Compact proximity sensor suppressing internal reflection

• US 8,748,856 B2
• Filed: 09/23/2011
• Issued: 06/10/2014
• Est. Priority Date: 11/30/2010
• Status: Active Grant

• Current Assignee: STMicroelectronics Limited (STMicroelectronics NV)
• Original Assignee: STMicroelectronics Limited (STMicroelectronics NV)
• Inventors: Campbell, Colin, Findlay, Ewan
• Primary Examiner(s): Ko, Tony
• Application Number:
  US13/242,271
• Publication Number:
  US 20120132793A1
• Time in Patent Office: 991 Days
• Field of Search: 250/221, 250/551, 250/239
• US Class Current: 250/551
• CPC Class Codes: H01L 27/14618 Containers
• 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 2924/1815 Shape
• CPC Class Codes: H01L 31/125 Composite devices with photosensitive elements and electroluminescent elements within one single body
• CPC Class Codes: H01L 31/173 formed in, or on, a common substrate
• CPC Class Codes: H03K 17/941 using an optical detector H03K17/968 takes precedence
• CPC Class Codes: H03K 2017/9455 constructional details of proximity switches using a magnetic detector H03K17/9505
• CPC Class Codes: H03K 2217/94108 making use of reflection

Abstract

A proximity sensor includes a sensor package having an attachment pad with a radiation source and a radiation detector housed within the sensor package. The source and the detector are held in a fixed relation to the attachment pad, and are mounted by one of a direct or indirect attachment to the attachment pad. A portion of the attachment pad is adapted to form a baffle which forms at least part of an optical isolator. The optical isolator is adapted to substantially prevent the internal propagation of radiation between the source and the detector within the sensor package.

Claims

1. A proximity sensor comprising:

a sensor package having an attachment pad;

a radiation source and a radiation detector housed within the sensor package using a substantially transparent over-molding, the source and the detector being held in a fixed relation to the attachment pad, wherein a portion of the attachment pad is adapted to form a baffle which forms at least part of an optical isolator, and wherein the baffle comprises material at least partially cut out from the pad, the optical isolator adapted to substantially prevent internal reflection within the substantially transparent over-molding between the source and the detector, and wherein at least one of the source and detector are one of directly and indirectly mounted on the attachment pad.

2. The proximity sensor of claim 1 wherein the attachment pad is substantially planar.

3. The proximity sensor of claim 2 wherein the baffle extends out from the plane of the pad.

4. The proximity sensor of claim 1 further comprising a bend in the partially cut out material away from the plane of the pad.

5. The proximity sensor of claim 1 wherein the baffle is substantially planar.

6. The proximity sensor of claim 5 wherein the plane of the baffle is perpendicular to the plane of the pad.

7. The proximity sensor of claim 1 wherein the baffle is positioned between the source and the detector.

8. The proximity sensor of claim 1 wherein the substantially transparent over-molding substantially covers the radiation source and the radiation detector.

9. The proximity sensor of claim 1 wherein the over-molding is substantially transparent to the radiation emitted by the radiation source.

10. The proximity sensor of claim 1 wherein the over-molding comprises a lens covering at least one of the radiation source or the radiation detector.

11. The proximity sensor of claim 1 wherein the over-molding comprises a collimating lens positioned over the radiation source for substantially collimating radiation emitted by the radiation source.

12. The proximity sensor of claim 11 wherein the collimating lens comprises a Fresnel lens formed in the over-molding.

13. The proximity sensor of claim 1 wherein the over-molding comprises a collection lens positioned over the radiation detector for focusing incident light onto the radiation detector.

14. The proximity sensor of claim 13 wherein the collection lens comprises a Fresnel lens formed in the over-molding.

15. The proximity sensor of claim 1 wherein the radiation source is a bare die light emitting diode.

16. The proximity sensor of claim 1 wherein the attachment pad is part of a lead frame which forms part of the sensor package.

17. The proximity sensor of claim 1 wherein the radiation detector comprises a plurality of light sensitive pixels.

18. The proximity sensor of claim 17 wherein at least one of the pixels is a single photon avalanche detector.

19. The proximity sensor of claim 1 wherein at least one of the source and the detector are mounted on an interposer which is mounted on the attachment pad.

20. The proximity sensor of claim 19 wherein an upper surface of the interposer to which the one of the source and detector are mounted is angled relative to a plane of the attachment pad.

21. A proximity sensor comprising:

a sensor package having an attachment pad;

a radiation source and a radiation detector housed within the sensor package using an over-molding, the source and the detector being held in a fixed relation to the attachment pad, wherein a portion of the attachment pad is adapted to form a baffle which forms at least part of an optical isolator, the optical isolator adapted to substantially prevent internal reflection between the source and the detector within the sensor package, wherein the over-molding comprises a trench formed above or adjacent the baffle, the trench forming part of the optical isolator, and wherein at least one of the source and detector are one of directly and indirectly mounted on the attachment pad.

22. The proximity sensor of claim 21 wherein the trench comprises first and second walls.

23. The proximity sensor of claim 22 wherein the first and second trench walls are substantially perpendicular to each other.

24. The proximity sensor of claim 21 wherein the bottom of the trench is positioned above an upper surface of the baffle.

25. The proximity sensor of claim 21 wherein the bottom of the trench is adjacent an upper surface of the baffle.

26. The proximity sensor of claim 21 wherein an upper edge of the baffle protrudes through the bottom of the trench.

27. The proximity sensor of claim 26 wherein the first and second trench walls extend from an intermediate portion of the baffle between the plane of the pad and an upper edge of the baffle.

28. A method of manufacturing a radiation sensor, the method comprising:

(a) holding a radiation source and a radiation detector in fixed relation to an attachment pad of a sensor package using a substantially transparent over-molding, at least one of the radiation source and the radiation detector being one of directly and indirectly mounted on the attachment pad; and

(b) adapting a portion of the attachment pad to form a baffle which forms at least part of an optical isolator, wherein the baffle comprises material at least partially cut from the attachment pad, the optical isolator substantially preventing internal reflection within the substantially transparent over-molding between the source and the detector within the sensor package.

29. The method of claim 28 wherein the pad is substantially planar.

33. The method of any of claim 28 further comprising substantially encapsulating the radiation source, radiation detector and attachment pad in an over-molding.

34. The method of claim 33 further comprising forming a trench in the over-molding above or adjacent the baffle, the trench forming part of the optical isolator.

35. The method of claim 28, wherein the baffle further comprising a bend in the partially cut out material away from the plane of the pad.

30. A method of manufacturing a radiation sensor, the method comprising:

(a) holding a radiation source and a radiation detector in fixed relation to an attachment pad of a sensor package, at least one of the radiation source and the radiation detector being one of directly and indirectly mounted on the attachment pad; and

(b) partially cutting out material from the attachment pad to form a baffle which forms at least part of an optical isolator, the optical isolator substantially preventing internal propagation of radiation between the source and the detector within the sensor package.

31. The method of claim 30 wherein step b further comprises bending the cut material away from the attachment pad.

32. A method of manufacturing a radiation sensor, the method comprising:

(a) holding a radiation source and a radiation detector in fixed relation to an attachment pad of a sensor package, at least one of the radiation source and the radiation detector being one of directly and indirectly mounted on the attachment pad; and

(b) partially cutting out material from a portion of the attachment pad adjacent the source; and

(c) bending the partially cut out material upwards towards the detector to form an optical isolator substantially preventing internal propagation of radiation between the source and the detector within the sensor package.