JPS63301480A - Manufacture of heat emitting body - Google Patents

Abstract

PURPOSE:To have an electrode with high mechanical strength without dislocation by hot pressing a metal foil fast to the whole surface of a sheet-shaped organic thermister element having positive characteristic, and forming electrode patterns by means of selective etching of specific places on the metal foil. CONSTITUTION:A metal foil is hot pressed fast to the whole surface of a sheet- shaped organic thermister element having positive characteristic, and specific places on this metal foil is selectively etched to form electrode patterns 2, 3. This selective etching turns the metal foil into a pair of comb-shaped electrode 2, 3. Performing etching in this process will provide electrodes 2, 3 consisting of metal foil having high mechanical strength with high locational accuracy.

Description

Detailed Description of the Invention (a) Industrial Field of Application This invention relates to a method for manufacturing a heating element in which electrodes are formed on a sheet-like organic positive temperature coefficient thermistor body. A product mixed and kneaded with conductive particles has the properties of a positive temperature coefficient thermistor, and by forming such an organic positive temperature coefficient thermistor body into a sheet shape and forming a pair of electrodes on its surface, a sheet heating element can be produced. It has been devised and developed for use in

Conventionally, when manufacturing this type of sheet heating element, in order to equalize the temperature distribution of the sheet heating element, which has a relatively wide area, silver paste was applied in a comb-like shape and baked, or a comb-like shape was used. Methods such as thermocompression bonding of metal foil to a sheet-like positive temperature coefficient thermistor element body have been adopted.

(C) Problems to be Solved by the Invention However, although the method of forming electrodes using silver paste has the feature that electrodes can be formed relatively easily,
Mechanical strength is low, and repeated heat generation tends to cause electrode peeling and disconnection, causing uneven heat generation. In addition, although the method of heat-compression bonding of comb-shaped metal foil has a high mechanical strength of the electrode, the comb-teeth may become misaligned due to the melting and elongation of the sheet-like positive temperature coefficient thermistor element during thermocompression bonding. This can easily lead to uneven heat generation, and in the worst case, short circuits may occur due to contact between the comb-shaped electrodes.

Furthermore, since the comb-shaped metal foil is obtained by punching out a metal foil with a thickness of 100 μm or more, the overall flexibility of the heating element is limited (for example, it is difficult to fit onto curved surfaces, etc.), which limits its use. There were also problems.

An object of the present invention is to provide a method of manufacturing a heating element in which electrodes with high mechanical strength are formed on the surface of a sheet-like positive temperature coefficient thermistor element without positional deviation, and the overall flexibility is not impaired.

(Means for Solving Problem d1) In the method for manufacturing a heating element of the present invention, a metal foil is thermocompression bonded to substantially the entire surface of a sheet-like organic positive temperature coefficient thermistor element body, and then specific portions of the metal foil are bonded. It is characterized by selectively etching to form an electrode pattern.

fe) Function In the method for manufacturing a heating element of the present invention, first, a metal foil is thermocompressed onto substantially the entire surface of the sheet-like organic PTC thermistor element, thereby forming a metal foil on the surface of the sheet-like organic PTC thermistor element. A planar electrode is formed. Thereafter, by selectively etching specific parts of the metal foil, the metal foil becomes, for example, a pair of comb-shaped electrodes. By performing etching with the metal foil thermocompressed on the surface of the sheet-like organic positive temperature coefficient thermistor body,
Electrodes made of metal foil with high mechanical strength can be formed with high positional accuracy. Furthermore, a relatively thin metal foil can be used and flexibility can be maintained.

(f) Example The structure of a heating element manufactured by the method for manufacturing a heating element according to the present invention is shown in FIGS. 1(A) and 1(B). The same figure (A
) represents the plane of the heating element, and (B) represents the cross section of A-A in (A), respectively. In the figure, 1 is an organic positive temperature coefficient thermistor body made by mixing and kneading conductive particles such as carbon black, graphite, and metal powder into a polyolefin resin such as polyethylene and molding the mixture into a sheet shape. A pair of comb-shaped electrodes 2.3 are formed on one surface of this element body. Terminals 4.5 are attached to these electrodes 2 and 3,
By applying a voltage between the terminals 4.5, a current flows through the organic positive temperature coefficient thermistor element sandwiched between the pair of comb-shaped electrodes, and heat is generated due to Joule heat. As shown in the figure, the heat generating portion is distributed over substantially the entire surface of the sheet-like organic positive temperature coefficient thermistor body, so that the entire body generates heat substantially uniformly.

The heating element described above is manufactured as follows. First, a metal foil is thermocompression bonded to one side of a sheet-like organic positive temperature coefficient thermistor body.

Next, an etching resist is screen printed on the areas where the metal foil is to be left and allowed to dry. Thereafter, the metal foil is etched to form a pair of electrode patterns as shown in FIG. 1(A). Thereafter, the etching resist film is removed if necessary.

The results of an experiment in which a heating element manufactured by the manufacturing method of the present invention was compared with a heating element manufactured by a conventional manufacturing method are shown below. The heating element used as a sample was 100X5
A 30 to 40 .mu.m Ni foil was thermocompression bonded to one side of a 0.times.0.5 mm sheet-like organic positive temperature coefficient thermistor body at 190.degree. C. for 10 minutes, and then etched to form a comb-shaped electrode in a predetermined shape. On the other hand, the samples produced by the prior art had sheet-like organic properties of the same size. Figure 2 shows the properties before and after aging. In the figure, (1) represents a sample (Example) manufactured by the manufacturing method of the present invention, and (2) represents a sample (Comparative Example) manufactured by the conventional technique. Further, the resistance value represents the resistance value between a pair of electrodes, the maximum temperature represents the temperature of the highest temperature region of the heating element, and 8T represents the temperature difference between the maximum temperature and the minimum temperature. Since the organic positive temperature coefficient thermistor bodies with the same composition and the electrode shapes are the same, the resistance values should be the same, but the reason why the initial resistance of the comparative example is higher is because of the silver paste electrode and the positive temperature coefficient thermistor. This is due to contact resistance between the elements. These two heating elements were attached to a 1 mm thick alumina substrate, and the DC12
When V was applied, ΔT was approximately 5°C in both the example and comparative example.
The surface temperature distribution is approximately average. When these heating elements were turned on for 30 minutes and turned off for 30 minutes intermittently for 1000 cycles, the comparative example showed an increase in resistance value of +150%. In addition, the surface temperature distribution also deteriorates, and ΔT=
The temperature was 23.4°C. This is because a portion of the electrode was disconnected or peeled off, resulting in a portion that hardly generated heat.

On the other hand, in the example, the resistance value change was only an increase of +20%, and the surface temperature distribution also hardly changed.

In the above embodiment, a pair of comb-shaped electrodes are arranged facing each other as the electrode shape, but the shape is not limited to this. In addition, for example, the pair of electrodes may be formed in a spiral shape, or the pair of electrodes may be arranged close to each other. The temperature distribution can be made uniform by forming the temperature distribution over substantially the entire surface. Furthermore, it is also possible to set the heat generation amount and temperature distribution pattern by changing the electrode spacing.

(g) Effects of the Invention As described above, according to the present invention, a metal foil is thermocompression bonded to almost the entire surface of a sheet-like organic positive temperature coefficient thermistor element body, and then specific portions of the metal foil are selectively etched. Since the electrode pattern is formed using metal foil, the electrode can be formed from metal foil, and the adhesion between the electrode and the surface of the sheet-like organic positive temperature coefficient thermistor body is high (contact resistance can be lowered. Because the electrodes have high mechanical strength, a highly reliable heating element can be obtained without problems of disconnection or peeling.Furthermore, since the electrode pattern is formed by etching, the dimensional accuracy of the electrode position and the distance between the electrodes can be improved. (This has the effect of making the temperature distribution uniform.

[Brief explanation of the drawing]

FIGS. 1(A) and 1(B) are a plan view and a sectional view showing the structure of a heating element manufactured by the heating element manufacturing method according to the present invention. FIG. 2 is a diagram comparing the characteristics of a heating element manufactured by the manufacturing method of the present invention and a heating element manufactured by the conventional technique. 1-Sheet organic positive temperature coefficient thermistor body, 2.3-Electrode (metal foil).

Claims (1)

[Claims] (1) Heat generation characterized by thermocompression bonding a metal foil over almost the entire surface of a sheet-like organic positive temperature coefficient thermistor element body, and then selectively etching specific parts of the metal foil to form an electrode pattern. How the body is manufactured.