JPH05315727A - Method of treating circuit conductor - Google Patents

Abstract

PURPOSE:To provide a method of treating a circuit conductor prevented from lowering of soldering strength by removing hydrogen in a conductor layer formed by electroless plating. CONSTITUTION:This treatment method includes a process forming a conductor layer (copper layer 14) constituting a prescribed circuit by an electroless plating on the surface of a circuit board 2 and a process of heating (heating source 16) the conductor layer formed on the surface of the circuit board.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating a circuit conductor formed on a surface of a circuit board by electroless plating.

[0002]

2. Description of the Related Art Conventionally, in a hybrid integrated circuit device, a desired circuit pattern is printed with a plating resist on the surface of a circuit board formed of an insulating material such as alumina or ceramic, and then immersed in a plating solution to form a conductor. A method of forming the layer by an electroless plating process has been adopted. For example, a copper layer is used as the conductor layer. The conductor layer formed by such electroless plating, that is, the copper layer constitutes a stable circuit conductor and is widely used because it is suitable for soldering.

[0003]

By the way, as shown in FIG. 2, when the solder layer 6 is formed by the soldering process on the copper layer 4 formed on the circuit board 2 by the electroless plating process, It is pointed out that there is a problem in the mechanical strength of the solder layer 6 and the copper layer 4. That is, since the solder layer 6 formed on the surface of the copper layer 4 contains tin as its component, this tin and copper forming the copper layer are combined, and as a result of this combination, tin-copper is formed. It is known that intermetallic compound 8 is formed and this tin-copper intermetallic compound 8 becomes brittle. This reduces the bonding strength between the solder layer and the copper layer, and is the reason why the required mechanical strength cannot be maintained.

The embrittlement of the tin-copper compound is due to hydrogen contained in the copper layer due to electroless plating and crystal defects in the copper layer.

Therefore, it is an object of the present invention to provide a method for treating a circuit conductor which prevents a decrease in soldering strength by removing hydrogen in a conductor layer formed by electroless plating.

[0006]

Therefore, according to the method for treating a conductor layer of the present invention, a conductor layer (copper layer 14) forming a predetermined circuit pattern (12) on the surface of a circuit board (2) by electroless plating treatment. And a step of heating (heating source 16) the conductor layer formed on the surface of the circuit board.

[0007]

[Function] When the conductor layer is formed by electroless plating and then the conductor layer is heated together with the circuit board, hydrogen in the conductor layer is diffused by the heat treatment and the crystal defects in the conductor layer are complemented by recrystallization. It As a result, the conductor layer is processed into a circuit conductor resistant to soldering.

[0008]

The present invention will be described in detail below with reference to the embodiments shown in the drawings.

FIG. 1 shows an embodiment of the method for treating a circuit conductor of the present invention. As shown in FIG. 1A, the circuit board 2 is formed of an insulating material such as alumina or ceramics, and a predetermined circuit pattern 12 is printed on the surface thereof by the plating resist layer 10. The surface of the circuit board 2 is exposed at the portion of the circuit pattern 12, and this exposed surface is the plated surface.

Next, this circuit board 2 is immersed in a plating solution to expose the circuit board 2 from the plating resist layer 10.
A copper layer 14 as a conductor layer is formed on the surface of the above by electroless plating. That is, the circuit pattern 12 is formed by this copper layer 14.

Next, as shown in FIG. 1B, when the plating resist layer 10 is removed, only the copper layer 14 remains on the surface of the circuit board 2, and the circuit pattern 12 is constituted by this copper layer 14. Will be done.

Next, as shown in FIG. 1C, the circuit board 2 and the copper layer 14 are heated by a heating source 16. By this heat treatment, the hydrogen contained in the copper layer 14 is vaporized and removed, and at the same time, the recrystallization treatment is also progressed.
The crystal defects therein are complemented by recrystallization. in this case,
Alternatively, only the copper layer 14 may be selectively heated.

According to such a processing method, the circuit board 2
The crystal defects can be complemented with the removal of hydrogen in the conductor layer formed by electroless plating on the surface of the, and even when soldering, the compound with tin contained in the solder does not become brittle, and the mechanical bond strength It is possible to surely prevent the deterioration, and it is possible to enhance the reliability of the electrical connection by soldering.

In the examples, the copper layer was used as an example of the conductor layer for explanation. However, the present invention is applied to the case where a copper compound or the like is used as the conductor layer and the soldering strength of various conductor layers is improved. It is not limited to the copper layer as it can be improved.

[0015]

As described above, according to the present invention,
Since hydrogen in the conductor layer can be removed by the heat treatment and crystal defects in the conductor layer can be complemented by recrystallization, the soldering strength can be increased and a highly reliable circuit conductor can be provided.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an embodiment of a method for treating a circuit conductor of the present invention.

FIG. 2 is a cross-sectional view showing the formation of a tin-copper compound formed of a copper layer and a solder layer formed as a conventional circuit conductor.

[Explanation of symbols]

 2 circuit board 12 circuit pattern 14 copper layer (conductor layer) 16 heating source

Claims (1)

[Claims] 1. A step of forming a conductor layer forming a predetermined circuit pattern on the surface of the circuit board by electroless plating, and a step of heating the conductor layer formed on the surface of the circuit board. A characteristic circuit conductor processing method.