Composition for forming silica based coating film, silica based coating film and method for preparation thereof, and electronic parts

A composition for forming silica based coating film comprising

• component (a):
• siloxane resin obtained by hydrolytic condensation of a compound represented by the following formula (1):
• R1nSi4-n (1)
• (wherein R1 represents an H atom or F atom, a group containing a B atom, N atom, Al atom, P atom, Si atom, Ge atom or Ti atom, or a C1-20 organic group, X represents a hydrolyzable group, and n represents an integer of 0-2, with the proviso that when n is 2, each R1 may be the same or different, and when n is 0-2, each X may be the same or different),
• component (b):
• a solvent capable of dissolving said component (a), and
• component (c):
• an onium salt,
• wherein said component (c) includes at least one species selected from the group consisting of tetramethylammonium nitrate, tetramethylammonium acetate, tetramethylammonium propionate, tetramethylammonium maleate and tetramethylammonium sulfate, and
• said component (a) contains siloxane resin which comprises at least one specific bonded atom selected from the group consisting of H, F, B, N, Al, P, Si, Ge, Ti and C atoms at, and a total number (M) calculated using the relationship represented by the following formula (6) is 0.20 or greater and no more than 0.50:
• M=(M1+(M2/2)+(M313))/Msi (6)
• where M1 represents a total number of atoms of said at least one specific bonded atom bonded to a single Si atom, M2 represents a total number of atoms of said at least one specific bonded atom shared by two Si atoms, M3 represents a total number of atoms of said at least one specific bonded atom shared by three Si atoms, and Msi represents a total number of Si atoms.