Patent Application
20080093620
The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.
It is to be understood that other embodiments may be utilized and structural changes may be made without departing from the scope of the present invention. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless limited otherwise, the terms “connected,” and “coupled,” and variations thereof herein are used broadly and encompass direct and indirect connections, couplings, and mountings.
Reference will now be made in detail to the present preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts.
The carrier 210 includes a first lead 212, a second lead 214, a heat slug 216 and a housing 218, for example. The heat slug 216 is disposed between the first lead 212 and the second lead 214 and the first lead 212 is connected to the heat slug 216. The adhering layer 220 is disposed on the heat slug 216. The housing 218 fixes the first lead 212, the second lead 214 and the heat slug 216. The LED chip 230 is electrically connected to the first lead 212 through the adhering layer 220 and the heat slug 216 and is electrically connected to the second lead 214 through a bonding wire 240. In addition, the LED package 200 may further include a molding compound 250 that covers the LED chip 230. The molding compound 230 is fabricated from a transparent material such as epoxy or silicone. The molding compound 230 protects the LED chip 230 and functions as a lens. Furthermore, the lead-free tin-based eutectic alloy is tin-zinc alloy, tin-bismuth alloy, tin-silver alloy, tin-silver-copper alloy, tin-silver-copper-antimony alloy, tin-silver-copper-germanium alloy or tin-silver-copper-indium alloy, for example.
The LED chip 230 (for example: a blue or green LED chip) in
In the present embodiment, the lead-free tin-based eutectic alloy has a thermal conductivity higher than silver epoxy. A tin-silver-copper alloy is taken as an example; its thermal conductivity is as high as 58 W/mK. When the heat produced by the LED chip 230 is transferred through the adhering layer 220 to the heat slug 216, the thermal resistance resulting from the adhering layer 220 is lower. Therefore, the heat dissipation efficiency of the LED package 200 in the present embodiment is higher and then the light emitting efficiency of the LED chip 230 increases. In addition, the adhesive strength of the lead-free tin-based eutectic alloy is higher while the coefficient of thermal expansion is lower. A tin-silver-copper alloy is taken as an example; its coefficient of thermal expansion is smaller than 29 ppm/K so that it is resistant to a higher thermal stress and therefore prevents the lowering of the thermal strength of the adhering layer 220 or the destruction of the adhering layer 220. In addition, the lead-free tin-based eutectic alloy is easier to obtain and the material cost is lower. Thus, the production cost of the LED package 200 is reduced.
The material and function of the adhering layer 220 and the molding compound 250a in the foregoing LED package 200a are similar to that of the adhering layer 220 and the molding compound 250 in the LED package 200. The advantages of the LED packages 200 and 200a are also similar. Thus, a detailed description thereof will not be repeated.
In the following, the manufacturing method of the LED package in
It should be noted that the adhering body in the present embodiment could be a paste. Hence, a dotting or a printing process can be used to place the paste on the heat slug 216. The paste is tin-bismuth alloy, tin-zinc alloy, tin-silver alloy, tin-silver-copper alloy, tin-silver-copper-antimony alloy, tin-silver-copper-germanium alloy or tin-silver-copper-indium alloy, for example.
Next, as shown in
After the die attaching process is completed, the LED chip 230 is electrically connected to the carrier 210 as shown in
As shown in
It should be noted that the method of manufacturing the LED package 200a in
In summary, the LED package and manufacturing method of the present invention has at least the following advantages:
1. The material of the adhering layer comprises lead-free tin-based eutectic alloy, which is capable of lowering the heat resistance in the adhering layer during heat transfer and increasing heat dissipation efficiency.
2. Since the lead-free tin-based eutectic alloy has a higher adhesive strength and a lower coefficient of thermal expansion, it can tolerate a higher thermal stress and prevent the lowering of the strength of the adhering layer or the destruction of the adhering layer due to thermal stress.
3. The lead-free tin-based eutectic alloy is less expensive than the Au80Sn20 alloy. Furthermore, the cost of the polymer material is also lower than that of the special polymer material with high temperature resistant. Therefore, production cost can be effectively reduced.
4. There is no need to cure the adhering layer after the die attaching process. Thus, throughput is increased.
5. The surrounding temperature in the process is only between 220° C. and 260° C. and therefore damage to the LED chip is avoided and the throughput can be increased.
The foregoing description of the preferred embodiment of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form or to exemplary embodiments disclosed. Accordingly, the foregoing description should be regarded as illustrative rather than restrictive. Obviously, many modifications and variations will be apparent to practitioners skilled in this art. The embodiments are chosen and described in order to best explain the principles of the invention and its best mode practical application, thereby to enable persons skilled in the art to understand the invention for various embodiments and with various modifications as are suited to the particular use or implementation contemplated. It is intended that the scope of the invention be defined by the claims appended hereto and their equivalents in which all terms are meant in their broadest reasonable sense unless otherwise indicated. Therefore, the term “the invention”, “the present invention” or the like is not necessary limited the claim scope to a specific embodiment, and the reference to particularly preferred exemplary embodiments of the invention does not imply a limitation on the invention, and no such limitation is to be inferred. The invention is limited only by the spirit and scope of the appended claims. The abstract of the disclosure is provided to comply with the rules requiring an abstract, which will allow a searcher to quickly ascertain the subject matter of the technical disclosure of any patent issued from this disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. Any advantages and benefits described may not apply to all embodiments of the invention. It should be appreciated that variations may be made in the embodiments described by persons skilled in the art without departing from the scope of the present invention as defined by the following claims. Moreover, no element and component in the present disclosure is intended to be dedicated to the public regardless of whether the element or component is explicitly recited in the following claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 95138336 | Oct 2006 | TW | national |
