JPH0680880B2 - Manufacturing method of ceramic circuit board with resistor - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for manufacturing a ceramic circuit board with a resistor,
The present invention relates to a method for manufacturing a ceramic circuit board in which a resistor is formed together with a normal wiring conductor circuit.

[Conventional technology]

As a method for manufacturing a ceramic circuit board with a resistor, a conventional general method is to print a precious metal conductor paste containing Ag / Pd or the like as a main component on a sintered ceramic substrate by a screen printing method or the like. After printing the frit-containing resistor paste containing RuO ₂ as the main component by screen printing, etc., the ceramic substrate is fired in an oxidizing atmosphere to simultaneously form a conductor circuit and a resistor layer. Has been adopted. In this manufacturing method, since the conductor circuit and the resistor layer are formed by firing the paste,
There is an advantage that the adhesion between them and the substrate is high.

However, in this manufacturing method, since a precious metal conductor is used, the cost is high, and there are drawbacks that migration due to Ag occurs and the wiring resistance is considerably high at about 10 to 30 mΩ / □.

Therefore, a method of using a base metal conductor paste instead of the noble metal conductor paste and firing it in a nitrogen atmosphere so that the base metal paste does not oxidize has been studied. In this case, LaB ₆ , Sn that can be fired in a nitrogen atmosphere
A frit resistor paste containing O ₂ etc. as the main component is used.

However, in this manufacturing method, since the resistor paste is fired in a nitrogen atmosphere, it is more difficult to remove the binder than in air, and the above-mentioned nitrogen atmosphere paste material may have a low degree of perfection. Compared to the method using the air-fired resistor paste, the performance is inevitably inferior.

In addition, in any of the manufacturing methods, since the screen printing method is used to form the conductor circuit, it is difficult to form a fine circuit of 100 μm or less, and since the conductor paste contains glass, the solder adhesion is poor. However, there are also problems that defective products are likely to be produced and failures are likely to occur when the circuit board is used.

As a method of forming a fine wiring circuit, a method of forming a conductor metal layer containing no glassy substance on the surface of a substrate by a metallizing method and forming a conductor circuit having a predetermined circuit pattern by using a photoengraving technique. Is also proposed.
However, even in this method, in order to suppress the oxidation of the conductor metal layer due to the high temperature in the firing process of the resistor paste, the resistor paste must be fired in an inert or reducing atmosphere, and the same problem as described above occurs. Remain.

Therefore, as a method for solving the above problems, the method disclosed in JP-A-61-185995 has been proposed. In this manufacturing method, a resistor layer is formed by printing and firing only a resistor paste on a ceramic substrate, and a part of this resistor layer is
After covering with a protective layer such as polyimide that is not affected by roughening treatment in the subsequent process, the exposed portion of the resistor layer and the surface of the substrate are simultaneously roughened using a strong acid such as 10% hydrofluoric acid. A conductor circuit is formed on the exposed surface of the substrate and the exposed portion of the resistor by plating means.

According to this manufacturing method, since the conductor circuit is formed after the firing of the resistor paste is completed, there is no fear of oxidation even if a base metal conductor is used, and as the resistor paste, an air firing paste excellent in performance is used. Can be used. Further, a circuit forming means by plating capable of forming a fine circuit can be used, and a conductor circuit, a resistor layer, and a substrate formed by plating are roughened by roughening a part of the resistor and the substrate. It has a high adhesiveness with, and can exhibit an excellent adhesiveness that is not inferior to the conductor circuit formed by firing the conductor paste.

[Problems to be Solved by the Invention]

In the above-described manufacturing method of the prior art, since the ceramic substrate and the resistor layer are roughened at the same time, as the roughening treatment agent,
It uses a strong acid that can roughen the ceramic substrate.

However, when a roughening treatment agent having a strong roughening action such as strong acid is used, the strong acid strongly attacks the resistor layer, adversely affects the resistor layer, and the performance of the resistor is deteriorated. However, since the ceramic substrate cannot be sufficiently roughened by a weak roughening treatment that does not adversely affect the resistors, the adhesion between the conductor circuit and the substrate cannot be sufficiently improved,
Adhesion becomes poor.

Therefore, an object of the present invention is to adversely affect a resistor in a manufacturing method of forming a conductor circuit by means such as plating after forming a resistor layer by printing and firing a resistor paste, as in the above-mentioned prior art. It is another object of the present invention to provide a method capable of increasing the adhesion between the conductor circuit and the resistor and the ceramic substrate.

[Means for Solving the Problems]

To solve the above problems, in the present invention, after roughening the surface of the ceramic substrate, to form a resistor layer on the ceramic substrate, on the resistor layer, after forming a protective layer except a part, The exposed part of the resistor layer is roughened by a treatment method that does not adversely affect the resistor layer under a roughening condition that is weaker than the roughening condition of the ceramic substrate surface, and then the surface of the ceramic substrate including the exposed part of the resistor layer A conductor circuit is formed on the.

[Action]

In the present invention, since the roughening of the resistor layer is performed separately from the roughening of the ceramic substrate, a strong treatment method such as strong acid capable of sufficiently roughening is used for the ceramic substrate, However, it can be roughened by a relatively weak treatment method that does not adversely affect the resistor layer.

〔Example〕

Next, the present invention will be described in detail below with reference to the drawings illustrating an embodiment.

FIG. 1 shows the flow of each step of the manufacturing method of the present invention, and FIGS. 2 to 5 show a schematic sectional structure in the middle of each step.

First, in the process, the ceramic substrate 1 is manufactured. As a material for the ceramic substrate, oxide-based ceramics such as alumina, forsterite, steatite, zirconia, mullite, cordierite, zircon, and titania are mainly used. Various ceramic substrates similar to plates can also be used.

In the process, as shown in FIG. 1, the surface 10 of the ceramic substrate 1 is roughened. By this roughening, the adhesion between the conductor circuit and the resistor layer formed in the subsequent step and the substrate is improved. A so-called anchor effect can be exerted. As the roughening treatment method, for example, a chemical method in which the ceramic substrate 1 is immersed in a solution of hot phosphoric acid, molten alkali, high-concentration hydrofluoric acid, or the like, or a physical method in which the ceramic substrate 1 is treated with a grindstone or sandblast, etc. For example, a relatively strong roughening method that can sufficiently roughen the ceramic substrate 1 is adopted.

In the process, as shown in FIG. 3, the resistor paste is applied and dried at a predetermined position on the roughened surface 10 of the ceramic substrate 1 by means such as screen printing, and then the resistor paste is applied to the ceramic substrate 1. By firing together with 1, the resistor layer 2 is formed. The resistor paste is formed by mixing a resistance component such as PdO / Pd / Ag system or Ru ₂ O system with glass containing an oxide such as Si, Ca, Al or an organic vehicle to form a paste. A resistor paste similar to that of a normal circuit board can be used, but a paste having excellent compatibility with the ceramic substrate 1 to be used is preferable, and a Ru ₂ O type having the most stable characteristics is preferable. used.

The steps of applying the resistor paste, drying and firing can be carried out in the same treatment steps as those for a normal ceramic circuit board with a resistor, but for example, the following method is preferable. That is, after a resistor paste is formed on the ceramic substrate 1 by screen printing or the like, the resistor paste is dried at 50 to 200 ° C. and then fired at a temperature at which the glass frit in the components is melt-bonded. The firing temperature is preferably 500 to 1100 ° C, more preferably 600 to 950 ° C.

In the step, as shown in FIG. 4, the protective layer 3 is formed so as to cover almost the entire surface of the resistor layer 2 except for a part such as an end portion which is a connection point with a conductor circuit described later. To form. The protective layer 3 protects the resistor layer 2 from being attacked or deteriorated in a roughening process or a conductor circuit forming process which will be performed later, and also has heat resistance, moisture resistance or chemical resistance of the resistor layer 2. It is intended to improve the use performance such as improving the property and reducing the drift of the resistance value.

As the protective layer 3, in addition to commonly used overcoat glass, organic and inorganic substances formed of photosensitive polyimide, polyimide, epoxy resin, triazine-based material, etc. Any one can be used as long as it has resistance to the acid used.

The protective layer 3 is formed by screen printing, for example.
The protective layer 3 can be formed by printing and forming the overcoat glass paste so as to cover a predetermined portion of the resistor layer 2 and then firing it at 300 to 800 ° C. However, a means for forming a protective layer, which is adopted in a usual method for manufacturing a circuit board with a resistor, can be used.

In the step, as shown in FIG. 4, the exposed portion 20 of the resistor layer 2 is roughened to improve the adhesive force between the conductor circuit formed in the subsequent step and the resistor layer 2. As a roughening treatment method, a chemical treatment method is usually used, but at the same time that the resistor layer 2 can be sufficiently roughened, the inside of the resistor layer 2 is eroded or the performance of the resistor layer 2 is deteriorated. Use a relatively weak treatment method that does not cause adverse effects such as deterioration. As such a method, for example, if an acid such as phosphoric acid, hydrofluoric acid, chromic acid, sulfuric acid, or an alkali such as NaOH is used at a relatively low concentration, the resistor layer 2 is not adversely affected.

Although the surface of the protective layer 3 and the surface of the ceramic substrate 1 may be simultaneously roughened by the roughening treatment, the roughening of the protective layer 3 does not adversely affect the protective effect of the resistor layer 2. Is preferred.

In the step, a conductor metal layer is formed on the roughened surface 10 of the ceramic substrate 1 and the roughened exposed portion 20 of the resistor layer 2. As a means for forming the conductor metal layer, other than chemical plating,
An ordinary circuit forming means such as a vapor phase method such as vapor deposition, sputtering and ion plating or a CVD method can be arbitrarily adopted.

For example, in the case of the chemical plating method, the well-known sentitizing-activation method is used, and the ceramic substrate surface 10
And metallic palladium is deposited on the exposed portion 20 of the resistor layer to activate the surface. The ceramic substrate 1 may be dipped in a chemical copper plating bath or a chemical nickel plating bath to form a copper or nickel metal conductor layer.

When the vapor phase method is adopted, the roughened ceramic substrate 1 is heated to about 400 ° C., a metal layer of Cr or Ti is formed in the first step, and then a metal layer of copper or nickel is formed in the second step. A forming method or the like can be adopted.

Next, in the step, electrolytic plating is performed on the conductor metal layer formed by the chemical plating or the like, if necessary. This is because the chemical plating method or the vapor phase method can form only a thin metal layer having a thickness of about 1 to several μm. Therefore, when it is necessary to increase the thickness of the conductor metal layer, the metal layer formed by chemical plating or the like is used. A thick metal layer of copper or nickel is formed thereon by electrolytic plating.

In the step, as shown in FIG. 5, a circuit is formed on the conductor metal layer by means such as etching, and the conductor circuit 4 is formed.
To form. As the circuit forming means, a general circuit forming method similar to that for a normal circuit board can be adopted. After forming the conductor metal layer on the entire surface of the ceramic substrate 1 as described above, the conductor circuit 4 is formed by etching away the conductor metal layer at unnecessary portions, or by a chemical plating method or a vapor phase method. It is also possible to form the metal conductor layer only in the portions necessary for the conductor circuit 4.

In the method of forming the conductor circuit 4 described in the above steps, the line width is reduced by using a base metal conductor having a smaller wiring resistance than the method of forming the conductor circuit by printing and firing the noble metal conductor paste which has been generally used conventionally. It becomes possible to form an extremely fine circuit pattern having a line interval of about 30 μm.

In addition, since the conductor circuit 4 is formed after the resistor layer 2 is fired, there is no concern that the base metal conductor is oxidized, and it is not necessary to use a nitrogen firing paste as the resistor paste, and Ru ₂ with high accuracy and high reliability is also provided. It becomes possible to use an air-firing paste such as O. Therefore, as the performance of the resistor layer, for example, it is possible to manufacture a highly accurate resistor-equipped ceramic circuit board in which the variation of the resistance characteristic with respect to the circuit constant is within ± 2% at a low price.

In the step, the ceramic substrate 1 on which the conductor circuit 4 is formed is heat-treated in a nitrogen atmosphere, if necessary. The treatment temperature is preferably in the range of 200 to 800 ° C, and more preferably 400 to 700 ° C. The processing time is, for example, about 1 to 100 minutes, but can be appropriately changed depending on the application. Further, the treatment atmosphere may be a nitrogen atmosphere or an atmosphere containing a trace amount of oxygen of about 2 to 200 ppm.

In the process, the resistor layer 2 is trimmed and adjusted to have a predetermined resistance value. As the trimming method, various ordinary trimming means can be adopted, for example,
There are methods such as aggressive trimming and laser trimming. Among them, the laser trimming method, which enables high-speed processing and has high performance, is the most preferable method.

Next, specific examples of manufacturing the ceramic circuit board with the resistor by the manufacturing method of the present invention described above will be described.

Example I As a ceramic substrate, a 96% alumina substrate was used, and the surface thereof had a maximum roughness of 1 by being immersed in hot phosphoric acid.
After roughening to ˜3 μm, it was thoroughly washed and dried. Next, the Ru ₂ O-based resistor paste on the roughened surface of the ceramic substrate was screen-printed, dried, and then fired in air at 850 ° C. to form a resistor layer.

Then, on the resistor layer, except for a part, after screen-printing a glass paste for overcoat and drying,
The protective layer was formed by firing in air at 600 ° C.

Further, the exposed portion of the resistor layer is roughened using a 5% hydrofluoric acid solution, sufficiently washed with water and dried, and then a copper layer is formed by a chemical plating method, and then a copper metal layer is formed by an electrolytic plating method. Thickening was performed to form a metal conductor layer having a thickness of 10 μm. When the adhesion of this metal conductor layer to the ceramic substrate was measured, it showed a high value of 2.0 to 3.0 kg / mm ² .

The metal conductor layer was subjected to pattern etching by using a photolithography technique to form a conductor circuit having a line width and a line spacing of 50 μm. When the resistance characteristic of the obtained resistor layer with respect to the circuit constant was measured, the variation was within ± 2%, which was a highly accurate value. After that, the resistor layer is trimmed using a laser trimmer to adjust to a predetermined resistance value,
Manufacture of ceramic circuit boards with resistors was completed.

Example II The description of the same steps as in Example I is omitted, and the differences are mentioned. A 92% alumina substrate was used as the ceramic substrate, and roughened to a maximum roughness of 2-3 μm with a molten NaOH salt. The firing temperature of the resistor paste was set to 900 ° C, and the firing temperature of the protective layer was set to 580 ° C. Furthermore, 10 is required for roughening the resistor layer.
% Chromic acid solution was used. As the method of forming the conductor circuit, a metal conductor layer having a thickness of 5 μm was formed only by the chemical plating method.

The adhesion of this metal conductor layer to the ceramic substrate is 2.
The value was 0 to 3.0 kg / mm ² , which was a high value as in the above-mentioned Examples. The resistance characteristics of the obtained resistor layer with respect to the circuit constant were also good as in Example I.

Example III The description of the same steps as in Example I is omitted, and the differences are mentioned. A 99% alumina substrate was used as the ceramic substrate, and the roughening treatment conditions were the same. The process of forming the resistor paste is also the same. The protective layer was formed by using a polyimide resin paste as a resin for overcoat and curing it at 240 ° C. to form a protective layer. Further, a 10% sulfuric acid solution was used for roughening the resistor layer. The method of forming the conductor circuit is
After forming the copper layer by the sputtering method, the thickness of the metal copper was increased by electrolytic plating to form a metal conductor layer having a thickness of 10 μm.

The adhesion of this metal conductor layer to the ceramic substrate is 2.
The value was 0 to 3.0 kg / mm ² , which was a high value as in the above-mentioned Examples. Further, the resistance characteristics of the obtained resistor layer with respect to the circuit constant were good within ± 2%.

Example IV The procedure was substantially the same as that of Example II. The difference is that a 96% alumina substrate is used and the resistor paste is directly drawn on the ceramic substrate. When the variation in the resistance value of the obtained ceramic circuit board with a resistor was measured, the result was almost the same as in Example II.

Example V The procedure was substantially the same as that of Example I. The difference is 99%
That is, an alumina substrate was used, and the conductor metal layer was formed to a thickness of 8 μm only by chemical plating. The variation of the resistance value of the obtained ceramic circuit board with resistors is
The results were almost the same as in Example II.

Comparative Example I In this comparative example, the resistor layer was 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 I 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 copper conductor layer was satisfactorily formed by the chemical plating method and the electrolytic plating method. When the adhesion of the copper conductor layer to the ceramic substrate was measured, it was a relatively high value of 1.5 to 2.5 kg / mm ² .

However, due to the roughening treatment, the glass component was attacked and damaged in the exposed portion of the resistor layer. As a result, 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 II This comparative example is a case where the surface of the ceramic substrate together with the resistor layer was roughened under a weak roughening condition suitable for the resistor layer.

The conditions were the same as in Example I 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, the roughening of the surface of the ceramic substrate became insufficient, and during the formation of the copper conductor layer by the chemical plating method, many “blisters” were thought to be caused by poor adhesion between the ceramic substrate and the copper conductor layer. . Therefore, the ceramic circuit board with a resistor could not exhibit sufficient performance.

[Advantages of the Invention] In the method for manufacturing the ceramic circuit board with a resistor according to the present invention described above, the ceramic substrate is roughened by a usual roughening treatment method before forming the resistor layer, and the resistor is The exposed part of the layer is roughened by a relatively weak treatment method that does not adversely affect the resistor layer, thereby preventing the resistor layer from being adversely affected by the strong treatment method for roughening the ceramic substrate. can do. As a result, the adhesion between the ceramic substrate and the conductor circuit can be increased without deteriorating the performance of the resistor layer, which can greatly contribute to the performance improvement of the resistor-equipped ceramic circuit board.

[Brief description of drawings]

FIG. 1 is a process flow chart according to the present invention, and FIGS.
The drawings are schematic cross-sectional views showing sequential process steps. 1 ... Ceramic substrate, 10 ... Roughened surface, 2 ... Resistor layer, 20
... Exposed part, 3 ... Protective layer, 4 ... Conductor circuit

 ─────────────────────────────────────────────────── --Continued from the front page (56) Reference JP-A-55-95396 (JP, A) JP-A-55-86183 (JP, A) JP-A-62-234301 (JP, A) JP-A 61- 185995 (JP, A)

Claims (1)

[Claims] 1. A method of manufacturing a ceramic circuit board in which a resistor is formed on a ceramic substrate together with a conductor circuit, which is characterized in that the following steps are sequentially performed. (1) a step of roughening the surface of the ceramic substrate; (2) a step of forming a resistor layer on the ceramic substrate; (3) a resistor after forming a protective layer on the resistor layer except a part thereof. A step of roughening the exposed portion of the body layer by a treatment method that does not adversely affect the resistor layer under a roughening condition that is weaker than that of the surface of the ceramic substrate; (4) a ceramic substrate including the exposed portion of the resistor layer Of forming a conductor circuit on the surface of the.