An aluminum or copper heat sink is attached to a ceramic cap or exposed semiconductor chip using an adhesive of silicone or flexible-epoxy adhesive. The aluminum may be coated by anodizing or chromate conversion or the copper may be coated with nickel or gold on chromium. Such structures are especially useful for flip chip attachment to flexible or rigid organic circuit boards or modules such as CQFP, CBGA, CCGA, CPGA, TBGA, PBGA, DCAM, MCM-L, and other chip carrier packages in which the back side of chips are connected directly to heat sinks. These adhesive materials withstand wet or dry thermal cycle tests of -65.degree. to 150.degree. C. for 1,000 cycles and 85.degree. C. and 85% relative humidity for 1000 hours while maintaining a tensile strenth of at least 500 psi. The adhesive contains materials having high thermal conductivity and a low coefficient of thermal expansion (CTE) in order to provide increased thermal performance.