Light emitting diode package and fabrication method thereof
An LED package and a fabrication method therefor. The LED package includes first and second lead frames made of heat and electric conductors, each of the lead frames comprising a planar base and extensions extending in opposed directions and upward directions from the base. The package also includes a package body made of a resin and configured to surround the extensions of the first and second lead frames to fix the first and second lead frames while exposing underside surfaces of the first and second lead frames. The LED package further includes a light emitting diode chip disposed on an upper surface of the base of the first lead frame and electrically connected to the bases of the first and second lead frames, and a transparent encapsulant for encapsulating the light emitting diode chip.
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This application claims the benefit of Korean Patent Application No. 2006-0034706 filed on Apr. 17, 2006, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.
BACKGROUND OF THE INVENTION1. Field of the Invention
The present invention relates to a Light Emitting Diode (LED) and, more particularly, to an LED package having a simple configuration with superior heat radiation efficiency, and a fabrication method thereof.
2. Description of the Related Art
A light emitting diode (LED) is a semiconductor device for generating various colors of light in response to current application. The colors generated from the LED are determined by the chemical substances constituting the semiconductor of the LED. Such an LED has various merits such as a long lifetime, low power, excellent initial driving characteristics, high resistance for vibration and high tolerance for frequent power on/off compared to a light emitting device based on filament, and thus there has been a steadily increasing demand for the LEDs.
LEDs are recently adopted as backlights for lighting devices and large sized Liquid Crystal Displays (LCDs), which require large outputs, and accordingly the LEDs used therefor require especially excellent heat radiation capacities.
First, referring to
Such an LED package 1 of
As described above, the LED package 1 shown in
However, this conventional heat radiation structure is complicated and requires many components. Therefore, it is difficult to automate the manufacturing process of the LED package with assembly of many components, thus increasing the manufacturing time and costs.
The LED package shown in
The LED package with the above described configuration requires a fewer number of components than that of
The present invention has been made to solve the foregoing problems of the prior art and therefore an aspect of the present invention is to provide an LED package which can achieve superior heat radiation efficiency with a simple configuration.
Another aspect of the invention is to provide a method of fabricating an LED package which can achieve superior heat radiation efficiency.
According to an aspect of the invention, the invention provides a light emitting diode package which includes: first and second lead frames made of heat and electric conductors, each of the lead frames comprising a planar base and extensions extending in opposed directions and upward directions from the base, the second lead frame having a smaller width than the first frame and arranged apart from the first frame at a predetermined interval; a package body made of a resin and configured to surround the extensions of the first and second lead frames to fix the first and second lead frames while exposing underside surfaces of the first and second lead frames; a light emitting diode chip disposed on an upper surface of the base of the first lead frame and electrically connected to the bases of the first and second lead frames; and a transparent encapsulant for encapsulating the light emitting diode chip.
In the light emitting diode package according to the present invention, ends of the extensions are positioned at side portions of the package body.
In the light emitting diode package according to the present invention, at least one of the extensions of the first lead frame extends out of the package body to form a terminal.
In the light emitting diode package according to the present invention, the package body has a recess formed around the light emitting diode chip and a protrusion is formed in a predetermined width on an upper end of the recess. In this case, it is preferable that a portion of the transparent encapsulant fills the recess and another portion of the transparent encapsulant protrudes over the protrusion in a predetermined curvature.
In the light emitting diode package according to the present invention, the underside surfaces of the bases of the first and second lead frames are coplanar with an underside surface of the package body.
In the light emitting diode package according to the present invention, the first and second lead frames are arranged in parallel with each other.
According to another aspect of the invention, the invention provides a method of fabricating a light emitting diode package. The method includes:
machining a plate made of a heat and electric conductor of a predetermined thickness into a frame structure, the frame structure comprising first and second lead frame parts each having a planar base and extensions extending in opposed directions from the base, the second lead frame part formed in a smaller width than the first lead frame part and arranged apart at a predetermined interval from the first lead frame part;
bending the extensions of the first and second lead frame parts in such a way that the bases are positioned lower than the extensions so that the extensions extend in upward directions from the bases;
injection-molding a resin to form a package body, the package body surrounding the extensions of the first and second lead frame parts adjacent to the bases and thereby fixing the first and second lead frame parts in such a way that at least a part of upper surfaces and bottom surfaces of the bases of the first and second lead frame parts are exposed from the package body and distal ends of the extensions of the first and second lead frame parts extend out of side portions of the package body;
disposing a light emitting diode chip on the exposed upper surface of the base of the first lead frame part and electrically connecting the light emitting diode chip with the first and second lead frame parts;
encapsulating the light emitting diode chip with a transparent encapsulant; and
cutting the extensions of the frame structure to obtain a light emitting diode package.
In the method according to the present invention, the step of forming a package body includes forming a recess around the light emitting diode chip and a protrusion in a predetermined width on an upper end of the recess. In this case, it is preferable that the step of encapsulating includes dispensing the transparent encapsulant in such a way that a portion of the transparent encapsulant fills the recess and another portion of the transparent encapsulant protrudes over the protrusion in a predetermined curvature.
In the method according to the present invention, the step of forming a package body includes forming the package body in such a way that the underside surfaces of the bases of the first and second frame parts are coplanar with an underside surface of the package body.
In the method according to the present invention, the step of forming a frame structure comprises forming the first and second lead frame parts in parallel with each other.
The above and other aspects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:
Exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings.
An LED package according to a first embodiment of the present invention is illustrated in
The LED package 100 according to this embodiment includes a pair of metal lead frames 110 and 120 and an insular package body 130 surrounding the lead frames 110 and 120.
The first lead frame 110 includes a planar base 112 and a pair of extensions 114 extending from opposed ends of the base 112. It is preferable that the base 112 is provided in an area as large as possible so that it has a large contact area as possible with a circuit board (see
The second lead frame 120 is formed in parallel with and at a predetermined interval from the first lead frame 110, and includes a base 122 and a pair of extensions 124. The base 122 and the extensions 124 are formed in the same width, but the present invention is not limited thereto.
Here, the extensions 114 and 124 are illustrated in the drawing as extending out of the package body 130, but the present invention is not limited thereto. The end surfaces of the extensions 114 and 124 can be coplanar with the side surface of the package body 130.
The configurations of the first and second lead frames 110 and 120 can be more clearly understood with reference to
The package body 130 is injection-molded around the lead frame 110 and 120 to surround the lead frames 110 and 120. At this time, the package body 130 has a recess or a cup-shaped part 132 formed therein to expose central portions of the bases 112 and 122 of the lead frames 110 and 120. This cup part 132 is the space for mounting the LED chip 140. An annular protrusion 134 is formed on an upper part of the cup part 132, and has a predetermined width W.
The package body 130 is formed in such a way that the underside surfaces of the bases 112 and 122 of the first and second lead frames 110 and 120 are exposed. That is, as shown in
The LED chip 140 is seated on an upper surface of the base 112 of the first lead frame 110 and electrically connected to the base 122 of the second lead frame 120 by a wire 142.
The illustrated LED chip 140 is a so-called vertical structure LED chip. With this LED chip, the positive and negative electrodes are formed on upper and lower surfaces, respectively. As illustrated, in a case where the upper surface is the positive electrode connected to the base by the wire 142, the LED chip is electrically connected by the negative electrode in the lower surface thereof to the base 112 of the first lead frame 110. Alternatively, in the case of a horizontal structure LED chip with both electrodes formed on the same surface thereof, the LED chip can be electrically connected to the base 112 of the first lead frame 110 using another wire (not illustrated).
As the LED chip 140 is seated on the base 112 to be electrically connected to the bases 112 and 122, the base 112 serves a function of transferring the heat generated from the LED chip 140 to the circuit board 160 (see
The LED package 100 according to the present invention further includes a transparent encapsulant 150 shown in
At this time, the height h of the portion of the encapsulant 150 that functions as the lens is determined according to the width W of the protrusion 134 and the viscosity and amount of the resin making up the encapsulant 150. For example, the width W of the protrusion 134 and the viscosity and amount of the encapsulant 150 can be adjusted to form the encapsulant 150 in a predetermined curvature with a desired height h.
The resin of the encapsulant 150 is preferably a transparent elastomer of gel type, for example, silicone. The silicone is less susceptible to changes incurred by the light of a short wavelength, such as yellowing, and has a high refractive index, thus possessing superior optical properties. In addition, unlike epoxy, it maintains a gel or elastomer state even after it is cured, thus protecting the LED chip 140 more stably from the stress by the heat, vibrations and external impacts. For the transparent encapsulant 150, phosphor and/or diffuser may be dispersed in the elastomer.
Now, the heat radiation operation of the LED package 100 will be examined with reference to
The LED package 100 is mounted on a circuit board 160 shown in
Then, when a voltage is applied, the LED chip 140 generates light together with heat. Referring to
In the meantime, referring to
The LED package 100-1 shown in
Such sloping surfaces 113 and 123 lengthen and complicate the path through which external impurities and moisture may eventually reach the chip 140. In addition, the sloping surfaces 113 and 123 are surrounded by the resin of the package body 130, enhancing the bonding and sealing qualities between the lead frame bases 112-2 and 122-2 and the package body 130.
In the meantime, the sloping surfaces 113 and 123 can be formed in only one portion of the bases 112-2 and 122-2 of the first and second lead frames 110-2 and 120-2, for example, only in a portion adjacent to the LED chip 140.
Like the sloping surfaces 113 and 123, these steps 115 and 125 lengthen and complicate the path through which the external impurities and moisture may eventually reach the chip 140. In addition, the steps 115 and 125 are surrounded by the resin of the package body 130, enhancing the bonding and sealing qualities between the lead frame bases 112-3 and 122-3 and the package body 130.
In the meantime, the steps 115 and 125 can be formed only in one portion of the bases 112-3 and 122-3 of the first and second lead frames 110-3 and 120-3, for example, only in a portion adjacent to the LED chip 140, depending on the needs.
Now, a method of fabricating an LED package 100 according to the present invention will be explained in a stepwise manner with reference to
First, a metal plate or a sheet metal of a predetermined thickness is prepared and made into a preliminary frame structure 102a shown in
The first lead frame part 110a is composed of a base 112 of a relatively larger area and a pair of extensions 114a extended from opposed ends of the base 112 to the peripheral portion 104. The second lead frame part 120a is formed at a predetermined interval from the first lead frame part 110a, in the shape of a narrow strip and has opposed ends connected to the peripheral portion 104.
In addition, holes H are formed in the corners of the frame structure 102. The holes H are used to fix or guide the frame structure 102a.
The frame structure 102a shown in
As a result, the extensions 114b of the first lead frame part 110b are bent in a shape that is identical to the one shown in
In addition, the second lead frame part 120b are bent in such a way that a base 122 is formed in the middle with the extensions 124b formed at opposed ends from the base 122.
Then, as shown in
Thereafter, an LED chip 140 is disposed and electrically connected on the base 112 of the first lead frame part 110b inside a recess 132 of the package body 130 while electrically connected to the base 122 of the second lead frame part 120b by a wire 142. The LED chip 140 is illustrated as a vertical structure but it can be a horizontal structure. In this case, the LED chip is electrically connected to the base 112 of the first lead frame part 110b by the wire.
Then, a resin is poured into the recess 132 to form a convex shape and cured to obtain an encapsulant 150 shown in
The method explained with reference to
In addition, the frame structure 102b can be modified to obtain the packages 100-2 and 100-3 shown in
For example, as shown in
In addition, instead of the sloping surfaces 123, the steps 115 and 125 can be formed as shown in
A plurality of LED packages can be fabricated simultaneously using a frame array sheet 1002 shown in
This frame array sheet 1002 is obtained by punching or blanking a metal plate or a sheet metal of a predetermined thickness. In the frame array sheet 1002, a plurality of frame structure regions 1102 are formed, which correspond to a plurality of the frame structure shown in
The frame structure regions 1102 are defined, respectively, by the peripheral portions 1004 and middle portions 1104 of the frame array sheet 1002, and the middle portions 1104 can be omitted in the frame array sheet 1002 if necessary. In addition, holes H are formed in the peripheral portions 1004 and the middle portions 1104 to fix or guide the frame array sheet 1002.
Using the frame array sheet 1002 allows manufacturing a plurality of LED packages 100 simultaneously.
An LED package 100-4 according to further another embodiment of the present invention will now be explained with reference to
In the LED package 100-4, the extension 114-4 can be extended out of the package body 130 to form a terminal 8 as in the prior art shown in
The LED package 100-4 with this configuration can also be fabricated easily by the method shown in
In addition, although not illustrated, the extensions 124 of the LED package 100 shown in
The present invention as stated hereinabove allows an LED package with a simple configuration which can achieve superior heat radiation efficiency. Furthermore, the present invention provides a method for easily fabricating an LED package which can achieve superior heat radiation efficiency.
While the present invention has been shown and described in connection with the exemplary embodiments, it will be apparent to those skilled in the art that modifications and variations can be made without departing from the spirit and scope of the invention as defined by the appended claims.
Claims
1. A light emitting diode package comprising:
- first and second lead frames made of a heat and electric conductor, each of the lead frames comprising a planar base and extensions extending in opposed directions and upward directions from the base, the second lead frame having a smaller width than the first frame and arranged apart at a predetermined interval from the first frame;
- a package body made of a resin and configured to surround the extensions of the first and second lead frames to fix the first and second lead frames while exposing underside surfaces of the first and second lead frames;
- a light emitting diode chip disposed on an upper surface of the base of the first lead frame and electrically connected to the bases of the first and second lead frames; and
- a transparent encapsulant for encapsulating the light emitting diode chip.
2. The light emitting diode package according to claim 1, wherein ends of the extensions are positioned at side portions of the package body.
3. The light emitting diode package according to claim 1, wherein at least one of the extensions of the first lead frame extends out of the package body to form a terminal.
4. The light emitting diode package according to claim 1, wherein the package body has a recess formed around the light emitting diode chip and a protrusion is formed in a predetermined width on an upper end of the recess.
5. The light emitting diode package according to claim 4, wherein a portion of the transparent encapsulant fills the recess and another portion of the transparent encapsulant protrudes over the protrusion in a predetermined curvature.
6. The light emitting diode package according to claim 1, wherein the underside surfaces of the bases of the first and second lead frames are coplanar with an underside surface of the package body.
7. The light emitting diode package according to claim 1, wherein the first and second lead frames are arranged in parallel with each other.
8. A method of fabricating a light emitting diode package comprising:
- machining a plate made of a heat and electric conductor of a predetermined thickness into a frame structure, the frame structure comprising first and second lead frame parts each having a planar base and extensions extending in opposed directions from the base, the second lead frame part formed in a smaller width than the first lead frame part and arranged apart at a predetermined interval from the first lead frame part;
- bending the extensions of the first and second lead frame parts in such a way that the bases are positioned lower than the extensions so that the extensions extend in upward directions from the bases;
- injection-molding a resin to form a package body, the package body surrounding the extensions of the first and second lead frame parts adjacent to the bases and thereby fixing the first and second lead frame parts in such a way that at least a part of upper surfaces and bottom surfaces of the bases of the first and second lead frame parts are exposed from the package body and distal ends of the extensions of the first and second lead frame parts extend out of side portions of the package body;
- disposing a light emitting diode chip on the exposed upper surface of the base of the first lead frame part and electrically connecting the light emitting diode chip with the first and second lead frame parts;
- encapsulating the light emitting diode chip with a transparent encapsulant; and
- cutting the extensions of the frame structure to obtain a light emitting diode package.
9. The method according to claim 8, wherein the step of forming a package body comprises forming a recess around the light emitting diode chip and a protrusion in a predetermined width on an upper end of the recess.
10. The method according to claim 9, wherein the step of encapsulating comprises dispensing the transparent encapsulant in such a way that a portion of the transparent encapsulant fills the recess and another portion of the transparent encapsulant protrudes over the protrusion in a predetermined curvature.
11. The method according to claim 8, wherein the step of forming a package body comprises forming the package body in such a way that the underside surfaces of the bases of the first and second frame parts are coplanar with an underside surface of the package body.
12. The method according to claim 8, wherein the step of forming a frame structure comprises forming the first and second lead frame parts in parallel with each other.
Type: Application
Filed: Apr 5, 2007
Publication Date: Oct 18, 2007
Applicant:
Inventors: Kyung Taeg Han (Hwasung), In Tae Yeo (Seoul), Hun Joo Hahm (Sungnam), Chang Ho Song (Seoul), Seong Yeon Han (Gwangju), Yoon Sung Na (Suwon), Dae Yeon Kim (Suwon), Ho Sik Ahn (Incheon), Young Sam Park (Seoul)
Application Number: 11/730,965