Resistive paste

#The present invention relates to a resistive paste which can be baked in a neutral or reducing atmosphere.

#A circuit pattern, which is composed of electrodes on which various electronic parts are mounted and resistors, has been generally formed on a ceramic base made of alumina, zirconia, etc. and the electrodes are generally formed by screen printing a conductive paste containing a noble metal, e.g., Ag or Ag--Pd, on the ceramic base followed by baking in air. Because of its expensiveness, the noble metallic paste has recently been displaced with a conductive paste containing a base metal, e.g., Cu, Ni or Al. In using such a base metallic paste, the screen-printed paste on a ceramic base is generally baked in a neutral or reducing atmosphere. If the base metallic paste is heated at high temperatures (i.e., baked) in an oxygen-containing atmosphere, such as air, a metal oxide would be formed which is an insulator. This is the reason why baking of a base metallic paste should be conducted in a neutral or reducing atmosphere.

#When electrodes are formed by using such a base metallic paste, resistors which are arranged to bridge over the electrodes should also be formed by using a resistive paste which can be baked in a neutral or reducing atmosphere. Known resistive pastes which can be baked in a neutral or reducing atmosphere include LaB.sub.6 -based pastes, NbB.sub.2 -based pastes, and the resistive paste proposed by the present inventors and disclosed in U.S. Pat. No. 5,036,027. The paste described in U.S. Pat. No. 5,036,027 comprises a mixture of a resistive material having a composition of Nb.sub.x La.sub.1-x B.sub.6-4x (wherein x is from 0.1 to 0.9 mol) and non-reducing glass frit, kneaded with an organic vehicle.

#The present invention will be illustrated in greater detail with reference to the following Example, but it should be understood that the present invention is not construed as being limited thereto. All the percents are by weight unless otherwise indicated.

#A conductive paste containing Cu as a base metal was screen printed on an alumina ceramic base and baked in a nitrogen atmosphere to form electrodes.

#Powdered NbB.sub.2 and LaB.sub.6 were weighed and mixed to provide a composition of Nb.sub.x La.sub.1-x B.sub.6-4x, with x being varied between 0.1 mol and 0.9 mol as shown in Table 1 below. The mixture was calcined in a nitrogen atmosphere for 2 hours at a temperature increase rate of 3.degree. C./min with the peak temperature set at 1000.degree. C. to prepare a solid solution of LaB.sub.6 in NbB.sub.2. The resulting mixture was ground in a vibration mill to an average particle size of 1 .mu.m and dried to obtain a resistive material having a composition of Nb.sub.x La.sub.1-x B.sub.6-4x (x:0.1 to 0.9 mol).