We often hear our customers say they want to “de-ionize” or “ionize” air flow to protect ungrounded electronics and work surfaces from holding a static charge.
Since charge sits on the surface of an object, we can use charged air molecules to dissipate the static on it.
Ionization is this process of positively and negatively charging thousands of air molecules so that when they come into contact with the charged molecules they attract them off the charged object, or push them off the charged object.
1. Ions and Emitter Points
Ionizers are made up of multiple emitter points– metal needles that conduct charge. When
This corona of ions then interacts with electrons in nearby gas molecules.
2. When Should I Use Ionization?
Static electricity is a problem for insulative materials and electrically isolated conductors.
Conductors can and should be grounded if possible. Grounding a conductor will discharge static electricity from it.
Conductors can be grounded because they hold charge uniformly across their surface.
Conductors can be charged by triboelectrification (contact and separation resulting in an exchange of electrons), induction (being in proximity to an electric field), or conduction (direct contact with a charged object.)
Insulators, by contrast, can hold multiple positive and negative charges in islands or pockets across their surface.
Insulators are charged by triboelectrification or rubbing against other materials where electrons are exchanged resulting in the creation of a charge.
While the creation of humidity can mitigate some static charges, most manufacturers decide to install an ESD air ionizer in their facility if people are being shocked regularly.
The second reason most people install ionization is that of product contamination. Static electricity attracts micro-particles that can alter the function or operability of certain electronic products.
Known as Electrostatic Attraction (ESA), it is a problem common to semiconductor and increasingly medical device manufacturing.
For more information about installing ESD air ionizers in a cleanroom please consult with our trained technical staff at Bennett & Bennett.
3. How does AC Corona Ionization Work?
In automated assembly-line applications where you need to ensure charge is dissipated evenly across the surface of an object quickly so that you are not waiting for the charge to dissipate the only option is to use AC ionizers.
If you were to use DC ionization on an automated assembly line, “streaking” can occur: one side of an object can be reduced of its charge, and the other side of the object can be left untouched.
This is because DC ionizers have emitter points spaced apart, and are forced to shoot ions in sequence to achieve the same effect as AC ionizers running at line frequency.
4. How Does DC Corona Ionization Work?
Direct current (DC) ionizers shoot both positive and negative ions through their emitter points at constant rates. Since the ions are emitted from separate points, there is much less recombination of ions over distance– which can cause charge to accumulate in the air.
In fact, some DC ionizers are used without using air flow at all.