JPH0548230A - Thin-film wiring substrate - Google Patents

Abstract

PURPOSE:To enable a need for limiting selection of a material of a wiring layer or setting of thickness of a layer to be eliminated in a thin-film wiring substrate. CONSTITUTION:A buffer layer 8 consisting of polyimide, etc., is provided be low a wiring layer in a thin-film wiring substrate 1, thus enabling a conductive particle to intrude the wiring layer easily when making connection to other wiring substrate using an adhesive 4 containing a conductive particle 5 by applying pressure. Therefore, a hard material can be used as a material for the wiring layer and its thickness may be thin.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film wiring board which does not require special restrictions on selection of material for wiring layers and setting of layer thickness.

[0002]

2. Description of the Related Art Wiring surfaces formed on an insulating substrate such as a glass substrate by a thin film process and wirings on another substrate are connected to each other by an adhesive containing conductive particles. There is. FIG. 2 is a diagram showing a state in which a conventional thin film wiring board is connected to another wiring board. In FIG. 2, 1 is a substrate,
Reference numeral 2 is a lower wiring layer, 3 is a wiring layer, 4 is an adhesive, 5 is conductive particles, 6 is a wiring portion, 7 is a substrate, A is a thin film wiring substrate, and B is a wiring substrate.

In the thin film wiring board A, a lower wiring layer 2 is formed on a substrate 1, and a wiring layer 3 is formed thereon.
Glass is used for the substrate 1, and aluminum is used for the wiring layer 3, for example. For the lower wiring layer 2, a material having good adhesiveness to both the substrate 1 and the wiring layer 3, for example, chromium is used. Chromium has good adhesion to glass and aluminum.

On the other hand, the wiring board B may have the same structure as the thin film wiring board A, or may be an FPC (flexible printed circuit ... with a wiring pattern) or a TAB (tape automated). -Bonding ... Wiring pattern and IC mounted) may be used. In the figure, the wiring portion 6 is drawn as one layer, but it is not shown that only one wiring layer is provided, but in short, it is shown that the surface includes the wiring layer. There is. Therefore, the configuration in which the insulating layer is provided below the wiring layer is also included in the wiring section 6.

Thin film wiring board A and wiring board B as described above
The wirings are bonded to each other by sandwiching the adhesive 4 containing the conductive particles 5 and applying pressure from above and below. The conductive particles 5 are, for example, silver (Ag) particles having a size of about 10 μm. As shown in FIG. 2, the conductive particles 5 dig into the wirings of the thin film wiring board A and the wiring layer of the wiring board B to establish electrical connection. The physical connection is made by the adhesive 4. Incidentally, for the connection of the wiring on the substrate, an anisotropic conductive film where fine particles of a thermoplastic resin whose surface is coated with a metal in a film-shaped thermosetting resin are dispersed,
Some of them are thermocompression-bonded between them.

Prior art documents relating to the connection between wiring boards include, for example, JP-A-62-246280, Nikkei Electronics, 1989.7.24 (no.478), pp112-113.

[0007]

In the above-mentioned conventional thin film wiring substrate, since the conductive particles 5 bite into the wiring layer 3 to make an electrical connection, the wiring layer 3 is easily bited. Soft material (eg aluminum)
There was a restriction that it had to be used and kept thick. The present invention aims to eliminate such a limitation.

[0008]

In order to solve the above problems, in the thin film wiring board of the present invention, a buffer layer is provided below the wiring layer.

[0009]

[Operation] In a thin film wiring board, if a buffer layer made of polyimide or the like is provided under the wiring layer, it will be electrically conductive when pressure is applied to another wiring board using an adhesive containing conductive particles. The particles are favorably cut into the wiring layer. Therefore, a hard material can be used as the material of the wiring layer, and the layer can be thin.

[0010]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a diagram showing a state in which the thin film wiring board of the present invention is connected to another wiring board. Reference numerals correspond to those in FIG. 2, and 8 is a buffer layer. On the substrate 1 made of glass or the like, a lower wiring layer 2 made of chromium or the like having good adhesiveness to the substrate 1 is deposited (eg, 0.5 μm). An elastic material such as polyimide is deposited on top of it (eg 1.5 μm).
m) and the buffer layer 8.

Although the wiring layer 3 is deposited on the buffer layer 8, a hard conductive material can be used as the material, and the thickness may be smaller than that of the conventional one (see the wiring layer 3 in FIG. 2). ..
The reason for this is that since the buffer layer 8 having elasticity is provided below the wiring layer 3, when the thin film wiring board A and the wiring board B are adhered by applying pressure, the buffer layer 8 penetrates into the conductive particles 5. This is because the conductive particles 5 (eg, silver having a thickness of about 10 μm) easily bite into the wiring layer 3 because they receive the temperature. If it is hard and thin, it easily breaks through, and since the tip only bites into the soft buffer layer 8, it can easily bite deeply. Therefore, ITO (indium tin oxide, for example, 0.06 μm) or the like that is hard and cannot be made too thick can be used as the conductive material of the wiring layer 3.
That is, when selecting the material of the wiring layer 3 and setting the thickness, there are no restrictions as in the past.

[0012]

As described above, according to the thin film wiring board of the present invention, since the buffer layer is provided and the wiring layer is provided thereon, another wiring board is formed by using the adhesive containing conductive particles. When connecting by applying pressure, the conductive particles can easily penetrate into the wiring layer. Therefore, when selecting the material of the wiring layer and setting the thickness, it must be a soft material,
It is no longer necessary to satisfy the conditions such as having to be thick.

[Brief description of drawings]

FIG. 1 is a diagram showing a state in which a thin film wiring board of the present invention is connected to another wiring board.

FIG. 2 is a diagram showing a state in which a conventional thin film wiring board is connected to another wiring board.

[Explanation of symbols]

1 ... Substrate, 2 ... Lower wiring layer, 3 ... Wiring layer, 4 ... Adhesive,
5 ... Conductive particles, 6 ... Wiring part, 7 ... Substrate, 8 ... Buffer layer,
A ... Thin film wiring board, B ... Wiring board

Claims (1)

[Claims] 1. A thin-film wiring board comprising a buffer layer provided below the wiring layer.