Low stress light-emitting diode mounting package

• US 4,920,404 A
• Filed: 05/12/1989
• Issued: 04/24/1990
• Est. Priority Date: 05/12/1989
• Status: Expired due to Term

• Current Assignee: Philips Lumileds Lighting Company LLC (Apollo Global Management, Inc.)
• Original Assignee: Hewlett-Packard Company (HP Inc.)
• Inventors: Shrimali, Dinesh C., Steranka, Frank M., McLeod, Cheryl L.
• Primary Examiner(s): Edlow, Martin H.
• Assistant Examiner(s): MONIN, DONALD L JR
• Application Number:
  US07/351,194
• Time in Patent Office: 347 Days
• Field of Search: 357/17, 357/72, 357/70, 357/55, 174/52.2, 437/224, 437/209
• US Class Current: 257/98
• 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 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• CPC Class Codes: H01L 33/54 having a particular shape
• 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

Abstract

A light-emitting diode is mounted in the bottom of a cavity in a metal lead and the assembly is potted in a transparent plastic material. The walls of the cavity surround the sides of the light-emitting diode in sufficiently close proximity to effectively shield the light-emitting diode from thermal expansion stresses from the plastic potting material which would induce light output degradation. Such a cavity may be a right-circular cylinder with a diameter less than 75 micrometers greater than the largest transverse dimension of the light-emitting diode. The front face of the light-emitting diode may be flush or beneath the face of the metal lead for minimizing stress. The cavity may be deep enough that the front face of the light-emitting diode is closer to the bottom of the cavity than to its open end. The front face may protrude beyond the open end of the cavity and be surrounded by a reflective surface. The edges of the front face of the light-emitting diode may be beveled for minimizing stress.

Claims

1. A light-emitting diode package comprising:

a metal lead;

a cavity having walls, a bottom and an open end in the metal lead;

a light-emitting diode having sides and a front face in the bottom of the cavity in electrical contact with the metal lead; and

a rigid plastic potting material between the light-emitting diode and the walls of the cavity, and

means for minimizing light degradation of the light-emitting diode comprising a sufficiently small clearance between the sides of the light-emitting diode and the walls of the cavity that the amount of plastic potting material between the sides of the light-emitting diode and the walls is insufficient for applying light degrading stresses on the light-emitting diode due to differential thermal expansion.

4. A package as recited in claim 1 wherein at least a portion of the wall of the cavity is in the form of a curved reflector for projecting light from the sides of the light-emitting diode in a direction generally perpendicular to the front face of the light-emitting diode.

7. A package as recited in claim 1 wherein the front face of the light-emitting diode is closer to the bottom of the cavity than to a face of the lead adjacent to the open end of the cavity.

2. A light-emitting diode package comprising:

a metal lead;

a cavity having walls, a bottom and an open end in the metal lead;

a light-emitting diode having a sides and a front face in the bottom of the cavity in electrical contact with the metal lead, a side wall of the cavity adjacent to at least the bottom of the cavity being substantially parallel to the side faces of the light-emitting diode; and

a plastic potting material between the light-emitting diode and the walls of the cavity, the amount of plastic potting material being insufficient to apply light degrading stresses on the light-emitting diode due to differential thermal expansion.

3. A package as recited in claim 2 wherein a portion of the wall of the cavity is in the form of a curved reflector for projecting light from the sides of the light emitting diode in a direction generally perpendicular to the front face of the light-emitting diode.

6. A package as recited in claim 2 wherein the front face of the light-emitting diode does not protrude above a face of the lead adjacent to the open end of the cavity.

10. A package as recited in claim 2 wherein edges of the light-emitting diode around the front face are beveled for relieving stress.

5. A light-emitting diode package comprising:

a metal lead;

a cavity having walls, a bottom and a open end in the metal lead;

a light-emitting diode having sides and a front face in the bottom of the cavity in electrical contact with the metal lead;

wherein the cavity is round and the diameter of the cavity is less than 75 micrometers greater than the largest transverse dimension of the light-emitting diode; and

a plastic potting material between the light-emitting diode and the walls of the cavity, the amount of plastic potting material being insufficient to apply light degrading stresses on the light-emitting diode due to differential thermal expansion.

8. A light-emitting diode package comprising:

a metal lead;

a cavity having walls a bottom and a open end in the metal lead;

a light-emitting diode having sides and a front face in the bottom of the cavity in electrical contact with the metal lead; and

a rigid plastic potting material outside the cavity and between the light-emitting diode and the walls of the cavity; and

means for shielding the light-emitting diode from light degrading differential thermal expansion stresses from potting material outside the cavity comprising a sufficiently deep cavity that the front face of the light-emitting diode is a sufficient distance below the face of the lead adjacent to the cavity that stresses from plastic potting material outside the cavity are not effectively coupled into the cavity to the depth of the front face of the light-emitting diode.

9. A package as recited in claim 8 wherein the thickness of the light-emitting diode is no more than forty percent of the depth of the cavity.

11. A light-emitting diode package comprising:

a metal lead;

a cavity having walls, a bottom and an open end;

a light-emitting diode having sides and a front face mounted on the metal lead;

a transparent plastic potting material surrounding the lead and light-emitting diode; and

means for effectively shielding the light-emitting diode front thermal expansion stresses applied by the plastic potting material on the light-emitting diode comprising a cavity in the lead having a wall surrounding the sides of the light-emitting diode in sufficiently close proximity to the sides of the light-emitting diode for effectively shielding the light-emitting diode from thermal expansion stresses applied by the plastic potting material on the light-emitting diode.

12. A package as recited in claim 11 wherein a side wall of the cavity is substantially parallel to the side faces of the light-emitting diode.

13. A package as recited in claim 11 wherein a portion of the wall of the cavity slopes away from the light-emitting diode for projecting light from the sides of the light-emitting diode in a direction generally perpendicular to the front face of the light-emitting diode.

14. A package as recited in claim 11 wherein the bottom of the cavity is round and the light-emitting diode is square, and wherein the diameter of the bottom of the cavity is less than 75 micrometers greater than a diagonal of the light-emitting diode.

15. A package as recited in claim 11 wherein the front face of the light-emitting diode does not protrude above the face of the lead adjacent to the open end of the cavity.

16. A package as recited in claim 15 wherein the front face of the light-emitting diode is recessed below a face of the lead adjacent to the open end of the cavity.

17. A package as recited in claim 16 wherein the front face, of the light-emitting diode is recessed below a face of the lead adjacent to the open end of the cavity at, least sixty percent of the cavity'"'"'s depth.

18. A package as recited in claim 11 wherein edges of the light-emitting diode around the front face are beveled for relieving stress.

19. A light-emitting diode package comprising:

a metal lead;

a light-emitting diode having sides and a front face mounted on the metal lead;

a rigid transparent plastic potting material surrounding the lead and light-emitting diode;

a cavity have walls, a bottom and an open end in the lead; and

means for effectively shielding the light-emitting diode from thermal expansion stresses exerted by the plastic potting material outside of the cavity comprising a cavity wall extending a sufficient distance beyond the front face of the light-emitting diode for effectively shielding the light-emitting diode from thermal expansion stresses exerted by the plastic potting material outside of the cavity.

20. A package as recited in claim 19 wherein a portion of the wall of the cavity slopes away from the light-emitting diode for projecting light from the sides of the light-emitting diode in a direction generally perpendicular to the front face of the light-emitting diode.

21. A package as recited in claim 19 wherein the front face of the light-emitting diode is recessed below the face of the lead adjacent to the open end of the cavity at least sixty percent of the depth of the cavity.

22. A package as recited in claim 19 wherein the front face of the light-emitting diode is closer to the bottom of the cavity than to the face of the lead adjacent to the open end of the cavity.

23. A light emitting diode package comprising:

a metal lead;

a substantially cylindrical cavity having walls, a bottom and an open end in the metal lead;

a light-emitting diode having sides and a front face in the bottom of the cylindrical cavity in electrical contact with the metal lead, at least a major portion of the light-emitting diode being below the open end of the cavity; and

a layer of rigid transparent plastic potting material surrounding the lead and between the wall of the cylindrical cavity and the sides of the light-emitting diode, the amount of plastic potting material being insufficient to apply light degrading stresses on the light-emitting diode due to differential thermal expansion.

24. A package as recited in claim 23 further comprising a wall portion diverging away from the open end of the cavity for reflecting light from the light-emitting diode in a direction generally perpendicular to the front face of the light-emitting diode.

25. A package as recited in claim 23 wherein the cavity comprises a right circular cylinder.

26. A package as recited in claim 23 wherein the entire light-emitting diode is below the open end of the cavity.

27. A package as recited in claim 23 wherein the light-emitting junction of the light-emitting diode is below the front face of the light-emitting diode and the light-emitting diode extends beyond the open end of the cavity a distance in the same order as the distance of the junction below the front face.

28. A package as recited in claim 23 wherein the bottom of the cavity is round and the light-emitting diode is square, and wherein the diameter of the bottom of the cavity is less than 75 micrometers greater than a diagonal of the light-emitting diode.

29. A package as recited in claim 23 wherein edges of the light-emitting diode around the front face are beveled for relieving stress.

30. A light-emitting diode package comprising:

a metal lead;

a cavity having walls, a bottom and an open end in the metal lead;

a light-emitting diode having sides in the bottom of the cavity in electrical contact with the metal lead, at least a major portion of the light-emitting diode being below the open end of the cavity; and

a transparent plastic potting material surrounding the light-emitting diode in the cavity; and

wherein

the walls of the cavity are within no more than 75 micrometers of the sides of the light-emitting diode.