Learning Forum

[kagankarakusx]

I'm running power and thermal simulations on a custom power PCB design, and I’m trying to determine safe design margins for both current density (A/m²) and power density (W/m³) in copper traces.

While there are many discussions and references for current density (e.g. IPC-2152), I’m struggling to find concrete numerical thresholds for both parameters — especially power density — in real-world, simulation-driven design flows.

In my simulations, I observe the following:

Current density in the range of 3–10 × 10⁶ A/m² depending on the trace

Localized power density hotspots reaching 1 × 10⁸ W/m³ or higher

I’m wondering whether those are acceptable or pose a thermal reliability risk.

 My Key Questions:
Do you have or follow any safe-limit chart or table (e.g. rule-of-thumb thresholds) for:

Current density (A/m²)

Outer layers, continuous power traces

Outer layers, short transient pulses

Inner layers continuous power traces

Inner layers, short transient pulses

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Power density (W/m³)


Current density (A/m²)

Outer layers, continuous power traces

Outer layers, short transient pulses

Inner layers continuous power traces

Inner layers, short transient pulses

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I want to set a reference table for myself

Have you correlated simulation results (thermal/power maps) with measured failures or temperature data in your designs?

Do tools like  solvers align well with lab observations in terms of these limits?

A structured reference (chart/table) would be incredibly helpful — something I can use to say “we are safe here” when looking at simulation results.

Thanks in advance for your experience and any data or papers you can share!

[Praneeth]

Hi,

Thank you for reaching out to the Ansys learning forum.

Please let us know which Ansys tool you are using to help us serve you better.

Also, it looks like your question is on safe limits for current and power densities. Kindly confirm.

Best regards,
Praneeth,
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[kagankarakusx]

hello its Ansys siwave dc ir drop simulation section , No information about current density limits

[Mrinmoy Bharadwaj]

Ansys SIwave is an analysis tool that allows you to simulate your PCB model and extract key electrical metrics—such as current density and power dissipation—through a DCIR simulation. These outputs are based on the input conditions you define (e.g., voltage/current sources, material stack-up, and geometry). As such, interpretation of the results depends on your engineering judgment and context-specific design goals.

The tool does support setting user-defined values for maximum legal current magnitude in bondwires, solderballs, solderbumps and vias. This is configured through the dc_coeff.txt file located in the installation directory.

In your case, you can export the power dissipation map from your DCIR results and use it as input for a thermal simulation to obtain the temperature distribution across the board. Evaluating whether the resulting temperatures are acceptable (safe) will depend on your design constraints (e.g., component thermal limits, reliability targets, and cooling methods applied).

If you're looking for reference data or benchmarks, you may refer scientific literature or technical journals, many of which provide correlation studies between electrical and thermal behavior in PCBs. Note that redistribution of such literature is typically restricted by copyright.

In summary, SIwave provides the analysis outputs with high fidelity, but final design decisions—especially regarding safety, thermal management, and reliability—remain the responsibility of the user.