JP2002299801A - Circuit board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a circuit board which is capable of restraining Ag contained in a surface wiring conductor film from being diffused into an overcoat layer. SOLUTION: An Ag wiring conductor film 2 is formed on the surface of a glass ceramic board 1, and an overcoat layer 6 of glass ceramic material is formed on the surface of the glass ceramic board 1 for the formation of a circuit board, partially covering the wiring conductor film 2. The overcoat layer 6 is formed of material composed of 100 pts.wt. inorganic solid component and 4.0 to below 6.0 pts.wt. metal oxide as an additive selected out of metal oxides such as MnO2 , CrO3 , and Fe2 O3 .

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circuit board in which a wiring conductor layer is formed on the surface of a circuit board and is covered with an overcoat layer made of substantially the same material as the board.

[0002]

2. Description of the Related Art Conventionally, a surface wiring conductor film has been formed on the surface of a circuit board, and a part of the surface has been covered with an overcoat layer. The surface wiring conductor film exposed from the overcoat layer is used, for example, as a connection pad or a terminal electrode of an electronic component element mounted on a substrate.

This overcoat layer is formed for the purpose of protecting the surface wiring conductor film and improving the weather resistance. Specifically, an insulating material having the same component as the glass material or the substrate material is used in consideration of the difference from the thermal expansion coefficient of the substrate.

[0004] Further, a circuit board having such an overcoat layer formed thereon is mounted on an electronic component element before mounting.
The appearance was inspected for the occurrence of print blurring and blurring of the overcoat layer.

In the appearance inspection, the overcoat layer has substantially the same white color as that of the substrate, and the silver-based surface wiring conductor film is silver-white. The contrast with the conductor film was poor, and the appearance inspection was very difficult. Conventionally, in order to easily perform such an appearance inspection, MnO2 was added as a coloring agent to the overcoat layer, and the color of the overcoat layer itself was light brown black. Thereby, as described above, the overcoat layer is made of a light brown-black color to facilitate discrimination.

[0006]

However, in such a circuit board, there is a problem that the Ag component of the surface wiring conductor film on the circuit board diffuses into the overcoat layer. When the diffusion of the Ag component in the overcoat layer as described above, the electrical characteristics of the circuit board deteriorate.
That is, the insulation resistance of the overcoat layer itself functioning as an insulating protective layer is reduced. In addition, the weather resistance of the overcoat layer is also deteriorated, and as a result, the degree of penetration of moisture is promoted, which may cause problems such as migration of the surface wiring conductor film.

Further, when only MnO ₂ is added, the color becomes pale black or brown, and the contrast between the surface wiring conductor film and the overcoat layer is required.

The present invention has been devised in view of the above problems, and has as its object to provide a circuit board capable of suppressing the diffusion of the Ag component of the surface wiring conductor film into the overcoat layer. It is.

Another object of the present invention is to provide a circuit board capable of making it easier to distinguish between a surface wiring conductor film and an overcoat layer of the circuit board.

[0010]

According to the present invention, a glass-ceramic material is formed on a substrate made of a glass-ceramic material having an Ag-based wiring conductor film formed on its surface so as to cover a part of the wiring conductor film. In the circuit board formed by covering the overcoat layer, the overcoat layer,
A circuit containing at least one of MnO ₂ , CrO ₃ , and Fe ₂ O ₃ and having a content of 4.0 to 6.0 parts by weight based on 100 parts by weight of the inorganic solid component of the overcoat layer. It is a substrate.

Further, Mn is contained in the overcoat layer.
O ₂ , CrO ₃ , Fe ₂ O ₃ , and the content is
The circuit board is 1.5 to 1.7 parts by weight based on 100 parts by weight of the inorganic solid component of the overcoat layer.

In the overcoat layer, MnO ₂ , Cr
One metal oxide of either O ₃ or Fe ₂ O ₃ is added to the inorganic material of the overcoat layer in an amount of 4.0 to 6.0 parts by weight based on 100 parts by weight.

Thus, it is possible to suppress the Ag component of the surface wiring conductor film of the circuit board from diffusing into the overcoat layer. That is, it is possible to suppress the deterioration of the insulating layer (deterioration of the insulating properties and deterioration of the moisture resistance) due to the diffusion of Ag.

Further, MnO added to the overcoat layer
₂ , by adding any of CrO ₃ and Fe ₂ O ₃ , the overcoat layer itself can be colored and the contrast between the surface wiring conductor film and the overcoat layer can be sharpened. . Moreover, MnO ₂ , Cr
By adding O ₃ and Fe ₂ O ₃ in amounts of 1.5 to 1.7 parts by weight with respect to 100 parts by weight of the inorganic material to be the overcoat layer, the color of the overcoat layer is particularly enhanced. It can be made to be a black system, making the contrast between the above surface wiring conductor film and the overcoat layer clearer,
Bleeding and blurring during printing of the material to be the overcoat layer can be easily visually inspected.

Incidentally, the total of MnO ₂ , CrO ₃ and Fe ₂ O ₃ should not exceed 6.0 parts by weight, and if a single metal oxide is added, it should not exceed 2.0 parts by weight. To As described above, when the addition amount of the metal oxide is excessive, the sintering behavior of the overcoat layer and the circuit board or the surface wiring conductor film is different, and the sintering conditions of the overcoat layer itself vary, Due to the difference from the sintered state of the circuit board or the surface wiring conductor film, the function of the overcoat layer cannot be sufficiently exhibited. In an extreme case, the overcoat layer is in an unsintered state.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a circuit board according to the present invention will be described in detail with reference to the drawings.

FIG. 1 is a sectional view of a circuit board according to the present invention. The structure of the circuit board 1 of the embodiment is, for example, 5
Two insulating layers are laminated and a via-hole conductor penetrates the layer,
A description will be given of a multilayer substrate in which internal wirings are arranged between the layers.

In FIG. 1, reference numeral 10 denotes a circuit board;
a to 1e are insulating layers, 3 is an internal wiring conductor film,
4 is a via hole conductor, 2 is a surface wiring conductor film, 5 is an electronic component element, and 6 is an overcoat layer.

The insulating layers 1a to 1e constituting the circuit board 10
Is made of a glass ceramic material. Specifically, the glass ceramic material includes, for example, crystallized glass and an inorganic filler. Cristobalite, quartz, corundum (α alumina), mullite,
Examples thereof include zirconia and cordierite, which include one or more types, and are collectively called ceramic materials. The average particle size of the ceramic material is 1.0 to 6.0.
μm is preferred.

The crystallized glass material is a glass frit containing a plurality of metal oxides, and when fired at a temperature of 800 to 1000 ° C., cordierite, mullite, anorthite,
Those that precipitate at least one type of crystal of Celsian, spinel, garnite, willemite, dolomite, petalite, osmillite and substituted derivatives thereof,
The average particle size of the crystallized glass material is 1.0 to 5.0 μm.
m is preferred. The composition ratio of the ceramic material and the glass material is such that the ceramic material is 10 to 60 parts by weight,
Preferably, 30 to 50 parts by weight, and the glass material is 9 parts by weight.
0 to 40 parts by weight, preferably 70 to 50 parts by weight
Parts by weight. Specifically, a slurry obtained by kneading these powders, an organic binder, a plasticizer and a solvent and forming a slurry is used as a green sheet by a doctor blade method or a pulling method. Is formed. Alternatively, coating and drying are repeated to form a multilayer substrate.

The insulating layers 1a to 1e are 50 to 3 per layer.
It has a thickness of about 00 μm, and the via-hole conductor 4 is formed in the thickness direction. Further, an internal wiring conductor film 3 forming a predetermined circuit network is formed between the insulating layers 1a to 1e.

The internal wiring conductor film 3 and the via hole conductor 4
It is made of a conductive material mainly composed of Ag, Ag-Pd or the like.

The substrate 1 is fired at 800 to 1000 ° C., at which the glass ceramic is sintered.

On the surface of the substrate 1, a surface wiring conductor film 2 made of a conductor material containing Ag or the like as a main component (Ag alone or an Ag alloy such as Ag-Pd or Ag-Pt) is disposed. The surface wiring conductor film 2 is formed by applying a conductor film to be the surface wiring conductor film 2 on the fired substrate 1 and firing it. The surface wiring conductor film 2 is electrically connected to the internal wiring conductor film 3 via the via-hole conductor 4 to form a predetermined circuit network, and is connected to an electrode pad portion 21 to which the electronic component element 5 is joined, and to an external circuit. Connection terminal 21
Etc. In addition, the surface wiring conductor film 2 contains a glass component or the like as necessary in the above-described metal material.

On the surface wiring conductor film 2, an overcoat layer 6 composed of a glass ceramic material (inorganic fixing component), which is substantially the same as the substrate material, and an organic binder as main components is formed. This overcoat layer 6
Is formed so as to expose the above-mentioned electrode pad portion and the portion serving as the connection terminal. The overcoat layer 6
Is to make the difference in thermal expansion coefficient of the substrate substantially the same or small, and to approximate the sintering conditions of the substrate, etc.
The main material is the same as the substrate material.

In the overcoat layer 6, MnO ₂ , CrO ₃ , and Fe ₂ O ₃ are added to the above-mentioned inorganic solid components. MnO ₂ , CrO ₃ , and Fe ₂ O ₃ (metal oxides) have a coloring effect, that is, at least a light brown color effect due to the addition of these metal products.

One or more of MnO ₂ , CrO ₃ and Fe ₂ O ₃ are added in an amount of 4.0 parts by weight or more based on 100% by weight of the inorganic solid component of the overcoat layer 6. I have. The upper limit is less than 6.0% by weight.

As described above, MnO ₂ , CrO ₃ , Fe ₂ O ₃
By setting the total addition amount to 4.0 parts by weight or more, it is possible to effectively suppress the Ag component of the surface wiring conductor film 2 that tends to diffuse into the overcoat layer 6. Specifically, the diffusion depth of the Ag component can be less than 10 μm from the contact interface with the surface wiring conductor film 2.

If the total amount of MnO ₂ , CrO ₃ , and Fe ₂ O ₃ is 6.0 parts by weight or more, the sintering behavior of the overcoat layer greatly varies, and the sintering conditions vary greatly. As a result, the substrate 1 may be warped or the moisture resistance and the adhesion may be deteriorated.

Further, the color of the overcoat layer 6 is
From brown to dark black, overcoat layer 6 and surface wiring
In order to increase the contrast with the conductor film 2, M
nO _Two, CrO_Three, Fe_TwoO_ThreeAdd the three of
MnO_Two, CrO_Three, Fe_TwoO_ThreeStrictly control the amount of
There is a need. That is, MnO_Two, CrO_Three, Fe_TwoO_ThreeSingle
The inorganic solid component which becomes the overcoat layer 6
1.5 to 1.9% with respect to 100 parts by weight. this
With this, the color of the overcoat layer 6 becomes dark black.
At the boundary between the overcoat layer 6 and the surface wiring conductor film 2.
The boundary area can be clearly identified, and the overcoat layer
The formation position and printing state (bleeding, blurring) of 6 were visually observed.
Can be inspected.

A method for manufacturing the above-described ceramic circuit board 10 will be described.

First, green sheets to be used as the insulating layers 1a to 1e are prepared. For example, a green sheet, for example,
An inorganic filler of ceramic powder, a crystallized glass material, an organic binder such as alkyl methacrylate, and a plasticizer such as DBP, and an organic solvent such as toluene are mixed, and the slurry is kneaded with a ball mill for 48 hours to form a slurry. create.

This slurry is tape-molded to, for example, 100 μm using a doctor blade method or a lifting method, and cut into a predetermined size to form a green sheet.

Next, a through hole serving as a via hole conductor 4 is formed in a predetermined green sheet, and a conductor serving as a via hole conductor 4 and a conductor film serving as an internal wiring conductor film 3 are formed in the through hole by printing and filling a conductive paste. I do.

Here, the conductive paste for forming the internal wiring conductor film 3 includes, for example, a predetermined amount of metal powder such as Ag powder, and if necessary, for example, a predetermined amount of borosilicate low melting point glass, and, for example, ethyl cellulose. And an organic solvent such as 2.2.4-trimethyl-1.3-pentadiol monoisobutyrate are mixed and kneaded with a three-roll mill. Here, the conductive paste for forming the via-hole conductor 4 is, for example, a predetermined amount of Ag.
Metal powder such as powder, β-quartz, an organic binder such as ethyl cellulose, and an organic solvent such as 2.2.4-trimethyl-1.3-pentadiol monoisobutyrate are mixed and kneaded by a three-roll mill. To create. Here, β-quartz makes the thermal expansion coefficient of the via hole conductor close to that of the ceramic substrate.

The green sheet on which the conductor film serving as the internal wiring conductor film 3 and the conductor serving as the via hole conductor 4 are formed is laminated in accordance with the lamination order of the substrate 1 to form an unfired substrate. I do.

Thereafter, the unfired substrate is integrated with 80
Baking at a relatively low temperature of 0 to 1000C. The binder removal process in this firing is a temperature range of approximately 600 ° C. or less, and is a process of burning off the insulating layers 1 a to 1 e, the conductor serving as the via hole conductor 4, and the organic binder contained in the internal wiring 3. The firing conditions are, for example, a peak temperature of 800.
It is an air atmosphere or a neutral atmosphere at a temperature of up to 1000 ° C., for example, 950 ° C. for 30 minutes.

On the surface of the substrate 1, a surface wiring conductor film 2 made of a conductor material containing Ag or the like as a main component (Ag alone or an Ag alloy such as Ag-Pd or Ag-Pt) is disposed. The surface wiring conductor film 2 is formed by applying a conductor film to be the surface wiring conductor film 2 on the fired substrate 1 and firing it. The surface wiring conductor film 2 is electrically connected to the internal wiring conductor film 3 via the via-hole conductor 4 to form a predetermined circuit network, and further includes an electrode pad portion connected to an external circuit or a mounted component, a connection connection terminal 21, and the like. become.

The surface wiring conductor film 2 contains a glass component or the like as necessary in the above-described metal material. Here, the conductive paste forming the surface conductor layer 2 may be, for example, 99 parts by weight or more of Ag powder and 1 part by weight or less of Pt powder in a metal component, and if necessary, for example, a predetermined amount of a borosilicate-based powder. A melting point glass or oxide, an organic binder such as ethyl cellulose, and an organic solvent such as 2.2.4-trimethyl-1.3-pentadiol monoisobutyrate are mixed and kneaded by a three-roll mill. I do.

In each conductive paste, the metal component is not limited to Ag-Pt, but may be an Ag alloy such as Ag-Pd.

The substrate 1 on which the surface wiring conductor film 2 is disposed
Glass ceramic material on top, MnO _Two, CrO_Three, Fe_Two
O_ThreeOvercopper made of metal oxides and organic binders
Using a coating material, apply a coating film to be the overcoat layer 6
Formed and fired in air or neutral atmosphere.
U.

In the above-described firing step, the firing step of the substrate 1, the firing of the surface wiring conductor film 2, and the firing of the overcoat layer 6 are all performed in the same manner, so that the firing step is simplified and the production is simplified. Efficiency is improved.

After that, various electronic components 5 are mounted on the electrode pads 21 and the like, which are the surface wiring conductor films 2 exposed from the overcoat layer 6.

Although the above-described manufacturing method is a multilayer method using green sheets, a printing multilayer in which slurry serving as an insulating layer and the internal wiring conductor film 3 are sequentially printed may be performed. At this time, a photocurable monomer may be added to the slurry, and a green sheet or a dielectric coating film coated and printed may be selectively exposed and developed. Alternatively, the substrate 1 in an unfired state may be formed in a shape that allows a plurality of substrates to be extracted, and division grooves may be formed as necessary before firing, and the substrate 1 may be divided into individual circuit boards after firing. MnO ₂ , CrO ₃ , Fe contained in the overcoat layer 6
₂ O ₃ is in the overcoat layer 6, Ag component of the surface wiring conductor film 2 acts as effectively suppressed from being diffused into the overcoat layer 6.

In order to effectively suppress the diffusion of the Ag component and to prevent the substrate 1 from warping during firing, the Mn
The total amount of O ₂ , CrO ₃ , and Fe ₂ O ₃ is controlled. That is, the total addition amount is 4.0 parts by weight or more and less than 6.0 parts by weight based on 100 parts by weight of the inorganic solid component (glass ceramic material) constituting the overcoat layer 6.

If the total amount is less than 4.0 parts by weight, the Ag component of the surface wiring conductor film 2 diffuses into the overcoat layer 6 at a depth of, for example, 10 μm or more. If the Ag component diffuses into the overcoat layer 6 by 10 μm or more, the properties of the overcoat layer 6 itself are deteriorated, for example, the dielectric constant is reduced, the insulation properties are deteriorated, and the moisture resistance is deteriorated. I will.

If the total amount exceeds 6.0 parts by weight, the material properties of the overcoat layer 6 are altered, and the firing behavior and firing conditions are changed. When peeling occurs between the surface wiring conductor film 2 and the overcoat layer 6, when the substrate warps, and when the overcoat layer 6 is integrally sintered, the sintering conditions of the overcoat layer 6 And sintering conditions of the substrate and the surface wiring conductor film 2, the overcoat layer 6 cannot be sufficiently sintered.

[0047]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present inventor formed an overcoat layer 6 using a coating member having the same inorganic solid component as the substrate material, and diffused the Ag component into the overcoat layer 6 (penetration into the overcoat layer 6). Distance), overcoat layer 6
I examined the colors of.

The manufacturing method is as follows.
A conductive film to be the Ag-based surface wiring conductive film 2 was printed, and then a coating film to be the overcoat layer 6 was formed and baked at 950 ° C. in the air atmosphere. The results are shown in Table 1.

[0049]

[Table 1]

Sample Nos. 1 to 10 correspond to the overcoat layer 6
At least one of MnO ₂ , CrO ₃ , and Fe ₂ O ₃ was added to the inorganic solid component. The total added amount is less than 4.0 parts by weight. In this case, the Ag component of the surface wiring conductor film 2 that diffuses into the overcoat layer 6 diffuses by 10 μm or more. That is, a large amount of Ag component is contained in the overcoat layer 6.
Will spread to the side. Thereby, the overcoat layer 6
This impairs the insulation and moisture resistance, which are the original functions.

Sample No. 23 is composed of MnO ₂ , Cr
The total added amount of O ₃ and Fe ₂ O ₃ is 6.0 parts by weight.
In this case, the diffusion of Ag into the overcoat layer 6 is 4.
1 μm, but conversely, the addition of the metal oxide is excessive,
The firing conditions and sintering behavior of the overcoat layer 6 fluctuate greatly, causing inconsistency with the substrate 1 and the surface wiring conductor film 2. As a result, the overcoat layer 6 and the substrate 1
Or separation from the surface wiring conductor film 2 occurs. In addition, since the overcoat layer 6 is not sufficiently sintered, its original function as the overcoat layer 6 is reduced.

As shown in Sample Nos. 11 to 22, by controlling MnO ₂ , CrO ₃ , and Fe ₂ O ₃ added to the overcoat layer 6, the color of the overcoat layer 6 can be made deep black. it can.

That is, the metal added to the overcoat layer 6
The oxide is MnO_Two, CrO_Three, Fe _TwoO_ThreeIncluding all of
That one addition amount is 1.5 parts by weight or more, 2.0 parts by weight
Parts.

Under these conditions, MnO ₂ , CrO ₃ , F
By adding e ₂ O ₃ , the overcoat layer 6
The overcoat layer 6 and the surface wiring conductor film 2 can be clearly contrasted in appearance inspection because of the dark black color. As a result, the coating material of the overcoat layer 6 is easily printed and blurred. Can be grasped.

[0055]

According to the present invention, Ag is mainly deposited on a circuit board.
Form an overcoat layer on the surface wiring conductor film as a component
In doing so, MnO was added to the overcoat layer._Two, Cr
O_Three, Fe _TwoO_ThreeAt least one added amount of 4.0 wt.
Parts or more and less than 6.0 parts by weight. As a result,
-Ag component that diffuses into the bar coat layer can be suppressed,
-Maintains the insulation and moisture resistance that are the original functions of the coat layer.
Wear.

Further, the color of the overcoat layer can be made dark black by defining the amount of each metal object to be added, and the appearance inspection of the boundary portion with the surface wiring conductor film becomes easy.

[Brief description of the drawings]

FIG. 1 is a sectional view of a ceramic circuit board according to the present invention.

[Explanation of symbols]

 10 Ceramic circuit board 1 Substrate 1a-1e Glass ceramic layer 2 Surface wiring conductor film 3 Internal wiring conductor film 5・ Electronic parts 6 ・ ・ ・ ・ ・ Overcoat glass

Claims (2)

[Claims] An overcoat layer made of a glass ceramic material is formed on a substrate made of a glass ceramic material having an Ag-based wiring conductor film formed on its surface so as to cover a part of the wiring conductor film. In the above circuit board, the overcoat layer is made of MnO ₂ , CrO 3, Fe ₂ O
_3. A circuit board comprising at least one of ( ₃ ) and 4.0 to 6.0 parts by weight based on 100 parts by weight of the inorganic solid component of the overcoat layer. 2. The method according to claim 1, wherein the overcoat layer comprises MnO ₂ , Cr
O ₃ , Fe ₂ O ₃ , and the content is 1.5 to 100 parts by weight of the inorganic solid component of the overcoat layer.
2. The circuit board according to claim 1, wherein the amount is 1.7 parts by weight.