JPH11307899A - Thick film circuit board and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain good adhesion for overcoat glass in spite of less manufacturing process. SOLUTION: Copper plating is applied to conductor patterns 12 on the surface of an alumina laminated board 11 to provide plated electrodes 13. A thick film resistor 14 whose both ends are connected with respective plated electrodes is formed on the alumina laminated board 11. Connecting portions 14b of both ends of the thick film resistor 14 are formed in a size that covers the overall plated electrode 13 and responds to variations in the positions of the plated electrodes 13 due to burning shrinkage of the alumina laminated board 11. Overcoat glass 15 is formed so as to cover the overall upper surface of the thick film resistor 14. This provides a simpler process as compared with those wherein a thick film resistor is connected via thick film conductors, and the thick film resistor 14 including glass frit allows good adhesion of the overcoat glass 15.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a thick-film circuit board having a thick-film resistor on a substrate such as a ceramic substrate, and a method of manufacturing the same.

[0002]

For example, the hybrid I
In the case of thick-film circuit boards used for C, etc., copper-plated surface conductors of alumina laminated substrates have been used as electrodes, and compared with gold-plated or nickel-plated electrodes. In addition to being low in cost, it has features of being excellent in bonding with a thick film and solder. As a structure for forming a thick film resistor on such an alumina laminated substrate, there is a technique disclosed in Japanese Patent Application Laid-Open No. 63-107087.

[0003] As shown in Figs. 8 and 9,
A conductor pattern 2 made of tungsten or the like and constituting an elongated rectangular electrode is provided on the surface of the alumina laminated substrate 1, and the surface of the conductor pattern 2 is plated with copper to form a copper-plated electrode 3. The metal (tungsten) constituting the conductor pattern 2 is also provided so as to fill the through hole 1a. A thick copper conductor 4 is formed on the substrate 1 so as to cover the entire copper plating electrode 3, and a thick resistor 5 is formed so as to be connected between the pair of thick conductors 4. Is done. Further, a protective overcoat glass 6 is formed so as to cover the entire thick film conductor 4 and thick film resistor 5.

As described above, in the structure in which the copper thick film conductor 4 is a so-called pillow electrode of the thick film resistor 5, the thick film resistor 5 can be formed without any problem. However, the thick film conductor 4 is printed on the substrate 1 on which the copper plating electrode 3 is formed.
The step of forming by firing, the step of forming the thick film resistor 5 by printing and firing, and the step of forming the overcoat glass 6 must be performed in order, and the number of manufacturing steps increases, which is relatively costly. Had become.

Therefore, another conventional example is disclosed in
There is one disclosed in Japanese Patent No. 146201. In this technique, a thick film resistor is directly connected to a plating electrode. Japanese Patent Publication No. 4-30199 discloses that Cu plating is used as plating, and La plating is used as a thick film resistor.
One using a B6 resistor is shown. According to these, the step of forming the thick film conductor 4 by printing and baking becomes unnecessary, and the step can be simplified to reduce the cost.

However, in these structures, the environment resistance of the resistor is not good because there is no overcoat glass as in JP-A-63-107087. FIGS. 10 and 11 show a structure in which a protective glass is formed on a resistor in these structures. In this structure, a part of the plating electrode 3 is directly covered by the overcoat glass 8, but the adhesion between the surface of the plating electrode 3 and the overcoat glass 8 is extremely weak. (A boundary portion indicated by), the overcoat glass 8 floats up and has a disadvantage that it is easily peeled off.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a thick-film resistor on a substrate, so that the number of manufacturing steps can be reduced.
It is an object of the present invention to provide a thick-film circuit board having excellent overcoat glass adhesion and a method for manufacturing the same.

[0008]

Means for Solving the Problems The reason why the plating electrode has poor adhesion to the overcoat glass is that the surface of the plating electrode is a pure metal, cannot be bonded to the glass, and the surface condition of the plating electrode is low. Is considered to be smooth. On the other hand, the thick film resistor exhibits excellent adhesiveness with the overcoat glass. This is because the thick film resistor is configured to include the glass frit, so that the glass components are bonded so as to fuse with the overcoat glass, and the surface roughness of the thick film resistor is reduced to the plating surface. It is thought to be due to the fact that it is larger than that. The present inventor has achieved the present invention by noting that sufficient adhesion is obtained between such a thick film resistor and overcoat glass.

That is, the thick film circuit board according to the first aspect of the present invention comprises a thick film resistor provided on a substrate such as a ceramic substrate and electrically connected to a plating electrode, and an end portion of the thick film resistor provided on the plating electrode. It is characterized in that it is provided so as to cover the entire top surface.

According to this, since the thick-film resistor is directly connected to the plating electrode without the intervention of the thick-film conductor serving as a pillow electrode, a step required for forming the thick-film conductor becomes unnecessary. The number of manufacturing steps can be reduced, and costs can be reduced. Further, the area on the substrate required for providing the thick film resistor can be reduced. And since the thick film resistor covers the entire upper surface of the plating electrode, the overcoat glass formed so as to cover the thick film resistor,
It does not come into contact with the plating electrode, and exhibits excellent adhesion to the thick film resistor.

According to a second aspect of the present invention, there is provided a thick film circuit board which covers an entire upper surface of a plating electrode on a substrate such as a ceramic substrate with an intermediate thick film resistor having a sheet resistance smaller than that of the thick film resistor. The feature is that the thick film resistor is connected to the intermediate thick film resistor.

According to this, the thick film resistor is connected to the plating electrode via the intermediate thick film resistor. However, the intermediate thick film resistor can be fired simultaneously with the thick film resistor. As compared with the case of forming a thick film conductor, the number of complicated and time-consuming firing steps is reduced by one, and as a result, the number of manufacturing steps can be reduced and the cost can be reduced. Further, the provision of the intermediate thick-film resistor makes it possible to reduce the variation in the resistance value due to the variation in the position of the plating electrode with respect to the thick-film resistor, which is caused by the variation in the firing shrinkage of the substrate. . Since the intermediate thick-film resistor covers the entire upper surface of the plating electrode, the overcoat glass formed so as to cover the thick-film resistor and the intermediate thick-film resistor does not contact the plating electrode. It exhibits excellent adhesion to the thick film resistor and the intermediate thick film resistor.

By considering the displacement of the plating electrode caused by the variation in the firing shrinkage of the substrate, when the entire upper surface of the plating electrode is covered with the thick film resistor or the intermediate thick film resistor as described above, it is not sufficient. It is necessary to provide a thick film resistor or an intermediate thick film resistor over a large area. Here, the plating electrode may be provided in a circular shape (the invention of claim 3). According to this, since the plating electrode can be made relatively small, the entire upper surface of the plating electrode can be formed as a thick film resistor. When covering with a body or an intermediate thick film resistor,
It is possible to reduce the area where the thick film resistor or the intermediate thick film resistor is provided in consideration of the displacement of the plating electrode.

According to a fourth aspect of the present invention, there is provided a method of manufacturing a thick film circuit board, wherein a resistor paste serving as a material of a thick film resistor is formed on a substrate on which a plated electrode is formed. A step of forming a thick-film resistor by baking the resistor paste, and a step of forming an overcoat glass so as to cover the entire thick-film resistor. Having.

According to this, since the thick film resistor is directly connected to the plating electrode, the number of manufacturing steps can be reduced, and the cost can be reduced. Further, the area on the substrate required for providing the thick film resistor can be reduced. Since the thick film resistor covers the entire upper surface of the plating electrode, the overcoat glass formed so as to cover the thick film resistor exhibits excellent adhesion to the thick film resistor. .

According to a fifth aspect of the present invention, there is provided a method of manufacturing a thick-film circuit board, wherein the intermediate-film resistor having a sheet resistance smaller than that of the thick-film resistor is used as a material for the board on which the plated electrode is formed. Applying a resistor paste for covering the entire upper surface of the plating electrode, and applying a resistor paste to be a material of the thick-film resistor so that an end thereof is connected to the intermediate resistor paste. Baking the intermediate resistor paste and the resistor paste to form an intermediate thick-film resistor and a thick-film resistor; and overcoating the intermediate thick-film resistor and the thick-film resistor so as to cover the entirety. And forming a glass.

According to this, the thick-film resistor is connected to the plating electrode via the intermediate thick-film resistor, but the intermediate thick-film resistor can fire the thick-film resistor at the same time. In addition, the number of manufacturing steps can be reduced, and the cost can be reduced. Further, the provision of the intermediate thick-film resistor makes it possible to reduce the variation in the resistance value due to the variation in the position of the plating electrode with respect to the thick-film resistor, which is caused by the variation in the firing shrinkage of the substrate. . Since the intermediate thick-film resistor covers the entire upper surface of the plating electrode, the overcoat glass formed to cover the thick-film resistor and the intermediate thick-film resistor exhibits excellent adhesiveness.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Some embodiments of the present invention will be described below. (1) First Embodiment First, a first embodiment (corresponding to claims 1 and 4) of the present invention will be described with reference to FIGS. 1 and 2 show a configuration of a main part (a part where a thick-film resistor is formed) of the thick-film circuit board according to the present embodiment.

The alumina laminated substrate 11, which is a ceramic substrate, is formed in a multilayer shape from an alumina material (only the surface layer is shown), and has a conductor pattern made of a refractory metal material such as tungsten or molybdenum on its surface. 12 are formed. Also, an inner layer conductor pattern made of the same high melting point metal material is formed between the respective layers. The conductor patterns between the respective layers are connected via through holes 11a (only a part of the surface layer is shown), and the through holes 11a are also buried with the high melting point metal material forming the conductor patterns 12. ing.

Then, copper plating is applied to the conductor pattern 12 on the front surface part, and a part of the plating is provided with a pair at predetermined intervals on the left and right in the figure to connect the thick film resistor. An electrode 13 is provided. At this time, in the plating electrode 13, as shown in FIG. 1, the conductor pattern 12 is formed in a rectangular shape that is long in the front-rear direction with the through hole 11 a as a center, and copper plating is applied to the conductor pattern 12. It is provided so as to cover the entire surface.

On the surface of the alumina laminated substrate 11, there are provided thick film resistors 14 whose both ends are electrically connected to the plating electrodes 13, respectively. At this time, as shown in FIG. 1, the thick-film resistor 14 is made of, for example, a LaB6 resistor, and a main portion 14a, which functions as a resistor when current actually flows, and connecting portions 14b located at both ends thereof. , 1
4b. Of which, the connecting portions 14b at both ends
Is formed in a rectangular shape sufficiently larger than the plating electrode 13 so as to cover the entire plating electrode 13,
Further, the main portion 14a is provided so as to connect the connection portions 14b at both ends thereof with the same width in the front-rear direction as the plating electrode 13.

On the surface of the alumina laminated substrate 11, a protective overcoat glass 15 (for convenience, is shown by a two-dot chain line in FIG. 1) so as to cover the entire upper surface of the thick film resistor 14. ) Is formed. The overcoat glass 15 is provided in a rectangular area sufficiently larger than the area where the thick film resistor 14 is formed.

Here, a procedure for manufacturing the thick film circuit board having the above configuration will be described. First, the alumina laminated substrate 1
1 is performed. Although not shown in detail,
In the step of forming the alumina laminated substrate 11, a through hole 11a is formed in an alumina green sheet forming each layer, and the through hole 11a is filled with, for example, a conductive paste of tungsten. Is applied. Then, after stacking and integrating the green sheets, the green sheets are fired at, for example, 1600 ° C. in a reducing atmosphere.

Thus, the alumina laminated substrate 11 on which the conductor patterns 12 are formed is obtained. Next, a step of performing copper plating on the conductor pattern 12 on the surface of the alumina laminated substrate 11 is performed. In this copper plating step, for example, a well-known electroless plating can be adopted,
Thus, the plating electrode 13 made of copper is formed on the alumina laminated substrate 11.

In the above firing, the alumina laminated substrate 1
For example, firing shrinkage of about 30% occurs in 1, and a certain degree of variation (for example, about ± 0.1 to ± 1%) occurs in the dimensions of the alumina laminated substrate 11 after firing. Therefore, as shown exaggeratedly in FIG.
The dimensions and formation positions of the upper conductor pattern 12 and thus the plating electrode 13 also vary to some extent as exemplified by reference numerals 13 'and 13 "in the figure.

Then, the step of forming the thick film resistor 14 on the alumina laminated substrate 11 is performed.
Here, first, a resistor paste as a material of the thick film resistor 14 is applied on the alumina laminated substrate 11 in the shape of the thick film resistor 14 by, for example, screen printing, dried, and then fired in a nitrogen atmosphere. Is done.

Thus, the thick film resistor 1 in which the connection portions 14b at both ends are connected so as to cover the plating electrodes 13 and 13, respectively.
4 is formed. At this time, as described above, the resistor paste is printed accurately at a predetermined position on the alumina laminated substrate 11 by screen printing, while the conductor pattern 12 on the alumina laminated substrate 11 is printed as described above.
The size and formation position of the plating electrode 13 (and thus the plating electrode 13) vary to some extent, as indicated by reference numerals 13 'and 13 "in Fig. 3. However, the connection portion 14b is sufficiently larger than the plating electrode 13. Since it is configured in a rectangular shape, the entire plating electrode 13 can be reliably covered by the connection portion 14b.

Finally, a step of forming the overcoat glass 15 is performed. This step is performed by applying a glass paste by, for example, screen printing so as to cover the whole of the thick film resistor 14 and baking it in a reducing atmosphere or a neutral atmosphere. However, at this time, since the thick film resistor 14 contains a glass component (glass frit), the glass component is adhered so as to fuse with the overcoat glass 15 and the thick film resistor 14 A high adhesive strength with the coat glass 15 can be obtained. The relatively rough surface state of the thick film resistor 14 also contributes to the improvement of the adhesive strength.

In the above configuration, the thick film resistor 14 is
Since it is directly connected to the plated electrode 13, it is necessary for forming the thick film conductor 4 unlike the conventional one in which the thick film resistor 5 as shown in FIGS. 8 and 9 is connected via the thick film conductor 4. Unnecessary steps become unnecessary. Also, since the thick film conductor 4 is not required,
The area on the alumina laminated substrate 11 required for providing the thick film resistor 14 can be reduced.

Then, the thick film resistor 14 is
10 and 11, the overcoat glass 8 is in contact with the copper-plated electrode 3 as shown in FIGS.
Overcoat glass 15 formed so as to cover
It does not come into contact with the plating electrode 13 and exhibits excellent adhesiveness to the thick film resistor 14, so that it does not float or peel off.

Therefore, according to this embodiment, the thick film resistor 14 is provided on the alumina laminated substrate 11, so that the number of manufacturing steps can be reduced and the cost can be reduced. The practical effect that the coated glass 15 has excellent adhesiveness can be obtained.

(2) Second Embodiment Next, a second embodiment (corresponding to claims 2 and 5) of the present invention will be described with reference to FIGS. In this embodiment, since the configuration of the alumina laminated substrate 11 and the like are the same as those in the first embodiment, the same parts as those in the first embodiment are denoted by the same reference numerals, and detailed description is omitted. Hereinafter, different points will be mainly described.

The thick-film circuit board according to the present embodiment also has a conductor pattern 12 on the surface of an alumina laminated board 11, and the conductor pattern 12 is plated with copper to form a plating electrode 13. The upper surfaces of the pair of plating electrodes 13 are respectively covered with the intermediate thick film resistors 21, and the thick film resistors 22 are formed so as to extend between the intermediate thick film resistors 21 and 21. . Further, an overcoat glass 23 is provided so as to cover the entire intermediate thick film resistor 21 and thick film resistor 22.

At this time, the intermediate thick-film resistor 21 is made of the same material (LaB6 resistor) as the thick-film resistor 22 and has a sheet resistance smaller than that of the thick-film resistor 22. You. Incidentally, in this embodiment, the sheet resistance of the thick film resistor 22 is, for example, 10 kΩ / □, whereas the sheet resistance of the intermediate thick film resistor 21 is, for example, 10Ω / □. If the material of the intermediate thick film resistor 21 is made equal to the material of the smallest sheet resistance value among the other resistors formed on the alumina laminated substrate 11, the formation can be performed without increasing the printing process. It becomes possible.

The intermediate thick-film resistor 21 is formed in a rectangular shape which is sufficiently larger than the plating electrode 13 and covers the entire plating electrode 13. Even if there is some variation in the position, the intermediate thick film resistor 21 can reliably cover the entire plating electrode 13. The thick-film resistor 22 has a slightly smaller width than that of the thick-film resistor 22 and is formed such that both ends are connected to the intermediate thick-film resistor 21.

In manufacturing the thick film circuit board having the above-described structure, the alumina laminated board 11 is formed in the same process as in the first embodiment, and the plating electrode 13 is formed.
Then, on the alumina laminated substrate 11 on which the plated electrodes 13 are formed, first, a step of applying a resistor paste serving as a material of the intermediate thick-film resistor 21 by, for example, screen printing and drying is performed. Thick film resistor 2
A step of applying a resistor paste as the material No. 2 by screen printing and drying is performed.

Thereafter, a baking step is performed in a nitrogen atmosphere, whereby the intermediate thick film resistor 21 and the thick film resistor 22 are formed on the alumina laminated substrate 11. Thereafter, a glass paste is applied by screen printing so as to cover the entire intermediate thick-film resistor 21 and the thick-film resistor 22, and baked in a reducing atmosphere or a neutral atmosphere to form the overcoat glass 23. The process is performed. At this time, since the intermediate thick-film resistor 21 and the thick-film resistor 22 contain a glass component (glass frit), the glass component is bonded so as to fuse with the overcoat glass 23 and has a high adhesive strength. Is obtained.

As described above, according to the present embodiment, the intermediate thick-film resistor 21 can be fired simultaneously with the thick-film resistor 22, so that the thick-film conductor 4 can be formed as compared with the conventional case where the thick-film conductor 4 is formed. The number of firing steps is reduced by one, and as a result, the number of manufacturing steps can be reduced, and cost can be reduced. Then, the intermediate thick film resistor 21 is
3, the overcoat glass 23 formed so as to cover the thick-film resistor 22 and the intermediate thick-film resistor 21 has excellent adhesiveness and floats or peels off. This can be prevented beforehand.

Further, in the present embodiment, the provision of the intermediate thick-film resistor 21 makes it possible to form the plating electrode 13 due to the variation in the firing shrinkage of the alumina laminated substrate 11 as compared with the first embodiment. Variations in the resistance value due to the displacement can be reduced.

That is, in the thick film resistor 14 of the first embodiment, since the connection portion 14b is wide in the front-rear direction in the drawing, a current flows from one plating electrode 13 to the other plating electrode 13. When flowing, the plating electrode 13 is
When the plating electrode 13 in the connection portion 14b is deviated in the front-rear direction in the drawing, a part of the current flows through the connection portion 13b.
The resistance value varies depending on the position of the plating electrode 13 such that the current flows around the corner between the a and the main portion 13b and the resistance becomes larger. In contrast,
By interposing the intermediate thick film resistor 21 having a sufficiently small sheet resistance value, the variation in the resistance value due to the variation in the position of the plating electrode 13 near the plating electrode 13 which causes the variation in the resistance value is reduced. You can do it.

(3) Third Embodiment FIGS. 6 and 7 show a third embodiment of the present invention.
). This embodiment differs from the first embodiment in that the plating electrode 31 (and thus the conductor pattern 32) formed on the alumina laminated substrate 11 is formed in a small size instead of having a long rectangular shape in the front-rear direction. The point is that it is circular.

The thick-film resistor 33 is provided so that both ends thereof cover the entire upper surface of the plating electrode 31, respectively. In this case, the thick-film resistor 33 is entirely the same in the front-rear direction. It is formed in a rectangular shape that is horizontally long in width. Further, an overcoat glass 34 is provided so as to cover the entire thick film resistor 33. Incidentally, such a thick film circuit board is manufactured by the same process as in the first embodiment.

According to such a configuration, the plating electrode 31
Can be made relatively small as compared with the case of a rectangular shape, so that the entire upper surface of the plating electrode 31 is covered with the thick film resistor 33.
In this case, it is possible to reduce the size of the connection portion in the front-rear and left-right directions. Therefore, the effect that the area on the alumina laminated substrate 11 necessary for providing the thick film resistor 33 can be reduced can be obtained. As in the case of the first embodiment and the like, it goes without saying that good adhesiveness of the overcoat glass 34 can be obtained while reducing the number of manufacturing steps.

In the third embodiment, the thick film resistor 3
3 is configured to cover the entire upper surface of the plating electrode 31, but as in the second embodiment, the plating electrode 31 is covered with an intermediate thick-film resistor, and the thick-film resistor is interposed through the intermediate thick-film resistor. May be connected so that the same operation and effect can be obtained.

In addition, the present invention is not limited to the above embodiments. For example, the substrate is not limited to an alumina laminated substrate, but may be another ceramic substrate, a glass substrate, a glass ceramic substrate, or the like. The material, sheet resistance, shape, and the like of the thick-film resistor and the intermediate thick-film resistor can be variously modified and appropriately changed without departing from the gist.

[Brief description of the drawings]

FIG. 1 shows a first embodiment of the present invention and is a plan view of a main part of a thick film circuit board.

FIG. 2 is a longitudinal sectional front view of a main part.

FIG. 3 is a plan view showing a state in which the position of a plating electrode varies with respect to a thick film resistor.

FIG. 4 is a view corresponding to FIG. 1, showing a second embodiment of the present invention;

FIG. 5 is a diagram corresponding to FIG. 2;

FIG. 6 is a view corresponding to FIG. 1, showing a third embodiment of the present invention.

FIG. 7 is a diagram corresponding to FIG. 2;

FIG. 8 is a diagram corresponding to FIG. 1 showing a conventional example.

FIG. 9 is a diagram corresponding to FIG. 2;

FIG. 10 is a diagram corresponding to FIG. 1 showing another conventional example.

FIG. 11 is a diagram corresponding to FIG. 2;

[Explanation of symbols]

In the drawing, 11 is an alumina laminated substrate (ceramic substrate),
12 and 32 are conductor patterns, 13 and 31 are plating electrodes,
Reference numerals 14, 22, and 33 indicate thick film resistors, 15, 23, and 34 indicate overcoat glass, and 21 indicates an intermediate thick film resistor.

Claims (5)

[Claims] A thick film resistor electrically connected to a plating electrode is provided on a substrate such as a ceramic substrate, and the thick film resistor and a plating electrode portion are covered with an overcoat glass. A thick-film circuit board, wherein the thick-film resistor is provided so that an end thereof covers the entire upper surface of the plating electrode. 2. A thick-film resistor electrically connected to a plating electrode is provided on a substrate such as a ceramic substrate, and the thick-film resistor and a plating electrode portion are covered with an overcoat glass. The whole upper surface of the plating electrode is covered with an intermediate thick-film resistor having a sheet resistance smaller than that of the thick-film resistor, and the thick-film resistor is formed on the intermediate thick-film resistor. A thick film circuit board which is connected. 3. The thick film circuit board according to claim 1, wherein the plating electrode is provided in a circular shape. 4. A method for manufacturing a thick film circuit board having a thick film resistor electrically connected to a plating electrode on a substrate such as a ceramic substrate, wherein the plating electrode is formed. Applying a resistor paste, which is a material of the thick film resistor, onto the substrate so that an end thereof covers the entire upper surface of the plating electrode; and baking the resistor paste to form a thick film resistor. A method for manufacturing a thick film circuit board, comprising: forming a body; and forming an overcoat glass so as to cover the entire thick film resistor. 5. A method for manufacturing a thick film circuit board having a thick film resistor electrically connected to a plating electrode on a substrate such as a ceramic substrate, wherein the plating electrode is formed. For the substrate, a step of applying an intermediate resistor paste that is a material of an intermediate thick film resistor having a smaller sheet resistance value than the thick film resistor so as to cover the entire upper surface of the plating electrode, A step of applying a resistor paste as a material of the thick-film resistor so that an end thereof is connected to the intermediate resistor paste; and baking the intermediate resistor paste and the resistor paste to obtain an intermediate thickness. A step of forming a film resistor and a thick film resistor; and a step of forming an overcoat glass so as to cover the entire intermediate thick film resistor and the thick film resistor. Production method.