Droplet ejecting apparatus

Abstract

The liquid droplet ejecting apparatus includes: a cylindrical ejection nozzle that has a planar tip surface and ejects liquid droplets; and a cover that has an opening through which the droplet passes, covers the ejection nozzle, and has a suction path between the ejection nozzle and the cover.

Description

Technical Field

[0001] The invention relates to a liquid drop ejecting device. Background Art

[0002] In order to achieve miniaturization and lightness of electronic devices, the miniaturization and lightness of electronic components mounted on electronic devices are being promoted. For example, there are small electronic components called "0402 components" with a mounting size of 400μm×200μm that can significantly reduce the mounting area, and they are mounted by solder printing based on metal plates.

[0003] In order to increase the degree of freedom in mounting, there is known a technique for ejecting droplets of a viscous medium such as a solder paste or an adhesive onto a base material such as an electronic circuit board instead of printing solder.

[0004] The nozzle for discharging the viscous medium is very fine, and when the viscous medium to be applied is attached to the tip of the nozzle, the subsequent discharging is affected, and there are problems such as loss of straightness of the discharged droplets.

[0005] Therefore, there is a technology in which a plate-like member having an opening through which the ejected droplets can pass is provided between the ejection nozzle and the substrate, and an air flow is generated between the ejection nozzle and the plate-like member, thereby removing residual droplets of the viscous medium attached to the vicinity of the front end of the ejection nozzle (for example, refer to Patent Document 1).

[0006] Figure 9A 1 is a diagram showing the periphery of a discharge nozzle of a discharge device described in Patent Document 1. The discharge device includes: a discharge nozzle 100 having a housing 190 having a liquid chamber 200 therein and a pressurizing unit 300 for pressurizing the liquid in the liquid chamber 200; and a cover 400 which is provided at a predetermined interval from the discharge nozzle 100 and has an opening 410 through which the discharged liquid droplets 101 can pass. A suction path 500 is provided between the discharge nozzle 100 and the cover 400, and is sucked to a negative pressure by a suction device (not shown).

[0007] When the droplets 101 are ejected, the suction path 500 becomes negative pressure due to the suction device. The surrounding gas entering from the opening 410 of the cover 400 passes between the cover 400 and the housing 190, and generates an airflow sucked by the suction device. In the case where a part of the droplets adheres to the periphery of the ejection port 105 of the ejection nozzle 100, the periphery of the opening 410 of the cover 400, etc., the attached droplets are removed by the airflow generated by the suction device.

[0008] Prior art literature

[0009] Patent Literature

[0010] Patent Document 1: Japanese Patent No. 4675105 Summary of the invention

[0011] In the above-mentioned ejection device, the ejection port 105 is surrounded by a concave portion 110 of a lower level, and a part of the droplets may adhere to the concave portion 110 ( Figure 9B ). The droplets 102 attached to the concave portion 110 are difficult to be removed by the airflow generated by the suction device, and there are problems such as the attached droplets 102 directly solidifying. In particular, in a device that ejects fine droplets 101, if the droplets 102 are attached to the periphery of the ejection port 105, the contact between the droplets 101 and the droplets 102 may hinder the application of an appropriate amount of the droplets 101 and the straightness of the ejection, so it is desirable to prevent the droplets 102 from attaching to the periphery of the ejection port 105.

[0012] An object of the present invention is to provide a liquid droplet discharge device capable of stabilizing the discharge amount, speed, and straightness of discharged liquid droplets.

[0013] One embodiment of the liquid droplet ejection device according to the present invention comprises: a nozzle having a planar front end surface and ejecting liquid droplets; and a cover having an opening for the liquid droplets to pass through and covering the nozzle, with a suction path between the nozzle and the cover.

[0014] In addition, one embodiment of the liquid droplet ejection device according to the present invention comprises: a nozzle having a front end surface and ejecting liquid droplets; and a cover having an opening for the liquid droplets to pass through and covering the nozzle, wherein the opening widens in diameter toward the ejection direction of the liquid droplets.

[0015] According to the present invention, the discharge amount, speed, and straightness of discharged droplets can be stabilized. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 1 is a diagram showing the overall structure of the liquid droplet ejection device in this embodiment.

[0017] Figure 2 It is an enlarged view showing the discharge nozzle and the front end portion of the cover in this embodiment.

[0018] Figure 3A This is a diagram showing a state in which the liquid droplet discharge device in this embodiment discharges liquid droplets.

[0019] Figure 3B This is a diagram showing a state in which the liquid droplet discharge device in this embodiment discharges liquid droplets.

[0020] Figure 4 It is a graph showing the flow velocity of the suction straight surface portion in this embodiment.

[0021] Figure 5A This is a diagram showing a suction straight surface portion without an external tapered portion.

[0022] Figure 5B This is a diagram showing the attracting straight surface portion from which droplets are being ejected.

[0023] Figure 6A This is a diagram showing Modification 1 of the nozzle in the present embodiment.

[0024] Figure 6B This is a diagram showing Modification 1 of the nozzle in the present embodiment.

[0025] Figure 7A This is a diagram showing Modification 2 of the ejection nozzle in the present embodiment.

[0026] Figure 7B This is a diagram showing Modification 2 of the ejection nozzle in the present embodiment.

[0027] Figure 8 This is a diagram showing Modification 3 of the nozzle in the present embodiment.

[0028] Figure 9A This is a diagram showing the periphery of the ejection nozzle of the ejection device described in Patent Document 1.

[0029] Figure 9B This is a diagram showing a state in which residual droplets adhere to the concave portion of the existing ejection device.

[0030] Explanation of Reference Numerals

[0031] 1: Droplet ejection device, 2: Droplet, 3: Residual droplet, 10: Ejection nozzle, 10a: Ejection port, 10b: Inner surface, 10c: Outer surface, 11: Front end face, 19: Housing, 20: Liquid chamber, 30: Pressurizing unit, 40: Cover, 41: Front end wall portion, 42: Side wall portion, 43: Opening, 44: Conical surface portion, 45: Straight surface portion, 46: Receiving surface, 47: Inner wall surface, 49: Suction path, 50: Decompression unit, 71: Vertical wall surface, 81: Chamfered portion. Detailed Embodiment

[0032] Hereinafter, embodiments of the present invention will be described with reference to the drawings. It should be noted that the embodiments described below are all specific examples of the present invention. Therefore, each component, the arrangement position of each component, the connection method, etc. shown in the following embodiments are examples and are not intended to limit the present invention. In addition, regarding the components in the following embodiments that are not described in the independent technical solution, they will be described as optional components.

[0033] In addition, each drawing is a schematic diagram and is not necessarily drawn precisely. It should be noted that in each drawing, substantially the same structures are labeled with the same reference numerals, and repeated descriptions are omitted or simplified.

[0034] Figure 1 Shows the overall structure of the droplet ejection device 1 in the present embodiment. Figure 2 Shows an enlarged view of the ejection nozzle 10 and the front end portion of the cover 40 in the present embodiment. The droplet ejection device 1 includes: a housing 19 with an internal liquid chamber 20, a pressurizing unit 30 for pressurizing the liquid in the liquid chamber 20, an ejection nozzle 10 provided on the housing 19 and ejecting the liquid from the front end, a cover 40 provided so as to cover the ejection nozzle 10, and a decompression unit 50 for sucking the suction path 49 formed between the ejection nozzle 10 and the cover 40.

[0035] The ejection nozzle 10 is substantially cylindrical, and its front end portion (the lower end portion in the figure) is provided as an ejection port 10a. The liquid pushed out from the liquid chamber 20 by the pressurizing unit 30 flows inside the ejection nozzle 10 toward the ejection port 10a, and the droplets 2 are ejected from the ejection port 10a.

[0036] The ejection nozzle 10 is formed as a cylindrical shape that tapers conically toward the front end. A passage for the droplets is formed on the central axis of the ejection nozzle 10, and the front end portion becomes the ejection port 10a. The front end face 11 of the ejection nozzle 10 is formed in a planar shape. If the wall thickness at the front end of the ejection nozzle 10 is thin (the width of the front end face 11 is narrow), it is easy to remove the liquid when it adheres to the front end face. For example, the wall thickness is desirably about 10 μm to 50 μm.

[0037] Regarding the material of the ejection nozzle 10, a material that is not likely to cause pressure attenuation and can transmit pressure to the front end of the ejection nozzle 10 is desired, and is appropriately selected according to the type of liquid, the size of the ejection nozzle 10, etc., such as stainless steel in metal materials, alumina, zirconia, silica in ceramic materials, etc.

[0038] The housing 19 has a liquid chamber 20 inside, and the liquid chamber 20 communicates with an external liquid supply tank through a supply path (not shown) to supply liquid to the inside. Regarding the material of the housing 19, it is desired that pressure attenuation is not likely to occur. For example, among metal materials, stainless steel, nickel, aluminum, etc. are selected. In addition, among ceramic materials, alumina, zirconia, silica, etc. are selected.

[0039] The pressurizing unit 30 pressurizes the liquid in the liquid chamber 20 and ejects the droplets 2 from the ejection nozzle 10. The pressurizing unit 30 has a function of changing the pressure of the liquid in the liquid chamber 20. It is also possible to adopt a structure in which the liquid chamber 20 is pressurized and decompressed by displacing a plunger in the Figure 1 Z-axis direction. Regarding the actuator for displacing the plunger, in order to obtain high responsiveness, it is desired to use, for example, a piezoelectric element, etc., but other mechanisms such as a solenoid valve and a spring can also be used.

[0040] The cover 40 is generally cylindrical and covers the ejection nozzle 10, having a front wall portion 41 at the front end in the ejection direction and a side wall portion 42 extending from the front wall portion 41 toward the base end in the ejection direction. An opening 43 through which the droplets 2 ejected from the ejection nozzle 10 pass is provided in the front wall portion 41.

[0041] An attraction path 49 is provided between the ejection nozzle 10 and the cover 40, and suction is performed by a decompression unit 50. The attraction path 49 is between the receiving surface 46 of the front wall portion 41 and the front end surface 11 of the ejection nozzle 10, and between the inner wall surface 47 of the side wall portion 42 and the outer surface 10c of the ejection nozzle 10, and extends to the decompression unit 50.

[0042] The distance between the ejection nozzle 10 and the cover 40 is designed according to the attraction force of the decompression unit 50, the type and properties of the ejected liquid, etc. In order to remove the residual droplets around the ejection nozzle 10 by the suction of the decompression unit 50, the gas flow in the attraction path needs to have a specified speed. Therefore, if the distance between the ejection nozzle 10 and the cover 4 is too wide, the specified speed cannot be obtained. Therefore, the distance between the ejection nozzle 10 and the cover 40 needs to be set to be below a specified distance.

[0043] On the other hand, for example, in the case of a solder paste containing particles, if the distance between the ejection nozzle 10 and the cover 40 is too narrow, the residual droplets may sometimes not be removed. Therefore, the distance between the ejection nozzle 10 and the cover 40 needs to be set to be above a specified distance. Specifically, the distance between the front end surface 11 and the receiving surface 46 and the distance between the outer surface 10c and the inner wall surface 47 are preferably set to be about 1 μm to 1 mm respectively.

[0044] In addition, an alignment mechanism (not shown) for positioning the relative position in the direction crossing the ejection direction of the ejection nozzle 10 is provided on the cover 40, and the opening 43 is arranged to be coaxial with the ejection port 10a of the ejection nozzle 10.

[0045] The inner surface of the opening 43 has a straight surface portion 45 with the same inner diameter on the side of the ejection nozzle 10, and a tapered surface portion 44 that is continuous with the straight surface portion 45 and whose diameter widens conically toward the ejection direction of the droplets. The inner diameter of the straight surface portion 45 is set to be larger than that of the ejection port 10a. This is because the width of the ejected droplets 2 is about 10 μm larger than the inner diameter of the ejection port 10a due to the action of surface tension, etc. Therefore, the inner diameter of the straight surface portion 45 is set to be more than about 10 μm larger than that of the ejection port 10a.

[0046] In addition, the inner diameter of the straight surface portion 45 is set to be smaller than the outer diameter of the front end surface 11. This is to ensure the flow rate of the gas sucked from the opening 43 and thus effectively remove the residual droplets.

[0047] The inclination angle of the conical face 44 is not particularly limited, but from the viewpoint of generating a specified air flow to remove residual droplets or ensuring the straightness of the droplets 2, it is preferably about 30 degrees to 60 degrees.

[0048] Regarding the material of the cover 40, resin, metal material, ceramic material, etc. are appropriately selected. For example, among resin materials, PEEK, PPS, ABS, etc. are selected; among metal materials, stainless steel, nickel, aluminum, etc. are selected; and among ceramic materials, alumina, zirconia, silica, etc. are selected.

[0049] The decompression unit 50 creates a negative pressure in the suction path 49 between the ejection nozzle 10 and the cover 40 to suck in gas. Since the sucked gas may contain excess droplets, the decompression unit 50 includes a filter for separating the air flow and droplets, a tank for storing the separated droplets, etc. It should be noted that the generation of negative pressure can also utilize a vacuum pump or the like.

[0050] Figure 3A and Figure 3B Fig. shows the state where the droplet ejection device 1 according to the present invention ejects droplets 2. When the liquid in the liquid chamber 20 is pressurized by the pressurization unit 30, the liquid that has passed through the ejection nozzle 10 becomes droplets 2 and is ejected from the ejection port 10a. The ejected droplets 2 are applied to a substrate (not shown) etc. through the opening 43 provided coaxially with the ejection port 10a.

[0051] When ejecting the droplets 2, the decompression unit 50 creates a negative pressure in the suction path 49 to suck in the gas in the suction path 49. When a negative pressure is generated in the suction path 49, the gas outside the cover 40 is sucked into the suction path 49 through the opening 43. The sucked gas flows between the front end face 11 of the ejection nozzle 10 and the receiving face 46 and in a direction away from the opening 43, and then flows between the outer surface 10c of the ejection nozzle 10 and the inner wall surface 47 of the cover 40 and in the direction of the base end of the ejection nozzle 10. Then, it is sucked by the decompression unit 50.

[0052] Figure 3A and Figure 3B Fig. shows the residual droplets 3 adhering to the peripheral portion of the opening 43 when ejecting the droplets 2. Although the inner diameter of the opening 43 is set larger than the width of the droplets 2, residual droplets 3 may sometimes adhere depending on the situation. At this time, the residual droplets 3 are removed from the peripheral portion of the opening 43 by the flow of the gas sucked into the suction path 49 through the opening 43, and are sucked into the suction path 49 and removed.

[0053] Figure 4The figure shows the flow velocity distribution in the Z-axis direction of the gas attracted to the suction path 49 through the opening 43. The solid line represents the case where the length of the straight surface portion 45 in the Z-axis direction is short, and the dashed line represents the case where the length of the straight surface portion 45 in the Z-axis direction is long. With respect to the inner diameter of the opening 43, the flow velocity is slower on the central side and faster on the peripheral side. When the length of the straight surface portion 45 in the Z-axis direction is short, the portion with a faster flow velocity is located more outward compared to the case where the length of the straight surface portion 45 in the Z-axis direction is long. Therefore, when the length of the straight surface portion 45 in the Z-axis direction is short, the ejected droplets 2 are not easily affected by the air flow, and the minute droplets do not scatter around and are coated while maintaining straightness.

[0054] In addition, due to the presence of the tapered surface portion 44, the gas outside the cover 40 flows along the tapered surface portion 44 in the direction toward the inside of the opening 43. Due to this flow, the residual droplets attached to the peripheral portion of the tapered surface portion 44 are directed toward the inside of the opening 43 and are more easily attracted toward the suction path 49. Therefore, by forming the tapered surface portion 44 and shortening the straight surface portion 45 as much as possible, the residual droplets 3 attached to the peripheral portion of the tapered surface portion 44 are easily attracted into the suction path 49 by the air flow.

[0055] Regarding the residual droplets 3 that remain on the peripheral portion of the cover 40 on the basis that the droplets attached to the straight surface portion 45 or the tapered surface portion 44 can be inhaled by the air flow in the Z direction, if the tapered surface portion 44 is present, it is at a distance of about the radius from the ejected droplets 2, and thus does not become an obstacle to the droplets 2.

[0056] It is preferable in terms of the straightness of the ejected droplets 2 and the attractiveness of the residual droplets 3 that the length of the straight surface portion 45 in the Z-axis direction is short. Although it is not necessary to provide the straight surface portion 45, when the straight surface portion 45 is formed due to processing necessity or the like, it is also preferable to shorten the straight surface portion 45 as much as possible.

[0057] Figure 5A And Figure 5B The figure shows a comparative example in which no tapered surface portion is formed in the opening 43. In the case where the inner diameter 62 of the straight surface portion 61 is the same as that of Figure 3A And Figure 3B the example of, as shown in Figure 4 the portion with a faster flow velocity of the attracted air flow is generated at the center of the opening 43. Therefore, the droplets 2 are affected by the air flow and their shape is damaged, and they are easily attached to the peripheral portion of the opening 43. In addition, since the velocity of the attracted air flow at the peripheral portion of the opening 43 is slow and the air flow toward the center of the opening 43 is small, the residual droplets 3 are not easily attracted into the suction path 49 and are not easily removed.

[0058] In addition, if the droplet 2 comes into contact with the residual droplet 3, it is impossible to ensure the specified coating amount or the straightness of the droplet 2. Moreover, the droplets adhering to the straight surface portion 61 at the peripheral edge of the cover 40 cannot be removed by the air flow suction in the Z direction and remain, thereby hindering the ejection of the droplet 2.

[0059] As described above, the ejection nozzle 10 of the present embodiment has a flat front end surface 11 without forming a recess, so even if droplets adhere to the periphery of the ejection port 10a, they are easily removed. In addition, since the tapered surface portion 44 is formed in the opening 43 formed in the cover 40, the straightness of the droplet 2 can be ensured, and it is also easy to remove the residual droplet 3 adhering to the peripheral edge of the opening 43.

[0060] In addition, when applying minute droplets 2 onto a substrate, in order to ensure the required coating amount, sometimes a quantity more than the required coating amount is ejected from the ejection nozzle 10. A part of the ejected droplets 2 sometimes scatters and adheres to the ejection nozzle 10 and the cover 40, but the adhering residual droplets 3 are removed by the air flow attracted to the suction path 49, so that the required coating amount is accurately applied onto the substrate.

[0061] <Variation 1>

[0062] Figure 6A And Figure 6B A variation of the cover 40 in the present embodiment is shown. When manufacturing the cover 40, the cover 40 may be provided with a bottom surface, i.e., a receiving surface 46, facing the front end surface 11 of the ejection nozzle 10 and an inner surface, i.e., a vertical wall surface 71 perpendicular to the XY plane, that intersects the receiving surface 46 perpendicularly at the lower end of the inner wall surface 47 ( Figure 6A )

[0063] In addition, the cover 40 may have a vertical wall surface 71 and a receiving surface 46 connected to the vertical wall surface 71 through a curved surface R ( Figure 6B ). Thereby, processing and forming can be performed more easily than in the above-described embodiment, and ensuring the required performance and reducing the component cost can be achieved concurrently. In addition, by providing the curved surface R, residual droplets are less likely to adhere to the inner surface of the cover 40.

[0064] <Variation 2>

[0065] Figure 7A And Figure 7B A variation of the ejection nozzle 10 in the present embodiment is shown. The corner between the front end surface 11 of the ejection nozzle 10 and the outer surface 10c of the ejection nozzle 10 may be a curved surface R' ( Figure 7A )

[0066] In addition, a conical chamfered portion 81 may be provided on the outer peripheral edge portion of the front end surface 11 of the ejection nozzle 10 from the curved surface R' toward the ejection port 10a of the ejection nozzle 10 ( Figure 7B). Thus, it is easy to remove the residual droplets adhering to the ejection nozzle 10. It should be noted that the chamfered portion 81 is not limited to the shape in which the outer peripheral edge portion of the front end face 11 of the ejection nozzle 10 is conical, and a conical chamfered portion 81 without a flat surface on the front end face 11 can also be provided.

[0067] <Modified Example 3>

[0068] Figure 8 A further modified example of the cover 40 is shown. When the chamfered portion 81 is provided on the front end face 11 of the ejection nozzle 10 facing the ejection port 10a, a conical portion 91 having a conical surface shape may be provided on the receiving surface 46 of the cover 40 facing the chamfered portion 81 in a manner substantially parallel to the chamfered portion 81. Since there may be a case where the conical portion 91 and the chamfered portion 81 are not completely parallel due to dimensional errors, design errors, etc., the conical portion 91 being substantially parallel to the chamfered portion 81 also includes the case where they are not completely parallel.

[0069] In Modified Example 2, the distance between the front end face 11 and the receiving surface 46 widens toward the outside, so the flow velocity of the gas decreases. However, in Modified Example 3, the distance does not widen, so the flow velocity of the gas does not decrease, and thus it is easier to remove the droplets.

[0070] The above describes the embodiments, but the present invention is not limited to the above embodiments.

[0071] In addition, the present invention also includes solutions obtained by making various modifications that those skilled in the art can think of to each embodiment, or solutions achieved by arbitrarily combining the components and functions in each embodiment without departing from the gist of the present invention.

[0072] Industrial Applicability

[0073] The present invention can be used in a droplet ejection device capable of stabilizing the ejection amount, velocity, and straightness of ejected droplets.

Claims

1. A liquid droplet ejection device, comprising: a spray nozzle having a planar front end surface and spraying liquid droplets; and a cover having an opening for the liquid droplets to pass through and covering the ejection nozzle, A suction path is provided between the ejection nozzle and the cover.

2. The liquid droplet ejection device according to claim 1, wherein: The wall thickness of the front end of the ejection nozzle is 5 μm to 3 mm.

3. A liquid droplet ejection device, comprising: a spray nozzle having a front end surface and spraying liquid droplets; and a cover having an opening for the liquid droplets to pass through and covering the ejection nozzle, The diameter of the opening increases toward the ejection direction of the liquid droplets.

4. The liquid droplet ejection device according to claim 1 or 3, wherein: A corner between the front end surface and the outer surface of the ejection nozzle is a curved surface.

5. The liquid droplet ejection device according to claim 1 or 3, wherein: The front end surface has a conical chamfered portion at an outer peripheral edge portion.

6. The liquid droplet ejection device according to claim 5, wherein: An inner surface of the cover facing the chamfered portion is substantially parallel to the chamfered portion.

7. The liquid droplet ejection device according to claim 1 or 3, wherein: The cover has a bottom surface opposite to the front end surface and an inner surface perpendicularly intersecting the bottom surface.

8. The liquid droplet ejection device according to claim 1 or 3, wherein: The cover has a bottom surface facing the front end surface and an inner surface connected to the bottom surface via a curved surface.

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