Light emitting diode and process for producing the same

• US 20050231092A1
• Filed: 04/24/2003
• Published: 10/20/2005
• Est. Priority Date: 04/25/2002
• Status: Active Grant

• Current Assignee: Opto-Device Co., Ltd., Pearl LAMP Works Limited
• Original Assignee: Tabuchi Electric Company Limited
• Inventors: Yamazaki, Shigeru
• Granted Patent: US 7,339,201 B2
• Time in Patent Office: Days
• US Class Current: 313/312
• CPC Class Codes: H01L 2224/32245 the item being metallic
• CPC Class Codes: H01L 2224/45144 Gold (Au) as principal constituent
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2224/48247 connecting the wire to a bond pad of the item
• CPC Class Codes: H01L 2224/73265 Layer and wire connectors
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/00012 Relevant to the scope of the group, the symbol of which is combined with the symbol of this group
• CPC Class Codes: H01L 2924/00014 the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details
• CPC Class Codes: H01L 2924/181 Encapsulation
• CPC Class Codes: H01L 33/54 having a particular shape
• CPC Class Codes: H01L 33/60 Reflective elements

Abstract

A light emitting diode includes a casing having a concave surface, a reflecting surface formed by depositing a metallic layer on a concave surface thereof, and a lead having a light emitting element fitted thereto so as to confront the reflecting surface. A cationic polymerization type transparent epoxy resin is filled within a cavity of the casing having the concave surface, and the resin is hardened while the resin, the reflecting surface and the casing form a sandwich structure. With this construction, the light emitting diode is provided, in which neither wrinkling nor cracking occur in the reflecting surface. In addition, there is no possibility of the reflecting surface being flawed during the handling and transportation. Also, even in a reflow furnace operation in which a soldering is carried out, thermal deformation including formation of wrinkling and cracking in the reflecting surface can be completely avoided. Yet, since the cationic polymerization type transparent epoxy resin has so low a rate of shrinkage after hardening that the planarity of a light radiating surface after the hardening can be maintained and, for this reason, rays of light emerging from the light radiating surface can be emitted to the outside without being refracted at the interface between the light radiating surface and the outside.

Claims

1. A light emitting diode comprising a casing having a concave cavity defined therein, a reflecting surface formed by depositing a metallic layer on a surface defining the concave cavity, and a lead having a light emitting element fitted thereto so as to confront the reflecting surface,

characterized in that a cationic polymerization type transparent epoxy resin is filled within the concave cavity of the casing, and

in that the cationic polymerization type transparent resin is cured while a sandwich structure is formed by the cationic polymerization transparent epoxy resin, the reflecting surface and the casing.

2. The light emitting diode as claimed in claim 1, characterized in that the lead is engaged in a groove formed on an upper end face of the casing, a light curable epoxy resin is filled in the groove, where the lead is engaged, to a level flush with the upper end face of the casing, and the light curable epoxy resin is cured by irradiation of ultraviolet rays of light to fix the lead in the groove in the casing, and further, the cationic polymerization transparent epoxy resin is filled to a level flush with the upper end face of the casing.

3. The light emitting diode as claimed in claim 2, characterized in that the casing is made of a heat resistant resin selected from the group consisting of a polycarbonate resin, PPC alloyed resin, and a polyether ether ketone resin.

4. The light emitting diode as claimed in claim 3, characterized in that the casing is made of a resin containing glass fibers, and in that an undercoat layer of a heat resistant epoxy resin is formed on the surface defining the concave cavity in the casing, and further, a metallic reflecting surface is formed on the undercoat layer.

5. The light emitting diode as claimed in claim 1, characterized in that a frame for covering the upper end face of the casing is provided, and in that the frame has a projection for filling up a gap between an upper surface of the lead, engaged in the groove, and the frame, the projection filling up the gap when the frame is mounted onto the casing.

6. The light emitting diode as claimed in claim 5, characterized in that the casing is made of a heat resistant resin selected from the group consisting of a polycarbonate resin, PPC alloyed resin, and a polyether ether ketone resin.

7. The light emitting diode as claimed in claim 6, characterized in that the casing is made of a resin containing glass fibers, and in that an undercoat layer of a heat resistant epoxy resin is formed on the surface defining the concave cavity in the casing, and further, a metallic reflecting surface is formed on the undercoat layer.

8. A method of making a light emitting diode, comprising a step of forming a casing having a concave cavity defined therein, a step of forming a metallic layer in the concave cavity to define a reflecting surface, and a step of forming a lead having a light emitting element fitted thereto so as to confront the reflecting surface, characterized in that there is provided:

a step of filling a cationic polymerization type transparent epoxy resin within the concave cavity of the casing, and

a step of curing the cationic polymerization type transparent epoxy resin while the cationic polymerization transparent epoxy resin, the reflecting surface and the casing are formed in a sandwich structure.

9. The method of making the light emitting diode as claimed in claim 8, characterized in that the step of filling the cationic polymerization type transparent epoxy resin includes:

a step of engaging the lead in a groove formed in an upper end face of the casing;

a step of filling a light curable epoxy resin in the groove, in which the lead is engaged, to the upper end face of the casing, irradiating the light curable epoxy resin with ultraviolet rays of light to thereby fix the lead in the groove in the casing.

a step of filling the cationic polymerization transparent epoxy resin to a level flush with the upper end face of the casing.

10. The method of making the light emitting diode as claimed in claim 9, characterized in that during the step of forming the casing having the concave cavity, a heat resistant resin selected from the group consisting of a polycarbonate resin, a PPC alloyed resin, and polyether ether ketone is used as material for the casing.

11. The method of making the light emitting diode as claimed in claim 10, characterized in that the step of forming the casing having the concave cavity defined therein further includes a step of, after glass fibers have been contained in the resin and an undercoat layer of a heat resistant epoxy resin has been formed on the surface defining the concave cavity in the casing, forming a metallic reflecting surface on the undercoat layer.

12. The method of making the light emitting diode as claimed in claim 8, characterized in that the filling step comprises:

a step of engaging the lead in a groove formed in an upper end face of the casing;

a step of covering the casing with a frame for covering the upper end face of the casing and having a projection at a location aligned with the groove in the casing; and

a step of filling the cationic polymerization type transparent resin to a level flush with the upper end face of the casing.

13. The method of making the light emitting diode as claimed in claim 12, characterized in that during the step of forming the casing having the concave cavity, a heat resistant resin selected from the group consisting of a polycarbonate resin, a PPC alloyed resin, and polyether ether ketone is used as material for the casing.

14. The method of making the light emitting diode as claimed in claim 13, characterized in that the step of forming the casing having the concave cavity defined therein further includes a step of, after glass fibers have been contained in the resin and an undercoat layer of a heat resistant epoxy resin has been formed on the surface defining the concave cavity in the casing, forming a metallic reflecting surface on the undercoat layer.