comprising:
- a base;
- an LED chip disposed on the base;
- an encapsulation member comprising a light-transmittable resin encapsulating the LED chip, the encapsulation member comprising a molded top surface; and
- a housing exposing a top portion of the encapsulation member and encompassing a side surface of the encapsulation member.
2. The LED package of claim 1, wherein the housing is transfer molded.
3. The LED package as claimed in of claim 2, wherein the housing is light-transmittable.
4. The LED package of claim 3, wherein the housing is a semitransparent housing comprising a diffuser adjusting a viewing angle of the LED package, wherein the diffuser is used as a reflector.
5. The LED package of claim 1, wherein the top surface of the encapsulation member comprises a planar or lens shape.
6. The LED package of claim 1, wherein the encapsulation member is transfer molded.
7. A light emitting diode (LED) package, comprising:
- a base;
- an LED chip disposed on the base;
- an encapsulation member comprising a light-transmittable resin encapsulating the LED chip; and
- a housing exposing a top portion of the encapsulation member and encompassing a side surface of the encapsulation member, wherein the housing is light-transmittable.
8. The LED package of claim 7, wherein the housing comprises a semitransparent housing that includes a diffuser adjusting a viewing angle of the LED package, wherein the diffuser is used as a reflector.
9. The LED package of claim 7, wherein the housing and the encapsulation member are transfer molded.
10. The LED package of claim 1, wherein an upper surface of the base comprises at least one recess to receive the LED chip or a bonding pad.
11. A method for fabricating a light emitting diode (LED) package, comprising:
- mounting an LED chip on a base;
- forming a housing supporting the base; and
- forming a light-transmittable encapsulation member encapsulating the LED chip, the housing encompassing a side surface of the encapsulation member,
- wherein forming the encapsulation member comprises molding the encapsulation member using a mold to form a molded to surface on the encapsulation member.
12. A method for fabricating a light emitting diode (LED) package, comprising:
- mounting an LED chip on a base;
- forming a light-transmittable encapsulation member encapsulating the LED chip and supporting the base; and
- forming a housing encompassing a side surface of the encapsulation member,
- wherein forming the encapsulation member comprises molding the encapsulation member using a mold to form a molded to surface on the encapsulation member.
13. The method of claim 11, wherein forming the housing comprises a transfer molding process.
14. The method of claim 13, wherein forming the housing comprises using a molding material comprising a diffuser and a transparent resin.
15. The method of claim 14, wherein the molding material is formed by mixing the diffuser and the transparent resin, and a mixing ratio of the diffuser is adjusted to change a viewing angle of the LED package.
16. The method of claim 14, wherein the diffuser is at least one selected from the group consisting of TiO2, SiO2, ZnO, and Y2O3.
17. The method of claim 11, wherein forming the encapsulation member comprises a transfer molding process.
18. The method of claim 11, wherein forming the encapsulation member or the housing comprises a multiple transfer molding process.
19. A light emitting diode (LED) package, comprising:
- a base;
- an LED chip disposed on the base;
- an encapsulation member comprising a light-transmittable resin encapsulating the LED chip; and
- a housing exposing a top portion of the encapsulation member and encompassing a side surface of the encapsulation member,
- wherein the housing is transfer molded.
20. The LED package of claim 19, wherein the encapsulation member comprises a liquefied light-transmittable resin that is injected into a cavity formed in the housing.
Type: Application
Filed: Dec 2, 2008
Publication Date: May 12, 2011
Applicant: Seoul Semiconductor Col, Ltd. (Seoul)
Inventors: Chung Hoon Lee (Ansan-si), Yoon Hee Kim (Ansan-si), Byung Yeol Park (Ansan-si), Bang Hyun Kim (Ansan-si), Eun Jung Seo (Ansan-si), Hyouk Won Kwon (Ansan-si)
Application Number: 12/746,447
International Classification: H01L 33/52 (20100101); H01L 33/48 (20100101);