JPH0682908B2 - Method for manufacturing ceramic circuit board with resistor - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a ceramic circuit board with a resistor, and a method for manufacturing a ceramic circuit board on which a resistor is formed together with a normal conductor circuit for wiring. It is a thing.

[Conventional technology]

As a method for manufacturing a ceramic circuit board including a resistor, conventionally, a precious metal paste containing Ag / Pd or the like as a main component to be a conductor circuit is printed on a sintered ceramic substrate by screen printing or the like, and RuO ₂ A general method is to form a conductor circuit and a resistor at the same time by printing a frit-containing resistor paste containing as a main component by screen printing or the like and firing it in an oxidizing atmosphere.

However, in the above method, migration is likely to occur and the wiring resistance is as high as 10 to 30 mΩ / □. Therefore, recently, as a method of improving the above method to prevent migration and reduce wiring resistance and reduce the cost of the paste material, a base metal paste containing Cu or the like as a main component is used.
A method of forming a conductor circuit and a resistor at the same time by combining frit-containing resistor pastes containing LaB ₆ , SnO ₂ or the like as a main component and firing both in a nitrogen atmosphere has become popular.

However, even in the above method, since the conductor metal paste is screen-printed, it is difficult to form fine wiring of 100 μm or less, and since the paste contains glass, the solder adhesion is poor, and defective products are likely to appear. There is a problem that it is easy to cause a failure during use. In addition, the resistor paste needs to be fired in a nitrogen atmosphere, and the degree of perfection of the paste material is low. Therefore, in comparison with the conventional resistor paste for air firing, the performance is sufficiently comparable in all aspects. I can't say that.

On the other hand, as a method of forming a fine wiring circuit, a method of forming a conductor metal layer not containing glass on the surface of a ceramic substrate by a metallizing method and forming the circuit by using a photoengraving technique has been proposed. . However, this method has a limitation that firing must be performed in an inert or reducing atmosphere in order to prevent the conductor metal layer from being oxidized at a high temperature when firing the resistor paste.
Further, in the subtractive method, when a photosensitive liquid resist is used, there is a problem that the reliability of the through hole portion provided on the double-sided circuit board is poor.

Therefore, after printing and firing a resistor paste for air firing mainly composed of RuO ₂ to form a resistor layer, a protective layer is formed on the resistor layer, and the surface of the ceramic substrate and the resistor layer are formed. The entire exposed part is simultaneously roughened with a strong acid, and then subjected to a catalyst / activation treatment, followed by chemical plating or chemical plating and electroplating to form a conductor metal layer, and this conductor metal layer is pattern-etched to form a conductor. A method for forming a circuit has been proposed and is disclosed in Japanese Patent Laid-Open No. 61-185995.

Further, each of the conventional techniques described above is disclosed in JP-A-61-270885.
JP-A-61-194794 and the like.
In addition, the applicant of the present application has filed Japanese Patent Application No. 61-357
Patent applications have been filed in No. 67 and Japanese Patent Application No. 63-623347.

[Problems to be Solved by the Invention]

However, in the prior art disclosed in the above-mentioned JP-A-61-185995, the conductor metal layer is formed on the entire surface of the ceramic substrate and the exposed portion of the resistor layer, and then pattern etching is performed to remove unnecessary portions of the conductor metal layer. Therefore, there is a problem that an etching process which is troublesome to work is required and unnecessary conductor metal other than the circuit portion is removed, so that the conductor metal is wasted and the cost is high.

Further, in order to increase the adhesion between the ceramic substrate and the conductor circuit or between the resistor layer and the conductor circuit, the exposed portions of the ceramic substrate and the resistor layer are roughened with a strong acid. There is also a problem in that the resistance layer is adversely affected and the quality performance of the resistor layer is adversely affected. In order to prevent such a problem, the roughening treatment should be suppressed to the extent that it does not affect the quality performance of the resistor layer, but if this is done, the conductor circuit and the ceramic substrate and the resistor layer will have poor adhesion. It becomes a thing.

Therefore, an object of the present invention is to eliminate the need for an etching step of the conductor metal layer in the above-mentioned conventional technique, to improve reliability of through-holes in a double-sided circuit board, to enable fine wiring, to reduce wiring resistance, and with high accuracy. It is an object of the present invention to provide a method of manufacturing a ceramic circuit board with a resistor having a highly reliable resistor layer.

[Means for Solving the Problems]

Among the inventions for solving the above problems, the invention according to claim 1 includes the following steps (1) to (5) in the manufacturing process.

(1) A step of roughening the surface of the ceramic substrate.

(2) A step of forming a resistor layer on the ceramic substrate and forming a protective layer on the resistor layer.

(3) A step of roughening the exposed portion of the resistor layer by a treatment method that does not adversely affect the resistor layer under roughening conditions weaker than the roughening conditions of the surface of the ceramic substrate.

(4) A step of forming a plating resist layer corresponding to a predetermined circuit pattern on the ceramic substrate on which the resistor layer and the protective layer are formed.

(5) A step of forming a circuit pattern made of a conductive metal on the surface of the ceramic substrate other than the plating resist layer and the exposed portion of the resistor layer by a plating method.

According to the second aspect of the present invention, in carrying out the first aspect of the invention, any one of copper, nickel and gold is used as a conductive metal forming a circuit pattern by a plating method.

[Action]

According to the first aspect of the invention, the conductor metal layer is formed by plating only on the portions required for the circuit pattern according to the formation pattern of the plating resist layer, so that the etching step is unnecessary.

Further, by roughening the surface of the ceramic substrate and the exposed portion of the resistor layer, the adhesion with the conductor metal layer formed thereon is increased.

Moreover, the resistor layer is roughened separately from the roughening of the ceramic substrate, and the ceramic substrate is subjected to a strong treatment method such as strong acid capable of sufficiently roughening the resistor layer. Is roughened by a comparatively weak treatment method that does not adversely affect the performance of the resistor layer, so that an appropriate roughening treatment can be performed on both the surface of the ceramic substrate and the resistor layer.

According to the second aspect of the invention, the performance of the conductor circuit can be improved by using copper, nickel and gold as the conductor metal.

〔Example〕

FIG. 1 shows an example of a method of manufacturing a ceramic circuit board with a resistor according to the present invention by a process flow chart, and the explanation will be sequentially added according to the flow chart. Also, in FIG.
The cross-sectional structure of the manufactured ceramic circuit board with a resistor is shown.

[Step] A sintered ceramic substrate 1 is prepared. The material of the ceramic substrate 1 is alumina, fosterite, steatite, zirconia, mullite, cordierite, zircon,
Mainly used oxide-based ceramic materials such as titania,
Any ceramic material such as a carbide type or a nitride type can be used.

[Step] The surface of the ceramic substrate 1 is roughened. By this roughening treatment, the adhesive force (so-called anchor effect) between the conductor metal layer 2 formed in the subsequent step and the substrate surface can be improved. In this invention, since the conductor metal layer 2 is formed by a plating method such as a chemical plating method, it is preferable to perform this roughening treatment. The roughening method is the ceramic substrate 1
There are, for example, a method of immersing in a solution of hot phosphoric acid, molten alkali, HF or the like, a method of physically roughening by polishing or sandblasting, and various other roughening treatment methods can be adopted.

[Step] At a predetermined position of the ceramic substrate 1, the resistor paste is
It is applied and dried by a means such as screen printing so as to have a predetermined pattern. Then, the resistor paste is fired together with the ceramic substrate 1 to form the resistor layer 3.

Resistor paste, PdO / Pd / Ag-based or RuO ₂ -based resistance component, such as Si, Ca, a mixture of glass containing an oxide such as Al or an organic vehicle, etc. to form a paste, etc. A material for forming a resistor is used. When using the resistor paste, it is preferable to select and use a material that is compatible with the material of the ceramic substrate, but usually, a RuO ₂ based material that has the most stable characteristics is suitable.

The method of drying and firing the resistor paste is performed in the same manner as the ordinary resistor forming method, but for example, the following conditions are common. That is, after the resistor paste printed on the ceramic substrate 1 by screen printing or the like is dried at 50 to 200 ° C., the temperature at which the glass frit in the components is melt-bonded, preferably 500 to 1100.
C., more preferably in the range of 600 to 950.degree.

[Step] The protective layer 4 is formed so as to cover a part of the resistor layer 3. The protective layer 4 is formed to improve the heat resistance, moisture resistance, chemical resistance, etc. of the resistor layer 3 and reduce the drift of the resistance value. The protective layer 4 covers the entire resistor layer 3 except a portion for connecting the resistor layer 3 and the conductor metal layer 2 in a later step. As the protective layer 4, an ordinary overcoat glass that is also used in the conventional manufacturing method can be used. However, instead of this overcoat glass,
A protective layer 4 made of an organic or inorganic substance formed of a photosensitive polyimide, a polyimide, an epoxy resin, a triazine-based material or the like and having resistance to an acid or the like used in a roughening treatment in a subsequent step. It can also be used.

The protective layer 4 can be formed by a usual method, but for example, the following conditions are common. That is, a protective layer is formed by printing a glass paste for an overcoat by printing using a screen printing method to cover the entire portion except a part of the resistor layer 3 and then firing the glass paste at 300 to 800 ° C. 4 is formed.

[Step] The exposed portion of the resistor layer 3 which is not covered with the protective layer 4 is roughened. When the conductor metal layer 2 is formed on the exposed portion of the resistor layer 3 thus roughened, the adhesion between the resistor layer 3 and the conductor metal layer 2 is improved by the so-called anchor effect. The roughening treatment does not need to use the treatment method having a strong roughening action such as the hot phosphoric acid described in the roughening treatment of the ceramic substrate 1. The body layer 3 can be roughened. As a specific treatment method, for example, a method using an acid such as phosphoric acid, hydrofluoric acid, chromic acid, sulfuric acid, or an alkaline solution such as NaOH can be applied. By this roughening treatment, at the same time as the exposed portion of the resistor layer 3,
Although the surfaces of the protective layer 4 and the ceramic substrate 1 may be roughened to some extent, a roughening treatment method that does not adversely affect the protection effect of the resistor layer 3 by the protective layer 4 and the performance of the resistor layer 3 is used. Apply.

[Step] A resist having plating resistance is applied onto the ceramic substrate 1 and dried to form a plating resist layer in a pattern opposite to the circuit pattern of the required conductor circuit.
As a method for forming a patterned plating resist layer, a method for forming a resist layer in ordinary circuit formation such as a screen printing method, a method using a photosensitive liquid resist, a method using a dry film, or the like can be applied.

Then, normal sensitizing-activation is performed to nucleate metallic palladium on the surface of the ceramic substrate 1 other than the patterned resist layer and the exposed portion of the resistor layer 3.

Next, the ceramic substrate 1 on which the resist layer is formed,
The conductor metal layer 2 is formed by a chemical plating method by immersing in a chemical plating solution and only in a portion corresponding to the circuit pattern having no resist layer. Through hole 5 on ceramic substrate 1
In the case of double-sided circuit board forming
It is possible to form the through holes 5 by plating at the same time. After the conductor metal layer 2 is formed, the plating resist layer is peeled and removed.

[Step] Next, if necessary, the ceramic substrate 1 on which the conductor metal layer 2 is formed is heat-treated in a nitrogen atmosphere. The treatment temperature is preferably 200 to 800 ° C, more preferably 400 to 700 ° C. Although this heat treatment improves the adhesion between the conductor metal layer 2 and the ceramic substrate 1, etc., it may be omitted if not necessary. The treatment time is appropriately set, but is, for example, about 1 to 100 minutes. The heating atmosphere is a vacuum or a nitrogen atmosphere. If necessary, in the above heating atmosphere, 2 to 20
It may contain a trace amount of oxygen of about 0 ppm.

[Step] If necessary, the resistor layer 3 is trimmed to adjust it to a desired resistance value. As the trimming method, the same method as that for a normal circuit board with a resistor is used, and for example, there are methods such as abrasive trimming and laser trimming. Among them, laser trimming, which is capable of high-speed processing and has high performance, is the most preferable for implementing the present invention.

Through the above steps, a ceramic circuit board with a resistor as shown in FIG. 2 is manufactured.

In the above embodiment, by using a base metal conductor such as copper or nickel having a small wiring resistance as the conductor metal layer 2, it is possible to form a conductor circuit having a fine pattern with a line width of 30 μm. In addition, if gold is used, there is no fear of migration, and solderability and the like will be good.

When a resistor paste for air firing such as RuO ₂ system is used, it is possible to form the resistor layer 3 with higher accuracy and higher reliability than the resistor paste for nitrogen firing. It is possible to manufacture a ceramic circuit board provided with the resistor layer 3 having extremely high accuracy, the characteristic being within ± 2%.

Next, specific examples in which the method for manufacturing a ceramic circuit board with a resistor according to the present invention is actually applied will be described.

-Example 1-As a sintered ceramic substrate 1, a 96% alumina substrate (4 "
× 4 ″ × 0.635 mm) was used to make holes for through holes of 200 μmφ in the ceramic substrate 1 with a laser. This substrate 1 was immersed in hot phosphoric acid to clean the surface of the substrate and the inner wall surface of the holes for through holes. After the roughening treatment, the surface roughness became a maximum roughness of 2 to 3 μm.
Thoroughly washed and dried. After drying, ceramic substrate 1
A RuO ₂ -based resistor paste was screen-printed on the resultant, dried and then fired in air at 850 ° C. to form a resistor layer 3.
After that, a glass paste for overcoat is screen-printed so as to cover the entire resistor layer 3 except a part which is a connection portion with the conductor metal layer 2, and after drying, 600 ° C. in air. The protective layer 4 was formed by firing under the conditions described above.

Next, the exposed portion of the resistor layer 3 was subjected to a roughening treatment using a 5% hydrofluoric acid solution, and then sufficiently washed with water and dried. A photosensitive liquid resist having plating resistance was applied to both surfaces of the ceramic substrate 1, and a plating resist layer was formed in a pattern opposite to the circuit pattern by using a photoengraving technique. The ceramic substrate 1 is sequentially immersed in a treatment liquid for sensitizing and activation,
Ceramic substrate 1 without plating resist layer
Nucleation of palladium was performed on the exposed part of the. The ceramic substrate 1 was immersed in a commercially available chemical copper plating solution to form a conductor metal layer 2 having a copper layer of about 10 μm.

After that, the plating resist layer was peeled off to obtain a conductor circuit having a line width and a line gap of 50 μm. At this time, no defect such as disconnection was observed in the through hole portion, and good conductor circuits and through holes were formed. Next, the ceramic substrate 1 was heat-treated at 600 ° C. in a nitrogen atmosphere containing 50 ppm of oxygen.

As a result, in the obtained ceramic circuit board with a resistor, the connection portion between the copper layer, which is a conductor metal layer, and the exposed portion of the resistor layer is firmly adhered, and the adhesion between the copper layer and the ceramic substrate 1 is strong. Showed an extremely high value of 2.0 to 3.0 kg / mm ² . Also,
When the resistance characteristic with respect to the circuit constant of the resistor layer 3 was measured, a highly accurate value was shown within ± 2%. After that, trimming adjustment is performed with a laser trimmer so that the resistance value of the resistor layer 3 becomes a desired value, thereby manufacturing a ceramic double-sided circuit board with a resistor having through holes 5 as shown in FIG. did it.

The double-sided circuit board manufactured in this manner has a higher reliability of the through hole than that of the conventional paste method, a fine circuit can be formed without using an etching step, and a wiring resistance is reduced. The resistor layer was also highly accurate and had good reliability.

—Example 2— A 92% alumina substrate was used as the sintered ceramic substrate 1, and the surface was roughened to a maximum roughness of about 2 μm by immersing it in hot phosphoric acid, and then thoroughly washed and dried. . After drying, screen-print a RuO ₂ -based resistor paste on the ceramic substrate 1 and dry it.
The resistor layer 3 was formed by firing under the condition of 0 ° C. Then, a glass paste for overcoating was screen-printed so as to cover a predetermined portion of the resistor layer 3, dried, and then baked in air at 600 ° C. to form a protective layer 4. Further, the exposed portion of the resistor layer 3 was roughened using a 10% chromic acid solution, sufficiently washed with water and dried.

On such a ceramic substrate 1, a dry film having resistance to plating was laminated, and a plating resist layer having a predetermined pattern was formed by using a photolithography technique. Then, a copper layer having a thickness of 15 μm was formed on the portion without the plating resist layer by the chemical plating method. After stripping the plating resist layer, 600 ℃ in a nitrogen atmosphere containing 70ppm oxygen.
Was heat-treated.

As a result, in the obtained ceramic circuit board with a resistor, the copper layer is firmly adhered to the exposed part of the resistor layer, and the adhesion of the copper layer to the substrate is as high as 2.0 to 3.0 kg / mm ^2. Indicated. Further, the resistance characteristic of the resistor layer 3 with respect to the circuit constant is ±
The precision was within 2%. After that, the resistor layer 3 was trimmed with a laser trimmer and adjusted to a predetermined resistance value, whereby the production of the ceramic circuit board with a resistor was completed.

-Example 3-A 99% alumina substrate was used as the sintered ceramic substrate 1, and the surface of this substrate was hydrofluoric acid to have a maximum roughness of 1-2.
After the roughening treatment to μm, a conductive circuit composed of a nickel layer was formed using a chemical nickel plating solution. Note that the other execution conditions were the same as in Example 1. As a result, it was possible to manufacture a ceramic circuit board with a resistor having excellent performance as in Example 1.

—Example 4— A 99% alumina substrate was used as the sintered ceramic substrate 1, and a resistor paste was formed in the same manner as in Example 2 except that the resistor paste was directly drawn on the ceramic substrate 1 to form a predetermined shape. A ceramic circuit board with a body was manufactured. as a result,
The same excellent characteristics as in Example 2 could be exhibited.

-Example 5-Using a sintered aluminum nitride substrate (2 "x 2" x 0.635 mm),
A ceramic circuit board with a resistor was manufactured by the same steps as in Example 2 except that the copper layer to be the conductor metal layer 2 was formed by chemical plating to have a thickness of 8 μm. As a result, the same excellent properties as in Example 2 could be exhibited.

-Comparative Example 1-This comparative example is a case where the resistor layer is roughened simultaneously with the surface of the ceramic substrate under a strong roughening condition suitable for the ceramic substrate.

The conditions were the same as in Example 1 except for the following differences.

The surface of the ceramic substrate was not roughened by hot phosphoric acid.

The exposed part of the resistor layer was roughened with a 12% hydrofluoric acid solution (30 ° C., 15 minutes) together with the surface of the ceramic substrate.

As a result, the surface of the ceramic substrate was satisfactorily roughened, and the conductor metal layer could be formed well. When the adhesion of the copper conductor layer thus formed to the ceramic substrate was measured, it was a relatively high value of 1.5 to 2.5 kg / mm ² .

However, the roughening treatment damaged and damaged the glass component in the exposed portion of the resistor layer. As a result, the electrical connection between the conductor and the resistor layer was not performed well, and the ceramic circuit board with a resistor could not exhibit sufficient performance.

-Comparative Example 2-This comparative example is a case where the surface of the ceramic substrate together with the resistor layer is roughened under a weak roughening condition suitable for the resistor layer.

The conditions were the same as in Example 1 except for the following differences.

The surface of the ceramic substrate was not roughened by hot phosphoric acid.

As a result, the exposed portion of the resistor layer was satisfactorily roughened, and the electrical connection with the copper conductor layer was also satisfactorily performed.

However, since the surface of the ceramic substrate was not sufficiently roughened, a large number of “blisters” were thought to be caused by poor adhesion between the ceramic substrate and the conductive metal layer when the conductive metal layer was formed by the plating method. Therefore, the ceramic circuit board with a resistor could not exhibit sufficient performance.

〔The invention's effect〕

According to the invention described in claim 1, among the methods for manufacturing a ceramic circuit board with a resistor according to the present invention described above,
On the ceramic substrate on which the resistor layer and the protective layer are formed,
After forming a plating resist layer corresponding to a predetermined circuit pattern, a circuit pattern made of a conductive metal is formed by plating on the exposed surface of the ceramic substrate surface and the resistor layer other than the plating resist layer. As described above, a troublesome process of etching the conductor metal layer is not necessary. Since the conductive metal is formed only where it is necessary to form a circuit, the material cost is reduced. Since the etching is not performed, the reliability of the through hole becomes high when the through hole is formed.

Moreover, as compared with a method of manufacturing a conductor circuit by firing a conductor metal paste, a fine circuit can be formed, and a conductor metal having a low resistance can be used, so that the wiring resistance becomes low,
Since a high-performance resistor layer can be used, it is possible to provide a ceramic circuit board provided with a resistor layer having high accuracy and high reliability.

Furthermore, before forming the resistor layer, the ceramic substrate is roughened by a normal strong roughening treatment method, so that the exposed portion of the resistor layer does not adversely affect the resistor layer,
By roughening with a relatively weak treatment method, it is possible to increase the adhesion between the ceramic substrate and the conductor circuit without degrading the performance of the resistor layer, and improve the performance of the ceramic circuit board with resistor. It will make a big contribution.

According to the invention of claim 2, in addition to the effect of claim 1, by using a base metal such as copper or nickel as a conductor metal for forming a circuit pattern by a plating method, material cost can be reduced and Wiring resistance can be lowered. Also, by using gold, there is no fear of migration.

[Brief description of drawings]

FIG. 1 is a process flow chart showing an embodiment of the present invention, and FIG. 2 is a sectional view of a manufactured ceramic circuit board with a resistor. 1 ... Ceramic substrate, 2 ... Conductor metal layer, 3 ... Resistor layer,
4 ... Protective layer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-55-95396 (JP, A) JP-A-61-185995 (JP, A) JP-A-63-124596 (JP, A) JP-A-55- 86183 (JP, A)

Claims (2)

[Claims] 1. A method of manufacturing a ceramic circuit board in which a resistor is formed together with a conductor circuit on a ceramic substrate, the method including the following steps (1) to (5): How to make a board. (1) A step of roughening the surface of the ceramic substrate. (2) A step of forming a resistor layer on the ceramic substrate and forming a protective layer on the resistor layer. (3) A step of roughening the exposed portion of the resistor layer by a treatment method that does not adversely affect the resistor layer under roughening conditions weaker than the roughening conditions of the surface of the ceramic substrate. (4) A step of forming a plating resist layer corresponding to a predetermined circuit pattern on the ceramic substrate on which the resistor layer and the protective layer are formed. (5) A step of forming a circuit pattern made of a conductive metal on the surface of the ceramic substrate other than the plating resist layer and the exposed portion of the resistor layer by a plating method. 2. The method for manufacturing a ceramic circuit board with a resistor according to claim 1, wherein the conductor metal forming the circuit pattern by plating is one of copper, nickel and gold.