JPH0690963B2 - Method for manufacturing PTC element - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing an electric resistance element, and more particularly, to a property that electric resistance rapidly increases in a relatively narrow temperature range as temperature rises (PTC characteristic. (Positive temperature coeffici
ent)], that is, a method for manufacturing a PTC element.

(Prior Art) A substance with PTC characteristics is a heater that stops heat generation when it rises to a certain temperature, a positive temperature coefficient thermistor (PTC thermiste).
r), thermal sensor, dry battery, etc., when the short circuit occurs, the current increases and self-heats due to Joule heat, thereby increasing the resistance and limiting the current below a predetermined value, while the circuit is removed when the short circuit is removed. It can be used as a protective element for recovering the current. Therefore, the development of materials with PTC characteristics has been promoted, and currently BaTiO ₃ is monovalent or trivalent.
There are those in which a valent metal oxide is added and those in which a conductive substance is dispersed in a crystalline polymer such as polyethylene.

Conventionally, a resistance element having PTC characteristics (hereinafter abbreviated as PTC element) is a substance 2 having PTC characteristics as shown in FIG.
And electrode plates 3a and 3b sandwiching this, and lead plates 4a and 4b connected to the electrode plates.

Conventionally, the PTC element is manufactured as follows. First, a (PTC composition) having PTC characteristics is prepared, the PTC composition is formed into a film, and electrodes of metal foils are thermocompression-bonded to the top and bottom of the film to form a laminate. This laminated body is cut into a predetermined size, and a lead plate is welded to the electrode surface of this laminated body by soldering or the like to manufacture a PTC element.

A preferable characteristic of the PTC element is that it has a large resistance value (peak resistance) at high temperature and a low resistance value (room temperature resistance) of 100 mΩ or less at room temperature. In order to reduce the room temperature resistance, it is considered that the filling amount of carbon black (conductive particles) in the PTC composition is increased, but a sufficient peak resistance / room temperature resistance ratio cannot be obtained.
Various methods for reducing the contact resistance between the PTC composition and the electrode and the contact resistance between the electrode and the lead plate have been proposed (US Pat. No. 4,238,812 and JP-A-53-95298).

(Problems to be Solved by the Invention) When manufacturing a PTC element, conventionally, a lead plate is welded to the surface of the electrode plate by soldering or the like. PT by the heat of this welding
Part of the PTC composition in contact with the C element, particularly the electrode plate, is thermally decomposed, causing heat damage such as gas generation and separation between the PTC composition and the electrode plate. Due to this heat damage, there is a problem that room temperature resistance, especially contact resistance, increases.

The present invention has been made based on the above background, and an object thereof is to reduce heat damage at the time of welding the electrode plate and the lead plate of the PTC element, reduce the contact resistance, and reduce the An object of the present invention is to provide a method of manufacturing an excellent PTC device having room temperature resistance.

(Means for Solving Problems) As a result of various tests and studies for achieving the above-mentioned object, the inventors of the present invention have found that if the contact area between the welding electrode and the lead plate is narrowed, the heat damage of the welding is reduced. Therefore, the present invention has been completed.

That is, according to the method for manufacturing a PTC element of the present invention, a lead plate for external connection is formed on a part of the surface of one electrode plate of a laminate composed of a substance having PTC characteristics and two electrode plates sandwiching the substance. When stacking and welding, contact the electrode plate surface portion not covered by the lead plate with a welding electrode having a wide contact area, while contacting the lead plate surface with a welding electrode having a narrow contact area. After that, the welding electrode is energized to weld the electrode plate and the lead plate.

In a preferred embodiment of the present invention, pressure can be applied to the lead plate on the electrode plate side simultaneously with welding.

Examples of the substance having PTC characteristics which can be used in the present invention include a mixture of a polymer and conductive particles. Examples of the polymer include polyethylene, polyethylene oxide, t-4-polybutadiene, polyethylene acrylate, ethylene-ethyl acrylate copolymer, ethylene-acrylic acid copolymer, polyester, polyamide, polyether, polycaprolactam, fluorinated ethylene-propylene. Copolymer, chlorinated polyeletin, chlorosulfonated ethylene, ethylene-vinyl acetate copolymer, polypropylene, polystyrene, styrene-acrylonitrile copolymer, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, polycarbonate, polyacetal, Polyalkylene oxides, polyphenylene oxides, polysulfones, fluororesins, blends thereof, and the like can be used to prepare materials with PTC properties. The type and composition ratio of the polymer can be appropriately changed depending on the desired performance, intended use and the like.

Further, as the conductive particles dispersed in the polymer, particles of a conductive substance such as graphite, tin, silver, gold and copper can be used in addition to carbon black.

In preparing a substance having PTC characteristics, the above polymer,
In addition to the conductive particles, various additives can be mixed if necessary. Examples of substances that can be added include flame retardants or flame retardants such as antimony compounds, phosphorus compounds, chlorine compounds and bromine compounds, and antioxidants.

In the present invention, the substance having PTC characteristics is prepared by mixing the raw materials thereof, for example, the polymer, the conductive particles, and other additives in a predetermined ratio.

The PTC element of the present invention comprises a substance having the above PTC characteristics,
It is composed of an electrode plate which holds this substance. The electrode plate that can be used here is a material that can be used as a normal electrode. As a method of sandwiching it here, a method of joining an electrode plate and a substance having PTC characteristics using a conductive adhesive, a method of heating a substance having PTC characteristics up to near the melting point and thermocompression-bonding the electrode plate thereto, etc. There is.

In the present invention, the welding of the electrode plate and the lead plate is performed by welding a lead plate for external connection on a part of the surface of the electrode plate and welding the electrode surface part not covered with the lead plate with a wide contact area. The electrodes are brought into contact with each other, the welding electrodes having a narrow contact surface are brought into contact with the surface of the lead plate, and then each welding electrode is energized. In the present invention, it is desirable to apply pressure to the lead plate on the electrode plate side simultaneously with welding. This is to strengthen the welding of the lead plate and the electrode plate.

The welding in the present invention will be specifically described with reference to FIGS. 1 and 2. A laminated body composed of the PTC composition 2 and two electrode plates 3a and 3b sandwiching the composition is prepared. An external connection lead plate is overlaid on a part of the upper surface of the electrode plate 3a of this laminated body, and the welding electrode 6 having a wide contact area is brought into contact with the surface part of the electrode plate not covered by the lead plate 4a. Further, the welding electrode 5 having a narrow contact area is brought into contact with the upper surface of the lead plate 4a. The procedure for making such a state is not limited to the above, and is arbitrary. At this time, it is desirable to apply pressure to the lead plate 4a by the welding electrode 5 toward the electrode plate 3a. Also, a welding electrode 6 having a wide contact surface
Preferably has a U-shaped contact surface that does not contact the lead plate 4a but surrounds the lead plate 4a. This is because a large current during welding is immediately dispersed after passing through the welded portion to minimize heat damage to the PTC composition.

In this state, the welding electrodes 5 and 6 are energized to weld the lead plate 4a and the electrode plate 3a. Since the sharpened electrode 5 is used at the time of welding, as illustrated in FIG.
The large current 7 is concentrated in one place and melts with low energy.
For example, a low welding energy of 5 to 50 w.s, preferably about 10 w.s can be used.

The molten portion solidifies by cooling, and as shown in FIG.
Form the nugget 8. The welding electrode is removed and welding is completed.

A resin film can be formed on the surface of the PTC element of the present invention as necessary. The type of resin that can be used in the present invention is not limited as long as it is not against the object of the present invention. Examples of the resin include polyethylene, polypropylene, polythretin, polyvinyl chloride, polyvinyl acetate, polyvinyl alcohol, acrylic resin, fluororesin, polyamide resin, polycarbonate resin, polyacetal resin, polyalkylene oxide, saturated polyester resin, polyphenylene oxide, polysulfone. , Poly
p-xylylene, polyimide, polyamideimide, polyesterimide, polybenzimidazole, polyphenylene sulfide, silicon resin, phenol resin, urea resin, melamine resin, furan resin, alkyd resin, unsaturated polyester resin, diallyl phthalate resin, epoxy resin, polyurethane Resins, blended polymers of these,
These include resins modified by reactions with chemical reagents, radiation crosslinking, copolymers and the like. Particularly preferable among these are epoxy resin and phenol resin.

These resins include various additives such as plasticizers, lubricants, cross-linking agents, vulcanizing agents, curing agents, antioxidants, UV absorbers, fillers, reinforcing agents, reinforcing agents, modifiers, electrostatic agents. Inhibitors, flame retardants, colorants, heat stabilizers, softeners, tackifiers, binders, anti-adhesives, surface treatments, fragrances, fungicides, termite control agents, murine repellents, etc. You may add.

The resin that can be used in the present invention has at least an insulating property, and is preferably an electrode surface and PT.
It has adhesion to the surface of substance C.

The coating method of the resin film is not particularly limited in this invention,
For example, spraying, applying, dipping in a resin liquid, or the like. The resin film coating should be at least PTC not covered by the electrodes.
It is preferably performed on the surface of the material and across the electrodes. However, other element surfaces may be coated.

Curing after the application of the resin can be carried out by a usual method depending on the resin, such as chemical treatment, heating, and radiation irradiation. The thickness of the resin film can be appropriately changed according to the type of resin, the use and size of the element, and the like.

The obtained PTC element is used for a predetermined purpose.

〔The invention's effect〕

The following effects can be obtained by the PTC element manufacturing method of the present invention.

Since the welding of the lead plate and the electrode plate is performed by using the welding electrode having a narrow contact surface, the large welding current concentrates at that location, and the desired heat generation with low energy is limited to the required welding area. You can Therefore, heat can be effectively used for welding, and heat damage to the PTC composition can be minimized. Furthermore, since heat damage due to welding can be suppressed to a minimum, the contact resistance between the PTC composition and the electrode plate can be suppressed to a low value, and an excellent element as a PTC element can be manufactured.

(Example) The present invention will be described more specifically by the following examples.

Example 1 A substance having a PTC characteristic having the following composition (PTC composition) was prepared.

PTC composition wt% Polymer: High-density polyethylene 60 (Toyo Soda, Nipolon Hard 5100) Conductive particles: Carbon black 38 (Cabot, Stirling V) Additive: Antioxidant 2 (Irganox 1010) The mixture was kneaded by the present roll mill, and further, a film having a thickness of 300 μ was formed by an extrusion molding machine or a roll molding machine. A 60 μm thick nickel foil electrode was thermocompression bonded to the top and bottom of the film to form a laminate. Preferably, the surface of the electrode is roughened to give it adhesiveness. The obtained laminate was cut into a predetermined size (10 × 10 × 0.40 mm).

On the other hand, a lead plate for external connection having a predetermined size was prepared, this was stacked on an electrode plate, and a welding electrode having a thin tip was placed on the lead plate as shown in FIG. Further, a welding electrode having a wide contact surface on the surface of the electrode plate not covered with the lead plate was contacted so as not to contact the lead plate. In such a state, welding output is about 10 w.s, energizing time
The PTC element was obtained by welding under the welding condition of 0.5 to 2.0 ms.

Room temperature resistance of PTC element before and after welding changed from 50mΩ to 56mΩ 6
We were able to reduce the resistance to mΩ.

Comparative Example A PTC element was manufactured in the same manner as in Example 1 except that the welding of the lead plate and the electrode plate was performed by soldering. Room temperature resistance of the obtained PTC element is 50mΩ to 254m before and after welding.
Greatly increased to Ω.

[Brief description of drawings]

FIG. 1 is a sectional view of a PTC element for explaining the manufacturing method of the present invention, and FIG. 2 is a PTC obtained by the manufacturing method of the present invention.
FIG. 3 is a cross-sectional view of the element, and FIG. 3 is a perspective view of the PTC element. 1 ... PTC element, 2 ... PTC composition, 3 ... electrode plate, 4 ...
... Lead plate, 5,6 ... Welding electrode, 7 ... Current path, 8 ...
…nugget.

Claims (2)

[Claims] 1. When a lead plate for external connection is overlapped and welded on a part of the surface of one electrode plate of a laminate composed of a substance having PTC characteristics and two electrode plates sandwiching the substance, On the electrode plate surface part not covered by the lead plate,
Welding electrodes with a wide contact area are brought into contact, while welding electrodes with a narrow contact area are brought into contact with the lead plate surface,
Then, a method for manufacturing a PTC element is characterized in that each electrode for welding is energized to weld an electrode plate and a lead plate. 2. The method for producing a PTC element according to claim 1, wherein pressure is applied to the lead plate on the electrode plate side simultaneously with welding.