JPH03217069A - Manufacture of wiring board - Google Patents

Abstract

PURPOSE:To enable reaction between a copper or a steel alloy and a polyimide to be controlled since the film does not become thick as compared with a case where other materials such as titanium are included and electrical resistance of wiring does not become large regarding interlayer connection by forming a polyimide resin after forming a metal hydroxide coating on the surface of the copper or the copper alloy. CONSTITUTION:In a method for producing a wiring board where a copper or a copper alloy is an electric conductor and a polyimide resin is an electric insulator, a metal hydroxide coating 4 is formed on the surface of the copper or the copper alloy 2 and then a polyimide resin 3 is formed. For example, after forming a copper conductor wire 2 on a ceramic substrate 1, the copper hydroxide coating 3 is formed on the surface of the copper conductor wire 2. As a method for forming the copper hydroxide, for example, after treatment within chlorine gas at 100 deg.C for 10 minutes, dipping is made within a 10% aqueous sodium hydroxide for 10 seconds or heat treatment is performed within an oxygen with a relative humidity of 60% at 250 deg.C. After that, a polyimide precursor film 3 is formed on the wiring board and a pattern is formed as needed. Further, the polyimide precursor is converted into polyimide resin by heat treatment.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method of manufacturing a wiring board having copper or copper alloy wiring and a polyimide resin insulating layer.

[Conventional technology] In recent years, there has been an increasing demand for higher density, smaller size, and faster speed for electronic devices. Therefore, wiring boards are also required to have high-density wiring and high-speed signal transmission capability. To meet these demands, low-resistance copper or copper alloys are used as electrical conductors, and high-density patterning is used as insulating materials. is possible,
Polyimide resins are attracting attention because of their high heat resistance and low dielectric constant.

Conventional wiring boards, for example, "IEICE Journal of Electronics, Information and Communication Engineers CJ
Vol1. J71-C, No. 11 (November 1988), PP1510-1515, the wiring board shown in No. 6
This is the structure shown in the cross-sectional view of the figure. In the figure, (1) is the substrate, (
2) is an electrical conductor made of copper, and (3) is a polyimide resin insulator.

In forming a polyimide resin as an insulating layer, a commonly used method is to apply a polyimide precursor soluble in a solvent onto a substrate, and then convert the polyimide precursor into a polyimide resin by heat treatment. However, copper and the polyimide precursor tend to chemically react during this heat treatment process, and the polyimide resin near the copper/polyimide interface changes in quality, making it impossible to obtain the electrical insulation and heat resistance properties inherent to the polyimide resin. There was a problem that it peeled off at the interface and did not function as a wiring board. The reaction is
This is thought to be caused by decomposition of the imide ring of polyimide.

Conventionally, in order to solve such problems, for example, F.
．． S. Ohuchi et al.'s rJ. Vac. Sci. Tec
hnol. J^, Vol. 6, No3, Aay/Ju
No. 1988, pp. 1004-1006, a wiring board is proposed in which another material such as titanium (8) is inserted between copper and polyimide resin to suppress the diffusion of copper into the polyimide. FIG. 7 is a sectional view of a wiring board in which another material (8) is inserted between such copper (2) and polyimide resin (3).

However, when other materials such as titanium are used as described above, a local electric field is generated due to contact between dissimilar metals, which tends to cause corrosion, resulting in a problem of reduced long-term reliability.

[Problem to be solved by the invention] Furthermore, copper or copper alloy and polyimide are physically separated from each other.
- Since other materials such as titanium are interposed for separation, the film thickness of the other materials such as titanium becomes thicker, and other materials such as titanium have higher resistivity than copper or copper alloys. For example, regarding interlayer connections, there was a problem in that the electrical resistance value of the wiring became high.

As a means to solve the above-mentioned problems, the present inventors have developed a method for manufacturing a wiring board in which the surface of copper or copper alloy is modified to suppress electron transfer between copper and a polyimide precursor. was discovered and filed a patent application on August 29, 1989.
The application was filed as Specification No. 2221. Furthermore, on January 10, 1990, Case No.
The application was filed as Specification No. E097. The present invention was made in order to solve the above problem by another means, and the film thickness is not thicker than when other materials such as titanium are used, and the electrical resistance of the wiring is high for, for example, a connection between the eyebrows. It is an object of the present invention to provide a method for manufacturing a wiring board that suppresses the reaction between copper or copper alloy and polyimide.

[Means for Solving the Problems] In the method for manufacturing a wiring board of the present invention, a metal hydroxide film is formed on the surface of copper or a copper alloy, and then a polyimide resin is formed.

Another invention of this invention is to form a polyimide resin after immersing copper or a copper alloy in an electrolytic solution and applying an electric field to a counter electrode to form a modified film on the surface of the copper or copper alloy. It was designed to do so.

[Effects] Since the polyimide resin is formed after forming a metal hydroxide film on the surface of copper or copper alloy, the metal hydroxide film is formed by chemical bonding between the copper or copper alloy and the polyimide precursor. suppress reactions. The metal hydroxide film only needs to have a chemical effect on the surface of the copper or copper alloy, and the metal hydroxide only needs to be in a rich state on the surface of the copper or copper alloy. The thickness is almost negligible. Therefore, the electrical resistance value of the wiring does not become high.

In another invention, copper or a copper alloy is immersed in an electrolytic solution and an electric field is applied to a counter electrode to form a modified film on the surface of the copper or copper alloy, and then a polyimide resin is formed. As such, the modified coating suppresses the chemical reaction between the copper or copper alloy and the polyimide precursor. The thickness of the modified film is
Since it is almost negligible, the electrical resistance of the wiring does not increase.

[Embodiments] Hereinafter, embodiments of the present invention will be described with reference to the drawings. 1 and 2 are cross-sectional views showing the manufacturing method of a wiring board according to an embodiment of the present invention in the order of steps. In the figures, (1) is a substrate, in this case a ceramic substrate, and (2) is a copper conductor. Wiring, (3) is a polyimide precursor film formed on copper conductor wiring (2), (
4) is a film made of metal hydroxide formed on the surface of the copper conductor wiring (2), in this case a copper hydroxide film.

As shown in FIG. 1, after forming a copper conductor wiring (2) on a ceramic substrate (1), a copper hydroxide film (3) is formed on the surface of the copper conductor wiring (2). As a method for forming copper hydroxide, for example, the material is treated in chlorine gas at 100° C. for 10 minutes, and then immersed in a 10% aqueous sodium hydroxide solution for 10 seconds. Alternatively, heat treatment is performed at 250° C. in oxygen at a relative humidity of 60%. Thereafter, as shown in FIG. 2, a polyimide precursor film (3) is formed on the wiring board, and patterned if necessary.

Furthermore, the polyimide precursor is converted into polyimide resin by heat treatment.

In this case, the copper hydroxide film formed on the surface of the copper conductor wiring (2) has the effect of suppressing the chemical reaction between the silk and the polyimide precursor, so the polyimide near the copper/polyimide interface is altered. The electrical insulation properties and heat resistance inherent to polyimide resin can be obtained without any heat generation.

Although the mechanism for suppressing the reaction between copper and polyimide is currently unknown, the present invention discloses this for the first time as an effect of the hydroxide. In the example using a copper hydroxide film, unlike the conventional example, different metals are not interposed, and the wiring conductor is made of copper alone, so that the battery effect that occurs locally between different metals is Corrosion of wiring conductors and deterioration of reliability can be prevented, and a highly reliable wiring board can be obtained.

-7 - As for the effect of the thickness of the film made of metal hydroxide, no significant effect can be obtained if the thickness is less than 25 mm.

Preferably, significant effects can be obtained in 50 or more people.

In the above example, only a coating made of copper hydroxide was described, but although copper is a different metal, coatings made of other metal hydroxides such as nickel, aluminum, iron, titanium, etc. can also be used with copper or copper alloy and polyimide. It can be applied because it has the effect of suppressing the reaction of Further, in the above embodiments, the above two methods are shown as methods for forming copper hydroxide, but other methods may be used.

FIGS. 3, 4, and 5 are new views showing the manufacturing method of a wiring board according to another embodiment of the present invention in the order of steps. In the figures, (1) is a substrate, in this case a ceramic substrate. , (2) is a copper conductor wiring, (3) is a polyimide precursor film formed on the copper conductor wiring (2), and (4) is a film formed on the surface of the copper conductor wiring (2) according to another invention of the present invention. This is a surface-modified coating. (5) is an electrolytic solution, in this case 2% copper sulfate (Cu
(6) is the counter electrode, in this case platinum (pt), which is a metal that has a negative effect on the copper conductor (2), (7) is the power source, and the copper conductor (2) is 2) is a DC power source with the positive electrode.

As shown in FIG. 3, after forming the copper conductor wiring (2) on the ceramic substrate (1), as shown in FIG. to the positive electrode and the opposite electrode (6
) is used as a negative electrode and a power source (7) is used to apply an electric field.

The voltage is 1 V, preferably 3 V, more preferably IOV or more, and the application time is 1 minute, preferably 3 minutes.
More preferably, 15 minutes or more is appropriate. This treatment modifies the surface of the copper to a light reddish-brown color. At present, the detailed structure of this surface-modified part has not been determined accurately, but like the first invention of the present invention, the copper of this invention has the effect of suppressing the reaction between copper and polyimide. The upper surface modified coating (4) is expected to contain copper hydroxide. Thereafter, as shown in FIG. 5, a polyimide precursor film (3) is formed on the wiring board and patterned as necessary. Furthermore, the polyimide precursor is converted into polyimide resin by heat treatment, and in this case, the surface modification film (4) formed on the surface of the copper conductor wiring (2) suppresses the chemical reaction between the copper and the polyimide precursor. Because of this effect, the polyimide near the copper/polyimide interface does not change in quality, and the electrical insulation and heat resistance inherent to polyimide can be obtained.

In the case of this example, unlike the conventional example, different metals are not interposed, and the wiring conductor is made of copper alone, so corrosion of the wiring and wire conductor due to the battery effect that occurs locally between different metals. Therefore, a highly reliable wiring board can be obtained. In this embodiment, a sulfuric acid steel aqueous solution is used as the electrolyte, but other electrolytes such as sodium hydroxide (NaOH) may be used.

Further, although a DC power source is used as the power source, other power sources such as an AC power source or a pulse power source may be used.

In these two inventions, only the treatment of copper conductor wiring on a ceramic substrate has been described, but the present invention is not limited to this and can be applied to copper conductor wiring on any substrate.

Furthermore, by sequentially repeating the formation of copper conductor wiring, the treatment of the copper conductor wiring according to the present invention, the formation of a polyimide precursor, and the heat treatment of the polyimide precursor, it is possible to manufacture a multilayer wiring board consisting of copper conductor wiring and a polyimide resin insulator. can.

Note that as a method for forming the copper conductor wiring, any conventionally known method such as vapor deposition, sputtering, plating, etc. may be used.

Furthermore, after forming a copper film on the substrate and processing according to the present invention,
The wiring may be formed by subjecting the copper film to an etching process or the like. Furthermore, the process according to the present invention may be performed after the wiring is formed.

[Effects of the Invention] As explained above, in the method for manufacturing a wiring board of the present invention, after forming a metal hydroxide film on the surface of copper or copper alloy,
Since a polyimide resin is formed, the metal hydroxide film suppresses the chemical reaction between the copper or copper alloy and the polyimide precursor, and the polyimide near the copper or copper alloy/polyimide interface does not deteriorate. , the electrical insulation and heat resistance inherent to polyimide resin can be obtained. In conventional methods in which titanium or the like is interposed to physically separate copper or copper alloy from polyimide, the titanium or the like inevitably becomes thick due to the physical separation. However, the metal hydroxide film of the present invention only needs to have a chemical action on the surface of the copper or copper alloy, and only needs to be rich in metal hydroxide on the surface of the copper or copper alloy. The thickness of the material film is almost negligible, and when using this film, for example, for interlayer connections, it is possible to prevent the electrical resistance value of the wiring on the wiring board from increasing.

Another method of manufacturing a wiring board according to the invention is to immerse copper or a copper alloy in an electrolytic solution, apply an electric field to a counter electrode, form a modified film on the surface of the copper or copper alloy, and then immerse the copper or copper alloy in an electrolytic solution. Since a resin is formed, the modified coating suppresses the chemical reaction between the copper or copper alloy and the polyimide precursor. Furthermore, since the thickness of the modified film can be almost ignored, it is possible to prevent the electrical resistance value of the wiring from increasing.

[Brief explanation of drawings]

FIGS. 1 and 2 are cross-sectional views showing an embodiment of the wiring board manufacturing method 11-method of the present invention in the order of steps; FIGS. 3 and 4;
FIG. 5 is a sectional view showing an embodiment of another invention in order of steps;
FIG. 6 and FIG. 7 are cross-sectional views showing a conventional wiring board manufacturing method, respectively. In the figure, (1) is a substrate, (2) is a copper conductor wiring, (3) is a polyimide precursor film, and (4) is a copper hydroxide film or a surface modified film. In addition, in the figures, the same reference numerals indicate the same or equivalent parts.

Claims (2)

[Claims] (1) In a method for manufacturing wiring boards in which copper or copper alloy is used as an electrical conductor and polyimide resin is used as electrical insulator, a metal hydroxide film is formed on the surface of copper or copper alloy, and then polyimide resin is formed. A method for manufacturing a wiring board, characterized in that: (2) In a method for manufacturing wiring boards using copper or copper alloy as an electrical conductor and polyimide resin as an electrical insulator, copper or copper alloy is immersed in an electrolytic solution and an electric field is applied to a counter electrode. Alternatively, a method for manufacturing a wiring board, characterized in that a modified film is formed on the surface of a copper alloy, and then a polyimide resin is formed.