ESD and Static Control Questions

Q: What is the difference betwen two layer and three layer ESD PVC Mat, and which one will be advisable for flooring?

A: We have a variety of bench and flooring mats and runners. The two and three layer mats would generally refer to our bench or table mats. Our Duro-Stat line is actually a homogenous vinyl ESD matting with great mechanical and electrical properties. But most BM’s are of the two-layer or three-layer type. The top layer would give the mats its resistance to chemicals, resistance to solder, flux, and the ability to keep it clean. The backing would typically promote an anti-skid and durable surface. The three-layer mats are going to have a conductive scrim center layer and work well with most wrist strap constant monitors.

For floor mats and runners, we’ve got our UltraCon Floor Mat which is made of highly conductive rubber. Your flooring mats and runners are going to be typically homogenous and don’t have layers per say. Our Tough One! line is made of embossed homogenous solid vinyl. The exception being our Anti-Fatigue II line, this static dissipative mat is a vinyl mat with a foamed vinyl backing. Our No-Slip II is made of a corrugated slip-resistant vinyl.

Q: What is the difference between anti-static and static dissipative floors? Which floor will be better to use if I’m going to have an electronic assembly line?

A: Anti-static is not the proper term to use for ESD flooring.

Anti-Static refers to the ability to suppress charge generation or the prevention of static build up. Anti-static materials will not safely attract or decay a static charge before it randomly discharges. Anti-static material is usually indicated by an electrical resistance range, measured in ohms, of a minimum of 1E10, (10 giga ohms), to a maximum of 1E12, (1 trillion ohms).

ESD flooring systems are referred to as static conductive (more conductive) or static dissipative (not as conductive, but will dissipate charges in an orderly fashion).

Static dissipative floors: 1E06 Ω or 1 Meg Ω to 1E09 Ω. I would consider SD material to be the minimum requirement per ANSI/ESD S7.1-2005 via ANSI/ESD S20.20-2007. If you choose this flooring system, the RTG readings may be at the low end of the scale and be in the E06 to E07 range or it may be at the high end and be in the E08 range. You want to keep you flooring system clean and always below a gig ohm.

Static conductive floors: 2.5E04 Ω to 1E06 Ω. These floors are the superior choice for an assembly environment and offer the lowest charge generation and quickest charge dissipation. These floors require proper cleaning and maintenance, but will likely exceed the requirements for 20.20 throughout its lifetime.

I’d recommend a static conductive flooring system for your application. You are dealing with ESD sensitive components, raw boards, and/or sub-assemblies that have a low threshold voltage tolerance. With a static conductive flooring system and proper ESD footwear, you will have an optimal ESDS area.

Q: We are removing old vinyl tile and replacing with ESD protective tile. We are wondering if ESD conductive or dissipative is best. Our business is dehydration baking, final functional testing and packaging semiconductor IC’s with design circuits typically in .25 micron range. We need recommendations on conductive vs. dissipative and epoxy vs vinyl tile. The area is not high traffic. Thanks.

A: Good questions. In selecting an electrical range there are several key factors to consider, these are in order of importance in our professional opinion:

1. Device sensitivity?
2. Does the type of work being performed in the protected area include, working with Power Supplies?
3. Is your staff going to be wearing personnel grounding protection?
   • ESD Shoes
   • Heel Straps
   • ESD Booties
   • Etc.
4. Are there any environmental conditions to consider?
5. How important is meeting industry standards to you and your company? e.g.
   • EOS/ESD S7.1
   • ANSI/ESD S20.20
   • ISO Compliance
   • In-House Standards
   • Customer Contract Standards

Based on what you have described in you e-mail, conductive range is best suited for your application, dissipative should not be considered. See the attached white paper on this specific subject. As this particular document has even been published yet, please keep this document confidential for your internal use only.

The factors that should be considered in choosing a Material Type are as follows:

1. What is the intended use for the floor? What type traffic will the floor see? Will liquids or spills be anticipated or utilized in this area? Do you own or lease the building? Will odors be a problem during the installation process? Are you fully operational and or will the work be done in phases? Budgetary factors Performance warranty Maintenance level expectations
2. Esthetics

I think this will give you some things to consider moving forward. Please see the attached floor comparisons chart for additional things you should consider, this chart may prove helpful to you and your team. Let us know if we can provide you with flooring sample submittals, product specification sheets, quotations, etc. I would like to talk to you in greater detail regarding Epoxy vs. Tile, we have many millions of square feet of experience in this category, so please call me when you have some time.

Please let us know how we can better support you and your company moving forward, as your satisfaction is our highest priority!
See also: ESD Open Forum(PDF); ESD Flooring Comparison Chart(PDF)

Q: Why can’t bare or sealed concrete be used as a method for controlling static electricity in a electronics manufacturing environment verse utilizing a Conductive or Static Dissipative covering and/or coating?

A: I’ve done some studies on ESD resistive characteristics of the several different floor surfaces. In light of the following question, I just snapped some photos of ESD readings on the following surfaces:

ESD reading on Dry Concrete

Bare concrete (dry). Results- barely conductive, very humidity dependant; in the insulative range(1E09-1E12)

ESD reading on Asphalt

Asphalt. Results- unacceptable; above insulative.

ESD reading on Dirt

Dirt. Results- pretty good, acually comes in at barely dissipative; Upside, cheap; Downside, hard to clean.

Reading on ESD Carpet

ESD Carpet (Ground Zero Information). Results- ESD conductive(2.5e4-1.0E6).

Reading on ESD Tile

ESD Tile (Ground Zero Information). Results – ESD dissipative(1.0E6-1.0E8).

Reading on Sealed Concrete

Sealed Concrete. Results-unacceptable; a sealed concrete is necessary for heavy foot traffic, but the very thing that would make the concrete conductive is sealed out- moisture. This floor could be made dissipative very easily with an ESD chemical (Ground Zero Information).

Reading on Particle Board

Particle board. See asphalt