JP2870930B2 - Method for forming conductive protrusions on lead portion of TAB tape - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a TAB (Tape Automaton) which is one of connection methods between electric circuit components in the field of microelectronics.
The present invention relates to a method for forming a conductive projection for connection to an electrode at a lead portion of a carrier tape used in a ted bonding method.

(Prior art)

In recent years, with the miniaturization of semiconductor elements, the electrodes on the elements connecting the semiconductor elements and external terminals tend to have narrower pitches and more pins. Accordingly, the TAB method has attracted attention as a mounting technology that has high connection reliability and enables high-speed mounting in response to such a tendency.

As a method of connecting the electrode on the semiconductor element and the electrode provided on the lead portion of the carrier tape by the TAB method, a method of transferring and forming a metal conductor on the electrode of the lead and connecting using this metal conductor is known. Yes (for example,
52147, JP-A-60-130147, etc.).

FIG. 5 is a schematic diagram showing the connection method. Conductive projections 37 are previously formed in a pattern on a substrate 39 by a plating method or the like, and the conductive projections 37 are aligned with the electrodes of the leads 36 of the carrier tape 38. The conductive protrusions 37 are transferred on a one-to-one basis, and the substrate 39 is removed (FIG. 5A). Next, the transferred and formed leads 36
After the conductive protrusion 37 on the electrode is aligned with the electrode 32 of the IC chip 31, the conductive protrusion 37 and the electrode 32 are connected by thermocompression bonding (FIG. 5B).

[Problems to be solved by the invention]

By the way, as IC chips 31 become more highly integrated,
The electrodes 32 on the IC chip are also reduced in size and pitch. Then, the leads 36 need to be miniaturized, narrowed, and narrowed in pitch. In such a case, each one as described above
In the lead 36 having two conductive protrusions 37 on the electrodes,
It becomes difficult for the conductive protrusion 37 to be transferred to the center of the lead width.

Therefore, the conductive protrusion 37 of the lead 36 and the electrode of the IC chip 31
When the conductive protrusions 37 are crushed and deformed when connecting the conductive protrusions 32, the leads 36 easily protrude in the width direction of the leads 36, and there is a problem that adjacent conductive protrusions 37 cause a bridge failure.

Separately, in the case of the lead 36 having the conductive protrusions 37 on the electrodes one by one, if the heat or the stress is applied in the use environment after the connection with the electrode 32 of the IC chip 31, the conductive There is also a problem that it is easy to peel off at the interface between the metal of the protrusion 37 and the electrode 32 of the IC chip 31.

Further, as described above, there is also a demand for transferring a small conductive protrusion which cannot secure sufficient alignment accuracy due to the miniaturization of the lead portion. In such a case, in the method in which the conductive protrusions 37 are transferred and formed on the leads 36 in a one-to-one manner, the conductive protrusions cannot be accurately transferred to the center of the electrode portions of the leads, and the position of the conductive protrusions 37 with respect to the electrodes of the IC chip is reduced. There is a problem in that a shift occurs, resulting in a decrease in connection strength or a short circuit between electrodes.

The present invention has been made in view of such circumstances, and does not cause a bridge failure between conductive protrusions provided on adjacent leads, and has a conductive portion of a TAB tape lead portion that is difficult to peel off from an electrode of an IC chip. It is another object of the present invention to provide a method for forming a projection without requiring high-precision alignment with respect to the lead portion.

[Means for solving the problem]

According to a first aspect of the present invention, there is provided a method for forming a conductive protrusion on a lead portion of a TAB tape, comprising: forming a conductive protrusion on each of the lead electrodes of the TAB tape having a plurality of wiring leads; In a wider area, using a conductor holding material in which conductors are scattered at an arrangement interval including a plurality in an area corresponding to the electrode, the conductor holding material is overlapped with the electrode of the lead, and The conductor located in the overlapping range is transferred to the electrode of the lead, and a plurality of conductive projections are formed on each of the electrodes by using these.

Further, in the method for forming conductive protrusions on the lead portion of a TAB tape according to the second invention of the present application, the conductor holding material used in the first invention holds a plurality of conductors in a layer having a laminated structure with the base. It is characterized by.

[Action]

In the method for forming a conductive protrusion on a lead portion of a TAB tape according to the first invention, a plurality of conductors are included in the conductor holding material in an area larger than the lead electrode and within a region corresponding to the lead electrode. When the electrodes of the lead are superimposed on the conductor holding material, a plurality of conductors overlap each of the electrodes, and the transfer of these conductors causes the electrodes of the lead to be scattered on the respective electrodes of the lead. A plurality of conductive protrusions are formed.

In the second invention, a part of the conductor group held in a layer having a laminated structure with the base is pressure-bonded to the electrode of the lead.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to the drawings showing the embodiments. FIG. 1 is a plan view and a side view of a lead portion of a TAB tape having conductive projections formed by the method of the present invention. FIG. 1 (a) shows a case where the electrode 1b is provided over the entire width of the lead 1a, and FIG. 1 (b) shows a case where the electrode 1b is provided only at the center in the width direction.
The electrode 1b can be formed by, for example, Sn plating. Each of the electrodes 1b is provided with a plurality of conductive protrusions 2a.

Hereinafter, a method for forming a conductive projection on the lead portion of the TAB tape as described above will be described.

FIG. 2 is a schematic view showing a step of connecting a TAB tape and an IC chip using the method for forming a conductive projection on a lead portion of a TAB tape according to the first invention of the present application.

First, as shown in FIG. 2 (a), a conductive projection is formed on an electrode 1b provided on a lead 1a of a TAB tape 1 by using a conductor holding material 2. FIG. 3 is an enlarged sectional view of the conductor holding member 2. On a holder 2b made of a photosensitive organic resin such as polyimide, a plurality of rod-shaped conductors 2a serving as conductive protrusions are arranged at predetermined intervals determined based on the area of the electrode 1b of the lead 1a, and both ends of the holder It is held protruding from both sides of 2b. Here, the conductor 2a is arranged in a region where one cross-sectional area is sufficiently smaller than the area of the electrode 1b of the lead 1a and larger than the area of the electrode 1b, and the conductor 2a is projected at least on one surface side of the holder 2b. It would be fine. Further, in order to dispose the conductor 2a on the holder 2a, a plurality of holes are formed in the holder 2b using a photolithography method, and a single layer of gold or the like is formed in these holes by a plating method, or another hole. It can be formed by filling a plurality of layers with a metal.

The conductor holding material 2 thus configured is connected to the surface of the holding body 2b on the side where the conductor 2a protrudes, and to the lead 1 of the TAB tape 1.
The conductor 2a is connected to the electrode 1b by thermocompression or crimping using the crimping substrate 3 and the bonding tool 4 (see FIGS. 2A and 2B). )).

At this time, the conductors 2a of the holder 2b are arranged in a region larger than the area of the electrode 1b at an arrangement interval that includes a plurality of areas within an area corresponding to the electrode 1b, so that the conductor 2a
Alignment between 2a and electrode 1b is not required. That is, since some of the plurality of conductors 2a of the group of conductors 2a are always joined to the electrode 1b, there is no need to make one-to-one correspondence between the conductor and the electrode as in the related art.

Next, as shown in FIG. 2 (c), the conductor holding material 2 excluding the conductor 2a joined to the electrode 1b of the lead 1a is removed using an organic solvent. As a result, a plurality of conductors 2a, 2a,.
It is formed as a conductive projection when connecting to the electrode of the chip. When the lead portion was observed at this time, no damage was observed.

Next, as shown in FIG. 2D, the electrodes 5a of the IC chip 5 are formed.
To connect the TAB tape 1 with the electrode 1 of the lead 1a.
b, ie, the conductive protrusions 2a formed thereon and the IC chip 5
And the electrodes 5a are opposed to each other, and pressure-bonded using the bonding tool 4.

As a result, as shown in FIG. 2 (e), the electrodes 5a of the IC chip 5 are connected via the plurality of conductive protrusions 2a at each connection portion.
Then, electrical connection with the electrode 1b of the lead 1a of the TAB tape 1 is made. During this connection, the conductive protrusion 2a may be crushed and deformed. However, since one conductive protrusion is small, the conductive protrusion 2a does not protrude in the width direction of the lead due to the deformation. Does not occur. Also, even if heat or stress is applied to this connection part,
As a result of mutually absorbing the stresses by the plurality of conductive protrusions 2a, it is difficult to peel off at the connection interface between the conductive protrusions 2a and the electrodes 5a.

The following Tables 1 and 2 show the results of conducting a conductivity test by forming conductive protrusions on the electrodes on the leads of the TAB tape by the above-described method and connecting the electrodes to the electrodes on the IC chip.
In both cases, the electrode area on the lead is equal to the electrode area on the IC chip, and Table 1 shows that the electrode is formed over the entire width of the lead as shown in FIG. 1 (a). If
Table 2 shows the case where the electrode is formed only at the center in the width direction as shown in FIG. 1 (b). For example, when the lead width in Table 1 is 50 μm and the electrode area is 50 × 50 μm on both the lead and the IC chip side, use a conductor holding material in which a plurality of conductors are arranged at a pitch of 15 μm vertically and horizontally. When 50 pins are connected together, that is, collectively connected with a TAB tape having 50 leads to 50 electrodes arranged on one side of the IC chip, both the crimped state and the conductive state are good. Was. The test was performed with the same number of connection pins for other lead widths and electrode areas.

As can be seen from the above table, by changing the arrangement pitch of the conductors according to the electrode area, the conductors arranged on the conductor holding material without fail in alignment to a lead width of about several μm without alignment. Is transferred to the lead electrode,
The plurality of transferred conductors make connection with the electrodes of the IC chip to maintain a good conduction state.

In Table 3 below, the lead width is 50 μm and the electrode area is 30 μm.
This is a continuity test result when collective connection is performed by changing the number of connection pins when × 30 μm and the conductor arrangement pitch is 5 μm. The continuity test result shows the number of continuity failures when 1000 samples were sampled.

As can be seen from the above table, the continuity test results are good even when the number of connection pins increases.

In the present embodiment, the conductor holding member 2 is formed by forming a plurality of holes in a photosensitive organic resin by using a photolithography method and forming a conductor 2a by using a plating method. An anisotropic conductive film, that is, a sheet-shaped organic resin in which a plurality of through holes are formed, and a rod-shaped conductor inserted therein may be used, and the same applies to the crimp strength and conductivity in that case. Good results are obtained.

FIG. 4 is a sectional view showing an embodiment of the conductor holding material used in the second invention. Conductor holding material 6 is made of glass and IT
A conductive base 6c composed of an O film 6d and a laminated body of a holder 6b made of a photosensitive organic resin, and a plurality of conductors 6a are provided on the holder 6b, and one end of the conductor 6a is provided on the holder 6b. It protrudes from the surface and is arranged at a predetermined pitch similarly to the conductor holding material 2. In order to manufacture the conductor holding material 6 configured as described above, first, a photosensitive organic resin serving as the holder 6b is applied on the base 6c, and the conductor 6a is disposed on the photosensitive organic resin. A plurality of holes reaching the ITO film 6d are formed by photolithography. Then, the conductor 6a is filled by a plating method and formed to a height protruding from the hole, thereby completing the process. The conductor 6a may have a single-layer structure or a multi-layer structure.

Since the conductor holding member 6 has the base 6c, the holding member 6b is not distorted or bent at the time of connection with the lead portion, so that connection reliability is high. And conductor
After the protruding portion of 6a is crimped to the lead electrode, the conductor holding member 6 is separated from the crimped conductor 6a. At this time, the conductor 6a crimped to the electrode is easily separated because the ITO film 6d is disposed at the other end, and only the crimped conductor 6a remains on the lead electrode. That is, in this case, the step of removing the photosensitive organic resin when the conductor holding material 2 is used, that is, the holder 2b is not required. Other steps are conductor holding material 2
In the same manner as in the case of using the conductor holding material 6, the crimp strength and the conduction test result when the present conductor holding material 6 was used were also good.

In the present embodiment, a photosensitive organic resin is used for the holder 6b, but a heat-resistant non-conductive material such as a heat-resistant nitride may be used.

Further, a material obtained by removing the holder 6b with an organic solvent before the transfer of the conductor 6a may be prepared as a conductor holder. That is, a plurality of conductors 6a are scattered on the base 6c, and the transfer method thereof is the same as described above.

Furthermore, in the present embodiment, a plurality of conductive protrusions on the electrode of the lead and the conductive material in the conductive material holding material are regularly arranged, but the present invention is not limited to this, and the form is freely determined. Can be

In addition, the present invention is not limited to a single-layer TAB composed of only copper foil, but also a two-layer TAB composed of copper foil and an organic resin, as well as a two-layer TAB composed of a copper foil and an organic resin. is there.

〔effect〕

As described above, in the method for forming conductive protrusions on the lead portion of a TAB tape according to the present invention, a plurality of wirings are included in an area larger than an electrode of a lead on which conductive protrusions are to be formed, within an area corresponding to the electrodes. Using conductor holding material with conductors scattered at the setting interval, and overlapping this conductor holding material on the lead electrode, multiple conductors can be positioned with high precision within the overlapping range with each electrode. It is located without necessity, and a plurality of conductive protrusions can be reliably formed on each electrode by transferring these conductors.

In addition, the conductive projections formed in this manner do not protrude from the leads even if they are crushed and deformed when connected to the IC chip, so that there is no occurrence of a bridge failure with the conductive projections of the adjacent leads. In addition, even if heat or stress is applied in a use environment after connection, the plurality of conductive protrusions absorb each other, so that it is difficult to peel off at a connection interface, and strong connectivity can be secured.

As a result, even if the TAB tape is made finer due to the narrower pitch of the electrodes on the IC chip and the increase in the number of pins, the bonding strength is reduced, or the electrodes are not short-circuited without fail.
The present invention has excellent effects, for example, the TAB tape and the IC chip can be electrically connected, and the reliability of the semiconductor device can be greatly improved.

[Brief description of the drawings]

FIG. 1 is a plan view and a side view of a lead portion of a TAB tape having conductive projections formed by the method of the present invention.
FIG. 3 is a schematic view showing a process of connecting a TAB tape and an IC chip using the method for forming conductive protrusions on a lead portion of a TAB tape according to the first invention; FIG. 3 is an enlarged sectional view of a conductor holding material;
FIG. 4 is a cross-sectional view of a conductor holding material used in the second invention, and FIG. 5 is a schematic view showing a process of connecting a conventional TAB tape and an IC chip. 1. TAB tape, 1b. Electrode, 2, 6 ... Conductor holding material, 2a, 6a ... Conductor (conductive protrusion), 2b, 6b ... Holder,
6c: Base, 6d: ITO film

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H01L 21/60 311

Claims (2)

(57) [Claims] 1. A method for forming conductive protrusions on each of the leads of a TAB tape having a plurality of leads for wiring, wherein a plurality of leads are provided in an area larger than the electrodes of the leads and within an area corresponding to the electrodes. Using a conductor holding material in which conductors are scattered at the included arrangement intervals, the conductor holding material is overlapped on the electrode of the lead, and the conductor located within this overlapping range is transferred to the electrode of the lead. And forming a plurality of conductive protrusions on each of the electrodes by using these. A method for forming conductive protrusions on a lead portion of a TAB tape. 2. The TA according to claim 1, wherein the conductor holding material has a plurality of conductors held in a layer having a laminated structure with the base.
A method for forming conductive protrusions on the lead portion of a tape for B.