Light emitting device comprising led chip

• US 20040012958A1
• Filed: 05/07/2003
• Published: 01/22/2004
• Est. Priority Date: 04/23/2001
• Status: Abandoned Application

• Current Assignee: Matsushita Electric Works Ltd (Panasonic Holdings Corporation)
• Original Assignee: Matsushita Electric Works Ltd (Panasonic Holdings Corporation)
• Inventors: Hashimoto, Takuma, Kuzuhara, Ikko, Takami, Sigenari, Sugimoto, Masaru, Kimura, Hideyoshi, Shiohama, Eiji
• Application Number:
  US10/415,653
• Publication Number:
  US 20040012958A1
• Time in Patent Office: Days
• US Class Current: 362/241
• CPC Class Codes: H01L 2224/05001 Internal layers
• CPC Class Codes: H01L 2224/05023 the whole internal layer protruding from the surface
• CPC Class Codes: H01L 2224/05099 Material
• CPC Class Codes: H01L 2224/05568 the whole external layer protruding from the surface
• CPC Class Codes: H01L 2224/05599 Material
• CPC Class Codes: H01L 2224/06102 the bonding areas being at different heights
• CPC Class Codes: H01L 2224/16 of an individual bump connector
• CPC Class Codes: H01L 2224/1703 Bump connectors having different sizes, e.g. different diameters, heights or widths
• CPC Class Codes: H01L 24/05 of an individual bonding area
• CPC Class Codes: H01L 24/06 of a plurality of bonding areas
• 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 33/20 with a particular shape, e.g. curved or truncated substrate
• CPC Class Codes: H01L 33/22 Roughened surfaces, e.g. at the interface between epitaxial layers
• CPC Class Codes: H01L 33/38 with a particular shape
• CPC Class Codes: H01L 33/405 Reflective materials
• CPC Class Codes: H01L 33/44 characterised by the coatings, e.g. passivation layer or anti-reflective coating
• CPC Class Codes: H01L 33/46 Reflective coating, e.g. dielectric Bragg reflector
• CPC Class Codes: H01L 33/60 Reflective elements
• CPC Class Codes: H01L 33/62 Arrangements for conducting electric current to or from the semiconductor body, e.g. lead-frames, wire-bonds or solder balls
• CPC Class Codes: H01L 33/642 characterized by the shape
• CPC Class Codes: H01L 33/647 : the elements conducting electric current to or from the semiconductor body

Abstract

A light emitting device comprising an LED chip including an n-type semiconductor layer (3) formed on a light-transmissive substrate (2), a p-type semiconductor layer (5) formed on the n-type semiconductor layer (3), and electrodes (6 and 7) that are provided at the side where the semiconductor layers are formed and that are connected to the respective layers. The LED chip is mounted face down on a mounting board (8). The electrodes (6 and 7) are configured and arranged to be flat so that the whole light-emitting surface of the LED chip (1) can emit light with a substantially uniform intensity. At least one of the electrodes functions as a light reflector. The electrodes have respective feeding points (15 and 16). The electrode provided on the semiconductor layer adjacent to the light-transmissive substrate (2) is tapered with distance from its feeding point. This structure can provide increased light emission area in the LED chip (1), thus enhancing the luminous efficiency and the light extraction efficiency.

Claims

1. A light emitting device comprising an LED chip, the LED chip including a light-transmissive substrate, a first semiconductor layer formed on the light-transmissive substrate, a second semiconductor layer formed on the first semiconductor layer, and first and second electrodes that are provided at a side where the semiconductor layers are formed and that are connected to the first and second semiconductor layers respectively, the LED chip being mounted face down on a mounting board,

wherein the first and second electrodes are configured and arranged to be flat so that the whole light-emitting surface of the LED chip can emit light with a substantially uniform intensity;

wherein at least one of the first and second electrodes is configured so as to function as a light reflector; and

wherein the first and second electrodes have respective feeding points, the first electrode provided on the first semiconductor layer adjacent to the light-transmissive substrate being tapered with distance from the feeding point on the first electrode.

2. The light emitting device according to claim 1, wherein a plurality of first electrodes and a plurality of second electrodes are provided on the respective first and second semiconductor layers.

3. The light emitting device according to claim 2, wherein the plurality of first and second electrodes are arranged alternately in parallel with each other at the side where the semiconductor layers are formed.

4. The light emitting device according to claim 3, wherein the electrodes are arranged in parallel with each other at substantially regular intervals.

5. The light emitting device according to claim 3, wherein the first and second electrodes are configured in a comblike structure.

6. The light emitting device according to claim 1, further comprising a light reflecting member provided, on a surface of the LED chip, separately from the electrodes.

7. The light emitting device according to claim 1, wherein either a surface of the mounting board that faces the LED chip or a filler applied to a space between the LED chip and the mounting board functions as a light reflector.

8. The light emitting device according to claim 1,

wherein the mounting board is a circuit board including a conductive plate having at least one surface provided with an insulating layer and an electrically conductive layer provided over the conductive plate with the insulating layer therebetween;

and

wherein at least one of the electrodes of the LED chip is electrically connected to the electrically conductive layer by the face down mounting, and a heat transfer medium that is higher in thermal conductivity than the insulating layer is disposed between the LED chip and the conductive plate.

9. The light emitting device according to claim 8, wherein each of the electrodes of the LED chip is connected to a respective electrically conductive layer.

10. The light emitting device according to claim 8, wherein the heat transfer medium is formed integral with the conductive plate.

11. The light emitting device according to claim 8, wherein the heat transfer medium is made of a metal.

12. The light emitting device according to claim 8, wherein the electrically conductive layer is partially extended to the surface of the circuit board opposite the LED chip, for connection to an external circuit.

13. The light emitting device according to claim 1, wherein the light-transmissive substrate of the LED chip has a roughened surface.

14. The light emitting device according to claim 13, wherein side surfaces of the light-transmissive substrate of the LED chip are cut at an oblique angle and serve as a mirror.