PCB Markings & Compliance
MDD400 v2.9 — Fabricated prototype. The silkscreen marks, fiducials, and stackup documented here are as-built on the V2.9 prototype boards. Compliance-mark content is locked (the marks themselves correspond to the EU RED 2014/53/EU, FCC Part 15, UKCA, RoHS, and China EFUP regulatory frameworks the MDD400 is targeted at), but final compliance-test confirmation (the test report that authorises affixing the CE / UKCA / FCC marks) is itself a V2.10 milestone — see the V2.10 backlog below.
Overview
This page documents the PCB-level markings on pcb_markings.kicad_sch: the fiducial markers that support automated assembly, the silkscreen marks that carry product identity and compliance information, and the PCB stackup that physically realises the four-layer construction described elsewhere in the docs.
Three sub-sections on this page, in narrative order:
- Silkscreen marks and compliance — board identity (S1), CE / UKCA / FCC / RoHS / China EFUP compliance marks (S2 / S7 / S4 / S3), Scadys logo (S5), product-documentation QR code (S6), copyright (S8).
- Fiducial markers — four 0.5 mm bare-copper fiducials (FID1–FID4) supporting pick-and-place machine-vision alignment on both sides of the board.
- PCB stackup detail — the layer-by-layer construction, copper weights, dielectric thicknesses, and surface finish.
The fourth engineer-drawn rectangle on this sheet is an empty placeholder.
Some board-level mechanical details (board outline, mounting hole positions) live in the MDD400_V2.9.kicad_pcb file rather than on pcb_markings.kicad_sch — they're summarised in the Mounting and board outline section below.
Functional specification and design objectives
The board markings, fiducials, and stackup must:
- carry the regulatory marks required by the target markets — EU RED 2014/53/EU (CE), UK Conformity Assessed (UKCA), FCC Part 15 (USA), RoHS (EU restricted-substances), and China EFUP (Environment Friendly Use Period);
- carry the manufacturer identity (Scadys logo + copyright) and the product identity (board variant + revision), with the variant / revision in copper for wear-resistant traceability;
- provide a machine-readable pointer (QR code) from the physical board to the live product documentation;
- provide reference markers for the pick-and-place machine's vision system so it can compensate for board-to-board placement variation and skew, with a wide diagonal baseline so small absolute fiducial-detection error translates to a small angular correction error across the whole board;
- mirror the F.Cu fiducials on B.Cu at the same XY coordinates so single-pass setup works for two-sided assembly;
- realise a four-layer construction giving two signal layers (F.Cu, B.Cu) and two inner layers (In1.Cu, In2.Cu) for power and ground distribution, with inner layers heavier (1 oz / 35 µm) than outer layers (0.5 oz / 17.5 µm) for low-resistance power planes; and
- hold a total board thickness of 1.6 mm — standard for marine enclosures and compatible with the panel-mount housing geometry — while letting layer roles change region-by-region so the SMPS, CAN-bus power, digital, and isolation domains each get a stack-up that suits them.
Board specification
| Parameter | Value |
|---|---|
| PCB dimensions | 95.2 × 95.2 mm (non-rectangular outline — see Mounting and board outline below) |
| Board thickness | 1.6 mm |
| Layer count | 4 (F.Cu / In1.Cu / In2.Cu / B.Cu) |
| Copper weight | 17.5 µm (0.5 oz) — F.Cu, B.Cu; 35 µm (1 oz) — In1.Cu, In2.Cu |
| Surface finish | ENIG (Electroless Nickel Immersion Gold) |
| Solder mask | Navy blue, both sides; 0.012 mm thickness; pad-to-mask clearance 0.075 mm |
| Min trace / space | Per design rules in the KiCAD project |
| Manufacturing class | IPC-6012 Class 2 |
Silkscreen marks and compliance
All marks listed below are silkscreen unless noted. They sit on the F.Cu (top) and / or B.Cu (bottom) silkscreen layers.
| Ref | Mark | Footprint | Purpose / placement |
|---|---|---|---|
| S1 | MDD400_v2.9 board identity | mdd400:Variant | Board identity in copper for version traceability — survives silkscreen wear |
| S2 | CE mark | SILKS:CE_3.5mm | EU Declaration of Conformity (Directive 2014/53/EU Radio Equipment Directive) — applied after the V2.10 compliance pre-screening |
| S3 | RoHS + China EFUP | SILKS:EFUP_RoHS_China_4 | RoHS compliance (EU restricted substances) and China EFUP (Environment Friendly Use Period — "4" = 4-year mark) |
| S4 | FCC mark | SILKS:FCC_3.5mm | FCC Part 15 compliance identifier (US RF emissions). The full FCC ID is carried by the ESP32-S3-WROOM-1 module's own marking (2AC7Z-ESP32S3WROOM1) since the module's pre-certification covers the MDD400's RF emissions |
| S5 | Scadys logo | SILKS:scadys_logo_10x10.f-mask | Manufacturer logo, 10 × 10 mm, F.Mask layer — visible through the soldermask aperture |
| S6 | Product-docs QR code | mdd400:qr_docs.scadys.io_products_mdd400_10 | Machine-readable link from the physical board to the product docs at docs.scadys.io |
| S7 | UKCA mark | SILKS:UKCA_3.5mm | UK Conformity Assessed mark (post-Brexit UK market replacement for CE on UK-only batches) |
| S8 | Copyright | SILKS:Copyright | © 2025 GM Consolidated Holdings Pty Ltd |
Why FCC ID isn't on the board directly. The ESP32-S3-WROOM-1 module carries its own FCC ID label on the module itself (visible through the module's metal can window). The board-level FCC mark (S4) is the generic Part 15 compliance identifier; the device-specific FCC ID for the MDD400 is the same as the module's because the module's pre-certification covers the device's RF emissions (subject to the antenna keep-out documented on the ESP32 Module page).
Why both CE and UKCA marks are present. Post-Brexit, the UK market requires UKCA rather than CE marking on goods placed on the UK market specifically. The MDD400 carries both so a single fabrication run can serve both EU and UK markets — the compliance test reports themselves are technically equivalent (both based on the same harmonised standards under different statutory instruments).
Mark permanence.
| Mark | Visible on | Permanence |
|---|---|---|
| S1 board identity | Copper (not silkscreen) | Permanent — copper etch survives field handling and solder wash |
| S2 CE, S4 FCC, S7 UKCA | F.Cu silkscreen | Standard silkscreen — durable in field use, may wear under prolonged direct contact |
| S3 RoHS / EFUP | F.Cu silkscreen | Same |
| S5 Scadys logo | F.Mask aperture | Visible through soldermask opening; very durable |
| S6 QR code | F.Cu silkscreen | Critical that the QR remains legible — survives operator wear under normal helm conditions |
| S8 Copyright | F.Cu silkscreen | Standard silkscreen |
Fiducial markers
Four 0.5 mm bare-copper fiducial markers (with 1.5 mm soldermask openings) form two mirrored pairs:
| Ref | Layer | Position (mm) | Pair |
|---|---|---|---|
| FID1 | F.Cu | (71.0, 47.0) | Front, top-left pair (mirrors with FID3) |
| FID2 | F.Cu | (157.0, 133.0) | Front, bottom-right pair (mirrors with FID4) |
| FID3 | B.Cu | (71.0, 47.0) | Back, co-located with FID1 |
| FID4 | B.Cu | (157.0, 133.0) | Back, co-located with FID2 |
The diagonal between FID1 / FID2 centres is √(86² + 86²) ≈ 121.6 mm — a wide baseline that gives the pick-and-place's angular-correction calculation low sensitivity to fiducial-detection noise. A 50 µm placement uncertainty at each fiducial translates to roughly ±0.024° of angular correction error — well below the 0.5° typical pick-and-place placement tolerance.
The mirrored front / back placement at identical XY coordinates means the same vision-system fixturing can index both sides without re-teaching coordinates — saves setup time on two-sided assembly runs.
| Parameter | Value | Notes |
|---|---|---|
| Fiducial copper diameter | 0.5 mm | Per IPC-7351 Class 2 recommendation |
| Soldermask opening | 1.5 mm | 3× copper diameter — sufficient for vision-system contrast |
| Diagonal baseline (FID1 → FID2) | ~121.6 mm | Wide baseline → low angular-error sensitivity |
| F/B co-location accuracy | 0 µm (by design) | FID1 / FID3 and FID2 / FID4 share the same XY in the .kicad_pcb |
| Vision-system suitability | Confirmed by prior production runs | Same fiducial pattern used on prior MDD400 hardware revisions through pick-and-place assembly |
PCB stackup detail
The physical stack-up, from top to bottom:
| Layer | # | Type | Thickness | Dielectric below | Notes |
|---|---|---|---|---|---|
| F.Cu | 1 | Signal + plane | 17.5 µm (0.5 oz) | F.Cu prepreg | Component side; carries VCC pour in the digital region, GNDREF moat fills under SMPS / CAN-power / isolation islands |
| In1.Cu | 2 | Power plane | 35 µm (1 oz) | Core | Unbroken GNDREF in the digital region (one half of the VCC plane pair); GNDREF moat inside the SMPS island |
| In2.Cu | 3 | Power plane | 35 µm (1 oz) | B.Cu prepreg | Unbroken GNDREF in the digital region (other half of the plane pair); domain-dependent fills elsewhere |
| B.Cu | 4 | Signal + plane | 17.5 µm (0.5 oz) | — | Back-of-board; carries VCC pour in the digital region (mirrors F.Cu), GNDREF fills under SMPS / CAN-power / isolation islands |
The VCC – GNDREF – GNDREF – VCC layer ordering across the digital region creates two distributed VCC↔GNDREF plane-pair capacitors (F.Cu↔In1.Cu and In2.Cu↔B.Cu, each separated by 0.1855 mm prepreg). The plane-pair capacitance is what gives the digital domain GHz-frequency bypass with no parasitic ESL or ESR — see the Power Supplies page for the full rationale and the ESP32 Module page for the force-commutated discrete-cap topology that hands off to the plane pair above the discrete caps' self-resonance.
In the SMPS and CAN-bus power islands, all four layers carry GNDREF inside a copper-keepout moat that contains switching return currents.
Across isolation boundaries (CAN domain to digital domain; legacy-serial domain to digital domain), all four layers carry copper-free 1.4 mm creepage gaps.
The stackup specification has been validated by prior MDD400 hardware revisions in production through pick-and-place assembly. No quantitative impedance / capacitance measurements have been re-taken on V2.9 specifically — see the V2.10 backlog.
Mounting and board outline
The MDD400 V2.9 board has a non-rectangular outline shared with the WTI400 V1.2 sister product (both fit the same housing concept). Board extent and mounting-hole pattern:
| Parameter | Value |
|---|---|
| Board outline | Non-rectangular with rounded corners (~2.4 mm radius) and a step on the right-hand edge for the enclosure interface |
| Board extent (KiCAD coordinates) | x: 66.4–161.6 mm, y: 42.4–137.6 mm |
| Mounting hole pattern | 60.2 × 89.2 mm rectangular pattern |
| Hole position (mm) | Location |
|---|---|
| (83.9, 45.4) | Top-left corner |
| (83.9, 134.6) | Bottom-left corner |
| (144.1, 45.4) | Top-right corner |
| (144.1, 134.6) | Bottom-right corner |
Each hole has a 4.065 mm courtyard radius — consistent with M3 hardware plus standoffs. The four mounting holes engage the housing's panel-mount inserts; no additional mechanical retention is needed.
PCB Layout
The board is a 4-layer stack-up (F.Cu / In1.Cu / In2.Cu / B.Cu) of 1.6 mm total thickness on FR4 (ε_r 4.5, prepreg 0.1855 mm, core 1.1 mm), with ENIG finish and dark-blue epoxy solder mask plus white direct-print silkscreen on both sides. F.Cu and B.Cu are the signal / component layers; In1.Cu and In2.Cu are dedicated GNDREF power planes carrying a solid ground pour beneath the entire SMPS region (the "VST" zone, 66.4–88.3 × 42.4–82.8 mm), giving a low-impedance return and EMI shielding between the switching converters on F.Cu and any signals on B.Cu.
- Grounding / via stitching. 195 GNDREF vias (0.3 mm drill) in the SMPS area (x 70–90, y 45–85 mm) stitch the F.Cu GNDREF pour to the In1.Cu and In2.Cu planes; all 1081 board vias use a uniform 0.3 mm drill / 0.6 mm size (0.15 mm annular ring).
- Converter isolation. Each buck converter (U1, U6) is enclosed by a 0.4 mm copper-keepout moat on F.Cu + In1.Cu + In2.Cu so no external pour enters the cell; SW nodes are copper pours (not traces) to minimise inductance; ferrite beads FB1 / FB2 at x = 89 mm and FB4 at (71.1, 82.9) are the sole HF connections between the SMPS copper and the digital VCC / VDD and CAN domains.
- Mask / silkscreen. Pad-to-mask clearance is 0.075 mm; soldermask is tented front and back; soldermask min width is not explicitly set (KiCAD default applies). Silkscreen marks and fiducials sit on these mask / silk layers — fiducials are bare-copper apertures in the mask for vision contrast.
- DRC. The configured-rule DRC (KiCAD 10.0.1, default constraints) returns 0 violations, 0 unconnected items, 0 schematic-parity errors. Zone refill was not re-run from the CLI (
--refill-zonesunavailable in this build) — a GUI refill is recommended before tape-out.
Components
| Ref | Type | Layer | Function | Source |
|---|---|---|---|---|
| S1 | Copper board ID MDD400_v2.9 | F.Cu copper | Permanent product / variant identifier | mdd400:Variant footprint |
| S2 | CE silkscreen mark | F.Cu silkscreen | EU RED 2014/53/EU compliance | SILKS:CE_3.5mm |
| S3 | RoHS / China EFUP silkscreen | F.Cu silkscreen | EU RoHS + China EFUP (4-year mark) | SILKS:EFUP_RoHS_China_4 |
| S4 | FCC silkscreen mark | F.Cu silkscreen | FCC Part 15 compliance | SILKS:FCC_3.5mm |
| S5 | Scadys logo | F.Mask aperture | Manufacturer identity, 10 × 10 mm | SILKS:scadys_logo_10x10.f-mask |
| S6 | Product-docs QR code | F.Cu silkscreen | Machine-readable link to live docs | mdd400:qr_docs.scadys.io_products_mdd400_10 |
| S7 | UKCA silkscreen mark | F.Cu silkscreen | UK Conformity Assessed | SILKS:UKCA_3.5mm |
| S8 | Copyright silkscreen | F.Cu silkscreen | © 2025 GM Consolidated Holdings Pty Ltd | SILKS:Copyright |
| FID1 | Fiducial marker | F.Cu | Pick-and-place vision alignment, top-left pair | 0.5 mm copper, 1.5 mm mask opening |
| FID2 | Fiducial marker | F.Cu | Pick-and-place vision alignment, bottom-right pair | 0.5 mm copper, 1.5 mm mask opening |
| FID3 | Fiducial marker | B.Cu | Mirror of FID1 on the back | 0.5 mm copper, 1.5 mm mask opening |
| FID4 | Fiducial marker | B.Cu | Mirror of FID2 on the back | 0.5 mm copper, 1.5 mm mask opening |
Testing & Verification
V2.9 is a fabricated prototype. The marks and fiducials are present on the prototype board, but a few items need verification before the V2.10 production fabrication run.
Hardware bring-up (rig at the bench):
- QR-code URL resolution — Scan S6 with a phone QR reader. Pass if the resolved URL matches the live docs URL exactly. (Earlier MDD400 hardware revisions had a
docs.scadys.com→docs.scadys.ioURL transition; the V2.9 schematic footprint readsdocs.scadys.iobut verify on the as-fabricated board.) - Compliance-mark legibility — Photograph each silkscreen mark under typical helm-position lighting. Pass if all marks (Scadys logo, CE, UKCA, FCC, RoHS / EFUP) are clearly readable and unambiguous at arm's length.
- Copyright year currency — Confirm S8 reads the correct year for the production batch. Pass if it reads "© 2025" on the V2.9 prototype; refresh for later batches.
- Pick-and-place fiducial recognition — Confirm at the start of the assembly run that the pick-and-place machine detects FID1–FID4. Pass if both F.Cu and B.Cu setups complete without operator override.
Gaps & next version
Before next production run
- Solder mask min width — Not explicitly set in the KiCAD setup block, so the default applies. Confirm with the fab house against the 0.012 mm mask thickness specified in the stackup.
- Finished copper weight — F.Cu / B.Cu are 0.0175 mm = 18 µm (≈ ½ oz) starting weight; ENIG adds a negligible ~0.075–0.12 µm Au. If the fab requires a minimum finished copper weight, confirm 0.5 oz + plating meets the requirement for the 1 A converter current.
- DRC zone refill — DRC ran on the existing filled zones; the CLI build lacks
--refill-zones. Run a manual zone refill in the KiCAD GUI before tape-out to confirm no fill changes. - Re-scan QR code URL — Confirm the deployed docs URL still matches the silkscreen QR (S6) on the V2.10 PCB before fabrication.
Next version (V2.10)
- Compliance test reports — The CE, UKCA, and FCC silkscreen marks indicate design intent only. The actual test reports that authorise affixing those marks are part of the V2.10 compliance pre-screening campaign (CISPR 32 conducted emissions, FCC Part 15 radiated, RED 2014/53/EU harmonised standards). The marks must not be affixed on production boards until the reports are signed off.
- Copyright year update — Refresh S8 to the V2.10 production year if it differs from 2025.
- Stackup re-validation — No quantitative impedance / plane-pair-capacitance measurements have been taken on V2.9 specifically; re-validate against the prior-revision production data if the stack-up changes.
References
- IPC-A-600: Acceptability of Printed Boards.
- IPC-6012: Qualification and Performance Specification for Rigid Printed Boards.
- IPC-7351: Generic Requirements for Surface Mount Design and Land Pattern Standard (fiducial-marker dimensions).
- EU, Radio Equipment Directive (RED) 2014/53/EU.
- FCC, Part 15 — Radio Frequency Devices.
- UK Government, UKCA Marking.
- EU, RoHS Directive 2011/65/EU.
- China SJ/T 11364-2014, Marking for the Restricted Use of Hazardous Substances in Electronic and Electrical Products (EFUP / China RoHS).
Related pages
- Power Supplies — the SMPS converters and VCC plane-pair this stack-up physically realises
- ESP32 Module — the RF module whose pre-certification covers the board-level FCC mark, plus its antenna keep-out
- Circuit Design Overview — the system-level stack-up rationale that this page realises physically
- Sister-product reference: WTI400 V1.2 PCB Markings & Compliance — same board outline and stack-up; minor differences in board-identity and QR-code URL