Printed Circuit Design & Fab - November 2008 - (Page 25)

SySTEM ModElinG minimize certain metrics such as inductive coupling in power nets. Integrating these geometric intricacies and multi-scale features with all the associated electromagnetic effects from package and board-level interactions is an added challenge for co-design. may also be crosstalk between different metal layers on the same chip or even between two stacked dies, depending on the orientation and the silicon thicknesses. When the signal emerges from the chip, there is possible crosstalk at the I/O pads, RDL layer and between C4 bumps. Crosstalk between bond wires presents itself both for signals from the same chip and from different chips, as in a stacked die case. There are significant crosstalk mechanisms in the package and PCB that must be accounted for. Trace-trace coupling, via-trace coupling, via-via coupling, coupling paths through voids and antipads, current return path spreading (for example with Electromagnetic Modeling Challenges FiGurE 2 depicts instances of the varied electromagnetic (EM) effects that are encountered in chip-package-board co-design. Whether the ultimate goal is power integrity (PI), signal integrity (SI) or electromagnetic interference (EMI) prediction, these EM effects have critical roles to play. The first order effects for signal (and power) propagation are shown by blue arrows. Within the confines of a digital chip, propagation along horizontal (traces) and vertical (via) structures needs to be modeled, including possible reflection at discontinuities and transitions. In an analog, radio frequency (RF) or mixed signal chip, the propagation modeling needs additional detail to model high-frequency effects such as through an onchip inductor or filter. Once the signal leaves the chip, the propagation (and reflection) is effected by discontinuities at the RDL layer or I/O pad where Peelable Resist XZ93-R the signal enters a BGA or bond wire. The signal then encounters another Reduces production costs discontinuity on the other side of the connection, at the package (or PCB in Easy to apply with a smooth finish a CoB) side. Once the signal enters the Withstands multiple wave and package, the dominant propagation through traces and vias is affected by reflow soldering processes reflections caused by impedance disCovers up to 5mm holes continuities including layer changes, antipads and voids and path dimenEasily recognised sion changes. Finally, impedance disdistinct red colour continuities may be encountered at the solder balls. Low odour at HASL Multi-port impedance, admittance or scattering-matrix models that can be used by circuit simulators are directly affected by the dominant first order path effects. In particular, selfworking for you. terms that account for reflection and transmission along a specific net (connected metal) are highly dependent on Sun Chemical these first order effects. The remainder Norton Hill of the models is populated by crosstalk Midsomer Norton Bath BA3 4RT terms that are typically undesirable United Kingdom but are produced by electromagnetic Tel: +44 1761 414 471 coupling. Fax: +44 1761 416 609 In Figure 2, the red arrows depict www.sunchemical.com EM crosstalk mechanisms. Within the chip, cross coupling between traces is an example of crosstalk. There Who makes your life easier and more cost effective? we do. NOVEMBER 2008 printEd CirCuit dESign & fAB 25 http://www.sunchemical.com http://www.sunchemical.com

Table of Contents Feed for the Digital Edition of Printed Circuit Design & Fab - November 2008

Printed Circuit Design & Fab - November 2008 Contents Our Line Market Watch Around the World Happenings ROI Positive Plating Ten Tips to Improve Manufacturability 3D Chip-Package-Board Modeling Improving Circuit Simulation With The Addition Of Real Measurements Ad Index PCB West: Interview with NBS Design Inc. The Influence of Final Finish on Lead-Free Assembly Reliability The Lead-free Soldering Challenges for Peelable Resists Off the Shelf Marketplace BGA Bulletin

Printed Circuit Design & Fab - November 2008

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