Droplet ejecting apparatus

Abstract

The invention provides a liquid droplet ejecting apparatus capable of rapidly and accurately applying a pressure necessary for ejecting a liquid material in a liquid chamber even when the amount of drop of a plunger is small in order to eject tiny liquid droplets. The liquid droplet ejecting apparatus includes: a housing having a liquid chamber, an ejection port for ejecting a liquid material in the liquid chamber, and a supply port for supplying the liquid material into the liquid chamber; and a plunger having a small-diameter portion formed at a tip portion thereof and a large-diameter portion formed on a base end side of the small-diameter portion, the plunger being provided so as to be capable of reciprocating into the liquid chamber, and the large-diameter portion being provided so as to be capable of moving back and forth at a retracted end position where the plunger is retracted, the large-diameter portion being formed on a base end side of the small-diameter portion and the large-diameter portion being formed on a base end side of the small-diameter portion. At least a portion of the supply port faces a side surface of the small-diameter portion at a forward end position at which the plunger is advanced, and at least a portion of the supply port faces a side surface of the large-diameter portion at a forward end position at which the plunger is advanced.

Description

Technical Field

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

[0002] A droplet discharge device is known for applying liquid materials such as solder paste to substrates for mounting small electronic components (Patent Document 1). With the miniaturization of electronic components, there is a demand for droplet discharge devices that can discharge minute droplets with high precision.

[0003] Figure 7 This figure shows a conventional droplet ejection device 1. The droplet ejection device 1 includes a housing 2 having a liquid chamber 29 therein to which a liquid material 50 is supplied, and a plunger 3 whose tip is positioned within the liquid chamber 29 and is arranged to reciprocate vertically (in the ±Z directions).

[0004] The housing 2 includes a main body 21 forming a liquid chamber 29, a nozzle plate 24 forming a discharge port 25 and covering the liquid chamber 29 from below, and a cover 26 forming a plunger port 27 and covering the liquid chamber 29 from above. A supply path 23 is also formed in the main body 21, and the supply path 23 communicates with the liquid chamber 29 via a supply port 22 formed in a side wall 30 of the liquid chamber 29.

[0005] The plunger 3 is inserted into the plunger port 27. The plunger 3 is driven up and down by an actuator (not shown).

[0006] An annular seal 28 is provided on the inner peripheral surface of the plunger port 27 to seal the space between the cover 26 and the plunger 3 in a liquid-tight manner.

[0007] Figures 8A to 8C This is a diagram showing the operation when the plunger 3 is driven up and down to discharge the liquid droplets 51 . Figure 8A The plunger 3 is shown in a state where it has risen and is at the retreat end. The liquid material 50 is supplied from the supply path 23 to the liquid chamber 29 and filled.

[0008] Figure 8B The figure shows a state where the plunger 3 is lowered and at the forward end and droplets 51 are ejected from the ejection port 25. When the plunger 3 is lowered, the liquid material 50 in the liquid chamber 29 is pressurized, and the droplets 51 are ejected from the ejection port 25 under the action of the pressure.

[0009] Figure 8C The plunger 3 rises and is again at the retreat end. When the plunger 3 rises, the liquid material 50 is supplied to the liquid chamber 29 through the supply path 23 from the unillustrated tank and the state is restored. Figure 8A Status shown.

[0010] By repeatedly Figures 8A to 8CThe action of the plunger 3 repeatedly discharges the liquid droplets 51 toward the discharge object such as the substrate. The discharge speed and size of the discharged liquid droplets 51 are adjusted by controlling the speed and the amount of the plunger 3 to descend.

[0011] Prior art literature

[0012] Patent Literature

[0013] Patent Document 1: Japanese Patent Application Laid-Open No. 2015-221442 Summary of the Invention

[0014] When the volume change of the liquid material 50 caused by the pressure applied by the plunger 3 is negligible due to its incompressibility, the volume of the liquid droplet 51 is ideally proportional to the amount of descent of the plunger 3. Therefore, if the amount of descent of the plunger 3 is reduced, small droplets 51 should be ejected. However, in reality, if the amount of descent of the plunger 3 is small, the volume of the droplet 51 becomes smaller than the desired volume, and sometimes, depending on the situation, the droplet 51 cannot be ejected. The inventors of the present invention investigated the cause of this and found that, as described below, the pressure applied to the liquid material 50 in the liquid chamber 29 by the plunger 3 dissipates from the supply port 22 toward the supply path 23, and the pressure required to eject the droplet 51 from the ejection port 25 cannot be appropriately applied to the liquid material 50.

[0015] Figure 9A The flow of the liquid material 50 in the liquid chamber 29 when the plunger 3 descends is schematically shown. Figure 9B is a diagram showing the change in pressure in the liquid chamber 29 at this time. Figure 9A In the embodiment, if the plunger 3 descends, pressure is applied to the liquid material 50. However, due to this pressure, part of the liquid material 50 flows back toward the tank through the supply path 23. Therefore, the droplets ejected from the ejection port 25 are smaller than the amount of descent of the plunger 3.

[0016] Figure 9B The horizontal axis represents the pressurization time of the plunger 3 and the vertical axis represents the pressure in the liquid chamber 29. The solid line represents the case where the plunger 3 is lowered for a longer time to increase the amount of the plunger 3 lowered and then raised after maintaining the lowered state for a certain time. The dotted line represents the case where the plunger 3 is lowered for a shorter time to reduce the amount of the plunger 3 lowered and then raised immediately after the plunger is lowered. Figure 9AAs shown, as the plunger 3 descends, a portion of the liquid material 50 flows toward the supply path 23. This slows the rise in pressure within the liquid chamber 29, prolonging the time it takes to exceed the discharge pressure (the pressure required to overcome flow resistance at the discharge port and discharge the liquid material as droplets). As a result, the amount of plunger 3's descent is disproportionate to the volume of the droplet 51. As shown by the dashed line, if the plunger 3 descends too quickly, the plunger's descent may complete before the pressure within the liquid chamber 29 has sufficiently risen, resulting in no discharge of the droplet 51 at all.

[0017] Figure 10 This graph shows the relationship between the time it takes to lower the plunger 3 and the amount of liquid droplets discharged. If the time it takes to lower the plunger 3 is too short, the pressure in the liquid chamber will not exceed the discharge pressure, and thus no liquid will be discharged. If the plunger 3 is lowered within a specified time Tmin, droplets of a specified minimum discharge volume Vmin will be discharged. Therefore, while it is necessary to reduce Tmin and Vmin to discharge fine droplets, there are limitations in the conventional droplet discharge device 1.

[0018] As described above, in the conventional droplet ejection device 1 , the descending amount of the plunger 3 is not proportional to the amount of ejected droplets. Furthermore, it is difficult to reduce the minimum descending time Tmin and the minimum ejection amount Vmin at that time, making it difficult to eject fine droplets at high speed.

[0019] An object of the present invention is to provide a liquid droplet discharge device capable of quickly and accurately applying the pressure required for discharge of a liquid material in a liquid chamber even when the plunger is lowered a small amount in order to discharge fine liquid droplets.

[0020] The droplet ejection device of the present invention comprises: a shell having a liquid chamber, an ejection port for ejecting liquid material in the liquid chamber, and a supply port for supplying the liquid material into the liquid chamber; and a plunger having a small-diameter portion formed at a front end portion and a large-diameter portion having a larger diameter than the small-diameter portion and formed on a base end side of the small-diameter portion, the plunger being configured to enter the liquid chamber and be able to reciprocate, and at a retracted end position of the plunger being retracted, at least a portion of the supply port is opposite to a side surface of the small-diameter portion, and at an advanced end position of the plunger being advanced, at least a portion of the supply port is opposite to a side surface of the large-diameter portion.

[0021] According to the droplet ejection device of the present invention, when the plunger descends, the large-diameter portion blocks the supply port, hindering flow from the liquid chamber to the supply path. Furthermore, the presence of the small-diameter portion creates flow resistance between the small-diameter portion and the sidewalls of the liquid chamber, hindering flow from the liquid chamber to the supply path. Consequently, the plunger's descent rapidly increases the pressure of the liquid material within the liquid chamber, enabling the rapid and highly precise ejection of tiny droplets. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a diagram showing a liquid droplet ejecting device.

[0023] Figure 2 It is a diagram showing details of the liquid droplet ejection device.

[0024] Figure 3A This is a diagram showing a state where the plunger is at the retreat end.

[0025] Figure 3B 1 is a diagram showing a state where the plunger is at the advanced end.

[0026] Figure 3C It is a diagram showing a state where the plunger is rising.

[0027] Figure 4A It is a diagram showing the flow of the liquid material when the plunger descends.

[0028] Figure 4B Graph showing changes in pressure in the liquid chamber when the plunger descends.

[0029] Figure 5A This is a graph showing the relationship between the pressurization time by the plunger and the droplet discharge speed.

[0030] Figure 5B This is a graph showing the relationship between the pressurization time by the plunger and the droplet discharge speed.

[0031] Figure 6A This is a diagram showing a state where fine particles are crushed by the front end surface of the plunger.

[0032] Figure 6B This is a diagram showing a state in which the crushing of the fine particles by the front end surface of the plunger is prevented.

[0033] Figure 7 This is a diagram showing a conventional liquid droplet ejection device.

[0034] Figure 8A This is a diagram showing a state in which a conventional plunger is at the retreat end.

[0035] Figure 8B This is a diagram showing a state where a conventional plunger is at the advanced end.

[0036] Figure 8C This is a diagram showing a conventional state where a plunger is raised.

[0037] Figure 9A This is a diagram showing the flow of a liquid material when a conventional plunger descends.

[0038] Figure 9B This is a diagram showing changes in the pressure in the liquid chamber when the conventional plunger descends.

[0039] Figure 10 This is a graph showing the relationship between the pressurization time and the discharge amount of the liquid droplet discharge device.

[0040] Description of Reference Numerals

[0041] 1 Droplet ejection device

[0042] 2 Housing

[0043] 4 plungers

[0044] 21 Main body

[0045] 22 Supply port

[0046] 221 upper edge

[0047] 222 lower edge

[0048] 23 Supply Road

[0049] 24 nozzle plate

[0050] 25 nozzle

[0051] 26 hood

[0052] 27 Plunger port

[0053] 28 seals

[0054] 29 Liquid Chamber

[0055] 30 sidewalls

[0056] 41 small path

[0057] 42 Large diameter part

[0058] 43 cone

[0059] 50 liquid materials. DETAILED DESCRIPTION

[0060] The following describes an embodiment of the present invention with reference to the accompanying drawings. It should be noted that the embodiments described below each illustrate a specific example of the present invention. Therefore, the various components, the configuration positions of the components, and the connection methods shown in the following embodiments are examples and are not intended to limit the present invention. In addition, components not described in the independent technical solutions among the components of the following embodiments are described as arbitrary components.

[0061] In addition, each figure is a schematic diagram and does not necessarily illustrate the true image. It should be noted that in each figure, the same reference numerals are attached to substantially the same structure, and repeated descriptions are omitted or simplified.

[0062] Figure 1This figure shows the overall structure of a droplet ejection device 1 according to the present invention. The droplet ejection device 1 comprises a housing 2 having a liquid chamber 29 therein, into which a liquid material 50 is supplied, and a plunger 4 , the distal end of which is positioned within the liquid chamber 29 and is arranged to reciprocate vertically (in the ±Z directions).

[0063] The housing 2 includes a main body 21 forming a liquid chamber 29, a nozzle plate 24 forming a discharge port 25 and covering the liquid chamber 29 from below, and a cover 26 forming a plunger port 27 and covering the liquid chamber 29 from above. A supply path 23 is also formed in the main body 21. The supply path 23 communicates with the liquid chamber 29 via a supply port 22 formed in a side wall 30 of the liquid chamber 29.

[0064] The discharge port 25 is an opening for the liquid material 50 pressurized by the plunger 4 to pass through and be discharged toward an object, and its diameter is designed according to the type of the liquid material 50 , the size of the discharged droplets, and the like.

[0065] The plunger 4 is inserted into the plunger port 27. The plunger 4 is driven up and down by an actuator (not shown).

[0066] An annular seal 28 is provided on the inner peripheral surface of the plunger port 27. The seal 28 seals the space between the cover 26 and the plunger 4 in a liquid-tight manner.

[0067] Figure 2 This figure shows details of the plunger 4. The plunger 4 has a small-diameter portion 41 at the distal end (lower end) and a large-diameter portion 42 at the proximal end (above) of the small-diameter portion 41. A tapered portion 43 is formed between the small-diameter portion 41 and the large-diameter portion 42, which increases in diameter from the small-diameter portion 41 toward the large-diameter portion 42.

[0068] A gap 31 is formed between the small-diameter portion 41 and the side wall 30 of the liquid chamber 29. Furthermore, a gap 32 is formed between the large-diameter portion 42 and the side wall 30. The gap g1 of the gap 31 is a gap that appropriately acts as a flow resistance on the liquid material 50 by suppressing the flow of the liquid material 50 from the liquid chamber 29 through the gap 31 toward the supply path 23 when the plunger 4 descends and pressurizes the liquid material 50 within the liquid chamber 29. Furthermore, the gap g1 is a gap that allows the liquid material 50 to quickly flow through the gap 31 and into the liquid chamber 29 when the liquid material 50 is supplied from the supply path 23 to the liquid chamber 29 using pressure from a pump (not shown). Specifically, the gap g1 is set so that the liquid material 50 is difficult to flow under pressure due to the descent of the plunger 4, but is easily flowable under pressure from a pump or the like. When the liquid material 50 contains particles such as solder paste, the gap g1 is set to about 12 to 20 times the diameter of the particles so that the particles are not crushed between the small diameter portion 41 and the side wall 30 when the plunger 4 moves up and down.

[0069] Here, the shape of the microparticles in this embodiment is defined as follows. A liquid material is used in which 90% or more of all particles are spherical particles whose ratio of the major diameter to the minor diameter is 1.2 or less, and the major diameter is set as the diameter of the microparticles. In addition, the particle size is measured, for example, by the following method. (1) Observe and measure the particles using a microscope. (2) Measure using a sieve-type particle size distribution measuring device using a sieve with a predetermined particle range. (3) Measure the particle size distribution of the microparticles contained in the liquid material using a laser diffraction particle size distribution measuring device, and set the average value as the particle size. There are various methods for measuring the diameter of microparticles, but (3) is adopted in this embodiment.

[0070] return Figure 2 The gap g2 of the gap 32 is set so that the amount of liquid material flowing into the gap 32 is minimized. However, when the liquid material contains fine particles, such as solder paste, the gap g2 is set to approximately 1.5 to 2 times the diameter of the fine particles so that the fine particles are not crushed between the large diameter portion 42 and the side wall 30 when the plunger moves up and down.

[0071] The retracted end position of the plunger 4 after its ascent is set so that the lower end 421 of the large-diameter portion 42 is located above the lower edge 222 of the supply port 22 and the side surface of the small-diameter portion 41 faces at least a portion of the supply port 22. Alternatively, the position may be set so that the lower end 421 is located above the upper edge 221 of the supply port 22 and the entire supply port 22 faces the side surface of the small-diameter portion 41.

[0072] The plunger 4 is positioned at its advanced end after descending, so that the lower end 421 of the large-diameter portion 42 is positioned below the upper edge 221 of the supply port 22 and the side surface of the large-diameter portion 42 faces at least a portion of the supply port 22. Alternatively, the plunger 4 may be positioned so that the lower end 421 is positioned below the lower edge 222 and the entire supply port 22 faces the side surface of the large-diameter portion 42.

[0073] Figures 3A to 3C This is a diagram showing an example of the operation of the plunger 4 of the present invention when it moves up and down. Figure 3A The plunger 4 is shown in a state where it is at the rear end after being raised. The lower end portion 421 of the large diameter portion 42 is located at substantially the same height as the upper edge 221 of the supply port 22 .

[0074] The liquid material 50 is pressurized by a pump (not shown) and supplied from the supply port 22 to the liquid chamber 29 through the gap 31. At this time, the liquid material 50 flows smoothly through the gap 31 and is supplied to the liquid chamber 29 quickly.

[0075] Figure 3BThe plunger 4 is shown driven downward by an actuator (not shown) and positioned at its forward end. The liquid material 50 in the liquid chamber 29 is pressurized by the plunger 4, and this pressure causes droplets 51 to be ejected from the ejection port 25. At this point, the lower end 421 of the large-diameter portion 42 has descended to a position below the lower edge 222 of the supply port 22.

[0076] When the plunger 4 descends, the side surface of the large-diameter portion 42 moves to a position opposite the supply port 22, blocking the supply port 22. This makes it difficult for the pressurized liquid material 50 to flow into the supply path 23. Furthermore, the gap 31 between the small-diameter portion 41 and the side wall 30 is narrow, making it difficult for the liquid material 50 to flow through the gap 31 due to flow resistance, making it difficult for the liquid material 50 in the liquid chamber 29 to flow into the supply path 23. Consequently, the pressure applied to the liquid material 50 by the plunger 4 does not cause the liquid material 50 to flow back into the supply path 23. Instead, substantially all of the pressure applied by the plunger 4 acts as pressure for ejecting the liquid droplets 51, enabling the rapid and efficient ejection of the tiny droplets 51.

[0077] Figure 3C The figure shows the state where the plunger 4 is raised and located at the raised end. When the plunger 4 is raised, the lower end 421 of the large diameter portion 42 moves to a position above the lower edge 222 of the supply port 22, and the liquid material 50 is supplied from the supply port 22. At this time, since the gap 31 between the side surface of the small diameter portion 41 and the side wall 30 is set to a level that does not hinder the supply of the liquid material 50, the liquid material 50 is quickly supplied to the liquid chamber 29 and returned to the liquid chamber 29. Figure 3A status.

[0078] Figure 4A The flow of the liquid material 50 in the liquid chamber 29 when the plunger 4 descends is schematically shown. Figure 4B is a diagram showing the change in pressure in the liquid chamber 29 at this time. Figure 4A In the embodiment of the present invention, if the plunger 4 descends, pressure is applied to the liquid material 50. Since the gap between the small-diameter portion 41 and the side wall 30 of the liquid chamber 29 is narrow, the liquid material 50 has difficulty flowing between the small-diameter portion 41 and the side wall 30. Furthermore, if the plunger 4 descends, the supply port 22 is blocked by the large-diameter portion 42, making it difficult for the liquid material 50 to flow toward the supply path 23. Therefore, it is possible to discharge a quantity of liquid droplets proportional to the amount of descent of the plunger 4.

[0079] Figure 4B The horizontal axis represents the pressurization time of the plunger 4 and the vertical axis represents the pressure in the liquid chamber 29. The solid line represents the case where the plunger 4 is lowered for a longer time to increase the amount of the plunger 4 lowered and then raised after maintaining the lowered state for a certain time. The dotted line represents the case where the plunger 4 is lowered for a shorter time to reduce the amount of the plunger 4 lowered and then raised immediately after the plunger is lowered. Figure 4A As shown in FIG, when the plunger 4 descends, the liquid material 50 flows into the supply path 23, so the pressure in the liquid chamber 29 rises rapidly. Then, when the discharge pressure exceeds the discharge pressure required for pressure discharge, the liquid material 50 is discharged from the discharge port 25.

[0080] When ejecting tiny droplets, the time required to pressurize the droplets is shortened, as indicated by the dotted line. In this embodiment, once pressurization begins, the pressure in the liquid chamber rises rapidly, shortening the time it takes for the pressure in the liquid chamber to exceed the ejection pressure. Consequently, tiny droplets can be ejected with a short pressurization period.

[0081] In this embodiment, when the plunger 4 begins pressurizing the liquid material 50, the pressure within the liquid chamber 29 rises rapidly. Therefore, the pressurization time is roughly proportional to the amount of droplets ejected (droplet size). When a small amount of droplet ejection is required, a short pressurization time is sufficient, while when a large amount of droplet ejection is required, a long pressurization time is sufficient. Consequently, the desired amount of droplets can be ejected quickly and appropriately.

[0082] Figure 5A as well as Figure 5B This is a graph showing the relationship between the time it takes to lower the plunger and the velocity of the ejected droplets. Solder paste containing solder particles with a particle size of 10 μm is used as the liquid material. Figure 5A This is the case where the liquid droplet ejection device of this embodiment is used. Figure 5B The case where a conventional droplet discharge device is used is shown. The plunger descending time T is the time when the discharge speed reaches the maximum in the conventional droplet discharge device, and the discharge speed at this time is set to 1.

[0083] exist Figure 5A Even if the descent time is shortened, the ejection velocity does not decrease. Figure 5B If the descending time is shortened, the ejection speed will decrease. Figure 5B If the falling time is short, the pressure in the liquid chamber will not rise sufficiently, so it is considered that even if the droplets are ejected, the speed will be reduced.

[0084] Therefore, in the liquid droplet ejection device of this embodiment, even if the time for pressurizing the liquid material 50 by the plunger 4 is short, minute liquid droplets can be ejected quickly.

[0085] Figure 6A as well as Figure 6B This figure explains the amount of descent of the plunger 4 when the liquid material 50 contains fine particles 52, such as solder paste. Figure 6A As shown in FIG. 1 , if the plunger 4 is too close to the nozzle plate 24, the particles 52 may be crushed by the front end surface of the plunger 4 and the nozzle plate 24. Figure 6BAs shown, at the forward end of the plunger 4 , the front end surface of the plunger 4 and the nozzle plate 24 are preferably spaced apart to such an extent that the fine particles 52 are not crushed. For example, a distance of 12 times or more of the diameter of the fine particles 52 is preferably ensured.

[0086] In this embodiment, the pressure of the liquid material 50 increases rapidly as the plunger 4 descends, so there is no need to increase the descending amount of the plunger 4 more than necessary. Therefore, the distance between the front end surface of the plunger 4 and the nozzle plate 24 can be appropriately ensured.

[0087] As described above, according to the liquid droplet ejection device 1 of the present invention, the pressure in the liquid chamber 29 increases rapidly as the plunger 4 descends, thereby enabling the rapid and highly accurate ejection of minute liquid droplets 51. Furthermore, since the fine particles 52 contained in the liquid material 50 are not crushed, the liquid droplets 51 can be ejected while maintaining the quality of the liquid material 50, thereby preventing problems such as clogging of the ejection port 25.

[0088] Industrial Applicability

[0089] The present invention can be suitably used as a liquid droplet ejecting device that ejects minute liquid droplets.

Claims

1. A liquid droplet ejection device, wherein: The droplet ejection device comprises: a housing having a liquid chamber, a discharge port for discharging the liquid material in the liquid chamber, and a supply port for supplying the liquid material into the liquid chamber; as well as The plunger has a small diameter portion formed at the front end portion and a large diameter portion having a larger diameter than the small diameter portion and formed on the base end side of the small diameter portion, and is configured to enter the liquid chamber and be reciprocatingly movable. At the retreat end position of the plunger, at least a portion of the supply port faces the side surface of the small-diameter portion. At the advanced end position of the plunger, at least a portion of the supply port faces a side surface of the large-diameter portion.

2. The liquid droplet ejection device according to claim 1, wherein: A tapered portion is formed between the small diameter portion and the large diameter portion, the diameter of which increases from the small diameter portion toward the large diameter portion.

3. The liquid droplet ejection device according to claim 1, wherein: The distance between the side surface of the small-diameter portion and the inner surface of the liquid chamber facing the side surface is 12 to 20 times the diameter of the fine particles contained in the liquid material.

4. The liquid droplet ejection device according to claim 1, wherein: The distance between the side surface of the large-diameter portion and the inner surface of the liquid chamber facing the side surface is 1.5 to 2 times the diameter of the fine particles contained in the liquid material.

5. The liquid droplet ejection device according to claim 1, wherein: At the advanced end position, the distance between the front end surface of the plunger and the inner surface of the liquid chamber facing the front end surface is 12 times or more the diameter of the fine particles contained in the liquid material.

6. The liquid droplet ejection device according to any one of claims 1 to 5, wherein: At the forward end position, the entire supply port faces the side surface of the large-diameter portion.

7. The liquid droplet ejection device according to any one of claims 1 to 5, wherein: At the retracted end position, the entire supply port faces the side surface of the small-diameter portion.

8. The liquid droplet ejection device according to claim 6, wherein: At the retracted end position, the entire supply port faces the side surface of the small-diameter portion.

Images