JPH0727473A - Vacuum drying method - Google Patents

Abstract

PURPOSE:To improve the moisture removing precision by a method wherein a drying chamber is made of a radiant heat permeable material, and an item to be dried is heated by a radiant heat generator heater installed outside the drying chamber after the drying chamber is evacuated. CONSTITUTION:When an item 2 to be dried is placed in a drying chamber 3 and the pressure inside the drying chamber 3 is gradually reduced to a vacuum by a vacuum device 6, moisture attached on the surface of the item 2 immediately evaporates and is discharged outside the drying chamber 2 along with air to be discharged. Therefore, the item 2 is heated by a radiant heat generator heater 4 because the temperature of the item 2 may drop 20-30 deg.C below normal temperatures if it remains unheated. A work to carry the item 2 in and out from the drying chamber 3 and others are preferably made of a radiant heat permeable material. Then, the inside of the drying chamber 3 is returned to normal pressures while the item 2 is kept at around normal temperatures. Thereby, the moisture removing precision is improved because uneven drying parts and stains are not produced on the surface of the item 2.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a vacuum drying method. More specifically, in a vacuum drying method for removing moisture adhering to the surface of a relatively small component member of various equipment including an optical lens, a semiconductor wafer, a wiring board, etc. by vacuum drying, Regarding improvement.

[0002]

2. Description of the Related Art Generally, after various processing is performed on relatively small component members of various kinds of equipment as described above,
It has been practiced to clean the processed surface with a fluorine-based organic solvent, a chlorine-based organic solvent, or the like. However, due to environmental damage, the use of fluorine-based organic solvents, chlorine-based organic solvents, etc. has come to be regulated. As an alternative, washing with water (ultra pure water), water-soluble detergent, ultrasonic waves, etc. Cleaning is often performed.

When such washing with water is performed,
Since water adheres to and remains on the surface of the component member after cleaning and causes various problems, it is necessary to positively remove the adhered water. Also,
Some of the component members have a property of easily adsorbing moisture in the atmosphere, and thus a treatment for removing moisture adhering to the surface may be required as a pretreatment for precision processing.

Conventionally, the vacuum drying method has been noted as the most suitable treatment means for removing the moisture adhering to the surface of the component member, and, for example, JP-A-3-2.
The one described in Japanese Patent No. 5283 is known.

In this conventional vacuum drying method, as shown in FIG. 2, a drying chamber 3 accommodating an article to be dried 2 composed of the above-mentioned component members mounted on a belt conveyor 1 is moved up and down from above and below the belt conveyor 1. It is a continuous drying type device configuration that has a possible two-part structure and is movable integrally with the belt conveyer 1. The material to be dried 2 is housed inside the drying chamber 3 and the inside of the drying chamber 3 is rapidly moved. The pressure is reduced to a vacuum, and the water adhering to the surface of the object to be dried 2 is vacuum dried to be removed. After the water is removed, the inside of the drying chamber 3 is rapidly returned to normal pressure to remove the object to be dried 2. It is taken out from the drying chamber 3.

In such a conventional vacuum drying method, since the inside of the drying chamber 3 is rapidly depressurized, the drying chamber 3 is depressurized during depressurization.
Water, dust, and the like adhering to the inner wall of the conveyor and the belt conveyor 1 are scattered and adhere to the article to be dried 2, and the drying chamber 3
Since the inside of the product is rapidly returned to the normal pressure, dew condensation occurs on the material to be dried 2 whose temperature has been lowered by the pressure reduction due to the rapid temperature change. For this reason, there is a problem in that unevenness in drying and spots are formed on the surface of the article 2 to be dried from which the water has been removed, and the accuracy of removing the water becomes low.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above problems, and an object of the present invention is to provide a vacuum drying method with high water removal accuracy.

[0008]

In order to solve the above problems, the vacuum drying method according to the present invention employs the following means.

That is, according to the first aspect of the present invention, in the vacuum drying method, the inside of the drying chamber accommodating the material to be dried is evacuated to vacuum-dry the moisture adhering to the surface of the material to be dried. The drying chamber is made of a radiant heat permeable material, and the inside of the drying chamber containing the material to be dried is gradually decompressed to a vacuum, and drying is performed simultaneously with this decompression or after the drying chamber is evacuated. Radiation heat is radiated from the outside of the chamber to the object to be dried to heat the object to be dried, and the inside of the drying chamber is returned to normal pressure while the object to be dried is heated to about room temperature. .

According to a second aspect of the present invention, in the vacuum drying method of the first aspect, when the inside of the drying chamber is returned to normal pressure,
It is characterized in that heated clean dry air is introduced little by little into the inside of the drying chamber to gradually return the inside of the drying chamber to normal pressure.

[0011]

According to the above-mentioned means, in the first aspect, the inside of the drying chamber is gradually depressurized to be evacuated, so that the scattering of water and dust inside the drying chamber during depressurization can be prevented. Also,
Since the material to be dried contained in the drying chamber is heated to prevent the temperature from decreasing due to the vacuum atmosphere, dew condensation at the time of returning to the normal pressure is prevented. Therefore, drying unevenness and spots are not formed on the surface of the dried object from which water is removed, and the problem of providing a vacuum drying method with high water removal accuracy is solved.

According to the second aspect of the present invention, in the operation of the first aspect, the heated and clean air is introduced little by little into the drying chamber to gradually return the inside of the drying chamber to the normal pressure. Condensation at the time is more surely prevented.

[0013]

EXAMPLE An example of the vacuum drying method according to the present invention will be described below with reference to FIG.

The apparatus configuration for carrying out this embodiment is as follows.
The drying chamber 3 is made of a radiant heat permeable material, and the radiant heat generating heater 4 is provided outside the drying chamber 3. That is, if the radiant heat generation heater 4 is an infrared ray generation type, the drying chamber 3 is formed of glass or the like.

Further, in this device configuration, the drying chamber 3 is provided with the vent hole 5 and the vacuum device 6 and the air supply device 7 are connected to each other. The vacuum device 6 degasses the inside of the drying chamber 3 to decompress and evacuate the interior thereof, and includes a vacuum pump, a decompression tank, and the like. The air supply device 7 introduces heated clean dry air into the drying chamber 3 to restore the inside of the vacuum chamber to normal pressure, and includes a heater, a filter, a control valve, and the like.

In order to carry out the operation using such an apparatus structure, first, as shown in FIG. 1 (A), the material to be dried 2 is housed inside the drying chamber 3, and the vacuum chamber 6 is used to dry the drying chamber. The pressure inside 3 is gradually reduced. As a means for gradually reducing the pressure, it is conceivable that the vacuum device 6 is provided with a plurality of vacuum pumps to gradually increase the number of operating units, or the control valve is used to gradually decrease the degassing amount.

When the inside of the drying chamber 3 is gradually decompressed in this manner, the pressure fluctuation inside the drying chamber 3 is small and the air flow is not generated, so that the scattering of water, dust and the like inside the drying chamber 3 is prevented. Will be. Therefore, this depressurization rate is affected by the dryness and cleanliness inside the drying chamber 3.

When the inside of the drying chamber 3 is decompressed and evacuated, the moisture adhering to the surface of the material to be dried 2 is immediately evaporated and discharged to the outside of the drying chamber 3 together with deaeration. Become. That is, when drying the material to be dried 2 in which water is impregnated such as grain drying, latent heat must be applied to the material to be dried 2, but the material to be dried such as the above-mentioned component member is dried. When drying the substance adhering to the surface of the object 2, it is not necessary to add latent heat. Therefore, the temperature of the material to be dried 2 will decrease in a vacuum atmosphere as it is (20 to 30 ° C. with respect to room temperature).

The radiant heat generation heater 4 heats the material to be dried 2 whose temperature has been lowered or whose temperature has been lowered as described above. That is, heating can be performed simultaneously with the decompression of the drying chamber 3, or the drying chamber 3 can be decompressed and evacuated before heating.

The radiant heat generating heater 4 radiates radiant heat such as infrared rays and directly heats the material to be dried 2 by the radiant heat passing through the drying chamber 2 and further passing through the vacuum region inside the drying chamber 3. Will be done. Therefore, this radiant heat generation heater 4
The heating by means of is superior in thermal efficiency to the heating means for sequentially conducting heat to the drying chamber 2 from the outside of the drying chamber 3.
Since there is no heat source provided inside, there is an advantage that the drying chamber 3 can be downsized. In order to make such heating more effective, so as not to block radiant heat,
It is desirable that a work or the like that puts the object to be dried 2 into and out of the drying chamber 3 is formed of a radiation heat permeable material.

This heating is continued until the material to be dried 2 reaches about room temperature and the inside of the drying chamber 3 returns to normal pressure as described later. In the experiment conducted by the present inventor, no problem occurred even if the heating temperature was 5 ° C. lower than the room temperature. Also,
The upper limit temperature of heating is not particularly limited, and it is possible to the extent that the material to be dried 2 is not altered or damaged.

Next, the material to be dried 2 is maintained in a state of being heated to about room temperature, and the inside of the drying chamber 3 is returned to normal pressure. This return to normal pressure can be made rapidly.

When the inside of the drying chamber 3 returns to normal pressure,
Unlike the conventional example, since the material to be dried 2 is heated to about room temperature, there is no rapid temperature change in the material to be dried 2 and dew condensation does not occur.

When the object to be dried 2 is a minute object and is vacuum-dried by depositing or laminating it, or when it is a complex structure having irregularities and complicated shapes, the radiant heat generation described above is performed. Since heating unevenness may occur in the material to be dried 2 due to the heating by the heater 4, as shown in FIG. 1B, a small amount of clean dry air heated from the air supply device 7 is placed inside the drying chamber 3. Then, the inside of the drying chamber 3 is gradually returned to normal pressure.

When the inside of the drying chamber 3 is gradually returned to the normal pressure in this way, the heated air comes into contact with the space between the objects to be dried 2 and the uneven portion, and the uneven heating disappears. Is reliably prevented.

[0026]

As described above, in the vacuum drying method according to the present invention, in claim 1, the interior of the drying chamber is gradually decompressed to be vacuumed to prevent the scattering of water and dust and to heat the material to be dried. Since the temperature is prevented from lowering due to the vacuum atmosphere and dew condensation is prevented, unevenness in drying and stains are not formed on the surface of the dried material from which moisture has been removed, so that the accuracy of removing moisture is improved. There is.

Further, according to the first aspect of the present invention, since the material to be dried is heated from the outside of the drying chamber by radiant heat, there is an effect that thermal efficiency is good and the device configuration around the drying chamber can be downsized.

Further, in addition to the effects of the first aspect, in the second aspect, when the material to be dried is a minute object or a complex structure,
There is an effect that uneven heating can be eliminated and dew condensation can be surely prevented.

[Brief description of drawings]

FIG. 1 shows an embodiment of a vacuum drying method according to the present invention, in which the order of steps is shown in the order of (A) and (B).

FIG. 2 is a side sectional view of a device configuration showing a conventional example.

[Explanation of symbols]

 2 Drying object 3 Drying room 4 Radiant heat generation heater

Claims (2)

[Claims] 1. A vacuum drying method for removing moisture adhering to the surface of an object to be dried by vacuuming the inside of the drying chamber containing the object to be dried by radiant heat. It is made of a permeable material, and the inside of the drying chamber containing the material to be dried is gradually depressurized to a vacuum, and simultaneously with this depressurization or after the drying chamber is evacuated, the drying chamber is covered from outside. A vacuum drying method, characterized in that radiant heat is radiated to a dried product to heat the dried product, and the inside of the drying chamber is returned to normal pressure while the dried product is heated to about room temperature. 2. The vacuum drying method according to claim 1, wherein when the inside of the drying chamber is returned to normal pressure, heated clean dry air is introduced little by little into the inside of the drying chamber. A vacuum drying method characterized by gradually returning to normal pressure.