JP2001326437A - Wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wiring board where warpage is small even if a metallic base is thin, and there is no difficulty when parts are mounted and assembled. SOLUTION: In this wiring board, a glass layer 2 is formed at one side of a metallic base 1 for forming a circuit 3 on the upper surface of the glass layer 2, and merely the glass layer is formed at the other. In this case, the thickness of the metallic base should be equal to 1 mm or less, and at the same time length should be 20 times larger than width.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wiring board widely used in the fields of electronics and electric industry.

[0002]

2. Description of the Related Art A wiring board used in the fields of the electronics and electric industries is a resin wiring board in which a conductor is fixed to a base material mainly composed of resin with an adhesive, and a metal powder and a glass powder are baked on a ceramic substrate. There are a ceramic wiring board, a metal wiring board in which a resin or glass is coated on a metal base, and the like. Among the above-mentioned wiring boards, glass-coated metal wiring boards have a higher heat resistance temperature than resin wiring boards, high impact resistance to cracks due to thermal shock, mechanical shock, etc. generated in ceramic wiring boards, small quantities It has the advantage that it can be applied to many kinds.

However, due to the material composition, the physical property value is controlled so that a compressive stress is generated in the glass due to the difference in thermal expansion between the metal and the glass, and the rigidity of the metal is smaller than that of the ceramic. If the board is 1 mm or less, which is generally used, there is a problem that the warpage of the wiring board becomes large, and it is difficult to mount components.
In particular, a so-called long wiring board having a long length with respect to the width has a problem that the warpage is remarkably large, and it is difficult to mount not only components but also the wiring board.

[0004]

According to the first and second aspects of the present invention, even if the thickness of the metal substrate is small, the warpage is small,
An object of the present invention is to provide a wiring board which does not hinder component mounting and assembly.

[0005]

SUMMARY OF THE INVENTION The present invention relates to a wiring board in which a glass layer and a circuit are formed on one surface of a metal substrate and only the glass layer is formed on the other surface. Also,
The present invention relates to a wiring board in which a metal substrate has a thickness of 1 mm or less and a length of 20 times or more the width.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The metal substrate used in the present invention is preferably made of a material having a heat resistance temperature higher than the baking temperature of the glass formed on the upper surface thereof. For example, iron, SUS330, SUS430, etc. may be used. Is preferred. Further, since glass is subjected to compressive stress after baking, it is preferable to use a glass material having a smaller expansion coefficient than a metal base material, for example, a glass material such as lead borate glass or silica glass. Further, a small amount of barium, titanium, or the like may be added to the glass material to improve wettability with metal.

A circuit (conductor) formed on the upper surface of the glass layer
Is a glass material similar to the above glass material, gold, platinum,
It is preferable to use a mixture of noble metal powders such as silver and palladium.

For the glass layer, for example, a glass material is dispersed in a binder such as ethyl cellulose and a solvent such as terpineol to prepare a glass paste, which is printed on a metal substrate by a method such as screen printing. It can be formed by baking at a melting temperature.

In addition, a circuit is prepared by dispersing a noble metal powder in a binder such as ethyl cellulose and a solvent such as terpineol to prepare a conductor paste, printing the paste on the upper surface of the glass layer by screen printing or the like, and then forming a conductor paste. The paste can be formed by baking.

In the present invention, the glass melted at the time of baking exerts a compressive stress on the glass due to a difference in thermal expansion between the glass and the metallic substrate in the process of cooling to room temperature, but at the same time, a difference in expansion occurs between the glass and the metallic substrate. Warpage occurs due to distortion. For this reason, a glass layer is also formed on the back surface of the surface on which the circuit is formed, to impart a reverse strain to the metallic base material, and to reduce the defects due to the warpage due to the rebound of the warp on both sides.
In this way, a metal substrate having a thickness of 1 mm or less and at least about 0.2 mm can be sufficiently used as a wiring board.

The thickness of the glass layer formed on the back surface of the circuit forming surface is preferably equal to the thickness of the glass layer on the circuit forming surface side. When a glass layer is further formed on the circuit to protect the circuit, it is preferable that the thickness of the glass layer including the glass layer on the circuit be equal to the thickness of the glass layer formed on the back surface.

The thickness of the glass layer is not particularly limited, and is preferably in the range of 30 to 100 μm.
More preferably, it is in the range of 0 to 75 μm. The thickness of the circuit is not particularly limited, and is preferably in the range of 5 to 30 μm, and more preferably in the range of 8 to 15 μm.

Further, in the present invention, the effect is great for a wiring board using an elongated metal base material having a shape whose length is large with respect to the width, and particularly, the length is at least 20 times the width. The effect is remarkable for the wiring board using the metallic base material.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a cross-sectional view of a wiring board according to an embodiment of the present invention, in which a glass layer 2 is formed on both surfaces of a metallic base material 1 and a circuit 3 is formed on the upper surface of one of the glass layers 2. Have been.

[0015]

The present invention will be described below with reference to examples.

EXAMPLE 1 A width of 7 mm, a length of 140 mm and a thickness of 1.2 mm, 1.0 mm
Silica-based glass paste (trade name: 3500N, manufactured by DuPont) is screen-printed on one side of a metal substrate of 0.6 mm and 0.6 mm (using SUS430) from the end of the metal substrate to 0.5 mm inside by screen printing. After printing and drying at 150 ° C. to volatilize the vehicle component in the glass paste, baking is performed with a profile at 850 ° C. for 10 minutes using a belt furnace. Thereafter, the printing and baking processes are repeated a plurality of times to reduce the thickness. A 45 μm glass layer was formed.

Then, a silver-based conductor paste (manufactured by DuPont, trade name: 3660) is printed on the upper surface of the glass layer by screen printing, leaving a width of 1 mm and a length of 1 mm from the end of the metallic base material. A circuit having a baked thickness of 10 μm was formed by profiling at 850 ° C. for 10 minutes.

Next, another one side (back side) of the metallic base material
The glass paste used above was printed to the same dimensions as above by screen printing, and baked under the same conditions as above to form glass layers having different thicknesses as shown in Table 1.
Was obtained. The thickness of the glass layer was measured using a shape measuring device (Surfcom, manufactured by Tokyo Seimitsu Co., Ltd.).

Comparative Example 1 A wiring board was obtained by using the same materials as in Example 1 except that no glass layer was formed on the back surface, and through the same steps as in Example 1.

Next, the wiring boards obtained in Example 1 and Comparative Example 1 were allowed to stand on a surface plate, and the amount of warpage due to deformation was measured with a gap gauge. Table 1 shows the results.

[0021]

[Table 1]

As shown in Table 1, even when a metal substrate having a thickness of 1 mm or less was used, the wiring board of Example 1 in which the glass layer was formed on the back surface was effective in reducing the amount of warpage, It is clear that a remarkable effect can be obtained by making the thickness of the glass layer on the surface side on which the surface is formed equal to the thickness of the glass layer on the back surface.

Example 2 Using a metal substrate (using SUS430) having a thickness of 0.6 mm, a width of 7 mm, a length of 70 mm, 140 mm and 270 mm, the thickness of the glass layer on the back surface is shown in Table 2. A wiring board was obtained through the same steps as in Example 1 except that the thickness was changed.

Comparative Example 2 A wiring board was obtained by using the same materials as in Example 2 except that no glass layer was formed on the back surface, and through the same steps as in Example 1.

Next, the warpage due to deformation of the wiring boards obtained in Example 2 and Comparative Example 2 was measured in the same manner as in Example 1. Table 2 shows the results.

[0026]

[Table 2]

As shown in Table 2, even when a metal substrate having a width to length ratio exceeding 1:20 was used, the wiring board of Example 2 in which the glass layer was formed on the back surface had a reduced amount of warpage. It is clear that a remarkable effect can be obtained by adjusting the thickness of the glass layer on the side where the circuit is formed and the thickness of the glass layer on the back side.

[0028]

The wiring board according to the first and second aspects is a wiring board which is extremely industrially suitable because it has a small warpage, can be mounted and assembled, even if the thickness of the metal substrate is small.

[Brief description of the drawings]

FIG. 1 is a sectional view of a wiring board according to an embodiment of the present invention.

FIG. 2 is a sectional view of a conventional wiring board.

[Explanation of symbols]

 1 Metal substrate 2 Glass layer 3 Circuit

Claims (2)

[Claims] 1. A wiring board comprising a metal substrate on which a glass layer and a circuit are formed on one surface and a glass layer is formed only on the other surface. 2. The metal substrate has a thickness of 1 mm or less,
2. The wiring board according to claim 1, wherein the length is at least 20 times the width.