JP6311894B2 - Threading prevention method in spray application - Google Patents

Description

In the present invention, liquid materials such as a liquid photoresist agent, a moisture-proof insulating agent, a surface protective film, and a functional coating agent are sprayed on the surface of a semiconductor silicon chip, a glass substrate, various mounting substrates, and metal objects. relates spray coating apparatus and method for forming a thin film formation by reduction, even especially when using a high liquid material viscosity, it relates to the stringing preventing method in a spray coating that can prevent the occurrence of so-called stringiness in advance Is.

  Techniques for partially applying various functional liquid coating agents, moisture-proof insulating materials, and the like to semiconductor silicon, glass substrates, and mounted circuit boards are essential.

  Also, in recent small circuit boards with high-density mounting, in addition to moisture-proof insulating materials, heat-dissipating heat conductive materials and conductive adhesives are locally applied, and liquids are used to provide various functional effects. There is also a need to apply the material locally.

  In such partial or local application of liquid material, scattering of the liquid material becomes a problem, and in many cases, it is necessary to provide masking in an area where application is not required. It leads to cost increase.

  The present inventor can form a clear coating spray width without causing foaming or pooled coating surfaces that cause coating film defects, and can be selectively applied to mounted circuit boards that require masking without masking. A liquid material injection valve (spray gun) that can be coated on the surface has been proposed (Patent Document 1).

Utility Model Registration No. 3191270

  As a result of further research on spray coating on a mounted circuit board, the present inventor has a tendency that the liquid coating material sags before drying, resulting in a thin film thickness when applied to a convex portion. I found out. This tendency is particularly noticeable in low-viscosity liquid coating materials containing a large amount of solvent. In order to obtain a uniform film thickness as much as possible regardless of the presence of irregularities, the viscosity of the liquid coating material must be made as high as possible.

When using high-viscosity liquid coating materials, especially undiluted solutions supplied by material manufacturers, the sprayed liquid material does not atomize and the thread exits into a thread shape (so-called stringing phenomenon, Generation of Angel Hair). May occur .

An object of the present invention is to provide a stringing prevention method in spray coating that prevents a so-called stringing phenomenon even when a liquid coating material having a high viscosity such as a stock solution is used.

  A spray coating apparatus according to the present invention includes a spray gun (coating valve apparatus) having a discharge hole for discharging a liquid coating material and a compressed air outlet for atomizing the liquid coating material discharged from the discharge hole. A liquid coating material supply device that supplies a liquid coating material, and a solvent mist mixed compressed air supply device that generates and supplies solvent mist mixed compressed air to be supplied to the compressed air outlet of the spray gun are provided.

  In one embodiment, the solvent mist mixed compressed air supply device includes a solvent tank, a compressed air supply device, and a solvent mist generator that atomizes the solvent from the solvent tank by compressed air supplied from the compressed air supply device. It is equipped with.

  In the spray coating method according to the present invention, a solvent mist is generated by using a spray gun for atomizing a liquid coating material discharged from a discharge hole of a nozzle by compressed air blown from a blower outlet in the vicinity thereof. Compressed air mixed with is supplied to the air outlet to atomize the liquid coating material.

  In a preferred embodiment, a stock solution of liquid coating material can be used as the fluid coating material.

  Liquid coating material undiluted solution uses a spray gun (coating valve device) having a discharge hole for discharging the liquid coating material and a compressed air outlet for atomizing the liquid coating material discharged from the discharge hole. This refers to a liquid coating material having a viscosity high enough to cause a stringing phenomenon when a stock solution is used as a material and only compressed air is blown out from the outlet. Generally, it is a material before being diluted with a solvent by a coating material sold by a liquid coating material manufacturer. Manufacturers sell liquid coating materials after adjusting the solids concentration in the liquid. There are no special provisions regarding the composition ratio and concentration of the composition for liquid coating material stocks, and the viscosity and solid content ratios vary. Even if the same type of coating liquid material is used, the stock solution However, the viscosities are about 200-1000 centipoise, and the volume solid content is about 20-70%.

  According to the present invention, since the solvent mist mixed (contained) compressed air is used as the compressed air for atomizing the liquid coating material discharged from the spray gun, the liquid coating material is diluted with the solvent mist in the process of atomization and sprayed. Is done. Therefore, even if the stock solution is used as the liquid coating material, it is possible to prevent the occurrence of the stringing phenomenon that would occur if the solvent mist mixed compressed air according to the present invention was not used. Although the sprayed coating material still has a high viscosity even though it is slightly diluted with solvent mist, it prevents dripping and flow even when applied to uneven surfaces, and keeps the film thickness thick. can do. No clogging of nozzles. Since the misted solvent is mixed with compressed air, the minimum amount of solvent used is sufficient, and the amount of solvent used can be reduced. This speeds up drying and requires a short drying time.

  In a preferred embodiment, a screw adapter for forming a swirl flow in the solvent mist mixed compressed air guided to the compressed air outlet is provided in the compressed air supply path of the spray gun. As a result, as described in Patent Document 1, it is possible to form a coating film with clear and narrow line width.

It is a perspective view which shows the outline | summary of the whole structure of a spray application system. The piping system in a spray coating system is shown. It is a longitudinal cross-sectional view which shows the whole structure of a coating valve apparatus, and shows the state in which the discharge hole is closed. It is a longitudinal cross-sectional view which shows the whole structure of an application | coating valve apparatus, and shows the state which the discharge hole has opened. FIG. 4 is an enlarged longitudinal sectional view of a liquid discharge nozzle and an extension portion, showing a state where discharge holes are open. It is an expanded sectional end view which follows the VI-VI line of FIG. The portion centered on the discharge nozzle is further enlarged and shows the liquid discharge operation stop state (corresponding to FIG. 3). The part centered on the discharge nozzle is further enlarged and shows the liquid discharge operation state (corresponding to FIG. 4). It is a front view of a screw adapter. It is a top view of a screw adapter. It is sectional drawing which shows an application | coating valve apparatus and a solvent mist generator (solvent mist injection valve apparatus). It is a partial expanded sectional view of a solvent mist generator, and shows the state where solvent mist is generated. It is sectional drawing which shows the other example (lubricator) of a solvent mist generator. FIG. 14 is an enlarged sectional view taken along line XIV-XIV in FIG. It is a disassembled perspective view of the other example (lubricator) of a solvent mist generator. It shows a good spray state of the liquid coating material. A state in which stringing is occurring is shown. An electronic component is soldered on a printed circuit board. The state which apply | coated to the pin leg of an electronic component by the Example of this invention is shown. The state where it was applied to the pin foot of the electronic component by film coating (conventional) is shown.

  FIG. 1 shows an outline of the overall configuration of the spray coating system.

  The housing 19 of the spray coating system 10 is provided on a machine base 19A and has a work port 10A on the front surface. An object 9 to be painted is placed in the housing 19. A coating valve device 20 (spray gun (device)) is arranged above the object 9, and this coating valve device 20 is supported by the robot device 14 and is movable in the three-dimensional directions of X, Y and Z directions. It is. On the upper front surface of the housing 19, a control panel, an indicator lamp, operating compressed air pressure regulators 24A and 124, an atomizing compressed air pressure regulator 123A, and the like are arranged. A control device (computer system) 11 and a CRT display device 12 are provided at an intermediate height position on the side surface of the housing 19. On the side of the spray coating system 10, there are placed a coating liquid pressure feed tank (liquid coating material storage tank) 21 and a solvent pressure feeding tank (solvent storage tank) (solvent tank) 121.

  FIG. 2 shows a piping system for liquid coating material (coating liquid), compressed air for operation, solvent, compressed air for solvent atomization, and compressed air for atomization containing solvent mist.

  A liquid application material (application liquid) is supplied from the liquid application material tank 21 through the liquid application material (application liquid) pressure feeding hose 22 to the application valve device 20. Also, solvent mist mixed compressed air is supplied to the coating valve device 20 from a solvent mist generating device (solvent mist mixed compressed air supply device) 120 described later through a solvent mist-containing (mixed) atomization air hose 23 to the coating valve device 20. Is sprayed with a coating material spray formed by atomizing the coating liquid with solvent mist-containing (mixed) compressed air. The coating material discharged from the coating valve device 20 is atomized (slightly diluted) by compressed air containing solvent mist, so that even if the supplied liquid coating material is a stock solution, so-called stringing is performed. Occurrence is prevented and occurrence of clogging in the discharge hole is avoided.

  Solvent mist generator 120 is supplied with solvent from solvent tank 121 through solvent pressure hose 122, and with compressed air through solvent atomization compressed air hose 123, and solvent mist is generated through hose 23. It is supplied to the coating valve device 20. The application valve device 20 and the solvent mist generator 120 are supplied with operation compressed air via the operation compressed air hoses 24 and 124, respectively. A more detailed description of this piping system will be described later. The solvent mist mixing (containing) compressed air supply device includes a solvent mist generator 120, an air hose 123 for supplying compressed air (operating compressed air) to the generator 120, an air relay valve 128, a pressure regulator 123A, and a solvent tank 121. Etc. The coating material supply device includes a liquid coating material tank 21, a pressure regulator 21A, a hose 22, and the like.

  The configuration of the coating valve device 20 will be described in detail below with reference to FIGS.

  3 and 4 are longitudinal sectional views showing the overall configuration of the application valve device 20, and FIG. 3 shows a state in which the discharge hole (nozzle hole) is closed and the application valve device 20 stops the liquid discharge operation. FIG. 4 shows a state where the discharge hole is opened and liquid is discharged. FIG. 5 is an enlarged view of the liquid discharge nozzle and the extension portion, and shows a liquid discharge state (corresponding to FIG. 4). FIG. 6 is an enlarged sectional end view taken along the line VI-VI in FIG. 7 and 8 are enlarged views showing a portion centered on the liquid discharge nozzle. FIG. 7 shows a liquid discharge operation stop state (corresponding to FIG. 3), and FIG. 8 shows a liquid discharge state (corresponding to FIG. 4). Show.

  3 and 4, the fluid body 30 is located slightly below the coating valve device 20, and reaches the liquid discharge nozzle 51 from the fluid body 30 downward through the extension portion 40. The upper part of the fluid body 30 is a drive unit.

  The fluid body 30 and the extension part 40 will be described with reference to FIGS. In the fluid body 30, a liquid coating material introduction hole 31 and a compressed atomized air (air) introduction hole 34 are formed in the lateral direction. A liquid coating material supply pipe 32 is connected to the introduction hole 31. A compressed atomizing air supply pipe 35 is connected to the introduction hole 34. The fluid body 30 is fixed to the cylinder joint 61 thereabove by a plurality of bolts (not shown) penetrating from the bottom to the top of FIG. Has been.

  The solvent mist-containing (mixed) compressed atomized air is supplied from the solvent mist generating device 120 to the compressed atomizing air introduction hole 34 of the coating valve device 20 through the solvent mist-containing atomizing air hose 23. If limited, the introduction hole 34 should be referred to as a solvent mist-containing (mixed) compressed atomizing air introduction hole 34, but the coating valve device 20 itself can be used for other purposes. Generally referred to as a compressed atomizing air introduction hole. The compressed atomized air is a concept including solvent mist-containing (mixed) compressed atomized air. This also applies to the compressed air supply pipe 35 and the compressed air supply path 43.

  The liquid coating material introduction hole 31 is bent downward at the center of the fluid body 30 (this portion is referred to as a center hole 33). The cross section of the center hole 33 is circular. The compressed atomizing air introduction hole 34 also bends and extends downward at a position separated from the center hole 33 (this portion is referred to as a communication hole 36). A liquid discharge needle 50 passes through the center hole 33 with a gap between the center hole 33 and the inner surface of the center hole 33. A bearing portion 37 including an O-ring is provided above the center hole 33 of the fluid body 30. The needle 50 is supported by an O-ring of the bearing portion 37 so as to be movable up and down while maintaining airtightness.

  A boss 30A protrudes downward from the lower portion of the fluid body 30, and an upper end portion of an extension outer tube 42 extending downward is fixed to the boss 30A by screwing. A female thread is formed on the lower inner surface of the center hole 33 of the fluid body 30, and the male thread at the upper end of the extension inner tube 41 is screwed to the female thread and fixed thereto. The needle 50 extends downward with a slight gap between it and the inner surface of the extension inner tube 41. A compressed air supply path 43 having an annular cross section is formed between the extension inner pipe 41 and the extension outer pipe. The compressed air supply path 43 is connected to the compressed air introduction hole 34 through the communication hole 36.

  A discharge nozzle 51 is fixed to the lower end portion of the extension inner tube 41 by screwing. The discharge nozzle 51 has a discharge hole 51A having a circular cross section at the center, and the discharge hole 51A becomes thinner toward the tip. On the other hand, the cross section of the liquid discharge needle 50 is circular, and the tip portion 50A becomes thinner toward the tip, and the tip is pointed. The front end portion 50A has a circular cross section. In the state in which the needle 50 has advanced, a part of the tip 50A of the needle 50 protrudes outward (downward) from the discharge hole 51A of the nozzle 51, as shown in FIG. The liquid application material is stopped closely (closed state of liquid discharge operation).

  In the state in which the needle 50 is retracted, a gap is formed between the outer surface of the tip 50A of the needle 50 and the inner surface of the discharge hole 51A of the discharge nozzle 51, as shown in FIG. Is possible (discharge operation state). The size of the gap between the needle tip 50A and the nozzle discharge hole 51A is one of the parameters for controlling the amount of liquid to be discharged (application width).

  An air cap 52 is fixed to the distal end portion (lower end portion) of the extension outer tube 42 by screwing. The air cap 52 covers the entire discharge nozzle 51 with a gap, has a converging inner wall 53 for converging the compressed air sprayed on the inner surface, and has a compressed air outlet 52A larger than the discharge hole 51A of the nozzle 51 at the tip. It has been. Further, a needle cover 54 is fixed to the air cap 52 by screwing. The needle cover 54 is open outward.

  A screw adapter 45 is housed and fixed (for example, bonded) in a compressed air supply path 43 between the extension inner tube 41 and the outer tube 42. As shown in FIGS. 9 and 10 in an enlarged manner, the screw adapter 45 has five screw grooves 46 formed on the peripheral surface, and these screw grooves 46 have an inclination angle of 15 to 25 degrees in the axial direction. doing. In the center, a hole 47 into which the inner tube 41 fits is formed. The screw adapter 45 forms a swirl flow in the atomized compressed air flowing in the supply passage 43 (containing solvent mist), and fine particles of liquid discharged from the gap between the discharge hole 51A of the nozzle 51 and the tip 50A of the needle 50 Promote

  That is, the pressure-adjusted liquid coating material (described later) is supplied to the discharge nozzle 51 through the supply pipe 32, the introduction hole 31, and the center hole 33, through the gap between the needle 50 in the extension inner pipe 41. The On the other hand, compressed atomized air that has been pressure-adjusted and mixed with solvent mist is supplied to the compressed air supply path 43 between the extension inner pipe 41 and the outer pipe 42 via the supply pipe 35, the introduction hole 34, and the communication hole 36. Then, it is turned into swirl air by the screw adapter 45 and blown out into the air cap 52 covering the discharge nozzle 51. The atomized particles of the liquid discharged from the discharge nozzle 51 are converged to a certain width by the compressed air containing solvent mist swirling along the inner wall 53 of the air cap 52 while converging the periphery of the air cap 52, thereby forming an ejection flow spray pattern SP. To do. The swirling solvent mist-containing compressed air accelerates atomization while sprinkling the solvent mist on the liquid ejected from the nozzle 51, and prevents the atomized particles from scattering.

  The screw adapter 45 mainly functions to limit the coating width by converging the atomized particles ejected from the nozzle 51. Prevention of so-called stringing can be achieved by using compressed atomized air containing solvent mist instead of compressed atomized air. Therefore, the screw adapter 45 is not always necessary for the purpose of preventing the occurrence of stringing, and therefore a coating valve device without a screw adapter is also applicable.

  Next, the drive unit of the liquid discharge needle 50 will be described mainly with reference to FIGS.

  On the cylinder joint 61, a joint 62 and a cylinder 63 thereon are arranged in a straight line, and these are fixedly connected to each other by bolts (not shown). A linear actuator 70 is disposed on the cylinder 63 and is fixed to the cylinder 63 with bolts. The linear actuator 70 controls the opening degree of the discharge nozzle 51. The adjuster shaft 71 that protrudes downward and forward from the linear actuator 70 functions as a kind of stopper, and the position of its lower end surface determines the opening degree.

  A piston 64 is slidably accommodated in the cylinder 63, and a piston rod 65 is fixed to the center of the piston 64. The lower part of the piston rod 65 is fixedly connected (coupled) to the upper part of the needle 50 by a coupling 66. The upper part of the piston rod 65 penetrates the piston 64, and a piston cap 68 is provided at the upper end. The piston cap 68 is in a position where it can contact the lower end surface of the adjuster shaft 71. The coupling 66 can move up and down in a cylindrical hole formed in the cylinder joint 61. A coil spring 69 in the cylinder 63 always urges the piston 64 downward. Compressed air supplied from a compressed air supply pipe 67 provided in the joint 62 is sent through a supply hole in the joint 62 to the inside of the cylinder 63 (a space below the piston 64).

  The linear actuator includes, for example, a motor and a mechanism that converts rotation of the motor into axial movement (movement) of the adjuster shaft 71 (for example, a ball screw rotated by the motor and a nut fitted to the ball screw).

  In a state where compressed air is not supplied into the cylinder 63, the piston 64 is pushed downward by the force of the spring 69, and the piston 64 is in contact with the joint 62 as shown in FIG. 3. In this state, the needle 50 connected by the coupling 66 to the piston rod 65 fixed to the piston 64 is in a lowered position, and the tip 50A of the needle 50 closes the discharge nozzle 51 (the state shown in FIG. 7). ).

  When compressed air is supplied, as shown in FIG. 4, the piston 64 rises against the biasing force of the spring 69, thereby raising the piston rod 65, and the cap 68 is moved to the lower end surface of the adjuster shaft 71. Stop by hitting. Therefore, the rise of the needle 50 is determined by the position of the lower end surface of the adjuster shaft 71. The outer peripheral surface of the lower end portion 50A of the needle 50 is separated from the inner surface of the discharge hole 51A of the discharge nozzle 51, and liquid is discharged (state shown in FIG. 8). The opening degree of the discharge nozzle 51 is determined by the position of the lower end surface of the adjuster shaft 71. That is, the opening degree of the discharge nozzle 51 is controlled by the linear actuator 70.

  FIG. 11 shows the above-described coating valve device (liquid coating material injection valve device) and a solvent mist generating device (solvent mist injection valve device) for supplying solvent-containing mist thereto. FIG. 12 shows an enlarged main part of the solvent mist generator. The solvent mist generator of this embodiment is a kind of spray gun in that it has a discharge hole (nozzle) for discharging the solvent and a compressed air outlet for atomizing (atomizing) the solvent discharged from the discharge hole. The basic structure is the same as that of the coating valve device 20 (although there are some differences in the absence of the extension part 40 and the screw adapter 45), a description overlapping with that described above will be omitted.

  In the fluid body 130, the solvent introduction hole 131 communicates with a center hole 133 that extends downward from the center of the fluid body 130. A lead-out pipe 141 is fixed in the lower part of the center hole 133. The center hole 133 communicates with the inside of the outlet pipe 141. A discharge nozzle 151 is screwed and fixed to the lower end portion of the outlet tube 141. The tip of the nozzle 151 is a solvent discharge hole. A solvent discharge needle 150 passes through the center hole 133, the lead-out hole 141, and the nozzle 151 so as to be movable up and down with a slight solvent passage around it. The tip of the needle 150 becomes thinner toward the tip, and the discharge hole of the nozzle 151 is opened and closed as the needle 150 advances and retreats.

  An ejector block 140 is fixed to the lower part of the fluid body 130 by screwing. In the ejector block 140, a space serving as the ejection path 143 is formed, and this space is opened as a blowout port 143A at the lower portion. In addition, a lead-out pipe 141 and a nozzle 151 enter the space, and a surrounding area is an ejection path 143 through which compressed atomized air passes. The compressed atomizing air introduction hole 134 of the fluid body 130 is connected to the ejection passage 143 by the communication hole 136. Compressed atomized air is introduced into the introduction hole 134 through the compressed atomized air supply pipe 135.

  When the needle 150 is raised, the solvent supplied from the supply pipe 132 is ejected from the discharge hole at the tip of the nozzle 151 through the space (gap) between the needle 150 and the center hole 133, the outlet pipe 141, and the inner surface of the nozzle 151. . At the same time, the compressed air supplied to the supply pipe 135 is ejected from the communication hole 136 through the ejection path 143 from the outlet 143A around the nozzle ejection hole, and the solvent is atomized. As a result, compressed air containing (mixed) the solvent mist is ejected from the ejector block 140. The sprayed solvent mist-containing compressed atomizing air is supplied to the compressed atomizing air supply pipe 35 of the coating valve device 20 through the hose 23 connected to the ejector block 140 by the joint 155. When the needle 150 is advanced, the discharge hole of the nozzle 151 is closed and the ejection of the solvent stops. At this time, the supply of compressed air may be stopped.

  The upper portion of the needle 150 is connected to the lower portion of the piston rod 165 by a coupling 166 in the cylinder joint 161, and the upper portion of the piston rod 165 is fixed to the piston 164 in the cylinder 163. The piston 164 is urged downward by a coil spring 169. Therefore, normally, the piston 164 is in the lowered position, the needle 150 is also lowered through the piston rod 165, and the discharge hole of the nozzle 151 is closed. When the compressed air for operation is introduced into the compressed air supply pipe 167, the piston 164 is raised, and the piston rod 165 and the needle 150 are raised accordingly, the discharge hole of the nozzle 151 is opened, and the solvent is removed as described above. Spray with compressed air. A cap 168 is fitted on the piston 164, and the cap 168 hits the lower end of an adjustment screw (stopper) 170 provided at the upper portion of the cylinder 163, and the ascending position of the piston 164 is restricted. The adjustment screw 170 can be turned to move the tip of the adjustment screw 170 forward and backward in the cylinder 163, whereby the opening of the discharge hole of the nozzle 151 is determined.

  Returning to FIG. 2, ON / OFF of the compressed air for operation for opening and closing the needles 50, 150 of the two valve devices 20, 120 is controlled by the electromagnetic valve 26 for application operation and the electromagnetic valve 127 for atomization operation. That is, compressed air supplied from a compressor or the like (not shown) branches to hoses (pipes) 126 and 27 through an air filter 28A and a mist separator 28B. Compressed air supplied to the hose 126 is supplied to the operating compressed air supply pipe 167 of the valve device 120 as the solvent mist generating device via the operating compressed air pressure regulator 124A when the solenoid valve 127 is opened, via the hose 124. Is done. Similarly, the compressed air supplied to the hose 27 is supplied to the compressed air supply pipe 67 for operation of the application valve device 20 when the electromagnetic valve 26 is opened.

  The atomized compressed air supplied to the valve device 120 as the solvent mist generating device is supplied by the hose 123 through the air relay valve 128 connected to the hose branched from the hose 27 and the compressed air pressure regulator 123A for atomization. Supplied to 135. The air relay valve 128 is opened by compressed air supplied through the hose 129 when the electromagnetic valve 127 is opened. The air relay valve 128 is for preventing oils and foreign matters from the electromagnetic valve 127 and the like.

  The solvent pressure feeding tank 121 is provided with a solvent pressure regulator 121A, and the compressed air supplied through the hoses 27 and 25 is pressure-regulated by the pressure regulator 121A and added to the tank 121. The solvent is fed to the solvent supply pipe 132 of the valve device 120 through the hose 122. Similarly, the coating liquid pressure feed tank 21 is provided with a coating liquid pressure regulator 21A, and the compressed air supplied through the hoses 27 and 25 is pressure-regulated by the pressure regulator 21A and added to the tank 21. Then, the coating liquid in the tank 21 is supplied to the coating liquid supply pipe 32 of the valve device 20 through the hose 22 and the coating liquid flowmeter 22A.

  13 to 15 show another embodiment of the solvent mist generator. This utilizes a so-called lubricator.

  The solvent mist generator 220 includes a tank 221 in which the solvent is stored. The tank 221 is provided with a lubricator body 222 as a lid, and the body 222 has a cylindrical portion 222A at the bottom. The male screw on the upper edge of the tank 221 is screwed into the female screw formed on the inner peripheral surface of the cylindrical portion 222A, and the body 222 is fixed to the tank 221. The body 222 has an inlet 223 and an outlet 224 for compressed air. A damper support 225 is fixed in the air passage between the inlet 223 and the outlet 224. The damper support body 225 has a passage 227 connected to an inlet 223 and an outlet 224, and a damper 226 made of an elastic body is fixed to the passage 227 on one side thereof. The compressed air that has entered from the inlet 223 passes through the damper 226 in the passage 227 while vibrating and flows toward the outlet 224.

  A narrow air passage 228 is formed in the damper support 225 from the inlet 223 side into the tank 221, and a stop valve 229 is provided at the outlet portion of the passage 228. Therefore, a part of the air supplied to the inlet 223 is supplied into the tank 221 through the passage 228 and presses the solvent in the tank 221. A pipe 237 extends downward from the damper support body 225. The compressed solvent ascends the pipe 237, and further ascends the passage 238 formed in the damper support body 225 and the body 222 via the stop valve 237A on the way.

  An outer case 230 and an inner case 231 are attached to the upper portion of the body 222. The upper ends of these cases 230 and 231 are closed in a hemispherical shape, and a space is formed between the outer surface of the inner case 231 and the inner surface of the outer case 230. The outer case 230 is fixed by screwing a screw portion 230 </ b> A thereof to a female screw of the attachment portion 230 </ b> B of the body 222. The solvent rising in the passage 238 fills the space between the inner and outer cases 231 and 230. A cylindrical body 231A protruding downward is formed at the upper end of the inner case 231. The lower end of the cylindrical body 231A is open. The solvent that has risen in the space between the inner and outer cases 231 and 230 drops from the cylinder 231A.

  A small hole 233 is formed in the body 222 at a position where the solvent dropped from the cylinder 231A falls. Below the hole 233, a shelf 234 is formed by a part of the upper portion of the support 225. The solvent is placed on the shelf 234 through the hole 233. Since the solvent is atomized by the flow of compressed air passing through the passage by vibrating the damper 226, the compressed air containing the atomized mist of the solvent is ejected vigorously from the outlet 224. The solvent is supplied into the tank 221 from a solvent supply port 236 provided in the body 222.

  In addition to the above, various atomizers (devices) can be used as the solvent mist generator.

  16 and 17 show the spray state of the liquid coating material. FIG. 16 shows a good spray atomization state where no stringing has occurred (indicated by SP). FIG. 17 shows a string drawing spray state in which the liquid material is not atomized but appears in a thread form (indicated by AH).

  As described above, when solvent-compressed compressed air is supplied to the compressed air outlet in a coating valve device (spray gun), even if a high-viscosity stock solution is used as the liquid coating material, the stringing status as shown in FIG. Does not occur.

  FIG. 18 shows a state where electronic (electrical) components are soldered to the substrate. A pin foot 302 of the electronic component 301 protrudes from the back surface (B surface) of the substrate 300, and solder 303 (FIGS. 19 and 20) is attached to the lower portion thereof.

  19 and 20 show a state in which the liquid coating material is spray-coated on the back surface of the substrate 300. It is assumed that the coating is performed so as to have a thickness of 30 μ (microns) on the surface of the substrate 300 (indicated by reference numeral 400). FIG. 19 shows a state where coating is performed by a method of supplying solvent-mixed compressed air using a stock solution having a high viscosity as a liquid coating material. The pin foot 302 is also applied to the upper end surface and side surfaces with a considerable film thickness (10 μ or more, 5 μ or more) (indicated by reference numerals 401 and 402). FIG. 20 shows a coating film formed when the liquid coating material is diluted in advance with a solvent to such an extent that stringing does not occur, and simple compressed air that does not mix the solvent is supplied to the compressed air suction port. Since the coating material is diluted, it is easy to flow, and the thickness of the coating on the top and side surfaces of the pin foot is extremely thin (less than 2μ).

  Table 1 shows a comparison result between the method of the present invention and the conventional representative method when a dry film thickness of 30 μm is formed on the solder surface side (back surface, B surface) of the printed circuit board as an object to be coated. . A moisture-proof insulating material (conformal coating) made by Nitto Shinko Elep Coat (model LSS520MH) was used.

  The meaning of this table seems to be clear with reference to FIGS. 19 and 20, but a little explanation is added.

  Drying during the drying time means dry to the touch (dry state where there is no solvent left and it can be touched by hand and installed without any problems).

  The direction of the tip of the coating means the direction of discharge at the tip of the coating gun nozzle. In substrate moisture-proof coating, the nozzle of the coating gun is usually placed downward on the horizontal surface of the substrate. . From below, apply from below the substrate with the nozzle facing up. From the side, the coating is done by spraying the substrate from the side while the substrate is standing vertically.

  The coating efficiency is the amount of coating solution applied to the substrate / the amount of coating solution used.

  The management maintainability was defined by the following criteria for the time and difficulty of daily inspection and cleaning of the application valve and accessories to maintain the application performance.

Continuous automatic application is possible, and stable application is possible without special viscosity control of coating material.
When continuous automatic application is possible, but there is a risk that NG products may be produced unless the viscosity of the coating material is controlled. Requires automatic viscosity adjuster. ○ After maintenance of automatic application, maintenance and inspection work for each automatic device is indispensable.
During continuous automatic application, manual work time is required to temporarily stop and clean or adjust a part or part of the application valve. Furthermore, it is essential to maintain and inspect each automatic device after the completion of automatic application.

  In summary, according to the present invention, the drying time can be shortened by 200% or more, the solvent usage fee can be reduced by 60% or more, and the acute convex film thickness is improved by 200% or more.

9 Object
10 Spray application system
14 Robotic equipment
19 Housing
20 Application valve device (spray gun (device))
21 Pressure tank for coating liquid (Liquid coating material storage tank) (Liquid coating material tank) (Liquid coating material supply device)
21A Coating liquid pressure regulator (Liquid coating material supply device)
22 Liquid coating material (coating liquid) pressure hose (liquid coating material supply device)
23 Air hose for atomization containing solvent mist
24A, 124A Compressed air pressure regulator for operation
24,124 Compressed air hose for operation
26 Solenoid valve for dispensing operation
30, 130 Fluid body
30A boss
31 Coating material introduction hole
32 Coating material supply pipe
33,133 Central hole
34 Compressed atomization air (air) introduction hole
35 Compressed atomizing air supply pipe
36 Communication hole
37 Bearing
40 Extension section
41 Extension inner pipe
42 Extension outer tube
43 Compressed air supply path
45 Screw adapter
46 Screw groove
47 holes
50 Liquid discharge needle
50A Needle tip
51 Discharge nozzle
51A Liquid application material discharge hole
52 Air cap
52A Compressed air outlet
53 Converging inner wall
54 Needle cover
60 Drive unit
61 Cylinder joint
62 Joint
63,163 cylinders
64, 164 piston
65,165 Piston rod
66 coupling
67 Compressed air supply pipe
68 Piston cap
69 Coil spring
70 Linear actuator
71 Adjuster shaft
120,220 Solvent mist generator (solvent mist mixed compressed air supply device)
121 Pressure tank for solvent (solvent storage tank, solvent tank) (solvent mist mixed compressed air supply device)
121A Solvent pressure regulator
122 Solvent pressure hose
123 Compressed air hose for solvent atomization (solvent mist mixed compressed air supply device)
123A Compressed air pressure regulator for atomization (solvent mist mixed compressed air supply device)
124A Compressed air pressure regulator for operation
127 Solenoid valve for atomization operation
128 Air relay valve (solvent mist mixed compressed air supply device)
131 Solvent introduction hole
132 Solvent supply pipe
134 Introduction hole
136 communication hole
140 Ejector
141 Outlet tube
143 Outlet
143A outlet
150 Solvent dispensing needle
151 Discharge nozzle
167 Compressed air supply pipe for operation
170 Adjustment screw
300 substrates
301 Electronic components
302 pin feet
400, 401, 402 Coating film

Claims (3)

A method for preventing the occurrence of stringing phenomenon in spray coating ,
The tip of the needle that advances and retreats in the discharge hole of the nozzle can protrude outward from the nozzle discharge hole, and a liquid coating material that is discharged through the gap between the outer surface of the needle tip and the inner surface of the discharge port Using a spray gun that atomizes by compressed air blown out from a nearby compressed air outlet,
A method for preventing stringing in spray coating, wherein solvent mist is generated, and compressed air mixed with the solvent mist is supplied to the outlet to atomize the liquid coating material.   The thread drawing prevention method in spray application according to claim 1, wherein a screw adapter is provided in a compressed air supply path of the spray gun to form a swirl flow in the solvent mist mixed compressed air guided to the compressed air outlet.   The tip of the needle that advances and retreats in the discharge hole of the nozzle can protrude outward from the nozzle discharge hole, and the solvent discharged through the gap between the outer surface of the needle tip and the inner surface of the discharge port The method for preventing stringing in spray application according to claim 1 or 2, wherein the solvent mist is generated using a spray gun that atomizes with compressed air blown from a compressed air outlet.

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