JPH0574875A - Method of connecting tab inner lead - Google Patents

Abstract

PURPOSE:To realize a stable connection with small scattering in a connection strength by a method of first connecting such an inner lead that a longitudinal direction thereof is perpendicular to a vibration direction of a bonding tool. CONSTITUTION:Using a round bonding tool 7 of which a tip is conical, after an Al electrode 2 of a semiconductor element 1 is superimposed an inner lead 5, the inner lead 5 of the fourth side is first bonded which is disposed in the direction perpendicular to the direction of an ultrasonic vibration 8 of a transducer 6. Next, the same operations are carried out in the order of the second side, the third side, the first side and all the inner leads 5 are connected to the Al electrode 2. Thus, a stable connection with a small scattering of a connection strength can be realized and further the relative location slippage between the inner lead and the electrode of the semiconductor element can be limited to the minimum and the narrow pitch TAB mounting can be realized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a TAB (Tape Automated Bo) used for mounting a semiconductor element.
nding: a method for joining inner leads of a tape carrier for tape automated bonding) and electrodes of a semiconductor element.

[0002]

2. Description of the Related Art Conventionally, in a single bonding method in which an inner lead of a TAB tape and an electrode of a semiconductor element are sequentially bonded, as shown in FIG.
After forming a protrusion to be the bump 10 on either one of the electrode portion 2 or the tip of the inner lead 5 of the TAB, the bonding was performed by the bonding tool 11 via the bump 10 by using both ultrasonic waves and heat. .. Generally, in order to form bumps, complicated steps such as lithography are required, and moreover expensive equipment is required. For this reason,
The joining method of the TAB inner leads, which requires a bump forming step, has a problem of high mounting cost.

Therefore, bumps are not necessary, and Al of a semiconductor element is used.
A direct single bonding method has been proposed in which the electrode and the TAB inner lead can be directly bonded (Japanese Patent Laid-Open No. 3-85895). In the direct single bonding, as shown in FIG. 2, first, the inner lead 5 and the Al electrode 2 of the semiconductor element 1 are aligned with each other, and then the bonding tool 7 is pushed into the inner lead 5 to bond the inner lead 5 to the bonding tool 7. Of the bonding tool 7 and the inner lead 5 are adhered to each other, and at the same time, the inner lead 5 is formed.
Is brought into pressure contact with the Al electrode 2. Next, while maintaining such a contact state, ultrasonic vibration 8 is applied to the bonding tool 7 to bond the inner lead 5 and the Al electrode 2. At this time, the semiconductor element is heated to 250 by the heating stage.
It is heated to about ℃.

Generally, in the order of bonding, adjacent inner leads are sequentially bonded in order to shorten the bonding time as much as possible. For example, in FIG. 1, the TAB tape is sequentially bonded from the end of the first side to the second side, the third side, and the fourth side.

[0005]

In order to obtain a stable bonding strength by the direct single bonding method by thermocompression bonding combined with ultrasonic wave, ultrasonic wave vibration sufficiently destroys the natural oxide film of Al existing on the Al electrode surface, Au and Al on the surface of the inner lead due to the heat energy from the heating stage
The condition is to form an alloy layer with Al on the electrode surface. Here, as indicated by an arrow 8 in FIG. 1, the vibration direction of ultrasonic waves is parallel to the longitudinal direction of the inner lead with respect to the first side and the third side, and with respect to the second side and the fourth side. Is a direction orthogonal to the longitudinal direction of the inner lead.

When the ultrasonic vibration is applied in the direction orthogonal to the longitudinal direction of the inner lead like the second side and the fourth side, the ultrasonic vibration can be sufficiently transmitted to the bonding interface. Therefore, the Al oxide film could not be sufficiently destroyed. Therefore, there is a problem that the bonding strength of the second side and the fourth side is lower than that of the first side and the third side. Further, when the bonding is sequentially performed from the first side, heat is radiated from the semiconductor element by heat conduction through the bonded inner leads, so that the temperature of the bonding surface decreases at the fourth side, which is the final bonding side, and the bonding strength is increased. There was a shortage of issues.

Generally, in the single bonding method, bonding is performed by thermocompression bonding together with ultrasonic waves as described above, so that the mechanical action of ultrasonic vibration causes relative movement between the inner lead and the electrode of the semiconductor element. Misalignment occurs. Further, since the polyimide tape, which is the support ring of the TAB tape, is deformed by the heat flowing out from the semiconductor element through the inner lead, there is a problem that a relative position shift occurs between the inner lead and the semiconductor element due to a thermal action. there were. Due to such a relative positional deviation between the inner lead and the electrode of the semiconductor element caused by the mechanical and thermal effects, there is a problem to be solved that it is difficult to perform TAB mounting with a narrow pitch.

An object of the present invention is to solve the conventional problems as described above and to provide a joining method of a TAB inner lead which realizes stable joining without variation in joining strength.

Another object of the present invention is to provide a method of joining TAB inner leads which enables TAB mounting with a narrow pitch.

[0010]

In order to achieve the above-mentioned object, the method of joining the TAB inner leads of the first invention comprises:
In the direct single bonding method in which the electrodes of the semiconductor element and the inner leads of the TAB tape are directly connected together by ultrasonic thermocompression bonding using a bonding tool, the inner leads are connected such that the longitudinal direction of the inner leads is the vibration of the bonding tool. It is characterized in that the connection is made from the inner leads orthogonal to the direction.

A second aspect of the present invention is the method of joining TAB inner leads according to the first aspect, wherein the inner leads located at the center of each side of the TAB tape are first connected, and then the unconnected inner leads are sequentially joined. It is characterized by doing.

[0012]

In the direct single bonding method using ultrasonic thermocompression bonding of the present invention, the second side and the fourth side are first bonded at the initial stage of bonding when the temperature of the bonding portion is high.
It is possible to make up for the lack of ultrasonic action and realize stable and good joining. Regarding the first side and the third side, the temperature of the joint decreases due to heat dissipation from the inner lead, but ultrasonic vibration can be sufficiently applied to the joint surface, so stable and favorable joint is realized. It becomes possible to do.

Regarding the relative pitch shift between the inner leads and the electrodes of the semiconductor element due to the mechanical action of ultrasonic vibration and the thermal action of heat dissipation, the inner leads located at the center of each side are first joined to each other. By reducing the pitch deviation due to mechanical action and by evenly distributing the effect of thermal deformation on both sides of the inner lead that is first joined, the effect of pitch deviation due to thermal action can be halved compared to the conventional joining method. .. By these, narrow pitch TAB
Implementation is possible.

[0014]

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a schematic diagram showing a method of joining inner leads of the present invention, and FIG. 2 is a schematic diagram illustrating a joining state by a bonding tool having a rounded tip. In FIGS. 1 and 2, 1 is a semiconductor element, 2 is an Al electrode, 3 is a passivation film, 4 is a tape carrier, 5 is an inner lead, 6 is a transducer, 7 is a bonding tool, 8 is a direction of ultrasonic vibration, and 9 is It is a dent. In the embodiment of the present invention, a TAB tape in which a Cu lead having an inner lead width of 60 μm, an inner lead pitch of 100 μm, and an inner lead thickness of 35 μm is plated with Au of 0.6 μm is used. Bonding with electrodes was performed.

First, the first embodiment will be described. As the bonding tool, the bonding tool 7 shown in FIG. 2 having a conical tip end and a rounded end was used. As shown in FIG. 1, the Al electrode 2 and the inner lead 5 of the semiconductor element 1
After aligning with, the inner lead 5 of the fourth side located in the direction orthogonal to the direction of the ultrasonic vibration 8 of the transducer 6 was first bonded.

As shown in FIG. 2, the bonding tool 7
A load of F = 60 gf was applied to and the bonding tool 7 was pressed against the inner lead 5. Next, with the load applied to the bonding tool 7 being maintained at F = 60 gf, ultrasonic vibration 8 is applied to the bonding tool 7 to heat the inner leads 5 at a heating temperature of 280 ° C. of the semiconductor element 1.
And Al electrode 2 were joined.

The above operation is performed in the order of the fourth side, the second side, the third side, and the first side, and after bonding all the inner leads 5 to the Al electrode 2, the bonding strength is measured and it is generated on the Al electrode surface 2. The presence or absence of cracks was observed. As a result, it was confirmed that the pull strength was 40 gf / lead or more on all sides from the first side to the fourth side with sufficient strength and the Al electrode surface 2 was not cracked.

In the second embodiment, as shown in FIG. 1, first, the inner leads 5 of the fourth side, the second side, the third side and the first side are sequentially bonded to form an Al electrode 2 and The inner lead 5 was fixed. Next, as in the first embodiment, all the inner leads 5 and Al electrodes 2 are joined in the order of the fourth side, the second side, the third side, and the first side, and the joint strength is measured and the inner leads are joined. 5 and the positional deviation amount of the Al electrode were observed. As a result, the pull strength was 40 gf / lead on average, which was a sufficient strength as in the first embodiment, and the amount of positional deviation between the inner lead 5 and the Al electrode was 10 μm, which was about half that of the first embodiment. We were able to.

It has been confirmed that the present invention has a similar effect to the conventional single bonding method using bumps as shown in FIG.

[0021]

As described above, according to the joining method of the TAB inner lead of the present invention, it is possible to realize stable joining with a small variation in the joining strength.
It is possible to minimize the relative positional deviation between the inner lead and the electrode of the semiconductor element, and to narrow the pitch TA
There is an effect that B mounting can be realized.

[Brief description of drawings]

FIG. 1 is a schematic view showing a method of joining inner leads according to the present invention.

FIG. 2 is a schematic diagram illustrating a bonding state with a bonding tool having a rounded tip.

FIG. 3 is a schematic view showing a conventional joining method of TAB inner leads.

[Explanation of symbols]

 1 Semiconductor Element 2 Al Electrode 3 Passivation Film 4 Tape Carrier 5 Inner Lead 6 Transducer 7 Bonding Tool 8 Ultrasonic Vibration 9 Dimple 10 Bump 11 Conventional Bonding Tool

Claims (2)

[Claims] 1. In a direct single bonding method in which an electrode of a semiconductor element and an inner lead of a TAB tape are directly connected together by ultrasonic thermocompression bonding using a bonding tool, the inner lead is connected in a longitudinal direction of the connecting inner lead. A method of joining TAB inner leads, characterized in that the connection is made from the inner leads orthogonal to the amplitude direction of the bonding tool. 2. The joining method of TAB inner leads according to claim 1, wherein the inner leads located at the center of each side of the TAB tape are first joined and then the unattached inner leads are joined sequentially. ..