JPH0547770A - Method of forming bump - Google Patents

Abstract

PURPOSE:To eliminate variation in bump heights by a wire bonding means. CONSTITUTION:A bump forming method is composed of (a) a process in which a ball B' is formed on the lower end tip of a wire 36 drawn out of a capillary tool 51 by a torch electrode 60, (b) a process in which the capillary tool 51 is made to descend and presses the ball B' to the electrode 64 of a chip P placed on a moving stage 16, (c) a process in which the capillary tool 51 is made to ascend and, after the moving stage 16 is shifted horizontally a little, the capillary tool 51 is made to descend again and the part 36a of the wire 36 rising from the ball B' is pressed against the upper surface of the ball B' by the lower surface of the capillary tool 51 and (d) a process in which the capillary tool 51 is made to ascend and the wire 36 is clamped by clampers 62 and 63 and pulled up to be cut off from the joint part between the wire 36 and the ball B'.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bump forming method,
More specifically, the present invention relates to means for forming bumps with uniform bump heights by wire bonding means.

[0002]

2. Description of the Related Art It is known to form flip chips by forming bumps on a chip by wire bonding means. The wire bonding means forms a ball by bringing the torch electrode close to the lower end of the wire drawn out from the capillary tool, and then pressing this ball to the electrode of the chip by the lower end of the capillary tool to bond it, and then the wire is clamped by a clamper. Is clamped and the wire is pulled up to cut the wire from the joint between the ball and the wire to form a bump.

FIG. 11 shows a bump formed by conventional means, where B is a bump and P is a chip.

[0004]

However, in the above-described conventional wire bonding means, when the wire is pulled up and cut, the wire cut portion is not stable, and the wire cut residue c is projected from the bump B in various lengths. Therefore, there is a problem that the bump height H easily varies.

Therefore, an object of the present invention is to provide a means capable of forming bumps without variations in bump height.

[0006]

According to the present invention, (a) a step of forming a ball with a torch electrode at the lower end of a wire led out from a capillary tool, and (b) lowering the capillary tool to move the ball And (c) raising the capillary tool and moving the moving stage slightly horizontally, and then lowering the capillary tool again to move the wire The step of pressing the rising part from the ball to the upper surface of the ball by the lower surface of the capillary tool, and (d) raising the capillary tool to clamp and pull the wire by the clamper to cut the wire from the joint of the wire and the ball And the step of forming a bump forming method.

[0007]

In the above structure, the ball formed at the lower end of the wire is pressed against the electrode of the chip mounted on the moving stage by the capillary tool to bond the ball.
Next, raise the capillary tool, move the moving stage slightly horizontally, and then lower the capillary tool again to press the rising part of the wire against the upper surface of the ball by the lower surface of this tool and flatten the upper surface of the ball. Pressure shaping. Next, the wire is cut from the joint between the wire and the ball by clamping and pulling the wire with a clamper.

[0008]

Embodiments of the present invention will now be described with reference to the drawings.

FIG. 1 is an overall perspective view of an inner lead bonding apparatus. Reference numeral 1 is a main body box, on which the components described below are arranged. Reference numerals 2 and 3 denote a supply reel and a take-up reel arranged on both sides of the main body box 1. A film carrier 4 and an interlayer paper 5 are wound around the supply reel 2. Between both reels 2 and 3,
Guide rollers 6 and 7 and sprockets 8 and 9 as pitch feeding means are provided. The film carrier 4 led out from the supply reel 2 goes around the roller 6 and is further pitch fed by the sprockets 8 and 9. It is wound around the take-up reel 3. The interlayer paper 5 goes around the roller 7 and travels below the film carrier 4, and then is wound around the winding reel 3 together with the film carrier 4. M1
Is a motor for driving the take-up reel 3.

In FIGS. 1 and 3, reference numeral 11 denotes an XY table provided on the main body box 1, and the X table 1
2, a Y table 13, an X motor MX1, and a Y motor (not shown). Base plate 14 on Y table 13
Is provided, and a tray 15 as a chip supply unit is placed on the base plate 14. Chips are mounted on the tray 15. A moving stage 16 on which chips are transferred from the tray 15 is provided on the side of the Y table 13. Mθ is a motor that rotates the cam 46. When the cam 46 rotates, the lever 47 that supports the moving stage 16 rotates, and the moving stage 1
6 rotates θ (horizontal rotation). 45 is a moving stage 16
It is a cylinder as an elevating means for elevating and lowering.

In FIG. 3, reference numeral 20 denotes a pickup head, which is constructed by mounting a camera 22 and a pickup nozzle 23 on a bracket 21. A block 24 is mounted on the rear portion of the bracket 21, and the block 24 is mounted on a vertical guide shaft 25 so as to be vertically movable. When the motor MZ1 is driven, the pickup head 20 moves up and down along the guide shaft 25.
That is, the block 24, the guide shaft 25, and the motor MZ1 form a Z table 26 that moves the pickup nozzle 23 up and down.

The XY table 11 is driven to drive the tray 15
The predetermined chip stored in the camera is moved directly below the camera 22 and observed by the camera 22 to detect the presence or absence of the chip. Further, the XY table 11 is driven to move this chip directly below the pickup nozzle 23, and the motor MZ
1, the pickup nozzle 23 is moved up and down to pick up this chip P (see FIG. 3). Then X
The Y table 11 is driven to move the moving stage 16 to directly below the chip sucked by the pickup nozzle 23, and the motor MZ1 is driven to move the pickup nozzle 23 up and down, whereby the chip P is moved.
6 (see FIG. 4).

Next, the XY table 11 is driven to move the chip P on the moving stage 16 directly below the camera 22, and the positional deviation of this chip P in the XYθ directions is detected.
The positional deviation in the XY directions is corrected by adjusting the movement stroke of the XY table 11. Further, as for the positional deviation in the θ direction, the motor Mθ is driven to move the moving stage 16 by θ.
Correct by rotating. By correcting the displacement of the chip P in the XYθ directions in this way, the bumps of the chip can be accurately joined to the leads of the film carrier 4.

In FIGS. 1 and 3, 31 is a second XY.
Tables, the X table 32, the Y table 33,
It is composed of an X motor MX2 and a Y motor MY2. A head portion 34 is provided on the Y table 33. Three
Reference numeral 8 is a main body case. A horn 35 is provided on the head portion 34. The horn 35 extends above the film carrier 4 and has a capillary tool 51 (see FIG. 2) and a pressing tool 52 (see FIG. 3) at its tip.
And FIG. 7) are exchangeably mounted. MZ2 is a motor for moving the horn 35 up and down. Inside the body case 38, means for oscillating the horn 35 in the US direction is housed. The head portion 34 is provided with a spool 37 around which a wire 36 is wound. This wire 3
6 is supplied to the capillary tool 51. Reference numeral 39 is a camera for observing the leads and the chip P of the film carrier 4.

In FIGS. 3, 6, and 7, reference numeral 40 is a suction stage. An opening 41 is opened at the center of the suction stage 40. A suction hole 42 is opened around the opening 41. 43 is a suction tube. With the pitch feeding of the film carrier 4 stopped, the upper surface of the film carrier 4 is adsorbed and fixed in the adsorption holes 42. Further, in this state, the moving stage 16 on which the chip P is mounted moves directly below the opening 41,
The bumps B (see FIG. 2) formed on the upper surface of the chip P are
It presses against the lead of the film carrier 4. In this embodiment, the suction stage 40 is provided above the film carrier 4, but it may be provided below the film carrier 4 so that the lower surface of the film carrier 4 is sucked and fixed.

In FIG. 8, 60 is a torch electrode,
By swinging horizontally, the capillary tool 51
A ball B ′ is formed at the lower end of the wire 36 by electrical spark, approaching the lower end of the wire 36 led out from. Reference numerals 62 and 63 are tension clampers and cut clampers for clamping the wire 36, and 64 is an electrode formed on the upper surface of the chip P. The ball B ′ is bonded to the electrode 64 to form the bump B. 1 to 5, the torch electrode 60 and the clampers 62 and 63 are omitted because the drawings become complicated.

The present apparatus has the above-mentioned structure, and its operation will be described below. As shown in FIG. 2, bumps B are formed on the electrodes 64 of the chip P prior to performing inner lead bonding. In this case, the supply reel 2 and the take-up reel 3 are removed from the apparatus, the film carrier 4 is removed from the suction stage 40, and the horn 35 holds the capillary tool 51.

In this state, the chips P on the tray 15 are transferred to the moving stage 16 by the pickup nozzle 23. Next, the chip P is moved to a position right below the camera 22, and the camera 22 detects the positional deviation of the chip P in the XYθ directions. Then, the XY table 11 is driven to move the chip P directly below the capillary tool 51. At that time, the displacement of the chip P in the XYθ directions is corrected by the means described above. Next, the XY table 31 is driven to move the capillary tool 51 in the XY directions to form bumps B on the chip P (see FIG. 2).

Next, a more detailed method of forming the bump B will be described with reference to FIGS.

The torch electrode 60 is brought close to the lower end of the wire 36 led out from the capillary tool 51, and a ball B'is formed at the lower end of the wire 36 by electrical spark (FIG. 8 (a)). Next, the torch electrode 60 is laterally retracted, the capillary tool 51 is lowered, and the ball B ′ is pressed against the electrode 64 of the chip P for bonding (FIG. 6B). Next, the capillary tool 51 is slightly moved upward, the moving stage 16 is moved slightly horizontally ((c) in the figure), and then the capillary tool 51 is lowered again, so that the lower surface of the capillary tool 51 causes the wire 36 to move. The rising part from the ball B'is pressed against the upper surface of the ball B '((d) in the figure).

FIG. 9 is a partially enlarged view of this pressing state. At the center of the capillary tool 51, a hole 51a for inserting the wire 36 is formed. The capillary tool 51 has a flat lower surface 51b.
By b, the rising portion of the wire 36 from the ball B ′ is pressed against the upper surface of the ball B ′ and embedded in the ball B ′ so as to be united, and the upper surface of the ball B ′ is pressed and shaped into a flat surface. There is. In the figure, a shaded portion 36a is a rising portion of the wire 36 embedded in the upper surface of the ball B'and united with the ball B '.

Next, the capillary tool 51 is raised (FIG. 8 (e)), and then the wire 36 is clamped by the cut clamper 63 to pull up the wire 36. Then, the wire 36 is cut from the necked joint portion a with the ball B ′, and the bump B is formed.

FIG. 10 shows the bump B thus formed. The upper surface b of the bump B is a flat surface because the lower surface 51b of the capillary tool 51 is pressed against it. c is a narrow joint a
(See FIG. 8E) These are the projections produced by the cutting. The protrusion c is extremely small and does not substantially affect the bump height. As described above, according to the present means, the bump B having the flat upper surface b and having the uniform bump height is obtained.
Can be easily formed. In particular, this means has an advantage that the bump B having the above-mentioned shape can be formed by using the conventional bump forming apparatus as it is.

Next, referring to FIG. 3, when the formation of the bump B is completed, the XY table 11 is driven, the moving stage 16 moves to the pickup nozzle 23 side, and the chip P on the moving stage 16 moves to the pickup nozzle. 23 is picked up and collected in the tray 15. By repeating the above operation, the bumps B are formed on all the chips P included in the tray 15.

Next, inner lead bonding is performed. In this case, instead of the capillary tool 51, the pressing tool 52 is held by the horn 35 (see FIG. 7).
Thus, by exchanging the capillary tool and the 51 pressing tool 52, the work of forming the bump B on the chip P and the inner lead bonding work of bonding the lead of the film carrier 4 to the bump B are performed.
It can be done in the same device. Next, in FIG. 1, the supply reel 2 and the take-up reel 3 are set, and the film carrier 4 is positioned below the suction stage 40.

Now, as shown in FIG. 3, the XY table 1
1 is driven to move a desired chip P in the tray 15 directly below the pickup nozzle 23, and the chip P is picked up. In this case, before adhering the chip P to the pick-up nozzle 23 and picking it up, the chip P is moved directly below the camera 22,
Presence or absence and whether or not this chip P is a non-defective product is inspected in advance, and only when it is a non-defective product, the pickup nozzle 23 picks it up.

Next, the XY table 11 is driven to move the moving stage 16 to a position right below the pickup nozzle 23, and the chip P sucked by the pickup nozzle 23 is transferred to the moving stage 16 (see FIG. 4). Next, the chip P mounted on the moving stage 16 is moved right below the camera 22 to detect the positional deviation of the chip P in the XYθ directions. It should be noted that such observation of the chip P is performed by
You may go at 9. Next, the XY table 11 is driven to move the moving stage 16 directly below the suction stage 40, as shown in FIG. At that time, the displacement of the chip P in the XYθ directions is corrected by the above-described means.
Next, the cylinder 45 is driven to raise the moving stage 16 to bond the bump B of the chip P to the lead of the film carrier 4. Note that the bumps B and the leads may be joined by lowering the film carrier 4 by lowering the sprockets 8 and 9 without raising the moving stage 16.

Next, while driving the XY table 31 and moving the pressing tool 52 in the XY directions, the leads of the film carrier 4 are pressed against the bumps B by the pressing tool 52, and the leads are bonded to the bumps B one by one. (See Figure 7). When the inner lead bonding is completed in this way, the sprocket 8,
The film carrier 4 is pitch fed by 9 and the next inner lead bonding is performed. By repeating such an operation, inner lead bonding is performed one after another. In the above embodiment, the bump formation and the inner lead bonding are performed by the same device, but the bump formation and the inner lead bonding may be performed by different devices separately.

[0029]

As described above, according to the present invention, (a) a step of forming a ball with a torch electrode at the lower end of the wire led out from the capillary tool, and (b) lowering the capillary tool, The step of pressing the ball against the electrode of the chip mounted on the moving stage, and (c) raising the capillary tool, moving the moving stage slightly horizontally, and then lowering the capillary tool again, The step of pressing the rising part from the ball to the upper surface of the ball by the lower surface of the capillary tool, and (d) raising the capillary tool and clamping and pulling the wire by the clamper Since the bump forming method is composed of the step of cutting,
It is possible to easily form bumps having uniform bump heights.

[Brief description of drawings]

FIG. 1 is a perspective view of an inner lead bonding apparatus according to the present invention.

FIG. 2 is a perspective view of the apparatus during bump formation.

FIG. 3 is a perspective view of the same apparatus during inner lead bonding.

FIG. 4 is a perspective view of the same apparatus during inner lead bonding.

FIG. 5 is a perspective view of the same apparatus during inner lead bonding.

FIG. 6 is a plan view of a suction stage used in the apparatus.

FIG. 7 is a front view of the suction stage.

FIG. 8 is an operation diagram showing the order of forming bumps by the apparatus.

FIG. 9 is a partially enlarged view of a state where a ball is pressed by the device.

FIG. 10 is a perspective view of a bump formed by the same device.

FIG. 11 is a side view of a conventional bump.

[Explanation of symbols]

 16 moving stage 36 wire 36a rising part 51 capillary tool 51b lower surface 60 torch electrode 62 clamper 63 clamper 64 electrode a joint part B bump B'ball P chip

Claims (1)

[Claims] 1. A step of (a) forming a ball by a torch electrode on the lower end of a wire led out from a capillary tool, and (b) lowering the capillary tool to place the ball on a moving stage. After pressing the electrode of the tip to the electrode of (c) and raising the capillary tool and moving the moving stage slightly horizontally,
By lowering the capillary tool again, pressing the rising part of the wire from the ball to the upper surface of the ball by the lower surface of the capillary tool, and (d) raising the capillary tool and clamping and pulling the wire by the clamper. And a step of cutting the wire from a bonding portion between the wire and the ball, the bump forming method.