Sensitivity to electrostatic discharge (ESD) is an important concern in PCB assembly manufacturing. Pinpointing where ESD events are occurring on an SMT line can be difficult determine. ESD exposure can take place anywhere in the process, including PCB loading, component handling, soldering, and operator interventions. ESD events generate electromagnetic radiation. The stronger the ESD event, the stronger the electromagnetic radiation. Detecting and measuring the unique waveform generated by an ESD event can help determine where the ESD event is occurring and reduce the time it takes to identify and solve the problem. Watch this video to see how continuous ESD Event Detection monitoring can be setup on an SMT Line to monitor the processes and triangulate where static voltage and ESD events are occurring in the process.
With electronic components getting smaller and more sensitive, it’s important to make sure they are protected from ESD events like static discharge. Per ANSI/ESD S20.20, “Protective packaging is required to store, transport, and protect ESDS electronic items during all phases of production.” Per the new 2018 requirements for ANSI/ESD S541, the shielding requirement was changed that remaining discharge for the bags should be less than 20 nanojules.
One of the more common used bags is a low charging Pink Poly bag. These bags are made from a tinted polyethylene material with an antistatic coating that can wear away. This turns the bag insulative over time, making it noncompliant to ANSI/ESD S541 recommendations. They also lack discharge shielding protection which makes components within the bag susceptible to ESD event damage. Metallized Shielding bags are constructed from a metalized polyester film and a low charging polyethylene laminate. This provides the bags with a shielding layer that creates a Faraday cage protecting the ESD sensitive components within the bag from possible ESD event damage. The low charging inner layer and outer layer of the bag prevent tribocharging from occurring, minimizing the build up of ESD charges when handling components.
Watch this video on Pink Poly vs Static Shielding Bag Testing and learn why Metallized Static Shielding Bags are the best packaging solution offering full protection against ESD events.
Have you been questioned by your quality manager about shelf life on ESD bags? Maybe it’s an internal quality procedure that is being written and you would like to know where the manufacturer stands on the shelf life of ESD packaging. Well today we will address the topic of ESD Static Control bag storage and the expected shelf life.
There are many ways to manufacture an ESD shielding bag with low charging properties on the inner and outer layers. This is the first factor to consider so I will address only the items that I convert here at SCS. In our process, I achieve shielding values via a buried metal layer. The metal layer is laminated between two layers of polyethylene. This process makes a very robust and long- lasting product in terms of shielding values as per ANSI/ESD S541-2018, the electronic industry’s most recognized standard for ESD packaging. Still the metal layer is exposed to oxidization if not stored properly and subject to extreme climate or moisture.
SCS Metal-In shielding bag layers
To achieve the outer and inner low-charging properties, I use a topical anti-stat solution. This provides the outer and inner resistance readings of >/= 1 x 10^4 to < 1 x 10^11 ohms as called out in ANSI/ESD S541-2018 packaging standard. This property is the most vulnerable to change and should be tested frequently.
How does all this pertain to shelf-life you ask? SCS provides a Static Control Bag Storage document with a 1 year warranty from the date of purchase. I have witnessed SCS ESD bags stored in a controlled climate, well-ventilated area that have maintained passing surface resistance results after 5 yrs. on the shelf. Some customers have relied on our Moisture Barrier products to archive various critical products for as long as 20 yrs. They found through extensive testing that SCS had the highest quality and most repeatable results to trust with their archived product.
End users cannot always provide a climate and humidity-controlled atmosphere for our raw material, so it is recommended that you test your bags periodically per the S541 standard and dispose of any materials that are found to be questionable. As a best practice, you can log your products by purchase date or lot number and create an annual spot check audit to assure that your bags are still in compliance. Using a FIFO First In First Out process is critical in keeping your inventory fresh. You can imagine that there are 1000’s of variations to consider when we discuss shelf life. Heat, storage rack conditions, travel method and local climate to name a few, so the points to take away are this:
Test your ESD bags periodically
Avoid extremes
Hot, Cold, sunlight, moisture
Add controls when possible
In a controlled environment, SCS ESD bags have seen 5 yrs. of proven shelf life.
Follow the FIFO process as a best practice for inventory.
SCS warranties the product for a period of 1 year from the date of purchase. You need to audit annually or prior to use as a best practice and assure that your devices are getting the best protection.
If the bags are questionable, recycle the product at your local recycler and order and new lot from SCS – Static Control Solutions.
Thank you, Kevin Cleary ESD Packaging Specialist – Sales Direct Line: (919) 903-1724
Welcome back to “A Minute with Miranda.” This week we will be covering how the EM Aware Monitor provides continuous monitoring to detect and measure ESD Events in your STM machine.
The SCS EM Aware Monitor is a continuous monitor for three key parameters that allow you to verify your ESD process in an automated insertion machine; ESD events, change in static voltage field, and ionizer balance. The thresholds for all three of these parameters are fully adjustable by the user. The EM Aware Monitor is a miniature radio receiver tuned to detect and measure the unique waveform generated by an ESD event. The EM Aware Monitor meets the Continuous Monitor requirements of ANSI/ESD S20.20 in accordance with ESD TR1.0-01 and ANSI/ESD STM3.1. It meets the recommendations of ESD Handbook ESD TR20.20 which includes “if the products that are being produced are of such value that the knowledge of a continuous, reliable ground is needed, then continuous monitoring should be considered or even required.”
Welcome back to “A Minute with Miranda.” This week we will be covering how the WS Aware provides continuous monitoring for an operator at an SMT line.
The SCS WS Aware Monitor is a continuous monitor for operators, ESD Worksurfaces and metal tools. It will continuously monitor the path-to-ground integrity and body voltage of two operators. It also monitors the path-to-ground integrity of two metal tools. In addition, it continuously monitors for electromagnetic interference (EMI) on two metal tools, which may cause electrical overstress (EOS) damage. The WS Aware Monitor eliminates the need for periodic testing and record keeping of wrist straps.
Per ESD Handbook ESD TR 20.20 section 5.3.2.4.4 “Typical Test programs recommend that wrist straps that are used daily should be tested daily. However, if the products that are being produced are of such value that knowledge of a continuous, reliable ground is needed, then continuous monitoring should be considered or even required.”
View the full range of SCS WS Aware Monitors here.
Welcome back to “A Minute with Miranda.” This week we will be covering how to test ESD footwear entering an ESD Protected Area (EPA).
Per the ESD Handbook ESD TR20.20, A system test of the footwear in combination with the existing or proposed flooring materials in the plant should be made to ensure that the criteria for the facility are met. When using a footwear checker it is important to make sure the upper and lower resistance limits of the checker match the user’s requirements. When testing the footwear should test within the range of 1 x 106 to 1 x 108 ohms.
Heel, sole and toe grounders should be worn on both feet to ensure effective use. They should be worn by all personnel and visitors within an ESD controlled area. If worn improperly, the heel, sole and toe grounders become ineffective. ESD footwear should be tested daily before use within an ESD Protected Area (EPA).
Welcome back to “A Minute with Miranda.” This week we will be covering how the WS Aware Monitor provides for continuous monitoring of an ESD Workstation setup.
The SCS WS Aware Monitor is a dual workstation continuous monitor for operators, ESD Worksurfaces and metal tools. It will continuously monitor the path-to-ground integrity and body voltage of two operators. It also monitors the path-to-ground integrity for two conductive or dissipative worksurfaces and two metal tools. It also continuously monitors for electromagnetic interference (EMI) on two metal tools which may cause electrical overstress (EOS) damage. The WS Aware Monitor eliminates the need for periodic testing and record keeping of wrist straps.
Per the ESD Handbook ESD TR20.20 section 18.4.2 “Some continuous monitors can monitor worksurface ground connections. A test signal is passed through the worksurface and ground connections. Discontinuity or over limit resistance changes cause the monitor to alarm. Worksurface monitors test the electrical connection between the monitor, the worksurface, and the ground point. However, the monitor will not detect insulative contamination on the worksurface.”
View the full range of SCS WS Aware Monitors here.
Welcome back to “A Minute with Miranda.” This week we will be covering why you need to use ESD footwear within your ESD Protected Area (EPA).
Per the ESD Handbook ESD TR20.20, Personnel may also be grounded through the use of ESD footwear with an ESD Flooring system. This method is useful for situations where personnel are mobile or standing in areas where a wrist strap is not feasible and ESDS items must be handled or transported. ESD protective footwear is designed to reduce body charge levels by providing a conductive path from the body to the ESD flooring material.
Heel, sole and toe grounders should be worn on both feet to ensure effective use. They should be worn by all personnel and visitors within an ESD controlled area. If worn improperly, the heel, sole and toe grounders become ineffective. ESD footwear should be tested daily before use within an ESD Protected Area.
Welcome back to “A Minute with Miranda.” This week we will be covering how to use the WS Aware Monitor for continuous monitoring of SCS wrist straps when at an ESD Workstation.
The SCS WS Aware Monitor is a dual workstation continuous monitor for operators, ESD Worksurfaces and metal tools. It will continuously monitor the path-to-ground integrity and body voltage of two operators. The WS Aware Monitor eliminates the need for periodic testing and record keeping of wrist straps. The WS Aware Monitor features operator body voltage detection. It will alarm if the operator generates or comes into contact with voltage that would be dangerous to an ESD susceptible item. Per the ESD Handbook ESD TR20.20 section 5.3.2.4.4 “Typical test programs recommend that wrist straps that are used daily should be tested daily. However, if the products that are being produced are of such value that knowledge of continuous, reliable ground is needed, then continuous monitoring should be considered or even required.”
Welcome back to “A Minute with Miranda.” This week we will be covering how to properly clean an ESD Worksurface Mat.
For optimum electrical performance, the ESD worksurface mat surface should be cleaned regularly using a recommended ESD mat cleaner. Per the ESD Handbook ESD TR20.20, “Ensure that cleaners that are used do not leave an electrically insulative residue common with some household cleaners.” We recommend using Reztore ESD Surface and Mat Cleaner. Reztore is alcohol free and does not contain silicone or other substances that will leave an insulative residue or inhibit the performance of the ESD worksurface mats.
After cleaning the ESD worksurface mat with Reztore it is recommended to test the surface to ensure that all insulative contaminates such as dirt and grime have been removed from the mat. SCS worksurface mats meet the ANSI/ESD STM4.1 and ANSI/ESD S20.20 required limit of 1 x 106 to less than 1 x 109 ohms for Rtt and Rtg and the recommendations of ANSI/ESD S4.1. View the range of Reztore Alcohol Free products here.
