Data

Tools

Indexes

Applications

Experiments

Awesome

An open API service indexing awesome lists of open source software.

https://github.com/poealex/kicad_thermal_sim

Fast Multi-Layer Copper Thermal Estimator for KiCad
https://github.com/poealex/kicad_thermal_sim

electronics kicad kicad-plugin pcb python simulation thermal thermal-simulation

Last synced: 2 months ago
JSON representation

Fast Multi-Layer Copper Thermal Estimator for KiCad

Awesome Lists containing this project

README 

          
# KiCad Thermal Sim — Fast Multi-Layer Copper Thermal Simulation for KiCad



![Simulation results](docs/images/result.png "6-layer thermal simulation results")



**KiCad Thermal Sim** is a lightweight KiCad PCB Editor plugin that performs a fast, layout-oriented **heat spreading simulation across all copper layers** (F.Cu…B.Cu including inner layers).



This is **not** a full 3D CFD/FEA solver. It is intended as a practical engineering tool to quickly answer:



- Where are the **hotspots** on each copper layer?

- How much do **copper pours/planes** and **via stitching** help?

- Which layout variant is **better** (A/B comparison)?

- How does heat distribute through the **stackup**?



---



## What it simulates (high level)



- **2D in-plane conduction** on each copper layer (heat spreading within a layer)

- **Vertical coupling** between adjacent copper layers (FR4 conduction + via enhancement)

- **Power injection** from selected pads (constant or **time-varying PWL profiles**)

- **Convection** to ambient on the **top and bottom** outer surfaces

- Optional: a **Thermal Pad zone** on `User.Eco1` used as an area with stronger bottom-side heat removal



---



## Installation



### Option A: KiCad Plugin Manager (recommended)



1. Download the latest `ThermalSim-vX.Y.Z.zip` from the [Releases](https://github.com/PoeAlex/KiCad_Thermal_Sim/releases) page.

2. In KiCad, open **Plugin and Content Manager**.

3. Click **Install from File…** and select the downloaded ZIP.

4. Restart KiCad.

5. On first run, the plugin will detect missing dependencies and offer to install them automatically.



### Option B: Manual copy



1. Download or clone this repository.

2. Copy the `ThermalSim` folder into KiCad's plugin directory:



   - **Windows**: `%APPDATA%\kicad\9.0\scripting\plugins\`

   - **Linux**: `~/.local/share/kicad/9.0/scripting/plugins/`

   - **macOS**: `~/Library/Application Support/kicad/9.0/scripting/plugins/`



3. Restart KiCad.

4. On first run, the plugin will offer to install missing packages (`numpy`, `scipy`, `matplotlib`) automatically. On supported Windows/Linux x86_64 systems, the installer also offers optional PyPardiso acceleration via a checked-by-default checkbox. Alternatively, install packages manually in the **KiCad 9.0 Command Prompt**:

   ```

   pip install numpy scipy matplotlib

   ```

   Optional for faster solves on supported Windows/Linux x86_64 systems: `pip install pypardiso` (Intel MKL sparse solver)



5. In PCB Editor, run via **Tools → External Plugins → 2.5D Thermal Sim**.



### Auto-Dependency Installation



If required packages are missing, the plugin automatically shows an install dialog instead of crashing. The dialog runs `pip install` in the background and streams the output. After installation, restart KiCad.



---



## Quick start



1. Open your PCB in **KiCad PCB Editor**.

2. Select one or multiple **pads** that represent your heat sources.

3. Run the plugin via **Tools → External Plugins → 2.5D Thermal Sim**.

4. Set **Power** (constant value or PWL file path), **Duration**, **Ambient**, and **Resolution**.

5. (Optional) Switch to the **Advanced** tab for geometry filters, thermal pad, and solver settings.

6. Click **Preview** (sanity check), then **Run**.



![GUI main tab](docs/images/gui_main.png "Simulation tab")



![GUI advanced tab](docs/images/gui_adv.png "Advanced tab")



---



## GUI settings



The dialog has two tabs: **Simulation** (main parameters) and **Advanced** (geometry filters, thermal pad, solver).



### Simulation tab



#### Board Info

Shows detected copper layers with thicknesses and dielectric gaps parsed from the board stackup. Selected heat-source pads are listed below.



#### Power (W or PWL file path)

Power assigned to each selected pad. The field accepts:



| Entry | Meaning |

|-------|---------|

| `1.0` | 1 W constant on every selected pad |

| `1.0, 0.5, 2.0` | Per-pad constant power (comma-separated) |

| `C:\sim\ramp.pwl` | Same PWL profile for all pads |

| `1.0, C:\sim\ramp.pwl` | Pad 1 = 1 W constant, Pad 2 = PWL file |



Use the **Browse PWL...** button to pick a file. Clicking it multiple times appends paths for each pad.



**PWL file format** (LTspice-compatible):

```

; Comment lines start with ; or *

; Time(s)  Power(W)

0.0        0.0

0.001      1.0

0.005      2.5

0.010      2.5

0.020      0.0

```

- Two whitespace-separated columns: time (seconds), power (watts)

- Time values must be monotonically increasing

- Linear interpolation between breakpoints; holds first/last value outside range



#### Duration (sec)

Total simulated time. Shorter durations emphasize transient peaks; longer durations approach quasi steady-state.



#### Ambient Temp (°C)

Reference temperature. All results are relative to ambient.



#### Resolution (mm)

Spatial discretization step size. Smaller (0.2–0.5 mm) gives better hotspot localization but is slower. Larger (0.8–1.5 mm) is faster but smears peaks.



#### Output

- **Show All Layers** — display results for all copper layers (stackup view)

- **Save Snapshots** — store intermediate time-step images

- **Snapshot Count** — number of intermediate snapshots

- **Output Folder** — where results are saved



### Advanced tab



#### Geometry Filters

- **Ignore Traces** — exclude copper traces from the conductivity map (zones/pours/pads still contribute)

- **Limit Area to Pads** — restrict simulation domain to an area around selected pads (major speedup on large boards)

- **Limit Distance (mm)** — radius around pads when area limiting is enabled (practical starting point: 20–40 mm)



#### Thermal Pad (User.Eco1)

- **Enable Pad Simulation** — treat `User.Eco1` geometry as a thermal interface zone with enhanced bottom-side heat removal

- **Pad Thickness (mm)** — TIM thickness (thicker = higher resistance)

- **Pad Cond. (W/mK)** — TIM thermal conductivity

- **Pad Heat Cap. (J/m²K)** — additional thermal capacitance of the thermal pad



#### Solver

- **Convection h (W/m²K)** — convection coefficient for top/bottom surfaces (default: 10)

- **PCB Thickness (mm)** — overall board thickness (auto-detected from stackup if available)



#### Capabilities

Shows detected solver backend (SciPy, PyPardiso).



---



## Preview



The **Preview** button generates a geometry visualization showing copper distribution, pad locations, and via regions on each layer — useful for verifying the simulation setup before running.



![Preview](docs/images/preview.png "KiCad editor with geometry preview")



---



## How to interpret results



This tool is most reliable for:

- **Relative comparisons** (layout A vs layout B)

- **Hotspot locations**

- Trends: more copper, more vias, better spreading



Absolute temperatures are **estimates** and depend on modeling assumptions.



---



## Architecture



The plugin is split into focused modules:



| Module | Purpose |

|--------|---------|

| `capabilities.py` | Runtime detection of numpy, scipy, matplotlib, pypardiso, numba |

| `dependency_installer.py` | Auto-install dialog for missing packages via pip |

| `stackup_parser.py` | Parse copper/dielectric layers from .kicad_pcb S-expressions |

| `gui_dialogs.py` | wxPython dialog for simulation parameters (tabbed UI) |

| `geometry_mapper.py` | Convert PCB geometry to discretized conductivity arrays |

| `thermal_solver.py` | Sparse matrix assembly, BDF2 time integration |

| `pwl_parser.py` | Parse LTspice-style PWL power profiles |

| `visualization.py` | Generate thermal plots and preview images |

| `thermal_report.py` | Generate HTML summary report |

| `thermal_plugin.py` | Orchestrate workflow, KiCad ActionPlugin interface |



---



## Limitations



- No component/package thermal model (junction → case → pad is not explicitly modeled)

- Convection is simplified (uniform top/bottom ambient coupling; no airflow field)

- Radiation is not modeled

- Via coupling is an approximation (via density enhancement heuristic)

- Results depend strongly on **Resolution (mm)** and (if used) **Limit Area/Distance**

- Thermal Pad (User.Eco1) is a simplification of real mechanical contact pressure, interface quality, and sink temperature



---



## Suggested workflow



1. Start with **Limit Area to Pads** enabled and a moderate **Limit Distance** (e.g., 30 mm).

2. Tune **Resolution** until hotspots are stable (try 0.5 mm then 0.3 mm).

3. Compare layout variants using the same settings.

4. Only enable **Thermal Pad (User.Eco1)** if you have a real bottom-side interface in the product.



---



## License / Disclaimer



MIT License



This plugin provides engineering estimates intended for fast iteration and comparative analysis.

For safety-critical or thermally constrained designs, validate with measurement and/or a full 3D thermal tool.