Information
-
Patent Grant
-
6560087
-
Patent Number
6,560,087
-
Date Filed
Friday, September 1, 200024 years ago
-
Date Issued
Tuesday, May 6, 200321 years ago
-
Inventors
-
Original Assignees
-
Examiners
- Sircus; Brian
- Rodriguez; Isabel
Agents
-
CPC
-
US Classifications
Field of Search
US
- 361 118
- 361 119
- 361 117
- 361 911
- 361 88
- 333 185
- 174 2
-
International Classifications
-
Abstract
An electronic signal filter is provided that includes a metal housing which has been adapted to be electrically grounded, and a circuit board positioned within the housing. The circuit board includes a first area and a second area, and has an electrically conductive trace formed on a portion of a top surface of the circuit board that provides electrical communication between the first and second areas of the circuit board. The filter further includes a metal shield connected to the housing, located between the first and second areas of the circuit board. The metal shield extends in a direction substantially perpendicular to the plane of the circuit board and has a slot formed therein for receiving the portion of the circuit board on which the electrically conductive trace is formed. The slot is dimensioned to provide a space between the metal shield and the conductive trace. The dimension of the space is selected to shunt current passing through the conductive trace to ground in the event of a voltage surge passing through the filter.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
For a fuller understanding of the nature and objects of the invention, reference should be made to the following detailed description of a preferred mode of practicing the invention, read in connection with the accompanying drawings, in which:
FIG. 1
is a view of a prior art CATV filter;
FIG. 2
is a cross sectional view of the metal shield of the prior art CATV filter shown in
FIG. 1
;
FIG. 3A
is a cross sectional view of a metal shield of a filter in accordance with one embodiment of the present invention;
FIG. 3B
is a cross sectional view of the metal shield of the filter in accordance with another embodiment of the present invention;
FIG. 4
is a partial cut-out view of the metal shield of the filter in accordance with the embodiment of the present invention as shown in
FIG. 3A
; and
FIG. 5
is a partial cut-out view of the metal shield of a CATV filter in accordance with another embodiment of the present invention as shown in FIG.
3
B.
DETAILED DESCRIPTION OF THE INVENTION
FIG. 3A
, read in connection with the corresponding view shown in
FIG. 4
, is a cross sectional view of a metal shield of a filter in accordance with one embodiment of the present invention. The grounded metal shield
104
(or
105
as shown in
FIG. 1
) includes a slot
106
. The slot
106
includes a first section
106
A, providing intimate contact with bottom surface
100
b
of circuit board
100
and with a portion of top surface
100
a
of circuit board
100
.
Slot
106
further includes a second section
106
B defining a space between the top surface
100
a
of circuit board
100
and shield
104
. A conductive trace
200
is positioned on top surface
100
a
of circuit board
100
within second section
106
B of slot
106
. A space of dimension d is formed between the surface of conductive trace
200
and the top of slot
106
in the region of
106
B. The dimension d of the space relates to the dielectric constant of the material, or air, located within the space. If a voltage surge passes through the filter along conductive trace
200
, a spark is generated within the space, and the current is shunted to ground via the grounded metal shield
104
.
It is believed that a space having the dimension d of about 0.013 inches will spark at a voltage surge of about 1000 volts passing through the conductive trace. Accordingly, d should be selected within a range of about 0.010 to 0.020 inches to provide a 1000-2000V surge protection rating.
FIG. 3A
also shows that the metal shield preferably includes a raised boss member
110
, which increases the effective thickness of the metal shield to more closely match the width of the shield-receiving slot
101
(
FIG. 1
) cut through the circuit board
100
. It is difficult to cut a slot through the circuit board that matches the relatively small thickness of the metal shield.
The metal shield
104
is made from a conductive metal, such as tin plated steel, which is grounded to the housing of the filter. The circuit board
100
is made from an electrically insulating material, an example of which is glass-epoxy composite. The conductive trace
200
is made from a conductive material, an example of which is solder-covered copper.
FIG. 3B
, read in connection with the corresponding view shown in
FIG. 5
, is a cross sectional view of the metal shield of a filter in accordance with another embodiment of the present invention. The metal shield
104
(or
105
as shown in
FIG. 1
) includes a slot
206
. Slot
206
includes a first section
206
A, providing intimate contact with a portion of bottom surface
100
b
of circuit board
100
and a portion of top surface
100
a
of circuit board
100
.
Slot
206
also includes a second section
206
B defining a space between top surface
100
a
of circuit board
100
and shield
104
. Slot
206
further includes a third section
206
C defining a space between bottom surface
100
b
of circuit board
100
and shield
104
.
A conductive trace
200
is located on top surface
100
a
of the circuit board
100
within the second section
206
B. A space of dimension d
2
is formed between the surface of the conductive trace
200
and slot
206
in the region of
206
B. An electrically conductive plated through-hole
201
passes from the top of conductive trace
200
, through circuit board
100
, and through a conductive contact pad
202
located on bottom surface
100
b
of circuit board
100
. A space having the dimension d
3
is formed between the surface of conductive contact pad
202
and slot
206
in the region of
206
C.
The dimensions of the spaces d
2
and d
3
relate to the dielectric constant of the material, or air, located within the respective spaces. If a voltage surge passes through the filter along conductive trace
200
, a spark is generated within the space, and the current is shunted to ground via the grounded metal shield
104
. The through-hole
201
is plated with a conductive material, an example of which is copper.
It is believed that a space having the dimension d
2
(or d
3
) of about 0.013 inches will spark at a voltage surge of about 1000 volts passing through the conductive trace. Accordingly, d
2
(or d
3
) should be selected within a range of about 0.010 to 0.020 inches to provide a 1000-2000V surge protection rating.
FIG. 3B
also shows that metal shield
104
preferably includes a raised boss member
110
, which increases the effective thickness of the metal shield to more closely match the width of the shield-receiving slot
101
(
FIG. 1
) cut through the circuit board
100
.
Although not shown in the present drawings, the interior of the housing can be filled with a potting compound, such as polyurethane foam.
While the present invention has been particularly shown and described with reference to the preferred mode as illustrated in the drawings, it will be understood by one skilled in the art that various changes in detail may be effected therein without departing from the spirit and scope of the invention as defined by the claims.
Claims
- 1. An electronic signal filter comprising:a metal housing adapted to be electrically grounded; a circuit board positioned within said housing, having a first area and a second area; an electrically conductive trace formed on a portion of a top surface of said circuit board providing electrical communication between said first and second areas of said circuit board; and a metal shield connected to said housing, in a position between said first and second areas of said circuit board, said metal shield extending in a direction substantially perpendicular to the plane of the circuit board and having a slot formed therein for receiving said portion of said circuit board on which said electrically conductive trace is formed, said slot being dimensioned to provide a space between said metal shield and said conductive trace, wherein the dimension of said space is selected to shunt current passing through said conductive trace to ground in the event of a voltage surge passing through the filter.
- 2. The filter of claim 1, wherein said slot comprises a first section in intimate contact with said circuit board, and a second section defining said space.
- 3. The filter of claim 2, wherein said slot further comprises a third section defining another space positioned below said circuit board.
- 4. The filter of claim 3, further comprising an electrically conductive plated through-hole extending from said electrically conductive trace and passing through said circuit board in the region of said metal shield, and an electrically conductive contact pad positioned on a bottom surface of said circuit board in electrical communication with said electrically conductive plated through-hole.
- 5. The filter of claim 3, wherein said other space has a dimension ranging from about 0.010 inches to 0.020 inches.
- 6. The filter of claim 1, wherein said space has a dimension ranging from about 0.010 inches to 0.020 inches.
- 7. The filter of claim 1, wherein said metal shield further comprises a raised boss member aligned laterally with said slot, for increasing the effective thickness of said metal shield.
- 8. The filter of claim 1, further comprising a foam material filling the interior of said metal housing.
US Referenced Citations (5)
Number |
Name |
Date |
Kind |
4451803 |
Holdsworth et al. |
May 1984 |
A |
4485447 |
Ericsson |
Nov 1984 |
A |
5150087 |
Yoshie et al. |
Sep 1992 |
A |
5262754 |
Collins |
Nov 1993 |
A |
5768084 |
Chaudhry et al. |
Jun 1998 |
A |