ABL ESD Machine Description
Test Purpose
The purpose of completing electrostatic discharge (ESD) sensitivity tests is to measure the sensitiveness of a material to ESD. The transition from no reaction to reaction must be determined to evaluate in-process risks. The in-process potential from esd scenarios is compared against the material response. For example below is shown a plot of an example transition from no-reaction at low esd energies to reaction at increasing energies. The ESD energy is used to compare in-process scenarios to the material response.
Equipment
The ABL ESD machine has been used by Hercules, ATK, SMS, and others to closely mimic in-process conditions and obtain reaction probabilities at various ESD energies for more than 25 years.
Key Parameters
Sample conditionRepeatably obtain results for a given sample Substances are tested in the worst-case or smallest-particle-size in-process condition.
| Key Parameter | Objectives | Origin | Specs |
|---|---|---|---|
| Supply voltage | Provide a calibrated high-voltage discharge pulse | Approximate a human or machine high-voltage discharge | Standardized to 5000 VDC ± 1% (adjustable) |
| System capacitance | Provide a calibrated high-voltage discharge pulse: actual discharge capacitance should be determined | Approximate a human or machine discharge | Standardized bank of capacitors from 0.0001 μF up to 0.5 μF |
| Approaching needle | Simulate discharge from a charged, approaching object through energetic material to a grounded object | Approaches the sample holder | |
| Shape of discharge electrode | Provide a energy discharge consistent with that of an approaching needle | Standardized as a needle-shaped electrode (phonograph needle) | |
| Gap between needle and sample holder | Sufficient gap to ensure the sample is not impacted by the needle; close enough that the needle will discharge through the gap | Typical gap between needle and sample holder is between 0.020 in and 0.060 in | |
| Sample thickness | Provide a test surface through which a spark can pass | Other sample thicknesses may be used to simulate specific process equipment conditions | Standardized to a monolayer of material; thickness of slices are typically 0.033 ± 0.004 in |
| Sample quantity | Provide a uniform area so that the pathway of least resistance is through the test sample (not around it) | ||
| Sample holder | Conductive and large enough to prevent edge effects | Standardized to 0.5-in diameter | |
| Firing circuit |
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| Reaction detection | Observation, detection, and documentation of a material’s response to the test stimuli | High-speed video, GoDetect, gas analyzer | |
| Characterization of reaction types | Provide consistent standards for judgment and evaluation of a material | Flash/ flame, audible report, smoke, flame trace, significant sample consumption, decomposition (change in color or odor), jetting | |
| Test Temperature and Humidity | Determine the temperature/ humidity dependence of the sample’s sensitivity as applicable. Energetics typically become more sensitive with an increase in temperature. | Standardized as ambient temperature and humidity. In-process conditions should be used as possible. | |
| Number of trials | Adequately determine the sensitivity result (characterization curve) with the fewest number of trials | At least 30 trials |
Indicators
| Indicators | Detection Method | Assessment |
|---|---|---|
| Reaction upon insult | Detection of explosion (high-speed video with GoDetect™, gas analysis, etc.) | The trial is considered “+” at the ONSET of material reaction. |
| Transition probability | Transition probability most efficiently defined by use of an algorithm such as SEQ, Neyer, or other step sized optimized method | Risk is assessed based on the comparison of the in-process energies to the material response. |
ABL ESD Setup Example
