JP2002164477A - Circuit board and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a circuit board having a low electric resistance layer to cope with a high operation speed or the like. SOLUTION: It is the circuit board 5 formed by simultaneously firing a first circuit layer 2 consisting of tungsten and/or molybdenum and copper and a second circuit layer 3 consisting of tungsten and/or molybdenum and iron group metal and a metal member 6 to be brazed thereto. A copper plated layer 8 covers the surface of the first circuit layer 2 and a nickel plated layer 9 covers the surface of the second circuit layer 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wiring board having, on a surface of an insulating substrate, a first wiring layer having a low resistance and a second wiring layer having a high adhesive strength and to which a metal member is attached. Things.

[0002]

2. Description of the Related Art Conventionally, a wiring board on which a semiconductor element or the like is mounted is generally a ceramic wiring board in which alumina ceramics is used as an insulating base, and a wiring layer made of a high melting point metal such as tungsten or molybdenum is formed on at least the surface thereof. It is heavily used. However, in a wiring layer made of a high melting point metal that has been widely used, a high melting point metal having a high electric resistance (electrical resistivity (20 ° C.) and tungsten: 5.
5 × 10 ⁻⁶ Ω · cm, molybdenum: 5.7 × 10 ⁻⁶ Ω ·
cm), there is a disadvantage that the wiring layer cannot have a sufficiently low resistance corresponding to an increase in the operation speed of a semiconductor element or the like.

On the other hand, in recent years, copper and silver (electrical resistivity (20 ° C.) and copper: 1.7 × 1
0 ^-6 Ω · cm, ^{silver: 1.6 × 10 -6 Ω · cm} ) and simultaneous possible firing, wiring board using a so-called glass ceramics have been proposed. However, since the adhesive strength of the metallized layer made of copper, silver or the like applied to the glass ceramic is as low as 2 kgf (19.6 N) or less at most, a metal member such as a lead terminal for external connection is attached to this wiring layer. In this case, there is a problem that the adhesive strength between the wiring layer and the insulating base becomes insufficient, and the wiring layer is easily peeled off.

As a method for simultaneously solving this electrical problem and the insufficient bonding strength of the wiring layer, the present applicant has previously reported that the relative density of aluminum oxide as a main component is 95%.
% Of a ceramic, and a first metallized layer containing 10 to 70% by volume of copper and 30 to 90% by volume of tungsten and / or molybdenum on the surface and / or inside of the insulating substrate. 1st wiring layer)
And tungsten and / or molybdenum at a rate of 50% by volume on the surface of the insulating base, 0.1 to 5% by volume of iron group element in terms of oxide, and 0 to 5% of aluminum oxide.
A wiring board including a second metallization layer (second wiring layer) containing 45% by volume and a method for manufacturing the same have been proposed (see JP-A-2000-188453).

According to this wiring board, the insulating base is made of an aluminum oxide sintered body or the like, has a high relative density and a high density, has a high thermal conductivity, and has a first metallized layer (first wiring layer). ) Contains low-resistance copper so that the electric resistance of the conductor forming the wiring layer is low (electrical resistivity (20 ° C.)
About 3 to 5 × 10 ⁻⁶ Ω · cm).

At the same time, since the second metallization layer (second wiring layer) is made of molybdenum and / or tungsten and an iron group element, the sinterability at low temperatures is good, and the adhesive strength of the wiring layer to the insulating substrate is good. And the first
Can be simultaneously fired with the metallized layer (first wiring layer).

This wiring board is manufactured by the following steps. That is, (1) a slurry obtained by adding an organic binder, a solvent, and the like to a raw material powder obtained by adding an auxiliary agent, a colorant, and the like to a ceramic powder such as aluminum oxide is formed into a sheet to form a ceramic green. A step of forming a sheet; and (2) a first conductor paste containing 30 to 90% by volume of tungsten and / or molybdenum and 10 to 70% by volume of copper on the surface of the ceramic green sheet. Applying, and applying a second conductor paste containing 0.1 to 5% by volume of iron group metal in terms of oxide and 95 to 99.9% by volume of tungsten and / or molybdenum; , (3)
The ceramic green sheet coated with the first and second conductive pastes is fired to form a first wiring layer made of tungsten and / or molybdenum and copper and a second wiring layer made of tungsten and / or molybdenum and an iron group metal Obtaining an insulating substrate having the following.

[0008]

However, in the above wiring board, the wiring layer has an electric resistivity of about 3 to 5 × 10 ⁻⁶ Ω ·.
m and lower conductors than conventional products, but with the recent reduction in power consumption of semiconductor elements, it is necessary to further reduce the loss of signals propagated in the wiring layer,
There is a growing demand for lower resistance.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide a low-resistance wiring layer capable of further reducing a signal loss in response to a reduction in power consumption of a semiconductor device. An object of the present invention is to provide a wiring board formed on a surface of an insulating base and a method of manufacturing the wiring board.

[0010]

According to the present invention, there is provided a wiring substrate comprising a first wiring layer made of tungsten and / or molybdenum and copper, and a tungsten and / or copper layer on a surface of an insulating base.
Alternatively, a wiring board made of molybdenum and an iron group metal, and formed by simultaneous firing with a second wiring layer to which a metal member is attached, wherein a copper plating layer is formed on a surface of the first wiring layer,
The present invention is characterized in that a nickel plating layer is applied to the surface of the wiring layer.

Further, in the wiring board according to the present invention, the first wiring layer is made of tungsten and / or molybdenum of 30 to 9%.
0% by volume, 10 to 70% by volume of copper, and 0.1 to 5% by volume of iron group metal in terms of oxide in the second wiring layer, with the balance being tungsten and / or molybdenum. It is.

Further, in the wiring board according to the present invention, the copper plating layer has a thickness of 2 μm to 15 μm.

Further, the wiring board of the present invention is characterized in that the nickel plating layer has a thickness of 0.8 μm or more and contains boron therein.

In the wiring board according to the present invention, the content of boron in the nickel plating layer is 0.05 to 3% by weight.

Further, the method for manufacturing a wiring board according to the present invention comprises:
(1) A first conductor paste containing 30 to 90% by volume of tungsten and / or molybdenum and 10 to 70% by volume of copper is applied to the surface of a ceramic green sheet, and an iron group metal is applied. A step of applying a second conductor paste containing 0.1 to 5% by volume in terms of oxide and 95 to 99.9% by volume of tungsten and / or molybdenum; The ceramic green sheet coated with the second conductor paste is fired, and the first wiring layer made of tungsten and / or molybdenum and copper, and the tungsten and / or
Or a step of obtaining an insulating base having a second wiring layer made of molybdenum and an iron group metal; and (3) coating the second wiring layer with a resist film and applying a copper plating layer on the surface of the first wiring layer. And (4) removing the resist film of the second wiring layer, and thereafter covering the copper plating layer on the surface of the first wiring layer with the resist film and applying a nickel plating layer on the surface of the second wiring layer. And (5) removing the resist film covering the copper plating layer on the surface of the first wiring layer.

According to the wiring board of the present invention, the first wiring layer is formed of tungsten and / or molybdenum and copper, and has an electric resistivity of 1.7 × 10 ^{-6 on} its surface.
A plating layer made of copper having a resistance of about Ω · cm and about 1/2 of that of the conductor forming the wiring layer is deposited, and the electric resistance of the wiring layer becomes extremely low due to the action of the copper plating layer having a very low resistance. , The first wiring layer has a much lower resistance,
The loss of the signal propagating through the first wiring layer can be extremely effectively reduced, and the semiconductor element can operate normally.

At the same time, according to the wiring board of the present invention, a copper plating layer is applied to the surface of the first wiring layer containing copper as a main component, and the bonding between the wiring layer and the plating layer is mainly made of copper of the same kind. Therefore, the copper plating layer can be firmly adhered to the first wiring layer.

Further, according to the wiring board of the present invention, the second wiring layer to which a metal member such as a lead terminal is attached is formed of tungsten and / or molybdenum and an iron group metal, so that the second wiring layer is insulated. The metal member can be firmly adhered to the base and the metal member can be fixed extremely firmly to the insulating base.

Further, according to the wiring board of the present invention, the second
Since the nickel plating layer is applied to the surface of the wiring layer, when the metal member is attached to the second wiring layer via the brazing material, the brazing material spreads uniformly and easily on the surface of the second wiring layer. The attachment strength of the metal member can be made extremely strong.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of the wiring board of the present invention will be described with reference to the accompanying drawings.

FIG. 1 shows an embodiment in which the wiring board of the present invention is used as a wiring board for mounting a semiconductor element, wherein 1 is an insulating base, 2 is a first wiring layer, and 3 is a second wiring layer. A wiring board 5 on which a semiconductor element 4 is mounted is formed by the insulating base 1, the first wiring layer 2, and the second wiring layer 3, and the second wiring layer 3 has lead terminals made of a metal material for external connection. 6 is brazed through a brazing material 7. In addition, the same conductor as that of the first wiring layer 2 is filled in the through hole 1a formed in the insulating base 1, so that the first wiring layer 2 and the second wiring layer 3 are electrically connected.

According to the present invention, as shown in the enlarged view of FIG. 2, the first wiring layer 2 is formed of tungsten and / or molybdenum and copper, and the second wiring layer 3 is formed of molybdenum and copper.
Is formed of tungsten and / or molybdenum and an iron group element, and the first wiring layer 2 and the second wiring layer 3 are formed by simultaneous firing with the insulating base 1.

The surface of the first wiring layer 2 is coated with a copper plating layer 8, and the surface of the second wiring layer 3 is coated with a nickel plating layer 9.

(Insulating Substrate) In the present invention, the insulating substrate 1
Acts as a base on which the semiconductor element 4 is mounted and supported, and includes a sintered body of aluminum oxide, a sintered body of aluminum nitride,
The semiconductor element 4 is formed on a ceramic sintered body such as a silicon carbide sintered body and mounted on the upper surface.

In order to improve the thermal conductivity and mechanical strength of the insulating substrate 1, it is desirable that the insulating substrate 1 be made of a high-density body having a relative density of 95% or more.

Further, according to the present invention, the insulating base 1 is formed of a first material.
In order to achieve shape retention by co-firing with the wiring layer 2,
It is necessary to fire at a low temperature of 1200 ° C. to 1500 ° C. According to the present invention, it is desirable to densify to a relative density of 95% or more even at such a low temperature.

From this point of view, the insulating substrate 1 according to the present invention is, for example, one having aluminum oxide as a main component,
Specifically, a material containing aluminum oxide in a proportion of 90% by weight or more is suitably used.
It is desirable that the n-compound be contained at a ratio of 2.0 to 6.0% by weight in terms of MnO ₂ . That is, when the amount of the manganese compound is less than 2.0% by weight, 1200 ° C. to 1500 ° C.
It is difficult to achieve densification at ℃, and if it is more than 6.0% by weight, the insulating property of the insulating base 1 is reduced. The optimum range of the manganese compound is 3 to 7% by weight in terms of MnO ₂ .

The insulating base 1 contains SiO ₂ and alkaline earth element oxides such as MgO, CaO and SrO as a third component in a total amount of from 0.4 to 0.4% in order to improve the low-temperature sinterability. It is desirable that the content be 8% by weight.

Further, in order to improve dielectric properties such as a coloring component and a dielectric constant, W, Mo, Cr
Such a metal as a coloring component may be contained in a proportion of 2% by weight or less.

The above-mentioned components other than aluminum oxide are present as an amorphous phase or a crystal phase at the grain boundaries of the main crystal phase of aluminum oxide. Desirably, a phase is formed.

When the insulating substrate 1 is formed mainly of aluminum oxide, the main crystal phase of aluminum oxide exists as granular or columnar crystals. The average crystal grain size of these main crystal phases is 1.5%. It is preferable that the thickness be from 5.0 to 5.0 μm. When the main crystal phase is composed of columnar crystals, the average crystal grain size is based on the minor axis diameter.
When the average crystal grain size of the main crystal phase is smaller than 1.5 μm, it is difficult to increase the thermal conductivity. When the average crystal grain size is larger than 5.0 μm, sufficient strength required when used as a substrate material is obtained. This is because it becomes difficult.

(Wiring Layer) The first wiring layer 2 functions as an electrode pad for connecting electrodes of the semiconductor element 4 mounted on the wiring board 5 and a conductive path for leading the electrodes of the semiconductor element 4 to the outside. The second wiring layer 3 acts as a connection pad for brazing and attaching a metal member such as a lead terminal 6 for external connection via a brazing material 7.

Preferably, the first wiring layer 2 contains 10 to 70% by volume of copper and 30 to 90% by volume of tungsten and / or molybdenum. this is,
This is to achieve a reduction in the resistance of the first wiring layer 2 and the simultaneous sinterability with the insulating base 1 and to maintain the formation of the first wiring layer 2 during the simultaneous firing. Less than 90% by volume of tungsten and molybdenum
If it is larger than the above, the electric resistance of the conductor forming the first wiring layer 2 becomes as high as about 5 × 10 ⁻⁶ Ω · cm or more. In addition, the copper amount is 7
More than 0% by volume and the amount of tungsten or molybdenum is 3
If the content is less than 0% by volume, the formation of the first wiring layer 2 during simultaneous firing is reduced, and bleeding occurs in the first wiring layer 2 or the first wiring layer 2 is aggregated by the molten copper and disconnected. Is caused, and the first wiring layer 2 is peeled off due to a difference in thermal expansion coefficient between the insulating base 1 and the first wiring layer 2. The optimum composition range is 40 to 60% by volume of copper and 60 to 40% by volume of tungsten and / or molybdenum.

In the present invention, tungsten and / or molybdenum in the first wiring layer 2 are dispersed and contained in a copper matrix as spherical or sintered particles of several particles having an average particle diameter of 1 to 10 μm. It is desirable to have. This is because the average particle size is 1 μm.
When the diameter is smaller than m, the shape retention of the first wiring layer 2 is deteriorated, the structure becomes porous, and the resistance of the first wiring layer 2 is increased. When the diameter exceeds 10 μm, the copper matrix is divided by tungsten or molybdenum particles. This is because the resistance of the first wiring layer 2 is increased and the copper component is separated to cause bleeding. Tungsten and / or molybdenum have an average particle size of 1.3 to 5 μm, especially 1.3.
Most preferably, the particles are dispersed in a size of about 3 μm.

In order to improve the adhesion to the insulating substrate 1, alumina or ceramics having the same composition as the insulating substrate 1 is contained in the first wiring layer 2 at a ratio of 0.05 to 2% by volume. It can also be contained.

Further, in the wiring board 5 of the present invention,
By co-firing the first wiring layer 2 containing copper with the insulating base 1 at a temperature exceeding the melting point of copper, the copper component in the first wiring layer 2 may diffuse into the insulating base 1. According to the present invention, it is desirable that the diffusion distance of copper into the ceramic around the first wiring layer 2 containing at least copper is 20 μm or less, particularly 10 μm or less. This is because, when the diffusion distance of copper into the ceramic exceeds 20 μm, the insulation between the first wiring layers 2 is reduced when the electric circuit is formed, and the reliability of the electric circuit is reduced.

By setting the copper diffusion distance to 20 μm or less, the minimum distance between the first wiring layers 2 formed on the same plane among the first wiring layers 2 is reduced to 100 μm or less, particularly 90 μm or less. Higher density can be achieved.

In the wiring board 5 of the present invention, a copper plating layer 8 is provided on the surface of the first wiring layer 2.

The copper plating layer 8 has an electric resistivity of 1.7.
Since the first wiring layer 2 is made of copper having a very low resistance of × 10 ⁻⁶ Ω · cm, the first wiring layer 2 has a much lower resistance, and the power consumption of the semiconductor element 4 mounted on the wiring board 5 has been reduced. Has the effect of reducing the loss of a signal propagated through the first wiring layer 2 to a very small value.

The copper plating layer 8 can be firmly adhered to the first wiring layer 2 because the first wiring layer to be adhered mainly contains copper of the same metal.

If the thickness of the copper plating layer 8 is less than 2 μm, the first wiring layer 2 cannot have a sufficiently low resistance. If the thickness exceeds 15 μm, the adhesion to the first wiring layer 2 decreases due to internal stress. However, there is a possibility that inconveniences such as blistering and peeling may occur. Therefore, the thickness of the copper plating layer 8 is preferably set in the range of 2 μm to 10 μm, and more preferably in the range of 3 μm to 6 μm.

When the amount of eutectoids of the plating solution components described later in the plating layer exceeds 0.1% by weight, these eutectoid components may be interposed between copper crystal grains. May cause an increase in electric resistance. Therefore, it is preferable that the copper plating layer 8 has a high purity in which the content of the eutectoid component is less than 0.1% by weight.

Further, in the wiring board 5 of the present invention, the second wiring layer 3 made of tungsten and / or molybdenum and an iron group element and having a metal member such as a lead terminal 6 attached to the surface of the insulating base 1. Are formed.

The second wiring layer 3 formed on the surface of the insulating base 1 and to which the metal member is attached is required to have high bonding strength with the metal member and high bonding strength with the insulating base 1. However, it is difficult to obtain sufficient adhesive strength with the composition of the first wiring layer 2.

Therefore, according to the present invention, by setting the second wiring layer 3 to the above composition, a high adhesive strength to the insulating base 1 can be provided.

When the second wiring layer 3 is formed by simultaneous firing with the first wiring layer 2 containing a large amount of copper having a low melting point as a conductor component, the firing temperature is 1200 to 1500 ° C.
Since it is necessary to fire at a low temperature, a conductor consisting only of tungsten or molybdenum cannot be sufficiently sintered at the time of firing at a low temperature.

Therefore, according to the present invention, in addition to tungsten and molybdenum, an iron-group metal is contained at a ratio of 0.1 to 5% by volume in terms of oxide to improve sinterability at low temperatures. it can. Therefore, when the amount of the iron group metal is less than 0.1% by volume, densification of the second wiring layer 3 does not proceed, resulting in poor sintering, and the adhesive strength to the insulating base 1 is reduced. Conversely, if the amount of iron group metal exceeds 5% by volume, tungsten and molybdenum particles grow abnormally, and the adhesive strength decreases. The amount of the iron group metal is particularly preferably 0.5 to 2% by volume in terms of oxide.

Further, the same type of ceramic powder as the insulating substrate 1 such as aluminum oxide is added to the second wiring layer 3 in order to increase the adhesive strength with the insulating substrate 1 containing aluminum oxide or the like as a main component. It is also effective. But,
If the content is more than 45% by volume, poor sintering will be caused and plating will be chipped (plating will not adhere) in the plating step described later. This lack of plating causes reduction in bonding reliability of the metal member such as the lead terminal 6. For example, in the case of aluminum oxide, its content is particularly preferably from 2 to 35% by volume.

The iron group metal in the second wiring layer 3 includes
Iron, nickel, and cobalt are mentioned, and among these, nickel is most desirable. The oxide equivalent is iron (F
e) is an amount converted to Fe ₂ O ₃ , nickel (Ni) is NiO, and cobalt (Co) is Co ₃ O ₄ .

The lead terminal 6 functions as a terminal for external connection of the wiring board, and is made of a metal material such as copper, an alloy containing copper as a main component, an iron-nickel alloy, and an iron-nickel-cobalt alloy. It is formed by subjecting a metal material to a well-known metal processing such as rolling and punching. The lead terminal 6 is bonded to the second wiring layer 3 via a brazing material such as silver brazing or solder, and, for example, the lead terminal 6 is placed on the second wiring layer 3 with a silver-copper eutectic brazing material therebetween. It is brazed and attached onto the second wiring layer 3 by being interposed therebetween and heat-treated at about 800 ° C.

Further, in the wiring board 5 of the present invention, a nickel plating layer 9 is applied on the surface of the second wiring layer 3.

The nickel plating layer 9 is formed of a first wiring layer 2 made of molybdenum and / or tungsten and an iron group metal.
In addition to the good adhesiveness to the lead wire and the good wettability and joining property of the brazing material 7, the lead terminals 6 can be firmly joined to the second wiring layer 3 via the brazing material 7.

In particular, if the nickel plating layer 9 has a thickness of 0.8 μm or more and contains boron therein, the second wiring layer 3 is formed of a dense plating layer having few pinholes. The coating can be surely performed, and the wettability of the brazing material 7 to the second wiring layer 3 can be further improved. Therefore, it is preferable that the thickness of the nickel plating layer 9 is 0.8 μm or more, and in consideration of preventing a problem such as a decrease in the adhesion strength due to an increase in the internal stress of the plating layer, a value of 0.
It is even more preferable that the thickness be in the range of 8 to 4 μm.

In this case, if the boron content in the nickel plating layer 9 is less than 0.05% by weight, the corrosion resistance of the nickel plating layer 9 tends to deteriorate. The resistance tends to increase and the loss of the propagated signal tends to increase. Therefore, when boron is contained in the nickel plating layer 9, the content is preferably in the range of 0.05 to 3% by weight.

When the nickel plating layer 9 contains boron, the content of sulfur as a trace component is 0.00
If it is less than 5% by weight, fine cracks are likely to occur in the nickel plating layer 9, and if it exceeds 0.08% by weight, the corrosion resistance of the nickel plating layer 9 tends to deteriorate. Therefore, when the nickel plating layer 9 contains boron, the content of sulfur, which is a trace component thereof, is preferably set to 0.005 to 0.08% by weight.

The copper plating layer 8 and the nickel plating layer 9 further have an exposed surface of 0.03 to 3 μm.
In this case, it is possible to effectively prevent oxidative corrosion and to further improve the bonding property of a bonding wire, which will be described later, by covering with a gold plating layer (not shown) having a thickness of it can. Accordingly, it is preferable that the exposed surfaces of the copper plating layer 8 and the nickel plating layer 9 are covered with a gold plating layer having a thickness of 0.03 to 3 μm.

Thus, according to the wiring board 5 of the present invention, the semiconductor element 4 is mounted on the upper surface of the insulating base 1 and each electrode of the semiconductor element 4 is electrically connected to the first wiring layer 2 via the bonding wire 10. Thereafter, if necessary, the semiconductor element 4 is hermetically sealed using a bowl-shaped lid made of metal or ceramic, a sealing resin (not shown), or the like, thereby completing a semiconductor device as a product. .

(Method of Forming Wiring Substrate) Next, the method of manufacturing the above wiring substrate will be described with reference to FIGS. 3A to 3E in the case where the insulating base is made of an aluminum oxide sintered body. I do. In the drawings, the same parts as those in FIGS. 1 and 2 are denoted by the same reference numerals.

(1) First, as shown in FIG. 3A, the surface of the ceramic green sheet 21 contains 30 to 90% by volume of tungsten and / or molybdenum and 10 to 70% by volume of copper. The first conductive paste 22 is applied by a screen printing method or the like, and contains 0.1 to 5% by volume of iron group metal in terms of oxide, and 95 to 99.9% by volume of tungsten and / or molybdenum. Is applied.

The ceramic green sheet includes:
The through hole 21a serving as a through conductor is formed in advance by a laser processing method, a mechanical punching method, or the like.
The first conductive paste 22 is also printed and filled in 1a.

The ceramic green sheet 21 is formed into a slurry (slurry) by adding an organic binder and a solvent to a raw material powder mainly composed of aluminum oxide, and is formed into a sheet by a doctor blade method or the like. Can be formed.

The aluminum oxide raw material powder has an average particle size of 0.5 μm to 2.5 μm, especially 0.5 μm.
A powder of μm to 2.0 μm is used. This is because if the average particle size is smaller than 0.5 μm, it is difficult to handle the powder,
Also, the cost of the powder increases, and if it is larger than 2.5 μm, it becomes difficult to fire at a temperature of 1500 ° C. or less.

Then, MnO ₂ is added as a _second component to the aluminum oxide powder at a ratio of 2.0 to 8.0% by weight, particularly 3.0 to 7.0% by weight.
If necessary, a third component such as SiO ₂ . MgO, Ca
0.4 to 8% by weight of O, SrO ₂ powder or the like, and a ratio of 2% by weight or less in terms of metal as a fourth component using a metal powder or oxide powder of a transition metal such as W, Mo or Cr as a coloring component Add in.

In addition, in addition to the oxide powder, the above oxides may be added as carbonates, nitrates, acetates, etc. which can form oxides by firing.

The first conductive paste 22 is made of, for example, copper powder having an average particle size of 1 to 10 μm,
% By volume, especially 40 to 60% by volume, having an average particle size of 1 to 1
It is prepared by adding and mixing an organic resin and a solvent to a solid component obtained by adding 30 μm to 90% by volume, particularly 40% to 60% by volume of a 0 μm tungsten and / or molybdenum powder. In order to enhance the adhesion to the insulating substrate 1, aluminum oxide powder or the same composition powder as the ceramic component forming the insulating substrate 1 is contained in the first conductive paste 22 in an amount of 0.05 to 2 parts.
It is also possible to add at a ratio of volume%.

The second conductive paste 23 is formed, for example, by adding tungsten and / or molybdenum having an average particle diameter of 0.5 to 5 μm to at least one of oxide powders of an iron group metal (iron, nickel, cobalt). It is prepared by adding and mixing an organic resin and a solvent to a solid component obtained by adding 0.1 to 5% by volume of a seed and 0 to 45% by volume of an aluminum oxide powder.

(2) Next, the ceramic green sheet 21 coated with the first and second conductor pastes 22 and 23 is used.
3B, an insulation having a first wiring layer 2 made of tungsten and / or molybdenum and copper and a second wiring layer 3 made of tungsten and / or molybdenum and an iron group metal as shown in FIG. The substrate 1 is obtained.

If the firing temperature at this time is lower than 1200 ° C., the insulating substrate made of an aluminum oxide sintered body cannot be densified to a relative density of 95% or more when ordinary raw materials are used, and the thermal conductivity and If the strength is lowered and is higher than 1500 ° C., sintering of tungsten or molybdenum itself proceeds, and a uniform structure with copper cannot be maintained. As a result, it is difficult to maintain a low resistance and the sheet resistance increases. In addition, the grain size of the main crystal phase of the oxide ceramics increases, abnormal grain growth occurs, and the diffusion speed increases as the length of the grain boundary, which is the path when copper diffuses into the ceramics, decreases. , Diffusion distance 30μm
This is because it is difficult to control the following. Preferably, the range is 1350 to 1450 ° C.

It is preferable that the non-oxidizing atmosphere at the time of firing is nitrogen or a mixed atmosphere of nitrogen and hydrogen. In particular, in order to suppress the diffusion of copper in the wiring layer, hydrogen and hydrogen are used. It is desirable that the atmosphere be a non-oxidizing atmosphere containing nitrogen and having a dew point of + 10 ° C or lower, particularly -10 ° C or lower.
Note that an inert gas such as an argon gas may be mixed into this atmosphere, if desired. If the dew point during firing is higher than + 10 ° C., the oxide ceramic reacts with moisture in the atmosphere during firing to form an oxide film, and this oxide film reacts with copper of the copper-containing conductor, resulting in a low conductor. This not only hinders resistance but also promotes copper diffusion.

Further, by controlling the firing temperature and atmosphere as described above, the arithmetic average roughness Ra of the surface of the insulating substrate 1 is 1 μm or less, particularly 0.7 μm.
The following surface having excellent smoothness can be formed.

(3) Next, as shown in FIG. 3C, the second wiring layer 3 is covered with a resist
A copper plating layer 8 is applied to the surface of the wiring layer 2.

The resist film 24 functions to prevent the copper plating layer 8 from being deposited on the surface of the second wiring layer 3 when the copper plating layer 8 is deposited on the first wiring layer 2.
Negative-type photosensitive synthetic rubber-based resin, acrylic ester-based photosensitive resin, and the like can be used.
A resist film 24 is applied by dip coating, flow coating, roller coating, or the like so as to cover almost the entire surface of the wiring substrate 5, and then patterned by exposure and development so as to cover only the first wiring layer 2. It is formed by doing.

The resist film 24 is immersed in a corrosive plating solution such as a highly alkaline solution or various processing solutions during copper plating or nickel plating to be described later. It is necessary to be excellent in chemical resistance to

The copper plating layer 8 is made of a first electroless copper plating solution containing a compound serving as a copper supply source such as copper sulfate and a reducing agent such as formalin and sodium hypophosphite as main components. By dipping the wiring layer 2 for a predetermined time, the wiring layer 2 is formed on the first wiring layer 2 so as to have a predetermined thickness.

In this case, in the copper plating layer 8 to be formed, the eutectoid component contained in the plating layer changes depending on the type of the reducing agent used. Is 99.9% by weight or more, and a high purity copper layer is formed. In the case of sodium hypophosphite, a copper layer containing several weight% of phosphorus is formed. Accordingly, since it is preferable that the copper plating layer 8 has a high purity in order to reduce the resistance, it is preferable to use a reducing agent such as formalin that does not contain an eutectoid component in the plating layer.

When the copper plating layer 8 is applied to the surface of the first wiring layer 2, as a pretreatment for plating, a high melting point metal of tungsten and / or molybdenum exposed on the surface of the first wiring layer 2 is used. Is removed as much as possible by etching, and the proportion of the copper component exposed on the surface of the first wiring layer 2 is determined as follows:
For example, it is preferable to increase the ratio to 80% or more, so that the adhesion strength of the copper plating layer 8 to the first wiring layer 2 can be further improved.

(4) Next, as shown in FIG. 3D, the resist film 24 covering the second wiring layer is removed, and then the copper plating layer on the surface of the first wiring layer 2 is removed. Membrane 2
4 and a nickel plating layer 9 is applied to the surface of the second wiring layer 3.

For removing the resist film 24, for example, if the resist film 24 is made of a photosensitive synthetic rubber-based resin, the resist film 24 is immersed in a stripping solution mainly containing an organic solvent such as xylene. It can be done by doing. Note that the immersion time may be determined as appropriate according to the working conditions such as the concentration of the resist film, the concentration of the stripper solution, and the temperature.

The resist film 24 for covering the first wiring layer 2 can be made of a photosensitive synthetic rubber-based resin or the like in the same manner as the one used for covering the second wiring layer 3 in the above step.
By pattern processing by the same exposure and development as described above, it can be formed so as to cover only the first wiring layer 2 on which the copper plating layer 8 is applied.

The nickel plating layer 9 is, for example,
It can be formed by an electroless plating method using a reducing agent such as sodium hypophosphite, dimethylamine borane, hydrazine, and the like. Depending on the type of the reducing agent, a nickel plating layer containing phosphorus and nickel containing boron Plating layer,
It is formed as a high-purity nickel plating layer having a nickel purity of 99.9% by weight or more.

When the nickel plating layer 9 is applied, for example, when boron is contained, the nickel plating layer 9 is mainly composed of a nickel compound serving as a nickel supply source such as nickel sulfate and a reducing agent such as dimethylamine borane. Acetic acid, malonic acid,
An electroless nickel plating solution prepared by adding and mixing an organic acid such as succinic acid and propionic acid or a complexing agent such as a sodium salt thereof, a stabilizer such as thiodiacetic acid, and a pH adjusting agent such as ammonium chloride. This can be performed by immersing the two wiring layers 3 for a predetermined time.

The content of trace components such as the boron content and sulfur in the nickel plating layer 9 is determined by the combination of the type of complexing agent and the stabilizer, the increase or decrease of the concentration, or the pH and solution in the nickel plating solution. By adjusting the plating conditions such as the temperature and the stirring speed, the temperature can be controlled within a predetermined range.

(5) Finally, by removing the resist film 24 covering the copper plating layer 8 on the surface of the first wiring layer 2, as shown in FIG. , A first wiring layer 2 made of tungsten and / or molybdenum and copper, and a second wiring layer 3 made of tungsten and / or molybdenum and an iron group metal to which a metal member such as a lead terminal is attached. Formed by
The wiring board 5 having the copper plating layer 8 on the surface of the first wiring layer 2 and the nickel plating layer 9 on the surface of the second wiring layer 3 is completed.

The resist film 2 covering the first wiring layer 2
As in the case of the resist film 24 covering the second wiring layer 3, the layer 4 can be stripped using a stripping solution mainly containing an organic solvent such as xylene.

The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the present invention. Is applied to a wiring board for mounting a semiconductor element, but this may be applied to a hybrid integrated circuit board or the like.

[0086]

According to the wiring board of the present invention, the first wiring layer is formed of tungsten and / or molybdenum and copper, and has an electric resistivity of 1.7 × 10
^A plating layer made of copper having a low resistance of ^-6 Ω · cm is applied, and the electric resistance of the wiring layer becomes extremely small due to the action of the copper plating layer having a very low resistance. With the use of the resistor, the loss of a signal propagating through the wiring layer can be extremely effectively reduced, and the semiconductor element can operate normally.

At the same time, according to the wiring board of the present invention, a copper plating layer is deposited on the surface of the first wiring layer containing copper as a main component, and the bonding between the wiring layer and the plating layer is mainly between coppers of the same kind. Therefore, the copper plating layer can be firmly adhered to the first wiring layer.

Further, according to the wiring board of the present invention, since the second wiring layer to which the metal member is attached is formed of tungsten and / or molybdenum and an iron group metal, the second wiring layer is firmly attached to the insulating base. The metal member can be adhered to the insulating base and fixed extremely firmly.

Further, according to the wiring board of the present invention, the second
Since the nickel plating layer is applied to the surface of the wiring layer, when the metal member is attached to the second wiring layer via the brazing material, the brazing material spreads uniformly and easily on the surface of the second wiring layer. The attachment strength of the metal member can be made extremely strong.

[Brief description of the drawings]

FIG. 1 is a sectional view showing one embodiment of a wiring board of the present invention.

FIG. 2 is an enlarged view of a main part of the wiring board shown in FIG.

FIGS. 3A to 3E are cross-sectional views for explaining steps of a method for manufacturing a wiring board according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Insulating base 1a ... Through-hole 2 ... 1st wiring layer 3 ... 2nd wiring layer 4 ... Semiconductor element 5 ... Wiring board 6 ... Lead terminal 7 Brazing material 8 Copper plating layer 9 Nickel plating layer 21 Ceramic green sheet 22 First conductor paste 23 Second conductor paste 24 ..Resist film

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4E351 AA07 BB01 BB31 CC12 CC22 CC31 CC33 DD17 GG02 GG07 5E343 AA02 AA24 BB08 BB14 BB16 BB52 BB72 DD03 DD33 EE52 ER12 ER18 ER36 ER39 GG01 GG13

Claims (6)

[Claims] 1. The method according to claim 1, wherein tungsten and / or
Alternatively, the wiring board is formed by simultaneously firing a first wiring layer made of molybdenum and copper and a second wiring layer made of tungsten and / or molybdenum and an iron group metal to which a metal member is attached. A wiring board, wherein a copper plating layer is applied on a surface of the first wiring layer, and a nickel plating layer is applied on a surface of the second wiring layer. 2. The method according to claim 1, wherein the first wiring layer contains 30 to 90% by volume of tungsten and / or molybdenum and 10 to 7% by volume of copper.
2. The wiring board according to claim 1, wherein the second wiring layer is made of 0% by volume, and the second wiring layer is made of 0.1 to 5% by volume of iron group metal in terms of oxide, and the balance is made of tungsten and / or molybdenum. 3. The copper plating layer has a thickness of 2 μm to 15 μm.
The wiring board according to claim 1, wherein m is m. 4. The thickness of the nickel plating layer is 0.8 μm.
2. The wiring board according to claim 1, wherein said wiring board contains boron. 5. The wiring board according to claim 4, wherein the amount of boron contained in the nickel plating layer is 0.05 to 3% by weight. 6. A first conductor paste containing 30 to 90% by volume of tungsten and / or molybdenum and 10 to 70% by volume of copper is applied to the surface of the ceramic green sheet. Applying a second conductor paste containing 0.1 to 5% by volume of iron group metal in terms of oxide and 95 to 99.9% by volume of tungsten and / or molybdenum;
(2) firing the ceramic green sheet to which the first and second conductor pastes have been applied, to form a first wiring layer made of tungsten and / or molybdenum and copper and a first wiring layer made of tungsten and / or molybdenum and an iron group metal; A step of obtaining an insulating base having two wiring layers; (3) a step of coating the second wiring layer with a resist film and applying a copper plating layer on the surface of the first wiring layer; (5) removing the resist film of the layer, and thereafter covering the copper plating layer on the surface of the first wiring layer with the resist film and applying a nickel plating layer on the surface of the second wiring layer;
Removing the resist film covering the copper plating layer on the surface of the first wiring layer.