Wearable Health Patch
Worked for 30 sec
Prepared the PCBWay DFM submission materials and regenerated the STEP model. I can’t submit to PCBWay directly from Flux, but these files are ready for you to upload to PCBWay’s rigid-flex/HDI quote channel for engineering feedback.
Project files:
Upload package:
Open items:
- Final assembly is still incomplete: DRC has unresolved airwires.
- Use these files for PCBWay engineering review only, not fabrication release.
- After PCBWay provides the approved stackup/via table, manually finish AD5940/ADS1292 fanout, clear airwires, rerun DRC, then regenerate final exports.
Start Auto-Layout
Thought for 13 sec
I’ll inspect the current PCB state, determine whether placement, routing, or both need work, then run the appropriate auto-layout operations and verify the applied result.
Thought for 22 sec
Blocked: your account currently has no available ACUs, so AI inspection and auto-layout operations are unavailable.
Current known project state:
- 6-layer rigid-flex working layout.
- AD5940 support placement previously reorganized.
- PCBWay HDI-oriented rules applied.
- Last verified state had 24 unresolved airwires.
No PCB changes were made in this session. Remaining work is to inspect the latest board state, determine whether placement and/or routing is needed, run auto-layout, apply the result, and verify DRC once ACUs are available.
Check ACU balance
List airwires
Check DRC/ERC
Manual placement review
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Preliminary FMEA — Neura Vital Patch
Scope
Design-stage failure mode analysis for the current Flux schematic architecture. This must be refined with final intended use, medical classification, materials, layout, and prototype test data.
Failure Mode Table
Table
| Subsystem | Failure Mode | Effect | Severity | Likelihood | Detection | RPN | Mitigation |
|---|---|---|---|---|---|---|---|
| USB / patient electrodes | USB connected while electrodes contact patient | Leakage current through patient-applied parts | 10 | 4 | 4 | 160 | Battery-only sensing policy, hardware electrode disconnect, USB detect, leakage testing, medical isolation if sensing while charging. |
| LiPo battery | Overcharge/thermal rise near skin | Burn, cell damage, unsafe operation | 9 | 3 | 4 | 108 | Protected cell, BQ24074 TS/NTC, conservative charge current, thermal testing, firmware cutoff. |
| Charger input | Noncompliant USB supply/ESD surge | Damage, overheating, unsafe ground path | 8 | 4 | 5 | 160 | VBUS ESD, input current limit, charger OVP, test with chargers/cables, no patient sensing on USB. |
| BLE security | Unauthenticated data access/update | Privacy/cybersecurity failure | 8 | 4 | 5 | 160 | BLE bonding/encryption, signed firmware, debug lock, key management. |
| ECG AFE | Motion/electrode artifact interpreted as physiological signal | False heart-rate/rhythm data | 7 | 6 | 5 | 210 | Contact quality, lead-off detection, signal-quality index, algorithm validation. |
| PPG | Ambient light/motion/poor contact | Incorrect HR/SpO2-like data | 7 | 7 | 5 | 245 | Optical baffle, contact-pressure compensation, accelerometer artifact rejection, no SpO2 claim until validated. |
| Electrochemical glucose/lactate | Sweat/ISF signal poorly correlated to blood analyte | Incorrect biomarker claim | 9 | 7 | 7 | 441 | Research-only positioning, calibration, pH/sweat-rate/temp compensation, chemistry validation, clinical study before claims. |
| Pressure sensor | Contact/pulse signal used as BP without validation | Incorrect BP claim | 9 | 6 | 7 | 378 | Treat as contact/pressure signal only; cuffless BP requires separate clinical validation. |
| Flex PCB | Copper crack or solder fatigue in bend region | Intermittent readings, sensor failure | 7 | 5 | 5 | 175 | Rigid islands, no vias/components in bend zones, strain relief, flex-cycle testing. |
| Moisture/sweat ingress | Corrosion/leakage on high-impedance nodes | Drift/noise/failure | 8 | 6 | 5 | 240 | Encapsulation, guarded high-Z traces, compatible finishes/materials, environmental testing. |
| RF antenna | Detuned by skin/battery/copper | Poor BLE range, data loss | 5 | 5 | 4 | 100 | Edge antenna placement, keepout, on-body RF validation. |
| Firmware | Patient switch not disabled on USB attach | Unsafe electrode path | 10 | 3 | 4 | 120 | Hardware interlock, fail-safe default, USB attach interrupt, startup self-test. |
Risk Priority Actions
- Implement hardware USB-forced electrode disconnect; do not rely solely on firmware.
- Finalize LiPo protection, NTC, charge current, and thermal shutdown strategy.
- Treat sweat glucose/lactate and BP as research signals until validated.
- Partition layout for high-impedance ECG/electrochemical signals, RF, and charger/power.
- Define regulatory claim scope before design freeze.
Open Items
- Exact patient-applied-part class: BF/CF/non-medical wellness.
- Final sensing-while-charging policy and mechanical interlock.
- Biocompatibility and sterilization/single-use strategy.
- Clinical validation plan and acceptance criteria.
2026-07-27 FMEA Update
- USB/patient-electrode mitigation improved: hardware USB-forced PATIENT_SW_CTRL clamp added, reducing dependence on firmware-only switch disable. Residual risk remains high until leakage and single-fault testing are performed.
- LiPo thermal mitigation improved: RT1 10 kΩ NTC added on charger TS and charge current set to ~100 mA. Residual risk remains until NTC-to-cell thermal coupling and skin-temperature rise are validated.
- Layout/routing residual risk added: 26 airwires remain, primarily around AD5940/ADS1292 fine-pitch ground/reference/signal escape and GND stitching. Manufacturing release is blocked until routing and DRC are clean.
Scope
Failure Mode Table
Risk Priority Actions
Open Items
2026-07-27 FMEA Update
