PURPOSE: To prevent the occurrence of thermal distorsion by providing a heat absorving pattern having high radiation factor on same plane with heater pattern while lapping over cathode terminal of cathode pattern thereby heating each section uniformly.
CONSTITUTION: Heat pattern 2 having zigzag pattern of conducting path and many heat absorbing patterns 3 having sufficiently higher radiation factor than that of substrate 1 are formed through screen printing method while lapping over the terminal section of cathode lead pattern 6. After coating alumina layer on its surface, cathode lead pattern 6 is formed then its terminal section 6b is secured to heat absorbing pattern 3 while cathode material is coated on base metal fixing section 6a. Since the radiation heat from heater 2 is absorved efficiently by pattern 3, each section is heated uniformly resulting in the prevention of thermal distortion due to heat cycle.
AOZUKA TORAO
SASAKI ATSUKO
