ESD Simulator

ESD (electrostatic discharge) done by galvanic contact or arcing. You can destroy components, especially microelectronic devices. Due to the resulting electromagnetic waves but they can also induce noise voltages in circuits. These need not necessarily cause irreversible damage, but may result in malfunctions or temporary (eg computer crash).

For the investigation of these two factors, there are therefore two sets of ESD discharge models:

  • 2.1 ESD - guns

ESD discharge models for the investigation of components destruction

Stress methods with two galvanic connections

A circuit is configured such that there is a complete current path for the line-connected discharge. Thus, the discharge current flows out again in a pluggable connector and out of another. Since, in principle, all combinations must be tested by terminals may result in multi-legged components ( at Integrated circuits are now 1000 terminals are not uncommon) come to a high number of combinations. The test can therefore take a long time, or it may be very complicated to figure out the relevant ( destructive ) combinations.

HBM - Human Body Model

This is historically the oldest model, starting from the discharge of a human body with less than 40 kV. The human body has a typical capacity of 100 pF to 300 pF and an electrical resistance R of about 1500 Ω ( skin resistance, spark gap ). For example, charging to 10 kV to 10 mJ stored as energy and the charge is 2 mu.C. The rise time of the discharge edge is in the nanosecond range, the current peaks reach up to 20 A at fingertip discharge. Apart from the history of a particular capacitor is discharged through a fairly large ohmic resistance in HBM. The stream must be assessed solely by the resistance and not by parasitic capacitances and inductances, the curve shape is well damped and does not oscillate. HBM structures are therefore now very reproducible.

MM - Machine Model

The basic idea here is the discharge of a machine against a component. Since a metallic contact is providing the resistance, in contrast to the HBM is very small. The capacity, however, is slightly larger and the line inductance gaining lot of influence. It therefore results in a weakly damped oscillation with an average frequency of 20-100 MHz. Because of the small resistance of the current peaks in mm, typically 10 times higher than in a structure with the same HBM precharge. The LRC parameters of the MM are less accurate standardized and implemented as the dominant parameter R HBM models, therefore, the reproducibility is poor.

System Level Model

There is inconsistent proposals that are based on the idea of ​​" man with a screwdriver ", such as manipulation of finished devices in the service area. That unlike HBM enters a metallic contact from your device on hand with screwdriver, causing a very hard, short, first surge up to 30 A, superimposed on the slower discharge of the remaining capacity of the arm and torso. Accordingly, the model circuit contains two charge storage with corresponding resistors. Individual components can not be protected, or just with uneconomic expenditure against such rabid events. However, this is only required in exceptional cases because the examination is no longer revolves around the use of the individual components, but the manufacture of devices or boards with several components. In this case, can receive the most energy and spark gaps natural components such as capacitors or special ESD protection devices, such that the extreme current peaks not arrive at the photosensitive elements.

Stress methods with displacement current

CDM - Charged - Device Model

Discharges a charged component - eg if mounted operations - against conductive parts occur so that only one connection the conductive part (eg the machine ) contacts. The circuit will be closed by the capacity of the device against the machine, so do not galvanic, but by a displacement current. The capacity of the RLC series circuit is formed that is relatively small and depends on the device itself, and its distance from the conductive surfaces. The R and L parameters are extremely small. The discharge is therefore extremely fast. Depending on the manufacturing technology, the internal protection circuitry of the devices can still react or not. In contrast to the other two methods with galvanic connections, the discharge paths are characterized by less than the signal terminals through the power connections in the component. This also leads to another error images. The (slow ) charging of the device can be achieved by wire or by means of a field plate, that fact alone for the measurement without meaning. Other hand, very large significance of the parasitic elements of structure (LRC ). For this reason, we distinguish different types of CDM devices. The peak value of the current and the waveform are less dependent on the pre-charge voltage and the meter so that the comparability of the results is not only given only on the basis of the precharge.

ESD discharge models for the investigation of radiation resistance

ESD guns

There are also " ESD test probes " to produce arcing and contact discharge according to IEC / EN 61000-4-2:2008 standard and others, harmonized standards. In practical use, the current pulses produced are highly variable because the environmental conditions (distances, etc. to conductive surfaces, length and location of the grounding wire ) vary widely, and the frequencies generated are high relative to the size of the current loop. However, the discharge through a 2 ohm resistor (after Pommerenke ) and a suitable oscilloscope be measured very accurately.

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