Molded LED indicator

• US 4,152,624 A
• Filed: 03/16/1978
• Issued: 05/01/1979
• Est. Priority Date: 03/16/1978
• Status: Expired due to Term

• Current Assignee: Solutia Incorporated (Eastman Chemical Company)
• Original Assignee: Monsanto Company (Bayer AG)
• Inventors: Knaebel, Vincent J.
• Primary Examiner(s): Demeo, Palmer C.
• Application Number:
  US05/887,382
• Time in Patent Office: 411 Days
• Field of Search: 313/499, 313/512, 357/72
• US Class Current: 313/499
• 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 2224/48465 the other connecting portion not on the bonding area being a wedge bond, i.e. ball-to-wedge, regular stitch
• 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 2924/00014 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 2933/0091 Scattering means in or on the semiconductor body or semiconductor body package H01L33/22 takes precedence
• CPC Class Codes: H01L 33/483 Containers
• CPC Class Codes: H01L 33/52 Encapsulations

Abstract

An LED device of the discrete type having a rectangular light emitting area suited for being arrayed with similar devices in contiguous relationship without optical cross-talk therebetween. An opaque but diffusely reflective housing of the device is molded of synthetic resin material with rectangular integral side walls defining a rectangular body. Their interior surfaces have peripheral upper and lower edges defining a principal cavity having a rectangular top opening. A pair of spaced electrodes extend through a bottom opening and have upper portions extending up into the cavity and there terminating so as to provide an electrode surface area below the top opening having a specularly reflective LED-containing cavity formed therein. An LED die within the electrode cavity is series-connected with the electrodes. Sloped inner walls of the body provide nonspecular reflection of light emitted from the LED. The principal cavity is filled with a synthetic resin material including dispersed light scattering particles. The construction results in a uniformly illuminated light-emitting area of arrayable rectangular format nearly as large as the top of the device.

Claims

1. A solid state electroluminescent device comprising a housing of molded synthetic resin material which is substantially opaque and which is diffusely reflective, the housing comprising integrally joined side walls defining a body for the device, said side walls having interior surfaces having peripheral upper and lower edges defining a principal cavity having a top and a bottom, the top constituting a light-emitting opening of predetermined shape, a pair of spaced electrodes of electrically conductive material extending generally vertically through the bottom, the electrodes each having upper portions extending from the bottom into the principal cavity and terminating within the cavity at upper ends, the upper ends of the electrodes presenting an area in at least one of the electrodes below the top opening and positioned within the cavity, said area including an integral specularly reflective LED-containing cavity having a bottom surface facing said top opening, an LED having a body of semiconductor material, the LED body being positioned within the LED-containing cavity, means for interconnecting the LED body in series-connected electrical circuit relationship with the electrodes, the lower portions of the electrodes extending below the bottom opening to permit connection of a source of electrical power to the electrodes for causing the LED to emit light, the housing side walls having inner surfaces which slope toward the LED-containing cavity, the principal cavity being filled with a light transmissive encapsulant of synthetic resin material having a light-scattering characteristic, the encapsulant surrounding said upper portions of the electrodes, the LED-containing cavity, and the LED, whereby said light-emitting opening emits light of substantially uniform intensity thereacross.

2. A device as set forth in claim 1 wherein the peripheral upper edges of the side walls of said housing are constituted by a thin region of said side walls to provide said light-emitting with dimensions which are nearly as great as corresponding dimensions of the housing when viewed from above the device.

3. A device as set forth in claim 2 wherein said light-emitting opening is of rectangular shape.

4. A device as set forth in claim 1 wherein the electrodes are constituted by a spaced lead pair formed from a metal lead frame strip.

5. A device as set forth in claim 1 wherein said LED comprises a monocrystalline semiconductor material having a substantial isotropic light emission characteristic.

6. A device as set forth in claim 5 wherein said LED comprises GaP.

7. A device as set forth in claim 1 wherein said LED comprises monocrystalline semiconductor material having a substantially Lambertian light emitting characteristic.

8. A device as set forth in claim 7 wherein said LED comprises GaAsP.

9. A solid state electroluminescent device having a light-emitting top area of rectangular format which is suited for being arrayed with other such devices in contiguous relationship without optical cross-talk therebetween, the device comprising a housing of molded synthetic resin material which is substantially opaque and which is diffusely reflective, the housing having four integrally joined side walls defining a generally rectangular body for the device, each of the side walls having exterior surfaces of generally rectangular shape, the interior surfaces of the side walls having peripheral upper and lower edges defining a principal cavity having a top and a bottom, the top being an opening of rectangular shape, a pair of spaced electrodes of electrically conductive material extending generally vertically through the bottom, the electrodes each having upper portions extending from the bottom into the principal cavity and terminating within the cavity at upper ends, the upper ends of the electrodes providing a surface area in at least one of the electrodes which is generally parallel to and below the top opening and which is positioned within the cavity, the surface area including an integral specularly reflective LED-containing cavity formed by the material of the electrodes, the LED-containing cavity having a bottom surface facing said top opening, an LED having a body of semiconductor material, the LED body being positioned within the LED-containing cavity, means for interconnecting the LED body in series-connected electrical circuit relationship with the electrodes, the lower portions of the electrodes extending below the bottom opening to permit connection to a source of electrical power to the electrodes for causing the LED to emit light, the side walls of the housing having in cross section a thickness which increases from peripheral upper edges of the side walls in a direction toward the bottom of the principal cavity to define sloped inner walls of the principal cavity which slope toward the LED-containing cavity, the principal cavity being filled to the top with a light transmissive encapsulant of synthetic resin material, the encapsulant including light-scattering particles dispersed therein, the encapsulant surrounding said upper portions of the electrodes, the LED-containing cavity, and the LED, whereby the opening of the principal cavity provides a light-emitting area of arrayable rectangular format which emits light of intensity which is substantially uniform across the light-emitting area.

10. A device as set forth in claim 9 wherein the bottom of said principal cavity defined by the side walls of said housing is constituted by a bottom opening of rectangular shape, the electrodes extending through the bottom opening.

11. A device as set forth in claim 9 wherein said light-scattering characteristic is constituted by light-scattering centers dispersed in said encapsulant.

12. A device as set forth in claim 9 wherein said encapsulant comprises a transparent epoxy resin, said light-scattering centers comprising borosilicate glass.

13. A device as set forth in claim 12, said LED emitting red light, said encapsulant including a red dye, said borosilicate glass constituting from about 20% to about 50% by weight of said encapsulant.

14. A device as set forth in claim 13, said LED comprising GaAsP.

15. A device as set forth in claim 13 wherein said borosilicate glass is approximately 325 mesh and constitutes about 33% by weight of said encapsulant.

16. A device as set forth in claim 11 wherein said housing comprises a diffusely reflecting material.

17. A device as set forth in claim 11 wherein said diffusely reflecting material comprises a polycarbonate plastic having about 8 to 12% by weight of TiO₂ therein.

18. A device as set forth in claim 9 wherein one of said electrodes is a cathode lead for the LED and the other of said electrodes is an anode lead for the LED, the peripheral lower edge of said housing having one or more protrusions integrally formed thereon adjacent one of said electrodes, such protrusion extending downward from said lower edge and signifying which of said electrodes is the anode lead and which of the electrodes is the cathode lead, such protrusion also spacing said device from a printed circuit board or the like when a device is mounted thereon.

19. A device as set forth in claim 9 wherein there are two of said protrusions adjacent one of the electrodes and one of said protrusions adjacent the other electrode, said three protrusions each extending downward from said lower edge of the housing by the same distance to provide an inherently stable spacing of said device from a printed circuit board or the like when mounted thereon.

20. A device as set forth in claim 9 wherein two of the side walls of said housing which are opposite from each other each have a channel formed in the exterior surface thereof, said channel extending across the width of said housing, said channel being useful for receiving means for retaining said device in a predetermined position for use as an indicator.