(19) United States
`(12) Patent Application Publication (10) Pub. No.: US 2005/0236639 A1
`Abe et al.
`(43) Pub. Date:
`Oct. 27, 2005
`
`US 20050236639A1
`
`(54) SEMICONDUCTOR LIGHT EMITTING
`DEVICE AND FABRICATION METHOD
`THEREOF
`
`Foreign Application Priority Data
`(30)
`Apr. 27, 2004 (JP).................................. JP2004-131774
`
`(75) Inventors: Munezo Abe, Shiki-gun (JP);
`Toshihiko Yoshida, Nara-shi (JP)
`Correspondence Address:
`MORRISON & FOERSTER LLP
`755 PAGE MILL RD
`PALO ALTO, CA 94304-1018 (US)
`(73) Assignee: SHARP KABUSHIKI KAISHA,
`Osaka-shi (JP)
`(21) Appl. No.:
`11/112,215
`(22) Filed:
`Apr. 22, 2005
`
`Publication Classification
`
`(51) Int. Cl." ..................................................... H01L 29/22
`(52) U.S. Cl. .............................................................. 257/100
`(57)
`ABSTRACT
`A Semiconductor light emitting device includes an LED
`element, a lead frame on which the LED is mounted, a lead
`frame electrically connected to the LED element via a wire,
`transparent resin formed on the LED element and on the lead
`frames, and light Shielding resin having a reflectance higher
`than the reflectance of the transparent resin, Surrounding the
`perimeter of the LED. The transparent resin includes a lens
`portion constituting a lens on the LED, and a holding portion
`holding the lead frame.
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`atent Application Publication Oct. 27, 2005 Sheet 2 of 4
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`Patent Application Publication Oct. 27, 2005 Sheet 3 of 4
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`Patent Application Publication Oct. 27, 2005 Sheet 4 of 4
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`US 2005/0236639 A1
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`US 2005/0236639 A1
`
`Oct. 27, 2005
`
`SEMCONDUCTOR LIGHT EMITTING DEVICE
`AND FABRICATION METHOD THEREOF
`0001. This nonprovisional application is based on Japa
`nese Patent Application No. 2004-131774 filed with the
`Japan Patent Office on Apr. 27, 2004, the entire contents of
`which are hereby incorporated by reference.
`
`BACKGROUND OF THE INVENTION
`0002) 1. Field of the Invention
`0003. The present invention relates to a semiconductor
`light emitting device, and a method of fabricating Such a
`Semiconductor light emitting device. Particularly, the
`present invention relates to a Semiconductor light emitting
`device employing a light emitting element Such as an LED
`(Light Emitting Diode), and a method of fabricating Such a
`Semiconductor light emitting device.
`0004 2. Description of the Background Art
`0005 Semiconductor light emitting devices employing a
`light emitting element Such as an LED are conventionally
`known.
`0006 For example, Japanese Patent Laying-Open No.
`11-087780 (first conventional example) discloses a light
`emitting device including a light emitting element, a lead
`frame on which the light emitting element is to be mounted,
`a lead frame for electrical connection to the light emitting
`element via a wire, and a molding covering most of the lead
`frames. Respective lead frames are arranged opposite to
`each other, passing through the molding to project outside.
`0007 Japanese Patent Laying-Open No. 2001-185763
`(Second conventional example) discloses an optical Semi
`conductor package including an optical Semiconductor ele
`ment, a lead frame on which the optical Semiconductor
`element is to be mounted on the main Surface, a first resin
`molding (lens) formed of light Shielding resin, arranged so
`as to cover the optical Semiconductor element, and a Second
`resin molding (case) formed of light transmitting resin with
`a bottom Supporting the inner lead of the lead frame and a
`Side Supporting the first resin molding. The lead frame is
`formed Such that the region at the back Side of the lead frame
`corresponding to the region where the optical Semiconductor
`element is mounted penetrates the bottom of the Second
`resin molding to be exposed outside, constituting a first heat
`dissipation region, and an outer lead portion constitutes a
`Second heat dissipation region.
`0008 Japanese Patent Laying-Open No. 06-334224
`(third conventional example) discloses a fabrication method
`of an LED light emitting device including the Steps of
`attaching an LED chip to a printed board, arranging a pair
`of molds with respect to the printed board, and introducing
`Synthetic resin for molding from a predetermined position
`that does not have an adverse effect on the lens character
`istics in the mold located at the LED chip mounting face.
`The printed board has a through hole near the LED chip.
`0009 Problems of such semiconductor light emitting
`devices will be described hereinafter.
`0010) If the semiconductor light emitting element in the
`first conventional example becomes thinner, the depth of the
`bowl-like concave formed by the molding will be reduced,
`leading to a wider angle of radiation of the output light.
`
`There is a possibility of the adjustment of the directivity
`being partially degraded when the light emitting element is
`reduced in size.
`0011. The light emitting devices of the second and third
`conventional examples have a lens formed of transparent
`resin on a printed board or lead frame. Accordingly, the
`angle of radiation of the output light can be reduced to
`improve the axial luminous intensity.
`0012. When a lens is to be formed as in the second and
`third conventional examples, the height of the lens must be
`ensured Such that the light emitting element (LED chip) and
`wire are covered. As a result, there are cases where reduction
`in the Size of the light emitting element is restricted.
`0013 In the second conventional example, the lead frame
`is Secured by the Second resin molding. To ensure the
`Strength of Security, the Second resin molding is made
`relatively large. As a result, there are cases where reduction
`in size of the light emitting element is restricted. It is to be
`noted that the third conventional example is Silent about the
`concept of employing a lead frame.
`SUMMARY OF THE INVENTION
`0014) An object of the present invention is to provide a
`Semiconductor light emitting device having a light emitting
`element mounted on a lead frame, directed to reducing the
`size thereof while allowing adjustment of the directivity of
`output light, or ensuring the Strength of the lead frame, and
`a fabrication method of Such a semiconductor light emitting
`device.
`0015 According to an aspect of the present invention, a
`Semiconductor light emitting device includes a Semiconduc
`tor light emitting element, a first lead frame on which the
`Semiconductor light emitting element is mounted, a Second
`lead frame electrically connected with the Semiconductor
`light emitting element via a wire, and a light transmitting
`resin formed on the Semiconductor light emitting element
`and on the first and Second lead frames. The light transmit
`ting resin includes a lens portion constituting a lens on the
`Semiconductor light emitting element, and a holding portion
`holding the first and Second lead frames.
`0016 Since the semiconductor light emitting device has
`the first and Second lead frames held by the light transmitting
`resin that also constitutes a lens, the device can be reduced
`in size while ensuring the Strength of the lead frame.
`0017. The width of the lens portion is preferably smaller
`than the width of the holding portion.
`0018. Accordingly, the lens portion exhibits the capabil
`ity of improving the axial luminous intensity whereas the
`holding portion exhibits the capability of fixedly holding the
`lead frame. By rendering the lens portion relatively Smaller,
`the light emitting device can be reduced in size.
`0019 Preferably, the leading end of the first lead frame
`and the leading end of the Second lead frame constitute a
`concave. The Semiconductor light emitting element is pro
`vided on the bottom face of the concave. The holding portion
`receives at least a portion of the concave. Preferably, the
`Semiconductor light emitting element is located at the con
`cave of the first lead frame, whereas the wire establishing
`connection between the Semiconductor light emitting ele
`ment and the Second lead frame is located at the concave of
`the Second lead frame.
`
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`US 2005/0236639 A1
`
`Oct. 27, 2005
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`0020. Accordingly, the height of the light emitting device
`can be reduced, allowing further reduction in size.
`0021. The semiconductor light emitting element is pref
`erably provided on the optical axis of the lens portion.
`0022. Accordingly, the directivity can be adjusted easily.
`0023 The back side of the first lead frame corresponding
`to the region where the Semiconductor light emitting ele
`ment is mounted is preferably exposed outside of the light
`transmitting resin.
`0024. Accordingly, heat dissipation of the light emitting
`device can be improved.
`0.025
`Preferably, light shielding resin having a reflec
`tance higher than that of the light transmitting resin is
`formed Surrounding the perimeter of the Semiconductor light
`emitting element.
`0026. By causing the output light to be reflected from the
`light Shielding resin, directivity of the output light can be
`adjusted further easily.
`0027. A material for scattering light may be mixed into
`the light transmitting resin.
`0028. Accordingly, unevenness in the light intensity of
`the output light can be reduced.
`0029. A fabrication method of a semiconductor light
`emitting device of the present invention includes the steps
`of forming light transmitting resin by insert molding,
`wherein the light transmitting resin holds the first and
`Second lead frames, and constitutes a lens on the Semicon
`ductor light emitting element mounted on the first lead
`frame, and forming light Shielding resin Surrounding the
`perimeter of the Semiconductor light emitting element using
`a mold provided around the Semiconductor light emitting
`element and lens.
`0.030. Accordingly, a semiconductor light emitting device
`directed to reducing its size while improving the axial
`luminous intensity or ensuring the Strength of the lead frame
`can be obtained.
`0031. The semiconductor light emitting device of the
`present invention can be reduced in size while allowing
`adjustment of the directivity of output light or ensuring the
`Strength of the lead frame.
`0.032 The foregoing and other objects, features, aspects
`and advantages of the present invention will become more
`apparent from the following detailed description of the
`present invention when taken in conjunction with the
`accompanying drawings.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`0.033
`FIG. 1 is a top view of a metal plate employed in
`fabricating a Semiconductor light emitting device according
`to an embodiment of the present invention.
`0034 FIG. 2 is a top view of an LED element mounted
`on a lead frame formed from the metal plate of FIG. 1.
`0.035
`FIG. 3 is an enlarged sectional view of the neigh
`borhood of the LED element taken along line III-III of FIG.
`2.
`
`0036 FIG. 4 is a sectional view of a mold provided to
`form light shielding resin at the lead frame on which an LED
`element is mounted.
`0037 FIG. 5 is a sectional view of a semiconductor light
`emitting device according to an embodiment of the present
`invention.
`0038 FIG. 6 is a sectional view of a modification of a
`Semiconductor light emitting device according to an
`embodiment of the present invention.
`
`DESCRIPTION OF THE PREFERRED
`EMBODIMENT
`0039 Embodiments of a semiconductor light emitting
`device and a fabrication method thereof according to the
`present invention will be described hereinafter with refer
`ence to FIGS. 1-6.
`0040. Referring to FIG. 5, a semiconductor light emitting
`device according to an embodiment of the present invention
`includes an LED element 2 (Semiconductor light emitting
`element), a lead frame 10A (first lead frame) on which LED
`element 2 is mounted, a lead frame 10B (second lead frame)
`electrically connected to LED element 2 via a wire 3,
`transparent resin 4 (light transmitting resin) formed on LED
`element 2 and lead frame 1 (10A, 10B), and light shielding
`resin 7 (resin that blocks light) having a reflectance higher
`than that of transparent resin 4, and Surrounding the perim
`eter of LED element 2. Transparent resin 4 includes a lens
`portion 4A constituting a lens on LED element 2, and a
`holding portion 4B holding lead frame 1.
`0041. The leading end of lead frame 1 is inserted into
`transparent resin 4. Accordingly, transparent resin 4 fixedly
`holds the leading end of lead frame 1 to ensure the Strength
`in the proximity of the leading end of lead frame 1 even in
`the case where light shielding resin 7 is formed relatively
`Small. As a result, the Semiconductor light emitting device
`can be reduced in size while ensuring the Strength in the
`proximity of the leading end of lead frame 1.
`0042 Lens portion 4A is formed to have a shape of a
`convex lens. LED element 2 is formed on an optical axis 40
`of lens portion 4A. Accordingly, the directivity of output
`light can be easily adjusted in the Semiconductor light
`emitting device. Specifically, the axial luminous intensity of
`output light can be improved by lens portion 4A.
`0043 Holding portion 4B has a sectional shape of an
`upside-down trapezoid, received in bowl-like concave 7A of
`light Shielding resin 7. In order to prevent disconnection
`between wire 3 and lead frame 10B, it is desirable that wire
`3 is pressed down from above by another wire (not shown)
`at the connection between wire 3 and lead frame 10B, and
`the other end of the another wire is fixedly attached to
`another site of lead frame 10B. This another wire not shown
`is generally referred to as a “Stitch wire'.
`0044) In order to reduce unevenness in the light intensity
`of the output light, a filler for Scattering light (Scattering
`material) may be mixed into transparent resin 4.
`0045. From the standpoint of protecting lens portion 4A,
`the top height of light Shielding resin 7 is preferably higher
`than the top height of lens portion 4A(for example, approxi
`mately 0.2 mm higher). Lens portion 4A has a predeter
`mined thickness So as to cover LED element 2 and wire 3.
`
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`US 2005/0236639 A1
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`Oct. 27, 2005
`
`0046. In the present embodiment, the leading ends of lead
`frames 10A and 10B constitute a concave 1C, as shown in
`FIG. 5. LED element 2 is provided on the bottom surface of
`concave 1C. The junction of wire 3 and lead frame 10B is
`located at concave 1C. Also, the aforementioned Stitch wire
`is located at concave 1C.. Holding portion 4B of transparent
`resin 4 receives at least a portion of concave 1C.
`0047 Thus, the top height of lens portion 4A is reduced
`together with the top height of light shielding resin 7 while
`ensuring a predetermined thickness of lens portion 4A and a
`height for lens effect (the distance from the LED element to
`the lens top face). As a result, the Semiconductor light
`emitting device can be reduced in size.
`0.048 LED element 2 generally provides more light from
`the side than from the top surface. The light output from the
`side of LED element 2 is reflected at the wall of concave 1C
`to be effectively employed as the light within the directive
`angle. The light arriving at holding portion 4B from the gap
`between lead frames 10A and 10B is reflected at the inter
`face between holding portion 4B and light shielding resin 7
`to reach lens portion 4A, where it is eventually used effec
`tively as the light within the directive angle.
`0049. The width of lens portion 4A (L1 in FIG. 5) is
`Smaller than the width of holding portion 4B (L2 in FIG. 5).
`0050. When the width of lens portion 4A becomes larger,
`a trend is towards increased thickness thereof Holding
`portion 4B must have a predetermined width in order to
`ensure the Strength of lead frame 1.
`0051. By setting L1-L2 as set forth above, the strength
`around the leading end of lead frame 1 can be ensured while
`allowing a Smaller Semiconductor light emitting device.
`0.052 A method of fabricating the semiconductor light
`emitting device of FIG. 1 will be described hereinafter.
`Referring to FIG. 1, a metal plate 1A employed in the
`fabrication of a Semiconductor light emitting device is a thin
`metal sheet formed of copper alloy that is Superior in heat
`conductivity. On metal plate 1A, lead frames of a plurality
`of elements are formed in alignment vertically and horizon
`tally. By Separating the lead frames, each individual element
`is obtained. A groove to separate lead frames 10A and 10B
`is formed by die-cutting.
`0053 FIG. 2 is a top view representing LED element 2
`mounted on the lead frame formed from the metal plate of
`FIG. 1. For the sake of convenience and simplification, the
`lead frame formation region is hatched in FIG. 2.
`0.054
`Referring to FIG. 2, LED element 2 has a quad
`rangle configuration in plane in which one side is at least 0.2
`mm and not more than 1.0 mm. LED element 2 is located on
`one of the lead frames divided by a groove. Wire 3 estab
`lishes connection between LED element 2 and the other lead
`frame. The gap between the two lead frames is equal to or
`slightly smaller than the thickness of the lead frame. Since
`the lead frame has a thickness of at least 0.3 mm and not
`more than 0.5 mm, the aforementioned gap is approximately
`0.25 mm. LED element 2 and wire 3 are located above
`bottom face 1D of concave 1C provided on the lead frame.
`Holes 1B are provided at the periphery of concave 1C.. Hole
`1B allows light shielding resin 7 formed afterwards to
`penetrate therethrough, Suppressing the lead frame from
`being detached from light Shielding resin 7.
`
`0055 FIG. 3 is an enlarged sectional view of the neigh
`borhood of the LED element taken along line III-III of FIG.
`2.
`0056 Referring to FIG. 3, LED element 2 is formed on
`lead frame 10 with Ag paste 2A thereunder. Transparent
`resin 4 is formed Such that LED element 2 and wire 3 are
`covered by lens portion 4A while lead frames 10A and 10B
`are received at holding portion 4B. Transparent resin 4 is
`formed through transfer molding (insert molding). By
`employing transfer molding, the configuration of lens por
`tion 4A can be worked in precision. Epoxy resin, Silicon
`resin, or the like, for example, is employed for transparent
`resin 4.
`0057 FIG. 4 is a sectional view representing the provi
`sion of a mold 5 directed to forming light shielding resin 7
`at lead frame 1 (10A, 10B) on which LED element 2 is
`mounted.
`0058 Referring to FIG.4, lens portion 4A is protected by
`mold 5 during the formation of light shield resin 7. Light
`Shielding resin 7 is typically applied by injection molding.
`The injection molding method is advantageous in that intro
`duction of resin between lens portion 4A and mold 5 is
`readily Suppressed since resin of low flowability is
`employed. Thus, damage of lens portion 4A caused by
`contact with resin of high temperature can be Suppressed.
`0059 Light shielding resin 7 is formed so as to cover the
`bottom Surface and side Surface of transparent resin 4. Resin
`of high reflectance with respect to visible light is preferably
`employed for light Shielding resin 7. For example, liquid
`crystal polymer, polyphenylene Sulfide, polypthalamide
`resin (product name: Amodel (R)), or nylon may be used.
`From the Standpoint of increasing the reflectance, white
`resin is preferably used for light Shielding resin 7. Accord
`ingly, the light from the gap of the lead frames arriving at the
`interface between transparent resin 4 and light Shielding
`resin 7 is reflected to be eventually output within the
`directive angle of the Semiconductor light emitting device.
`Thus, the light emitting efficiency of the Semiconductor light
`emitting device is improved.
`0060. To summarize, the fabrication method of a semi
`conductor light emitting device according to the present
`embodiment includes the step (FIG. 3) of providing trans
`parent resin 4 (light transmitting resin) through transfer
`molding (insert molding) to hold lead frame 1 (first and
`Second lead frames) and constitute lens portion 4A on LED
`element 2 (Semiconductor light emitting element) mounted
`on lead frame 10A, and the step (FIGS. 4 and 5) of
`providing light shielding resin 7 (resin with light blocking
`effect) Surrounding the perimeter of LED element 2 using a
`mold 5 provided around LED element 2 and lens portion 4A.
`0061. A modification of the semiconductor light emitting
`device set forth above will be described hereinafter with
`reference to FIG. 6.
`0062). In the modification of FIG. 6, a concave 8 is
`formed in resins 4B and 7 at the side opposite to the side of
`lead frame 10A corresponding to the region where LED
`element 2 is mounted. This relevant portion of lead frame
`10A is exposed outside of transparent resin 4.
`0063. Accordingly, the heat generated from LED element
`2 escapes easily outside (improved heat dissipation) and the
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`US 2005/0236639 A1
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`Oct. 27, 2005
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`light emitting efficiency is improved. Energy consumption
`of the light emitting element can be Suppressed.
`0064.
`Furthermore, by filling a material of high heat
`conductivity Such as Silicon grease between the exposed
`region of lead frame 10A and a radiator (not shown), the heat
`dissipation characteristic can be further improved.
`0065. Although the description set forth above in FIGS.
`5 and 6 is based on a structure in which only one LED
`element 2 is provided, a plurality of LED elements may be
`mounted on one Semiconductor light emitting device. Fur
`thermore, the configuration of lens portion 4A is not limited
`to a convex lens, and may be a concave lens. In the case of
`a concave lens, the directive angle of output light will
`become larger whereas the total luminous energy can be
`increased.
`0.066 The reflector formed of light shielding resin 7 may
`take the configuration of an elliptic conical frustum instead
`of a bowl-like configuration (frustum of a cone). This
`provides anisotropic reflectance.
`0067. Although the present invention has been described
`and illustrated in detail, it is clearly understood that the same
`is by way of illustration and example only and is not to be
`taken by way of limitation, the Spirit and Scope of the present
`invention being limited only by the terms of the appended
`claims.
`What is claimed is:
`1. A Semiconductor light emitting device comprising:
`a Semiconductor light emitting element,
`a first lead frame on which Said Semiconductor light
`emitting element is mounted,
`a Second lead frame electrically connected to Said Semi
`conductor light emitting element via a wire, and
`light transmitting resin formed on Said Semiconductor
`light emitting element and on Said first and Second lead
`frames,
`wherein Said light transmitting resin comprises a lens
`portion constituting a lens on Said Semiconductor light
`emitting element, and a holding portion holding Said
`first and Second lead frames.
`2. The Semiconductor light emitting device according to
`claim 1, wherein Said lens portion has a width Smaller than
`the width of said holding portion.
`3. The Semiconductor light emitting device according to
`claim 1, wherein
`
`a leading end of Said first lead frame and a leading end of
`Said Second lead frame constitute a concave,
`Said Semiconductor light emitting element is provided on
`a bottom Surface of Said concave, and
`Said holding portion receives at least a portion of Said
`COCVC.
`4. The Semiconductor light emitting device according to
`claim 1, wherein
`a leading end of Said first lead frame and a leading end of
`Said Second lead frame constitute a concave,
`Said Semiconductor light emitting element is located at
`Said concave of Said first lead frame, and
`Said wire connecting Said Semiconductor light emitting
`element and Said Second lead frame is located at Said
`concave of Said Second lead frame.
`5. The Semiconductor light emitting device according to
`claim 1, wherein Said Semiconductor light emitting element
`is provided on an optical axis of Said lens portion.
`6. The Semiconductor light emitting device according to
`claim 1, wherein a backside portion of Said first lead frame
`corresponding to a region where Said Semiconductor light
`emitting element is mounted is exposed outside of Said light
`transmitting resin.
`7. The Semiconductor light emitting device according to
`claim 1, wherein light Shielding resin having a reflectance
`higher than the reflectance of said light transmitting resin is
`formed Surrounding a perimeter of Said Semiconductor light
`emitting element.
`8. The Semiconductor light emitting device according to
`claim 1, wherein a material for Scattering light is mixed into
`Said light transmitting resin.
`9. A fabrication method of a Semiconductor light emitting
`device comprising the Steps of:
`forming light transmitting resin through insert molding,
`Said light transmitting resin holding first and Second
`lead frames, and constituting a lens on a Semiconductor
`light emitting element mounted on Said first lead frame,
`and
`providing light Shielding resin Surrounding a perimeter of
`Said Semiconductor light emitting element using a mold
`provided around Said Semiconductor light emitting ele
`ment and Said lens.
`
`Cree Ex. 1010
`
`Page 9
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