A new material called Electrasil-3 utilizes a thin-film or screen-printed paste to efficiently transfer heat from the groundplane of a printed-circuit board (PCB) to the heatsink. The silicon-based conductive adhesive comes in thicknesses from 3 to 200 mils. It is rated for 2.0 to 3.0 0.1 for specific gravity with 68 to 77 on the Shore Durometer "A" scale. Electrasil-3 boasts a minimum of 180 PSI tensile strength with 100-percent minimal elongation. It offers tear and bond strength of 40 and 20 PPI, respectively. The material provides thermal conductivity of 5 to 8 W/ mK. Although it was formulated for power-amplifier and other electronic applications requiring effective cooling, it also lends itself to specialized PCBs that need to be mounted to a metal surface or housing. As a thin sheet of thermoplastic elastomer material, it provides a highly conductive, strong bonding between the adjacent surfaces. Being an elastomer, it accommodates any thermal coefficient of expansion (TCE) mismatch of the bonded layers. As a result, there is no residual stress left in the bonded assembly. Electrasil-3 can withstand a continuous operating temperature of +260C as well as multiple excursions to +288C for subsequent operations, such as solder reflow for component installation. Its flexible nature makes it well suited for improved life-cycle performance when used with thermoplastic circuit materials, such as polytetrafluoroethylene (PTFE), where large X and Y dimensional tolerances are tight.
American Standard Circuits, Inc.
475 Industrial Dr.
West Chicago, IL 60175