JPH0695539B2 - Wire bonding method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention provides a wire between a first bonding point, for example, an electrode on an IC chip and a second bonding point, for example, an external lead, in a semiconductor device assembling process. The present invention relates to a wire bonding method of connecting in a loop and electrically connecting them.

[Conventional technology]

Conventionally, various efforts have been made to accurately shape the wire into a loop shape when bridging the wire.
After the bonding at the first bonding point 2 is completed, as shown in FIG. 4, the trajectory of the capillary is raised slightly and then moved slightly horizontally in the direction opposite to the second bonding point 3 so that the wire 1 It is possible to perform a second bonding by making a bend near the loop-shaped top 4 of the above, then raising the capillary to a predetermined height, and moving it to the second bonding point 3 with a curved track and a vertical descending track. Proposed (JP-A-63-421)
No. 35).

[Problems to be Solved by the Invention]

However, as shown in FIG. 5 (shown in the state after loop formation), the bent half-fitting method of the first half of this method is likely to cause damage to the wire rising base 5 such as wrinkles 6 and cracks 7. , Greatly affects reliability in wire bonding.

Further, since the ascending movement and the horizontal retreat movement are separately performed, the required time is increased, which hinders the improvement of productivity in the semiconductor device assembly process.

Further, since a vertical descending orbit is used to move the latter half of this method to the second bonding point 3, a large wire sag 9 is generated near the tip of the capillary 8 at the point A which starts to descend vertically. Then, when the capillary 8 reached the second bonding point, it was found that a flat region of about 0.35 to 0.4 mm was actually formed near the second bonding point 3 as shown in FIG. In this case, if the wire sagging 9 does not reach the second bonding point 3, for example, the surface of the external lead, the wire 1 connected between the first bonding point 2 and the second bonding point 3 may have a defective bonding loop. Dripping and bending are likely to occur. This tendency is remarkable in wire bonding of a multi-pin semiconductor device using a lead frame having a narrow outer lead.

The present invention is intended to solve these conventional problems, and to reduce damage such as wrinkles and cracks in the wire rising base, shorten the required time as much as possible, and reduce the sagging and bending of the wire. It is an object of the present invention to provide a wire bonding method capable of stabilizing the height and shape of the wire.

[Means for Solving the Problems]

The present invention relates to a wire bonding method for connecting a wire between a first bonding point and a second bonding point, and after the first bonding is completed, the capillary is raised and moved in a direction opposite to the second bonding point. A curve without a straight descending trajectory connecting the rising point and the second bonding point to the capillary by raising the wire rising portion in a parabolic curved trajectory and then raising the capillary to a prescribed position to further retract a predetermined amount of wire. The wire bonding method is characterized in that the second bonding is performed by moving the orbit to a second bonding point.

[Action]

According to the present invention, after the completion of the first bonding, the capillary is moved up in a direction opposite to the second bonding point in a substantially parabolic curved path, that is, in a curved path having no straight path, the wire is raised. Since the part (the part that rises almost vertically on the first bonding point when forming the loop) is extended, the force is not concentrated at one point and is dispersed so that no excessive force is applied to the wire and the upper end part of the wire rising part (capillary The part of the wire located at the lower end of the wire has a bend, and there is no difficulty in squeezing, and wrinkles, cracks, and other damage do not occur easily at the base of the wire that rises up. Can be shorter than.

Further, according to the present invention, the capillary which moves further to the ascending point and pays out a predetermined amount of wire has a curved trajectory connecting the ascending point and the second bonding point, that is, a straight trajectory or a curved trajectory without a vertically descending trajectory. Since the second bonding is performed by moving the wire to, the sagging of the wire generated near the tip of the capillary is reduced, and the flat area of the wire formed near the second bonding point is shortened. This is because when the experiment was performed by changing the trajectory of the capillary under the same conditions as when a flat area of 0.35 to 0.4 mm was actually measured as shown in Fig. 7, only a flat area of 0.1 to 0.2 mm was obtained as shown in Fig. 3. It was confirmed because it did not occur. Therefore, loop sagging and bending, which cause defective bonding, are reduced, and the height and shape of the wire can be stabilized.

〔Example〕

 An embodiment of the present invention will be described with reference to FIGS.

FIG. 1 shows the movement trajectory of the capillary 8. In this example, the first half movement for bending and bending is set as a substantially parabolic curved trajectory, and a horizontal trajectory or a linear trajectory shown by a broken line in which the force is concentrated at one point of the wire rising base on the first bonding point. Instead, the capillary 8 is moved along a curved orbit that combines the upward movement and the horizontal movement in the direction opposite to the second bonding point 3, and the wire rising portion is fed out along a locus where no excessive force is applied to the wire 1. . It should be noted that it took about 15 ms shorter than the time required for the bend-bending of the conventional example shown in FIG. 4 when the bend-bending was made along the locus shown in FIG.

Further, the movement from the ascending point of the capillary 8 to the second bonding point 3 is a substantially parabolic curved path connecting the ascending point and the second bonding point 3, avoiding a straight path as shown by the broken line, and descending vertically. As a result of experiments, it is important to avoid using orbits. If the vertical descending orbit is not used, the large wire sag 9 as shown in FIG. 6 of the related art does not occur in the state of the capillary 8 approaching the second bonding point 3 as shown in FIG. Point 3
The flat area in the state of FIG.
Therefore, the height and shape of the wire could be stabilized.

When the capillary 8 is moved in this way and the second bonding is performed, the wire 1 that has been fed out is surely bent at the loop-shaped top portion 4 having a bend, as shown by the two-dot chain line in FIG. It is formed into a proper loop shape and bridged between the first bonding point 2 and the second bonding point 3.

〔The invention's effect〕

According to the present invention, after the completion of the first bonding, the capillary is moved upward in a direction opposite to the second bonding point along a substantially parabolic curved trajectory to extend the wire rising portion, and then the capillary is moved to a predetermined position. Since a predetermined amount of wire is further unrolled and then the capillary is moved to the second bonding point with a straight line connecting the ascending point and the second bonding point or a curved track without a vertical descending track, the second bonding is performed. It is possible to bend and be forced without exerting excessive force.
It is possible to reduce damage such as wrinkles and cracks that tend to occur at the rising base of the wire connected to the bonding point,
Further, the time required to bend the wire can be shortened as compared with the conventional one, and the flat area of the wire in the vicinity of the second bonding point is conventionally 0.35 mm or less.
-0.4 mm can be reduced to about 0.1-0.2 mm.Therefore, even in wire bonding of a multi-pin semiconductor device using a lead frame with a narrow width of external leads, there is no loop sag or bending that causes bonding failure. It does not occur, and it is easy to adjust and stabilize the height and shape of the wire connected between the first bonding point and the second bonding point, and it is possible to easily cope with thinning of the wire and contribute to cost reduction.

[Brief description of drawings]

1 to 3 show an embodiment of the method of the present invention, FIG. 1 is an explanatory view showing the trajectory of the capillary, and FIG. 2 shows the state of the wire 1 when the capillary 8 approaches the second bonding point 3. FIG. 3 and FIG. 3 are explanatory views showing the state of the wire 1 when the capillary 8 reaches the second bonding point 3. 4 to 7 show the conventional method, FIG. 4 is an explanatory view showing the trajectory of the capillary, FIG. 5 is an explanatory view showing damage to the rising base portion 5, and FIG. 6 is a capillary 8 with the second bonding point 3
Explanatory drawing showing the sagging 9 of the wire (when the height of the capillary 8 is the same as in FIG. 2) when it descends to just above
FIG. 7 is an explanatory view showing the state of the wire 1 when the capillary 8 reaches the second bonding point 3. 1 ... Wire, 2 ... 1st bonding point, 3 ... 2nd bonding point, 4 ... Loop-shaped top part, 5 ... Wire rising base part, 6 ... Wrinkle, 7 ... Crack, 8 ... Capillary, 9 ... Wire sag.

Claims (1)

[Claims] 1. A wire bonding method for connecting a first bonding point and a second bonding point with a wire, wherein after the completion of the first bonding, the capillary is raised and the shape is substantially parabolic in a direction opposite to the second bonding point. The wire rising portion is extended by moving along the curved orbit, then the capillary is raised to a predetermined position and a predetermined amount of wire is further extended, and then the capillary is not provided with a straight downward trajectory connecting the rising point and the second bonding point. A wire bonding method, wherein the second bonding is carried out by moving to a second bonding point with a curved track.