JPH034587A - Method and device for cleaning printed board - Google Patents

Abstract

PURPOSE:To realize the cleaning method and the device of a printed board without being accompanied by pollution by a method wherein the residual flux of the printed board is removed by a water soluble cleaning agent, the cleaning agent is removed with water or warm water, and the printed board is heated at a prescribed temperature and dried up in a vacuum under a specific pressure or below. CONSTITUTION:A printed board P is held on a conveyer 4, and the board P is cleaned by separating flux residue from the board P by a water-soluble cleaning agent spouted from a nozzle 5 against the board P in a cleaning agent removing device 2. The cleaning agent attached to the board P is removed with water or warm water spouted out from a nozzle 9 in rinsing devices 3' and 3'', and the board P is dried with an air nozzle 7. The board P is heated at a temperature of 50 deg.C or above in a heating device 10 and dried up in a vacuum of 200Torr or below in a vacuum dryer 11. By this setup, a cleaning method and a device free of pollution can be realized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method and apparatus for cleaning printed circuit boards soldered with pine resin flux with a water-soluble detergent.

[Background of the invention]

Generally, a flux containing pine resin as a main component is used for soldering printed circuit boards.

Pine resin is a good insulator and does not conduct electricity by itself, so for printed circuit boards used in consumer equipment such as televisions, radios, and tape recorders, it is assembled into the equipment without soldering. . However, since pine resin is sticky, over a long period of time, dirt and dust may adhere to the flux residue after soldering, but dirt and dust absorb moisture when the humidity is high, worsening insulation resistance. There are things to do. In general consumer equipment, a slight drop in insulation resistance does not have much effect on functionality, but in precision electronic equipment such as large computers and communication equipment, even a small drop in insulation resistance can cause errors. For this reason, it is said that flux residue must be removed from printed circuit boards used in precision electronic equipment after soldering.

Conventionally, fluorine-based mulberry or chlorine-based organic solvents, which dissolve pine resin well, have been used to remove flux residue from printed circuit boards after soldering. However, since fluorine-based solvents destroy the ozone layer surrounding the earth, a large amount of the sun's ultraviolet rays reach the earth from this destruction, causing skin cancer in humans. It seeps into the water and mixes with groundwater, and drinking it can cause cancer. Therefore, it is conceivable that these solvents cannot be used.

Therefore, research into alternatives to these organic solvents has been actively conducted, and recently several water-soluble detergents that are effective in removing pine resin have been developed (for example, the detergent manufactured by Vetropharm in the United States). :Product name "Bio-Act EC-7J"
).

However, until now, only the above-mentioned organic solvents have been used to clean flux residue from printed circuit boards, and various cleaning methods and devices using them have been proposed and implemented. Cleaning methods and equipment did not exist.

The object of the present invention is to provide a completely new method and apparatus for cleaning printed circuit boards using this new detergent.

[Structure of the invention]

In the present invention, flux residue on a printed circuit board is washed with a water-soluble detergent, the detergent adhering to the printed circuit board is washed away with water or hot water, and then the printed circuit board is heated to 50° C. or higher and placed in a vacuum of 200 torr or lower. This method of cleaning printed circuit boards is characterized by drying them with water, and the cleaning process of printed circuit boards includes a detergent cleaning device that cleans the flux residue on the printed circuit boards with a water-soluble detergent, and the detergent cleaning device removes the attached detergent. It consists of a washing device that washes with water or hot water, a heating device that heats the printed circuit board after washing to 50°C or higher, and a vacuum drying device that dries the wet printed circuit board. There is a conveyor running in the equipment that transports printed circuit boards.
Moreover, the printed circuit board cleaning device is characterized in that it has a mechanism in which the printed circuit board conveyed by the conveyor is automatically fed into the vacuum drying device.

In the cleaning method of the present invention, the printed circuit board is washed with water for 50 minutes.
The reason why the material is heated above .degree. C. is that during vacuum drying after the washing step, the higher the temperature of the material to be dried, the shorter the drying time, which improves productivity.

According to experiments conducted by the present inventors, the drying time in vacuum drying is proportionally related to the temperature of the material to be dried.
It has been found that even if the degree of vacuum is the same, if the temperature of the material to be dried increases even slightly, the drying time will be drastically shortened. For example 60
It takes more than 40 minutes to dry a water-wet printed circuit board in a TORR vacuum dryer when the temperature of the printed circuit board is 40℃, but it takes 3 minutes and 20 minutes when the temperature of the printed circuit board is 60℃.
It will be a short time of seconds. Since the effective temperature for shortening the drying time is 50° C. or higher, in the present invention, the temperature of the printed circuit board after washing with water is set to 50° C. or higher. Also, the lower the degree of vacuum in the vacuum dryer, the shorter the drying time will be, but the effective degree of vacuum to shorten the drying time by keeping the printed circuit board at 50 degrees Celsius is 200 tons.
orr or less.

〔Example〕

In the printed circuit board cleaning method of the present invention, first, flux residue adhering to the printed circuit board is removed using a water-soluble detergent that is effective in removing pine resin. At this time, the cleaning method can be effectively removed by using physical or mechanical means such as ultrasonic vibration, brushing, or spraying detergent under pressure.

Once the flux residue has been removed with detergent, the detergent adhering to the flux must be removed next. Detergents are water-soluble, so water is used to remove them, but even in this case, washing with water can be effective if ultrasonic waves, brushing, spraying with pressurized water, etc. If you do a rough wash with a cloth and then finish wash with purified water a second time, you can reduce the amount of water used and create an effective water wash area.

The printed circuit board in the water washing section is heated to 50°C or higher. This is done to shorten the drying time in the next vacuum drying step. Examples of the heating means include blowing hot water and hot air, as well as using an infrared heater.

The printed circuit board heated to 50° C. or more is placed in a vacuum drying device and dried in a vacuum of 200 torr or less.

It is a front sectional view for explanation.

The washing tank 1 is composed of a detergent washing device 2 and a water washing device 3, and a conveyor 4 that holds and conveys the printed circuit board P with its claws is installed in the washing tank. A plurality of nozzles 5 for spraying detergent onto the front and back surfaces of the printed circuit board are installed in the printed circuit board travel section of the detergent cleaning device 2. The lower part of the detergent washing device 2 is a tank that temporarily stores the solvent 6 ejected from the nozzle 5 and then transfers it to the nozzle 5 using a pump (not shown).
It is designed to be sent to the United States for reuse. Further, the nozzle 5 Next, a printed circuit board cleaning apparatus, which is another invention that implements the above-described printed circuit board cleaning method, will be described with reference to the drawings.

Fig. 1 is a schematic diagram of the cleaning device of the present invention, and Fig. 2 is a schematic diagram of the washing device of the present invention.
- Detailed cross-sectional view of line ■, Figure 3 is a plan view illustrating the delivery and removal of printed circuit boards to multiple vacuum drying devices, and Figures 4 to 6 are delivery and removal of printed circuit boards in one vacuum drying device. It consists of a first water washing device #L3' and a second water washing device 3'', and the lower part is a tank for storing water 8.

The water washing device is equipped with a plurality of nozzles 9 that spray pressurized water onto the front and back surfaces of the running printed circuit board. In the first water washing device 3', the water stored in the lower tank is sent to the nozzle 9 by a pump (not shown) for reuse, but clean water is spouted from the nozzle of the second water washing device g13''. Near the nozzle 9 of the second water washing device, there is a
An air nozzle 7 is installed to blow compressed air onto the printed circuit board. A heating device 10 is installed at the place where the washing tank 1 exits.
is installed. The heating device shown in the embodiment is an electric heater that heats a printed circuit board using infrared rays.

A vacuum drying device 11 is installed near the end of the conveyor 4 in the direction of travel. The vacuum drying device 11 is a box with a frontage facing the conveyor 4, and the frontage can be sealed with a lid 12. One end of the vacuum drying device 11 is supported by a shaft 13, and the other end is supported by a vertical movement device t14 so as to be tilted. A large number of rollers 15 are installed in the vacuum drying device 11 to allow printed circuit boards to be taken in and out smoothly. 16
is an exhaust port leading to a vacuum pump (not shown). There are three vacuum drying devices 11A, 11B, and II as shown in Figure 3.
C is installed so that it can be moved laterally as shown by the arrow h.

Here, cleaning of a printed circuit board using the printed circuit board cleaning apparatus having the above-mentioned configuration will be explained.

The printed circuit board P is held at 74 by a controller running in the direction of arrow A, and is caused to run inside the cleaning tank l. The printed circuit board P is first cleaned in the detergent cleaning device 2 with detergent jetted from the nozzle 5. At this time, since the detergent applies pressure, the force of the detergent peels off the flux while cleaning. The solvent 6 ejected from the nozzle is stored in a tank at the bottom and sent to the nozzle again by a pump (not shown) for reuse. The printed circuit board whose flux has been removed with detergent is connected to air nozzle 7.
A large amount of detergent adhering to the printed circuit board is wiped off by compressed air, which prevents the detergent from being carried over to the next process.Next, flux residue is removed.
The printed circuit board with less detergent adhesion enters the first washing device 3' of the washing device 3. Here, pressure water is sprayed by the nozzle 9 to remove the detergent. Since the water in the first washing device is circulated by a pump (not shown), the amount of water used can be saved, but a small amount of the solvent is removed and the water is mixed with detergent, so it is not a complete washing process. However, in the second water washing device 3'', clean water is ejected from the nozzle 9 to wash the printed circuit board, so this is the final cleaning.
The water adhering to the surface is blown away. The printed circuit board, which has almost no water left, is heated by the infrared rays of the heating device 10.
The material is heated to 0° C. or higher, and the final step is drying.

In the present invention, a vacuum drying device capable of removing moisture from fine parts is used as a drying means. Three vacuum drying devices (IIA, IIB% IIC) are arranged in parallel at the end of the conveyor 4, and the three vacuum drying devices can be moved laterally as shown by arrow Y.

Insert the printed circuit board in the vacuum dryer here,
Explain drying and removal.

Vacuum drying bag @11 is the 41st! As shown in I, the lid 12 of the frontage is raised upward, and the vertical movement device is in an inclined state with the bottom being open and the back being lowered. In this state, when the printed circuit board P heated to 50° C. or more is sent by the conveyor 4, the printed circuit board is introduced into the vacuum drying device 11 which is inclined from the frontage. The printed circuit board P released from the conveyor 4 is automatically introduced into the vacuum drying apparatus because the vacuum drying apparatus is tilted and a large number of rollers 15 are installed inside the vacuum drying apparatus. When the printed circuit board is introduced into the vacuum drying apparatus, the lid 12 closes the opening as shown in FIG.
At the same time that the vertical movement device moves up a little to level the vacuum drying device, the air inside is removed from the exhaust port 16 by a vacuum pump (not shown). In this state, the printed circuit board is vacuum-dried, and when moisture is completely removed, outside air is introduced into the vacuum drying device, and the lid 12 is raised upward to create a gap. Then, as shown in FIG. 6, the lifting device 14 rises and takes out the printed circuit board P to the outside.

The status of the three vacuum drying devices 11A, 11B, and IIC is as shown in Figure 3. When a printed circuit board is introduced into IIB, vacuum drying is performed in IIC, and vacuum drying is completed in IIA. The printed circuit board is being removed. After removing the printed circuit board from the IIA and receiving it from the IIB, after drying in the IIC is completed, the lid is placed on the IIB, and the lid is opened on the IC and the printed circuit board is taken out. The drying device moves to the right side of the drawing, and
The printed circuit board is received at 1A. While vacuum drying is performed in one vacuum drying apparatus in this manner, printed circuit boards are received and taken out in other vacuum drying apparatuses.

In the embodiment, the printed circuit board is introduced into the vacuum drying apparatus by tilting the vacuum drying apparatus, but it is also possible to use a pusher or other transfer device.

〔Effect of the invention〕

According to the present invention, cleaning of printed circuit boards with a water-soluble detergent, which was completely unthinkable in the past, has been made practical, and the entire process from detergent cleaning, water washing, and drying can be automated, making it possible to clean the printed circuit board with a water-soluble detergent, which was completely unthinkable in the past. It has excellent effects in that it can clean as well as it cleans, and there is no pollution problem at all.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of the printed circuit board cleaning HR of the present invention;
Figure 2 is a detailed cross-sectional view taken along the line ■-■ in Figure 1, Figure 3 is a plan view illustrating the delivery and removal of printed circuit boards to multiple vacuum drying devices, and Figures 4 to 6 are one vacuum dryer. FIG. 3 is a front sectional view illustrating delivery and removal of a printed circuit board in the apparatus. 4... Conveyor 5... Detergent spray nozzle 7...
Air nozzle 9...Water jet nozzle 10...Heating bag @11...Vacuum drying device P...Printed circuit board

Claims (2)

[Claims] (1) After washing the flux residue on the printed circuit board with a water-soluble detergent and removing the detergent adhering to the printed circuit board with water or hot water, the printed circuit board is heated to 50° C. or higher and dried in a vacuum of 200 torr or lower. A method for cleaning a printed circuit board, characterized by: (2) The cleaning process for printed circuit boards includes a detergent cleaning device that cleans the flux residue on the printed circuit board with a water-soluble detergent, a water cleaning device that uses water or hot water to wash off the detergent that has adhered to the printed circuit board, and a It consists of a heating device that heats the printed circuit board to 50°C or higher and a vacuum drying device that dries the wet printed circuit board, and a conveyor that transports the printed circuit board runs through the detergent washing device, water washing device, and heating device. A cleaning device for printed circuit boards, further comprising a mechanism in which the printed circuit boards conveyed by the conveyor are automatically fed into a vacuum drying device.