JPH019156Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a wire bonding apparatus, and more particularly, to a wire bonding apparatus capable of applying back tension to a bonding wire to perform accurate and reliable bonding during ball bonding.

In the assembly process of semiconductor devices, thermocompression bonding is the most commonly used method for wire bonding between the bonding pad of a semiconductor pellet and an external lead, and especially when gold wire is used, bonding strength is high. Ball bonding is often used because it is non-directional. In ball bonding, a ball is formed at the tip of a thin bonding wire 1 that is inserted into a capillary 3 and pulled out, as shown in FIGS. . Next, the capillary is moved upward, and a hydrogen flame 4 is applied to the wire to melt and cut the wire, while forming balls 5 and 5' at the tip of the cut portion. Next, the wire, one end of which is connected to the pellet, is tilted and air is injected from above, the tip 5' of the wire is positioned on the external lead 7, and a suitable bonder die 8 is used to press and connect the wire.

In order to perform good bonding, it is necessary to create an appropriate ball on the wire without deformation or damage, and when pressing, use the capillary 3 as shown in Figure 2a.
It is necessary that the ball be accurately incorporated into the tapered portion at the tip of the ball. In order to accurately position the ball and properly feed the wire, a method is used to apply back tension to the wire. As a conventional method of applying back tension, the method shown in FIG. 3 is common. That is, the bonding wire passes from the reel 11 through the guide 12 and the like, and is first clamped by the clamper 13. Tension is applied to the clamped wire by a leaf spring 14. Due to this tension, the ball formed at the tip of the gold wire is accurately held in the tapered portion of the capillary, and is prepared for the next bonding. The wire clamp is adjusted to have a holding force sufficient to apply tension and a pressure suitable for pulling out the wire. FIG. 4 is an explanatory diagram of a conventional clamper, in which the wire is connected to flat clamping parts 20 and 21 of two metal plates.
However, sometimes an elastic member 22 is inserted between one of the metal plates and the support arm. The metal plate 21 on the side to be adjusted is connected to the arm 23, and the other end is fixed by a fixing part 26.
On the other hand, the adjustment arm 2 fixed by the fixing part 27
4 is adjusted by a tension adjustment screw 25, and finally the holding force of the wire 1 is adjusted.

However, with the recent increase in the speed of bonding equipment, it has become inevitable for the arm 23 to vibrate, and each time this vibration occurs, the wire repeats the states shown in FIGS. 5a to 5c, causing tension instability. In other words, in FIG. 5a, the wire is properly held by the metal plates 20 and 21, but when the plates approach each other as shown in FIG.
It may get scratched or may curl after passing through the clamper due to stress. In particular, if the wire becomes thinner, such as 25 μm or less, it may cause or break the wire. On the other hand, in the state shown in FIG. 5c, the holding force is lost and such repetition causes instability of the tension and prevents normal bonding.

The leaf spring 14 according to FIG. 3 also has the disadvantage that it cannot accommodate rapid tension adjustments and tends to exacerbate the clamper's shortcomings. In addition, the adjustment of the conventional metal plate clamp was delicate, and there was a problem that the wire could easily break if it was tightened a little too much.

The relationship between the above problems and bonding results in metal plate clamps, especially in high-speed bonding, is shown in Figure 2 a~
Let us explain h. FIG. 2a shows the ball 9 and the capillary 3 in a preferable relationship, and when such components are bonded, the shape shown in FIG. 2e is obtained and a connection with good adhesive strength can be achieved. In FIG. 2b, stress is applied to the wire, causing the wire to curl and the relative position between the ball 9' and the capillary 3 to be incorrect, resulting in an uneven connection and some areas where no bonding occurs, as shown in FIG. 2f. Figure 2c shows the connection of Figure 2g, where the relationship between the ball 9'' and the capillary 3 is good, but vibration or over-tightening causes the wire to become constricted, resulting in a defect in the wire. Figure d
Due to vibrations, etc., a clamping failure occurs, and tension is not applied to the wire, and the ball cannot be pulled up. As a result, bonding is performed while the wire is stuck, resulting in a connection at a point other than the ball, as shown in Figure 2h.

An object of the present invention is to provide a bonding device that can uniformly and properly clamp the wire without causing distortion or damage to the bonding wire due to poor adjustment or vibration, and can perform bonding with excellent reliability.

According to the present invention, in a wire clamping means for applying tension to a wire for wire bonding that connects a bonding pad of a semiconductor pellet and an external lead with a wire, at least a part of the part in contact with the wire is an elastic body. A wire bonding device with characteristics can be obtained.

The details of the present invention will be explained below with reference to the drawings.

FIG. 6 is an explanatory view of the main parts of the clamp part of a bonding device according to an embodiment of the present invention. In FIG. 6a, 20' and 21' are made of an elastic body, especially a relatively soft elastic body such as sponge or felt 23 is an adjustable arm that supports 21', and 28 is a fixed arm that supports 20'. In addition, in FIG. 6b, one of the clamping parts 20 is made of metal, as in the conventional one, and only the other clamping part 21' is made of sponge. Further, in FIG. 6c, sponges 20'' and 21'' are attached to both sides to the required thickness.

With this configuration, since the clamping part is made of a relatively soft elastic material such as a sponge, the movable arm can be adjusted over a wide range with respect to the wire, and even if the contact area increases, the metal It is extremely unlikely that the wire will be damaged or deformed like a plate.

Due to the above-mentioned features, the adverse effect on the wire due to the vibration of the adjusting arm that conventionally occurs due to increased speed can be almost eliminated as shown in FIGS. 7a to 7c. FIGS. 7a to 7c are explanatory diagrams showing the relationship between the clamping part and the wire as the clamping part changes.

FIG. 7a shows a normally held state. Although it depends on the softness and elasticity of the elastic body, it is more convenient for the wire and the elastic body to be in contact over a considerable area. When the movable elastic body plate 21' moves in a direction approaching the fixed elastic body plate 20', the elastic body becomes depressed as shown in FIG. 7b, and the contact area increases. However, since it is a soft elastic material, it does not damage the wire, and the variation in clamping force is small. Furthermore, when the clamping parts 20' and 21' move apart, as shown in Fig. 7c, even a slight change will only reduce the contact area, and the two will separate as in the case of metal plates, resulting in a state of zero clamping force. Must not be. The elastic body is not limited to sponge or felt, and any material that meets the bonding conditions can be used by appropriately changing the type, shape, size, etc. Further, the wire holding portion can be easily adjusted by using opposing plate-like bodies, which is convenient for renewing the elastic body. Further, the position of the line can be freely changed or maintained by guides provided at the front and rear of this clamping part.

As explained above, according to the present invention, the wire bonding clamp can be easily adjusted and fixed clamping can be performed, and the wire is not damaged, deformed, or curled, and can be used for high-speed, thin wire bonding, and is reliable. is possible.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of the process of the conventional wire bonding method, Fig. 2 a to h is an explanatory diagram showing the relative position of the ball and the capillary taper part and the shape of the bonding part formed thereby, and Fig. 3 is the process explanatory diagram of the conventional wire bonding method. 4 is an explanatory diagram of a conventional clamper; FIGS. 5 a to 5 c are explanatory diagrams showing the relative positions of the clamper and the wire caused by vibrations of the clamper;
6a to 6c are explanatory cross-sectional views of the wire clamping part of the bonding apparatus according to the present invention, and FIG. 7 is an explanatory view showing the relative position of the wire clamping part and the wire when the bonding apparatus according to the present invention vibrates. 1...Bonding wire, 2...Semiconductor pellet, 3...Capillary, 4...Hydrogen flame, 5,
5', 9, 9', 9'', 9...ball, 10, 1
0', 10'', 10... Connection part, 11... Reel, 12, 12', 17... Guide, 13, 1
3'... Clamper, 14... Leaf spring, 20,2
1... Clamper holding part (metal), 22, 20',
21', 20'', 21''... Clamper holding part (elastic body), 23, 24... Arm, 25... Adjustment screw, 26, 27... Arm fixing part, 28... Fixed arm.

Claims (1)

[Scope of utility model registration request] In a wire clamping means for applying tension to a wire in wire bonding that connects a bonding pad of a semiconductor pellet and an external lead by a wire, at least a part of the part that contacts the wire is made of sponge or felt, and the wire is contacted with the wire. 1. A wire bonding device characterized in that said parts are each held by two opposing plate-shaped bodies.