Project Brainstorming for Collaboration Device

flux

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
  1. 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.
  1. 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).
  1. 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:
    • Diodes: D1, D2, D3 mark cathode.
    • LED: LED1 orientation per footprint indicator.
    • Switches/Buttons: SW1, SW2, SW3, SW4 per silkscreen outlines.
    • Module: U1 castellations; keep antenna region unobstructed.
  • 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.
  1. 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 |
  2. 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.
  1. 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:
    • Buttons SW1–SW3 respond; RGB LED1 drives.
    • Mic U6 capture recognized by MCU U1.
  • ESD/EMI: Verify no resets or latch-ups under ESD on USB and user I/O.
  1. 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.
  1. 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.
  1. 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
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Secure Classroom Handheld Student-Response Device

Properties

Hole1, Hole2, Hole3, Hole4, GND, U5 SCL - R3 P1, J1 VBUS1 - J1 VBUS2, U1 3.3V - R4 P2, D1 GND - GND GND, U2 BAT - C8 P1, U1 IO17 - LED1 A_G, U1 IO0 - J2 JTMS, U1 IO16 - LED1 A_R, U3 OUT - U4 IN, U1 IO14 - SW2 1, U1 IO15 - SW4 1, J1 CC - R1 P1, D3 K - J1 VBUS, U1 IO13 - SW1 1, U6 WS - U1 IO26, U1 GND - J2 JTDI, J1 VBUS3 - U2 VCC, U6 SCK - U1 IO27, U1 IO18 - LED1 A_B, U1 IO12 - SW3 1, SW3 2 - SW4 2, U5 SDA - R4 P1, U6 SD - U1 IO33, J1 VCONN - R2 P1, U1 RXD0 - J2 NJTRST, U1 TXD0 - J2 RESET, U1 EN - J2 JTDO

WiFi

Switches

USB

Battery

Standard 4 Layer

Display

Bluetooth

Buttons

flowchart TD Battery["1S Li-ion Battery"] --> Charger["Li-ion Charger (USB-C)"] Charger --> Buck["3.3V Buck Converter"] Buck --> MCU["Wi-Fi+BLE MCU"] Buck --> LDO["Optional Quiet LDO"] MCU --> Mic["PDM/I2S Microphone"] MCU --> Secure["I2C Secure Element"] MCU --> Buttons["2–3 Buttons"] MCU --> RGB["RGB LED"] MCU --> Mute["Mic Hard-Mute Switch"] USB_C["USB-C CC/ESD"] --> Charger

Consumer Electronics

Pricing & Availability

Distributor

Qty 1

Arrow

$6.75–$12.20

Digi-Key

$15.97–$17.05

LCSC

$11.99–$12.51

Mouser

$18.85–$19.44

TME

$5.49

Verical

$3.92–$27.40

Controls