JPH0521136A - Ceramic heater - Google Patents

Abstract

PURPOSE:To stand long service as well as to prevent the occurrence of break away by making up an electrode of a connecting section which is directly overlapped on the surface of a heater end section, and of a power receiving section on the surface of a substrate while electrically being connected to the connecting section. CONSTITUTION:In a heater 2 made out of a membrane body made. of a silver palladium alloy, both the end sections 22 of a heating section 21 roughly 270mm long and roughly 4mm wide are widened to the full width of a substrate 1 while being extended to 3mm. An electrode 3 is made of the membrane body of silver, and is made up of a connecting section 31 which is closely adhered and overlapped on the whole surface of each end section 22, and of an initial power receiving section 32 which is directly formed on the surface of the substrate 1 to the full width while being continued to the connecting section. The exposed surface of the substrate 1 including the surface of the heater 2 is covered with a protective film 4, and the end section ranging from the whole surface of the connecting section 31 to a boundary section with the initial power receiving section 32 is also covered with the film. This constitution thereby does not allow metals contained in the heater 2 to be immersed into the initial power receiving section 32 so as to be increased in electrical resistance, but allows the receiving section to be prevented from being deteriorated even if the initial power receiving section 32 is heated by means of energizing, the receiving section will therefore never be broken away even if it is used for a long time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a ceramics heater used for fixing a toner in a facsimile or a copying machine, and is particularly suitable for a high output type ceramics heater.

[0002]

2. Description of the Related Art Conventionally, for example, a low-power type ceramics heater for a copying machine is provided with silver.
Form a thin film heating element made of palladium alloy, etc., and form an electrode made of a silver film at the end of this heating element, press the socket contact metal fitting to this electrode, or solder the wire directly to this electrode. I used it by attaching the power supply.

To obtain such a ceramic heater,
For example, a paste of silver-palladium alloy powder is applied to the surface of the substrate to form a heating element pattern, which is then fired to form a heating element, and then silver paste is applied in a film form on the end of the heating element and baked. It was formed on the electrode. In the method of pressing the contact metal fittings, if the thickness of the electrode is insufficient, sufficient electrical connection cannot be obtained.Therefore, by making the end of the heating element wide enough and stacking the electrode on the surface, the electrode film The thickness was substantially increased and a sufficient contact area was obtained.

[0004]

Such a conventional ceramics heater has no problem when it is used with a small electric power (about 500W), but a ceramics heater having the same structure has a large electric power (about 1kW). Problem occurs when used with. For example, some heat is generated in the electrode to raise the temperature, and oxidation progresses to deteriorate the contact with the contact fitting. Also, when an electric wire is soldered to the electrode or when a terminal is soldered to the electrode, the electrode also generates heat, which causes the electrode to oxidize and deteriorate, or to interpenetrate with the silver film. As a result, the adhesive strength is reduced.

When the present inventors investigated the reason for this,
When the above-mentioned silver paste was baked to form a silver film, palladium in the heating element penetrated into the silver film to increase the electrical resistance of the silver film, and it was found that the current density is high and the amount of heat generated increases. did.

Therefore, an object of the present invention is to prevent the heat generation of the electrodes or prevent the electric connection from being damaged even when the electrodes generate heat.

[0007]

The present invention relates to a ceramics heater in which an electrode made of a silver film is provided at the end of a metal film heating element formed on the surface of a ceramics substrate, and the electrode is directly laminated on the end surface of the heating element. The connection portion and the power reception portion electrically connected to the connection portion and formed on the surface of the substrate prevent the power reception portion from generating heat.

[0008]

[Function] Since the electrode is formed by the connecting portion directly overlaid on the surface of the heating element and the power receiving portion formed on the surface of the substrate, even if palladium of the heating element penetrates into the connecting portion when baking the silver film or the glass layer. Does not reach the power receiver. Therefore, the electric resistance of the connecting portion increases, but the electric resistance of the power receiving portion does not increase. However, even if the temperature rises when electricity is applied due to the electrical resistance of the connection part, there is no crimping of the metal fittings in this part and there is no soldering of the wires or terminals. There is even an advantage that a uniform temperature distribution can be obtained by compensating for the decrease in the end temperature of the heating element. Further, the power receiving portion is made of a silver film and does not contain palladium, and has a sufficiently large area so that it does not generate heat, so that the contact resistance does not increase and the soldering does not deteriorate. Then, it is sufficient that at least the power receiving portion of the electrode is made of a silver film.

[0009]

The details of the present invention will be described below with reference to the embodiments shown in the drawings. In FIG. 1, (1) is made of alumina ceramics, for example, length 300 mm, width 15 mm, thickness 1
mm substrate, (2) heating element provided on the surface of the substrate (1) in the longitudinal direction of the substrate (1), (3), (3)
Is an electrode connected to both ends of the heating element (2), and (4) is a vitreous protective film covering the surface of the heating element (2).

As shown in the enlarged view of FIG. 2, the heating element (2) is a film made of a silver-palladium alloy (Ag.Pd) and has an elongated heating section (2) with a length of about 270 mm and a width of about 4 mm.
Both ends (22) and (22) of 1) are spread over the width of about 3 mm to the full width of (1) of the substrate.

As shown in FIG. 2, the electrode (3) is a film body made of silver (Ag) and has a connecting portion (31) in which the entire surface of the end portion (22) of the heating element (2) is adhered and laminated. ) And a power receiving portion (32) continuously formed on the surface of the substrate (1) continuously with the connecting portion (31).

The protective film (4) covers the exposed surface of the substrate (1) including the surface of the heating element (2), and the end portion of the protective film (4) extends from the entire surface of the connecting portion (31) to the power receiving portion (32). ) Is covered up to the boundary.

Next, a method for manufacturing this ceramic heater will be outlined. First, a paste of silver-palladium alloy powder is printed on the surface of the substrate (1) to form a heating element pattern, which is then fired to form the heating element (2). Then,
Silver paste is printed on a part of the heating element (2) and the surface of the substrate (1) to form an electrode pattern, which is then fired to form an electrode (3) made of a silver film. Then, a glass paste is applied to the exposed surfaces of the heating element (1), the connecting portion (31) and the substrate (1) and baked to form the vitreous protective film (4), thereby completing the ceramic heater.

However, during the above-mentioned silver paste baking and glass paste baking, both the heating element (2) and the electrode (3) are heated to a high temperature, and therefore, the heating element end portion (22) and the connection portion (31). ), A molecular migration occurs, and palladium in the silver-palladium alloy forming the end portion (22) of the heating element is transferred to silver in the connection portion (31),
The electrical resistance of the connection part (31) increases. However, since the power receiving part (32) is formed directly on the surface of the ceramic substrate (1), palladium and other metals penetrate into the power receiving part (32) despite the high temperature of the above-mentioned silver paste baking and glass paste baking. Without doing this, the connection part (31)
The palladium that has penetrated into the power receiving unit (3
You cannot reach up to 2). As described above, in the ceramic heater of the present embodiment, the power receiving portion (2) of the electrode (2) is
Since palladium and other metals cannot penetrate into 2), it is formed almost as a pure silver film, has a low electric resistance, and does not increase even after long-term use.

Next, the function and effect when the ceramic heater is connected to the power source by various connecting methods will be described. FIG. 3 shows the power receiving part (32) of the electrode (3) of the ceramics heater, which is press-fitted with a socket fitting (5) (not shown). The parts of the heater are designated by the same reference numerals as in FIG. There is. As described above, this product has a low electric resistance because palladium and other metals do not penetrate into the power receiving part (32) of the electrode (3) during the manufacturing process, and therefore the power receiving part (32) hardly generates heat due to energization. ,
Further, since the amount of heat transferred from the heating element (2) is small, the temperature of the power receiving section (32) is low, so that the contact resistance with the connection fitting (5) is small, and the resistance increases even after long-term use. The power receiving section (32) will not be oxidized and peeled off.

Further, FIG. 4 shows that the electric wire (6) is soldered (7) to the power receiving portion (32) of the electrode (3) of the ceramic heater.
Are electrically connected, and the same reference numerals are given to the respective parts of the heater in correspondence with FIG. This product also has a low electric resistance because palladium or other metal does not penetrate into the power receiving part (32) during the manufacturing process, or solder (7) has a low welding temperature, so that there is almost no penetration of solder, and therefore the power receiving part ( 32) does not generate heat and the heat transfer from the heating element (2) is small, so the power receiving section (32)
Therefore, the power receiving portion (32) is not oxidized and deteriorated, and the power receiving portion (32) and the solder (7) are not oxidized and separated.

Further, in FIG. 5, the terminal (8) is connected to the power receiving portion (32) of the electrode (3) of the ceramic heater by solder (7), and the electric wire (6) is soldered to this terminal (8). It is connected in (7). This one also has a power receiving unit (3
Since 2) does not contain palladium or other metals, it has a small electric resistance, and therefore generates little heat when energized, and the heat transfer from the heating element (2) is also small, so the temperature of the power receiving section is low and even after long-term use. The power receiving part (32) and the solder (7) will not be oxidized and deteriorated to prevent peeling.

Although the heating element is made of a silver-palladium alloy film in the above-mentioned embodiments, the present invention is not limited to this, and is an electrothermal material containing a metal that easily penetrates into silver, such as nickel or tin. You may comprise. Further, in the electrode, if at least the power receiving portion is made of a silver film, the connecting portion does not necessarily need to be pure silver. The present invention is particularly suitable for high power type ceramics heaters. Further, in the present invention, the base material may be ceramics, and the shape thereof does not matter.

[0019]

As described above, in the ceramic heater of the present invention, an electrode made of a silver film is connected to the end of the metal film heating element formed on the surface of the ceramic substrate, and the electrode is formed on the end surface of the heating element. Since it is composed of the directly overlapped connection part and the power reception formed on the substrate surface by being electrically connected to this connection part, the metal in the heating element penetrates into the power reception part of the electrode due to heating in the manufacturing process, and the electrical resistance Therefore, the power receiving portion does not generate heat due to energization, is not oxidized and deteriorates, and is not peeled off even after long-term use.

[Brief description of drawings]

FIG. 1 is a plan view of an embodiment of a ceramic heater according to the present invention.

FIG. 2 is a cross-sectional view of a main part of the heater of the above embodiment.

FIG. 3 is a cross-sectional view showing an example of electrical connection by the socket of the heater of the embodiment.

FIG. 4 is a cross-sectional view showing an example of solder connection of electric wires of the heater of the embodiment.

FIG. 5 is a cross-sectional view showing an example of terminal connection of the heater of the above embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Substrate 2 ... Heating element 21 ... Heating part 22 ... End part 3 ... Electrode 31 ... Connection part 32 ... Power receiving part 4 ... Protective film 5 ... Contact metal fitting 6 ... Electric wire 7 ... Solder 8 ... Terminal

Claims (1)

Claim: What is claimed is: 1. A ceramic heater in which an electrode made of a silver film is connected to an end portion of a metal film heating element formed on a surface of a ceramic substrate, wherein the electrode is an end portion of the heating element. A ceramic heater comprising a connecting portion directly layered on the surface and a power receiving portion electrically connected to the connecting portion and formed on the surface of the substrate.