The following is based on a recent process analysis regarding the benefits of an ESD floor at a particular end user. The end user currently has ESD Flooring and they are adding an additional production area. Upper management questioned the cost of the ESD Floor and asked the ESD Coordinator and Production Manager to evaluate the process changes needed if there was no ESD Floor. Below is the analysis of the burn-in processes. The end user prefers to remain anonymous.
Process steps during the burn-in – oven process with ESD flooring:
1) Operator places burn-in board on ESD cart
2) Operator rolls ESD cart to the burn-in oven
3) Operator removes the burn-in board from the ESD cart and places in the oven
Process steps during the burn-in board – oven process with no ESD flooring:
1) Operator connects their wrist strap ground cord to ground
2) Operator connects the cart ground cord to ground
3) Operator places a container having discharge shielding on the cart
4) Operator loads the board into the container
5) Operator covers the container with lid
6) Operator disconnects wrist strap from ground
7) Operator disconnects the cart ground cord from ground
8) Operator rolls the cart to the burn-in oven
9) Operator connects their wrist strap ground cord to ground
10) Operator connects the cart ground cord to ground
11) Operator uncovers the container
12) Operator removes the burn-in board from the container and places in the oven
13) Operator disconnects the cart ground cord from ground
14) Operator disconnects wrist strap from ground
25 personnel who work in this area would now have some level of static voltage on their body when not wearing a grounded wrist strap. If anyone reaches out and mistakenly touches a part, defects and product scrap is possible. Use of ground cords may also cause dropped product / scrap.
36 ESD carts are used in this area. Many are used for transporting unprotected product. With no ESD floor to ground these carts via conductive casters or by the Operator grounding the cart while moving it every cart will have some static charge on them and all product would now need to be transported in a covered container having the discharge shielding ESD control property.. If someone mistakenly placed an unprotected part on a cart, product defects and scrap are possible.
The most significant process challenge (product safety/throughput) with a no ESD floor scenario is the burn-in process. Populated burn-in boards will need to be transported in covered discharge shielding containers as a functioning Faraday Cage. Burn-in board carts will need to be modified for these new containers and will carry less burn-in boards after the modification. More handling (packing / unpacking) will increase the possibility of dropped product.
The ESD floor is used in every process, by every product builder, technician, and support engineer. Each added step is an added risk to the product from both ESD and the added handling is an opportunity for dropped product. If the ESD floor was not added to the new production area, every production and production maintenance process step would somehow change, and the ESD control culture in this area could shift dramatically.
Per ANSI/ESD S20.20 flooring is an optional ESD protected area ESD control item. However, per ESD Handbook ESD TR20.20 “For standing operations, personnel shall be grounded via a wrist strap system or by a flooring/footwear system.” “The use of floor materials to control personnel or equipment generated static has a number of benefits. Floor materials tend to be passive. Employees who work in areas protected with floor materials simply need to wear and test the appropriate footwear. They do not need to implement any additional actions themselves to assure that the floor material is functioning properly.” (ESD Handbook TR20.20 section 220.127.116.11)
To download a complimentary .pdf of ANSI/ESD S20.20-2014, go to the ESD Association web site www.ESDA.org