JP2703426B2 - 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 parts such as semiconductor elements and passive parts such as resistors and capacitors and forms a predetermined electronic circuit is usually made of alumina ceramics or the like. Made of electrically insulating material,
Inside tungsten (W), molybdenum (Mo), manganese (M
n) A circuit board having a structure in which a circuit conductor made of copper (Cu) is attached to an outer surface of an insulating base in which a wiring conductor made of a high melting point metal such as a metal is embedded so that a part of the circuit conductor is connected to the wiring conductor. Prepared, and then formed by mounting a semiconductor element, a capacitor, a resistor, etc. on the surface of the circuit board and joining each electrode terminal to a circuit conductor via solder (Sn-Pb alloy) or the like. I have.

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.

[0007]

However, recently,
Semiconductor elements are rapidly increasing in density and integration, and the amount of heat generated per unit area and unit volume is increasing rapidly.The thermal conductivity of alumina ceramics that constitute the insulating base is about 20 W / mK. When a semiconductor device is mounted on a circuit board for operation because of its low temperature, the heat generated by the semiconductor device is not transmitted and absorbed well to the outside and accumulates in the semiconductor device itself, resulting in a high temperature of the semiconductor device. Therefore, there is a disadvantage that the semiconductor element is thermally destructed or a characteristic is changed by heat to cause a malfunction.

In addition, the conventional circuit board has poor wettability (reactivity) between tungsten, molybdenum, manganese or the like forming the wiring conductor and copper forming the circuit conductor, so that a part of the wiring conductor is covered with the circuit conductor. Even when they are attached, they do not adhere firmly, and as a result, there is also a drawback that the electrical conduction between the wiring conductor and the circuit conductor is extremely poor.

[0009]

According to the present invention, a circuit conductor made of copper is formed on an outer surface of an insulating substrate provided with a wiring conductor made of at least one of tungsten and molybdenum. A circuit board having a portion contacted with the wiring conductor, the insulating base having an oxide film on at least a surface on which the wiring conductor is to be adhered, An intermediate metal layer made of an alloy of at least one of nickel and cobalt and at least one of tungsten and molybdenum is interposed in the contact portion.

[0010]

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.

The insulating substrate 1 is made of an aluminum nitride sintered body. Aluminum nitride powder (AlN) is mixed with yttrium oxide (Y ₂ O ₃ ) and calcia (CaO) as a sintering aid.
Powder and an appropriate organic solvent, and a solvent are added and mixed to form a slurry, and a doctor blade method is used to form a ceramic green sheet (ceramic green sheet). It is manufactured by performing appropriate drilling and stacking a plurality of sheets, and firing at a temperature of about 1800 ° C. in a reducing atmosphere.

The aluminum nitride sintered body constituting the insulating base 1 has a high thermal conductivity of 80.0 W / m · K or more,
Even if a semiconductor element that generates a large amount of heat is mounted on the insulating base 1 because it easily conducts heat, the heat generated by the semiconductor element is well absorbed by the insulating base 1, and as a result, the semiconductor element always breaks down at a low temperature and is thermally destroyed. Or a thermal change in the characteristics, and a malfunction does not occur.

The insulating substrate 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 and molybdenum.

The wiring conductor 2 is prepared by adding an organic solvent and a solvent to a 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 nickel on its exposed outer surface at least at a portion where a circuit conductor 4 to be described later is attached.
An intermediate metal layer 3 made of an alloy of at least one of cobalt and at least one of tungsten and molybdenum is formed on the exposed outer surface of the wiring conductor 2 by electrolytic plating, electroless plating, or the like. And a thick film method known in the art. The intermediate metal layer 3 is composed of at least one of the constituent metals, that is, at least one of nickel and cobalt and at least one of tungsten and molybdenum.
The alloy with the seed wets both the wiring conductor 2 and the circuit conductor 4 (
When the circuit conductor 4 is adhered on the wiring conductor 2, the two are completely adhered to each other, and the electrical conduction between them is extremely excellent.

The metal constituting the intermediate metal layer 3 is copper.
(Cu)
Even when the circuit conductor 4 is attached with the intermediate metal layer 3 interposed therebetween, part of the copper of the circuit conductor 4 does not directly contact the wiring conductor 2 at all, and this also allows The adhesion to the conductor 4 can be made more complete, and the electrical continuity between the two can be made extremely good.

When the total weight of at least one of tungsten and molybdenum is less than 2.0% with respect to the total weight of at least one of nickel and cobalt 100, the effect of suppressing the diffusion of copper is reduced. 4 is partially diffused in the intermediate metal layer 3
Directly, the adhesiveness between the wiring conductor 2 and the circuit conductor 4 tends to be deteriorated, and if it exceeds 50.0%, the wettability (reactivity) between the intermediate metal layer 3 and the circuit conductor 4 deteriorates. Since the circuit conductor 4 tends to be unable to adhere to the wiring conductor 2 with good adhesion, the total weight of at least one of tungsten and molybdenum is the total weight of at least one of nickel and cobalt. It is preferable to set the range of 2.0 to 50.0% with respect to 100.

The intermediate metal layer 3 contains boron in an amount of 0.1 to
When 5.0% by weight or 2.0 to 15.0% by weight of phosphorus is contained, the formation of an oxide film on the surface of the intermediate metal layer 3 is suppressed, and the adhesion between the intermediate metal layer 3 and the circuit conductor 4 is improved. I can do it. Therefore, the intermediate metal layer 3 has 0.
It is preferable to contain 1 to 5.0% by weight of boron or 2.0 to 15.0% by weight of phosphorus.

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.

Also, at least a circuit conductor of the insulating base 1
An oxide film 5 is formed on the surface on which
The oxide film 5 makes the adhesion strength between the circuit conductor 4 and the insulating substrate 1 strong, whereby the circuit conductor 4 adheres very firmly to the surface of the insulating substrate 1.

The oxide film 5 is formed by sintering the insulating substrate 1 in the air at a temperature of 1000 to 1200 ° C. to convert aluminum nitride to aluminum oxide (Al ₂ O ₃ ). If it is less than μm, the adhesion strength of the circuit conductor 4 to the insulating substrate 1 tends to be weak, and if it exceeds 3.0 μm, the bonding strength between the oxide film 5 and the insulating substrate 1 tends to decrease. Therefore, the thickness of the oxide film 5 is in the range of 0.5 to 3.0 μm, more preferably 0.8 to 3.0 μm.
It is preferable to set the range to 2.0 μm.

The circuit conductor 4 is made of copper powder, for example,
_{PbO, B 2 O 3, SiO} 2, Al 2 O 3, Na 2 O, K 2 O,
A glass paste made of CaO, ZnO, or the like, an organic solvent, and a solvent are added and mixed to form a metal paste, and the metal paste is brought into contact with the intermediate metal layer 3 that is partially adhered to the wiring conductor 2. The outer surface of the insulating substrate 1 is applied by printing, and then fired in a neutral atmosphere at a temperature of about 800 ° C. to adhere to the outer surface of the insulating substrate 1. In this case, the circuit conductor 4 hardly spreads on the outer surface of the wiring conductor 2,
Since the intermediate metal layer 3 having good wettability (reactivity) is interposed between the circuit conductor 4 and the circuit conductor 4, the circuit conductor 4 can be adhered to the wiring conductor 2 with good adhesion and good electrical continuity between them.

Further, if the amount of glass contained in the circuit conductor 4 is less than 0.2% by weight, it becomes difficult to firmly adhere the circuit conductor 4 to the insulating base 1, and 8.0% by weight. When the temperature exceeds the limit, the solder wettability (reactivity) of the circuit conductor 4 deteriorates, and it becomes difficult to firmly join a semiconductor element or a resistor to the circuit conductor 4 via solder. It is preferable that the amount of glass to be added is in the range of 0.2 to 8.0% by weight.

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

It should be noted that 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.
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.

[0028]

According to the circuit board of the present invention, since the insulating substrate is formed of an aluminum nitride sintered body having a high thermal conductivity, even when a semiconductor element having a large amount of heat is mounted, the heat generated by the semiconductor element can be reduced. As a result, the semiconductor substrate is not absorbed by the insulating substrate, and as a result, the semiconductor element is not always thermally degraded at a low temperature, or a characteristic does not change and a malfunction does not occur.

Further, since an intermediate metal layer made of at least one kind of nickel and cobalt and at least one kind of alloy of tungsten and molybdenum is disposed at a contact portion between the wiring conductor and the circuit conductor, the wiring conductor and the circuit conductor are separated from each other. Can be adhered with good adhesion and good electrical conduction.

Further, since an oxide film is formed on at least a portion of the insulating base on which the circuit conductor is to be attached, the circuit conductor can be very firmly attached to the insulating base.

[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 5 ... Oxide film

Claims (3)

(57) [Claims] 1. A circuit conductor made of copper is formed on an outer surface of an insulating substrate provided with a wiring conductor made of an aluminum nitride sintered body and made of at least one of tungsten and molybdenum. Wherein the insulating substrate has an oxide film on at least a surface on which the wiring conductor is to be deposited, and nickel, cobalt, or the like is provided at a contact portion between the wiring conductor and the circuit conductor. And an intermediate metal layer made of an alloy of at least one of tungsten and molybdenum. 2. The intermediate metal layer according to claim 1, wherein the total weight of at least one of tungsten and molybdenum is 2.0 to 50.0% based on 100 of the total weight of at least one of nickel and cobalt.
The circuit board according to claim 1, wherein 3. The intermediate metal layer has a thickness of 0.1 to 10.0 μm.
The circuit board according to claim 1, wherein