Abstract: A microelectronic assembly (10) includes an integrated circuit component (14) attached to a polymeric substrate (12) by a plurality of unencapsulated solder bump interconnections (16). A collar (18) is affixed to the polymeric substrate (12) about the integrated circuit component (14) and is formed of an inorganic material having a coefficient of thermal expansion less than that of the substrate (12). The collar (18) constrains thermal expansion of the polymeric substrate (12) in the die attach region (22), thereby lessening any deleterious effects caused by a mismatch in the thermal expansion of the polymeric substrate (12) and the integrated circuit component (14).