Abstract: The attachment of an electrical component to an electrical termination on a component-carrying substrate by a solder bump technique of a thermally curable adhesive composition for encapsulating purposes is described which comprises a thermosetting polymer and a chemical cross-linking agent which has fluxing properties but which is unreactive or of severely restricted reactivity with the polymer without the action of heat and/or catalyst. The composition is to be thermally curable when heated to soldering temperatures in a reaction which is catalyzable merely by metal oxide fluxed from metal surfaces by cross-linking agent then dissolved in the thermosetting polymer.