3. Equipment Qualification and Waveform Verification
Rigorous calibration and frequent verification are essential to the integrity of the test results.
3.1 Calibration and Safety
- Calibration Schedule: Equipment must be calibrated upon initial acceptance. Recalibration is required at least every 12 months and any time repairs are made that could affect the waveform.
- Worst-Case Verification: Calibration must be performed using the “worst-case pin combination”—the pin sockets with the shortest and longest electrical paths from the pulse-generating circuit—to ensure the system performs within limits under all conditions.
- Safety Training: All personnel must receive system operational and electrical safety training. The operating location should be inspected by a safety engineer to ensure the equipment is not operated in a combustible or hazardous environment.
3.2 Waveform Specifications
The current pulse delivered by the simulator must meet precise specifications at different voltage levels. These are verified using both the shorting wire and the 500 ohm resistor.
| Voltage Level (V) | Positive Ipeak for Short, Ipsi (A) | Positive Ipeak for 500 Ohm, Ipr (A) | Current at 100 ns for 500 Ohm, I100 (A) | Maximum Ringing | Resonance Frequency, Fr (MHz) |
| 100 | 1.5 – 2.0 | N/A | N/A | Ipsi x 30% | 11 – 16 |
| 200 | 2.8 – 3.8 | N/A | N/A | Ipsi x 30% | 11 – 16 |
| 400 | 5.8 – 8.0 | 4.5 maximum | 0.29 +/- 20% | Ipsi x 30% | 11 – 16 |
3.3 Routine Waveform Verification
- Frequency: Verification must be performed at the beginning of each shift or any time the DUT socket or board is changed.
- Procedure: A 400-volt pulse (both positive and negative) is applied through the worst-case pins, and the resulting waveform is checked for compliance with the specifications in the table above.
- Compliance: If the waveform is non-compliant, testing must be halted until the issue is resolved. All subsequent ESD test data must be supported by a preceding, satisfactory waveform check.