JPH01289086A - Vacuum heating device - Google Patents

Abstract

PURPOSE:To make a substance to heat in a vacuum heating condition in a short time with a good reproducibility by composing to connect a throwing-in power shifting device and a heater power controller. CONSTITUTION:A substance to heat 3 is placed in a vacuum furnace 1 of the atmospheric condition, the inside of the vacuum furnace 1 is evacuated up to a specific vacuum degree, a power is thrown in to a heater 2 from a heater power controller 7, and at the same time, the passing time after the heating is started is integrated by a timer 9. The power amount fed to the heater 2 is determined by the output direction signal in the heating time from a throwing-in power shifting device 10 to the heater power controller 7. When the heating is continued to raise the temperature of the vacuum furnace 1 and the detected temperature of a thermocouple is raised, and its temperature exceeds a set value of a temperature detector 8, or when the integrated time by the timer 9 exceeds a set time, the output direction signal from the throwing-in power shifting device 10 to the heater power controller 7 is shifted to the signal to maintain the temperature. As a result, the power amount red to the heater 2 from the heater power controller 7 is shifted to the value of maintaining the heat.

Description

DETAILED DESCRIPTION OF THE INVENTION (Objective of the Invention) (Industrial Application Field) The present invention relates to a vacuum heating device suitable for a preliminary vacuum heating device of a thin film forming vacuum device.

(Prior Art) Generally, in an apparatus for heat-treating industrial products in a vacuum, a preliminary vacuum heating chamber is provided in front of the processing chamber in order to achieve mass productivity.

For example, in thin film forming vacuum equipment used to manufacture thin film transistors used in active matrix liquid crystal displays, etc., in order to continuously and efficiently form films on substrates, preliminary vacuum heating is performed before film formation. There is a room. In addition, in a thin film forming vacuum apparatus that performs continuous film forming, after carrying the substrate mounted on a tray in the air at room temperature into a pre-vacuum heating chamber, it is evacuated to a vacuum state in the shortest possible time and the prescribed amount required for film forming is achieved. It is necessary to raise the temperature of the substrate to a temperature (for example, 300'C).

Hereinafter, a vacuum heating apparatus used as a preliminary vacuum heating chamber of a conventional thin film forming vacuum apparatus will be described with reference to FIG.

FIG. 3 is a schematic configuration diagram showing a vacuum heating device, in which a substrate and the like are attached to the heated part (2). Furthermore, the heated part (2) is installed at a predetermined position in the vacuum furnace (2), and the inside of the vacuum furnace (ω) is evacuated by the exhaust part.

In this state, by supplying power from the heater power controller ω to the heater (2), the object (2) to be heated is heated. A temperature gradient setter (2) and a PID controller (2) are connected to the heater power controller (2), and the temperature gradient setter (2) limits the maximum value of the power applied to the heater (2) from the heater power controller (2). On the other hand, a thermocouple (A) is connected to the PID controller (■) at an arbitrary position within the vacuum furnace (■), and the heater power controller (■) is activated depending on the temperature inside the vacuum furnace detected by this thermocouple (A). Heater power controller 1~
He is giving instructions to Laura ■.

(Problems to be Solved by the Invention) However, the vacuum heating device described above has the following problems. In other words, when performing vacuum heating using a PID controller, in order to prevent the heated object from overshooting the target temperature, the temperature gradient set by the PID controller must be made gentle over time. Therefore, it takes time for heating.

In general, general PID controllers and PID with learning function
When a controller is used, the initial conditions for performing vacuum heating, such as the temperature of the furnace, the temperature of the object to be heated, the temperature of the heater, etc., do not become constant values during continuous heating.

Therefore, if the initial conditions are not constant and the object to be heated is heated to the set temperature in a short period of time, overshoot will occur.

The present invention has been made to solve the above problems,
The present invention provides a vacuum heating device capable of bringing a heated object into a heating equilibrium state with good reproducibility in a short time even if the initial conditions are not constant.

(Structure of the Invention) (Means for Solving the Problems) A vacuum heating apparatus of the present invention includes at least a heater in a vacuum furnace, and a heater power controller for controlling the heater. Temperature detection means that detects the temperature inside the furnace and outputs a command signal to switch the power for heating or keeping warm according to the set temperature; a timer that outputs a power switching command signal; and an input power switching means that connects the switching command signals from the temperature detection means and the timer with an OR circuit to output an OR condition signal to enable selection of a heating or keeping-warm state. The present invention is characterized in that the input power switching means and the heater power converter roller are connected.

(Function) In the present invention, the input power switching means instructs the heater power controller the amount of power to be input to the heater based on the actual temperature inside the vacuum furnace or the elapsed time after the start of heating using a timer. The temperature after a certain period of time has elapsed from the start of heating the object can be vacuum heated with good reproducibility in a short time.

(Example) Hereinafter, an example of the vacuum heating apparatus of the present invention will be described with reference to the drawings. Note that the same parts as in the prior art are given the same reference numerals.

FIG. 1 is a schematic configuration diagram showing a vacuum heating apparatus, in which a substrate etc. are attached to the object to be heated (2), which is placed in a vacuum furnace (ω). The heater (2) uses a lamp heater, and is placed in the vacuum furnace (2) so as to have a predetermined distance from the object (2) to be heated. The heater power controller ■ is connected to the heater ■ and supplies power to the heater ■. The heater power controller ω is connected to input power switching means 0Φ, and the heater power controller ω is connected to input power switching means 0.
The amount of electric power supplied to the heater (2) can be controlled by the output command signal (e). Input power switching part 0Φ
A temperature detector (8) and a timer (9) are connected to the temperature detector (8), and a thermocouple (a) is connected to the temperature detector (8) at a predetermined position inside the vacuum furnace α). The temperature detector ■ determines whether the internal temperature of the vacuum furnace ■ detected by the thermocouple (A) is higher than a preset temperature, and if it is higher than the preset temperature, the input power switching means 00 is Outputs switching command signal.

The timer ■ starts at the same time as heating starts, and integrates the elapsed time after heating starts, and determines whether or not this elapsed time is longer than a preset time, and if it is longer than the set time. In this case, a switching command signal is output to the input power switching means 0Φ. When input power switching means 0Φ receives either a switching command signal from a temperature detector (8) or a timer (9), it can switch the output command signal to the heater power controller by an OR circuit.

In particular, in this embodiment, the input power switching means 0Φ is equipped with two temperature gradient setting devices that can be set in advance according to the target temperature. The temperature gradient setting device 1 sets an output command signal to the heater power controller ■ during heating until the heated object ■ reaches the set temperature of the temperature detector (c) or the set time of the timer (9). is possible. On the other hand, the degree gradient setting device 2 sets an output command signal to the heater power controller ■ during so-called warming after the heated object ■ reaches the set temperature of the temperature detector (8) or the set time of the timer (9). is possible. Zarani, temperature detector■
Alternatively, a switching signal from the timer selectively switches the output of the temperature gradient setting device 1 during heating and the output of the temperature gradient setting device 2 during keeping warm, and generates an output signal from the input power switching means 0Φ to the heater power controller ■. A switch using a relay or the like is provided to

The vacuum heating apparatus configured as described above performs vacuum heating in the following manner.

First, the object to be heated (2) is placed in a vacuum furnace at atmospheric pressure.

Next, the inside of the vacuum furnace ■ is evacuated by the exhaust section until a predetermined degree of vacuum is reached. After that, power is supplied to the heater ■ from the heater power controller ■, and at the same time, the timer ■ adds up the elapsed time after heating. start.

In this case, the heater power controller
The amount of power supplied to is determined by the output command signal from input power switching means CΦ to heater power controller (2) during heating. Normally, this power amount is the maximum allowable power outlet of the heater (2), and the heating time is kept to a minimum.

Heating continues in this state, and as time passes, the temperature inside the vacuum furnace rises, and the temperature detected by the thermocouple rises. When this temperature exceeds the set temperature of the temperature detector (c), or when the cumulative time by the timer ■ exceeds the set temperature, the input power switching means (lΦ) outputs an output command signal to the heater power controller ■. Therefore, the amount of power supplied from the heater power controller (2) to the heater (2) becomes a value for keeping warm.

Here, the output command signal from the input power switching means 00 at the time of suspension is a value uniquely determined according to the target temperature attainment of the object to be heated (2).

Even if an arbitrary period of time elapses after switching from the heating state to the heat retention state, the heated part (2) remains in a vacuum atmosphere with extremely good reproducibility.

For example, FIG. 2 shows the measurement results of the substrate temperature when a glass substrate is used as the object to be heated and the target temperature is set to 300°C. .

FIG. 2 υ shows temporal changes in substrate temperature during initial heating and continuous heating when using a conventional vacuum heating device. The substrate temperature overshoots the set temperature of 300° C. by about 100° C. during continuous heating. In addition, the equilibrium temperature reached by the substrate during continuous heating is 34°C for the set temperature of 300'C.
In contrast, when the vacuum heating apparatus of the present invention is used under the same conditions as above, the substrate temperature is 0'C, as shown in Figure 2). Even at times, it's almost impossible to shoot. Therefore, the reproducibility is also 3%, which is a dramatic improvement.

In the embodiment of the present invention, the power switching means 00 is configured to output two types of output command signals, one for heating and one for keeping warm, but the power switching means 00 is configured to output a plurality of output command signals. Also good. In addition, multiple temperature detectors (c) and timers 〇 may be installed. For example, when heating the object to be heated (■) that requires multiple target heating temperatures using the same vacuum heating device, It is only necessary to make it possible to select each operation section.

〔Effect of the invention〕

According to the vacuum heating device of the present invention, it is possible to bring the object to be heated into a vacuum heated state with good reproducibility in a short time without being influenced by the initial conditions immediately before heating, and reliability is significantly improved.

[Brief explanation of the drawing]

Fig. 1 is a schematic configuration diagram for explaining one embodiment of the vacuum heating device of the present invention, and Fig. 2 is a graph showing the relationship between heating time and temperature reached as a result of heating a substrate using the vacuum heating device. 3) is a characteristic diagram of the present invention, υ is a conventional characteristic diagram, and FIG. 3 is a schematic configuration diagram for explaining a conventional vacuum heating device. ■...Vacuum heating furnace■...Heating heater (A)...Thermocouple■...Power controller (F)...Temperature detector■...Timer 0Φ...Substitute for input power switching means Person Patent Attorney Nori Ken Yudo Takehana Kikuo Figure 1 Le 1! Fence TIT (4th (a) (b) Fig. 2

Claims (1)

[Scope of Claims] A vacuum heating apparatus including at least a heater in a vacuum furnace and a heater power controller for controlling the heater, which detects the temperature in the vacuum furnace and performs heating or heat retention according to a set temperature. temperature detecting means for outputting a command signal for switching the power for use; a timer for integrating the elapsed time after the start of heating and outputting a command signal for switching the power for heating or keeping warm according to the set time; the temperature detecting means and the timer input power switching means that connects both switching command signals by an OR circuit to output an OR condition signal to enable selection of the heating or heat retention state; and the input power switching means and the heater power controller are connected. A vacuum heating device characterized by: