Description LIGHT EMITTING DEVICE, PACKAGE STRUCTURE
THEREOF AND MANUFACTURING METHOD THEREOF
Technical Field
[1] The present invention relates to a light emitting device, a package structure thereof and a method of manufacturing the same, and more particularly, to a light emitting device having a heat dissipating structure suitable for high power output, a package structure thereof and a method of manufacturing the same.
Background Art
[2] As light emitting diodes (LEDs) capable of emitting white light using phosphors have recently become known, applicability of the LEDs has been expended to the field of illuminating devices as being substitutes for traditional illuminators as well as s imply serving as light emitting displays. ContiniDUS research into high-output LEDs suitable for illuminating purposes is under way. Lifetime and performance characteristics of an LED as a semiconductor device deteriorate at a temperature higher than a rated operation temperature. Thus, in order to increase power output of the LED, it is necessary for the LED to have a dissipation structure capable of operating at as low a temperature as possible by effectively dissipating heat produced therefrom.
[3] In conventional LEDs, a plastic molding package is used to encapsulate a LED chip mounted on a lead frame. In such an LED, heat is generally dissipated through the lead frame, so that heat dissipating efficiency of the LED is too low to attain high power device. Further, in a case where an ultraviolet LED chip is used, plastic used as the molding package material easily degrades by an ultraviolet ray emitted from the ultraviolet LED chip, resulting in deterioration in durability of the LED. More recently, in order to increase light emitting efficiency and heat dissipating capability, flip type LED chips have been developed. Accordingly, there exists a need for LED structures compatible with flip type LED chips while having a large-area heat dissipating plate. Disclosure of Invention
Technical Problem
[4] To solve the above problems, it is an object of the present invention to provide a light emitting device suitable for high power output by increasing heat dissipating capability and light emitting efficiency, a package structure thereof and a method of manufacturing the same. It is another object of the present invention to provide a high- power light emitting device in which a flip type light emitting device chip is easily mounted while increasing heat dissipating capability, a package structure thereof and a method of manufacturing the same.
Technical Solution
[5] To accomplish the above object of the present invention, there is provided a light emitting device package structure comprising a main substrate for heat dissipation, including a reflecting mirror having an inner space whose an upper part is open and which is formed by a side wall protruding upward a predetermined height between an edge and a middle portion of the main substrate and is made of a metal material, the middle portion being where a light emitting device chip is to be mounted, an auxiliary circuit board which is interposed between the edge and the side wall of the main substrate, the auxiliary circuit board having a bottom surface partially being exposed to the main substrate, and which has at least one conductive pad formed on the exposed bottom surface and a chip bonding pad electrically connected to the conductive pad formed on a surface exposed upward, and a lead frame which is adhered to the conductive pad.
[6] Preferably, the auxiliary circuit board comprises a base layer which is formed on the main substrate and has a first insertion hole capable of being coupled to the outside of the side wall, and an upper layer which has a second insertion hole larger than the first insertion hole to expose a part of an upper surface of the base layer and is formed on the base layer, wherein the chip bonding pad is formed on the exposed upper surface of the base layer.
[7] In another aspect of the present invention, there is provided a light emitting device package structure comprising a main substrate for heat dissipation, which has a chip mounting part protruding a predetermined height upward in a middle portion thereof and is made of a metal material, an auxiliary circuit board which has an insertion hole capable of passing through the chip mounting part to be mounted around the chip mounting part of the main substrate, a bottom surface partially exposed to the main substrate, the exposed bottom surface having at least one conductive pad formed thereon, and a chip bonding pad electrically connected to the conductive pad formed on an upper surface thereof, a reflecting mirror which is formed on the auxiliary circuit board to focus a beam diffused from a light emitting device chip to be mounted on the chip mounting part to the periphery, and a lead frame which is adhered to the conductive pad.
[8] Preferably, the upper surface of the auxiliary circuit board is formed parallel with an upper surface of the chip mounting part in a horizontal direction. [9] In still another aspect of the present invention, there is provided a light emitting device comprising a main substrate for heat dissipation, including a reflecting mirror having an inner space whose an upper part is open and which is formed by a side wall protruding upward a predetermined height between an edge and a middle portion of the main substrate and is made of a metal material, at least one light emitting device chip which is mounted on the middle portion of the main substrate, an auxiliary circuit board which has an insertion hole capable of passing through the chip mounting part to be mounted around the chip mounting part of the main substrate, a bottom surface partially exposed to the main substrate, the exposed bottom surface having at least one conductive pad formed thereon, and a chip bonding pad electrically connected to the conductive pad formed on an upper surface thereof, a lead frame which is adhered to the conductive pad, and a lens which is adhered to the auxiliary circuit board.
[10] Here, three LED chips which emit red, green and blue emissions, respectively, are mounted in an inner space of the main substrate, and at least four chip bonding pads and at least four lead frames are formed for a common electrode and driving electrodes, respectively.
[11] Alternatively, the light emitting device chip may be an ultraviolet LED chip emitting ultraviolet ray, and the lens may have a non-reflecting coating layer formed on a surface thereof.
[12] In a further aspect of the present invention, there is provided a light emitting device comprising a main substrate for heat dissipation, including a chip mounting part protruding a predetermined height upward in a middle portion thereof and made of a metal material, at least one light emitting device chip which is mounted on the chip mounting part, an auxiliary circuit board which has an insertion hole capable of passing through the chip mounting part to be mounted around the chip mounting part of the main substrate, a bottom surface partially exposed to the main substrate, the exposed bottom surface having at least one conductive pad formed thereon, and a chip bonding pad electrically connected to the conductive pad formed on an upper surface thereof, a reflecting mirror which is formed on the auxiliary circuit board to focus a beam diffused from the light emitting device chip mounted on the chip mounting part to the periphery, a lead frame which is adhered to the conductive pad, and a cap which is coupled with the reflecting mirror to encapsulate an inner space between the reflecting mirror and the light emitting device chip.
[13] Preferably, the cap is a lens for focusing light emitted from the light emitting device chip. [14] Also, the light emitting device chip is a flip type light emitting device chip having an electrode formed on a bottom surface opposite to the light emitting surface, and the electrode of the flip type light emitting device chip is electrically connected to the chip bonding pad by soldering.
[15] In a still further aspect of the present invention, there is provided a method of manufacturing an LED package comprising (a) forming a main substrate for heat dissipation, including a reflecting mirror having an inner space whose an upper part is open and which is formed by a side wall protruding a predetermined height upward between an edge and a middle portion, in which a light emitting device chip is mounted, of the main substrate, (b) forming an auxiliary circuit board in which a part of a bottom surface thereof is exposed to the main substrate , at least one conductive pad is formed on the exposed bottom surface, and a chip bonding pad electrically connected to the conductive pad is formed on an upward exposed surface so that the auxiliary circuit board is mounted between the edge and the side wall of the main substrate, (c) adhering the auxiliary circuit board to the main substrate, (d) adhering a lead frame to the conductive pad formed on the bottom surface of the auxiliary circuit board, and (e) plating a region of an object to be plated of an assembly formed after adhering the lead frame.
[16] Preferably, step (e) comprises (e-1) plating the chip bonding pad and the lead frame and an exposed portion of the main substrate with N, (e-2) plating the chip bonding pad and the lead frame with Au, and (e-3) plating an inside of a reflecting mirror of the main substrate with at least one reflective material selected from the group consisting of Ag, Al and glossy N.
[17] In another aspect of the present invention, there is provided a method of manufacturing a light emitting device package comprising (1) forming a main substrate for heat dissipation, which has a chip mounting part protruding a predetermined height in a middle portion thereof so as to be higher than at an edge thereof and is made of a metal material, (2) forming an auxiliary circuit board which has an insertion hole capable of passing through the chip mounting part, a conductive pad which is formed to expose a part of a bottom surface of the auxiliary circuit board to the main substrate , and a chip bonding pad which is electrically connected to the conductive pad on an upper surface of the auxiliary circuit board, (3) adhering the auxiliary circuit board to the periphery of the chip mounting part of the main substrate through the insertion hole, (4) adhering a lead frame to the conductive pad formed on the bottom surface of the auxiliary circuit board, and (5) adhering a reflecting mirror, which is formed to focus a beam diffused from a light emitting device chip to be mounted on the chip mounting part to the periphery, on the auxiliary circuit board.
Description of Drawings [18] FIG. 1 is a perspective view showing an LED having a package structure according to a first embodiment of the present invention; [19] FIG. 2 is a cross-sectional view of FIG. 1;
[20] FIG. 3 shows light exit paths of the LED shown in FIG. 2;
[21] FIG. 4 is a partially extracted perspective view of some parts for explaining a process of manufacturing a package structure shown in FIG. 1; [22] FIG. 5 is a rear view of an auxiliary circuit board shown in FIG. 4;
[23] FIG. 6 is a cross-sectional view showing adherence between the auxiliary circuit board and a main substrate for heat dissipation, shown in FIG. 4; [24] FIG. 7 is a perspective view showing an LED having a package structure according to a second embodiment of the present invention; [25] FIG. 8 is a rear view of an auxiliary circuit board shown in FIG. 7;
[26] FIG. 9 is a rear view of the LED shown in FIG. 7;
[27] FIG. 10 is a cross-sectional view showing an LED having a package structure according to a third embodiment of the present invention; [28] FIG. 11 is a perspective view showing an LED having a package structure according to a fourth embodiment of the present invention; [29] FIG. 12 is a cross-sectional view shown in FIG. 11;
[30] FIG. 13 is a cross-sectional view showing a state in which a flip type LED chip is mounted to the package structure shown in FIG. 11 ; [31] FIG. 14 is a partially extracted perspective view of some parts for explaining a process of manufacturing a package structure shown in FIG. 11; [32] FIG. 15 is a rear view of an auxiliary circuit board shown in FIG. 14;
[33] FIG. 16 is a cross-sectional view explaining adherence between each of the auxiliary circuit board, a main substrate for heat dissipation and a reflecting mirror shown in FIG. 14; [34] FIG. 17 is a perspective view showing an LED having a package structure according to a fifth embodiment of the present invention; and [35] FIG. 18 is a cross-sectional view showing an LED having a package structure according to a sixth embodiment of the present invention
Best Mode [36] Preferred embodiments of the present invention will now be described in more detail with reference to the accompanying drawings.
[37] FIG. 1 is a perspective view showing an LED having a package structure according to a first embodiment of the present invention.
[38] Referring to FIG. 1, an LED 100 includes an LED chip 110, a lens 120 and a package structure 200. The package structure 200 includes a main substrate 210 for heat dissipation, an auxiliary circuit board 230 and a lead frame 250. As shown in FIG. 2, the main substrate 210 has a side wall 211 having a predetermined height concentrically formed between its edge and middle portion. Further, the inside of the side wall 211 tapers downward, that is, a radius of curvature of the inside of the side wall 211 is smaller at a lower part than at an upper part, producing a reflecting mirror structure capable of focusing light emitted from the LED chip 110.
[39] As shown in FIG. 4, the main substrate 210 is shaped crosswise so as to expose edge portions of the auxiliary circuit board 230 mounted thereon.
[40] The main substrate 210 is made of a metal material having good thermal conductivity.
[41] Examples of the material useful as the main substrate 210 include copper and a copper alloy exemplified by brass, W-Cu alloy and Mo-Cu alloy.
[42] Preferably, the main substrate 210 is formed by forming a metal plate having a structure shown in FIG. 4 using the above-described material, primarily plating nickel on the entire surface of the metal plate, and secondly plating a highly reflective material on a surface of an inner space 213 defined by the side wall 211.
[43] It is preferable that at least one reflective material selected from the group consisting of silver, aluminum and glossy nickel is used as a material plated on the surface of the inner space 213.
[44] Here, the glossy nickel is prepared by adding a glossy material to nickel. Examples of the glossy material include saccharin, formalin and materials prepared by adding nickel sulfate, nickel chloride and boron thereto.
[45] At least one LED chip 110 is mounted on a chip mounting part 214 which is flattened in the inner space 213 of the main substrate 210. Here, the LED chip 110 can be mounted on the chip mounting part 214 through a sub-mount (not shown), unlike in the illustrative example.
[46] The auxiliary circuit board 230 is coupled to an upper surface of the main substrate
210 between the side wall 211 and the edge of the main substrate 210. A mounting surface 234 is formed stepwise in the auxiliary circuit board 230 to have an L-shaped section so that a lens 120 can be fittingly coupled to the auxiliary circuit board 230. [47] The auxiliary circuit board 230 is formed to electrically connect the LED chip 110 with the lead frame 250 which is to be electrically connected to external circuitry.
[48] A chip bonding pad 238 is installed on the mounting surface 234 of the auxiliary circuit board 230. The chip bonding pad 238 is connected to the LED chip 110 via wires made of Au.
[49] The chip bonding pad 238 is electrically connected to a conductive pad which is exposed to a bottom surface of the auxiliary circuit board 230 to which the lead frame 250 is coupled, by a conductive pattern. Preferably, the auxiliary circuit board 230 is formed such that the chip bonding pad 238 is electrically connected to the conductive pad using at least one ceramic sheet containing A12O3 as a main constituent.
[50] A preferable embodiment of the auxiliary circuit board 230 is described in reference to FIGS. 4 to 6.
[51] The auxiliary circuit board 230 has a structure in which a first ceramic layer 231, a second ceramic layer 233 and a third ceramic layer 235 are laminated sequentially.
[52] A conductive pad 237 for coupling with the lead frame 250 is formed in an edge of a bottom surface of the first ceramic layer 231. It is preferable that the conductive pad 237 is formed by primarily forming W or Mo-Mn alloy on the bottom surface of the first ceramic layer 231, and secondly plating N on the resultant surface.
[53] The chip bonding pad 238 is formed on an upper surface of the second ceramic layer 233. It is preferable that the chip bonding pad 238 is formed by primarily plating W or Mo-Mn alloy on the upper surface of the second ceramic layer 233, secondly plating N thereon, and finally plating Au or Ag thereon
[54] A conductive pattern is formed to electrically connect the conductive pad 237 with the chip bonding pad 238 in the first ceramic layer 231 and the second ceramic layer 233. Here, the first ceramic layer 231 and the second ceramic layer 233 correspond to a base layer and the third ceramic layer 235 corresponds to an upper layer, respectively.
[55] The conductive pattern includes a first conductive pattern 241a, a second conductive pattern 241b and a third conductive pattern 241c. The first conductive pattern 241a passes through the second ceramic layer 233 at a position at which it is connected with the chip bonding pad 238. The second conductive pattern 241b is formed on an upper surface of the first ceramic layer 231 and connected with the first conductive pattern 241a. The third conductive pattern 241c passes through the first ceramic layer 231 to connect the second conductive pattern 241b with the conductive pad 237. [56] The first and third conductive patterns 241a and 241c are formed by forming holes on the second and first ceramic layers 233 and 231, respectively and then filling the holes with a conductive material.
[57] It is preferable that the conductive pattern 241a, 241b, 241c is formed of W or Mo-
Mn alloy.
[58] A second insertion hole 239a which is formed in the middle of the third ceramic layer 235 is larger than a first insertion holes 239b which are formed in the middle of the second ceramic layer 233 and the first ceramic layer 231. Thus, when the third ceramic layer 235 to the first ceramic layer 231 are adhered to each other, a region ranging from an edge of the second insertion hole 239a of the third ceramic layer 235 to an edge of the first insertion hole 239b of the second ceramic layer 233 becomes a mounting surface 234.
[59] A portion defined by reference numeral 244 among hatched portions in FIG. 5 showing the bottom surface of the first ceramic layer 231 corresponds to an adhering auxiliary pad which is spaced apart from the conductive pad 237 to be easily adhered to the main substrate 210.
[60] It is preferable that the auxiliary pad 244 is formed by primarily forming W or Mo-
Mn alloy and then secondly plating N thereon.
[61] According to another aspect of the present invention, it is a matter of course that the chip bonding pad 238 is electrically connected to the conductive pad 237 by extending the second conductive pattern 241b to an edge of a side surface of the first ceramic layer 231 and forming a lateral conductive pattern (not shown) in the edge of the side surface for connecting the second conductive pattern 241b to the conductive pad 237.
[62] Further, in a case where red, green and blue LED chips are mounted within the inner space 213 together, the four chip bonding pads are formed to be connected to independently the corresponding conductive pads for driving each of the red, green and blue LED chips, respectively.
[63] In a case where the plurality of auxiliary circuit boards 230 or the plurality of package structures 200 are arrayed and manufactured in a batch manner, edge portions 249 which are rounded to be inward recessed at the respective corners of the auxiliary circuit board 230 facilitate a cutting work of the auxiliary circuit boards 230 and can be used to form the lateral conductive pattern as described above.
[64] The lens 120 is constructed to be fittingly coupled between the mounting surface
234 and the upper surface of the auxiliary circuit board 230. A portion where the lens 120 is adhered to the auxiliary circuit board 230 is sealed by a sealing material for encapsulation of the inner space 130.
[65] In the LED 100 having the above-described structure, as shown in FIG. 3, light emitted from the LED chip 110 mounted on the main substrate 210 is focused on the side wall 211 and the lens 120 to then be emitted at a desirable divergent angle.
[66] The curvature and shape of the lens 120 can be appropriately designed according to a divergent angle of light to be employed, other than those shown above. Transparent synthetic resins or glass, and so on, can be used as a material of the lens 120.
[67] The inner space 130 formed between the lens 120 and the package structure 200 can be filled with a material having a refractive index similar to that of the lens 120 to be used. For example, the inner space 130 formed between the lens 120 and the package structure 200 can be filled with silicon. In this case, light emitted from the LED chip 110 is suppressed from being reflected at an inside surface of the lens 120, thereby increasing the utilization efficiency of light.
[68] The lead frame 250 is coupled to the conductive pad 237 of the auxiliary circuit boards 230.
[69] It is a matter of course that a surface mounted lead frame other than a pin type lead frame as shown can be applied to the lead frame 250.
[70] An LED having a package structure according to a second embodiment in which a surface mounted lead frame is used will now be described with reference to FIGS. 7 to 9, in which like reference numerals denote like functional elements as those shown above.
[71] Referring to FIGS. 7 to 9, an LED 300 includes a main substrate 310 for heat dissipation, and a lead frame 350. The main substrate 310 extends from both sides of an auxiliary circuit board 330 and coupled thereto.
[72] As shown in FIG. 8, a conductive pad 337 for mounting the surface mounted lead frame 350 is formed in an edge of a side of a lower surface of the auxiliary circuit board 330. An auxiliary pad 344 for adhering to the main substrate 310 is spaced apart from the conductive pad 337. The chip bonding pad 238 and the conductive pad 337 are connected by a conductive pattern which is formed according to a manner described above.
[73] The main substrate 310 has a width capable of exposing the conductive pad 337 of the auxiliary circuit board 330 according to a direction perpendicular to an extending direction of the lead frame 350 and is longer than the auxiliary circuit board 330 by a certain length. The length and width of the main substrate 310 are not limited to the shown structure and can be properly applied according to a required heat dissipating amount.
[74] A hole 311 formed around both edges of the main substrate 310 is formed for coupling a screw and it is a matter of course that the hole 311 may be omitted according to a coupling manner.
[75] FIG. 10 shows an LED 400 in which an ultraviolet LED chip 410 is used.
[76] In FIG. 10, like reference numerals denote like functional elements shown above.
Referring to FIG. 10, the LED 400 has a flat lens 320 adhered to the auxiliary circuit board 230.
[77] The flat lens 320 has a base plate 321 made of a transparent material and non- reflecting coating layers 322 and 323 formed on an upper and lower surfaces of the base plate 321. A method of forming and a material applied to the non-reflecting coating layers 322 and 323 are known variously. For example, it is disclosed in Korea Patent Published Application N>. 2001-0104377 (WO2000/65639) that the non- reflecting coating layer can be formed using SixOyNz which is an ultraviolet non- reflecting coating material.
[78] It is a matter of course that the non-reflecting coating layer can be applied to the surface of the curved lens 120 shown in FIG. 1.
[79] Hereinafter, a process of manufacturing the LED having the structure explained through FIGS. 1 to 10 is described.
[80] First, the auxiliary circuit boards 230 and 330, the main substrates 210 and 310 and the lead frames 250 and 350 are formed, respectively.
[81] The auxiliary circuit boards 230 and 330 are formed to have the structure described above. That is, the auxiliary circuit board 230 shown in FIG. 4 is explained as one example. First, the insertion holes 239a and 239b and conductive holes corresponding to the first and third conductive patterns are formed on ceramic sheets corresponding to each of the first ceramic layer 231, the second ceramic layer 233 and the third ceramic layer 235. Next, the conductive holes formed on the first ceramic layer 231 and the second ceramic layer 233 are filled with a metal paste so that the first and third conductive patterns 241a and 241c are formed. The second conductive patterns 241b, the chip bonding pad 238, the conductive pad 237 and the auxiliary pad 244 are printed using a metal paste made of the same material as the above metal paste. Here, W or Mo-Mn alloy can be used as the metal paste.
[82] Next, the first ceramic layer 231, the second ceramic layer 233 and the third ceramic layer 235 are sequentially laminated and then fired at a known firing temperature. It is preferable that the conductive pad 237 and the auxiliary pad 244 formed on the exposed surface of the auxiliary circuit board 230 are plated with nickel.
[83] Meanwhile, the main substrates 210 and 310 are manufactured into the above- described structure before molding or pressing a metal material to be used.
[84] Preferably, the main substrates 210 and 310 are formed by forming a metal plate made of copper having good thermal conductivity or a brass material into the shown structure and then plating nickel on the entire surface of the metal plate.
[85] As described above, lead frames of known various types such as a lead pin type and a surface mounted type according to a mounting manner can be applied to the lead frames 250 and 350. It is preferable that the lead frames 250 and 350 are plated with nickel.
[86] When the main substrates 210 and 310, the auxiliary circuit boards 230 and 330 and the lead frames 250 and 350 thus formed are prepared, they are adhered to each other by a soldering bonding agent.
[87] The main substrates 210 and 310, the auxiliary circuit boards 230 and 330 and the lead frames 250 and 350 may be adhered to each other simultaneously or in any arbitrary order.
[88] As one example, as shown in FIGS. 4 and 6, the main substrates 210 and 310, the auxiliary circuit boards 230 and 330 and the lead frames 250 and 350 are mutually assembled in a state in which brazing sheets 280 and 281 are inserted between the auxiliary circuit board 230 and the main substrate 210 and between the conductive pad 237 of the auxiliary circuit board 230 and the lead frames 250 and 350, respectively, and then fused at a temperature higher than a melting point of the brazing sheets 280 and 281 so that they are adhered to each other. Here, the brazing sheets 280 and 281 can be made of Ag-Cu alloy or Au-Sn alloy.
[89] Otherwise, they may be adhered by soldering using Ag-Cu alloy or Au-Sn alloy formed in a paste state.
[90] When such assembly is completed, the chip bonding pad 238 formed on the auxiliary circuit board 230, the lead frame 250 and the exposed portions of the main substrates 210 and 310 are plated with nickel.
[91] Next, the chip bonding pad 238 and the lead frames 250 and 350 are plated with
Au.
[92] Finally, the surfaces of the inner spaces 213 of the main substrates 210 and 310 are coated with at least one reflective material selected from the group consisting of Ag, Al and glossy N. [93] Otherwise, when the assembly is completed, after the above-described N plating, the chip bonding pad 238, the lead frames 250 and 350 and the surfaces of the inner spaces 213 of the main substrates 210 and 310 are plated with Ag.
[94] When the package structure is completed through the above-described processes, the LED chip 110 to be used is mounted on the chip mounting part 214 of the main substrates 210 and 310 directly or through the sub-mount (not shown). Then, the LED chip 110 and the corresponding chip bonding pad 238 are bonded via wires 140. Next, the lens 120 is fixed to the auxiliary circuit boards 230 and 330. When a coupling portion between the lens 120 and the auxiliary circuit board 230 is sealed with a sealing material, for example, epoxy, the manufacture of the LEDs 100, 300 and 400 is completed.
[95] In order to produce white light, three LED chips (not shown) emitting red, green and blue emissions can be mounted in the inner space 213.
[96] In a case where the plurality of LED chips emitting light of different colors are mounted together as described above, the LED has a chip bonding pad for a common electrode, chip bonding pads for driving electrodes of each of the LED chips and lead frames corresponding to the chip bonding pads. In this case, a first lead frame 250a among the four lead frames 250 is used for the common electrode and second to fourth lead frames 25Cb, 250c and 250d are used for the driving electrodes of the red, green and blue LED chips in reference to FIG. 4. Further, the four chip bonding pads 238 are formed, and the lead frames 250a to 250d are independently connected to the corresponding chip bonding pads, respectively. It is a matter of course that the number of the lead frame 250 and the number of the chip bonding pad 238 may be four or more.
[97] FIGS. 11 to 18 show an LED according to still another embodiment capable of mounting a flip type LED chip, in which like reference numerals denote like functional elements shown above.
[98] FIG. 11 is a perspective view showing an LED having a package structure according to a fourth embodiment of the present invention, in which like reference numerals refer to like functional elements shown above.
[99] Referring to FIG. 11, an LED 500 includes an LED chip 110, a lens 120 and a package structure 600.
[100] The package structure 600 includes a main substrate 610, an auxiliary circuit board
630, a lead frame 250 and a reflecting mirror 670.
[101] As shown in FIG. 12, the main substrate 610 has a chip mounting part 611 for mounting the LED chip which protrudes a predetermined height upward in a middle portion of a base 612.
[102] In the illustrative embodiment, the chip mounting part 611 is shaped of a rectangle.
[103] Of course, the chip mounting part 611 may take various forms, including a circle.
[104] It is preferable that the main substrate 610 is plated with nickel using a material having good thermal conductivity explained in FIG. 1.
[105] The auxiliary circuit board 630 is coupled to the exposed upper surface of the base
612 of the main substrate 610.
[106] A chip bonding pad 238 is formed on an upper surface of the auxiliary circuit board
630, and a conductive pad which is electrically connected to the chip bonding pad 238 by a conductive pattern is formed on a bottom surface of thereof.
[107] In a case where the LED chip 110 is a flip type LED chip, as shown in FIG. 13, the chip bonding pad 238 can be electrically coupled to an electrode of the flip type LED chip 111 by soldering. A reference numeral 115 denotes solder for coupling the flip type LED chip 111 to the main substrate 610.
[108] An insertion hole (639 shown in FIG. 14) which can pass through the chip mounting part 611 of the main substrate 610 is formed in the auxiliary circuit board 630.
[109] It is preferable that a thickness of the auxiliary circuit board 630 is determined to arrange the upper surface of the auxiliary circuit board 630 and an upper surface of the chip mounting part 611 in a row in a state in which the auxiliary circuit board 630 is adhered to the main substrate 610.
[110] In this case, not only the flip type LED chip 111 but also a top-emission type LED chip can be mounted.
[I l l] The auxiliary circuit board 630 is formed to internally and mutually connect the chip bonding pad 238 and the conductive pad to the known various circuit board, for example, a printed circuit board (PCB). Preferably, the auxiliary circuit board 630 is formed to internally and mutually connect the chip bonding pad 238 with the conductive pad using at least one ceramic sheet containing A12O3 as a principal component.
[112] As shown in FIGS. 14 to 16, such auxiliary circuit board 630 has a structure in which a first ceramic layer 631 and a second ceramic layer 633 are laminated sequentially.
[113] Preferably, an adhering auxiliary pad 245 which is spaced apart from the chip bonding pad 238 in an area corresponding to a potential adherence portion of the reflecting mirror 670 is formed on an upper surface of the second ceramic layer 633. [114] The reflecting mirror 670 is formed to focus light emitted from the LED chips 110 and 111.
[115] That is, a hole is formed in the middle of the reflecting mirror 670. The internal surface of the reflecting mirror 670 tapers downward such that an upper part thereof is smaller than a lower part thereof, thereby enabling light emitted from the LED chips 110 and 111 to be focused.
[116] At least inside surface of the reflecting mirror 670 is formed of a highly reflective material. For example, the inside surface of the reflecting mirror 670 is formed of at least one selected from the group consisting of Ag, N and Al.
[117] That is, the reflecting mirror 670 is formed of any one among Ag, N and Al.
Otherwise, the reflecting mirror 670 is formed by primarily molding synthetic resin or a metal and then coating at least inside surface thereof with a highly reflective material. Here, it is preferable that at least one reflective material selected from the group consisting of Ag, Al and glossy N is used as the coating highly reflective material.
[118] The lens 120 is used as one example of a cap for encapsulating and protecting the
LED chips 110 and 111 and adhered to the reflecting mirror 670. A portion where the lens 120 is adhered to the reflecting mirror 670 is sealed by a sealing material to encapsulate the inner space of the reflecting mirror 670.
[119] Otherwise, it is a matter of course that the inner space of the reflecting mirror 670 is molded with a transparent material such as silicon or epoxy instead of the lens 120 so that the cap can be formed.
[120] FIG. 17 shows an LED having a package structure according to a further embodiment in which a surface mounted lead frame is used.
[121] Referring to FIG. 17, an LED 700 includes a main substrate 710 which is extended from and coupled to both sides of an auxiliary circuit board 730 and a lead fram750. A chip mounting part 611 protrudes on a base 712 in the main substrate 710.
[122] As shown in FIG. 8, a conductive pad and an auxiliary pad are formed on a bottom surface of the auxiliary circuit board 730. A structure other than the conductive pad and the auxiliary pad is the same as that shown in FIG. 14.
[123] FIG. 18 shows an LED 800 having ultraviolet LED chips.
[124] Referring to FIG. 18, the LED 800 includes a flat lens 320 which is adhered to a reflecting mirror 670.
[125] It is preferable that the reflecting mirror 670 is formed of Al having high reflectivity in an ultraviolet area. [126] Hereinafter, a process of manufacturing the LED having the structure explained through FIGS. 11 to 18 is explained.
[127] First, the auxiliary circuit boards 630 and 730, the main substrates 610 and 710, the reflecting mirror 670 and the lead frames 250 and 350 are formed, respectively. The auxiliary circuit boards 630 and 730 are formed to have the structure described above.
[128] As described above, the reflecting mirror 670 is formed of a highly reflective material, for example, Al, or by forming a mold made of a metal other than Al or synthetic resin and then coating a surface thereof with a highly reflective material.
[129] In a case where the reflecting mirror 670 is formed by forming the mold made of a metal or synthetic resin and then coating the surface thereof with a highly reflective material, after plating N on the surface of the mold, an adhering process which will be described below is performed.
[130] When the main substrates 610 and 710, the auxiliary circuit boards 630 and 730, the lead frames 250 and 350 and the reflecting mirror 670 are prepared, they are adhered together.
[131] Here, the above-described adhering methods are optionally used. As one example, in a case where the reflecting mirror 670 is formed by sequentially plating N and Ag, they are adhered to each other using the brazing sheets 280, 281 and 283 as shown in FIGS. 14 and 16 or soldering paste.
[132] When the assembly is completed, all of the conductive elements, that is, the chip bonding pad 238 formed on the auxiliary circuit board 630, the lead frame 250, the main substrate 610 and the reflecting mirror 670 are again plated with N.
[133] Next, the chip bonding pad 238, the lead frame 250, the main substrate 210 and the reflecting mirror 670 are plated with Ag.
[134] Otherwise, it is a matter of course that the inside surface of the reflecting mirror
670 can be coated with at least one reflective material selected from the group consisting of Al and glossy N.
[135] Meanwhile, in a case where the reflecting mirror 670 is formed of Al, it is a matter of course that the main substrates 610 and 710, the auxiliary circuit boards 630 and 730 and the lead frames 250 and 350 are adhered to each other by a soldering bonding agent, the adhered assembly is sequentially plated with N and Ag, and the reflecting mirror 670 can be adhered to the auxiliary circuit board 630 using a coupling agent such as epoxy.
[136] When the package structure 600 is completed, the LED chip 110 to be used is mounted on the chip mounting part 611 directly or through the sub-mount (not shown). Then, the LED chip 110 is bonded to the corresponding chip bonding pad 238 by the wires 140.
[137] Otherwise, in a case where of the flip type LED chip 111, after thermal conductivity and fixing solder is deposited on the chip mounting part 611 and the electrically connecting solder is deposited on the chip bonding pad 238, the LED chip 111 is mounted.
[138] Next, the lens 120 is fixed to the reflecting mirror 670. When a coupling portion between the lens 120 and the reflecting mirror 670 is sealed with a sealing material, for example, epoxy, the manufacture of the LEDs 500, 700 and 800 is completed.
[139] As described above in conjunction with FIGS. 11 to 18, in order to produce white light, it is a matter of course that light emitting devices can also be configured to have a chip bonding pad for a common electrode so as to mount three LED chips (not shown) for red, green and blue emissions, respectively, chip bonding pads for independent driving electrodes for the respective LED chips, and lead frames corresponding thereto.
[140] Although the present invention has been described that the LED chip is used, it is a matter of course that known other various light emitting semiconductor chips, including laser diode chips, can be used.
Industrial Applicability
[141] As described above, in the LED, a package structure thereof and a method of manufacturing the same in accordance with the present invention, a LED chip is mounted on a large-sized, metallic main substrate and is capable of focusing light, thereby increasing the light emitting efficiency and heat dissipating capability.