ESD protection in electronics manufacturing protects sensitive components from damage due to electrostatic discharge.
Electronics manufacturers need to protect sensitive components from damage due to ESD, or electrostatic discharge. There are a lot of techniques to do this. What high-volume offshore facilities do is not always the best for high-mix manufacturers in the USA.
Video Transcript
Electronics manufacturers have to protect components from electrostatic discharge, or ESD.
ESD is caused when an electrical charge builds up on a person or object, typically due to friction between two different materials — such as your shoes on a carpet. When you touch – or sometimes just get close to – a conducting object, that build-up of electrical charge can be discharged in a sudden flow of electricity. It is enough to damage many components, even if it is too small for you to feel, hear or see.
There are a lot of techniques we can use to mitigate this issue. When choosing a contract manufacturer, you should verify that they use redundant layers of protection and monitor their effectiveness.
Humidity
First is controlling humidity. Humid air is more conductive than dry air. Keeping the air at 30% relative humidity allows electrostatic charge to dissipate harmlessly into the air rather than building up on people or surfaces. Any electrostatic charge that DOES build up, must be conducted safely to ground.
Flooring
There should be conductive flooring throughout the facility – in this case a concrete floor with a conductive wax. Anti-fatigue mats need to be conductive and properly grounded. Regular industrial mats don’t meet this requirement.
Flooring and heel straps
Employees should wear ESD shoes or heel straps — on both feet, to ensure constant contact with the conductive flooring. Wires inside the heel straps drain off any charge the wearer picks up. Heel straps wear out and need to be tested regularly. At Z-AXIS all manufacturing employees test twice per shift.
Work benches and wrist straps
Work benches can be covered with a static dissipative mat tied to ground. This bleeds off any excess charge that accumulates on objects moved around manufacturing. Some companies use wrist grounding straps instead of mats. The straps are less convenient in high-mix manufacturing settings, where workers move about the facility during the day. If used, wrist straps must be plugged securely into the jack… and the jack properly grounded.
Chairs, cars and shelves
Chairs should have conductive casters. Roller carts should be made of metal, or special conducting plastic. A hanging strap grounds them to the floor so they can’t build up excess charge. Any racks on the cart need to be grounded as well. If there are plastic spacers, you can add conductive tape across the gap.
Storage shelves also need to be conductive and grounded. Check that all shelves are conducting to the main post, and therefore to ground.
Packing and shipping
In shipping, it’s best to use ALL-new packaging materials that are known to be anti-static. Regular Stryo-foam materials can induce a static charge on components, even without direct contact. Here we use anti-static bubble-wrap, pads and custom-formed ESD-safe trays.
Inspection and audits
Regular inspection and testing of ESD protection measures is essential. At Z-AXIS we routinely inspect all aspects of manufacturing, and perform a full ESD audit once a quarter. In an audit, we follow the product flow through the facility, from receiving materials to shipping finished assemblies, looking at all potential sources of static & verifying they are effectively controlled. We’ll also use our knowledge do an ESD audit our customers’ facilities on request, at no charge.
Standards and experience
Our ESD practices are based on IPC-A-610 and J-STANDARD-00 for Electronic Assembly, along with our own knowledge of electronics.
Tips for evaluating an EMS provider
When evaluating your contract manufacturer’s ESD protection, keep in mind that much has been published about ESD protection that just is not true, often by companies trying to sell unnecessary items. For example, you probably don’t need conductive trash cans to protect your scrap from ESD damage. At Z-AXIS we work with a lot of very sensitive parts but have a zero ESD damage rate because of our redundant layers of protection.