Starting point in static control
07 February 2006
The complexity of BS IEC 61340, the latest standards for protecting static sensitive products, makes establishing Electro Static Protected Areas (EPAs) seem a daunting task especially for those inexperienced in the dark arts of static control and protection. With this in mind, Mark Lineker, Static Control Products Manager for TBA Electro Conductive Products (ECP), wrote the ESD Coordinators Guide to Static Control extracts from which are published below.
The intention of this guide is to provide pointers and ideas for establishing an Electro static Protected Area (EPA) in accordance with the principles of BS IEC 61340.
Q. Why should we bother with static control?
A. To save money, reduce defects and increase business. It has long been established that electronic components are easily damaged by electro static discharges as small as 30 to 50V, with increased miniaturisation this problem will get worse.
We become aware of static when fields of around 20kV (20,000V) are present, for instance opening a door and receiving an electric shock would occur at around this potential. Given the frequency of these events it is easy to understand that smaller potentials well in excess of 50 to 100V can be generated all the time without operatives being aware of the damage being caused to company profitability and quality reputation.
Q. How is static generated?
A. Static is generated by a process known as tribo-charging, this occurs when two or more insulative surfaces are rubbed together. As Electro Static Discharge Sensitive devices (ESDS) are a mixture of insulative and conductive materials they can act as the source of the problem.
Q. What can be done?
A. Introducing systems compliant with BS IEC 61340-5-1:1998, Protection of electronic devices from electrostatic phenomena into the manufacturing process mitigates the effects of Electro Static Discharge (ESD).
Q. Where do I start?
A. Appoint an ESD coordinator! It is the responsibility of this individual to drive the implementation of BS IEC 61340-5-1:1998.
The standard is meant to run alongside Quality Assurance systems such as ISO 9002 etc. Therefore a prospective ESD coordinator should have knowledge of internal quality systems and procedures. More importantly the coordinator should have an intimate knowledge of the manufacturing process as, ideally, the ESP system should add value to that process through cleaner working, better handling, improved flow etc.
Once a coordinator has been appointed senior management responsibility does not end there. The coordinator will be bringing about changes to established working practices so continued support will be needed, both financial and moral. Remember the changes being introduced will benefit the organisation at many levels.
Q. What next?
A. Before purchasing Electro Static Protection product, it is important to instigate an internal training and awareness programme. Unless all staff understand why they are being asked to work new systems, implementation will prove unsuccessful. Additionally suppliers should be contacted and informed of the new electro static protection requirements and what they will be expected to do.
Q. How is an EPA established?
A. To decide on the best equipment look at where EPAs are needed. A good approach to making this decision is to consider the product's journey through the factory from goods received to final despatch. An EPA may take the following forms:
a bench
a store
an area of work
a field work area
a work station and equipment (for example, a solder flow machine)
Once the number of EPAs required has been established, thought can be given to the equipment required within.
To establish an EPA it is necessary first to define its boundaries - obviously existing physical boundaries such as walls etc. will assist in this - then it is simply a case of suitable entry and exit signs on the doors. In a larger open area it may be more convenient to mark the EPA off using for example floor marking tape or paint.
Q. What equipment do I need?
A. The equipment required breaks down into several areas that must be considered, these are as follows :
work surfaces - e.g. ECP 1500 series matting
floors - e.g. ECP 525 SD floor paint
seating - e.g. ECP 1470 series chairs
grounding/personnel - e.g. ECP 1450 footstraps
ionisation - e.g. ECP SL-001 ionising blowers
tools and machinery - e.g. ECP 1800/254 cutters
trolleys/carts/storage - e.g. ECP 1100 series conductive bins and ECP 1140 series trollies and racks.
Q. What should be packaged in ESP packaging?
A. The standard is very clear! Within an EPA everything should be in an ESP container of some description. This is to prevent items such as enclosures tribo-charging and damaging ESDSs. It is a false economy to try and use cheaper non-ESP packaging for items not deemed to be static sensitive as the result will be to damage ESDSs at a greater cost to the business in scrap, returns, lost customers etc.
Outside an EPA only ESDSs need be packaged. Outside an EPA, packaging has to be to a higher specification than inside an EPA. The primary functions of packaging outside the EPA are to provide shielding against electro static fields and discharges plus limiting tribo-charging
The need for brevity in this article has limited the information that can be included here and readers are invited to download the complete ESD Coordinators Guide to Static Control from TBA ECP's website at www.tbaecp.co.uk/downloads
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