JP2842710B2 - Circuit board - Google Patents

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 for a hybrid integrated circuit device or the like, and more particularly to a circuit board containing a high melting point metal powder such as tungsten (W), molybdenum (Mo), and manganese (Mn). The present invention relates to an improvement of a circuit board having a wiring conductor made of copper (Cu) on the outer surface.

[0002]

2. Description of the Related Art Conventionally, a hybrid integrated circuit device which mounts a large number of active components such as a semiconductor element and a plurality of passive components such as a resistor and a capacitor to form a predetermined electronic circuit usually has a tungsten (Tungsten) inside. W), a circuit conductor made of copper (Cu) is partially connected to the wiring conductor on the outer surface of an insulating base in which a wiring conductor made of a high melting point metal such as molybdenum (Mo) or manganese (Mn) is embedded. Prepare a circuit board having a structure adhered in the following manner, and then place a semiconductor element, a capacitor, a resistor, etc. on the surface of the circuit board and solder each electrode terminal to a circuit conductor (Sn-Pb alloy) It is formed by joining through such as.

A circuit board used in such a conventional hybrid integrated circuit device is generally manufactured by employing a ceramic laminating technique and a thick film technique such as screen printing. Produced by

[0004] First, an organic solvent is added to a ceramic raw material powder such as alumina (Al ₂ O ₃ ), silica (SiO ₂ ), magnesia (MgO), and calcia (CaO) which has excellent electrical insulation properties.
A solvent is added and mixed to obtain a plurality of ceramic raw sheets, and a conductive paste made of a high melting point metal powder such as tungsten, molybdenum, manganese or the like is formed on the upper and lower surfaces of each ceramic raw sheet by a conventionally known thick film method such as screen printing. Is applied in a predetermined pattern by printing.

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

Finally, on the outer surface of the insulating substrate,
A copper paste obtained by adding and mixing an organic solvent and a solvent to copper (Cu) powder is applied by a well-known screen printing method so that a part of the copper paste is connected to the wiring conductor, and the paste is applied to a neutral atmosphere (nitrogen atmosphere). (Atmosphere) at a temperature of about 900 ° C., and a copper powder is deposited on the insulating substrate and the wiring conductor to obtain a circuit board as a product.

However, the conventional circuit board has poor wettability (reactivity) between tungsten, molybdenum, manganese, etc. forming the wiring conductor and copper forming the circuit conductor. Even if they are applied, 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 drawbacks, nickel, which has good wettability (reactivity) with tungsten, molybdenum, manganese, and copper, is interposed as an intermediate metal layer on the outer surface of the wiring conductor where the circuit conductor comes into contact. It has been proposed to improve the adhesion between the conductor and the circuit conductor (see
58 30194).

[0009]

However, in the above-mentioned 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 an intermediate metal layer interposed therebetween, Inter-diffusion occurs between the copper that forms the metal and the nickel that forms the intermediate metal layer, and some of the copper in 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 conduction between the two is good, but when thermal stress such as a temperature cycle is applied, the difference in the thermal expansion coefficient between the wiring conductor and the circuit conductor is reduced. This has the drawback that it is greatly reduced.

[0010]

SUMMARY OF THE INVENTION The present invention is directed to tungsten,
In a circuit board, a circuit conductor made of copper is adhered on an outer surface of an insulating base provided with a wiring conductor made of at least one of molybdenum and manganese so that a part of the circuit conductor comes into contact with the wiring conductor. 0.1 to 30.0% by weight of tungsten in nickel at the contact between the conductor and the circuit conductor
The present invention is characterized in that an intermediate metal layer containing 0.01 to 10.0% by weight of cobalt and 0.01 to 20.0% by weight of phosphorus is interposed.

[0011]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. FIG. 1 is a partially enlarged sectional view for explaining a circuit board of the present invention, and 1 is an insulating base made of an electrically insulating material.

[0012] The insulating substrate 1 is made of, for example, electrically insulating material alumina ceramics, alumina (Al ₂ O
₃ ), silica (SiO ₂ ), magnesia (MgO), calcia
An organic solvent is added to a ceramic raw material powder such as (CaO), a solvent is added and mixed to form a slurry, and a ceramic raw sheet is obtained by employing a doctor blade method,
Thereafter, the ceramic green sheet is subjected to an appropriate drilling process and a plurality of the sheets are laminated, and in a reducing atmosphere, 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, and the wiring conductor 2 is formed of at least one of tungsten, molybdenum, and manganese.

The wiring conductor 2 is prepared by adding and mixing an organic solvent and a solvent to powder of tungsten, molybdenum, and manganese to form a conductor paste, and printing the conductor paste on the upper and lower surfaces of the ceramic green sheet in a predetermined pattern by screen printing or the like. By being applied, it is adhered to the inside and the surface of the insulating base 1.

The wiring conductor 2 has an intermediate metal layer on its exposed outer surface at least at a portion where a circuit conductor 4 to be described later is attached.
3 is formed, and the intermediate metal layer 3 is
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 has a thickness of 0.1 to 3 on nickel.
The intermediate metal layer 3 contains 0.0% by weight of tungsten, 0.01 to 10.0% by weight of cobalt, and 0.01 to 20.0% by weight of phosphorus, and the intermediate metal layer 3 has wettability (reactivity) for both the wiring conductor 2 and the circuit conductor 4. ) Is good, and the circuit conductor
When 4 is adhered, the two adhere to each other and make the electrical conduction between them extremely excellent.

Tungsten contained in nickel constituting the intermediate metal layer 3 is a material for suppressing 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 attached, a part of the copper of the circuit conductor 4 does not diffuse into the intermediate metal layer 3 and directly contact the wiring conductor 2 at all, so that the wiring conductor 2 and the circuit conductor
4 and the electrical conductivity between them can be made extremely good.

If the content of tungsten contained in the 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 the copper constituting the circuit conductor 4 is reduced. Is diffused in the intermediate metal layer 3 and
2 and directly deteriorates the adhesion between the wiring conductor 2 and the circuit conductor 4. If the content exceeds 30.0% by weight, the wettability (reactivity) between the intermediate metal layer 3 and the circuit conductor 4 is reduced. As a result, the circuit conductor 4 cannot be adhered to the wiring conductor 2 with good adhesion. Therefore, the content of tungsten contained in the nickel constituting the intermediate metal layer 3 is 0.1%.
To 30.0% by weight.

Cobalt contained in nickel constituting the intermediate metal layer 3 is a material for suppressing mutual diffusion of nickel and copper and improving the adhesion strength between the intermediate metal layer 3 and the circuit conductor 4. Intermediate metal layer on wiring conductor 2
When the circuit conductor 4 is attached with the
Part of the copper does not diffuse into the intermediate metal layer 3 and does not directly contact the wiring conductor 2, so that the adhesion between the wiring conductor 2 and the circuit conductor 4 is made more complete and the electrical continuity between them is extremely high. It can be good.

If the content of cobalt contained in the 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 reduced. Diffuses inside the intermediate metal layer 3 and directly contacts the wiring conductor 2, deteriorating the adhesion between the wiring conductor 2 and the circuit conductor 4, and if the content exceeds 10.0% by weight, the intermediate metal layer 3 When it becomes hard and brittle, and a thermal stress such as a temperature cycle is applied, a crack is generated, and electrical conduction between the wiring conductor 2 and the circuit conductor 4 is deteriorated. Therefore, the content of cobalt contained in the nickel constituting the intermediate metal layer 3 is specified in the range of 0.01 to 10.0% by weight.

Further, the phosphorus contained in the nickel constituting the intermediate metal layer 3 is a material that suppresses the formation of an oxide film on the surface of the intermediate metal layer 3, and the intermediate metal layer 3 is formed on the wiring conductor 2. Even if the circuit conductor 4 is adhered between them, an 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 does not deteriorate at all. The adhesion between the circuit conductor 2 and the circuit conductor 4 can be made more perfect, and the electrical continuity between the two can be made very good.

If the content of phosphorus contained in the 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 reduced. When the content exceeds 20.0% by weight, the intermediate metal layer 3 may be weakened, and the adhesion between the intermediate metal layer 3 and the circuit conductor 4 may be deteriorated, thereby deteriorating the adhesion between the wiring conductor 2 and the circuit conductor 4. When it becomes hard and brittle, and a thermal stress such as a temperature cycle is applied, a crack is generated, and electrical conduction between the wiring conductor 2 and the circuit conductor 4 is deteriorated. Therefore, the content of phosphorus contained in nickel constituting the intermediate metal layer 3 is specified in the range of 0.01 to 20.0% by weight.

Further, the intermediate metal layer 3 has a thickness of 0.1 mm.
If the thickness 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 through the intermediate metal layer 3 and directly contacts the wiring conductor 2 to form a wiring conductor. Two
And the circuit conductor 4 tends to deteriorate.
If the thickness exceeds 0.0 μm, a crack occurs due to internal stress in the intermediate metal layer 3, and a part of the circuit conductor 4 directly contacts the wiring conductor 2 via 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 tends to deteriorate.

The intermediate metal layer 3 attached to 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 base 1, and the circuit conductor 4 has electrode terminals of active components such as semiconductor elements and passive components such as resistors and capacitors. Is connected.

The circuit conductor 4 is made by adding a glass powder, an organic solvent, and a solvent to copper powder and mixing them to form a metal paste.
The metal paste is applied on the outer surface of the insulating substrate 1 by printing so that a part of the metal paste comes into contact with the intermediate metal layer 3 adhered to the wiring conductor 2, and then the resultant is put in a neutral atmosphere at about 800 ° C.
By baking at the above temperature, the insulating substrate 1 is adhered to the outer surface.

In this case, it is difficult for the circuit conductor 4 to spread on the outer surface of the wiring conductor 2, so that the circuit conductor 4 is wettable (reactive) with the circuit conductor 4.
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 them.

Since the circuit conductor 4 has a function of suppressing oxidation of phosphorus contained in the circuit conductor 4, even if a large amount of oxygen is contained in the firing atmosphere, an oxide film is hardly formed on the surface. As a result, a semiconductor element, a resistor, and the like can be firmly joined to the circuit conductor 4 via solder.

Further, the glass contained in the circuit conductor 4 is as follows:
For example _{PbO, B 2 O 3, SiO} 2, Al 2 O 3, Na 2 O, K
₂ O, CaO, ZnO, etc., the amount of addition is 0.2% by weight
If the amount is less than 10%, it tends to be difficult to firmly attach the circuit conductor 4 to the insulating base 1. If the amount exceeds 8.0% by weight, the solder wettability (reactivity) of the circuit conductor 4 deteriorates, and the circuit conductor 4 deteriorates. 4) It tends to be difficult to firmly join semiconductor elements, resistors, etc. via solder. Therefore, it is preferable that the amount of glass added to the circuit conductor 4 be in the range of 0.2 to 8.0% by weight.

Thus, the circuit board has a semiconductor element, a resistor, a capacitor, and the like mounted on the surface thereof, and the semiconductor element and the like are joined to circuit conductors via solder to form a hybrid integrated circuit device.

The present invention is not limited to the above-described embodiment, and various modifications are possible without departing from the scope of the present invention.
If a coating layer made of (Au) is applied to a thickness of 0.1 to 5.0 μm, oxidation corrosion of the circuit conductor 4 is effectively prevented, and the electrode terminals of semiconductor elements, resistors, capacitors, etc. are more firmly connected to the circuit conductor 4. Can be joined.

The outer surface of the circuit conductor 4 has 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 is applied to the circuit conductor 4 so that electrode terminals of a semiconductor element, a capacitor or the like can be formed. When soldering is performed via solder, the wettability between the circuit conductor 4 and the solder is 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 the following experimental examples.

EXPERIMENTAL EXAMPLE 1 First, a metal paste composed of tungsten powder was printed on the upper surface of a ceramic green sheet mainly composed of alumina (Al ₂ O ₃ ), and a pair of patterns having a width of 1.0 mm and a length of 10.0 mm was formed. The distance between the tips was 5.0 mm and 20 pairs were adhered. Thereafter, this was fired at a temperature of about 1500 ° C. in a reducing atmosphere,
A wiring conductor is formed on an insulating substrate made of an alumina sintered body. Next, 99.4% by weight of nickel, 0.5% by weight of tungsten, 0.05% by weight of cobalt,
Plating an intermediate metal layer consisting of 0.05% by weight of phosphorus
and a copper (Cu) paste is printed to a thickness of about 30 μm between the pair of wiring conductors and fired at a temperature of about 800 ° C. in a neutral atmosphere to form circuit conductors. The copper paste was brought into contact with the wiring conductor such that the copper paste was in contact with the tip 1.0 mm of the wiring conductor. Finally, the initial electrical resistance between the pair of wiring conductors and the electrical resistance after 100 cycles of a temperature cycle test at −65 to + 150 ° C. are measured, and the rate of change (increase rate) is measured.
And the average value was calculated, and the magnitude of the average increase rate was evaluated for the electrical continuity between the wiring conductor and the circuit conductor. As a result, the average increase rate was as small as 1.4%, indicating that the electrical conduction between the wiring conductor and the circuit conductor was extremely good.

EXPERIMENTAL EXAMPLE 2 The intermediate metal layer of Experimental Example 1 was composed of 70.0% by weight of nickel, 15.0% by weight of tungsten, 5.0% by weight of cobalt and 10.0% by weight of phosphorus.
The thickness was set to 3 μm, and the average increase rate of the electric resistance between the wiring conductors was measured in the same manner as in Experimental Example 1. As a result, the average increase rate was as small as 1.3%, indicating that the electrical conduction between the wiring conductor and the circuit conductor was extremely good.

EXPERIMENTAL EXAMPLE 3 The intermediate metal layer of Experimental Example 1 was composed of 52.0% by weight of nickel, 25.0% by weight of tungsten, 8.0% by weight of cobalt and 15.0% by weight of phosphorus.
The thickness was set to 3 μm, and the average increase rate of the electric resistance between the wiring conductors was measured in the same manner as in Experimental Example 1. As a result, the average rate of increase was as small as 1.2%, indicating that the electrical conduction between the wiring conductor and the circuit conductor was extremely good.

[0036] The intermediate metal layer of Comparative Example Experimental Example 1 and 3μm thick while forming with pure nickel were measured an average increase rate of the electrical resistance between the wiring conductors by the same method as Experimental Example 1. as a result,
The average increase rate is as large as 10.0%, which indicates that the electrical conduction between the wiring conductor and the circuit conductor is poor.

[0037]

According to the circuit board of the present invention, 0.1 to 30.0% by weight of tungsten and 0.01 to 10.0% by weight of cobalt and 0.01 to 2% by weight of nickel are provided between the wiring conductor and the circuit conductor.
Since the intermediate metal layer containing 0.0% by weight of phosphorus is interposed, the wiring conductor and the circuit conductor have good electrical continuity between them, and can be adhered with good adhesion. It is extremely useful as a circuit board to be used.

[Brief description of the drawings]

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Insulating base 2 ... Wiring conductor 3 ... Intermediate metal layer 4 ... Circuit conductor

Continuation of the front page (56) References JP-A-59-117189 (JP, A) JP-A-61-236192 (JP, A) JP-A-63-144554 (JP, A) JP-A-1-209783 (JP) , A) JP-B 63-42879 (JP, B2) (58) Fields investigated (Int. Cl. ⁶ , DB name) H05K 1 / 09,3 / 10-3/26 H05K 3 / 38,3 / 46

Claims (1)

(57) [Claims] 1. A circuit conductor made of copper is adhered to an outer surface of an insulating substrate provided with a wiring conductor made of at least one of tungsten, molybdenum, and manganese so that a part of the circuit conductor comes into contact with the wiring conductor. In the circuit board, the contact portion between the wiring conductor and the circuit conductor has a thickness of 0.1 to
A circuit board comprising an intermediate metal layer containing 30.0% by weight of tungsten, 0.01 to 10.0% by weight of cobalt, and 0.01 to 20.0% by weight of phosphorus.