Electromagnetic compatibility modeling for integrated circuits

Abstract

The integrated circuit (IC) packaging electromagnetic compatibility (EMC)/signal integrity (SI)/power integrity (PI) problems have been broadly attested. But IC packaging electromagnetic interference (EMI) was seldom addressed. Because the electromagnetic emission from IC packagings becomes more critical as the data rate of digital system continues increasing. Its working mechanism and modeling technology are very important.

In this thesis, EM emission behaviors of IC packaging are systematically studied for the first time. It was never seen from other literatures. The fundamental principles and properties of electromagnetic radiations caused by heat sinks, vias, traces, and pin maps in IC packaging structures are carefully investigated and modeled. Both theoretical analysis based on first principles and simulated results based on numerical full wave solvers are provided to find out critical impact factors to IC packaging EMI. This work establishes basic modeling components for comprehensive radiation studies. It directly benefits fundamental understandings and guideline development for the optimization of the packaging EMI reduction. Some measurement results are also included to support concluded characterizations and analysis. A summary for IC packaging EMI design rules is discussed in details to conclude the derived design guidelines.

Second, a novel data pattern based electromagnetic superposition method is developed to model the IC packaging electromagnetic emission. It employs the equivalence principle to obtain the electromagnetic field response over a broad spectrum. Then it uses the linear property of the passive parasitic system to superimpose the contribution of different signals on the packaging. As a result, with certain pre-calculations, it is convenient to compute the electromagnetic emission efficiently from different signals with various signal pattern combinations, which benefits identifying the worst case scenario. The proposed method can be implemented between different tools for specific purposes. In addition, data reconstruction can be evaluated through the phase shift, and it benefits identifying the EMI of any pulse bit pattern. This work offers great convenience for the post-processing, and allows the flexibility of real digital pulse signals. It provides a basic modeling framework for comprehensive radiation studies for IC packaging and PCB EMI reductions.

Third, the performance of IC interconnects has been stretched tremendously in recently years by high speed IC systems. Their EM emission and SI modelings have to consider the existence of I/O active devices, such as buffers and drivers. The I/O model is difficult to obtain due to the IP protection and limited information. We proposed to use the X-parameter to model the IC interconnect system. Based on the PHD formalism, X-parameter models provide an accurate frequency-domain method under large-signal operating points to characterize their nonlinear behaviors. Starting from modeling the CMOS inverter, the whole link modeling primarily based on X-parameter for the pulse digital signals was presented. I/O modeling can also be investigated by the proposed new method to understand the impedance effects at high speed serial links. It is the first complete examination of the X-parameter to IC interconnect SI analysis. The nonlinear I/O property represented by IBIS models is also investigated to model its impact to IC packaging EMI. Statistical analysis is proposed to provide insightful results on random bit patterns.