Whitepapers

Simulate Heat Generation and Impact on Signals with Ansys SIwave Ansys SIwave helps you model, simulate, and validate the power integrity, signal integrity, EMI, and thermal performance of IC packages and PCBs. Any industry standard PCB description filetype can be used to read a design into it's stackup-based geometry model, which can then be simulated in many solvers such as the SYZ Solver for S-parameter and AC impedance extraction, the DC-IR solver for DC simulations of power distribution networks (PDNs), and the IcePak CFD Thermal solver which can find heat transfer and convection on the design. With Release 1 in 2022, Ansys launched significant enhancements to the SYZ Solver, allowing AC circuits to take into account how the electric properties of materials change with temperature. Practically, for users of the software, this paves the way for workflows such as the following: ► Perform a DCIR simulation to see how much heat your power delivery network generates ► Simulate the ambient and generated heat in a simple enclosure with IcePak ► NEW! Review the impact the resulting true-to-life heat distribution has on the AC response with the SYZ Solver ► If needed, adjust the design and iterate ► Document results for stakeholders, potential clients, regulators, etc. This thermal and electrical co-simulation approach produces realistic and detailed results that can greatly reduce the risk of developing a physical prototype with digital communication that fails due to the impact of high temperatures. Of course, the results from the aforementioned workflow come on top of the already useful temperature information given from the IcePak simulation in the second step. These temperature distributions can be used to ensure that your mounted components and board materials are within their rated temperature ranges. Example/Comparison Below are images from an example SIwave workflow showing how one could overestimate their designs' performance were they not to account for temperature, how one can detect when failure will occur when accounting for temperature, and one method of exploring solutions to SI failures caused by thermal performance. 1. Uniform Temperature AC Simulation: Pictured below is an edge-mount DDR3 RAM stick PCB loaded into SIWave, commonly used in personal computers. On the board, we have 8 LPDDR3 capable 78 BGA DRAM chips, as well as many other peripheral components for insuring signal and power integrity. One line was selected to produce eye diagrams, and was compared to a mask which would be typical of the kind required for proper LPDDR operation measured after the channel. As we can see, the eye diagram passes the mask, but at this point no temperature has been taken into account. Over the next couple of sections, we will see how simply assuming room temperature as this simulation has could lead to poor performance in the actual manufactured channel.

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