Snap-cure epoxy adhesives

An adhesive formulation for microelectronics use comprising in parts by weight:

• (i) 20-80 parts of a liquid epoxy resin having a center flexible portion, characterized in that it has a total chlorine content of less than 0.1% by weight and the general structure ##STR20## in which:
• R' is H, C.sub.1-18 alkyl, C.sub.1-5 alkoxy or aryl or alkylaryl, C.sub.1-5 perfluoroalkyl, or C.sub.1-5 acyl;
• and
• n is an integer 1-3;
• and
• the flexible chain is CH.sub.2 CH.sub.2 CH.sub.2 CH.sub.2 O when r is an integer 1-10;
• the flexible chain is CH.sub.2 CH.sub.2 O when r is an integer 3-10;
• or
• the flexible chain is CH.sub.2 when r is an integer 10-20;
• and
• (ii) 80-20 parts of an aromatic O-glycidyl ether resin having one or more aromatic rings, the aromatic rings substituted with two or more O-glycidyl ether groups and optionally one or more C.sub.1 -C.sub.3 groups, the aromatic O-glycidyl ether having an epoxy equivalent weight (WPE, weight per epoxy) of 200 or less,
• the total parts of (i) and (ii) to equal 100 parts by weight, and
• (iii) a curing catalyst, and
• (iv) optionally, a conductive filler, and
• (v) 20-50 parts per hundred parts of resin of a phenolic hardener.