Light emission device

• US 7,935,972 B2
• Filed: 03/11/2008
• Issued: 05/03/2011
• Est. Priority Date: 03/09/2007
• Status: Active Grant

• Current Assignee: Ivoclar Vivadent AG
• Original Assignee: Ivoclar Vivadent AG
• Inventors: Plank, Wolfgang
• Primary Examiner(s): Andújar; Leonardo
• Assistant Examiner(s): HARRISTON, WILLIAM A
• Application Number:
  US12/075,474
• Publication Number:
  US 20080217630A1
• Time in Patent Office: 1,148 Days
• Field of Search: 257/88, 257/89
• US Class Current: 257/89
• CPC Class Codes: H01L 2225/06562 at least one device in the stack being rotated or offset
• CPC Class Codes: H01L 25/0756 Stacked arrangements of devices
• 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

Abstract

The invention relates to a light emission device, comprising at least two light-emitting semiconductor chips and a substrate. At least one first semiconductor chip (12) is fitted on the substrate and a second semiconductor chip (14) is fitted on the first semiconductor chip (12).

Claims

1. A light emission device, comprising at least two light-emitting semiconductor chips and a substrate, wherein at least one first semiconductor chip (12) is fitted on the substrate (66) and a second semiconductor chip (14) is fitted on the first semiconductor chip (12), the emission device further including a third semiconductor chip (16) fitted on the second semiconductor chip (14), and wherein the second semiconductor chip (14) leaves free an upwardly facing area of the first semiconductor chip (12), and wherein at least the left-free area of the first semiconductor chip (12) and at least one area of the second semiconductor chip (14) are light-emitting, wherein the semiconductor chips (12, 14, 16) are connected to one another by means of a reflection-free adhesive layer having a thermal conductivity having approximately the same magnitude as the thermal conductivity of the semiconductor chips (12, 14, 16).

2. The light emission device as claimed in claim 1 wherein the first semiconductor chip (12) is applied to an electrically at least semiconducting substrate (66), and wherein an electrical connection area of the first semiconductor chip (12) is formed by the substrate.

3. The light emission device as claimed in claim 1, wherein lateral light emission areas (50, 52, 56, 58) extend laterally at the chips, which are offset with respect to one another.

4. The light emission device as claimed in claim 1, wherein a lateral light emission area (50, 52) of the second semiconductor chip (14) extends, relative to a lateral light emission area (56, 58) of the first semiconductor chip (12), in a manner shifted toward the center of the semiconductor chip (14).

5. The light emission device as claimed in claim 1, wherein the semiconductor chips (12, 14, 16) are constructed essentially pyramidally with respect to one another.

6. The light emission device as claimed in claim 1, the semiconductor chips (12, 14, 16) are at least partly transmissive to emitted radiation.

7. The light emission device as claimed in claim 1, wherein the light emission device has a reflector fitted below the first semiconductor chip (12), and wherein no reflector is provided between the first, a second and the third semiconductor chip (16).

8. The light emission device as claimed in claim 1, wherein a reflector is fitted below the first semiconductor chip (12), which extends laterally beyond the semiconductor chip.

9. The light emission device as claimed in claim 1, wherein the semiconductor chips (12, 14, 16) which emit light have different spectral wavelengths.

10. The light emission device as claimed in claim 1, wherein the semiconductor chips (12, 14, 16) are at least partly electrically connected in series with one another.

12. The light emission device as claimed in claim 1, wherein the semiconductor chips (12, 14, 16) have at least one electrical connection zone on their top side in the region of the left-free area.

13. The light emission device as claimed in claim 1, wherein the substrate (66) carries a reflection layer.

14. The light emission device as claimed in claim 1, wherein the third semiconductor chip (16) is smaller than the first semiconductor chip (12), the size difference corresponding approximately to twice the thickness of each semiconductor chip (12, 14, 16).

15. The light emission device as claimed in claim 1, wherein semiconductor chips (12, 14, 16) fitted one on top of another are rotated relative to one another at an angle of 45°

.

16. The light emission device as claimed in claim 1, wherein the substrate has a projection, the dimensions of which essentially correspond to the dimensions of the first semiconductor chip (12) and on which the first semiconductor chip (12) is fitted.

17. The light emission device as claimed in claim 1, wherein a ring reflector (80) surrounds the semiconductor chips (12, 14, 16) fitted one on top of another, the orientation of which reflector is oblique or parabolic in a manner known per se and which reflector reflects the lateral light emission of the semiconductor chips (12, 14, 16) toward the front.

18. The light emission device as claimed in claim 1, wherein a printed circuit board is provided, which printed circuit board has free areas, and electrical connection areas (26, 28, 20) are adjacent to the free areas (20, 22, 24) to which areas they are electrically connected by means of bonding wires.

19. The light emission device as claimed in claim 18, wherein the printed circuit board extends laterally alongside the semiconductor chips (12, 14, 16) in a manner at least partly surrounding said semiconductor chips, and runs with conductor tracks below a ring reflector (80).

20. The light emission device as claimed in claim 1 wherein the thickness of the adhesive layer is less than 100 μ

m.

11. A light emission device, comprising at least two light-emitting semiconductor chips and a substrate, wherein at least one first semiconductor chip (12) is fitted on the substrate (66) and a second semiconductor chip (14) is fitted on the first semiconductor chip (12), the emission device further including a third semiconductor chip (16) fitted on the second semiconductor chip (14), and wherein the second semiconductor chip (14) leaves free an upwardly facing area of the first semiconductor chip (12), and wherein at least the left-free area of the first semiconductor chip (12) and at least one area of the second semiconductor chip (14) are light-emitting, wherein the semiconductor chips (12, 14, 16) are at least partly electrically connected in parallel with one another.