JPH0370151A - Junction method for semiconductor device - Google Patents

Abstract

PURPOSE:To improve reliability and yield rate by thermocompression-bonding the finger lead on a carrier tape to the bump electrode on an IC chip by means of a thermocompression-bonding head so as to form the curvature of a finger lead. CONSTITUTION:When a thermocompression bonding head 21 falls, the projection end of a finger lead 15 is pressed against the top of a bump electrode 12 by the flat bottom face of the thermocompression-bonding head 21. In this condition, when small currents flow to the thermocompression bonding head 21, the finger lead 15 is heated. After this, when the thermocompression-bonding head 21 falls further, an IC chip 11 falls, and accompanying this the finter lead 15 is curved in the direction of being separated from the IC chip 11. Large currents flow to the thermocompression-bonding head 21, and solder plating at the surface of the finger lead 15 fuses, and the projection end of the finger lead 15 is junctioned (thermocompression bonded) onto the top of the bump electrode 12.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for bonding semiconductor devices, and in particular, to a method for bonding semiconductor devices, and in particular, to a method for bonding semiconductor devices using an ICC bonding technique.
In the bonding method for semiconductor devices called the bonding method, first, as shown in Figure t55, the tip of the finger lead 2 on the carrier tape l is attached to the bump electrode 4 on the IC chip 3 using a thermocompression head (not shown). ) to prevent the finger leads 2 from coming into contact with the top surface of the IC chip 3 and short-circuiting, as shown in FIG. It is bent in a direction away from the top surface of 3.

[Problems to be Solved by the Invention] However, in such a conventional bonding method for semiconductor devices, in the step of bending the finger leads 2, the bent portion 2 of the finger lead 2 near the bump electrode 4
There have been problems in that cracks may occur in a, making it easier to cut or causing the film to be cut, resulting in lower reliability and lower yield.

In other words, in order to sufficiently prevent the finger leads 2 from coming into contact with the top surface of the IC chip 3 and causing a short circuit, the larger the sprouting angle θ (see Fig. 6 f!!) of the finger leads 2, the better; Therefore, the length Lo (see Fig. 5) from the proximal end of the finger lead 2 before bending to the bent portion 2a on the distal end side is set to 5004 m, and the bending angle is When θ is 20', the length L+ after bending (see Figure 6) is the original length LO
The length is 324 m longer than that, and the elongation rate E is 61%, as is clear from the following equation.

E= (L+ -Lo)XI/Lo XI 0O=
8.4 However, the elongation rate of copper foil, which is a common material for finger leads 2, is 6.4% at room temperature, which is the limit (I PC standard says that the elongation rate of general electrolytic copper foil is 3 at room temperature
．． It is specified as 0%. ), which makes cracks and cuts more likely to occur.

This invention is as described above! ! ! This was done in consideration of the current situation, and its purpose is to provide a method for bonding semiconductor devices that can prevent cranking or cutting even when the finger leads are sufficiently broken. be.

[Means for Solving the Problems] In order to solve the above problems, the present invention connects finger leads made of copper or copper alloy on a carrier tape to bump electrodes on an IC chip placed on a bonding table. ,
At the same time as thermocompression bonding with the 8ff bonding head, the MIE hair head bonding table is moved downward relative to the carrier tape, thereby bonding the finger lead and bump electrode and bending the finger lead in the same process. This is what I decided to do.

[Function] According to the present invention, the finger leads are bent in a state where the finger leads are heated with a thermocompression bonding head instead of at room temperature, so that the finger leads stretch more easily than when they are at room temperature. Even if the elongation rate of the finger leads exceeds the limit at room temperature, cranking and cutting are less likely to occur, and therefore reliability and yield can be improved.

[Embodiment] Hereinafter, an embodiment of the present invention will be described in detail with reference to FIGS. 1 to 4.

First, to explain with reference to FIG. 1, the IC chip 1
1, a wiring pattern (not shown) is provided on the upper surface, and bump M poles 12 made of gold or the like are provided on the left and right sides of the upper surface of this wiring pattern, and the upper surface of the wiring pattern except for the bump electrodes 12 is provided with a wiring pattern (not shown). The structure includes an I film (not shown). The carrier tape 13 is provided with an opening 14 larger than the external shape of the IC chip 11 at a predetermined location, and a finger lead 15 made of copper or copper alloy is provided on the upper surface around the opening 14 at one end. The finger lead 15 has a 4I structure in which solder plating (not shown) is sunk on the surface.

On the other hand, the thermocompression bonding head 21 is formed of a metal material such as stainless steel or copper into a substantially U-shape, and is arranged to be movable downward. A bonding table 4In composite body 22 is arranged below the thermocompression bonding pad 21. As shown in FIG. 2, the bonding table structure 22 includes a cylindrical base 23 with a bottom, a cover 25 attached to the upper surface of the base 23 with screws 24, and a guide bin 26 inside the base 23. The structure includes a bonding table 27 which is housed so as to be vertically movable through the bonding table 27, and a coil spring 28 for urging the bonding table 27 upward.

Among these, a rectangular IC chip J & placement part 3o is provided protruding from the center of the upper surface of the bonding table 27. An intake port 31 is provided in the center of the IC chip mounting section 30 .

A circular hole 32 is provided in the center of the cover 25 to allow movement of the ICC chip side portion 30 and the like. At the center of the bottom of the base 23, from the top to n, there is a large diameter recess 33;
Four medium-diameter portions 34 and a small-diameter through hole 35 are provided. A stopper 3 consisting of a cylindrical body with a short axis is provided at the four large diameter parts 33.
The lower part of 6 is fitted.

The lower part of an elastic member 37 made of a long-sleeved cylindrical body is fitted into the medium-diameter recess i'1134.The upper end surface of the elastic member 37 is pressed against the lower surface of the bonding table 27 around the intake port 31. . A tube 38 is inserted into the small diameter through hole 35.
One end is fitted from the outside. The other end of the tube 38 is connected to a vacuum pump (not shown) 11i.

Thereby, the intake port 31 of the bonding table 27 is connected to the vacuum pump through the inside of the first elastic member 37 and the tube 38.

Then, the IC chip 11 is attached to the IC chip device section 30 of the bonding table 27 at the center of the opening 14 of the carrier tape 13! ! IC chip! is attracted to the placement part 30. Furthermore, the protruding ends of the finger leads 15 of the carrier tape 13 are superimposed on the upper surface of the bump electrodes 12 of the IC chip 11.

In this state, when the rad 21 descends to thermocompression bonding, the first
As shown in the figure, the protruding end of the finger lead 15 is simply pressed against the upper surface of the bump electrode 12 by the flat lower end surface of the thermocompression bonding pad 21. In this state, when a small current flows through the thermocompression lead 21, its lower end surface generates heat to about 150 to 200°C due to generation of Joule heat, and the finger lead 15 is heated by this heat.

After this, when the 12 door 21 is further lowered to thermocompression bonding.

fjS3 As shown in FIG. fjS3, as the bonding table 27 descends against the force of the coil spring 28 and the elastic member 37, the IC chip 11 is placed between the thermocompression bonding head 21 and the IC chip a on the bonding table 27. 130, and along with this, the finger lead 15
is bent in a direction away from the IC chip 11. When the lower surface of the bonding table 27 comes into contact with the upper surface of the stopper 36 and the thermocompression bonding pad 21 reaches the bottom dead center,
A large current flows through the thermocompression bonding lead 21, and its lower end surface generates heat of about 400 to 500°C. This heat melts the solder plating on the surface of the finger lead 15, and the protruding end of the finger lead 15 is thereby The finger leads 15 and the bump electrodes 12 are bonded (thermocompression bonded) to the upper surface of the bump electrodes 12 by thermocompression bonding at 400 to 500° C. for about 0.5 to 2 seconds.

After this, when the temperature of the thermocompression bonding head 21 is lowered to 150 to 250°C and held for a predetermined time (about 1 second), and the thermocompression bonding head 21 is raised, the coil spring 28 and the elastic Due to the force of the member 37, the bonding table 27 is raised and returned to its original position, the vacuum pump is stopped, and the suction state of the IC chip 11 to the IC chip mounting portion 30 is released.

In this way, in this semiconductor device bonding method, the finger leads 15 are bent not at room temperature but in a state where the finger leads 15 are heated by the thermocompression bonding pad 21. Therefore, when the finger leads 15 are at room temperature, This makes it easier to stretch than Finger Lead 15.
Even if the elongation rate exceeds the limit at room temperature, cracks and cuts will not occur, thus improving reliability and yield.

For example, the finger leads 15 are formed of copper or a copper alloy that elongates by about 35% at high temperatures (170° C. or higher), and the finger leads 15 are formed by thermocompression bonding rad 21 at high temperatures (170° C. or higher).
Assume that the finger lead 15 is made of newspaper and its bending angle 0 (see FIG. 6) is 40 degrees while heated to a temperature of 0° C. or higher. Then.

If the length Lo (see Figure 5) from the base end of the finger lead 15 to the folded part on the distal end side in the state before newspapering is 5004 m, the length LI after folding (see Figure 6) is 153gm longer than the original length Lo,
As is clear from the following equation, the elongation rate E is 30.6%.

E = (LI - Lo) Xi/Lo XI 0
0=30. fi Therefore, even if the bending angle θ is quite large as 40e', the elongation E is about 31%, which is smaller than 35% and within the allowable range, so cracks and cuts do not occur, and reliability and A semiconductor device with a high yield can be obtained.

Further, in this semiconductor device bonding method, the finger leads 15 are bent while the IC chip 11 is held between the thermocompression bonding head 21 and the bonding table 27 for thermocompression bonding the finger leads 15 to the bump electrodes 12. Therefore, the process for bending the finger leads 15 can also be used as the thermocompression bonding process.
There is no need for a dedicated process for bending 5, and the number of assembly steps can be reduced.

In the above embodiment, the finger leads 15 are thermocompression bonded to the bump electrodes 12 after the finger leads 15 are bent, but in contrast, the finger leads 15 are thermocompression bonded to the bump electrodes 12 and then the finger leads 15 are bent. 15 may be bent.

In other words, the finger leads 15 are bonded by the thermocompression bonding pad 21.
At the time when the pad 21 is pressed against the bump electrode 12 in the state shown in FIG.
0° C.), and while maintaining that temperature, the ladder 21 is lowered into thermocompression bonding, and the finger leads 15 are folded and formed as shown in FIG. After the bonding time (0.5 to 2 seconds) has elapsed, the Rad 21 is heated to the solidification temperature (150
~250℃) and maintained that state for a predetermined period of time,
Heat is applied to the J''ERER head 21. In this method, the step of bonding the finger leads 15 is included in the step of bonding the finger leads 15 to the bump electrodes 12. In other words, the step of bonding the finger leads 15 to the bump electrodes 12 Bump electrode 1
In the time to join 2, the finger lead 15 fold +lt+
Molding has also been achieved. Therefore, it is very efficient.

Furthermore, when the thermocompression bonding head 21 is slowly raised so that a predetermined pressure is applied to the finger leads and the bump electrodes 12 by the force of the coil spring 28 and the elastic member 37, while the thermocompression bonding head 21 is raised, It is also possible to lower the temperature to the solidification temperature.

[Effects of the Invention j As explained above, according to the present invention, the finger leads are bent in a state where the finger leads are heated with a thermocompression bonding head instead of at room temperature. As a result, even if the elongation rate of the finger leads exceeds the limit at room temperature, cracks and cuts are less likely to occur, which improves reliability and yield. Since the process for bending the finger leads can also be used in the thermocompression bonding process, there is no need for a dedicated process for bending the finger leads, and the number of assembly steps can be reduced.

[Brief explanation of drawings]

1 to 4 are for explaining a method for bonding semiconductor devices in one embodiment of the present invention. Of these, Fig. 1 is a cross-sectional view showing the state in which the finger leads of the carrier tape are simply pressed against the bump electrodes of the IC chip by the thermocompression bonding head, Fig. 1I42 is an exploded perspective view of the complete bonding table a, and Fig. 3 is the carrier tape. FIG. 4 is a sectional view showing the state where the finger leads of the tape are bent; FIG. 4 is a sectional view showing the state after the bending and thermocompression bonding process; FIG.
Figures and wS6 are for explaining an example of a conventional bonding method for semiconductor devices. FIG. 6 is a sectional view showing the process of bending the finger leads of the carrier tape. 11...IC chip, 12...bump electrical information. 13...Carrier tape, 15...Finger lead, 21...Thermocompression bonding head, 22...
. . . Bonding table structure, 27 . . . Bonding table. Figure 1 Figure and 24 [24 Figure 24

Claims (1)

[Claims] Finger leads made of copper or copper alloy on a carrier tape are thermocompression bonded to bump electrodes on an IC chip placed on a bonding table using a thermocompression head, and at the same time, the thermocompression bonding head and the bonding table are placed on the carrier. 1. A method for bonding a semiconductor device, comprising moving the finger lead downward relative to the tape, thereby performing bonding of the finger lead and the bump electrode and bending the finger lead in the same step.