Patent Publication Number: US-2009236716-A1

Title: Rectifying diode package structure

Description:
FIELD OF THE INVENTION 
     The present invention relates to a rectifying diode and particularly to a rectifying diode package structure. 
     BACKGROUND OF THE INVENTION 
     Solid state diodes are widely used on a lot of electronic devices. Each solid state diode has a positive terminal and a negative terminal corresponding to each other. Voltage and current presented between them have non-linear characteristics. One type of diode has one way conductive characteristic, and can transform AC power to DC power to achieve rectification effect so that a power supply can output steady DC power. Such type of diode also is called rectifying diode or rectifier. It has been adopted in a wide variety of applications, such as information, communication, consumer electronic, aviation and space exploration, medical, motor vehicles, business equipment and the like. 
     The basic structure of the conventional rectifying diode, such as U.S. Pat. Nos. 5,005,069, 5,886,403 and 6,362,546, includes a base, a diode chip mounted onto the base, and an electrode connecting to another side of the diode chip. The diode chip and electrode are sealed through an insulating filling material to provide protection of the connection of the diode chip and electrode. Although the diode chip gets some protection from the encased filling material, during installation of the rectifying diode on a rectification board, it still could receive pressure from the rectification board and result in deformation or fracture. In order to enhance protection of the sealed chip, many improved techniques have been proposed. References can be found in U.S. Pat. Nos. 6,060,776, 6,667,545, 6,958,530, 7,009,223 and 2007105454. They mostly have a base surrounded by an integrated protective wall or sleeve to resist external pressure so that the filling material does not directly receive pressure from the rectification board. But they still cannot fully eliminate the external pressure from transmitting to the diode chip caused by press-fit relationship. And deformation or damage of the diode chip could still occur. China patent application No. CN1879212A discloses a technique of encasing the diode chip with resin and surrounding the resin with a protective sleeve. The perimeter of the protective sleeve perimeter and the base are spaced by a gap. However, the gap creates a height limitation on the edge structure when the protective sleeve is installed by press-fit. This results in an undesirable anchoring of the protective sleeve. Hence there are still rooms for improvement, especially on providing a desired package environment for the diode chip and increasing the life span thereof. 
     SUMMARY OF THE INVENTION 
     The primary object of the present invention is to effectively release the external pressure of a rectifier chip and prevent deformation or damage of the chip. To achieve the foregoing object, the present invention provides a rectifying diode package structure which has a base including a holding deck to hold a diode chip and a protective portion formed on the perimeter of the base. The protective portion has a sealing space filled by a filling material to seal the diode chip in an integrated manner. The diode chip has a conductive element extended outside the sealing space. The holding deck and the protective portion are interposed by a buffer ring embedded in the filling material. The buffer ring has at least one retaining ridge formed with at least a first end and a second end of different cross sections in an upright manner so that a retaining relationship is formed between the buffer ring and the filling material. 
     In one embodiment, a first pressure-release trench is formed between the holding deck and the protective portion to prevent moisture from seeping into the sealing space through a gap formed between the protective portion and the filling material. A second pressure-release trench can also be formed at the bottom of the base opposite to the first pressure-release trench. 
     In another embodiment, the holding deck has a protrusive ring formed on the perimeter in a diagonal manner to wedge in the filling material to prevent the filling material from breaking away from the sealing space when subject to drawing or squeezing of the external force. 
     By providing the buffer ring between the holding deck and the protective portion, when the rectifying diode package structure of the invention is compressed by the external force, the buffer ring can release a great amount of pressure to protect the diode chip on the base without deforming or damaging. In addition, the stress-release trench formed between the holding deck and the protective portion can incorporate with the buffer ring to release the external pressure force. Such a structure also can prevent moisture from seeping through the gap formed between the protective portion and the filling material to contact the diode chip. Thus the diode chip can function normally as desired. The protrusive ring can wedge in the filling material to make the entire rectifying diode package structure firmer. 
     The foregoing, as well as additional objects, features and advantages of the invention will be more readily apparent from the following detailed description, which proceeds with reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a first embodiment of the invention. 
         FIG. 2  is an exploded view of the first embodiment of the invention. 
         FIG. 3A  is a sectional view of the first embodiment of the invention. 
         FIG. 3B  is a fragmentary enlarged view of the first embodiment of the invention. 
         FIG. 4A  is a sectional view of a second embodiment of the invention. 
         FIG. 4B  is a fragmentary enlarged view of the second embodiment of the invention. 
         FIG. 5  is a fragmentary enlarged view of a third embodiment of a buffer ring of the invention. 
         FIG. 6  is a fragmentary enlarged view of a fourth embodiment of a buffer ring of the invention. 
         FIG. 7  is a schematic cross section of an embodiment of a first end of the retaining ridge of the buffer ring. 
         FIG. 8  is a schematic cross section of another embodiment of a first end of the retaining ridge of the buffer ring. 
         FIG. 9  is an exploded view of yet another embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Please refer to  FIGS. 1 through 3B  for a first embodiment of the invention. The present invention provides a rectifying diode package structure which has a base  10 . The base  10  has a holding deck  11  to hold a diode chip  20  and a protective portion  12  formed on the perimeter of the base  10 . The protective portion  12  has a plurality of jutting ridges  121  formed on an outer surface and a sealing space  13  inside filled by a filling material  30  (such as epoxy resin or silicone gel and the like) to seal the diode chip  20  in an integrated manner. As the base  10  and the filling material  30  are made from different materials, during packaging process, the filling material  30  and the base  10  have different degrees of expansion or retraction, and a gap or infirm fitting could form between them. In this embodiment, a protrusive ring  111  is formed on the perimeter of the holding deck  11  in a diagonal manner to wedge in the filling material  30 . Hence it is to prevent the filling material  30  from breaking away the sealing space  13  when subject to external squeezing or drawing. And the diode chip  20  on the holding deck  11  can be maintained and sealed in the filling material  30 . The diode chip  20  has a conductive element  40  extended outside the sealing space  13  to form electric connection with an electronic device. The conductive element  40  has a conductive root  41  connecting to the diode chip  20 , and an elongate stem connecting to the electronic device that might be deformed or broken due to excessive drawing or twisting caused by external force. To remedy this problem, the conductive element  40  has an elastic section  42  to absorb the external force from different directions. The elastic section  42  may be formed in a helical or bend-neck fashion. 
     When the protective portion  12  receives the external force, the external force could be transmitted through the filling material  30  to the diode chip  20 . A first pressure-release trench  14  located between the holding deck  11  and the protective portion  12 , and even a second pressure-release trench  15  located at the bottom of the base  10  opposite to the first pressure-release trench  14 , provides a shock-absorbing effect for the diode chip  20 . 
     In addition, there is a buffer ring  16  interposed between the holding deck  11  and the protective portion  12  and embedded in the filling material  30  to isolate the external force from directly transmitting from the protective portion  12  through the filling material  30  to the diode chip  20 . By incorporating the buffer ring  16  with the protective portion  12  and the first and second pressure-release trenches  14  and  15 , the diode chip  20  can get sufficient protection. To prevent the buffer ring  16  from separating from the filling material  30  by shaking or drawing, referring to  FIG. 3B , the buffer ring  16  further has at least one retaining ridge  161  which has at least one first end  162  and one second end  163  formed in an upright manner with different cross sections. The retaining ridge  161  is wedged in the filling material  30  with the first and second ends  162  and  163  form a cubical hindrance so that the buffer ring  16  can be securely retained in the filling material  30 . 
     In this embodiment, the cross section of the first end  162  is larger than the second end  163 . The first end  162  is located in the center of the retaining ridge  161 , while the second end  163  is located respectively at two sides of the retaining ridge  161 , thus substantially form a shuttle shape. When the buffer ring  16  sealed in the filling material  30  and the retaining ridge  161  wedged in the filling material  30 , the buffer ring  16  can be securely held in the filling material  30  without turning or moving. Moreover, with the first end  162  of the retaining ridge  161  formed a cross section larger than the second end  163  and embedded in the filling material  30 , vertical movement of the buffer ring  16  relative to the filling material  30  can be prevented. Thus the buffer ring  16  retained in the filling material  30  not only can prevent relative movement between them, also can prevent separation thereof. 
     Refer to  FIGS. 4A and 4B  for a second embodiment of the invention. It differs from the first embodiment previously discussed by having a horizontal protrusive ring  111  formed on the perimeter of the holding deck  11  to wedge in the filling material  30 . The base  10  has a second pressure-release trench  15  at the bottom extended outwards from the center. It also has the retaining ridge  161  the same as the first embodiment, but may be at the different length (referring to  FIG. 4B ). The protrusive ring  111 , second pressure-release trench  15  and retaining ridge  161  provide functions the same as the first embodiment. 
     The buffer ring  16  may be formed in varying embodiments.  FIG. 5  illustrates another one in which the first end  162  is respectively located at two sides of the retaining ridge  161 , while the second end  163  is located in the center of the retaining ridge  161 . As shown in  FIG. 6 , the first end  162  and second end  163  are respectively located at two sides of the retaining ridge  161  and form a conical fashion. In addition, the first end  162  may also be formed in various profiles. As shown in  FIG. 7 , the first end  162  has a jutting cross section in a symmetrical manner. As shown in  FIG. 8 , the first end  162  jutting to form an asymmetrical cross section. With the buffer ring  16  formed in a desired profile as previously discussed, it can be firmly wedged in the filling material  30  to prevent movement or separation from the filling material  30 . 
     Refer to  FIG. 9 . It has a plurality of arched flanges  112  formed on the perimeter of the holding deck  11  and spaced from each other in a diagonal or horizontal manner. The arched flanges  112  equally located on the perimeter of the holding deck  11  to serve the function of the protrusive ring  111  to form a secured bonding with the filling material  30  without separating when subject to squeezing or drawing of the external force. Therefore, the diode chip  20  mounted onto the holding deck  11  can be securely sealed in the filling material  30 . 
     As a conclusion, the rectifying diode package structure of the invention provides a buffer ring  16  between the protective portion  12  and holding deck  11  and sealed in the filling material  30  in an integrated manner, thus can effectively resist the pressure transmitted to the filling material  30  from the protective portion  12 , and provide improved protection for the diode chip  2 . The invention further provides at least one retaining ridge  161  wedged in the filling material  30  to form retaining of the buffer ring  16  in the filling material  30  so that the buffer ring  16  can be firmly held in the filling material  30  without moving or separating when subject to the external force or twisting. The whole structure can be maintained intact. It provides a significant improvement over the conventional techniques. 
     While the preferred embodiments of the invention have been set forth for the purpose of disclosure, modifications of the disclosed embodiments of the invention as well as other embodiments thereof may occur to those skilled in the art. Accordingly, the appended claims are intended to cover all embodiments which do not depart from the spirit and scope of the invention.