JPH0521935A - Circuit board - Google Patents

Abstract

PURPOSE:To provide a circuit board where a wiring conductor and a circuit conductor can be clad with an improved adhesion property by enhancing electrical conductivity between the two. CONSTITUTION:In a circuit substrate where a circuit conductor 4 which consists of copper is clad on an outer surface of an insulation substrate 1 where a wiring conductor 2 which consists of at least one type out of tungsten, molybdenum, and manganese so that it partially contacts a wiring conductor, a middle metal layer 3 which contains a molybdenum of 1-10.0wt.%, a cobalt of 0.01-10.0wt.%, and a phosphor of 0.01-20.0wt.% in nickel is included at a contact portion between the wiring conductor 2 and the circuit conductor 4. The wiring conductor 2 and the circuit conductor 4 are clad with an improved adhesion property by the middle metal layer 3 and electrical conduction between the wiring conductor 2 and the circuit conductor 4 is extremely superior.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circuit board used in a hybrid integrated circuit device or the like. More specifically, it is made of a high melting point metal powder such as tungsten (W), molybdenum (Mo), manganese (Mn), etc. The present invention relates to an improvement of a circuit board having a wiring conductor made of copper (Cu) on the outer surface thereof.

[0002]

2. Description of the Related Art Conventionally, a hybrid integrated circuit device, in which a large number of active components such as semiconductor elements and passive components such as resistors and capacitors are mounted to form a predetermined electronic circuit, usually has a tungsten ( W), molybdenum (Mo), manganese (Mn) and other high melting point metal wiring conductors are embedded in the outer surface of the insulating substrate so that a part of the circuit conductor made of copper (Cu) is connected to the wiring conductors. Prepare a circuit board having a structure that is adhered to, then place semiconductor elements, capacitors, resistors, etc. on the surface of the circuit board and solder each electrode terminal to the circuit conductor (Sn-Pb alloy) And the like.

The circuit board used in such a conventional hybrid integrated circuit device or the like is generally manufactured by adopting a ceramics lamination technique and a thick film technique such as screen printing. Specifically, the following method is used. Produced by.

[0004] That is, first, ceramic raw material powders such as alumina (Al ₂ O ₃ ), silica (SiO ₂ ), magnesia (MgO) and calcia (CaO) which have excellent electric insulation properties are mixed with an organic solvent,
A solvent is added and mixed to obtain a plurality of ceramic green sheets, and a conductive paste made of a refractory metal powder of tungsten, molybdenum, manganese, etc. is formed on the upper and lower surfaces of each ceramic green sheet by a conventionally known thick film method such as screen printing. By adopting, the print application is performed in a predetermined pattern.

Next, each of the ceramic green sheets is laminated to obtain a laminated body, which is fired at a temperature of about 1500 ° C., and a wiring conductor made of a refractory metal such as tungsten, molybdenum, or manganese is provided inside and on the surface. Obtain an insulating substrate.

Finally, on the outer surface of the insulating substrate,
An organic solvent to copper (Cu) powder, a copper paste obtained by adding and mixing a solvent is applied by a conventionally known screen printing method so that a part of the copper paste is connected to the wiring conductor and a neutral atmosphere (nitrogen) is applied. Circuit board as a product by baking in an atmosphere) at a temperature of about 900 ° C and depositing copper powder on the insulating base and the wiring conductor.

However, this conventional circuit board has a poor wettability (reactivity) between tungsten, molybdenum, manganese, etc. forming the wiring conductor and copper forming the circuit conductor, and therefore the circuit conductor is partially formed on the wiring conductor. Even if they are adhered, the adhesion between them is poor, and as a result, there is a drawback that the electrical conduction between the wiring conductor and the circuit conductor is extremely poor.

In view of the above-mentioned drawbacks, therefore, nickel, which has good wettability (reactivity) with tungsten, molybdenum, manganese, and copper, is layered as an intermediate metal layer on the outer surface of the wiring conductor to contact the circuit conductor, and the wiring is formed. It has been proposed to improve the adhesion between conductors and circuit conductors (Japanese Patent Laid-Open No. Sho 61-2
58 30194).

[0009]

However, in the above circuit board, when the copper paste is fired at a temperature of about 800 ° C. and the circuit conductor is applied on the wiring conductor with the intermediate metal layer interposed therebetween, Interdiffusion occurs between the copper that forms the metal and the nickel that forms the intermediate metal layer, and part of the copper of the circuit conductor directly contacts the wiring conductor made of tungsten, molybdenum, etc., which has poor wettability (reactivity). The adhesion between the wiring conductor and the circuit conductor deteriorates, and at the same time the electrical continuity between them is good, but when thermal stress such as temperature cycle is applied, the difference in the coefficient of thermal expansion between the wiring conductor and the circuit conductor may occur. It has a drawback that it is greatly reduced.

[0010]

The present invention provides tungsten,
In the circuit board, a circuit conductor made of copper is attached to an outer surface of an insulating substrate provided with a wiring conductor made of at least one of molybdenum and manganese so that a part of the circuit conductor is in contact with the wiring conductor. 0.1 to 10.0 wt% molybdenum in nickel and 0,0 in the contact area between conductor and circuit conductor.
It is characterized by interposing an intermediate metal layer containing 01 to 10.0 wt% cobalt and 0.01 to 20.0 wt% phosphorus.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described in detail with reference to the accompanying drawings. FIG. 1 is a partially enlarged sectional view for explaining a circuit board of the present invention, and 1 is an insulating substrate made of an electrically insulating material.

The insulating substrate 1 is made of an electrically insulating material such as alumina ceramics, and is made of alumina (Al ₂ O
₃ ), silica (SiO ₂ ), magnesia (MgO), calcia
An organic solvent and a solvent are added to and mixed with a ceramic raw material powder such as (CaO) to form a slurry, and a ceramic raw sheet is obtained by employing the doctor blade method.
After that, the ceramic green sheets are subjected to appropriate perforating processing and a plurality of layers are laminated, and in a reducing atmosphere, at about 1500 ° C.
It is manufactured by firing at a temperature of.

The insulating base 1 is provided with a wiring conductor 2 extending from the inside to the upper surface thereof, and the wiring conductor 2 is made of at least one of tungsten, molybdenum and manganese.

For the wiring conductor 2, a conductor paste is prepared by adding an organic solvent and a solvent to powders of tungsten, molybdenum, and manganese, and printing the conductor paste in a predetermined pattern on the upper and lower surfaces of the ceramic green sheet by screen printing or the like. By coating, the insulating substrate 1 is adhered and formed inside and on the surface thereof.

The wiring conductor 2 has an intermediate metal layer on the exposed outer surface thereof at least at a portion where a circuit conductor 4 described later is applied.
3 is deposited and the intermediate metal layer 3 is a wiring conductor 2
Is formed on the exposed outer surface by a plating method such as electrolytic plating or electroless plating or a conventionally known thick film method.

The intermediate metal layer 3 is made of nickel 0.1 to 1
It is composed of 0.0 wt% molybdenum, 0.01 to 10.0 wt% cobalt and 0.01 to 20.0 wt% phosphorus, and the intermediate metal layer 3 wets both the wiring conductor 2 and the circuit conductor 4 (reactivity). ) Is good, circuit conductor 4 on top of wiring conductor 2
When they are adhered to each other, they are in close contact with each other and the electrical conduction between them is extremely excellent.

Molybdenum contained in nickel forming the intermediate metal layer 3 is a material that suppresses mutual diffusion of nickel and copper, and the circuit conductor 4 is covered on the wiring conductor 2 with the intermediate metal layer 3 interposed therebetween. Even if it is deposited, part of the copper of the circuit conductor 4 does not diffuse into the intermediate metal layer 3 and come into direct contact with the wiring conductor 2, which causes the wiring conductor 2 and the circuit conductor 4
There is no perfect adhesion with and electrical conductivity between the two can be extremely good.

When the content of molybdenum contained in nickel constituting the intermediate metal layer 3 is less than 0.1% by weight, the effect of suppressing the diffusion of copper is weakened, and a part of copper constituting the circuit conductor 4 is weakened. Are diffused in the intermediate metal layer 3 and the wiring conductor 2
Directly contact with the wiring conductor 2 to deteriorate the adhesion between the wiring conductor 2 and the circuit conductor 4, and if the content exceeds 10.0% by weight, the wettability (reactivity) between the intermediate metal layer 3 and the circuit conductor 4 is poor. Therefore, the circuit conductor 4 cannot be adhered to the wiring conductor 2 with good adhesion. Therefore, the content of molybdenum contained in nickel constituting the intermediate metal layer 3 is 0.1 to
It is specified in the range of 10.0% by weight.

Further, the cobalt contained in nickel forming the intermediate metal layer 3 is a material for suppressing the interdiffusion of nickel and copper and improving the adhesion strength between the intermediate metal layer 3, the circuit conductor 4 and Intermediate metal layer on wiring conductor 2
When circuit conductor 4 is attached with 3 in between,
Part of the copper in the copper does not diffuse into the intermediate metal layer 3 and come into direct contact with the wiring conductor 2, and the adhesion between the wiring conductor 2 and the circuit conductor 4 is made more complete, and the electrical continuity between them is extremely reduced. You can be good.

When the content of cobalt contained in nickel constituting the intermediate metal layer 3 is less than 0.01% by weight, the effect of suppressing the diffusion of copper is weakened, and a part of the copper constituting the circuit conductor 4 is formed. Diffuses in the intermediate metal layer 3 and comes into direct contact with the wiring conductor 2, deteriorating the adhesion between the wiring conductor 2 and the circuit conductor 4, and when the content exceeds 10.0% by weight, the intermediate metal layer 3 is formed. It becomes hard and brittle, and when heat stress such as a temperature cycle is applied, cracks are generated and the electrical continuity between the wiring conductor 2 and the circuit conductor 4 deteriorates. Therefore, the content of cobalt contained in nickel forming the intermediate metal layer 3 is specified in the range of 0.01 to 10.0% by weight.

Further, the phosphorus contained in nickel forming the intermediate metal layer 3 is a material for suppressing the formation of an oxide film on the surface of the intermediate metal layer 3, and the phosphorus is contained on the wiring conductor 2. Even if the circuit conductor 4 is adhered in between, the oxide film is not formed on the surface of the intermediate metal layer 3 and the adhesion between the intermediate metal layer 3 and the circuit conductor 4 is not deteriorated at all. The adhesion between 2 and the circuit conductor 4 can be made more perfect, and electrical conduction between the two can be made extremely good.

When the content of phosphorus contained in nickel constituting the intermediate metal layer 3 is less than 0.01% by weight, the effect of suppressing the formation of an oxide film on the surface of the intermediate metal layer 3 is obtained. It weakens, the adhesion between the intermediate metal layer 3 and the circuit conductor 4 deteriorates, and the adhesion between the wiring conductor 2 and the circuit conductor 4 deteriorates. It becomes hard and brittle, and when heat stress such as a temperature cycle is applied, cracks are generated and the electrical continuity between the wiring conductor 2 and the circuit conductor 4 deteriorates. Therefore, the phosphorus contained in nickel forming the intermediate metal layer 3 is specified in the range of 0.01 to 20.0% by weight.

Furthermore, the intermediate metal layer 3 has a thickness of 0.
If it is less than 1 μm, the diffusion of copper forming the circuit conductor 4 cannot be completely prevented, and a part of the circuit conductor 4 diffuses the intermediate metal layer 3 to directly contact the wiring conductor 2 and 2
The adhesion between the circuit conductor and the circuit conductor 4 tends to deteriorate.
When the thickness exceeds 0.0 μm, cracks are generated in the intermediate metal layer 3 due to internal stress, and part of the circuit conductor 4 directly contacts the wiring conductor 2 through the crack in the intermediate metal layer 3 and the wiring conductor 2 and the circuit conductor 4 It is preferable that the thickness of the intermediate metal layer 3 be in the range of 0.1 to 10.0 μm because the adhesion of the intermediate metal layer 3 tends to deteriorate.

Intermediate metal layer 3 deposited on the wiring conductor 2
A circuit conductor 4 made of copper is adhered to the outer surface of the substrate and the outer surface of the insulating substrate 1. The circuit conductor 4 has electrode terminals for active components such as semiconductor elements and passive components such as resistors and capacitors. Are connected.

For the circuit conductor 4, copper powder is mixed with glass powder, an organic solvent, and a solvent to form a metal paste.
The metal paste is printed and applied on the outer surface of the insulating substrate 1 so that a part of the metal paste is in contact with the intermediate metal layer 3 adhered to the wiring conductor 2, and then this is applied in a neutral atmosphere at about 800 ° C.
It is adhered to the outer surface of the insulating substrate 1 by firing at the temperature of.

In this case, it is difficult for the circuit conductor 4 to diffuse on the outer surface of the wiring conductor 2 and the wettability (reactivity) with the circuit conductor 4 is high.
Since the good intermediate metal layer 3 is interposed, the circuit conductor 4 can be adhered to the wiring conductor 2 with good adhesion and good electrical continuity between the two.

Further, since the circuit conductor 4 has a function of suppressing the oxidation of phosphorus contained therein, an oxide film is hardly formed on the surface even if the firing atmosphere contains a large amount of oxygen. As a result, it becomes possible to firmly bond the semiconductor element, the resistor, or the like to the circuit conductor 4 via the solder.

Further, the glass contained in the circuit conductor 4 is
For example PbO, B ₂ O ₃ , SiO ₂ , Al ₂ O ₃ , Na ₂ O, K
Consists of ₂ O, CaO, ZnO, etc., with an addition amount of 0.2% by weight
If the amount is less than 10%, it tends to be difficult to firmly adhere the circuit conductor 4 to the insulating substrate 1, and if it exceeds 8.0% by weight, the solder wettability (reactivity) of the circuit conductor 4 deteriorates and the circuit conductor 4 deteriorates. There is a tendency that it becomes difficult to firmly bond the semiconductor element, the resistor, etc. to 4 through solder. Therefore, the glass added to the circuit conductor 4 is preferably added in an amount of 0.2 to 8.0% by weight.

Thus, this circuit board has a semiconductor element, a resistor, a capacitor, etc. mounted on the surface thereof, and is bonded to the circuit conductor via solder to form a hybrid integrated circuit device.

The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the present invention. For example, the outer surface of the circuit conductor 4 can be made of metal.
If a coating layer made of (Au) is applied to a thickness of 0.1 to 5.0 μm, oxidative corrosion of the circuit conductor 4 can be effectively prevented, and the electrode terminals of semiconductor elements, resistors, capacitors, etc. can be made stronger by the circuit conductor 4. Can be joined to.

Further, on the outer surface of the circuit conductor 4, nickel (Ni),
If a coating layer containing at least one of iron (Fe) and manganese (Mn) as a main component is applied to a thickness of 0.2 to 12.0 μm, the coating layer will be applied to the circuit conductor 4 and the electrode terminals of semiconductor elements, capacitors, etc. When soldering is performed via solder, the wettability between the circuit conductor 4 and the solder can be improved, and electrode terminals such as semiconductor elements and capacitors can be firmly joined to the circuit conductor 4.

(Experimental Example) Next, the operation and effect of the present invention will be described based on an experimental example described below.

Experimental Example 1 First, a metal paste made of tungsten powder was applied by printing onto the upper surface of a ceramic green sheet containing alumina (Al ₂ O ₃ ) as a main component, and a pair of patterns having a width of 1.0 mm and a length of 10.0 mm were formed, Twenty pairs are attached with the distance between the tips set to 5.0 mm, and after that, this is baked in a reducing atmosphere at a temperature of about 1500 ° C,
A wiring conductor is formed on an insulating base made of an alumina sintered body. Next, an intermediate metal layer consisting of 99.4% by weight of nickel, 0.5% by weight of molybdenum, 0.05% by weight of cobalt and 0.05% by weight of phosphorus was plated on the surface of the wiring conductor of the insulating substrate to a thickness of 2 μm.
Of copper and between the pair of wiring conductors.
A (Cu) paste is printed to a thickness of about 30 μm, and this is baked in a neutral atmosphere at a temperature of about 800 ° C. to form a circuit conductor. The copper paste was brought into contact with the wiring conductor such that the copper paste came into contact with the tip of the wiring conductor 1.0 mm. And finally, the initial electrical resistance value between the pair of wiring conductors and −
The electrical resistance value after 100 cycles of the temperature cycle test of 65 to +150 ℃ is measured, the rate of change (rate of increase) is calculated, and the average value is calculated to determine the magnitude of the average rate of increase. Was evaluated for electrical continuity. As a result, the average increase rate is as small as 1.5%, and it can be seen that the electrical continuity between the wiring conductor and the circuit conductor is extremely good.

Experimental Example 2 The intermediate metal layer of Experimental Example 1 was formed by 84.0% by weight of nickel, 3.0% by weight of molybdenum, 3.0% by weight of cobalt and 10.0% by weight of phosphorus and had a thickness of 3 μm. The average increase rate of the electrical resistance between the wiring conductors was measured. As a result, the average increase rate is as small as 1.3%, and it can be seen that the electrical continuity between the wiring conductor and the circuit conductor is extremely good.

Experimental Example 3 An intermediate metal layer of Experimental Example 1 was formed by nickel 69.0% by weight, molybdenum 8.0% by weight, cobalt 8.0% by weight and phosphorus 15.0% by weight, and had a thickness of 3 μm. The average increase rate of the electrical resistance between the wiring conductors was measured. As a result, the average increase rate is as small as 1.3%, and it can be seen that the electrical continuity between the wiring conductor and the circuit conductor is extremely good.

Comparative Example The intermediate metal layer of Experimental Example 1 was formed of pure nickel and had a thickness of 3 μm, and the average increase rate of electric resistance between wiring conductors was measured by the same method as in Experimental Example 1. as a result,
The average rate of increase is as large as 10.0%, indicating that the electrical continuity between the wiring conductors and circuit conductors is poor.

[0037]

According to the circuit board of the present invention, nickel is 0.1 to 10.0 wt% molybdenum, 0.01 to 10.0 wt% cobalt and 0.01 to 20.0 between the wiring conductor and the circuit conductor.
Since an intermediate metal layer containing phosphorus by weight is interposed, the wiring conductor and the circuit conductor can be adhered to each other with good electrical continuity and good adhesion, which is used for a hybrid integrated circuit device or the like. It is extremely useful as a printed circuit board.

[Brief description of drawings]

FIG. 1 is a partially enlarged sectional view for explaining a circuit board according to the present invention.

[Explanation of symbols]

 1 ... Insulating substrate 2 ... Wiring conductor 3 ... Intermediate metal layer 4 ... Circuit conductor

Claims (1)

Claim: What is claimed is: 1. A circuit conductor made of copper is partly in contact with the wiring conductor on the outer surface of an insulating substrate provided with a wiring conductor made of at least one of tungsten, molybdenum and manganese. In the circuit board thus deposited, nickel is added to the contact portion between the wiring conductor and the circuit conductor with 0.1 to 0.1
A circuit board comprising an intermediate metal layer containing 10.0 wt% molybdenum, 0.01 to 10.0 wt% cobalt, and 0.01 to 20.0 wt% phosphorus.