Patent ID: 7965146

Claim:
A constant-temperature type crystal oscillator comprising: a crystal unit, in which a metal base from which a pair of lead wires are led out and a flange of a metal cover are bonded to hermetically encapsulate a crystal element; an oscillator output circuit comprising an oscillating stage and a buffering stage formed along with the crystal unit; a temperature control circuit that keeps an operational temperature of the crystal unit constant; and a circuit substrate, on which circuit elements of the crystal unit, the oscillator output circuit and the temperature control circuit are installed, wherein the temperature control circuit comprises heating resistors, a power transistor that supplies electric power to the heating resistors and a temperature sensing element that detects an operational temperature of the crystal unit, wherein a principal surface of the crystal unit is installed so as to face one side board plane of the circuit substrate with interposing a first heat conducting resin between the principal surface of the crystal unit and the one side board plane of the circuit substrate, and the heating resistors are installed to be adjacent to the crystal unit to be thermally coupled to the crystal unit via a second heat conducting resin, wherein the flange of the crystal unit is inserted into a groove provided in the circuit substrate, and the principal surface of the crystal unit adheres to the one side board plane of the circuit substrate with interposing the first heat conducting resin between the principal surface of the crystal unit and the one side board plane of the circuit substrate, and wherein the heating resistors are installed on the one side board plane of the circuit substrate so as to sandwich the lead wires including a portion between the pair of lead wires of the crystal unit, and the heating resistors surround an outer circumference of the crystal unit.