JPH04270067A - Method and device for coating flux - Google Patents

Abstract

PURPOSE:To uniformly and thinly coat the work and to surely solder by once buffering the spray flux supplied from the spray gun, jetting from the upper part of the jetting nozzle on the slit extending to the direction crossing the work advancing direction and coating the work. CONSTITUTION:The flux liquid supplied from the flux tank 2 is jetted in the nozzle box 3 by using the spray gun 1. The jetting pressure is reduced with the buffer action of the nozzle box, etc., and the fluid velocity is also reduced. There is an inner pressure in the nozzle box, a light and fine flux is floated in the upper side, the heavy and granular flux is settled to the lower side. The fine flux is jetted from the jetting hole 3a of the upper side of the slit in fog like. The flux is made to move almost nearly vaporous, the uniform and thin coating can be executed. Therefore, the work of the printed board, etc., can be coated with the flux uniformly and thinly, the soldering is made sure, the printed board washing after then is made needless and the coating of flux with well recovering efficiency is realized.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a flux application method and apparatus, and more particularly, a flux application method and apparatus for applying atomized soldering flux (activator) to a relatively moving work such as a printed circuit board. The present invention relates to a coating method and apparatus.

0002

2. Description of the Related Art Conventionally, when various electronic components are mounted on an electronic printed circuit board, the electronic components are first mounted on the printed circuit board using a chip mounter or the like. In order to mount the printed circuit board and electronic components in a state where they are electrically fixed, flux is applied uniformly to the connection points between the solder and electronic components on the printed circuit board, and then the electronic components are passed through a heated solder bath to the printed circuit board. It is completely fixed. When soldering a printed circuit board, the flux applied to the printed circuit board before soldering may be in the form of a paste or in the form of a viscous solvent. Flux melts at high heat during soldering and improves solder adhesion.

Conventionally, the following method has been generally adopted as a method for applying this flux to a printed circuit board.

(1) A foaming method in which a flux solvent placed in a flux tank is heated to form a large amount of flux bubbles, and the flux is applied by bringing the flux bubbles into contact with the lower surface of the printed circuit board and passing it through.

(2) A spray gun atomization method in which the flux liquid is atomized using a spray gun using compressed air and sprayed onto the bottom surface of the printed circuit board.

[0006]

[Problem to be solved by the invention] However, as mentioned above (1)
) Foam type, and conventional methods related to (2) spray gun atomization method, it is difficult to apply flux to the printed circuit board with a uniform thickness, and the flux may be applied too thickly in some areas. On the contrary, there are areas where the coating is applied too little or not at all.

For example, in the case of a spray gun spraying method, a plurality of flux injection nozzles (for example, 1 to 3) are arranged in a direction transverse to the traveling direction of the printed circuit board being transported, and flux is sprayed directly onto the printed circuit board under high pressure. However, depending on the number of spray nozzles and the width of the printed circuit board, uneven coating occurs depending on the coverage area of the spray nozzles. Also, since it is a diffused spray (
(Even if you use only one spray gun), you will be applying multiple coats from the beginning to the end of the application, and as the flux binds and solidifies, a flux residue will remain. If the number of spray nozzles is small, there will be areas where the amount of coating is small, and if there are too many injection nozzles, there will be areas where the amount of coating will be too large, or because the coating will be spread out, there will be many overlapping areas. Variations in thickness occur. Therefore, when the next soldering process is carried out with such uneven flux application, there will be areas where the soldering is not done or where the soldering is insufficient, resulting in poor soldering. The frequency of occurrence of printed circuit boards increases.

On the other hand, since flux is originally an insulating material, it is necessary to completely remove it from the printed circuit board after soldering so that it does not remain as a non-conducting part in the circuit network of the printed circuit board. Therefore, the printed circuit board after soldering is usually cleaned using a separate cleaning device that uses Freon as a cleaning agent to remove the flux as well as impurities such as microscopic dust and grime adhering to the printed circuit board. Is going. However, in recent years, there has been a tendency for restrictions to be imposed on the use of fluorocarbons due to environmental protection issues such as their negative impact on the formation of the atmospheric layer (ozone layer), and the use of fluorocarbon cleaning equipment has become inappropriate.

[0009] Thus, when applying flux, it is desirable to apply it thinly and uniformly using the minimum required amount.
There must be no residual coating. Further, during soldering, it is best to apply the flux in such an amount and thickness that most of the flux melts into the solder, no flux remains (flux residue), and cleaning is not required.

However, with the conventional method, it is difficult to uniformly apply flux to a printed circuit board with a uniform thickness, and there is a problem in that the flux must be removed using Freon. Ta.

Furthermore, in order to spray the flux at high pressure and apply the flux to the printed circuit board with uniform pressure, the spray nozzle must be placed quite far from the printed circuit board, which increases the size of the device and increases the cost. However, there is a problem in that excess flux is wastefully discharged without being applied to the printed circuit board, and the amount of flux consumed increases. This surplus flux further increases the amount attached to the area around the coating device, which has the drawback of staining the device and making maintenance difficult.

[0012] The present invention solves these conventional drawbacks, and makes it possible to uniformly and thinly apply flux to a workpiece such as a printed circuit board, thereby ensuring solder adhesion, and further eliminating the need for subsequent cleaning of the board. In addition, it is an object of the present invention to provide a flux application method and apparatus with improved flux regeneration efficiency.

[0013]

[Means for Solving the Problems] In order to solve such problems, the present invention provides a method for applying flux to a relatively moving workpiece by atomizing the flux, which is sprayed at high pressure from a flux supply source. A configuration was adopted in which the sprayed flux is temporarily buffered and retained, and the retained mist flux is discharged from the upper part of a slit-shaped discharge port extending in a direction transverse to the traveling direction of the workpiece to be applied to the workpiece.

Furthermore, in the present invention, an apparatus for atomizing flux and applying it to a relatively moving workpiece includes a flux supply source that atomizes a flux liquid at high pressure, and a system that buffers the atomized flux and retains the flux. A structure was also adopted in which a buffering means and a mist flux rising from the buffering means were discharged from a discharge opening of a slit line extending in a direction transverse to the traveling direction of the workpiece and applied to the workpiece.

[0015]

[Function] With this configuration, the high-pressure spray flux supplied from the flux supply source such as the spray gun is reduced in injection pressure by the buffering action of the nozzle box, etc.
The flow rate decreases and it stays in the nozzle box. Due to this retention, the light and minute fluxes float to the top, and the heavy granular fluxes are deposited at the bottom and removed. The floating minute flux rises as it is pushed up by the spray pressure from the spray gun, and is ejected as ultrafine particles from a slit-shaped outlet formed at the top of the nozzle box. Since the workpiece moves close to the upper part of this slit-shaped discharge port, the mist flux is evenly and thinly applied to the workpiece without overlapping the coating.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will be described in detail below with reference to the drawings.

In each figure, the reference numeral 1 designates a spray gun that injects flux at high pressure. This spray gun 1 injects a flux liquid stored in a flux tank 2 into a nozzle box 3 at high pressure. The nozzle box 3 is a box-shaped container extending horizontally, and has a flux discharge port 3a projecting from the top on the side opposite to the side where the spray gun 1 is attached. A slit 3b extending substantially perpendicular to the direction of movement of the printed circuit board 10 being transported is formed in the discharge port 3a.

As shown in FIGS. 2 and 3, the nozzle box 3 has its upper surface covered with a lid 3c, and the flux liquid sprayed by the spray gun 1 becomes a mist and floats inside the nozzle box 3. The injection pressure, flow velocity, etc. of the accumulated flux are attenuated, exerting a buffering effect on the flux.

Further, as shown in FIGS. 3 and 4, rectifier plates 5 are attached on both sides along the slit 3b formed in the discharge port 3a of the nozzle box 3 to collect excess flux. Suction nozzles 6 are arranged further outside of the rectifying plate 5 to suck up excess flux.

As shown in FIG. 1, the printed circuit board 10 is transported from the device connected to the previous stage via the first transport conveyor 11 into the device through the insertion port 20 of the device, and then transferred to the second transport device. It is delivered to the conveyor 12. This second conveyor 12 is lowered together with the printed circuit board 10 by a lifting device (not shown) and moved to a position close to the nozzle box 3 . The printed circuit board on the conveyor 12 that has descended is then moved to the third conveyor 13,
At this time, the printed circuit board 10 passes through the nozzle 3b of the nozzle box 3, as will be described later, and is coated with atomized flux. The third conveyor 13 is lifted upward by a lifting device (not shown), and the printed circuit board coated with flux is discharged from the discharge port 21 of the device.

The flux coating apparatus shown in FIG. 1 is also provided with a dust collector 22 for collecting excess flux when the flux is discharged from the discharge port 3a through the nozzle, as will be described later. Further, a collection box 24 is disposed at the lower part of the nozzle box 3 for collecting surplus flux liquid deposited at the lower part of the nozzle box 3 via a valve 25.

In FIG. 1, a control box 23 is arranged in the upper left corner, and this box is provided with switches and the like for operating various control devices or drive devices.

Next, the operation of the flux coating apparatus having such a configuration will be explained.

The spray gun 1 is used to spray the flux liquid supplied from the flux tank 2 into the nozzle box 3. The flux ejected into the compressed air at high pressure runs inside the box, with lighter masses hitting the top and heavier fluxes colliding against the walls and depositing inside the nozzle box 3. In such a high-pressure sprayed flux, the ejection pressure is lowered due to the buffering effect of the nozzle box, etc., and the flow rate is also reduced. The internal pressure inside the nozzle box 3 increases as the spray gun 1 continues to eject, and the relatively light minute flux floats to the top, while the heavy granular flux settles to the bottom. The minute flux rises as it is pushed up by the atomized flux from the spray gun, and passes through the slit-shaped discharge port 3a formed at the top of the nozzle box 3.
It is discharged in a more atomized form.

This state is illustrated in FIG. 4, where the flux is discharged from the slit 3b of the nozzle box 3 as indicated by the arrow. This discharged flux further rises and collides with the printed circuit board 10 being conveyed with a relatively weak pressure, so that it is uniformly and thinly applied to the printed circuit board 10. That is, since the flux ejected from the slit 3b is selected to be only small particles with light mass in the nozzle box, the ejection force of the flux is relatively soft, and there is no accumulation even when it touches the bottom surface of the printed circuit board 10. become wet. In addition, the flux behaves almost like a gas, making it difficult for flux particles to clump together, making it possible to apply a uniform and thin coating.

In this case, the slit 3c has an inner width of about 2
, and extends almost perpendicularly to the traveling direction of the printed circuit board over the entire length of the maximum printed circuit board width. Further, the distance between the slit 3b of the discharge port and the printed circuit board 10 is set in a range of about 5 to 15 degrees depending on the thickness of the flux to be applied, the conveyance speed of the printed circuit board, and the rising speed of the flux flow.

Although some of the flux discharged from the slit 3b passes through the through-hole of the printed circuit board 10 and comes above the printed circuit board, the flux generally runs under the printed circuit board 10 and depends on the suction nozzles 6 arranged on both sides. was collected,
The dust is collected by the dust collector 22 shown in FIG.

At this time, the surplus flux that has passed through the through hole of the printed circuit board 10 is sucked by the suction port 30 and similarly collected by the dust collector 22 via the filter box 31, as shown in FIG. At this time, in order to increase the recovery efficiency of the surplus flux that has passed through the through hole, it is flown in the direction of the suction port 30 by the blow fan 33 and collected. (At this time, the collection device is not placed on the printed circuit board, so that the printed circuit board is not contaminated.) The above-mentioned surplus flux is ejected from the discharge port 3a, so it is limited to flux with a relatively light mass. Moreover, since the discharge amount itself is small, it can be processed with extremely small equipment. On the other hand, inside the nozzle box 3, a relatively heavy flux collides with the inner wall surface of the nozzle box 3, and flows down the wall surface. The flux deposited below this nozzle box can be collected into the collection box 24 via the valve 25. The flux liquid collected in this way is the one that remained in the nozzle box 3, so
There is relatively little deterioration due to oxidation, and it can be used again almost as is, making it possible to apply flux with extremely high recycling efficiency.

As described above, in the present invention, the surplus flux of relatively small particles discharged from the discharge port 3a is as shown in FIG.
With the recovery system shown in FIG. 5, the flux having a large mass and relatively large particles is recovered from the nozzle box 3 to the recovery box 24.

As explained above, in the embodiment of the present invention,
The following advantages can be obtained.

(1) Regarding the flux that remains in the nozzle box, minute flux with a relatively light mass settles at the top, heavy granular flux settles at the bottom, and the minute flux is washed away by the sprayed flux from the spray gun. The flux rises in a slit shape and is discharged as a mist from the slit-shaped outlet formed at the top of the nozzle box, so that the workpiece moving close to the top of the outlet is uniformly coated with atomized flux. It is applied thinly.

(2) By being able to apply the flux uniformly and thinly, the absolute amount of flux liquid consumed is reduced, reducing costs, and it is also possible to remove the flux along with impurities such as fine dust and grime attached to the printed circuit board. The need for cleaning with cleaning fluids such as Freon is reduced. This corresponds to so-called no-cleaning.

(3) The flux liquid having a large mass is deposited in the lower part of the nozzle box and can be easily recovered, thereby improving the recycling efficiency of the flux.

(4) Since the discharge port of the nozzle box and the printed circuit board can be placed close to each other, the entire device can be made smaller, and the amount of flux liquid that scatters during application is significantly reduced, making the device and surrounding area cleaner. This makes maintenance easier.

[0035]

As described above, in the present invention, the atomized flux supplied from the spray gun is temporarily buffered, and the rising atomized flux is discharged from the upper part of the discharge port on the slit extending in a direction transverse to the traveling direction of the workpiece. Since the flux is applied evenly and thinly to the workpiece such as a printed circuit board, it is possible to ensure solder adhesion, and furthermore, there is no need to clean the board afterwards, and the flux is regenerated efficiently. Flux coating becomes possible.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing the overall arrangement of a flux coating device.

FIG. 2 is a perspective view showing details of the nozzle box.

FIG. 3 is a perspective view showing details of the vicinity of the discharge port of the nozzle box.

FIG. 4 is a sectional view showing details of the vicinity of the discharge port of the nozzle box.

FIG. 5 is an explanatory diagram illustrating recovery of surplus flux.

[Explanation of symbols]

1 Spray gun 3 Nozzle box 3a Discharge port 3b Nozzle 10 Printed circuit board 22 Dust collector 24 Collection box

Claims (2)

[Claims] Claim 1: In a method of atomizing flux and applying it to a relatively moving workpiece, the atomized flux injected at high pressure from a flux supply source is temporarily buffered and stagnated, and the stagnant atomized flux is applied to the workpiece. A flux application method characterized in that flux is applied to a workpiece by discharging it from the upper part of a slit-shaped discharge port extending in a direction transverse to the direction of flux. 2. An apparatus for atomizing flux and applying it to a relatively moving workpiece, comprising: a flux supply source that atomizes a flux liquid at high pressure; a buffering means that buffers the atomized flux and retains the flux; A flux coating device characterized in that the atomized flux rising from the buffer means is discharged from a discharge opening of a slit line extending in a direction transverse to the traveling direction of the workpiece and applied to the workpiece.