JP3255801B2 - Wire bonding method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to wire bonding for electrically connecting a substrate having an obstacle higher than a chip mounting portion and a chip mounted on the mounting portion with a wire.
It is about the method .

[0002]

2. Description of the Related Art Many types of wire bonding apparatuses are known for connecting electrodes on the upper surface of a substrate and electrodes on the upper surface of a chip mounted on the upper surface with wires (for example, Japanese Patent Application Laid-Open No. Hei 3-22545). No.).

A conventional wire bonding apparatus of this kind includes a horn for holding a capillary tool.
The electrodes on the substrate and the electrodes on the chip are connected by wires while inserting a wire into the capillary tool and swinging the horn up and down about the rotation axis.

[0004] As an electronic component, an electronic component having a pin grid array (hereinafter, referred to as a "pin grid array electronic component") is used. In this pin grid array electronic component, pins are arranged on an upper surface of a substrate, a concave portion is formed on the upper surface, a chip is mounted in the concave portion, and an electrode on the upper surface of the substrate and an electrode on the upper surface of the chip are connected by wires. Manufactured.

FIG. 5 is a front view of a main part of a conventional wire bonding apparatus in a state where wire bonding of a pin grid array electronic component is performed. In the figure, reference numeral 1 denotes a pin grid array electronic component, and a large number of pins 3 are erected around an upper surface of a substrate 2. A recess 4 is formed in the center of the upper surface, and a chip 5 is mounted in the recess 4. Reference numeral 6 denotes a positioning table. A horn 7 holds a capillary tool 8 at its tip. A wire 9 is inserted through the capillary tool 8. A discharge torch 10 is provided on the moving path of the capillary tool 8.

Next, the operation will be described. As shown in the figure, the lower end of the wire 9 extending from the lower end of the capillary tool 8 at the position a is positioned near the tip of the torch 10,
By applying a high voltage to the torch 10 in this state, a discharge is generated between the tip of the torch 10 and the lower end of the wire 9 to form a ball 9 a at the lower end of the wire 9.

Next, the horn 7 is swung to lower the capillary tool 8 to the lower position, and the ball 9a is pressed against an electrode (not shown) on the upper surface of the chip 5 for bonding. This bonding is called 1st (fast) bonding. Next, the capillary tool 8 is moved to the position C, and the wire 9 is bonded to the electrode 11 formed inside the recess 4 of the substrate 2. This bonding is called 2nd (second) bonding. The electrode 11 and the pin 3 are connected to the wiring 12 wired inside the substrate 2.
Connected by

[0008]

In the above operation, if the torch 10 is too close to the upper end of the pin 3, the torch 1
Since there is a possibility that discharge may occur between the torch 10 and the pin 3, there is a sufficient safety distance L 1 between the torch 10 and the pin 3.
Must be secured. On the upper surface of the substrate 2, pins 3 which are obstacles to wire bonding are provided upright.
Further, since the electrode 11 is provided on the bottom surface of the concave portion 4, the capillary tool 8 must be lowered deeply in order to perform the first bonding and the second bonding described above. Therefore, since the vertical stroke L2 of the capillary tool 8 is considerably long, the vertical stroke of the capillary tool 8 must be increased.

However, if the swing stroke of the horn 7 is increased, the tact time becomes longer and the work efficiency is not improved, and the capillary tool 8 moves up and down by rotating about the rotation axis of the horn 7. The larger the swing stroke, the lower the lower end of the capillary tool 8 becomes.
As a result, the ball 9a and the wire 9 cannot be firmly pressed against the electrode of the chip 5 or the electrode 11 of the concave portion 4, and there is a problem that a bonding failure is likely to occur.

When the inclination of the capillary tool 8 increases, the wire 9 inserted through the capillary tool 8
In addition, unnecessary stress is applied to the wire 9 and the wire 9 is easily deformed. This is the connected wire 9
Has an adverse effect on the loop shape.

[0011] Accordingly, the present invention is to solve the problems of the prior means, by vertically moving the capillary tool with a small stroke, as a pin grid array electronic part
Has a higher obstacle in the chip mounting area than the mounting area
An object of the present invention is to provide a wire bonding method capable of performing wire bonding to a substrate .

[0012]

For this purpose, a wire bonding method according to the present invention is characterized in that a discharge is generated between a lower end of a wire drawn out from a lower end of a capillary tool held by a horn and a torch, thereby forming a lower end of the wire. Forming a ball in the portion, and after forming the ball, raising the table for positioning the substrate by a vertical movement mechanism,
Bonding the ball to the first bonding point of the chip, and then raising the capillary tool
Lowering the wire to the second bonding point of the substrate, and then raising the capillary tool and lowering the table.

[0013]

According to the above construction, a part of the vertical stroke of the capillary tool can be borne by driving the vertical movement mechanism to move the substrate up and down. Accordingly, the swing stroke of the horn can be reduced, and stable wire bonding at a high speed can be performed.

[0014]

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view of a wire bonding apparatus according to an embodiment of the present invention, FIG. 2 is a sectional view of the same, and FIG. 1 and 2, the pin grid array electronic component 1 is positioned on a table 20. 21
Is a vertical movement mechanism for vertically moving the table 20. A cam 23 and a cam follower 24 abutting on the cam 23 are housed inside a box 22. Cam Follower 2
Reference numeral 4 is attached to a lower end of a bar 25 that supports the table 20. The bar 25 is repelled downward by a spring 26, and the spring force causes the cam follower 24 to resiliently contact the peripheral surface of the cam 23. Reference numeral 27 denotes a motor for rotating the cam 23 about its shaft 28. Therefore, when the motor 27 is driven to rotate the cam 23, the table 2
0 moves up and down.

A base 30 is provided on the side of the vertical movement mechanism 21. The X table section 31 and the Y table
The table part 32 is stacked. A box 33 is provided on the Y table 32. Reference numeral 34 denotes a horn, which extends from the box 33 to above the table 20, and a capillary tool 35 is held at the tip of the horn. The wire 9 wound around the reel 36 is inserted through the capillary tool 35. X table part 31 and Y
When the table unit 32 is driven, the capillary tool 35 moves horizontally in the X direction and the Y direction.

In FIG. 2, the base end of the horn 34 is rotatably mounted on a rotating shaft 37 so as to be vertically rotatable. Two upper and lower arms 39 extend rearward from a bearing 38 of the rotating shaft 37. The rear end of the arm 39 has a cam 4
A roller 40 for holding the roller 1 from above and below is mounted on the shaft. Therefore, the motor 42 is driven and the cam 41 is
When the horn 34 rotates about the center 3, the horn 34 swings up and down around the rotation shaft 37, and the capillary tool 35 moves up and down. Reference numeral 44 denotes an ultrasonic vibrator attached to the base end of the horn 34, which ultrasonically vibrates the horn 34 and the capillary tool 35 during wire bonding.

In FIG. 1, a cylinder 45 is provided on the front surface of the box 33. Rod 4 of cylinder 45
6 includes an arm 47 extending forward in parallel with the horn 34.
Is supported, and a torch 4 is
8 are held. Therefore, when the rod 46 of the cylinder 45 projects and retracts, the torch 48 moves up and down.

This wire bonding apparatus has the above-described configuration, and its operation will be described with reference to FIG.
In FIG. 3, stages a to d show a series of operations. In FIG. 3, level D1 is the height of the upper surface of the table 20 during ball formation, level D2 is the height of the torch 48, and level D3 is the height of the lower end of the capillary tool 35.

In the first stage a, the capillary tool 35 is located immediately above the first bonding point A. In this state, a discharge is generated between the torch 48 and the lower end of the wire 9 derived from the lower end of the capillary tool 35, and a ball 9a is formed at the lower end of the wire 9.

Next, at the stage b, the torch 48 is raised, the table 20 is raised, the substrate 2 is raised, and the capillary tool 35 is lowered to bond the ball 9a to the first bonding point A. In this case, the torch 4 is raised by raising the torch 48 by projecting the rod 46 of the cylinder 45.
8 can be prevented from hitting the pin 3 and a sufficient safe distance can be secured so that no discharge occurs between the pin 3 and the pin 8.

Next, at the stage c, the capillary tool 35 is slightly raised, and in this state, the X table 31 and the Y table 32 are driven to horizontally move the substrate 2 on the table 20, so that the second bonding point B
The wire 9 is bonded to the electrode 11 at the second bonding point B by positioning the (position of the electrode 11) immediately below the capillary tool 35 and then lowering the capillary tool 35.

Next, at the stage d, the capillary tool 35 is raised to the level D3, the torch 48 is lowered to the level D2, and the table 20 is lowered to the level D1, thereby returning to the initial state. By repeating the above operation, wire bonding is performed one after another. Here, as is apparent from FIG. 3, the vertical stroke of the capillary tool 35 in the above operation is L, and the vertical stroke L is much shorter than the conventional vertical stroke L2 shown in FIG. This is because the table 20 side bears a part of the vertical stroke of the capillary tool 35 by driving the vertical movement mechanism 21 to move the table 20 up and down. The above-mentioned problem of the prior art is solved by reducing the length of the conventional technology.

FIG. 4 is an explanatory diagram of another operation of the wire bonding apparatus according to one embodiment of the present invention. First, the ball 9a is formed on the stage a. At this time, the capillary tool 35 is located directly above the first bonding point A. Next, the table 20 is raised in the stage b,
The electrode on the upper surface of the chip 5 is pressed against the ball 9a at the lower end of the capillary tool 35 to perform first bonding. At the time of the first bonding, the capillary tool 35 does not move up and down and remains stationary. Also in this case,
The torch 48 is retreated upward so as not to obstruct the ascent of the table 20.

Next, at the stage c, the capillary tool 35 is moved up and down, and the table 20 is moved in the X direction and the Y direction to perform the second bonding.
This 2nd bonding operation is the same as the 2nd bonding operation in FIG.

Next, at stage d, the capillary tool 35, the torch 48, and the table 20 are each moved to the level D.
3, D2 and D1 are returned to the initial state. In this method, since the first bonding is performed without moving the capillary tool 35 up and down on the stage b, the vertical stroke L ′ of the capillary tool 35 is shorter than the stroke L in FIG.

In this embodiment, the torch 48 is retracted upward. However, the torch 48 may be moved in the horizontal direction to avoid the rising pins 3. Further, the present invention is not limited to wire bonding to the pin grid array electronic component 1, but is also effective to wire bonding to the substrate 2 having a high obstacle such as the pin 3 around the chip 5.

[0027]

As described above, according to the present invention, since the table for positioning the substrate is moved up and down by the up-down movement mechanism, a part of the up-down stroke of the capillary tool can be borne on the table side. Accordingly, wire bonding can be performed at a high speed by shortening the vertical stroke of the capillary tool. In addition, since the swing stroke of the horn is also shortened, the inclination of the capillary tool at the time of the first bonding or the second bonding can be reduced, and the capillary tool can be held in a vertical posture as much as possible, and good wire bonding can be performed. Further, when raising the table, the torch is retreat removed by so as not hit a high obstacle such as a pin, and so the discharge is not generated between the torch and the pin, it is possible to ensure a sufficient safety distance between them .

[Brief description of the drawings]

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

FIG. 2 is a sectional view of a wire bonding apparatus according to one embodiment of the present invention.

FIG. 3 is an explanatory diagram of the operation of the wire bonding apparatus according to one embodiment of the present invention.

FIG. 4 is an explanatory diagram of another operation of the wire bonding apparatus according to the embodiment of the present invention.

FIG. 5 is a front view of a main part of a conventional wire bonding apparatus.

[Explanation of symbols]

 1 Pin Grid Array Electronic Component 2 Substrate 3 Pin 4 Depression 5 Chip 9 Wire 11 Electrode 20 Table 21 Vertical Movement Mechanism 34 Horn 35 Capillary Tool 37 Rotary Axis 40 Roller 41 Cam 42 Motor 45 Cylinder (Vertical Movement Means) 48 Torch

Claims (2)

(57) [Claims] 1. A wire bonding method for electrically connecting a substrate having a higher obstacle portion than a mounting portion around a mounting portion on which a chip is mounted and a chip mounted on the mounting portion by wires. a step of forming a ball at the lower end portion of the wire by generating a discharge between the lower portion and the torch of the wire led out from the lower end of the capillary tool held in the horn, after forming the ball, the substrate Raising the table to be positioned by a vertical movement mechanism;
Bonding the ball to the first bonding point of the chip, and then raising the capillary tool
A wire bonding method, comprising: a step of bonding a wire to a second bonding point of the substrate by lowering the substrate; and a step of raising a capillary tool and lowering the table. 2. The wire bonding method according to claim 1, wherein when the table is raised, the torch is moved away so as not to hit the high obstacle.