Effects of no-clean flux residue on the performance of flip-chip devices

Organic flux residues deposited onto the surfaces of flip-chip assemblies during reflow soldering operations have been shown, in some cases, to affect the thermal and mechanical properties of underfill materials. Flux removal techniques are used in many electronics manufacturing and assembly processes as a means of assuring consistent materials properties and improving product reliability. Recently, however, no-clean flux formulations have been used in flip chip assemblies. These flux formulations do not require post-reflow cleaning operations, and therefore serve as a means of improving manufacturing productivity and reducing waste. Model flip-chip components were assembled using no-clean formulations and encapsulated using a commercial epoxy-based underfill material. These test assemblies were used to evaluate the effects of various no-clean flux residues on the properties of the epoxy underfill material and on the electrical and mechanical performance of experimental flip-chip components.