Compact 32-Pin IO Board Design

I am finalising the architecture for a 32-pin I/O board that must squeeze into a very tight 57.20 × 46.10 mm envelope while cleanly switching 12 V lines. The board will sit behind an external controller, so every pin should be easy to drive from common 3 V–5 V logic without introducing extra noise or latency.

Key electrical requirements
• Reliable 12 V switching on all 32 channels
• Optocoupler isolation between logic side and load side to guarantee galvanic separation and minimise crosstalk
• Built-in overcurrent protection on the incoming supply
• Careful layout and filtering for low signal noise (both conducted and radiated)

Compliance
The finished design has to meet the relevant government standard for industrial interface modules; I will provide the exact clauses during schematic review. Clearances, creepage, labelling and test points should be planned with that in mind so certification is straightforward.

Deliverables
1. Complete schematic in Altium, KiCad or Eagle (your choice)
2. Two-layer or four-layer PCB layout that respects the 57.20 × 46.10 mm outline and any keep-out zones we define together
3. Gerber and drill files ready for fabrication, plus pick-and-place and BOM (with manufacturer part numbers and alternates)
4. Simple simulation or calculation sheet justifying thermal limits of the overcurrent protection and optocouplers
5. Assembly and functional test procedure that I can hand to a contract manufacturer

Acceptance criteria
• All 32 outputs switch 12 V at the specified load without exceeding temperature rise limits.
• Logic inputs tolerate 3.3 V and 5 V.
• Isolation barrier withstands 2.5 kVrms for one minute.
• Board passes preliminary EMC scan for conducted noise within the government standard’s limits.

If you have handled similarly dense I/O cards or obtained certifications before, let me know; otherwise please describe your proposed isolation components and protection strategy so I can verify they align with my cost and sourcing constraints.