Fluxing underfill compositions

A curable composition comprising:

• (a) an epoxy resin;
• (b) a latent fluxing agent which liberates a phenolic compound or a carboxylic acid containing compound when heated above 140° C.;
• and
• (c) a compound for effecting cure of the epoxy resin wherein the latent fluxing agent is selected from the group consisting of an α-alkoxyalkyl ester of a carboxyl-containing compound, an α-alkoxyalkyl phenyl ether, and a compound having one or more of the following structures I through VI:
• wherein X denotes or
• Y denotes
• E denotes an organic group derived from a 1-alkenyl ether and is selected from the group consisting of a hydrocarbon, ether, thioether, ester, thioester, carbamate, amide, and a combination thereof;
• F denotes an organic group fragment derived from a multifunctional 1-cycloalkenyl ether wherein the cyclic ether groups are linked through F, and is selected from the group consisting of a hydrocarbon, ether, thioether, ester, thioester, carbamate, amide, and a combination thereof;
• R1 represents a C1–C6 alkyl group;
• R2 and R3 are independently selected from the group consisting of hydrogen, substituted or unsubstituted linear or branched C1–C22 alkyl, aryl, alkaryl, cycloalkyl, alkoxy and phenyl;
• R4 is selected from the group consisting of a substituted or unsubstituted linear or branched C1–C22 alkylene, alkenylene, arylene, alkylenearyl, cycloalkylene, alkyleneoxy and phenylene;
• R5 and R6 are independently selected from the group consisting of linear or branched C1–C22 alkylene, alkenylene, arylene, alkylenearyl, cycloalkylene, alkyleneoxy and phenylene;
• n is an integer of from 2–30, p is an integer of 1 or 2 and q is an integer of from 5–30.