3. Phase 3: The Testing Procedure – Applying the Pulses
This phase outlines the core sequence of steps for stressing the microcircuit (the DUT) with ESD pulses to determine its sensitivity.
- Establish a Baseline Before any ESD pulses are applied, the devices must undergo standard parametric and functional testing at room temperature. The reason for this is simple: you need to know that the device works perfectly before you expose it to potentially damaging static discharges. This gives you a clear “before and after” comparison.
- Select Pin Combinations An ESD test isn’t just a single zap to the whole chip. Instead, pulses are systematically applied to various combinations of the device’s pins. This process involves testing individual pins against groups of other pins (such as all the power pins or all the ground pins) to ensure all possibilities for current flow are covered.
- Stress the Device The actual stressing procedure follows a strict recipe to ensure consistency.
- Sample Size: 3 devices are required for testing. The same set of 3 devices can be used to test successive voltage levels (e.g., 100V, then 200V, etc.) as long as all devices pass at each level.
- Pulses: For each selected pin combination, 1 positive pulse and 1 negative pulse are applied.
- Timing: A minimum delay of 1 second is required between each pulse.
- Find the Failure Threshold The test is iterative. You don’t just zap the device at the highest voltage. Instead, the test begins at the lowest voltage level (e.g., 100 volts) and, if the devices pass, progresses to the next higher level. This process continues until the devices fail, allowing you to pinpoint the voltage level at which the microcircuit can no longer survive.
After the stressing procedure is complete, the final step is to analyze the results and officially classify the device.