Project Brainstorming for Collaboration Device
Thought for 2 mins 9 sec
Below is a single-page, PDF-ready “Fabrication & Assembly Package” document for PCBWay. Paste this into a doc and export to PDF. All components are linked to your Flux project.
Project: Secure Classroom Handheld Student-Response Device
- Summary and build intent
- Purpose: Handheld device for classroom polling and short voice clips. BLE onboarding, HTTPS REST to teacher dashboard, OTA A/B updates, enterprise Wi-Fi (EAP-TLS).
- Use profile: 8 hours active per day.
- Core modules:
- MCU: U1 Wi-Fi + BLE with PDM/I2S mic input (no speaker).
- Power: 1-cell Li-ion charger U2, 3.3 V buck U3, optional quiet LDO U4.
- Security: I2C secure element U5.
- Audio: Digital mic U6 via PDM/I2S.
- I/O: Buttons SW1, SW2, SW3; RGB LED LED1; mic hard-mute switch SW4.
- Connectors/Protection: USB-C J1, USB ESD array D1, reverse-polarity diode D2, VBUS TVS D3.
- Programming: 6-pin header J2.
- PCB fabrication specifications
- Layers/stackup: 4 layers (Standard 4 Layer in Flux).
- Material: FR-4, Tg ≥ 135 C.
- Thickness: 1.6 mm nominal.
- Copper: 1 oz outer, 0.5–1 oz inner.
- Finish: ENIG preferred (lead-free HASL acceptable).
- Soldermask/Silkscreen: Green/White, both sides.
- Tolerances/quality: IPC Class 2.
- Vias: Through-hole; tent SMD-area vias if needed.
- NPTH mounting holes: Hole1, Hole2, Hole3, Hole4.
- Controlled impedance: Not required.
- Antenna keep-out: Strict keep-out under/near U1 module antenna (no copper or tall parts in near field).
- Assembly specifications
- Standards: IPC-A-610 Class 2, RoHS lead-free (SAC305).
- Stencil: 0.12 mm laser-cut stainless; 1:1 apertures for 0402 passives. Reduce only if tombstoning observed.
- Polarity/orientation:
- ESD handling: Treat U1, U5, U6 as ESD sensitive.
- Cleaning: No-clean acceptable.
- DNP option: U4 and its caps may be DNP if buck output noise is acceptable.
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Key BOM line items (for reference) | RefDes | Description | |---|---| | U1 | Wi-Fi+BLE MCU module (ESP32-class) with PDM/I2S | | U2 | Li-ion charger (USB-C input) | | U3 | 3.3 V buck regulator | | U4 | Optional low-noise 3.3 V LDO (DNP optional) | | U5 | I2C secure element | | U6 | PDM/I2S digital microphone | | J1 | USB-C receptacle | | D1 | USB data/CC ESD array | | D2 | Reverse-polarity protection diode | | D3 | TVS diode (VBUS surge/ESD) | | LED1 | RGB LED | | SW1, SW2, SW3 | Momentary buttons | | SW4 | Mic hard-mute switch | | R1, R2 | USB-C CC/VCONN resistors | | R3, R4 | I2C pull-ups | | C3–C9 | Decoupling/bulk capacitors | | J2 | 6-pin programming header | | GND | Ground reference |
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Critical DFM/DFA notes
- Antenna keep-out for U1: no copper pours, traces, or tall parts within the module’s antenna near field.
- Switching regulator locality: Keep U3 high-di/dt loop tight; manage local ground to prevent coupling into audio and RF; stitch locally to plane.
- USB ESD path: Place D1 near J1; provide short, direct returns to GND.
- Mic routing: Keep U6 away from switch node; route PDM clock/data short with continuous ground return.
- Placement margin: Leave space for routing and vias and use airwires to visualize the routing paths.
- Test and programming (DFT)
- Programming/debug: Access J2 for firmware flash and bring-up.
- Basic power checks: Validate charger U2 from J1, 3.3 V rail from U3, optional LDO U4.
- Functional checks:
- ESD/EMI: Verify no resets or latch-ups under ESD on USB and user I/O.
- Deliverables included (from us)
- Fabrication: Gerbers (RS-274X), Excellon drill files, board outline, IPC-356 netlist (if requested).
- Assembly: BOM (CSV), Pick-and-Place/Centroid (CSV), top/bottom assembly drawings (PDF), schematic PDF, this README.
- Optional: Panel drawing if panelization requested.
- Panelization and labeling
- Panelization: Not specified; fabricate as single boards unless instructed otherwise.
- Labeling: Add assembly revision, date code, and device ID/QR on silkscreen if available.
- Acceptance criteria
- Electrical: No shorts/opens; charger operates from 5 V USB-C; 3.3 V rails within ±5%.
- Visual: Solder quality per IPC-A-610 Class 2; correct orientations for U1, U5, U6, D1, D2, D3, LED1.
- Functional: Buttons/LED operate; MCU boots via J2; mic capture path functional.
If you want, I can add compact top/bottom assembly drawings with RefDes callouts and a one-line panel note. Do you want panelization now (units per panel, rail size, break-away style), or proceed as single boards?
Ask for panelization
Clarify antenna keep-out
Refine stencil guidance
Request assembly drawing help
Improve test strategy
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