JP2002299778A - Wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wiring board, which can effectively prevent a thick film wiring layer from separating from an underlayer, or the underlayer of the thick-film wiring layer from being damages, and which is superior in productivity. SOLUTION: In a wiring substrate, in which a plurality of thick-film wiring layers 3 composed of a conductive material are arranged on a substrate 1, a buffer layer 2 which comprises a porous metal 2a in the inside, having cavities and a glass 2b which is arranged on the porous metal and of which a part is impregnated into the porous metal, is interposed between the substrate and the thick-film wiring layer. Furthermore, cavity rate of the porous metal is set to 90% to 98%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wiring substrate used for forming a head substrate or the like of an LED array head.

[0002]

2. Description of the Related Art Hitherto, a wiring substrate has been used to constitute a head substrate of an LED array head.

As shown in FIG. 3, for example, such a conventional wiring board has a structure in which a plurality of thick film wiring layers 12 are adhered in a predetermined pattern on an upper surface of a substrate 11 made of glass, ceramic, or the like. I have.

The material of the thick film wiring layer 12 is silver (A).
g) or a conductive material containing a metal such as aluminum (Al) is used. Such a thick film wiring layer 12 is made of a predetermined conductive paste obtained by mixing, for example, silver powder, glass frit, an organic solvent or the like with a conventionally known screen. A predetermined pattern is printed and applied on the upper surface of the substrate 11 by printing or the like.
It is formed by baking at a temperature of 800 ° C.

[0005]

However, in the conventional wiring board described above, since the upper surface of the substrate 11 is extremely smooth, when the thick film wiring layer 12 is formed by baking a conductive paste, these heat The thick film wiring layer 12 may be separated from the substrate 11 due to thermal stress applied between the thick film wiring layer 12 and the substrate 11 due to the shrinkage, and this significantly reduces the productivity of the wiring substrate. .

Therefore, in order to solve the above-mentioned drawback, the substrate 1
A buffer layer made of bismuth-based borosilicate glass or the like is interposed between the thick film wiring layer 12 and the thick film wiring layer 12, and the thick film wiring layer 12 is firmly adhered to the buffer layer. It has been proposed to prevent delamination.

However, the substrate 11 and the thick wiring layer 12
When a buffer layer made of bismuth-based borosilicate glass or the like is interposed between the thick film wiring layer 12 and the substrate 11, the thermal stress between the substrate 11 and the thick film wiring layer 12 is absorbed in the buffer layer. Although peeling is prevented, the buffer layer itself that has absorbed the thermal stress may cause a problem such as cracking, and the productivity of the wiring board has not been sufficiently improved.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned drawbacks, and an object of the present invention is to effectively prevent peeling of a thick wiring layer from a base and breakage of the base of the thick wiring layer. It is an object of the present invention to provide a wiring board which is excellent in productivity.

[0009]

A wiring board according to the present invention is a wiring board having a plurality of thick film wiring layers made of a conductive material disposed on a substrate, wherein the wiring board is provided between the substrate and the thick film wiring layer. A buffer layer comprising a porous metal having pores therein and glass partially disposed on the porous metal and impregnated in the porous metal. .

[0010] In the wiring board according to the present invention, the porosity of the porous metal is 90% to 98%.

Further, the wiring board according to the present invention is characterized in that the porous metal is made of any one of nickel, iron, copper and chromium.

Further, in the wiring board according to the present invention, the porous metal has a three-dimensional network skeleton.

Still further, in the wiring substrate according to the present invention, the porous metal is electrically connected to at least one of the thick film wiring layers via a via hole in the glass. Is what you do.

According to the wiring substrate of the present invention, a porous metal having pores therein between the substrate and the thick film wiring layer, and the porous metal is disposed on the porous metal, and a part of the porous metal is impregnated in the porous metal. When the thick film wiring layer is formed by baking a conductive paste, a large heat generated between the conductive paste and the substrate or the buffer layer due to heat shrinkage of the conductive paste is formed by interposing a buffer layer made of glass. Even if stress is applied, the thermal stress can be favorably absorbed and moderated by deformation of the porous metal constituting the buffer layer, and the thick film wiring layer peels off from the base or cracks in the buffer layer or the like. Is effectively prevented from occurring. Thereby, the productivity of the wiring board is dramatically improved.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a cross-sectional view of a wiring board according to an embodiment of the present invention, in which 1 is a substrate, 2 is a buffer layer, 2a is a porous metal, 2b is a glass layer, and 3 is a thick film wiring layer. .

The substrate 1 is made of an electrically insulating material such as alumina ceramics, mullite, aluminum nitride, glass ceramics, quartz, alkali glass, non-alkali glass, etc., and has a buffer layer 2 and a plurality of thick film wirings on its upper surface. The layers 3 are sequentially deposited and formed, and function as a supporting base material for supporting them.

When the substrate 1 is made of, for example, alumina ceramics, an appropriate organic solvent and a solvent are added to and mixed with a ceramic raw material powder of alumina, silica, magnesia or the like to form a slurry. A ceramic green sheet (ceramic green sheet) is formed by employing the doctor blade method, the calender roll method, and the like, and thereafter, the obtained green sheet is punched into a predetermined shape and fired at a high temperature (about 1600 ° C.). It is produced by doing.

A buffer layer 2 is provided on the upper surface of the substrate 1.
And a plurality of thick film wiring layers 3 are sequentially applied, and the buffer layer 2 is interposed between the substrate 1 and the thick film wiring layer 3.

The buffer layer 2 is provided over the entire upper surface of the substrate 1, and has a porous metal 2a having pores therein, and is disposed on the porous metal 2a, and a part of the buffer metal 2a is provided in the porous metal 2a. And impregnated glass 2b.

The porous metal 2a constituting a part of the buffer layer 2 is formed of a metal such as nickel, iron, copper, chromium, etc., and has a porosity of, for example, 90% to 98%. The shape is occupied mostly by pores,
When a thick wiring layer 3 described later is formed by baking a conductive paste or the like, even if a large thermal stress due to thermal contraction is applied between the conductive paste and the substrate 1 or the buffer layer 2, the thermal stress is reduced. The porous metal 2a present in the buffer layer 2 can be favorably absorbed and relaxed by deformation, and the glass 2b of the buffer layer 2 is compatible with the conductive material such as silver forming the thick film wiring layer 3. It is made of good bismuth borosilicate glass etc.
The glass 2 forming the upper part of the buffer layer 2 with the thick film wiring layer 3
b can be firmly adhered.

Therefore, there is almost no problem that cracks occur in the buffer layer 2 or the like which is the base of the thick film wiring layer 3 or the thick film wiring layer 3 is separated from the buffer layer 2 or the like. Substrate productivity is dramatically improved.

The porous metal 2a in the buffer layer 2
Adds and mixes foaming agents such as pentane, neopentane, hexane, isohexane, isoheptane, benzene, octane, and toluene, water-soluble resin binders such as methylcellulose, polyvinyl alcohol, carboxymethylcellulose ammonium, and water to metal powders such as copper. The predetermined foaming slurry obtained as described above is formed into a green sheet of a predetermined thickness by employing a conventionally known doctor blade method or the like, and after the foaming agent in the green sheet is foamed under high-humidity conditions, The green sheet is manufactured at a high temperature by sintering to form a three-dimensional network skeleton of the metal, and the obtained porous metal 2a is placed on the upper surface of the substrate 1 via an adhesive such as epoxy resin. The porous metal 2a is fixed on the substrate 1 by curing the adhesive.

The glass 2b on the porous metal 2a
For example, a predetermined glass paste obtained by adding and mixing an appropriate organic solvent, an organic binder, or the like to a powder of bismuth-based borosilicate glass or the like is printed and applied on the porous metal 2a by a conventionally known screen printing or the like. After impregnating a part thereof in the upper region of the porous metal 2a (for example, a region having a depth of 1% to 40% from the upper surface of the porous metal 2a), a predetermined amount of air bubbles are present in the porous metal 2a. The glass paste is baked at a high temperature in this state to form the glass 2b, thereby completing the buffer layer 2 having a film thickness of about 50 μm to 5000 μm and including the porous metal 2a and the glass 2b.

On the other hand, the thick film wiring layer 3 deposited on the buffer layer 2 functions as an electrode wiring for supplying a power supply or an electric signal.
Alternatively, a predetermined pattern is formed by a conductive material containing an alloy of these metals in an amount of 85 wt% or more.

The thick-film wiring layer 3 is formed by a conventionally known thick-film technique, specifically, a predetermined conductive paste obtained by mixing silver powder, glass frit, an organic solvent, or the like, by a conventionally known screen printing method or the like. A predetermined thickness (for example, 3 μm to 20 μm) and a predetermined pattern on the upper surface of the buffer layer 2.
It is formed by coating and baking it at a temperature of 350 ° C to 800 ° C.

At this time, the thick film wiring layer 3, the buffer layer 2,
Thick film wiring layer 3 -buffer layer 2 with heat shrinkage of substrate 1 etc.
The thermal stress applied between the thick film wiring layer 3 and the substrate 1 depends on the porous metal 2 existing in the buffer layer 2 as described above.
Since the buffer layer 2 and the like underlying the thick-film wiring layer 3 are not easily broken or broken, the buffer layer 2 or the like underlying the thick-film wiring layer 3 does not occur because the deformation a is favorably alleviated and absorbed.

It should be noted that the present invention is not limited to the above-described embodiment, and various modifications and improvements can be made without departing from the gist of the present invention.

For example, in the above-described embodiment, the thick film wiring layer 3
A plating layer made of gold, nickel, or the like may be applied to the entire upper surface or a part of the upper surface, or the thick film wiring layer 3 may be covered with a protective film made of glass, epoxy resin, or the like.

In the above-described embodiment, as shown in FIG. 2, one or more of the thick film wiring layers 3 are
To be held at the ground potential GND or the like. In this case, the thick film wiring layer 3 and the porous metal 2a are electrically connected via a via hole 2c formed by filling a connection conductor inside a through hole provided in the glass 2b of the buffer layer 2. Become.

Further, in the above embodiment, the porous metal 2
a is formed into a three-dimensional network skeleton to integrate the air bubbles in the porous metal 2a. The porous metal 2a may be formed.

Further, in the above embodiment, a buffer layer having the same configuration as the buffer layer 2 is laminated on the thick film wiring layer 3, and a thick film wiring layer is further laminated thereon to form a multilayer wiring board. It does not matter.

Further, in the above embodiment, an adhesive made of epoxy resin or the like is used to fix the porous metal 2a to the upper surface of the substrate 1, but instead of this, an inorganic material such as a glass paste is used. May be used as an adhesive to fix the porous metal 2 a to the upper surface of the substrate 1.

[0033]

According to the wiring board of the present invention, a porous metal having pores therein between the substrate and the thick film wiring layer, and a part disposed on the porous metal, and a part thereof is contained in the porous metal. Since the buffer layer made of impregnated glass is interposed, when the thick film wiring layer is formed by baking a conductive paste, the heat shrinkage occurs between the conductive paste and the substrate or the buffer layer due to the heat shrinkage. Even when a large thermal stress is applied, the thermal stress can be favorably absorbed and relaxed by the deformation of the porous metal constituting the buffer layer, and the thick film wiring layer is peeled off from the underlayer, or the buffer layer, etc. Cracks are effectively prevented. Thereby, the productivity of the wiring board is dramatically improved.

[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 cross-sectional view of a wiring board according to another embodiment of the present invention.

FIG. 3 is a cross-sectional view of a conventional wiring board.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Substrate, 2 ... Buffer layer, 2a ... Porous metal, 2b ... Glass layer, 3 ... Thick film wiring layer

Claims (5)

[Claims] 1. A wiring board comprising a substrate and a plurality of thick film wiring layers made of a conductive material disposed thereon, wherein a porous metal having pores therein is provided between the substrate and the thick film wiring layer; A wiring substrate, wherein a buffer layer made of glass disposed on the porous metal and partially impregnated in the porous metal is interposed. 2. The porous metal has a porosity of 90% to 98%.
%. The wiring board according to claim 1, wherein 3. The wiring board according to claim 1, wherein the porous metal is made of any one of nickel, iron, copper, and chromium. 4. The wiring board according to claim 1, wherein the porous metal has a three-dimensional network skeleton. 5. The method according to claim 1, wherein said porous metal is electrically connected to at least one of said thick film wiring layers via a via hole in said glass. Wiring board.