The major advantage* of ESD shoes is that they do not require a tab to connect to the operator. Conductive additives are blended into the sole (inside to outside) of the ESD shoes and connects (through the sweat layer) to the operator’s feet. However, there are a number of other considerations to when selecting ESD footwear:
Does the footwear meet the ESD Association (ESDA) standards?
Many manufactures of ESD shoes often reference ASTM standards for their ESD spec, but state nothing about ESDA standards. The ESDA standards are written specifically for electronics manufacturing and handling. The walking test defined in the ANSI/ESD STM97.2-2006 is one of the most important methods for qualifying ESD footwear for used in ESD Protected Areas.
Not all ESD footwear is created equal.
There are different styles of both ESD shoes and ESD footwear. In most cases the specs of each style will vary. While one style of ESD footwear may retain its ESD properties for 6 months or longer, another will start failing within 90 days. The performance of all styles of ESD footwear should be verified on an on-going basis (twice daily testing is the norm) and records should be kept for quality control purposes.
Involve operators in the selection process.
The intentions of a ESD Control Plan are always to improve the quality control process of a facility. However, getting employees to participate and support the program is not always that simple. When selecting an ESD footwear is a good idea to consider the opinion on the operators. They may not find the style of ESD shoe being considered to be comfortable or they may become frustrated that the ESD foot grounder that has been selected does not stayed secured properly. In some facilities, many operators are temporary or on a flexible schedule that would not justify certain types of ESD footwear and it is never recommended that operators share footwear due to hygiene issues.
Consider the cost/value of the footwear program.
In most cases a ESD footwear-flooring system is an ongoing program that will need to be continuously managed. With ESD footwear there are is two major value components of an ESD footwear product- ESD properties and the durability of the footwear. ESD footwear must maintain a consistent Point to Groundable Point Resistance of < 1 x 109 (ANSI/ESD STM97.1) and Walking Voltage Generation of <100 volts (ANSI/ESD STM97.2) throughout the useful life of the product. The concern with the ESD footwear’s durability is that a breakdown can contribute to foot, leg, back pain or other discomfort in the operator. Initial qualification of footwear for both the ESD properties and physical structure is an important factor in the ESD footwear selection process.
Desco offers samples of foot grounders for product qualification and sizing purposes.
*In some cases protective footwear (shoes, boots, etc) is required to prevent foot injuries due to falling or rolling objects, or from objects piercing the sole. Safety of the operator takes priority over ESD control at all times. If protective footwear with reliable ESD properties is not available or foot grounders cannot be worn with the protective footwear in the ESD Protected Area, other personnel grounding devices such as wrist straps should be used.