There are THREE types of Static Control Garments that are compliant to the ANSI/ESD S20.20-2014 Standards.
1) Static Control Garment – Level 1
These smocks are primarily designed to shield the technician’s clothing from the ESD Sensitive product. They DO NOT come with a ground snap and DO NOT require a ground cord. When these static control garments come into contact with the users skin (the user’s skin is about as electrically conductive as the garment) the static charge is equalized and goes to ground via the technician’s primary ground source (normally an ESD wrist strap and or ESD heel grounders).
2) Groundable Static Control Garment – Level 2
These smocks are primarily designed to shield the technician’s clothing from the ESD Sensitive product but they also provide redundant protection in the unusual event the smock does not make contact with the users skin. The ESD smock has a snap on the hip that can connect a ground cord to create a path to electrical ground. A Groundable Static Control Garment is NOT recommended as the technician’s primary ground source (an ESD wrist strap and or ESD heel straps are still required).
3) Groundable Static Control Garment System – Level 3
These smocks are designed to act as a primary ground source for the technician (they can act as a replacement for a wrist strap). In addition to grounding the technician, they will also help to shield the technician’s clothing from the ESD sensitive product. They are reliant on good skin to smock contact. Hence, they may come with ESD cuffs or snap style cuffs that fit snugly around the users wrist.
The wireless wrist strap has been available for over 10 years. We have seen them used in the field and have received several inquiries about their performance.
In this blog, we test and report on the effectiveness of the wireless wrist strap. Our results indicate wireless wrist straps fail to ground operators or keep operators sufficiently neutral. Read why the wireless wrist strap system results in a potential nightmare of problems.
Background: The Wireless Wrist Strap Dream
It would be nice to be able to effectively drain the charge from a person without them tethered to a work station with standard wrist straps or other ground connection. ESD flooring and footwear is an option, however it can require a significant investment for it to be effective.Hence, the dream of the wireless wrist strap.
So what about the wireless wrist strap? The advertising says “This compact wrist strap eliminates static without the need for a pesky grounding cord. This allows you freedom of movement so you can leave your work area without needing to unclamp yourself and lose your anti-static protection.” It also states that the band “…ensures that you have a much smaller static build-up and dissipates it quickly.”
Dreams vs. Physics
That all sounds wonderful in theory, unfortunately it does not work as advertised. If you are following an ANSI/ESD S20.20 program in order to keep human body voltage less than 100 volts, it will not meet the requirements of the standard.
The standard states “All personnel shall be bonded or electrically connected to the grounding/equipotential bonding system when handling ESDS items.” The standard goes on to list the requirement of a resistance between the operator and ground of less than 35 megohms. This requirement seems quite impossible to meet with the wireless wrist strap.
Resistance to Ground of person wearing a corded wrist strap
Resistance to Ground of person wearing wireless wrist strap
But what if you are not tied to the industry standard and just want to make sure that you are not generating excessive voltage that could harm electronic devices or assemblies? The voltage generated and stored on the person is what is important. So let us conduct another measurement that compares the voltage generated on a person that is a: not grounded, b: grounded through a conventional wrist strap/cord system and c: a person wearing the wireless wrist strap.
The Walking Test
For this test we will use the Warmbier WT5000 walking test instrument. This instrument measures and records the voltage on a person while walking or simply standing. To measure the voltage we held the test electrode on the instrument and repeated the six step walking test described in ANSI/ESD STM97.2 – Voltage Measurement in Combination with a Person.
Figure 1: Standard shoes, tile floor, with no wrist strap
You see that from Figure 1 that the voltage on the person wearing standard shoes on a tile floor and no wrist strap was greater than -500 volts. This voltage is well in excess of the damage thresholds for many devices today. Next we will try the same floor and footwear but the operator will wear a standard wrist strap with coil cord (Figure 2).
Figure 2: Standard shoes, tile floor, wearing corded wrist strap
In this case you should notice that the voltage is minimal. The peak voltage was -1.41 volts and the valley was +0.46 volts.
Finally, we test the same floor and footwear with the wireless wrist strap (Figure 3).
Figure 3: Wireless wrist strap
The graph in Figure 3 shows that while wearing the wireless wrist strap, voltages of greater than
-100 volts were reached within one second of the test and peak voltages exceeding -500v were reached in less than 10 seconds.
Wireless Wrist Straps are Unacceptable
So in addition to not being electrically bonded to ground, the wireless wrist strap does not prevent charge build-up or decay charge at a rate that is acceptable for handling electronic devices.
It would be nice to be able to handle electronic devices without that bothersome coil cord getting in the way or without having to invest in a flooring and footwear system, however the reality is that a person must be physically and electrically attached to ground to drain charge from their body.
Transforming Technologies provides comprehensive knowledge of electrostatic issues, effective solution-oriented products and outstanding, friendly service.
Because customer needs periodically include requirements for consultation, training, auditing or verification, we offer Professional ESD Services such as trainings or audits.
Please contact us for more information on our professional services and insure that your static control program is as effective and efficient as possible.
General Static Charge Audit
Find out if your facility has static charge in locations that can be harmful to your manufacturing process. The work includes benchmarking of each step of the production line, measuring electric fields and electromagnetic interference caused by electrostatic discharge. A report is supplied with interpretation of results and assessment of the magnitude of each item found.
Additionally, this service can also include a search for ESD induced transient EMI. This can be important in facilities with lots of computer-driven robotics or automated testing. This type of EMI can disturb microprocessor operations resulting in locked up or stopped robots, other robotic unexplained behavior or cause good parts to test bad.
Includes a complete static charge audit and detailed review of each step in the manufacturing process. If you prefer, the study can focus on one part of the manufacturing process, for example photolithography.
Where problems are identified a selection of choices of solutions are recommended. In addition. The study focuses on identifying the steps required to achieve best practices concerning personnel grounding, garments, equipment grounding, hand tools, chairs, work surfaces and automated handling procedures. A report is supplied with recommended upgrades to the facility intended to improve facility ESD safety.
Ionizer Performance Verification
Find out if the ionizers in the process are working properly and if they are correctly designed in so that they can achieve the results required, If the ionizers are in need of maintenance or adjustment you will know it. If ther ionizers can be made to work better, you will receive recommendations. If the ionizers used are the wrong type or if additional ionizers are required, the report will include these facts.
Ionizer Service: Clean and Calibrate
Corona ionizers collect material from the environment much like a dust precipitator. That material lowers the efficiency of the ionizer and must be removed. Also as tools and fixtures are moved in the cleanroom, the balance of the ionizer is effected. For both of these reasons and because the control circuitry in the ionizer drifts over time, the ionizers require maintenence.
No ESD control program can succeed without the help and cooperation of the production team. LBL offers a seminar to teach the people manning your production floor about static charge and how the various steps in a control program work.
ESD Issues for the Senior Manager
LBL understands the complex issues that arise from being in charge of quality management and safety. LBL will work with senior management to consolidate best the practices and drive standardization across the organization.
Specific Problem Solving
Wether you are just starting your ESD control program or static discharge has been a main concern for years, LBL understands that every static problem is unique, ranging from the simple to the incredibly complex. Contact LBL to discuss any issues, big or small that you may have.
Contact us today for more information on ESD professional services
Introducing Transforming Technologies ESD Mat Selection Guide
Whether it be an ESD Table Mat or an ESD Floor Mat, making the best choice can be difficult. With the help of our new ESD Mat Selection Guide, we have condensed all the selection criteria such as material construction, resistance ranges, surface, color, style, or size into two separate charts for your convenience.
ESD garments, also commonly known as ESD smocks, ESD lab coats or ESD jackets, are designed to be antistatic, low tribocharging and offer protection from electrostatic fields generated by clothing on the user’s body. ESD garments are worn where ever static damage is a concern.
How Do ESD Garments Work?
ESD garments are constructed out of polyester or cotton (or a blend of both) that impregnated with a grid of woven conductive fibers. The grid creates a “Faraday Cage” effect around the body of the operator that shields charges generated from the operators clothing from damaging ESD sensitive devices.
ESD Garments as part of a complete ESD program.
ESD garments are a recommended addition to a program that already includes typical grounding measures, such as wrist straps and heel grounders. This is because of the potential hazard of the operator’s clothing. The ESD TR20.20-2008 states: “While a person may be grounded using a wrist strap or other grounding methods, that does not mean that insulative clothing
fabrics can dissipate a charge to that person’s skin and then to ground. Personnel clothing usually is electrically separate or isolated from the body.” “Groundable Static Control Garment System, Garments that are used to establish the primary ground path for a person shall provide a resistance of less than 35 megohms from the person to the groundable point of the garment.”[ESD TR20.20-2008 section 5.3.13 Garments]
Any facility that mandates ESD garments demonstrates a commitment ESD protection.
Styles of ESD Garments
ESD Garments come in many shapes and sizes. Typical distinctions are collar type, sleeve terminations and lengths. Collar options typically include lapel, v-neck or military style. Sleeve terminations are either a three snap cuff that adjusts for a proper fit or an ESD cuff that allows for hands free grounding. There are three lengths of jackets, waist length, 3/4ths and full length. Fabrics composition will vary by manufacture but there are typically a polyester fabric or a cotton polyester blend.
ComfortTREAD diamond-plate ESD anti-fatigue mats keep your workers comfortable and your ESD sensitive equipment safe. The 100% conductive rubber mats are embossed with raised diamond-plate treads for superior traction and feature wide beveled borders to promote safety. A fully molded honeycombed cell design absorbs shock and cushions the feet from constant contact with hard surfaces. The mat will not separate, bubble-up, ripple, tear, compress or lose resiliency. Available in interlocking sections which can be quickly dismantled to make moving and cleaning easy. Two FM9E connected creates a 2.5′ x5′ workstation mat or you can pair the two FM9E with any number of FM9C pieces to create a runner in 30” increments. For use with ESD footwear such as heel grounders and sole grounders.
Meets or exceeds requirements of ANSI ESD-S20.20 and the recommendations of ESD STM7.1
Benefits & Features of the Transforming Technologies ComfortTREAD ESD Matting:
100% conductive rubber: 10^3-10^5
Diamond-plate treads for superior traction
Interlocking sections create a 5’ long work-station mat or runners in 30” increments.
Beveled borders for safety
Specifications of the Transforming Technologies conductive ComfortTREAD ESD Matting:
Point-to-point resistance: 10e3-10e5
Inlocking mats for floor runners
Meet or exceeds requirements of ANSI ESD-S20.20 and the recommendations of ESD STM7.1
Ionizers remove static from surfaces that cannot be grounded. You will find two common types: AC or Alternating Current and DC or Direct Current. This presentation reviews the pros and cons of each technology and will help you decide which ionizer will work best for your application.
For more information, contact Transforming Technologies 419-841-9552.
The combination of ESD flooring and footwear can be an effective way to ground personnel to control electrostatic discharges when using a wrist strap is not practical. For this system to be effective, the ESD flooring and footwear must have a low enough resistance to allow the voltage from the operator to flow to ground. There also must be a good contact between the person and the ESD footwear.
While ESD shoes may be made with conductive materials, they require a layer of perspiration in the sock to provide a path-to-ground. This is a concern because there are many variables between people. Per ESD Handbook TR20.20 section 22.214.171.124 Common Testing Problems “Occasionally, footwear may indicate a high resistance… [A contributor being] heavy or insulative socks, or the absence of a sweat layer due to differences in temperature between the inner surfaces of the shoes and the wearer’s feet.”
You may see inconsistent resistance measurements from person to person, especially during colder months when employees wear heavier socks and sweat less. One person may fail a test at the start of a shift, and pass ten minutes later after a sweat layer is formed.
How much time is wasted waiting for shoes to pass a test? Or worse, how many sensitive items does a person come into contact with before their ESD shoes are truly acting as a path-to-ground?
Eliminate these variables and ensure a consistent path-to-ground with conductive ESD socks from Transforming Technologies. ESD socks are made with conductive yarn which provides a reliable electrical path from the start and rely less on the wearer’s skin resistance for repeatable performance regardless of the environment.
Microscopes are a common instrument found in electronic assembly operations. Microscopes are used for inspection and for assembly of very small objects. It is critical that the microscope lenses remain clear and free of dust and other contamination. When not in use, microscopes should be covered to protect the optics.
Some manufactures of microscopes provide covers for the time when the scopes are not in use. Typically the covers are made of vinyl. While vinyl may provide good protection from dust and fumes, it is a significant static generator.
The vinyl cover in the photo above shows an electrostatic voltage of -5,500 volts. Once the cover is removed from the scope the voltage jumps even higher to -12,000 volts.
ANSI/ESD S2020, the industry standard for ESD control programs, states that all nonessential insulators should be removed from the ESD protected area.
Since it is critical that microscopes be covered when not in use, it could be argued that the microscope cover is a process essential insulator. ANSI/ESD S2020, Section 8.3.1 states that the ESD control program “shall include a plan for handling process required insulators in order to mitigate field induced CDM damage.”
The standard goes on to say that if the field is greater than 2000 volts/inch it must be kept more than 12” from the ESD sensitive item. If the microscope is not in use, but work on ESD sensitive devices is being performed at the station, the vinyl scope cover becomes a significant risk. The vinyl cover becomes even a greater risk if it is removed while there are ESD sensitive items at the workstation.
The best solution is to replace the vinyl cover with a microscope cover that is ESD safe, such as the Transforming Technologies MC1221W. This scope cover is constructed of ESD safe material and does not generate a significant charge.
Even when the cover is removed, the charge remains very low.
With Transforming Technologies’ MC1221W you can protect your microscope optics from contamination while keeping your work station ESD safe.
Transforming Technologies is proud to announce the addition of the StaticCare ESD Hand Lotion to our line of ESD Products.
StaticCareTM ESD Hand Lotion is specially created for use by individuals in the electronics industry. This fast absorbing, non-greasy ESD hand lotion enhances the contact between a persons skin and grounding devices such as wrist straps and heel grounders, specifically for those with dry skin. It is free of glycerin, mineral oils, silicones, and lanolin which will keep your work area ESD safe and free from contamination.
Directions Apply a small amount of Static CareTM lotion with hands to desired areas where grounding devices are used. Rub evenly into skin until absorbed. Any excess lotion may be removed with a towel. To re-move from skin completely, warm water and a mild soap may be used.
Benefits & Features of the Transforming Technologies Antistatic Lotion:
Fast absorbing for improved contact be-tween personnel and grounding device
Contaminant free to keep work station ESD safe
Contains aloe vera, natural moisturizers, and vitamins to promote happy and healthy skinNon-greasy formula will not interfere with grip or agility
Clean and refreshing scent
Meets or exceeds requirements of ANSI ESD-S20.20 and ANSI/ESD S-6.1