JP4735177B2 - Molten metal discharging apparatus, molten metal discharging method, and bump forming method - Google Patents

Description

  The present invention relates to a molten metal discharging apparatus, a molten metal discharging method, and a bump forming method using the discharging method.

  When mounting a semiconductor component such as an LSI (Large Scale Integration) on a build-up board or the like, soldering is performed during the mounting process in order to make an electrical connection.

  Conventional molten metal discharging apparatuses have been used for forming solder bumps on electrode pads of resin substrates such as build-up wiring boards, and forming solder balls on electrode pads in flip chip or chip size packages of semiconductor elements, for example. It was. Molten metal such as solder is dropped from a discharge port of a nozzle of the apparatus using a molten metal discharging apparatus, and solder bumps are formed on lands such as a semiconductor chip and a resin substrate.

A conventional molten metal discharge device includes a storage chamber that stores molten metal such as solder, a diaphragm that is an upper component of the storage chamber, and a piezoelectric element that pressurizes the molten metal in the storage chamber in a pulsed manner through the diaphragm. The nozzle hole was provided in the lower part of the storage chamber.
Bump formation by a conventional molten metal discharging apparatus has been performed by the following procedure.
(1) A predetermined pulse voltage is applied to the piezoelectric element to deform the diaphragm to increase the pressure in the storage chamber. (2) By increasing the internal pressure, the molten metal is discharged as a droplet from the nozzle hole. Once the deposited droplets are deposited on the lands on the substrate, and a plurality of droplets are repeatedly ejected until the total ejection amount reaches a desired amount, (4) the solder deposited on the substrate or the like is reheated, It was melted and integrated into a large-diameter bump (Patent Document 1).

  In the above-described conventional technology, it is necessary to repeatedly discharge the solder droplets for each land, and the work time is long and there is a problem in productivity. Therefore, depending on the total amount of solder necessary for forming bumps, The nozzle opening diameter was adjusted and set to increase the diameter of the discharged droplets. However, the nozzle opening diameter must be small enough so that the liquid droplets do not fall down on its own, and there is a limit to the expansion of the nozzle opening diameter, and the diameter of about 150 to 200 μm is the limit. For this reason, when forming a large-diameter bump corresponding to a land having a large area, the amount of solder of one droplet is still insufficient even when a droplet of solder having the maximum diameter (hereinafter referred to as a solder droplet) is dropped. Therefore, it was inevitable to supply the droplets multiple times.

  Therefore, in order to avoid the inconvenience described above, when the amount of solder necessary for the land is insufficient with one drop, a plurality of solder drops can be simultaneously discharged with one discharge operation. Nozzle holes were provided at the bottom of the storage chamber. The solder once dropped onto the lands from a plurality of nozzle holes was reheated after deposition, and became a molten state and integrated into a desired large-diameter bump (Patent Document 2).

JP 2003-334654 A (paragraph [0029], FIG. 1) JP 2003-318218 A (paragraph [0029], FIG. 4)

However, the molten metal discharge device having a plurality of nozzle holes disclosed in Patent Document 2 has the following problems.
Since the discharged solder droplets fly directly under each nozzle hole, a land must always exist directly under the nozzle hole, and the number of nozzle holes arranged is limited by the size of the land. Therefore, there is a problem that a predetermined amount of molten solder necessary for a large-diameter bump cannot be dropped onto a small land.

  The present invention has been made to solve such a problem, and an object of the present invention is to provide a molten metal discharging method and a molten metal discharging apparatus capable of discharging a desired amount of molten metal droplets. To do.

The molten metal discharge device of the present invention includes a storage chamber that has a plurality of nozzle holes arranged at equiangular intervals on a concentric circle at the bottom, and stores the molten metal; Pressurizing means for discharging droplets at the same time, and the central axes of the plurality of nozzle holes converge on an extension line and collide and integrate until the droplets reach the discharge target It is characterized by being arranged so as to fly vertically downward toward the discharged object .

Furthermore, the molten metal discharge method of the present invention comprises a plurality of nozzle holes arranged at equiangular intervals on a concentric circle at the bottom, and the central axes of the nozzle holes are converged on an extension line and discharged from the nozzle holes. The molten metal collides until it reaches the object to be ejected and is integrated and stored in a storage chamber arranged so as to fly vertically downward toward the object to be ejected , and the molten metal is pulsed The molten metal droplets are simultaneously ejected from a plurality of nozzle holes under pressure.

  According to the present invention, since the discharged molten metal droplets collide during flight, a molten metal discharge method capable of discharging a desired amount of droplets according to the number of nozzle holes can be realized. Moreover, the molten metal discharge apparatus which can use this discharge method can be provided.

Embodiment 1 FIG.
FIG. 1 is a longitudinal sectional view schematically showing a molten metal discharging apparatus according to the first embodiment. In the drawings, the same reference numerals denote the same or corresponding parts, and this is common throughout the entire specification. Further, the description of the constituent elements appearing in the whole specification is merely an example and is not limited to these descriptions.

  First, the structure of the molten metal discharge apparatus in Embodiment 1 is demonstrated, referring FIG. As shown in FIG. 1, the molten metal discharge device includes a discharge head 10 including a body 11, a solder tank 12, a heater 16, a piezoelectric element 17, a molten solder chamber 14, a nozzle plate 22, a table 30, and a control device 20. And is configured. The discharge head 10 has a mechanism for discharging the molten solder 13 in order to form the solder bumps 33. The table 30 is a table for placing the substrate 31 on which the bumps 33 are formed, and the substrate 30 is configured so that the solder droplets 37 discharged from the discharge head 10 can be dropped onto a predetermined land 32 disposed on the substrate 31. A mechanism for moving 31 is provided. The control device 20 performs control for discharging a desired amount of molten solder 13 from the discharge head 10 and control for moving the table 30 to a predetermined position.

  The substrate 31 is, for example, a substrate, a semiconductor chip, or a semiconductor wafer. The substrate is a resin substrate such as a printed circuit board, a build-up wiring board, or a flexible printed wiring board, a ceramic substrate, a glass substrate, or the like, and is not limited to these as long as it is a substrate on which bumps are formed.

Further, the land 32 may be anything as long as it is an electrode for forming a solder bump. The electrode here is, for example, an electrode pad provided on a semiconductor substrate such as silicon, a glass substrate, or a ceramic substrate, or provided on a semiconductor substrate such as silicon, a glass substrate, or a ceramic substrate. In addition to these, a gold stud bump, a pad provided on a resin substrate such as a build-up substrate or a printed substrate, and other semiconductor substrates such as silicon, glass substrates, ceramic substrates, etc. Alternatively, a through hole (referred to as a via hole or a through hole) provided in a resin substrate or the like is also included.
The above is only an example of an electrode and is not limited to these descriptions.

Hereinafter, the discharge head 10 will be described in detail.
In FIG. 1, a body 11 has a function as a casing for fixing components (for example, a solder tank 12) of the discharge head 10, and a lower portion of the body 11 is filled with molten solder 13. A molten solder chamber 14 is disposed, and a heater 16 is installed on the outer periphery of the body 11 to keep the solder in a molten state. A solder tank 12 is housed inside the body 11. The molten solder chamber 14 is connected to a solder tank 12 provided on the upper portion of the body 11 by a solder supply path 15 and supplied with molten solder 13. A thin plate-like diaphragm 21 is attached to the upper surface of the molten solder chamber 14.

  Further, the piezoelectric element 17 is attached in close contact with the upper surface of the diaphragm 21, and the piezoelectric element 17 pressurizes and presses the diaphragm 21 in a pulsed manner to discharge solder droplets 37 from the plurality of nozzle holes 23. A flat nozzle plate 22 is disposed on the bottom surface of the molten solder chamber 14, and the nozzle plate 22 is attached to the body 11 side by a holding body 18. That is, the molten solder chamber 14 has a nozzle plate 22 having a plurality of nozzle holes 23 at the bottom, a diaphragm 21 at the top, and a molten metal storage chamber comprising a holding body 18 on the side surface.

  A plurality of nozzle holes 23 are arranged at the center of the nozzle plate 22, and the center axis of each nozzle hole 23 is inclined at a predetermined angle with respect to the vertical direction. The center axis of each nozzle hole 23 is The plurality of nozzle holes 23 are arranged so as to converge on the extension line.

In FIG. 1, two nozzle holes 23 are shown. Solder droplets 37 are discharged from the nozzle holes 23 in the direction of the central axis. The discharged solder droplets 37 collide with each other after discharge to be integrated, become large-diameter solder droplets 38 and are dropped onto the lands 32 on the substrate 31 to form bumps 33.
Further, the holding body 18 is provided with an inert gas supply path 19 and is connected to an inert gas supply source (not shown), and an inert gas (for example, N ₂ gas, Ar) is provided in the vicinity of the nozzle hole 23. Gas or the like) is supplied to prevent the solder droplet 37 from becoming a large diameter solder droplet 38 in the process of oxidation.

  The main feature of the molten metal discharging apparatus in the first embodiment is that a plurality of nozzle holes 23 are arranged in the nozzle plate 22, and the central axis of each nozzle hole 23 is focused on an extension line in the discharge direction of the molten metal. . Note that “the central axes of the plurality of nozzle holes converge on the extension line in the ejection direction” means that the extension lines of the central axes of the nozzle holes intersect to form a focal point.

  FIG. 2 is a schematic diagram for explaining this feature. FIG. 2A is an enlarged view of the nozzle plate 22 shown in FIG. 2B is a plan view when the nozzle plate 22 is viewed from the lower side of FIG. That is, it is a state of the nozzle hole 23 when the nozzle plate 22 is viewed from the outside of the molten metal discharging apparatus. A dashed line shown in FIG. 2A indicates the central axis of the nozzle hole 23. The nozzle holes 23 are arranged so that the central axes of the two nozzle holes 23 intersect on the extension line. Similarly, the alternate long and short dash line shown in FIG. The arrow at the tip of the alternate long and short dash line indicates the discharge direction of the molten metal. Moreover, the broken line shown in (b) in FIG. 2 is a hidden line and indicates the central axis on the molten solder chamber 14 side. In other words, the central axis of each nozzle hole is focused on an extension line outside the nozzle plate (downward in the drawing in FIG. 2A) to form a focal point. The center axis of the nozzle hole means the center line of the nozzle hole. Note that it is not a rod-like object like a shaft.

  Next, a method for forming the bumps 33 on the substrate 31 using the molten metal discharging apparatus will be described with reference to FIGS. FIG. 3 is an enlarged view of the nozzle plate portion of the apparatus shown in FIG. 1, and is a schematic diagram showing a process in which solder droplets discharged from each nozzle hole of the nozzle plate collide and are integrated.

  In FIG. 3, when the piezoelectric element 17 pushes the diaphragm 21 in a pulsed manner, the pressure in the molten solder chamber 14 rises, and the flow of solder along the central axis of the nozzle hole 23 occurs. Therefore, a plurality of solder droplets 37 are simultaneously ejected in the direction of the central axis of the nozzle hole 23 as shown in FIG. Since the central axes are arranged so as to converge on the extension line, the discharged solder droplets 37 collide at the focal point as shown in FIG. Due to the collision, the horizontal velocity component of each solder droplet 37 is canceled out, and as shown in FIG. 3C, it becomes one large diameter solder droplet 38 and flies vertically downward toward the land. Here, since the inert gas is supplied around the nozzle hole 23, formation of an oxide film on the surface of the solder droplet is suppressed, and integration can be performed without being inhibited by the oxide film.

  Further, a method for forming bumps on the substrate will be described. As shown in FIG. 1, a substrate 31 is mounted on the table 30 in advance, and the table 30 is moved by the control of the control device 20 so that a desired land 32 is directly below the ejection head 10. After being moved to a predetermined position, the control device 20 performs control for discharging the molten solder 13 from the discharge head 10 to the piezoelectric element 17. As described above, the large-diameter solder droplets 38 are caused to fly and the solder is dripped onto the desired lands 32 disposed on the substrate 31 to form the large-diameter bumps 33 on the substrate 31.

  According to the method for discharging molten metal in the first embodiment, since the central axes of the plurality of nozzle holes 23 are arranged so as to converge on the extension line, the solder droplets 37 are discharged from the plurality of nozzle holes 23, and the substrate Each solder droplet 37 collides and integrates until it reaches 31, so that a desired amount of solder droplets 38 corresponding to the number of nozzle holes can be ejected. In addition, by using a molten metal discharge device that can use this discharge method, a large-diameter solder droplet 38 can be dropped on the land 32 to form a desired large-diameter bump 33 on the substrate 31.

  In addition, since it is possible to drop a large amount of solder according to the number of nozzle holes 23 at a time, it is possible to discharge a desired amount of solder with a single pressurizing operation, and it is possible to discharge molten metal with high work efficiency. Equipment can be provided.

Furthermore, a method of manufacturing the solder bump 33 that omits the fusion integration step after dropping onto the land 32 is possible, and the formation of an oxide film on the surface of the solder droplet during reheating is suppressed, which causes a decrease in the bonding strength of the solder. A large-diameter bump 33 with less contained oxide can be formed.
That is, in the conventional method, the individual solder droplets accumulated on the land are reheated in a later step and are melted and integrated. During this reheating process, the solder surface is oxidized to produce oxides, and voids are involved in the oxides to melt and integrate the solder. There was a possibility of becoming. However, in the method of the first embodiment, since the fusion integration step after dropping on the land can be omitted, such a problem does not occur.

Moreover, since the fusion | melting integration process after dripping at the land 32 can be skipped, it leads to the improvement of productivity. Further, an apparatus for supplying N ₂ gas to the substrate for the purpose of preventing oxidation at the time of reheating becomes unnecessary, and the entire molten metal discharging apparatus can be configured compactly.
That is, in the conventional molten metal discharging apparatus, N ₂ gas is supplied in the vicinity of the nozzle to prevent oxidation of the solder droplet immediately after discharging. In the reheating step, it is necessary to avoid the oxidation of the solder deposited on the land, and an apparatus for supplying N ₂ gas around the land is necessary. Therefore, there is a problem that the entire apparatus becomes large. However, in the apparatus of the first embodiment, such a problem does not occur because the fusion integration step after dropping onto the land can be omitted.

Here, an advantage of “the ejected solder droplets collide before reaching the substrate” will be described. Usually, the substrate 31 is not an ideal flat plate without unevenness but has a bend. For example, in the case of a resin substrate, since there is a bend of 0.5 mm to 1.0 mm, the distance between the ejection head 10 and the land 32 is between 0.5 mm and 1.0 mm, and differs for each land. If the focal point where the solder droplets 37 collide with each other is “on the land”, the focal point of the central axis of each nozzle hole 23 must be adjusted for each land.
However, in the first embodiment, since the solder droplets 37 are collided and coalesced during the flight until reaching the substrate 31, it is not necessary to adjust the focal point even for the substrate having the deflection. Operation of a typical device becomes possible. Therefore, it is possible to provide a method for producing a large-diameter bump with a high productivity and a small amount of contained oxide even for a substrate having bending.

Further, a large-diameter solder droplet 38 can be dropped on the land 32 narrower than the pitch of the nozzle holes 23.
That is, in the conventional molten metal discharging apparatus, since the solder droplets fly right below each nozzle hole, the solder droplets are collected on the land of the substrate at a pitch equal to the arrangement pitch of the nozzle holes. Therefore, there must be a land directly under the nozzle hole. If solder is dropped onto a land having a width smaller than the arrangement pitch of the nozzle holes, the solder droplet is dropped outside the land. It became the result. Further, the pitch of the nozzle holes could not be reduced indefinitely due to machining restrictions. However, in the apparatus of the first embodiment, the arrangement of the nozzle holes is not limited to the size of the land, so that the number of nozzle holes necessary for discharging a desired amount of solder by one pressurizing operation can be arranged. . Therefore, a desired amount of solder droplets 38 can be dropped on a small land.

Although FIG. 1 and FIG. 3 show the case where there are two nozzle holes 23, the number of molten metal discharge devices of the first embodiment is not limited to two, and there may be three or more. . In other words, the central axis of the nozzle hole 23 may be converged on an extension line in the discharge direction and the discharged solder droplets 37 may collide at the focal point.
In addition, when the number of nozzle holes 23 is three or more, the mounting position accuracy can be improved as compared with the case where the nozzle holes 23 are arranged at equiangular intervals on a concentric circle. This is because the horizontal velocity component has a certain degree of variation and can be effectively canceled out by increasing the number of nozzle holes 23.

  Furthermore, if the nozzle holes 23 are arranged so that the droplets discharged from the plurality of nozzle holes 23 collide during flight, the nozzles “the central axes of the plurality of nozzle holes are not necessarily focused on the extension line” as described above. The arrangement state of the hole 23 is not required. Hereinafter, another embodiment will be described.

  FIG. 4A is a cross-sectional view of a nozzle plate 22 illustrating another embodiment. In FIG. 4A, the central axes of the two nozzle holes 23 do not intersect on the extension line, but are parallel to each other. The arrow shown in (a) in FIG. 4 indicates the traveling direction of the pressure wave generated by the piezoelectric element 17. In the form shown in FIG. 3 described above, a pressure wave is generated in the molten solder chamber 14 when the piezoelectric element 17 pushes the diaphragm 21 in a pulse manner. Here, for example, by providing an acoustic lens (not shown), the traveling direction of the pressure wave can be controlled. FIG. 4A shows an example in which a pressure wave is advanced toward each nozzle hole 23. Since the molten metal droplet is pushed out from each nozzle hole 23 by the pressure wave, it is discharged in the direction along the broken line in FIG.

  With the molten metal discharging apparatus having the above-described configuration, the droplets can be integrated by colliding with each other during the flight, so that it is possible to fly the molten metal droplets in an amount corresponding to the number of the nozzle holes 23. A possible method for discharging molten metal can be provided.

  Moreover, as another form, it is possible to bend the discharge direction of a molten metal using the wettability of a molten metal, and to make droplets collide during flight. Such a configuration will be described with reference to (b) to (d) in FIG. FIG. 4B is a cross-sectional view of the nozzle plate 22. 4C is a plan view when the nozzle hole portion of the nozzle plate 22 shown in FIG. 4B is viewed from the lower side (downward in FIG. 4B). is there. (D) in FIG. 4 is a diagram schematically illustrating a molten metal discharge process. FIG. 4B shows a state in which the protrusions 29 are provided on the opposite sides of the two nozzle holes 23, respectively. As shown in (c) of FIG. 4, the protrusion 29 has a shape surrounding a part of the periphery of the nozzle hole 23.

Next, a process of discharging solder droplets as molten metal will be described with reference to FIG. When the piezoelectric element 17 pushes the diaphragm 21 in a pulsed manner, the pressure in the molten solder chamber 14 increases, and the solder droplets 37 a and 37 c are pushed out from the nozzle hole 23. At this time, due to the wettability between the protrusion 29 and the solder, the solder droplets 37a and 37c are bent toward the protrusion 29 and discharged. The solder droplets indicated by reference numerals 37b and 37d are in a state where they are detached from the protrusion 29 and are flying. The solder droplets 37b and 37d whose ejection direction is bent collide with each other and become large-diameter solder droplets 38.
With the molten metal discharging apparatus having the above-described configuration, the solder droplets can be integrated by colliding with each other during the flight, so that it is possible to fly the solder droplets in an amount corresponding to the number of the nozzle holes 23, A large-diameter solder bump can be formed on the land.

Embodiment 2. FIG.
FIG. 5 is a vertical cross-sectional view schematically showing the molten metal discharging apparatus in the second embodiment. FIG. 7 is an enlarged view of the nozzle plate 25 portion of the apparatus shown in FIG. 5, and is a schematic diagram showing a process in which the solder droplets 37 discharged from the nozzle holes 27 of the nozzle plate 25 collide and are integrated. It is. FIG. 8 is a plan view showing the shape of the recess 26 provided at the center of the nozzle plate 25 shown in FIG. 7 and the arrangement of the nozzle holes 27 provided in the recess 26. (A) in FIG. 8 is an example in which the nozzle hole 27 is arranged on the side surface 28 of the truncated conical recess 26. 8B shows an example in which the nozzle hole 27 is disposed on the side surface 28 of the hexagonal truncated pyramid-shaped recess 26, and FIG. 8C shows the side surface 28 of the quadrangular pyramid-shaped concave portion 26. This is an example in which nozzle holes 27 are arranged.

  In the second embodiment, a plurality of nozzle holes 27 are arranged in the nozzle plate 25, and the central axis of each nozzle hole 27 converges on an extension line in the ejection direction, as in the first embodiment. The molten solder chamber 14 has a nozzle plate 25 having a plurality of nozzle holes 27 at the bottom, a diaphragm 21 at the top, and a molten metal storage chamber comprising a holding body 18 on the side surface. The main feature of the second embodiment is that the nozzle hole 27 is provided in the recess 26 of the nozzle plate 25.

First, a state in which the central axis of each nozzle hole 27 provided in the bottom portion is converged on an extension line in the discharge direction will be described with reference to FIG. FIG. 6 shows an example where there are two nozzle holes 27 in the recess 26. 6B is a plan view when the nozzle plate 25 is viewed from the lower side of the sheet of FIG. That is, it is a state of the nozzle hole 27 when the nozzle plate 25 is viewed from the outside of the molten metal discharge device. A dashed line shown in FIG. 6A indicates the central axis of the nozzle hole 27. The nozzle holes 27 are arranged so that the central axes of the two nozzle holes 27 intersect on the extension line. Similarly, the alternate long and short dash line shown in FIG. The arrow at the tip of the alternate long and short dash line indicates the discharge direction of the molten metal. Further, the broken line shown in FIG. 6B is a hidden line and indicates the central axis on the molten solder chamber 14 side.
That is, the center axis of each nozzle hole is focused on an extension line outside the nozzle plate (lower side of the paper surface in FIG. 6A) to form a focus.
For the sake of brevity, FIG. 6 shows two nozzle holes 27. Even if there are three or more nozzles, the central axis of each nozzle hole 27 converges on the extended line in the ejection direction as in the above description.

  Next, the structure of the molten metal discharge apparatus in Embodiment 2 is demonstrated, referring FIG.5, FIG.7 and FIG.8. Since the entire configuration of the molten metal discharging apparatus is the same as that of the first embodiment, the structure and function of the nozzle plate 25 characteristic of the second embodiment will be mainly described. Moreover, even if the recessed part 26 is the cone shape shown to (a) in FIG. 8 or the polygonal pyramid shape shown to (b) and (c) in FIG. 8, the effect mentioned later can be anticipated. The following description will be made without distinguishing (a) to (c) in FIG.

  As shown in FIGS. 5 and 8, a concave portion 26 that is depressed when viewed from the outside of the apparatus is provided in the central portion of the nozzle plate 25, and a plurality of nozzle holes 27 are provided on a side surface 28 of the concave portion 26. The nozzle holes 27 are arranged at equiangular intervals on a concentric circle with the center of the recess 26 as the center. In addition, each nozzle hole 27 is arranged such that the extension of the central axis converges at one point. That is, the central axis of each nozzle hole 27 is inclined at a predetermined angle with respect to the vertical direction, and the central axis of each nozzle hole 27 converges on an extension line in the discharge direction, so that each discharged solder droplet 37 is in focus. It becomes a collision.

  Further, the operation of discharging the solder droplet 37 will be described with reference to FIG. In FIG. 7, the piezoelectric element 17 pushes the diaphragm 21 in a pulsed manner, whereby the pressure in the molten solder chamber 14 rises, and the flow of solder along the central axis of the nozzle hole 27 occurs. Therefore, as shown in FIG. 7A, the solder droplets 37 are simultaneously discharged from the nozzle holes 27. Since the central axes are arranged so as to converge at one point, the discharged solder droplets 37 collide at the focal point as shown in FIG. As a result of the collision, the horizontal velocity component of each solder droplet 37 is canceled and becomes one large-diameter solder droplet 38 as shown in FIG. Here, since the inert gas is supplied around the nozzle hole 27, the formation of the oxide film on the surface of the solder droplet is suppressed, and the oxide film is integrated without being inhibited by the oxide film.

  In the second embodiment, since the nozzle hole 27 is disposed in the recess 26, the effects described in the first embodiment (depending on the fact that a large-diameter solder droplet can be dropped on the land and the number of nozzle holes) Solder can be dripped at once, large-diameter bumps with less oxide can be formed, the entire molten metal discharge device can be made compact, and it is also productive for substrates with flexure. In addition to the capability of forming a large-diameter bump and the ability to drop a large-diameter solder drop onto a small land, the specific effects of the second embodiment described below are added.

  In the discharging process of the solder droplet 37, the piezoelectric element 17 pushes the diaphragm 21 in a pulse manner, so that the internal pressure of the molten solder chamber 14 increases. The increased internal pressure acts on the nozzle plate 25 in the vertical direction. As shown in FIG. 7, since the nozzle hole 27 is disposed in the recess 26, the direction in which the internal pressure acts and the central axis of the nozzle hole 27 can be matched. For this reason, the discharge direction of the solder droplet 37 can be defined reliably, and an effect of suppressing variation in the flying direction of the solder droplet 37 is produced.

That is, the internal pressure generated in a pulsed manner should ideally be the same every time, but is actually slightly different. If the configuration in which the direction in which the internal pressure acts and the central axis of the nozzle hole 27 are deviated (when the two vector directions are different), the discharge direction of the solder droplet 37 is shifted every discharge. However, when the direction in which the internal pressure acts and the central axis of the nozzle hole 27 are matched, the central axis direction of the nozzle hole 27 always coincides with the discharge direction of the solder droplet 37 even if the internal pressure for discharging changes. This is because the discharge direction is not influenced by the internal pressure.
Therefore, it is possible to realize a molten metal discharge device that can drop the large-diameter solder droplet 37 onto the desired land 32 with high positional accuracy.

  Further, since the nozzle hole 27 is disposed in the recess 26, the distance between the focal point and the nozzle plate 25 can be shortened, and the distance between the nozzle hole 27 and the land 32 can be shortened. For this reason, even if the flying direction of the large-diameter solder droplets 38 deviates from the vertical direction for some reason, the large-diameter solder droplets 38 can be landed at a point close to a predetermined position. Therefore, bumps can be formed with high positional accuracy even on small lands.

  The nozzle holes 27 shown in FIG. 8 are arranged at equal angular intervals on the same circle, but are not limited to the example shown in FIG. For example, as shown in FIG. 9, the recess 26 may be hemispherical, and the nozzle hole 27 may be arranged on a double concentric circle. 9A is a schematic diagram of a longitudinal section of the nozzle plate 25 corresponding to FIG. 7A, and FIG. 9B is a plan view showing the arrangement of the nozzle holes 27. FIG. In the example shown in FIG. 9, since the focal point where each solder droplet 37 collides is the center of the hemisphere regardless of which nozzle hole 27 is in the hemispherical recess 26, each solder discharged from each nozzle hole 27 simultaneously. The droplet 37 collides with the focal point using the radius of the hemisphere as a track. Therefore, with this configuration, it is possible to provide a molten metal discharge device capable of discharging a desired amount of large-diameter solder droplets 38 corresponding to the number of nozzle holes 27.

  The arrangement of the nozzle holes 27 is such that the horizontal velocity component of each solder droplet 37 is offset, and the distance from the nozzle hole 27 to the focal point where each solder droplet 37 collides is the same. For example, it is not necessarily arranged in the hemispherical recess, and an arbitrary recess shape is possible.

It is the longitudinal cross-sectional view which showed typically the structure of the molten metal discharge apparatus which concerns on Embodiment 1 of this invention. It is the schematic diagram which showed the structure of the nozzle hole which concerns on Embodiment 1 of this invention. It is a schematic diagram which shows the process after the solder droplet discharge which concerns on Embodiment 1 of this invention. It is the schematic diagram which showed the modification of the discharge head which concerns on Embodiment 1 of this invention. It is the longitudinal cross-sectional view which showed typically the structure of the molten metal discharge apparatus which concerns on Embodiment 2 of this invention. It is the schematic diagram which showed the structure of the nozzle hole which concerns on Embodiment 2 of this invention. It is a schematic diagram which shows the process after the solder droplet discharge which concerns on Embodiment 2 of this invention. It is a top view of the nozzle plate principal part concerning Embodiment 2 of the present invention. It is a schematic diagram which shows the modification of the nozzle plate principal part which concerns on Embodiment 2 of this invention.

Explanation of symbols

10 Discharge head, 13 Molten solder, 14 Molten solder chamber, 17 Piezoelectric element,
19 Inert gas supply path, 21 Diaphragm, 22 Nozzle plate,
23 nozzle holes, 25 nozzle plates, 26 recesses, 27 nozzle holes,
28 Side surface of recess, 31 Substrate, 33 Bump, 37 Solder drop, 38 Large diameter solder drop

Claims (6)

A storage chamber for storing molten metal with a plurality of nozzle holes arranged at equiangular intervals on a concentric circle at the bottom;
Pressurizing means that pressurizes the molten metal in a pulsed manner to form droplets from a plurality of the nozzle holes and discharges them simultaneously;
The central axes of the plurality of nozzle holes converge on an extension line , collide and collide until the droplets reach the discharged object, and fly vertically downward toward the discharged object. A molten metal discharge device, characterized in that it is arranged. A recess is provided at the bottom of the storage room,
The molten metal discharging apparatus according to claim 1, wherein the plurality of nozzle holes are provided in the concave portion.   The molten metal discharging apparatus according to any one of 1 and 2, wherein means for supplying an inert gas to the nozzle hole is provided. A plurality of nozzle holes arranged at equiangular intervals on a concentric circle are provided at the bottom, and the central axes of the nozzle holes are converged on an extension line, so that the liquid droplets discharged from the nozzle holes reach an object to be discharged. The molten metal is housed in a storage chamber arranged so as to collide and integrate and fly toward the discharge target vertically downward ,
Discharging method of the molten metal, characterized in that discharging the droplets of the molten metal from a plurality of the nozzle hole by applying a pulse to pressurizing the molten metal at the same time. Integrating molten metal droplets discharged from multiple nozzle holes,
The molten metal droplet discharge method according to claim 4, wherein a molten metal droplet larger than the diameter of the nozzle hole is created.   The bump formation method which uses a solder as a molten metal and forms a solder bump on an electrode by the molten metal discharge method according to claim 5.

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