CA2228012A1 - Flexible printed circuit board for use with metal oxide varistor, applicable to a surge protector - Google Patents
Flexible printed circuit board for use with metal oxide varistor, applicable to a surge protector Download PDFInfo
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- CA2228012A1 CA2228012A1 CA 2228012 CA2228012A CA2228012A1 CA 2228012 A1 CA2228012 A1 CA 2228012A1 CA 2228012 CA2228012 CA 2228012 CA 2228012 A CA2228012 A CA 2228012A CA 2228012 A1 CA2228012 A1 CA 2228012A1
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Abstract
A flexible printed circuit board capable of being used in a surge protector, the printed circuit board is associated with a metal oxide varistor.
A first metalization layer and a second metalization layer are also associated with the printed circuit board. The first metalization layer supplies electricity to the metal oxide varistor while the second metalization layer connects said metal oxide varistor to a ground/neutral plane. A
minimal thickness insulative layer separates said first metalization layer from said second metalization layer. In one embodiment, the insulative layer comprises the printed circuit board, and the first and second metalization layers are on opposed sides of the printed circuit board.
A first metalization layer and a second metalization layer are also associated with the printed circuit board. The first metalization layer supplies electricity to the metal oxide varistor while the second metalization layer connects said metal oxide varistor to a ground/neutral plane. A
minimal thickness insulative layer separates said first metalization layer from said second metalization layer. In one embodiment, the insulative layer comprises the printed circuit board, and the first and second metalization layers are on opposed sides of the printed circuit board.
Description
PATENT
Attorney Docket No. 0267-001-1 109 Title: FLEXIBLE PRINTEDCIRCUITBOARDFORUSE
WITH METAL OXIDE VARISTOR, APPLICABLE
TO A SURGE PROTECTOR
Inventor: Robert Romeo CROSS-REFERENCE TO RELATED APPLICATION
Reference is made to U.S. Application Serial No. 08/514,202, filed August ] 1, 1995, entitled APPARATUS FOR AND METHOD OF
SUPPRE,SSING POWER SURGES UTILIZING ELECTRICAL
STRIPL:[NES, invented by Albert Zaretsky, and assigned to the assignee of the present invention. Such application is incorporated herein by reference.
BACKGROUND OF THE INVENTION
Currently, most transient voltage suppressor devices (TVSS devices) use a metal oxide varistor (MOV). The MOV can redirect most of the surge voltage to ground during voltage spikes. Redirecting surge voltage to ground can be achieved in different ways. One way is to redirect the voltage using an MOV from the phase (hot) line to ground. Another way is using the MOV to redirect the voltage from the phase line to the neutral line. Typically, the neutral line is connected to the ground line at the service entrance in buildings. Thus, by redirecting to the neutral line, the surge will find its way to ground. The MOV functions similarly to (and may include) a zener diode, and breaks down using avalanche principles at a desired voltage level. When used across an electric transmission line, the MOV starts conducting at a voltage above the normal operating building voltage, such as occurs from lightning or switching of power supply systems. and redirects the surge to ground/neutral.
All MOVs have rated clamping levels according to test specifications outlined by the Underwriter Laboratories (UL) or the IEEE.
These or~g~ni~tions test the devices by transmitting pulses of known current waveforms through the MOV, and measuring the resultant current through the device. A typical UL waveform applied across the MOV
device has characteristics such as 8msec x 20msec, 3000 Amps, 6000 Volts in combination. The clamping voltage is the measured voltage across the MOV device under these conditions. It is desirable to have as small of a clampinjg voltage level as possible.
Surge protection devices that incorporate MOV devices also have voltage clamping levels. The design of a printed circuit board incorporating MOV devices affects the voltage clamping levels. A low voltage clamping level for a surge protector means that with a given surge, less voltage is applied l;o the equipment being protected by the surge protector. Reducing the clamping voltage level is therefore an important consideration in the design of surge protectors. The wiring from the power source to the MOV
affects the clamping voltage level due to electrical impedance in the wires, specifically wire inductance and capacitance between the wires. This can be seen in FIG. 1, which shows a prior art wiring diagram for a surge protector. MOV 10, housed in a module 12, is coupled through wires 14, 16 to a terminal board 18 having pins 20, 22, 24, 26, 27. The pins are electrically connected to a power source, such as 120 VAC, with lines L 1 and neutral N. A load 29 is coupled in parallel with MOV 10. The wires 14, 16 have a self-inductance, shown as phantom coils 28, 32 in FIG. 1.
The wires also have a capacitance between them, shown as phantom capacitor 30 in FIG. 1. The electrical impedance Z "seen" by MOV 10 in FIG. 1 is represented by the well-known relationship:
Z = ~ L/C
where L is the inductance of the wires and C is the capacitance between the wires. Typically, L is relatively high due to the type of wiring required, and C is relatively very low due to the spacing between the wires. Accordingly, Z is typically relatively high.
The design of the MOV and the printed circuit board itself is therefore an important consideration in surge protector design. U.S. Patent No. 5,303,116, issued April 12, 1994 to Grotz is one prior art attempt at optimizing surge protector design. The Grotz attempt, however, relies upon a standard, relatively thick, rigid printed circuit board. (Col. 2, line 20).
Such boards are usually on the order of 0.062 inch thick. Therefore, electrical conductors on opposed sides of the printed circuit boards are separated by a considerable distance. This separation distance allows for the generation of significant magnetic flux encircling each conductor.
Another disadvantage with conventional rigid printed circuit boards is the dii'ficulty they present with mounting of the MOVs and other components, and with fitting the entire assembly into cramped locations.
In certain applications, multiple layers of printed circuit boards may be needed. This increases the wiring length to the MOV devices and further penalize, transient suppression performance due to the increased impedance. In conventional wiring implementation, it is often impossible to place ;311 components in one place, adjacent to the power source terminal ,. . . . .
strip, especially when the components are housed in modules. Wiring in three-phase implementations is even more difficult, given the required low impedance's between the product entrance terminal board and the suppression components.
l hese limitations are known to exist in present devices and methods It would therefore be advantageous to provide an alternate device and technique to overcome the limitations set forth above. Accordingly, a suitable alternative includes features more fully disclosed hereinafter.
SUMM:ARY OF THE rNVENTION
l he present invention limits magnetic flux impedance generated by flexible printed circuit board wiring which is connected to a surge protector One or more metal oxide varistors are mounted on the printed circuit board A first ]metalization layer and a second metalization layer are laid down on the printed circuit board. The first metalization layer supplies electricity to the metal oxide varistor while the second met~li7~tion làyer connects it to a ground/neutral plane. A minim~l thickness insulative layer separates the first mel:alization layer from the second metalization layer.
BRIEF ]DESCRIPTION OF THE DRAWINGS
FIG. 1 illustrates a schematic diagram of a prior art embodiment of a metal oxide varistor surge protector connected to a power terminal board using conventional discrete wiring.
FIG. 2 illustrates a perspective view of one embodiment of a flexible printed circuit board of the present invention.
FIG. 3 illustrates a cross-sectional view of the flexible printed circuit board oi'FIG. 2.
FIG. 4 illustrates an alternative embodiment of the present invention.
F IG. 5 illustrates a further embodiment of the present invention.
DETAILED DESCRIPTION OF THE PRESENT INVENTION
Overall Design lF IG. 2 illustrates a surge protector 10 of one embodiment of the present invention. The surge protector is connected to power lines L 1 and N
and in parallel with a load 29. Load 29 may be any electrical device requiring an eleckic supply where there is a desire to protect against electrical power spikes. These spikes primarily occur from lightning and power supply switching. The surge protector 10 protects against any voltage level above a desired threshold. It is important that the surge protector respond quickly to any power spike. FIG. 2 shows a printed circuit bloard 40 on which is mounted a metal oxide varistor (MOV) 10, housed in module 12. The metal oxide varistor 10 breaks down when a large voltage level is reached. This break down is accomplished using an avalanche mechanism, as is well known in the art.
In FIG. 2, there is a f1rst electrical path 42 from a power source 60 to an MOV 10 along the top surface of printed circuit board 40. There is also a seconcl electrical path 44 from MOV 10 to a ground/neutral plane 18 along the bottom surface of the printed board 40. In this disclosure, the term "first metalization layer" is synonymous with the term "electrical path". T here can be one or more electrical paths associated with each metalization layer. Each metalization layer is applied to printed circuit boards using masking or other well known technologies. The present invention relates to embodiments of the printed circuit board that can quickly respond to electrical surges by actuating the MOV device. This quick response is accomplished by limiting the impedance along the first electrical path 42 and along the second electrical path 44. There are several techniques that can be used to limit the impedance along the first and second e lectrical paths 42, 44.
The first technique is to ensure that the path material used has a high electrical conductivity. There has been little recent improvement in this material. Copper and other conductors are commonly used. Therefore, chip layout design becomes more important when optimizing surge suppressor performance.
Flexible Printed Circuit Board Configuration The FIG. 2 embodiment of the present invention illustrates a configuration where the printed circuit board 40 is a flexible printed circuit board. T he flexible printed board has a major advantage in that it is extreme]y thin. This thinness allows the first electrical path 42 to lie close to the second electrical path 44. In determining the direction of generated magnetic flux due to electrical current flow, as shown by dashed line 46 in FIG. 2, the right hand rule is used. If the electric flow in path 42 is along the direction shown by the arrow, then the generated magnetic flux extends in a circumferential magnetic flux path 47. The flow of electricity along electrical path 44 in the opposite direction as that in path 42 results in a magnetic flux being generated in circumferential magnetic flux path 46.
To achieve the best results, i.e., lowest impedance, at any given point on the printed circuit board, the directions of the circumferential magnetic flux pathls 46, 47 should oppose and cancel each other. Assuming that the electric paths 42, 44 have a similar configuration, are formed from a similar material, and have a similar current, then the magnetic flux at points equidista~nt from each electric path 42, 44 should be substantially equal.
One object of the present invention is to ensure that the electric paths are as close to each other as possible, so that the magnetic flux generated at each point by the first electric path 42 will be as close to equal and opposed to the magnetic flux generated by the second electrical path 44 as possible.
This teclmique of matching the electric path 42, 44 material and configuration is called "strip line technique".
The canceling of the respective magnetic fluxes as described above results in limiting the impedance in each electric path 42, 44, in accordance with the relationship:
Z = ~ L/C
where, in this case, the inductance L is very low and the capacitance C is very high due to the close spacing of the copper tracings on the printed circuit board. Thus, the impedance Z is much lower than it would be if the MOV were connected to the terminal board by discrete wiring.
This results in more responsive electrical flow along the electrical paths 42, 44 to and from the MOV. It is worth noting that each printed circuit board may have a plurality of MOVs, so that limiting the generated magnetic flux not only eases the electric flow along the electrical paths 42, 44 generating the magnetic flux, but along any electric paths in the vicinity that supply electricity to and from other MOVs as well.
T:he FIG. 2 configuration limits the distance between the electrical paths 42, 44 by using a flexible printed circuit board instead of a rigid printed circuit board. Rigid printed circuit boards have a common thickness of about 0.062 inch, while flexible printed circuit boards have a thickness of about 0.() 10 inch. In one embodiment, the insulative material used for the board is plastic, such as Mylar. Using the thinner flexible printed circuit board permits the first electrical path 42 to be placed closer to the second electrica]l path 44. Placing the electrical paths 42, 44 closer to each other limits the generated magnetic field in the vicinity of the electrical paths 42, 44 by cancellation, as described above. The capacitance between the paths is increased. Both flexible and rigid printed circuit boards are formed from electrically insulative material, but the material of the printed circuit boardsdoes not shield magnetic fluxes.
FIG. 3 shows the printed circuit board 40 of FIG. 2 in cross section.
Met:~11i7:~tion layers 42 and 50 are laid down on top of board 40, while met~lli7:~tion layers 44, 48 are laid down on the bottom of board 40.
Layers 42, 44, 48 and 50 are commonly of copper but may be of any electrically conductive metal or other material.
Another advantage of the flexible printed circuit board over rigid printed circuit boards is that the flexible printed circuit board may be bent or twisted if needed. This bending or twisting permits flexible printed circuit boards to be packaged in smaller packages than a similarly sized rigid printed circuit board. Thus, great freedom in mechanical design of the product iis achieved, without penalizing transient suppression performance because of long lengths of wiring or multiple levels of PC boards and the required wiring connections between them. The need for manual wiring is also redwced or elimin~ted, and use of the printed circuit board facilitates controlled transient tr~n.smi.~.~ion parameters by facilitating the adjustment of board thickness and copper trace widths.
F][G. 4 illustrates an alternative embodiment (mating boards) of the present invention. In this embodiment, there are provided a plurality of flexible printed circuit boards 60, 62, with their respective electrical paths 78, 80, 74, 76 facing each other. A thin, flexible electrically insulative layer64 is placed between circuit boards 60 and 62. The electrically insulative layer 64 is preferably formed from plastic, but may be formed from any other material that permits magnetic flux to pass though, but limits passage .rdll./llr~ C~
of electric voltage across. In the FIG. 4 embodiment, the first circuit board layer 60 has an electric paths 78, 80 across the inner facing surface 79 of board 6(); the second circuit board layer 62 has an electric paths 74, 76 across the inner facing surface 81 of board 62. The first inner facing surface 79 of the first circuit board 60 faces the first inner facing surface 81 of the second circuit board 62. The spacing between the two surfaces 79, 81 is determined by a thickness of the electrically insulative layer 64. The thickness of the first circuit board 60 and the second circuit board 62 therefore do not make a difference in the spacing between the electric paths 74, 78 and 76, 80.
B,oth the flexible printed circuit board configuration and the mating printed circuit board configuration enable the first and second electric paths to be very close to each other. Therefore, the description under the flexible printed circuit board segment applies to both configurations. All embodirnents of the present invention permit very close electric path spacing, while ensuring proper insulation between the two electric paths. In addition, the insulator in all embodiments does not effect the cancellation of magnetic fluxes caused by substantially even electric flow through the two electric paths.
Another embodiment of the invention is shown in FIG. 5. Here, a portion 91 of a met~lli7~tion layer consisting, for example, of copper, is laid down near two other portions 93 and 95. Portion 91 may be connected to the phase line, portion 93 may be connected to the neutral line and portion 95 may be connected to the ground line. As can be seen, all three portions are on the same side. Each portion is connected to a separate met~lli7Ation layer 10 l, 103 through leads (not shown), and the met~lli7~tion layers are ra~ r~ a~
separated by one or more layers 97, 99 of a plastic substrate, to form a multilayer board.
~ Ihile only a few embodiments of the present invention have been described in this disclosure, it is understood that many changes and modifications that would be obvious to one having ordinary skill in the art upon consideration of the disclosure and the drawings are within the scope of the present invention.
I ~wor~ r~!lle~
Attorney Docket No. 0267-001-1 109 Title: FLEXIBLE PRINTEDCIRCUITBOARDFORUSE
WITH METAL OXIDE VARISTOR, APPLICABLE
TO A SURGE PROTECTOR
Inventor: Robert Romeo CROSS-REFERENCE TO RELATED APPLICATION
Reference is made to U.S. Application Serial No. 08/514,202, filed August ] 1, 1995, entitled APPARATUS FOR AND METHOD OF
SUPPRE,SSING POWER SURGES UTILIZING ELECTRICAL
STRIPL:[NES, invented by Albert Zaretsky, and assigned to the assignee of the present invention. Such application is incorporated herein by reference.
BACKGROUND OF THE INVENTION
Currently, most transient voltage suppressor devices (TVSS devices) use a metal oxide varistor (MOV). The MOV can redirect most of the surge voltage to ground during voltage spikes. Redirecting surge voltage to ground can be achieved in different ways. One way is to redirect the voltage using an MOV from the phase (hot) line to ground. Another way is using the MOV to redirect the voltage from the phase line to the neutral line. Typically, the neutral line is connected to the ground line at the service entrance in buildings. Thus, by redirecting to the neutral line, the surge will find its way to ground. The MOV functions similarly to (and may include) a zener diode, and breaks down using avalanche principles at a desired voltage level. When used across an electric transmission line, the MOV starts conducting at a voltage above the normal operating building voltage, such as occurs from lightning or switching of power supply systems. and redirects the surge to ground/neutral.
All MOVs have rated clamping levels according to test specifications outlined by the Underwriter Laboratories (UL) or the IEEE.
These or~g~ni~tions test the devices by transmitting pulses of known current waveforms through the MOV, and measuring the resultant current through the device. A typical UL waveform applied across the MOV
device has characteristics such as 8msec x 20msec, 3000 Amps, 6000 Volts in combination. The clamping voltage is the measured voltage across the MOV device under these conditions. It is desirable to have as small of a clampinjg voltage level as possible.
Surge protection devices that incorporate MOV devices also have voltage clamping levels. The design of a printed circuit board incorporating MOV devices affects the voltage clamping levels. A low voltage clamping level for a surge protector means that with a given surge, less voltage is applied l;o the equipment being protected by the surge protector. Reducing the clamping voltage level is therefore an important consideration in the design of surge protectors. The wiring from the power source to the MOV
affects the clamping voltage level due to electrical impedance in the wires, specifically wire inductance and capacitance between the wires. This can be seen in FIG. 1, which shows a prior art wiring diagram for a surge protector. MOV 10, housed in a module 12, is coupled through wires 14, 16 to a terminal board 18 having pins 20, 22, 24, 26, 27. The pins are electrically connected to a power source, such as 120 VAC, with lines L 1 and neutral N. A load 29 is coupled in parallel with MOV 10. The wires 14, 16 have a self-inductance, shown as phantom coils 28, 32 in FIG. 1.
The wires also have a capacitance between them, shown as phantom capacitor 30 in FIG. 1. The electrical impedance Z "seen" by MOV 10 in FIG. 1 is represented by the well-known relationship:
Z = ~ L/C
where L is the inductance of the wires and C is the capacitance between the wires. Typically, L is relatively high due to the type of wiring required, and C is relatively very low due to the spacing between the wires. Accordingly, Z is typically relatively high.
The design of the MOV and the printed circuit board itself is therefore an important consideration in surge protector design. U.S. Patent No. 5,303,116, issued April 12, 1994 to Grotz is one prior art attempt at optimizing surge protector design. The Grotz attempt, however, relies upon a standard, relatively thick, rigid printed circuit board. (Col. 2, line 20).
Such boards are usually on the order of 0.062 inch thick. Therefore, electrical conductors on opposed sides of the printed circuit boards are separated by a considerable distance. This separation distance allows for the generation of significant magnetic flux encircling each conductor.
Another disadvantage with conventional rigid printed circuit boards is the dii'ficulty they present with mounting of the MOVs and other components, and with fitting the entire assembly into cramped locations.
In certain applications, multiple layers of printed circuit boards may be needed. This increases the wiring length to the MOV devices and further penalize, transient suppression performance due to the increased impedance. In conventional wiring implementation, it is often impossible to place ;311 components in one place, adjacent to the power source terminal ,. . . . .
strip, especially when the components are housed in modules. Wiring in three-phase implementations is even more difficult, given the required low impedance's between the product entrance terminal board and the suppression components.
l hese limitations are known to exist in present devices and methods It would therefore be advantageous to provide an alternate device and technique to overcome the limitations set forth above. Accordingly, a suitable alternative includes features more fully disclosed hereinafter.
SUMM:ARY OF THE rNVENTION
l he present invention limits magnetic flux impedance generated by flexible printed circuit board wiring which is connected to a surge protector One or more metal oxide varistors are mounted on the printed circuit board A first ]metalization layer and a second metalization layer are laid down on the printed circuit board. The first metalization layer supplies electricity to the metal oxide varistor while the second met~li7~tion làyer connects it to a ground/neutral plane. A minim~l thickness insulative layer separates the first mel:alization layer from the second metalization layer.
BRIEF ]DESCRIPTION OF THE DRAWINGS
FIG. 1 illustrates a schematic diagram of a prior art embodiment of a metal oxide varistor surge protector connected to a power terminal board using conventional discrete wiring.
FIG. 2 illustrates a perspective view of one embodiment of a flexible printed circuit board of the present invention.
FIG. 3 illustrates a cross-sectional view of the flexible printed circuit board oi'FIG. 2.
FIG. 4 illustrates an alternative embodiment of the present invention.
F IG. 5 illustrates a further embodiment of the present invention.
DETAILED DESCRIPTION OF THE PRESENT INVENTION
Overall Design lF IG. 2 illustrates a surge protector 10 of one embodiment of the present invention. The surge protector is connected to power lines L 1 and N
and in parallel with a load 29. Load 29 may be any electrical device requiring an eleckic supply where there is a desire to protect against electrical power spikes. These spikes primarily occur from lightning and power supply switching. The surge protector 10 protects against any voltage level above a desired threshold. It is important that the surge protector respond quickly to any power spike. FIG. 2 shows a printed circuit bloard 40 on which is mounted a metal oxide varistor (MOV) 10, housed in module 12. The metal oxide varistor 10 breaks down when a large voltage level is reached. This break down is accomplished using an avalanche mechanism, as is well known in the art.
In FIG. 2, there is a f1rst electrical path 42 from a power source 60 to an MOV 10 along the top surface of printed circuit board 40. There is also a seconcl electrical path 44 from MOV 10 to a ground/neutral plane 18 along the bottom surface of the printed board 40. In this disclosure, the term "first metalization layer" is synonymous with the term "electrical path". T here can be one or more electrical paths associated with each metalization layer. Each metalization layer is applied to printed circuit boards using masking or other well known technologies. The present invention relates to embodiments of the printed circuit board that can quickly respond to electrical surges by actuating the MOV device. This quick response is accomplished by limiting the impedance along the first electrical path 42 and along the second electrical path 44. There are several techniques that can be used to limit the impedance along the first and second e lectrical paths 42, 44.
The first technique is to ensure that the path material used has a high electrical conductivity. There has been little recent improvement in this material. Copper and other conductors are commonly used. Therefore, chip layout design becomes more important when optimizing surge suppressor performance.
Flexible Printed Circuit Board Configuration The FIG. 2 embodiment of the present invention illustrates a configuration where the printed circuit board 40 is a flexible printed circuit board. T he flexible printed board has a major advantage in that it is extreme]y thin. This thinness allows the first electrical path 42 to lie close to the second electrical path 44. In determining the direction of generated magnetic flux due to electrical current flow, as shown by dashed line 46 in FIG. 2, the right hand rule is used. If the electric flow in path 42 is along the direction shown by the arrow, then the generated magnetic flux extends in a circumferential magnetic flux path 47. The flow of electricity along electrical path 44 in the opposite direction as that in path 42 results in a magnetic flux being generated in circumferential magnetic flux path 46.
To achieve the best results, i.e., lowest impedance, at any given point on the printed circuit board, the directions of the circumferential magnetic flux pathls 46, 47 should oppose and cancel each other. Assuming that the electric paths 42, 44 have a similar configuration, are formed from a similar material, and have a similar current, then the magnetic flux at points equidista~nt from each electric path 42, 44 should be substantially equal.
One object of the present invention is to ensure that the electric paths are as close to each other as possible, so that the magnetic flux generated at each point by the first electric path 42 will be as close to equal and opposed to the magnetic flux generated by the second electrical path 44 as possible.
This teclmique of matching the electric path 42, 44 material and configuration is called "strip line technique".
The canceling of the respective magnetic fluxes as described above results in limiting the impedance in each electric path 42, 44, in accordance with the relationship:
Z = ~ L/C
where, in this case, the inductance L is very low and the capacitance C is very high due to the close spacing of the copper tracings on the printed circuit board. Thus, the impedance Z is much lower than it would be if the MOV were connected to the terminal board by discrete wiring.
This results in more responsive electrical flow along the electrical paths 42, 44 to and from the MOV. It is worth noting that each printed circuit board may have a plurality of MOVs, so that limiting the generated magnetic flux not only eases the electric flow along the electrical paths 42, 44 generating the magnetic flux, but along any electric paths in the vicinity that supply electricity to and from other MOVs as well.
T:he FIG. 2 configuration limits the distance between the electrical paths 42, 44 by using a flexible printed circuit board instead of a rigid printed circuit board. Rigid printed circuit boards have a common thickness of about 0.062 inch, while flexible printed circuit boards have a thickness of about 0.() 10 inch. In one embodiment, the insulative material used for the board is plastic, such as Mylar. Using the thinner flexible printed circuit board permits the first electrical path 42 to be placed closer to the second electrica]l path 44. Placing the electrical paths 42, 44 closer to each other limits the generated magnetic field in the vicinity of the electrical paths 42, 44 by cancellation, as described above. The capacitance between the paths is increased. Both flexible and rigid printed circuit boards are formed from electrically insulative material, but the material of the printed circuit boardsdoes not shield magnetic fluxes.
FIG. 3 shows the printed circuit board 40 of FIG. 2 in cross section.
Met:~11i7:~tion layers 42 and 50 are laid down on top of board 40, while met~lli7:~tion layers 44, 48 are laid down on the bottom of board 40.
Layers 42, 44, 48 and 50 are commonly of copper but may be of any electrically conductive metal or other material.
Another advantage of the flexible printed circuit board over rigid printed circuit boards is that the flexible printed circuit board may be bent or twisted if needed. This bending or twisting permits flexible printed circuit boards to be packaged in smaller packages than a similarly sized rigid printed circuit board. Thus, great freedom in mechanical design of the product iis achieved, without penalizing transient suppression performance because of long lengths of wiring or multiple levels of PC boards and the required wiring connections between them. The need for manual wiring is also redwced or elimin~ted, and use of the printed circuit board facilitates controlled transient tr~n.smi.~.~ion parameters by facilitating the adjustment of board thickness and copper trace widths.
F][G. 4 illustrates an alternative embodiment (mating boards) of the present invention. In this embodiment, there are provided a plurality of flexible printed circuit boards 60, 62, with their respective electrical paths 78, 80, 74, 76 facing each other. A thin, flexible electrically insulative layer64 is placed between circuit boards 60 and 62. The electrically insulative layer 64 is preferably formed from plastic, but may be formed from any other material that permits magnetic flux to pass though, but limits passage .rdll./llr~ C~
of electric voltage across. In the FIG. 4 embodiment, the first circuit board layer 60 has an electric paths 78, 80 across the inner facing surface 79 of board 6(); the second circuit board layer 62 has an electric paths 74, 76 across the inner facing surface 81 of board 62. The first inner facing surface 79 of the first circuit board 60 faces the first inner facing surface 81 of the second circuit board 62. The spacing between the two surfaces 79, 81 is determined by a thickness of the electrically insulative layer 64. The thickness of the first circuit board 60 and the second circuit board 62 therefore do not make a difference in the spacing between the electric paths 74, 78 and 76, 80.
B,oth the flexible printed circuit board configuration and the mating printed circuit board configuration enable the first and second electric paths to be very close to each other. Therefore, the description under the flexible printed circuit board segment applies to both configurations. All embodirnents of the present invention permit very close electric path spacing, while ensuring proper insulation between the two electric paths. In addition, the insulator in all embodiments does not effect the cancellation of magnetic fluxes caused by substantially even electric flow through the two electric paths.
Another embodiment of the invention is shown in FIG. 5. Here, a portion 91 of a met~lli7~tion layer consisting, for example, of copper, is laid down near two other portions 93 and 95. Portion 91 may be connected to the phase line, portion 93 may be connected to the neutral line and portion 95 may be connected to the ground line. As can be seen, all three portions are on the same side. Each portion is connected to a separate met~lli7Ation layer 10 l, 103 through leads (not shown), and the met~lli7~tion layers are ra~ r~ a~
separated by one or more layers 97, 99 of a plastic substrate, to form a multilayer board.
~ Ihile only a few embodiments of the present invention have been described in this disclosure, it is understood that many changes and modifications that would be obvious to one having ordinary skill in the art upon consideration of the disclosure and the drawings are within the scope of the present invention.
I ~wor~ r~!lle~
Claims (34)
1. A surge protector comprising:
a flexible printed circuit board;
a metal oxide varistor mounted on said printed circuit board;
a first metalization layer and a second metalization layer applied to said printed circuit board, the first metalization layer arranged to supply electricity to said metal oxide varistor, said second metalization layer arranged to connect said metal oxide varistor to a ground/neutral plane; and a minimal thickness insulative layer separating said first metalization layer from said second metalization layer.
a flexible printed circuit board;
a metal oxide varistor mounted on said printed circuit board;
a first metalization layer and a second metalization layer applied to said printed circuit board, the first metalization layer arranged to supply electricity to said metal oxide varistor, said second metalization layer arranged to connect said metal oxide varistor to a ground/neutral plane; and a minimal thickness insulative layer separating said first metalization layer from said second metalization layer.
2. The surge protector of claim 1, wherein said minimal thickness insulative layer comprises at least a segment of said printed circuit board.
3. The surge protector of claim 2, wherein said first metalization layer is affixed to a first side of said printed circuit board, and said second metalization layer is affixed to a second side of said printed circuit board, said first side being opposed to said second side.
4. The surge protector of claim 3, wherein said first metalization layer is spread less than .03 inches from said second metalization layer.
5. The surge protector of claim 1, wherein said flexible printed circuit board has a thickness of approximately 0.01 inches.
6. The surge protector of claim 1, wherein said printed circuit board comprises a first printed circuit board and a second printed circuit board, said first metalization layer is affixed to a metalized side of said first printed circuit board, while said second metalization layer is affixed to a metalized side of said second printed circuit board.
7. The surge protector of claim 6, further comprising an insulative plastic material positioned between said metalized side of said first printed circuit board and said metalized side of said second printed circuit board.
8. The surge protector of claim 6, further comprising an insulative plastic material positioned between said metalized sides of said first printed circuit board and said second printed circuit board.
9. The surge protector of claim 1, wherein said first metalization layer further comprises a first electrical path capable of providing a conductive path from a power source to the metal oxide varistor.
10. The surge protector of claim 9, wherein said conductive path is low in impedance.
11. The surge protector of claim 10, wherein said conductive path is a very short distance, but relatively wide.
12. The surge protector of claim 10, wherein said second metalization layer further comprises a second electrical path capable of providing a conductive path from the metal oxide varistor to an electrical ground/neutral.
13. The surge protector of claim 12, wherein said second metalization layer on the second mirrors a path of the first metalization layer as closely as possible.
14. A method of producing a flexible printed circuit board for use in a surge protector, comprising:
affixing a first metalization layer to a first side of said flexible printed circuit board, wherein voltage supplied from a voltage source to an MOV module passes through said first metalization layer;
affixing a second metalization layer to a second side of said flexible printed circuit board, the outline of said second metalization layer largely following the outline of said first metalization layer, the maximum distance between any point in said first metalization layer and a corresponding point in said second metalization layer being less than or equal to .03 inches.
affixing a first metalization layer to a first side of said flexible printed circuit board, wherein voltage supplied from a voltage source to an MOV module passes through said first metalization layer;
affixing a second metalization layer to a second side of said flexible printed circuit board, the outline of said second metalization layer largely following the outline of said first metalization layer, the maximum distance between any point in said first metalization layer and a corresponding point in said second metalization layer being less than or equal to .03 inches.
15. A method for producing a surge protector, comprising:
affixing a first metalization layer to a first side of a first printed circuit board;
affixing a second metalization layer to a second side of a second printed circuit board;
positioning said first side of said first printed circuit board and said first side of said second printed circuit board on opposed sides of an insulative plastic layer.
affixing a first metalization layer to a first side of a first printed circuit board;
affixing a second metalization layer to a second side of a second printed circuit board;
positioning said first side of said first printed circuit board and said first side of said second printed circuit board on opposed sides of an insulative plastic layer.
16. The method of claim 15, wherein said insulative layer has a maximum thickness of .05 inches.
17. The method of claim 15, wherein said first metalization layer further comprises:
a first electrical path capable of providing a conductive path from a power source to the metal oxide varistor.
a first electrical path capable of providing a conductive path from a power source to the metal oxide varistor.
18. The method of claim 17, wherein said conductive path is low in resistance.
19. The method of claim 17, wherein said conductive path is a very short distance, but relatively wide.
20. The method of claim 19, wherein said second metalization layer further comprises:
a second electrical path capable of providing a conductive path from the metal oxide varistor to an electrical ground/neutral.
a second electrical path capable of providing a conductive path from the metal oxide varistor to an electrical ground/neutral.
21. The method of claim 20, wherein said second metalization layer on the second mirrors a path of the first metalization layer as closely as possible.
22. The method of claim 15, wherein said positioning step comprises affixing said first side of said first printed circuit board and said first side of said second printed circuit board to opposed sides of an insulative plastic layer.
23. A printed circuit board capable of being associated with a surge protector, comprising:
a metal oxide varistor;
a first metalization layer and a second metalization layer attached to said printed circuit board, the first metalization layer arranged to supply electricity to said metal oxide varistor, said second metalization layer arranged to connect said metal oxide varistor to a ground/neutral plane; and a minimal thickness insulative layer separating said first metalization layer from said second metalization layer.
a metal oxide varistor;
a first metalization layer and a second metalization layer attached to said printed circuit board, the first metalization layer arranged to supply electricity to said metal oxide varistor, said second metalization layer arranged to connect said metal oxide varistor to a ground/neutral plane; and a minimal thickness insulative layer separating said first metalization layer from said second metalization layer.
24. The printed circuit board of claim 23, wherein said first metalization layer is affixed to a first side of said printed circuit board, and said second metalization layer is affixed to a second side of said printed circuit board, said first side being opposed to said second side.
25. The printed circuit board of claim 24, wherein said printed circuit board comprises a first printed circuit board and a second printed circuit board, said first metalization layer is affixed to a metalized side of said first printed circuit board, while said second metalization layer is affixed to a metalized side of said second printed circuit board.
26. The printed circuit board of claim 25, further comprising:
an insulative material positioned between the metalized side of said first printed circuit board and the metalized side of said second printed circuit board.
an insulative material positioned between the metalized side of said first printed circuit board and the metalized side of said second printed circuit board.
27. The printed circuit board of claim 26, wherein said insulative material is formed from plastic.
28. The printed circuit board of claim 24, wherein said first metalization layer further comprises:
a first electrical path capable of providing a conductive path from a power source to the metal oxide varistor.
a first electrical path capable of providing a conductive path from a power source to the metal oxide varistor.
29. The printed circuit board of claim 28, wherein said conductive path is low in impedance.
30. The printed circuit board of claim 29, wherein said conductive path is a very short distance, but relatively wide.
31. The printed circuit board of claim 30, wherein said second metalization layer further comprises:
a second electrical path capable of providing a conductive path from the metal oxide varistor to an electrical ground/neutral.
a second electrical path capable of providing a conductive path from the metal oxide varistor to an electrical ground/neutral.
32. The printed circuit board of claim 31, wherein said second metalization layer on the second mirrors a path of the first metalization layer as closely as possible.
33. The printed circuit board of claim 23, wherein said first metalization layer is affixed to a portion of a first side of said printed circuit board, andsaid second metalization layer is affixed to a second portion of said printed circuit board, both portions being on the same side of said printed circuit board.
34. A multilayer printed circuit board capable of being associated with a surge protector, comprising:
a metal oxide varistor;
first, second and third metalization layers attached to said printed circuit board said first metalization layer being separated into different portions, said first portion being arranged to supply electricity to said metal oxide varistor, said second portion being arranged to connect said metal oxide varistor to a ground/neutral plane, and said third portion being arranged to connect said metal oxide varistor to a phase plane; and a plurality of minimal thickness insulative layers separating said first, second and third metalization layers from each other.
a metal oxide varistor;
first, second and third metalization layers attached to said printed circuit board said first metalization layer being separated into different portions, said first portion being arranged to supply electricity to said metal oxide varistor, said second portion being arranged to connect said metal oxide varistor to a ground/neutral plane, and said third portion being arranged to connect said metal oxide varistor to a phase plane; and a plurality of minimal thickness insulative layers separating said first, second and third metalization layers from each other.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US79112697A | 1997-01-30 | 1997-01-30 | |
| US08/791,126 | 1997-01-30 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2228012A1 true CA2228012A1 (en) | 1998-07-30 |
Family
ID=25152774
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2228012 Abandoned CA2228012A1 (en) | 1997-01-30 | 1998-01-26 | Flexible printed circuit board for use with metal oxide varistor, applicable to a surge protector |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2228012A1 (en) |
-
1998
- 1998-01-26 CA CA 2228012 patent/CA2228012A1/en not_active Abandoned
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