The invention will become more fully understood from the detailed description given herein below illustration only, and thus is not limitative of the present invention, and wherein:
The present invention will be apparent from the following detailed description, which proceeds with reference to the accompanying drawings, wherein the same references relate to the same elements.
Referring to
The circuit board 40 is not particularly restricted and may be a printed circuit board (PCB) or a low-temperature co-fired ceramic (LTCC) circuit board, which is typically used. A plurality of contact pads 43 is exposed from a surface of the circuit board 40 and serves as connections between the light-emitting chip L and a circuit layout of the circuit board 40. The light-emitting chip L is a LED chip, such as a high power light-emitting diode (HP LED), a light-emitting diode array (LED Array), an organic light emitter diode (OLED) or an organic light emitter. diode array (OLED Array). The thermally conducting element 42 is preferably a heat pipe, such as a pulsating heat pipe or a loop heat pipe, having a thermal coefficient greater than about 6000 W/m·K. The light-emitting chip L may be disposed on the thermally conducting element 42 by soldering method, and connected to the contact pads 43 of the circuit board 40 by wire bonding method.
The heat pipe utilizes the cooling technology according to the property of absorbing or dissipating heat during the phase changing procedure. More particularly, the heat pipe is a vacuum body filled with a liquid that may easily evaporate (the evaporating temperature approaches the environment temperature), and is then encapsulated. One end of the heat pipe is an evaporating section, and the other end of the heat pipe is a condensing section. When one end of the heat pipe is heated, the liquid evaporates and vaporizes, and the vapor flows to the other end under the minor pressure difference and releases the heat to condense into the liquid. The liquid flows back to the evaporating section according to the capillary action. Thus, a circulating loop is formed so that the heat may be continuously dissipated. So, the heat pipe is suitable for the heat dissipation of the light-emitting chip L with any power, and is particularly suitable for the heat dissipation of the light-emitting chip with the high power.
In this embodiment, the recess 41 comprises a first recess 411 and a second recess 412 formed on the surface of the circuit board 40. The first recess 411 associates with the second recess 412, and the first recess 411 is deeper than the second recess 412. The first recess 411 is sized to just receive the thermally conducting element 42 and has a longitudinal structure in this embodiment. The thermally conducting element 42 is embedded in the first recess 411 by embedding, adhering or soldering method. The contact pads 43 of the circuit board 40 are formed on a bottom surface of the second recess 412, and the light-emitting chip L is formed with connecting wires S to be electrically connected to the contact pads 43 of the circuit board 40 by wire bonding method. According to the circuit layout in the circuit board 40, the light-emitting chips L may be connected in parallel, in series or in parallel and in series by any suitable method. Because the circuit layout can be easily implemented in the prior art and does not pertain to the most important feature of the invention, detailed descriptions thereof will be omitted.
In order to enhance the light reflecting effect, a reflective layer R may be formed on a sidewall of the second recess 412. Of course, the contact pads 43 electrically connected to the light-emitting chip L may also be formed on a top surface of the circuit board 40, as shown in
Referring again to
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The circuit board 51 has a slot 511 and one surface of the carrier 52 has at least one recess 521 and at least one thermally conducting element 53 disposed in the recess 521. In this embodiment, the carrier 52 has a recess 521 and a thermally conducting element 53. The circuit board 51 is disposed on the carrier 52, and the slot 511 is correspondingly disposed on the recess 521 so that the thermally conducting element 53 is also disposed in the slot 511, and the light-emitting chip L is disposed on the thermally conducting element 53 and packaged on the circuit board 51.
The structures, features and effects of the light-emitting chip L and the thermally conducting element 53 of this embodiment are the same as those of the light-emitting chip L and the thermally conducting element 42 of the above-mentioned embodiment (see
The circuit board 51 may be a printed circuit board or a low-temperature co-fired ceramic circuit board, which is typically used, and the circuit board 51 has a circuit layout (not shown). The circuit layout is not particularly restricted and may be connected in series or in parallel. The circuit board 51 has a plurality of contact pads 512 connected to the circuit layout. The light-emitting chips L are electrically connected to the contact pads 512 via the connecting wires S by way of wire bonding. Finally, the light-emitting chips L, the contact pads 512 and the connecting wires S are packaged by a filler 54 and are thus not exposed to the outside.
In addition, the material of the carrier 52 of this embodiment is not particularly restricted, and may be a heat conducting material, such as a metal material or a polymer. In this embodiment, the composition, feature and effect of the filler 54, the connecting wire S and the contact pad 512 are the same as those of the filler 45, the connecting wire S and the contact pad 43 of the above-mentioned embodiment (see
Because the thermally conducting element 53 is disposed in the recess 521 of the carrier 52 in the light-emitting heat-dissipating device 5, the heat produced by the light-emitting chip L after being used for a period of time is conducted to the carrier 52 by the thermally conducting element 53. Since the carrier 52 is disposed under the circuit board 51, the heat may be rapidly dissipated in a short period of time, and the temperatures of the light-emitting chip L and the circuit board 51 may be lowered so that the heat dissipating effect is enhanced.
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In summary, compared with the prior art, the light-emitting chip contacts the thermally conducting element in this invention. So, the heat produced by the light-emitting chip can be simultaneously, rapidly and uniformly transferred and dissipated in the same direction from the hot junction to the cold junction of the thermally conducting element through the thermally conducting element. This method can achieve the rapid heat dissipation in a short period of time, makes the overall circuit board have the uniform temperature distribution, and thus enhances the reliability and heat dissipating efficiency of the light-emitting heat-dissipating device. In addition, when the circuit board is disposed on the carrier, the thickness of the circuit board may further be reduced so that the manufacturing cost can be reduced.
Although, the invention has been described with reference to specific embodiments, this description is not meant to be construed in a limiting sense. Various modifications of the disclosed embodiments, as well as alternative embodiments, will be apparent to persons skilled in the art. It is, therefore, contemplated that the appended claims will cover all modifications that fall within the true scope of the invention.
Number | Date | Country | Kind |
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095127657 | Jul 2006 | TW | national |