JPH07201459A - Ceramic heater - Google Patents

Abstract

PURPOSE:To provide temperature control in high accurate and further to improve a follow-up property relating to setting a temperature by providing a metal heating unit layer of high electric conductivity, having high adhesive strength, in an aluminum nitride sintered base body surface of good heat conductivity. CONSTITUTION:By using a metal heating unit mainly composed of Ag-Pd alloy containing palladium in a specific range, even when repeated a heating/cooling cycle, adhesive strength to an aluminum nitride base body is not decreased, and further high accurate and quick temperature control can be attained. That is, by forming a metal heating unit layer, mainly composed of alloy with 0.3:99.7 to 40:60 weight ratio of palladium to silver by consisting of palladium and silver, in a surface of the aluminum nitride sintered body, a high accurate further quick increasing/decreasing temperature speed is obtained, and further temperature distribution can be uniformly obtained.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a novel ceramic heater. In detail, high-accuracy and rapid heating rate,
It is a ceramic heater that has a cooling rate and enables a uniform temperature distribution.

[0002]

2. Description of the Related Art Ceramic heaters having a metal heating element layer formed on or between aluminum nitride ceramic substrates are excellent in that they can generate a large amount of heat per unit area, and can be made smaller and lighter and heat resistant. Since it has high properties, it is beginning to be widely used in home appliances, various manufacturing equipment, and the like.

However, the above-mentioned ceramic heater has a problem that it is difficult to apply it to, for example, heating / cooling and thermostatic devices for the fields of medicine, chemistry and biotechnology, which require a highly accurate and rapid temperature rising / falling rate. there were.

On the other hand, the aluminum nitride sintered body has a drawback that the surface has a poor wetting property with respect to the metal and the adhesion of the metal heating element is poor, and in order to eliminate such a drawback, an alloy of palladium and platinum is used. A ceramic heater used as a metal heating element has been proposed.

[0005]

However, although the ceramic heater using the above alloy has improved adhesion to the aluminum nitride sintered body, there is still room for improvement in high precision and quick temperature control. It was

[0006]

Means for Solving the Problems As a result of intensive studies to solve the above-mentioned problems, the present inventor has found that by using a metal heating element whose main component is an Ag--Pd alloy containing palladium in a specific range, The inventors have found that a ceramic heater can be obtained in which the adhesion strength to an aluminum nitride substrate does not decrease even when a heating / cooling cycle is repeated and the temperature can be controlled with high accuracy and speed, and the present invention has been completed. .

The present invention is directed to a metal heating element which is composed of palladium and silver on the surface of an aluminum nitride sintered body, and whose main component is an alloy having a weight ratio of palladium to silver of 0.3: 99.7 to 40:60. It is a layered ceramic heater.

In the present invention, the aluminum nitride sintered body may be of any known material and shape as a ceramic heater and may be used without particular limitation. For example, a material having a thermal conductivity of 160 W / m · K (room temperature) or higher is suitable.

The shape may be an arbitrary shape such as a plate shape or a cylindrical shape depending on the purpose of use, but the surface is flat because of the ease of printing a paste for forming a metal heating element described later. Preferred shapes are preferred.

A feature of the present invention is that the surface of such an aluminum nitride sintered body is made of palladium and silver, and the weight ratio of palladium to silver is 0.3: 99.7 to 40:60, preferably 6 :. This is because a metal heating element layer containing an alloy of 94 to 27:73 as a main component was formed. That is, when the ratio of palladium is less than 0.3, the mechanical properties of the metal heating element to be formed are not sufficient, and the adhesion to the surface of the aluminum nitride sintered body decreases.

Therefore, not only the temperature of the ceramic heater cannot be controlled accurately, but also the durability is lowered.

When the ratio of palladium exceeds 40, heating / heating of the heating element of the obtained ceramic heater is performed.
The cooling rate becomes slow, and it becomes impossible to accurately raise and cool the temperature. The specific resistance of the heating element is 50 μΩ.
-Because it becomes cm or more, it becomes difficult to apply the first applied power (because of high voltage and low current), and there is a problem that the rise at the time of temperature rise is delayed. Further, the wettability of the brazing material and the solder for joining the electrodes to the leads is deteriorated, which makes it difficult to incorporate the brazing material into other devices.

In the present invention, the method of forming the metal heating element layer having the above composition on the surface of the aluminum nitride sintered body is not particularly limited, but in general, a palladium powder having a particle diameter of 1.5 to 2.7 μm and a particle diameter are used. Silver powder of 1.1 to 2.3 μm was mixed in a weight ratio of Pd / Ag = 0.3 / 99.7 to 40/60, and this was kneaded and dispersed with an organic vehicle to prepare a paste. Examples include a method in which the paste is applied on the substrate by a method such as screen printing, and then dried and baked.

In the above method, as the organic vehicle, ethyl cellulose, di-n-butyl phthalate, butyl carbitol acetate and the like are preferably used. Further, an organic solvent such as terpineol may be added to adjust the viscosity.

Further, the addition of 2 to 7% by weight of an active metal such as Ti and Zr to the above alloy composition and 10% by weight or less of a glass component is equivalent to heat generation of metal formed on the surface of the aluminum nitride sintered body. It is preferable from the viewpoint of improving the adhesion of the body layer.

The firing conditions after applying and drying the paste may be appropriately determined, and in the air, it is 810 to 870 ° C.
In the temperature range of, about 10 to 180 minutes is suitable.

In the present invention, the pattern of the metal heating element layer is not particularly limited, but a linear pattern arranged at regular intervals is preferable.

The thickness of the metal heating element layer may be appropriately determined according to the width of the pattern, the ratio of palladium contained, the applied voltage and the like.

[0019]

As described above, according to the present invention, a metal heating element layer having a high adhesion strength and a high electric conductivity is provided on the surface of an aluminum nitride sintered body substrate having a good thermal conductivity. It is possible to control the temperature and has excellent followability to the temperature setting.

Therefore, it has become possible to provide a heating / cooling device capable of rapidly raising / lowering the temperature by combining with the cooling device.

[0021]

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

Examples 1 to 7 and Comparative Examples 1 to 2 According to the formulations shown in Table 1, a palladium powder having an average particle size of 2.0 μm and a silver powder having an average particle size of 1.0 μm together with an organic vehicle were used in a three-roll machine. The mixture was kneaded and dispersed to obtain a paste. This paste was screen-printed on an aluminum nitride sintered body substrate in the shape shown in FIG.

After printing, after drying at 100 ° C. for 30 minutes,
It was fired in the air at 850 ° C. for 30 minutes to form a metal heating element layer on the surface of the sintered body. The total length of the heating element formed is 290 m
m, the width is 250 μm, and the thickness is 14 μm. In addition,
Example 6 was fired in argon at 850 ° C. for 30 minutes.

First, the solder wettability of this resistance heating element was evaluated. In addition, regarding this metallized substrate, -65 ° C
A heat cycle test was conducted for 30 minutes to 125 ° C for 30 minutes. After the test was completed, a nickel lead having a width of 3 mm was brazed and a 90 degree peel test was performed to measure the adhesion strength of the metallization. The results are shown in Table 2.

Next, as shown in a sectional view in FIG. 2, thermocouples 5 and 5 are formed on the surface of the ceramic heater having the metal heating layer 2 formed on the surface of the aluminum nitride sintered body 1.
Stack the aluminum nitride sintered substrate 1'with the
Further, an aluminum cooling plate 7 in which cooling water at 10 ° C. is flowing was prepared, a heating / cooling device was prepared, and its characteristic test was conducted.

The size of the heating / cooling device is 45 in width.
X depth 30 x height 25 mm. Electric power was applied to the external electrodes when the temperature was raised. When the temperature was lowered, the applied power was turned off, and at the same time, the heater was immediately placed on the cooler 7 for cooling. Figure 2
A thermocouple was installed at No. 5 (center of the heating element), the temperature change was measured, and the difference between the measured temperature and the set temperature was evaluated as the temperature accuracy.

The heating resistor is energized at a rated voltage of 200V ×
Power control was performed using a 20 A thyristor.

Further, a heat pattern as shown in FIG.
That is, a program is set up that heats from 20 ° C to 100 ° C in 8 seconds, holds for 10 minutes, then cools to 10 ° C in 18 seconds, holds for 10 minutes, and sets the actual temperature rise when power is applied. The time T1 required and the time T2 required for lowering the temperature to 10 ° C. when the applied power was turned off immediately after holding at 100 ° C. for 10 minutes and then placed on the cooling plate were measured. In addition, another thermocouple is installed at 5'of Fig. 2 (the boundary between the heating element and the current-carrying part), and the temperature difference (temperature distribution accuracy) from the 5'position is measured when the 5'position is 100 ° C. did. The results of temperature control and measurement are shown in Table 3. The temperature accuracy shown in Table 3 is the difference between the set temperature (100 ° C) and the actual temperature 20 seconds after the program starts when the time required from 20 ° C to 100 ° C is programmed to 8 seconds. It is shown.

Comparative Example 3 As a metal heating element, an organic vehicle was added to tungsten powder having an average particle diameter of 2.5 μm, and the mixture was kneaded and dispersed by a three-roll machine to obtain a resistor paste. This resistor paste was screen-printed on an aluminum nitride sintered body substrate in the shape shown in FIG. 1 and fired at 1400 ° C. for 30 minutes in an atmosphere of N ₂ / H ₂ = 2/1 to form a resistance heating element. Obtained. The resistance value of the heating element at this time was 50Ω.

This resistance heating element was subjected to an evaluation test and a characteristic test under the same conditions as in the examples, and the solder wettability, the adhesion strength of metallization after the heat cycle test and the heating / cooling rate were compared. The results are summarized in Tables 2 and 3.

Comparative Example 3 As a resistor component, a 0.1 μm powder having a composition of 18% by weight of platinum / 82% by weight of palladium has a softening point of 700.
C. and 8% by weight of glass fillet having a crystallization temperature of 800.degree. C. were mixed to obtain a resistor paste. This resistor paste was screen-printed on the aluminum nitride sintered body substrate in the shape as shown in FIG. 1 and fired in the same manner as in Example to obtain a resistance heating element. The heating resistor at this time was 119Ω.

The resistance heating element was subjected to an evaluation test and a characteristic test under the same conditions as in the examples, and the solder wettability, the adhesion strength of the metallization after the heat cycle test, and the heating / cooling rate were compared. The results are summarized in Tables 2 and 3.

[0033]

[Table 1]

[0034]

[Table 2]

[0035]

[Table 3]

[Brief description of drawings]

FIG. 1 Pattern of metal heating element layer

FIG. 2 is a sectional view of an embodiment in which a ceramic heater and a cooler of a typical embodiment of the present invention are combined.

FIG. 3 is a graph showing a heat pattern

[Explanation of symbols]

 1 Aluminum Nitride Sintered Body 1'Aluminum Nitride Sintered Body with Thermocouple 2 Metal Heating Element 3 Current-carrying Part 4 Electrode 5 Thermocouple 5'Thermocouple 6 Cooling Water 7 Cooler 8 Applied Power

Claims (1)

[Claims] 1. A surface of an aluminum nitride sintered body is composed of palladium and silver, and the weight ratio of palladium to silver is 0.1.
A ceramic heater having a metal heating element layer containing an alloy of 3: 99.7 to 40:60 as a main component.