Droplet discharge device

Abstract

To provide a droplet discharge device that can stabilize a discharge amount, velocity, and straight travel property of a discharged droplet.SOLUTION: A droplet discharge device includes: a cylindrical discharge nozzle including a flat-plate-like tip surface and discharging a droplet; a cover including an opening through which a droplet passes and which covers the discharge nozzle; and a suction route located between the discharge nozzle and the cover.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to a droplet ejection device.

Background Art

[0002] In order to reduce the size and weight of electronic devices, the miniaturization and weight reduction of electronic components mounted on electronic devices have been progressing. For example, there is a small electronic component with a mounting dimension of 400 μm × 200 μm called a "0402 component" that can significantly reduce the mounting area, and it is mounted by solder printing on a metal plate.

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

[0004] The nozzle for ejecting the viscous medium is very fine, and if the viscous medium to be applied adheres to the tip of the nozzle, it will affect subsequent ejection and cause problems such as impairing the straightness of the ejected droplets.

[0005] Therefore, there is a technique of providing a plate-like member having an opening through which the ejected droplets can pass between the ejection nozzle and the substrate, and generating an air flow between the ejection nozzle and the plate-like member to remove the remaining droplets of the viscous medium adhering near the tip of the ejection nozzle (see, for example, Patent Document 1).

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

[0007] When the droplet 101 is ejected, the suction path 500 is set to a negative pressure by a suction device, and the surrounding gas that enters through the opening 410 of the cover 400 passes between the cover 400 and the housing 190, generating an air flow that is suctioned by the suction device. When a part of the droplet adheres to the periphery of the discharge port 105 of the discharge nozzle 100 or the periphery of the opening 410 of the cover 400, etc., it is removed by the air flow generated by the suction device.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0009] In the above-described ejection device, the periphery of the discharge port 105 is a recess 110 that is one step lower, and a part of the droplet may adhere to this recess 110 (Fig. 9B). The droplet 102 adhering to the recess 110 is difficult to remove by the air flow generated by the suction device, and there are problems such as the adhered droplet 102 simply solidifying. Particularly in a device that ejects fine droplets 101, if a droplet 102 adheres to the periphery of the discharge port 105, the droplet 101 and the droplet 102 may come into contact, which may prevent the appropriate amount of application or the straightness of ejection of the droplet 101. Therefore, it is desirable to prevent the droplet 102 from adhering to the periphery of the discharge port 105.

[0010] An object of the present disclosure is to provide a droplet ejection device capable of stabilizing the ejection amount, speed, and straightness of the ejected droplets.

Means for Solving the Problems

[0011] To solve the above problems, one aspect of the droplet ejection device according to the present disclosure includes a discharge nozzle having a planar tip surface for ejecting droplets, and a cover having an opening through which the droplets pass and covering the discharge nozzle, and a suction path is provided between the discharge nozzle and the cover.

[0012] Also, one aspect of the droplet ejection device according to the present disclosure includes a discharge nozzle having a tip surface for discharging droplets, and a cover having an opening through which the droplets pass and covering the discharge nozzle, wherein the opening expands in diameter toward the droplet discharge direction.

Effects of the Invention

[0013] According to the present disclosure, it is possible to stabilize the discharge amount, speed, and straightness of the discharged droplets.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Figure 3A

Figure 3B

Figure 4

Figure 5A

Figure 5B

Figure 6A

Figure 6B

Figure 7A

Figure 7B

Figure 8

Figure 9A

Figure 9B

Mode for Carrying Out the Invention

[0015] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Note that each of the embodiments described below shows a specific example of the present disclosure. Therefore, each component, the arrangement position and connection form of each component, etc. shown in the following embodiments are examples and are not intended to limit the present disclosure. In addition, among the components in the following embodiments, components not described in the independent claims are described as optional components.

[0016] Also, each figure is a schematic diagram and is not necessarily drawn precisely. In each figure, the same reference numerals are given to substantially the same configurations, and duplicate explanations are omitted or simplified.

[0017] FIG. 1 shows the overall configuration of the droplet discharge device 1 in the present embodiment, and FIG. 2 shows an enlarged view of the tip of the discharge nozzle 10 and the cover 40 in the present embodiment. The droplet discharge device 1 includes a housing 19 with an internal liquid chamber 20, a pressurizing unit 30 that pressurizes the liquid in the liquid chamber 20, a discharge nozzle 10 provided on the housing 19 from which the liquid is discharged from the tip, a cover 40 provided so as to cover the discharge nozzle 10, and a decompression unit 50 that sucks the suction path 49 formed between the discharge nozzle 10 and the cover 40.

[0018] The discharge nozzle 10 is substantially cylindrical, and its tip (the lower end in the drawing) is a discharge port 10a. The liquid pressurized by the pressurizing unit 30 and pushed out from the liquid chamber 20 flows through the inside of the discharge nozzle 10 toward the discharge port 10a, and the droplets 2 are discharged from the discharge port 10a.

[0019] The ejection nozzle 10 is formed in a cylindrical shape that tapers and narrows towards the tip. A passage for droplets is formed on the central axis of the ejection nozzle 10, and the tip portion serves as the ejection port 10a. The tip surface 11 of the ejection nozzle 10 is formed in a planar shape. It is easier to remove droplets adhering to the tip surface when the wall thickness at the tip of the ejection nozzle 10 is thin (the width of the tip surface 11 is narrow). For example, the wall thickness is preferably about 10 μm to 50 μm.

[0020] The material of the ejection nozzle 10 is preferably one that is less likely to cause pressure attenuation and can transmit pressure to the tip of the ejection nozzle 10. For example, among metal materials, stainless steel, etc., and among ceramic materials, alumina, zirconia, silicon dioxide, etc. are appropriately selected according to the type of liquid, the size of the ejection nozzle 10, etc.

[0021] The housing 19 has a liquid chamber 20 inside. The liquid chamber 20 communicates with an external liquid supply tank through a supply path (not shown), and liquid is supplied inside. The material of the housing 19 is preferably one that is less likely to cause pressure attenuation. For example, among metal materials, stainless steel, nickel, aluminum, etc. are selected. Also, among ceramic materials, alumina, zirconia, silicon dioxide, etc. are selected.

[0022] 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 varying the pressure of the liquid in the liquid chamber 20. It may be configured to pressurize and depressurize the liquid chamber 20 by displacing the plunger in the Z-axis direction of FIG. 1. In order to obtain high responsiveness, the actuator for displacing the plunger preferably uses, for example, a piezoelectric element, but other means such as a solenoid valve and a spring may also be used.

[0023] The cover 40 is in a substantially cylindrical shape that covers the ejection nozzle 10, and has a tip wall portion 41 at the tip in the ejection direction and a side wall portion 42 extending from the tip wall portion 41 to the base end in the ejection direction. The tip wall portion 41 has an opening 43 through which the droplets 2 ejected from the ejection nozzle 10 pass.

[0024] The space between the discharge nozzle 10 and the cover 40 is a suction path 49, which is suctioned by a decompression unit 50. The suction path 49 extends to the decompression unit 50 through the space between the receiving surface 46 of the tip wall portion 41 and the tip surface 11 of the discharge nozzle 10, and through the space between the inner wall surface 47 of the side wall portion 42 and the outer surface 10c of the discharge nozzle 10.

[0025] The distance between the discharge nozzle 10 and the cover 40 is designed according to the suction force of the decompression unit 50, the type and properties of the liquid to be discharged, etc. In order to remove the remaining droplets around the discharge nozzle 10 by the suction of the decompression unit 50, a predetermined speed is required for the gas flow in the suction path. Therefore, if the distance between the discharge nozzle 10 and the cover 40 is too wide, the predetermined speed cannot be obtained, so the distance between the discharge nozzle 10 and the cover 40 needs to be set to a predetermined distance or less.

[0026] On the other hand, for example, in the case of solder paste containing particles, if the distance between the discharge nozzle 10 and the cover 40 is too narrow, the remaining droplets may not be removable, so the distance between the discharge nozzle 10 and the cover 40 needs to be set to a predetermined distance or more. Specifically, the distance between the tip surface 11 and the receiving surface 46, and the distance between the outer surface 10c and the inner wall surface 47 are each desirably about 1 μm to 1 mm.

[0027] The cover 40 is provided with an alignment mechanism (not shown) for positioning the relative position in the direction intersecting the discharge direction of the discharge nozzle 10, and is arranged so that the opening 43 and the discharge port 10a of the discharge nozzle 10 are coaxial.

[0028] The inner surface of the opening 43 has a straight surface portion 45 with a uniform inner diameter on the discharge nozzle 10 side, and a tapered surface portion 44 that is continuous with the straight surface portion 45 and whose diameter expands in a tapered shape toward the discharge direction of the liquid droplets. The inner diameter of the straight surface portion 45 is set larger than that of the discharge port 10a. This is because the width of the discharged liquid droplet 2 becomes about 10 μm larger than the inner diameter of the discharge port 10a due to the action of surface tension, etc. Therefore, the inner diameter of the straight surface portion 45 is set to be about 10 μm or more larger than that of the discharge port 10a.

[0029] Further, the inner diameter of the straight surface portion 45 is set smaller than the outer diameter of the tip surface 11. This is to ensure the flow velocity of the gas sucked from the opening 43 and effectively remove the remaining droplets.

[0030] The inclination angle of the tapered surface portion 44 is not particularly limited, but is preferably about 30 degrees to 60 degrees from the viewpoint of generating a predetermined air flow to remove the remaining droplets or ensuring the straightness of the liquid droplets 2.

[0031] The material of the cover 40 is appropriately selected from resin, metal materials, ceramic materials, etc. For example, in the case of resin materials, PEEK, PPS, ABS, etc., in the case of metal materials, stainless steel, nickel, aluminum, etc., and in the case of ceramic materials, alumina, zirconia, silicon dioxide, etc. are selected.

[0032] The decompression unit 50 generates a negative pressure in the suction path 49 between the discharge nozzle 10 and the cover 40 to suck the gas. Since the sucked gas may contain extra liquid droplets, the decompression unit 50 includes a filter for separating the air flow and the liquid droplets, a tank for storing the separated liquid droplets, etc. Note that a vacuum pump or the like may be used to generate the negative pressure.

[0033] FIGS. 3A and 3B show a state in which the droplet discharge device 1 according to the present disclosure discharges the droplets 2. When the liquid in the liquid chamber 20 is pressurized by the pressurization unit 30, the liquid passing through the discharge nozzle 10 becomes droplets 2 and is discharged from the discharge port 10a. The discharged droplets 2 pass through the opening 43 provided in the cover 40 coaxially with the discharge port 10a and are applied onto a substrate (not shown) or the like.

[0034] When discharging the droplet 2, the decompression unit 50 generates a negative pressure in the suction path 49 and sucks 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 in a direction away from the opening 43 through the space between the tip surface 11 of the discharge nozzle 10 and the receiving surface 46, and then flows in the direction of the proximal end of the discharge nozzle 10 through the space between the outer surface 10c of the discharge nozzle 10 and the inner wall surface 47 of the cover 40. Then, it is sucked by the decompression unit 50.

[0035] Figures 3A and 3B show the residual droplets 3 adhering to the peripheral edge of the opening 43 when discharging the droplet 2. The inner diameter of the opening 43 is set larger than the width of the droplet 2, but in some cases, the residual droplets 3 may adhere. At this time, the residual droplets 3 are removed from the peripheral edge 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.

[0036] Figure 4 shows the flow velocity distribution in the Z-axis direction of the gas sucked into the suction path 49 through the opening 43. The solid line indicates the case where the length of the straight surface portion 45 in the Z-axis direction is short, and the dotted line indicates the case where the length of the straight surface portion 45 in the Z-axis direction is long. The flow velocity is slower at the center side and faster at the outer peripheral side with respect to the inner diameter of the opening 43. When the length of the straight surface portion 45 in the Z-axis direction is short, the faster-flowing portion is located more outside than when 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 discharged droplet 2 is less affected by the air flow, and the minute droplets do not scatter around and are applied while maintaining straightness.

[0037] 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 toward the inside of the opening 43. Due to this flow, the remaining droplets adhering to the peripheral edge of the tapered surface portion 44 move toward the inside of the opening 43 and are more likely to be sucked toward the suction path 49. Therefore, by forming the tapered surface portion 44 and making the straight surface portion 45 as short as possible, the remaining droplets 3 adhering to the peripheral edge of the tapered surface portion 44 are more likely to be sucked into the suction path 49 by the airflow.

[0038] The droplets adhering to the straight surface portion 45 or the tapered surface portion 44 at the peripheral edge of the cover 40 can be sucked in by the airflow in the Z direction. Moreover, even if there are any remaining droplets 3 left at the peripheral edge of the cover 40, with the tapered surface portion 44, they are located about the radius distance away from the ejected droplets 2, so they do not interfere with the droplets 2.

[0039] It is desirable that the length of the straight surface portion 45 in the Z-axis direction is short in terms of the straightness of the ejected droplets 2 and the suction property of the remaining droplets 3. Although it is not essential to provide the straight surface portion 45, even when the straight surface portion 45 is formed due to processing requirements or the like, it is desirable to make the straight surface portion 45 as short as possible.

[0040] Figs. 5A and 5B show a comparative example in which no tapered surface portion is formed in the opening 43. Assuming that the inner diameter of the straight surface portion 61 is the same as that in the examples of Figs. 3A and 3B, as shown in Fig. 4, since the portion where the flow velocity of the sucked airflow is fast is generated closer to the center of the opening 43, the droplets 2 are affected by the airflow and their shape collapses, and they are likely to adhere to the peripheral edge of the opening 43. Also, the velocity of the sucked airflow at the peripheral edge of the opening 43 is slow, and since there is little airflow toward the center of the opening 43, the remaining droplets 3 are difficult to be sucked into the suction path 49 and are difficult to be removed.

[0041] Moreover, when the droplets 2 and the remaining droplets 3 come into contact, it may not be possible to ensure a predetermined coating amount or the straightness of the droplets 2 may not be ensured. Furthermore, the droplets adhering to the straight surface portion 61 at the peripheral edge of the cover 40 cannot be sucked in by the airflow in the Z direction and remain, interfering with the ejection of the droplets 2.

[0042] As described above, since the discharge nozzle 10 of the present embodiment has a flat front end surface 11 without a recess formed therein, droplets are likely to be removed even if they adhere to the periphery of the discharge port 10a. Further, since the tapered surface portion 44 is formed in the opening 43 formed in the cover 40, the straightness of the droplets 2 is ensured, and the remaining droplets 3 adhering to the peripheral edge of the opening 43 are also likely to be removed.

[0043] Further, when applying the minute droplets 2 onto the substrate, in order to ensure the required application amount, the discharge nozzle 10 may discharge more than the required application amount. Although a part of the discharged droplets 2 may scatter and adhere to the discharge nozzle 10 or the cover 40, the adhering remaining droplets 3 are removed by the airflow sucked into the suction path 49, and the required application amount is accurately applied onto the substrate.

[0044] <Modification Example 1> FIGS. 6A and 6B show a modification example of the cover 40 in the present embodiment. In manufacturing the cover 40, a vertical wall surface 71 perpendicular to the XY plane, which is an inner surface perpendicular to the receiving surface 46, may be provided at the lower end portion of the inner wall surface 47 and the receiving surface 46 facing the front end surface 11 of the discharge nozzle 10 (FIG. 6A).

[0045] Further, the cover 40 may have the vertical wall surface 71 and the receiving surface 46 connected to the vertical wall surface 71 by a curved surface R (FIG. 6B). Thereby, it is easier to process and mold than in the above-described embodiment, and it is possible to achieve both ensuring the required performance and reducing the member cost. Further, by providing the curved surface R, it becomes difficult for the remaining droplets to adhere to the inner surface of the cover 40.

[0046] <Modification Example 2> FIGS. 7A and 7B show a modification example of the discharge nozzle 10 in the present embodiment. The corner between the front end surface 11 of the discharge nozzle 10 and the outer surface 10c of the discharge nozzle 10 may be a curved surface R' (FIG. 7A).

[0047] Further, a chamfered portion 81 having a conical surface shape may be provided on the outer peripheral edge portion of the tip surface 11 of the discharge nozzle 10 toward the discharge port 10a of the discharge nozzle 10 from the curved surface R' (FIG. 7B). This makes it easier to remove the remaining droplets adhering to the discharge nozzle 10. Note that the chamfered portion 81 is not limited to a shape in which the outer peripheral edge portion of the tip surface 11 of the discharge nozzle 10 has a conical surface shape, and a chamfered portion 81 having a conical surface shape without any flat surface on the tip surface 11 may be provided.

[0048] <Modification 3> FIG. 8 shows a further modification of the cover 40. When a chamfered portion 81 is provided on the tip surface 11 of the discharge nozzle 10 toward the discharge port 10a, a conical tapered portion 91 may be provided on the receiving surface 46, which is the inner surface of the cover 40 facing the chamfered portion 81, so as to be substantially parallel to the chamfered portion 81. The tapered portion 91 being substantially parallel to the chamfered portion 81 includes cases where the tapered portion 91 and the chamfered portion 81 are not completely parallel due to dimensional errors, design errors, etc.

[0049] In Modification 2, the distance between the tip surface 11 and the receiving surface 46 increases toward the outside, causing the gas flow velocity to decrease. However, in Modification 3, the distance does not increase, so the gas flow velocity does not decrease, making it easier to remove the droplets.

[0050] The embodiments have been described above, but the present disclosure is not limited to the above embodiments.

[0051] In addition, forms obtained by applying various modifications conceivable by those skilled in the art to each of the embodiments, or forms realized by arbitrarily combining the components and functions in each of the embodiments without departing from the spirit of the present disclosure are also included in the present disclosure.

Industrial Applicability

[0052] The present disclosure can be used in a droplet discharge device capable of stabilizing the discharge amount, speed, and straightness of the discharged droplets.

Description of Reference Numerals

[0053] 1 Droplet ejection device 2 Droplet 3 Remaining droplet 10 Ejection nozzle 10a Ejection port 10b Inner surface 10c Outer surface 11 Tip surface 19 Housing 20 Liquid chamber 30 Pressurizing unit 40 Cover 41 Tip wall portion 42 Side wall portion 43 Opening 44 Tapered surface portion 45 Straight surface portion 46 Receiving surface 47 Inner wall surface 49 Suction path 50 Vacuum unit 71 Vertical wall surface 81 Chamfered portion

Claims

1. A discharge nozzle having a planar tip surface for discharging droplets, A cover having an opening through which the droplets pass and covering the discharge nozzle, Comprising, A droplet discharge device having a suction path between the discharge nozzle and the cover.

2. The thickness of the tip of the discharge nozzle is 5 μm to 3 mm, The droplet discharge device according to Claim 1.

3. A discharge nozzle having a tip surface for discharging droplets, A cover having an opening through which the droplets pass and covering the discharge nozzle, Comprising, A droplet discharge device in which the diameter of the opening expands in the droplet discharge direction.

4. The corner between the tip surface and the side surface of the discharge nozzle is a curved surface, The droplet discharge device according to Claim 1 or 3.

5. The tip surface has a chamfered portion in a conical surface shape at the outer peripheral edge portion, The droplet discharge device according to Claim 1 or 3.

6. The inner surface of the cover facing the chamfered portion is substantially parallel to the chamfered portion, The droplet discharge device according to Claim 5.

7. The cover has a bottom surface facing the tip surface and an inner surface perpendicular to the bottom surface, The droplet discharge device according to Claim 1 or 3.

8. The cover has a bottom surface facing the tip surface and an inner surface connected to the bottom surface by a curved surface, The droplet discharge device according to Claim 1 or 3.

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