JP3181263B2 - Method for manufacturing electrical device - 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

DETAILED DESCRIPTION OF THE INVENTION

[0001]

FIELD OF THE INVENTION The present invention relates to electrical devices and, more particularly, to a method for fabricating a circuit protection device including a PTC conductive polymer configuration.

[0002]

Introduction to the Invention Conductive polymer compositions exhibiting PTC (positive temperature coefficient) properties and electrical devices containing them are well 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. 76237
07 (Moyer); European Patent Specification No. 158,410 and serial number 141,989 (MP07
15, Evans); 656,04 filed as EP 63,440
6 (MP0762, Jacobs et al.); 818,846 and 75,929 filed as EP 231,068 (MP1100, Barma); 83,09
3 (MP1090, Kleiner); 102,989 (MP1220, Fang and others); 103,077 (MP1222, Fang and others); 115,089 (MP090
6, Fang other); 124,696 (MP0906, Fang other), 150,0
05 (MP0906, Fahey and others); and 219,416 (MP1266, Ho
rsma and others).

[0003] 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 excessive current or temperature, the device is "tripped", i.e., has 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 a 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 prophylactic measurements are described in U.S. Patent Nos. 4,317,027 and 4,352,083.
And described herein with reference to these disclosures.

[0004] Reference is made to US Patent 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, for the purpose of achieving a close thermal coupling between the two resistors, are placed on one side of the ceramic substrate that carries the thick-film resistor, and It is mounted face-to-face or on each side of another insulating layer. The purpose of this configuration is that a failure occurs in the voltage of the power line applied to the thick film resistor, and the thick film resistor is overheated.
This is to prevent this thick film resistor from being exposed to fire. If such a failure occurs, an increase in the initial temperature of the thick film resistor will heat the PTC 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 in such a way as to provide as close a thermal connection as possible between the ceramic material and the thick film resistor.

[0005] Circuit protection devices having excellent physical properties and excellent 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.

[0006]

If an attempt is made to crosslink the PTC element by electron beam irradiation in order to obtain a suitable circuit protection performance, the gas formed will cause the electrodes formed on the PTC element to peel off.

[0007]

SUMMARY OF THE INVENTION A good circuit protection against excessive currents (and the voltages that cause such currents) is a PTC device.
(The terms “PTC device” and “PTC resistor” are used interchangeably) and a second that modifies the PTC device's response to a fault condition to a desired degree, at least under certain fault conditions where protection is required. And the use of a composite protective device comprising the electrical components of the present invention. 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 so that the "trip time" of the device,
In other words, so that the circuit current is reduced to a safe level,
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 in current by the PTC device may help protect the second element and / or protect other elements of the circuit.

According to the present invention, in the circuit protection configuration including the PTC resistor and the second resistor which is connected in series with the PTC resistor and does not enter an open circuit state, two important protection mechanisms exist. I also discovered that
The first mechanism is that a relatively low voltage is added to the protection configuration,
Protection is provided by the PCT resistor increasing the resistance and reducing the current to a safe level. The second mechanism is that a relatively high voltage is applied to the protection mechanism and protection is provided by the second resistor not being an open circuit. According to the present invention, it has further been discovered that the degree of thermal coupling between the PTC resistor and the second resistor has a profound effect on making these protection mechanisms work 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.

[0009] The PTC resistor may be of any type, for example, a ceramic or a conductive polymer. However, the present invention has specific values for PTC materials, especially conductive polymers,
Dangerous situations can be reduced if they are subject to excessive electrical strain (ie, greater than those involved in normal expected fault conditions). 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 similar excessive stresses (or electrical stresses related to electrical stress in a certain way to the PTC resistance), the PTC material is not subjected to dangerous degradation for a sufficiently short period of time. In the open circuit state. With such a configuration,
Under the influence of excessive electrical stress, the reversal of the rule previously performed 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.

[0010] The second resistor may be of any type, but is preferably a ZTC resistor, and the ability to eliminate open circuit conditions is achieved in any manner. 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. The open circuit condition is eliminated as a result of the difference in the 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, e.g., 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 created, for example, by means of electrical leads and / or by means of metal surfaces or bands through which current does not flow (extending from the substrate), and / or by, 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 may be 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 circuit protection system comprising a PTC resistor and a second resistor connected in series with the PTC resistor and in thermal contact with the PTC resistor. And this system
The breaking current I _B (measured as described below) and the holding current I _H (measured as described below), and at most 20, preferably at most 15, and particularly preferably at most 10 I _B /
It has an _IH ratio.

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.
Accordingly, in a second aspect, the present invention provides an electrical device comprising: (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) having a resistance R ₁ , and (iii) (a) P at switching temperature Ts
Thin P made of conductive polymer exhibiting TC characteristics
A TC element, and (b) a first electrical element having at least two thin plate-like electrodes connected to a power supply such that current flows between the electrodes through the PTC element; (3) (a) at least Physically approaching one of the substrates,
(b) there is at least good thermal contact with the one of the first element is electrically connected to at least a first element (c), has a resistance R ₂ which changes as a function of (d) Voltage ,
At least one second electrical element; (4) electrically connected to at least one of the first elements;
An electrical connector in thermal contact with at least one second element.

[0014] The use of a sheet-like PTC device in a composite device is advantageous for achieving sufficient contact and rapid heat transfer between the PTC device and the second element;
And it 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 that the PTC device be illuminated, and for many applications where the applied voltage is 60 VAC or higher,
High irradiation, for example greater than 50 Mrad, 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 that under these circumstances, during the crosslinking process, gas is generated more rapidly than is consumed. As a result, devices designed for use under high voltage conditions, in order to avoid layer separation of the metal foil electrodes due to gas generation, have a device-like, sheet-like element attached to the surface of a sheet-like conductive polymer element. Rather than being formed by metal foil or mesh electrodes, they are formed by parallel columnar electrodes diffused in a matrix of conductive polymer. For example, U.S. Pat. No. 656,046, filed as European Patent Application No. 63,440, requires that a sheet-like conductive polymer element be irradiated before a sheet-like electrode is mounted to form a device. It is. 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 fabricate sheet-like devices, sheet-metal foil electrodes are attached prior to irradiation, and the device with columnar electrodes is a rapid gas at the polymer / electrode interface. It is desirable not to suffer from the formation of spaces as a result of the release. It is also desirable that the sheet-like device can withstand relatively high voltages and currents without laminating the sheet-like electrodes. If the conductive polymer element is kept at a low temperature during irradiation,
It has been discovered that electrical devices with excellent performance can be manufactured.

Therefore, in a third aspect, the present invention provides:
(1) a PTC element comprising a crosslinked conductive polymer exhibiting PTC properties and comprising a polymer element, and comprising particles of a conductive filler dispersed within the polymer element; and (2) a PTC element.
Providing a method of making an electrical device comprising: two electrodes electrically connected to a TC element and connectable to a power supply to generate a current through the PTC element. Cross-linking is carried out, the cross-linking being carried out by using an electron beam, and the following conditions: (a) the average irradiation rate is as fast as 3.0 Mrad / min; (b) each current-supply part of the PTC element Is at least 50 Mrad, and in the crosslinking reaction, no part of the PTC element in contact with the electrodes reaches a temperature above (Tm-60) ° C., where Tm is the polymer The temperature measured at the peak of the endothermic curve by the differential scanning calorimeter of the polymer having the lowest melting point in the element.

The present invention further includes a power supply, a load and a circuit protection device or an electrical circuit including the above-described device. In such a circuit, the first and second electrical components are under normal operating and fault conditions of the circuit (eg, the second
Is the surge resistance in the telephone circuit), both are connected in series, or the second element is
No current flows through this under normal operating conditions, but a fault condition
(Eg, when the second element is a VDR connected to ground to provide clamping means in the telephone circuit), it is in series with the first element.

DETAILED DESCRIPTION OF THE INVENTION The circuit protection device of the present invention
It exhibits PTC characteristics. Term the "PTC", in this specification, has at least 2.5 of the R ₁₄ value or at least 10 of the R ₁₀₀ value, and preferably have both values, and particularly preferably at least 6 having a R ₃₀ value, is used to mean a device (e.g., PTC resistor) or structure, where the R _14, the ratio of the resistivity of the beginning and end of the range of 14 ° C., R ₃₀
Is the ratio of the end-to-start resistivity in the 30 ° C. range, and R ₁₀₀ is the end-to-start resistivity ratio in the 100 ° C. range. "ZTC characteristics" is used to mean a device or configuration whose resistivity increases by a factor of 6, preferably 2 or more over any temperature range of 30 ° C within the operating range of the heater.

[0019] The invention described herein relates to electrical devices that include conductive polymer elements, and to a method of making such devices. This conductive polymer element is
It comprises 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 also contains non-oxides, inert fillers, prorads, stabilizers,
It may be a dispersing agent or other element. 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 has a switching temperature T
s exhibits a PTC characteristic, which is defined as the intersection of the tangent to the relatively flat portion of the logarithmic curve of resistivity versus temperature and the steep portion of the curve. Suitable configurations and PTC devices including configurations are disclosed in U.S. Patent Nos. 4,237,411; 4,238,812; 4,255,698; 4,315,237; 4,317,02
7; 4,329,726; 4,452,083; 4,413,301; 4,450,496; 4,475,13
8; 4,481,498; 4,534,889; 4,562,313; 4,647,894; 4,647,89
6; 4,685,025; 4,724,417; 4,774,024; and U.S. Patent Application No. 141,989 (MP0715), the disclosures of which are incorporated herein by reference. If the PTC element 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 element may exhibit PTC properties. Must.
The conductive polymer has a temperature of Ts to (Ts + 20) ° C., preferably T
s to (Ts + 40) ° C., particularly preferably Ts to (Ts + 7)
5) Should have a resistivity that does not decrease in the range of ° C.

The two electrodes attached to the PTC element are adapted to be connected to a power supply in order to generate a current in the PTC element. The electrode may be an embedded parallel columnar electrode in a conductive polymer,
Alternatively, it may be a thin plate-like electrode including a hard or perforated metal or metal net attached to the surface of the PTC element. 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 efficiency, speed and cost of irradiation. The device may be irradiated at any level, but for devices intended for use with high voltage application, 50 to 100 Mrad or more (e.g.
Irradiation at 50 Mrad) is preferred. This irradiation may be performed in one or more stages, each irradiation being performed in P
The TC element is heated to a temperature above the melting point of the polymer element;
It may then be separated by a heat treatment step, which is cooled to crystallize the polymer element. The cross-linking treatment is
This is done with or without electrodes 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 laminar electrode where current flows in the laminar electrode in a direction normal to the surface (i.e., 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 central portion of the PTC element between and parallel to the electrodes should be illuminated with a minimum dose.

During the irradiation phase, the temperature of any part of the PTC element that is in contact with the electrodes is (Tm-6
0 ° C., preferably (Tm−80). For devices composed of high concentration polyethylene having a Tm of approximately 130 ° C., the temperature is 6
0 ° C. or lower, preferably 50 ° C. or lower, particularly preferably 40 ° C.
It is important to keep the temperature below ° C. For an electron beam,
Irradiation is performed using a fan or gas, or by placing the device adjacent to an object having a large heat-absorbing capacity and cooling the device. Alternatively, the temperature may be maintained at 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 (i.e., hydrogen from the crosslinking step) will be balanced with the rate of diffusion of the gas from the device,
Almost no gas bubbles are observed at the boundary between the PTC element and the electrode, even if there is gas generation. As a result, in the case of a thin plate device, the thin plate electrode does not lead to layer separation,
When the cylindrical electrode is embedded, the polymer /
The number of bubbles and voids is limited at the electrode boundaries. This results in improved electrical performance while the current is being applied.

The thin plate-shaped electric device of the present invention
It may include a PTC element that includes one 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, it comprises first, second and third layers,
Devices are preferred in which all current paths between the electrodes pass continuously through the first, second and third layers. The second layer, sandwiched between the first and third layers, is preferably located at a hot line formed when the device is exposed to current. This configuration is achieved through the use of a second layer having a greater room temperature resistivity than both the first and third. During operation, heat is generated at the point of maximum resistivity through the heating of the I ² R, and this action is applied to the top or bottom of the (first or third layer) of the device by the (second Enhanced by the limited heat dissipation of the central region of the layer.
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, It has been found that a useful configuration is achieved when the volume is at least 2, preferably at least 3, particularly preferably at least 4% by volume. The resistivity of the second layer is preferably at least 20%, in particular at least 2%, higher than the first and third resistivity.
Times, particularly preferably at least 5 times higher. The PTC element formed with three layers may include a second layer having a resistivity of 50 ohm-cm or less, or a resistance of 100 ohm or less. In another embodiment, the resistivity of the first and third layers is 0.1 times the resistivity of the second layer.

The stacked devices are described in the section for the formation of PTC and ZTC materials that differ in resistivity by at least an order of magnitude. If the switching temperature T of each layer
If s is within 15 ° C. of the switching temperature of the second layer, 3
It has been found that effective lamellar devices can be formed when all of the layers exhibit PTC properties. It is preferred that the Ts be 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. Useful sheet-like devices have also been formed. Preferred devices are
At least 0.060 inches, especially at least 0.10
It has a total thickness of 0 inches. They have a resistance of less than 100 ohms. Such devices are advantageous for circuit protection applications, especially when exposed to irradiation at applied voltages of 120 V or higher, especially at levels of 50 Mrad or higher. Particularly for such applications, preference is given to devices in which at least the second layer, preferably the first and the third layer, likewise comprise an inorganic filter. Particularly preferred are those inorganic filters,
It preferably serves as a means of controlling the arc and, when heated in the absence of air, decomposes to provide water, carbon dioxide or nitrogen. References regarding suitable materials, including alumina trioxide and magnesium hydroxide, are disclosed in U.S. Patent No. 4,774,024 and Application No. 141,989.

[0028] Aspects of the electrical device of the present invention include at least one first element, at least one second element, often a laminar PTC resistor, a laminar substrate, and electrical leads. 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. The resistance value of the resistor at 23 ° C. is preferably at least twice, particularly preferably at least 5 times, compared to the resistance of the PTC element at 23 ° C.
In particular it is at least 10 times or even higher, for example at least 20 times. The resistance of the resistor preferably does not substantially increase with temperature. For example, for a 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, or even higher, for example at least 1
It is 00 times. The combined 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, generally 1 to 5 ohms.

[0029] Two or more second electrical elements may be provided, each of which may 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 double hybrid protection, such as comprising 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 second electrical element). (Element 2) to the 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
Device, the resistance of the device is
It is determined as the resistance of the C element and the resistance of the coupled second element (ie, those second elements connected in series with the PTC element). For such a device, P
The resistance of each "unit" comprising the TC 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 wire, ink connector pads, clips or other suitable means. When the element is located on the opposite side of the substrate, the connection means may be formed by metallizing a portion drilled through the substrate.

Preferred substrates are electrically insulating, but have some thermal conductivity, such as, for example, alumina or berylia. 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, it is preferred that the alumina (or other) substrate have a maximum dimension of 0.100 inch thick, 1.5 inch wide, and 0.400 inch high . With this configuration, 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 perpendicular 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. This PTC
The 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 systems with circuit protection, the holding current
(The current flowing through the system is high when the PTC device has high resistance.)
The maximum current that does not cause a "trip" condition) and the breaking current
Both (ie, 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 means that when the second element includes a thick film resistor that exhibits cracking if the thermal gradient is too severe,
Of particular importance. Thus, for many systems, it is desirable that at least a portion of the PTC device not overlap the second element when the system is viewed at right angles to the plane of 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 resistor (when viewed perpendicular to the plane of the thick film resistor) is preferably at most 50%, especially At most 25%, especially 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 will degrade.

The holding current I _H and the breaking current I _B can be determined by testing the electrical device including the PTC device and the second element with two test circuits. In the first circuit shown in FIG. 1, the composite device R ₁ is connected in series with a variable resistor R ₂ , a DC power supply _VDC , and an ammeter A. R ₂ value
(Fixed during the test) means that when the voltage is changed from 0 V to 70 V, the current measured by the ammeter is 0 to 100 m
A is selected to change to A. 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. The voltage at which the current drops to zero (or approximately equals 10% of the maximum measured current) is recorded as _VH . The holding current is calculated from the following equation. I _H = V _H / (R ₁ + R ₂ )

The cutoff current is determined 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
Variable resistor R ₃ is adjusted to 1000 ohms. 110V
AC power is applied for one 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 resistance of the variable resistor in the last “cut-off” 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 Current I _B and holding current I _H , and I _B / I _H
The ratio is at most 20, preferably at most 15, and particularly preferably at most 10. I _B / I _H ratio is also at least 3,
Preferably at least 5, particularly preferably at least 7
It is preferred that

FIG. 3 is a view showing the state of the 2
1 shows a circuit protection device (that is, a PTC device) 1 having a plurality of sheet metal electrodes 2 and 3. This PTC element includes 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. Lead 2 for connecting this device to the circuit
1, 22 are provided at one end of the silver conductive pad 9 under thick film resistance and 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 They are arranged on opposing surfaces. Lead wire 2
1, 22 are suitable for insertion into 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.

FIGS. 9 and 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. Between the PTC device 1 and the thick film resistor 6, and the PTC
The electrical connection between the device 1 'and the thick film resistor 6' is made independently by means of solder paste or solder leads 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 the PTC element 1 'is made by means of a lead wire 41'. 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 an alumina substrate 5,
Shown is a device with PTC1 stacked between two ruthenium oxides 6,6 ', each printed on 5'. This P
The TC device has foil electrodes 2 and 3 formed with electrodes and resistors 6 and
It is attached to the substrate by means of the solder layer 40 between 6 '. The wire leads 21 and 22 are connected to the conductor pads 91 and
Mounted at 91 ', it allows current to flow from the lead through the first resistor 6, the PTC device 1 and the second resistor 6'.

FIG. 12 shows an apparatus including a plurality of elements. The two PTC devices 1, 1 'are soldered by means of a layer 40 onto resistors 61, 61' printed on the respective side of the laminar substrate 5 ". Two additional substrates 5 , 5 'are attached to the remaining faces of the PTC element, and wire leads 21, 22, 21', 22 'are provided with conductor pads 91, to provide two separate units to which power is applied individually. , 91 '.

FIGS. 13-18 show possible designs for a composite device including a PTC resistor.
C resistance, a second resistance, and / or, separated from the means for influencing the relationship between I _B and I _H, as its means, for example, an additional lead wire (FIG. 15), the heat - Shrinkable tip (Fig. 14), irregular (eg narrowing) resistance
(FIG. 16), cut or cut substrates (individually
7 and 18).

Example 1 The conductive compounds A and B listed in Table 1
Prepared by micronizing and extruding into sheets using a (Banbury) mixer. Two 0.025 inch (0.064 cm) thick Compound A sheets are each combined with a 0.020 inch (0.051 cm) thick Compound B sheet.
By laminating on each side of the sheet, a thickness of 0.1
A 20 inch (0.304 cm) thinned plate was made. 0.0014 inch (0.00
A 36 cm) electrodeposited nickel foil electrode was mounted on each side of the plate. The PTC device is placed at 0.
It was prepared by cutting into 3 x 0.3 inch (0.76 x 0.76 cm) chips. These chips are 1
It was heated at 50 ° C. for 1 hour, irradiated at 5 mA with an electron beam of 1.5 MeV at an irradiation value of 25 Mrad, heated for 2 hours, and irradiated at 5 mA with an electron beam of 1.5 MeV.
The treatment was carried out by irradiating at an irradiation value of 0 Mrad and heating for 3 hours. The electrical performance of the device is
It 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 C at 40% by volume and Compound D at 60% by volume are mixed and the mixture is 0.010 inch (0.025 cm).
Compound E was prepared by extruding into a sheet of thickness. Five Compound E sheets were laminated on both sides of a single layer of Compound B sheet, and 0.130 inches (0.3).
30 cm). After attaching the nickel electrode, the device was cut and tested as described in Example 1. The results are shown in Table 2. 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 were prepared and individually 0.014 inch
(0.036 cm) and 0.024 inches (0.061 cm) thick. By laminating two sheets of compound F on both sides of the sheet of compound G, the thickness of the compound G is increased to 0.2.
A 082 inch (0.208 cm) thick plate was made and the electrodes were mounted. The device is disconnected and, as in example 1, in the first stage 4.5 MeV, 15 mA
Is irradiated to 25 Mrad using an electron beam of 1.5 MeV and 5 mA using an electron beam of 5 mA in the second stage.
Irradiated. These devices are connected to 260V AC, 1
The results tested at 0A and 260V, 1A are shown in Table 2.

Example 4 Compound H was prepared and extruded to a thickness of 0.020 inches (0.051 cm). Two compounds F are combined with one layer of compound H
Are laminated on both sides of the substrate to form a 0.080 inch (0.0
(203 cm) thick, and after electrode attachment, the device was cut and tested according to the procedure of Example 3. As shown in Table 2, the results show that the device with the non-organic filter in the center performs better than a device similar to Example 3 without the filter.

[0050]

[Table 1] Mariex 6003 is a high-concentration polyethylene commercially available from Philippe Petroleum. Raven600 is a carbon black commercially available from Columbia Chemical Company. Kisuma 5A is a magnesium hydroxide commercially available from Mitsui.

[0051]

[Table 2]

Example 5 The conductive compounds I, J, L and M as shown in Table 3 were:
Each was prepared by micronizing each using a Bambury mixer. Equal amounts of Compounds I and J were mixed to make Compound K 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. PTC
The device is cut from the plate and processed according to the procedure of Example 1, i.e., irradiating to 25 Mrad with a 2.5 MeV electron beam in the first stage and 150 Mrad in the second stage.
Irradiation to the Mrad, during which the device reaches a surface temperature of 70 ° C. Thereafter, when electric power was applied under an alternating current of 250 V and 2 A, the nickel foil was immediately peeled off.

Example 6 The device was prepared according to the procedure of Example 1, except that the second stage emission was at 2.5 MeV with 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, 2A, and 60% of the devices survived 60 cycles at 600V, 1A.

Example 7 An electrical device made in accordance with Example 7 is shown in FIGS. A conductive pad 9 made of thick silver ink (commercially available from ESL) is mounted on a 1.0 × 0.375 × 0.050 inch (2.54 × 0.95 × 0.13 cm) aluminum substrate 5. Screen printed on the edges. A layer 6 of ruthenium oxide thick-film resistive ink (a mixture of 10 ohms / unit area and 100 ohms / unit area of the ESL3900 system and having a resistance of 20 ohms / unit area) is provided at one end of the aluminum substrate, 0.6 x 0.375 inch (1.
It was printed in a pattern of 52 × 0.935 cm) and bridged the conductor pads. A PTC device 1 having a resistance of 2.5 ohms was soldered at the other end to the top of the contact pad. The thick film resistor and the PTC device were connected by means of wire 4. Lead wires 21 and 22
Attached to the top surface electrode 2 of the PTC device and the end of the thick film resistor. As a result, the composite device has a resistance of approximately 37.5 ohms.

[0055]

[Table 3] Mariex HXM50100 is a high-density polyethylene manufactured by Philippe Petroleum. Statex G is a carbon black commercially available from Columbia Chemical Company. Kisuma 5A is a magnesium hydroxide commercially available from Mitsui. Non-oxide is 4-4'-
It is an oli-gomer of thiobis and has an average degree of polymerization of 3-4 as described in US Pat. No. 3,986,981.

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 conductive pad 9 of silver ink has a size of 0.8 × 0.4.
Screen printing was performed on both sides of a .times.0.050 inch (2.0.times.1.0.times.0.13 cm) aluminum substrate. The ruthenium oxide thick film resistor 6 was screen printed in a 0.8.times.0.3 inch (2.0.times.0.76 cm) rectangle on one side of the substrate. The PTC device was soldered to the other side. Electrical connection between the elements was made 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, as shown in FIG.
It is placed close to the TC device and each other. 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. 9 and 8. The two PTC devices 1, 1 'are placed on one side of the alumina substrate, close to the voltage limiting device 30. Thick film resistance 6,6 'of two ruthenium oxides
Are provided close to each other on opposite sides of the substrate. Resistance 6
The electrical connection between the device and the PTC 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. Conductor pads 9, 9 ', 91, 91' and thick film resistors 6,
6 'is screen-printed on one side of two alumina substrates as in Example 7. P with resistance 2 ohms
TC device 1 is located between the resistors on each substrate,
And it is attached with solder 40. Lead wire 21,2
2 are attached to the conductor pads 91, 91 'on each substrate, and when this lead wire is connected to a power supply, a current flows from the lead wire 21 through the resistor 6, the PTC device 1, and the resistor 6'. The total resistance of the device is 100 ohms.

EXAMPLE 12 The electrical device of this example is shown in FIG. Two PTC devices were made according to the procedure of Example 6. 2
The 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 surface of both laminar substrates. Between the two-layer coated substrate 5 "and the two-layer coated substrate 5"
It is provided between the layer coating and the substrate 5 '. The four wires 21, 22, 21 ', 22' were attached to the four conductor pads 91, 91 '.

EXAMPLE 13 A thick film resistor having a resistance of 148.5 ohms is provided on one surface of the alumina substrate, and a PTC device having a resistance of 1.5 ohms is provided in the center of the surface opposite the resistor. Was done. The resulting device was tested at 23 ° C
, A current of approximately 100 mA (60 mA at 70 ° C.) was maintained, and the cutoff current was 2 A.

Example 14 An electrical device was prepared according to the procedure of Example 13, but PT
The PTC device was placed on the substrate such that no part of the C 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.

[0064]

As described above, according to the production method of the present invention, the generation of gas at the time of cross-linking is suppressed, and thus the peeling of the electrode can be prevented.

[Brief description of the drawings]

FIG. 1 is a circuit diagram for determining I _H and I _B

FIG. 2 is a circuit diagram for determining I _H and I _B

FIG. 3 is a plan view of the electric device of the present invention.

FIG. 4 is a plan view of the device of the present invention.

FIG. 5 is a sectional view taken along line AA of FIG. 4;

FIG. 6 is a plan view of another apparatus of the present invention.

FIG. 7 is a sectional view taken along line BB of FIG. 6;

FIG. 8 is a sectional view of still another apparatus of the present invention.

FIG. 9 is a plan view of the additional device of the present invention from two different sides.

FIG. 10 is a plan view of the additional device of the present invention from two different sides.

FIG. 11 is a cross-sectional view of an optional device of the present invention.

FIG. 12 is a cross-sectional view of an optional device of the present invention.

FIG. 13 shows a possible design for the composite device of the present invention.

FIG. 14 shows a possible design for the composite device of the present invention.

FIG. 15 shows a possible design for the composite device of the present invention.

FIG. 16 shows a possible design for the composite device of the present invention.

FIG. 17 shows a possible design for the composite device of the present invention.

FIG. 18 shows a possible design for the composite device of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Circuit protection device 2 Sheet metal electrode 3 Sheet metal electrode 5 Substrate 6 Thick film resistor 9 Conductive pad 10 PTC element 11 Conductive polymer layer 12 Third polymer layer 13 Second polymer layer 21 Lead wire 22 Lead wire

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Sho-Mean Fan No. 94924, Regent's Boolabad, Union City, CA 94587, USA (72) Inventor David A. Horsma USA 94301 California, Palo Alto, Parkinson Avenue 1141 (72) Inventor Jirom Pelonet United States 94301 California, Palo Alto, Cooper Street 215 (72) Inventor Charles H. Camphouse United States 94040 California, Mountain View, Number Four, Victor Way 602 ( 56) References JP-A-57-176605 (JP, A) JP-A-61-218117 (JP, A) JP-A-62-98601 ( JP, A) JP-A-60-250601 (JP, A) JP-A-62-93902 (JP, A)

Claims (10)

(57) [Claims] 1. A PTC element exhibiting PTC properties and comprising a crosslinked conductive polymer comprising polymer elements and comprising particles of conductive filler dispersed within the polymer elements; and , (2) electrically connected to the PTC element,
A method of making an electrical device, comprising: two electrodes connectable to a power supply to generate a current through a TC element, the method comprising: applying an electron beam to a PTC element with the electrodes attached; A method for producing an electrical device, wherein irradiation and crosslinking are performed by use, and the average irradiation rate at this time is high and is 3.0 Mrad / min. 2. The method according to claim 1, wherein the polymerizable element is a polymer having a crystalline structure. 3. The method of claim 1, wherein the particulate conductive filler comprises carbon black, graphite, metal or metal oxide. 4. The method according to claim 1, wherein the two electrodes include a metal foil. 5. The method according to claim 1, wherein the irradiation crosslinking is performed in one step. 6. The method according to claim 1, wherein the irradiation crosslinking is performed in two stages. 7. The method according to claim 1, wherein the electrical device is in the form of a thin plate, and the current flows in the thickness direction of the PTC element. 8. The method of claim 7, wherein the PTC device includes one or more layers. 9. The method according to claim 1, wherein the polymerizable element comprises a high concentration of polyethylene, and the PTC element having no part in contact with the electrodes does not reach a temperature higher than 60 ° C. during the crosslinking step. 10. A PTC element exhibiting PTC properties and comprising a crosslinked conductive polymer comprising polymer elements and comprising particles of conductive filler dispersed within the polymer elements; and , (2) electrically connected to the PTC element,
A method of making an electrical device comprising: two electrodes connectable to a power source to generate a current through a TC element, comprising: (a) using an electron beam on the PTC element with the electrodes attached; (B) the dose absorbed in each current-supplying portion of the PTC element should be at least 50 Mrad, and the Tm should be different from the polymer having the lowest melting point in the polymer element. When the temperature was measured by a scanning calorimeter, any part of the PTC element in contact with the electrode was prevented from reaching a temperature higher than (Tm−60) ° C. during the crosslinking reaction. Method for manufacturing electrical device.