ANSI SP14.5-2015 pdf free download
ANSI SP14.5-2015 pdf free download.For Electrostatic Discharge Sensitivity Testing – Near-Field Immunity Scanning – Component/Module/PCB Level.
5.0 EQUIPMENT All equipment within the test system must be able to withstand the maximum current and voltage for any pulse width applied. Oscilloscope inputs are generally vulnerable to damage from high voltages and may require external overvoltage protection devices. Care should be taken to use oscilloscope probes that are also rated for the highest voltages to be encountered. 5.1 Scanning System The scanning system as shown in Figure 2 moves a probe to a predefined location. Typically, XYZ flatbed scanners are used, although any other robotic system could be suitable for this testing. Besides moving in XYZ direction it should also be possible to rotate the probe. Keeping a defined distance, from 0 mm to 1 0 mm (0.40 inch), between the device under test (DUT) surface and the probe should be allowed by the mechanical positioning system. A variety of probes should be made available, to change the localization of the field and to create different field components. For automatic scanning, the scanning system needs to have a feedback to the DUT which allows it to identify (soft) errors that are caused by the field injection, and the system needs to be able to reset the DUT. The supervision of errors is typically done by one or more of the following but any method capable of detecting a fault can be used: · Specific error checking software. · Loss of USB or LAN connectivity. · Changes in indicator LEDs. · Static changes in displayed screens by comparison of before and after camera capture. · Changes in audio playback. · Changes in the current consumption or in voltage levels. · Feedback from bit error analysis or eye diagrams, an oscilloscope display commonly used as an indicator of the quality of high-speed digital signals.
5.2 Pulse Source / Transmission Line Pulser The recommended pulse source is a transmission line pulser having a fast rise time, but a slow fall time. See Section 6.0 for waveform clarification. A double exponential pulser would also be suitable. A rise time of less than 300 ps is recommended using the 1 0-70% measurement bracket. Using low pass filters able to withstand the high voltage pulses can change the spectral content of the pulse and are therefore not recommended. The pulse source should be able to provide 2 kilovolts into a 50-ohm load from a 50-ohm source (4 kilovolts open circuit voltage). For most testing, 4 kilovolts is sufficient. However, when using smaller diameter probes, i.e. 0.5 mm (0.01 9 inch), a 2x factor in voltage or 8 kilovolts, may be required. The repeatability and consistency of the pulse shape, levels and rise/fall time are critical for meaningful comparisons between samples within a dataset, as well as making relative characterizations between datasets. Confidence levels can of course be ascertained by taking multiple scans of the same DUT and noting the differences.
5.3 Probes The scanning operation provides the field-coupled pulse to the IC’s via the electromagnetic near- field from an injection probe. Probes are needed for electric (E-field) and magnetic (H-field) fields of different orientations. Normally, there is a trade-off between the strength of the coupled signal and the probe size. H-field probes consist of small loops and E-field probes generally consist of small horizontal discs. Typically, probes ranging from 50 mm (1 .97 inches) down to 0.5 mm (0.01 9 inch) in diameter should be used. The larger probes are for a coarse evaluation of sensitive areas where as the smaller ones are for the identification of individual sensitive nets. A good starting point is using a 1 0 mm (0.40 inch) diameter magnetic field and a 1 0 mm (0.40 inch) diameter electric field probe and scan between 0 and 2 mm (0.078 inch) away from the module or IC to approximately locate sensitive areas. In a second scan, using a finer probe which is limited to the sensitive areas identified in the first coarse scan, sensitive nets can be located. It should be noted that coarse scans can also introduce aliasing of upset levels as the sampling points become more distant. Two points on the DUT, which may be equally susceptible to damage, may appear different in the data due to a “direct hit” on one point and a near-miss on the other. This issue may be somewhat addressed in the data visualization and post-processing phase. 6.0 WAVEFORM The suggested waveform is depicted in Figure 1 . It has a fast rise time, but a slow fall time to avoid injecting two pulses via the loop and magnetic field, which would happen with both fast rise and fall times. A rise/fall time ratio of greater than 20 is suggested.
