JP2002111152A - Circuit board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a circuit board where bonding strength in a surface wiring conductor, warpage in a substrate, and sheet resistance are superior even if a laminate substrate and the surface wiring conductor are simultaneously sintered. SOLUTION: In this circuit board 10 where the surface wiring conductor 4 is formed on the surface of a laminate substrate 1 where a plurality of dielectric layers 1a to 1e are laminated, the surface wiring conductor 4 contains 0.05 to 2 wt.% rhodium, and 1-3 wt.% manganese oxide to 100 wt.% Ag-based conductive material.

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 surface wiring conductor is formed on a laminate substrate.

[0002]

2. Description of the Related Art Conventionally, a firing temperature of 800 to 1050 has been used.
A circuit board using a material that can be fired at a relatively low temperature of ° C. has been widely proposed.

[0003] A circuit board includes a substrate on which a plurality of dielectric layers are laminated, an internal wiring conductor disposed between the dielectric layers of the laminated substrate, a surface wiring conductor disposed on the surface of the laminated substrate, and It is composed of predetermined internal wiring conductors in the thickness direction of the dielectric layer, and via hole conductors connecting between the predetermined internal wiring conductors and the surface wiring conductor.

[0004] Various electronic components such as an IC chip are mounted on the surface wiring conductor arranged on the surface of the laminated substrate.

In order to increase the conductivity of the above-mentioned internal wiring conductors to increase the circuit speed, the internal wiring conductors, via-hole conductors and surface wiring conductors may be composed of Ag alone or Ag-Pd, Ag-Pt, or the like. Ag-based material composed of the above Ag alloy is used. In addition, the dielectric layer is formed at a low temperature (800 to 1050 ° C.) from the melting point of the Ag-based material described above.
A material that can be fired is used. For example, a glass-ceramic material composed of a glass component and a ceramic component.

[0006]

However, the surface wiring conductor material mainly composed of Ag having a melting point of about 960 ° C. is required to be co-fired with a low-temperature sinterable substrate such as a glass ceramic as described above. In many cases, the surface wiring conductor on the substrate is over-sintered, resulting in the surface wiring conductor having a porous structure. When a plating treatment is applied to the surface wiring conductor having such a porous structure, a treatment liquid such as an acid or an alkali penetrates from the pores of the surface wiring conductor, and the gap between the structures inside the surface wiring conductor or the surface wiring conductor. There is a problem that the adhesive strength of the surface wiring conductor is greatly deteriorated.

Here, in order to simply avoid oversintering of the surface wiring conductors, the substrate on which the internal wiring conductors are formed is fired without the surface wiring conductors, and then the surface layer is plated with secondary metallization. There is a way to bake a good Ag conductor. However, this increases the number of steps, which is disadvantageous in terms of cost. In the case of a product having a cavity, it is difficult to form an Ag conductor in the cavity by secondary metallization.

The present invention has been devised in view of the above-mentioned problems, and has an object to achieve good adhesive strength even when a low-temperature sinterable substrate and a surface wiring conductor are simultaneously fired. An object of the present invention is to provide a circuit board capable of obtaining a proper surface wiring conductor.

[0009]

A circuit board according to the present invention is a circuit board having a surface wiring conductor formed on the surface of a laminated substrate formed by laminating a plurality of dielectric layers, wherein the surface wiring conductor is made of an Ag-based material. 0.05 to 100 parts by weight of the conductor material
It contains 2 parts by weight of rhodium and 1 to 3 parts by weight of manganese oxide.

According to the present invention, the surface wiring conductor contains 0.05 to 2 parts by weight of rhodium and 1 to 3 parts by weight of manganese oxide based on 100 parts by weight of the Ag-based conductor material.

That is, since rhodium (Rh) is contained in an amount of 0.05 to 2 parts by weight with respect to 100 parts by weight of the Ag-based conductor material, it is necessary that the Ag conductor obtained by firing has a porous structure. Has the effect of suppressing. For this reason, a chemical solution used when plating the Ag conductor surface is less likely to penetrate into the Ag conductor tissue. as a result,
Good adhesion of the Ag conductor to the substrate is maintained.

If the content of rhodium is less than 0.05 parts by weight, the abnormal grain growth of the Ag conductor, which occurs at the time of simultaneous firing with the substrate at 840 to 950 ° C., cannot be suppressed.
The conductor tends to have a porous structure. On the other hand, if it exceeds 2 parts by weight, rhodium itself does not sinter, so that sintering of the Ag powder is hindered and the sheet resistance increases.

Further, since manganese oxide (MnO) is contained in an amount of 1 to 3 parts by weight based on 100 parts by weight of the Ag-based conductor material, MnO _{2 is} added to the reaction layer at the interface between the dielectric and the surface wiring conductor. Precipitates, and the contact area between the ceramic substrate and the surface wiring conductor increases, so that the so-called anchor effect (Ag constituting the Ag-based conductive paste) is obtained.
Since the particles and the glass component of the substrate material are strongly bonded to each other) and the adhesive strength between the ceramic substrate and the surface wiring conductor is increased, high adhesive reliability is achieved.

If the manganese oxide content is less than 1 part by weight, the anchor effect cannot be sufficiently exhibited. on the other hand,
If it is added in excess of 3 parts by weight, the needle-like crystals are deposited on the surface of the surface wiring conductor 4, and the sheet resistance increases.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a circuit board according to the present invention will be described with reference to the drawings. FIG. 1 is a sectional view of a circuit board according to the present invention. In FIG. 1, reference numeral 10 denotes a circuit board,
Is a laminated substrate, 2 is an internal wiring conductor formed in the laminated substrate 1, 3 is a via-hole conductor formed in the laminated substrate 1,
Reference numeral 4 denotes a surface wiring conductor formed on the surface of the laminated substrate 1;
Reference numeral 6 denotes a C chip component, and reference numeral 6 denotes another electronic component.

The laminated substrate 1 includes dielectric layers 1a to 1e made of a glass-ceramic material, and internal wiring for achieving a predetermined circuit network and generating a capacitance component between the dielectric layers 1a to 1e. The conductor 2 is arranged.

In the dielectric layers 1a to 1e, via-hole conductors 3 are formed so as to penetrate the layers in the thickness direction.

Further, a surface wiring conductor 4 is formed on the surface of the laminated substrate 1 on which the dielectric layers 1a to 1e are laminated.

The dielectric layers 1a to 1e are, for example, 850 to 1
It is made of a glass-ceramic material that can be fired at a relatively low temperature of around 050 ° C. Specific ceramic materials include insulating ceramic materials such as cristobalite, quartz, corundum (α-alumina), mullite, cordierite, dielectric ceramic materials such as BaTiO ₃ , Pb ₄ Fe ₂ Nb ₂ O ₁₂ , TiO ₂ , and Ni -Zn ferrite, M
n-Zn ferrite (ceramic in a broad sense)
And other magnetic ceramic materials. In addition,
Its average particle size is 1.0 to 6.0 μm, preferably 1.5 to 6.0 μm.
Use the one crushed to 4.0 μm. Further, two or more ceramic materials may be used in combination. In particular, the use of corundum is advantageous in terms of cost.

The frit of the glass component is subjected to a baking treatment to obtain cordierite, mullite, anorthite,
Serdian, spinel, garnite, willemite, dolomite, petalite or a substituted derivative thereof or a crystal of a spinel structure may be precipitated, for example,
Glass frit containing B ₂ O ₃ , SiO ₂ , Al ₂ O ₃ , ZnO, and alkaline earth oxide can be used. Such a glass frit has a wide vitrification range and a yield point of 600
~ 800 ° C.

The thickness of the dielectric layers 1a to 1e is, for example, about 100 to 300 μm.

The internal wiring conductor 2 and the via hole conductor 3
The internal wiring conductor 2 is made of a conductor film (conductor) mainly composed of a g-based material (Ag alone, an Ag alloy such as Ag-Pd, Ag-Pt), and the thickness of the internal wiring conductor 2 is about 8 to 15 μm. The diameter of the via-hole conductor 3 can be set to an arbitrary value, but is set to 80 to 350 μm in order to increase the diameter and reduce the resistance. In particular, the via-hole conductor 3 is made of an Ag-based material, β-quartz, a glass component substantially the same as the glass component constituting the dielectric layers 1a to 1e, cordierite, mullite, anorthite, Celsian, spinel, garnite, willemite, dolomite, A crystal phase of petalite or a substituted derivative thereof or a crystal phase having a spinel structure can be precipitated, for example, B ₂ O ₃ , S
Glass frit containing iO ₂ , Al ₂ O ₃ , ZnO, and alkaline earth oxide may be used.

The glass components substantially the same as the glass components in the dielectric layers 1a to 1e may be the same as the glass components contained in the dielectric layers 1a to 1e, or may have a slightly different composition ratio. Additives to improve properties,
The composition may be changed or deleted without significantly changing the basic characteristics (thermal characteristics).

The surface wiring conductor 4 is made of Ag (Ag alone, A
(Ag alloys such as g-Pd, Ag-Pt, etc.) as a main component, and forms a predetermined circuit wiring mainly on the surface of the laminated substrate 1 and also connects the electronic components 6 joined via solder. It becomes a pad, or a terminal electrode of a thick-film resistive film or a thick-film capacitor element. In particular, the internal wiring conductor 2
The surface wiring conductor 4 is connected to the via-hole conductor 3 exposed from the dielectric layer 1a.

The feature of the present invention is that the surface wiring conductor 4
Is 0.05 to 100 parts by weight of the Ag-based conductor material.
It contains 2 parts by weight of rhodium and 1 to 3 parts by weight of manganese oxide.

The electronic component 6 can be exemplified by a chip-shaped electronic component such as a multilayer ceramic capacitor or a chip resistor, other oscillating devices or transistors, and is connected to the surface wiring conductor 4 via solder.

The IC chip 5 is connected to the surface wiring conductor 4 via a pump member formed on the lower surface of the IC chip 5 and a thin Al or Au bonding wire. Next, a method for manufacturing the circuit board 10 will be described.

First, the dielectric layers 1a to 1e of the laminate substrate 1
For example, an Ag-based conductive paste for forming the large green sheet, the internal wiring conductor 2 and the via-hole conductor 3, for example, an Au-based for forming the surface wiring conductor 4,
An Ag-based conductive paste and a glass paste for forming the overcoat glass layer 5 are prepared.

The green sheet has a plurality of circuit board regions so that a plurality of circuit boards can be extracted, and is made of a glass-ceramic material. For example, ceramic powder, frit of low melting glass component, organic binder,
The slurry obtained by uniformly kneading the organic solvent is tape-formed to a predetermined thickness by a doctor blade method, and cut into a predetermined size to form a sheet.

The ceramic powder includes insulating ceramic materials such as cristobalite, quartz, corundum (α-alumina), mullite, cordierite, BaTiO ₃ , Pb ₄ Fe
Dielectric ceramic materials such as ₂ Nb ₂ O ₁₂ and TiO ₂ , N
Magnetic ceramic materials such as i-Zn ferrite and Mn-Zn ferrite (referred to as ceramic in a broad sense) are mentioned, and their average particle size is 1.0 to 6.0 μm, preferably 1.5 to 4.0 μm. Crushed. Note that two or more ceramic materials may be used in combination. In particular, the use of corundum is advantageous in terms of cost.

The frit of the low-melting glass component precipitates a crystal phase of cordierite, mullite, anorthite, serdian, spinel, garnite, willemite, dolomite, petalite or a substituted derivative thereof or a crystal phase having a spinel structure by firing. Any material may be used, for example, glass frit containing B ₂ O ₃ , SiO ₂ , Al ₂ O ₃ , ZnO, and alkaline earth oxide.

The composition ratio between the ceramic material and the glass material is 10 to 60 wt%, preferably 30 to 50 wt%, for firing at a relatively low temperature of 850 to 1050 ° C. 90-40w
t%, preferably 70 to 50 wt%.

The organic binder also needs to pay attention to wettability with solids (ceramic powder, frit of low-melting glass component). Excellent ones are preferable, and ethylenically unsaturated compounds having a carboxyl group and an alcoholic hydroxyl group such as acrylic acid or methacrylic acid-based polymers are preferable.

As the solvent, an organic solvent or an aqueous solvent can be used. For example, in the case of an organic solvent,
For example, 2,4-trimethyl-1,3-pentadiol monoisoventate or the like is used. In the case of an aqueous solvent, it needs to be water-soluble, and the monomer and the binder include a hydrophilic functional group such as carboxyl. A group has been added.

The amount of addition is 2 to 300, preferably 5 to 100, in terms of acid value. If the added amount is small, the solubility in water, the dispersibility of the powder of the fixed component becomes poor,
When the amount is large, the thermal decomposability deteriorates. Therefore, the addition amount is appropriately added in the above range in consideration of solubility in water, dispersibility, and thermal decomposability.

Next, a through hole serving as a via hole conductor 3 is formed in each circuit board region of the green sheet serving as the dielectric layers 1a to 1e by punching. At the same time, a conductor serving as the via-hole conductor 3 is formed in the through hole by printing and filling with an Ag-based conductive paste, and particularly, a conductor serving as the internal wiring conductor 2 is formed on the green sheet serving as the dielectric layers 1b to 1e. The film is formed by printing and drying an Ag-based conductive paste. On the green sheet serving as the dielectric layer 1a, a conductor film serving as the surface wiring conductor 4 is formed of Ag.
It is formed by printing and drying a system conductive paste.

Here, the Ag-based conductive paste of the via-hole conductor 3 and the internal wiring conductor 2 is made of an Ag-based paste (Ag alone, Ag-based).
-Ag alloys such as Pd), borosilicate low melting point glass frit, organic binders such as ethylcellulose, and a homogeneous mixture of solvents are used.

The Ag-based conductive paste of the surface wiring conductor 4 is obtained by homogeneously mixing Ag-based (Ag alone, Ag alloy such as Ag-Pd) powder, Pt powder, low-melting glass frit, organic binder, and solvent. Is used.

Next, a via hole conductor 3 is formed in each circuit board area.
, A green sheet that becomes the dielectric layers 1b to 1e on which the conductor film that becomes the internal wiring conductor 2 is formed, and a green sheet that becomes the dielectric layer 1a on which the conductor film that becomes the surface wiring conductor 4 is formed. Laminated according to the order, for example, 60kg
A large-sized laminate substrate is formed by pressure bonding or the like at a pressure of f / cm ³ .

Next, division grooves are formed in the large-sized laminate substrate in an unfired state so as to divide each circuit board region.

Next, the unsintered large-sized laminated substrate is subjected to a simultaneous firing treatment in an oxidizing atmosphere or an air atmosphere. The firing step includes a binder removal step and a sintering step.

The binder removal process burns off organic components contained in the green sheets serving as the dielectric layers 1a to 1e, the conductor film serving as the internal wiring conductor 2, the conductor serving as the via hole conductor 3, and the conductor film serving as the surface wiring conductor 4. Is to let
For example, it is performed in a temperature range of 500 to 600 ° C.

In the sintering process, the glass component of the glass-ceramic green sheet is crystallized and simultaneously dispersed uniformly at the grain boundaries of the ceramic powder to give a certain strength to the laminated substrate, and the internal wiring conductor 2 A conductive powder of a conductive film, a conductor of a via hole conductor 3, and a metal powder or an Ag powder of a conductive material of a conductive film of the surface wiring conductor 4 are grain-grown to reduce the resistance, and are integrated with the dielectric layers 1a to 1e. It is.
This is done until a peak temperature of 850-1050 <0> C is reached.

At this time, at a temperature (for example, 550 ° C.) lower than the temperature (about 600 ° C.) at which the glass-ceramic material starts the sintering reaction (sintering shrinkage), the metal powder of the conductive material is turned (sintering shrinkage). Will start.

As a result, a large-sized circuit board having the internal wiring conductor 2 and the via-hole conductor 3 formed inside each circuit board area and the surface wiring conductor 4 formed on the surface is achieved.

Next, the thick film resistance element connected to the surface wiring conductor 4 and various electronic components 6 are joined and mounted by soldering or the like.

Finally, a dividing process is performed along the dividing grooves for dividing each circuit board. Thus, a plurality of circuit boards 10 shown in FIG. 1 are extracted from the large circuit board.

As described above, in the present invention, the surface wiring conductor 4 is 0.05% by weight based on 100 parts by weight of the Ag-based conductor material.
Contains ~ 2 parts by weight rhodium and 1-3 parts by weight manganese oxide.

In the present invention, the surface wiring conductor contains 0.05 to 2 parts by weight of rhodium and 1 to 3 parts by weight of manganese oxide based on 100 parts by weight of the Ag-based conductor material.

That is, since rhodium (Rh) is contained in an amount of 0.05 to 2 parts by weight with respect to 100 parts by weight of the Ag-based conductor material, the Ag conductor obtained by firing has a porous structure. Has the effect of suppressing. For this reason, a chemical solution used when plating the Ag conductor surface is less likely to penetrate into the Ag conductor tissue. as a result,
Good adhesion of the Ag conductor to the substrate is maintained.

If the content of rhodium is less than 0.05 parts by weight, the abnormal grain growth of the Ag conductor which occurs at the time of simultaneous firing with the substrate at 840 to 950 ° C. cannot be suppressed.
The conductor tends to have a porous structure. On the other hand, if it exceeds 2 parts by weight, rhodium itself does not sinter, so that sintering of the Ag powder is hindered and the sheet resistance increases.

Further, since manganese oxide (MnO) is contained in an amount of 0.05 to 3 parts by weight based on 100 parts by weight of the Ag-based conductor material, the reaction layer at the interface between the dielectric and the surface wiring conductor has MnO _2. A needle-like crystal peculiar to the addition precipitates and the contact area between the substrate and the surface wiring conductor increases, so that the so-called anchor effect (the Ag particles constituting the Ag-based conductive paste and the glass component of the substrate material are strongly bonded to each other) ) To enhance the adhesive strength between the laminate substrate 1 and the surface wiring conductor 4, thereby achieving high adhesive reliability.

When the content of manganese oxide is less than 1 part by weight, the anchor effect cannot be sufficiently exhibited. on the other hand,
If it is added in excess of 3 parts by weight, the needle-like crystals are deposited on the surface of the surface wiring conductor 4, and the sheet resistance increases.

The thickness of the entire laminated substrate is made uniform,
In order to enable uniform pressing, a glass layer is formed at predetermined positions on the surface wiring conductor, for example, at a portion excluding a portion on which various electronic components are mounted and a terminal electrode portion for making an electrical connection to the outside. May be.

[0054]

Next, the present invention will be described in more detail with reference to examples.

The inventor manufactured the circuit board 10 by the above-described manufacturing method. Note that the dielectric layer 1 is 100 μm × 5
The thickness of the layer and the internal wiring conductor 2 was set to 10 μm.

Sample Nos. 1 to 3 and 5 to 6 contained 0.05 to 2 parts by weight of rhodium and 1 to 3 parts by weight of manganese oxide based on 100 parts by weight of the Ag-based conductor material.

Sample Nos. 8 and 9 had rhodium contents of 0% and 1.5%, respectively.

Sample Nos. 4 and 7 had manganese oxide contents of 0.5% and 4%, respectively.

The adhesive strength, warpage, and sheet resistance of the circuit board 10 thus obtained were measured and evaluated. Table 1 shows the results.

[0060]

[Table 1]

The adhesive strength (kgf) in Table 1 was used.
Is 0.6 m on a surface wiring conductor of 2 mm square formed by the peeling method, that is, baking of a conductive paste.
This value is obtained by soldering a tin-plated copper lead wire having a diameter of mφ and then pulling the lead wire. Thus, in this embodiment, 2 mm of eutectic solder containing 2% Ag (Ag) adjusted to 235 ± 5 ° C.
A thick-film conductor having a size of × 2 mm is immersed for only 5 ± 1 seconds, and a tin-plated copper wire having a diameter of 0.8 mm, which is a lead wire, is connected to the thick-film conductor by soldering. Figure 3 shows the bond strength measured by pulling the lead wire at a speed of 20 cm / min with a tensile tester. The adhesive strength of each of the surface wiring conductors before and after plating was examined. 1.5k for evaluation of adhesive strength
g or more was determined to be good, and less than 1.5 kg was determined to be defective.

The method for measuring the warpage is as follows. A substrate having a size of 8.5 mm square after firing is formed, and the substrate is placed flat on a flat surface with the conductor facing upward. The difference in height between the lower surface of the substrate indicating the height and the upper surface of the conductor indicating the highest height is measured by applying a probe of a contact film thickness meter. Was regarded as defective.

The sheet resistance (mΩ / □) has a dimensional relationship (L / W = 100) where the length (L) and the width (W) are 100: 1.
100/1) on a patterned thick film conductor having
It is a conductor resistance value obtained by measuring a point by a well-known four-terminal method (resistance measurement method using a Wheatstone bridge) and then converting the film thickness. When the sheet resistance is evaluated to be 2.5 mΩ / □ or less, it satisfies practical conditions. The number of samples was 100 each.

The surface wiring conductor 4 is made of an Ag-based conductor material 100
0.05 to 2 parts by weight of rhodium and 1 part by weight
When manganese oxide is contained in an amount of 1 to 3 parts by weight (sample numbers 1 to 3 and 5 to 6), the initial and post-plating adhesive strength is 1.
5 kg or more, the warpage was less than 50 μm, and the sheet resistance was 2.5 mΩ / □ or less.

On the other hand, when the rhodium content was 0% (sample No. 8), the warpage was 60 μm. On the other hand, when the rhodium content was 1.5% (Sample No. 9), the sheet resistance was 2.7 mΩ / □.

When the manganese oxide content was 0.5% (Sample No. 4), the adhesive strength after plating was 1.0 k.
g. On the other hand, when the manganese oxide content was 4% (Sample No. 7), the sheet resistance was 2.8 mΩ / □.

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

[0068]

As described above, according to the present invention, the surface wiring conductor is used in an amount of 0.1 to 100 parts by weight of the Ag-based conductor material.
Since 0.5 to 2 parts by weight of rhodium is contained, the Ag conductor obtained by firing has an effect of suppressing the formation of a porous structure. For this reason, a chemical solution used when plating the Ag conductor surface is less likely to penetrate into the Ag conductor tissue. As a result, good adhesion of the Ag conductor to the substrate is maintained.

The surface wiring conductor is made of Ag-based conductor material 1
Since 1 to 3 parts by weight of manganese oxide is contained with respect to 00 parts by weight, a needle-like crystal peculiar to MnO ₂ addition precipitates in the reaction layer at the interface between the laminated substrate 1 and the surface wiring conductor 4. ,
The contact area between the laminate substrate and the surface wiring conductor increases, so-called anchor effect (the Ag particles constituting the Ag-based conductive paste and the glass component of the substrate material are strongly bonded).
To enhance the adhesive strength between the laminate substrate and the surface wiring conductor, thereby achieving high bonding reliability.

Therefore, a small and high-performance circuit board can be manufactured by a simple and inexpensive method.

[Brief description of the drawings]

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

[Explanation of symbols]

 REFERENCE SIGNS LIST 10 circuit board 1 laminated board 1 a to 1 e dielectric layer 2 internal wiring 3 through-hole conductor 4 surface wiring 5 IC chip 6 electronic component

Claims (1)

[Claims] 1. A circuit board in which a surface wiring conductor is formed on the surface of a laminated substrate formed by laminating a plurality of dielectric layers, wherein the surface wiring conductor is used in an amount of 0.1 to 100 parts by weight of the Ag-based conductor material. A circuit board comprising 0.05 to 2 parts by weight of rhodium and 1 to 3 parts by weight of manganese oxide.