3D PCB and ECAD-MCAD Sync

Overview#

Fusion's main advantage over standalone ECAD is that the board can live inside the mechanical model. The electronic design generates a 3D PCB: the board body, copper, holes and component models. Mechanical designers reference it to design enclosures, check connector alignment and height, and run interference checks. Changes flow both ways: board outline or hole changes from the mechanical side, and component moves from the electronics side.

Where to find it#

• From the 2D PCB Design toolbar, click Switch > 3D PCB. If no 3D PCB exists, Fusion creates and links one; this replaces the old "Push to 3D PCB" workflow. In the 3D PCB, PCB > 2D PCB switches back.
• The 3D PCB is a separate Fusion design document. Insert it into an enclosure by right-clicking it in the Data Panel and choosing Insert into Current Design.
• Synchronization is now a pull: an Out-Of-Date icon appears in the Application bar of the document that needs updating (3D PCB, 2D PCB or assembly); click it and review the result. Push to 2D PCB (3D PCB > Modify) still exists for referencing PCB Sketch construction geometry in the 2D PCB.
• From the Design workspace you can also start from the mechanical side: Create > Create PCB offers Create Linked PCB (preferred), Derive PCB, Create Unlinked PCB, and Create Independent / Associative PCB from a sketch.

Step by step#

Electronics to mechanical#

1. Complete the board outline and place the parts. Make sure each footprint has a 3D package; otherwise a plain box appears.
2. Choose Switch > 3D PCB. Choose how it is generated in PCB > 3D PCB Settings: presets Recommended, Fastest (2D images for everything except board and components), Most Detailed (full 3D geometry) or User Defined, plus which 3D geometry and components to include and Silkscreen Quality (Low, Medium, High).
3. Check component heights and connector positions; optionally use Modify > Move Component and Flip Component in the 3D PCB.
4. In your enclosure design, right-click the 3D PCB in the Data Panel and choose Insert into Current Design; position it with the manipulator handles or joints.
5. Use the board's Outline Sketch (or a derived PCB) so the enclosure can reference the outline.

Mechanical to electronics#

1. In the 3D PCB, edit the Outline Sketch (constraints and projections are supported there), add holes, or move components. Edit-in-place from a mechanical design requires the Associative setting.
2. Save. The 2D PCB shows an Out-Of-Date icon in the Application bar; click it and review the new component positions and outline changes.
3. Re-run DRC.

Keeping them in sync#

1. When you edit the 2D PCB, an Out-Of-Date icon appears in the 3D PCB; click it. Saving the 3D PCB then flags referenced assemblies as out of date.
2. If you modify the 3D board shape and sync to the 2D PCB, the outline can from then on only be changed through the 3D Outline Sketch. If the outline is edited in 2D and differs from the sketch, the 3D PCB Settings dialog enables Replace Board Outline.

Options reference#

Tips and pitfalls#

Tip: Model tall components (connectors, electrolytic capacitors, headers) with accurate 3D packages first; low parts matter less for enclosure fit.

Warning: Edit the board outline in one place. Autodesk recommends editing a constrained outline only in the 3D PCB, because it is read-only in the 2D PCB to preserve sketch data.

Tip: Keep board and enclosure in the same Fusion project so references stay valid; moving documents between projects can break links.

Warning: Older tutorials describe "Push to 3D PCB"; Autodesk says it was replaced by Switch > 3D PCB and a pull-style sync.

Tip: Use the Fastest preset for early fit checks; Autodesk notes that copper shown as canvases is not physical geometry, so use full solids when you need precise mass or volume.

Practice exercise#

Take your 40 x 25 mm board, give the connector and LED real 3D packages, and switch to the 3D PCB. Create an enclosure design, insert the 3D PCB, and cut an opening for the connector. Then move the connector 2 mm on the board, save, and check that the opening is now misaligned and the Out-Of-Date icon appears.

Understanding the document relationships#

The electronics design, the 3D PCB and the enclosure form a chain. The 3D PCB is generated from the electronics design; the enclosure references the 3D PCB. Data flows between them when you click the Out-Of-Date icon in the document that is behind.

Worked example: fitting a board into an enclosure#

A 45 x 30 x 1.6 mm board has a USB-C connector 3.2 mm tall and 9 mm wide on the left edge, an LED 1 mm tall and an electrolytic capacitor 8 mm tall. The enclosure interior is 47 x 32 mm, giving 1 mm of clearance on each side.

1. Switch to the 3D PCB. The tallest part is the capacitor: 8 mm above the 1.6 mm board, so 9.6 mm above the board's bottom face.
2. Insert the 3D PCB into the enclosure assembly on four 3 mm standoffs. The capacitor top is then 3 + 9.6 = 12.6 mm above the floor; with a 1 mm gap to the lid, the interior height must be at least 13.6 mm.
3. Create a cut in the left wall for the connector. The receptacle is 9 mm wide and 3.2 mm tall; with 0.3 mm of clearance on each side the opening is 9.6 x 3.8 mm, centred on the connector.
4. Move the connector 1.5 mm in the electronics design, save, and click the Out-Of-Date icon in the assembly. If the cut was dimensioned from the board origin it is now misaligned by 1.5 mm; if it was sketched from a projection of the connector body it can follow the move.
5. Keep a user parameter such as board_h for the board's thickness and a second for the standoff height, so wall and lid dimensions update when either changes.

Interference and clearance checks#

Use the assembly's interference analysis between the 3D PCB and the enclosure bodies. Interpretation:

• Zero interference volume is not the same as a good fit: a 0.0 mm gap fails in production once tolerances stack.
• Interference with a connector is usually intentional if the connector snaps into a notch; model the notch.
• Allow about 0.2 mm on each side of the board for printed enclosures and 0.1 mm for CNC-machined or molded ones.

Controlling what gets generated#

3D PCB Settings lets you choose between a lighter board representation (faster; copper is not modelled solidly) and a fuller one. For a first fit check, the light version is enough; use the full version for final checks. Components without a 3D package appear as plain boxes based on their footprint, so give tall or mechanically important parts real packages.

Round-trip rules of thumb#

Version and project hygiene#

• Keep the electronics design, 3D PCB and enclosure together (the Create Linked PCB tool saves the PCB next to its parent by default).
• Use meaningful version notes ("moved J1 1.5 mm, v1.3") so out-of-date indicators in the assembly can be traced.
• Do not move or rename the electronics document after the 3D PCB has been inserted without checking that the references still resolve.
• When sharing with people who do not use Fusion, export a STEP of the 3D PCB (general guidance; STEP carries geometry, not connectivity).

Failure modes and fixes#

Practice exercise#

Run a complete tolerance loop.

1. Give the capacitor a real 8 mm tall 3D package, the LED 1 mm, and the USB-C 3.2 mm. Switch to the 3D PCB.
2. Build a box with an interior of 47 x 32 x 14 mm; position the board on 3 mm standoffs. Verify with interference analysis that nothing intersects.
3. Cut a 9.6 x 3.8 mm connector opening, dimensioned from the connector body, not the origin.
4. Shift the connector 1.5 mm in the electronics design, save, update, and observe whether the cut follows.
5. Increase the board length to 50 mm in the Outline Sketch, sync the 2D PCB with the Out-Of-Date icon, run DRC and record any new errors.

Related#

• Libraries, Symbols, Footprints and Devices
• Board Layout
• Manufacturing Outputs