JP2001077141A - Device for forming solder ball - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a solder ball by extruding a fused solder from an orifice without using an extruding member which moves forward and backward while keeping contact with the high temperature of fused solder. SOLUTION: A solder ball forming device 1 is provided with the first and the second solder storing parts 3 and 4 which store a fused solder 2 and which communicate through a communicating path 7. The second solder storing part 4 is composed of a close-end cylindrical part 4a and a ceiling part 4b which extends from the upper end of the part 4a and the circumference of which becomes narrower toward the above, and the part 4 comprises an orifice 6 at the center of the bottom which makes the solder storing part 4 communicate with the outside. The end of a path 11 for supplying nitrogen gas for the fused solder 2 is connected to the cylindrical part 4a. In the solder ball forming device 1, a switching valve 12 for controlling the supply of nitrogen gas from a nitrogen bomb to the path 11 is arranged. The valve 12 is driven by a Langevin vibrator 14. When the nitrogen gas is supplied to the solder storing part 4, the fused solder 2 is extruded from the orifice 6 so as to form a solder ball 24.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a solder ball forming apparatus, and more particularly to a solder ball forming apparatus suitable for forming a solder ball directly on an electrode pad of a flip chip or CSP (chip size package). Things.

[0002]

2. Description of the Related Art In order to further reduce the size of electronic devices, it is important to increase the mounting density of components. As a high-density mounting technology, there is a method using flip chips or CSPs. In this case, solder ball bumps (hereinafter simply referred to as solder balls) are formed on the electrode pads of the semiconductor IC.
Is formed, and the IC chip is directly mounted on the printed wiring board.

As a method of forming a solder ball, there is a method of forming a film by vacuum evaporation and a lift-off of a photoresist film, or a method of printing solder and then melting the solder by heating to finally form a solder ball. However, these methods require a heat treatment after forming the solder in a desired pattern on the electrode pad, and the process of forming the solder ball is complicated.

As a method for solving the above problem, there is a method in which solder balls are formed directly on electrode pads of an IC chip from molten solder. For example, there is an apparatus shown in FIG. 3 (a metal jet apparatus (MPM manufactured by U.S.A.), which is used for manufacturing solder bumps for connecting a flip chip and a wafer by spraying solder as particles in a molten state). Product name)).

As shown in FIG. 3, the metal jet device includes a cartridge 52 for storing a solder 51 in a molten state, and an orifice 53 is formed below the cartridge 52. The cartridge 52 is provided with a piezoelectric transducer 54 (piezo element) for promoting the flow of the molten solder 51 from the orifice 53. An electrostatic ring (Charge Tube) 55 is provided below the cartridge 52.
And a pair of deflection plates 56 arranged in parallel in a vertical state. A pipe 57 connected to a source of compressed inert gas (for example, nitrogen gas) is connected to an upper portion of the cartridge 52.

In this apparatus, a pressure is applied to the molten solder 51 in the cartridge 52 with nitrogen gas, and the flow of the solder 51 is promoted by the piezoelectric transducer 54 so that the solder 51 becomes small particles and passes through the orifice 53. Fall. The solder particles are charged when passing through the orifice 53 and are deflected by the electric field of the deflection plate 56. Therefore, the combination of deflecting the charged solder particles in the Y-axis direction (left-right direction in FIG. 3) and moving the substrate 58 in the X-axis direction (perpendicular to the plane of FIG. 3) allows the solder particles to be formed. Solder bumps 59 are formed at predetermined positions on the substrate 58.

[0007]

The piezo element has a Curie point of about 300.degree. C. and is usually used at 150.degree. C. or less, whereas the temperature of molten solder is about 200.degree. There is a problem that the life is severely shortened. And it takes time to replace the piezo element.
It is also difficult to ensure the heat resistance of the wiring for supplying voltage to the piezo element.

The present invention has been made in view of the above problems, and has as its object to melt molten solder without using an extruding member that reciprocates while contacting the molten solder at a high temperature (about 200 ° C.). An object of the present invention is to provide a solder ball forming apparatus capable of forming a solder ball by extruding from an orifice.

[0009]

To achieve the above object, according to the first aspect of the present invention, there is provided a solder storage portion for storing solder in a molten state, and provided below the solder storage portion,
An orifice for communicating the solder reservoir with the outside, a passage capable of supplying a compressed non-oxidizing gas into the molten solder in the solder reservoir, and a compressed non-oxidizing gas from a supply source of the compressed non-oxidizing gas to the passage. And an opening and closing means for controlling the supply of the solder ball.

According to a second aspect of the present invention, in the first aspect of the present invention, the opening / closing means is driven by a piezo actuator using a piezo element. In the invention described in claim 3, in the invention described in claim 1 or 2, the non-oxidizing gas is an inert gas.

According to a fourth aspect of the present invention, in the third aspect of the invention, the inert gas is nitrogen gas.
Therefore, in the first aspect of the present invention, when the opening / closing means is opened, the compressed non-oxidizing gas is supplied from the supply source of the compressed non-oxidizing gas into the molten solder through the passage. The molten solder stored in the solder storage section is pushed out of an orifice provided at a lower portion of the solder storage section by the action of the compressed non-oxidizing gas supplied into the molten solder in the solder storage section. The extruded molten solder falls into a spherical solder ball due to its own surface tension.

According to a second aspect of the present invention, in the first aspect of the present invention, the opening and closing means is driven by a piezo actuator using a piezo element. It will be easier.

According to the third aspect of the present invention, since the non-oxidizing gas is an inert gas in the first or second aspect of the present invention, it is easier to handle than the reducing gas. .

According to a fourth aspect of the present invention, in the third aspect of the present invention, the inert gas is nitrogen gas, so that the gas can be easily obtained and the handling can be simplified.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. 1 (a) and 1 (b).

The solder ball forming apparatus 1 includes a first solder storage unit 3 for storing a molten solder 2 (molten solder) 2 and a second solder storage unit 3.
Is provided. The first solder storage section 3 includes a main body 3a formed in a cylindrical shape with a bottom and a lid 3b covering an upper opening of the main body 3a. Heater 5 for holding in the range of
Is equipped.

The second solder storing section 4 has a bottomed cylindrical section 4a.
An orifice 6 is provided at the center of the bottom and communicates with the outside at the center of the bottom. The second solder storage section 4 is also provided with a heater (not shown). The second solder storage section 4 is provided below the first solder storage section 3, and is connected via a communication path 7 having one end connected to the bottom of the first solder storage section 3 and the other end connected to the cylindrical section 4 a. And is communicated with the first solder storage section 3.

The center of the ceiling 4b communicates with an exhaust passage 8 which extends vertically above the ceiling 4b. A discharge valve 9 is provided at an upper end of the exhaust passage 8. In addition, the exhaust passage 8 is provided with respect to the first solder storage 3.
The upper part of the molten solder 2 is communicated via a solder return path 10. The solder return path 10 is formed so as to be inclined downward toward the first solder storage section 3 side.

A passage 1 for supplying a compressed non-oxidizing gas into the molten solder 2 is provided in the cylindrical portion 4 a of the second solder reservoir 4.
One end is in communication. In this embodiment, an inert gas nitrogen gas is used as the non-oxidizing gas.
A switching valve 12 serving as an opening / closing means for controlling the supply of nitrogen gas from a nitrogen cylinder (not shown) as a supply source of a compressed non-oxidizing gas to the passage 11 is provided above the solder ball forming apparatus 1. Have been. The passage 11 is formed to be substantially L-shaped and communicates with the port A of the switching valve 12. The supply port P of the switching valve 12 is connected to the other end of the pipe 13 whose one end is connected to the nitrogen cylinder.

The switching valve 12 is driven by a Langevin-type vibrator 14 as a piezo actuator using a piezo element. The Langevin-type vibrator 14 includes a pair of ring-shaped piezo elements 15 a and 15 b and a piezo element 15.
a, a ring-shaped electrode plate 15c disposed between
It is constituted by tightening and fixing metal rods 16a, 16b arranged at positions contacting the outer surfaces of the piezo elements 15a, 15b with bolts (not shown).
The bolt is screwed into a screw hole (not shown) formed in the metal bar 16a from the metal bar 16b side. Both piezo elements 15a and 15b are formed so that the polarization direction is formed parallel to the axial direction and the polarization directions are opposite to each other. Both metal rods 16a and 16b are in a state where they are electrically connected to each other via bolts.

At the tip of one metal rod 16a, a valve is moved to an open position for holding the supply port P in communication with the port A and a closed position for closing the communication between the supply port P and the port A. A spool valve portion 17 as a body is integrally formed. The spool valve portion 17 is formed with a wear-resistant coating (not shown).

The material of the piezo elements 15a and 15b is PZ
T (polycrystal of zirconic acid / lead titanate) is used. Aluminum is used as the material of the metal rods 16a and 16b.

The Langevin-type vibrator 14 has the piezo elements 15a and 15b and the other metal rod 16b protruding outside the solder ball forming apparatus 1 and extending vertically, and the other metal rod 16b is fixed to the bracket 18. Thus, it is arranged at a predetermined position. In addition, one metal rod 1
A seal ring 20 for maintaining the airtightness between the peripheral surface of the metal bar 16a and the insertion portion 19 is mounted in a groove formed on the wall surface of the insertion portion 19 through which the 6a is slidably inserted.

The electrode plate 15c is connected to the oscillator 21 via the wiring 22, and the ground terminal of the oscillator 21 is connected to the metal rod 16b via the wiring 23. The piezo element 1
The periphery of the electrodes 5a, 15b and the electrode plate 15c is covered with an insulating material (for example, silicone rubber). The oscillator 21 is driven by a control signal from a control device (not shown).

Next, the operation of the above-configured device will be described. The molten solder 2 in the solder storage sections 3 and 4 is heated by a heater 5 or the like and maintained at a predetermined temperature, and is maintained in a pressurized state by a nitrogen gas having a predetermined pressure equal to or lower than a set pressure of a discharge valve 9. . Although the orifice 6 is always open, the diameter of the orifice 6 is small, so that when the nitrogen gas is not supplied from the passage 11 into the second solder reservoir 4, the molten solder 2 is externally moved from the orifice 6 by the surface tension. Is held in a state where it is not extruded. Further, the spool valve portion 17 is held in the closed position when the oscillator 21 is not driven. However, the diameter of the passage 11 is small, and nitrogen gas of a predetermined pressure exists in the passage 11 in advance. Therefore, even when the switching valve 12 is in the closed state, the molten solder 2 flows through the passage 11.
Do not enter.

The driving of the oscillator 21 causes the piezo element 15
When a high frequency voltage (e.g., several tens of kHz) of the resonance frequency of the Langevin-type vibrator 14 is applied to a and 15b, the Langevin-type vibrator 14 vibrates. With the vibration of the Langevin type vibrator 14, the spool valve portion 17 reciprocates integrally with the metal rod 16a, and the supply port P and the port A
Is moved to an open position where the communication between the supply port P and the port A is interrupted.

When the spool valve section 17 is located at the open position, compressed nitrogen gas is supplied from the nitrogen cylinder to the second solder storage section 4 through the passage 11. Second solder reservoir 4
The nitrogen gas supplied to the solder becomes bubbles 25 in the molten solder 2 and is heated by the molten solder 2 to grow rapidly. Then, with the expansion, the force for moving the molten solder 2 acts above and below the bubbles 25, and the molten solder 2 is pushed out of the orifice 6 by the force acting downward. When the molten solder 2 separates from the lower end of the orifice 6,
A spherical solder ball 24 is formed by its own surface tension.
The solder ball 24 is attached to an electrode formed on a flip chip, an IC package, or the like mounted on a table (not shown) movable in the X and Y directions. Solder ball 24
Is determined by the diameter of the orifice 6, the pressure of the nitrogen gas, the height from the opening end of the passage 11 to the upper surface of the molten solder 2, and the like, but is set to a desired value in the range of about several tens μm to 300 μm. .

The spool valve 17 is reciprocated at a high speed with the vibration of the Langevin-type vibrator 14, and the nitrogen gas is intermittently supplied to the second solder reservoir 4 at the same speed as the frequency of the Langevin-type vibrator 14. Is done. Then, the same number of solder balls 24 as the frequency are intermittently supplied from the orifice 6.
Is extruded. The nitrogen gas supplied into the molten solder 2 rises in the molten solder 2 and escapes from the center of the ceiling 4b to the exhaust passage 8. When the nitrogen gas escapes from the inside of the second solder storage section 4 to the exhaust passage 8, even if a part of the molten solder 2 rises in the exhaust passage 8, if it rises to a position corresponding to the solder return passage 10, It is returned to the first solder storage section 3 via the return path 10. When the pressure of the nitrogen gas that has escaped to the exhaust passage 8 exceeds the set pressure of the discharge valve 9, the discharge valve 9 is opened and the nitrogen gas is discharged to a fume duct (not shown).

This embodiment has the following effects. (1) A compressed non-oxidizing gas is supplied into the molten solder 2 in the solder storage section (second solder storage section 4), and the molten solder 2 is extruded from an orifice 6 provided below the solder storage section. To form solder balls. Therefore, the molten solder 2 is pushed out of the orifice 6 without using an extruding member that reciprocates while being in contact with the high-temperature molten solder 2 and the solder ball 2
4 can be formed. Further, the amount of movement of the valve element constituting the opening / closing means for controlling the supply of the compressed non-oxidizing gas may be smaller than the amount of movement of the pushing member, and it is easy to reduce the size.

(2) Since the solder storing section (second solder storing section 4) and the opening / closing means are connected via the passage 11, the passage 11 is elongated so that the solder storing section and the opening / closing means are connected. Can be separated. Therefore, the heat resistance of the opening / closing means can be secured without providing the cooling means.

(3) Opening / closing means for controlling the supply of the compressed non-oxidizing gas from the supply source of the compressed non-oxidizing gas to the passage 11 capable of supplying the compressed non-oxidizing gas into the molten solder 2 in the solder storage section , And are driven by piezo actuators using piezo elements 15a and 15b. Therefore, it becomes easier to drive at a higher speed than the solenoid valve. In addition, the size can be easily reduced as compared with the solenoid valve.

(4) The Langevin type vibrator 14 was used as a piezo actuator, and the spool valve portion 17 was integrally formed with one of the metal rods 16a constituting the Langevin type vibrator. Therefore, the number of parts is reduced and the assembling is simplified as compared with a configuration in which the valve body is formed separately. Also, because a reciprocating spool valve is used,
When the opening / closing means is configured to be held at the closed position when the driving of the Langevin type vibrator 14 is stopped and the movement between the open position and the closed position is repeated at the time of driving, no excessive force acts on the valve element.

(5) Since the non-oxidizing gas supplied to the solder storing section (second solder storing section 4) is an inert gas, it is easier to handle than the reducing gas. (6) Since nitrogen gas is used as the inert gas, the gas is easily available and handling is simplified.

(7) The molten solder 2 in the solder storage section is pressurized by the non-oxidizing gas. Accordingly, oxidation of the molten solder 2 is prevented, and when the compressed non-oxidizing gas is supplied into the molten solder 2, the molten solder 2 is smoothly pushed out of the orifice 6.

(8) The solder ball forming apparatus 1 has a discharge valve 9 which is opened when the pressure becomes equal to or higher than a predetermined pressure. Therefore, even if the non-oxidizing gas is supplied to the solder storage section, the pressure in the solder storage section is maintained at a predetermined pressure or less, and the molten solder 2 is smoothly pushed out of the orifice 6 with the opening and closing operation of the opening and closing means.

The embodiment is not limited to the above, and may be embodied as follows, for example. ○ Monomorph (unimorph) instead of the structure in which the valve element is driven by the Langevin type vibrator 14 as the opening / closing means
It is good also as a structure which drives a valve body using a piezo actuator of a shape. For example, as shown in FIG. 2, the supply port P and the passage 1
A valve chamber 27 having a port A communicating with the valve chamber 27 is formed. Then, a piezo actuator 31 to which a metal plate 29 and a piezo element 30 are joined by an adhesive is attached to a lower end of a plug 28 that closes an upper open portion of the valve chamber 27. Plug 28
Is screwed onto the upper part of the valve chamber 27 in a state of contact with the seal ring 32. The metal plate 29 and the piezo element 30 are connected to the oscillator 21 via wiring (not shown). When the piezo actuator 31 is driven, the piezo element 30
Directly opens and closes the port A and plays a role of a valve body. In this case, the cost is lower than that of the Langevin type vibrator 14, and the size is reduced.

Instead of using a piezo actuator as the opening / closing means, an electromagnetic valve may be used. The solder storage section may not be composed of the first and second solder storage sections 3 and 4 but may be composed of only one solder storage section.

A means for preventing overheating may be provided, such as disposing a heat insulating material around the opening / closing means or providing a passage for the cooling medium. In this case, even if the opening / closing means is arranged near the solder storing section, the entirety of the solder ball forming apparatus can be made compact without overheating of the opening / closing means.

The number of the piezo elements constituting the Langevin-type vibrator 14 is not limited to two, and a plurality of sets of two piezo elements having different polarization directions, that is, 2n pieces (n is a natural number of 2 or more) are used. Is also good. The larger the number of piezo elements, the larger the amount of displacement at the same voltage.

The piezo elements 15a and 15b, the electrode plate 15c and the metal rod 1 constituting the Langevin type vibrator 14
Instead of fixing the 6a and 16b with bolts, they may be fixed with an adhesive. In this case, the piezo elements 15a, 15
It is not necessary to process b and the electrode plate 15c into a ring shape.

The material of the metal rods 16a and 16b may be a material other than aluminum, for example, stainless steel. Instead of integrally molding the valve body with the metal rod 16a of the Langevin-type vibrator 14, a valve body formed separately may be fixed or fixed to the metal rod 16a.

The non-oxidizing gas to be charged into the tank may be at normal pressure instead of pressurized state. ○ An inert gas other than nitrogen gas, such as helium or argon, may be used as the non-oxidizing gas, or a reducing gas (eg, hydrogen gas) may be used instead of the inert gas.

A charging means for charging the molten solder 2 passing through the orifice 6 is provided, and a deflecting electrode is provided below the orifice 6 so that the movement direction of the solder ball 24 falling from the orifice 6 can be changed by the action of the deflecting electrode. It may be. As the charging means, the second solder storage section 4
The structure for applying a high voltage to the bottom of the device is simple. In this case, by adjusting the voltage applied to the deflection electrode, the drop position of the solder ball 24 can be adjusted.

The non-oxidizing gas that has reached the exhaust passage 8 may be directly exhausted to the fume duct without providing the discharge valve 9. Technical ideas (inventions) other than those described in the claims that can be grasped from the embodiment will be described below together with their effects.

(1) In the solder ball forming apparatus according to any one of the first to fourth aspects of the present invention, the non-oxidizing gas is filled in the solder reservoir at a predetermined pressure. In this case, oxidation of the molten solder is prevented, and the molten solder is smoothly pushed out of the orifice with the opening / closing operation of the opening / closing means.

(2) The solder ball forming apparatus of the invention of (1) is provided with a discharge valve which is opened when the pressure exceeds a predetermined pressure. In this case, even if a non-oxidizing gas is supplied to the solder storage section, the pressure in the solder storage section is maintained at a predetermined pressure or less,
With the opening and closing operation of the opening and closing means, the molten solder is smoothly pushed out of the orifice.

(3) The solder ball forming apparatus according to any one of the first to fourth aspects of the present invention includes an overheating prevention means for preventing the opening / closing means from overheating. In this case, even if the opening / closing means is provided near the solder storage part for the purpose of downsizing the device, it is possible to prevent the opening / closing means from being heated to a high temperature, and to suppress a decrease in the durability of the opening / closing means.

(4) In the invention according to claim 2,
A Langevin type vibrator is used as the piezo actuator, and one of the metal rods constitutes a valve body.
In this case, the valve structure for opening and closing the passage is simplified.

(5) Compressed non-oxidizing gas is supplied to a solder storage section having an orifice at the bottom while storing the solder in a molten state to form bubbles in the molten solder, and the pressure of the bubbles is increased. A method of forming a solder ball by extruding molten solder from an orifice using a surface tension of the molten solder. In this case, unlike the method of extruding the molten solder from the orifice by the vibration of the piezo element surrounded by the molten solder, it is not necessary to consider the heat resistance of the piezo element and the wiring to the piezo element.

[0050]

As described above in detail, according to the first to fourth aspects of the present invention, the molten solder is removed from the orifice without using an extruding member that reciprocates while contacting the high-temperature molten solder. It can be extruded to form a solder ball.

According to the second aspect of the invention, it is easy to drive at a higher speed than the solenoid valve. In addition, the size can be easily reduced as compared with the solenoid valve. According to the third aspect of the present invention, since the non-oxidizing gas supplied to the solder storing section is an inert gas, it is easier to handle than the reducing gas.

According to the fourth aspect of the present invention, since nitrogen gas is used as the inert gas, the gas is easily obtained and the handling is simplified.

[Brief description of the drawings]

1A is a schematic cross-sectional view of a solder ball forming apparatus according to an embodiment, and FIG. 1B is a partially enlarged view of FIG.

FIG. 2 is a schematic sectional view showing an opening / closing means according to another embodiment.

FIG. 3 is a schematic sectional view of a conventional metal jet device.

[Description of Signs] 1 ... Solder ball forming apparatus, 2 ... Molten solder, 3 ... First solder storage section, 4 ... Second solder storage section, 6 ... Orifice, 1
DESCRIPTION OF SYMBOLS 1 ... Channel | pass, 12 ... Switching valve which comprises opening / closing means, 14 ... Langevin type vibrator as a piezo actuator, 1
5a, 15b, 30: Piezo element, 31: Piezo actuator.

Claims (4)

[Claims] A solder storage portion for storing a molten solder; an orifice provided at a lower portion of the solder storage portion for communicating the solder storage portion with the outside; An apparatus for forming a solder ball, comprising: a passage capable of supplying a compressive non-oxidizing gas; 2. The solder ball forming apparatus according to claim 1, wherein said opening / closing means is driven by a piezo actuator using a piezo element. 3. The solder ball forming apparatus according to claim 1, wherein the non-oxidizing gas is an inert gas. 4. The solder ball forming apparatus according to claim 3, wherein said inert gas is nitrogen gas.