KR20060033438A - High power light emitting diode device having improved thermal reliability - Google Patents

Abstract

A high power LED device having improved thermal reliability is disclosed. The high power LED device according to an embodiment of the present invention includes a package substrate, an LED chip, a support structure, and a light transmitting lens. The package substrate includes external connection terminals for electrical connection with the outside, and a die pad is formed at the center of the upper surface. The LED chip is attached on the die pad and electrically connected to an external connection terminal. And, the supporting structure is attached to the edge of the package substrate to surround the LED chip, it is higher than the LED chip. The light transmitting lens is attached to the support structure together with the package substrate and the support structure to form an air-cavity sealed on top of the LED chip. The lower surface of the light transmitting lens is formed on the top of the package substrate. It forms a plane parallel to the surface, and the upper surface of the light transmitting lens is recessed toward the lower surface to form a concave curved surface.

Description

High power light emitting diode device having improved thermal reliability

1 is a schematic cross-sectional view showing an example of a high power LED device according to the prior art.

2 is a cross-sectional view schematically showing an embodiment of a high power LED device according to the present invention.

3 is a cross-sectional view schematically showing another embodiment of a high power LED device according to the present invention.

4A to 4C are cross-sectional views illustrating a modified example of the light transmitting lens of the high power LED device according to the embodiment of the present invention.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emitting diode (LED) device, and more particularly to a high output LED device having improved thermal reliability.

The LED element basically comprises an LED chip, a substrate on which the LED chip is mounted, a lead and a wire electrically connecting the LED chip and the lead, and a molding body that encapsulates these components. . Among them, the molding body should not only have robust characteristics at least externally to maintain the structural robustness of the LED element, but also have flexible characteristics internally to not damage the LED chip or the bonding wire. In addition, the molding body preferably does not affect the characteristics of the light emitted from the LED chip, such as the brightness of the light or the light spectrum.

On the other hand, high-power LED device is a LED device with a rated current of several hundred mA to a maximum of 720mA, and consumes a lot of power compared to a typical LED device having a rated current of about 20mA. These high power LED devices are inevitably generating a lot of heat in comparison with general LED devices during light emission operation. In addition, as the application range of the LED device is expanded, on the other hand, since the LED chip is being enlarged, the amount of heat generation also increases in the case of a large, high output LED device. Therefore, in the case of such a high-power LED device, it is necessary to manufacture a material and / or a structure having excellent thermal properties in order to effectively discharge the heat generated to the outside, especially in the case of a molding body should be excellent in these thermal properties.

1 is a cross-sectional view showing an example of a high power LED device according to the prior art. The high power LED device shown in Fig. 1 is disclosed in Japanese Laid-Open Patent Publication No. 2003-318448, "Light Emitting Device and Its Forming Method". Referring to FIG. 1, the high power LED device 10 includes an LED chip 12, a metal substrate 16, a lead 15, and molding bodies 13 and 14. The molding bodies 13, 14 comprise a flexible member 13 and a rigid member 14, both of which are formed of a light transmissive material. The plastic package 11 may be further provided at the edge to maintain the shape of the flexible member 13. In addition, a wire 7 for electrically connecting the LED chip 12 and the lead 5 may be further provided, and a phosphor is further coated around the LED chip 12 to obtain light having a complex wavelength. Or phosphors may be further dispersed inside the molding bodies 13 and 14. In addition, one surface of the metal substrate 16 is exposed to the outside in order to effectively radiate heat generated from the LED chip 12, and a heat sink (not shown) is further attached to the exposed surface of the LED device 10. It may be.

In the high power LED device 10 according to the related art as described above, the flexible member 13 is filled as a molding body around the LED chip 12 and the wire 17. By the way, the flexible member 13 is excellent in thermal properties and formed of a flexible material to reduce the thermal and mechanical stress applied to the LED chip 12 or the wire 17, although the strength is small Even if the LED chip 12 or the wire 17 has a limit that can not be completely prevented from applying thermal and mechanical stress. Therefore, the LED device 10 is inferior in reliability when used for a long time, and there is a limit to continuously increasing the output of the LED device is limited in its application range.

In addition, although the high power LED device 10 according to the related art makes the flexible member 13 made of a material having good transparency, the light transmittance of the flexible member 13 may not be better than that of air or vacuum. Therefore, while the light emitted from the LED chip 12 passes through the flexible member 13, its brightness deteriorates inevitably.

In addition, the high power LED element 10 according to the prior art uses a convex lens structure protruding upward as the rigid member 14. Therefore, the thickness of the entire LED device 10 is increased, and there is a limit to miniaturization of the LED device 10, and the brightness is lowered in front of the LED device 10 because the emitted light is dispersed by the convex lens. There is this.

The technical problem to be achieved by the present invention is to completely prevent the thermal and mechanical stress applied to the LED chip and / or wire, to prevent the luminance of the emitted light deteriorated, and to provide a high-power LED device that is advantageous for miniaturization It is.

High power LED device according to an embodiment of the present invention for achieving the above technical problem includes a package substrate, an LED chip, a support structure and a light transmitting lens. The package substrate includes an external connection terminal for electrical connection with the outside, and a die pad is formed at the center of the upper surface. The LED chip is attached to the die pad and electrically connected to the external connection terminal. In addition, the support structure is attached to the edge of the package substrate to surround the LED chip, the height is higher than the LED chip. The light transmitting lens is attached to the support structure to form a sealed air-cavity on the LED chip together with the package substrate and the support structure, and a lower surface of the light transmitting lens is formed on the package substrate. A plane parallel to the upper surface of the upper surface of the translucent lens forms a concave curved surface.

According to one aspect of the above embodiment, the lower surface of the translucent lens may be jagged. In this case, the teeth may be shaped to form an angle of 30-45 ° with respect to an axis perpendicular to the plane of the lower surface of the light transmitting lens.

According to another aspect of the above embodiment, the phosphor may be evenly dispersed in the interior of the light-transmitting lens, or the phosphor layer may be coated on the surface of the light-transmitting lens. It may be coated on one side of the top surface or on both sides.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, embodiments of the invention may be modified in many different forms and should not be construed as limited to the embodiments set forth hereinbelow. Like reference numerals denote like elements throughout the specification.

2 is a schematic cross-sectional view showing a high power LED device according to a preferred embodiment of the present invention. Referring to FIG. 2, the high power LED device 100 is an air-cavity type device, which is a package substrate 110, an LED chip 120, a support structure 130, and a light transmitting lens 140. It includes.

The die pad 122 is attached or defined at the central portion of the upper surface of the package substrate 110. The high output LED chip 120 is attached to the die pad 122. As shown, the high power LED chip 120 may be attached so that the bonding pads (not shown) formed on the upper surface thereof face upward. Alternatively, the high power LED chip 120 may be attached in a flip-chip manner unlike that shown. However, the former case is more preferable when considering the heat dissipation characteristics. The package substrate 110 is provided with an external connection terminal 112 for electrical connection with the outside. There is no particular limitation on the position, shape and structure of the external connection terminal 112. For example, as illustrated, the external connection terminal 112 may be provided at the edge of the lower surface of the package substrate 110.

The package substrate 110 is preferably made of a material having excellent heat dissipation characteristics. This is because a large amount of heat is generated in the high output LED chip 120, so it is necessary to effectively discharge it to the outside. Therefore, the heat dissipation plate may be further attached to the lower surface of the package substrate 110 to improve heat dissipation characteristics.

The LED chip 120 is attached onto the die pad 114 of the package substrate 110 via the adhesive 122. The LED chip 120 is a high output LED chip 120 whose rated current is from about several hundred mA to about 720 mA. As described above, there is no particular limitation on how the LED chip 120 is mounted on the package substrate 110. As illustrated, when the LED chip 120 is mounted so that the bonding pad of the LED chip 120 faces upward, the LED chip 120 and the external connection terminal 112 are bonded wires formed of a material such as Au. 124 may be electrically connected to each other.

The supporting structure 130 is attached on the package substrate 110 to surround the LED chip 120. The support structure 130 should be at least higher than the upper surface of the LED chip 120 and / or the loop height of the bonding wire 124. This is to form the air-cavity 150 in the upper space of the LED chip 120 using the support structure 130. Therefore, the contact surface of the supporting structure 130 and the package substrate 110 should be sealed. When the above conditions are satisfied, the method of attaching the support structure 130 to the package substrate 110 is not particularly limited. For example, an adhesive (not shown) may be used or the contact surface of the support structure 130 and the package substrate 110 may form a suitable coupling structure of concave / convex structure.

The support structure 130 is attached on the edge of the package substrate 110. In the case of the package type in which the bonding wire 124 is present, the supporting structure 130 is preferably located outside the bonding wire 124. That is, the bonding wire 124 is also preferably present in the air-cavity 150 defined in the support structure 130.

The support structure 130 may be formed of a material such as a transparent material, for example, an epoxy mold compound, so that light emitted from the LED chip 120 may pass therethrough. In this case, the light emitted from the LED chip 120 is emitted not only in the upward direction but also in the lateral direction. In addition, depending on the use of the high-power LED device 100, the reflector is further attached to the inner wall of the support structure 130, or the reflector itself may support the structure so as to emit a lot of light only through the light transmitting lens 140. It can also be used as (130).

The transmissive lens 140 forms an air-cavity 150 on the LED chip 120 together with the package substrate 110 and the support structure 130. That is, the air-cavity 150 is a space sealed by the package substrate 110, the support structure 130, and the light transmitting lens 140. Accordingly, the translucent lens 140 and the supporting structure 130 are bonded using an adhesive or bonded to each other using another suitable structure so that the contact surface is completely sealed. In addition, at least the LED chip 120 is positioned in the air-cavity 150.

The light transmitting lens 140 may be formed of a material having good light transmittance, for example, glass or a plastic material having good light transmittance. And it is preferable that the translucent lens 140 also has a structure of a concave lens whose lower surface is straight but its upper surface is convex downward. That is, the lower surface of the translucent lens 140 as a whole has a structure that can form a plane parallel to the upper surface of the LED chip 120 more accurately than the upper surface of the package substrate 110, the translucent lens 140 It is preferable that the upper surface of the) has a convex structure toward the lower surface of the light transmitting lens 140, that is, downward. Since the emitted light can be converged using the shape of the transmissive lens 140, the luminance of the high power LED device 100 can be increased.

According to the exemplary embodiment of the present invention, the air-cavity 150 defined by the package substrate 110, the supporting structure 130, and the light transmitting lens 140 maintains a low pressure, that is, a vacuum state. If there is such a vacuum air-cavity 150, even if a large amount of heat generated in the LED chip 120 as in the prior art does not cause thermal expansion of the molding body thermal damage occurs in the high-power LED device It is also possible to prevent cracks in the molding body. In addition, since the luminance of the light emitted from the LED chip 120 passes through the air-cavity 150, almost no damage occurs and only the light-transmitting lens 140 having a relatively thin thickness passes through the present embodiment. It is possible to manufacture high power LED devices with improved intensity.

Although not shown, a hole penetrating the air-cavity 150 may be further formed at the support structure 130 itself or at an interface between the support structure 130 and the light transmitting lens 140. In addition, a sealing member such as a stopper may be inserted into the hole. These holes and sealing members are structures that can be added as needed in the manufacturing process to make the interior of the air-cavity as vacuum as possible.

4A to 4C, modifications of the light transmitting lens 140 of the high power LED device 100 according to the above-described embodiment are respectively shown. Here, the modification shown in Fig. 4A and the modification shown in Figs. 4B and 4C are not opposed to each other. That is, the technical idea of the modification shown in FIG. 4A can be applied to the modification of FIG. 4B or 4C at the same time.

Referring first to FIG. 4A, the translucent lens 140a has a structure in which its lower surface 144 is entirely parallel to the package substrate (not shown), and its upper surface 142 is convex downward. In FIG. 2, it is the same as the light transmitting lens 140 of FIG. 2. However, in more detail, the lower surface 144 of the light transmitting lens 140a has a sawtooth structure. Using the sawtooth lower surface 144 can converge and filter the light passing through the translucent lens 140a, thereby improving the brightness of the light by approximately 20-30%. Preferably, the lower surface 144 of the translucent lens 140a is perpendicular to the plane formed by the teeth of the lower surface 144 of the transmissive lens 140a so that the brightness of the light can be maximized by converging the light. The angle θ with one axis can be about 30-45 °.

4B, another modification of the light transmitting lens 140 of FIG. 2 is illustrated. Referring to FIG. 4B, the material and shape of the light transmitting lens 140b is the same as the light transmitting lens 140 shown in FIG. 2. However, in the present modified example, the phosphor 146 is evenly distributed inside the light transmitting lens 140b, but the type of the phosphor 146 is not particularly limited. The phosphor 146 is a material that absorbs light having a predetermined wavelength emitted from the LED chip 120 and changes the fluorescent light into light having a longer wavelength and emits the light. For example, the phosphor 146 may be a material that absorbs blue light and emits yellow light. By using such a light transmitting lens 140b, it is possible to manufacture a white LED element using, for example, a blue LED chip and having an air-cavity therein.

4C, another modification of the light transmitting lens 140 of FIG. 2 is illustrated. Referring to FIG. 4C, the material and the shape of the light transmitting lens 140c are the same as the light transmitting lens 140 shown in FIG. 2. However, in the present modified example, phosphor layers 148a and 148b are formed on the surface of the light transmitting lens 140b. Similarly to the modified example, the type of the phosphors 148a and 148b is not particularly limited.

According to the present modification, the phosphor layers 148a and 148b are formed on only one surface of the lower surface or the upper surface of the light transmitting lens 140, or the phosphor layers (both on both surfaces of the light transmitting lens 140). 148a and 148b may be formed. In the latter case, the kinds of phosphors forming the phosphor layers 148a and 148b may be the same, but they are not necessarily limited to this case.

As shown in FIGS. 4B and 4C, the transparent lens 140b having the phosphor 146 evenly dispersed therein is used, or the transparent lens having the phosphor layers 148a and 148b formed on the surface thereof. Using 140c), it is possible to manufacture high power LED devices that emit light of complex wavelengths. For example, the high power LED device may be a device emitting white light or a device emitting pastel color light of various colors.

3 is a schematic cross-sectional view showing a high power LED device according to a second preferred embodiment of the present invention. Referring to FIG. 3, the high power LED device 200 is an air-cavity type device, which is a package substrate 210, an LED chip 120, a support structure 130, and a light transmitting lens 140. It is the same as the high-power LED device 100 according to the first embodiment described above in that it includes. In order to avoid duplicate explanation, the present embodiment will be briefly described only for the differences from the above-described first embodiment.

The high power LED device 200 shown in FIG. 3 differs from the high power LED device 100 shown in FIG. 2 in that the LED chip 120 is attached on the lead frame 210 including the leads 212. Do. This embodiment differs from the above-described first embodiment in that the package substrate has a lead frame structure including external leads. That is, in the high power LED device 200 illustrated in FIG. 3, a lead 212 is formed on an upper surface of the lead frame 210, and one end of the lead 212 is a high power LED device for electrical connection with the outside. It is exposed to the outside of 200.

In addition, the present invention can be modified in various other ways. In other words, the present invention is limited to the air-cavity 150 sealed around the LED chip 120, and also has a high-power LED device (100, 200) having a transmissive lens 140 of the structure described above Regardless of the structure and material of the package substrate and the package type, the package can be applied.

In the high power LED device according to the present invention, a vacuum air-cavity is defined around the LED chip. Therefore, even if a large amount of heat is generated in the high power LED chip, it is possible to prevent the thermal stress and / or mechanical stress applied to the LED chip and / or wire.

In addition, according to the present invention, since the molding body is not formed around the LED chip, the luminance of emitted light can be prevented from deteriorating, and no problem such as cracking occurs in the molding body.

In addition, according to the present invention, since the structure of the high-power LED device is simple, there is an advantage in miniaturization.

Claims (4)

A package substrate including an external connection terminal for electrical connection with the outside, wherein a die pad is formed at a central portion of the upper surface; An LED chip attached to the die pad and electrically connected to the external connection terminal; A support structure attached to an edge of the package substrate to surround the LED chip and having a height higher than that of the LED chip; And A projection lens attached to the support structure to form a sealed air-cavity on top of the LED chip with the package substrate and the support structure, wherein the bottom surface of the light projection lens is an upper surface of the package substrate And a plane parallel to the upper surface of the light transmitting lens, the upper surface of which is recessed toward the lower surface to form a concave curved surface. The high output light emitting diode device of claim 1, wherein the lower surface of the light transmitting lens is serrated. 3. The high power light emitting diode device according to claim 2, wherein the teeth form an angle of 30 to 45 degrees with respect to an axis perpendicular to the plane of the lower surface of the light transmitting lens. The high power light emitting diode device according to claim 1, wherein a phosphor is evenly dispersed in the light transmitting lens or a phosphor layer is coated on a surface of the light transmitting lens.

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