Most people tend to believe that if a person is wearing a wrist strap, an ESD Lab Coat or smock is redundant. This is due to the belief that any charge on the person or their clothes would find its way to ground via the wrist strap. This is a very common misconception so in today’s blog post we will explain in more detail why you should be considering the use of ESD lab coats or smocks in your ESD Protected Area (EPA).
Put simply, it is to shield or replace standard high charging insulative clothing.
Clothing, particularly when made from synthetic fibres, is a significant charge generator. Worse still, the fabrics are insulative so the charge cannot be taken away to ground. As we have learned previously, all process essential insulators should be kept at a minimum distance of 30 cm from ESD Sensitive (ESDS) items. Is this feasible for operator’s clothing?
By wearing groundable static control garments such as an ESD Smock or Lab Coat you can shield the insulative clothing and minimise the electric fields generated from their clothing.
Some believe that Static Control Garments represent the single most important step to demonstrate commitment to an ESD Control Programme.
Most lab coats are constructed of a dissipative material that incorporates texturised polyester and carbon nylon fibres. The conductive nylon fibres are woven in a chain-link design throughout the material, providing continuous and consistent charge dissipation.
ESD Lab Coats are an ESD protective product that should possess the following ESD control characteristics:
Follow the directions below for proper installation and grounding:
ESD lab coats are a conductor and therefore should be grounded. If not grounded, the ESD garment can be a potentially threatening isolated charged conductor. If an operator is wearing a lab coat but is not electrically connecting the lab coat to either their body’s skin or ground, then charges on the lab coat may have nowhere to go or discharge to.
Panel-to-panel conductivity is essential to ensure portions of the lab coat are not left as isolated charged conductors. A Surface Resistance Test Kit can quickly measure the resistance of the fabric and ensure panel-to-panel conductivity by placing five-pound electrodes on different fabric panels.
To ensure that the fabric is low tribocharging, a Static Field Meter can be used to measure charges generated by causing contact and separation with other materials. In addition, the Static Field Meter can demonstrate shielding by measuring a charged object and then covering the charged item with the ESD lab coat. Being shielded the measured charge should be greatly reduced.
The proper method to clean a lab coat is to wash the garment in cool or warm water, tumble dry with low heat or hang dry. Do not bleach your ESD lab coats! Make sure you only use non-ionic softeners and detergents when laundering.
Please also note that lab coats should not be altered in any way. The lab coat’s effectiveness is in fully covering the human body and their clothes – especially at the wrists and front of the body. Altering the lab coat in any way will nullify its effectiveness.
The typical useful and effective life of a lab coat under normal wearing and recommended washing conditions is a minimum of 75 washes.
Questions for you: Do you use lab coats? If so, what’s the reason you started using them?
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And about ESD T-shirts with short sleeves, when use only ESD t-shirt (short sleeves) is necessary use ESD coat in SMT Process?
It is only necessary to wear a long sleeve ESD Lab coat or smocks over the ESD T-shirt if there is standard/normal clothing underneath, such as a long sleeve t-shirt. If it is just skin, then it is not required. However, you should make sure you ESD T-shirts are in compliance to the standard.