JPH03214748A - Method of forming bump of tab inner lead - Google Patents

Abstract

PURPOSE:To simplify a bump forming process without creating the plastic deformation of an inner lead by a method wherein, after the bump is formed by a press process, a punch is removed from the inner lead while it is made to rotate around the punch axis. CONSTITUTION:When a hollow bump is formed by a mechanical press process, the circumference of the protrusion 15 of a punch 11 adheres tightly to the inner surface of the hollow bump 16 after the protrusion 15 of the punch 11 is pushed into an inner lead 14. Therefore, when the punch 11 is removed, the inner lead 14 is lifted above the die hole 13 of a die 12 and the plastic deformation of the inner led 14 is created. In order to avoid this problem, the punch 11 is removed from the inner lead while it is made to rotate around the punch axis. With this constitution, the adhesion between the punch 11 and the inner surface of the hollow bump 14 is released, so that the punch 11 can be removed easily without creating the deformation of the inner lead 14.

Description

[Detailed Description of the Invention] [Industry] Second Field of Application] The present invention is applied to T A B (
T aJ) 0Δ old. omatcd Bonding)
The present invention relates to a method for forming bumps on the tips of inner leads of tape carriers by mechanical press processing.

[Prior Technology] Generally, in order to mount a ``-1'' conductor element on an ``I'AB tape carrier,'' either the ``receptor rfl'' of the semiconductor element or the inner lead tip of the tape carrier is It is necessary to form protrusions that serve as bumps.For example, the method of forming bumps on the electrodes of semiconductor devices is as described in "IBM Journal, Vol. 8, p. 102, 1964. electrode f
There is a method of forming protrusions that become bumps directly on the plating method, and a method of forming bumps directly on
Kaging & Production) J, 198
As described in the December 2004 issue, pages 33-39, the Bedestal method using etching technology, that is, masking the part where the bump will be formed and half-etching the other inner lead parts, is used to reduce the thickness of 30 to 7 lOμm. A method of forming protrusions with a height of A transfer bump method is used in which bumps are formed and then transferred to electrode portions.

However, forming bumps using these methods not only requires expensive exposure equipment and plating equipment, but also lithography and etching processes for patterning, making it difficult to form bumps. The problem is that the process becomes long.

For this reason, as shown in Fig. 4 (Tokuko Sho 64-1009/
1), a force method has been proposed in which the pedestal 18 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 mold, and an upper mold having a convex portion larger than the width of the inner lead is lowered from above to press a recess 17 at the tip of the inner lead. This is a method in which a pedestal 18, which becomes a bump, is formed by processing at the tip of the inner lead. Note that cutouts are provided in the width direction to allow the material of the four parts 17 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 almost as a rigid body against the compressive load applied in the step of joining the half-body element and the bump by thermocompression bonding.

Therefore, if there is variation in the height of the 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. In order to prevent connection failures, it is necessary to keep the variation in bump height to at least 0.5 pm or less, and it is required to form bumps with extremely high precision. Further, there are problems such as the need to process the four parts of the inner lead to provide notches in advance.

The purpose of the present invention is to solve these conventional problems, and to provide sufficient bonding strength even when the bump formation is oily and uneven in bump height, yet highly reliable. An object of the present invention is to provide a method for forming TAI' {inner lead bumps that can achieve bonding with a semiconductor element.

[Dingdan for deciding the rhyme ↓ theme] In order to achieve the above-mentioned [-1 goal], the l'. according to the present invention. '
l F3 = 3- In the inner lead bump formation method, 'l' A
A method of forming a bump near the tip of an inner lead of a tape carrier for ll using a punch and a die, the method comprising: after forming the bump by pressing, rotating the punch around the punch axis; The inner lead is detached from the inner lead while causing the inner lead to move.

[('I; JfJ) 10. As a bump structure for a TAB inner lead that solves the above-mentioned problem, a hollow structure bump 16 formed in a dome shape smaller than the width of the inner lead l4 using a punch and die as shown in FIG. 2 can be considered. The hollow structure bump 16 has the advantage that the bump formation process can be greatly simplified since the pre-addition for bump formation is unnecessary, and the bump structure is more easily deformed by compressive force compared to a solid structure. Even if there is variation in the height of the bumps, the bumps will be plastically deformed by the compressive load when hot and pressurized, resulting in uniform and uniform bump heights.
It can be corrected to a suitable height. Therefore, even if there is variation in the bump height, the hollow bump can be brought into uniform contact with all the electrode parts of the 0-/1-layer element, and a good bonding can be achieved.

However, when forming a hollow bump using a mechanical press, the convex portion 1 of the punch 11 as shown in FIG.
5 is pushed into the inner lead l4, the punch 11
The outer periphery of the convex portion l5 and the inner surface of the hollow bump l6 are closely spaced i゜゛1.
Therefore, when the punch 11 is removed, the inner lead 14
There was a problem in that the inner leads 14 were lifted from the die hole 13 of the die 12 by being held in both directions, causing plastic deformation of the inner leads 14. Here, if the inner lead 14 is deformed,
Good bonding with the electrode portion of the semiconductor element cannot be achieved.

Therefore, as in the present invention, by rotating the punch around the punch axis when detaching the punch from the inner lead, the close contact between the punch and the inner surface of the hollow bump can be released, causing deformation to the inner lead. It is possible to easily remove the punch without any trouble.

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

FIGS. 1(a) to ←) are partially cross-sectional side views showing the outline of the inner lead bump forming method of the present invention in TLIJl order, and FIG. 2 is a hollow bump formed according to an embodiment of the present invention. FIG.

First, as shown in FIG. 1(a), the convex portion I5 of the punch 11 is
After adjusting the position of the punch l1 so that the center axis of the die hole 13 on the die I2 coincides with the inner lead 4, the inner lead 4 is fixed to the die 121-. The inner lead 14 used here has a width of 80 lm, a pitch of 160 pm, and a thickness of 35! The lead Il1 was made of copper (with lpm of Au plating formed on the surface). The diameter of the convex tip 15 of the punch 11 was 30ttm, and the diameter of the die hole 13 was 50Bn+.

Next, as shown in FIG. 1(b), the punch 11 is pushed into the inner lead 14 to press-form the hollow bump 16. Finally, as shown in Figure 1(e), punch 1l.
When the inner lead 1 was pulled up to one side and separated from the inner lead 14 while rotating around the punch axis, the inner lead 1
The punch 11 could be easily removed from the inner lead 14 without causing plastic deformation to the inner lead 4. At this time, a hollow bump 16 with a height of 30±3 μm and a diameter of 50 lIm at the bottom surface was formed as shown in FIG. Bonding method (element heating temperature:
150'C, pressure tool temperature: 450°C, pressure 50g
As a result of bonding using the I-lead, 1 second), a good connection was achieved both in terms of strength and electrically, and it was confirmed that the formed hollow bumps could be sufficiently used as bumps for inner leads. Despite the ±3 μm variation in bump height, we were able to achieve a good connection because the bump has a hollow structure and the push load during thermocompression bonding was able to correct the variation in bump height. It is.

[Effects of the Invention] As explained above, the bump formation process of the TAB inner lead of the present invention is as follows. J is the bump forming process force < li
i'i Jit has the effect of achieving sufficient bonding strength and highly reliable bonding to a semiconductor element even if there are variations in bump height.

[Brief explanation of drawings]

1(a) to 0) are schematic diagrams illustrating the process order of the method for forming bumps on a TAB inner lead of the present invention, and FIG. 2 is a sectional view showing a hollow structure bump formed according to an embodiment of the present invention. Fig. 3 is a schematic diagram showing the deformation of the inner lead that occurs when removing the punch, and Fig. 4 is a schematic diagram showing the deformation of the inner lead when removing the punch.
FIG. 3 is a schematic diagram showing a method for forming bumps on inner leads. +1... Punch 13... Die hole l5... Convex portion 17... Concave portion l2... Dice l4... Inner lead 16... Hollow bump 18... Pedestal

Claims (1)

[Claims] (1) A method in which a bump is formed by pressing using a punch and a die near the tip of the inner lead of a TAB tape carrier, and after the bump is press-formed, the punch is rotated around the punch axis. A TAB characterized in that the TAB is detached from the inner lead while being rotated.
How to form bumps on inner leads.