JPH0684878A - Evaporation molecular activation type vacuum drying method - Google Patents

Abstract

PURPOSE:To reduce a drying time of a work in water soluble cleaning while ensuring drying state at high degree by drying the work by repeating several sets of an evacuation process of an airtightly closed container and a heating process for filling an inside of tone airtightly closed container with heated gas after completion of the evacuation process. CONSTITUTION:A work W is loaded inside an airtightly closed container which is enclosed with a stand 5 and a cover container 6. The work W is dried by repeating several sets of an evacuation process for evacuating an inside of the airtightly closed container and a heating process for filling an inside of the airtightly closed container with heated gas after completion of the evacuation process. The processes are performed in order of an operation a heating gas heat exchanger 14, opening and closing of a gas supplying electormagnetic valve 15, opening and closing of a gas leak electromagnetic valve 9, operation of a vacuum pump 16 and control of opening and closing timing of a vacuum pump electromagnetic valve 17. Thereby, the work receives heat directly from heated gas and a temperature of the work is raised and evaporation of water is promoted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an evaporative molecule activated vacuum drying method for water-soluble cleaning of semiconductors, electric parts, substrates, ultraprecision parts and the like.

[0002]

2. Description of the Related Art With the prohibition of the use of fluorocarbons, trichloroethane, etc., which are used as cleaning solvents for semiconductors, electric parts, substrates, ultra-precision parts, etc., water-soluble cleaning is becoming the mainstream. However, with water-soluble cleaning, drying is a major problem, and the transition to water-soluble cleaning has not progressed slowly even now. Conventional drying methods include (1) spin drying in which the water is shaken off at high speed to dry the work, and (2) air knife drying in which air is blown away to dry the work.
(3) Warm air drying to dry the work by blowing warm air, (4) Vacuum drying to vacuum the atmosphere to promote evaporation, and (5) Heating-type vacuum drying that uses heating by reflected heat and radiant heat in combination. The scheme is known.

[0003]

However, among the above-mentioned drying methods, the vacuum drying of (4) and the heating type vacuum drying of (5) are considered to be good in that the dry state can be ensured at a high level. However, in the vacuum drying of (4), when the water is evaporated from the work, the latent heat of evaporation is removed and the work is cooled, which makes it difficult to dry, and it takes time to dry.

Further, in the heating-type vacuum drying of (5), evaporation is further promoted by applying vacuum while heating the work so as not to cool the work. However, since there is no gas as a medium for transmitting heat, only reflected heat and radiant heat can be used as heat transfer means, so the heat transfer efficiency to the work is poor, and the temperature rise in the irradiated portion of the work is higher than that of the work. The temperature rise in the non-irradiated portion is small, the temperature of the work is still low, it is difficult to dry, and it takes time to dry.

In short, both of the vacuum drying processes take a long time to dry, and in some cases, drying may occur or dry stains may occur. In particular, the work is not sufficiently dried in the work with a narrow interval, in the ultrafine tube such as the injection needle, and in the gap where the thin metal plates are overlapped.

The present invention has been made to solve the above-mentioned problems, and an object thereof is to evaporate molecules capable of shortening the drying time of a work in water-soluble cleaning while ensuring a high degree of dryness. It is to provide an active vacuum drying method.

[0007]

SUMMARY OF THE INVENTION According to the present invention, a plurality of sets are provided, each of which includes a vacuum process for evacuating the closed container and a heating process for filling the closed container with heated gas after completion of the vacuum process. The feature is that the work is repeatedly dried.

[0008]

In the present invention, a vacuum process for vacuuming the inside of the closed container and a heating process for filling the closed container with heated gas after the completion of the vacuum process are set as one set, and a plurality of sets are repeated to dry the work. Let

In the vacuum process, when the atmosphere is evacuated, the boiling point is lowered, the evaporation of water is promoted, and the water is leached from the gap of the work and the inside of the thin tube (work), but the latent heat of evaporation is removed. The work becomes colder, and the evaporation rate of water decreases steadily.

In the heating step, when the heated gas is filled in the closed container, the heated gas molecules collide with the work and water molecules due to free molecular motion, and the temperature of the work in the closed container is increased. Rise, the evaporation of water is promoted, and the work is dried. Moisture that has leached from the gap between the work and the inside of the thin tube (work) is also evaporated.

That is, the heated gas molecules enter the inside of the thin tube (work) or the gap between the workpieces to exchange heat with the water molecules, or collide with the water molecules to transfer the water molecules inside the thin tube (work). It may be driven from the gap of the work to another place, and in addition, the temperature of the work rises faster and the drying is promoted.

Then, after the heating process, the process returns to the vacuum process again. The reason why this vacuum process is necessary is as follows. As described above, in the heating step, evaporation under high temperature conditions is promoted, but especially in the narrow tube (work) or in the gap between the works, the movement of water molecules is hindered by the gas molecules and the saturated state is reached. Or it is thought to reach a state close to it.

Of course, the water molecules diffuse into the gas due to their molecular motion, but the diffusion speed becomes slower. By evacuating the atmosphere to vacuum again, the saturated vapor pressure is removed, and the temperature of the heated work is already higher than the boiling point (1 to 1.5) under the atmospheric pressure during evacuation.
Since it is doubled, the drying progresses quickly. at the same time,
Moisture of the work left behind last time also leaches into the work surface at the same time as the heated gas flows out.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 and FIG. 2 show a drying system to which an evaporative molecule activated vacuum drying method according to an embodiment of the present invention is applied.

In the figure, reference numeral 1 is a conveyor line having a predetermined height, and the upstream side of the conveyor line 1 has a first
An air knife dryer 2 is arranged as a dryer,
On the downstream side, an evaporative molecule activated vacuum drying device 3 is arranged as a second drying device.

The air knife drying device 2 has an air nozzle 4A in the upper part and an air nozzle 4B in the lower part.
The evaporative molecule activation type vacuum drying device 3 has a mounting table 5 on which a work W is placed, and a covering container 6 having an opening downward is provided above the mounting table 5 so as to be vertically movable by a cylinder 8 provided on a support 7. ing.

A gas leak electromagnetic valve 9 is mounted on the upper surface of the covering container 6, and a plurality of infrared heaters 10 are mounted inside the covering container 6. A reflection plate 11 is attached to each infrared heater 10. A vacuum gauge 12 and a pressure gauge 13 are attached to the side surface of the covering container 6.

A heating gas heat exchanger 14 is disposed below the table 5, a gas inlet 14A is formed on a side surface of the heating gas heat exchanger 14, and a gas supply solenoid valve 15 is provided on an upper surface. Is installed.

A vacuum pump 16 has an exhaust hole 1 on its upper surface.
The vacuum pump electromagnetic valve 17 of the vacuum pump 16 is mounted on the lower surface of the stand 5.
Next, the operation of this embodiment will be described.

First, the work W is conveyed to the air knife drying device 2 by the conveyor line 1, and in the air knife drying device 2, the air is blown to the work W by the air nozzles 4A and 4B, and the water content is removed. In addition,
Examples of the work W include semiconductors, electric parts, substrates, and other ultra-precision parts.

Next, the work W slides on the conveyor line 1 and is conveyed to the placing table 5, and the cover container 6 descends on the placing table 5. As a result, the work W is housed in the closed container surrounded by the table 5 and the cover container 6.

Thus, the work W is dried by repeating a plurality of sets with one set consisting of a vacuum process for evacuating the closed container and a heating process for filling the closed container with heated gas after completion of the vacuum process. It The order of the operation of the heat exchanger 14 for heating gas, the opening / closing of the gas supply solenoid valve 15, the opening / closing of the gas leak solenoid valve 9, the operation of the vacuum pump 15, and the opening / closing of the vacuum pump solenoid valve 17 are controlled by a timer. This is done by controlling the timing.

In the vacuum process, the electromagnetic valve 17 for the vacuum pump is opened to suck the inside of the closed container by the operation of the vacuum pump 15, so that the inside of the closed container becomes a vacuum of 1 mmHg to 200 mmHg. In the heating step, heated nitrogen (gas) having a pressure of 1 atm or more is supplied from the heat exchanger 14 for heated gas into the closed container through the electromagnetic valve 15 for gas supply, and the work W is 40 ° C. to 150 ° C. To be heated. The pressure of nitrogen is
It is adjusted by the gas leak solenoid valve 9.

In the vacuum process, when the atmosphere is evacuated by the vacuum pump 16, the boiling point is lowered (for example, 100 mm).
Hg is about 52 ℃, 30mmHg is about 30 ℃), evaporation of water is promoted, and the gap of work W and thin tube (work W)
Although water leaks from the inside of the work, the latent heat of evaporation is removed and the work W is cooled, the atmosphere reaches a saturated state, and the water does not evaporate. The infrared heater 10 irradiates the work W with secondary heat, but since the inside of the closed container is in a vacuum, the temperature rise of the atmosphere is insufficient.
Moreover, the temperature rise in the non-irradiated part of the work is smaller than that in the irradiated part.

In the heating process, the infrared heater 10
When the workpiece W is irradiated with the secondary heat by the heat exchanger and the nitrogen heated by the heating gas heat exchanger 14 is filled in the closed container, the heated nitrogen molecules are moved by the free molecular motion. When the temperature of the work W in the closed container rises, the atmosphere becomes unsaturated, the evaporation of water is promoted, and the work W is dried.
Moisture leached from the gap of the work W and the inside of the thin tube (work W) is also evaporated. Note that not only the temperature rise in the irradiated portion of the work W, but also the temperature rise in the non-irradiated portion is remarkable.

That is, the heated nitrogen molecules enter the inside of the thin tube (work W) or the gaps of the work W to exchange heat with the water molecules, or collide with the water molecules to transfer the water molecules to the thin tube (work W). The temperature of the work W is increased by driving it to another place from inside the space or between the gaps of the work W, and the drying is promoted.

Then, after the heating process, the process returns to the vacuum process again. The reason why this vacuum process is necessary is as follows. As described above, in the heating step, evaporation in a high temperature state is promoted, but especially in the narrow tube (work W) or in the gap portion of the work W, movement of water molecules is hindered by nitrogen molecules, It is considered to reach a saturated state or a state close to it.

Of course, water molecules diffuse into nitrogen due to their molecular motion, but the diffusion rate becomes slower. By evacuating the atmosphere to vacuum again, the saturated vapor pressure is removed, and the temperature of the heated work is already higher than the boiling point (1 to 1.5) under the atmospheric pressure during evacuation.
Since it is doubled, the drying progresses quickly. at the same time,
Moisture of the work left behind last time also leaches into the work surface at the same time as the heated gas flows out.

Since nitrogen molecules are used as gas molecules, oxidation in the closed container is prevented. As described above, the work W
After being dried, the covering container 6 is raised and sent to the carry-out conveyor 1A of the conveyor line 1.

Next, an experimental example of the above operation will be described with reference to FIG. In FIG. 3, reference numeral 21 is a desiccator, and on both sides of the desiccator 21, a first infrared lamp 22 having an ability of 500 W and a second infrared ray 23 having an ability of 500 W are arranged toward the desiccator 21. The desiccator 21 is equipped with a vacuum gauge 21A and a thermometer 21B.

A supply pipe 24 is connected to the desiccator 21, a heat exchanging heater 25 having a capacity of 2 KW is installed in the middle of the desiccator 21, and a nitrogen cylinder 26 capable of arbitrarily changing the nitrogen supply amount is installed at the tip thereof. There is.

A vacuum rotary pump 28 (exhaust speed 50 liters / min) is provided at a portion of the supply pipe 24 between the desiccator 21 and the heat exchange heater 25 via a suction pipe 27.
Is installed.

Then, as an experimental sample, a size of 180
1 mm x 30 mm lead frame piece with a thickness of 38 μm
00 lead frames R are prepared, ultrasonically cleaned for 2 minutes, set in the same jig, and then housed in the desiccator 21.

The three drying conditions (1) are as follows:
The drying test according to (2) and (3) was carried out to check the drying condition. Under the drying condition (1),
The infrared lamps 22 and 23 are not irradiated and only the vacuum rotary pump 28 is operated.

In this case, small water droplets do not disappear easily,
After about 4 minutes, the surface of the lead frame R freezes and becomes white. That is, the moisture cannot be removed from the lead frame R by only drying in vacuum.

Under the drying condition (2), the infrared lamps 22 and 23 are irradiated and the vacuum rotary pump 2 is used.
8 operation is performed. In this case, small water droplets gradually become smaller from the outer surface of the lead frame R, but do not easily disappear. The water droplet disappeared in 4 minutes and 30 seconds. At this time, the degree of vacuum was about 1 mmHg. When the lid of the desiccator 21 was opened and the dried state between the lead frame pieces on which the lead frame R overlaps was observed, it was found that the lead frame R was hardly dried and water droplets remained. At this time, the temperature was room temperature with the infrared rays not hitting the temperature sensor.

Next, when the dried state between the lead frame pieces was observed at intervals of 5 minutes, it was found that the portion between the lead frame pieces where the lead frame R overlaps was almost dried after 20 minutes. In the drying condition (3), the infrared lamps 22, 2
With the irradiation of No. 3 continued, the operation of the vacuum rotary pump 28 and the injection of nitrogen gas are repeated. That is, the inside of the desiccator 21 was evacuated to a vacuum degree of about 1 mmHg in about 10 seconds, and then nitrogen gas heated to 150 ° C. was injected into the desiccator 21 at a supply rate of 100 liter / min. About 10 seconds after the injection, the lid of the desiccator 21 moved, and it was confirmed that the pressure of the nitrogen gas was 1 atm or higher. At the same time, it was confirmed that small water droplets disappeared from the outer surface of the lead frame R.

Considering drying between the overlapping lead frame pieces of the lead frame R, nitrogen gas heated to 150 ° C. is injected for 30 seconds and the injection is stopped. And
After operating the vacuum rotary pump 28 for 20 seconds, nitrogen gas at 150 ° C. is injected again for 30 seconds and the vacuum is drawn again.

In summary, vacuum 10 seconds heated nitrogen gas injection 30 seconds vacuum 20 seconds heated nitrogen gas injection 30 seconds vacuum 20 seconds Lead frame R was taken out in a total of 2 minutes of leakage, and each lead frame piece on which lead frame R overlaps When the dry state during the period was examined, it was confirmed that the water droplets were completely disappeared.
The temperature of the lead frame R at that time was 75 ° C.

Summarizing the experimental results, (1), (2),
According to the drying test under the three conditions of (3), the drying time of (3) in which heated nitrogen gas was injected into the desiccator 21 was 2 minutes, while (1) was not dried and was heated. (2) where nitrogen gas is not injected into the desiccator 21 is 20 minutes.

As described above, in order to secure the same or more dry condition, the drying time under the drying condition (3) is much shorter than the drying time under the drying conditions (1) and (2). Was confirmed.

According to the above construction, there is a heating step of filling the sealed container with heated nitrogen after completion of the vacuum step, and the work W receives heat directly from the heated nitrogen in the heating step. The temperature of the work W can be raised to 40 ° C. to 150 ° C. to accelerate the evaporation of water. Therefore, the heat transfer efficiency is improved as compared with the conventional heating type vacuum drying that uses only reflected heat and radiant heat as heat transfer means.
The drying time can be shortened.

Further, since the water is leached from the inside of the thin tube or the gap between the works W in the vacuum step and the evaporation is repeated in the heating step, the dry state can be enhanced. Moreover, not only the oxidation of the work W can be prevented, but also the oxidation of water and other molecules intervening therein can be prevented and the surface can be cleaned.

Therefore, it is possible to shorten the drying time of the work W in the water-soluble cleaning while ensuring a high degree of dryness. In this embodiment, nitrogen is used as the heating gas, but the gas is not limited to this, and carbon dioxide gas, air, an inert gas or the like can be used.

[0045]

As described above, the present invention has the heating step of filling the heated gas into the airtight container after the completion of the vacuum step. Therefore, in the heating step, the work gas is heated from the heated gas. Can directly receive heat, raise the temperature of the work, and accelerate evaporation of water. Therefore, the heat transfer efficiency can be improved and the drying time can be shortened as compared with the conventional heating type vacuum drying which uses only reflected heat and radiant heat as the heat transfer means.

Further, in the vacuum process, water is leached from the gap between the works and the inside of the thin tube as the work, and this is repeatedly evaporated in the heating process, so that the dry state can be enhanced.

Therefore, there is an effect that the drying time of the work in the water-soluble cleaning can be shortened while ensuring a high dry state.

[Brief description of drawings]

FIG. 1 is a side view showing a drying system to which an evaporation molecule activated vacuum drying method according to an embodiment of the present invention is applied.

FIG. 2 is a plan view showing the vacuum drying system.

FIG. 3 is an explanatory diagram of a vacuum experimental apparatus for an evaporative molecule activation type vacuum drying apparatus of the same vacuum drying system.

[Explanation of symbols]

 1 Evaporative molecule activation type vacuum dryer W work

Claims (1)

[Claims] 1. A vacuum process for evacuating the closed container and a heating process for filling the closed container with a heated gas after completion of the vacuum process are set as one set, and a plurality of sets are repeatedly dried. A vacuum drying method characterized by evaporative molecule activation.