It is important for electronics manufacturers to protect their products from harmful electrostatic discharge (ESD). ESD is a leading cause of product faults and without proper controls can hurt a company’s operations, finances, and reputation.
Static build-up generally occurs from friction between two different types of materials, such as shoes and the floor. Charge can build up over a short period of time and when another object is touched, the static build-up can be discharged in a sudden flow of electricity. It can be so subtle that you don’t even feel it, however it can be enough to damage sensitive electronic components.
Ensuring you have effective ESD control procedures in place is essential to reduce the risks of damage to electronics components.
The ESD Audit Process
During an audit we follow the product through the facility, from receiving materials to finished assemblies, looking at all potential sources of static. We document each control point and measure their effectiveness. Some common sources of ESD include:
- Soldering Areas
- And more
We need to make sure anything that contacts the product will conduct any current safely to ground.
ESD Audit Tools
Our audit tools include a static charge meter and a resistivity meter. They allow us to audit the use and effectiveness of all items and materials that contact the product throughout the manufacturing and/or re-work process.
An electrostatic field-meter, also called a static meter is used for non-contact measurement of electricity charge on an object. It measures the electrostatic field of an object in volts, measuring both the initial peak voltage and the rate at which it ‘falls away’. If we discover any ESD build-up we find and eliminate the source.
If ESD wrist straps are used, we not only check that each connection jack is secure and working correctly, we also audit the use of grounding points by users. If heel straps are used, we ensure they are used on both feet in order to give adequate contact with the flooring. The flooring must be conductive, and we recommend the use of ESD floor sprays and matting as well as conductive chair casters. Wrist straps and heel straps typically wear out in six months due to the constant bending of the wires inside the straps. Therefore, they need to be tested regularly and replaced when necessary.
We recommend all staff complete a personal ESD test several times during an 8-hour day, using a heel strap and wrist strap tester, recording the results in a test record. During an audit we inspect each test record to ensure compliance.
Transport and Storage
During an audit, we take a close look at how products are transported and stored around the facility. It’s important to ensure that electronics products are transported in ESD conductive plastic carts or on metal racks grounded to the floor.
Storage shelves also need to be conductive and grounded. If the storage system is metal, we test the floor by using a resistance meter and use a multimeter to ensure the shelves are conducting to the main post and to the ground. A safer way is to use ESD safe plastic storage bins for storage.
Anti-fatigue mats also need to be conductive and properly grounded. Once again, we use a resistance tester to ensure mats are compliant and make recommendations for improvements if necessary.
One of the final areas we audit is how products are shipped from the facility. Common areas of concern include the use of regular Styrofoam material for packing, which can cause a static charge to occur. ESD safe packaging must be used to reduce the risk of damage to products in transit.
When to audit?
We recommend an audit of ESD protection measures every quarter, and an audit of an entire facility once every year. Even the smallest electrostatic discharge can cause big issues. This can render the product immediately faulty or can cause latent issues that reduces the life of the product and its reliability.
An ESD audit is a simple and non-intrusive process that drastically reduces operational and financial risks.