Abstract
This paper presents a new method to suppress the electromagnetic radiation between the heatsink and packaging substrate in the system-in-package by using a resistance film absorber. The proposed absorber is designed with the indium tin oxide sputtered on both sides of the glass substrate, and the top layer adopts the combination of Jerusalem cross-shaped, ring-shaped, and L-shaped resistive film to expand the bandwidth. The unit size of the absorber is 0.14 λ L × 0.14 λ L and the thickness is 0.049 λ L . It has an absorptivity of more than 90% in the frequency range of 21 GHz to 55 GHz with polarization insensitivity, and angular stability. Moreover, the radiated electric field from the chip package at 3 m is significantly reduced when employing the proposed absorber, and the maximum suppression of the electric field reaches 18 dB. Finally, the measurement results are carried out to verify the simulation results. Both simulation and experiment results demonstrate that the proposed absorber has excellent radiation suppression, which can be properly applied to electromagnetic interference suppression of the printed circuit board.
Highlights
With the continuous improvement of the operating frequency and integration density of RF chips, electromagnetic interference and heat dissipation gradually become a great challenge for electronic devices [1]. e heatsink is usually mounted on packages to dissipate heat from ICs to free space [2]
Since a resonant cavity is formed between the ground plane and heatsink, the electromagnetic wave is reflected back and forth between the two metal planes, resulting in a substantial enhancement of electromagnetic radiation [3]. ere are gaps between the package lid/heatsink and the chip package substrate to provide sufficient space for the cables and components in the circuit system, which makes radiation leak out through these gaps, and results in radiation exceedance [4]
Due to the parasitic effect of grounding posts, this method only works well at low frequency and has no obvious suppression at high frequency, which is constrained by high-density layout [5]. e radiation-suppression methods include the use of absorbing material, which is coated on the surface of signal alignments or placed around the package substrate [6]
Summary
With the continuous improvement of the operating frequency and integration density of RF chips, electromagnetic interference and heat dissipation gradually become a great challenge for electronic devices [1]. e heatsink is usually mounted on packages to dissipate heat from ICs to free space [2]. EBG structure maintains the integrity of the power supply and ground planes, but the size is too large when applied to the high-density-layout space between the heatsink and the package substrate [9]. Compared with traditional absorbing technology, metamaterial absorbers have the advantages of simple structure, lightweight, and high absorptivity [10, 11], which become an important research direction of electromagnetic absorbing, but the traditional absorbers based on the resonant of metal structures have a less-stable equivalent impedance, and at deviations from the resonant frequency, the surface input impedance of the absorber is poorly matched to the impedance of free space, and the effective absorption bandwidth is too narrow to be suitable for engineering applications [12]. Compared with traditional absorbing technology, metamaterial absorbers have the advantages of simple structure, lightweight, and high absorptivity [10, 11], which become an important research direction of electromagnetic absorbing, but the traditional absorbers based on the resonant of metal structures have a less-stable equivalent impedance, and at deviations from the resonant frequency, the surface input impedance of the absorber is poorly matched to the impedance of free space, and the effective absorption bandwidth is too narrow to be suitable for engineering applications [12]. e high surface resistance film pattern has electromagnetic filtering characteristics and has a more stable surface impedance, the absorption characteristics of the metamaterial absorber can be further improved by rational designing the resistive film structure to achieve effective adjustment of the resonance characteristics [13]
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