JP2001168509A - Flux coating method and apparatus - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To eliminate the application of flux to unnecessary parts. SOLUTION: In a flux applying apparatus 10, an ejection head unit 12 is mounted on an XY table 14, and is movable along a surface of a member to be joined. Discharge head unit 1
Numeral 2 is formed similarly to the printer head of the ink jet printer, and is provided with a plurality of discharge ports 16 for discharging a flowable flux by a predetermined amount in a linear or staggered manner. The ejection head unit 12 and the XY table 14
Controlled by the control device 40, the flux can be discharged to and applied to a portion to be welded at an arbitrary position of the member to be welded.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for applying a flux, and more particularly to a method and an apparatus suitable for applying a liquid flux to a portion to be welded such as soldering.

[0002]

2. Description of the Related Art In recent years, it has been practiced to provide solder balls on a semiconductor chip, melt the solder balls and bond the solder balls to a copper pattern on a mounting board, thereby electrically connecting the semiconductor chip and the mounting board. As described above, when a semiconductor chip is mounted on a substrate via a solder ball, it is difficult to directly join the solder ball and the copper pattern due to the influence of a natural oxide film or the like existing on the surface of the copper pattern. , Using a flux. Conventionally, when applying flux, the flux is applied to the entire surface of the mounting substrate. Conventionally, when a solder ball is mounted on an aluminum pad of a semiconductor chip, a flux is applied to the entire active surface of the semiconductor chip, and the solder ball is melt-bonded to the aluminum pad.

[0003]

However, when the flux is applied to the entire surface of the semiconductor chip or the mounting substrate, the flux containing an ionic substance such as halogen is applied also to the insulator of the semiconductor chip or the mounting substrate. For this reason, phenomena such as migration may occur after the semiconductor chip is mounted on the mounting board due to the influence of the ionic substance applied on the insulator, which may cause malfunction or inability to operate, resulting in reduced reliability. I do. Therefore, conventionally, after solder balls are mounted on a semiconductor chip, or after mounting a semiconductor chip on a substrate, cleaning is performed to remove flux adhering to unnecessary parts such as insulators. Is complicated and time-consuming.

The present invention has been made to solve the above-mentioned drawbacks of the prior art, and has as its object to eliminate the application of flux to unnecessary portions.

Another object of the present invention is to eliminate a cleaning step after bonding.

[0006]

SUMMARY OF THE INVENTION The present invention has been made to achieve the above-mentioned object, and is intended to discharge and apply a flux having fluidity to a portion to be bonded of a member to be bonded by using a discharging means. It is characterized by doing. According to the present invention configured as described above, the flux can be applied only to the joining target portion such as the pad portion of the semiconductor chip and the land portion of the mounting board. Therefore, for example, when the flux is applied to the mounting substrate which is the member to be joined, the flux is not applied to the insulating portion which is not the portion to be joined, and it is not necessary to remove the flux by washing after mounting the semiconductor chip. Therefore, the mounting process can be simplified and the time can be shortened, the reliability is improved, and no flux is applied to an extra portion such as an insulating portion.
The amount of flux used can be reduced, and the cost can be reduced.

[0007] A flux coating apparatus for carrying out the above-described flux coating method includes a main body having a discharge port capable of facing a portion to be welded of a member to be bonded, and a communication with the discharge port of the main body. It has a storing part which stored fluid flux, and a discharge mechanism provided in the above-mentioned main part, and discharges the above-mentioned flux toward the above-mentioned joining object part from the above-mentioned outlet.

In the present invention having the above-described structure, the flux is selectively applied only to the portion to be joined by driving the ejection mechanism with the ejection port provided in the main body facing the portion to be joined of the member to be joined. can do. Therefore, washing after bonding can be eliminated, and waste of flux can be omitted. In particular, if the discharge mechanism is formed by a constant-rate discharger that can discharge a fixed amount of flux at a time, such as a printer head of an inkjet printer, for example,
It is possible to apply the flux uniformly, and it is possible to eliminate the excess and deficiency of the amount of the applied flux and to achieve good bonding.

The main body is preferably attached to a scanning section for moving the main body along the surface of the member to be joined. When the main unit is attached to the scanning unit, by driving the scanning unit, the discharge port provided in the main unit can be easily moved to a position opposed to a desired position of the member to be joined, so that a large number of target portions can be connected. Can be quickly applied. Further, when a plurality of the discharge ports are provided in the main body, the discharge mechanism is provided corresponding to each of the discharge ports, and each of these discharge mechanisms is independently driven by the control unit. And the flux can be easily applied to a minute joining target portion or a complicated-shaped joining target portion.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the flux coating method and apparatus according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a perspective view of a flux coating device according to an embodiment of the present invention as viewed from below. In FIG. 1, the flux applying apparatus 10 is mounted on a so-called XY table 14 in which a discharge head section 12 as a main body section constitutes a scanning section. The ejection head unit 12 has a large number of ejection ports 16 provided on the front surface serving as the lower surface, and a flux having fluidity (for example, a liquid flux) from the ejection ports 16 is not shown in the drawing, as will be described in detail later. It can be applied to a bonding target portion such as a land portion of a circuit board by discharging.

The XY table 14 comprises an X table 18 and a Y table 20 on which the X table 18 is mounted. The X table 18 has the discharge head section 12 fixed and a storage section storing flux therein. On the other hand, the Y table 20 is screwed with a ball screw 22 having one end rotatably supported on a frame (not shown). The other end of the ball screw 22 is connected to a Y servo motor 24 attached to the frame, and the Y screw motor 24 is driven so that the ball screw 22 can be rotated. A guide bar 26 fixed to the frame and arranged in parallel with the ball screw 22 is slidably penetrated through the Y table 20. Therefore, the Y table 20 is
The rotation of the ball screw 22 is prevented by the guide bar 26 by rotating the ball screw 22 through the ball screw 22.
In the Y direction.

The Y table 20 is provided with a ball screw 28 arranged in the X direction at right angles to the ball screw 22. The ball screw 28 is screwed to the X table 18, one end is rotatably supported via a bearing 30 attached to the Y table 20, and the other end is connected to an X servo motor 32 attached to the Y table 20. I have.
A guide bar 38 is provided on the Y table 20 via brackets 34 and 36 in parallel with the ball screw 28. The guide bar 38 slidably penetrates one end of the X table 18 to prevent rotation of the X table 18 and guide the X table 18 in the X direction. Therefore, the X table 18
When the X servo motor 32 is driven to rotate the ball screw 28, the ball screw 28 moves in the X direction along the ball screw 28.
The Y servo motor 24, the X servo motor 32, and the ejection head unit 12 are connected to a control device 40, which is a control unit, and are driven and controlled by the control device 40.

The discharge port 16 provided in the discharge head section 12
A plurality (for example, 24) are arranged linearly or in a staggered manner. The size of these discharge ports 16 can be changed in accordance with the size of the joining target portion to which the flux is applied. It is formed to about 30 μm. The discharge head section 12 is formed in a structure substantially similar to that of the printer head of the ink jet printer, and functions as a fixed-quantity discharge machine for the flux, so that the flux can be discharged at a constant rate.

That is, as shown in FIG. 2, a part of the cross section of the discharge head section 12 is provided with a liquid storage chamber 42 corresponding to each discharge port 16. The liquid storage chamber 42 has a flow path 44
Through the supply path 4
The fluid 6 communicates with a flux tank 48 serving as a storage part for storing the flux. A second liquid storage chamber 50 is provided in the flow path 44 to prevent outside air from entering the liquid storage chamber 42 after the flux is discharged.

A diaphragm 52 is provided on the back (or side) of the liquid storage chamber 42. In addition, the diaphragm 52
The piezoelectric element 54 for driving the diaphragm 52
Is provided. The piezoelectric element 54 includes a diaphragm 52
Together, they form a flux discharge mechanism. The piezoelectric element 54 is connected to a drive circuit (not shown) controlled by the control device 40. When a voltage is applied through the drive circuit, the diaphragm 52 vibrates in the left-right direction in FIG. Then, the flux in the liquid storage chamber 42 is discharged from the discharge port 16 as a droplet 56 having a predetermined size (for example, 3 to 6 μL).

FIG. 3 is a view for explaining the operation of the flux applying apparatus 10 according to the above embodiment, and shows a process of applying a flux to a pad portion of a semiconductor chip and mounting a solder ball.

In FIG. 3A, a semiconductor chip 60 as a member to be joined has elements such as a transistor, a resistor, and a capacitor and a metal wiring connected to these elements formed on a semiconductor substrate 62. (Neither is shown). The metal wiring is provided with an aluminum pad 64 serving as an external terminal at an appropriate location. The upper surface of the semiconductor substrate 62 is covered with a protective film (passivation film) 66 made of an insulator such as a silicon oxide film. This passivation film 66 is formed of an aluminum pad 64
Is removed by etching or the like, and the aluminum pad 64 is exposed.
To allow solder balls to be joined.

Control device 40 of flux coating device 10
Is provided with a processing program including position information of the aluminum pad of the semiconductor chip 60 and the like. And the control device 4
0, when a process start command is given, the XY table 14 is driven according to the processing program, and as shown in FIG. Aluminum pad 6 to be joined
4 Then, a control signal is given to a driving circuit of the piezoelectric element 54 to drive the piezoelectric element 54, and the diaphragm 5 is driven.
2 is operated to discharge the liquid flux 68 into fine particles of 3 to 6 μL from the discharge port 16 of the discharge head unit 12 toward the aluminum pad 64 for application.

The control device 40 has one aluminum pad 64
When a predetermined amount of flux 66 is discharged and applied,
The ejection head unit 12 is moved above the next aluminum pad 64, and the flux 6 is applied to the aluminum pad 64 in the same manner as described above.
8 is applied. Repeat for all aluminum pads 6
4 is coated with a flux 68. Note that the semiconductor chip 6
The flux 68 may be dried by heating 0 to an appropriate temperature (for example, 50 to 80 ° C.).

As shown in FIG. 3B, solder balls 70 are arranged on the respective aluminum pads 64 to which the flux 68 has been applied. The semiconductor chip 60 on which the solder balls 70 are arranged is carried into a reflow furnace (not shown),
The solder ball 70 is heated to a temperature at which it melts. And
When the solder balls 70 melt, the semiconductor chip 60 is carried out of the reflow furnace and cooled. As a result, the solder balls 70 are removed from the flux 6 as shown in FIG.
By the action of 8, it is melt-bonded to the aluminum pad 64 and solidified while maintaining a spherical shape by surface tension.

As described above, in the embodiment, since the flux 68 can be applied only to the portion of the aluminum pad 64 that is to be joined, the flux 68 is applied to the portion of the passivation film 66 that is an insulator. Never. For this reason, there is no risk of migration due to the ionic substance contained in the flux 68, and there is no need to clean the semiconductor chip 60 after joining the solder balls 70. Therefore, the mounting (joining) process of the solder ball 70 is simplified, and the flux 70
Savings. Moreover, in the embodiment, since the diaphragm 52 is actuated to discharge the flux 68 at a constant rate, the application amount of the flux 68 can be accurately controlled, and the excess and deficiency of the application amount can be prevented. As a result, good joining of the solder balls 70 can be performed, and usage efficiency of the flux 68 can be improved.

The same operation can be performed when the semiconductor chip 60 is mounted on a mounting board. It goes without saying that the present invention may be applied to a device other than the semiconductor chip and the mounting substrate.

[0024]

As described above, according to the present invention, since the flux can be selectively applied only to the portion to be joined of the members to be joined, the application of the flux to unnecessary portions such as an insulating portion can be performed. As a result, the cleaning step after bonding can be omitted. Further, since the flux can be applied only to the portion to be joined, the waste of the flux can be omitted.

[Brief description of the drawings]

FIG. 1 is a perspective view of a flux coating device according to an embodiment of the present invention as viewed from below.

FIG. 2 is a partial cross-sectional view of a discharge head unit of the flux coating device according to the embodiment.

FIG. 3 is a view for explaining the operation of the flux applying apparatus according to the embodiment, and is an explanatory view of a step of mounting a solder ball on a semiconductor chip.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Flux coating device 12 Main part (discharge head part) 14 Scanning part (XY table) 16 Discharge port 18 X table 20 Y table 24 Y servomotor 32 X servomotor 40 Control part (control device) 48 Storage part (flux tank) 52, 54 Discharge mechanism (diaphragm, piezoelectric element) 60 Member to be joined (semiconductor chip) 64 Part to be joined (aluminum pad) 68 Flux 70 Solder ball

Claims (4)

[Claims] 1. A flux application method, comprising: applying a flux having fluidity to a joining target portion of a member to be joined by using an ejection means to apply the flux. 2. A main body having an outlet capable of facing a portion to be joined of a member to be joined, a reservoir communicating with the outlet of the main body and storing a fluid flux, and provided in the main body. And a discharge mechanism for discharging the flux from the discharge port toward the joining target portion. 3. The flux coating apparatus according to claim 1, wherein the main body is attached to a scanning unit that moves the main body along a surface of the member to be joined. 4. The main body section has a plurality of the discharge ports, and the discharge mechanism is provided corresponding to each of the discharge ports, and the discharge mechanisms are provided based on a given command. The flux application device according to claim 3, wherein the flux application device is connected to a control unit that drives the ejection mechanism.