November 7, 2011. American Standard Circuits Inc. (ASC) has developed a new type of thermally and electrically conducting bonding material to bond the PCB ground plane with the heat sink for RF circuits and electromagnetic shielding applications.
The new material, called Electrasil-3A, is a silicone based elastomeric interface that is suitable for bonding surfaces that have widely dissimilar values of coefficient of thermal expansion (CTE). Being elastomeric in nature, Electrasil-3A can easily absorb mechanical shock or dimensional changes with changing temperature or other sudden movements. Thus, it is suited for airborne PCBs, particularly in military fighter planes or missiles. Such elastomeric bonding agents are also very pliable and are therefore suitable for flexible circuitries, as silicones can be bent without cracks or disjoints.
Electrasil-3A can be supplied as bonding sheets of any uniform thickness starting from 3 mils and higher, or as a putty material that can easily fill circuitry with complex shapes that are not necessarily planar. Therefore, the putty form can replace air in complex shaped cavities between the heat sink body and the PCB ground layer. By changing the catalyst of the curing process, the bonding characteristics of these interface materials can be customized to suit the need for both permanent bonding and temporary bonding when the components have to be assembled and disassembled multiple times, such as in rework applications.
www.asc-i.com.
