Low profile mount for plural upper electrode metal oxide varistor package and method

• US 20010015686A1
• Filed: 04/27/2001
• Published: 08/23/2001
• Est. Priority Date: 09/22/1999
• Status: Active Grant

• Current Assignee: Littelfuse Incorporated
• Original Assignee: Harris Ireland Development Co., Ltd.
• Inventors: McLoughlin, Neil
• Granted Patent: US 6,507,268 B2
• Time in Patent Office: Days
• US Class Current: 338/21
• CPC Class Codes: H01C 7/126 Means for protecting against excessive pressure or for disconnecting in case of failure
• CPC Class Codes: H05K 3/301 by means of a mounting structure H05K3/325 takes precedence

Abstract

A low profile mount for a disc varistor. A thermally sensitive switch is provided both for single and multiple electrode embodiments. The switch may be placed in a shorting circuit and include a spring biased conductor prevented from closure by a heat sensitive element which softens in responsive to excessive heat. The varistor may be fused to prevent excessive current from a short circuited but not open circuited varistor. Methods are also provided.

Claims

1. A low profile mount for a disc varistor comprising:

an insulative base having a circular receptacle for a varistor disc;

an exposed bottom electrical contact in said receptacle in position to contact an electrode on the bottom flat side of a varistor disc when placed in said receptacle; and

an upper electrode extending upwardly from an said base outside of said receptacle and being downwardly biased toward said base over said receptacle in position to contact the electrode on the bottom flat side of a varistor disc when placed in said receptacle.

2. The mount of

claim 1

wherein said upper electrode is a conductive metal spring.

3. The mount of

claim 1

wherein the low profile device is surface mounted on a printed circuit board.

4. The mount of

claim 1

wherein the low profile device is through hole mounted on a printed circuit board.

5. The mount of

claim 1

wherein the disc varistor is 14-20 mm in diameter.

6. The mount of

claim 1

wherein the disc varistor is 7-45 mm in diameter.

7. The mount of

claim 1

wherein the low profile device is coated with a moisture barrier.

8. The mount of

claim 1

including a shorting electrode upwardly extending from said base outside of said receptacle and being downwardly biased towards said base over said receptacle in position to contact the electrode on the upper flat side of a varistor disc when placed in said receptacle,

said shorting electrode being electrically connected to said bottom electrode;

and

an insulator intermediate said shorting electrode and the upper electrode of a varistor disc when placed in said receptacle in position to prevent contact between the shorting electrode and the upper electrode, said insulator being thermally reactive to permit contact between said shorting electrode and the upper electrode of a varistor disc under the bias of said shorting electrode

whereby the elevation in the temperature of a varistor disc in said receptacle causes said insulator to react to short the electrodes of the varistor disc.

9. The mount of

claim 8

wherein said shorting disc is a metal spring.

10. The mount of

claim 8

wherein said shorting disc is magnetically biased.

11. The mount of

claim 8

wherein said insulator melts at temperatures above a predetermined value.

12. The mount of

claim 8

wherein the insulator deteriorates between 150-200°

C.

13. The mount of

claim 8

wherein the insulator deteriorates at 163°

C.

14. The mount of

claim 8

wherein the insulator consists essentially of benzanilide.

15. The mount of

claim 1

including at least one additional upper electrode extending upwardly from an said base outside of said receptacle and being downwardly biased toward said base over said receptacle in position to contact an electrode on the top flat side of a varistor disc when placed in said receptacle, said upper electrodes being spaced apart to thereby be positioned to contact different upper electrodes on a segmented varistor disc.

16. The mount of

claim 1

including at least one additional exposed bottom electrical contact in said receptacle in position to contact an electrode on the bottom flat side of a segmented varistor disc when placed in said receptacle.

17. A mount for an electrical component having exposed upper and lower electrodes comprising:

a insulative body with an upwardly open receptacle adapted to receive an electrical component;

a lower contact carried by said body within said receptacle in position to contact the lower electrode of a component when received therein;

an upper contact carried by said body above said receptacle in position to contact the upper electrode of the component when received therein, said upper contact being downwardly biased toward said receptacle.

18. The mount of

claim 17

including a second upper contact carried by said body above said receptacle in position to contact a second upper electrode of the component when received therein, said second upper contact being downwardly biased toward said receptacle.

19. The mount of

claim 18

wherein said second upper contact is electrically connected to said lower electrical contact;

and

including a thermally responsive insulator between said second upper contact and the upper electrode of the electrical component for preventing contact therebetween under predetermined thermal conditions within the component, said insulator being responsive to a predetermined thermal condition within the component to permit contact between said second contact and the upper electrode of the component.

20. The mount of

claim 19

wherein the insulator consists essentially of benzanilide and wherein the insulator deteriorates between 150-200°

C.

21. The mount of

claim 19

wherein the insulator deteriorates at 163°

C.

22. The mount of

claim 18

wherein said second upper contact is electrically isolated from both said lower contact and said first mentioned upper contact to thereby adapt said mount for use with components with segmented upper electrodes.

23. A mount for an electrical component having an exposed lower electrode and a plurality of exposed upper electrodes comprising:

a insulative body with an upwardly open receptacle adapted to receive an electrical component;

a lower contact carried by said body within said receptacle in position to contact the lower electrode of a component when received therein;

a plurality of spaced upper contacts carried by said body above said receptacle in position to contact spaced upper electrodes of the component when received therein, each of said plurality of upper contacts being downwardly biased toward said receptacle.

24. The mount of

claim 23

wherein said plurality is four.

25. The mount of

claim 24

wherein said component is a varistor.

26. A mount for an electrical component having an exposed upper electrode and a plurality of exposed lower electrodes comprising:

a insulative body with an upwardly open receptacle adapted to receive an electrical component;

a plurality of spaced lower contacts carried by said body within said receptacle, each of said lower contacts being in position to contact one of the segmented lower electrodes of a component when received therein;

an upper contacts carried by said body above said receptacle in position to contact the upper electrodes of the component when received therein, said upper contacts being downwardly biased toward said receptacle.

27. The mount of

claim 26

wherein said component is a varistor.

28. The mount of

claim 27

wherein said plurality is four.

29. A method of mounting an electrical component having exposed upper and lower electrodes on a printed circuit board comprising the steps of:

(a) providing an insulative body having an upwardly open receptacle adapted to receive an electrical component;

(b) positioning a lower contact within the receptacle in the body in position to contact the lower electrode of a component when received therein;

(c) providing an upper contact carried by the body above the receptacle in the body in position to contact the upper electrode of the component when received therein;

(d) downwardly biased the upper contact toward the receptacle in the body, so that an electrical component when received within the receptacle in the body will electrically contact the lower contact within the receptacle and be contacted by the upper contact under the downward bias thereof.

30. The method of

claim 29

wherein the component is a varistor.