JPS62106602A - Manufacture of organic positive characteristics thermistor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a method for manufacturing an organic positive temperature coefficient thermistor that utilizes the positive resistance/temperature characteristics of an organic polymer material in which conductive particles are mixed and dispersed. More specifically, the present invention relates to a method of forming electrodes on the element body of the organic positive temperature coefficient thermistor.

<Prior Art> FIG. 5 is a sectional view of a conventional organic positive temperature coefficient thermistor, and FIG. 6 is an enlarged sectional view of the thermistor body. In these figures, 1o is the thermistor body. The thermistor body 1° is constructed by forming electrodes 3° and 3° on both main surfaces of an element body 2°, respectively. The element body 2° is made of an organic polymer in which conductive particles are mixed and dispersed. As the conductive particles, powders such as carbon blank, carbon graphite, and metal are used.

Further, as the organic polymer, polyethylene, polypropylene, or polybutadiene resins are used.

An organic polymer material in which conductive particles are mixed and dispersed exhibits positive resistance/temperature characteristics. Organic positive temperature coefficient thermistors utilize the resistance/temperature characteristics of this organic polymer material.

4o and 4o are lead terminals. Each lead terminal 4° is attached to the outer surface of the electrode 3° by soldering. 5
o is a coating portion that insulates the thermistor body 1° and the base of the lead terminal 4°. The coat portion 5° is made of resin.

Therefore, in manufacturing the organic positive temperature coefficient thermistor, in order to form the thermistor main body 1° by forming electrodes 3° and 3° on both main surfaces of the element body 2°, conventionally,
The following two methods are generally used.

The first method is to apply metal plating to both main surfaces of the element body 2°. The second method is to thermocompress metal foils that will become the electrodes 3o onto both main surfaces of the element body 2°. In this thermocompression bonding method, an element body 2° and a metal foil 03° are placed between a pair of press plates. ．． 3. and set both as element 2.
゜Thermocompression bonding is carried out at a temperature above the melting point of the material.

<Problems to be Solved by the Invention> By the way, in the electrode forming method using plating, the adhesive strength between the electrode 3° and the element body 2° is not sufficient. In addition, the expansion rate of the plating film at 3° for the electrode is about 40, which is the expansion rate for the 2° element body.
Because it is extremely small, about 1/2 of that, the element body 2° and the electrode 3° repeatedly expand and contract at different expansion rates during subsequent heating processes such as soldering and baking of the coated portion. Therefore, peeling of the electrode at 3° tends to occur.

On the other hand, according to the electrode forming method using thermocompression bonding, the surface layer of the element body 2° is melted and bonded to the metal foil 3°, so that the surface layer of the element body 2° is bonded to the metal foil 3°. The adhesive strength between No. 1 and the 3° electrode is high, and the 3° electrode does not peel off even during heating processes such as soldering.

However, when the metal foil 3° is thermocompressed, a considerable amount of air remains between the element body 2o and the metal foil 3°. Since the element body 2° is bonded to the metal foil 3o by thermocompression and melting at the same time, the remaining air is trapped without flowing out to the outside, and the element body 2° and the metal foil 3o are bonded together as shown in FIG. A gas layer of 6° is created between the two.

This gas layer 6° expands by repeatedly expanding and contracting due to heating during the soldering process and heating during a heat cycle test. This enlarged gas layer 6o increases the resistance value of the thermistor, causing the disadvantage that the initial resistance value deviates significantly from the desired value.

In view of the problems of the conventional both methods, the present invention provides an element body and a 71i
The purpose is to eliminate the generation of a gas layer between the element body and the electrode while maintaining a sufficient adhesive strength with Ti, and to prevent an increase in the initial resistance value due to the gas layer.

<Means for Solving the Problems> In order to achieve the above object, the present invention includes a step of bringing metal foils serving as electrodes onto both main surfaces of an element body, and a step of bringing the element body and the metal foil into contact with each other. A first heating and pressing process of heating and pressing at a temperature lower than the melting point of the body material, and after the first heating and pressing process, thermocompression bonding the element body and metal foil at a temperature higher than the melting point of the element material. A method for manufacturing an organic positive temperature coefficient thermistor was constructed, including a second heating and pressurizing step.

Effect> According to the above configuration, in the first stage heating and pressurizing step,
While the metal foil is heated and pressure welded to the element body at a temperature below the melting point of the element material, the air remaining between the two is pushed out and flows out to the outside, and air remains between the two. It disappears. In this state, the element body and the metal foil are pressed together at a temperature higher than the melting point in the second heating and pressing step, so that the element body and the metal foil are in close contact with each other over the entire surface without any gaps. Therefore, a thermistor body without a gas layer between the element body and the electrode can be obtained.

Therefore, even if heat is applied in subsequent soldering steps, the resistance value will not increase due to the gas layer.

<Example> Hereinafter, the present invention will be explained in detail based on the example shown in FIGS. 1 and 2. FIG. 1 is a sectional view of the main body of an organic positive temperature coefficient thermistor obtained by method 4 of the present invention. In the figure, the thermistor main body 1 is composed of an element body 2 and a pair of electrodes 3.3. The element body 2 is made of an organic polymer in which conductive particles are dispersed.

Furthermore, the electrode 3 is made of metal foil. The metal foil 3
are bonded to both main surfaces of the element body 2 by thermocompression bonding. 4.4 is a lead terminal, and 5 is a coat portion. The basic structure of these organic positive temperature coefficient thermistors is the same as that of the conventional examples shown in FIGS. 5 and 6. Also,
As for its constituent materials, the same materials as those of the conventional example can be used.

Next, a method for forming the thermistor body 1 having the above configuration will be specifically explained.

(A) First Embodiment FIGS. 2(A), 2(B), and 2(C) are explanatory views showing each step of an embodiment of the method of the present invention. First, as the element body 2, an element body whose constituent material is a polyethylene resin mixed and dispersed with carbon black was used.

Further, as the metal foil 3 serving as an electrode, a nickel metal foil was used. Then, as shown in FIG. 2(A), the element body 2 and a pair of metal foils 3.3 were set between a pair of press plates 6.6 for thermocompression.

Next, as shown in FIG. 2(B), in the first heating and pressing step, the element body 2 and the metal foil 3°3 are pressed by both press plates 6.6 at a temperature lower than the melting point of the element material. It was heated and pressurized. In this case, the melting point of the element material was 130°C, while the heating temperature was set at 50°C. The pressing force was 150 kg/cm2. The heating and pressurization under these conditions was repeated three times for 2 minutes each.

By heating and pressurizing at a temperature below the melting point, all the air remaining between the element body 2 and the metal foil 3 leaked out to the outside.

Note that the heating temperature in this step should just be below the melting point of the base material and higher than the ambient temperature.

Following the first heating and pressing process, the heating temperature was raised to 190°C, which is higher than the melting point of the base material, and both presses were temporarily pressed at 6.
Heating and pressurizing was carried out using 6. This is the second heating and pressing step. The pressing force was 150 kg/cm''.Heating and pressing under these conditions was repeated three times for 2 minutes each.

As a result, the surface layer of the element body 2 was melted and firmly bonded to the metal foil 3. Moreover, since the element body 2 and the metal foil 3 were pressed together without any air remaining between them, no gas layer was formed between them.

By going through each of the above steps, a thermistor body l as shown in FIG. 1 was obtained. A lead terminal 4.4 is soldered to each electrode 3.3 of this thermistor body I, and then the entire thermistor body I and the base of the lead terminal 4.4 are coated with resin, and the coating portion 5 is It is formed. These steps are the same as in the conventional method, so detailed explanations will be omitted.

Next, the characteristics of the thermistor body l obtained through each of the above steps were investigated. In other words, the thermistor body l is 1c
It was cut into m square pieces, and the rate of change in resistance due to subsequent processing steps was examined. The state of change is shown in the characteristic diagram of FIG. The conventional thermocompression bonding method used nickel foil.

As is clear from the characteristic diagram in Figure 3, the rate of change in resistance of the thermistor body by the conventional method was over 50% due to the soldering process and the coating part forming process.
The resistance change rate of the thermistor body 1 according to the method of the present invention does not change significantly after soldering and after the formation of the coated part, and is 10%.
It fell below.

In addition, a heat cycle test was conducted on the same objects as those tested above. The results are shown in the characteristic diagram of FIG.

In this test, -20°C for 30 minutes, 25°C for 3 minutes, 120°C
This cycle was repeated many times with temperature/time conditions of 30 minutes at °C and 3 minutes at 25 °C as one cycle.

As is clear from the figure, the thermistor body is made using conventional metal wires, or the thermistor body is made using conventional thermocompression bonding. While the resistance change rate increased to nearly 100% at 00 cycles or 1000 cycles,
It can be seen that in the thermistor body 1 manufactured by the method of the present invention, even after 1000 cycles, the rate of change in resistance was approximately 10%, and the rate of change in resistance hardly changed.

(B) Second Embodiment In the first embodiment described above, in the second heating and pressing step, the heating temperature was set to 19°C, which was 60°C higher than the melting point of the element body + material.
In this second example, the heating temperature was set at 140°C, which is 10°C higher than the melting point of the element material, and 240°C, which is 110°C higher than the melting point of the element material.

The materials used in this example and the steps leading to the second heating and pressing step are the same as in the first example.

The results of testing the resistance value and the adhesive strength of the electrode 3 for the thermistor body 1 obtained by carrying out the second heating and pressurizing process under the above temperature conditions are shown in Table 1 below. The resistance value and adhesive strength of the thermistor main body l obtained in the first example are also listed. The resistance value test samples were all Icm square thermistor bodies. The adhesive strength was tested using a thermistor main body I having a width of I cm and a length of 10 cm, and the electrode 3 was peeled off in the length direction at a speed of 2 m/min. In the table, the resistance values are values at room temperature (25° C.).

(Left below) (Table 1) 140 10.19 1 0.2319
0 1 0.1.1 1 0.53
240 0.24 10. Sword: From the results shown in Table 1, when the heating temperature is close to the melting point of the element material, the resistance value is relatively small, but the adhesive strength is not sufficient; It can be seen that when the temperature is significantly higher than the melting point of the material, the adhesive strength increases, but the resistance value also increases.

Therefore, the temperature difference ΔT between the heating temperature in this second heating and pressing step and the melting point of the element material is set at 20'C to 100°C.
It is preferable to keep it within the range of . When the temperature difference ΔT is kept within this range, the increase in resistance value can be suppressed to a slight extent, and sufficient adhesive strength can be obtained.

<Effects of the Invention> As described above, according to the present invention, the air remaining between the element body and the metal foil is pushed out in the first stage heating and pressurizing process and flows out to the outside. In the heating and pressurizing process, the element body and the metal foil are bonded under heat and pressure without any air remaining between them, so no gas layer is generated between the element body and the metal foil, and there is no gap between the two over the entire surface. Close contact without any problem. Therefore, not only sufficient adhesive strength can be obtained, but also a desired low initial resistance value can be obtained without the inconvenience of increased resistance due to a gas layer, which is the case with conventional thermistors.

In addition, since there is no gas layer between the element body and the electrode, there is no problem of increased resistance due to soldering of the lead terminal or baking of the coated part, so soldering can be carried out over a wide range of temperature conditions. This makes it easy to process the thermistor body.

Furthermore, in conventional thermocompression bonded thermistors, resistance values vary from one thermistor to another depending on the size, number, and location of gas layers, but with the thermistor of the present invention,
Since there is no gas layer that causes a change in resistance value, the resistance value is constant for each thermistor, and as a result, the rate of non-defective products is improved.

[Brief explanation of drawings]

1 and 4 relate to an embodiment of the present invention, and FIG. 1 is a sectional view of a thermistor body obtained by an embodiment of the present invention;
Figures 2 (A), (B), and (C) are explanatory diagrams showing each process of the above embodiment, Figure 3 is a characteristic diagram showing the rate of change in resistance due to heating of the thermistor body, and Figure 4 is the thermistor body. FIG. 3 is a characteristic diagram showing the resistance change rate by a heat cycle test. 5 and 6 relate to conventional examples, FIG. 5 is a sectional view of a thermistor obtained by the conventional method, and FIG. 6 is an enlarged sectional view of the thermistor body obtained by conventional thermocompression bonding. l... Thermistor body, 2... Element body, 3... Electrode (metal foil), 4... Lead terminal, 5... Coating part, 6
...Press board.

Claims (2)

[Claims] (1) In manufacturing an organic positive temperature coefficient thermistor whose element body is made of an organic polymer mixed and dispersed with conductive particles, forming electrodes on both main surfaces of the element body, a step of bringing metal foils to serve as electrodes onto both main surfaces, a first heating and pressing step of welding the element body and the metal foil together at a temperature lower than the melting point of the element material; A method for manufacturing an organic positive temperature coefficient thermistor, comprising a second heating and pressing step of thermocompression bonding the element body and metal foil at a temperature equal to or higher than the melting point of the element material after the heating and pressing step. . (2) The organic material according to claim 1, wherein the heating temperature in the second heating and pressing step is set within a range of 20°C higher to 100°C higher than the melting point of the base material. A method for manufacturing a positive characteristic thermistor.