JPS63136601A - Thick film resistor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a thick film resistor in which a resistive film is formed on an aluminum nitride substrate.

BACKGROUND OF THE INVENTION Oxide ceramics have been widely used as heat-resistant insulating substrates for electronic circuits. In particular, alumina substrates have excellent electrical insulation and mechanical properties, and are most commonly used as circuit boards. When a large amount of heat is generated from the element, there is a drawback that the heat is not dissipated well. Also, the coefficient of thermal expansion is 7
．． 5x 10-6/℃, Si(3,5~4.0)
X There is a strong demand for substrate materials with excellent dissipation properties and a low coefficient of thermal expansion. Therefore, non-oxide ceramics such as aluminum nitride, water carbide, and silicon nitride have high thermal conductivity and a coefficient of thermal expansion close to 81. In particular, aluminum nitride ceramics have a thermal expansion coefficient of 4.3x 1O-1i/''C, high thermal conductivity, and are superior to conventional oxide ceramics in terms of electrical and mechanical properties. It is attracting attention as a well-balanced board material with excellent performance comparable to that of 2000, and there is an increasing demand for its use in circuit boards.

However, when forming a thick film circuit on this aluminum nitride substrate, printing and firing a resistive material mainly composed of conductive powder and amorphous glass frit, which has been commonly used in the past, results in a combination of glass and aluminum nitride. Gas is generated due to the reaction with
No resistive film is formed. Attempts have also been made to form an oxide film on the substrate and then bake a resistive film on it, but thick film resistors, which have been used on normal alumina substrates, can be formed, but the resistive film and nitride film cannot be used. Due to the large difference in thermal expansion coefficient from the aluminum substrate, cracks occur after firing, making it impossible to form a stable resistor. Even if we try to match the thermal expansion coefficient of the resistor to the aluminum nitride substrate, there is no glass that matches the thermal expansion coefficient with the substrate and is compatible with conductive particles. could not be used.

The purpose of the present invention is to use an aluminum nitride-based ceramic substrate that is free from defects such as cracks, agglomeration, and foaming, has excellent electrical properties such as stability of resistance value and TCR, and is reliable. The purpose is to make the resistor with high resistance blue.

Means for Solving the Problems The present invention is characterized in that the resistive film provided on the aluminum nitride substrate has a porous structure.

The resistive coating consists of a conductive component, an inorganic binder, and optionally a metal oxide additive, and any means may be used to create a porous structure.

For example, ■ using crystallized glass with strong crystallinity as an inorganic binder, ■ using a combination of strongly crystallized glass-ceramic with amorphous glass as an inorganic binder, ■ using a small amount of amorphous glass as an inorganic binder. ■Using a mixture of glass and ceramic filler as an inorganic binder are effective methods. It is desirable to use an inorganic binder that does not permeate into the aluminum nitride substrate.

The resistive coating of the present invention may further include a protective glass layer for protection from the environment.

1. In conventional thick film resistors, in order to improve the compatibility between the inorganic binder such as glass and the conductive particles, and to form a stable II#S network in the molten glass matrix, the resistive film is generally kept as thin as possible. It has been thought that it is necessary to have a homogeneous II4 structure with no voids. However, the present invention is characterized by a porous structure.

That is, by making the resistive coating porous, gas generated by the reaction between the substrate and the inorganic binder can pass through the coating and be easily extracted from the coating.

Therefore, it is considered that a good resistive film can be formed on the aluminum nitride substrate without foaming or destruction of the resistive film or significant agglomeration of conductive particles.

In addition, in conventional thick film resistors, microcracks are likely to occur when there is a large difference in the coefficient of thermal expansion between the substrate and the resistive coating, but in the present invention, the porous structure has a large difference in the coefficient of thermal expansion between the aluminum nitride substrate and the resistive coating. Because it absorbs and relieves the stress caused by stress, no cracks occur and a stable conductive network is formed.

As a result, it is possible to manufacture a highly reliable resistor that has small variations in resistance value, good characteristics such as noise and TCR, excellent reproducibility, and is stable over a long period of time.

Furthermore, forming a protective glass layer on the resistive coating improves moisture resistance,
Water resistance is improved and resistance value drift is improved. It also acts as a protective layer when soldering terminals. The protective glass layer may be made of conventionally commonly used amorphous glass, crystalline glass, or a mixture of these glasses and ceramic fillers, but it must be soft and fluid during firing to completely fill the voids in the resistive coating. It is desirable to have something that will not cause damage.

As the conductive component of the resistive film, any of the conventionally used ruthenium oxides, pyrochlore type multi-component oxides containing ruthenium, palladium, silver, metal borides, tin oxides, metal silicides, etc. can be used. To adjust the resistance value,
This is done by changing the blending ratio of the conductive component and the inorganic binder in the usual manner.

TCP and other resistance characteristics can be adjusted by suitably blending metal oxide additives as necessary, as in conventional resistors. For example, known TCR modifiers include copper oxide, manganese oxide, lanthanum oxide, neodymium oxide, niobium oxide, vanadium oxide, titanium oxide, silcanium oxide, antimony oxide, and silicon oxide.

The resistor of the present invention is manufactured by printing a resistor paste containing conductive powder and a non-dispersing binder dispersed in a vehicle on an aluminum nitride substrate using a conventional thick film method, and then firing the resistor paste.

friend i-dan EXAMPLES The present invention will be specifically explained below using Examples.

In the examples, "parts" and "%" are all based on weight 1.

Example 1 RU 02 powder 38.0 parts Si 0
2-AI 203-B203-Ca O-Zn 0-T
i 02-MgO-based crystalline glass frit
62.0 parts MnO2 powder
8.0 parts means vehicle 36.0 parts The resistance paste having the above composition was screen printed on an aluminum nitride substrate (manufactured by Tokuyama Soda Co., Ltd.) on which Aq/Pd electrodes had been formed in advance to form a resistance pattern of 21111×41u11. After drying at 150° C. for 10 minutes, the resistor was baked at a peak temperature of 870° C. for 30 minutes. The resulting resistive coating had a porous M4 structure as shown in FIG.

The sheet resistance value of this resistor is 113.21Ω/mouth, TC
R is 14.0 ppl/” on the high temperature side (+25 to +125℃, hereinafter referred to as HTCR).
°C, hereinafter referred to as CTCR) at -34,0f)l)TI/
“It was C.

Example 2 15.5 g of Rum2 powder 84.5 parts of the same crystalline glass frit as in Example 1 36.0 parts of organic vehicle The above resistance paste was baked on an aluminum nitride substrate in the same manner as in Example 1 to form a porous A resistive film was formed.

The sheet resistance values of the obtained resistor, HTCR and CTCR, were 8.708Ω/mouth and 53.4pp+b/”C, respectively.
154, 61) I) l/mouth.

Example 3 Rum2 powder 12.4 parts Si 0
2 -AI 2 03-82 03 -Ca O-
ZnO-TiO2 crystalline glass frit 83.2 parts Alumina powder 4.4 parts CuO powder 0.15 parts Organic vehicle
36.0 parts The above resistance paste was baked onto an aluminum nitride substrate in the same manner as in Example 1 to form a porous resistance film.

The sheet resistance values of the obtained resistor, HTCR and CTCR, were 109.47 Ω/mouth and 32.3 ppIl/'', respectively.
C165, 7 ppm/mouth.

Example 4 RlJ 02 powder 20.0 parts Aa powder 45.0 fg3Pd powder
11.0 parts Pb 0-8203-8
i02 series amorphous glass frit
22.0 parts MnO2 powder 2.0 parts Organic vehicle 30.0 parts Above 11 [
A one-component resistor paste was preliminarily coated with Ag/Pd in the same manner as in Example 1.
2 m printed on an aluminum nitride substrate with electrodes formed.
Form a 1x 4 u resistor pattern 1) at 150°C.
After drying for 0 minutes, it was fired at a peak temperature of 850° C. for 60 minutes to produce a resistor. The obtained resistive film has a porous structure, and the sheet resistance value, HTCR, CTC
R is 2.03Ω/mouth, -25, 31) l) 11
/'C117,91)l)11/mouth.

Example 5 RuO2 powder 37.0 parts A (+ powder 12.3 parts Pd powder
10.0 parts Pb 0-8203-8i 0
2 series amorphous crow frit 38
．． 0 parts MnO2 powder 3.0 parts Organic vehicle 35.0 parts The above resistance paste was baked on an aluminum nitride substrate in the same manner as in Example 4 to form a porous resistance film.

The sheet resistance values of the blued resistors, HTCR and CTCR, are 9.24Ω/mouth and -50.4ppl/'C1, respectively.
-84.61) l) 11/mouth.

Comparative Example 1 When a resistance paste of the same composition and composition as in Example 1 was baked on an aluminum nitride substrate except that PbO-3203-8i 02 series amorphous glass was used as the glass frit, the film foamed significantly and the RLl 02 particles aggregate,
No resistive coating was formed.

Example 6 Overcoat glass paste was printed to cover the resistive film of the same resistor as that manufactured in Example 1,
It was dried and fired at 600°C to form a protective glass layer.

The resistor of Example 6 and the resistor of Example 1 without a protective film were subjected to a pressure crushing force test under the conditions of 2 atmospheres and 121°C, and the rate of change in resistance value after the test was measured and the results were reported. It is shown in Table 1.

Table 1 From this, it can be seen that those having a protective glass layer have a small resistance value change rate and have significantly improved water resistance.

According to the present invention, by forming the resistive film into a porous structure, it is possible to form a resistor with excellent characteristics using an aluminum nitride ceramic substrate. Therefore, aluminum nitride ceramics, which have higher thermal conductivity and lower coefficient of thermal expansion than alumina substrates, can be used as substrates for circuits containing thick film resistors, making it possible to create more reliable high-density mounting substrates. will be refunded ¥J.

[Brief explanation of the drawing]

FIG. 1 is an electron micrograph showing a cross section of the porous resistance coating of the resistor of the present invention manufactured in Example 1.

Claims (1)

[Claims] 1. A thick film resistor comprising a porous resistive film provided on an aluminum nitride substrate. 2. The thick film resistor according to claim 1, wherein the porous resistive coating comprises a conductive component and an inorganic binder. 3. The thick film resistor according to claim 1, wherein the porous resistive coating comprises a conductive component, an inorganic binder, and a metal oxide additive. 4. The thick film resistor according to claim 2 or 3, wherein the inorganic binder in the porous resistance coating is glass or a mixture of glass and ceramic filler. 5. The thick film resistor according to any one of claims 1 to 4, wherein the porous resistance coating has a protective glass layer.