JP2002280709A - Method of manufacturing ceramic circuit board and board thereby - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing ceramic circuit board by which a ceramic circuit board on which a copper conductor film circuit having a sharp edge is mounted and the occurrence of short circuits in a circuit formed by fine lines is inhibited can be manufactured without performing any complicated process, and to provide a ceramic circuit board manufactured by this method. SOLUTION: In this method, the copper conductor circuit 2 is formed by printing copper conductor paste on a ceramic substrate 1 and baking the paste. After the circuit 2 is formed, the edge 4 of the circuit 2 is sharpened by removing the stained portion of the copper conductor generated on the edge 4 of the circuit 2 by dissolving the portion.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a ceramic circuit board and the obtained board, and more particularly, to a method for manufacturing a printed circuit board by printing a copper conductor paste and firing the same. The present invention relates to a method for manufacturing a ceramic circuit board capable of dissolving and removing a bleeding portion of a conductor, sharpening an edge, and eliminating spread of electroless plating, which is a post-process, and the obtained board.

[0002]

2. Description of the Related Art Today, a conductor paste is used to obtain a copper conductor by printing and firing a circuit on a ceramic substrate. Recently, a copper paste that can be plated in a post-process to prevent oxidation and improve solderability has been proposed.

For example, lead glass, which has been used for bonding conventional copper pastes, has poor chemical resistance and has a problem in that the adhesion decreases after plating. This method enables plating by using excellent lead-free glass. This method can be plated, but since the copper conductor circuit is formed by the printing method, there are bleeding parts such as sagging that occur at the edge of the circuit that can not be avoided by the printing method, and the plating process in the later process There is a problem that plating is deposited even at the bleeding portion and short-circuits occur in a fine line circuit.

As a method for solving these problems, a copper conductor paste capable of forming a copper conductor which can be etched has been proposed.
No. 126971.

[0005]

In these methods, a copper conductor that can be etched is formed by reacting and adhering to a ceramic substrate using reactive adhesion of copper fine particles, and a sharp edge is formed by forming a circuit by photoetching. It is a method that can obtain a simple copper conductor and does not spread even in the plating process in the subsequent process, but requires equipment and processes required for photo etching, and is not suitable for circuit formation that can be done by ordinary printing method Met.

The above-mentioned copper conductor paste which can be etched is effective as a method for obtaining a copper conductor having a sharp edge and a very small thickness. However, it is necessary to go through a copper conductor production step and an etching step by a normal printing method. Was.

In this etching step, a metallized substrate obtained by printing and firing an etchable copper conductor paste can be patterned to produce a ceramic wiring board having a circuit pattern formed thereon. Then, the entire surface of the metallized substrate is covered with a resist film. As the resist film, a dry film or a resist ink is used. Next, in order to form a desired circuit pattern on the resist film, a negative film with a transparent portion formed in the same shape as the conductor circuit is placed on the resist film, and cured by irradiating with an ultraviolet exposure lamp and exposing it. Let it.

The negative film is removed, and the uncured portion, that is, the portion of the resist film that has not been exposed is developed and removed. On the copper film, a cured resist film is formed in the same manner as the conductive circuit.

Next, copper other than the circuit pattern is removed using an etching solution of copper, for example, an aqueous solution of ferric chloride or cupric chloride.

Subsequently, the resist film covering the circuit pattern is removed using a solvent, for example, dichloromethane, to form a ceramic circuit board having fine-line copper conductor circuits with sharp edges. Had to go through.

The present invention provides a method for manufacturing a ceramic circuit board in which the edge of a copper conductor film circuit is sharp and a short circuit in a fine line circuit is prevented without passing through such a complicated process, and the obtained board. The purpose is to do.

[0012]

According to a first aspect of the present invention, there is provided a method for manufacturing a ceramic circuit board in which a circuit is formed by printing and firing a copper conductor paste on a substrate. After printing on a substrate made of ceramics and firing to form a copper conductor circuit,
A method for manufacturing a ceramic circuit board in which a bleeding portion of a copper conductor generated at the edge of the circuit is dissolved and removed, and the edge is sharpened. Since a conductor can be formed, processing cost can be reduced.

According to the second aspect of the present invention, the solution for dissolving the bleeding portion of the copper conductor is at least one type of etching solution selected from ferric chloride and cupric chloride. According to the invention, when the ferric chloride is used as an etching solution, the concentration is 1 to 15 as an etching condition.
%, The immersion time is set to 1,800 to 10 seconds. In the invention according to the fourth aspect, the ceramic circuit board having the sharpened edge is subjected to an electroless plating process, and in the invention according to the fifth aspect, Electroless plating is electroless nickel
-It is in a method of manufacturing a Lamix circuit board that is phosphor-plated.

According to the invention of claim 6 of the present application, a copper conductor paste is printed on a substrate made of ceramics and baked to form a copper conductor circuit. It is on a ceramic circuit board whose edges have been removed and sharpened.

According to the invention of claim 7 of the present application, a plating layer is provided on the surface of the copper conductor circuit, and in the invention of claim 8, the plating layer is nickel-phosphorous on a ceramic circuit board.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, first, a copper conductor paste is screen-printed on the surface of a substrate 1 made of ceramics selected from aluminum oxide sintered body, aluminum nitride sintered body, barium titanate sintered body and the like. Printing is performed on a desired copper conductor circuit 2 having a thickness of 10 to 1,000 nm.

In the screen printing procedure, a printed board is placed under a horizontally placed screen (for example, stainless steel plain fabric, 300 mesh) at an interval of 0.1 to 2 mm. After the copper conductor paste is placed on the screen, it is spread over the entire screen using a squeegee. At this time, the screen and the substrate 1 have an interval. Subsequently, the screen is pressed and moved with a squeegee to such an extent that the screen comes into contact with the substrate 1,
Print. Thereafter, this is repeated.

Thereafter, firing is performed in nitrogen to form a copper conductor circuit 2.
To form In the firing, the substrate 1 is directly placed in a belt furnace, and fired in nitrogen at a temperature of 600 to 1,000 ° C. for a firing time of 20 to 60 minutes and a peak holding time of 4 to 12 minutes,
Then, the firing step is completed in a cooling time of 9 to 27 minutes, and the copper powder is sintered and reactively bonded to the base material. During this firing step, a predetermined amount of oxygen is fed into the furnace, and the adhesion between the copper conductor circuit 2 and the substrate 1 is increased to reduce the electric resistance of the circuit.

As shown in the cross-sectional view of FIG. 1, the copper conductor circuit 2 after firing has a bleeding portion 3 such as a sag projecting from the periphery of the root of the copper conductor circuit 2. The distance L between the bleeding parts 3 is close. If this distance L is equal to or more than half of the pattern interval W, a short circuit occurs. Further, it is preferable that there is no bleeding part in the circuit design, and it is preferable that the interval W of the pattern and L ′ from which the bleeding part 3 is removed as shown in FIG. 2 be as close as possible.

The copper conductor paste used here is fine particles composed of copper, copper oxide, or a mixture thereof as the first component, and the fine particles are reduced, for example, by a method called a precipitation method, that is, by a reduction from a metal salt solution. This is a method of directly precipitating and depositing metal fine particles using an agent. Fine metal particles can be obtained by adding a reducing agent such as formalin, hydrazine, sodium hypophosphite, or borohydride salt to an aqueous solution containing metal ions under appropriate conditions. The fine particles are subjected to a surface treatment with an organic fatty acid or a coupling agent to improve oxidation resistance, dispersibility, and the like.
The average particle diameter of the fine particles is in the range of 1 to 200 nm. Preferably, the thickness is in the range of 100 to 200 nm. In this range, aggregation of the fine particles is eliminated, a dense fired film is formed, and the electric resistance value is reduced.

The mixed copper powder as the second component of the copper conductor paste is based on copper powder having an average particle diameter in the range of 0.5 to 5 μm, and auxiliary copper powder having a smaller average particle diameter. At least 1 to 3 or more are added. Specific mixed copper powder is a base copper powder having the largest average particle diameter in the range of 2 to 5 μm in average particle diameter, and a first auxiliary copper powder having the second largest average particle diameter in the range of 1 to 2 μm in average particle diameter. And a case where the second auxiliary copper powder has the smallest average particle diameter in the range of 0.5 to 1 μm in the three-stage particle diameter range, or the average particle diameter is 0.5 to 1 μm.
And the average particle diameter of 0.1 to 0.5
It consists of a two-stage particle size range of the auxiliary copper powder in the range of μm.

When the mixed copper powder is composed of three stages of particle size ranges, the base copper powder in the mixed copper powder is 80 to 98%.
The first auxiliary copper powder accounts for 1 to 19% by mass and the second auxiliary copper powder accounts for 1 to 19% by mass with respect to the mass%. In particular, the auxiliary copper powder is not limited to this, and a third auxiliary copper powder having an average particle diameter range or less may be used.

It is desirable that each copper powder of the above auxiliary copper powder has a relatively spherical shape. This is because the copper powders are arranged with a reduced number of voids. When copper powders having different average particle diameters are used, auxiliary copper powder having a small average particle diameter fills gaps and voids generated when the base copper powder having the largest average particle diameter is arranged. There is an effect that the number of internal defects is small and the compaction becomes good.

When the average particle size of the base copper powder exceeds 5 μm, the sintering conditions are set to be wide and the influence of oxidation is reduced. Of the adhesive decreases. Further, the copper powder may be crushed in the ink roll process to form a copper foil, which may cause mesh displacement during screen printing.
On the other hand, when the average particle diameter of the base copper powder is less than 0.5 μm,
Since the total particle area of the mixed copper powder becomes too large, the influence of oxidation increases, and the electric resistance value increases. In addition, since the bulk density is high, the compaction property deteriorates.

When the amount of the base copper powder exceeds 98% by mass, the material does not sinter sufficiently at a low temperature, resulting in insufficient compaction and a decrease in the adhesive strength between the fired film and the substrate.
If it is less than 1, the total particle area of the mixed copper powder becomes too large, and the same problem as described above occurs. The auxiliary copper powder is added to fill gaps and voids generated when the base copper powder is arranged, and the average particle size and the amount added are greatly affected by those of the base copper powder.

The binder resin as the third component of the copper conductor paste includes, for example, celluloses such as nitrocellulose, ethyl cellulose, cellulose acetate and butyl cellulose; polyethers such as polyoxymethylene; polyvinyls such as polybutadiene and polyisoprene. And acrylics such as polybutyl methacrylate and polymethyl methacrylate, and polyamides such as nylon 6, nylon 6.6, and nylon 11. Although not particularly limited, they need to be decomposed during firing.

The binder resin preferably contains at least two kinds of resins having different thermal decomposition temperatures. This is because even when fired, the binder resin does not thermally decompose at once but decomposes according to the environmental temperature, so that it does not remain in the fired film.

Examples of the organic solvent for dissolving the binder resin include carbitol, carbitol acetate, terpineol (terpinol), metacresol, dimethylimidazolidinone, dimethylformamide, terpinol, diacetone alcohol, triethylene glycol,
It is a high-boiling organic solvent such as para-xylene, ethyl lactate, and isophorone, and may be used in combination of two or more.

The glass powder, which is the fourth component added to the present invention, is lower than the sintering temperature of fine particles or mixed copper powder composed of copper, copper oxide or a mixture thereof, and the thermal decomposition temperature of the binder resin. Those with higher softening points are used. In particular, in the firing process of the copper conductor paste, the copper fine powder is melted, and the reaction with the substrate is promoted or the wettability with the substrate is improved. This is important for smoothing the film, improving the solderability to the fired film, improving the adhesion between the substrate and the fired film, and maintaining its reliability.

This glass powder does not contain lead,
It has a low softening point of 500 to 600 ° C in the average particle size range of 1 to 10 µm. Specifically, SiO ₂ —B ₂ O ₃ —
_{ZnO-based, SiO 2 -B 2 O 3 -Bi} 2 O 3 system, SiO ₂ -B
₂ O ₃ —CaO system, SiO ₂ —B ₂ O ₃ —TiO ₂ system, Si
O ₂ -B ₂ O ₃ -MgO _{based, SiO 2 -B 2 O 3 -Na} 2 O
System, SiO ₂ -B ₂ O ₃ -ZrO based, SiO ₂ -B ₂ O ₃ -A
It is at least one kind of glass material composed of l ₂ O ₃ . However, it is not necessary to limit to this.

Among them, SiO is relatively easy to melt copper.
₂ -B ₂ O ₃ and -ZnO based glass, spreads easily on the substrate surface when the glass frit is softened SiO ₂ -B ₂ O ₃ -
By using Bi ₂ O ₃ -based glass, the molten copper component reacts with the substrate, and good adhesion can be obtained. At that time, by using a copper fine powder having high activity, it was possible to positively melt the copper component in the glass frit and improve the adhesion.

The amount of addition is preferably 0.25 to 3% by mass with respect to the total amount of the paste, and the total amount of the two types of glass frit is preferably 0.5 to 4% by mass. If the addition amount exceeds 3.0% by mass, the glass powder remains in the fired film after firing, so that the electrical resistance of the fired film tends to increase, and the interface between the fired film and the substrate tends to increase. A glass layer is formed, which tends to cause distortion due to thermal expansion, and weakens thermal shock. If it is less than 0.25% by mass, a highly reliable adhesive force to a substrate cannot be expected.

The copper conductor paste of the present invention has an organic content of 2 to 16% by mass consisting of a binder resin and an organic solvent.
And the viscosity is adjusted. When the organic content is less than 2% by mass, the viscosity of the copper conductor paste becomes high, and when the organic content exceeds 14% by mass, the viscosity becomes low and the printability is poor.

Further, fine particles comprising all of the contained copper powder and copper oxide, copper, or a mixture thereof are 84%.
９８98% by mass. If the content exceeds 98% by mass, the paste becomes highly viscous, causing insufficient shrinkage, and the adhesive strength between the fired film and the substrate is reduced. Happens.

Subsequently, the bleeding portion 3 such as a sauce projecting from the periphery of the base of the copper conductor circuit 2 is dissolved and removed, and the edge 4 is removed.
Process sharply. As shown in FIG. 2, the distance L ′ between the roots of the adjacent copper conductor circuits 2 is larger than L, and is closer to the pattern distance W. In this step, the purpose is to remove the bleeding portion 3 other than the circuit 2, and it is not necessary to dissolve the circuit 2. Therefore, it is necessary to control the immersion time. Specifically, the substrate 1 is immersed in an etching solution having a predetermined concentration for a predetermined time to dissolve the bleeding portion 3. Etching solutions include ferric chloride, cupric chloride, nitric acid, sulfuric acid, acetic acid, aqueous ammonia, and alkali cyanide solutions that dissolve copper.

The concentration of the etching solution is not particularly limited, but when ferric chloride is used as the etching solution, the concentration is 1 to 15% by mass, and the immersion time is 1,800.
10 seconds to 10 seconds, the concentration of the etching solution is adjusted to be low, and the processing time is lengthened.

If necessary, an electroless plating process can be performed as a post-process. In this case, since only the bleeding portion 3 other than the copper conductor circuit 2 is removed, the plating does not spread. In this electroless plating treatment, the substrate 1 is immersed in an electroless plating solution to provide a plating film 5 on the surface of the copper conductor circuit 2. The electroless plating treatment includes copper plating, nickel plating, gold plating, and the like. Silver plating, aluminum plating, rhodium plating,
By performing a cobalt plating process and a ruthenium plating process, a substrate having various plated layers formed thereon is formed.

[0038]

Next, the present invention will be described in more detail with reference to specific examples. Examples 1 to 3 and Comparative Examples 1 to 4 (Preparation of Copper Conductor Substrate) An alumina substrate was used as a ceramic substrate, and a copper conductor paste (Cu fine powder having an average primary particle size of 5 nm: 80 parts by mass, an average primary particle size of 3 μm) was used. Cu powder:
500 parts by mass, Cu powder having an average primary particle size of 1 μm: 15 parts by mass, Cu powder having an average primary particle size of 0.5 μm: 30 parts by mass, glass powder SiO ₂ —B ₂ O ₃ —ZnO-based lead-free glass: 5 parts by mass , Acrylic resin: 30 parts by mass, terpineol: 3
0 parts by mass, butyl carbitol acetate: 30 parts by mass) using a stainless 325 screen to print a 2 mm × 2 mm circuit for evaluating adhesion and a line / space = 100 μm / 100 μm circuit for plating spread evaluation, Leveling at room temperature for 15 minutes, drying at 150 ° C for 2 minutes
It went for 0 minutes. Put these samples directly into the belt furnace,
The firing step was completed at a peak temperature of 900 ° C. and a peak holding time of 10 minutes in nitrogen to produce a substrate having a copper conductor circuit.

(Etching treatment) After immersing for a predetermined time in an aqueous ferric chloride solution (concentration: 150 g / liter, liquid temperature: 40 ° C), the substrate was sufficiently washed with water to obtain a ceramic circuit board having sharp edges.

(Evaluation Method) Observation of pattern edges, adhesion of copper conductor circuits, and spread of electroless nickel plating were measured by the following methods. Table 1 shows the results obtained by the above evaluation method.

1. Observation of Circuit Edge Observation was performed with a loupe of 100 times. When the edge was less than 10 microns from the edge of the pattern, it was evaluated as ○, and when it was 10 microns or more, it was evaluated as x.

2. Adhesion strength of fired film (L-peel strength) Tin-plated copper wire with a diameter of 0.8 mm bent into L-shape is 2 mm
Solder to the surface of the baked film baked to a size of × 2 mm, fix it by soldering, measure the adhesive force of the vertically bent copper wire with a spring meter, determine the adhesive force between the substrate and the baked film, and calculate 2.0 kg When it exceeded, it was evaluated as 、, when it was less than 1.2 kg, it was evaluated as Δ, and when it was less than 1.2 kg, it was evaluated as ×.

3. Evaluation of Spread of Electroless Nickel Plating Electroless nickel plating was applied and observed with a magnifier of 100 times. When the edge was less than 10 microns from the edge of the circuit, it was evaluated as ○, and when it was 10 microns or more, it was evaluated as x.

[0044]

[Table 1]

As a result, an aqueous ferric chloride solution (concentration: 15
If the immersion time (0 g / liter, liquid temperature 40 ° C.) is within the range of 10 to 20 seconds, the substrate has sharp circuit edges, does not decrease the adhesion of the copper conductor circuit, and does not spread electroless nickel plating. Was produced. When the immersion time was shorter than this range, the edge did not become sharp, and the electroless nickel plating also spread. When the immersion time was longer than this range, the conductor pattern itself was also eroded, and the adhesion was reduced.

Further, the etching treatment was carried out using an aqueous solution of ferric chloride at a liquid temperature of 40 ° C. with a concentration of 1 to 15% by mass and an immersion time of 5 to 1,800 seconds and 1,800 seconds or more. A substrate having the same copper conductor circuit as described above was produced. The circuit edge was observed and the adhesion of the fired film was measured. The results are shown in Tables 2 and 3.

[0047]

[Table 2]

[0048]

[Table 3]

As a result, when an aqueous ferric chloride solution is used as an etching solution, the immersion time can be adjusted to a predetermined concentration in order to satisfy both the circuit edge and the adhesion.

[0050]

As described above, according to the invention described in the claims of the present application, a copper conductor paste that can be etched is printed on a desired circuit by a screen printing method, and then baked to form a copper conductor circuit. By removing the bleeding portion other than the circuit with the dissolving etching solution, a copper conductor circuit having a sharp edge can be obtained, and if necessary, the concentration of the etching solution can be adjusted to a low concentration to prolong the processing time. It is also possible to perform electroless plating as a post-process if necessary. In this case, since the bleeding portion other than the circuit is removed, there is also an effect that the plating does not spread.

[Brief description of the drawings]

FIG. 1 shows a cross-sectional view of a fired copper conductor circuit obtained in this example.

FIG. 2 is a cross-sectional view after a bleed portion of the copper conductor circuit shown in FIG. 1 is subjected to an etching process.

[Explanation of symbols]

 Reference Signs List 1 base material 2 copper conductor circuit 3 bleeding part 4 edge

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Satoshi Saito 4-1-1, Hamazoe-dori, Nagata-ku, Kobe-shi, Hyogo Mitsuboshi Belting Co., Ltd. F term (reference) 5E343 AA02 AA23 BB24 BB72 BB77 DD04 EE52 EE55 EE58 ER35 ER36 ER39 ER53 FF02 FF11 GG08 GG11

Claims (8)

[Claims] 1. A method of manufacturing a ceramic circuit board, wherein a circuit is formed by printing and firing a copper conductor paste on a substrate, wherein the copper conductor paste is printed on a ceramic substrate and fired to form a copper conductor circuit. After forming
A method for manufacturing a ceramic circuit board, comprising: dissolving and removing a bleeding portion of a copper conductor generated at an edge of the circuit; and sharpening the edge. 2. The method for manufacturing a ceramic circuit board according to claim 1, wherein the solution for dissolving the bleeding portion of the copper conductor is at least one etching solution selected from ferric chloride and cupric chloride. 3. An etching condition when ferric chloride is used as an etching solution, the concentration is set to 1 to 15% by mass, and the immersion time is set to 1,800 to 10 seconds.
The manufacturing method of the ceramic circuit board described in the above. 4. The method for manufacturing a ceramic circuit board according to claim 1, wherein the ceramic circuit board having a sharp edge is subjected to electroless plating. 5. The method according to claim 4, wherein the electroless plating is electroless nickel-phosphorus plating. 6. A method in which a copper conductor paste is printed on a substrate made of ceramics and fired to form a copper conductor circuit, and a bleeding portion of the copper conductor generated at an edge of the circuit is removed to sharpen the edge. A ceramic circuit board characterized by the above-mentioned. 7. The ceramic circuit board according to claim 6, wherein a plating layer is provided on a surface of the copper conductor circuit. 8. The ceramic circuit board according to claim 7, wherein the plating layer is nickel-phosphorus.