When do we experience electrostatic discharge?
The electrostatic discharge (ESD) is a well known phenomenon. We experience it in everyday situations such as walking, wearing clothes, undressing. Walking causes alternating contact of the shoes’ soles with the ground. Dressing and undressing means friction between your hair, outerwear and underwear.
What effects might an uncontrolled and excessive electrostatic charge have?
Contact with electrostatically charged material is a frequent occurrence. Uncontrolled, excessive electrostatic charge might lead to:
- disruption of technological processes
- disruption of electric and electronic devices’ operation
- damaged electric and electronic devices
- a threat of fire or explosions
- endangering human lives
The triboelectric series is used to present the materials’ vulnerability to amass or lose electrons, so in other words, the ability to gaining a positive or negative charge. The generated electrostatic potential is usually harmless to us, but can be very dangerous when it comes to many electronic devices.
What are ESDS?
In the era of miniaturisation voltages as low as 100V can be unsafe to some electronic devices. Humans, for an example, can feel 3000V by touch, hear cracking at 5000v and observe an electric spark at 10000V. Electrostatic discharge sensitive devices (ESDS) can be damaged by static electricity (the word “static” signifies the limited movement capabilities of such a charge, which are in turn conditioned by conductive properties of a given material. We use certain parameters to predict and evaluate risk, as well as the effectivenss of ESD protection. These parameters signify the material’s charge and its ability to lower the charge:
- electrostatic voltage
- electric intensity
- discharge energy
- surface resisitivity
- volume resistivity
- leakage resistivity
- charge relaxation time
What are the norms used in ESD protection?
According to the norm, materials are divided into 3 groups: conductive, dissipative and shielding. The basic methods used for ESD protection are:
- grounding of conductive elements
- field shielding
- use of anti electrostatic products
- increasing humidity
- air ionisation
- personnel anti electrostatic protection
All materials are classified in norms and directives according to their physical properties.
What are the European (and therefore Polish) norms?
PN-EN 61340-5-1 – Electrostatics – Part 5-1: Protection of electronic devices from electrostatic phenomena – General requirements
PN-EN 61340-5-2 – Electrostatics – Part 5-2: Protection of electronic devices from electrostatic phenomena – User guide
Because plastic packaging is an integral part of ESDS packing, protection and storage, 3 sets of protective qualities are used – conductivity, dissipation and shielding. The norms are used to classify packaging according to its usability in given conditions.
Future of “antistatics”.
The conductivity is introduced in plastic materials by using:
- carbon filings and carbon fibres
- graphite
- aluminium
- metallised glass fibres
- internally dissipative polymers
- internally conductive polymers
- migrating chemical admixtures (with time and humidity sensitive properties)
The future of antistatics (both in packaging and in other industries using plastics) lies in solutions based on nanocomposites, mainly carbon nanotubes, physical and mechanical properties of which are practically invaluable. Nanotubes provide stability of the electrical properties of plastics in variable weather conditions.