4.6 System Test, Calibration, and Pack-Out Specification

A PCBA that passes In-Circuit Test (ICT) is not a finished product. System integration introduces unique failure modes: pinched cables, occluded microphones, thermal shutdowns, and mechanical misalignment. The System Test is the final filter before the customer opens the box. If you do not test the device in its fully assembled state, your customer becomes your QC inspector.

Functional Test Strategy: Objective over Subjective

Eliminate operator judgment. "Does it sound good?" is not a test spec. "Does the 1kHz sine wave measure > 85 dB SPL?" is a test spec.

1. Power and Boot

• Current Profiling: Measure current consumption during boot, sleep, and max load.
  • Logic: If Sleep Current > 50 µA (Target: 10 µA) ⭢ Then FAIL. (Indicates leakage or firmware not entering sleep state).
• Button/UI: Do not ask operators to "press all buttons." Use a fixture with pneumatic actuators or require the operator to follow a screen prompt sequence to verify interrupt mapping.

2. Audio and Optics

• Audio: Use a shielded box. Play a frequency sweep. Measure response using a calibrated reference microphone. Compare against a Golden Curve mask.
• Sensors (Proximity/ALS): Use a grey-card target at a fixed distance. The sensor must read within a specific Lux/Count range. This verifies the sensor window is not occluded by a misaligned gasket.

Calibration vs. Verification

Distinguish between checking a value and tuning it.

• Calibration: The software reads a reference value (e.g., 25˚C chamber temp) and writes an offset to the EEPROM.
• Verification: The device reads the value. If it is outside tolerances (± 1˚C), it fails.
• Rule: Calibrate first, then Verify. Never calibrate and ship without a post-cal check.

Safety Compliance (High Voltage/Mains)

If the device plugs into a wall outlet (AC Mains), safety testing is not optional; it is a legal mandate.

• Hi-Pot (Dielectric Strength): Apply high voltage (e.g., 1500 VAC) between Live/Neutral and the Enclosure/Ground. Leakage must be < 5 mA.
• Ground Bond: Verify the earth pin has a low-resistance path (< 0.1 Ω) to all exposed metal parts.
• Warning: This test can degrade insulation. Use "DC Hi-Pot" if repeated testing is required, or strictly limit duration.

Burn-In and Run-In

Burn-in targets "Infant Mortality" (early failures).

• If New Product/New Process: Implement 100% Burn-In (e.g., 4 hours at 40˚C + Power Cycling).
• If Mature Product: Move to ORT (Ongoing Reliability Testing). Pull 5 units per lot, run for 24 hours. If 1 fails, quarantine the whole lot.

Pack-Out: The Final Assembly Step

Packing is a Bill of Materials process, not a "cleanup" task. Missing accessories cause returns just as often as broken boards.

1. The Packaging BOM

Treat the box, inserts, and bags as engineering parts.

• Sequence: Define the exact order. (e.g., 1. Insert Foam A. 2. Place Unit. 3. Place Accessory Box. 4. Insert Manual).
• Scanning: The operator must scan the Serial Number of the Unit and the barcode on the Gift Box to link them.
• Weigh Scale Check: Place the final sealed box on a scale.
  • Logic: If weight deviates by > weight of 1 cable ⭢ Then Reject. (Detects missing accessories).

2. Visual Quality (OBA Simulation)

Before closing the box, perform a "Cosmetic Final Check" under standardized lighting (800 Lux).

• Criteria: Inspect for fingerprints, scratches, and gap consistency. Wipe down with microfiber if needed.

The As-Built Record (Device History Record - DHR)

Every serialized unit must have a digital birth certificate stored in the cloud/database. Do not ship without generating this record.

Mandatory Fields:

1. System Serial Number.
2. PCBA Serial Number (Child-Parent link).
3. MAC Addresses / IMEIs.
4. Firmware Version (at time of ship).
5. Calibration Offsets (Audio/Thermal/RF values).
6. Test Results: Pass/Fail status for every test step (Safety, Functional, Vision).
7. Timestamp & Operator ID.

Final Checklist

Check	Criterion	Critical Threshold / Requirement
Automation	Subjectivity Removed?	Audio/Vision tests use sensors/cameras, not human ears/eyes.
Safety	Hi-Pot/Ground Bond?	Mandatory for AC-powered devices. Records stored.
Calibration	Sequence?	Calibrate ⭢ Verify. Never skip verification.
Sleep Mode	Current Check?	Leakage current measured to guarantee battery life.
Traceability	DHR Complete?	Cloud record links SN, FW Version, and Test Data.
Pack-Out	Weight Check?	Final box weight validates accessory presence.
Firmware	Version Lock?	Script verifies FW version matches BOM requirement.
Cosmetics	Lighting?	Inspection station has defined lux (800 – 1000 Lux).