JPH10163243A - Method for forming loop of lead wire in wire bonding equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a loop forming method in a wire bonding equipment which is excellent in loop forming capability and can cope with diversified semiconductor devices. SOLUTION: After a lead wire is bonded to a first bonding point 2, a capillary 1 is a little lifted and reverse operation is performed. After the capillary 1 is lifted up to a loop-up point 4, the capillary 1 is moved from the loop-up point 4 to a second bond point 3, along a reference circular arc (d) wherein the first bond point 2 is the center. In this loop forming method, from the loop-up point 4 to a step point 7 set at an intermediate point inside the reference circular arc, a bending point 6 of a lead wire formed by reverse work is set as the center, and first loop-down operation is performed along a first circular arc setting the loop-up point 4 as a radius. From the step point 7 to the second bond point 3, the center position and the radius are changed, and second loop- down operation is performed along a second circular arc which gradually approaches the reference circular arc (d) from the step point 7 and comes into contact with the circular arc.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for forming a loop of a lead wire in a wire bonding apparatus.

[0002]

2. Description of the Related Art In a wire bonding apparatus, a gold wire having a diameter of about 20 to 38 μm is usually used as a lead wire connecting a pad (electrode) on a semiconductor chip and a lead of a lead frame. The loop shape of the lead wire connecting this pad and the lead affects the product quality, and the loop shape is determined by the mechanical properties of the gold wire used, the supply amount, the path of the capillary movement during bonding, etc. Is done. In particular, the trajectory of the capillary has a significant effect on the loop shape.

With reference to FIGS. 3 to 5, a method for forming a loop of a lead wire in a conventional wire bonding apparatus will be described. FIG. 3 is a diagram of the movement locus of the capillary at the time of wire bonding, FIG. 4 is a loop shape diagram when the supply amount of the gold wire is about the same as the loop length, and FIG. 5 is a case where the supply amount of the gold wire is longer than the loop length. It is a loop shape figure.

In a conventional wire bonding apparatus, as shown in FIG. 3, a capillary 1 is slightly pulled up after a gold wire (not shown) is bonded to a first bond point (pad) 2, and the capillary 1 is pulled up. After being pulled back at the position by a small distance in the direction opposite to the second bond point 3 (hereinafter, this operation is referred to as “reverse operation a”), the first bond point 2
(Hereinafter, this operation is referred to as “loop-up operation b”). Further, from the loop-up point 4 to the second bond point 3
After moving toward a certain point, for example, an arc having a radius r around the first bond point 2 as shown in the figure (hereinafter, this operation is referred to as “loop-down operation c”)
A gold wire is bonded to the second bond point 3.

When the capillary 1 is moved along a locus as shown in FIG. 3, the loop shape of the formed gold wire changes as follows depending on the supply amount. That is, FIG. 4 shows a loop shape diagram in the case where the supply amount of the gold wire 5 is set to be approximately the same as the loop length. , The supplied gold wire 5 is always pulled. Therefore, the finally formed loop shape becomes a shape in which the bending habit 6 of the gold wire 5 formed by the reverse operation a (see FIG. 3) is elongated, and a sufficient loop height cannot be obtained.

FIG. 5 shows that the supply amount of the gold wire 5 is
FIG. 3 shows a loop shape when the wire is long enough not to break the wire, and the loop shape at this time can maintain the shape of the bending habit 6 because the gold wire 5 is supplied extra. The straight portion following the bending habit 6 hangs down, and it is not possible to take a sufficient gap between the gold wire 5 and the chip edge.

[0007]

As described above, in the case of the conventional loop forming method, the loop forming ability is limited, and it has been difficult to cope with various semiconductor devices. The present invention has been made in order to solve such a problem, and an object of the present invention is to provide a loop forming method in a wire bonding apparatus which is excellent in loop forming ability and can cope with various semiconductor devices. .

[0008]

In order to achieve the above object, the method of the present invention comprises the steps of bonding a lead wire to a first bond point, slightly raising the capillary to perform a reverse operation, and then to a loop-up point. In the method of forming a loop of a lead wire in a wire bonding apparatus, the wire is moved from a loop-up point to a second bond point along a reference arc centered on the first bond point after being pulled up. Up to a step point set at an intermediate appropriate position inside the reference arc, the center point is the bending habit of the lead wire formed by the reverse operation, and along the first arc having the loop-up point as a radius. Perform the first loop-down operation, and change the position and radius of the center point from the step point to the second bond point. It is characterized in that to perform the second loop-down operation along more from the step point to a second arc contact and gradually approach toward the reference arc.

[0009]

With the above arrangement, the capillary moves along the first arc between the loop-up point and the step point, so that the lead wire is not pulled and the bending habit does not extend. Also, the second from the step point
Between the bond points, the capillary moves so as to contact the reference arc along the second arc while gradually changing its center position and radius from the above-mentioned curl, so that the curl of the lead wire can be moderately adjusted. Wiring can be performed in an appropriate amount while pulling with a great force. For this reason, the gold wire is not pulled by an extra force at the time of forming the loop, and the extra gold wire is not supplied, so that a stable loop shape can be obtained.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing the movement locus of a capillary in the loop forming method according to the present invention. In order to make the description easy to understand, the same parts as those in the above-described conventional example are denoted by the same reference numerals.

The method of the present invention is different from the above-described conventional loop forming method in that a step point 7 is set during the loop-down operation from the loop-up point 4 to the second bond point 6, and this step point 7 is set. This is a point in which a two-step loop-down operation e, f is performed as a relay point.

That is, according to the method of the present invention, the gold wire 5 formed by the reverse operation a and the bending habit 6 at the appropriate position inside the reference arc d formed by the conventional loop-down operation c ₁ and a step point 7 is set on a first arc g having a radius of the loop-up point 4, and a center between the step point 7 and the loop-up point 5 is a bending habit 6. By performing a first loop-down operation e along a first arc g having a fixed radius r ₁ , the capillary 1 is moved to the first arc g.
Is moved to the step point 7 along the inside of the reference arc d, and between the step point 7 and the second bond point 3, a second point connecting the step point 7 and the second bond point 3 is formed.
From the step point 7 as a starting point, the arc h gradually approaches and touches the reference arc d from the inside thereof.
The center point of the second arc h with moves from C ₁ to the position of the C _2, its radius by going changed from r ₁ to r _2, the second along the second arc h A loop-down operation f is performed to move the capillary 1 to the second bond point 3 along the second arc h.

As described above, step point 7 is sandwiched between 2 points.
When the loop-down operation of the stage is performed, the first loop-down operation e from the loop-up point 5 to the step point 7 is performed.
Since the capillary 1 sometimes passes through the inside of the reference arc d, the gold wire 5 is not pulled and the bending habit 6 is not extended, and the step point 7 and the second bonding point 3
At the time of the second loop-down operation f leading to
The second arc h connecting from to the second bond point 3 moves so as to be in contact with the reference arc d while gradually changing the position and radius of the center point as C ₁ → C ₂ , r ₁ → r _2. Therefore, the bending habit 6 of the gold wire 5 is also gradually pulled, and the supply amount of the gold wire 5 becomes appropriate.

As a result, the gold wire is not pulled by an extra force at the time of forming the loop, and the extra gold wire is not supplied, so that as shown in FIG. In the loop shape, the bending habit 6 remains as it is,
A stable loop shape in which the gold wire portion following the bending habit 6 extends linearly can be obtained. For this reason, a sufficient loop height can be obtained, and at the same time, a sufficient gap can be provided between the gold wire and the chip edge, so that the semiconductor device can be used for any semiconductor device.

In the above-mentioned example, for the sake of simplicity, the final center point C _{2 of} the second arc h is shown for the sake of simplicity.
The position has been drawn to match the first bonding point 2, the final position of the center point C ₂ is not limited to this position. At least a position at which the second arc h finally comes into contact with the reference arc d may be used. Further, in the above-described example, the gold wire is used as the lead wire.

[0016]

As described above, according to the method of the present invention, the bending habit of the lead wire formed by the reverse operation is centered from the loop-up point to the step point set at an appropriate intermediate position inside the reference arc. A first loop-down operation is performed along a first circular arc having a point and a loop-up point as a radius, and the position and radius of the center point are changed from the step point to the second bond point. As a result, the second loop-down operation is performed along the second arc that gradually approaches and comes into contact with the reference arc from the step point, so that the lead wire may be pulled by extra force when forming the loop. No extra lead wire is supplied, and a loop having a stable shape can be formed. Therefore, the present invention can be applied to any semiconductor device. Further, since the loop shape is stabilized, the incidence of defective products is reduced, and the production efficiency can be improved.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a movement locus of a capillary in a loop forming method according to the present invention.

FIG. 2 is a loop shape diagram of a gold wire in the loop forming method of the present invention.

FIG. 3 is a movement locus diagram of a capillary in a conventional loop forming method.

FIG. 4 is a loop shape diagram when a supply amount of a gold wire is approximately the same as a loop length in a conventional loop forming method.

FIG. 5 is a diagram showing a loop shape when a supply amount of a gold wire is longer than a loop length in a conventional loop forming method.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 Capillary 2 First bond point (pad) 3 Second bond point (lead) 4 Leap-up point 5 Gold wire (lead wire) 6 Bending habit 7 Step point 8 Gold wire (lead wire) a Reverse operation b Loop-up operation c loop down operation d reference arc e first loop down operation f the second loop-down operation g first arc h second arc C ₁ first arc center point C ₂ second circular final center point r ₁ Radius of the first arc r ₂ Final radius of the second arc

Claims (1)

[Claims] After bonding a lead wire to a first bond point,
After the capillary was slightly raised to perform the reverse operation, and then raised to the loop-up point, the capillary was moved from the loop-up point to the second bond point along a reference arc centered on the first bond point. In the method of forming a loop of a lead wire in a wire bonding apparatus, from the loop-up point to a step point set at an intermediate appropriate position inside the reference arc, a bending habit of the lead wire formed by the reverse operation is set as a center point, In addition, a first loop-down operation is performed along a first arc having the loop-up point as a radius, and the position and radius of the center point are changed from the step point to the second bond point. A second loop down along a second arc gradually approaching and coming into contact with the reference arc from the step point. Loop forming method of the lead in a wire bonding apparatus, characterized in that to perform the operation.