Resin-encapsulated semiconductor devices

A resin-encapsulated semiconductor device comprising a die pad, a silicon chip on the die pad, a lead frame electrically connected to the silicon chip, and an encapsulating resin molded over the elements, wherein

• at least the rear surface of the die pad remote from the silicon chip is treated with a primer comprising a silane coupling agent having the general formula
• X--(CH.sub.2).sub.n --Si(OR).sub.m R'.sub.3-m
• wherein X is an organic radical having up to 15 carbon atoms and having at least one member selected from the group consisting of epoxy, amino, carboxyl, hydroxyl, ureido, malemide, and trialkoxysilyl radicals,
• R is a monovalent hydrocarbon radical having 1 to 6 carbon atoms,
• R' is a monovalent hydrocarbon radical having 1 to 6 carbon atoms,
• n is an integer of from 1 to 10, and
• m is an integer of from 1 to 3, or a partial hydrolyzate thereof, and a bond-improving agent selected from the group consisting of organotitanates, primary, secondary and tertiary amines and cycloamidine derivatives in an amount of 0.001 to 100 parts by weight to 100 parts by weight of the silane coupling agent, and
• the encapsulating resin comprises an epoxy resin encapsulant having a tensile elongation of at least 0.7% at room temperature (25.degree. C.) and a moisture pickup of up to 0.6% by weight after it is allowed to stand for 72 hours in an atmosphere at 85.degree. C. and a relative humidity of 85%.