JPS6120761Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a bonding tool for connecting lead wires of electronic equipment, and has a long soaking length compared to the entire length of the heat generating part and prevents deformation of the heat generating part due to heat or external mechanical force. The purpose is to prevent

The structure of a conventional bonding tool is shown in FIG. In the figure, reference numeral 1 denotes a bonding tool, which has power supply terminals 2 and 3 and is configured to be attached to a machine body (not shown) through a hole 4. Reference numeral 5 denotes a heat generating part, and 6 a shell supporting the heat generating part 5. Normally, the power supply terminals 2 and 3, the heat generating part 5, and the shell 6 are formed integrally. Reference numeral 7 denotes a wiring portion (not shown), that is, a pressing surface that presses a plurality of lead wires or a plurality of lead wires, or a lead wire and semiconductor bumps, etc. to bond them all at once. The back surface 8 of the pressing surface 7 is formed to be convex upward when the pressing surface is viewed from below, and the center portion 10 is higher than the end portions 9.
Further, a notch 11 is provided at the joint between the shank 6 and the heat generating portion 5 so as to reduce the cross-sectional area. 1
2 is a thermocouple for detecting the temperature of the heat generating part 5 and controlling the current flowing through the heat generating part so that the temperature becomes a predetermined temperature.

The apparatus shown in FIG. 1 is used for bonding using a heating method in which current is passed for 2 to 5 seconds, which is usually referred to as a pulse current heating method. The procedure is to first press the wiring part to be connected with the pressing surface 7, then apply a voltage between the power supply terminals 2 and 3 to generate heat by the resistance of the heat generating part 5, and use that heat to bond the wiring part. . Since the heat capacity of the heat generating portion 5 is small, the temperature rises to a predetermined temperature in a short time. When the temperature rises to a predetermined temperature, the temperature of the heat generating portion 5 is kept constant for 2 to 5 seconds by the thermocouple 12 and current control means (not shown). Bonding is performed during this time, and then the current is turned off. When the current is cut off, the heating part 5
Since its heat capacity is small, its temperature drops quickly,
Furthermore, the temperature of the wiring section also decreases. Next, when the bonding tool 1 is raised to separate the pressing surface 7 from the wiring section, the bonding operation is completed.

In the above-mentioned operation, the central part 10 of the heat generating part 5 has a middle height, so the cross-sectional area of the central part is large.
Therefore, the resistance at the center is small. Therefore, the amount of heat generated in the center part 10 is smaller than that in the end part 9, but since it is further away from the terminals 2 and 3, it is difficult for heat to escape to the terminals, and the temperature easily rises. Conversely, the end portion 9 generates a large amount of heat, but since it is close to the terminals 2 and 3, a large amount of heat escapes through the shank 6, making it difficult for the temperature to rise. As shown in FIG. 1, the temperature distribution of the pressing surface 7 of a conventional bonding tool in which the back surface 8 faces the pressing surface 7 and forms an upwardly convex surface is as shown in FIG. Soaking length becomes considerably shorter. In order to lengthen this soaking length, the amount of heat generated at the end portion 9 is further increased, and in order to reduce the heat escaping to the shank 6 and the terminals 2 and 3, the notch 11
, and the cross-sectional area of the end portion 9 is reduced.

However, if the resistance at the end 9 is made extremely large,
At the start of energization, the temperature of the heat generating part 5 is low and the resistance is low, so a large inrush current flows, and this inrush current causes a region 13 near the notch 11 of the end part 9 (colored black in FIG. Only the ivy portion (the ivy part) is heated rapidly and instantaneously, which further increases the resistance and heats up to an even higher temperature, sometimes resulting in a red-hot state. On the other hand, the temperature of the central portion 10 increases more slowly than that of the end portions 9, and after reaching a predetermined temperature, the current is controlled and the temperature is maintained at a predetermined temperature. After the center portion 10 reaches a predetermined temperature, the end portions 9 have a lower temperature than the center portion because heat escapes more easily from the end portions 9 than the center portion for the same reason as described above.

FIG. 3 shows the above-mentioned temperature change over time. In the same figure, curve F is the temperature change at E ₁ and E ₂ when the notch 11 is large, and G is the temperature change in the notch 11.
When _E1 and _E2 are small, H is the temperature change in the C part. Thermocouple 12 for temperature control
is fixed near the C part, so there is not much difference in the temperature of the C part whether the notch 11 is large or small. Therefore, if the notch 11 is made larger, the soaking length is slightly improved, but the overshoot becomes larger and the product becomes red hot. When the bonding tool becomes red hot, its life is significantly shortened due to oxidation of the bonding tool, deterioration of mechanical properties due to coarsening of the bonding tool's crystal grains, and the like. Furthermore, if the notch 11 is made larger, there is a drawback that the strength is reduced. Therefore, with the structure shown in FIG. 1, there is a limit to how long the soaking length can be while suppressing overshoot.

On the other hand, the bonding tool 1 is normally held fixed to the body of a bonding apparatus (not shown) through the attachment holes 4 of the power supply terminals 2 and 3, and is supplied with power and a pressing force P is applied thereto. The heat generating part 5 is supported by shank 6 at both ends, and pressurizing force is applied to both ends. Therefore, as shown in FIG. Since the rigidity of the portion 5 is low, the heat generating portion 5 receives an external force that causes the upper portion to deform into a convex shape. Also, during bonding, the pressing surface 7 is
5. Since heat is taken away by the material 14 to be joined, the temperature is lower than that of the back surface 8. For this reason, the elongation of the back surface 8 due to heat becomes greater than the elongation of the pressing surface 7, and the heat generating portion 5 receives a force that causes it to curve upward in a convex manner. When the heat generating part 5 curves upward in a convex manner, the material to be joined 14
Both ends of the bonding tool come into contact with the pressing surface 7 of the bonding tool, but the center part is not sufficiently heated and pressurized because there is a gap between the pressing surface 7 and the material 14 to be bonded, resulting in a poor connection in the central part. occurs.

The present invention is intended to improve the above-mentioned drawbacks, and FIG. 5 shows an embodiment of the present invention. In the figure, 16 is a bonding tool of the present invention;
Reference numeral 17 denotes a heat generating part thereof, and shank 18 is integrally formed at both ends of the heat generating part 17, and each shank 18
Power supply terminals 20 and 21 are provided at the ends of the shank 19, and a power supply terminal 22 is also provided at the center of the heat generating portion 17 and at the end thereof. 23 is a hole for fixing this bonding tool 16 to the body. The power supply terminals 20 and 21 are electrically short-circuited on the aircraft body side, and by applying a voltage between this and the power supply terminal 22 in the center, current flows between the power supply terminals 20 and 22 and 21 and 22. Heat generating part 1
7 has a fever. This can be thought of as two bonding tools having the configuration shown in FIG. 1 brought into close contact with each other. The shape of the back surface 24 of the heat generating part 17 is medium and high, and the heat generated by the heat generating parts 25 and 26 close to the shank 18 at the end and the shank 19 in the center is increased to transfer heat to the shank 18 and 19, as in the conventional example described above. This reduces the temperature drop in the heat generating parts 25 and 26 due to the escape of heat.

However, the shape is simply two bonding tools of the conventional shape, that is, shank 1.
When the cross-sectional area of the bonding tool 9 is twice the cross-sectional area of the shank 18, the heat generated in the center C of the bonding tool is the heat generated in the vicinity of both ends 25 through the shank 18 at both ends to the power supply terminals 20, 21. In the same way as when escaping, connect the power supply terminal 2 through the shank 19 in the center.
However, the amount of heat that escapes through radiation and heat conduction to the air is smaller in shank 19. Therefore, in the temperature distribution of the pressing surface 27, as shown in FIG. 6, the temperature drop at the center portion C is smaller than at both end portions E ₁ and E ₂ . However, the effect of improving the soaking length due to the difference in the amount of heat escaping by radiation or heat conduction to the air is not so remarkable.

Therefore, in the present invention, since approximately twice as much current flows through the shank 19 at the center as the shank 18 at the end, the current speed in the shank 19 at the center is set to be higher than the current density at the shank 18 at the end. This is to set the cross-sectional area of the shank 19. In this way, the amount of heat generated by the heat generating part 26 near the shank 19 at the center increases, and the heat escaping to the power supply terminal 22 through the shank 19 also decreases, so the temperature of the heat generating part 26 is lowered by the shank at the end. The temperature can be made higher than the temperature of the heat generating section 25 in the vicinity of the heat generating section 18. In this case, the temperature distribution on the pressing surface 27 is as indicated by L in FIG. 7. In order to increase the temperature in the central part, in addition to making the shank 19 in the central part thinner, the cross-sectional area near the central part of the heat generating part 26 may be reduced within a range that does not cause overshoot.
Both of these change the amount of heat generated and the amount of heat dissipated in the central part, but the smaller the cross-sectional area of the shank 19, the more
The temperature in the center increases, and from the characteristic of L in Figure 7, M
changes to a state like In other words, by achieving an appropriate heat balance, the temperature in the center can be maintained within the allowable range, and compared to conventional bonding tools, the soaking length that can maintain the same temperature range is significantly longer. Can be done.

In the present invention, as shown in FIG. 8, the bonding tool 16 has power supply terminals 20 and 21 at both ends and a power supply terminal 22 at the center fixed to the body of the bonding apparatus, and the heat generating part 17 is applied with a pressure P at three points. Because of the pressure, the shank 19 in the center has a reinforcing effect, and the heat generating part 17 does not curve upwardly due to external mechanical force or heat.

The power supply terminals 20 and 21 at both ends may be short-circuited on the bonding tool 16 side as shown in FIG. In addition, when the total length of the bonding tool is long, as shown in FIGS. 10 and 11, the power supply terminals 22 in the center are provided in plurality, and every other one is short-circuited as shown in the figure. A similar effect can be obtained by configuring the current flowing through the terminal to be approximately twice the current flowing through the power supply terminal at the end.

As described above, the present invention provides a shank and a power supply terminal at both ends and the center of the bonding tool, fixes these terminals to the body, and makes the current density of the shank at the center larger than the current density of the shank at both ends. The following effects can be obtained by setting the cross-sectional area of the central shank so that: That is, 1. It is possible to increase the amount of heat generated in the central part of the heat generating part, and to reduce the escape of heat, and it is possible to lengthen the soaking length of the central part of the heat generating part. Therefore, to obtain the same soaking length, the length of the bonding tool can be made shorter than that of the conventional one.

2. The power supply terminal in the center reinforces the deformation of the heat generating part due to mechanical external force or heat, eliminates bonding defects in the center, and enables uniform bonding.

[Brief explanation of the drawing]

Figure 1 is a perspective view of an example of a conventional bonding tool, Figure 2 is the temperature distribution in the longitudinal direction on the pressing surface of the conventional example, Figure 3 is the temperature curve at the center and end of the bonding tool, and Figure 4 is Figure 5 is a perspective view of an embodiment of the bonding tool of the present invention, and Figure 6 shows the temperature of the pressing surface when two conventional bonding tools are connected. Figure 7 is a diagram showing the temperature distribution in the longitudinal direction on the pressing surface of the bonding tool of the present invention, Figure 8 is a diagram explaining the usage state of the bonding tool of the present invention, Figure 9 is a diagram showing the temperature distribution of the bonding tool of the present invention. A perspective view of another embodiment of
10 and 11 are front views of other embodiments of the present invention, respectively. 1, 16... Bonding tool, 14... Joined material, 15... Substrate, 17... Heat generating part, 18,
19...Shank, 20, 21, 22...Power supply terminal, 23...Mounting hole, 27...Press surface.

Claims (1)

[Claims for Utility Model Registration] 1. A pressing surface constituted by a conductor, a first shank extending from the conductor at both ends of the conductor, and a first shank provided at the end of the first shank. and at least one second power supply terminal provided in the center of the conductor and extending from the conductor.
shank, and a second power supply terminal provided at the end of the second shank, and the current density of the second shank at the center of the conductor is equal to the current density of the first shank at both ends of the conductor. A bonding tool characterized in that the cross-sectional area of the second shank is set to be larger. 2. Utility model registration claim 1, characterized in that the first power supply terminal at both ends of the conductor and the second power supply terminal at the center of the conductor are fixed to the fuselage so that the pressing surface of the conductor is not deformed. bonding tool.