JPH05326643A - Film carrier for tab - Google Patents

Abstract

PURPOSE:To provide a film carrier for TAB excellent in bent mounting properties. CONSTITUTION:A slit 5 for bending is made through a base film 1 having one surface applied with a copper lead pattern 11, which is subjected to Sn or Sn alloy plating 12 thus producing a film carrier for TAB. At least the bending part lead 11A of the film carrier is not subjected to plating 12. Consequently, fragile Cu-Sn alloy layer is not formed at the bending part and thereby breaking resistance is enhanced. Furthermore, an insulating and plate resistant flexible resin film is applied on the surface at the bending lead 11A and the surface of the copper lead 11, not covered with resin film, is subjected to Sn plating. This film carrier relaxes concentration of stress to the copper lead and enhances break resistance, corrosion resistance, and oxidation resistance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a film carrier for TAB which is excellent in bending mountability.

[0002]

2. Description of the Related Art In recent years, in semiconductor mounting such as IC, T
The AB (Tape Automated Bonding) method has been actively used as a suitable direction for thinning the package, increasing the number of pins, and assembling automation.

Generally, a film carrier used for TAB type IC mounting has a sprocket hole 2 for film feeding, a device hole 3 for arranging elements, an outer lead hole 4, etc., as shown in FIG. A copper foil is laminated on a base film 1 such as a polyimide film with an adhesive, and the copper foil is etched by a photo-etching process, and inner leads 6 for joining with the electrodes of the IC element and outer leads 7a for connecting to an external substrate, It is manufactured by forming a desired lead pattern including 7b and then plating the lead surface.

One of the applications utilizing such characteristics of TAB is a driving element for a liquid crystal panel used in a display device such as an OA device.

In the case of the film carrier used for the liquid crystal driving TAB, the output signal outer lead 7a is provided on one side,
The input signal outer leads 7b are formed on the other side, and the output signal outer leads 7a are opposed to and connected to the electrodes formed on the peripheral portion of the liquid crystal substrate via an anisotropic conductive adhesive. Are mounted by soldering to external board terminals.

On the other hand, in order to reduce the drive element mounting area at the peripheral portion of the liquid crystal substrate in accordance with the recent demand for miniaturization and high density of the device, as shown in FIG. The film carrier used for this type of application uses a mounting method of bending at a portion, and in order to facilitate bending at an acute angle while maintaining close contact with the substrate, a slit hole 5 is formed in the bent portion of the base film 1. It is generally known that a copper foil lead is bent in advance and only the copper foil lead is bent. In addition, 8 is an IC chip, 9 is a liquid crystal substrate, and 10 is an anisotropic conductive adhesive.

[0007]

However, in the case of the above configuration, since there is no base film 1 in the bent portion (the portion of the slit hole 5), the mechanical stress at the time of mounting and the stress due to the heat cycle etc. are thin copper. There is a problem that cracks and fractures of the leads are likely to occur concentrated on the foil leads.

Particularly in the case of a film carrier plated with Sn or Sn-Pb, which is the most commonly used plating for TAB, Cu, which is brittle at the interface between the material copper and the plating, is heated by heating in the IC package assembly process. Since the -Sn diffusion alloy layer is formed, there is a problem that the folding endurance of the leads is significantly reduced.

The present invention has been made in view of the above problems, and an object thereof is to provide a TAB film carrier having excellent folding endurance.

[0010]

In order to solve the above problems, a first invention is to provide a flexible insulating film with slit holes for bending, and to provide a copper lead pattern in a region including the slit holes on one surface of the film. And a Sn or Sn alloy plating on the surface of the copper lead, wherein at least the surface of the copper lead located on the slit hole is not Sn or Sn alloy plated. Characterize.

A second aspect of the present invention is to provide a flexible insulating film with a bending slit hole, and a flexible resin film having plating resistance and insulating property on the surface of the copper lead located on the bending slit hole. And the surface of the copper lead not covered with the resin coating is plated with Sn or Sn alloy.

[0012]

According to the first aspect of the invention, since the bending portion of the copper lead is not plated with Sn or Sn alloy, a brittle Cu-Sn alloy layer is not formed at this bending portion, and the folding endurance is improved. ..

According to the second aspect of the present invention, the concentration of stress on the copper lead can be dispersed by the resin coating provided on the bent portion of the copper lead, the folding resistance is improved, and the corrosion resistance and the oxidation resistance are also improved.

[0014]

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

First Embodiment Since the overall structure of the TAB film carrier according to this embodiment is almost the same as that of the conventional TAB film carrier described above, the same parts are designated by the same reference numerals and the description thereof will be omitted. To do.

The TAB film carrier of this embodiment is
In the structure of the conventional TAB film carrier,
As shown in FIGS. 1A and 1B, Sn or Sn alloy plating (hereinafter referred to as “Sn plating”) 12 is applied to the surface of a copper lead 11 (a portion corresponding to the output signal outer lead 7a of the prior art). .. At this time, the Sn plating 12 is not applied to the portion of the copper lead 11 located on the bending slit hole 5 of the base film 1 (hereinafter referred to as the “bending portion lead 11A”). Note that FIG.
(A) is a partial cross-sectional view showing the film carrier for TAB according to the present embodiment, which is a cross-sectional view corresponding to the upper half-side partial cross-sectional view taken along the line AA of FIG. 2. Figure 1
FIG. 3B is a sectional view corresponding to the sectional view taken along the line BB of FIG.

The TAB film carrier having the above structure is manufactured as follows.

A sprocket hole 2, a device hole 3, an outer lead hole 4 and a bending slit hole 5 having a width of 0.5 nm are press-punched on a film obtained by applying a 20-μm-thick epoxy adhesive to a 75-μm-thick polyimide film. Then, an electrolytic copper foil having a thickness of 35 μm is laminated. Then, the copper foil is etched by a photoetching method to form a film carrier material (base film 1) having a predetermined lead pattern.

An alkali-acceptable acid resistant plating resist containing acrylic resin as a main component is applied to the surface of the bent portion lead 11A located on the slit hole 5 of the base film 1 and dried. After that, this base film 1
Was immersed in electroless Sn hot air liquid (LT-34, Shipley Far East Co., Ltd.) kept at 60 ° C. for 8 minutes, and the thickness was about 0.6 μm only on the surface of the copper lead 11 not coated with the resist.
m Sn plating layer is formed. Then, the plating resist was peeled and removed using an alkaline peeling liquid to obtain a film carrier having a cross-sectional structure having Sn plating 12 in a range excluding the bent portion lead 11A.

With the above construction, the Sn plating 12 is not applied to the bent portion lead 11A of the copper lead 11, so that a brittle Cu-Sn alloy layer is not formed on the bent portion lead 11A. This improves the folding endurance of the bent portion lead 11A.

Second Embodiment The TAB film carrier of this embodiment is shown in FIG.
As shown in (B), in the TAB film carrier of the first embodiment, the bent portion lead 11A not subjected to the Sn plating 12 has an insulation excellent in plating resistance and insulation,
The flexible resin film 13 is provided.

The TAB film carrier having the above structure is manufactured as follows.

Bending portion lead 11 of base film 1
On the surface A, a coating mainly composed of a polyimide resin, which has excellent chemical resistance, insulation, heat resistance, etc., is applied, heated and dried, and a flexible polyimide resin coating (insulation, flexible resin) having a thickness of 15 μm is applied. A coating 13) is formed. Then, Sn plating 12 is applied in the same manner as in the first embodiment. The resin coating 1
As the material 3, epoxy resin, silicone resin or the like can be used in addition to polyimide resin.

As a result, a film carrier was obtained in which the bent and bent leads 11A were provided with the insulating and flexible resin coating 13 and the other parts of the copper leads 11 were provided with the Sn plating 12.

As described above, by forming the resin coating 13 on the bent portion lead 11A, it is possible to disperse the stress concentration on the copper lead 11 at the time of bending mounting, and the durability is greatly improved. Furthermore, since the resin film 13 has excellent oxidation resistance and corrosion resistance, the durability and long-term reliability of the film carrier are secured.

Further, as the protective film 13, a resin having excellent plating resistance is applied before plating, so that it simultaneously functions as a plating resist, lead protection, and a reinforcing film.
A film carrier having excellent durability and long-term reliability can be easily manufactured, and the manufacturing cost can be reduced.

As the film carrier of each of the above-mentioned examples, a three-layer tape structure in which copper foil is attached to an arbitrary flexible insulating film such as polyimide or polyester with an adhesive and leads are formed by etching, A two-layer tape structure in which copper leads are directly formed on a polyimide film without using an adhesive is used.

As the Sn plating 12, pure Sn plating using either electroless plating or electrolytic plating, Sn-
There is Pb solder plating and the like.

Bending portion lead 11 in the first embodiment
As a method of not forming the Sn plating 12 on A, there is a method of applying a peeling resistant plating resist by a printing method, a photoengraving method, etc., followed by plating, and then peeling and removing the resist, and insulation during plating. A mechanical mask method may be used in which a seal member such as a flexible rubber is brought into contact with the bent portion lead 11A.

A lead breakage experiment was conducted on the film carriers obtained in the above examples. In addition, in order to compare the experimental values with the film carrier according to each of the above-mentioned examples, as a comparative example, as shown in FIG. A film carrier provided with a Sn plating layer was prepared under the same conditions as in the examples. As each film carrier, a sample before heating and a sample heated at 150 ° C. for 3 hours by simulating heat treatment such as sealing resin curing in the IC packaging process were used.

In this experiment, as shown in FIG. 7, the film carrier was sandwiched between clamp supports 14 and alternately bent back and forth by 90 ° between the lead surface side and the film surface side, and bent.
The number of times of bending until the lead was broken was examined by setting the reciprocal bending to once. The contact surface on the clamp support 12 side when the film carrier was bent was set to a phase of R0.5 mm.

As a result, as shown in Table 1, in the film carrier of Comparative Example, the lead broke 20 to 30 times before heating and 3 to 8 times after heating. On the other hand, in the film carrier of the first example, the lead broke 20 to 30 times before heating and 20 to 30 times after heating. In the film carrier of the second example, 30 to 40 times before heating and 30 to 40 after heating.
The lead broke at the number of times.

[0033]

[Table 1]

From the results of this experiment, it can be seen that the film carriers of the respective examples show almost no deterioration due to heating. This is Sn plating 12 on the bent portion lead 11A.
This is because the brittle Cu—Sn alloy layer formed after heating cannot be formed by applying the heat treatment. Thereby, the folding endurance can be significantly improved.

In the film carrier, the area where the Sn plating 12 is not applied is the bent lead 11
Not only A, but also other portions can be applied if there is a portion that is bent at the time of mounting the film carrier.

[0036]

As described in detail above, the TAB film carrier of the present invention has the following effects.

Since the surface of the copper lead located above the slit hole is not plated with Sn or Sn alloy, a brittle Cu-Sn alloy layer is not formed even after heating, and folding resistance is greatly improved. To improve. This improves the reliability when mounting the film carrier.

[Brief description of drawings]

FIG. 1 is a sectional view showing a TAB film carrier according to a first embodiment of the present invention (a partial sectional view taken along the line AA of FIG. 2 and a sectional view corresponding to the sectional view taken along the line BB). Is.

FIG. 2 is a plan view showing a conventional TAB film carrier.

3 is a cross-sectional view taken along the line AA of FIG.

FIG. 4 is a cross-sectional view showing a mounted state of a TAB film carrier.

FIG. 5 is a sectional view showing a TAB film carrier according to a second embodiment of the present invention (a partial sectional view taken along the line AA of FIG. 2 and a sectional view corresponding to the sectional view taken along the line BB). Is.

FIG. 6 is a partial cross-sectional view showing a comparative example used in a lead breakage experiment.

FIG. 7 is an explanatory diagram showing an example of a lead breakage experiment.

[Explanation of symbols]

 1 Base Film 2 Sprocket Hole 3 Device Hole 4 Outer Lead Hole 5 Slit Hole 6 Inner Lead 11 Copper Lead 12 Sn Plating 13 Insulation, Flexible Resin Protective Coating

Claims (2)

[Claims] 1. A flexible insulating film is provided with a slit hole for bending, a copper lead pattern is formed in a region including a slit hole on one surface of the film, and a copper lead pattern is formed on the surface of the copper lead.
A film carrier for TAB which is plated with n or Sn alloy, wherein at least the surface of the copper lead located on the slit hole is not plated with Sn or Sn alloy. 2. A flexible insulating film is provided with a bending slit hole, and a copper resin layer positioned on the bending slit hole is provided with a flexible resin film having plating resistance and insulation properties. A film carrier for TAB, characterized in that a copper lead surface not covered with a resin coating is plated with Sn or Sn alloy.