JP2760035B2 - Thick film circuit board - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a thick film circuit board having a thick film hybrid IC circuit.

(Prior Art) Conventionally, a thick film circuit board in which a conductive layer, a resistor layer, an insulator layer, and the like are formed on a ceramic substrate such as alumina by a screen printing method is known. , For example, as shown in FIG.

The method of manufacturing this thick-film circuit board will be described. First, for example, an Ag-based conductor paste is printed on an insulating substrate 1 formed of a ceramic material such as alumina by a screen printing method, and is then placed in an oxidizing atmosphere at 800 to 900 mm. The conductor layer 2 is formed by baking in a temperature range of ° C. Next, a resistor paste of, for example, ruthenium oxide is printed on the insulating substrate 1 so as to overlap the conductor layer 2 and baked in a temperature range of 800 to 900 ° C. to form the resistor layer 3. Also, usually, a protective glass paste is printed on the conductor layer 2 and the resistor layer 3, and the temperature is 450 to 600 ° C.
To form a protective glass layer.

In this case, the resistance value R of the resistor layer 3 is adjusted to a design value by the sheet resistance of the resistor paste and the shape of the resistor. Here, as shown in FIG. 3, for example, assuming that the length of the resistor is L and the width of the resistor is W, when a resistor having a resistance value R of, for example, R = 10 kΩ is formed, the sheet resistance is 10 kΩ.
A resistive paste of Ω / □ is printed and baked so that L = 1 mm and W = 1 mm. If the resistance value needs to be finely adjusted, the resistance value is adjusted to a set value by a laser trimming method or the like.

(Problems to be Solved by the Invention) However, the conventional thick film circuit board using the alumina insulating substrate described above has a problem called a resistor shape effect. Here, the “shape effect” means that the sheet resistance of a resistor obtained by printing and printing on a substrate differs depending on the shape of the resistor. In addition, as shown in FIG. 4, for example, it is generally known that the relationship between the length L of the resistor and the sheet resistance varies depending on the combination of the conductor and the resistor.

For this reason, in the case of a commercially available resistor, the shape effect may be described in the catalog data. In this case, the user can design a pattern based on the description of the catalog data. However, in practice, the shape effect is slightly different due to the different printing conditions for each user, so the user must perform pattern design after confirming the shape effect with a test pattern, which makes pattern design complicated. It tends to be.

Also, as is well known, with the recent miniaturization and high performance of electronic devices, thick film circuit board materials are required to have materials with higher thermal conductivity, lower thermal expansion, and lower dielectric properties than alumina, Various types of alumina nitride substrates and low-temperature fired substrates (LFC substrates) have been developed as suitable substrate materials.

However, according to an experiment conducted by the present inventors, when a commercially available conductor and a commercially available resistor are used for an alumina nitride substrate or an LFC substrate, cracks occur in the resistor at the boundary between the resistor and the conductor when the resistor is baked. It has been found that cracking of the resistor is unlikely to occur when printing only the resistor on the substrate without a conductor. Regarding the shape effect, the aluminum nitride substrate and the LFC substrate exhibited the same effect as the alumina substrate.

Here, the effect of the conductor on the resistor to generate a shape effect of the resistor and the occurrence of cracks in the resistor are defined as “electrode effect”.

The cause of the electrode effect is due to the diffusion of components from the conductor into the resistor when the resistor is baked, which changes the electrical and thermal properties of the resistor in the vicinity of the conductor due to deterioration of the resistor. it is conceivable that. More specifically, the cause of the shape effect is a main component in the conductor.
This is probably due to the reaction between Ag and the resistor. On the other hand, the occurrence of cracks is thought to be due to the reaction between the glass component in the conductor film and the resistor. However, in order to satisfy the conductor characteristics (solderability, ensuring the adhesion strength to the substrate),
Since additives such as Bi ₂ O ₃ , glass, and transition metal oxides are indispensable, the glass in the conductor film can be extremely reduced,
Also, the composition cannot be changed significantly.

The present invention has been made in view of the above circumstances, and has a structure in which a thick film circuit board has a structure in which the electrode structure has almost no electrode effect, cracks do not occur during manufacturing, and the characteristics of the conductor are not impaired. It is an object of the present invention to provide a method for manufacturing a film circuit board. (Means for Solving the Problems) A method for manufacturing a thick film circuit board according to the present invention for solving the above-mentioned problems is provided on a ceramic insulating substrate. A thick-film circuit board provided with a silver-based conductor layer and a resistor layer, wherein the silver-based conductor layer comprises a first conductor layer and a second conductor layer,
Is formed so as not to overlap with the resistor layer,
The second conductor layer is formed so that a part thereof overlaps a part of the first conductor layer and a part of the resistor layer, and forms the first conductor layer and the resistor layer by 800 to 900. Sintering in an atmosphere at a temperature of 500 ° C.
Characterized by sintering in an atmosphere of

Here, a material suitable for the first conductor layer is a material having good conductor properties such as solder wettability, solder resistance, and durable adhesive strength after soldering, for example, Ag-Pd, Ag-Pt
It is desirable to use a high temperature baking paste with a baking temperature of 800-900 ° C in the system.

The material suitable for the second conductor layer has a baking temperature lower than the softening temperature of the resistor glass (for example, 650 ° C. or lower), glass and metal oxides other than Ag as little as possible, and Ag and glass components diffuse into the resistor. It is desirable to use a material that is difficult to perform, has sufficient Ag sintering, and has a sufficiently low sheet resistance (for example, 20 mΩ / □ or less).

The protective glass layer may be formed by printing a protective glass paste on the first conductor layer, the second conductor layer, and the resistor layer, and baking the paste at 450 to 600 ° C. is there.

Hereinafter, the present invention will be described in detail with reference to the drawings.

The basic structure of the thick-film circuit board according to the present invention is as shown in FIG. 1, and the thick-film circuit board 20 includes a first conductor layer 22 formed on an insulating substrate 21 and a A resistor layer 23 formed so as not to overlap the first conductor layer 22, and a portion on the first conductor layer 22 and a portion on the resistor layer 23 on the insulating substrate 21. It consists of a second conductor layer 24 with a small electrode effect formed.

The thick film circuit board having such a structure was tested in comparison with the conventional one. Materials used in Examples and Comparative Examples of the present invention are common and are as shown below.

The “insulating substrate” is a low-temperature fired substrate containing alumina as a main component, and has a thermal expansion coefficient of 5.3 × 10 ⁻⁶ / ° C. in a temperature range from room temperature to about 500 ° C.

The “first conductor” is an Ag—Pd-based conductor containing Ag and Pd at a weight ratio of Ag: Pd = 85: 15, and PbO—B ₂ O as an additive.
It is a material containing a total of about 10 wt% of _3- SiO ₂ -ZnO-based glass, Bi ₂ O ₃ , ZnO, and a small amount of transition metal oxide with respect to the metal component. By baking this material on a substrate at 850 ° C., good conductor characteristics (solder wettability, solder break resistance, durable adhesive strength after soldering, low wiring resistance) can be obtained.

The "second conductor" is a commercially available Ag conductor with a low-temperature baking specification, and the baking temperature is 500 to 600 ° C. as specified by the manufacturer. The composition is
A material obtained by adding about 7% lead borosilicate and Bi ₂ O ₃ with respect to AG100, a sheet resistance 10 m [Omega / □ by baking the material at 500 to 600 ° C.. However, since the solder is easily broken, it is not suitable for a site where solder is used.

“Resistors” are Pb ₂ Ru ₂ O _7-X (pyrochlore) and Ru
Conductive particles and PbO-SiO ₂ -B ₂ in O ₂ O ₃ is a mixture of -Al ₂ O ₃ based glass, the ratio of the conductive particles and the glass is 20:80 by weight. The baking temperature is 850 ° C.

The “protective glass” is a PbO—SiO ₂ —B ₂ O ₃ —Al ₂ O ₃ system glass and has a baking temperature of 600 ° C.

 The test results are as shown in Table 1.

In Table 1, Comparative Examples 1 to 4 belong to the prior art, and Examples 1 and 2 belong to the present invention.

Comparative Example 1 As shown in FIG. 5, the structure of the thick film circuit board of Comparative Example 1 is such that the first conductor component is printed on a substrate 51 and baked at 850 ° C. to form the first conductor 52. Formed. Next, a resistor component was similarly printed and baked to form a resistor 53.

Observation of the obtained 10 thick-film circuit boards revealed that the resistor 20
Cracks occurred in 35 of the 0 resistors.

Comparative Example 2 In the structure of the thick film circuit board of Comparative Example 2, as shown in FIG. 6, a resistor component was printed on a substrate 61 and baked at 850 ° C. to form a resistor 62. Next, a second conductor component was printed, and a second conductor 63 was formed by low-temperature baking at 600 ° C. Next, a protective glass component was printed so that a part of the second conductor 63 was exposed, and baked at 600 ° C. to form a protective glass 64.

When the obtained thick film circuit board was immersed in a solder bath at 235 ° C. for about 5 seconds, it was found that the solder was severely cracked and was not practical.

Comparative Example 3 In the structure of the thick-film circuit board of Comparative Example 3, as shown in FIG. 7, a resistor component was printed on a substrate 71 and baked at 850 ° C. to form a resistor 72. Next, the first conductor component is printed and baked at 850 ° C.
Formed three.

Observation of the obtained 10 thick-film circuit boards revealed that the resistor 20
Cracks occurred in all of the 0 resistors.

Comparative Example 4 In the structure of the thick film circuit board of Comparative Example 2, as shown in FIG. 8, a resistor component was printed on a substrate 81 and baked at 850 ° C. to form a resistor 82. Next, the second conductor component is printed and baked at 850 ° C.
Formed three.

Observation of the obtained 10 thick-film circuit boards revealed that the resistor 20
Cracks occurred in 41 of the 0 resistors.

Embodiment 1 As shown in FIG. 9, the structure of the thick-film circuit board of Embodiment 1 is such that a first conductor component and a resistor component are sequentially printed on a substrate 91 and simultaneously printed at 850 ° C. The first conductor 92 and the resistor 93 were formed at the same time. Next, a second conductor component was printed, and a second conductor 94 was formed by low-temperature baking at 600 ° C.
Next, a protective glass component was printed so that a part of the first conductor 92 was exposed, and the protective glass 95 was formed by baking at 600 ° C.

The characteristics of this thick film circuit board were good as shown in Table 1.

Embodiment 2 The structure of the thick film circuit board according to Embodiment 2 is as shown in FIG. 10 by sequentially printing a first conductor component and a resistor component on a substrate 91 and simultaneously printing at 850 ° C. The first conductor 92 and the resistor 93 were formed at the same time. Next, the second conductor component and the protective glass component were sequentially printed, and the second conductor 94 and the protective glass 95 were formed simultaneously by simultaneous baking at 600 ° C.

 This characteristic was good as shown in Table 1.

(Effects of the Invention) As described above, according to the thick film circuit board of the present invention, since the circuit board structure has a configuration in which the conductor characteristics are not impaired and the shape effect does not occur, the shape effect of the resistor can be reduced. The resistance value can be designed without taking into account
This has the effect of simplifying the design of the resistor pattern and preventing the resistor from being damaged such as cracks during manufacturing.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a structure of a thick film circuit board according to an embodiment of the present invention, FIG. 2 is a schematic sectional view showing a thick film circuit board for explaining a conventional example, and FIGS. FIGS. 5A, 5B, 6A, 6B, 7A, and 8B are schematic sectional views showing the structure of a thick film circuit board belonging to the prior art, FIGS. 9A and 10B, respectively. 1 is a schematic sectional view showing the structure of a thick film circuit board according to an embodiment of the present invention. 20: thick film circuit board, 21: insulating substrate, 22: first conductor layer, 23: resistor layer, 24: second conductor layer.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kazuyoshi Otake 1-1-1, Showa-cho, Kariya-shi, Aichi Japan Inside Denso Co., Ltd. (72) Inventor Yasuo Miura 1-1-1, Showa-cho, Kariya-shi, Aichi Japan Japan Denso Stock In-company (72) Inventor Sanshin Niwa 1-1-1, Showa-cho, Kariya-shi, Aichi Japan Inside Denso Co., Ltd. (56) References JP-A-63-226901 (JP, A) Jpn. (58) Fields surveyed (Int.Cl. ⁶ , DB name) H05K 1/09 H05K 1/16

Claims (1)

(57) [Claims] 1. A thick film circuit board comprising a ceramic insulating substrate provided with a silver-based conductor layer and a resistor layer, wherein the silver-based conductor layer comprises a first conductor layer and a second conductor layer. The first conductor layer is formed so as not to overlap with the resistor layer, and the second conductor layer has a part thereof a part of the first conductor layer and a part of the resistor layer. And sintering the first conductor layer and the resistor layer in an atmosphere at 800 to 900 ° C., and then forming the second conductor layer to 500 to 600
A method for producing a thick-film circuit board, characterized by sintering in an atmosphere at a temperature of ° C.