Semiconductor light emitting device

A semiconductor light emitting device has an outer lead disposed along an outer wall of a mold resin portion perpendicular to a light-emitting plane of a light emitting diode. An outer lead is also disposed at an outer wall of the mold resin portion parallel to and opposite to the light-emitting plane. The outer wall of the resin mold where the outer lead is disposed is taken as a mount face. Each outer wall of the mold resin portion constituting a mount face includes at least one outer lead for an anode and a cathode. According to the present configuration, there is provided a semiconductor light emitting device that allows selection of side-emission mounting or top-emission mounting with the same components on a mount substrate.

This nonprovisional application is based on Japanese Patent Application No. 2007-077348 filed with the Japan Patent Office on Mar. 23, 2007, the entire contents of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a semiconductor light emitting device employing a light emitting diode and the like.

2. Description of the Background Art

A surface-mount type semiconductor light emitting device employing a light emitting diode (hereinafter, referred to as “LED”) has a configuration as represented inFIGS. 12-14.FIGS. 12,13and14are a front view, a bottom view, and a side view, respectively, of a conventional surface-mount type semiconductor light emitting device. The conventional surface-mount type semiconductor light emitting device has a resin portion102provided by insert-molding or the like in a manner fastening a lead frame101. On lead frame101, an LED chip103is electrically and mechanically connected by silver (Ag) paste104and gold wire105. LED chip103is surrounded by epoxy resin106to be protected and encapsulated.

Lead frame101is formed in a specified pattern shape, and insert-molded in resin102in a bonded state or a state plated with silver. LED chip103is electrically and mechanically connected on lead frame101by silver paste104and gold wire105, followed by encapsulation with epoxy resin106. Then, the lead has the unnecessary region cut and is bent in an inverted block upper case C shape. Thus, a terminal portion107for coupling with a mounting board including electric circuitry such as a driving circuit is formed. The conventional device shown inFIG. 12has a light-emitting face108parallel to the mount face, and is qualified as a top emission type surface-mount LED light emitting element.

As prior art documents disclosing a conventional surface-mount LED light emitting element set forth above, Japanese Patent Laying-Open Nos. 2004-071675 and 2006-222382 can be cited.

In the packaging process of the convention surface-mount LED light emitting element set forth above on a mounting board that includes electrical circuitry such as a driving device, selection of a top emission type for mounting parallel to the light-emitting plane, or a side emission type for mounting perpendicular to the light-emitting plane depends upon the arrangement of the terminal portion of the LED light emitting element. Therefore, there was no option in mounting on a substrate between a side emission type or a top emission type with the same components.

SUMMARY OF THE INVENTION

In view of the foregoing, an object of the present invention is to provide a semiconductor light emitting device that allows selection of either a side emission type or top emission type for mounting on a substrate, based on the same components, corresponding to the status or the like of an irradiation subject.

A semiconductor light emitting device of the present invention directed to solving the above problem includes a semiconductor light emitting element, a lead frame including a plurality of inner leads having a placement face where the semiconductor light emitting element is mounted and an extraction electrode, and a plurality of outer leads for electrodes, and a mold resin portion to fasten the lead frame. Each of the outer leads is disposed along a first outer wall face of the mold resin portion perpendicular to a light-emitting plane of the semiconductor light emitting element, and along a second outer wall face of the mold resin portion parallel to and opposite to the light-emitting plane. Each of the first and second outer wall faces constitutes a mount face and includes at least one outer lead for each of an anode and cathode electrically connected to an anode electrode and a cathode electrode of a semiconductor light emitting element.

Each outer lead is disposed over the first and second outer wall faces, and all pairs of an anode terminal and a cathode terminal electrically connected to the anode and cathode of each semiconductor light emitting element are arranged at each of the first and second outer wall faces.

Each of the outer leads is preferably disposed over the first and second outer wall faces, and a plurality of outer leads, respectively linked with inner leads arranged in the direction of the width of the outer leads, are facing each other on the first and second outer wall faces. In addition, the surface of the outer lead is preferably parallel to and flat on the face of the wall of the mold resin portion.

In a preferable embodiment of the present invention, the outer lead includes eight terminals, among which four terminals are disposed for shared usage at the first and second outer wall faces. One pair of two terminals among the remaining four terminals is disposed at the first outer wall face and the other pair of two terminals is disposed at the second outer wall face. According to this structure, the first outer wall face is to be used as a mount face for the side-emission mounting mode and the second outer wall face is to be used as a mount face for the top-emission mounting mode.

In addition, a common lead can be split into two terminals in the lead frame, one that is formed for a side-emission terminal and the other formed for a top-emission terminal. Furthermore, a plurality of semiconductor light emitting elements are mounted. The anode and cathode of each of the plurality of semiconductor light emitting elements may have an outer lead terminal, allowing independent driving and independent current adjustment of the plurality of semiconductor light emitting elements.

In addition, the semiconductor light emitting element may be formed of a chip of one of the three primary colors (red, green, blue), allowing current adjustment of each chip. Further, the outer lead may be configured corresponding to a body of poor solder wettability such as Cu plated with metal of favorable solder wettability such as Sn, Au or Ag.

The mold resin portion fastening the lead frame may be configured to cover a portion of the surface of the inner lead at an opening face of the light-emitting plane side. In contrast, the mold resin portion fastening the lead frame may be configured to avoid covering the surface of the inner lead at the opening face at the light-emitting plane side.

Thus, side-emission type mounting or top-emission type mounting can be selected with the same component. The availability of a semiconductor light emitting device is rendered extensive with one component.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

First Embodiment

A first embodiment of the present invention will be described hereinafter with reference toFIGS. 1-8. The first embodiment is directed to a surface-mount semiconductor light emitting device employing an LED as the light emitting element.FIGS. 1 and 2are perspective views of the surface-mount semiconductor light emitting device, viewed from different directions. Referring toFIG. 1or2, a lead frame including terminals1a,1b,1c,1d,1e,1f,1gand1hqualified as outer leads are insert-molded and protected in a mold resin portion2formed of a well known sealing material for a semiconductor element such as polyphthalamide (PPA), polycarbonate resin, epoxy resin, and the like. An LED3is mounted on lead frame1. This LED3is connected mechanically and electrically to lead frame1by silver paste4and gold wire5. For the purpose of holding and fixing lead frame1, there is provided mold resin portion2formed of white resin, surrounding a placement face1xof LED3, filling the gap in the lead frame at placement face1x, and covering the entire bottom face.

In addition, LED3is surrounded by encapsulation resin6to be sealed and protected. Encapsulation resin6is transparent or opalescent having a diffusing agent mixed, formed of epoxy resin or silicone resin, casted mainly by the potting method. Transfer formation, injection formation, or the like is also allowed. The light-emitting plane7that is the front region from which light is emitted from LED3can be formed in an arbitrary shape such as a lens.

In lead frame1, a common lead is split into two terminals. One of these terminals is formed for a side-emission terminal. Terminals1gand1a, and also terminals1hand1fcorrespond to the same electrode, split into two inside. The layout is established to allow usage as a mount face2afor side-emission and a mount face2bfor top-emission.

The configuration of the semiconductor light emitting device of the present embodiment will be described in further detail based onFIGS. 3-8hereinafter. Lead frame1is formed integrally with resin mold portion2directed to holding, protecting, and fastening lead frame1. Lead frame1includes a plurality of inner leads1yhaving a placement face1xwhere LED3is to be mounted, and terminals1a,1b,1c,1d,1e,1f,1gand1hqualified as a plurality of outer leads for electrodes. Among the outer lead terminals, terminals1a,1b,1c,1d,1eand1fare disposed along side-emission mount face2athat is the outer wall of resin mold portion2perpendicular to light-emitting plane7where the light emitting region of LED3is located. Terminals1b,1c,1d,1e,1gand1hare disposed at top-emission mount face2bthat is the outer wall of resin mold portion2parallel to and opposite to light emitting plane7. Terminals1a,1gand terminals1h,1fof the outer leads constitute terminal pairs, extending and split from a closest-located inner lead with a placement face, qualified as terminal pairs for a cathode. Terminals1b,1eand1care terminals for an anode, each extending from the closest-located inner lead directed to wire leading. The inner lead located at the middle of the placement face extends, corresponding to a cathode terminal leading to terminal1d. Specifically, at mount face2aand mount face2b, the anode terminal and cathode terminal corresponding to the anode electrode and cathode electrode of each LED3are arranged, one pair each. A complicated mounting structure is avoided no matter which mount face is selected. Mounting on a flat substrate is allowed with one surface.

Outer lead terminals1b,1c,1d,1eand terminals1a,1f, and also terminals1b,1c,1d,1eand terminals1g,1hare arranged opposite to each other respectively at mount faces2aand2b. The surface of each terminal is parallel to and flat on the face of the outer wall of mold resin portion2. Therefore, an unstable fixed state such as inclination is eliminated regardless of which of mount faces2aand2bis employed.

In the present embodiment, three LEDs3are placed. The anode and cathode of each LED3include terminals1aand1gand terminals1fand1hof the outer lead electrically connected, allowing independent driving and current adjustment of LED3(not shown), constituting the LED configuration for the three primary colors (red, green and blue). The reason why eight terminals are provided in the present embodiment is to allow the mounting of three chips at most in order to realize full color display by incorporating the three primary colors and controlling respective current independently. Four among the eight terminals are shared for side-emission and top-emission, and one pair of the remaining four terminals is used exclusively for side-emission, and the second pair of the remaining four terminals is used exclusively for top-emission. Thus, shared usage for side-emission and top-emission is allowed.

Each outer lead terminal is advantageously formed by having a body of poor solder wettability plated with metal of favorable solder wettability. Cu is employed for the body. Sn, Au, Ag, or SnBi is employed for the metal plating. For the purpose of mounting on a flat printed board where the interconnection pattern is formed without inclination, each terminal is formed to a thickness such that the surface of each terminal disposed at the outer wall qualified as the mount face of mold resin is parallel to and flush with the outer wall.

The outer lead linking to inner lead1ywhere light emitting diode3is mounted in the present embodiment is set to have an area larger than the area of other leads where light emitting diode3is not mounted. By increasing the volume of the lead where LED3is mounted as much as possible, heat generated at the time of light emission by LED3to cause increase in temperature can be dispersed efficiently. Degradation such as discoloring caused by the heat of the entire device package where LED3is incorporated can be prevented. Furthermore, by rendering the lead where LED3is mounted thick, identification of which of the plurality of leads an LED3is mounted can be readily made. Leads1a,1g,1f,1hand1dshown inFIG. 5or7correspond to the terminals (outer lead) made larger than outer leads1b,1c, and1elinking to an inner lead where LED3is not mounted.

Furthermore, the lead may be formed integrally using ceramic instead of encapsulation resin6. By using ceramic, heat dissipation of the light emitting element can be improved.

Second Embodiment

A second embodiment of the present invention will be described hereinafter with reference toFIG. 9. In the present embodiment, a corner of resin mold portion2at the light-emitting plane side, parallel to placement face1xwhere LED3is mounted, or a corner of the face perpendicular to placement face1x, is formed as a chamfered face2xthat differs in configuration from the other corner. By employing a chamfered face2xfor one corner in the present embodiment taking a different configuration, the directivity of the package of the LED semiconductor light emitting device qualified as a product can be indicated. This facilitates identification of the direction of the LED light emitting element by means of an outer shape recognition device or the like.

Third Embodiment

A third embodiment of the present invention will be described with reference toFIG. 10. In the present embodiment, the exposed area of inner lead1yfrom resin mold portion2where LED3is mounted is set to the minimum area required for chip mounting of LED3and wire bonding, as shown inFIG. 10. By reducing the exposure of inner lead1yand increasing the area covered with resin mold portion2, the take-off efficiency of light emitted from LED3can be improved in the case where the mold resin is white resin having high reflectance to visible light. Furthermore, the bonding area between resin mold portion2and encapsulation resin6is increased, allowing improvement of the adherence therebetween. In the device of the third embodiment, chips of 1-wire light emitting diodes are applied as LED3. The chip of a 1-wire light emitting diode has an electrode provided at the top and bottom of the light emitting diode chip. The electrode at the bottom side is coupled to the frame of inner lead8by means of silver paste or the like to obtain electrical junction. The electrode at the top side is wire bonded with gold wire5to obtain electrical junction with inner lead9.

Fourth Embodiment

A fourth embodiment of the present invention will be described with reference toFIG. 11. The semiconductor light emitting device of the present embodiment shown inFIG. 11corresponds to application to chips of 2-wire light emitting diodes as LED3, as compared to the device of the third embodiment shown inFIG. 10corresponding to chips of 1-wire light emitting diodes.

The 2-wire light emitting diode chip has two gold wires arranged in a configuration including the anode and cathode electrodes at the top of the LED chip, as shown inFIG. 11. The required connection is established exclusively at the top. The anode at the top of the LED chip and inner lead8for the anode are connected by gold wire5. The cathode at the top of the LED chip and inner lead for the cathode are connected by gold wire5.

According to the present embodiment, a semiconductor light emitting device having a frame layout configuration applicable to both a 1-wire chip shown inFIG. 10or a 2-wire chip shown inFIG. 11for establishing connection between the inner lead and LED3can be implemented.

According to each of the embodiments set forth above of the present invention, a mounting method directed to side emission and a mounting method directed to top emission can be carried out selectively using the same components for mounting a light emitting element on a circuit board and the like in the fabrication of a device that requires a light emitting element.