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Plastic-encapsulated-semiconductor-light-emitting-device-with-a-cover-of-fluorescent-particles

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Plastic encapsulated semiconductor light emitting device with a cover of fluorescent particles

Details

Inventors: Sano, Takeshi; Kawae, Hiroyuki;
Assignee: Sanken Electric Co., Ltd. (Saitama-pref., JP)
Primary Examiner: Chaudhuri; Olik
Assistant Examiner: Trinh; Hoa B.
Attorney, Agent or Firm: Bachman & LaPointe, P.C.

A plastic encapsulated semiconductor light emitting device comprises a plurality of leads 1, 2, one of which is formed with a dished portion 5; a semiconductor light emitting element 3 attached on a bottom surface 6 of the dished portion 5 for electrical connection of the light emitting element across the plurality of leads 1, 2; a plastic encapsulant 9 for sealing each end of the leads 1, 2, and the semiconductor light emitting element 3; a light-permeating cover 20 attached to an outer surface of the plastic encapsulant 9; and fluorescent particles 16 contained in the cover 20. As the number of fluorescent particles 16 at the vertex of the upper portion 22 is larger than that of the fluorescent particles 16 in the cylindrical lower portion 21, the semiconductor light emitting device can emit light with the nearly uniform light wavelength at any angular distance from the central axis of the plastic encapslant 9.

DETAILED DESCRIPTION The plastic encapsulated semiconductor light emitting device according to the present invention comprises a plurality of leads 1, 2; at least one of which is formed with a dished portion 5; a semiconductor light emitting element 3 attached on the bottom surface of the dished portion 5 for electrical connection of the light emitting element 3 across the leads 1, 2; a plastic encapsulant 9 for sealing each one end of the leads 1, 2 and the semiconductor light emitting element 3; and a light-permeating cover 20 preferably removably attached to an outer surface of the plastic encapsulant 9 with fluorescent particles 16 contained in the cover 20.
The plastic encapsulant 9 comprises a sealing portion 10 formed into a substantially cylindrical shape, and a lens portion 11 formed into a substantially hemispherical shape integral with the sealing portion 10.
The cover 20 comprises a lower portion 21 formed into a substantially cylindrical shape matched to the sealing portion 10 of the plastic encapsulant 9, and an upper portion 22 formed into a substantially hemispherical shape integral with the lower portion 21 and matched to the lens portion 11 of the plastic encapsulant 9.
A blue light irradiated from the semiconductor light emitting element 3 passes through the plastic encapsulant 9 and reaches the fluorescent particles 16 in the cover 20 to activate or excite the fluorescent particles 16 for wavelength-conversion of the light emitted from the semiconductor light emitting element 3.
As a result, the fluorescent particles 16 generates a white light from the cover 20 with its wavelength different from that of the light from the semiconductor light emitting element 3.
The number of the fluorescent particles 16 is greater in the upper portion 22 of the cover 20 than in the lower portion 21 to produce the substantially homogeneous white light from any outer surface of the cover 20.
As the semiconductor light emitting element 3 emits intense light of the extremely sharp directivity at the tip of the lens portion 11 of the plastic encapsulant 9, a greater number of fluorescent particles 16 are positioned in the cover 20 near the tip of the lens portion 11 of the plastic encapsulant 9 to increase the amount of light impinging on the fluorescent particles 16

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