Light emitting diode assembly

Disclosed is a light emitting diode assembly. The light emitting diode assembly comprised: a red light emitting diode chip; a short-wavelength light emitting diode chip emitting a light having a wavelength relatively shorter than that of a light emitted from the red light emitting diode chip; a first heat-dispersion member for dispersing most of the heat generated in the short wavelength light emitting diode chip; and a second heat-dispersion member for dispersing most of the heat generated in the red light emitting diode chip. Further, the second heat-dispersion member has heat dispersion performance relatively superior to that of the first heat dispersion member. Thus, spectrum movement in the red light emitted from the red light emitting diode chip may be prevented so as to prevent a color-coordinate transformation during the operation time of same.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is the National Stage Entry of International Application PCT/KR2012/004180, filed on May 25, 2012 and claims priority from and the benefit of Korean Patent Application No. 10-2011-0052970, filed on Jun. 1, 2011, all of which are incorporated herein by reference in their entireties for all purposes as if fully set forth herein.

BACKGROUND

The present invention relates to a light emitting diode assembly, and more particularly, to a light emitting diode assembly including a red light emitting diode chip.

2. Discussion of the Background

Light emitting diodes are used as light sources in various products. Particularly, light emitting diodes are used as light sources for backlight units, displays, lighting fixtures, and the like, and can emit white light through combination of light emitting diodes emitting various colors, or combination with phosphors. Particularly, white light can be realized through combination of a blue light emitting diode and a yellow phosphor. However, since the combination of the blue light emitting diode and the yellow phosphor provides white light showing a lack of red emission, a light emitting diode assembly based on this combination has relatively poor color rendering index and relatively high color temperature. Accordingly, a light emitting diode assembly designed to emit white light through combination of light emitting diodes and phosphors also employs a red light emitting diode in order to improve the color rendering index and the color temperature.

As compared with AlInGaN-based blue or UV light emitting diodes, AlInGaP-based red light emitting diodes emit relatively large amounts of heat. Moreover, the red light emitting diodes exhibit significant spectrum shifts according to change of temperature.

As a result, in a light emitting diode assembly including a red light emitting diode, spectrum shift of red light occurs as the junction temperature of the red light emitting diode increases. Thus, even in the case where the light emitting diode assembly realizes white light in desired color coordinates in initial operation, the color coordinates change over time, making it difficult to realize desired white light.

SUMMARY

Exemplary embodiments of the present invention provide a light emitting diode assembly capable of preventing spectrum shift of a red light emitting diode chip.

Exemplary embodiments of the present invention also provide a light emitting diode assembly capable of reducing thermal interference between a red light emitting diode chip and other light emitting diode chips emitting light of different wavelengths.

An exemplary embodiment of the invention provides a light emitting diode assembly including: a red light emitting diode chip; a short wavelength light emitting diode chip emitting light having a shorter wavelength than light emitted from the red light emitting diode chip; a first heat dissipator dissipating heat generated from the short wavelength light emitting diode chip; and a second heat dissipator dissipating heat generated from the red light emitting diode chip. In addition, the second heat dissipator has higher heat dissipation capability than the first heat dissipator.

Since heat generated from the red light emitting diode chip can be more rapidly dissipated through the second heat dissipator, it is possible to prevent increase in junction temperature of the red light emitting diode chip, whereby spectrum shift of red light can be prevented.

In some embodiments, the light emitting diode assembly may further include a base substrate. In this case, the first heat dissipator may include a first landing pad placed on the base substrate, and the second heat dissipator may include a second landing pad placed on the base substrate. In addition, the short wavelength light emitting diode chip is thermally coupled to the first landing pad, and the red light emitting diode chip is thermally coupled to the second landing pad.

Further, the first heat dissipator may include a first external pad placed under the base substrate and a first via connecting the first landing pad to the first external pad, and the second heat dissipator may include a second external pad placed under the base substrate and a second via connecting the second landing pad to the second external pad.

In order to allow the second heat dissipator to have higher heat dissipation capability than the first heat dissipator, the second landing pad may have a larger surface area than the first landing pad, the second external pad may have a larger area than the first external pad, the second external pad may have a larger surface area than the first external pad, and/or the second via may have a larger volume than the first via. For example, the number of second vias may be greater than the number of first vias.

In some embodiments, the light emitting diode assembly may further include a main body. In addition, the first heat dissipator may include a first internal lead placed within the main body and a first external lead extending from the first internal lead and exposed outside the main body, and the second heat dissipator may include a second internal lead placed within the main body and a second external lead extending from the second internal lead and exposed outside the main body. Such a light emitting diode assembly may be formed using a lead frame.

Further, the short wavelength light emitting diode chip may be thermally coupled to the first internal lead; the red light emitting diode chip may be thermally coupled to the second internal lead; and the second heat dissipator may occupy a larger area than the first heat dissipator. For example, the second internal lead may be wider than the first internal lead and/or the second external lead may be wider than the first external lead.

In some embodiments, the first heat dissipator may include a first heat dissipation slug, and the second heat dissipator may include a second heat dissipation slug. The second heat dissipation slug may have a larger volume than the first heat dissipation slug, and thus can relatively rapidly dissipate heat generated from the red light emitting diode chip.

The light emitting diode assembly may further include a main body; a first internal lead placed within the main body; a first external lead extending from the first internal lead and exposed outside the main body; a second internal lead placed within the main body; and a second external lead extending from the second internal lead and exposed outside the main body. Here, the short wavelength light emitting diode chip is thermally coupled to the first heat dissipation slug, and the red light emitting diode chip is thermally coupled to the second heat dissipation slug.

The first heat dissipation slug is placed adjacent the second heat dissipation slug. In a certain embodiment, the second heat dissipation slug may surround the first heat dissipation slug. Since the second heat dissipation slug is disposed outside the first heat dissipation slug, the second heat dissipation slug can more rapidly dissipate heat generated from the red light emitting diode chip.

The first heat dissipator may be separated from the second heat dissipator. With this structure, it is possible to reduce thermal interference between the short wavelength light emitting diode chip and the red light emitting diode chip.

The light emitting diode assembly may further include a wavelength converter which converts wavelengths of light emitted from the short wavelength light emitting diode chip. For example, the wavelength converter may be encapsulated within a molding portion, or may be disposed as a conformal layer on a light emitting diode chip. The light emitting diode assembly may emit white light containing a red component of the red light emitting diode chip.

In addition, the short wavelength light emitting diode chip may be a light emitting diode chip emitting blue or ultraviolet light. The short wavelength light emitting diode chip may be an AlGaInN-based light emitting diode chip, and the red light emitting diode chip may be an AlGaInP-based light emitting diode chip.

In accordance with another aspect of the present invention, a light emitting diode assembly includes a red light emitting diode chip; a short wavelength light emitting diode chip emitting light having a shorter wavelength than light emitted from the red light emitting diode chip; a first heat transfer passage thermally coupled to the short wavelength light emitting diode chip; and a second heat transfer passage thermally coupled to the red light emitting diode chip. Here, the second heat transfer passage has higher heat transfer capability than the first heat transfer passage.

With this structure, the light emitting diode assembly can relatively rapidly transfer heat from the red light emitting diode chip, thereby preventing spectrum shift of red light emitted from the red light emitting diode chip.

For example, the second heat transfer passage may have a larger total volume than the first heat transfer passage. Alternatively, the number of second heat transfer passages may be greater than the number of first heat transfer passages.

According to the embodiments of the invention, the light emitting diode assembly can prevent spectrum shift of light emitted from a red light emitting diode chip over time and thus can prevent change in color coordinates over time. Furthermore, the light emitting diode assembly suppresses thermal interference between the red light emitting diode chip and the short wavelength light emitting diode chip, whereby the red light emitting diode chip can be less influenced by heat generated from the short wavelength light emitting diode chip, or the short wavelength light emitting diode chip can be less influence by heat generated from the red light emitting diode chip, thereby improving operational stability

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

Embodiments of the present invention will be described in more detail with reference to the accompanying drawings. It should be understood that the following embodiments are given by way of illustration only to provide thorough understanding of the invention to those skilled in the art. Therefore, the present invention is not limited to the following embodiments and may be embodied in different ways. Further, like components will be denoted by like reference numerals throughout the specification, and the widths, lengths, and thicknesses of certain elements, layers or features may be exaggerated for clarity.

FIG. 1is a schematic sectional view of a light emitting diode assembly according to one embodiment of the present invention.

Referring toFIG. 1, the light emitting diode assembly according to this embodiment includes a base substrate21, a housing23, a first landing pad25a, a second landing pad27a, a first via25b, a second via27b, a first external pad25c, a second external pad27c, a short wavelength light emitting diode chip31, a red light emitting diode chip33, a molding portion35, and phosphors36.

The base substrate21may be a ceramic substrate or a printed circuit board. The base substrate21supports the landing pads25a,27a, and provides through-holes forming the vias25b,27b. The housing23provides a cavity. When the base substrate21is a ceramic substrate, the housing23may be formed together with the base substrate21using a ceramic material. The housing23may act as a reflector that reflects light. The housing23may be omitted.

The first landing pad25ais a pad on which the short wavelength light emitting diode chip31is mounted, and the second landing pad27ais a pad on which the red light emitting diode chip33is mounted. Both the first and second landing pads25a,27aare placed on the base substrate21. The first and second landing pads25a,27aare formed of a conductive material and thus have higher thermal conductivity than the base substrate21.

The first external pad25cand the second external pad27care placed under the base substrate21. The first and second external pads25c,27cmay act as connection terminals for supplying electric power to the light emitting diode chips31,33. The second external pad27chas a larger area than the first external pad25c. The area of the second external pad27cmay be larger than the first external pad25cin consideration of the ratio of heat generated from the red light emitting diode chip33to heat generated from the short wavelength light emitting diode chip31. For example, when the quantity of heat generated from the red light emitting diode chip33is two times greater than that of heat generated from the short wavelength light emitting diode chip31, the area of the second external pad27cmay be about two times greater than the area of the first external pad25c.

The first landing pad25amay be connected to the first external pad25cthrough the first via25b, and the second landing pad27amay be connected to the second external pad27cthrough the second via27b.

The short wavelength light emitting diode chip31is mounted on the first landing pad25aand is thermally connected to the first landing pad25a. The short wavelength light emitting diode chip31may be an AlInGaN-based light emitting diode chip emitting blue or UV light. The red light emitting diode chip33is mounted on the second landing pad27aand is thermally coupled to the second landing pad27a. The red light emitting diode chip33is an AlInGaP-based light emitting diode chip emitting red light. The short wavelength light emitting diode chip31may have any structure, for example, a lateral structure or a vertical structure, without being limited to a certain structure. The red light emitting diode chip33may have any structure, for example, a lateral structure or a vertical structure, without being limited to a certain structure. These light emitting diode chips31,33may be electrically connected to the landing pads25a,27athrough bonding wires (not shown) in various ways according to the structures thereof. In addition, the light emitting diode chips31,33may be connected to each other in series or in parallel, without being particularly limited to a certain connection method.

The molding portion35may cover the short wavelength light emitting diode chip31and the red light emitting diode chip33. The molding portion35protects the light emitting diode chips31,33and the bonding wires from moisture and the like. In addition, the molding portion35may contain the phosphors36therein. The phosphors36convert wavelengths of light emitted from the short wavelength light emitting diode chip31. For example, when the short wavelength light emitting diode chip31is a blue light emitting diode chip, the phosphors36may be yellow phosphors. As a result, white light can be realized by combination of blue light emitted from the blue light emitting diode chip, yellow light emitted from the yellow phosphors and red light emitted from the red light emitting diode chip31. Alternatively, when the short wavelength light emitting diode chip31is a UV light emitting diode chip, the phosphors36may include blue phosphors and yellow phosphors.

According to this embodiment, heat generated from the short wavelength light emitting diode chip31is mainly discharged through the first landing pad25a, the first via25band the first external pad25c, and heat generated from the red light emitting diode chip33is mainly discharged through the second landing pad27a, the second via27band the second external pad27c. The first landing pad25a, the first via25band the first external pad25cconstitute a first heat dissipator as a first heat transfer passage, and the second landing pad27a, the second via27band the second external pad27cconstitute a second heat dissipator as a second heat transfer passage. Here, since the second external pad27chas a greater area than the first external pad25c, the second heat dissipator has higher heat dissipation capability than the first heat dissipator. As a result, heat generated from the red light emitting diode chip can be more rapidly discharged, thereby preventing deterioration of the red light emitting diode chip over time.

In this embodiment, the first landing pad25amay be formed of the same material as that of the second landing pad27a, the first via25bmay be formed of the same material as that of the second via27b, and the first external pad25cmay be formed of the same material as that of the second external pad27c, without being limited thereto. Alternatively, they may be formed of different materials having different coefficients of thermal conductivity. For example, the second landing pad27amay be formed of a material having a higher coefficient of thermal conductivity than that of the first landing pad25a; the second via27bmay be formed of a material having a higher coefficient of thermal conductivity than that of the first via25b, and the second external pad27cmay be formed of a material having a higher coefficient of thermal conductivity than that of the first external pad25c.

In this embodiment, the first heat dissipator may be separated from the second heat dissipator, whereby thermal interference between the light emitting diode chips31,33can be reduced.

FIG. 2is a schematic sectional view of a light emitting diode assembly according to another embodiment of the present invention.

Referring toFIG. 2, the light emitting diode assembly according to this embodiment is generally similar to the light emitting diode assembly described with reference toFIG. 1, except that phosphors36are provided only to a short wavelength light emitting diode chip31.

Specifically, a molding portion44containing the phosphors covers the short wavelength light emitting diode chip31and a red light emitting diode chip is placed outside the molding portion44. In addition, a molding portion45does not contain the phosphors and covers the light emitting diode chips31,33.

According to this embodiment, the phosphors36are placed only around the area of the short wavelength light emitting diode chip31, whereby light emitted from the red light emitting diode chip33can be prevented from being lost by the phosphors36and the amount of phosphors used in the light emitting diode assembly can be reduced.

FIG. 3is a schematic sectional view of a light emitting diode assembly according to a further embodiment of the present invention.

Referring toFIG. 3, the light emitting diode assembly according to this embodiment is generally similar to the light emitting diode assembly described with reference toFIG. 1, except that the phosphors36of the light emitting diode assembly shown inFIG. 1are provided in a conformal coating layer54.

Specifically, the conformal coating layer54containing phosphors covers a short wavelength light emitting diode chip31, and a red light emitting diode chip is separated from the conformal coating layer54. In addition, a molding portion45does not contain the phosphors and covers the light emitting diode chips31,33.

According to this embodiment, the phosphors are placed only around the area of the short wavelength light emitting diode chip31, whereby light emitted from the red light emitting diode chip33can be prevented from being lost by the phosphors36and the amount of phosphors used in the light emitting diode assembly can be reduced. In addition, the phosphors are provided by the conformal coating layer54, thereby achieving uniform wavelength conversion.

FIG. 4is a schematic sectional view of a light emitting diode assembly according to yet another embodiment of the present invention.

Referring toFIG. 4, the light emitting diode assembly according to this embodiment is generally similar to the light emitting diode assembly described with reference toFIG. 1, except that a second landing pad27ahas a larger area than a first landing pad25a.

Specifically, the second landing pad27aplaced on a base substrate21occupies a larger area than the first landing pad25a. As a result, the second heat dissipator can more rapidly dissipate heat generated from a red light emitting diode chip33.

In this embodiment, phosphors36are included in a molding portion35. Alternatively, the phosphors36may be included in the molding portion44as shown inFIG. 2, or may be provided by the conformal coating layer54as shown inFIG. 3.

FIG. 5is a schematic sectional view of a light emitting diode assembly according to yet another embodiment of the present invention.

Referring toFIG. 5, the light emitting diode assembly according to this embodiment is generally similar to the light emitting diode assembly described with reference toFIG. 1, except that the light emitting diode assembly includes another second via27din addition to the second via27b.

Specifically, according to this embodiment, the number of second vias27b,27dis greater than the number of first vias25bto allow more rapid discharge of heat generated from the red light emitting diode chip33. Alternatively, instead of increasing the number of second vias, the size of the second via, that is, the volume of the second via, may be increased.

In this embodiment, phosphors36are included in a molding portion35. Alternatively, the phosphors36may be included in the molding portion44as shown inFIG. 2, or may be provided by the conformal coating layer54as shown inFIG. 3.

FIG. 6is a schematic sectional view of a light emitting diode assembly according to yet another embodiment of the present invention.

Referring toFIG. 6, the light emitting diode assembly according to this embodiment is generally similar to the light emitting diode assembly described with reference toFIG. 5, except that the light emitting diode assembly includes a dummy pad37cin addition to a second via27d, which is connected to the dummy pad37c.

The dummy pad37cprovides an additional heat transfer passage to aid in discharge of heat from a red light emitting diode chip33.

In addition to the second landing pad27a, a bonding pad (not shown) is provided such that a second external pad27ccan be connected to the bonding pad through the second via27b. In this case, a bonding wire may be connected to the bonding pad, thereby facilitating electrical connection between the light emitting diode chips31,33. This structure will be described below with reference toFIG. 9.

FIG. 7is a schematic sectional view of a light emitting diode assembly according to yet another embodiment of the present invention.

Referring toFIG. 7, the light emitting diode assembly according to this embodiment is generally similar to the light emitting diode assembly described with reference toFIG. 1, except that a second external pad27cis formed with protrusions and depressions on a surface thereof.

That is, since the protrusions and depressions are formed on the surface of the second external pad27c, it is possible to increase a surface area of the second external pad27cwithout increasing the width of the second external pad27c. With the increased surface area of the second external pad27c, the light emitting diode assembly may have improved heat dissipation through the second external pad27c.

In this embodiment, phosphors36are included in a molding portion35. Alternatively, the phosphors36may be included in the molding portion44as shown inFIG. 2, or may be provided by the conformal coating layer54as shown inFIG. 3.

FIG. 8is a schematic plan view of a light emitting diode assembly according to yet another embodiment of the present invention.

Referring toFIG. 8, the light emitting diode assembly includes a base substrate51, a first landing pad55a, a second landing pad57a, a first via55b, a second via57b, a first external pad55c, a second external pad57c, a short wavelength light emitting diode chip61, and a red light emitting diode chip63. In addition, although not shown in the drawings, the light emitting diode assembly according to this embodiment may further include a wavelength converter, which converts wavelengths of light emitted from the short wavelength light emitting diode chip61, for example, a molding portion containing phosphors (seeFIG. 1orFIG. 2) or a conformal coating layer (seeFIG. 3), and a housing placed on the base substrate51.

The base substrate51is the same as the base substrate21described with reference toFIG. 1, and a detailed description thereof will be omitted.

The first landing pad55ais a pad on which the short wavelength light emitting diode chip61is mounted, and the second landing pad57ais a pad on which the red light emitting diode chip63is mounted. Both the first and second landing pad55a,57aare placed on the base substrate21. The first and second landing pads55a,57aare formed of a conductive material and thus have higher thermal conductivity than the base substrate51.

The second landing pad57amay have a larger area than the first landing pad55a, and may be disposed to surround three sides of the first landing pad55a, as shown in the drawing. The first landing pad55ais disposed over a central region from one edge of the base substrate51. As the second landing pad57ais disposed along the edge of the base substrate51, the second landing pad57acan more efficiently discharge heat generated from the red light emitting diode chip63. In addition, as the second landing pad57aoccupies a larger area than the first landing pad55a, it is possible to form a greater number of second vias57bthan the number of first vias55b.

The first external pad55cand the second external pad57care placed under the base substrate51. The first and second external pads55c,57cmay act as connection terminals for supplying electric power to the light emitting diode chips31,33. The second external pad57cmay have a larger area than the first external pad55c.

The first landing pad55ais connected to the first external pad55cthrough the first via55b, and the second landing pad57ais connected to the second external pad57cthrough the second via57b. The first via55btransfers heat from the first landing pad55ato the first external pad55c, and the second vias57btransfer heat from the second landing pad57ato the second external pad57c.

The short wavelength light emitting diode chip61and the red light emitting diode chip63are the same as the light emitting diode chips31,33shown inFIG. 1, respectively, and thus, detailed descriptions thereof will be omitted. In this embodiment, the short wavelength light emitting diode chip61has a lateral structure, in which two electrode pads (not shown) are placed on an upper surface thereof, and the red light emitting diode chip63has a vertical structure, in which an n-electrode pad and a p-electrode pad are placed on upper and lower surfaces of the red light emitting diode chip, respectively.

For example, when the n-electrode pad of the red light emitting diode chip63is placed on the upper surface of the chip, the second external pad57cacts as a positive terminal and the first external pad55cacts as a negative terminal. The n-electrode pad of the red light emitting diode chip63is connected to a p-electrode pad of the short wavelength light emitting diode chip61via a bonding wire W, and an n-electrode pad of the short wavelength light emitting diode chip61is connected to the first landing pad55avia another bonding wire W. As a result, the short wavelength light emitting diode chip61and the red light emitting diode chip63are connected to each other in series between the first external pad55cand the second external pad57c.

In this embodiment, the second landing pad57ahas a larger area than the first landing pad55a, whereby the light emitting diode assembly has a greater number of second vias57bthan the number of first vias57a, thereby enabling more rapid discharge of heat generated from the red light emitting diode chip63. Furthermore, the second external pad57cis formed to have a larger area than the first external pad55c, thereby enabling further improved heat dissipation.

Although the short wavelength light emitting diode chip61and the red light emitting diode chip63are illustrated as being connected to each other in series in this embodiment, the short wavelength light emitting diode chip61may be connected in parallel to the red light emitting diode chip63.

According to this embodiment, heat generated from the short wavelength light emitting diode chip61is mainly discharged through the first landing pads55a, the first via55band the first external pad55c, and heat generated from the red light emitting diode chip63is mainly discharged through the second landing pad57a, the second via57band the second external pad57c. The first landing pad55a, the first via55band the first external pad55cconstitute a first heat dissipator as a first heat transfer passage, and the second landing pad57a, the second via57band the second external pad57cconstitute a second heat dissipator as a second heat transfer passage. Here, since the second heat dissipator has higher heat dissipation capability than the first heat dissipator, heat generated from the red light emitting diode chip can be more rapidly discharged, thereby preventing deterioration of the red light emitting diode chip over time. Particularly, since the number of second vias57bis greater than the number of first vias55b, the number of heat transfer passages is increased, thereby improving heat transfer capabilities.

In this embodiment, the first landing pad55amay be formed of the same material as that of the second landing pad57a, the first via55bmay be formed of the same material as that of the second via57b, and the first external pad55cmay be formed of the same material as that of the second external pad57c, without being limited thereto. Alternatively, they may be formed of different materials having different coefficients of thermal conductivity.

In this embodiment, the first heat dissipator may be separated from the second heat dissipator, whereby thermal interference between the light emitting diode chips31,33can be reduced.

FIG. 9is a schematic plan view of a light emitting diode assembly according to yet another embodiment of the present invention.

Referring toFIG. 9, the light emitting diode assembly according to this embodiment is generally similar to the light emitting diode assembly shown inFIG. 8, except that the short wavelength light emitting diode chip61has a vertical structure. In this embodiment, the short wavelength light emitting diode chip61has an n-electrode pad placed on an upper surface thereof.

In addition to the first landing pad55aand the second landing pad57a, a bonding pad59ais placed on the base substrate51. The light emitting diode assembly according to this embodiment further includes a third external pad59cplaced under the base substrate51such that the bonding pad59ais connected to the third external pad59cthrough a third via59b.

The n-electrode pad placed on the upper surface of the short wavelength light emitting diode chip61is connected to the second landing pad57avia a bonding wire W, and an n-electrode pad placed on an upper surface of the red light emitting diode chip63is connected to the bonding pad59athrough another bonding wire W.

In this embodiment, the first external pad55cacts as a positive terminal, the third external pad59cacts as a negative terminal, and the short wavelength light emitting diode chip61and the red light emitting diode chip63are connected in parallel to each other between the first external pad55cand the third external pad59c.

In the light emitting diode assembly according to this embodiment, the bonding pad59ais additionally placed on the base substrate51, thereby increasing the degree of freedom for selection of the light emitting diode chips61,63having various structures. For example, as described in the embodiment ofFIG. 8, a lateral type short wavelength light emitting diode chip and a vertical type red light emitting diode chip can be mounted on the first landing pad55aand the second landing pad57a, respectively, whereby the bonding pad59cmay remain un-used.

FIG. 10andFIG. 11are a schematic sectional view and a schematic plan view of a light emitting diode assembly according to yet another embodiment of the present invention, respectively.

Referring toFIGS. 10 and 11, the light emitting diode assembly according to this embodiment includes a main body71, a first internal lead75a, a first external lead75b, a second internal lead77a, a second external lead77b, a short wavelength light emitting diode chip81, a red light emitting diode chip83, a molding portion85, and phosphors36.

The main body71may be formed of plastics, for example, by insert-molding a lead frame. The main body71has a cavity through which the internal leads75a,77aare exposed. Here, the cavity may have a slanted sidewall to form a reflective face71a.

The first internal lead75aand the second internal lead77aare placed on a bottom of the cavity of the main body71, the first external lead75bextends from the first internal lead75ato be exposed outside the main body71, and the second external lead77bextends from the second internal lead77ato be exposed outside the main body71. The first and second external leads75b,77bmay be bent outside the main body.

The second internal lead77amay occupy a larger area than the first internal lead75a, and/or the second external lead77bmay occupy a larger area than the first external lead75b. For example, as shown inFIG. 11, the second internal lead77amay be disposed to surround three sides of the first internal lead75a, and the second external lead77bmay be formed to have a larger area than the first external lead75a.

The short wavelength light emitting diode chip81is mounted on the first internal lead75ato be thermally coupled thereto, and the red light emitting diode chip83is mounted on the second internal lead77ato be thermally coupled thereto. The short wavelength light emitting diode chip81and the red light emitting diode chip83may be connected to each other in series or in parallel via bonding wires (not shown).

According to this embodiment, the first internal lead75aand the first external lead75bconstitute a first heat dissipator, and the second internal lead77aand the second external lead77bconstitute a second heat dissipator. In other words, heat generated from the short wavelength light emitting diode chip81is mainly discharged through the first internal lead75aand the first external lead75b, and heat generated from the red light emitting diode chip83is mainly discharged through the second internal lead77aand the second external lead77b. In this embodiment, since the second internal lead77aand/or the second external lead77bhas a larger area than the first internal lead75aor the first external lead75b, heat generated from the red light emitting diode chip83can be more efficiently discharged.

The molding portion85may cover the short wavelength light emitting diode chip81and the red light emitting diode chip83. In addition, the molding portion35may contain the phosphors36. The molding portion85is the same as the molding portion35described with reference toFIG. 1, and thus a detailed description thereof will be omitted.

Although the phosphors36are illustrated as being included in the molding portion85in this embodiment, the phosphors36may be included in the molding portion44as shown inFIG. 2, or may be provided by the conformal coating layer54as shown inFIG. 3.

FIG. 12andFIG. 13are a schematic perspective view and a schematic plan view of a light emitting diode assembly according to yet another embodiment of the present invention, respectively, andFIG. 14is a plan view of a heat dissipation slug, illustrating various modification of the light emitting diode assembly ofFIGS. 12 and 13.

Referring toFIGS. 12 and 13, the light emitting diode assembly according to this embodiment includes a main body91, first internal leads92a,94a, first external leads92b,94b, second internal leads96a,98a, second external leads96b,98b, a first heat dissipation slug95, a second heat dissipation slug97, a short wavelength light emitting diode chip101, and a red light emitting diode chip103. Although not shown, the light emitting diode assembly may further include a molding portion and phosphors.

The main body91may be formed of plastics, for example, by insert-molding a lead frame and heat dissipation slugs95,97. The main body91may have a cavity through which the internal leads92a,94a,96a,98aand the heat dissipation slugs95,97are exposed.

The first heat dissipation slug95and the second heat dissipation slug97are placed on a bottom of the cavity of the main body91, and the first internal leads92a,94aand the second internal leads96a,98aare placed around the heat dissipation slugs95,97. The first internal leads92a,94aextend from the first external leads92b,94bto be exposed outside the main body91, respectively, and the second internal leads96a,98aextend from the second external leads96b,98bto be exposed outside the main body91, respectively. The first and second external leads92b,94b,96b,98bmay be bent outside the main body.

The second heat dissipation slug97has a larger volume than the first heat dissipation slug95. For example, the first heat dissipation slug95and the second heat dissipation slug97may be separated from each other and may have a divided cylindrical shape. As shown inFIG. 11andFIG. 12, an upper surface of the second heat dissipation slug97may have a larger area than an upper surface of the first heat dissipation slug95.

The short wavelength light emitting diode chip101is mounted on the first heat dissipation slug95ato be thermally coupled thereto, and the red light emitting diode chip103is mounted on the second heat dissipation slug97to be thermally coupled thereto. The short wavelength light emitting diode chip101and the red light emitting diode chip103may be connected to each other in series or in parallel via bonding wires (not shown). For example, when the short wavelength light emitting diode chip101and the red light emitting diode chip103have a lateral structure, a p-electrode pad and an n-electrode pad of the short wavelength light emitting diode chip101may be connected to the first and second internal leads92a,98a, respectively, and a p-electrode pad and an n-electrode pad of the red light emitting diode chip101may be connected to the first internal lead94aand the second internal lead96a, respectively. As a result, the short wavelength light emitting diode chip101and the red light emitting diode chip103may be connected to each other in parallel and may also be individually operated. In addition, the short wavelength light emitting diode chip101may be connected to the red light emitting diode chip103in series by a bonding wire. Various connections may be obtained according to the structures of the short wavelength light emitting diode chip101and the red light emitting diode chip103, and the structures of the internal and external leads.

According to the embodiment, the first heat dissipation slug95constitutes a first heat dissipator and the second heat dissipation slug97constitutes a second heat dissipator. Specifically, heat generated from the short wavelength light emitting diode chip101is mainly discharged through the first heat dissipation slug95, and heat generated from the red light emitting diode chip103is mainly discharged through the second heat dissipation slug97. Here, since the second heat dissipation slug97has a larger volume than the first heat dissipation slug95, the second heat dissipation slug can more efficiently discharge heat generated from the red light emitting diode chip103.

The molding portion (not shown) may cover the short wavelength light emitting diode chip101and the red light emitting diode chip103. In addition, the molding portion may contain the phosphors therein. The molding portion is the same as the molding portion35described with reference toFIG. 1, and thus a detailed description thereof will be omitted.

In this embodiment, the phosphors are included in the molding portion. Alternatively, the phosphors may be included in the molding portion44as shown inFIG. 2, or may be provided by the conformal coating layer54as shown inFIG. 3.

In addition, although the number of each of the first internal leads and second internal leads is two in this embodiment, it should be understood that the present invention is not limited thereto, and the number of first or second internal leads may be one or three or more.

Further, although the number of each of the first and second heat dissipation slugs95,97is one in this embodiment, the number of heat dissipation slugs may be changed depending on the number of light emitting diode chips used in the assembly. For example, when a single short wavelength light emitting diode chip101and two red light emitting diode chips103a,103bare used, the light emitting diode assembly may include a single first heat dissipation slug95and two second heat dissipation slugs97a,97b, as shown in (a) ofFIG. 14. In this case, each of the second heat dissipation slugs97a,97bmay have a larger volume than the first heat dissipation slug95. In addition, when one short wavelength light emitting diode chip101and three red light emitting diode chips103a,103b,103care used, the light emitting diode assembly may include a single first heat dissipation slug95and three second heat dissipation slugs97a,97b,97c, as shown in (b) ofFIG. 14. In this case, each of the second heat dissipation slugs97a,97b,97cmay have a larger volume than the first heat dissipation slug95.

Although the plural red light emitting diode chips are illustrated as being respectively placed on the second heat dissipation slugs separated from each other in this embodiment, the red light emitting diode chips may also be placed on a single second heat dissipation slug. In this case, the single second heat dissipation slug may have a larger size than the first heat dissipation slug by taking into account the number of red light emitting diode chips (n) mounted thereon and thermally coupled thereto. For example, in (a) ofFIG. 14, the second heat dissipation slugs97a,97bmay be provided as a monolithic second heat dissipation slug instead of being divided from each other.

FIG. 15is a schematic plan view of a light emitting diode assembly according to yet another embodiment of the present invention, andFIG. 16is a schematic sectional view taken along line A-A ofFIG. 15. Here, a chip-on-board (COB) type light emitting diode assembly is illustrated.

Referring toFIGS. 15 and 16, a light emitting diode assembly according to this embodiment includes a metal base substrate201, an insulation layer203, a first landing pad205, second landing pads207:207a,207b,207c,207d, a solder resist209, a dam portion211, short wavelength light emitting diode chips221:221a,221b,221c,221d, red light emitting diode chips223:223a,223b,223c,223d, and bonding pads213a,213b.

The metal base substrate201may be, for example, an aluminum substrate. The insulation layer203may be formed of, for example, a pre-preg, and insulates a metal layer204from the metal substrate201.

Each of the landing pads205,207may include the metal layer204and a reflective layer206. The metal layer204may include copper (Cu) and the reflective layer206may include silver (Ag). The landing pads205,207may be formed on the insulation layer by patterning the metal layer204or by patterning the metal layer204and the reflective layer206.

The solder resist209covers the metal layer204and the reflective layer206to prevent electrical disconnection due to soldering. The solder resist209exposes bonding pads213a,213bfor connecting sheathed electric wires, and landing pad areas for mounting the light emitting diode chips221,223thereon. In addition, the solder resist209may expose landing pad area215for connecting bonding wires.

The short wavelength light emitting diode chips221a,221b,221c,221dare disposed on the first landing pad205to be thermally coupled to the first landing pad205. Although a plurality of short wavelength light emitting diode chips221is illustrated as being mounted on a single first landing pad205in this embodiment, the first landing pad205may be divided into a plurality of areas such that the short wavelength light emitting diode chips can be mounted on the divided areas of the first landing pad205, respectively. For example, the short wavelength light emitting diode chips221a,221b,221c,221dmay be mounted on the divided areas of the first landing pad205, respectively.

The red light emitting diode chips223a,223b,223c,223dare mounted on the second landing pads207a,207b,207c,207dto be thermally coupled thereto, respectively. Each of the second landing pads207has a larger volume than the first landing pad205. For example, when four short wavelength light emitting diode chips221are mounted on the first landing pad205, each of the second landing pads207a,207b,207c,207dhas a larger volume than each quadrisectional area of first landing pad205. Further, the second landing pads207may be disposed around the first landing pad205. With this structure, it is possible to improve heat dissipation through the second landing pads as compared with the first landing pad205.

The short wavelength light emitting diode chip221may be an AlInGaN-based light emitting diode chip, for example, a blue or UV light emitting diode chip, and the red light emitting diode chip223may be an AlInGaP-based light emitting diode chip.

InFIG. 15, the short wavelength light emitting diode chips221and the red light emitting diode chips223are illustrated as being connected to each other in series through bonding wires (W). In this embodiment, all of these light emitting diode chips221,223have a lateral structure. However, it should be understood that the light emitting diode chips221,223according to the present invention are not limited to a particular structure. That is, according to the present invention, all of the light emitting diode chips may have a vertical structure, or the light emitting diode chips may be combination of a lateral structure and a vertical structure. In order to connect the light emitting diode chips having various structures to each other, an additional bonding pad (not shown) may be provided together with the landing pads205,207.

The dam portion211surrounds the light emitting diode chips221,223. The dam portion211is formed to define the molding portion217in a mounting area of the light emitting diode chips and may, for example, be formed in a circular ring shape using a silicone resin. A dam alignment mark (not shown) may be formed on the solder resist209in order to adjust a location of the dam portion211.

The molding portion217covers the light emitting diode chips221,223inside the dam portion211. The molding portion217may be formed of a silicone resin and may contain phosphors. White light can be obtained through combination of the light emitting diode chips221,223and the phosphors.

The phosphors may be placed only on the short wavelength light emitting diode chip221as shown inFIG. 2, or may be provided as a conformal coating layer as shown inFIG. 3.

FIG. 17is a schematic plan view of a light emitting diode assembly according to yet another embodiment of the present invention, andFIG. 18is a schematic plan view of a heat dissipation slug ofFIG. 17. In this embodiment, a bulb type light emitting diode assembly will be described.

Referring toFIGS. 17 and 18, the light emitting diode assembly includes a first heat dissipation slug305, a second heat dissipation slug307, a casing320, a socket base325, and a cap330. The casing320is an upper side open type casing, which is open at an upper side thereof, and the first and second heat dissipation slugs305,307may be received in the casing through the upper side open type casing.

The first heat dissipation slug305may have an elongated cylindrical shape, and a short wavelength light emitting diode chip311is disposed on the first heat dissipation slug305. The second heat dissipation slug307surrounds the first heat dissipation slug305and is provided with a through-hole, through which the first heat dissipation slug305can be inserted into the second heat dissipation slug307. Red light emitting diode chips313may be disposed on the second heat dissipation slug307. The red light emitting diode chips313may be arranged at constant intervals to surround the short wavelength light emitting diode chip311.

In addition, the short wavelength light emitting diode chip311and the red light emitting diode chips313may be mounted on a printed circuit board310to be disposed on the heat dissipation slugs305,307, or may be disposed in package form.

The first heat dissipation slug305mainly discharges heat generated from the short wavelength light emitting diode chip311, and the second heat dissipation slug307mainly discharge heat generated from the red light emitting diode chips313. The second heat dissipation slug307is configured to have higher dissipation capabilities than the first heat dissipation slug305. For example, an upper surface of the second heat dissipation slug307has a larger area than that of the first heat dissipation slug305, and a total surface area of the second heat dissipation slug307is also larger than that of the first heat dissipation slug305. For example, as shown inFIG. 18, when a single short wavelength light emitting diode chip311is placed on the first heat dissipation slug305and six red light emitting diode chips313are placed on the second heat dissipation slug307, the upper surface of the second heat dissipation slug307has an area six times larger than that of the first heat dissipation slug305. Further, the second heat dissipation slug307may have a pattern of protrusions and depressions324,326, which may be used as screws.

Although not shown, the molding portion may cover the light emitting diode chips311,313, and phosphors36may be contained in the molding portion. Alternatively, a conformal coating layer may be formed on the short wavelength light emitting diode chip311. Further, a phosphor coating layer may be formed on a surface of the cap330.

According to this embodiment, the second heat dissipation slug307has a larger size than the first heat dissipation slug305, whereby heat generated from the red light emitting diode chips313can be rapidly discharged through the second heat dissipation slug307. In addition, the second heat dissipation slug307surrounds the first heat dissipation slug305, thereby further improving heat dissipation through the second heat dissipation slug307.