Abstract:
An LED package structure comprises an LED chip and a fuse electrically connected to the LED chip in series. The fuse has a low melting point such that the fuse melts under a high current to form an open circuit to prevent the high current from flowing through the LED chip.

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS 
     This application claims priority to U.S. patent application Ser. No. 12/540,380, filed on Aug. 13, 2009, which claims priority to Taiwan Patent Application Number 098117650, filed on May 27, 2009. These patent applications are herein incorporated in their entirety by reference. 
     BACKGROUND 
     1. Technical Field 
     The present disclosure relates to a light emitting diode (LED) package structure, and more particularly, to an LED package structure with a fuse. 
     2. Description of Related Art 
     Since an LED possesses advantages of long lifetime, small size, shock-proof property, low heat emission and low electric power consumption, LEDs have been widely used as indicative lamps or light sources for various household appliances and instruments. LEDs are even used in various types of mobile electronic products or large-sized array-type LED products such as car electronic products, wireless communication products, traffic signal system and outdoor bulletin boards. 
     LED chips are typically current-driven, and thus a stable current flow should be supplied to the LED chips as a power source, such that the LED chips can emit stable illumination lights. In the past, most of the LED chips are low power LED chips, which require low driving current to provide light. Nevertheless, the high illumination and high power applications of LED have gradually become trendy. In addition, most circuit systems now require and drive a plurality of LED chips electrically connected in series or in parallel, instead of a single LED chip. In view of the above, a circuit system has to supply higher current to drive the LED chips than before. It should be noted that when the driving current increases, the probability of short circuit increases as well. Particularly, as the power source is normally a voltage source and as the impedance of each of the LEDs may be substantially different, the current may become unstable. For this reason, when the current inside the circuit system becomes extremely high, the LED chips may be damaged or burned down. Therefore, prevention of damage to LED chips due to increase of input current and increasing the circuit protection of LED package structure are critical issues. 
     SUMMARY 
     One objective of the present disclosure is to provide an LED package structure to protect the LED chip and the circuit system electrically connected to the LED chip from damage. 
     In one aspect, an LED package structure may comprise an LED chip and a fuse electrically connected to the LED chip in series. The fuse may have a low melting point such that the fuse melts under a high current to form an open circuit to prevent the high current from flowing through the LED chip. 
     In one embodiment, the fuse may comprise a chip fuse. The chip fuse may comprise a substrate, a first electrode, a second electrode, and a metal conductive pad, the metal conductive pad melting under the high current to prevent the high current from flowing through the LED chip. 
     The LED package structure may further comprise a lead frame having a first lead pin, a second lead pin, and a loading part connected to the first lead pin. 
     In one embodiment, the LED chip may be disposed on the loading part of the lead frame, and the fuse may be disposed on the first lead pin of the lead frame. 
     In another embodiment, the LED chip may be disposed on the loading part of the lead frame, and the fuse may be disposed on the second lead pin of the lead frame. 
     In still another embodiment, the LED chip may be disposed on the loading part of the lead frame, and the fuse may be disposed on the loading part of the lead frame. 
     The LED package structure may further comprise a plurality of metal conductive wires that electrically connect the LED chip and the fuse in series between the first lead pin and the second lead pin of the lead frame. The metal conductive wires may comprise metal conductive wires made of gold. 
     Alternatively or additionally, the LED package structure may further comprise an encapsulation surrounding the LED chip and the fuse, and covering a part but not all of the lead frame. 
     In another aspect, an LED package structure may comprise a lead frame having a first lead pin, a second lead pin, and a loading part connected to the first lead pin. The LED package structure may also comprise an LED chip disposed on the lead frame, and a fuse disposed on the lead frame. The fuse may be electrically connected to the LED chip in series between the first lead pin and the second lead pin of the lead frame. 
     In one embodiment, the LED chip may be disposed on the loading part of the lead frame, and the fuse may be disposed on the first lead pin of the lead frame. 
     In another embodiment, the LED chip may be disposed on the loading part of the lead frame, and the fuse may be disposed on the second lead pin of the lead frame. 
     In yet another embodiment, the LED chip may be disposed on the loading part of the lead frame, and the fuse may be disposed on the loading part of the lead frame. 
     In one embodiment, the fuse may comprise a chip fuse. The chip fuse may comprise a substrate, a first electrode, a second electrode, and a metal conductive pad with a low melting point. The metal conductive pad may melt under a high current to form an open circuit to prevent the high current from flowing through the LED chip. 
     The LED package structure may further comprise a plurality of metal conductive wires that electrically connect the LED chip and the fuse in series between the first lead pin and the second lead pin of the lead frame. 
     Alternatively or additionally, the LED package structure may further comprise an encapsulation covering the LED chip, the fuse, and at least a part of the lead frame. The encapsulation may comprise epoxy, silicone, polyamide, or any combination thereof. 
     These and other objectives of the present disclosure will become apparent to those of ordinary skill in the art after reading the following detailed description of the preferred embodiments that are illustrated in the various figures and drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-sectional schematic diagram illustrating an LED package structure of a first embodiment of the present disclosure. 
         FIG. 2  is a top view schematic diagram illustrating an LED package structure of a first embodiment of the present disclosure. 
         FIG. 3  is a top view schematic diagram illustrating the chip fuse. 
         FIG. 4  is a cross-sectional schematic diagram illustrating a resettable fuse. 
         FIG. 5  is a top view schematic diagram illustrating an LED package structure of a second embodiment of the present disclosure. 
         FIG. 6  is a top view schematic diagram illustrating an LED package structure of a third embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     With reference to  FIG. 1  and  FIG. 2 ,  FIG. 1  is a cross-sectional schematic diagram illustrating an LED package structure of a first embodiment of the present disclosure, and  FIG. 2  is a top-view schematic diagram illustrating an LED package structure of the first embodiment of the present disclosure. As illustrated in  FIG. 1  and  FIG. 2 , the LED package structure  50  includes a lead frame  52 , an LED chip  54  and a fuse  56 . The lead frame  52  includes a first lead pin  58 , a second lead pin  60  and a loading part  62  connected to the first lead pin  58 . The LED chip  54  includes a positive electrode  54 A and a negative electrode  54 B disposed on the loading part  62  of the lead frame  52 . In addition, in this embodiment, the fuse  56  is disposed on the second lead pin  60  of the lead frame  52 , a first electrode  56 A of the fuse  56  is electrically connected to the positive electrode  54 A of the LED chip  54 , and a second electrode  56 B of the fuse  56  is electrically connected to the second lead pin  60  of the lead frame  52 . 
     In addition, as illustrated in  FIG. 2 , the LED package structure  50  further includes a plurality of metal conductive wires  64  configured to electrically connect the fuse  56 , the LED chip  54  and the lead frame  52 . The metal conductive wires  64  may be made of gold, but not limited to gold. In this embodiment, by virtue of wire bonding process, the metal conductive wires  64  are configured to electrically connect the positive electrode  54 A of the LED chip  54  and the first electrode  56 A of the fuse  56 , to electrically connect the second electrode  56 B of the fuse  56  and the second lead pin  60  of the lead frame  52 , and to electrically connect the negative electrode  54 B of the LED chip  54  and the first lead pin  58  of the lead frame  52 , such that the LED chip  54  and the fuse  56  are electrically connected in series between the first lead pin  58  of the lead frame  52  and the second lead pin  60  of the lead frame  52 . However, the circuit connection of the present disclosure is not limited to the aforementioned connection. For instance, the locations of the positive electrode  54 A and the negative electrode  54 B of the LED chip  54  illustrated in  FIG. 2  may be exchanged. That is, in the present disclosure, the metal conductive wires  64  may be used to electrically connect the negative electrode  54 B of the LED chip  54  and the first electrode of the fuse  56 , to electrically connect the second electrode of the fuse  56  and the first lead pin  58  of the lead frame  52 , and to electrically connect the positive electrode  54 A of the LED chip  54  and the second lead pin  60  of the lead frame  52 . 
     As illustrated in  FIG. 1 , the LED package structure  50  further includes an encapsulation  66 . The encapsulation  66  covers parts of the first lead pin  58  and the second lead pin  60  of the lead frame  52 , the loading part  62  of the lead frame  52 , the LED chip  54 , the fuse  56  and the metal conductive wires  64  so as to efficiently protect the LED chip  54  and the fuse  56 . With the encapsulation  66 , the stable electrical connections between the metal conductive wires  64 , the LED chip  54 , the fuse  56  and the lead frame  52  are enhanced. Accordingly, the malfunction in the LED package structure  50  obviated. The present disclosure is not limited to the aforementioned package structure. For example, the encapsulation  66  may cover only parts of the lead frame  52  and surround the LED chip  54 , the fuse  56  and the metal conductive wires  64 . In such a case, the components surrounded by the encapsulation  66  are protected from damages due to external force. The material of the encapsulation  66  can be epoxy, silicone and, polyamide, etc. 
     It should be noted that the fuse  56  is electrically connected to the LED chip  54  in series. Therefore, when a higher current in excess of the current limit threshold is supplied to the circuit system, the internal circuit of the fuse  56  will be melted so as to protect the LED chip  54 . In such a connection, damages or burning of the LED chip  54  due to high current may be prevented. In this embodiment, the fuse  56  is preferably, but not limited to, a chip fuse. With reference to  FIG. 3 ,  FIG. 3  is a top view schematic diagram illustrating a chip fuse. As illustrated in  FIG. 3 , the chip fuse  70  includes a substrate  72 , a first electrode  74 A, a second electrode  74 B and a low melting point metal conductive pad  76  disposed on the substrate  72 . The first electrode  74 A and the second electrode  74 B are disposed on the substrate  72 , and electrically connected together through the low melting point metal conductive pad  76 . The preferred material of the substrate  72  is, but not limited to, silicon. Also, the melting point of the metal conductive pad  76  is substantially low. Thus, when the current provided by the circuit system passes through the metal conductive pad  76 , the temperature of the low melting point metal conductive pad  76  will increase. After that, the low melting point metal conductive pad  76  will be melted to form an open circuit. Furthermore, the width of the low melting point metal conductive pad  76  may be adjusted according to required current load. The fuse of the present disclosure is not limited to a chip fuse, and may be a resettable fuse. With reference to  FIG. 4 ,  FIG. 4  is a schematic diagram illustrating a cross-sectional structure of the resettable fuse. As illustrated in  FIG. 4 , the resettable fuse  80  includes a conductive polymer layer  82  and two electrodes  84  disposed on the two sides of the conductive polymer layer  82 . When the current exceeds the current load limit of the resettable fuse  80 , the temperature of the resettable fuse  80  will increase so as to form polymer chain scission inside the conductive polymer layer  82 , such that the conductive polymer layer  82  will transfer from a conductor to a non-conductor. When the temperature falls down, the conductive polymer layer  82  will turn to a conductor again. Consequently, the occurrence of higher current passing through the LED chip  54  can be avoided. 
     The location of the fuse of the present disclosure is not limited to the aforementioned embodiment.  FIG. 5  is a top view schematic diagram illustrating an LED package structure  100  of a second embodiment of the present disclosure, and  FIG. 6  is a top view schematic diagram illustrating an LED package structure  150  of a third embodiment of the present disclosure. Moreover, in order to simplify the description, identical elements denoted by the same numerals indicate the same devices, and redundant description of the structure identical to the first embodiment is no longer detailed. As illustrated in  FIG. 5 , as compared with the first embodiment, the fuse  56  of the LED chip package structure  100  of the second embodiment is disposed on the loading part  62  of the lead frame  52 , the fuse  56  is disposed on one side of the LED chip  54  and is not in contact with the LED chip  54 . In addition, as illustrated in  FIG. 6 , as compared with the first embodiment, the fuse  56  of the LED package structure  150  of the third embodiment is disposed on the first lead pin  58  of the lead frame  52 . The first electrode  56 A of the fuse  56  is electrically connected to the first pin  58 , and the second electrode  56 B of the fuse  56  is electrically connected to the positive electrode  54 A of the LED chip  54 . The negative electrode  54 B of the LED chip  54  is electrically connected to the second lead pin  60 . The location of the positive electrode  54 A and the negative electrode  58 B is not limited, and can be exchanged. 
     In summary, the present disclosure provides an LED package structure with a fuse, wherein the fuse is electrically connected to the LED chip in series. In such a connection, the LED chip and the circuit system electrically connected to the LED chip are free from high current. 
     Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the present disclosure.