Protective encapsulation for a phototransducer including a surfactant film

• US 6,433,332 B1
• Filed: 09/26/2000
• Issued: 08/13/2002
• Est. Priority Date: 09/26/2000
• Status: Expired due to Term

• Current Assignee: Rockwell Technologies, LLC
• Original Assignee: Rockwell Automation Technologies Incorporated (Allen-Bradley Co., Inc.)
• Inventors: Chin, Gerald J., Johnson, Philip E., Miller, E. Geoffrey, Hazen, Brian J., McEachern, Gary L.
• Primary Examiner(s): LE, QUE TAN
• Application Number:
  US09/669,539
• Time in Patent Office: 686 Days
• Field of Search: 250/239, 250/216, 250/208.1, 250/214.1, 257/80-84, 257/431-435, 438/55, 438/64
• US Class Current: 250/239
• CPC Class Codes: H01L 2224/05599 Material
• CPC Class Codes: H01L 2224/45015 being circular
• CPC Class Codes: H01L 2224/45144 Gold (Au) as principal constituent
• CPC Class Codes: H01L 2224/48091 Arched
• 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 2224/85399 Material
• CPC Class Codes: H01L 2224/8592 Applying permanent coating, e.g. protective coating
• CPC Class Codes: H01L 23/3121 a substrate forming part of the encapsulation
• CPC Class Codes: H01L 24/45 of an individual wire connector
• CPC Class Codes: H01L 24/48 of an individual wire connector
• CPC Class Codes: H01L 27/14618 Containers
• CPC Class Codes: H01L 27/14632 Wafer-level processed structures
• 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 2924/00012 Relevant to the scope of the group, the symbol of which is combined with the symbol of this group
• 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 2924/12041 LED
• CPC Class Codes: H01L 2924/181 Encapsulation
• CPC Class Codes: H01L 2924/20752 larger or equal to 20 microns less than 30 microns

Abstract

A method of encapsulating a phototransducer comprises mounting the phototransducer on a substrate, depositing a surfactant on the substrate, and depositing an encapsulant on the substrate over the surfactant. The surfactant alters a surface tension of the substrate. The encapsulant forms a protective structure that protects the phototransducer.

Claims

1. A method of encapsulating a phototransducer, comprising:

mounting said phototransducer on a substrate;

depositing a surfactant on said substrate, said surfactant altering a surface tension of said substrate; and

depositing an encapsulant on said substrate over said surfactant, said encapsulant forming a protective structure that protects said phototransducer.

2. A method according to claim 1, wherein said surfactant reduces a surface tension of said substrate in a region upon which said encapsulant is deposited.

3. A method according to claim 1, wherein said protective structure is generally dome-shaped.

4. A method according to claim 1, wherein said encapsulant depositing step is performed only once such that said protective structure is formed of a single deposit layer of said encapsulant.

5. A method according to claim 1, wherein said substrate is either a printed circuit board substrate or a ceramic substrate.

6. A method according to claim 1 wherein said surfactant is deposited as a liquid and subsequently dries to a thin film with a surface energy that is in the range of about twelve to thirty dyne.

7. A method according to claim 1, wherein said phototransducer is a light emitting device.

8. A method according to claim 1, wherein said phototransducer is a light-sensitive device.

9. A method according to claim 1, further comprising permitting said encapsulant to cure on said substrate at approximately room temperature for at least one hour.

10. A method according to claim 1, further comprising permitting said encapsulant to cure on said substrate, including

permitting said encapsulant to cure at approximately room temperature for approximately twenty-four hours, and then

permitting said encapsulant to cure at approximately 130° C. for approximately one hour.

11. A method according to claim 1, wherein said surfactant is deposited only on a perimeter region around said phototransducer on said substrate, and wherein said encapsulant is deposited both on said substrate over said surfactant and on said substrate in a region inward of said perimeter region.

12. An apparatus comprising:

a substrate, said substrate having a surface that includes a surfactant film;

a phototransducer, said phototransducer being mounted on said substrate; and

an encapsulant deposit that is located on said surfactant film and that encapsulates and protects said phototransducer.

13. An apparatus according to claim 12, wherein said encapsulant deposit is generally dome-shaped.

14. An apparatus according to claim 12, wherein said surfactant film reduces a surface tension of said substrate.

15. An apparatus according to claim 12, wherein said surfactant film is in a perimeter region around said phototransducer, and wherein said encapsulant deposit is located both on said surfactant film and on a region inward of said perimeter region.

16. A method of encapsulating a phototransducer that is mounted on a substrate, consisting essentially of:

depositing a surfactant on said substrate adjacent said phototransducer;

permitting said surfactant to dry;

depositing a single generally dome-shaped layer of encapsulant on said phototransducer; and

permitting said encapsulant to cure on said substrate.

17. A method according to claim 16, wherein said encapsulant is permitted to cure at approximately room temperature for at least one hour.

18. A method according to claim 16, wherein said encapsulant is permitted to cure in two steps, including a first curing step in which said encapsulant is permitted to cure at approximately room temperature for approximately twenty-four hours, and a second curing step in which said encapsulant is permitted to cure at approximately 130°

C. for approximately one hour.

19. An industrial control system comprising:

(A) a plurality of input devices, at least one of said plurality of input devices comprising a photoelectric sensor, said photoelectric sensor further including

(1) a substrate, said substrate having a surface that includes a surfactant film,

(2) a phototransducer, said phototransducer being mounted on said substrate, and

(3) a generally dome-shaped encapsulant deposit that is located on said surfactant film and that encapsulates and protects said phototransducer;

(B) a plurality of output devices;

(C) a programmable controller, said programmable controller controlling said plurality of output devices based on inputs from said plurality of input devices.

20. An industrial control system according to claim 19, wherein said photoelectric sensor is a proximity sensor.

21. An industrial control system according to claim 19, wherein said photoelectric sensor is a presence sensor.