Optical sensing element arrangement with integral package
A sensor assembly is disclosed that includes a hollow casing having a radiation entrance opening. A radiation-transmissive optic is at the radiation entrance opening. A substrate is inside and sealed against the hollow casing. An optical sensing element is coupled to the substrate and configured to sense radiation that has passed through the radiation-transmissive optic. A method of manufacturing the sensor assembly also is disclosed.
1. A sensor assembly comprising:
a hollow casing having a radiation entrance opening;
a radiation-transmissive optic at the radiation entrance opening,
a substrate inside and sealed against an inner surface of the hollow casing; and
an optical sensing element coupled to the substrate and configured to sense radiation that has passed through the radiation-transmissive optic,
wherein the hollow casing is a single structure that extends from a top of the hollow casing around an edge of the radiation-transmissive optic down to a bottom of the portion of the hollow casing that contains a potting compound, and
wherein a portion of the hollow casing that is adhered to an upper surface of the substrate thermally expands and contracts with a portion of the hollow casing that is adhered to an edge of the substrate.
2. The sensor assembly of claim 1 wherein the hollow casing, the radiation-transmissive optic and the substrate cooperatively define an inner compartment.
3. The sensor assembly of claim 2 further comprising:
an inert gas contained within the inner compartment.
4. The sensor assembly of claim 1 further comprising:
a potting compound covering a side of the substrate opposite the optical sensing element.
5. The sensor assembly of claim 1 further comprising:
an electrical connector coupled to electrical circuitry on the substrate and extended through a potting compound.
6. The sensor assembly of claim 1 wherein the hollow casing has an inner surface with a first flange and the substrate abuts the first flange.
7. The sensor assembly of claim 6 further comprising sealant between the first flange and the substrate.
8. The sensor assembly of clam 7 further comprising sealant between an edge of the substrate and an inner surface of the hollow casing proximate the first flange.
9. The sensor assembly of claim 8 wherein a surface of the first flange that the substrate abuts is substantially perpendicular to the inner surface of the hollow casing proximate the first flange.
10. The sensor assembly of claim 1 wherein the hollow casing has an inner surface with a second flange at or near the radiation entrance window and the radiation-transmissive optic abuts the second flange.
11. The sensor assembly of claim 10 further comprising sealant between the radiation-transmissive optic and the second flange as well as between the radiation-transmissive optic and an inner surface of the hollow casing proximate the second flange.
12. The sensor assembly of claim 11 wherein a surface of the second flange that the radiation-transmissive optic abuts is substantially perpendicular to the inner surface of the hollow casing proximate the second flange.
13. The sensor assembly of claim 1 further comprising:
a microcontroller, one or more capacitors, and signal processing circuitry physically coupled to the substrate.
14. The sensor assembly of claim 13 wherein at least one of the microcontroller, the one or more capacitors, and the signal processing circuitry is physically coupled to an opposite side of the substrate from the optical sensing element.
15. The sensor assembly of claim 1 wherein the substrate is a printed circuit board.
16. The sensor assembly of claim 1 wherein the optical sensing element is a thermopile sensor array.
17. The sensor assembly of claim 1 wherein a portion of the hollow casing that is adhered to a lower surface of the radiation-transmissive optic thermally expands or contracts with a portion of the hollow casing that is adhered to an edge of the radiation-transmissive optic.
18. A method comprising:
providing a hollow casing having a radiation entrance opening;
coupling a radiation-transmissive optic to the hollow casing at the radiation entrance opening;
positioning a substrate having an optical sensing element thereupon inside the hollow casing; and
sealing the substrate against one or more inner surfaces of the hollow casing,
wherein, with the substrate positioned inside the hollow casing, the optical sensing element is configured to sense radiation that has passed through the radiation-transmissive optic, and the hollow casing, the radiation-transmissive optic and the substrate cooperatively define a sealed inner compartment, and wherein
proving the hollow casing comprises forming the hollow casing as a single structure that extends from a top of the hollow casing around an edge of the radiation-transmissive optic down to a bottom of the portion of the hollow casing that contains a potting compound, such that a portion of the hollow casing that is adhered to an upper surface of the substrate thermally expands and contracts with a portion of the hollow casing that is adhered to an edge of the substrate.
19. The method of claim 18 , the method further comprising:
purging the inner compartment with an inert gas.
20. The method of claim 19 wherein the substrate has surfaces that define an opening, through which the inert gas can flow, and wherein purging the inner compartment comprises:
positioning the hollow casing, the radiation transmissive optic and the substrate in an environment that contains the inert gas so that the inert gas can flow through the opening and into the inner compartment; and
plugging the opening while the hollow casing, the radiation transmissive optic and the substrate are inside the inert gas environment to seal the inert gas within the inner compartment.
21. The method of claim 18 wherein the hollow casing has an inner surface with a first flange, and
wherein positioning the substrate inside the hollow casing comprises positioning the substrate to abut the first flange.
22. The method of claim 21 wherein sealing the substrate against one or more surfaces of the hollow casing comprises:
providing a sealant between the substrate and the first flange.
23. The method of claim 22 wherein sealing the substrate against one or more surfaces of the hollow casing further comprises:
providing the sealant between an edge of the substrate and an inner surface of the hollow casing proximate the first flange.
24. The method of claim 22 wherein a surface of the first flange that the substrate abuts is substantially perpendicular to the inner surface of the hollow casing proximate the first flange.
25. The method of claim 18 wherein the hollow casing has an inner surface with a second flange at or near the radiation entrance window, and
wherein coupling the radiation-transmissive optic to the hollow casing at the radiation entrance opening comprises positioning the radiation-transmissive optic to abut the second flange.
26. The method of claim 25 further comprising:
providing a sealant between the radiation-transmissive optic and the second flange as well as between the radiation-transmissive optic and an inner surface of the hollow casing proximate the second flange.
27. The method of claim 26 wherein a surface of the second flange that the radiation-transmissive optic abuts is substantially perpendicular to the inner surface of the hollow casing proximate the second flange.
28. The method of claim 18 further comprising:
covering a side of the substrate opposite the optical sensing element with a potting compound.
29. The method of claim 18 further comprising:
coupling an electrical connector to electrical circuitry at the substrate,
wherein the electrical connector is configured such that when the side of the substrate opposite the optical sensing element is covered with a potting compound, the electrical connector extends through and is exposed for connection outside of the potting compound.
30. The method of claim 29 further comprising:
forming a cutout in a portion of the hollow casing, through which the electrical connector is exposed for connection when the electrical connector is coupled to the electrical circuitry at the substrate and the substrate is sealed against the one or more surfaces of the hollow casing.
31. The method of claim 18 further comprising:
physically coupling a microcontroller, one or more capacitors, and signal processing circuitry to the substrate.
32. The method of claim 31 wherein at least one of the microcontroller, the one or more capacitors, and the signal processing circuitry is coupled to an opposite side of the substrate from the optical sensing element.
33. The method of claim 18 wherein the substrate is a printed circuit board.
34. The method of claim 18 wherein the optical sensing element is a thermopile sensor array.
35. The method of claim 18 wherein the substrate is coupled to a panel that includes a plurality of similar substrates, the method further comprising:
separating the substrate from the panel.