JPH04168787A - Manufacture of ceramic circuit board - Google Patents

Abstract

PURPOSE:To remove copper residue of a ceramic board while holding the width of a conductive circuit by removing the residue remaining in the recess of the board in an etchant by supersonic cleaning after etching. CONSTITUTION:After etching, copper residue 6 in a recess 6 of a board 1 is removed by supersonic cleaning while dipping it in etchant. As the etchant, etchant having the same type as that of the etchant used to form a conductive circuit 4 and small capacity is desirably used.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a method for manufacturing a ceramic circuit board.

[Prior Art] A ceramic is made by forming a circuit in a predetermined pattern on the surface of a ceramic substrate, which is an inorganic insulating substrate.

Conventionally, the conventional methods for producing circuit boards include drawing a circuit on a green sheet of alumina ceramics before firing using a conductor paste such as tungsten or molybdenum-manganese, and firing this green sheet in a reducing atmosphere. A conductive paste made by mixing fine metal powder such as /Pd, Ag/Pt, Cu or Au with a glass frit or an organic vehicle is screen printed on a sintered ceramic circuit board, and then the conductive paste is applied to a ceramic circuit board. A method of firing at a temperature for fusion bonding is generally known. However, these methods have in common that it is difficult to form fine conductive circuits, and in particular, the former method is not suitable for forming fine conductive circuits due to the large resistance of the wiring circuit, and the latter method is difficult to form fine conductive circuits. , conductor pace (・
With screen printing, it is difficult to form fine conductive circuits of 100 μm or less, and the paste contains glass, resulting in poor solder adhesion and, as a result, failures during use.

Other methods for forming circuits on ceramic circuit boards include electroless plating, vapor deposition, sputtering, and vapor phase methods such as ion blasting, and these methods are superior in that they do not have the above-mentioned drawbacks. However, the adhesion between the conductor and the ceramic substrate is insufficient. In order to improve this adhesion, it was necessary to roughen the ceramic substrate and then metalize it to physically bond the substrate and the conductor using the so-called anchor effect.

In this way, if a roughened ceramic substrate is used to increase the bonding strength or adhesion between the ceramic substrate and the conductor, when etching is performed to form a circuit,
There is a problem in that copper residue is generated in the concave portions of the surface of the substrate formed by roughening, and this copper residue causes defects such as short circuits and migration of conductive circuits. In order to eliminate such defects, if the etching process is continued until the copper residue is completely removed, there is a problem in that the conductive circuits are eluted and the line width becomes excessively thin.

[Problems to be Solved by the Invention] Therefore, an object of the present invention is to provide a novel method for manufacturing a ceramic circuit board in which copper residue formed on the surface of the board is removed while maintaining the line width of the conductive circuit. shall be.

[Means for Solving the Problems] In order to solve the above-mentioned problems, a method for manufacturing a ceramic circuit board according to the present invention includes forming a conductive metal layer in a predetermined pattern on a ceramic substrate on which a conductive metal layer is formed. In a method for manufacturing a ceramic circuit board in which a circuit is formed by etching after being covered with an etching resist layer, copper residue remaining in the recesses on the surface of the ceramic substrate after the etching is cleaned using ultrasonic waves in an etching solution. It is characterized in that it is removed by

Hereinafter, materials and processes for carrying out the present invention will be sequentially explained with reference to the drawings.

(1) Ceramic substrate A sintered ceramic substrate 1 is prepared. Ceramic substrate materials include alumina, forsterite, steatite, zirconia, mullite, cordierite, zircon,
Although oxide-based ceramic materials such as titania are mainly used, any ceramic material such as carbide-based or nitride-based ceramic materials can be used as the insulating substrate for forming the conductive circuit.

(2) Roughening process If necessary, the surface of the ceramic substrate 1 is roughened.

This roughening can improve the adhesion between the conductive metal layer 2 to be formed in a later step and the surface of the ceramic substrate 1 due to the anchor effect. When the conductive metal layer 2 is formed by the above-mentioned vapor phase method, this roughening treatment is not particularly necessary (although it is okay to do so, when the conductive metal layer 2 is formed by a chemical plating method etc., this roughening treatment is not performed). It is preferable to do so.

Methods for roughening treatment include, for example, immersing the ceramic substrate 1 in a solution of hot phosphoric acid, molten alkali, hydrogen fluoride, etc., or physical roughening methods such as polishing and sandblasting. Other roughening methods can also be employed.

(3) Formation process of conductive metal layer The conductive metal layer 2 is formed on the entire exposed portion of the surface of the ceramic substrate 1. For the conductive metal layer 2, various metal materials used as constituent materials for ordinary conductor circuits are used, and the formation method thereof is selected from among ordinary thin film formation methods such as chemical plating, sputtering, and ion blasting. formed by any method.

In the case of chemical plating, metal palladium is deposited on the surface of the ceramic substrate 1 to activate the surface using a normal sensitizing-activation method. Thereafter, the activated ceramic substrate 1 is immersed in a chemical copper plating bath or the like to form a conductive metal layer 2 such as copper.

The conductive metal layer 2 can also be formed using a vapor phase method such as evaporation, sputtering, or ion blasting, or a CVD method. When using the vapor phase method, a metal layer of Cr or TI is formed in the first step, and a metal layer of copper or the like is formed thereon in the second step, or a rough surface heated to about 400°C is used. The same Cr as described above is applied to the ceramic substrate 1 which has already been cured.
Alternatively, by adopting a method of sequentially forming a metal layer for activating Ti and a conductive metal layer 2 such as copper, the adhesion between the ceramic substrate 1 and the conductive metal layer 2 can be increased.

(4) Step of thickening the conductive metal layer If necessary, the conductive metal layer 2 is thickened with a metal such as copper by electrolytic plating. This process is useful when it is necessary to increase the thickness of the conductive metal layer 2, since the chemical plating or vapor phase method described above can only form a thin metal layer of about 1 to several μm.

(5) Etching resist layer formation process As shown in Figure 1, which is a cross-sectional view of the intermediate product after this process is completed,
In this step, an etching resist layer 3 is formed on the conductive metal layer 2 of the ceramic substrate 1. In order to form the etching resist layer 3 in a predetermined circuit pattern, a photosensitive liquid resist material or a dry film is used as the material, and depending on these materials, the same etching as the circuit backing is performed by screen printing or the like. A resist layer 3 is formed. A normal etching resist layer formation method can be applied.

(6) Formation process of conductor circuit by etching The portions of the conductor metal layer that are unnecessary as the conductor circuit 4 are removed by etching. As the etching solution, there may be mentioned an etching solution such as cupric chloride or ferric chloride.
Other common etching solutions can be used. The etching method is not limited, and not only the spray method but also various other methods can be used.

(7) Copper coin removal process After the etching process, the recesses 5 on the surface of the ceramic substrate 1
The remaining copper coins 6 are removed by ultrasonic cleaning while immersing them in an etching solution. As the etching liquid at this time, the same type of etching liquid as that used in the process of forming the conductive circuit 4 described above is used,
A solution having a lower etching ability than the above-mentioned etching solutions is preferable. This is because if the etching effect occurs excessively, the line width of the conductive circuit 4 becomes thinner. The etching solution is not limited to the above-mentioned solutions, and includes, for example, acidic aqueous solutions such as hydrochloric acid, and etching solutions based on sodium persulfate and hydrogen peroxide.

(8) Etching resist layer removal process The etching resist 3 on the conductive circuit 4 is peeled off and removed. The liquid used for peeling includes alkaline solutions such as NaOH and Na2C03,
Etching resist 3 using other ordinary stripping liquid
Ceramic circuit boards with .

(9) Finishing process Once the etching resist 3 is removed, the ceramic circuit board is completed. If necessary, the surface of the conductive circuit 4 is polished, degreased, and cleaned as a finishing process. The amount of polishing is preferably about 0.1 μm to 10 μm, more preferably 0.1 μm to 10 μm.
．． 2 to 2 μm is preferable. As described above, the polishing method is generally a physical method.

(Function) According to the method for manufacturing a ceramic circuit board according to the present invention, when the copper coins 6 remaining in the recesses 5 on the surface of the ceramic substrate 1, which contribute to the adhesion between the conductive circuit 4 and the ceramic substrate 1, are removed using an etching solution, the recesses are removed. Due to the shaking action of ultrasonic cleaning, the remaining copper coins 6 can be effectively removed even with an etching solution with low etching ability. It is possible to manufacture a ceramic circuit board that is equipped with a conductive circuit 4 having an extremely fine circuit pattern and has a high adhesion between the conductive circuit 4 and the ceramic substrate 1.

[Example] Next, Examples and Comparative Examples of the present invention will be listed below.

(Example 1) 96% by weight of alumina as the sintered ceramic substrate 1
Alumina substrate (4/l'14 //×0.635〃)
The ceramic substrate 1 was immersed in hot phosphoric acid to uniformly roughen the surface of the substrate. This roughening resulted in a maximum surface roughness of 3 to 5 μm. On this surface, 10μ
The presence of four parts 5 on the order of m was observed. After thoroughly cleaning and drying the roughened substrate 1, chemical plating was applied to the entire surface of the substrate 1 to form a copper layer with a thickness of 10 μm to form a conductive metal layer 2.

Next, after polishing the surface of the conductive metal layer 2 formed on the ceramic substrate 1 with a polishing machine, an L-lye film is laminated on the conductive metal layer 2, and a circuit pattern is formed on the conductive metal layer 2 by a photographic method. Formed. Then, unnecessary conductive metal layers were removed by etching using a spray. As a result, a conductive circuit 4 with a line width and a line spacing of 5 μm was obtained. At this point, the intermediate product ceramic circuit board on which the conductive circuit 4 was formed was observed with an optical microscope.
The presence of copper coins 6 deviating from the lines constituting the conductive circuit 4 was observed. The ceramic circuit board on which the copper coin 5 was observed was kept immersed in an etching solution of hydrogen peroxide and subjected to ultrasonic cleaning.

By immersing the etching liquid in this process, the conductive circuit 4
The line width was narrowed by 2 μm. Furthermore, after this, the resist of the dry film was peeled off with a 3% NaOH aqueous solution, and degreased and washed with an acidic organic aqueous solution to obtain a ceramic circuit board.

For the ceramic circuit board obtained in this way,
When the surface of the substrate 1 was observed with an optical microscope, the copper coins 6 in the recesses 5 of the ceramic substrate 1 before ultrasonic cleaning in the etching solution disappeared and were not observed.

(Example 2) Using the same ceramic substrate 1 as that used in Example 1, a 10 μm thick copper layer was formed on both sides of the substrate 1 by sputtering to form a conductive metal layer 2.
After physically polishing the surface of the conductive metal layer 2 using a polishing machine, a circuit pattern for etching was formed by photography using a photosensitive liquid resist. Next, unnecessary conductive metal layers were removed by etching using a spray, and a conductive circuit 4 having a line width of 70 μm between lines was formed on the ceramic substrate.

At this point, when the intermediate product ceramic circuit board on which the conductive circuit 4 was formed was observed with an optical microscope, the presence of copper coins 6 deviating from the lines constituting the conductive circuit 4 was observed. The ceramic circuit board on which the copper coin 6 was observed was immersed in a mixed solution of sodium persulfate (40 g/r) and sulfuric acid (20 g/42), and simultaneously subjected to ultrasonic cleaning. Due to this immersion, the line width of the conductive circuit 4 was reduced by 1 μm. Further, the remaining etching resist 3 was peeled off with a 3% NaOH aqueous solution, and the ceramic circuit board was degreased and washed with an acidic organic aqueous solution. When the surface of the substrate 1 was observed with an optical microscope, the copper coins 6 in the recesses 5 of the ceramic substrate before ultrasonic cleaning in the etching solution disappeared and were not observed.

(Example 3) An alumina substrate (4//X4//X0.635〃) containing 99% alumina by weight was used as the sintered ceramic substrate, and the ceramic substrate 1 was immersed in hydrofluoric acid to make the surface of the substrate 1 uniform. It became rough. This roughening resulted in a maximum surface roughness of 1 to 2 μm. The surface of this roughened ceramic substrate was chemically plated and then electroplated to form a 35 μm thick copper layer to form a conductive metal layer 2.

Next, after polishing the surface of the conductive metal layer 2 formed on the ceramic substrate 1 with a polishing machine, a dry film is laminated onto the conductive metal layer 2, and a circuit is formed on the conductive metal layer 2 by a photographic method. formed a pattern. Then, unnecessary conductive metal layers were removed by etching using a spray. As a result, a conductive circuit 4 with a line width and a line spacing of 5 μm was obtained. At this point, the intermediate product ceramic circuit board on which the conductive circuit 4 was formed was observed with an optical microscope.
The presence of copper bases 6 deviating from the lines constituting the conductive circuit 4 was observed. This ceramic circuit board, on which the copper substrate 6 was observed, was kept immersed in an etching solution of hydrogen peroxide and subjected to ultrasonic cleaning.

By immersing the etching liquid in this process, the conductive circuit 4
The line width was narrowed by 2 μm. Thereafter, the etching resist 3 on the dry film was peeled off with a 3% NaOH aqueous solution, and degreased and washed with an acidic organic aqueous solution to obtain one ceramic circuit.

For the ceramic circuit board obtained in this way,
When the surface of the ceramic base Fji1 was observed using an optical microscope, it was found that the copper base 6 in the recess 5 of the ceramic substrate 1 before ultrasonic cleaning in the etching solution had disappeared and was not observed.

(Example 4) Sintered aluminum nitride substrate (4tt
, 635〃) as the ceramic substrate 1, and the copper layer that will become the conductive metal layer 2 is made 10μ thick by sputtering method.
It was formed into m. The process of polishing the conductive metal layer 2 to the final degreasing and cleaning process were performed under the same conditions as in Example 1.

When an intermediate product ceramic circuit board having a conductive circuit 4 formed by removing unnecessary conductive metal layers through an etching process was observed with an optical microscope, it was found that the copper substrate 6 deviated from the lines constituting the conductive circuit 4. presence was observed. When a ceramic circuit board that had been degreased and cleaned with an acidic organic aqueous solution was similarly observed under an optical microscope, it was found that the copper base 6 in the recess 5 of the ceramic substrate 1 before ultrasonic cleaning in the etching solution was Disappeared and was not observed.

[Effect of the invention],.

According to the method for manufacturing a ceramic circuit board according to the present invention, when removing copper bases remaining in, for example, recesses on the surface of a ceramic substrate with an etching solution, even an etching solution with low etching ability is effective due to the shaking action of ultrasonic cleaning. Therefore, it is possible to manufacture a ceramic circuit board with a conductor circuit having an extremely fine circuit pattern with the same line width and line spacing maintained.

[Brief explanation of drawings]

1 and 2 relate to an embodiment of the present invention, and FIG. 1 shows an etching process consisting of a conductive metal layer formed on the surface of a ceramic substrate and a resist covering this conductive metal layer in accordance with a circuit pattern. FIG. 2 is an enlarged cross-sectional view of the main parts of the previous intermediate product of the ceramic circuit board, and FIG. be. ■・・・・・・・・・ Ceramic substrate 2...
......Conductor metal layer 3...
...Etching resist 4...Conductive circuit 5...Concavity 6...Copper residue

Claims (2)

[Claims] (1) In a method for manufacturing a ceramic circuit board, in which a ceramic circuit board on which a conductive metal layer is formed is covered with an etching resist layer having a predetermined pattern, and then subjected to an etching process to form a circuit, the etching process is performed. Remove the copper residue remaining in the recesses on the surface of the ceramic substrate after
A method for manufacturing a ceramic circuit board, characterized in that the removal is performed by ultrasonic cleaning in an etching solution. (2) The method for manufacturing a ceramic circuit board according to claim 1, wherein the conductive metal layer is bonded to the recessed portion of the surface of the ceramic substrate with an anchor effect.