US 6,548,787 B2 · Ceramic heater

Abstract

A ceramic substrate for a ceramic heater includes aluminum nitride, silicon nitride or silicon carbide as the main component for increasing mechanical strength and improving thermal shock resistance, and a proper additive for controlling thermal conductivity. A temperature gradient from a heating element to a power feeding electrode is reduced by providing a dimensional ratio of the substrate effective for preventing oxidation of a power feeding contact that contacts the electrode of the heating element formed on the surface of the ceramic substrate. The dimensional ratio A/B≧20 is satisfied, wherein A represents the distance from the contact between a circuit of the heating element and the electrode to an end of the ceramic substrate closer to the electrode, and B represents the thickness of the ceramic substrate. The thermal conductivity of the ceramic substrate is adjusted to 30 to 80 W/m·K.

Claims24

Dependent claims

A ceramic heater comprising:

a ceramic substrate including a surface and having a certain thickness and an overall thermal conductivity;
a heating element having a circuit formed on the surface of said ceramic substrate;
and
an electrode formed on the surface of said ceramic substrate and connected to said circuit of said heating element;
wherein:
A and B satisfy a relational expression A/B≧20 wherein A represents a distance from a contact between said circuit of said heating element and said electrode to an edge of said ceramic substrate closer to said electrode and B represents said certain thickness of said ceramic substrate;
the overall thermal conductivity of said ceramic substrate is at least 30 W/m·K and not more than 80 W/m·K;
and
said ceramic substrate is formed of a material that contains a main component of at least one material selected from a group consisting of aluminum nitride, silicon nitride and silicon carbide and a subsidiary component having a subsidiary component thermal conductivity of not more than 50 W/m·K.

6 more elements

Dependencies are inferred from the claim text.

Ceramic heater

Life of this patent

Ceramic heater

Life of this patent

Abstract

Claims24