JPH0572105B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application This invention relates to a wire bonding method for manufacturing electronic components, and more specifically, to prevention of interference between a capillary and a wire.

(b) Prior Art Conventional wire bonding will be explained using the case of manufacturing a thermal head as an example with reference to FIG. In FIG. 2a, 15 is a ceramic substrate, 14 is a conductor pattern formed on the ceramic substrate 15, and 13 is a driving IC. Further, 12 is a capillary, which passes through the hollow part 12a and from the lower end surface 12b, for example, Au.
(Gold) wire 11 hangs downward. The lower end of the Au wire 11 is heated by an electric torch or a hydrogen flame torch to form a ball 11a.

Next, the lower end surface 12b of the capillary is connected to the drive IC 1.
The ball 11a is pressed against the band 13a of No. 3.
is crushed and crimped onto the bread 13a. At this time, in order to facilitate crimping, the drive IC 13 is heated, and together with or in place of this, ultrasonic vibration is applied to the capillary 12.

FIG. 2c shows a state in which the capillary 12 has moved upward, and shows a state in which the Au wire 11 stands up vertically. Furthermore, Figure 2 d
shows a state in which the capillary 12 moves to the right and then moves downward, the lower end surface 12b of the capillary is pressed against the conductor pattern 14, and the wire 11 is crimped to the conductor pattern 14. The wire 11 is cut by the pressing force at this time. Thereafter, the capillary 12 rises again, causing the wire 11 to protrude from the lower end surface 12b, and the ball 1 as shown in FIG. 2a.
1a is formed.

(C) Problems to be Solved by the Invention In FIG. 2d, when the capillary 12 moves to the right, the wire 11 does not bend laterally from the base of the ball 11a, but bends at the softening point 11.
Bend laterally from c. A crystallized Au wire 11 is used, and when the Au wire 11 is heated to form the ball 11a, the portion above the ball 11a recrystallizes (see FIG. 2a). The softening point, which is the softest point of this recrystallized portion 11d, is 11c, which is formed above the ball 11a, so that the wire rises perpendicularly from the ball 11a, as shown in FIG. 2d, and softens. If the wire 11 is not bent laterally from the point 11c, the wire 11 will be damaged.

In thermal heads and the like, the density of wire bonding becomes high and the distance between adjacent pads becomes small. Therefore, as shown in FIG. 2e, when pressing the ball 11a onto the pad 13a,
The capillary 12 hits the wire 11' of the adjacent pad 13a', and the wire 11' bends from directly above the ball 11a', damaging this portion.
Also, since the wire itself has elasticity, it tries to return to its original position, but it may return too much and fall to the opposite side as shown at 11'' in Figure 2e. If the wires were to fall down like this, there was a risk that adjacent wires would come into contact with each other during resin sealing and cause a short circuit.

In order to prevent such interference between the capillary and the wire, it is desirable to make the cone angle α of the capillary as small as possible (see FIG. 2a). However, since the capillary is pressed against pads, conductor patterns, etc. even with a certain amount of load, there is a problem that the capillary is easily damaged and lacks durability.

This invention was made in view of the above,
The purpose of this invention is to provide a wire bonding method that can prevent interference between wires and capillaries.

(d) Means and Effects for Solving the Problems In order to solve the above problems, the wire bonding method of the present invention protrudes one end of the wire from the lower end of the capillary and heats the one end of the protruding wire to form a ball. forming a lower end of the capillary against a first bonding location, crimping the ball of the wire, moving the capillary onto a second bonding location, and pressing the capillary against the second bonding location again; In the device in which the other end of the wire is crimped to the second bonding location, when heating one end of the wire to form a ball, the softening point of the wire is located directly above the ball, and the wire is heated to form the ball. It is characterized in that the wire can be bent directly above the bonding point, and the wire is raised obliquely upward from the first bonding point. Since the wire rises diagonally upward in this way, it becomes difficult for the wire already installed at the lower end of the capillary to come into contact with it, and interference between the capillary and the wire can be prevented.

(e) Embodiment An embodiment of the present invention will be described below based on FIG. 1.

In this embodiment, the present invention is applied to wire bonding between a thermal head driving IC and a conductor pattern. In FIG. 1a, the Au wire 1 is protruded from the lower end surface 2b of the capillary 2,
The tip of the Au wire 1 is heated with an electric torch or a hydrogen flame torch (both not shown) to form a ball 1a. At this time, the composition and heating conditions of the Au wire 1 are adjusted so that the softening point 1c of the wire 1 is located directly above the ball 1a.

In FIG. 1b, numeral 3 indicates a driving IC, numeral 4 a conductor pattern, and numeral 5 a ceramic substrate. The driving IC 3, the conductive pattern 4, and the ceramic substrate 5 are heated to a temperature of, for example, 300° C. to facilitate crimping of the wires.

Capillary 2 is connected to the pad (first
(bonding point) 3a, and ball 1
a is crushed by the lower end surface 2b of the capillary and crimped to the pad 3a. At this time, ultrasonic vibration is applied to the capillary 2 to achieve more complete crimping. Of course, only either heating or ultrasonic vibration may be applied.

Next, the capillary 2 is raised and the wire 1 is pulled out from the capillary hollow part 2a. Then, the ceramic substrate 5 moves to the left in the paper of FIG. 1c. At this time, since the softening point 1c of the wire 1 is located directly above the ball 1a, the ball 1a
Wire 1 is bent directly above, and wire 1 is connected to pad 3.
It stands diagonally upwards from a.

As the ceramic substrate 5 further moves to the left, the capillary 2 descends and the conductor pattern (second
bonding point) 4, the other end 1 of the wire 1
b is crimped (see Figure 1d). The wire 1 is cut during this crimping, and then the capillary 2 is raised to form the ball 1a again.

The wire 1 thus installed rises obliquely upward from the pad 3a, is bent at a curvature R, and then turns obliquely downward to reach the conductor pattern 4.
Therefore, when wire bonding is performed to adjacent pads, interference between the already installed wire and the capillary is less likely to occur even if the distance between the pads is small. Therefore, the wire is less likely to be damaged, and an accident in which the wire bends and shorts with other wires is avoided. In addition, since interference between the wire and the capillary is less likely to occur, the cone angle α of the capillary 2 is
[See FIG. 1a] can be increased, and the durability of the capillary can also be improved.

In the above embodiment, the capillary is moved vertically and the ceramic substrate is moved horizontally, but a structure in which only the capillary is moved vertically or horizontally, or only the ceramic substrate is moved vertically or horizontally may be used. , the design can be changed as appropriate.

(f) Effects of the Invention As explained above, in the wire bonding method of the present invention, when heating one end of the wire to form a ball, the softening point of the wire is located directly above the ball, and the wire bonding method Since the wire can be bent directly above the ball and is raised diagonally upward from the first bonding location, interference between the wire and the capillary can be prevented. Therefore, damage to the wires and short circuits between the wires can be prevented, and the durability of the capillary can be improved.

[Brief explanation of the drawing]

Figure 1a, Figure 1b, Figure 1c and Figure 1d
2A, 2B, 2C, and 2D are diagrams illustrating a conventional wire bonding process. , FIG. 2e is a diagram illustrating the problems of conventional wire bonding. 1: wire, 1a: ball, 1c: softening point,
2: Capillary, 2b: Capillary lower end surface, 3
a: padded, 4: conductor pattern.

Claims (1)

[Claims] 1. One end of a wire is made to protrude from the lower end of a capillary, one end of the protruding wire is heated to form a ball, the lower end of the capillary is pressed against a first bonding location, and the ball of the wire is heated. In the wire bonding method, the capillary is moved onto a second bonding location after crimping, the capillary is again pressed against the second bonding location, and the other end of the wire is crimped to the second bonding location, When heating one end of the wire to form a ball, the softening point of the wire is located directly above the ball so that the wire can be bent directly above the ball;
A wire bonding method characterized in that the wire is raised diagonally upward from the first bonding location.