JPH03109793A - Manufacture of wiring circuit board with resistor - Google Patents

Abstract

PURPOSE:To prevent a resistor layer from undergoing a bad influence in a formation process of a conductor circuit by covering the upper part of the resistor layer formed on a ceramic insulated board. CONSTITUTION:A resistor layer 20 is formed on a ceramic insulated board 10 and a glass protective layer 40 is formed covering the resistor layer 20 followed by forming a conductor circuit layer 50 for being given heat treatment. That is, the upper part of the resistor layer 20 is in advance covered with the glass protective layer. Thereby, by dipping in an electroless plating bath, or the like in a formation process of the conductor circuit layer 50, erosion of the resistor layer 20 and bad influence thereon can be surely prevented thus to well maintain reliability of the resistor layer 20.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for manufacturing a wired circuit board with a resistor,
More specifically, the present invention relates to a method for manufacturing a wired circuit board with a resistor, which includes a conductor circuit layer made of a fully bent conductor such as copper, and a resistor layer serving as a resistor element in the circuit.

[Conventional technology]

Conventionally, in order to incorporate a resistance element into the wiring circuit of a printed circuit board, the terminals of the separately manufactured resistance element are connected by soldering or the like to the printed circuit board on which a conductor circuit has been formed using circuit forming means such as plating. It was equipped. On the other hand, in recent years,
A method was devised to form a resistor layer directly on the substrate by applying a resistor paste made of a material with high electrical resistance to an insulating substrate by printing or other means, and then firing the resistor paste. A wired circuit board with a resistor has been proposed in which a resistor layer is formed on the wired circuit board at the same time as a normal conductive circuit layer.

An example of a method for manufacturing such a wired circuit board with a resistor will be explained.

First, after chemically roughening the surface of the ceramic substrate, Pd is planted. Next, the substrate is immersed in an electroless copper plating solution to form a conductive metal layer of copper on the surface of the substrate. A conductive circuit layer is formed by etching this conductive metal layer according to a desired wiring pattern. moreover,
To form a resistor layer, a resistor paste is applied to a predetermined position and then fired, but there is a problem in that the copper in the conductor circuit layer is oxidized by the heating during firing. Therefore, in order to prevent oxidation of copper, it is necessary to sinter the resistor paste in an N8 atmosphere. As the resistor paste, N2 sintered type resistor paste, for example, T i S i z series, LaB series, strontium
A ruthenate-based resistor paste is used.

Among the resistor pastes, there is also a ruthenium oxide-based resistor paste that is fired in the atmosphere, and is known to have superior performance such as reliability compared to the N2 fired type. However, as mentioned above, in order to prevent copper from oxidizing, it is not possible to bake it in the atmosphere, so this ruthenium oxide-based resistor paste cannot be used for printed circuit boards with resistors as described above. I could not do it.

Therefore, at present, N2 firing type resistor paste is used, which is temporary, so only resistors with low reliability can be formed.Also, since it is not in the atmosphere, special atmosphere control and an atmosphere furnace are required, making the work difficult. It was difficult and expensive to manufacture. Furthermore, there was also the problem that the organic binder in the resistor paste was easily carbonized.

Therefore, a method was devised in which a resistor layer was first formed on an insulating substrate, and then a conductive metal layer made of copper was formed.
It is disclosed in JP-A No. 3-28094, JP-A-63-202987, and the like.

In these methods, a ruthenium oxide resistor paste is first applied to a ceramic substrate and fired in the atmosphere to form a resistor layer, and then a copper conductor layer is formed over the entire surface of the board, including the resistor part. This conductive layer is patterned to form a conductive circuit layer.

With this method, there is no fear that copper will oxidize, so a ruthenium oxide resistor paste with excellent performance such as reliability can be used.

In the above method, it has also been proposed to improve the connectivity between the resistor layer and the conductor circuit layer by interposing a connection layer such as silver palladium at the connection portion between the resistor layer and the conductor circuit layer.

[Problem to be solved by the invention]

However, in the prior art method described above, the ceramic substrate is immersed in a high-temperature, highly alkaline electroless copper plating bath while the resistor layer formed on the ceramic substrate is bare. There was a problem that the reliability of the resistor layer was lowered due to adverse effects such as being eroded by the plating liquid.

Furthermore, since the bonding force between the resistor layer and the conductive circuit layer is not sufficient, there is also the problem that the connection reliability between the two is poor. As mentioned above, it has been considered to provide a connection layer between the resistor layer and the conductor circuit layer to improve bonding properties, but in this case as well, the resistor layer and the conductor circuit layer are connected via the connection layer. Since the connection was made only mechanically, the bonding performance was not significantly improved, and the connection reliability was still inferior.

Therefore, an object of the present invention is to solve the problems of the prior art described above, to prevent the resistor layer from being adversely affected in the process of forming the conductor circuit layer, and to improve the connection performance between the resistor layer and the conductor circuit layer. It is an object of the present invention to provide a method for manufacturing a printed circuit board with a resistor having high reliability.

[Means to solve the problem]

A method for manufacturing a wired circuit board with a resistor according to the present invention that solves the above problems is a method for manufacturing a wired circuit board with a resistor in which an insulating substrate is provided with a conductor circuit layer and a resistor layer, the ceramic insulating substrate After forming a resistor layer and forming a glass protective layer covering the resistor layer, a conductor circuit layer is formed and then heat treatment is performed.

The method of the invention will now be described in detail with reference to the accompanying drawings, which illustrate embodiments of the invention.

As shown in step (2), a ceramic insulating substrate 1° is prepared. As the ceramic insulating substrate 10, an insulating substrate made of various ceramic materials similar to ordinary wiring boards, such as a 96% alumina substrate, is used. By chemically or physically roughening the surface of the substrate 10, when a conductive circuit layer is formed thereon, the adhesion between the insulating substrate and the conductive circuit layer can be improved. This roughening treatment creates a kind of anchor effect between the conductive circuit layer and the insulating substrate, thereby increasing their adhesion to each other and effectively preventing defects such as blistering and peeling. A specific example of the roughening treatment includes a method of immersing the substrate 10 in phosphoric acid heated to 250 to 330°C for 2 to 20 minutes.

As shown in step (B), a resistor layer 20 is formed. In order to form the resistor layer 20, various resistor pastes similar to those for ordinary printed circuit boards with resistors are used, and the resistor paste is applied in a predetermined pattern onto the insulating substrate 10, and then baked. be done. Firing temperature is 800-9
The temperature is preferably about 50°C. The resistor paste used is made of a material that can be fired in the atmosphere, such as ruthenium oxide.

In order to improve the connectivity between the resistor layer 20 and the conductor circuit layer, Ag/P is applied to the connection point between the resistor layer 20 and the conductor circuit layer.
A connection layer 30 made of a conductive metal such as d can be formed in advance. For example, before applying the resistor paste, a conductor paste that will become the connection layer 30 is applied to the surface of the board at the connection point, and then the resistor paste is applied so as to partially cover it, and then fired. As a result, a portion of the connection layer 30 is formed in a state where the end portion of the resistor layer 20 covers a portion thereof.

Note that, contrary to the above, the resistor layer 20 may be placed downward and its end portion may be covered with a portion of the connection layer 30. A conductor circuit layer is formed so as to be bonded to such a connection layer 30.

Step (As shown in Q, a glass protective layer 40 is formed to cover the resistor layer 20. The glass protective layer 40 covers the entire resistor layer 20 except for the connection portion with the conductor circuit layer.
It is formed by applying a dielectric glass paste such as borosilicate type and then firing it.

The firing temperature is preferably about 800 to 950°C.

The thickness of the formed glass protective layer 40 is 20 to 50 μm
degree is preferred. In addition, when forming the connection layer 30 as described above, the glass protection N40 covers the resistor layer 2 except for a part of the connection Jfi 30 that connects to the conductor circuit layer.
0 and up to the connection layer 30.

The glass protective layer 40 is preferably one that can reliably protect the resistor layer 20 from the electroless plating bath and can also satisfactorily prevent the entire resistor JWi 20 from being reduced in the heat treatment process. A material having chemical durability such as alkalinity is used.

As shown in step (D), a conductive circuit layer 50 is formed.

The conductor circuit layer 50 is formed by, for example, a conventional film method such as an electroless plating method in which Pd nuclei are implanted on the entire surface of the substrate 10 by immersion in an electroless plating bath or a sputtering method using the well-known Scentsy Act method. After forming a conductive metal layer such as copper or nickel using a forming method, by etching,
A predetermined circuit pattern is formed. Further, if sputtering is performed after covering the insulating substrate 10 with a mask corresponding to the wiring circuit pattern, etching is not necessary. In addition, the method for forming the conductive circuit [50] can be carried out in the same manner as for a normal printed circuit board. The thickness of the conductor circuit layer 50 is
Although it can be set arbitrarily as necessary, for example, it can be formed to a thickness of about 50 mm using the electroless plating method. If it is necessary to increase the thickness of the conductive circuit layer 50, a thick conductive metal may be applied on the electroless plating by electrolytic plating. The conductor circuit layer 50 extends from the surface of the insulating substrate 10 to the glass protective layer 40 of the resistor layer 20 or the connection layer 30.
The conductive circuit layer 50, the resistor layer 20, and the connection layer 30 are electrically connected to each other.

The insulating substrate 10 on which the resistor layer 20 and conductor circuit layer 50 are formed in this way is heat-treated at 500 to 950°C. The heat treatment temperature is preferably lower than the firing temperature of the resistor layer 20 and the glass protective layer 40. The heat treatment is
It is preferable to carry out in a nitrogen atmosphere containing 1100 pp or less of oxygen. By performing heat treatment in such an atmosphere, oxidation of the conductive circuit layer 50 can be prevented and the adhesion between the ceramic insulating substrate 10 or the resistor layer 20 and the conductive circuit layer 50 can be improved.

When the heat treatment is completed, the resistor layer 20 is trimmed with a laser or the like to adjust the resistance to a predetermined value, and then the entire surface of the board 10 is coated with a solder resist, etc., in the same process as a normal printed circuit board. Through these steps, a printed circuit board with a resistor is completed.

[For production]

By covering the resistor layer formed on the ceramic insulating substrate with a glass protective layer, the resistor layer will not be eroded or adversely affected by immersion in an electroless plating bath during the process of forming the conductive circuit layer. It is possible to reliably prevent this from occurring, and it is possible to maintain good performance such as reliability of the resistor layer. Further, in the present invention, a heat treatment step is performed after forming the conductor circuit, but the glass protective layer can also prevent the entire resistor layer from being reduced by this heat treatment step.

By heat-treating the insulating substrate on which the resistor layer and the conductor circuit layer are formed, the connectivity between the resistor layer and the conductor circuit layer can be improved. This is because the metal constituting the conductor circuit layer diffuses into the connection part with the resistor layer or the connection layer provided between the resistor layer and the conductor circuit layer due to heat treatment.
It is thought that the integrity of the joint portion is improved. Moreover, chemical bonding also occurs between the conductor circuit layer and the ceramic insulating substrate, improving adhesion.

〔Example〕

Next, specific embodiments of the invention will be described.

Example 1 It was carried out according to the illustrated steps (--(D)).

Commercially available 96% alumina substrate 10 (size 100x100
An Ag/Pd conductor paste and a ruthenium oxide resistor paste, which will serve as a connection layer, were sequentially applied to predetermined positions on the surface of the X0.8n) by screen printing. After drying, the resistor layer 20 and the connection layer 30 were formed by firing at 850° C. in the air [steps (4) to (g))].

The resistor layer 20 is made of borosilicate dielectric glass paste.
It was applied by screen printing. glass paste is
The entire resistor layer 20 and a part of the connection layer 30 were covered. After drying the glass paste, 85
A glass protective layer 40 having a thickness of 30 mm was formed by firing at 0''C [Step (0)].

A metal mask having a predetermined wiring pattern is placed on the substrate 10, and a conductor circuit layer 50 having a predetermined wiring circuit pattern is formed to a thickness of approximately Ion on the surface of the substrate including the exposed portion of the connection layer 30 by high-speed sputtering. I did [process■
)].

The substrate 10 is placed in a nitrogen atmosphere containing 1100 pp of oxygen.
Heat treatment was performed at 800°C.

Finally, the resistor layer 20 was trimmed using a laser to adjust the resistance to a predetermined value, and then a solder resist was applied to the entire surface of the substrate 10 to complete a resistor-attached wired circuit board.

The obtained printed circuit board has excellent performance, such as high performance and reliability such as the resistance value of the resistor layer 20, and high adhesion between the conductive circuit layer 50 and the insulating substrate 10 and the connection layer 30. there were.

Example 2 - A wired circuit board with a resistor was manufactured through the same steps as in Example 1 except that the Ag/Pd connection layer 30 was not formed. Note that when forming the glass protective layer 40 on the resistor layer 20, the resistor 520 is formed while leaving a portion of the connection portion necessary for connection with the conductive circuit layer 50 at both ends of the resistor layer 20. The top was covered with a glass protective layer 40.

Therefore, the conductor circuit layer 50 does not involve the connection layer 30,
It was directly bonded to the exposed portion of the resistor layer 20.

The obtained printed circuit board with a resistor had excellent performance similar to that of Example 1. Note that the connection portion of the resistor layer 20 with the conductor circuit layer 50 is reduced in the heat treatment process, so that good electrical conductivity with the copper metal of the conductor circuit 50 formed on the connection portion is achieved. It had become.

Example 3 Commercially available 96% AI□02 substrate (100x100x0.8
1 m) in a phosphoric acid solution heated to 300° C. for 4 minutes to roughen the surface of the insulating substrate 10, and then add a ruthenium oxide resistor paste and an Ag conductor paste to serve as the contact VEFj 30 to the substrate in this order. Ten predetermined positions were screen printed. That is, the resistor paste was applied in such a way that both ends of the resistor paste were covered with the connection paste. After that, 90 in the atmosphere
The resistor layer 20 and the connection layer 30 were formed by firing at 0°C.

A glass protective layer 40 was formed in the same process as in Example 1.

Next, the entire surface of the substrate 10 was treated with a Pd core material by the known Sensi-Acchi method, and then immersed in a high-speed electroless copper plating bath to form a conductive metal layer of about 10 μm. Next, a conductive circuit layer 50 having a predetermined wiring circuit pattern was formed by ordinary etching. Further, a heat treatment process similar to that in Example 1 was performed to complete a wired circuit board with a resistor. The obtained printed circuit board had excellent performance similar to Example 1.

Example 4 In Example 3, in the process of forming the conductor circuit ff150,
A printed circuit board with a resistor was manufactured in the same process as in Example 3, except that a conductor circuit [50] having a thickness of about 10 μm was formed by high-speed sputtering without using the high-speed electroless plating method. A product having excellent performance similar to No. 3 was obtained.

Example 5 In Example 3, the process was the same as in Example 3, except that the insulating substrate 10 was a substrate with a through hole of 0.3 mm diameter made by laser processing at a predetermined position. . The ruthenium oxide resistor paste was fired at a temperature of 900°C, and Ag was used as the conductor paste for the connection layer.
/Pd paste was used and fired at 850°C. Further, the dielectric glass paste was fired at 850°C.

As a result, the wiring circuit board with a resistor obtained in Example 3
It had excellent performance as well. Further, in this example, a through hole that conducts both sides of the insulating substrate 10 can be formed by the through hole, and it has been confirmed that the present invention can be applied to a double-sided wiring circuit board.

Comparative Example 1 In Example 3, a glass protective layer 4 is provided on the resistor layer 20.
A wired circuit board with a resistor was manufactured through the same process except that 0 was not formed.

As a result, after high-speed electroless copper plating, the resistance value of the resistor layer 20 became much larger than the predetermined value, and the resistor layer 20 could no longer exhibit sufficient performance. This seems to be because the high-speed electroless plating solution is high temperature and highly alkaline, so the resistor layer 20 was eroded. Furthermore, during the heat treatment, the entire resistor layer 20 is reduced, making it unable to function as a resistor.

〔Effect of the invention〕

According to the above-described method for manufacturing a printed circuit board with a resistor according to the present invention, since the resistor layer formed on the ceramic insulating substrate is covered with the glass protective layer, the formation process of the conductor circuit layer So, when immersed in an electroless plating bath,
The glass protective layer can reliably protect the resistor layer from being affected by adverse effects such as erosion. Further, it is also possible to effectively prevent the entire resistor layer from being reduced in the subsequent heat treatment step. As a result, it is possible to provide a printed circuit board including a resistor layer with excellent performance such as reliability.

Furthermore, by applying heat treatment after forming the resistor layer and conductor circuit layer, it is possible to improve the adhesion between the conductor circuit layer and the surface of the insulating substrate or between the conductor circuit layer and the resistor layer, thereby ensuring continuity of the wiring circuit. Therefore, it is possible to provide a wired circuit board with a resistor that has excellent performance and reliability.

In the method of this invention, the resistor layer is formed before forming the conductor circuit layer, so even if the resistor layer is fired in the atmosphere, the problem of oxidation of the conductor metal of the conductor circuit does not occur. . Therefore, as the resistor layer, it becomes possible to use an air-fired resistor paste such as a ruthenium oxide based resistor paste which has excellent performance such as reliability, and can greatly contribute to improving the performance of the resistor layer.

[Brief explanation of drawings]

The figures are cross-sectional views showing an embodiment of the present invention in the order of steps. 10... Ceramic insulating substrate 20... Resistor layer 3
0... Connection layer 40... Glass protective layer 50...
conductor circuit layer

Claims (1)

[Claims] 1. A method for manufacturing a wired circuit board with a resistor including a conductive circuit layer and a resistor layer on an insulating substrate, the resistor layer being formed on a ceramic insulating substrate, and a glass protective layer covering the resistor layer. A method for manufacturing a wired circuit board with a resistor, the method comprising: forming a conductor circuit layer and then subjecting it to heat treatment.