JPH0523629A - Dry preventing device for droplet adhesive injection nozzle - Google Patents

Abstract

PURPOSE:To obtain a dry preventing device for adhesive injection nozzles where the wetting condition of a nozzle tip is kept constant and the injected quantity of adhesive is not dispersed on restart of use by providing a sponge body which can freely come into contact with the tip of an adhesive injection nozzle and water supply equipment. CONSTITUTION:A water tank 35 is filled with clean water. When a piston 37 and a cylinder 39 are operated to make a sponge body be on standby, the sponge sucks water to be in a state of being capable of supplying water. When the injection nozzle 5 moves, the sponge body 31 is rised to position in the dry preventing state. Excess water is returned to the water tank 35 by its dead weight, causing the upper surface of the sponge body 31 to be in the constant wetted state to make the sponge come into contact with the lower end of the injection nozzle 5. Since the sponge body 31 sucks up the retained water by capillary action, the nozzle tip is always kept in the wetted state. On the restart of use, when the piston is retreated, the sponge body 31 leaves the nozzle tip, causing excess water not to be remained in the nozzle tip, permitting the number of times of trying out the nozzle to be restrained to minimum.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an anti-drying agent for an adhesive injection nozzle for supplying an adhesive used for temporarily attaching electronic parts to a printed circuit board in the form of a required amount of flying droplets. Regarding the device.

[0002]

2. Description of the Related Art To mount a small electronic component on a printed circuit board, the electronic component is temporarily attached to a predetermined position on the printed circuit board with an adhesive, and then soldered by molten solder to fix the electronic component to the wiring conductor. It is widely practiced to make an electrical connection with. Various methods are performed to automatically perform this step, but basically, a large number of electronic components are temporarily mounted on a horizontally placed printed circuit board by an automatic mounting device, and then the printed circuit board is turned upside down (or (Not turned over), contacting the entire printed circuit board with molten solder. Therefore, the adhesive used for temporary attachment requires sufficient adhesive strength to prevent the electronic components from falling off or slipping even when the printed circuit board is inverted or heated, while it can correct the posture even if it shifts. Requires liquidity. or,
It is necessary to supply efficient adhesive. There are various factors as the requirements for this, but the main ones are that the tackiness of the adhesive is sufficiently high, that the adhesive can be supplied in a sufficient amount that can be adjusted at one time and with good reproducibility, Good cutting (no threading from the dispenser nozzle),
And so on.

As an adhesive satisfying these requirements, Japanese Patent Application Nos. 2-11925 and 2-2344, which are the prior applications of the present applicant, can be used.
There are thermoplastic or thermosetting acrylic modified emulsion adhesives described in No. 21 and the like. According to the same application, such an adhesive can be dispensed efficiently by using an adhesive supply device as shown in FIGS. The supply tank 2 of the adhesive 11 is maintained at a predetermined constant pressure so that the droplet of the adhesive is ejected from the injection nozzle 5 by opening the electromagnetic valve 4, and preferably the viscosity of the adhesive passing through the injection nozzle 5 is constant. In order to keep the temperature constant, the temperature is kept constant including the other parts. The adhesive 11 is led from the conduit 3 to the solenoid valve 4. By controlling the opening time in the solenoid valve 4, a fixed amount of adhesive measured is discharged from the injection nozzle 5. The tip of the injection nozzle 5 when not in use is always wet with water to prevent it from drying. The tip of the injection nozzle is preferably coated with a water-repellent material such as a fluororesin in order to improve liquid drainage. The adhesive enters the valve chamber 19 from the conduit 3 via the internal passage 17 of the housing 25. The upper end of the injection nozzle 5 is formed with an outlet valve seat 26, and the outlet 20 is normally closed because the valve body 20 is always biased downward by the compression spring 21. When the valve body 20 is pulled up by the electromagnetic coil 24, the valve body 20 enables the adhesive to flow to the injection nozzle 5, and the adhesive under pressure is dropletized and discharged from the injection nozzle 5. Disc 20
Is made of a soft magnetic material, and a magnetic core 22 is similarly screwed above and fixed by a nut 23.
The electromagnetic coil 24 is powered by the lead 27. The power supply time is set to an arbitrary predetermined value by an unillustrated regulator,
The supply amount of one drop of the adhesive necessary for temporarily fixing the electronic component is adjusted.

[0004]

The tip of the injection nozzle 5 may be dried when not in use or in standby to increase the viscosity of the adhesive or further solidify. Therefore, the tip of the nozzle must always be moistened to prevent it from drying. For example, Japanese Patent Application No. 2-193870 proposes spraying water spray onto the tip of a nozzle while the injection nozzle is not in use (for example, during a soldering work rest period).
Although this method is effective, (1) the wet state of the tip of the nozzle cannot be constantly controlled due to insufficient or excessive amount of attached water, and therefore, when the use of the nozzle is restarted, the adhesive The number of trial shots must be increased because the injection amount of the nozzle varies. (2) When the nozzle tip is soiled with the adhesive, the tension of the nozzle tip against the ejected adhesive changes and There was a problem that I could not eject.

[0005]

According to the present invention, there is provided a drying prevention device comprising a sponge body which is capable of contacting the tip of an adhesive injection nozzle and a water supply device for wetting the sponge body.
The above problems are solved. The water supply device may be arbitrary, but in a preferred example, it is a water tank, and in this case, the sponge body has a drying prevention position in direct contact with the injection nozzle in a rest state,
It is advisable to support it by a supporting means that is movable between the rest position and the submerged position in the water tank. Further, it is preferable to provide an air supply unit for aerating the inside of the sponge body in order to clean the sponge body by removing the adhesive attached to the contact portion with the nozzle.

According to this structure of the present invention, since the sponge body is in direct contact with the tip of the nozzle, the water content is always constant without excess or deficiency, and the adhesive adhered to the tip of the nozzle is removed by the sponge body. The state of the tip is always maintained in a preferable state.

[0007]

1 and 2 are perspective views of a drying prevention apparatus according to a preferred embodiment of the present invention. FIG. 1 shows a sponge body 31 at the tip of the injection nozzle 5 which is moved from the working position to the illustrated position. FIG. 2 shows the spout body 31 in a standby state where it is in direct contact with the anti-drying position.

A sponge member 31 such as an open-cell polyurethane resin is supported by a cup-shaped support member 33, and the support member is supported by a vertical piston 37. The movable piston 37 is supported by a stationary cylinder 39 provided on the base 41, and communicates with liquid ports 45 and 46 in the cylinder 39. When the pressurized liquid is introduced from the liquid port 45, the piston 37 descends. When the pressurized liquid is introduced from the liquid port, the piston 37 moves up to bring the sponge body 31 into contact with the tip of the nozzle. Sponge body 31, support 3
3 and the piston 37 are surrounded by a water tank 35, and the inside thereof is filled with water. A flexible air pipe 43 is connected to the support 33, and air is supplied into the sponge body 31.

In use, the water tank 35 is filled with clean water, and the piston 37 and the cylinder 39 are operated to bring the sponge body into the standby state shown in FIG. The sponge absorbs water and becomes ready for water supply. The injection nozzle 5 is in a rest state, as shown in FIG.
When it is moved to the position of, the sponge body 31 is lifted to be positioned in the dry prevention state of FIG. The excess water returns to the water tank 35 by its own weight, the upper surface of the sponge body 31 is in a constant wet state, and contacts the lower end of the injection nozzle 5. If left in this state, the sponge body 31 absorbs the water held by itself by a capillary phenomenon, so that the tip of the nozzle is always kept in a wet state.

When the nozzle is required for the operation of supplying the adhesive, when the piston 37 is retracted, the sponge body 31 is separated from the tip of the nozzle, but at that time, excess water is not left at the tip of the nozzle. Moreover, at that time, the adhesive at the tip of the nozzle is removed by the sponge. When the piston 37 is retracted to the standby state in FIG. 2, the sponge body 31 is completely submerged in water and filled with water. Bubbling is caused by introducing air from the pipe 43 into the support 33 and ejecting it from the sponge body 31, thereby removing the adhesive agent attached to the sponge body.

[0011]

As described above, according to the present invention, the wet state of the tip of the nozzle can be made constant and the dirt can be removed. Therefore, the injection amount of the adhesive does not vary when the use of the nozzle is resumed. You can minimize the number of trial shots,
Substantially no adhesive injection failures occur. Although the above embodiment is preferable, the present invention is not limited to this, and any device may be used as long as the sponge body absorbing water can be brought into direct contact with or separated from the tip of the nozzle.

[Brief description of drawings]

FIG. 1 is a partially cutaway perspective view showing a drying prevention device of the present invention in a drying prevention state.

FIG. 2 is a partially cutaway perspective view showing the anti-drying device of the present invention in a standby state.

FIG. 3 is a front view showing an adhesive supply device to which the present invention is applied.

4 is a cross-sectional view showing details of a solenoid valve of the adhesive supply device of FIG.

[Explanation of symbols]

31 Sponge body with open cells 31, 33 support 33, 37 Movable piston 39 stationary cylinder 39, 45, 46 Liquid mouth 35 aquarium 43 air pipe

Claims (3)

[Claims] 1. Drying for an adhesive injection nozzle for injecting an adhesive in the form of droplets, which comprises a sponge body that can freely contact the tip of the adhesive injection nozzle and a water supply device for wetting the sponge body. Prevention device. 2. The water supply device is a water tank, and the sponge body is supported by a support means that is movable between a drying prevention position in contact with the injection nozzle and a standby position buried in the water tank. The anti-drying device as described in. 3. The anti-drying device according to claim 1, further comprising an air supply means for aerating the sponge body.