Patent Publication Number: US-2012043570-A1

Title: Semiconductor device and method of manufacturing the same

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2010-182228, filed on Aug. 17, 2010; the entire contents of which are incorporated herein by reference. 
     FIELD 
     Embodiments of the invention relate generally to a semiconductor device and method for manufacturing the same. 
     BACKGROUND 
     Semiconductor devices incorporating optical semiconductor elements, for example, semiconductor devices in which a high intensity Light Emitting Diode (LED) element is incorporated in a Surface Mount Device (SMD) package that is surface mountable on a printed circuit board, are used in various types of apparatuses. 
     Moreover, in order to effectively utilize the luminescent light of the LED, a lens is provided in a radiation direction of the light to improve directionality. For example, with an LED of an SMD-type, a molded lens using a transparent resin can be provided on a frame face that will become a reflection face of the luminescent light. 
     However, depending on conditions of the frame face, for example, depending on shape and unevenness, air may be trapped during molding, and air bubbles may be caught between the frame face and the lens. As a result, defects such as weakening of the bonding strength between the lens and the frame, and variations of the radiation pattern may occur. Therefore, semiconductor devices having a structure in which the generation of air bubbles between the frame face and the lens can be suppressed, and a method for manufacturing the same, are needed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view illustrating a cross-section of a semiconductor device according to a first embodiment; 
         FIG. 2A to 5  are cross-sectional views schematically illustrating manufacturing processes of the semiconductor device according to the first embodiment; 
         FIGS. 6A and 6B  are schematic views illustrating a semiconductor device according to a variation of the first embodiment. 
         FIG. 7A  is a schematic perspective view illustrating a semiconductor device, and  FIG. 7B  is a schematic cross-sectional view illustrating an internal structure of the semiconductor device according to a second embodiment; 
         FIGS. 8A and 8B  are schematic cross-sectional views illustrating a manufacturing process of the semiconductor device according to the second embodiment; 
         FIG. 9A  is a schematic view illustrating a partial cross-section of the semiconductor device according to the second embodiment, and  FIG. 9B  is a schematic view illustrating a partial cross-section of a semiconductor device  250  according to a comparative example; 
         FIGS. 10A and 10B  are schematic cross-sectional views illustrating a manufacturing process of the semiconductor device according to a variation of the second embodiment; 
         FIG. 11A  is a perspective view illustrating a semiconductor device, and  FIG. 11B  is a cross-sectional view illustrating an internal structure of the semiconductor device according to another variation of the second embodiment; and 
         FIG. 12A  is a perspective view of a lens according to a comparative example and  FIG. 12B  is a perspective view of a lens according to another variation of the second embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     In general, according to one embodiment, a semiconductor device includes a lead, a frame, an optical semiconductor element, a sealing resin and a lens. The frame includes a main body covering a portion of the lead and being provided with a recess, another portion of the lead being exposed in the recess, and a casing part provided along an opening edge of the recess, the casing part including a cutout portion. The optical semiconductor element is provided in the recess and is in electrical connection with the lead. The sealing resin fills the recess from a bottom to the casing part, thereby covering the optical semiconductor element. The lens is joined to the sealing resin. 
     Embodiments of the invention will now be described while referring to the drawings. Note that in the following embodiments, the same numerals are applied to constituents that have already appeared in the drawings and, and repetitious detailed descriptions of such constituents are appropriately omitted. 
     First Embodiment 
       FIG. 1  is a schematic view illustrating a cross-section of a semiconductor device  100  according to a first embodiment. 
     The semiconductor device  100  is, for example, an LED device using a lead having a resin molded cup, and includes a lead  2  and a frame  3  provided so as to cover a portion of the lead  2 . 
     The frame  3  has a main body  3   a  and a casing part  5 . A cup-like recess  3   b  is provided in the main body  3   a  and another portion  2   a  of the lead  2  is exposed at a bottom of the recess  3   b . The casing part  5  is provided on an opening end  3   c  of the recess  3   b  of the main body  3   a . A cutout portion  15  (see  FIG. 2A ) is provided in the casing part  5 . The casing part  5  is arranged as a wall-like body surrounding the recess  3   b . The cutout portion  15  is formed so as to cut into the casing part  5  from an edge of the casing part  5 , which is formed as a wall-like body, toward a direction of the recess  3   b . In other words, a height of the casing part  5  when viewed from the opening end  3   c  (in  FIG. 1 , the height in the vertical direction looking straight on) is lower in the cutout portion  15 . 
     An LED chip  7 , which is an optical semiconductor element in electrical connection with the lead  2 , is disposed in an interior of the recess  3   b.    
     For example, as illustrated in  FIG. 1 , the LED chip  7  is mounted on one of the two leads  2  exposed at the bottom of the recess  3   b , and another of the leads  2  and the LED chip  7  are connected using a metal wire  9 . 
     Then, from the bottom of the recess  3   b  to a height reaching the casing part  5  is filled with a sealing resin  12 , thereby covering the LED chip  7 . A surface  10  of the sealing resin  12  that the recess  3   b  is filled with is a frame face on which a lens will be provided. For example, a molded lens  13  is joined thereon. 
     A transparent resin that transmits luminescent light of the LED chip  7  is used, for example, for the sealing resin  12 . Furthermore, the lens  13  can also be molded using a transparent resin that transmits the luminescent light of the LED chip  7 . For example, a thermosetting epoxy resin, a silicone resin, or the like can be used. 
     On the other hand, the frame  3  can be formed by insert molding using a thermoplastic resin such as, for example, polyphthalamide (PPA) or the like. Furthermore, by mixing a powder such as potassium titanate or the like with the resin, the frame  3  can be formed so as to reflect the luminescent light of the LED chip  7 . 
     Hereinafter, a method for manufacturing the semiconductor device  100  will be described while referring to  FIGS. 2 to 5 . 
     The method for manufacturing the semiconductor device  100  according to this embodiment includes processes of: filling from the bottom of the recess  3   b  formed on the main body  3   a  of the frame  3  to a height reaching the casing part  5  with the sealing resin  12 , thereby covering the LED chip  7  that is an optical semiconductor element; and hardening the sealing resin  12 . While the hardening process, a portion of the sealing resin  12  flows out from the cutout portion  15 , thereby forming an indentation  12   a  on an inner side of the casing part  5  that corresponds with the cutout portion  15 . Furthermore, the method includes a process of molding the lens  13  on the sealing resin  12 . 
     As illustrated in  FIG. 2A , the frame  3  includes the casing part  5  of the wall-like body arranged on the opening end  3   c  (see FIG.  1 ) of the cup-like recess  3   b  so as to surround the recess  3   b . The cutout portion  15  is provided in the casing part  5  from the edge thereof in the direction of the recess  3   b.    
     First, the LED chip  7  is disposed at the bottom of the recess  3   b  (see  FIG. 1 ). Then, from the bottom of the recess  3   b  to a top of the casing part  5  is filled with the sealing resin  12 . Thereafter, heat treating is performed to harden the sealing resin  12 , thus sealing the LED chip  7 . 
       FIG. 2B  illustrates the frame after filling with the sealing resin  12 . Here, the sealing resin  12  is a liquid having viscosity, prior to hardening by being subjected to heat treating. 
     For example, when using a thermosetting epoxy resin for the sealing resin  12 , the epoxy resin will have adequate viscosity. Therefore, after filling, the epoxy resin will not spill out from the cutout portion  15 , that is lower than other portion of the casing part  5 , to an outside of the casing part  5 . 
     Next, after the heat treating and the hardening of the sealing resin  12 , the lens  13  is formed on the sealing resin  12 . At this time, it is preferable that a center P of the sealing resin  12  bulges, having a convex shape. If the center P of the sealing resin  12  has an indented concave shape after hardening, air will be trapped when forming the lens  13  and air bubbles will easily form between the sealing resin  12  and the lens  13 . 
     In other words, if a filling amount of the sealing resin  12  is insufficient, the resin surface will become concave shaped due to the contracting action while thermosetting. On the other hand, if the amount of the sealing resin  12  is increased, it is possible to fill to a state in which the center P of the sealing resin  12  bulges due to the viscosity of the resin. However, the resin will spill over to the outside of the casing part  5  due to a temporary decrease in viscosity in the thermosetting process. Therefore, the surface may not become convex shaped. The shape of the sealing resin  12  after hardening is dependent on the degree to which the recess  3   b  and the interior of the casing part  5  are filled. Therefore, the filling amount must be precisely controlled. This results in a challenging problem of forming the surface of the sealing resin  12  that fills the interior of the casing part  5  into a stable convex shape. 
     In the semiconductor device  100  according to this embodiment the cutout portion  15  is provided in the casing part  5 . Hereinafter, the function of the cutout portion  15  will be described. 
     As illustrated in  FIG. 2B , after filling the interior of the recess  3   b  with the sealing resin  12 , heat treatment is performed and the sealing resin  12  is hardened. 
     For example, when using a thermosetting resin, in this process, the viscosity of the sealing resin  12  temporarily decreases and, thereafter, the resin is hardened. At this time, a portion of the sealing resin  12  having decreased viscosity spills out from the cutout portion  15 , which is lower than the other portion of the casing part  5 , to the outside of the casing part  5 . As schematically illustrated in  FIG. 3A , the indentation  12   a  corresponding to the cutout portion  15  is formed in the surface of the sealing resin  12  hardened in the interior of the casing part  5 . 
     A shape and a depth of the indentation  12   a  formed in the surface of the sealing resin  12  is dependent on a shape and a size of the cutout portion  15  and, furthermore, on the properties of the sealing resin. For example, as illustrated in  FIG. 3B , the indentation  12   a  can be formed into a groove shape continuing from the interior of the casing part  5  to the cutout portion  15 . 
     For example, if a width (in a direction along an edge of the casing part  5 ) of the cutout portion  15  is increased, an area of the indentation  12   a  will increase. Alternatively, if the width of the cutout portion  15  is made relatively smaller and the cutout portion  15  is formed with an increased depth in the direction of the recess  3   b , then it will be possible to form the indentation  12   a  having a groove shape. 
     The cutout portion  15  illustrated in  FIGS. 2A and 2B  and  FIGS. 3A and 3B  is formed of a cup-like shape in the direction of the recess  3   b , but may also be formed of a rectangular shape. 
     Next, the lens  13  is formed on the sealing resin  12 . 
     For example, as illustrated in  FIG. 4 , the frame  3  filled with the sealing resin  12  is engaged with a mold  17  that is filled with a resin that will become the lens  13 . An interior of the mold  17  is processed into a shape of the lens  13 . 
     As illustrated in the same drawing, by engaging (or inserting) the casing part  5  with (or into) an opening  17   a  of the mold  17 , the surface of the sealing resin  12  and the resin that the interior of the mold  17  has been filled with can be joined. 
       FIG. 5  is a cross-sectional view schematically illustrating a state in which the casing part  5  of the frame  3  and the mold  17  are engaged. 
     As previously described, the indentation  12   a  is provided in the surface of the sealing resin  12  that the interior of the recess  3   b  is filled with. The indentation  12   a  is formed, for example, into a groove shape connected to the cutout portion  15 . Thus, when a resin  13   a  that the mold  17  is filled with is engaged with the surface of the sealing resin  12 , air remaining between the sealing resin  12  and the resin  13   a  can be released from the cutout portion  15  to the outside via the indentation  12   a.    
     Thereby, for example, even if the amount of the sealing resin  12  that the recess  3   b  is filled with is insufficient, air will not remain between the sealing resin  12  and the resin  13   a  that will become the lens  13 . Therefore, the generation of air bubbles between the lens  13  and the sealing resin  12  can be suppressed. 
     Furthermore, as illustrated in  FIGS. 6A and 6B , the number of the cutout portions  15  may be increased. 
       FIG. 6A  is a perspective view schematically illustrating a state in which the heat treatment has been performed and the sealing resin  12  has been hardened after filling from the bottom of the recess  3   b  to the top of the casing part  5  with the sealing resin  12 .  FIG. 6B  is a plan view thereof. 
     In an example illustrated in  FIGS. 6A and 6B , four of the cutout portions  15  are provided in the casing part  5 . The sealing resin  12  spills from each of the cutout portions  15  to the outside of the casing part  5  and four of the indentations  12   a  are formed. Thereby, air remaining between the sealing resin  12  and the resin  13   a  that will become the lens  13  can be assuredly released to the outside and the generation of air bubbles can be suppressed. 
     The number of the cutout portions  15  provided in the casing part  5  is not limited to two or four as described above in this embodiment. The number of the cutout portions  15  can be determined as desired based on the frame  3  and the size of the recess  3   b  and the casing part  5 . For example, one of the cutout portions  15  may be provided or the number of the cutout portions  15  may be increased to three to five or six. 
     Second Embodiment 
       FIGS. 7A and 7B  are schematic views illustrating a semiconductor device  200  according to a second embodiment.  FIG. 7A  is a perspective view illustrating a form of the semiconductor device  200 .  FIG. 7B  is a cross-sectional view illustrating an internal structure. 
     As with the semiconductor device  100  illustrated in  FIG. 1 , the semiconductor device  200  according to this embodiment also includes a lead  2  and a frame  3  provided so as to cover a portion of the lead  2 . As illustrated in  FIG. 7A , a lens  13  is provided on the frame  3 . A flange portion  14  is provided at a bottom of the lens  13  that is in contact with the frame  3 . 
     As illustrated in  FIG. 7B , the frame  3  includes a main body  3   a  and a casing part  25 . A recess  3   b  in which another portion  2   a  of the lead  2  is exposed is provided in the main body  3   a . The casing part  25  that is a wall-like body is arranged on an opening end  3   c  of the recess  3   b . In this embodiment, a point of difference with the semiconductor device  100  according to the first embodiment is that a cutout portion  15  is not formed in the casing part  25 . 
     An LED chip  7 , which is an optical semiconductor element in electrical connection with the lead  2 , is disposed in the recess  3   b . Then, from the bottom of the recess  3   b  to a height reaching a top of the casing part  25  is filled with a sealing resin  12 , thereby covering the LED chip  7 . 
     A lens  13  is provided on the sealing resin  12  that the recess  3   b  is filled with. The lens  13  includes the flange portion  14  formed along a periphery of the casing part  25 . 
     Next, a method for manufacturing the semiconductor device  200  will be described while referring to  FIGS. 8A and 8B .  FIG. 8A  is a schematic cross-sectional view illustrating a state prior to the frame  3  filled with the sealing resin  12  being engaged with a mold  18 .  FIG. 8B  is a schematic cross-sectional view illustrating a state in which the frame  3  is engaged with the mold  18 . 
     The method for manufacturing the semiconductor device  200  also includes a process of filling from the bottom of the recess  3   b  to a height reaching the casing part  25  with the sealing resin  12 , thereby covering the LED chip  7  that is an optical semiconductor element. 
     As illustrated in  FIG. 8A , when engaging the frame  3  and the mold  18 , the frame  3  side is filled with an excess of the sealing resin  12  to prevent air bubbles from being generated due to air becoming trapped between the resin  13   a  that will become the lens  13  and the sealing resin  12 . On the other hand, the mold  18  is also filled with an extra amount of the resin  13   a  so that air bubbles are not generated due to an insufficient amount of the resin  13   a.    
     Furthermore, in this embodiment, an inner surface of the mold  18  is processed into a shape of the lens  13 , and a flange portion  19 , which has an expanded inner diameter, is provided around an opening  18   a.    
     As illustrated in  FIG. 8B , when the frame  3  is engaged with the mold  18 , the casing part  25  of the frame  3  engages by being inserted into the inner side of the flange portion  19 . 
     The resin  13   a  that the interior of the mold  18  is filled with is joined with the surface of the sealing resin  12 , and the lens  13  is formed. Here, a liquid level of the resin  13   a  that the interior of the mold  18  is filled with is pushed up, and the resin  13   a  is hardened at a height reaching the flange portion  19 . The excess resin  13   a  fills in a gap between the flange portion  19  and the casing part  25 , and the flange portion  14  of the lens  13  is formed along the periphery so as to surround the casing part  25 . 
       FIGS. 9A and 9B  are schematic views illustrating partial cross-sections of the semiconductor device  200  and a semiconductor device  250  according to a comparative example, respectively. 
     As illustrated in  FIG. 9A , in the semiconductor device  200 , the excess resin  13   b  is contained in the gap between the flange portion  19  formed on the mold  18  and the casing part  25  of the frame  3 , and can be formed into the flange portion  14  of the lens  13 . 
     In contrast, in the semiconductor device  250  according to the comparative example illustrated in  FIG. 9B , the opening  17   a  of the mold  17  not provided with the flange portion  19  is engaged with the casing part  25 . In this case, because there is no space to contain the excess resin, the liquid level of the resin that the mold  17  is filled with rises, and the excess of the resin  13   b  spills out to the outside of the casing part  25 . Then, the resin  13   b  is hardened around the lens  13  which leads to burrs being formed, which is a factor contributing to the generation of visual appearance defects. 
     Therefore, with the method for manufacturing according to this embodiment, by using the mold  18  that has the flange portion  19 , the excess resin is formed into the flange portion  14  of the lens  13 , and the generation of burrs on the lens  13  can be suppressed. Thereby, visual appearance defects caused by variations in the filling amount of the sealing resin  12  and the filling amount of the resin  13   a  that will become the lens  13  can be prevented. 
     For example, even if the filling amounts of the sealing resin  12  and the resin  13   a  are increased so that air bubbles are not generated at an interface between the lens  13  and the sealing resin  12 , the excess resin  13   b  is formed into the flange portion  14  of the lens  13 . Therefore, the generation of burrs can be suppressed. 
       FIGS. 10A and 10B  are cross-sectional views schematically illustrating a manufacturing process for a semiconductor device  300  according to a variation of the second embodiment.  FIG. 10A  illustrates a state prior to the frame  3  filled with the sealing resin  12  being engaged with the mold  18 .  FIG. 10B  illustrates a state in which the frame  3  is engaged with the mold  18 . 
     As illustrated in  FIG. 10A , in the semiconductor device  300  according to this variation, just as with the semiconductor device  100 , a cutout portion  15  is provided in the casing part  5  that is provided on the opening end  3   c  of the recess  3   b  of the frame  3 . An indentation  12   a  is formed in a surface of the sealing resin  12  that the interior of the recess  3   b  is filled with. 
     As illustrated in  FIG. 10B , when engaging the frame  3  and the mold  18  and joining the sealing resin  12  and the resin  13   a  that will become the lens  13 , air can be released to the outside via the indentation  12   a  in the sealing resin  12 . Furthermore, due to the flange portion  19  provided on the mold  18 , spilling of the excess of the resin  13   a  to the outside can be suppressed. Thereby, the generation of air bubbles at the interface between the sealing resin  12  and the lens  13  can be suppressed, and the generation of burrs on the lens  13  can also be suppressed. 
     For example, compared to the semiconductor device  100  that does not have the flange portion  14 , the filling amount of the sealing resin  12  and the filling amount of the resin  13   a  that the mold  18  will be filled with can be increased. On the other hand, compared to the semiconductor device  200  that does not have the cutout portion  15 , even if the filling amounts of the sealing resin  12  and the resin  13   a  are small, the generation of air bubbles at the interface between the sealing resin  12  and the lens  13  can be suppressed. As a result, with the semiconductor device  300  according to this variation, the allowable range of the filling amounts of the sealing resin  12  and the resin  13   a  can be widened. 
       FIGS. 11A and 11B  are schematic views illustrating a semiconductor device  400  according to a variation of the second embodiment.  FIG. 11A  is a perspective view illustrating a form of the semiconductor device  400 .  FIG. 11B  is a cross-sectional view illustrating an internal structure of the semiconductor device  400 . 
     As illustrated in  FIG. 11A , the semiconductor device  400  includes a lead  2 , a frame  3  provided covering a portion of the lead  2 , and a lens  13  provided on the frame  3 . The lens  13  has a flange portion  14   b  on a bottom of a side contacting the frame  3 . 
     In the semiconductor device  400  according to this variation, it is different from the semiconductor device  200  illustrated in  FIG. 7A  in that the flange portion  14   b  is tapered so as to expand towards the frame  3 . 
     As illustrated in the cross-section of  FIG. 11B , the frame  3  and the internal structure thereof are the same as in the semiconductor device  200 . The only difference is the shape of the flange portion  14   b  provided on the lens  13 . Therefore, a shape of the flange portion  19  of the mold  18  that molds the lens  13  is different and has a shape that expands angularly in the direction of the opening  18   a  (see  FIGS. 8A and 8B ). 
       FIG. 12  A is a perspective view illustrating a shape of the lens  13  according to a comparative example and  FIG. 12B  is a perspective view illustrating a shape of the lens  13  according to the variation of the second embodiment. 
       FIG. 12A  illustrates an example of the lens  13  according to the semiconductor device  200 . In the example illustrated in the same drawing, the filling amount of the resin  13   a  that forms the lens  13  is small, and a formed flange portion  14   c  is thin. Thus, when the formed flange portion  14   c  is thin, there is a risk that the flange portion  14   c  may peel away from the lens  13 , which is a factor, as with burrs, that may contribute to the generation of visual appearance defects. 
       FIG. 12B  illustrates an example of the lens  13  according to the semiconductor device  400 . In this case, because a flange portion  14   d  is tapered, even if the filling amount of the resin  13   a  is insufficient, only a width of the flange portion  14   d  in a tapering direction will be formed with a reduced width. Therefore, burrs will not be formed as with the flange portion  14   c , and the insufficient filling amount will not contribute to the generation of visual appearance defects. As with the semiconductor device  400 , there are instances in which it is advantageous to form the flange portion  14   b  with a tapered shape. 
     While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel devices and methods described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the devices and methods described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the invention.