JPH04249334A - Tape carrier for tab use - Google Patents

Abstract

PURPOSE:To obtain the title tape carrier whose lead pitch is small, especially at 80mum or lower, whose strength in an inner lead part is sufficiently large by a method wherein an wiring pattern is constituted of a mulitlayer conductor layer which includes a copper layer and a nickel or nickel-based alloy layer. CONSTITUTION:At a tape carrier, for TAB use, where desired interconnection patterns 20 have been formed on a flexible insulating film 10, each wiring pattern 20 is composed of a multilayer conductor layer which includes a copper layer 21 and a nickel or nickel-based alloy layer 22. For example, a conductor layer which has been clad with a copper foil 21 having a thickness of 25mum and with a nickel foil 22 having a thickness of 10mum via a bonding layer 14 having a thickness of 10mum is formed on a polyimide flexible insulating film 10 whose thickness is at 75mum and whose width is at 35mum. This assembly is etched by using a ferric chloride solution and, a wiring pattern 22 is formed. Thereby, the spread of lower slopes of the copper foil 21 to the face of the bonding layer 14 is reduced. As a result, a problem that leads are connected is not caused.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to TAB (Tape
Regarding tape carriers used when mounting integrated circuits (ICs) using the Automated Bonding method, T is especially suitable for mounting highly integrated ICs, etc.
This invention relates to an AB tape carrier.

0002

2. Description of the Related Art The TAB method is a method developed for efficiently mounting highly integrated ICs, in which IC elements are mounted on a tape carrier. FIGS. 4 and 5 are
This figure shows a plan view and a sectional view of such a TAB tape carrier, in which an IC is mounted on a long flexible insulating film 10.
A device hole 11 for mounting an element, a pilot hole (feeding hole) 12 for positioning, etc. are formed, and a wiring pattern 13 made of copper foil is further formed. This wiring pattern 13 is the inner lead part 1
3a and an outer lead portion 13b.

[0003] The flexible insulating film 10 generally has a thickness of 5
It is made of an organic polyimide film, a glass-reinforced epoxy film, etc. with a width of 0 to 126 μm and a width of 35 to 70 mm. Further, the device hole 11 and the pilot hole 12 are formed by punching the flexible insulating film 10. Further, the wiring pattern 13 is formed by bonding a copper foil such as a rolled copper foil or an electrolytic copper foil having a thickness of 18 to 35 μm to the flexible insulating film 10 via an adhesive layer 14, and then using an etching solution such as a ferric chloride solution. It was formed by removing unnecessary portions 15 of the copper foil so as to obtain a predetermined pattern using the photo-etching method used as a method. Note that the inner lead portion 13a is an IC
Since it is bonded to microelectrodes on the element by heat and pressure bonding, the surface of the inner lead part 13a is coated with adhesive metal (for example, gold) or a low melting point metal bonding agent (for example, tin, solder, etc.) in a process called CAG bonding. ) coated with Generally, electroless tin or electrolytic solder plating is applied.

0004

[Problems to be Solved by the Invention] Recently, there has been a strong desire for IC devices to have a very large number of pins and be made very fine. However, at present, a TAB tape carrier with an inner lead portion having a lead pitch of 90 μm or less and having a sufficiently high strength, which is desired from the IC element mounting process, has not been put into practical use. In other words, in conventional TAB tape carriers, when the inner lead portion is formed by photo-etching, the copper foil remains on the film surface after etching, resulting in the problem that adjacent leads are connected. . This has limited the ability to increase the number of pins and miniaturize ICs that can be mounted using the TAB method. for example,
When the thickness of the copper foil constituting the wiring pattern is 35 μm, the lead pitch of the inner lead part is limited to 100 μm (lead width 50 μm, lead spacing 50 μm).
In the case of copper foil with a thickness of 18 μm, the lead pitch is 80 μm.
is the limit. Moreover, in the case of copper foil having a thickness of 18 μm, since the foil is thin, there is a problem that the strength of the formed wiring pattern is low. Therefore, the use of alloy foil has been considered in order to increase the strength, but this has not been realized at present.

[0005] Therefore, an object of the present invention is to have a small lead pitch, especially 80 μm or less, and a sufficiently strong inner lead portion, in order to be able to cope with the ultra-high pin count and ultra-fine design of IC devices. The purpose of the present invention is to provide a tape carrier for TAB.

[0006]

[Means for Solving the Problems] According to the present invention, a wiring pattern formed on a flexible insulating film is composed of a multilayer conductor layer including a copper layer and a nickel-based alloy layer. This multilayer conductor layer consists of a two-layer conductor layer of copper layer-nickel alloy layer, a three-layer conductor layer of copper layer-nickel alloy layer-copper layer, and a three-layer conductor layer of nickel alloy layer-copper layer-nickel alloy layer. It is desirable that the multilayer conductor layer has a total thickness of 35 μm, of which the thickness of the nickel alloy layer is 5 μm.
It is desirable that it is μm. Furthermore, the copper layer preferably comprises oxygen-free copper. This oxygen-free copper generally refers to copper with an oxygen content of 10 ppm or less and a copper purity of 99.99% or more.
The appropriate thickness is 10 to 20 μm. Further, the nickel-based alloy layer includes, for example, pure nickel, a nickel-chromium alloy, or a nickel-iron alloy, and its thickness is 5 to 5.
15 μm is appropriate. Note that when the copper layer and the nickel-based alloy layer are used as a cladding, a total thickness of 25 μm or less is sufficient.

[0007]

[Operation] When forming a wiring pattern by etching a multilayer conductor layer consisting of a copper layer and a nickel-based alloy layer by photo-etching using ferric chloride as an etching solution, the copper layer and nickel-based alloy layer are The etching rate with ferric chloride is different, with the copper layer being etched more quickly than the nickel-based alloy layer. Therefore, even if the etching of the copper layer progresses sufficiently, the etching of the nickel-based alloy layer on the copper layer progresses relatively slowly. As a result, the degree of etching of the copper layer located on the adhesive side is large and the extent of the base to the adhesive side is small, while the nickel alloy layer has a sufficient width. Therefore, there is no problem that the leads are connected due to the broadening of the base of the copper layer on the adhesive surface, unlike in the conventional case. On the other hand, since the lead width is determined by the width of the nickel-based alloy layer, the lead pitch depends on the etching rate of the nickel-based alloy layer. Therefore, even if the etching of the copper layer progresses, the problem of so-called over-etching, in which the lead width becomes too narrow, does not occur. Further, since the nickel-based alloy layer may have a relatively small thickness, adopting a thin layer facilitates etching control and is advantageous for miniaturization. Furthermore, since the strength of the nickel-based alloy layer is added to the strength of the copper layer, the bending strength of the lead is approximately twice that of the case where only the copper layer is used.

[0008]

Embodiments Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

Example 1 As shown in FIG. 1, a 10 μm thick film was placed on a polyimide flexible insulating film 10 with a thickness of 75 μm and a width of 35 mm.
A copper foil 21 with a thickness of 25 μm and a copper foil 21 with a thickness of 1
A conductor layer made of a 0 μm nickel foil 22 as a cladding was formed and etched using a ferric chloride solution to form a wiring pattern 20.

As is clear from FIG. 1, the spread of the base of the copper foil 21 toward the surface of the adhesive layer 14 is small, so that the problem of the leads being connected does not occur. On the other hand, the nickel foil 22 has a larger width than the copper foil 21. The lead spacing of the wiring pattern 20 can be determined by the etching rate of the thin nickel foil 22 with a thickness of 10 μm, so it can be set to 80 μm or more, which was impossible when using conventional copper foil with a thickness of 35 μm. It has become possible to manufacture a TAB tape carrier with an extremely narrow lead spacing of 60 μm. Furthermore, the bending strength of the lead is approximately twice that of the case of only copper foil due to the addition of the strength of nickel foil.

Example 2 As shown in FIG. 2, a copper foil 31 with a thickness of 20 μm and a nickel foil 32 with a thickness of 10 μm are placed on a flexible insulating film 10.
A conductor layer was formed by laminating copper foil 33 having a thickness of 5 μm, and etching was performed using a ferric chloride solution to form a wiring pattern 30. Also in the TAB tape carrier of this embodiment, a lead spacing of 60 μm is possible, and lead strength can also be improved. In this embodiment, since the copper foil 33 is provided on the top layer, the tin and solder plating work is facilitated.

Example 3 As shown in FIG. 3, a nickel foil 41 with a thickness of 5 μm, a copper foil 42 with a thickness of 20 μm,
A conductor layer was formed by laminating copper foil 43 with a thickness of 10 μm, and etching was performed using a ferric chloride solution to form a wiring pattern 40. In the case of this embodiment, since the bottom layer is the nickel foil 41, there is no widening of the base, which is advantageous for further miniaturization.

[0013]

Effects of the Invention As explained above, the TAB tape carrier of the present invention has a small lead pitch, particularly 80 μm.
In addition, since the strength of the inner lead portion is sufficiently high, it is possible to cope with an ultra-high number of pins and ultra-miniaturization of IC elements. Furthermore, since etching accuracy during manufacturing is improved, productivity is also improved.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a TAB tape carrier according to an embodiment of the present invention.

FIG. 2 is a sectional view showing a TAB tape carrier according to a second embodiment of the present invention.

FIG. 3 is a sectional view showing a TAB tape carrier according to a third embodiment of the present invention.

FIG. 4 is a plan view showing a TAB tape carrier.

FIG. 5 is a sectional view showing a conventional TAB tape carrier.

[Explanation of symbols]

10 Flexible insulation film 11 Device hole 12 Pilot hole 13, 20, 30, 40 Wiring pattern 13a
Inner lead part 13b Outer lead part 14 Adhesive layer 15 Copper foil unnecessary parts 21, 31, 33, 42 Copper foil

Claims (4)

[Claims] 1. A TAB tape carrier comprising a desired wiring pattern formed on a flexible insulating film, wherein the wiring pattern comprises a copper layer and a nickel or nickel-based alloy layer (hereinafter referred to as "nickel-based alloy layer"). .) A tape carrier for TAB, comprising a multilayer conductor layer including: 2. The multilayer conductor layer includes (1) a two-layer conductor layer in which the first layer is a copper layer and the second layer is a nickel-based alloy layer; (2) the first layer is a copper layer and the second layer is a nickel-based alloy layer; (3) A three-layer conductor layer in which the first layer is a nickel-based alloy layer, the second layer is a copper layer, and the third layer is a nickel-based alloy layer. The TAB tape carrier according to claim 1, wherein the TAB tape carrier is any conductor layer selected from the following layers. [Claim 3] The multilayer conductor layer has a total thickness of 35 μm.
The TAB tape carrier according to claim 1 or 2, wherein the nickel-based alloy layer has a thickness of 5 μm. 4. The TAB tape carrier according to claim 1, wherein the copper layer is made of oxygen-free copper.