JPS614570A - Draining method of coating solution - Google Patents

Abstract

PURPOSE:To recover efficiently an excess coating soln. by performing the drainage of the surplus soln. generated in the drip-coating of the coating soln. and of the surplus soln. when the coating is finished over a coating soln. vessel. CONSTITUTION:When the coating on the desired surface of a printed board 1 is finished, draining is carried out, and the board 1 is conveyed to a position where the board leaves the underside of a drip cup 7 and within the range of a coating soln. vessel 5. The board 1 is stopped temporarily at said position, and the excess coating soln. on both coated surfaces of the board is drained. In addition to the draining when the coating is finished, since each stage including the coating and the reversion stage is carried out within the range of the soln. vessel 5, excess coating soln. is drained into the soln. vessel 5, recovered, and reutilized.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is a method of drop-coating a coating liquid to form a substantially uniform coating film on an article having a relatively flat surface, such as a printed circuit board. The present invention relates to a tedding liquid drop coating device, and in particular relates to a method for draining excess coating liquid during drop coating of teding and after completion of coating.

[Prior Art] Generally, in the process of assembling printed circuit boards, after soldering is completed, the entire surface of the printed circuit board is dipped in moisture-proof paint, or sprayed with silicone paint to coat the surface of the printed circuit board. The coating has been applied and all assembly steps for the printed circuit board have been completed.

Common methods for coating this type of article include the above-mentioned dipping method and spraying method. The technique described in Japanese Unexamined Patent Publication No. 58-159862 relates to the formation of a coating film by dipping. As described in the above publication, in order to form a coating film on the surface of an article by immersing it in a coating liquid, the immersion speed is determined depending on the viscosity of the coating liquid and the thickness of the film to be formed.
The coating process is carried out by arbitrarily setting the relationship between the vertical pulling position and time. In the method of spraying silicone paint, etc., the coating process is carried out by arbitrarily setting the transport speed and spraying distance of the article.

[Problems to be Solved by the Invention] However, in the immersion method, for example, when a connector, relay, or buzzer is attached to a printed circuit board, etc., these are also immersed in the coating liquid, so they are electrically damaged. If the connecting portion is insulated by the coating, or if the mechanical vibration sounding portion is covered with a coating, electrical disturbances may occur.

Similar problems occur in the spraying method, and since the spraying method uses a large amount of diluting solvent, there are problems such as air pollution and a large amount of coating liquid being scattered.

In addition, for printed circuit boards, etc. in which electrical parts are inserted that do not like the adhesion of coating liquid, the method of printing or
However, there are problems in that both methods must be done manually and that coating liquid may adhere to other coating liquids during transfer to the drying process.

Therefore, the present invention employs a coating liquid drop applicator that applies the coating liquid dropwise, thereby automating the process and applying the coating liquid only to arbitrary locations.

However, although this type of coating liquid applicator that is capable of applying dropwise coating liquids causes little scattering of the diluting solvent, it uses a large amount of coating liquid and has problems in recovering it.

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One of our objectives is to provide a liquid draining method that improves the efficiency of collecting liquid.

[Means for Solving the Problems] In order to achieve the above-mentioned problems, the present invention includes a first application step of applying the coating liquid to a specific surface of a printed circuit board by dropping the coating liquid from a dripping cup; First coating on a specific surface - Reversing step of inverting the surface of the substrate to the pudding 1 that has completed the culm, and dropping the coating liquid from the dripping cup onto the other surface of the printed circuit board] -
The second coating step of applying a coating liquid and the wave-cutting step of draining the pudding liquid are performed on the coating oil tank in which the dripping cup is settled and the coating liquid is drawn. .

[Effect 1] In the above configuration, a first coating step of dropping the coating liquid from a dripping cup to apply the coating liquid to a specific surface of the printed circuit board, and a first coating step of the specific surface are completed. A reversing process that avoids reversing the surface of the printed circuit board,
A second coating step of applying a coating liquid to the printed circuit board by dropping the coating liquid from the dripping cup onto the other surface of the printed circuit board, and a liquid draining step of draining the liquid from the printed circuit board are performed using the dripping cup. Since the coating is carried out in a coating liquid tank that sinks and draws up the coating liquid, excess coating liquid that is unnecessary for coating the printed circuit board falls into the coating liquid tank, and the excess coating liquid can be collected and reused. can.

[Example] Next, an example of the coating liquid droplet applicator of the present invention will be described with reference to the drawings.

FIG. 1 is a flowchart of each process showing a droplet coating apparatus according to an embodiment of the present invention. In the figure, 10 is an attachment process, 20 is a first application process, 30 is an inversion process, 40 is a second application process, 5'CN liquid removal process, 60 is a drying process, and 7
0 is the extraction process.

2 is a perspective view showing the coating process shown in FIG. 1, and FIG. 3 is a bottom view of the dripping cup 7.

First, the constituent parts of this embodiment will be explained with reference to a perspective view showing the coating process in FIG. 2 and a bottom view of the dripping cup in FIG. 3.

Both ends of the printed circuit board 1 are held by a holder 3 that constitutes a transfer means that moves back and forth on a guide rail 4 by a chain 2.

The dripping cup 7 is normally settled in the coating liquid tank 5 when the printing board 1 is not being transported, and as the printing plate 1 and the substrate 1 approach the dripping cup 7,
The coating liquid 6 is pumped into the dripping cup 7 and rises, and when the coating liquid 6 is coated and covered, it settles again into the coating liquid 6 in the dripping liquid tank 5. At the bottom of the dripping cup 7, there is a dripping cup 7 shown in FIG.
As shown on the bottom of the , a plurality of drip holes 8 are bored, and the width L1 thereof is determined based on the width of the coating surface required for the printed circuit board 1] - the falling speed of the Tinda liquid, viscosity, surface tension, etc. This is the width given.

The spacing a between the dripping holes 8 and the row spacing 2 are to ensure the spacing a necessary for the coating liquid to drip in a linear manner, and a plurality of rows of the dripping holes 8 are drilled accordingly. It is something to do.

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．． □In order to make it difficult for good eyoting liquids to merge together when dripping, a hole is formed by punching from inside the dripping cup 7, and the punched piece is exposed to the outside, or
It is preferable to connect a drop guide tube to the drip hole 8 of the drip cup 7. In any case, the drip hole 8 may be formed to have a uniform thickness so as to prevent unevenness in the thickness of the coating film.

The coating liquid 6 in the coating liquid tank 5 is always set at a constant coating liquid concentration and liquid level by mixing the coating liquid and a diluting solvent by an external coating liquid adjustment device (not shown). in in the diagram
"out" means the supply from the coating liquid concentration adjustment device, and "out" means the discharge to the coating liquid 'a trace adjustment device.

Next, an embodiment of the coating liquid application method will be described in detail in accordance with the flowchart of each step in FIG. 1 and using explanatory diagrams of each step in FIGS. 4 to 9.

In the mounting process 10, as shown in the explanatory diagram of FIG. 4, both ends of the printed circuit board 1 are soldered to the holding parts (not shown) of the holder 3 so that the soldering surfaces are positioned at an angle in the -circle. Attach to. The inclination of the printed circuit board 1 is determined by the falling speed, viscosity, and surface tension of the coating liquid, the conveyance speed of the printed circuit board, and the like.

The printed circuit board 1 held by the holder 3 is conveyed in the direction of the droplet F cup 7 and enters the first coating step 20. When the conveyance of the printed circuit board 1 is started, the dripping cup 7 starts to rise and rises above the printed circuit board 1 being conveyed by the time the holder 3 comes under it. The coating liquid 6 in the dripping cup 7 becomes a linear dripping coating liquid 6a and drips from the dripping hole 8.

In the first coating step 20, the holder 3 moves along the guide rail 4, and as shown in the explanatory diagram of the coating state in FIG. The droplet collision speed is a vector combination of the falling speed of the linearly dropped coating liquid 6a and the conveyance speed of the printed circuit board 1, and is determined by the viscosity of the coating liquid and the like.

Generally, to apply the coating liquid to the soldering surface, the linear dripping coating liquid 6a is dripped and collided with the soldering surface without reducing the conveyance speed of the print 1 and the substrate 1. It is better to scatter it in all directions,
The coating layer can be made uniform, and a wide area can be coated.

The printed circuit board 1 whose soldering surface has been coated with the linear drop coating liquid 6a enters an inversion step 30. That is, the printed circuit board 1 is transported by the holder 3, and the holder 3 is turned in the opposite direction within the range that it does not come off the top of the coating liquid tank 5, and then the printed circuit board 1 is reversed as shown in FIG. The reversal angle θ is determined by the type of electronic component mounted, the falling speed of the coating liquid, viscosity, surface tension, etc.

Although the reversing mechanism of the holder 3 is used to reverse the movement of the holder 3 in response to a change in the moving direction of the guide rail 4, it may be any other reversing mechanism that is independent of the moving direction of the guide rail 4.

When the reversal of the printed circuit board 1 is completed, the conveyance direction of the printed circuit board 1 is changed, and the printed circuit board 1 is again conveyed under the dripping cup 7 of the print 1 to the circuit board 1, and the printed circuit board 1 is reprinted as shown in the explanatory diagram of FIG.
A second coating step 40 begins in which the linear drop coating liquid 6a is applied onto the electronic component mounting surface of the device. At this time, the conveyance of the printed circuit board 1 is stopped at a slow speed or as necessary,
It is preferable to avoid dropping the coating liquid 6a to improve the mounting of electronic components. That is, on the electronic component mounting surface of the printed circuit board 1, it is necessary to suppress the scattering of the coating liquid 6 and apply it only to a predetermined area.
a and the droplet collision speed with the printed circuit board 1 are reduced. Then, by stopping the conveyance of the printed circuit board 1 at an arbitrary point, the liquid can be sufficiently distributed even to the feet of the ICs and the like.

Once the coating liquid has been applied to the electronic component mounting surface of the printed circuit board 1, the next liquid removal step 50 begins. As shown in the explanatory diagram of the wave cutting process in FIG. 8, when the printed circuit board 1 is conveyed to a position C away from under the dripping cup 7, it is temporarily stopped, and there, the printed circuit board 1 is placed on both sides of the Zolin 1-g board 1. Drain the excess coating liquid. Matter 1 [The location is such that the excess coating liquid can be collected] - It is desirable that the coating liquid be located at the upper part of the coating liquid tank 5. Of course, it may be further away, but in that case, use a gutter, etc.
It is preferable to collect the excess coating liquid into the coating liquid tank 5.

In addition, liquid removal in a broad sense is the first coating step 20 shown in FIG.
and a reversing step 30 shown in FIG. 6, a second coating step 40 shown in FIG. 7, and a wave cutting step 50 shown in FIG. Since each process is performed at the upper part of the coating liquid tank 5, the coating liquid always falls into the coating liquid tank 5.

The printed circuit board 1 that has completed the corrugation process 50 is further transported and enters a drying process 60. As shown in the explanatory diagram of the drying process shown in Fig. 9, the printed circuit board 1 is
is transported. Drying process 6 ← In 〇, dry air is blown from the bottom of the printed circuit board 1.
The coating liquid applied to the printed circuit board 1 is dried by pouring out the liquid. At this time, since the ejection port is only at the lower part, by alternately inverting the surface of the printed circuit board 1 at an angle δ, it is possible to dry both sides at the same time. The printed circuit board 1 is reversed by switching the direction of movement of the holder 3 within a minute range, but as mentioned above, the reversal of the printed circuit board 1 is performed using a mechanism in which a holding part is separately provided. Hit the action - C is also good. According to the above-mentioned alternating reversal, not only double-sided drying but also uniformity of the coating film can be expected. Of course, the same effect can be obtained when the dry air blowout is disposed at a location other than the lower part, and the same effect can be obtained for heat radiation such as secondary heat other than IC% dry air. Incidentally, the angle δ at which the surface of the printed circuit board 1 is reversed to the intersection H may be set to the same angle as the reversal angle θ at which the printed circuit board 1 is reversed in the reversing step 30.

In addition, in this embodiment, the printed circuit board 1 is alternately inverted to induce an air flow on the surface of the printed circuit board, so that it can be efficiently dried simply by using dry air as a drying means, and in particular, temperature rise is averse to Suitable for drying electronic parts.

Furthermore, in devices equipped with this type of reversing mechanism, pudding can be achieved by drying air from only one side.・Since the coating film on the substrate 1 is dried, the toluene, xylene, etc. contained in the coating liquid can be flowed in the opposite direction from the operator depending on the purpose, and can be removed from the exhaust path that is cut off from the outside air. , the aforementioned toluene, xylene, etc. can be discharged, and there is no risk of harm to the health of workers.

After the drying process 60 is completed, the extraction process 70 begins.

In the take-out step 70, the coated printed circuit board 1 is taken out and packed into a shipping box or the like, or transported to the next production line.

Then, when the removal step 70 is completed, the first attachment step 10 is started again.

As described above, the coating liquid drop coating device of the present embodiment drips the coating liquid from the dripping cup onto the attached printed circuit board, thereby applying the coating liquid to a specific surface of the printed circuit board. a reversing step of inverting the surface of the printed circuit board that has undergone the specific first coating step, and a step of applying the coating liquid to the printed circuit board by pouring the coating liquid from the dripping cup onto the other surface of the printed circuit board. Since the coating liquid is applied to the printed circuit board in the second coating process, the coating liquid will not adhere to the electronic components mounted on the printed circuit board, such as connectors, relays, buzzers, etc., and electrical connections will be damaged. Pronunciation will not be hindered due to conduction or covering of the mechanical swing J sounding part.

In addition, since this embodiment applies the coating liquid onto the printed circuit board by dropping the coating liquid from the dripping cup, the coating liquid is used without becoming fine particles, so there is no possibility of scattering of the coating liquid. There is no risk of air pollution.

In this embodiment, since the holder 3 for transferring the printed circuit board 1 is reciprocated in the reversing step 30, the coating liquid application apparatus can be made into a small J-shape.

The coating liquid drip application device of this embodiment can also be modified as follows.

That is, in the first coating step 20 and the second coating step 40, the linear dripping coating liquid 6a was applied using a single dripping cup 7, but instead of applying the coating liquid 6a in a linear droplet using a single dripping cup 7, two cups may be used to draw the coating liquid 6 from the same or different coating liquid tanks. The application widths of the first application step 20 and the second application step 40 may be changed depending on the dropping cup. In this case, since the linear drip coating liquid is applied to the printed circuit board 1 using different drip cups, the coating area between the soldering surface and the electronic component mounting surface of the printed circuit board 1 can be changed. Of course, one of the first coating process 20 and the second coating process 40 can be omitted to perform the coating process on only one surface.

[Effects of the Invention] As described above, the coating liquid draining method of the present invention has the following effects:
The first application process, the reversal process, the second application process, and the wave-cutting process are carried out on a liquid tank in which the dropping cup is lowered to draw up the coating liquid.
Since surplus coating liquid can be directly dropped into the coating liquid tank during all of these steps, the surplus coating liquid can be recovered with high efficiency and can be reused.

[Brief explanation of drawings]

FIG. 1 is a flowchart of each process showing a dripping coating device according to an embodiment of the present invention, FIG. 2 is a perspective view showing the coating process of FIG. 1, and FIG. 3 is a bottom view of a dripping cup. Fig. 4 is an explanatory diagram of the installation process, Fig. 5 is an explanatory diagram of the first coating process, Fig. 6 is an explanatory diagram of the reversing process, and Fig. 7 is an explanatory diagram of the second coating process. FIG. 8 is an explanatory diagram of the liquid draining process, and FIG. 9 is an explanatory diagram of the drying process. In the figure, C1 1...Print 1 to substrate, 3...Holder,
5... Coating liquid tank, 6... Coating liquid, 7... Dripping cup, 10... Mounting process, 20... First coating process, 30... Reversing process, 40... Third 2nd application process, 50... Liquid draining process, 60... Drying process, 70... Taking out process. In addition, in the figures, the same reference numerals and the same symbols indicate the same or equivalent parts.

Claims (1)

[Claims] a mounting step for attaching the printed circuit board to a transfer holder for transporting the printed circuit board; and a first application step for applying the coating liquid to a specific surface of the printed circuit board by dropping the coating liquid from a dripping cup onto the attached printed circuit board. , a reversing step of reversing the surface of the printed circuit board that has completed the first coating step on the specific surface, and a second step of applying the coating liquid to the printed circuit board by dropping the coating liquid from a dripping cup onto the other surface of the printed circuit board. a second coating step, a liquid draining step for draining the printed circuit board, and a drying step for drying the printed circuit board coated with the coating liquid;
In the coating liquid droplet applicator comprising a taking-out step, the first applying step, the reversing step, the second applying step, and the liquid draining step are performed on a coating liquid tank in which the dropping cup is lowered to draw the coating liquid. Characteristic coating liquid draining method.