Patent Application
20070081340
The present invention generally relates to a light emitting diode (LED) light source module, and more specifically to an efficient heat resistant lighting module, and its application lighting fixtures with high power and super bright LED light source with efficient heat dissipation.
The maturity of the light emitting diode (LED) technology has set fire on the global revolution of the lighting industries. Almost in all aspects of daily lives, such as traffic lights, large screen display, home/office lighting, automobile lighting, commercial art lighting, etc., it is an obvious trend that LEDs will replace all conventional lighting facilities. To efficiently use LEDs for general light source, however, there is one major technical barrier needs to be resolved. Brighter LEDs need higher power and also generate mass heat. Taking the LED arrays used for street lighting as an example, without an efficient heat dissipating facility, the resulting mass heat greatly shortens the life spend of the LED arrays and even affects the overall reliability of the whole lighting unit.
The present invention provides an LED light source module featured with high heat dissipation. The high efficient heat dissipation effect is accomplished as follows: one or a few punctured holes are made on the printed circuit board right underneath each emitter LED; the surface of the punctured holes is coated with material with high thermal conductivity; alternatively, the whole punctured holes are filled with materials with high thermal conductivity. This thus facilitates efficient heat dissipation into the surrounding atmosphere.
To achieve the efficient heat resistant effect, the present invention provides an LED light source module, which comprises a printed circuit board with LED array installed. Wherein, right underneath each emitter LED, there is at least one punctured hole, wherein the surface of the punctured holes is coated with a thermal conductive layer.
According to the present invention for an LED light source module, a lighting equipment can be designed as follows: one lighting fixture rack; one LED array installed on one side of a printed circuit board; one printed circuit board on which, right underneath each emitter LED, there is at least one punctured hole; the surface of said hole is coated with thermal conductive material; one light cover which tightly affixes to the lighting fixture rack; wherein the side of the printed circuit board without said LED array also affixes to the inner side of the lighting fixture rack.
The foregoing and other objects, features, aspects and advantages of the present invention will become better understood from a careful reading of a detailed description provided herein below with appropriate reference to the accompanying drawings.
Each said emitter LED 30 is a high efficiency, super bright LED, which is mounted on the printed circuit board 2 and connects to the electrical conductivity layer of the printed circuit board via a transmission line 31. According to the application diversity, the LED array layout pattern, number of LEDs for the array and the color of the LED light source, etc. can vary to achieve the desired need for color, brightness and chromaticity.
Referring to
On the printed circuit board 2, there are metal patches 5 for setting each emitter LED 30. The material of the metal patches 5 can be gold, copper, etc.; the metal patches also connect to the thermal conductive layer 22 on the surface of the punctured hole 21 right underneath each emitter LED 30. Wherein, each metal patch 5 is for heat dissipation, and is different from the electrical metal circuitry 24 on the printed circuit board, which are for the electrical transmission. Metal patches 5 and metal circuitry 24 on the printed circuit board 2 are not connected to each other and are insulated by a soldering layer 25 to prevent short circuitry. Moreover, on the back side of said printed circuit board 2 with no LED array, there is an auxiliary thermal conductive layer 6. The thermal conductive layer 6 can be made of gold, copper, silver, etc., and is connected to the thermal conductive layer 22 on the surface of the punctured hole 21, which is right underneath of each emitter LED. This said auxiliary thermal conductive layer 6 can be designed as a small area which only connects to the thermal conductive layer 22 of the local punctured hole 21; alternatively, the auxiliary thermal conductive layer 6 can also be designed as a global area thermal conducting layer, which connects to the thermal conductive layer 22 of all the punctured holes 21 on the printed circuit board 2. All the metal patches 5, thermal conductive layers 22 and the auxiliary thermal conductive layer 6 can be pre-laid and made available while the printed circuit board 2 is first fabricated. This facilitates the application manufactures with ease of assembly. With the multiple channels of heat dissipation enhancement facilities, the mass heat generated from each emitter LED 30 can be efficiently dissipated on to the printed circuit board 2 through the thermal conductive layer 4, and the metal patch 5. With the thermal conductive layer 22 and the auxiliary thermal conductive layer 6 according to the present invention, the heat from the LED arrays can be further dissipated to the back side of said printed circuit board 2. The overall heat dissipation effect of the whole unit can be further enhanced with complimentary thermal conductive parts on the back side of said printed circuit board 2. Examples are a thermal conducitive fixture or the lighting fixture rack which will be described in the later section.
The present invention can also be enhanced by changing the thickness of the printed circuit board. When the thickness of the printed circuit board is less than 400 μm, (or it is even better with the thickness less than 200 μm), the heat dissipation effect of the whole module can be further improved due to the much shorter and faster thermal transmission with the thin film structure. The thinner version of a printed circuit board also provides the advantage of bendable flexibility for non-planar geometric design for the LED lighting modules, and thus extends the application varieties.
According to the present invention, the punctured holes on the printed circuit board can be made by a standard drilling process. The excimers used for laser drillers can be a gas CO2 RF laser excimer, or an UV solid state Nd:YAG laser excimer. Using Plated-Through-Hole technology for process of de-smear, deformation, micro etching, pre-activating, activating, acceleration, electroless copper (or chemical copper), etc. to achieve a fine-grained thermal conductive metal layer on the surface of the punched holes on the non-conducting printed circuit board. Wherein, the electroless copper is a process to chemically deposit a copper layer on a surface with plating solution containing cupric salt and reducing agents without using electrodes. The plating solution used mainly contains cupric salt (for example cupric sulfate), reducing agents (for example aldehyde acid), chelating agents (for example ethylenediaminetetraacetic acid, EDTA), PH adjuster agent, stabilizing agent and surface-active agent, etc. Wherein, the reducing agent plays the most important role for the self activated reactions. The metal reducing agent is self oxidized to provide the electrodes to reduce the metallic ions in the solution back to metallic atoms and form the metal deposit on a prepared surface. For example, the cupric iron concentration of said deposition solution is 0.035M, the concentration of the reducing agent, aldehyde acid, is 0.06M, and the concentration of the chelating agent, EDTA, is 0.087M. Under the temperature of 60° Celsius, doing the electroless copper deposition with said deposition solution to form the copper layer on the prepared surface of the drilled holes. Then fill the copper coated holes with a thermal paste with high conductivity, such as 2×10−3cal/cm sec. ° C. One example of a thermal paste is made of silicone ketone paste with silver oxide particles. Other than copper, silver is also a good candidate for the thermal dissipation layer.
Although the present invention has been described with reference to the preferred embodiments, it will be understood that the invention is not limited to the details described thereof. Various substitutions and modifications have been suggested in the foregoing description, and others will occur to those of ordinary skill in the art. Therefore, all such substitutions and modifications are intended to be embraced within the scope of the invention as defined in the appended claims.
