Ionisation – The Big Three
Have you ever wondered if your electronics manufacturing or handling process requires the use of Ionisation? Or perhaps you have considered how to handle insulators within your EPA. In this post, we reveal:
- 3 Reasons for Ionisation
- 3 Types of Ionisers
- 3 Functions of an Ioniser
Apparently, THREE really is a magic number!
3 Reasons for Ionisation
You will have heard us say that one of the key principles of ESD Control is to ground all conductors, including people. By grounding conductors, you are removing the electrostatic charges from them, limiting their capability of causing Electrostatic Discharge (ESD). Well, not all materials are conductive, therefore not all materials are groundable. Some, like plastic, glass, or cardboard, are insulative and therefore you cannot remove their electrostatic charge to ground. You might presume this is where Ionisation comes in, Ionisers are designed to neutralise static charges, but they are only required if at first insulators cannot be:
- Removed from the ESD Protected Area. This requires strict procedures for not allowing unnecessary insulators into the EPA, a good product qualification programme and good training for all personnel that might bring items into the EPA.
- Substituted with an ESD Protective Alternative. Where something is required in order to do the job, then it may be replaced with a suitable ESD safe alternative, such as antistatic tape, static dissipative hand tools, or ESD safe document holders.
- Controlled with a topical antistat. Finially, before you consider Ionisation, an antistatic spray such as Reztore® Antistatic Coating might be suitable for coating the insulator, making it temporarily static dissipative.
“Air ionization is not a replacement for grounding methods. It is one component of a complete ESD control program. Ionizers are used when it is not possible to properly ground everything and as backup to other ESD control methods.”
User Guide IEC TR 61340-5-2 clause 5.3.3.4.6.1 Introductory remarks
And there we have it… 3 reasons for Ionisation.
3 Types of Ionisers
There are three main types of Ionisers, all of which will neutralise static voltages on insulators, but each have slightly different applications.
Designed to sit on the work bench, or be hung from an arm, directed where needed. Bench top ionisers tend to be compact, lightweight, portable and include one fan. They are designed to neutralise a smaller area than the overhead. Perhaps more suitable for smaller assemblies, or to be used inside machinery.
Overhead ionisers come with either 2 or 3 fans; more fans equal a larger coverage area for neutralising. They are hung above the work area or workbench, so they don’t use valuable workspace and the airflow doesn’t tend to get obstructed. Some come with lights to illuminate the work area. They would be recommended for larger assemblies.
Sometimes known as Compressed Air Point-of use Ionisers or Ion Guns, these ionisers are designed not only to neutralise charges from an ESD standpoint but are also designed to eliminate visual defects and prevent contamination such as dust. The strong forced air blows away the debris and because it has neutralised the surface, the dust is not attracted back by any static.
3 Functions of an Ioniser
- Minimise Static Charges on Process Essential Insulators. When it is not possible to keep an insulator a minimum of 30 cm (12″) away from your ESD Sensitive Device (ESDS), it’s not possible to replace it with an ESD protective versions and periodic coating of topical antistat isn’t possible, an insulator is termed “process essential” and therefore neutralisation using ionisers becomes necessary. Ionisers neutralise static charges by creating large numbers of positively and negatively charged ions, then the fans or forced air blow the ions over the surfaces it is directed at. If there are static charges present on an item, it will be reduced and neutralised by attracting opposite polarity charge from the air. Ionisation can neutralise static charges on an insulator in a matter of seconds, thereby reducing their potential to cause ESD damage.
- Reduce Static Charges on Isolated Conductors. Ionisers neutralise sensitive devices that are not grounded (isolated conductors) An example of isolated conductors can be conductive traces or components loaded on a PC board that is not in contact with the ESD worksurface.
- Remove Particulate Contamination. Ionisers neutralise insulators where particulate contaminations can cause visual defects (e.g. dust on plastic). Per User Guide IEC TR 61340-5-2 clause 5.3.3.4.6.2 Contamination control “Ionisation neutralises charges on critical surfaces and reduces the attraction of particles to these surfaces.”
“Air ionization can neutralize the static charge on insulated and isolated objects by charging the molecules of the gases of the surrounding air. Whatever static charge is present on objects in the work environment, this will be neutralized by attracting opposite polarity charges from the air. Because it uses only the air that is already present in the work environment, air ionization may be employed even in clean rooms where chemical sprays and some static dissipative materials are not usable”
User Guide IEC TR 61340-5-2 clause 5.3.3.4.6.1 Introductory remarks
Summary
The best way to keep electrostatic sensitive devices (ESDs) from damage is to ground all conductive objects and remove insulators. This is not always possible because some insulators are “process-essential” and are necessary to build or assemble the finished product. The only way to control charges on these necessary non-conductive items is the use of ionisation systems. Applications include:
- eliminating charges on process essential insulators,
- neutralising workstations where ESDS are handled,
- removing charged particulates to create a static free work area.
For more information and to select the right ioniser for your application, check out our Ioniser Selection Guide and our video Why Use Ionisers…
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