Thick film varistor and method of producing same
AssigneeSiemens Aktiengesellschaft
InventorsNaresh Chakrabarty, Richard Einzinger, Artur Weitze
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Abstract
A glass-free thick film varistor operable at operating voltages ranging from about 30 to 200 volts per mm of active varistor material is produced by providing a screen-printable paste comprised of a non-glass containing substantially homogeneous mixture of granular varistor materials which have ZnO as the main component thereof and an organic binder, applying such paste in a desired pattern onto an insulating substrate and sintering such applied paste at relatively high temperatures so as to convert the paste into thick film varistors.
Claims9
In a method of producing thick-film varistors having zinc oxide as the main component thereof, the improvement comprising:
- forming a glass-free varistor paste by admixing varistor materials with an organic binding agent, said paste comprising, on a 100% by weight solid material basis, about 87.5% to 98.0% by weight of ZnO, about 1.0% to 7.0% by weight of Bi.sub.2 O.sub.3, about 0.2% to 3.5% by weight Co.sub.2 O.sub.3 and about 0.1% to 1.0% by weight of MnO.sub.2 ;
- applying a substantially uniform relatively thick layer of said varistor paste onto a surface of an insulating substrate;
- and
- sintering at least such paste layer at a temperature in the range of about 1100.degree. C. to 1360.degree. C. for a period of time sufficient to convert said paste layer into a thick film varistor.
A glass-free thick film varistor consisting essentially of a thick film comprised of a substantially homogeneous glass-free mixture containing, on a 100% by weight solid material, basis about 87.5 to 98.0% by weight of Zn, about 1.0 to 7.0% of Bi.sub.2 O.sub.3, about 0.2 to 3.5% by weight of Co.sub.2 O.sub.3, about 0.1 to 1.0% by weight of MnO.sub.2 and a material selected from the group consisting of Sb.sub.2 O.sub.3, Cr.sub.2 O.sub.3, SnO.sub.2, TiO.sub.2 and mixtures thereof in an amount sufficient to make a 100% by weight solid material within said thick film, and a pair of electrodes attached to said thick film, said varistor being characterized by a steepness value of at least above 20.
Dependencies are inferred from the claim text.