JPH0147893B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] This invention involves introducing a wire led out from a wire feeding device of a bonding device into a bonding tool via a clamp, bonding it to a pellet, and then bonding it to a lead frame. This invention relates to a bonding method that reliably controls the loop shape of a wire.

[Technical background of the invention and its problems]

In the assembly process of semiconductor devices, a bonding apparatus as shown in FIG. 1 is generally used as a means for connecting pellets and lead frames with wires. Reference numeral 1 in FIG. 1 is a main body of the apparatus, and a wire feeding device 2 such as a wire spool equipped with a clamp portion 2a is provided on the upper part of the main body 1. A wire guide 4 for guiding the wire 3 is provided on the wire feeding side of the main body 1.
This wire guide 4 has a base end attached to a mounting portion 5 of the main body 1.
It consists of a leaf spring that is attached to the plate so that it can swing freely in the vertical direction, and is always given an upward elastic force.
The amount of downward swing is regulated by. Further, the free end of the wire guide 4 is provided with the wire 3.
A curved portion 8 is formed for guiding the material downward. An upper clamp 9 for clamping and releasing the introduced wire 3 is provided at the lower part of the curved portion 8 of the wire guide 4. The support structure for the upper clamp 9 is such that the upper clamp 9 is fixed to the main body 1 via an arm 9a, and the arm 9a rotates in the vertical direction about a rotation axis 9b, and the upper clamp 9 is fixed to the main body 1 via an arm 9a. There are two types: one that moves up and down.

The upper clamp 9 of either structure is opened and closed by a solenoid (not shown) to clamp or release the wire 3. A tube-shaped wire guide 10 is attached to a swing arm 12 of a lower clamp 11 below the upper clamp 9, and is adapted to guide the wire 3 to the lower clamp 11. The lower clamp 11 is provided at the tip of the swing arm 12 and is driven by a solenoid (not shown) to open and close, thereby clamping and releasing the wire 3. A capillary arm 13 is provided below the swing arm 12 and parallel to the swing arm 12. A bonding tool 14 through which the wire 3 is inserted is provided at the tip of the capillary arm 13. The capillary arm 13 is connected to the base end of the swing arm 12 of the lower clamp 11 via a leaf spring 13a, and is centered around a rotation shaft 15 that pivotally supports the base end of the swing arm 12. It is designed to rotate in the vertical direction. That is, wire guide 1
0, lower clamp 11 and bonding tool 1
4 are integrated and are designed to move in the vertical direction. Note that a torch 16 or a spark electrode is provided below the bonding tool 14 to heat the tip of the wire 3 protruding below the bonding tool 14 to form a ball 17. Then, the bonding is performed by arranging the pellet 18 and the lead frame 19 below the bonding tool 14, bonding the ball 17 to the pellet 18, and then bonding the wire 3 to the lead frame 19 to connect the pellet 18 and the lead frame 19. It is done by doing.

By the way, in order to perform bonding with the bonding apparatus shown in FIG. 1 in which the upper clamp 9 is fixed to the main body 1 via the arm 9a, as shown in FIG. 2A, the upper clamp 9 is closed and the wire 3 is
is clamped with a weak clamping force, and the lower clamp 11 is opened to form a ball 17 at the lower end of the bonding tool 14. As shown in B, when the upper clamp 9 is opened and the bonding tool 14 is lowered, the ball 17 is 17 comes in close contact with the lower end of the bonding tool 14 and descends to form a pellet 18.
will be bonded to. Next, as shown in C, the bonding tool 14 is raised and the lead frame 19 to which the pellet 18 is fixed is moved, and as shown in D, the bonding tool 14 is lowered and the upper clamp 9 is moved at the same time or a little later.
is clamped for a short time with a weak clamping force of 1gr or less to form a loop L of the wire 3 at the bottom of the bonding tool 14, and as shown in E, the wire 3 inserted through the bonding tool 14 is crimped to the lead frame 19. do. After connecting the wire 3 and the lead frame 19 in this way, when the lower clamp 11 is closed and the bonding tool 14 is raised as shown in F, the wire 3 is cut off from the lead frame 19 and a pellet is formed. 18
The connection between the lead frame 19 and the lead frame 19 is completed. Next, the tip of the wire 3 protruding from the lower end of the bonding tool 14 is heated or sparked with a torch 16 to form a ball 17, completing one cycle of the bonding operation.

On the other hand, when bonding is performed using a bonding device in which the upper clamp 9 is configured to be movable in the vertical direction, as shown in FIG. 3A, the upper clamp 9 is closed, the lower clamp is opened, and the ball 17 is
When the bonding tool 14 is lowered, the ball 17 that is in close contact with the lower end of the bonding tool 14 is connected to the pellet 18 as shown in B. Next, as shown in C, the bonding tool 14 is raised and the upper clamp 9 is lowered.
At the same time, the lead frame 19 to which the pellet 18 is fixed is moved to face the bonding tool 14, and then the bonding tool 14 is lowered as shown in D, and at the same time the lower clamp 11 is lowered in the open state. Then raise the upper clamp 9 while clamping the wire 3 with a weak clamping force of 1gr or less to form a loop L on the wire 3 at the bottom of the bonding tool 14, and then open the upper clamp as shown in E. condition lower clamp 1
1 to the closed state and lower the bonding tool 14.
The wire 3 inserted through the lead frame 19 is crimped onto the lead frame 19 to connect the wire 3 and the lead frame 19. Next, as shown in F, when the bonding tool 14 is raised and the lower clamp 11 is raised while being in the closed state, the wire 3 is cut off from the lead frame 19, and the connection between the pellet 18 and the lead frame 19 is completed. Become.

However, in the conventional bonding method, when forming the loop L at the bottom of the bonding tool 14, the height H of the loop L is reduced as shown in FIG. This has disadvantages in that the shape does not hold, and under-loop UL is likely to be formed, requiring modification, resulting in lower product yields and higher manufacturing costs.

[Purpose of the invention]

To provide a bonding method that can control the shape of a loop formed at the bottom of the bonding tool when bonding the ball at the lower end of the bonding tool to the pellet surface and then bonding the wire inserted through the bonding tool to the lead frame surface. This is what I am trying to do.

[Summary of the invention]

With the ball in close contact with the lower end of the bonding tool, lower the bonding tool to bond the ball to the pellet, then move the bonding device in the opposite direction to the direction in which the loop is to be stretched, and then tighten the bonding device to stretch the loop. The shape of the loop is controlled so that the neck portion stands upright and the height of the loop becomes sufficiently high by moving it in the direction.

[Embodiments of the invention]

The bonding device will be explained with reference to FIG. 1. An arm 9a supporting the upper clamp 9 is attached to the main body
In particular, the main body 1 is slidably provided on the bed 1a in the left-right direction as shown by the arrow 1b. The structure other than the above is the same as that of the conventional bonding apparatus, so the explanation thereof will be omitted. Next, the bonding method will be explained based on FIG. As shown in A, the bonding tool 14 rises to a predetermined position and the upper clamp 9
is closed and the lower clamp 11 is open, the ball 17 is attached to the lower end of the bonding tool 14.
When the bonding tool 14 is lowered from this state as shown in B, the ball 17 comes into close contact with the lower end of the bonding tool 14 and the pellet 18
will be bonded to. After the ball 17 is bonded to the pellet 18 in this way, the bonding tool 14 is raised, but at this time, the C
As shown in FIG. 3, the bonding tool 14 is vertically raised to point a, and the portion corresponding to the neck portion N of the loop L is made to stand upright. Next, the bonding tool 14 is raised to point b, and then moved to point c in a direction opposite to the direction in which the loop L is formed (leftward in the figure). Due to this operation, the wire 3 is bent obliquely in the moving direction of the bonding tool 14 using the vicinity of point a as a fulcrum, and has a tendency to bend. Furthermore, the bonding tool 14 is raised from point c to point d. Further, as shown in D, after moving the bonding tool 14 in the direction of forming the loop L (to the right in the figure), as shown in E, the bonding tool 14 is lowered and raised at the same time or with a slight delay. The wire 3 is bonded to the lead frame 19 while applying back tension to the wire 3 by clamping the clamp 9 for a short time with a weak force of 1 g or less.
Due to this back tension, the loop L of the wire 3 becomes high and has an ideal loop shape with no under-loop. After connecting the wire 3 and the lead frame 19 in this way, when the lower clamp 11 is closed and raised together with the bonding tool 14 as shown in G, the wire 3 is cut off from the lead frame 19 and the pellet 18 and Connection with lead frame 19 is completed. Next, the tip of the wire 3 protruding from the lower end of the bonding tool 14 is heated with a torch 16 or a ball 17 is formed by a spark, thereby completing one cycle of the bonding operation.

In the above embodiment, the upper clamp 9 is fixed to the main body 1, but it may be movable up and down.

〔Effect of the invention〕

As explained above, in this invention, after bonding the wire to the pellet, when the bonding tool rises again, the bonding device is moved an appropriate amount in the direction opposite to the direction in which the loop is formed, thereby forming the neck of the loop. Since the loop is made to stand upright, the height of the loop can be made sufficiently high, which has the effect of improving the yield of the product.

Furthermore, by applying back tension to the wire when bonding to the lead frame, there is an effect that underloop can be prevented.

[Brief explanation of drawings]

Fig. 1 is a side view showing the schematic configuration of a general bonding device, Figs. 2 and 3 are explanatory diagrams of the operation of the conventional bonding method, and Fig. 4 shows the shape of the loop formed by the conventional bonding method. The side view, FIG. 5, is an explanatory diagram of the operation of the method of the present invention. 2... Wire feeding device, 9, 11... Clamp, 14... Bonding tool, 18... Pellet.

Claims (1)

[Claims] 1. After bonding the wire led out from the wire feeding device to the pellet in the bonding device, the bonding tool is vertically raised to a predetermined height so that the portion corresponding to the neck portion of the loop stands upright, and then the bonding tool is After moving the bonding tool by a predetermined amount in the direction opposite to the direction of forming the loop, the bonding tool is raised, and after the bonding tool is further moved in the direction of forming the loop, the bonding tool is lowered at the same time or with a slight delay. A bonding method characterized in that the wire is bonded to a lead frame while applying back tension to the wire.