astra/iphone-encoder-counter

FABRICATION.md

# Prototype fabrication and assembly

**RELEASE HOLD:** U2/U3 inventory is insufficient for the assumed five-board batch, and the antenna needs measurement in the final case. The ZIP is a prototype candidate, not a production-approved order package. See ANTENNA.md and STOCK.md.

Upload `fabrication/iphone-encoder-counter-jlc.zip`. Select 2-layer FR-4, 60 × 100 mm, 1.6 mm thickness, 1 oz copper, ordinary solder mask, ENIG finish for bare programming contacts, and top-side assembly. Review the manufacturer's preview before ordering. No order has been placed.

The package contains copper, solder mask, paste, legend, outline, plated drill, BOM and placement files. Native coordinates are signed millimeters with the board centered at the origin; all assembly coordinates share that origin. The outline is the single 60 × 100 mm rectangle. Minimum routed trace is 0.15 mm, via hole 0.30 mm, via pad 0.60 mm. Independent copper checks use 0.15 mm clearance and 0.30 mm board-edge clearance. The NFC spiral uses 0.25 mm trace/space.

The finishing script changes only F_SilkScreen.gbr and F_Paste.gbr. Top legend uses a 0.15 mm stroke and 0.20 mm clearance from mask openings. Paste is removed on four bare J2 contacts, two L1 terminals. All copper, mask, drill, BOM and placement files are byte-identical to native tscircuit export. See validation/gerber-finishing.json.

Use `bom.csv` and `pick_and_place.csv` for 23 top-side components. L1 and J2 are intentionally absent. L1 is printed copper, J2 is bare contact copper. U2 is NVE ADT002-10E, JLCPCB C17208043, and is included in the BOM, placement and paste stencil. The direct catalog page reports no stock and assemblyComponentFlag=false / assemblyMode=manualWeld. Confirm sourcing and the assembly process with JLC before ordering; it is not presently confirmed as a turnkey stocked SMT part. Its exposed pad connects to ground. Align pin 1 to the manufacturer's land pattern and review the assembly preview before approval. All remaining assembly parts carry their existing JLCPCB numbers.

Install the CR2450 only after soldering and cleaning; observe holder polarity. U3's exposed pad is electrically floating as required by this design. No adhesive, ferrite, magnets, cell, rotor or case is included in the JLC BOM.

Initial bring-up: inspect for shorts, use a current-limited 3 V supply with the cell removed, program/provision through J2, measure idle current across removed R0 with an ammeter, test both rotation directions and button debounce, verify power-loss recovery, then tune/test NFC in the final case. Verify reading while attached to the actual iPhone before building a batch. The portable C files are not a flashable MCU image; follow FIRMWARE.md to implement and validate the platform port.