Electrical Overstress, or EOS, has become a widely-used term over the past few years. However, a lot of people are still unsure as to what exactly it is and how it differs from ElectroStatic Discharge (ESD). Today’s blog post is intended to put an end to the confusion.

What is Electrical Overstress?
One huge problem with Electrical Overstress, or EOS, is the fact that people use the phrase in different ways. Up until now there has been no widely recognized definition. A White Paper on EOS published by the Industry Council on ESD Target Levels in 2016 uses the following definition: “An electrical device suffers an electrical overstress event when a maximum limit for either the voltage across, the current through, or power dissipated in the device is exceeded and causes immediate damage or malfunction, or latent damage resulting in an unpredictable reduction of its lifetime.

Simplified, EOS is the exposure of a component or PCB board to a current or voltage beyond its maximum ratings.  This exposure may or may not result in a catastrophic failure.

ElectoStatic Discharge (ESD) versus Electrical Overstress (EOS)
You can compare an ESD event with a knocked-over glass of water on a floor: you’ll get a small puddle but once all the water has spilt from the cup, it’s gone. There is no more water left and the damage is fairly limited. [Source]

ESD can be compared to a knocked-over glass of water
ESD can be compared to a knocked-over glass of water

However, an EOS event can be compared to an open tap; there may be just a little drip in comparison but there is an unlimited amount of water available. After a while, the entire floor may be flooded and could cause some serious damage. As you can see, EOS events last several magnitudes longer than most ESD events. [Source]

EOS can be compared to a dripping tab
EOS can be compared to a dripping tab

By many, ESD is seen as just one type of electrical stress. EOS on the other hand, describes a wide number of outcomes resulting from multiple stresses or root causes.

ESD does not require a “victim” or damaged product. There will be an ESD event if two objects are at different charge levels and a rapid, spontaneous transfer of an ElectroStatic charge between them occurs. An electrical stress can only become an overstress (as in EOS) if we’re aware of how much stress the “victim” (i.e. sensitive device) can withstand. One specification used to document these limits is the “Absolute Maximum Rating” (AMR). More on that in a little while. Back to EOS and ESD for now. The below image highlights the relationship and contrast between EOS and ESD:

Relationship between EOS and ESD
Relationship between EOS and ESD [Source]
Generally speaking, EOS describes extreme signals other than ESD. The following table lists the main differences:

  ESD Event EOS Event
Cause Rapid discharge of accumulated charge Voltage and/or currents associated with operation of equipment or with power generating equipment
Duration Once accumulated charge is consumed, ESD event can no longer manifest itself Lasts as long as originating signals; no inherent limitation
Characteristics Have specific waveform which includes rapid rising edge and asymptotic read edge Can have any physically possible waveform as sources of EOS are often unpredictable
Occurrence Non-periodic and non-repeatable (accumulation of charge cannot be guaranteed) Mostly (but not always) periodic and repeatable

Differences between EOS and ESD [Source]

The importance of Electrical Overstress (EOS)
Many failures in the electronics industry can be contributed to EOS. Yes, ESD has received a lot of attention over the past years. However, ESD represents only a small percentage of total EOS damages.

Typical causes of device failures
Typical causes of device failures [Source]
As explained further above, EOS and ESD are NOT the same thing. This is extremely important because:

  1. EOS damages are much more common compared to failures caused by ESD.
  2. A comprehensive ESD Control Program will provide protection against ESD but not EOS.

Now that you have learned what EOS is, how it’s different from ESD and that ESD protection is not effective for EOS damage, the obvious question will be “How can I protect my sensitive devices from EOS failures?”. That’s where we go back to our “Absolute Maximum Rating” (AMR) mentioned earlier.

Absolute Maximum Rating (AMR) and Electrical Overstress (EOS)
We’ve established earlier that EOS is caused by exceeding specific limits of a device, the so called Absolute Maximum Rating or AMR.
AMR represents “the point beyond which a device may be damaged by a particular stress” [Source].

Interpretation of AMR*
Interpretation of AMR* [Source]
*the yellow line represents the number of components suffering catastrophic damage

  • Region A is the safe operating area in which devices are to operate as anticipated.
  • Region B does not guarantee for the device to function as it should. No physical damage is expected in this area; however, if a device is operated in this region for extended periods of time, it may cause reliability problems.
  • The upper limit of region B represents the AMR. Issues will arise if a device is operated beyond this point.
  • Region C is the first area of electrical overstress causing latent failures.
  • Region D is the second area of electrical overstress causing immediate damages.

Protecting your sensitive devices from Electrical Overstress (EOS)
As already stated, ESD Protection measures are useless when it comes to protecting your sensitive devices from EOS. “Rather, improvement and mitigation of EOS failure causes will only advance through better communication between the supplier and the customer. This includes proper understanding of AMR, realistic specifications for it, finding the root cause of EOS damage incidents, and identifying the field and system application issues.” [Source]

References:

Happy Friday to everyone! Are you ready for another round of ESD updates? We’ve got a real gem for you today so let’s jump right in.
We’ve so far learned what ESD is and why ESD Protected Areas are so important. In today’s post, we want to arm you with 3 simple tactics to protect your ESD sensitive items. It’s easier than you think!

ESD Protection is a Requirement!
As electronic technology advances, electronic circuitry gets progressively smaller. As the size of components is reduced, so is the microscopic spacing of insulators and circuits within them, increasing their sensitivity to ESD. Industry experts estimate that average electronics product losses due to static discharge range from 8 to 33%. Others estimate the actual cost of ESD damage to the electronics industry as running into the billions of dollars annually. It is therefore critical to be aware of the most sensitive items being handled in your factory as the need for proper ESD protection increases every day.
Per ESD Handbook ESD TR20.20-2008 section 2.2: “Electronic items continued to become smaller, faster and their susceptibility to static damage increased…all electronic devices required some form of electrostatic control to assure continued operation and product reliability.”

Below you will find 3 simple tips to get ahead of the game.

1. Establish your ESD Protected Area
As a reminder, an ESD Protected Area (EPA) is a defined space within which all surfaces, objects, people and ESD Sensitive Devices (ESDs) are kept at the same potential. That means:

  • All surfaces, products and people are linked to ground.
  • Moveable items, such as containers and tools, are bonded by standing on a grounded surface or being held by a grounded operator.
  • Everything that does not readily dissipate a charge must be excluded from the EPA.

In our last post we talked in detail about how to set-up an ESD Protected Area so if you’re unsure where to start, catch-up with the post here.

Remember that it’s just as important to mark your ESD Protected Area as it is to have it set-up correctly in the first place. If your EPA is not clearly identified, operators will not realize that special pre-cautions are required when entering. You really don’t want an unprotected person wandering over and touching things on the ESD workbench. All your hard work, time and money could be wasted. Make sure you use signs and tape to distinguish your EPA from the rest of your workshop.

Employee working at an ESD Protected Workstation
An employee working at an ESD Protected Workstation

Some take-away points for you:

  • The ESD Protected Area (EPA) should have signage to clearly identify where it is.
  • All conductors including personnel must be grounded. Operators must either wear wrist straps or footwear in combination with an ESD floor. ESD working surfaces (e.g. mats) are to be grounded.
  • Wristbands are to be worn snug; the grounding tab of foot grounders must be placed under the foot in the shoe; ESD smocks need to cover all clothing on the torso.
  • Wrist straps and footwear are to be tested daily. For wrist straps a continuous monitor can be used instead.
  • Remove all non-essential insulators or neutralize essential insulators with ionizers.
  • Use packaging with shielding properties to store or transport ESDS outside the EPA.
  • Only handle unpackaged ESDs in an EPA when grounded.
  • Periodic checks of installed products (e.g. ESD working surfaces, ESD flooring etc.) are required.
  • Only trained or escorted people are to be allowed in the EPA.

2. Determine your ESD sensitive items
It is critical to be aware of the most sensitive item being handled in your factory. As with any type of control, there are several levels of protection. The method for choosing the necessary degree of ESD protection starts with defining your static sensitivity for electronic components. The ESD Association defines different classes of sensitivity for the HBM (Human Body Model) and CDM (Charged Device Model).

ESDS Component Sensitivity Classification
ESDS Component Sensitivity Classification

How can you determine the class of sensitivity of the devices within your facility? Look at your product flow through your facility, start at receiving and walk the components or products through until they are at dispatch ready to ship. Chances are, you have several different product flows through your facility. Each flow or loop will have specific components that enter or travel the loop. Make a list of all the sensitive components in each loop and determine the static voltage sensitivity or rating from each of the manufacturers. The lowest voltage sensitivity will dictate the sensitivity class of each loop. The philosophy here is “the chain is only as strong as the weakest link”. Each loop should have the required ESD protection for the most sensitive components that will travel this loop. This will define what class of protection is needed for each loop. You can have different class loops as long as the loops are closed, not allowing other components in. The objective here is to define a static control program to safeguard your most sensitive component.

Per ESD Handbook ESD TR20.20-2008 section 4.1.1 Determining Part ESD Sensitivity “The first step in developing an ESD Control Program plan is to determine the part, assembly or equipment sensitivity level under which the plan is to be developed. The organization can use one of several methods to determine the ESD sensitivity of the products that are to be handled. Some of the various methods are: 1) Assumption that all ESD products have a HBM sensitivity of 100 volts; 2) Actual testing of products using accepted test methods.”
Any ESD sensitive item should be identified with the ESD sensitivity symbol, either on itself or its container. The ESD Sensitivity Symbol (also called Susceptibility or Warning Symbol) identifies items that can be damaged by ESD and should ONLY be unpackaged and handled while grounded at an ESD protected workstation.

3. Train, train train!
No, we’re not talking about railway cars here. What we are referring to is teaching your employees. “Initial and recurrent ESD awareness and prevention training shall be provided to all personnel who handle or otherwise come into contact with any ESDS [ESD sensitive] items. Initial training shall be provided before personnel handle ESDS items. The type and frequency of ESD training for personnel shall be defined in the Training Plan. The Training Plan shall include a requirement for maintaining employee training records and shall document where the records are stored. Training methods and the use of specific techniques are at the Organization’s discretion. The training plan shall include the methods used by the Organization to verify trainee comprehension and training adequacy.” [ANSI/ESD S20.20-2007 section 7.2]

Training is an essential part of an ESD Control Program
Training is an essential part of an ESD Control Program

Perhaps the most important factor in a successful static control program is developing an awareness of the “unseen” problem. People are often a major factor in the generation of static charges. Studies have shown that personnel in a manufacturing environment frequently develop 5000 volts or more just by walking across the floor. Again, this is “tribocharging” produced by the separation of their shoes and the flooring as they walk.
A technician seated at a non-ESD workbench could easily have a 400-500 volt charge on his or her body caused not only by friction or tribocharging but additionally by the constant change in body capacitance that occurs from natural movements. The simple act of lifting both feet off the floor can raise the measured voltage on a person as much as 500-1000 volts.
Educating your personnel is therefore an essential basic ingredient in any effective static control program. A high level of static awareness must be created and maintained in and around the protected area. Once personnel understand the potential problem, it might help to reinforce this understanding by hanging up a few static control posters in strategic locations. The technician doesn’t need an unprotected person wandering over and touching things on the service bench.

In our last post, we talked about ESD: what it is, what types of ESD damage there are and what costly effects ESD can have. Missed our very first post? Catch-up here.
All caught up? Right, moving on. Today you will learn how to avoid ESD damage and protect your ESD sensitive items. So, let’s jump right in.

The fundamental ESD Control Principles
We’ve established that ESD is the hidden enemy in the electronics industry. Therefore, the BIG question is: how exactly do you control ElectroStatic Discharge (ESD) in your workplace? Easy – just follow these ESD fundamentals:

  1. Ground all conductors including people
  2. Remove all unnecessary non-conductors (also known as insulators)
  3. Place ESD sensitive devices inside of shielding packaging when transported outside of an ESD Protected Area (EPA)

Per ESD Handbook ESD TR20.20-2008 section 2.4 “It should be understood that any object, item, material or person could be a source of static electricity in the work environment. Removal of unnecessary nonconductors, replacing nonconductive materials with dissipative or conductive materials and grounding all conductors are the principle methods of controlling static electricity in the workplace, regardless of the activity.

These are the essential principles of ESD Control. If you implement all three points above, you will be in control of ESD and your sensitive items will be protected. Well, that wasn’t hard, was it? Don’t be terrified – we’ll go through everything in detail. We’ll cover #2 and #3 in future points – today’s focus is #1.

Definition of an ESD Protected Area (EPA)
An ESD Protected Area (EPA) is a designated zone – all surfaces, objects, people and ESD Sensitive Devices (ESDs) within are kept at the same electrical potential. This is achieved by simply using ‘groundable’ materials for covering of surfaces and for the manufacture of containers and tools. This applies to all items with an electrical resistance of less than 109 ohms.

An EPA could be just one workstation or it could be a room containing several different workstations. It can be portable as used in a field service situation or permanent.

Example-EPA-Area
Example of an ESD Protected Area

The user guide CLC/TR 61340-5-2:2008 defines an EPA as follows:
An ESD protected area (EPA) is an area that is equipped with the ESD control items required to minimize the chance of damaging ESD sensitive devices. In the broad sense, a protected area is capable of controlling static electricity on all items that enter that work area. Personnel and other conductive or dissipative items shall be electrically bonded together and connected to ground (or a common connection point when a ground is not available) to equalize electrical potential among the items. The size of an EPA can vary greatly. A protected area may be a permanent workstation within a room or an entire factory floor encompassing thousands of workstations. A protected area may also be a portable worksurface or mat used in a field service situation.” [CLC/TR 61340-5-2:2008 Use guide clause 4.6 Protected areas (EPA)]

You’re probably wondering now, how exactly you can get all surfaces, objects and operators to the same electrical potential. Fear not – we’ve got you covered!

  1. Personnel Grounding
    As previously stated, a fundamental principle of ESD control is to ground conductors including people at ESD protected workstations.Wrist straps are the first line of defense against ESD, the most common personnel grounding device used, and are required to be used if the operator is sitting. The wristband should be worn snug to the skin with its coil cord connected to a common point ground which is connected to ground, preferably equipment ground.

    Wearing-Wrist-Strap
    Wearing a wrist strap and connecting it to a common point ground

    If you are not using a continuous or a constant monitor, a wrist strap should be tested while being worn at least daily. This quick check can determine that no break in the path-to-ground has occurred. Part of the path-to-ground is the perspiration layer on the person; an operator with dry skin may inhibit the removal of static charges and may cause a test failure.
    The wrist strap system should be tested daily to ensure proper electrical value. Nominally, the upper resistance reading should be ” [ANSI/ESD S1.1 Annex A, 3 Frequency of Functional Testing]

    A Flooring / Footwear system is an alternative for personnel grounding for standing or mobile workers. Foot grounders or other types of ESD footwear are worn while standing or walking on an ESD floor. ESD footwear is to be worn on both feet and should be tested independently at least daily while being worn. Unless the tester has a split footplate, each foot should be tested independently, typically with the other foot raised in the air.
    Compliance verification should be performed prior to each use (daily, shift change, etc.). The accumulation of insulative materials may increase the foot grounder system resistance. If foot grounders are worn outside the ESD protected area testing for functionality before reentry to the ESD protected area should be considered.” [ESD SP9.2 APPENDIX B – Foot Grounder Usage Guidance]

    Both ESD footwear and ESD floor are required. Wearing ESD footwear on a regular, insulative floor is a waste of time and money.

    Wearing-Foot-Grounders
    Wearing foot grounders on an ESD floor

    Part of the path-to-ground is the perspiration in the person’s shoes. The conductive tab or ribbon of foot grounders should be placed inside the shoe under the foot with the excess length tucked into the shoe. Thanks to the perspiration in the shoe, direct contact with the skin is normally not necessary.

    If an operator leaves the EPA and walks outside wearing ESD footwear, care should be taken not to get the ESD footwear soiled. Dirt is typically insulative, and the best practice is to re-test the ESD footwear while being worn each time when re-entering the EPA.

  2. Working Surfaces
    ESD working surfaces, such as mats, are typically an integral part of the ESD workstation, particularly in areas where hand assembly occurs. The purpose of the ESD working surface is two-fold:

    1. To provide a surface with little to no charge on it.
    2. To provide a surface that will remove ElectroStatic charges from conductors including ESDS devices and assemblies) that are placed on the surface.

    ESD mats need to be grounded. A ground wire from the mat should connect to the common point ground which is connected to ground, preferably equipment ground. For electronics manufacturing a working surface resistance to ground (RG) of 1 x 106 to less than 1 x 109 ohms is recommended.
    The single most important concept in the field of static control is grounding. Attaching all electrically conductive and dissipative items in the workplace to ground allows built-up electrostatic charges to equalize with ground potential. A grounded conductor cannot hold a static charge.” [Grounding ANSI/ESD S6.1 Foreword]
    Per ANSI/ESD S20.20 section 6.2.1.2 Grounding / Bonding Systems Guidance, “In most cases, the third wire (green) AC equipment ground is the preferred choice for ground.
    Best practice is that ground connections use firm fitting connecting devices such as metallic crimps, snaps and banana plugs to connect to designated ground points. The use of alligator clips is not recommended.

    The working surface must be maintained and should be cleaned with an ESD cleaner. Regular cleaners typically contain silicone, and should never be used on an ESD working surface. ESD Handbook ESD TR20.20-2008 section 5.3.1.14 Maintenance “Periodic cleaning, following the manufacturerís recommendations, is required to maintain proper electrical function of all worksurfaces. Ensure that cleaners that are used do not leave an electrically insulative residue common with some household cleaners that contain silicone.

  3. Other moveable objects
    Moveable items (such as containers and tools) are grounded when placed on a grounded surface or being held by a grounded operator. Everything that does not readily dissipate charge must be excluded from the EPA (refer to #2 of our ESD Control Principles above). Regular plastics, polystyrene foam drink cups and packaging materials, etc. are typically high charging and have no place at an ESD protective workstation.

    Intention of an ESD Protected Area (EPA)We’ve learnt in our previous blog post that ElectroStatic discharge (ESD) can damage components and products that contain electronics. A lot of the time, this damage is not detected during quality inspection and can cause significant problems further down the line.An ESD Protected Area (EPA) is an area that has specifically been created to control ESD; its purpose is therefore to avoid ALL problems resulting from ESD damage. Workers need to understand AND follow the basics of ESD control to limit the generation of electrostatic charges as well as limit and slow discharges in the EPA.Recognizing an ESD Protected Area (EPA)
    An ESD Protected Area must be clearly identified using signs and/or aisle tape. This ensures operators and visitors are alerted when entering (or leaving) an ESD Protected Area which require special precautions (grounding via wrist straps and/or foot grounders etc.). It also indicates that they are entering (or exiting) areas where exposed ESDS items can be handled safely.Remember to be consistent throughout your shop floor, i.e. use the same signs. This will avoid confusion for your operators.

    EPA-Caution-Sign
    Example of an EPA caution sign

    While signs are one way of indicating the boundaries of an EPA, it is not the only way. Any alternate method that alert the personnel that an EPA begins is acceptable to ANSI/ESD S20.20. Some of the alternate ways to mark the boundaries of an EPA are:

    • tape on the floor
    • different color floor tiles
    • different color carpet
    • any other way to establish boundary conditions

    Anyway to distinguish the boundaries of an EPA would be acceptable as long as the personnel are aware of the indications and take the proper precautions while inside the EPA.” [ESD TR20.20-2016 section 9.1.2 EPA Boundary Indicators]

    Building an ESD Protected Area (EPA)
    A basic form of an ESD Protected Area is a workstation consisting of the following components:

    • An ESD working surface mat
    • A grounding cord
    • A wristband
    • A coiled cord
    • A common point ground

    To set-up an EPA:

    1. Connect the ESD working surface mat to the common point ground using the grounding cord.
    2. Link the operator to the common point ground using the wristband and coiled cord.

    Congratulations – you’ve just created an ESD Protected Area!
    By following the above steps, each component (the ESD mat and the operator) is kept at the same electrical potential (ground). Any ElectroStatic charge (ESD) is removed to ground via the common point ground.

Welcome to this little corner of the interwebs! Today marks the beginning of something truly amazing: our very own blog! You’re currently reading through our first blog post and we appreciate you taking time out of your busy life and spending it here.

The intention of this blog is to provide you with resources, information and tools – all focused around ESD! So, if you have any ideas for future blog posts or suggestions on what we could do better, don’t be a stranger and leave a comment! We look forward to hearing from you.

Now, for this first post we thought we’d start right at the beginning: what is ESD? It’s the core of our business but a lot of people don’t understand what it’s all about so let’s clear that up – right here and right now!

ElectroStatic Charge
Everything you see around you is made from atoms – your mouse, keyboard, screen, cup of coffee etc. Every atom is constructed of a nucleus, which includes positively charged protons, and one or more negatively charged electrons bound to the nucleus. As atoms have an equal number of electrons and protons, it balances out having no charge. No problems so far!

Structure of an AtomStructure of an Atom (Source)

Unfortunately, all materials can tribocharge and generate ElectroStatic charges. Most of the time this happens through contact and separation; some everyday life examples are:

  • Opening a plastic bag
  • Combing hair
  • Walking across a floor

Walking across a floor.pngWalking across a floor can generate an ElectoStatic Charge

For most people, static electricity is represented by the noise or crackle heard on a radio that interferes with good reception or the shock experienced when touching a metal object after walking across a carpeted room or sliding across a car seat. Static electricity is also observed as static cling when clothes are stuck together after coming out of a clothes dryer. Most of the time, people observe static electricity when the weather is cold and dry.” “While many people tend to think of static electricity as being at rest or not moving, static electricity causes the most concern when it ceases to be stationary.” [ESD Handbook ESD TR20.20 section 2.1 Basics of Static Electricity, Introduction]

When two materials make contact and are then separated, a transfer of electrons from one surface to the other may take place. The amount of static electricity generated depends upon the materials subjected to contact or separation, friction, the area of contact or separation, and the relative humidity of the environment. At lower relative humidity (as the environment is drier) charge generation will increase significantly. Common plastics generally will create the greatest static charges.
Electrostatic charge is most commonly formed by the contact and separation of two materials. The materials may be similar or dissimilar although dissimilar materials tend to liberate higher levels of static charge. An example is a person walking across the floor. Static electricity is produced when the person’s shoe soles make contact, then separate from the floor surface. Another example is an electronic device sliding into or out of a bag, magazine or tube.” [ESD Handbook ESD TR20.20 section 2.3 Nature of Static Electricity]

ElectroStatic Discharge (ESD)
If two items are at different ElectroStatic charge levels (i.e. one is positively and the other negatively charged) and approach one another, a spark or ElectroStatic Discharge (ESD) can occur. This rapid, spontaneous transfer of an ElectroStatic charge can generate heat and melt circuitry in electronic components.

ESD.png

ElectroStatic Discharge (ESD)

ESD events are happening around us all the time – yet, most of these cannot be seen or felt. For a person to sense ElectroStatic Discharge (ESD) (the dreaded ‘zap’), a discharge of about 2,000V is needed. To actually see ESD (in form of an arc, e.g. lightning) even greater voltages are required.

While ESD in your home can be annoying, it’s generally harmless. However, in the electronics industry ESD is the hidden enemy. Damages caused by invisible and undetectable ESD events can be understood by comparing ESD damage to medical contamination of the human body by viruses or bacteria. Although invisible, they can cause severe damage. In hospitals, the defense against this invisible threat is extensive contamination control procedures including sterilization. In the electronics industry, it’s ESD Protection; we will get into more detail on that in a later post.

Many of the common activities you perform daily may generate charges on your body that are potentially harmful to electronic components. Some of these activities include:

  • Walking across a carpet: 1,500V to 35,000V
  • Walking over untreated vinyl floor: 250V to 12,000V
  • Worker at a bench: 700V to 6,000V
  • Picking up a common plastic bag from a bench: 1,200V to 20,000V

Many of the CMOS technology components can be damaged by discharges of less than 1,000 volts. Some of the very sophisticated components can be damaged by charges as low as 10 volts.

Types of ESD Device Damage
So, we’ve established what ESD is and learned that ESD can damage electronics components. But what exactly does this damage look like? We’re so glad you asked!

The industry differentiates between catastrophic failures and latent defects. Per ESD Handbook ESD TR20.20 section 2.7 Device Damage – Types and Causes “Electrostatic damage to electronic devices can occur at any point, from the manufacture of the device to field service of systems. Damage results from handling the devices in uncontrolled surroundings or when poor ESD control practices are used. Generally damage can manifest itself as a catastrophic failure, parametric change or undetected parametric change (latent defect).

Catastrophic failures occur when a component is damaged to the point where it is DEAD NOW and will never again function. In these cases, the ESD event may have caused a metal melt, junction breakdown or oxide failure. This is the easiest type of ESD damage to find since it can be detected during inspection and testing.
When an electronic device is exposed to an ESD event it may no longer function. The ESD event may have caused a metal melt, junction breakdown, or oxide failure. The device’s circuitry is permanently damaged, resulting in a catastrophic failure.” [ESD Handbook ESD TR20.20 section 2.7.1 Catastrophic Failures]

Catastrophic Failures

Catastrophic failures will lead to completely failed or dead components.

Latent defects occur when ESD weakens or wounds the component to the point where it will still function properly during testing, but over time the wounded component may cause poor system performance. Later, after final inspection, perhaps in the hands of your customer, a latent defect may become a catastrophic failure.
A device that is exposed to an ESD event may be partially degraded, yet continue to perform its intended function. However, the operating life of the device may be reduced dramatically. A product or system incorporating devices with latent defects may experience a premature failure after the user places them in service. Such failures are usually costly to repair and in some applications may create personnel hazards.” It is easy with the proper equipment to confirm that a device has experienced catastrophic failure or that a part is degraded or fails test parameters. Basic performance tests will substantiate device damage. However, latent defects are virtually impossible to prove or detect using current technology, especially after the device is assembled into a finished product. Some studies claim that the number of devices shipped to users with latent defects exceeds the number that fail catastrophically due to ESD in manufacturing.” [ESD Handbook ESD TR20.20 section 2.7.2 Latent Defects]

Latent Defects

Latent defects lead to degraded or wounded components

Costly Effects of ESD
Catastrophic failures are straight forward: they can be detected and repaired at an early manufacturing stage. This is the least costly type of ESD damage.

Latent defects on the other hand are not only hard to find, but they can also severely affect the reputation of your company’s product. Latent defects can cause upset or intermittent failures and can be very frustrating: customers return a product with a problem which the factory fail to detect so it ends up at the customer’s again with the problem unresolved.

ESD Damage on an Integrated Circuit

The cost for repairing latent defects increases as detection of the failure moves through the system. One study indicated the repair cost to be:

  • $10 Device
  • $10 Device in board: $100
  • $10 Device in board and in system: $1,000
  • $10 Device and system fails: $10,000

Industry experts estimate that product losses in the electronics industry due to static discharge range from 8 to 33%. Others believe the actual cost of ESD damage amount to billions of dollars annually.

Conclusion
ESD is the hidden enemy in the electronics industry:

  • It cannot be felt
  • It cannot be seen
  • It cannot necessarily be detected through normal inspection procedures.

Therefore, it is absolutely crucial to be aware of the most sensitive items in your factory. Technology advances all the time: electronic circuitry gets progressively smaller which leads to a reduction of microscopic spacing of insulators and circuits within components. “Electronic items continued to become smaller, faster and their susceptibility to static damage increased…all electronic devices required some form of electrostatic control to assure continued operation and product reliability.” [ESD Handbook ESD TR20.20 section 2.2]. While this is great news for the consumer with better, faster and stronger computers, tablets, phones etc., it’s bad news for the manufacturers. The evolution of technology leads to devices being even more sensitive to ESD. As a result, the need for appropriate ESD Protection is now more important than ever.

Over the next few weeks, we will provide you with all the tips, tools and techniques to create an effective ESD Control Program so that your sensitive components are protected against damages from ESD.