Sheet-like ceramic substrate for tip parts

A substantially flat ceramic substrate, comprising a ceramic sheet having a substantially square shape having a pair of first opposing sides and a pair of second opposing sides, said ceramic sheet having formed on one face thereof a plurality of first primary dividing grooves which extend in parallel to said first opposing sides and have the opposite ends extending to said second opposing sides and a plurality of first secondary dividing grooves which extend in parallel to said second opposing sides and perpendicularly to said first primary dividing grooves and having the opposite ends spaced from said first opposing sides, said ceramic sheet further having formed on the other face thereof a plurality of second primary dividing grooves which extend at locations corresponding to said first primary dividing grooves and have the opposite ends spaced from said second opposing sides and a plurality of second secondary dividing grooves which extend at locations corresponding to said first secondary dividing grooves and have the opposite ends spaced from said first opposing sides.