AU613450B2 - Overvoltage protection device and material - Google Patents
Overvoltage protection device and material Download PDFInfo
- Publication number
- AU613450B2 AU613450B2 AU30424/89A AU3042489A AU613450B2 AU 613450 B2 AU613450 B2 AU 613450B2 AU 30424/89 A AU30424/89 A AU 30424/89A AU 3042489 A AU3042489 A AU 3042489A AU 613450 B2 AU613450 B2 AU 613450B2
- Authority
- AU
- Australia
- Prior art keywords
- binder
- material according
- conductive particles
- materials
- overvoltage protection
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Ceased
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Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B1/00—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors
- H01B1/20—Conductive material dispersed in non-conductive organic material
- H01B1/24—Conductive material dispersed in non-conductive organic material the conductive material comprising carbon-silicon compounds, carbon or silicon
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B1/00—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors
- H01B1/14—Conductive material dispersed in non-conductive inorganic material
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B1/00—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors
- H01B1/14—Conductive material dispersed in non-conductive inorganic material
- H01B1/16—Conductive material dispersed in non-conductive inorganic material the conductive material comprising metals or alloys
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B1/00—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors
- H01B1/14—Conductive material dispersed in non-conductive inorganic material
- H01B1/18—Conductive material dispersed in non-conductive inorganic material the conductive material comprising carbon-silicon compounds, carbon or silicon
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B1/00—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors
- H01B1/20—Conductive material dispersed in non-conductive organic material
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B1/00—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors
- H01B1/20—Conductive material dispersed in non-conductive organic material
- H01B1/22—Conductive material dispersed in non-conductive organic material the conductive material comprising metals or alloys
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01C—RESISTORS
- H01C7/00—Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material
- H01C7/10—Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material voltage responsive, i.e. varistors
- H01C7/105—Varistor cores
Description
PCT:
OPI DATE 11/08/89 APPLN. I D 304~24 89 INTERNATIONAL APPLICA' AOJ.P. DATE 07/09/89 PCT NUMBER PCT/US89/00048 (51) International Patent Classification~ (1t) International Publication Number: WO 89/ 06859 HOICFr 7/1 Date: nt 27 July 1989 (27.07.89) Pubcrioa (21) International Application Number: PCT/US89/00048 (22) International Filing Date: I11 January 1989 (11.01.89) (81) Designated States: AU, BE (European patent), DE (European paitent), DK, FR (European patent), GB (European patent), IT (European patent), JP, NL (European patenQ), SE (European patent).
Published Without iternational search report and to be republished upon leeceipt of that report.
(31) Priority Application Number: 143,615 (32) Priority Date:, (33) Priority Country-, I I January 1988 (11,01.88) (71X72) Applicant and Inventor, SHR1ER, Karen, P. [US/ US]; 2399 Purisima Creek Road, Route I, Box 313H, Half Moon Bay, CA 94019 (US).
(74) Agents: Di'.TON, Philip, A, et at.; Flehr, Hohbacl, Test, Albritton Herbert, Four Embarcadero Center, Suite 3400, San Francisco, CA 94111-4187 (US), (54)Titte: OVERVOLTAGE PROTECTION DEVICE AND MATERIAL 2 3 2 1
L
202J2 %G GU O6oOGUG G G Q O1)~ct o)o00 7 3 Q 0 Q Q o3C) C? 0C? -24 1A 2 (57) Abstract A material device (12) for electronic circuitry that provides protection from fast. transient overvoltage pulses (11).
The electroded device (24) can additionally be tailored to provide electrostatic bleed, k onductlve particles (22) are urn iformly dispersed in an Insulating matrix or binder (23) to provide material having r~ontlineair resistance characteristc,, The non-inear resistance characteristics of the material are determined by the Interparticle spacing within the binder, as well as by the electrical properties of the, Insulating binder, By tailoring, the separation, between conductive partk..1c,,, there.
by controlling quantum-mechanilcal tunneling, the electrical properties or the non-linear material can be varied over a wide range.
-1- OVERVOLTAGE PROTECTION DEVICE AND MATERIAL SUMMARY OF THE INVENTION The present invention relates to materials, and devices using said materials, which protect electronic circuits from repetitive transient electrical overstresses. In addition to providing overvoltage protection, these materials can also be tailored to provide both static bleed and overvoltage protection.
According to the present invention there is provided an overvoltage protection material for placement between and in contact with spaced conductors, said material Icomprising a matrix formed of an insulating binder and only close y spaced conductive particles: said only closely spaced conductive particles homogeneously distributed "t 15 in said insulating binder, said particles being in the range of 0.1 microns to two hundred microns and spaced to provide quantum-mechanical tunneling therebetween; and said insulating binder selected to provide a quantum-mechanical tunneling media and predetermined resistance between said conductive particles.
Preferably, the materials have non-linear electrical resistance characteristics and can respond to repetitive electrical transients with nanosecond rise times, have low electrical capacitance, have the ability to handle substantial energy, and have electrical resistances in the range necessary to provide bleed off of static charges.
Still more particularly, the materials formulations and device geometries can be tailored to provide a range of on-state resistivities yielding clamping voltages ranging from fifty (50) volts to fifteen thousand (15,000) volts. The materials formulations can also be simultaneously tailored to provide off-state resistivities yielding static bleed resistances ranging from one hundred thousand ohms to ten meg-ohms or 9104174q*dt.6,3XO424.,1 O )CF
V
jj la greater. If static bleed is not required by the final application the off-se .ate resistance can be tailored to range from ten meg-ohms Wo one thousand meg-ohms or greater while still maintaining the desired on-state resistance for voltage clamping purposes.
0 0 00 0 jo 00 6000 0000 0 0 0 0 0 0 19 0 0 I P 000000 O 0 0404 0 00 04 0 *0 a0 0 0 Y> N 910417.gcpdat.063,304244 WO 89/06859 PCT/US89/00048 2 In summary the materials described in this invention are comprised of conductive Particles dispersed uniformly in an insulating matrix or binder. The mnaximumn size of the particles is determined by the spacing between the electrodes. In the desired embodiment the electrode spacing should equal at least five particle diameters. For example, using electrode spacings of approximately one thousand microns, maximum particle size is approximately two hundred microns. Smaller particle sizes can also be used in this example. Inter-particle separation must be small enough to allow quantum mechanical tunneling to occur between adjacent conductive particles in response to incoming transient electrical overvoltages.
Even more particularly, the nature of the dispersed particles in a binder allows the advantage of making the present invention in virtually unlimited sizes, shapes, and geometries depending on the desired application. In the case of a polymer binder, for example, the material can be molded for applications at virtually all levels of electrical systems, including integrated circuit dies, discrete electronic devices, printed circuit boards, electronic equipment chassis, connectors, cable and interconnect wires, and antennas, 7be nature of the dispersed particles iW a binder allows the advantage of mtW~kng the present invention in virtually unlimited sizes, shapes, and geometries dependig on the desired application.
WO 89/06859 PCT/US89/00O48 3 BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a typi.al electronic circuit application using devices of the present invention.
Figure 2 is a magnified view of a cross-section of the non-linear material.
Figure 3 is a typical device embodiment using the materials of the invention.
Figure 4 is a graph of the clamp voltage versus volume percent conductive particles.
Figure 5 is a typical test setup for measuring the over-voltage response of devices made from the invention.
Figure 6 is a graph of voltage: versus time for a transient over-voltage pulse applied to .0 a device zpade from the present invention.
DETAILED DESCRIPTION OF THE INVENTION As shown in Figure 1, devices made from the present invention provide protection of associated circuit components and circuitry against incoming transient overvoltage signals. The electrical circuitry IC' in Figure 1 operate at voltages generally less than a specified value termed Vi and can be damaged by incoming transient overvoltages of -4more than two or three times V1. In Figure 1 the transient overvoltage 11 is shown entering the system on electronic line 13. Such transient incoming voltages can result from lightning, EMP, electrostatic discharge, and inductive power surges. Such transient incoming voltages can damage two terminal devices, electroded devices, and leaded electroded devices.
Upon application of such transient overvoltages the non-linear device 12 switches from a high-resistance state to a low-resistance state thereby clamping the voltage at point 15 to a safe value and shunting excess electrical current from the incoming line 13 to the system ground 14.
.The non-linear material is comprised of conductive particles that are uniformly dispersed in an insulating matrix or binder by using standard mixing techniques. The on-state resistance and off-state resistance of the material are determined by the inter-particle spacing within the binder as well as by the electrical properties of the insulating binder. The binder serves two roles electrically: first it provides a media for tailoring separation between conductive particles, thereby controlling quantummechanical tunneling, and second as an insulator it allows the electrical resistance of the homogeneous dispersion to be tailored. During normal operating conditions and 20 within normal operating voltage ranges, with the non-linear material in the off-state, the resistance of the material is quite high. Typically, it is either in the range required for bleed-off of electrostatic charge, ranging from one hundred thousand ohms to ten meg-ohms or more, or it is high resistance, in the gig-ohm region. Conduction by static bleed in the off-state, and conduction in response to an overvoltage transient is i 25 primarily between closely adjacent conductive particles and results from quantum mechanical tunneling through the insulating binder material separating the particles.
910417,&cpdaI.D63,30424,4 'WO 89/06859 PCT/US89/00048 Figure 2 illustrates schematically a two terminal device with inter-particle spacing between conductive particles, and electrodes 24. The electrical potential barrier for electron conduction from particle 21 to particle 22 is determined by Lhe separation distance 20 and the electrical properties of the insulating binder material 23. In the off-state this potential barrier is relatively high and results in a high electrical resistivity for the non-linear material. The specific value of the bulk resistivity can be tailored by adjusting the volume percent loading of the conductive particles in the binder, the particle size and shape, and the composition of the binder itself. For a well blended, homogeneous system, the volume percent loading determines the interparticle spacing.
Application of a high electrical voltage to the non-linear material dramatically reduces the potential barrier to inter-particle conduction and results in greatly increased current flow through the material via quantum-mechanical tunneling. This low electrical resistance state is referred to as the on-state of the non-linear material. The details of the tunneling process and the effects of increasing voltages on the potential barriers to conduction are well described by the quantum-mechanical theory of matter at the atomic level. Because the nature of the conduction is primarily quantum mechanical tunneling, the time response of the material to a fast rising voltage pulse is very quick. The transition from the off-state resistivity to the on-state resistivity takes place 1,f 20 in the sub-nanosecond regime, -6- A typical device embodiment using the materials of the invention is shown in Figure 3. The particular design in Figure 3 is tailored to protect an electronic capacitor in printed circuit board applications. The material of this invention 32 is moulded between two parallel planar leaded copper electrodes 30 and 31 and encapsulated with an epoxy. For these applications, electrode spacing can be between 0.005 inches and 0.050 inches.
In the specific application of the device in Figure 3 a clamping voltage of 200 volts to 400 volts, an off-state resistance of ten meg-ohms at ten volts, and a clamp time less than one nanosecond is required. This specification is met by moulding the material between electrodes spaced at 0.010 inches. The outside diameter of the *see device is 0.25 inches. Other clamping voltage specifications can be met by adjusting the thickness of the material, the material formulation, or both.
15 An example of the material formulation, by weight, for the particular embodiment i* shown in Figure 3 is 35% polymer binder, 1% cross linking agent, and 64% conductive powder. In this formulation the binder is Silastic 35U silicone rubber, the crosslinking agent is Varox peroxide, and the conductive powder is nickel powder with 10 micron average particle size.
Those skilled in the art will understand that a wide range of polymer and other binders, conductive powders, formulations and materials are possible. The binder may be a polymer which has had its resistance characteristics modified by addition of materials such as powdered metallic compounds, powdered metallic oxides, powdered semiconductors, organic semiconductors, organic salts, coupling agents, and dopants.
Other conductive particles which can be blended with a binder to form the non-linear material in this invention include metal powders of aluminum, beryllium, iron, gold, silver, platinum, lead, tin, bronze, brass, copper, bismuth, cobalt, magnesium, molybdenum, palladium, tantalum, tungsten and alloys thereof, carbides including titanium carbide, boron carbide, tungsten carbide, and tantalum carbide, powders based on carbon including carbon black and graphite, as well as metal nitrides and metal 910417cpd&LQE3,30424,c,6 I I I ;i -7borides. Insulating binders can include but are not limited to organic polymers such as polyethylene, polypropylene, polyvinyl chloride, natural rubbers, urethanes, and epoxies, silicone rubbers, fluoropolymers, and polymer blends and alloys. Other insulating binders include ceramics, refractory materials, waxes, oils, and glasses.
Other insulating binders include fumed silicon dioxide, quartz, alumina, aluminum trihdrate, feld spar, silica, barium sulphate, barium titanate, calcium carbonate, woodflour, crystalline silica, talc, mica, or calcium sulphate. The primary function of the binder is to establish and maintain the inter-particle spacing of the conducting particles in order to ensure the proper quantum mechanical tunneling behaviour during application of an electrical overvoltage situation.
The binder, while substantially an insulator, can be tailored as to its resistivity by adding to it or mixing with it various materials to alter its electrical properties. Such materials include powdered varistors, organic semiconductors, coupling agents, and antistatic agents.
A wide range of formulations can be prepared following the above guidelines to provide clamping voltages from fifty volts to fifteen thousand volts. The interparticle spacing, determined by the particle size and volume percent loading, and the 20 device thickness and geometry govern the final clamping voltage. As an example of this, Figure 4 Shows the Camping Voltage as a function of Volume Percent Conductor for materials
C
0SO* 0O 0 S6 go.* 0 *000
S
50000 0 00 hi i 9M17gCPtW3,Vo4247 WO 89/06859 PCT/US9/00048 8 of the same thickness and geometry, and prepared by the same mixing techniques.
The off-state .resistance of the devices tested for Figure 4 are all approximately ten meg-ohms.
Figure 5 shows a test circuit for measuring the electrical response of a device made with materials of the present invention. A fast rise-time pulse, typically one to five nanosecond rise time, is produced by pulse generator 50. The output impedance 51 of the pulse generator is fifty ohms. The pulse is applied to non-linear device under test 52 which is connected between the high voltage line 53 and the system ground 54.
The voltage versus time characteristics of the non-linear device are measured at points 55 and 56 with a high speed storage oscilloscope 57.
The typical electrical response of a device tested in Figure 5 is shown in Figure 6 as a graph of voltage versus time for a transient overvoltage pulse applied to the device, In Figure 6 the input pulse 60 has a rise time of five nanoseconds and a voltage amplitude of one thousand volts. The device response 61 shows a clamping voltage of 360 volts in this particular example. The off-state resistance of the device tested in Figure 6 is eight meg-ohms.
Processes of fabricating the material of this invention include standard polymer processing techniques and equipment. A preferred process utilizes a two roll rubber mill for incorporating the conductive particles into the binder material, The polymer material is banded on the mill, the crosslinking agent if required is added, and the conductive i I WO&89/06859 PCT/US89/00048 9 particles added slowly to the binder. After complete mixing of the conductive particles into the binder the blended is sheeted off the mill rolls. Other polymer processing techniques can be utilized including Banbury mixing, extruder mixing and other evmilar mixing equipment. Material of desired thickness is molded between electrodes.
Further packaging for environmental protection can be utilized if required.
Claims (4)
1. An overvoltage protection material for placement betwein and in contact with spaced conductors, said material comprising a matrix formed cf, .i~sulating binder and only closely spaced conductive particles: said only closely spaced conductive particles homogeneously distributed in said insulating binder, said particles being in the range of 0.1 microns to two hundred microns and spaced to provide quantum-mechanical tunneling therebetween; and said insulating binder selected to provide a quantum-mechanical tunneling media and predetermined resistance between said conductive particles. O:0O
2. A material according to Claim 1 wherein the binder is an electrical insulator. *e 15
3. A material according to Claim 1 wherein the binder material has electrical resistivity ranging from 108 to about 10'6 ohm-centimetret, 0
91417.cp41W,30424,cj "WO 89/06859 PCT/US&9/00048 11
4. A material according to claim 1 wherein the binder is a polymer which has had its resistance characteristics modified by addition of materials such as powdered metal- 1c compounds, powdered metallic oxides, powdered semiconductors, organic semi- conductors, organic salts, coupling agents, and dopants. A material according to claim 1 wherein the binder is selected from the class of or- ganic polymers such as polyethylene, polypropylene, polyvinyl chloride, natural rub- bers, urethanes, and epoxies. 6. A material according to claim I wherein the binder is selected from silicone rub- bers, fluoropolymers, and polymer blends and alloys. 7. A material according to claim 1 wherein the binder is selected from the class of materials including ceramics, and refractory allow. 8. A material according to claim I wherein the binder is selected from the class of materials including waxes and oIL 9, A materlal according to claim I wherein the binder is selected from the class of materials including glasses, A mateial according to claim 1 wherein the binder includes fumed silicon dioxide, quartz, alumina, ,,9luminmm trihydrate, feld spar, silica, barium sulphate, barium WO 89/06859 12 PCT/US89/00048 titanate, calcium carbonate, woodflour, crystalline silica, talc, mica, or calcium sul- phate. 11. A material according to claim 1 wherein the conductive particles include powders of aluminum, beryllium, iron, gold, silver, platinum, lead, tin, bronze, brass, cop- per, bismuth, cobalt, magnesium, molybdenum, palladium, tantalum, tungsten and alloys thereof, carbides including titanium carbide, boron carbide, tungsten carbide, and tantalum carbide, powders based on carbon including carbon black and graphite, as well as metal nitides and metal borides. 12. A material according to claim 1 wherein the conductive particles include-uniform- y-sized-hellow-or-selid-glass-sph e coated with a conductor such as inelude pow- ders of aluminum, beryllium, iron, gold, silver, platinum, lead, tin, bronze, brass, copper, bismuth, cobalt, magnesium, molybdenum, palladium, tantalum, tungsten and alloys thereof, carbides including titanium carbide, boron carbide, tungsten car- bide, and tantalum carbide, powders based on carbon including carbon black and gr-pnite, as well as metal nitrides and metal borides. 13. A material according to claim 1 wherein the conductive particles have resistivities ranging from about 10' 1 to 10 ohm-centimeters. 14. A material according to claim 1 wherein the percentage, by volume, of conductive particles in the material is greater than about 0.5% and less than about I i WO 89/06859 PCT/US89/00048 13 A two terminal device utilizing materials in any one of Claims 1 through 14 to provide nanosecond transient overvoltage protection to electronic circuitry between terminals. 16. An electroded device utilizing materials in any one of Claims 1 through 14 to provide nanosecond transient over- voltage protection to electronic circuitry. 17. A leaded electroded device utilizing materials in any one of Claims 1 through 14 to provide nanosecond transient overvoltage protection to electronic circuitry. 18. A& device utilizing materials in any one of Claims 1 through 14 to provide nanosecond transient overvoltage protection to electronic circuitry and electrostatic bleed. 1c An electroded device utilizing materials in any one of Claims 1 through 14 to provide nanosecond transient over- voltage protection to electronic circuitry and electrosta- tic bleed. A leaded electroded device utilizing materials in any one of Claims 1 through 14 to provide nanosecond transient overvoltage protection to electronic circuitry and electrostatic bleed.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US07/143,615 US4977357A (en) | 1988-01-11 | 1988-01-11 | Overvoltage protection device and material |
| PCT/US1989/000048 WO1989006859A2 (en) | 1988-01-11 | 1989-01-11 | Overvoltage protection device and material |
| US143615 | 2002-05-10 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| AU3042489A AU3042489A (en) | 1989-08-11 |
| AU613450B2 true AU613450B2 (en) | 1991-08-01 |
Family
ID=26779276
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| AU30424/89A Ceased AU613450B2 (en) | 1988-01-11 | 1989-01-11 | Overvoltage protection device and material |
Country Status (1)
| Country | Link |
|---|---|
| AU (1) | AU613450B2 (en) |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US472699A (en) * | 1892-04-12 | Louie e | ||
| AU508717B2 (en) * | 1977-03-16 | 1980-03-27 | General Electric Company | Electrical overvoltage surge arrestor |
| AU519633B2 (en) * | 1978-04-14 | 1981-12-17 | Asea Brown Boveri, Inc. | Composition of and a method for fabricating a zinc oxide voltage limiter |
-
1989
- 1989-01-11 AU AU30424/89A patent/AU613450B2/en not_active Ceased
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US472699A (en) * | 1892-04-12 | Louie e | ||
| AU508717B2 (en) * | 1977-03-16 | 1980-03-27 | General Electric Company | Electrical overvoltage surge arrestor |
| AU519633B2 (en) * | 1978-04-14 | 1981-12-17 | Asea Brown Boveri, Inc. | Composition of and a method for fabricating a zinc oxide voltage limiter |
Also Published As
| Publication number | Publication date |
|---|---|
| AU3042489A (en) | 1989-08-11 |
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