JP2002509348A - Electrical device - Google Patents

Abstract

An electrical device (1) containing a resistive element (9) composed of a conductive polymer composition which exhibits PTC behavior which is attached to two metal foil electrodes (11, 13). The device is prepared by a method which includes the steps of (a) cutting the device from a laminate containing the conductive polymer composition positioned between two metal foils; (b) exposing the device after the cutting step to at least one thermal excursion from a first temperature which is at most (Tm-100) DEG C to a second temperature which is at most (Tm-25) DEG C; and (c) crosslinking the conductive polymer composition after the thermal excursion. The devices of the invention have low resistance and are useful as circuit protection devices.

Description

DETAILED DESCRIPTION OF THE INVENTION

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrical device containing a conductive polymer and a method for manufacturing the device.

(Introduction to the Invention) Electric devices containing a conductive polymer composition exhibiting PTC (positive temperature coefficient of resistance) behavior are well known and are used as circuit protection devices and heaters. . Such a circuit protection device comprising a conductive polymer composition with low resistance,
Sensitive to changes in ambient temperature and / or current conditions. Under normal conditions, a circuit protector device maintains a low temperature and low resistance state when in series with a load in an electrical circuit. However, when the device is exposed to overcurrent or overheating conditions, the resistance increases and effectively shuts off current to loads in the circuit. In many applications, it is desirable that the device have as low a resistance as possible to minimize the contribution to the total resistance of the electrical circuit during normal operation. In addition, low resistance means that the device has a higher holding current, i.e., under certain environmental conditions, flows through the circuit protection device without causing the device to "trip" to a high resistance state. To have the maximum steady state current that can be achieved. Low resistance devices can be made from the desired composition by changing the dimensions, for example, by making the inter-electrode distance very small or by making the device area very large, Preferably, it is small. Such devices take up less space on the circuit board and generally have favorable thermal properties.

SUMMARY OF THE INVENTION The most common technique for achieving device miniaturization is to use compositions with low resistance. It is known that various processing steps, such as high temperature exposure during irradiation, encapsulation, or reflow soldering, increase the resistance of the composition during device manufacture. Therefore, it is desirable to use a processing technique that allows the increase in resistance of the composition to be as small as possible, so that the final device has low resistance. We have just found a special procedure in the processing steps that helps to produce low resistance devices.

In a first aspect, the present invention relates to (A) a polymer component exhibiting PTC behavior and having (1) a polymer component having a crystallinity of at least 20% and a melting point Tm, and (2) a polymer component. (B) (i) attached to the resistive element, (ii) including a metal foil, and (iii) including a metallic foil, wherein the resistive element comprises a conductive polymer composition including a dispersed particulate conductive filler. An electrical device comprising: two electrodes capable of being connected to a power source, comprising: (a) a thin body comprising a conductive polymer composition disposed between two metal foils; Cutting the device; and (b) after the cutting step, raise the device at most (Tm-100)
(C) exposing at least once to a thermal process from a first temperature which is at most (Tm-25) ° C to a second temperature which is at most (Tm-25) ° C; Cross-linking the molecular composition.

In a second aspect, the invention relates to (A) (i) at most 0.51 mm thick, (ii) cross-linked with at least 2 Mrad equivalents, and (iii) (1) at least 20 %, A resistive element comprising a conductive polymer composition comprising a polymer component having a crystallinity of 0.5% and a melting point Tm, and (2) a particulate conductive filler dispersed in the polymer component; B) A method of manufacturing an electrical device comprising (i) two electrodes attached to a resistive element, (ii) including a metal foil, and (iii) capable of being connected to a power source. (A) cutting the device from a thin body containing the conductive polymer composition disposed between two metal foils; and (b) after the cutting step, the device can be raised at most. (Tm-100)
° C from the first temperature to a second temperature of at most (Tm-25) ° C,
Providing a method comprising: exposing to a thermal cycle at least once to return to a first temperature; and (c) cross-linking the conductive polymer composition after the thermal cycling step.

In a third aspect, the present invention provides a battery comprising: (I) a battery including first and second terminals; and (II) further comprising: (C) a first conductive lead attached to the first electrode. And (D
B.) A device according to the first aspect of the present invention comprising: a) a first terminal of the battery; Providing an assembly wherein the first conductive lead is in physical and electrical contact with the terminal. The present invention is illustrated by the accompanying drawings.

(Detailed Description of the Present Invention) An electric device according to the present invention comprises a resistive element made of a conductive polymer composition, and first and second members attached to the resistive element and sandwiching the resistive element in a sandwich shape. Metal foil. The conductive polymer composition includes a polymer component and a particulate conductive filler dispersed therein. The polymeric component comprises one or more polymers, one of which is preferably at least 20% crystallinity as measured unfilled by a differential scanning calorimeter (Differential Scanning Calorimeter). Is a crystalline polymer having Suitable crystalline polymers are polymers of one or more olefins, especially polyethylene such as high density polyethylene; copolymers such as ethylene / acrylic acid, ethylene / ethyl acrylate, ethylene / vinyl acetate and ethylene / butyl acrylate. A copolymer of at least one olefin and at least one monomer copolymerizable therewith, such as a polymer; a copolymer of polyvinylidene fluoride (PVDF) and ethylene / 4-fluoroethylene (ETFE)
, Terpolymers) and melt-formable fluoropolymers; and mixtures of two or more of these polymers. In some applications, one crystalline polymer is combined with another polymer, such as an elastomer or amorphous thermoplastic polymer, to achieve a particular physical or thermal property, such as flexibility or maximum exposure temperature. It may be desirable to mix. The polymeric component generally comprises from 40 to 90% by volume, preferably from 45 to 80% by volume, particularly preferably from 50 to 90% by volume, based on the total volume of the composition.
Occupies 75% by volume.

[0008] The particulate conductive filler dispersed in the polymer component may be carbon black, graphite, metal, metal oxide, glass or ceramic beads with a conductive coating, particulate conductive polymer, or a particulate conductive polymer. Any suitable material including a combination of The fill may be in the form of powder, beads, flakes, fibers, or any other suitable shape. The amount of conductive filler required is based on the resistance of the composition required and the resistance of the conductive filler itself. For many compositions, the conductive filler is 10-60% by volume, preferably 20-55% by volume, based on the total volume of the composition,
For low-resistance compositions used in low-resistance circuit protection devices,
5 to 50% by volume.

The conductive polymer composition may include an antioxidant, an inert filler, a non-conductive filler, a radiation cross-linking agent (eg, triallyl isocyanurate, often referred to as pro-rad or cross-linking enhancer), Additional components such as stabilizers, dispersants, binders, acid scavengers (eg, CaCO ₃ ), or other components may be included. These components generally comprise up to 20% by volume of the total volume of the composition. Dispersion of the conductive filler and other components into the polymer component can be achieved by any suitable mixing means, for example, melt processing means or solvent mixing means. The mixed components are combined in any suitable manner to create a resistive element, such as melt extrusion, injection molding, compression molding,
Alternatively, it can be melt-formed by sintering. The elements are preferably layered, but may be of any shape, for example rectangular, square, circular or annular. The resistive element often has a maximum of 1.02 mm (0.040 mm).
Inches), but in many applications even thinner, up to 0.51 mm (0.020 inches), preferably up to 0.38 mm (0.015 inches) thick.

[0010] The composition used for the resistive element exhibits a positive temperature coefficient (PTC) behavior. sand
That is, in a relatively small temperature range, the resistance increases rapidly with temperature. This
In the US patent application, the term "PTC" refers to at least 2.5 R₁₄Value and / or at least 10 R₃₀Is used to mean a composition or device with
And the composition or device has at least 6 R₃₀It preferably has a value. here
Where R₁₄Is the ratio of resistance at the end and the beginning of the 14 ° C. range, and R ₁₀₀ Is the ratio of resistance at the end and at the beginning of the 100 ° C. range, and R₃₀Is the ratio of resistance at the end and at the beginning of the 30 ° C. range. In general, the invention
The compositions used in such devices have a resistance much higher than these minimums.
Indicates an increase.

Suitable conductive polymer compositions are described in US Pat. Nos. 4,237,441 (Van Connenberg et al.), 4,545,926 (Fout et al.), And 4,724,417 (Au et al.). No. 4,774,024 (Deep et al.), No. 4,935,156 (Van Koninenberg et al.), No. 5,049,850 (Evans et al.), No. 5,250,228 ( Begley et al.), No. 5,378,407 (Chandra et al.), 5.4
No. 51,919 (Chu et al.), 5,582,770 (Chu et al.), 5,747,147 (Watenberg et al.) And 5,801,612 (Chandra et al.), And general succession International Application Publication No. WO 96/29711 (Raychem, 1997
Issued September 26, 1998).

[0012] The resistive element is attached to first and second thin-layer electrodes attached to the first and second faces of the resistive element, respectively. Preferably, the conductive polymer composition is extruded or otherwise shaped into a sheet and the electrodes are mounted thereon to form one thin layer. That is, the conductive polymer is preferably sandwiched between the foils. Both the first and second electrodes comprise a conductive material, preferably a foil metal, such as nickel, copper, brass, stainless steel, or an alloy of one or more of these metals. However, one or both of the electrodes may include a conductive paint layer or a graphite layer. A tie layer, such as a conductive adhesive, may be used to attach the electrodes to the resistive element. It is particularly preferred that the first and second electrodes comprise an electrodeposited metal foil, such as nickel, copper, or nickel-coated copper. Suitable electrodes are described in U.S. Pat. Nos. 4,689,475 (Mathesensen) and 4,800,253 (Kleina et al.) And International Application Publication No. ).

[0013] The device may also include an insulating layer that provides electrical or environmental protection to the device. The insulating layer generally covers part or all of the metal foil electrode and the exposed surface of the resistive element. Suitable insulating materials include polymers such as polyamide, polybutylene terephthalate, polyester, polyethylene, polyvinylidene fluoride, liquid crystal polymers, or epoxy resins.

In the method according to the present invention, in the cutting step, the device is cut from the thin body including the conductive polymer composition disposed between the two metal foils. In this application, the term “cut” refers to any method of isolating or isolating the resistive element of the device from the thin body, for example, International Patent Publication WO 95/34084 (Dec. 1995).
Dicing, punching, shearing, cutting,
Used to include etching and / or destruction.

The device is then subjected to a heat treatment step. The heat treatment step includes at least one process from the _first temperature T ₁ to the second temperature T ₂ . Preferably, the heat treatment step includes a return to the first temperature after exposure to the second temperature, thus forming a cycle from T ₁ through T ₂ to T ₁ . The first temperature may be as high as (Tm-10
0) ° C, preferably at most (Tm-120) ° C, particularly preferably at most (
Tm-150) ° C. Here, Tm is a melting point of a polymer component measured by an endothermic peak of a differential scanning calorimeter (differential scanning calorimeter). When more than one peak is present, for example when the polymeric component comprises a mixture of crystalline polymers, Tm is taken to be the temperature of the highest temperature peak. The second temperature is at most (Tm-25) ° C., preferably at most (Tm-35).
) ° C, particularly preferably at most (Tm-50) ° C. It is important that the first temperature is higher than the glass transition temperature Tg of the polymer component. T ₁ is often a temperature below room temperature, ie below 20 ° C. In a preferred embodiment of the method, the device comprises at least two thermal cycles,
Preferably, it is exposed to at least three thermal cycles. In some applications, the device may be exposed to more cycles, for example, six thermal cycles.
During the heat treatment step, for the thermal process or each thermal cycle, the device is held at both the first and second temperatures for a sufficient time to ensure that all devices reach the specified temperature. You. The period during which the device is held may be the same or different for T ₁ and T ₂ , but is generally at least 1 minute, preferably at least 1 minute, measured from the time the device reaches the specified temperature. Is at least 3 minutes, more preferably at least 5 minutes, particularly preferably at least 10 minutes, even more particularly preferably at least 15 minutes, particularly preferably at least 30 minutes, for example 60 minutes.
During the heat treatment step, a suitable heat source, for example an oven (especially a programmable oven) or other environmental chamber, or a heating lamp can be used. From T ₁ of the the T ₂ (The return cases to T ₁ is) heating rate, appropriate rate, may be a e.g. 2 to 30 ° C. / min. When the heat treatment step is a thermal cycle, the rate from T ₁ to T ₂ are may be the same as the rate from T ₂ to T _1, may be different.

Following the heat treatment step, the conductive polymer composition is crosslinked. Crosslinking can be carried out by chemical means or by irradiation, for example using an electron beam or a Co ⁶⁰ γ radiation source. The level of crosslinking depends on the required irradiation of the composition, but is generally less than 200 Mrad equivalent, preferably substantially less, i.e. 1-20 Mrad, preferably 1-15 Mrad. Particularly preferably 2 to 10 Mrad for the application of low voltages (ie below 60 volts). Useful circuit protection devices for applying voltages below 30 volts can be fabricated by exposing the device to at least 2 Mrad, but at most 10 Mrad.

For many applications, it is necessary to attach at least one conductive lead, the first conductive lead, to one of the metal foil electrodes. Often the first
The first and second conductive leads are attached to the first and second electrodes, respectively.
The conductive leads allow the electrodes to be easily connected to a power source, such as a battery or power supply, or circuit, and can be used to control the thermal output of the device. Conductive leads, often formed as part of a lead frame for ease of manufacture, are preferably attached to the electrodes by an intermediate layer, such as solder or conductive adhesive. This lead mounting step is preferably performed after the cutting step and before the heat treatment step. Other assembly processes, such as the formation of an insulating layer, such as an epoxy resin or other polymer, are preferably performed in an assembly process that includes a lead mounting process and is inserted after the trimming process and before the heat treatment process.

Subsequent to the method according to the invention, the conductive polymer has a low resistance, ie a resistance lower than 100 ohm-cm, preferably lower than 20 ohm-cm, particularly preferably lower than 10 ohm-cm. Devices can be prepared, more particularly preferably less than 5 ohm-cm, particularly preferably less than 2 ohm-cm, for example less than 1 ohm-cm. For most applications, the device is generally less than 1 ohm at 20 ° C, preferably less than 0.5 ohm, particularly preferably less than 0.25 ohm, for example 0.050 to 0.150 ohm Has lower resistance.

The device according to the invention is particularly suitable for use in a battery assembly in which the device is preferably mounted on a first or second terminal of a battery. The attachment may be made directly between the battery and the first or second electrode, or may be attached to the battery and to a first conductive lead or a second electrode attached to the first electrode. Between the second conductive lead and the second conductive lead. For batteries where either the first and / or the second terminal is in the form of a "button", the device is physically or electrically attached to the button terminal. The device is
It can be attached to either the negative or positive terminal of the battery. Suitable batteries for use include nickel-cadmium batteries, nickel-metal hydride batteries, alkaline batteries, or lithium batteries. Frequently, battery assemblies include two or more batteries. Such a battery assembly is disclosed in International Patent Publication WO9
7/06538 (Raychem, issued February 20, 1997) and WO98 / 20
567 (Raychem, issued May 14, 1998).

The present invention is illustrated by the accompanying drawings, in which FIG. 1 includes a PTC component 3, a first conductive lead 15, a second conductive lead 18, and an insulating material 23. 1 shows a cross section of an electric device 1 according to the present invention. The PTC component 3 includes a first electrode 11, a second electrode 13, and a resistive element 9 made of a conductive polymer sandwiched therebetween. In the PTC component 3 shown in FIG. 1, both electrodes facing each other form a first surface 43 and a second surface 41.

FIG. 2 shows a top view of the PTC component 3. The PTC component 3 has a surface 41
43, an outer edge 5 and an inner edge 7 and are of disk shape with an opening 27 in the center. The inner edge 7 defines an opening 27.

FIG. 3 shows a top view of the first conductive lead 15, which is connected to the first electrode 11 and the second portion 17 extending across the opening 27 of the PTC component 3. And a first portion 16 attached thereto. In this embodiment, the first part 1
6 covers the entire surface of the first electrode 11. The second portion 17 of the first lead 15, covering at least a portion of the opening 27, is used to make a direct electrical contact to the button terminal of the battery by soldering, pressure or welding. . Second
Portion 17 covers at least a part of the opening 27.

FIG. 4 shows a top view of the second conductive lead 18 including the first portion 19 and the second portion 21. The first portion 19 is attached to the second electrode 13 and covers at least a part of the surface of the second electrode 13. The second part 21 is
It extends away from outer edge 5 and can be bent, if necessary, to make electrical contact with a second battery or other electrical component. The first and second conductive leads 15, 18 can be formed of any suitable material, for example, nickel, stainless steel, copper, or an alloy such as brass or bronze. To facilitate manufacturing, the second lead 18 is often part of a lead frame.

FIG. 5 shows a top view of the device 1 encapsulated by the electrically insulating layer 23. When the positive terminal of the battery is located in the inner opening 27 ', there is no electrical contact between the terminal and the PTC component 3, so there is no short circuit.

The present invention is illustrated by the following specific examples, where specific examples 1 and 2
Is a comparative example. The following steps were performed for each specific example.

Preparation of PTC Device 54% by weight of carbon black (Raven 430U®, available from Columbia Chemical) and 46% by weight of high density polyethylene (Petrothene LB832, available from Millenium; “HDPE”) A first compound was prepared by premixing in a Henschel mixer, mixing the mixture with a bus kneader and extruding into pellets. 51.4% by weight of carbon black and 48.
A second compound was prepared by premixing 6% by weight HDPE in the same manner. The pellets of the first and second compounds are premixed to give a final compound having 52.7% by weight of carbon black and 47.3% by weight of HDPE, which compound is an Eagan extruder. And extruded through a sheet-like die to give a 0.25 mm (0.010 inch) thick sheet. The extruded sheet was thinned between two layers of electrodeposited nickel foil (available from Fukuda) having a thickness of about 0.0133 mm (0.0013 inches) at 200 ° C. using a press set. Stratified. The thinned sheet is immersed in solder having a composition of 63% lead / 37% tin heated to 230 ° C., and the device having the shape shown in FIG. 2 is obtained from the thin sheet. Was punched out.

Device Assembly First and second conductive leads are 63/3, as shown in FIGS.
The PTC device was mounted on a PTC device with a 7 lead / tin solder, which was reflowed in a hot air oven heated from 30 ° C. to a maximum of 230 ° C. for about 2 minutes. Thereafter, an insulating layer made of a liquid crystal polymer was formed and added by transfer means or injection molding.

The irradiation device was irradiated using a radiation source of cobalt 60γ, and the total irradiation was 14 Mrad.

The temperature cycling device is subjected to six thermal cycles, each cycle being ramped from 40.degree. C. to 80.degree. C. at a rate of 1.degree. It returned to 40 ° C.

Specific Examples 1 and 2 (Comparative Examples) Devices were prepared according to the specifications shown in Table 1. Here, numerals 1 to 4 indicate the order of processing steps when these were performed. Is shown. The resistance at 25 ° C. was measured for 100 devices prepared for each specific example. The average resistance of the device thus obtained was at least 5% higher than that of the device according to the invention (Example 3).

Example 3 The device was prepared according to the specifications shown in Table 1. The resistance of the device thus obtained was lower than that of the conventional device. FIG. 6 shows a comparison of the resistance distribution of these devices.

[Table 1]

Although the various figures and descriptions in this specification relate to particular embodiments of the present invention, where particular features are disclosed in connection with particular figures, such features may also include: It should be understood that in connection with other figures, in combination with other features, or generally, it can be widely used in the present invention. The devices having the above configurations and the methods according to them are merely examples of the application of the present invention or its theory, and many other embodiments and modifications are
It will be understood that the following claims are created without departing from the spirit and scope of the invention.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a device according to the present invention.

FIG. 2 is a top view of the device according to the present invention.

FIG. 3 is a top view of a first conductive lead forming a part of the device according to the present invention.

FIG. 4 is a top view of a device according to the present invention with a second conductive lead attached.

FIG. 5 is a top view of a device according to the invention, including an insulating layer.

FIG. 6 is a graph showing resistance distributions of devices manufactured by a method according to the present invention and a method according to a comparative example.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shaw Mean Pan 200335 Shanghai, Hong Kiao Road No. 2419, Cesson Park No. 20 F term (reference) 5E034 AA10 AB07 AC09 DB16 DE05

Claims (10)

[Claims] (A) exhibiting PTC behavior and (1) at least 20
(B) a resistance element comprising a conductive polymer composition including a polymer component having a degree of crystallinity and a melting point Tm, and (2) a particulate conductive filler dispersed in the polymer component. an electrical device comprising: (i) two electrodes attached to a resistive element, (ii) including a metal foil, and (iii) capable of being connected to a power source; (B) cutting the device from a thin layer containing the conductive polymer composition disposed between the foils; and (b) after the cutting step, the device is at most (Tm-100)
(C) exposing at least once to a thermal process from a first temperature which is at most (Tm-25) ° C to a second temperature which is at most (Tm-25) ° C; Cross-linking the molecular composition. 2. The method of claim 1, wherein the method further comprises attaching at least one conductive lead to one of the metal foil electrodes after step (a) and before step (b). The described device. 3. The device according to claim 1, wherein the resistance is at most 0.100 ohm. 4. The device according to claim 1, which is crosslinked in step (c) with an equivalent of 1 to 20 Mrad. 5. The device according to claim 1, wherein the polymer component includes polyethylene, an ethylene copolymer, or a fluoropolymer. 6. In step (b), the device is moved from a first temperature to a second temperature.
Exposed to a thermal cycle at least one time and returning to the first temperature,
A device according to any one of the preceding claims. 7. The device according to claim 1, wherein in step (b) the first temperature T ₁ is lower than 23 ° C. 8. The resistive element (1) is (i) at most 0.51 mm thick and (ii) cross-linked with at least 2 Mrad equivalent, (2) after the cutting step In step (b), the device changes from a first temperature of at most (Tm-100) ° C. to a second temperature of at most (Tm-25) ° C., and a first temperature of The method of claim 1, wherein the method is adapted to be exposed at least once to a thermal cycle returning to step (b). 9. The method of claim 8, wherein in step (b), the device is exposed to at least three thermal cycles. 10. A battery including: (1) a battery including first and second terminals; (2) further comprising: (a) a first conductive lead attached to the first electrode;
A battery assembly comprising: a) a second conductive lead attached to a second electrode; and a device according to claim 1, wherein the device contacts a first terminal of the battery. An assembly wherein the first conductive lead is in physical and electrical contact with the terminal.