Patent Publication Number: US-2010112734-A1

Title: Apparatus and method for manufacturing led device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2008-284681, filed on Nov. 5, 2008 and the prior Japanese Patent Application No. 2009-246184, filed on Oct. 27, 2009; the entire contents of which are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to an apparatus and a method for manufacturing an LED device. 
     2. Background Art 
     An LED device emitting white light typically includes an LED (light-emitting diode) chip emitting blue light and a phosphor absorbing blue light and emitting light of yellow color, which is complementary to blue. Thus, the blue light emitted from the LED chip and the yellow light emitted from the phosphor are emitted outside the LED device and mixed into white light (see, e.g., International Publication WO 2002/059982 (FIG. 1)). 
     One method for manufacturing such an LED device is as follows. A package with a recess formed in the upper surface is fabricated, and an LED chip is mounted on the bottom surface of the recess. Next, a resin liquid with phosphor particles dispersed in a transparent resin is poured into the recess. Subsequently, it is left standing for a certain period of time to spontaneously precipitate the phosphor particles in the resin liquid and deposit the phosphor particles in a layer so as to cover the bottom surface of the recess and the LED chip. Subsequently, by heating treatment, the resin liquid is heat-cured to form a resin member. Thus, the aforementioned LED device is manufactured. 
     However, in this conventional method for manufacturing an LED device, it takes a long period of time, such as approximately 10 hours, to spontaneously precipitate the phosphor particles, which decreases the productivity of the LED device. Furthermore, the resin liquid absorbs water and expands during the spontaneous precipitation. Then, during heat curing, the absorbed water is separated out at the interface with the package, and the resin liquid shrinks. Consequently, the resin member is delaminated from the package, which causes the problem of degradation in the quality of the LED device. 
     SUMMARY OF THE INVENTION 
     According to an aspect of the invention, there is provided an apparatus for manufacturing an LED device, the LED device having a package with a recess formed in its upper surface, an LED chip mounted in the recess, a resin member filled in the recess, and phosphor particles precipitated in a lower portion of the resin member, the apparatus including: a base; a rotary member rotatably attached to the base and having a rotation axis extending vertically; and a holder coupled to the rotary member and supporting the package, an upper surface of the package being flexible to turn to the direction opposite to the resultant of gravity and the centrifugal force applying to the package. 
     According to another aspect of the invention, there is provided a method for manufacturing an LED device, including: mounting an LED chip on a bottom surface of a recess formed in an upper surface of a package, the LED chip emitting light of a first wavelength; pouring a resin liquid containing phosphor particles into the recess, the phosphor particle emitting light of a second wavelength longer than the first wavelength upon incidence of light of the first wavelength; precipitating the phosphor particles in the resin liquid by applying a centrifugal force to the package in a direction from the upper surface to a lower surface of the package; and curing the resin liquid. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-sectional view illustrating an LED device manufactured in an embodiment of the invention; 
         FIG. 2  is a front view illustrating an apparatus for manufacturing the LED device according to the embodiment; 
         FIGS. 3A to 3C  are process cross-sectional views illustrating a manufacturing method of the LED device according to the embodiment; 
         FIGS. 4A to 4C  are process cross-sectional views illustrating a manufacturing method of the LED device according to the embodiment; and 
         FIG. 5  is a front view illustrating an apparatus for manufacturing an LED device according to a variation of the embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     An embodiment of the invention will now be described with reference to the drawings. 
       FIG. 1  is a cross-sectional view illustrating an LED device manufactured in this embodiment. 
       FIG. 2  is a front view illustrating an apparatus for manufacturing an LED device according to this embodiment. 
     In  FIG. 1 , the phosphor particles are drawn schematically, larger than in reality. Furthermore, the solder layer  115  is drawn thicker than in reality. The same also applies to  FIGS. 3 and 4  described later. 
     First, an LED device manufactured in this embodiment is described. 
     As shown in  FIG. 1 , an LED device  101  includes a package  111 , and a recess  112  is formed in the upper surface of the package  111 . The recess  112  is illustratively shaped like a funnel with the side surface beveled and opening upward. The package  111  is formed from a package body  111   a  made of an insulating material, such as a white ceramic or white resin, in which a negative electrode  111   b  and a positive electrode  111   c  are embedded. The negative electrode  111   b  and the positive electrode  111   c  are exposed to the bottom surface  113  of the recess  112 . 
     An LED chip  114  is provided in the recess  112 . The LED chip  114  is illustratively a light-emitting element, which emits blue light, and its shape is like a rectangular plate. The LED chip  114  is mounted at the center of the bottom surface  113  of the recess  112 , and the lower surface of the LED chip  114  is connected to the negative electrode  111   b  through a solder layer  115 . The upper surface of the LED chip  114  is connected to the positive electrode  111   c  through a wire  116 . 
     A resin member  117  made of a transparent resin is filled in the recess  112 . The resin member  117  is illustratively formed from silicone resin or epoxy resin. The depth of the recess  112  is larger than the thickness of the LED chip  114 , and the LED chip  114  and the wire  116  are embedded in the resin member  117 . Furthermore, numerous phosphor particles  118  are mixed in the resin member  117  and deposited in a layer in contact with the bottom surface  113  and with the upper surface and the side surface of the LED chip  114 . Thus, a deposition layer  118   a  made of the phosphor particles  118  covers the LED chip  114 . The phosphor particle  118  is formed from a fluorescent material, which is excited upon incidence of the blue light emitted from the LED chip  114  and emits light, such as yellow light, having a longer wavelength than the incident light. The fluorescent material can be a silicate material or silicon oxynitride material with an alkaline earth metal used as a host material, or one of these fluorescent materials activated with rare earth ions, excited primarily by visible light. The resin member  117  transmits the blue light emitted by the LED chip  114  and the yellow light emitted by the phosphor particle  118 . 
     In such an LED device  101 , upon energization by the negative electrode  111   b  and the positive electrode  111   c,  the LED chip  114  emits blue light in all directions. Of the emitted lights, the downward light is blocked by the package  111 , but the upward and lateral light penetrate into the resin member  117 . Part of the blue light penetrated into the resin member  117  is incident on and absorbed by the phosphor particles  118 . Thus, the fluorescent material forming the phosphor particle  118  is excited and emits light, such as yellow light, having a longer wavelength than the incident light. This yellow light penetrates into the resin member  117 . On the other hand, the rest of the blue light penetrated into the resin member  117  is not incident on the phosphor particles  118 , but propagates in the resin member  117  as blue light. The yellow light and blue light propagated in the resin member  117  are emitted from the opening of the recess  112  to the outside of the recess  112  directly from the resin member  117  or after being reflected by the side surface of the recess  112 , and thereby emitted outside the LED device  101 . Here, the blue light emitted from the LED chip  114  and the yellow light emitted from the phosphor particles  118  are mixed, and hence the light emitted from the LED device  101  exhibits a white color. 
     Next, an apparatus for manufacturing an LED device according to this embodiment is described. 
     The apparatus for manufacturing an LED device according to this embodiment is an apparatus for manufacturing the LED device  101  shown in  FIG. 1 . 
     As shown in  FIG. 2 , the LED device manufacturing apparatus  1  (hereinafter also simply referred to as “apparatus  1 ”) according to this embodiment includes a base  11 . The base  11  has such rigidity as not to move or significantly vibrate even during operation of the apparatus  1 , and is illustratively fixed with respect to the installation position of the apparatus  1 . 
     A rotary shaft member  12  is rotatably attached to the base  11 . The rotary shaft member  12  is shaped like a cylinder and penetrates through the base  11 , and its central axis extends in the vertical direction. Furthermore, the rotary shaft member  12  rotates with its central axis serving as a rotation axis C. Here, the “vertical direction” is the direction of gravity. 
     A rotary driving unit  13  for rotating the rotary shaft member  12  is provided on the base  11 . The rotary driving unit  13  is illustratively a speed controlling motor. The rotary driving unit  13  is fixed to the base  11 , and its rotary shaft is coupled to the upper end portion of the rotary shaft member  12  through a coupling (not shown). Furthermore, the apparatus  1  includes a controller (not shown) for controlling the rotary driving unit  13 . 
     A rotary support member  14  is fixed to the lower end portion of the rotary shaft member  12 . Hence, when the rotary shaft member  12  rotates, the rotary support member  14  rotates integrally therewith. The rotary support member  14  is a bar-shaped member extending in the horizontal direction. Here, the “horizontal direction” is a direction orthogonal to the vertical direction. The rotary shaft member  12  and the rotary support member  14  constitute a rotary member  15 . 
     In the tip portion of the rotary support member  14 , that is, at a position E displaced from the rotation axis C in the rotary member  15 , a through hole  16  extending in a horizontal direction orthogonal to the direction from the rotation axis C to the position E is formed, and a pivot shaft member  17  is fitted in the through hole  16 . The pivot shaft member  17  is shaped like a cylinder and pivotably attached to the rotary support member  14 . That is, the through hole  16  and the pivot shaft member  17  constitute a bearing mechanism. The extending direction of the pivot axis D of the pivot shaft member  17  is the same as the extending direction of the through hole  16 , hence extending in the horizontal direction orthogonal to the direction from the rotation axis C to the position E. The pivot shaft member  17  has a pivot angle of 90° or more, and is illustratively rotatable. 
     A pair of frames  18  is coupled to the pivot shaft member  17 . The pair of frames  18  is arranged at a certain angle therebetween so that the frames  18  are spaced farther from each other with the distance from the pivot shaft member  17 . A package fixing plate  19  is coupled between the tip portions of this pair of frames  18 . The pair of frames  18  and the package fixing plate  19  constitute a holder  20 . The holder  20  is suspended at the position E in the rotary member  15 . 
     As viewed along the extending direction of the pivot axis D, the holder  20  is shaped like an isosceles triangle with the apex at the pivot axis D and the base at the package fixing plate  19 . A plurality of containers  19   a,  each for containing the package  111  (see  FIG. 1 ) of the LED device  101  described above, are formed on the major surface of the package fixing plate  19 . Thus, the holder  20  can hold a plurality of packages  111 . For instance, a plurality of containers  19   a  are arranged in a matrix on the package fixing plate  19 . 
     By pivoting of the pivot shaft member  17  at a pivot angle of at least 90°, the direction from the position E to the container  19   a  of the package fixing plate  19  is pivotable between the vertical downward direction and the horizontal direction from the rotation axis C to the position E. Thus, the direction which the upper surface of the package turns to is flexible between the vertical upward direction and the horizontal direction to the rotation axis c. Consequently, the upper surface of the package  111  can change to turn to the direction opposite to the resultant of gravity and the centrifugal force applying to the package  111  when the rotary member  15  rotates. 
     Next, the operation of the LED device manufacturing apparatus according to this embodiment configured as above, that is, a method for manufacturing an LED device according to this embodiment, is described. 
       FIGS. 3A to 3C  and  4 A to  4 C are process cross-sectional views illustrating the method for manufacturing an LED device according to this embodiment. 
     First, as shown in  FIG. 3A , a package  111  is fabricated. As described above, in the package  111 , a recess  112  is formed in the upper surface of the package body  111   a,  and a negative electrode  111   b  and a positive electrode  111   c  are embedded in the bottom surface  113  of the recess  112 . 
     Next, as shown in  FIG. 3B , a solder layer  115  is formed at the center of the bottom surface  113  of the recess  112 . The solder layer  115  is connected to the negative electrode  111   b.    
     Next, as shown in  FIG. 3C , an LED chip  114  is bonded to the solder layer  115 . Thus, the lower surface of the LED chip  114  is connected to the negative electrode  111   b  through the solder layer  115 , and the LED chip  114  is mounted on the bottom surface  113 . 
     Next, as shown in  FIG. 4A , a wire  116  is bonded between the upper surface of the LED chip  114  and the positive electrode  111   c.  Thus, the upper surface of the LED chip  114  is connected to the positive electrode  111   c  through the wire  116 . 
     Next, as shown in  FIG. 4B , a resin liquid  120  is poured from a dispenser  200  into the recess  112 . The resin liquid  120  is made of a transparent resin such as silicone resin or epoxy resin, and contains numerous phosphor particles  118 . At this stage, the resin liquid  120  is in a liquid state, and the phosphor particles  118  are uniformly dispersed in the resin liquid  120 . The phosphor particle  118  is solid. 
     Next, as shown in  FIG. 2 , with the rotary member  15  stopped, the package  111  is fixed to the container  19   a  of the package fixing plate  19  of the apparatus  1 . Thus, the holder  20  holds the package  111 . At this time, by the weight of the holder  20  and the package  111  held on the holder  20  (hereinafter collectively referred to as “package-mounting holder  20   a ”), the direction from the pivot axis D to the center of gravity of the package-mounting holder  20   a  is directed vertically downward. That is, the package-mounting holder  20   a  is suspended at the position E of the rotary member  15 . Furthermore, because the holder  20  is shaped like an isosceles triangle as viewed along the extending direction of the pivot axis D, the major surface of the package fixing plate  19  is made horizontal, and the upper surface of the package  111  is also held horizontally. Thus, the resin liquid  120  poured into the recess  112  does not spill out. 
     Next, the controller (not shown) of the apparatus  1  is operated to drive the rotary driving unit  13 . Thus, with the package  111  held on the holder  20 , the rotary member  15  is rotated. As a result, besides gravity, a centrifugal force acts on the package-mounting holder  20   a  suspended at the position E displaced from the rotation axis C in the rotary member  15 . Furthermore, the pivot shaft member  17  is pivotable with respect to the rotary member  15 . Hence, the direction from the pivot axis D to the center of gravity of the package-mounting holder  20   a  is inclined in alignment with the direction of the resultant of gravity and the centrifugal force acting on the package-mounting holder  20   a.  In other words, the upper surface of the package  111  turns to the direction opposite to the resultant of gravity and the centrifugal force applying to the package  111 . 
     Then, if the rotation speed of the rotary driving unit  13  is sufficiently increased, the centrifugal force becomes significantly larger than gravity, and the direction from the pivot axis D to the center of gravity of the package-mounting holder  20   a  is made nearly horizontal. Thus, the centrifugal force is applied to the package  111  in a direction from the upper surface to the lower surface of the package  111 , and forcibly precipitates the phosphor particles  118  in the resin liquid  120 . Also at this time, the resin liquid  120  does not spill out of the recess  112  because the force applied to the package  111  is directed from the upper surface to the lower surface of the package  111 . 
     Then, the package-mounting holder  20   a  is rotated for a certain period of time. When the phosphor particles  118  in the resin liquid  120  are sufficiently precipitated, the rotary driving unit  13  is stopped. Thus, the centrifugal force ceases to act on the package-mounting holder  20   a,  and the direction from the position E to the center of gravity of the package-mounting holder  20   a  returns to the vertically downward direction. Subsequently, the package  111  is detached from the apparatus  1 . 
     Thus, as shown in  FIG. 4C , the phosphor particles  118  are precipitated in the resin liquid  120 . Also at this stage, the resin liquid  120  remains in the liquid state. Because the pivot shaft member  17  is pivotable with respect to the rotary member throughout the above process of rotating the package-mounting holder  20   a,  the force acting on the package  111  is always directed from the upper surface to the lower surface of the package  111 . Hence, the deposition layer of the phosphor particles  118  has a uniform thickness. Furthermore, the resin liquid  120  does not spill out of the recess  112  of the package  111 . 
     Next, the package  111  is heated. For instance, in a thermostatic bath, the package  111  is maintained at a temperature of 150° C. for one hour. Thus, the resin liquid  120  is heat-cured into a resin member  117 . Consequently, the LED device  101  shown in  FIG. 1  is manufactured. 
     In the following, a numerical example of this embodiment is described. 
     The rotation radius of the package  111  in the apparatus  1 , that is, the sum of the distance from the rotation axis C to the position E and the distance from the position E to the container  19   a  of the package fixing plate  19 , is approximately 30 cm. The rotation speed of the rotary driving unit  13  is approximately 1000 rpm. In this case, a centrifugal force of approximately 335 G is applied to the package  111 . Thus, precipitation of phosphor particles, which takes 10 hours in spontaneous precipitation, can be completed within one hour. 
     Next, the effect of this embodiment is described. 
     According to this embodiment, when the phosphor particles  118  in the resin liquid  120  are precipitated to form a deposition layer  118   a  covering the LED chip  114 , by applying a centrifugal force to the package  111  with the apparatus  1 , the time required for precipitation can significantly be reduced. For instance, in the above example, by application of a centrifugal force, precipitation is completed within one hour, although it takes 10 hours in spontaneous precipitation. 
     This significantly increases the productivity of the LED device  101 . Furthermore, the amount of water absorbed by the resin liquid  120  during precipitation is small, and the volume expansion is small. Hence, the volume shrinkage in heat-curing the resin liquid  120  is also small, and the amount of water separated out between the resin liquid  120  and the side surface of the recess  112  is also small. This can prevent delamination of the resin member  117  from the recess  112 . Furthermore, by application of a large centrifugal force to the phosphor particles  118 , the thickness of the deposition layer  118   a  can be made uniform. Hence, light emission of the deposition layer  118   a  is made uniform. Thus, according to this embodiment, it is possible to efficiently manufacture an LED device with good quality. 
     Furthermore, a plurality of containers  19   a  are formed in the package fixing plate  19  of the apparatus  1 . Hence, the precipitation treatment can be simultaneously performed on a plurality of packages  111 . This can further increase the productivity of the LED device. 
     Next, a variation of this embodiment is described. 
       FIG. 5  is a front view illustrating an apparatus for manufacturing an LED device according to this variation. 
     As shown in  FIG. 5 , the LED device manufacturing apparatus  2  according to this variation is different from the apparatus  1  (see  FIG. 2 ) according to the above embodiment in the configuration of the holder. 
     More specifically, like the holder  20  (see  FIG. 2 ) of the apparatus  1 , the holder  30  of the apparatus  2  includes a pair of frames  18  coupled to a pivot shaft member  17 . However, the frames  18  do not directly hold a package fixing plate  19 , but hold a package fixing plate  19  through a carrier  31 . The carrier  31  holds a plurality of package fixing plates  19  arranged in multiple stages. For instance, each package fixing plate  19  is removable from the carrier  31 . Furthermore, as in the above embodiment, each package fixing plate  19  includes a plurality of containers  19   a  formed in a matrix. The holder  30  is pivotably suspended at the position E of the rotary member  15  through the pivot shaft member  17 . 
     According to this variation, more packages can be rotated at a time. The configuration of the apparatus  2  other than the foregoing, the method for manufacturing an LED device, and the configuration of the LED device manufactured in this variation are the same as those in the above embodiment. 
     The invention has been described with reference to the embodiment and its variation. However, the invention is not limited to these embodiment and variation. For instance, those skilled in the art can suitably modify the above embodiment and variation by addition, deletion, or design change of components, or by addition, omission, or condition change of processes, and such modifications are also encompassed within the scope of the invention as long as they fall within the spirit of the invention. 
     For instance, in the LED device manufacturing apparatus  1  according to the above embodiment, a plurality of containers  19   a  is formed in the package fixing plate  19  to simultaneously hold a plurality of packages  111 . However, the invention is not limited thereto, but the package fixing plate  19  may hold only one package  111 . 
     Alternatively, the apparatus  1  can include a plurality of holders  20  to hold more packages  111 . In this case, to provide n holders  20  (n is an integer of two or more), these holders  20  are preferably placed at positions with n-fold symmetry about the rotation axis C. Then, even if the rotary member  15  is rotated, the center of gravity of the apparatus  1  does not change, and vibration of the apparatus  1  can be suppressed. For instance, in the case of providing two holders  20 , they can be provided at both end portions of the rotary support member  14 . In the case of providing three or more holders  20 , the rotary support member  14  can be shaped like a disc instead of a bar, and the holders  20  can be placed equidistantly along the periphery of the disc. In this case, the holders  20  are placed so as to avoid interference with each other. Also in the apparatus  2  according to the above variation, a plurality of holders  30  can be provided. 
     Furthermore, in the above embodiment, the apparatus  1  illustratively includes a rotary driving unit  13 . However, the invention is not limited thereto, but the rotary member  15  may be manually rotated. 
     Furthermore, in the above embodiment, the rotary shaft member  12  and the rotary support member  14  illustratively constitute the rotary member  15 . However, the invention is not limited thereto, and the rotary member  15  may integrally be formed. Moreover, a through hole  16  may be formed in the tip of the overhang portion of the rotary member  15 , and a pivot shaft member  17  may be fitted in the through hole  16 . 
     Furthermore, the above embodiment illustratively indicates that the holder  20  is suspended at the position E in the rotary member  15  by the frames  18  and rocked by a centrifugal force. However, the invention is not limited thereto. It is sufficient that a holder supports the package  111 , and the upper surface of the package  111  is flexible to turn to the direction opposite to the resultant of gravity and the centrifugal force applying to the package  111  when the rotary member  15  rotates. For instance, while the holder is fixed to the rotary member  15  and supports the package  111 , the holder may be movable for the rotary member  15 . 
     In specific, the holder may be fixed to the rotary member  15 ; the interior surface of the holder near the rotation axis c of the rotary member  15  may be horizontal but may continuously change to become vertical with the distance from the rotation axis c; and the package  111  may be able to move along the interior surface of the holder. For instance, the interior surface of the holder may be a hemispherical shape having a center in a point on the rotation axis c; a plurality of rails may be formed from the lowest part in a radial fashion; and the package  111  may be guided by the rails and become movable.