Light emitting device
A light emitting device includes: a ceramic substrate; a plurality of LED chips; a printed resistor(s) connected in parallel with the plurality of LED chips; a dam resin made of a resin having a low optical transmittance; a fluorescent-material-containing resin layer; and an anode-side electrode and a cathode-side electrode, (a) which are provided on a primary surface of the ceramic substrate so as to face each other along a first direction on the primary surface and (b) which are disposed below at least one of the dam resin and the fluorescent-material-containing resin layer. With the configuration in which a plurality of LEDs, which are connected in a series-parallel connection, are provided on a substrate, it is possible to provide a light emitting device which can achieve restraining of luminance unevenness and an improvement in luminous efficiency.
1. A light emitting device comprising:
a substrate;
a plurality of LED chips positioned around a center of a primary surface of the substrate;
a resin frame formed on the primary surface of said substrate and provided annularly so as to surround a mounting area in which said plurality of LED chips are provided;
an anode-side electrode land and a cathode-side electrode land which are electrodes to be connected to an external voltage supply of said light emitting device, the anode-side electrode land and the cathode-side electrode land being provided on the primary surface of the substrate and outside said resin frame; and
an electrode wiring pattern formed on the primary surface of said substrate including (i) a first anode pattern and (ii) a first cathode pattern, the first anode pattern and the first cathode pattern electrically connecting the plurality of LED chips to the anode-side electrode land and the cathode-side electrode land,
the plurality of LED chips including a first chip, a second chip, a third chip, and a fourth chip,
the first chip, the second chip, the third chip, and the fourth chip being electrically connected in series so as to constitute each of at least one series circuit,
the light emitting device further comprising:
a first wire connecting an anode electrode of the first chip and the first anode pattern directly to each other;
a second wire connecting a cathode electrode of the first chip and an anode electrode of the second chip directly to each other;
a third wire connecting a cathode electrode of the third chip and an anode electrode of the fourth chip directly to each other; and
a fourth wire connecting a cathode electrode of the fourth chip and the first cathode pattern directly to each other,
the first wire having a length larger than that of the second wire,
the fourth wire having a length larger than that of the third wire.
2. The light emitting device as set forth in claim 1 , wherein the first anode pattern is provided on a portion under said resin frame, and the first cathode pattern is provided on the other portion under said resin frame.
3. The light emitting device as set forth in claim 1 , wherein said substrate has a rectangular outer shape in a top view.
4. The light emitting device as set forth in claim 3 , wherein the cathode-side electrode land is provided near a corner of the primary surface of the substrate, and the corner is diagonally opposite a corner where the anode-side electrode land is provided.
5. The light emitting device as set forth in claim 3 , wherein the anode-side electrode land and the cathode-side electrode land are disposed diagonally on the primary surface of the substrate.
6. The light emitting device as set forth in claim 1 , further comprising a fluorescent-material-containing resin layer provided attaching to an inner side of the resin frame and covering the plurality of LED chips.
7. The light emitting device as set forth in claim 6 , wherein the fluorescent-material-containing resin layer is provided along a shape of the resin frame so as to have a circular shape in the top view.
8. The light emitting device as set forth in claim 1 , wherein said anode-side electrode land has a width larger than that of the first anode pattern, and said cathode-side electrode land has a width larger than that of the first cathode pattern.
9. The light emitting device as set forth in claim 1 , wherein said substrate comprises ceramic, and said plurality of LED chips are attached to the primary surface of said substrate via a resin adhesive agent comprising silicone.
10. The light emitting device as set forth in claim 1 , wherein the electrode wiring pattern further includes (iii) a second anode pattern connected between said anode-side electrode land and the first anode pattern and (iv) a second cathode pattern connected between said cathode-side electrode land and the first cathode pattern.
11. The light emitting device as set forth in claim 10 , further comprising protection films provided on the second anode and cathode patterns.
12. The light emitting device as set forth in claim 1 , wherein each of the first wire, the second wire, the third wire, and the fourth wire is a metal wire formed by wire bonding.
13. The light emitting device as set forth in claim 1 , wherein the at least one series circuit is a plurality of series circuits,
the plurality of series circuits being connected in parallel with each other.
14. The light emitting device as set forth in claim 1 , wherein the electrode wiring pattern further includes (v) a third anode pattern extending from the anode-side electrode land to a portion under said resin frame, and (vi) a third cathode pattern extending from the cathode-side electrode land to the other portion under the resin frame.
15. The light emitting device as set forth in claim 14 , further comprising protection films provided on the third anode and cathode patterns.