JP3335348B2 - Electrical device containing conductive polymer - Google Patents

Abstract

Circuit protection systems which comprise a PTC resistor (1) and a second resistor (6), e.g. a thick film resistor (6), which is thermally and electrically connected to the PTC resistor have a break current IB and a hold current IH such that the ratio IB/IH is at most 20. Suitable PTC resistors (1) are conductive polymer devices which comprise a PTC element (10) which has been radiation crosslinked under conditions such that the average dose rate is at most 3.0 Mrad/minute or during which no part of the PTC element (10) which is in contact with the electrodes (2, 3) reaches a temperature greater than (Tm-60) DEG C, where Tm is the melting point of the polymeric component of the conductive polymer (10).

Description

Description: TECHNICAL FIELD This invention relates to electrical devices, and more particularly, to circuit protection devices that include a PTC conductive polymer configuration.

Introduction to the Invention Conductive polymer configurations exhibiting the properties of PTC (Positive Temperature Coefficient) and electrical devices containing them are widely known. A specification has been prepared in this regard, for example, in the United States, Patent Numbers: 3,243,753; 3,351,882; 3,861,029; 4,
177,376; 4,237,441; 4,238,812; 4,255,698; 4,286,376; 4,
315,237; 4,317,027; 4,329,726; 4,330,703; 4,352,083; 4,
413,301; 4,426,633; 4,450,496; 4,475,138; 4,481,498; 4,
534,889; 4,543,474; 4,562,313; 4,647,894; 4,647,896; 4,
685,025; 4,654,511; 4,689,475; 4,724,417; 4,761,541; and 4,774,024; French Patent Specification No. 7623707 (Moyer);
EP 158,410 and serial number 141,989 (MP0715, Evans) filed as EP 38,713;
656,046 filed as European Patent 63,440 (MP0762, Ja
cobs et al.); 81 filed as EP 231,068
8,846 and 75,929 (MP1100, Barma); 83,093 (MP1090, Kle
iner); 102,989 (MP1220, Fang and others); 103,077 (MP122
2, Fang other); 115,089 (MP0906, Fang other); 124,69
6 (MP0906, Fang et al.), 150,005 (MP0906, Fahey et al.); And 219,416 (MP1266, Horsma et al.).

In particular, useful devices that include PTC conductive polymers are circuit protection devices. Such devices have a relatively low resistance under normal operating conditions, but when a fault condition occurs, such as when excessive current or temperature occurs.
The device is "tripped", that is, transitioned to a high resistance state. When the device is tripped due to excessive current, the current passing through the PTC element causes the PTC element to self-heat and rise to a temperature at which it becomes a high resistance state. When the circuit protection device is "tripped", a thermal gradient is created. At the point where the thermal gradient flows in the same direction as when the current flows, measurement can be performed to confirm the peak temperature of the thermal gradient. That is, "hot lines" and "hot zones" are not formed near the electrodes. Such a prophylactic measurement is described in U.S. Pat.
7,027 and 4,352,083, which are described herein with reference to these disclosures.

Reference is made here to U.S. Pat. No. 4,467,310 (Jacab), which describes resistors powered by batteries, including thick-film resistors and disc-shaped PTC resistors. The thick-film resistor and the PTC resistor are electrically connected in series, and on one side of the ceramic substrate that carries the thick-film resistor, for the purpose of achieving close thermal coupling between the two resistors.
They are mounted facing each other or on each side of another insulating layer. The purpose of this configuration is to break down the power line voltage applied to the thick film resistor,
This is to prevent the thick film resistor from being exposed to a danger of fire due to overheating of the thick film resistor. If such a failure occurs, the rise in the initial temperature of
Heats the C resistor, thereby rapidly increasing the resistance and reducing the current to a safe level before the thick film resistor is overheated. As a result, PTC resistors provide protection (both for thick film resistors and other components of the circuit) by reducing the current to a weaker current. In all devices according to Jacab, the PTC resistor is composed of a ceramic material and is mounted so as to provide as close a thermal connection as possible between this ceramic material and the thick film resistor.

Circuit protection devices with good physical properties and good electrical performance are obtained when the conductive polymer tissue containing the device is cross-linked. Such cross-linking can be achieved by a chemical cross-linking agent or gamma ray or electron irradiation, or a combination thereof. It is often true that electron beam generated ion irradiation is the fastest and most cost-effective means of crosslinking.

SUMMARY OF THE INVENTION Good circuit protection against excessive currents (and the voltages that cause such currents) is due to the fact that PTC devices (the terms "PTC device" and "PTC resistor" are used interchangeably)
It has been discovered that at least under certain failure situations where protection is needed, the response of the PTC device to a failure condition can be obtained by using a composite protection device that includes a second electrical element that modifies the desired degree. For example, the second element may be a resistor that generates heat in a fault condition, and this heat is applied to the PTC device, resulting in a device "trip time", that is, a reduction in circuit current to a safe level. As a result, the time required for the PTC device to be converted to a high resistance state and a high temperature state is reduced. The second element may function to substantially reduce trip time only, but is preferably part of a circuit protection system. The reduction of current by PTC device
It may help to protect the second element and / or to protect other elements of the circuit.

According to the present invention, the PTC resistor and the second PTC resistor are connected in series with the PTC resistor and do not enter the open circuit state.
It has also been discovered that there are two important protection mechanisms in a circuit protection configuration with the following resistors. The first mechanism works when a relatively low voltage is applied to the protection configuration, increasing the resistance and reducing the current to a safe level.
Protection is provided by PTC resistors. The second mechanism functions when a relatively high voltage is applied to the protection configuration, and the second mechanism does not enter the open circuit state even in this state.
Protection is provided by the resistance of According to the present invention, PT
It has further been discovered that the degree of thermal coupling between the C resistance and the second resistance has a profound effect on the ability of these protection mechanisms to function with a particular voltage. The better the thermal coupling between the resistors, the higher the voltage required to cause the second mechanism to take precedence over the first mechanism.

The PTC resistor may be of any type, for example, it may be composed of a ceramic or a conductive polymer.
However, the present invention has specific values for PTC materials, especially conductive polymers, which allow them to be subjected to excessive electrical stress (i.e., those included in normal expected failure conditions). Can also reduce dangerous situations when subjected to high stress. Such a dangerous situation can be avoided according to the invention by coupling the PTC resistor with the second resistor. That is, when subjected to a similar excessive stress (or an electrical stress related to the electrical stress in a certain way to the PTC resistance), the PTC material is short enough that it does not suffer from dangerous degradation. Ensure that the second resistor does not go into an open circuit state in time. With such a configuration, under the influence of excessive electrical stress, the reversal of the rule that previously worked in the protective configuration including the PTC resistor and the second resistor occurs. That is, the PTC resistor protects the second resistor before (before) the second resistor protects the PTC resistor.

The second resistor may be of any type, but is preferably a ZTC resistor, and the ability to eliminate open circuit conditions is achieved by any method. The present invention relates to specific values for thick films or other resistors supported by a ceramic substrate. Such a thick film resistor may have different resistances and / or different parts of the substrate and / or on the substrate which, under excessive electrical stress, can lead to different parts of the resistance and / or the substrate and / or separation of the resistance. Open circuit conditions as a result of the differential expansion of one or more connections to the resistor located at As a result, conditions that can eliminate such open circuit conditions are highly dependent on the dimensions and configuration of the substrate, for example, weak surfaces (e.g., drawn with a laser or diamond) that can crack due to thermal gradients that exist during use. (A constricted portion or groove). Such thermal gradients may be provided, for example, by means of electrical leads and / or by means of metal surfaces or strips (extending from the substrate) through which current does not flow, and / or such as, for example, wedge-shaped The use of irregularly shaped resistors can be affected by differences in heat penetrating the substrate.

The PTC resistor and the second resistor are preferably part of one composite device.

There are many PTC resistors, such PTC resistors may be the same or different, connected in series or parallel to each other, and / or there may be many second resistors, such resistors may be the same or different And are connected in series or in parallel.

Accordingly, in its first aspect, the present invention provides a PTC
There is provided a circuit protection system comprising a resistor and a second resistor connected in series with the PTC resistor and in thermal contact with the PTC resistor, the system comprising an interrupting current I (measured as described below). _B , and a holding current I _H (measured as described below), and an I _B / I _H ratio of at most 20, preferably at most 15, and particularly preferably at most 10.

A composite device in which the PTC resistor is connected to a second element that is not a resistor is also provided by the present invention. Therefore, the second
In an aspect, the present invention provides an electrical device,
The apparatus comprises: (1) at least one sheet-like substrate; and (2) at least one first electrical element,
(I) physically approaching at least one of the above substrates;
(Ii) the resistance R ₁ has, and (iii) (a) switching temperature Ts in laminar PTC element composed of a conductive polymer exhibiting PTC behavior, and (b) current through the PTC element between the electrodes (A) physically approaching at least one of said substrates; and (b) providing a first electrical element having at least two sheet-like electrodes connected to a power supply such that in good thermal contact with the at least one of the first element is electrically connected to at least a first element (c), it has a resistance R ₂ which changes as a function of (d) the voltage, at least a And (4) an electrical connector electrically connected to at least one of the first elements and in thermal contact with the at least one second element.

The use of a sheet-like PTC device in a composite device requires sufficient contact between the PTC device and the second element,
It is advantageous to achieve rapid heat transfer, and provides optimal utilization of the available space, especially when the composite device is designed for use on a printed circuit board. For most applications, it is desirable for the PTC device to be illuminated, and for many applications where the applied voltage is 60V AC or higher, high illumination, e.g., greater than 50Mrad, is useful. . One difficulty with electron beam irradiation is that there is a rapid rise in temperature in the conductive polymer as a result of high irradiation to them. An additional problem is
Under these circumstances, the evolution of gas during the crosslinking process is more rapid than is consumed. As a result, devices designed for use under high voltage conditions to avoid delamination of the metal foil electrode due to gas evolution were mounted on the surface of the laminar conductive polymer element,
Rather than being formed by sheet metal foil or mesh electrodes, they are formed by parallel columnar electrodes that are diffused into a conductive polymer matrix. For example, European Patent Application No. 6
U.S. Pat. No. 656,046, filed as 3,440, requires irradiating a lamellar conductive polymer element before the lamellar electrodes are mounted to form a device. For devices that include diffused columnar electrodes, rapid heating and gassing during irradiation results in the formation of a space at the polymer / electrode interface, resulting in contact resistance and high voltage application. Occupies a position for electrical failure during operation.

In order to efficiently and inexpensively manufacture thin plate devices,
A sheet metal foil electrode is attached prior to irradiation, and
It is desirable that such devices with columnar electrodes not suffer from the formation of spaces at the polymer / electrode interface as a result of rapid outgassing. It is also desirable that the sheet-like device can withstand relatively high voltages and currents without laminating the sheet-like electrodes. It has been discovered that if the conductive polymer element is kept at a low temperature during irradiation, an electrical device with excellent performance can be manufactured.

Thus, in a third aspect, the present invention relates to a method for preparing a crosslinked conductive polymer that exhibits (1) PTC properties and includes a polymer element and includes particles of a conductive filler dispersed within the polymer element. And (2) two electrodes electrically connected to the PTC element and capable of being connected to a power supply to generate a current through the PTC element. (A) the average irradiation rate is as fast as 3.0 Mrad / min; and the method comprises subjecting the PTC device to radiation crosslinking, the crosslinking being performed by using an electron beam, and the following conditions: b) The dose absorbed in each current-supplying part of the PTC element is at least 50 Mrad, and in the crosslinking reaction any part of the PTC element in contact with the electrode (T
m-60) ° C., where Tm is the temperature measured at the peak of the differential scanning calorimeter endothermic curve for the polymer with the lowest melting point in the polymer element. Meet one.

The invention further includes an electrical circuit comprising a power supply, a load and a circuit protection device or the device described above. In such a circuit, the first and second electrical elements are connected in series under normal operating and fault conditions of the circuit (eg, when the second element is a surge resistor in a telephone circuit). Alternatively, the second element may have no current flowing under normal operating conditions, but have a fault condition (eg, when the second element is a VDR connected to ground to provide clamping means in a telephone circuit). ) Is in series with the first element.

DETAILED DESCRIPTION OF THE INVENTION The circuit protection device of the present invention exhibits PTC characteristics.
The term "PTC" is used in this specification for at least 2.
A 5 R ₁₄ value or at least 10 R ₁₀₀ value of, and preferably have both values, and particularly preferably means having the R ₃₀ value of at least 6, the device (e.g., PTC resistor) or structure Where:
R ₁₄ is the ratio of the end-to-start resistivity in the range of 14 ° C., R ₃₀ is the ratio of the end-to-start resistivity in the range of 30 ° C., and R ₁₀₀ is 100 It is the ratio of the end-to-start resistivity in the range of ° C. “ZTC characteristics”
Is used to mean a device or configuration whose resistivity increases by a factor of 6, preferably 2 or more, at any temperature range of 30 ° C. within the operating range of the heater.

The invention described herein relates to electrical devices that include a conductive polymer element, and a method for making such devices. The conductive polymer element is composed of a polymerizable element and a particulate conductive filler dispersed in the polymerizable element. The polymerizable element is preferably a polymer of crystalline structure or a mixture comprising at least one polymer of crystalline structure, such terms being used to include siloxane. The polymer element has a melting point defined as the peak temperature in the endothermic curve generated by the differential scanning calorimeter. If the polymer element is a mixture of polymers, its melting point is defined as the melting point of the lowest melting polymerizable element. The conductive filler is graphite, carbon black, a metal, a metal oxide, itself containing an organic polymer and a particulate conductive filler, a particulate conductive polymer or a composite of these. Is also good. The conductive polymer element may also be a non-oxide, inert filler, prorads, stabilizers, dispersing agents, or other elements. Dispersion of the conductive filler and other elements may be accomplished by dry mixing, melt processing or diffusion. The resistivity of the conductive polymer is
Measured at 23 ° C (ie, room temperature).

The conductive polymer element exhibits PTC characteristics at the switching temperature Ts, which is defined as the intersection of the tangent to the relatively flat part of the logarithmic curve of resistivity versus temperature and the steep part of the curve. . Suitable configurations and PTC devices including configurations are described in U.S. Pat.Nos. 4,237,411;
12; 4,255,698; 4,315,237; 4,317,027; 4,329,726; 4,452,0
83; 4,413,301; 4,450,496; 4,475,138; 4,481,498; 4,534,8
89; 4,562,313; 4,647,894; 4,647,896; 4,685,025; 4,724,4
17; 4,774,024; and U.S. Patent Application No. 141,989 (MP0715)
And are described herein with reference to these disclosures. If the PTC device includes one or more layers and one or more of the layers that do not exhibit PTC properties are made from a polymerizable configuration, the composite layer device is a PTC device.
Must exhibit characteristics. The conductive polymer can be converted from Ts to (Ts
+20) ° C, preferably from Ts to (Ts + 40) ° C, particularly preferably from Ts to (Ts + 75) ° C.

Two electrodes attached to the PTC element are adapted to be connected to a power source to generate a current in the PTC element. This electrode may be an embedded parallel columnar electrode in a conductive polymer, or a sheet-like electrode comprising a hard or perforated metal or metal mesh attached to the surface of the PTC element. You may. Particularly preferred is an electrode made of a metal foil of nickel or copper having a microscopic surface roughness by electrodeposition.

The electrical device may be cross-linked by use of a chemical cross-linking agent or an ionizing radiation source such as a cobalt source or an electron beam. Electron beams are particularly preferred for irradiation efficiency, speed and cost. The device may be irradiated at any level, but for devices intended for use with high voltage application, 50 to 10
Irradiation at 0 Mrad or more (eg 150 Mrad) is preferred. This irradiation may be performed in one or more stages, each irradiation being heated to a temperature above the melting point of the polymer element and cooled to crystallize the polymer element. And the heat treatment step. The cross-linking treatment is performed with or without an electrode attached to the PTC element. Irradiation is defined as the minimum amount of radiation absorbed by each current-carrying portion of the PTC element. In the case of a lamella where current flows through the lamella in a direction normal to the plane (ie in the thickness direction of the PTC element), the entire PTC element must be irradiated to a minimum dose. For devices with embedded columnar electrodes, the center of the PTC element between and parallel to the electrodes is
It should be irradiated at the minimum dose.

During the irradiation phase, it is preferred that the temperature of any part of the PTC element in contact with the electrode does not rise above (Tm-60) C, preferably above (Tm-80) C.
For devices composed of high-concentration polyethylene having a Tm of approximately 130 ° C., the temperature is below 60 ° C., preferably
It is important to keep the temperature at 50 ° C or lower, particularly preferably at 40 ° C or lower. In the case of an electron beam, the device is cooled using a fan or gas or by placing the device adjacent to an object with a large heat-absorption capacity.
Irradiation is performed. Alternatively, it may be performed while maintaining a low temperature by using a low electron beam current of 3.0 Mrad / min at a high average irradiation speed. This value is based on the intensity of the electron beam and the speed at which the device passes through the beam path, taking the half height value in the instantaneous irradiation rate bell curve plotted as a function of the position of the device in the beam path. Is calculated. If the device is kept cool during the irradiation process, the rate of evolution of gas (ie, hydrogen from the cross-linking step) will be balanced with the rate of diffusion of gas from the device, and even if there is gas evolution,
Almost no bubbles are observed at the boundary between the PTC element and the electrode. As a result, in the case of lamellar devices, lamellar electrodes do not lead to layer separation, and the number of bubbles and voids is limited at the polymer / electrode boundary when columnar electrodes are embedded. . This results in improved electrical performance while the current is being applied.

The laminar electrical device of the present invention may include a PTC element containing three or more layers of conductive polymer. This layer may have the same or different polymerizable elements, or the same or different conductive fillers. In particular, a device having the first, second, and third layers, and in which all current paths between the electrodes continuously pass through the first, second, and third layers, is preferable. The second sandwiched between the first and third layers
Is preferably located at a hot line formed when the device is exposed to current. This configuration,
A room temperature resistivity is achieved by using a second layer that is greater than both the first and third. During operation, I ² R
Through the heating of the device, heat is generated at the point of maximum resistivity, the effect of which is to limit the central region of the (second layer) to the top or bottom of the (first or third layer) of the device. Enhanced heat dissipation. If the hot line is controlled in the center of the device, the hot line is not formed with electrodes, eliminating one mechanism of failure common to laminar devices.

The resistivity of the three layers can be varied in several ways. The polymerizable elements of the layers are the same, but the loading of the conductive filler is different for the second layer. In most cases, higher resistivity is achieved by lowering or equaling the loading of conductive filler, which has a lower conductivity than the filler of the first layer. In some cases, higher resistivity may be achieved by using the same amount of conductive filler but less non-conductive filler. When the conductive filler is carbon black, the polymerizable element is the same for the layers, but the loading of carbon black in the second layer is less than in the first and third layers, At least 2, preferably at least 3,
It has been found that a useful configuration is achieved, especially when at least 4% by volume. The resistivity of the second layer is preferably at least 20%, in particular at least two times, particularly preferably at least five times higher than the first and third resistivity. The PTC element formed by three layers is 50
A second layer having a resistivity of less than ohm-cm or less than 100 ohms may be provided. In another embodiment,
The resistivity of the first and third layers is the resistivity of the second layer.
It is 0.1 times.

Stacked devices differ in resistivity by at least an order of magnitude
Reference is made to the formation of PTC and ZTC materials.
It has been found that if the switching temperature Ts of each layer is within 15 ° C. of the switching temperature of the second layer, an effective lamellar device can be formed when all three layers exhibit PTC properties. Preferably, the Ts is the same for all three layers, which can be achieved by using the same polymerizable element in the conductive polymer configuration for each layer.

When the second layer has a thickness of 1/4 or less, especially 1/5 or less of the total thickness of the first, second and third layers, the hot line is controlled and useful lamination. Laminated devices are also formed. Preferred devices are at least 0.06
It has a total thickness of 0 inches, especially at least 0.100 inches. They have a resistance of less than 100 ohms. Such a device is advantageous for circuit protection applications, especially when the applied voltage is 120 V or higher and is exposed to irradiation at a level of 50 Mrad or higher. Particularly for such applications, preference is given to devices comprising a configuration in which at least the second layer, preferably the first and third layers, likewise comprise an inorganic filter. It is particularly preferred that these inorganic filters serve as arc control means and decompose to provide water, carbon dioxide or nitrogen when heated in the absence of air. Suitable materials, including alumina trioxide and magnesium hydroxide, include:
Nos. 4,774,024 and 141,989, the disclosures of which are incorporated herein by reference.

The embodiment of the electric device of the present invention is often a thin plate-shaped PT.
Including at least one first element, at least one second element, a laminar substrate, and electrical leads that are C-resistance. The second element is typically a resistor, whose resistance is relatively independent of voltage, but in one aspect of the invention, the second element has a resistance that varies as a function of voltage. It is preferred to have. Such elements include voltage-dependent resistance (VDR) such as varistors, transistors or other electrical elements. Separately, the second element may be, for example, a thick film resistor, a thin film resistor, a metal film resistor, a carbon resistor, a metal wire or, for example, melt molding (including melt extrusion, transfer molding and injection molding), melt molding (printing). , Sintering, or any other suitable technique. The resistance value of a resistor formed by one of these techniques can be changed by a laser trimming technique. Resistance value of resistor at 23 ° C is PTC at 23 ° C
Preferably at least twice the resistance of the device,
Particularly preferably at least 5 times, especially at least 10 times
Double or even higher, for example at least 20 times. The resistance of the resistor preferably does not substantially increase with temperature. For example, for high voltage application of about 200 V or more, the resistance of the resistor is generally at least 20 times, preferably at least 40 times, particularly preferably at least 60 times, compared to the resistance of the PTC element at 23 ° C. Or even higher, for example at least 100 times. The total preferred resistance of the first and second components at 23 ° C. depends on the intended use,
For example, it may be 3 to 2000 ohms, for example, 5 to 1500 ohms, but is generally 5 to 200 ohms, and the resistance value of the PTC element is, for example, 1 to 100 ohms, and is generally 1 to 5 ohms. is there.

Two or more second electrical components can be provided, each of which can be the same or different. Preferably, one of the second electrical components comprises a thick film resistor and the other second electrical component comprises a hybrid protection of two layers, wherein the second electrical component comprises a voltage limiting device. If two or more second electrical elements are provided, the combined resistance of the second electrical element connected in series with one PTC element will be the resistance (or other 2) is used to determine a desired ratio of the resistance of the PTC element to the resistance of the PTC element. If the electrical device comprises a plurality of PTC elements and a plurality of second elements, the resistance of the device is the resistance of each individual PTC element and the resistance of the combined second element (ie, the PTC (These second elements connected in series with the element). For such a device, the resistance of each "unit" comprising the PTC element and the second element is preferably the same. An electrical device comprising a plurality of first and / or second components and a substrate is advantageous in that it can provide a compact device. Such devices require less space on circuit boards, require smaller encapsulation or insulating containers, and respond more quickly to electrical fault conditions based on better thermal contact between elements. . Alternatively, the use of multiple elements provides voltage for multiple functions.

The electrical connection between the elements is made by wires, connector pads with ink, clips, or other suitable means. When the element is on the opposite side of the board,
The connection means may be formed by metallizing a portion drilled through the substrate.

Preferred substrates are electrically insulating, but for example, alumina or berylia,
It has some thermal conductivity. Such a substrate can be easily mounted on a printed circuit board by means of wires, screen printing inks, sputter traces or other suitable materials. To minimize the size of the device on the circuit board, the alumina (or other) substrate preferably has a maximum dimension of 0.100 inches thick, 1.5 inches wide, and 0.400 inches high. When configured in this manner, the device generally allows the maximum restraint height on many circuit boards to be less than 12 mm (0.47 inches).

The relative positions of the elements are important in determining the electrical response of the device. In certain embodiments, the first and second electrical elements are preferably configured such that the thermal gradient created in the PTC element is orthogonal to the direction of the current in the PTC element. This is important because the heat flow would otherwise create an undesirable hot zone close to one of the electrodes. When a laminar PTC device is used, it provides better thermal contact to the laminar substrate and can be smaller than other comparable resistance configured PTC elements. Such sheet PTC devices also exhibit flexibility. The PTC device may be provided directly on the surface of the laminar element or the second element, or may be mounted on the opposite side of the substrate. For circuit protection systems, holding current (the maximum current through the system that does not cause the PTC device to go into a high-resistance "trip" condition) and breaking current (that is, the minimum current that causes the system to open circuit) Are affected by the rate of heat dissipation into and out of the PTC device. Heat transfer is affected by the distance between the PTC device and the second element. For some applications, the PTC device preferably has a position that is an offset of the second element. This is the second
Is especially important if the thermal gradient is too severe, including a thick film resistor that exhibits cracking. Thus, for many systems, when the system is viewed at right angles to the plane of the second element, at least a portion of the PTC device will
Desirably, it does not overlap the second element. When the PTC element and the thick film resistor are substantially parallel to each other, the portion of the PTC element that overlaps the thick film resistance (when viewed perpendicular to the plane of the thick film resistor) is preferably at most 50%, especially At most 25%
In particular, it is 0%.

In some cases, the devices of the present invention may be used to protect thick film resistors or other second electrical components from degradation caused by exposure to high temperatures. Under these circumstances, the PTC device is selected to be changed to a high resistance state at a temperature below which the resistance degrades.

Holding current I _H and a breaking current I _B is, PTC device and a second
Can be determined by testing an electrical device including the above components with two test circuits. In the first circuit shown in FIG.
Composite device R ₁ is a variable resistor R _2, are connected a DC power source V _DC, and a current meter A series. The value of R ₂ (during the test is fixed), when a voltage is changed to 70V from 0V, it is selected so that the current measured by the ammeter changes from 0 to 100mA. The composite device is installed in a chamber where the air flow and temperature are controlled and stabilized at 23 ° C. Thereafter, the voltage is increased and the current in the circuit is monitored. When the current drops to zero (or nearly equals 10% of the maximum measured current)
Recorded as _VH . The holding current is calculated from the following equation.

I _H = V _H / (R ₁ + R ₂ ) The breaking current is determined by using the circuit shown in FIG. Composite device with a resistance R ₁ is connected to a variable resistor R ₃ and the AC power supply V _AC series. The resistance of the device at 23 ° C. is measured to obtain R ₀ , and the variable resistance R ₃ is 1000
Adjusted to ohms. 110V AC power is applied for 1 second. The device is then cooled to 23 ° C. for one hour and the resistance is measured. If the composite device has tripped sufficiently high resistance state during the test, the resistance is equal to 0.5 R ₀ not to 1.5R _0. Under these circumstances, the test reduced the R ₃ are repeated. This test, as resistance increases in cooled state, i.e. the device to the open state, the test is repeated until R ₃ is sufficiently small.

This interruption current is calculated from the following equation.

I _B = V / (R ₁ f + R ₃ f) where R ₁ f is the resistance of the device measured before the last “cut-off” cycle and R ₃ f is the last “cut-off”
This is the resistance of the variable resistor in the cycle.

When tested under these two circumstances, the device of the present invention, including a PTC resistor and a second resistor connected in series with the PTC resistor and in thermal contact with the PTC resistor, has has a current I _B and the holding current I _H, the I _B / I _H ratio is often 20, preferably at most 15, particularly preferably at most 10. I _B / I _H ratio is also at least 3, preferably at least 5, and particularly preferably at least 7.

FIG. 3 shows a circuit protection device (that is, a PTC device) 1 having two thin metal electrodes 2, 3 mounted on a PTC element 10. This PTC element comprises a first conductive polymer layer 11 and a third polymer layer 12 sandwiching a second conductive polymer layer 13.

FIGS. 4 to 12 show a modification of the present invention in which the circuit protection device 1 is close to a hard thin insulating substrate. In each variation, silver or other conductive paste is provided by screen printing or other means in a pattern suitable for making a connection between the PTC device 1 and the second electrical element.

FIG. 4 shows an apparatus in which the PTC device 1, the second electric element, and the thick film resistor 6 are arranged on the same side of the substrate 5. As shown in FIG. 5, which is a cross-sectional view taken along the line AA in FIG. 4, the PTC element 1 is thin and includes a PTC element as shown in FIG. Leads 21, 22 for connecting the device to the circuit are provided at one end of the silver conductive pad 9 under thick film resistance and at the top electrode 2 of the PTC device.

FIGS. 6 and 7 (cross-sectional views taken along the line BB in FIG. 4) show another modification of the present invention, in which the thick film resistor 6 and the PTC device 1 It is arranged in each. The leads 21 and 22 are suitable for passing through the printed circuit board 30 as shown.

FIG. 8 is a cross-sectional view of an apparatus including two devices of the type shown in FIG. 6, packaged to minimize the space required on a circuit board.

FIG. 9 and FIG. 10 show the respective surfaces of the alumina substrate 5 used in the modification of the present invention including three electrode elements. The two thick film resistors 6, 6 'are screen printed on one side of the substrate so as to approach each other. On the other side of the substrate, two PTC devices 1, 1 'are provided close to the voltage limiting device 30. The electrical connection between the PTC device 1 and the thick-film resistor 6 and between the PTC device 1 'and the thick-film resistor 6' are made of solder paste or solder lead.
Performed independently by means of 4,4 '. The connection between the PTC device 1 and the voltage limiting device 30 is made by means of a lead wire 41. Similarly, the connection to PTC element 1 'is
This is performed by means of 1 '. Lead wires 21,22 and 23,24
Used to connect devices to circuits. The ground lead 25 is attached to the voltage limiting device 30.

FIG. 11 shows a device in which the PTC 1 is stacked between two ruthenium oxides 6, 6 ′ printed on separate alumina substrates 5, 5 ′, respectively. This PTC device is mounted on a substrate by means of a solder layer 40 between the foil electrodes 2, 3 on which the electrodes are formed and the resistors 6, 6 '. Wire leads 21,22
Are mounted on the conductor pads 91 and 91 ', the first resistor 6, the PTC
Allow current to flow from the lead through device 1 and second resistor 6 '.

FIG. 12 shows an apparatus including a plurality of elements. The two PTC devices 1, 1 'are laminated by means of layer 40
Solder over resistors 61, 61 'printed on each side of the 5 ". Two additional boards 5, 5' are attached to the remaining sides of the PTC element. Wire leads 21, 22,21 ', 22'
Are attached to the conductor pads 91, 91 'to provide two separate units to which power is applied individually.

Figure 13 through Figure 18 show a possible design for a composite device including a PTC resistor, the PTC resistor, a second resistor, and / or from means for influencing the relationship between I _B and I _H Separated means include, for example, additional leads (FIG. 15), heat-shrinkable tips (FIG. 14), irregular (eg, tapering) resistors (FIG. 16), cuts or cuts. There is the use of substrates (FIGS. 17 and 18 respectively).

Example 1 The conductive compounds A and B listed in Table I were prepared by micronizing and extruding into sheets using a Banbury mixer. Each is thick
By laminating two 0.025 inch (0.064 cm) compound A sheets on each side of a 0.020 inch (0.051 cm) thick compound B sheet, a 0.120 inch (0.3 mm) thick
(04 cm). Electrodes of 0.0014 inch (0.0036 cm) electrodeposited nickel foil, commercially available from Fukuda, were mounted on each side of the plate. The PTC device was prepared by cutting 0.3 × 0.3 inch (0.76 × 0.76 cm) chips from the board. These chips were heated at 150 ° C for 1 hour, irradiated at 5 mA with a 1.5 MeV electron beam at an irradiation value of 25 Mrad, heated for 2 hours, and irradiated at 5 mA with a 1.5 MeV electron beam at 50 Mrad. By irradiation and heating for 3 hours,
It has been processed. The electrical performance of the device was determined by testing on two circuits. The leads were attached to the electrodes by solder. The electrical performance of the device was performed by testing on two circuits. In the first test, 260V AC, 10A power was applied to the device for 5 seconds, and in the second test, 600V AC, 1A power was applied to the device for 5 seconds. The number of devices that survived the test without flame, spark, or electrode delamination was determined after each cycle.

Example 2 Compound E was prepared by mixing 40% by volume of Compound C with 60% by volume of Compound D and extruding the mixture into a 0.010 inch (0.025 cm) thick sheet. Five Compound E sheets were laminated on both sides of a single layer of Compound B sheet, forming a 0.130 inch (0.330 cm) thick face. After attaching the nickel electrode, the device was cut and tested as described in Example 1. The results are shown in Table II. It can be seen that devices with non-organic filters in all three layers perform better than those with filters in the middle layer only.

Example 3 Compounds F and G are prepared and individually 0.014 inch (0.014 inch).
(36 cm) and 0.024 inch (0.061 cm) thick sheets. By laminating two sheets of compound F on both sides of the sheet of compound G, a 0.082 inch (0.208 inch)
cm) thick plates were made and electrodes were mounted. The device is disconnected and, as in Example 1, the first
Is irradiated to 25 Mrad using an electron beam of 4.5 MeV and 15 mA in the step, and is irradiated in a second step by using an electron beam of 1.5 MeV and 5 mA.
Irradiated at 0 Mrad. Connect these devices to 260V AC, 1
The results tested at 0A and 260V, 1A are shown in Table II.

Example 4 Compound H was prepared and extruded to a thickness of 0.020 inches (0.051 cm). The two compounds F were laminated on both sides of a single layer of compound H to form a 0.080 inch (0.203 cm) thick plate, and after electrode attachment, the device was cut and processed. The test was performed according to the following procedure.
As shown in Table II, the results show that the device with the non-organic filter in the center performs better than a similar device as Example 3 without the filter.

Mariex6003 is a high-density polyethylene marketed by Phillip Petroleum.

Raven600 is a carbon black commercially available from Columbia Chemical Company. Kisuma5A is a magnesium hydroxide commercially available from Mitsui.

Example 5 The conductive compounds I, J, L, and M as shown in Table III were prepared by using a Bambury mixer, each of which was refined. Equal amounts of compounds I and J are mixed and
Compound K was extruded into a 0.010 inch (0.025 cm) thick sheet. Equal amounts of Compounds L and M were mixed to make Compound N extruded into a 0.020 inch (0.050 cm) thick sheet. A plate was made by laminating 5 layers of compound K on both sides of 1 layer of compound N and attaching nickel foil electrodes. The PTC device is cut from the plate and processed according to the procedure of Example 1, i.e., irradiating 25 Mrad with a 2.5 MeV electron beam in the first stage and 150 Mrad in the second stage, during which the device is Reaches a surface temperature of 70 ° C. When this is done,
Power was applied under 250V, 2A and the nickel foil was immediately removed.

Example 6 A device was prepared according to the procedure of Example 1, except that the second stage radiation was performed at 2.5 MeV and an electron beam current of 2 mA, and the device reached a surface temperature of approximately 35 ° C. All of these devices survived 60 cycles at 250 VAC, 2 A, and 60% of those devices survived 60 cycles at 600 VAC, 1 A.

Example 7 An electrical device made according to Example 7 is shown in FIGS. A conductive pad 9 made of thick silver ink (commercially available from ESL) is 1.0 × 0.375 × 0.050 inch (2.5
Screen printing is performed on the edge of the aluminum substrate 5 (4 × 0.95 × 0.13 cm). Thick film resistance ink with ruthenium oxide (10 ohm / unit area and 100 ohm /
A layer 6 with a unit area mixed and a resistance of 20 ohms / unit area) is placed on one end of the aluminum substrate at 0.6 ×
Printed on a 0.375 inch (1.52 x 0.935 cm) pattern,
The conductor pads were bridged. PTC with 2.5 ohm resistance
Device 1 was attached by solder to the top of the contact pad at the other end. The thick film resistor and the PTC device were connected by wire 4 means. Lead wires 21 and 22 are PTC
Attached to the surface electrode 2 at the top of the device and the end of the thick film resistor. As a result, the composite device has a resistance of approximately 37.5 ohms.

Mariex HXM50100 is a high concentration polyethylene marketed by Philippe Petroleum.

Statex G is a carbon black commercially available from Columbia Chemical Company.

 Kisuma5A is a magnesium hydroxide commercially available from Mitsui.

The non-oxide is an oli-gomer of 4-4'-thiobis and is described in U.S. Pat. No. 3,986,981.
The average degree of polymerization is 3-4, as described in the above item.

Example 8 Five sheets of Compound K were laminated between two electrodeposited nickel foil electrodes. The PTC device was cut from the board and processed according to the procedure of Example 6. Electrical devices prepared according to this example are shown in FIGS. 4 and 5.

The silver ink conductor pads 9 were screen printed on both sides of a 0.8 x 0.4 x 0.050 inch (2.0 x 1.0 x 0.13 cm) aluminum substrate. The ruthenium oxide thick film resistor 6 was screen printed in a 0.8 x 0.3 inch (2.0 x 0.76 cm) rectangle on one side of the substrate. The PTC device was soldered to the other side. The electrical connection between the elements
This was done by means of screen printed leads from the electrode 3 at the bottom of the PTC device to one end of the thick film resistor 6.

Example 9 An electrical device was made according to the procedure of Example 6. The two individual units are in the same plane, as shown in FIG.
Placed close to each other with PTC device. This combination makes it possible to adapt the two units to the same space on the circuit board as one unit.

Example 10 An electrical device according to this example is shown in FIGS. The two PTC devices 1, 1 'are placed on one side of the alumina substrate, close to the voltage limiting device 30. The two ruthenium oxide thick film resistors 6, 6 'are provided on opposite sides of the substrate and close to each other. Resistance 6 and PTC
The electrical connection to the device 1 is made by means of screen printed leads 4. The electrical connection between the PTC device 1 and the voltage limiting device 30 is also made by means of another screen printed lead 41. The second resistor 6 'is connected to the second PTC device 1' by a lead 4 '. This second PTC device 1 'is connected to the voltage limiting device 10 by means 41' similar to the first PTC element.

Example 11 An electrical device made in accordance with this example is shown in FIG. The PTC device was made according to the procedure of Example 1. Contact pads 9, 9 ', 91, 91' and thick film resistors 6, 6 '
In the same manner as described above, screen printing is performed on one surface of two alumina substrates. PTC device 1 with 2 ohm resistance
Are located between the resistors on each substrate and are attached with solder 40. Leads 21 and 22 are attached to conductor pads 91 and 91 'on each substrate, and when the leads are connected to a power supply, lead 21 passes through resistor 6, PTC device 1 and resistor 6'. Electric current flows. The total resistance of the device is 100 ohms.

Example 12 The electrical device of this example is shown in FIG. two
A PTC device was made according to the procedure of Example 6. Two sheet-like substrates 5, 5 'were prepared as described in Example 11. A third laminar substrate 5 "was prepared by printing contact pads and ruthenium oxide on the surfaces of both laminar substrates. Using solder, the PTC device was combined with a one-layer coated substrate 5 Between the two-layer coated substrate 5 ″ and the two-layer coated substrate 5 ″ and the one-layer coated substrate 5 ′.
21 ', 22' were attached to four conductive pads 91, 91 '.

Example 13 A thick film resistor having a resistance of 148.5 ohms was provided on one surface of the alumina substrate, and a PTC device having a resistance of 1.5 ohms was provided in the center of the surface opposite the resistor. The resulting device was tested and tested at 23 ° C for almost 10
0mA (60mA at 70 ° C) current is maintained and the cutoff current is 2A
Met.

Example 14 An electrical device was prepared according to the procedure of Example 13, but the PTC
The PTC device was positioned on the substrate so that no part of the device was located on any part of the thick film resistor. The device had the same holding current as in Example 13, but the breaking current was 1A.

BRIEF DESCRIPTION The present invention in the drawings are illustrated in the accompanying drawings, in the drawings of Korare, FIGS. 1 and 2 is a circuit diagram for determining the I _H and I _B, FIG. 3 is FIG. 4 is a plan view of an apparatus of the present invention, FIG. 5 is a cross-sectional view taken along line AA of FIG. 4, and FIG. 6 is a plan view of the electric device of the present invention. FIG. 13 is a plan view of another device of FIG.
FIG. 8 is a cross-sectional view taken along the line BB of FIG. 6, FIG. 8 is a cross-sectional view of still another apparatus of the present invention, and FIGS. Plan views from different sides, FIGS. 11 and 12 are cross-sectional views of an optional device of the present invention, FIGS. 13 to 18 show possible designs for the composite device of the present invention It is.

Continuation of the front page (31) Priority claim number 124,696 (32) Priority date November 24, 1987 (November 24, 1987) (33) Priority claim country United States (US) (72) Inventor Pelonet United States 94301 California, Palo Alto, Cooper Street, 215 (72) Inventor Camphouse, Charles H. USA Takashi Kimoto, Judge Yuji Sugasawa (56) Reference US Patent 4,467,310 (US, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H02H 5/04, 9/02

Claims (5)

(57) [Claims] 1. A circuit protection system, comprising: (1) a PTC resistor composed of a conductive polymer and a PTC resistor comprising a sheet-like PTC element having at least two sheet-like electrodes; A circuit protection system comprising a second resistor connected in series with the PTC resistor and in thermal contact with the PTC resistor, comprising: (a) viewing the system from a direction perpendicular to the plane of the second resistor; And at least a portion of the PTC resistor is formed such that it does not overlap the second resistor, and (b) the system provides a blocking current when the PTC resistor transitions to a high resistance state to cut off circuit current. When the maximum current at which I _B and the PTC resistance do not become high resistance is defined as the holding current I _H , I _B / I
A circuit protection system characterized in that the _H ratio is at most 20. 2. The system according to claim 1, wherein the ratio of I _B / I _H is at least three. 3. The system according to claim 1, wherein the second resistor is a ZTC resistor whose resistivity becomes twice or more at a temperature change of 30 ° C. 4. The system of claim 3, wherein said second resistor is a thick film resistor formed on an insulating substrate ceramic. 5. The PTC element, wherein the plane of the PTC element is substantially parallel to the plane of the thick-film resistance, and when viewed from a direction perpendicular to the plane of the thick-film resistance, many PTC elements overlap the thick-film resistance. 75%
The system of claim 1 wherein: