Impact of TIM Dielectric Constant on EMI Radiation
The electromagnetic radiation from an IC was modeled using a vertically oriented loop source. This type of source has been shown to best emulate the actual radiation from an IC. Embedding the source in a material with a dielectric constant (dk) greater than 1 increases the total radiated power (TRP) vs the TRP of the antenna in a vacuum. The TRP increases as the dk increases. This phenomenon is still seen if the source is just below the material with dk>1 as it would be in a TIM application. This phenomenon is due to wavelength compression in the TIM material. This wavelength compression increases the effective size of the source in terms of a wavelength which increases the radiated power.
A TIM with absorptive properties (Coolzorb) could reduce the total radiated emissions however it has limited affect at lower frequencies due to the small physical volume in terms of a wavelength. At higher frequencies Coolzorb will give significantly improved performance in reducing radiated emissions.
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