High Performance Electrically Conductive Silicone Adhesives

Silicones have long been recognised as attractive materials for use in electronics applications because of their unique combination of properties. Now, technology which couples high electrical conductivity with silicone performance characteristics has been developed. The new silver‐filled silicone adhesives were processed and cured in a manner similar to that used in conventional heat cured silicone compositions. Resultant cured products were both highly flexible and highly conductive, exhibiting volume resistivities down to 2 × 10−4 ohm‐cm. Both flexibility and electrical conductivity were retained after extended periods at elevated temperature. The electrical performance obtained while the new adhesives were under strain (induced either mechanically or thermally) was attributed to changes in the spatial packing of the silver. Low temperature characterisation indicated that the materials remain soft and stress‐relieving even down to −60°C. Other physical characteristics of these compositions, such as high ionic purity, low moisture uptake and good adhesion, are typical of high performance electrically conductive adhesives. This combination of properties suggests that these new silicone adhesives should be attractive for the electrical interconnection of microelectronics substrates having a mismatch of thermal coefficients of expansion (TCE) which would normally lead to failure due to thermomechanical stresses, and for the manufacture of flexible circuitry.