JPH0346961B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a thick film circuit, and is particularly characterized by a connection between a thick film resistor and a thick film conductor.

(b) Prior Art When forming a resistor and a conductor connected thereto by thick film technology, which of them should be formed first depends on the material of the resistor or conductor. For example, make a resistor using ruthenium oxide paste,
Further, when each conductor is made using copper paste, as shown in FIG. 1, it is necessary to first form a resistor 2 on a substrate 1, and then form conductors 3, 3.

This is because the sintering of ruthenium oxide paste must be carried out in an oxidizing atmosphere, such as air, whereas the conductor made of copper formed by sintering the copper paste oxidizes instantly when exposed to a high temperature oxidizing atmosphere after its formation. This is because you end up doing it.

As a way to solve this problem, for example,
As disclosed in Publication No. 55-43810 (HOlC7/00), a method of using silver, which is a noble metal, as a conductive material is known, but there is a problem that noble metals are expensive.

By the way, the resistance value of a thick film resistor is determined by the mixing ratio of the metal or metal oxide powder and the binder in the paste, and the higher the resistance, the greater the amount of the binder. Therefore, in a paste for high resistance of several hundred kilohms or more, the proportion of the binder becomes extremely large, and the surface layer of a resistor obtained by firing such a paste is almost entirely occupied by the binder.

That is, in the example shown in FIG. 1 above, since the resistor paste mainly consists of ruthenium oxide powder and glass powder as a binder, the fired resistor 2 as shown in FIG. The surface layer 2a is glass rich, and the bottom layer 2b is ruthenium oxide rich.

However, in such a case, as shown by the arrow in FIG. The resistance value fluctuates greatly from the initially expected resistance value, and since the state of occurrence of such a glass-rich portion is unstable, the resistance value also varies greatly.

(c) Problems to be Solved by the Invention Therefore, the present invention solves the problem that the resistance value of the thick film resistor deviates from the intended resistance value due to the surface layer containing a large amount of binder component appearing on the surface of the thick film resistor. It is an object of the present invention to provide a thick film circuit in which this phenomenon is prevented and the variation in resistance value is reduced.

(d) Means for Solving the Problems In view of the above-mentioned points, the thick film circuit of the present invention includes a resistor paste containing a metal or a metal oxide as a main component and a binder at a predetermined interval on a substrate. A pair of thick-film low-resistance elements prepared, printed, and fired, and a resistor paste containing a metal or metal oxide and a binder as main components, with both ends thereof respectively positioned on the pair of thick-film low-resistance elements. A first layer containing a large amount of a binder component and a second layer containing a large amount of a metal or metal oxide component located below the first layer are printed and fired on the substrate as shown in FIG. A thick-film high-resistance element and a conductor paste containing a base metal as a main component are printed and fired on the substrate on which both of the thick-film resistors are formed so that the ends thereof are located on the thick-film low-resistance element. a second thick film conductor of the thick film low resistance body and the thick film high resistance body;
A current path is formed between the layers.

(E) Effect With the above configuration, the current flowing through the thick film low resistance element flows through the second layer of the thick film low resistance element and the thick film high resistance element, so that the first layer containing a large amount of binder component layer.

(F) Example An example of the present invention will be described below in the order of manufacturing steps shown in FIGS. 3 to 7.

In the process shown in FIG. 3, a pair of low resistance pastes 5' and 5' are printed and dried on the alumina substrate 4, and then in the process shown in FIG. Print resistor paste 6',
After firing, the low resistance element pastes 5', 5' and the high resistance element paste 6' are simultaneously fired in the process shown in FIG. 5 to form the low resistance elements 5, 5 and the high resistance element 6.

Low resistance pastes 5' and 5' include low resistance pastes of several ohms to several hundred ohms, and high resistance pastes 6'.
Ruthenium oxide paste for high-resistance elements of several hundred kilohms to several megaohms is used for each, and the firing is performed in air at 850°C.

In the process shown in FIG. 6, a conductor paste is printed in a predetermined pattern, dried and fired to form conductors 7, 7 which overlap the ends of the low resistance elements 5, 5. As the conductive paste, a copper paste sold by DuPont and others is used, and the baking is performed in a nitrogen atmosphere at 500 to 600°C.

In the thick film circuit manufactured in this way, the seventh
As shown in the figure, the surface layer (first layer) 6a of the high-resistance element 6 is glass-rich, the bottom layer (second layer) 6b is ruthenium oxide-rich, and the conductors 7, 7 are the low-resistance element 5, It is electrically coupled to the ruthenium oxide-rich bottom layer 6b of the high-resistance element 6 via the ruthenium oxide layer 6b.

As a result, the current flowing through the high-resistance element 6 hardly passes through the glass-rich surface layer 6a, so that there is no variation or dispersion in the resistance value as in the conventional case.

By the way, in the above embodiment, the high resistance element 6 is connected to the low resistance elements 5, 5 through a ruthenium oxide rich surface, so the high resistance element 6 is connected from one low resistance element 5 to the other. The current flowing toward the low resistance element 5 flows in a portion excluding the high resistance element surface layer, which has an extremely large glass component. Therefore, the substantial resistance value of the high-resistance element 6 is determined by the portion containing the ruthenium oxide component excluding the surface layer. In other words, the substantial resistance value of the high-resistance element 6 is determined without much variation depending on the state of occurrence of the glass-rich portion of the high-resistance element surface layer.

Although such a substantial resistance value is slightly lower than the resistance value of the entire thick-film high-resistance element 6 (the desired resistance value determined by the mixing ratio of the ruthenium oxide component and the glass component), as described above, the substantial resistance value Since the resistance value is determined by the portion containing the ruthenium oxide component excluding the surface layer, there is little variation depending on the state of occurrence of the portion containing a large amount of glass component, and a substantially constant value can be obtained.

This decrease in the resistance value of the thick-film high-resistance element 6 is extremely small compared to the intended resistance value, but since the decrease value is almost constant, if necessary,
It is easy to correct this decrease in resistance value in advance. For example, a method can be considered in which the area of the high-resistance paste 6' is made slightly larger than the intended size.

(G) Effects of the Invention According to the present invention, even if the surface layer of a thick-film resistor contains a large amount of binder, the current flowing through the resistor will be reduced due to the presence of the low-resistance element. Since almost no surface layer is passed through, almost the desired resistance value can be obtained, and there is little variation in the resistance value. Furthermore, since the above-mentioned resistor can be produced simultaneously with the formation of other similar resistors in the thick film circuit, there is no need to increase the number of steps for producing the above-mentioned low-resistance element. Furthermore, it is also possible to use an inexpensive base metal paste such as copper paste as the conductor paste.

[Brief explanation of drawings]

Figures 1 and 2 are side views showing the conventional example;
7 to 7 are side views for explaining one embodiment of the present invention. 5... Thick film low resistance element, 6... Thick film high resistance element, 6
a... Surface layer (first layer), 6b... Bottom layer (second layer), 7... Thick film conductor.

Claims (1)

[Scope of Claims] 1. A pair of thick film resistor pastes 5', 5' mainly composed of a metal or metal oxide and a binder are printed and fired on a substrate 4 at a predetermined distance. The resistors 5, 5 and the resistor paste 6' mainly composed of a metal or a metal oxide and a binder are placed so that both ends thereof are located on the pair of thick film low resistance elements 5, 5, respectively. A first layer 6a printed and fired on the substrate 4 and containing a large amount of a binder component, and a second layer 6b containing a large amount of metal or metal oxide component located below the first layer 6a. The thick film high resistance element 6 and a conductive paste mainly composed of base metal are placed on the substrate 4 on which both the thick film resistors 5, 5, and 6 are formed.
A thick film conductor 7 printed and fired such that its end portions are located on the thick film low resistance elements 5, 5, and the thick film low resistance elements 5, 5 and the thick film high resistance element 6.
A thick film circuit characterized in that a current path is formed with the second layer 6b.