Patent Publication Number: US-8981419-B2

Title: Led

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This patent application is a divisional application of patent application Ser. No. 13/330,688, filed on Dec. 20, 2011, entitled “LED AND METHOD FOR MANUFACTURING THE SAME,” which is assigned to the same assignee as the present application, and which is based on and claims priority from Chinese Patent Application No. 201110198444.7 filed in China on Jul. 15, 2011. The disclosures of patent application Ser. No. 13/330,688 and the Chinese Patent Application No. 201110198444.7 are incorporated herein by reference in their entirety. 
    
    
     BACKGROUND 
     1. Technical Field 
     The present disclosure relates to LEDs (light emitting diodes) and methods for manufacturing the LEDs, and more particularly, to an LED having a good waterproof capability and a method for manufacturing the LED. 
     2. Description of Related Art 
     As a new type of light source, LEDs are widely used in various applications. A typical LED includes a base, a pair of metal leads fixed on the base, a housing formed on the leads, a light emitting chip fixed in the housing and electrically connected to the leads via wires, and an encapsulant attached on the housing and sealing the light emitting chip. The housing is often formed by molding a material of PPA (polyphthalamide) on the two metal leads. However, the attachment between the housing and the leads is unreliable due to poor adherent capability of PPA to metal. Therefore, moisture of the outside environment may enter the LED through an interface between the leads and the housing, causing malfunction of the light emitting chip. 
     What is needed, therefore, is an LED and a method for manufacturing the LED which can overcome the limitations described above. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Many aspects of the present disclosure can be better understood with reference to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present disclosure. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views. 
         FIG. 1  shows an LED in accordance with a first embodiment of the present disclosure. 
         FIG. 2  is a top view of the LED of  FIG. 1 . 
         FIG. 3  is a block diagram showing manufacturing processes of the LED of  FIG. 1 . 
         FIG. 4  shows a first process of manufacturing the LED of  FIG. 1 . 
         FIG. 5  shows a second process of manufacturing the LED of  FIG. 1 . 
         FIG. 6  shows a third process of manufacturing the LED of  FIG. 1 . 
         FIG. 7  is a top view showing a semi-finished product in a third process of manufacturing an LED in accordance with a second embodiment of the present disclosure. 
         FIG. 8  shows a fourth process of manufacturing the LED of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Referring to  FIG. 1 , an LED (light emitting diode)  10  in accordance with a first embodiment of the present disclosure is shown. The LED  10  includes a base  11 , a pair of leads  12  fixed on the base  11 , a housing  15  secured on the leads  12 , a light emitting chip  13  received in the housing  15  and electrically connected to the pair of leads  12  and an encapsulant  16  sealing the chip  13 . 
     The base  11  may be made of plastic such as PPA (polyphthalamide). The base  11  may have a rectangular shape. The leads  12  are made of metal such as copper or aluminum. The two leads  12  are spaced from each other. Each of the leads  12  includes a pair of horizontal sections  120  and a vertical section  122  interconnecting the two horizontal sections  120 . 
     Also referring to FIGS.  2  and  5 - 6 , the housing  15  is formed on the leads  12  by injection-molding, transfer-molding or other suitable methods. The housing  15  may also be made of PPA. The housing  15  defines a cavity  150  extending from a bottom face  151  to a top face  152  thereof to expose top faces of the leads  12 . The housing  15  further defines a chamber  153  surrounding the cavity  150 . The chamber  153  is spaced from the cavity  150 . The chamber  153  includes an upper groove  156  and a lower groove  155  communicating with the upper groove  156 . The upper groove  156  has a width less than that of the lower groove  155 , and a height larger than that of the lower groove  155 . The lower groove  155  extends through the bottom face  151  of the housing  15 . The upper groove  156  is located beneath the top face  152  of the housing  15  and communicates with an outside of the LED  10  through two holes  158  (see  FIG. 2 ) extending through the top face  152  of the housing  15  into the upper groove  156 . A blocking wall  14  is formed by filling blocking material in the chamber  153  through the two holes  158 . The blocking wall  14  may be made of epoxy or silicon. The blocking wall  14  includes an upper portion  142  filled in the upper groove  156  and a lower portion  141  filled in the lower groove  155 . The lower portion  141  has a bottom face  143  (see  FIG. 6 ) joining the top faces  126  of the leads  12 , and a top face  144  of the upper portion  142  is flush with the top face  152  of the housing  15 . The blocking wall  14  surrounds the chip  14 . Furthermore, the blocking wall  14  extends over a width and a length of each of the leads  12 . Since the blocking wall  14  is made of epoxy or silicon and thus has a bonding force with the metal leads  12  which larger than that of the housing  15  made of PPA with the metal leads  12 , outside moisture entering the LED  10  through an interface between the bottom face  151  of housing  15  and the top faces  126  of the leads  12  would be effectively blocked by the blocking wall  14 . Thus, safety and performance of the chip  13  received in the cavity  150  are ensured. 
     The chip  13  is fixed on one of the two leads  12  by silver epoxy gluing, eutectic bonding or other methods. The chip  13  may be a GaN chip, an InGaN chip, an AlInGaN chip or other light emitting semiconductor chips. The chip  13  is electrically connected to the two leads  12  via wire bonding of two wires  131 . The encapsulant  16  is filled in the cavity  150  to seal the chip  13  and the wires  131 . The encapsulant  16  may be made of epoxy, silicon or other transparent materials. Fluorescent material such as YAG (yttrium aluminum garnet), TAB (terbium aluminum garnet), phosphide or sulfide can be uniformly distributed in the encapsulant  16  to covert the color of light from the chip  13  to a desired color. 
     A method for manufacturing the LED  10  is also disclosed. The method mainly includes multiple steps from S 01  to S 05  as follows. 
     First, as shown in  FIG. 4 , a base  11  having a pair of leads  12  fixed thereon is provided. The base  11  may be molded to the pair of leads  12  via injection-molding, transfer-molding or other suitable methods. 
     As shown in  FIG. 5 , a housing  15  is then molded on the pair of leads  12  by injection-molding, transfer-molding or other suitable methods. The housing  15  defines a cavity  150  in a central area thereof and a chamber  153  surrounding the cavity  150 . The cavity  150  may be formed during the molding of the housing  15  on the leads  12 . The chamber  153  may be formed by firstly forming a wall made of photoresist and having a shape the same as that of the chamber  153  prior to molding the housing  15  onto the leads  12 . After the molding of the housing  15  on the leads  12 , the wall made of photoresist is accommodated in the housing  15 . The wall is removed by dipping the housing  15  together with the leads  12  and the base  11  into a chemical solution, wherein the wall is dissolved to thereby form the chamber  153  in the housing  15 . That is to say, the chamber  153  is formed after the cavity  150  has been formed. 
     As shown in  FIG. 6 , a blocking wall  14  is further formed in the chamber  153  by injection-molding blocking material such as epoxy or silicon in the chamber  153  through the two holes  158 . The blocking wall  14  substantially fills the chamber  153  to connect the top faces  126  of the leads  12 . In this embodiment, the blocking wall  14  is annular and surrounds the cavity  150 . However, as shown in  FIG. 7 , the shape of the chamber  153  may vary to two separate parts so that the blocking wall  14  filling in the chamber  153  is also changed to two separate parts  149  respectively fixed to the two leads  12 . Each part  149  of the blocking wall  14  has a length larger than a width of a corresponding lead  12 , whereby the interfaces between the bottom face  151  of housing  15  and the top faces  126  of the leads  12 , are substantially blocked and sealed from the outside moisture. The two separate parts  149  of the blocking wall  14  are parallel to each other. 
     As shown in  FIG. 8 , a chip  13  is fixed on one of the leads  12  via silver epoxy gluing, eutectic bonding or other methods. Two wires  131  electrically connect the chip  13  to the top faces  126  of the leads  12 . 
     Finally, an encapsulant  16  is filled into the cavity  150  to seal the chip  13  in the cavity  150  as shown in  FIG. 1 . Therefore, the manufacture of the LED  10  is completed. 
     It is believed that the present disclosure and its advantages will be understood from the foregoing description, and it will be apparent that various changes may be made thereto without departing from the spirit and scope of the present disclosure or sacrificing all of its material advantages, the examples hereinbefore described merely being preferred or exemplary embodiments.