JPH03211846A - Method for forming bump of tab inner lead - Google Patents

Abstract

PURPOSE:To attain an improvement of productivity, making it possible to bond bumps to semiconductor elements well even when there are variations in the heights of the bumps by pressing downward and forming inner leads with a punch, locating the centers of the protruding parts of the punch at the predetermined positions of the inner lead. CONSTITUTION:Plural inner leads 12 are mounted on a hard rubber 11. Then, a punch 17, which has plural protruding parts 15 arranged on it with the same pitch as the one of the inner leads and has plural flat parts 16 on the peripheries of the protruding parts 15, is placed, opposing the inner leads 12. The centers of the protruding parts 15 of the punch 17 are located at predetermined positions of the inner leads 12, and the inner leads are molded, pressurizing them downward with the punch 17. The inner leads 12 are pressed downward by the protruding parts 15 and the flat parts 16 and are pushed into the hard rubber 11 by the protruding part 15 of the punch 17 to form plural hollow bumps 18 collectively at the predetermined positions of the inner lead 12. Thereby, the process of forming the bumps is simplified and even when there are variations in th heights of the bumps, the bumps can be bonded to semiconductor elements, and further productivity can be improved.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to TAB (Tap) used for mounting semiconductor devices.
The present invention relates to a bump forming method in which a plurality of bumps are collectively formed at the tip of an inner lead of a tape carrier for (Automated Bonding) by mechanical press processing.

[Prior Art] Generally, in order to mount a semiconductor element on a tape carrier for TA[3, it is necessary to form protrusions that serve as bumps on either the electrode part of the semiconductor element or the tip of the inner lead of the tape carrier. be. A method for forming bumps on the electrode portions of semiconductor devices includes, for example, using a plating method to form protrusions that will become bumps directly on the electrode portions, as described in [IBM Journal (113M Journal)] J Vol. 8 (1964), p. 102. [Electronic Packaging and Production ([1e
ctronic Packaging &1'rodu
ction)”, February 1984 issue, 33-39
30 to 40. The pedestal method using an etching technique is used as described on page 30 to 40. In other words, the part where the bump is to be formed is masked and the other inner lead parts are half-etched. - a method for forming a protrusion with a height of
Or, as described in Proceedings of the 1985 IEICE Semiconductor/Materials Division National Conference, Lecture No. 2J (November 1985), a method in which bumps are formed on a glass substrate and then transferred to the electrode section. Examples include the transfer bump method.

However, forming bumps using these methods not only requires the installation of expensive exposure equipment and plating equipment, but also requires high material costs and a long process for patterning, such as photolithography and etching. There is a problem in that the bump forming process becomes longer because of the necessity.

For this reason, a method has been proposed in Japanese Patent Publication No. 10094/1984, in which a pedestal is manufactured at the tip of the inner lead using a mechanical press forming technique using a mold. In this method, a tape carrier in which a film and an inner lead are integrated is attached to a lower die, and an upper die having a protrusion larger than the width of the inner lead is lowered from one side to form a protrusion at the tip of the inner lead. This is a method in which a pedestal, which becomes a bump, is formed at the tip of the inner lead by press working. Note that a notch is provided in one width direction to allow the material in the recessed portion of the inner lead pressed by the convex portion of the upper die to escape.

[Problems to be Solved by the Invention] However, the bumps formed at the tips of the inner leads by such a press working method are bumps whose cross-sectional shape is solid, which is obtained by molding the outer shape of the inner leads using a mold. Therefore, it acts as a rigid body against the compressive load applied in the process of bonding the semiconductor element and the bump by thermocompression bonding.

For this reason, if there is variation in the height of individual bumps, there is a problem that when bonding the bumps to the semiconductor element, it is not possible to bond all the bumps uniformly, resulting in electrical connection failures. To prevent connection failures,
It is necessary to keep the variation in the height of the bumps to at least 0.5 pm or less, and it is required to form the bumps with extremely high precision. Further, there is a problem in that the recessed portion of the inner lead requires processing to provide a notch in advance.

The purpose of the present invention is to eliminate such conventional drawbacks, simplify the bump forming process, and improve productivity by achieving good bonding with semiconductor elements even when there are variations in bump height. An object of the present invention is to provide a method for forming bumps on inner leads.

[Means for Solving the Problems 1] In order to achieve the above object, a method for forming bumps on TAB inner leads according to the present invention is a method for forming bumps near the tips of inner leads of a TAB tape carrier, comprising: a first step of mounting a plurality of inner leads on a hard rubber at a constant pitch; a plurality of protrusions equal to the pitch of the inner leads and smaller than the width of the inner leads; A punch with a flat periphery is placed opposite the inner lead on the hard rubber,
The method includes a second step of positioning the center of the convex portion of the punch at a predetermined position of the inner lead, and a third step of compressing and molding the inner lead with the punch.

[Operation] By forming a bump smaller than the width of the inner lead 12 as shown in FIG. 3 using a punch and a die, the bump 18 having a dome-shaped hollow structure can be formed. Hollow structure bump! 8 has the advantage of greatly simplifying the bump forming process by eliminating the need for glue for bump formation; Thermocompression bonding B, even if there are variations in ? The bumps are plastically deformed by the compressive load, and all the bumps can be straightened to a uniform height. Therefore, even if there is variation in bump height, the hollow bump can be brought into uniform contact with all the electrode parts of the semiconductor element, and good bonding can be achieved.

Such hollow bumps generally have a diameter of 1 as shown in Figure 4.
It is formed using a set of dies 42 and a rod-shaped punch.

In this case, one bump per inner lead 12.
Since bumps 8 are formed one by one, it is sufficiently effective for high-mix, low-volume production applications, but for mass production applications, it takes a long time to form the bumps (approximately 1 second per bump). , there is a problem of low productivity. In order to improve productivity, a die with multiple die holes and a punch with multiple protrusions are used to press multiple inner leads at the same time to form multiple hollow bumps at the same time. Good.

-1- In order to form multiple bumps at the same time with high precision and high productivity, it is necessary to position each inner lead, punch, and die with high precision and instantly. This is required.

However, as the number of bumps to be formed at once, that is, the number of inner leads, increases, the cumulative error in positioning increases, which requires more advanced positioning technology.Furthermore, as the number of bumps to be formed increases, the positioning generally becomes more difficult. Since the time required also increases, a problem also arises in terms of productivity.

Therefore, in the present invention, as shown in FIGS. 1(a) to G),
A plurality of inner leads 12 are attached to a hard rubber 11'', and then a flat portion 1 having a plurality of protrusions 15 equal to the pitch of the inner leads 12 and having a flat periphery around the protrusions 15 is formed.
A punch 17 having a diameter of 6 is disposed opposite to the inner lead 12, and positioned at a predetermined position of the inner lead I2 at the center of the convex portion 15 of the punch 17, and the inner lead 12 is pressed down and molded by the punch 17. Inner lead! 2
Ha, convex part! 5 and the flat portion 16, the inner lead 12 is pushed out toward the hard rubber 11 side by the convex portion I5 of the punch 17, and a plurality of hollow bumps I8 are collectively formed at a predetermined position on the inner lead 12.

As described above, in the bump forming method of the present invention, since no die is used, alignment between the punch and the die is not required, and productivity is improved. Furthermore, by using inexpensive hard rubber, it is possible to reduce the cost of manufacturing the die.

〔Example〕

Hereinafter, the present invention will be explained in detail using the drawings.

FIGS. 1(a) to 1(a) are cross-sectional views illustrating the method for forming bumps on inner leads according to the present invention in the order of steps, and the second leap is a plan view showing the TAII tape on which the inner leads I2 are formed.

In the figure, 11 is hard rubber, 12 is inner lead,
13 is an XY stage, 14 is double-sided tape, 15 is a convex part formed at the tip of the punch, 16 is a flat part formed around the convex part, 17 is a punch, 18 is a hollow bump, 21 is TAB tape, and 22 is a film. show.

Specific examples of the present invention will be shown below.

The punch I7 has a punch convex portion 1 as shown in FIG.
5 has a diameter of 30±2pm, and the flat part 16 around the punch has a width of 6
7±lpm and a length of 500±5 μm, the pitch of each punch convex portion 15 is 140±2 pm, and 30 punch convex portions 15 are formed in a row. The hard rubber 11 has a rubber hardness of 80 or higher, has a size of 7M square, and has a thickness of 2 cylinders, and is fixed to the XY stage 13 with double-sided tape 14. The TAB tape 21 has 30 inner leads 12 each having a width of 70 p m and a thickness of 35 μm arranged at a pitch of 140 μm, and a polyimide film 2 on all sides.
Use the one reinforced in step 2. Next, in the bump manufacturing method, first, as shown in FIG. 1(a), the inner lead 12 of the TAB tape 21 shown in FIG. 2 is fixed onto a hard rubber il. Next, as shown in FIG. 1(b), the inner lead 12 is positioned on the XY stage 13 so that the convex portion I5 of the punch 17 is at a predetermined position.

Finally, as shown in Figure 1 G), a pushing load of 12 kg r was applied to the punch 7, and the inner lead 12 was pressed down to form a hollow bump 18, resulting in a semicircular shape as shown in Figure 3. It was possible to form 120 hollow bumps 18 at once. The hollow bump 18 shown in FIG. 3 formed at the tip of the inner lead 14 and the semiconductor element with the ^e set of electrodes are bonded together using a low-temperature bonding method (element heating temperature =
275°C, pressure tool temperature = 450°C.

When bonding was performed using a pressure of 60 gf/lead and a pressure application time of 1 second, the bonding was achieved with good strength both electrically and mechanically.

The method for forming bumps by press working of the present invention was able to form 120 bumps on all inner leads 12 of the film 22'' in a cycle time of 10 seconds or less.

In one embodiment of the misfire 1j, a bump is formed on one side of 30 inner leads in a row, and the same process is continuously performed on four inner leads on four sides, thereby forming a film 22''. Bumps are formed on all inner leads 12 on all four sides, but bumps may be formed on all inner leads 12 on all four sides at once, or bumps 18 may be formed on several inner leads 12 at once. The process may be repeated in multiple cycles to form bumps on all inner leads.

[Effects of the Invention] - As explained above, according to the J method for forming bumps on TAB inner leads of the present invention, the bump forming process is simple, and even if there is variation in bump height, the bump formation process can be easily achieved. It has the effect of achieving good bonding and realizing bump formation with excellent productivity.

[Brief explanation of drawings]

FIGS. 1(a) to (c) show the bump forming method of the present invention]-
2 is a plan view showing a film used in an embodiment of the present invention, FIG. 3 is a side view showing a bump formed by an embodiment of the present invention, and the 4th figure is a sectional view shown in order of process. FIG. 3 is a cross-sectional view showing a method of forming l bumps using a set of punches and dies. II...Hard rubber 13...XY stage 15...Protrusion 17...Punch 2I...T/\B tape old...rod-shaped punch! 2... Inner lead 14... Double-sided tape I6... Flat part! 8...Hollow bump 22...Film 42...Dice

Claims (1)

[Claims] (1) A method of forming bumps near the tips of the inner leads of a TAB tape carrier, which includes a first step of mounting a plurality of inner leads on a hard rubber at a constant pitch, and a step equal to the pitch of the inner leads. A punch having a plurality of convex portions smaller than the width of the inner lead and having a flat periphery is placed opposite to the inner lead on the hard rubber, and the center of the convex portion of the punch is aligned with the center of the convex portion of the inner lead. a second step of positioning the inner lead at a predetermined position;
A method for forming bumps on a TAB inner lead, comprising a third step of forming the inner lead under pressure using the punch.