Electromagnetic and Thermal Characteristics of Graphite for Radiation Suppression in Wire-Bonded Package Heat Sink

Heat sink is widely mounted on the integrated circuits to optimize thermal performance. Unfortunately, the cavity resonance between heat sink and package substrate could lead to severe radiation problem, causing that the product fail to satisfy the relevant electromagnetic interference (EMI) standards. It is a critical challenge to simultaneously obtain the excellent radiation attenuation and desirable thermal performance. In order to solve the problem, a combination of ring-shaped absorbing material and flat-shaped graphite is proposed in this paper. Based on a typical wire-bonded package, the effect of graphite on mitigating radiation and optimizing the thermal performance is investigated. As the graphite size varies from 20 to 45 mm, temperature reduction 5 °C and radiation attenuation 10 dB absorption bandwidth is realized. The experiment for EMI radiation is conducted in a semianechoic chamber, and the results of simulation and experiment matched well.