JP2002329960A - Wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wiring board excellent in productivity, which can effectively prevent a thick wiring layer from peeling off from a foundation or the foundation of the thick wiring layer from breaking. SOLUTION: In the wiring board where a plurality of thick wiring layers 3 formed of conductive materials are arranged on a substrate 1, a buffer layer 2 formed of porous metal 2a which has pores inside and a resin material 2b of 20-150 in Shore hardness being arranged on the porous metal and partially permeated in the porous metal 2a is interposed between the substrate 1 and the thick wiring layer. The porosity of the porous metal 2a is set to 90-98%.

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 above-described conventional wiring board, since the upper surface of the substrate 11 is formed extremely smooth, when the thick film wiring layer 12 is formed by baking a conductive paste, 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 heat shrinkage, which significantly reduces the productivity of the wiring substrate. I was letting it.

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 porous metal having pores therein, and a Shore hardness of 2 disposed on the porous metal and partially impregnated in the porous metal.
A buffer layer made of a resin material of 0 to 150 is interposed.

[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 board 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 resin material. It is assumed that.

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 at least a part of the porous metal is impregnated in the porous metal. When the thick film wiring layer is formed by baking of a conductive paste, the heat shrinkage between the conductive paste and the substrate or the buffer layer is caused by interposing the buffer layer made of the resin material. Even when a large thermal stress is applied, the thermal stress can be favorably absorbed and relaxed by deformation of the porous metal or resin material constituting the buffer layer, and the thick film wiring layer peels off from the base, Alternatively, generation of cracks in the buffer layer or the like is effectively prevented. 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 resin material, 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. Shore hardness 20-1 impregnated
And 50 resin materials 2b.

The porous metal 2a in the buffer layer 2
Since it is formed of a metal such as nickel, iron, copper, and chromium and has a high porosity of, for example, 90% to 98%, most of the porosity is occupied by pores. When the wiring layer 3 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 applied to the buffer layer 2. By deforming the constituent porous metal 2a and the soft resin material 2a impregnated therein, the absorption and relaxation can be favorably achieved.

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 resin material 2b on the porous metal 2a
Is made of, for example, an organic high molecular polymer such as a polyimide resin, a silicone resin, or a liquid crystal polymer, and its raw material is printed on the porous metal 2a by a conventionally known screen printing or the like.
Apply and partially cover 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).
After that, the resin material 2b is formed by heating and polymerizing the resin material, thereby completing the buffer layer 2 having a thickness of about 50 μm to 5000 μm including the porous metal 2a and the resin material 2b.

If the shore hardness of the resin material 2b is smaller than 20, the resin material 2b is too soft, and it is difficult to maintain its shape well. When the thickness is larger than 150, the resin material 2b is hardly deformed.
There is a possibility that it may be difficult to favorably absorb and relax the thermal stress applied at the time of formation.

Therefore, the resin material 2b has a Shore hardness of 2
It is important to set it in the range of 0 to 150.

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 method, for example, a predetermined conductive paste obtained by mixing silver powder, glass frit, an organic solvent, etc., by a conventionally known screen printing or the like. A predetermined thickness (for example, 3 μm to 20 μm) and a predetermined pattern on the upper surface of
It is formed by applying and baking this at a temperature of 350 ° C. to 450 ° 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.
As described above, the thermal stress applied between the thick film wiring layer 3 and the substrate 1 is favorably alleviated and absorbed by the deformation of the porous metal 2a and the resin material 2b constituting the buffer layer 2 as described above. Therefore, a problem such as a crack does not occur in the buffer layer 2 or the like which is a base of the thick film wiring layer 3.

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, a plating layer made of gold, nickel, or the like is applied to the entire upper surface or a part of the upper surface of the thick film wiring layer 3, or the thick film wiring layer 3 is made of glass or epoxy resin. May be covered with a protective film.

In the above embodiment, as shown in FIG. 2, one or more of the thick film wiring layers 3 are
b, and may be maintained at the ground potential GND or the like. In this case, the thick film wiring layer 3 and the porous metal 2a
Is electrically connected via a via hole 2c formed by filling a connection conductor into a through hole provided in the resin material 2b of the buffer layer 2.

Further, in the above-described embodiment, the porous metal 2a is formed into a three-dimensional network skeleton to integrate the bubbles in the porous metal 2a. Instead, the average pore diameter is 5 μm to 5 μm. A large number of air bubbles of 1000 μm may be dispersed inside the metal plate to form the porous metal 2a.

Further, in the above-described embodiment, a buffer layer having the same structure 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. You may do it.

Further, in the above-described embodiment, the resin material 2b is impregnated only in the upper region of the porous metal 2a. However, the resin material 2b may be impregnated with the porous metal 2a instead.
a, or a part of the impregnated resin material 2b may be used as an adhesive for adhering the porous metal 2a and the substrate 1; The same effect as in the embodiment can be obtained.

[0035]

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 the impregnated resin material having a Shore hardness of 20 to 150 is interposed, when the thick film wiring layer is formed by baking a conductive paste, the conductive paste and the substrate or the buffer layer are not bonded to each other. Even if a large thermal stress due to these thermal contractions is applied during this time, the thermal stress can be favorably absorbed and moderated by deformation of the porous metal or resin material constituting the buffer layer, and the thick film wiring It is possible to effectively prevent the layer from peeling off from the underlayer or to cause cracks in the buffer layer or the like. 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 ... Resin material, 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 board, comprising a buffer layer disposed on the porous metal and at least partially comprised of a resin material having a Shore hardness of 20 to 150 impregnated in the porous metal. 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 the porous metal is electrically connected to at least one of the thick film wiring layers via a via hole in the resin material. Wiring board.