ESD Overview
ESD stands for Electrostatic Discharge. Static electricity is an everyday phenomenon and while we see the big stuff (lightening for example) at lower levels whilst we cannot see the phenomena, It may nevertheless cause damage to sensitive electronic components.
Static can build up rapidly on everyday objects, to produce surprisingly high voltages. When two objects with different potentials approach each other, charge may pass from one object to the other in a very rapid electrostatic discharge.
While this only lasts a moment the peak discharge voltage can be very high (Far more than is needed to damage an Electronic Circuit)
Definitions
- Intimate Packaging is packaging that actually makes contact with ESDS
- Proximity Packaging is material which is not making contact with ESDS but which is used to enclose one or more devices
- Secondary Packaging is material which is used primarily to give additional physical protection to the outside of a proximity package
- EPA ESD Protected Area
- Low Charging Packaging – Exhibiting properties which minimise any charge generation
- Electrostatic discharge shielding Barrier limits the passage of current and attenuates the energy resulting from an electrostatic discharge such that the maximum energy form 1 000 V HBM discharge is less than or equal to 50 Nano Joules
Shipping Considerations
The Shipping of Parts and electronic equipment containing Electro Static Discharge Sensitive (ESDS) Product creates a number of unique challenges compared to the shipping of other materials and equipment.
This is due to the need to protect the shipment from any form of electric charges.
Many electronic parts are highly sensitive to electrical charges and consequently susceptible to damage both directly and indirectly (known as latent damage).
Introduction of an ESD Protected Area (EPA)
An EPA is an area that is maintained safely for handling static sensitive components by keeping electrostatic fields and voltages to an insignificantly low level. An EPA should have well-defined boundaries so that it is clear where the safe area is entered and left.
There are two simple principles we can use to protect ESD sensitive components from ESD damage:
a) Only handle sensitive components in an ESD Protected Area (EPA) under protected and controlled conditions
b) Protect sensitive devices outside the EPA using ESD protective packaging
c) Using a grounded wrist strap (this is the preferred method)
d) Using conductive footwear (conductive or dissipative shoes, or heel & toe straps on both feet) in conjunction with a grounded conductive floor.
The Use of Antistatic Material for Protection
ESD Protective Packaging comprises all “items and materials that provide intimate protection for ESDS parts during all phases of handling, shipping and storage”.
Anti-static material prevents the build-up of static electricity by enabling the dissipation of the electrical charge. Effective use of ESD packaging materials can greatly contribute to minimising the possibility of losses due to ESD events.
The objective of ESD protective packaging is to
a) Prevent a direct electrostatic discharge to the ESDS item contained within and allow for dissipation of charge from the exterior surface.
b) The packaging should minimize charging of the ESDS item in response to an external electrostatic field and triboelectrification.
Using the Correct Standard of ESDS Packaging for the Required Purpose
a) Evaluate the ESD sensitivity and distribution environment to select optimum material
b) Is the packaging intended for 1-time use only or it is required to be returnable or reusable.
c) Review the following packaging considerations
i) Understand the sensitivity of the product (analysis or using provided data)
ii) Understand the environment where the product is being shipped (Humidity Considerations are very important)
iii) Is the packaging intended for 1-time use only or it is required to be returnable or reusable. (Some companies choose less expensive packaging for less valuable parts.)
iv) Handling: If rigorous handling is expected, cushioned packaging may need to be considered.
v) Are there any aesthetic requirements for the packaging?
d) If items are susceptible to moisture, barrier material should be chosen to prevent excessive humidity exposure.
Note – Avoid any possibility of condensation building up inside the packaging if temperatures vary around the dew point of the established interior conditions. (If relevant to consider the use of, desiccant)
e) In preference choose low charging or static dissipative materials when in contact with ESD sensitive devices.
f) Also, consider the need to protect packaging contents from the potential of a direct discharge or exposure to electric fields.
g) Criteria for choosing the Correct Packaging Product
i) If the package is primarily used to transport product in an ESD protected environment then a low charging, static dissipative package will suffice.
ii) If the product is moving between ESD protected areas (uncontrolled environment) a low charging, discharge shielding package should be considered.
iii) When the package is shipped into a totally uncontrolled environment a low charging discharge shielding package is recommended.”
General Packaging Conditions
Packaging is to be determined for all material movements inside and outside of the ESD Protected Area (EPA).
Best practice is to define the required packaging or material handling item on the product’s bill of materials. (Remember: the ESD packaging is just as important as a component part.)
The organization shall define ESD protective packaging requirements for ESDS for all material movement within EPAs, between EPAs, between job sites, field service operations and to the customer.” (reference EN 61340-5-1 -5.3.5 Packaging]
Can ESD Bags and Packaging be Reused?
ESD Bags Are Generally Reusable, however, the protection may be lost if there is any potential conduction path from the charge on the outside of the bag to the inside layer and ESDS parts within.
It should be part of the inspection procedures to ensure in every case that the ESDS Packaging Material is inspected prior to use. Any ESD Shielding Bags that are ripped, torn, or scratched should also be discarded. Distortions of the ESD Bag may also cause a loss of static shielding properties
Important Note – Do not leave packaging or containers open when not protected (Due to the potential exposure to Electrostatic fields)
Documenting your ESD Packaging Program
Develop a working procedure which can be used as a guidance and training document to educate all staff regarding the need for special considerations related to ESDS
The Procedure should cover all of the following requirements – ensuring that the process and procedures are useable within your organisation
a) ESD training program management to ensure all personnel complete
b) Control and Management of all ESDS Instructions
c) Procedures to ensure the handling of ESD sensitive (ESDS) products only in an ESD Protected Area (EPA).
d) Take steps to ensure all possible “conductors” (including persons) are maintained at on the same electrical charge potential.
e) Ensure the removal of material especially plastic which can generate charge
f) Surround all ESDS with ESD safe packaging materials, except when they are being actively worked on.
Considerations related to volume use of packaging
Where there is a need for multiple packages, for example in support of volume production it is worth to test the final packaging design for effectiveness
Testing could include any or all of the following:
a) High voltage discharges to the exterior of the packaging;
b) Simulated over the road vibration;
c) Drop tests;
d) Environmental exposure.
Checklist for ESD protective packaging
a) Checking of packaging (for incoming goods)
b) Evaluate Packaging requirements of the product:
c) Determine Product sensitivity related to electrical properties
d) Consider Mechanical properties
e) Consider Single use or re-usability
Sofema Aviation Services www.sassofia.com and SofemaOnline www.sofemaonline.com provide ESDS training courses Electrostatic Discharge Sensitive (ESDS) – 1/2 Day if you want “Classroom” or “In-company” training and Electrostatic Discharge Sensitive with VO if you rather online training. For further questions please email office@sassofia.com or online@sassofia.com
