Light emitting diode package including a lead frame with a cavity

The present invention provides a light emitting diode package which includes a lead frame with a cavity; a mold exposing the cavity and housing the lead frame; and an LED chip mounted on the cavity, wherein light passing an upper edge of the LED chip passes an upper edge of the cavity.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of Korean Patent Application No. 10-2008-0064367 filed with the Korea Intellectual Property Office on Jul. 3, 2008, the disclosure of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a light emitting diode package, and more particularly, to a light emitting diode package capable of improving reliability.

2. Description of the Related Art

As a light emitting diode has various advantages a long lifespan, low consumption power, rapid response speed, an excellent drive property in comparison with a light emitting device based on a filament, the light emitting diode is widely applied to a lighting apparatus, an electric signboard, an electronic appliance, for example, a backlight of a display device. In addition, the light emitting diode can be downsized and light-weighted, applications of the light emitting diode are increasingly extended.

The light emitting diode is used in a package type. That is, a light emitting diode package includes a light emitting diode chip, a lead frame mounted with the light emitting diode chip, and a mold receiving the lead frame and exposing the light emitting diode chip. Herein, the mold is provided with the light emitting diode and a cavity allowing a part of the lead frame to be exposed so as to efficiently emit heat generated from the light emitting diode chip. At this time, although light generated from the light emitting diode chip is emitted upwards, a part of the light generated from the light emitting diode chip, that is, light emitted from a side surface of the light emitting diode chip may be irradiated onto a side wall of the cavity. At this time, the light irradiated onto the side wall, that is, the mold deteriorates the mold, thereby lowering reliability of the light emitting diode package. In particular, as an output of the light emitting diode chip becomes higher, the deterioration of the mold is accelerated, whereby there is a limit in applying the light emitting diode package to a high-output light emitting diode package.

Accordingly, a conventional light emitting diode package has a problem in that the mold is deteriorated due to the light generated from the light emitting diode chip, thereby lowering the reliability of the light emitting diode package.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a light emitting diode package capable of preventing reliability from being lowered due to deterioration of a mold by preventing light generated from a light emitting diode chip to the mold from being irradiated with a lead frame having a cavity for mounting the light emitting diode chip.

In order to achieve the above-described object, there is a provided a light emitting diode package in accordance with an aspect of the present invention which includes a lead frame with a cavity; a mold exposing the cavity and housing the lead frame; and an LED chip mounted on the cavity, wherein light passing an upper edge of the LED chip passes an upper edge of the cavity.

Herein, a depth of the cavity is designed to satisfy the following Equation 1.
h=y/x×c+y/2  Equation 1

Herein, H is the depth of the cavity, x is a width of the LED chip, y is a height of the LED chip, and c is a width of the cavity.

The lead frame includes a bottom surface, a lateral wall surface extending upward to be inclined from the bottom surface, and a horizontal surface horizontally extending from the lateral wall surface.

The upper edge of the cavity is an area where the lateral wall surface and the horizontal surface are in contact with each other.

The light emitting diode package may include a reflective film covering the lead frame.

The LED chip may be provided in the cavity in plural numbers such as one or two or more.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1is a cross-sectional view of a light emitting diode package in accordance with a first embodiment of the present invention.

Referring toFIG. 1, a light emitting diode package100includes an LED chip140, lead frames110and120, and a mold130.

The LED chip140may be a semiconductor device emitting light by an applied current. The LED chip140may be a rectangular parallelepiped light source. However, in this embodiment of the present invention, the LED chip140is not limited to the rectangular parallelepiped light source. That is, the LED chip140may have various shapes such as a regular hexahedron and a trapezoid hexahedron.

The lead frames110and120may include a first lead unit110and a second lead unit120which are separated from each other. At this time, the first lead unit110includes a bottom surface110amounted with the LED chip140, a lateral wall surface110bextending upward to be inclined from the bottom surface110a, and a horizontal surface110chorizontally extending from the lateral wall surface110b. Hence, the first lead unit110forms a cavity160by the bottom surface110aand the lateral wall surface110b. That is, the LED chip140is mounted within the cavity160. Herein, although not shown in the figure, the LED chip140may be electrically connected to the bottom surface110aby a conductive member, for example, a solder ball or a wire. At this time, the second lead unit120and the LED chip140may be electrically connected to each other by the wire.

The mold130houses the lead frames110and120. At this time, the mold130includes an opening portion170for exposing the cavity160including the LED chip140. That is, the mold130exposes the bottom surface110aand the lateral wall surface110bat least. In addition, the mold130may further expose the second lead frame120. Accordingly, heat generated from the LED chip140may efficiently be discharged. Herein, a part of the lead frame, for example, a part of the horizontal surface110cmay be exposed by being drawn to an outside with penetrating the mold130.

The mold130may efficiently discharge the heat generated from the LED chip140by exposing rear surfaces of the lead frames110and120.

It is possible to prevent light generated from the LED chip140from being radiated to the mold130by stably design a length of the cavity160. As a result, it is possible to prevent the reliability of the light emitting diode package100from being lowered due to deterioration of the mold130. This will hereinafter be described in more detail.

Further, a sealing member150may further be provided in an opening portion170of the mold130. Herein, the sealing member150may have a single layer structure. Contrary to this, the sealing member150may have a double layer structure having different refractive indexes. At this time, in order to efficiently discharge the light generated from the LED chip140to the outside, a lower layer of the sealing member150may have a refractive index smaller than an upper layer of the sealing member150.

Although not shown in the figure, a reflective film for increasing reflectivity of the light may further be provided on surfaces of the lead frames110and120. The reflective film may be made of a metal having high light reflectivity. For example, a material of the reflective film may be Ag or Al. Herein, the reflective film may be formed by a plating method. Accordingly, it is possible to further increase light extraction efficiency of the light emitting diode package100.

Hereinafter, referring toFIGS. 2 and 3, a preferred design of a cavity in accordance with an embodiment of the present invention will be described in more detail.

FIG. 2is a diagram illustrating an optical characteristic of the LED chip shown inFIG. 1.

As shown inFIG. 2, the LED chip140may be a rectangular parallelepiped light source. At this time, in case that a current is applied to the LED chip140, the light generated from the LED chip140may be discharged through a top surface and a lateral surface of the LED chip140. Herein, light formed in a center F of the LED chip140is discharged through the lateral surface of the LED chip140, the light may be distributed between an angle of first light L1passing an upper edge of the LED chip140and an angle a of second light L2. At this time, Lights directed toward lower parts of the lead frames110and120among lights generated from the lateral surface of the LED chip140are reflected and discharged toward an upper parts of the lead frames110and120. However, some of the lights directed toward the upper parts of the lead frames110and120among the lights generated from the lateral surface of the LED chip140are radiated to the mold130, causing the mold130to be deteriorated. At this time, it is possible to prevent the lights generated from the lateral surface of the LED chip140from being radiated to the mold130by adjusting a depth of the cavity160. Herein, it is preferable to adjust the depth of the cavity160so that the first light L1passes the upper edge of the cavity160. As a result, most of the lights generated from the lateral surface of the LED chip140may be radiated to the lateral wall surface110bof the lead frames110and120. This is a reason why the light passing the upper edge of the LED chip140, that is, the first light L1is outermost light discharged from the lateral surface of the LED chip140. Herein, the upper edge of the cavity160is an area where the lateral wall surface110band the horizontal surface110care in contact with each other.

FIG. 3is a diagram illustrating a design of a lead frame in accordance with a first embodiment of the present invention.

As shown inFIG. 3, the depth of the cavity should satisfy the following Equation 2.
h=d+y/2  Equation 2

Herein, h is the depth of the cavity160. d is a length of an area where the lights discharged to the upper parts of the lead frames110and120among the lights generated from the lateral wall surface110bof the LED chip140can be radiated to the lateral wall surface of the lead frames110and120. y is a height of the LED chip140.

At this time, the length d of the area where the light is radiated to the lateral wall surface of the lead frames110and120can be acquired by the following Equation 3.
tan(a/2)=y/x=d/c, therebyd=y/x×cEquation 3

Herein, x is a width of the LED chip140. c is a width of the cavity160.

Accordingly, the depth h of the cavity160satisfies the following Equation 1.
h=y/x×c+y/2  Equation 1

Herein, h is a depth of the cavity160. x is the width of the LED chip140. y is the height of the LED chip140. c is the width of the cavity160.

FIG. 4is a graph illustrating a high-temperature load reliability test result performed for a light emitting diode package in accordance with a type of a lead frame.

As shown inFIG. 4, it is verified that a light emitting diode package S1including a lead frame with a cavity has deterioration rate smaller than a light emitting diode package S2having a flat lead frame.

Accordingly, in case that the cavity is provided in the lead frame, it is possible to prevent the mold from being deteriorated due to light generated from the LED chip. In addition, it is possible to more effectively prevent the mold from being deteriorated by stably designing the depth of the cavity.

FIG. 5is a cross-sectional view of a light emitting diode package in accordance with a second embodiment of the present invention. Herein, except for the number of the LED chips, the light emitting diode package in accordance with the second embodiment of the present invention has the same configuration as the light emitting diode package in accordance with the first embodiment of the present invention. Accordingly, like reference numerals refer to the same elements in the second embodiment as the elements in the first embodiment and repetitive description will be omitted.

Referring toFIG. 5, the light emitting diode package in accordance with the present invention lead frames110,120a, and120bhaving the cavity160, a mold130exposing the cavity160and housing the lead frame110, and LED chips140aand140bmounted on the cavity160. Herein, in order to prevent the mold130from being deteriorated due to light generated from lateral surfaces of the LED chips140aand140b, the cavity160is designed so that light passing upper edges of the LED chips140aand140bpasses an upper edge of the cavity160.

The lead frames110,120a, and120bmay include a first lead unit110mounted with the LED chips140aand140b, and second and third lead units120aand120bwhich are spaced from the first lead unit110and are electrically insulated from each other. At this time, the cavity160is formed in the first lead unit110.

The LED chips140aand140bmay include a first LED chip140aand a second LED chip140bwhich are provided in the first lead unit110, that is, the cavity160. Herein, the first and second LED chips140aand140bare the same as each other or can implement lights of different colors.

The first and second LED chips140aand140bmay be electrically connected to the first lead unit110. With this, the first LED chip140ais electrically connected to the second lead unit120athrough a first wire180a. The second LED chip140bis electrically connected to a third lead unit120bthrough a second wire180b.

In this embodiment of the present invention, an example that two LED chips are mounted has been described, but is not limited to it. Two or more LED chips may mounted by adjusting the number of the lead units.

Accordingly, the number of the LED chips mounted on the lead frame can be selectively selected by adjusting the number of the lead units which are electrically insulated from each other.

A light emitting diode device has a lead frame having a cavity for mounting a chip and thus light generated from a light emitting diode chip is prevented from being radiated to a mold, whereby there is provided a light emitting diode package capable of preventing reliability from being lowered due to deterioration of the mold.

Since it is possible to prevent the deterioration due to the light radiated to the mold, a high-output light emitting diode chip can be applied.

The mold exposes the lead frame mounted with the light emitting diode chip, thereby efficiently discharging heat generated from the light emitting diode chip.