How to Properly Use An ESD Shielding Bag

A basic principle of ESD control in a manufacturing environment is that ESD susceptible items should only be removed from ESD protective packaging when they are in an ESD protected area (EPA). Most EPAs are made up of “Islands” of control; the packaging / materials handling system must provide proper protection for ESD susceptible items during transport and storage outside those “islands” of control. When moving ESD susceptible items outside an EPA, it is necessary for the product to be packaged in closed ESD Shielding Packaging.

BagUseLabel

Tip# 1 – Not a Worksurface

Do not use a shielding bag as an ESD worksurface. Although a shielding bag is safe to use around ESD susceptible products, it is not intended to be a worksurface for product. It should be set aside or discarded after removing the product from the bag.

BagUseProbe

Tip# 2 – No Potholders or Tacos

BagUseTaco

Do not use a shielding bag as an “ESD potholder” or “ESD taco.” This type of use offers no ESD protection to the product.

Tip# 3 – Enclose Product

BagUseCircuitBoard

Shielding bags should be large enough to enclose the entire product and closed with a label or zipper style bag. 

Tip# 4 – Remove Charges

BaguseMat

Place closed bag on an ESD worksurface before removing product to remove any charge that might have accumulated on the surface of the bag.

Tip# 5 – Don’t Over-Use

BagUseOveruse

Re‐using shielding bags is acceptable so long as there is no damage to the shielding layer. Bags with holes, tears, or excessive wrinkles should be discarded.

So, are you using your ESD bags correctly?

If you have questions regarding shielding bags or ESD control, please click HERE.

Click for more information on Metal-In Shielding Bags.

 

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Why Use Desiccants with Moisture Barrier Bags?

What is Desiccant?

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Desiccant is a drying agent that is used to absorb moisture from the air inside moisture barrier bags. Desiccant absorbs moisture vapor (humidity) from the air left inside that barrier bag after is has been sealed. Any moisture that penetrates the bag will also be absorbed. Desiccant remains dry to the touch even when it is fully saturated with moisture vapor.

Why are Electronics Moisture Sensitive?

SMD

Certain kinds of electronic devices called “Surface Mount Devices” or SMD’s are mounted on a circuit card by high temperature soldering. The body of the SMD is made from plastic that absorbs moisture from the air. When the case is heated during soldering, the moisture inside turns to steam and may break the device as the steam escapes. Keeping SMD’s dry before soldering means that the devices will not be damaged.

How is Desiccant Purchased?

Desiccant is sold by the “Unit” or fractional Unit. One unit of desiccant will absorb a specific amount of moisture. A unit weighs about 28 grams or 1 ounce. The pouches of desiccant are placed into metal pails to keep the desiccant dry during shipping and storage.

How is Desiccant Packaged?

Desiccant is packaged in small sealed pouches made from a white plastic called “Tyvek”, or brown “Kraft” paper. Tyvek pouches are very clean and sulfur free. Kraft pouches are economical.

How Much Desiccant Do I Need?

Method 1 (per MIL-P-116)

1. Formula: Unit = 0.011 x bag area in square inches

2. Example: 10″ x 20″ barrier bag

3. Find Bag Area: 10″ x 20″ x 2″ sides = 400 sqin

4. Apply Formula: Units = 0.011 x 400 sqin = 4.4

Use 4.5 Units of desiccant

Method 2 (per EIA 583. This formula allows you to tailor the desiccant to your specific needs)

What do you need to know?

Bag area, Bag MVTR, Months of Storage, Maximum Interior Humidity (MIH)

Formula

Units = 0.231 x Bag Area x Bag MVTR x Months divided by Moisture Capacity

Example

For a 10″ x 20″ bag with a 0.02 MVTR, a 12 month storage time and a MIH of 20%

Apply formula Units =

0.231 x 400 sqin x 0.02 MVTR x 12 divided by 4.8g / unit = 4.6

Use 4.5 Units of Desiccant

Moisture Capacity

10% MIH: 3.0 g/unit

20 MIH: 4.8 g/unit

30% MIH: 5.8 g/unit

40% MIH: 6.2/unit

For more information on desiccant packs and moisture barrier bags, visit ProtektivePak.com

CircuitBoard_Desiccant.jpg

 

 

What is Returnable Packaging?

ReturnablePackaging.jpg

“Returnable Packaging,” as defined by Returnable Packaging Association (RPA), is packaging which includes “…reusable pallets, racks, bulk containers, hand-held containers and dunnage that move product efficiently and safely throughout the supply chain. Reusable packaging is typically used by manufacturers/processors and their suppliers/customers in a well-organized supply chain, with very tightly managed shipping loops.”

So what does this mean? Returnable packaging is manufactured of durable materials and is specifically designed for multiple trips and extended life.

When a vehicle leaves a facility to drop off product and then returns to pick up more product, you have what is called a “milk run”. Milk runs are perfect for returnable packaging.

Utilizing returnable packaging cuts down on material costs as well as total cost. There is much less need for repeated purchasing of disposable containers.  The money saved will now go towards your profit line! In addition, returnable packaging cuts down on waste by re-using packaging rather than just using it once and throwing it away. No more dumpsters full of unneeded waste!

Protektive Pak In-Plant Handlers are a great choice for reusable packaging. Made to protect ESD sensitive components, the boxes are constructed with double thick sides and double or triple thick ends and are extremely durable. They withstand the abuse of transporting. After transporting product to another facility, the boxes can be reused to ship more product or collapsed and stored for future use.

Why Use ESD Shielding vs Non-Shielding Containers

ShieldingVsNonShieldingElectroStatic Discharge (ESD) is silent, quick and potentially lethal to electronic parts. When electronic parts are not properly handled during manufacturing, assembly, storage, or shipping, damage from ESD can reach into the millions of dollars each year.

For an ESD control container to be effective against ElectroStatic Discharge, it must possess certain electrical characteristics:

  • Surface resistance <1 x 1011 ohms per ANSI/ESD STM11.11
  • Energy penetration <50 nanoJoules per ANSI/ESD STM11.31

Non-shielding containers might be cheaper, but they are not less costly when it comes to handling ESD sensitive items. Anytime ESD sensitive parts and assemblies are handled, regular containers are not a sound option, even part of the time, as the risk of ESD damage is always lingering. As a result, costs will be incurred, either via ESD damage or as an additional investment in discharge shielding packaging and material handling containers.

The disadvantages of cross-using shielding and non-shielding containers include:

  • Increased cost
  • Risk from ESD damage
  • Handling inconvenience

The cost of a discharge shielding container is far less than the cost associated with damaged parts or extra handling that result with a “less expensive” non-shielding container.

ESD Control – Other Considerations

Application Photo of Surface Resistance Test Kit

OTHER CONSIDERATIONS
Discipline
A significant increase in the discipline of implementing the fundamentals of ESD control noted in ANSI/ESD S20.20 Foreword, calls for:

  • Ground all conductors in the EPA including people
  • Remove all insulators from the EPA or use ionizers for process necessary insulators
  • Package ESD sensitive items going outside the EPA in packaging that provides electrostatic discharge shielding

Insulators
We encourage developing a hatred for insulators. The alternatives are:

    Remove the insulative item from the EPA

  • Substitute the item with an ESD protective version (such as tape, document holders, material handling containers, plastic bottles, etc.)
  • Periodically treat insulative surface with a topical antistat
  • Neutralize electrostatic charges using ionization

Other ESD Control Items
Other EPA ESD control items to add to the ESD control program might include shelving, mobile equipment (carts), gloves, and/or seating.

Improve Compliance Verification Plan

  • Consider greater frequency of internal audits per ESD TR53
  • Use of computer data collection system for wrist straps and footwear testing, continuous monitors, and ionizers
  • Use of ground continuous monitors for worksurfaces and other ESD elements
  • Test ionizers more frequently, consider self monitoring ionizers, consider computer based data collection
  • Increased testing using static field meter to verify that automated processes (like auto insertion, tape and reel, etc) are not generating charges above acceptable limits.

Application Photo of Volt Meter and Software in Factory STM97.2 Testing Voltage Charge on Person (Photograph courtesy of TREK, INC.)

Improve Training

  • ESD awareness training for all in the EPA or who may come into the EPA including suppliers
  • Testing to verify comprehension and training adequacy
  • Training on the proper use of test equipment
  • Training on proper compliance verification test procedures

Application Photo CD-ROM ESD Training

Conclusion
Just to maintain a company’s current level of quality and reliability may require a substantial improvement in a company’s ESD control program. Now is the time for improvement as ESD sensitivity withstand voltages continue to get lower and companies may soon be handling class 0A HBM items. To combat HBM failures improved personnel grounding is required. For example, heel grounders should be replaced with full coverage foot grounders. However, most failures are CDM. To combat CDM failures, ionization should be added or improved, and conductive surfaces should be covered with dissipative material. In general, disciple should be enhanced implementing ESD control fundamentals, compliance verification testing should be increased, and training should be improved.

From published article “Now is the Time for ESD Control Programs to be Improved” by Fred Tenzer and Gene Felder. See full article at InCompliance Magazine- September 2012

Tips for Addressing Charged Device Model Failures


CHARGED DEVICE MODEL

It may seem to some that CDM has newly arrived as a problem for ESD control programs. However, the ESD Association first published ANSI/ESD STM5.3.1 in 1999 – ESD Association Standard for Electrostatic Discharge Sensitivity Testing – Charged Device Model (CDM) – Component Level. Basically, CDM testing has to do with “testing, evaluating and classifying the electrostatic discharge (ESD) sensitivity of components to the defined charged device model (CDM)” … “to allow for accurate comparisons of component CDM ESD sensitivity levels.”

JESD22-C101C Field-Induced Charged-Device Model Test Method for Electrostatic-Discharge-Withstand Thresholds of Microelectronic Components Table 3
Devices shall be classified as follows:
CLASS I <200 volts
CLASS II 200 to <500 volts
CLASS III 500 to 1000 volts
CLASS IV >1000 volts

The importance of CDM came about primarily because of the increased use of automated component handling systems. The Foreword of ANSI/ESD STM5.3.1 states “In the CDM a component itself becomes charged (e.g., by sliding on a surface (tribocharging) or by electric field induction) and is rapidly discharged (by an ESD event) as it closely approaches a conductive object.”

In November 2002, Roger Peirce published an article entitled “The Most Common Causes of ESD Damage”. There were actually 23 causes. As the founder and president of ESD Technical Services, Roger had investigated hundreds of companies for over eight years. All 23 causes were CDM failure modes. So CDM is really not so new, it has just received a lot of attention in the last few years.


TACKLING CDM

So, what are the things companies should look at to improve their ESD control program regarding CDM? It would seem to be easy: don’t slide ESDS devices and assemblies unless grounded at all times, keep insulators at least 12” away from ESDS, and don’t allow ESDS items to make contact with a conductive surface. Seems simple, but in actual application . . . not so easy.

If the ESD control program has not used ionization that should be considered. If the ESDS items becomes charged, ionization will help neutralize the charge. The primary function of ionizers with regard to ESDS items are:

  • To remove / neutralize charges from process necessary insulators, which can charge ESDS items, thus creating the potential for a damaging CDM event
  • Remember that the PCB substrate is a process necessary insulator and can become charged during automated handling processes
  • To remove / neutralize charges from a charged, isolated/floating conductor, which, when grounded can result in a potentially damaging CDM event
  • Remember that during automated handling processes, the ESDS devices on the PCB are isolated or floating conductors

Application Photo Overhead Ionizer

The ESD Standards Committee has a Working Group (WG-17) which is currently involved with developing a Standard for Process Assessment to help the electronics community assess their manufacturing and handling processes to determine what levels of devices their process can handle. Once one fully understands where their process is with regards to ESDS devices and assemblies, they will have a clearer picture on what actions need to be taken to further improve the ESD Control Program.

If ionizers are already in use, the company should consider reducing the ionizer offset voltage limit of ±50 volts (the required limit in ANSI/ESD S20.20) to ±25 volts and maybe less, depending on the application and device sensitivity. Discharge times are user defined and should be considered for reducing the time required to neutralize a ± 1,000 volt charge to ± 100 volts.

The required limit for worksurfaces per ANSI/ESD S20.20 is less than 1 x 10^9 ohms with no lower limit. Most companies handling electronics should be following the recommendation of Worksurface standard ANSI/ESD S4.1 that the lower limit be 1 x 10^6 ohms. To combat CDM failures, all surfaces that might come into contact with ESDS items should be dissipative at the 1 x 10^6 to less than 1 x 10^9 ohms range used for worksurfaces where possible. Items such as Static Shielding bags will have a higher resistance on the interior & exterior surfaces, but it still must be less than 1 x 10^11 ohms.

Application Photo Statfree Worksurface Mat

From published article “Now is the Time for ESD Control Programs to be Improved” by Fred Tenzer and Gene Felder. See full article at InCompliance Magazine- September 2012

What’s Happening to Electronics Device ESD Sensitivity

Factory ESD control is expected to play an ever-increasing critical role as the industry is flooded with even more HBM (Human Body Model) and CDM (Charged Device Model) sensitive
designs.

ElectroStatic Discharge (ESD) is the hidden enemy within your factory. You cannot feel or see most ESD events but they can cause electronic components to fail or cause mysterious and annoying problems. There are two types of ESD damage: 1) catastrophic failures, and 2) latent defects. By definition, normal quality control inspections are able to identify catastrophic failures, but are not able to detect latent defects.

In general, the ESD susceptibility of modern electronics are more sensitive to ElectroStatic Discharge; that is the withstand voltages are lower. This is due to the drive for miniaturization and with electronic devices operating faster. Thus the semiconductor circuitry is getting smaller. What’s happening currently? The width of electronic device structures continues to get smaller. Intel began selling its 32nm processors in 2010 that would be 0.032 micrometer equal to 0.000032 millimeter or 0.00000128 inch.

See www.ESDA.org, the ESD Association’s latest White Paper “Electrostatic Discharge (ESD) Technology Roadmap” Revised April 2010” forecasts increased ESD sensitivities continuing the recent “trend, the ICs became even more sensitive to ESD events in the years between 2005 and 2009. Therefore, the prevailing trend is circuit performance at the expense of ESD protection levels.” The White Paper’s conclusions include:

  • With devices becoming more sensitive through 2010-2015 and beyond, it is imperative that companies begin to scrutinize the ESD capabilities of their handling processes. Factory ESD control is expected to play an ever-increasing critical role as the industry is flooded with even more HBM (Human Body Model) and CDM (Charged Device Model) sensitive designs. For people handling ESD sensitive devices, personnel grounding systems must be designed to limit body voltages to less than 100 volts.
  • To protect against metal-to-device discharges, all conductive elements that contact ESD sensitive devices must be grounded.
  • To limit the possibilities of a field induced CDM ESD event, users of ESD sensitive devices should ensure that the maximum voltage induced on their devices is kept below 50 volts.
  • To limit CDM ESD events, device pins should be contacted with static-dissipative material instead of metal wherever possible.

See May 2010 article by Dr. Terry L. Welsher The “Real” Cost of ESD Damage which includes “Recent data and experience reported by several companies and laboratories now suggest that many failures previously classified as EOS [Electrical Overstress] may instead be the result of ESD failures due to Charged Board Events (CBE). Some companies have estimated that about 50% of failures originally designated as EOS were actually CBE or CDE [Charged Device Events].”

ANSI/ESD S20.20, the ESD Association document covering the development of an ESD control program, lists numerous ESD Protected Area (EPA) ESD control items. Each company can pick and choose which ones are appropriate for their program. The selection of specific ESD control procedures or materials is at the option of the ESD Control Program Plan preparer and should be based on risk assessment and the established electrostatic discharge sensitivities of parts, assemblies, and equipment.” [ANSI/ESD S20.20-2007 Annex B] “An EPA [ESD protected area] shall be established wherever ESDS [ESD Sensitive] products are handled. However, there are many different ways to establish ESD controls within an EPA. Table 3 lists some optional ESD control items which can be used to control static electricity. [ANSI/ESD S20.20-2007 section 8.3 ESD Protected Areas (EPAs)]

There are companies with good ESD control programs who are pleased with their quality and reliability results. But to maintain that level, they would be wise to consider ESD control program improvements. Now might be a good time to do that.

From published article “Now is the Time for ESD Control Programs to be Improved” by Fred Tenzer and Gene Felder. See full article at InCompliance Magazine– September 2012

NEW Plastek™ ESD Trash Receptacles

ESD Safe Trash Receptacle and Liner

Trash Receptacles:

  • ESD protective product to replace high charging plastic trash cans
  • Chemical and moisture resistant
  • Superior strength and durability; made from extruded
    high impact polypropylene material
  • Convenient fold down design for easy storing
  • Conductive Rtt 1 x 10E2 < 1 x 10E5 ohms
  • Reusable
  • ESD protective liners also available
  • Made in the United States of America

Economy Pink Liners:

  • Ideal for use inside ESD protected areas
  • Low cost, economical
  • Surface Resistance: < 10E11 ohms
  • Durable Thickness: 0.002 in (2.0 mil)
  • Packaged 50 bags per pack
  • Made in the United States of America
Item Description 1+ 25+ 50+ 100+*
37816 Trash Receptacle, 12-1/2” x 10” x 14”, 10 Gal. $35.93 $34.85 $33.81 $32.12
37817 Trash Receptacle, 21” x 12-3/4” x 28”, 36 Gal. $54.29 $52.66 $51.08 $48.53
37822 Economy Pink Liner, 26” x 26”, 10 Gal. $25.90 $24.61 $22.70 $22.01
37823 Economy Pink Liner, 36” x 40”, 36 Gal. $62.10 $60.24 $58.43 $56.68

“It should be understood that any object, item, material or person could be a source of static electricity in the work environment.
The 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.”

*The prices in the Protektive Pak Online Catalog supersede all pricing on new product announcements and may change without notice.

Click HERE for Printable Version | Request a sample HERE | See a list of sales reps HERE
All items & programs are available through your participating distributor | Submit your question HERE

Images of ESD Damage

Seeing ElectroStatic Discharge (ESD) damage is basically impossible. Damage to semiconductor device structure is NOT visible at ordinary magnifications of an optical microscope. If the microscope is capable of 1000X-1500X magnifications, you just might be able to “see” something. The method used, only occasionally as there is considerable expense, is by delayering and etch enhancement producing high magnification photographs using a scanning electron micrograph (SEM). See Images of ESD Damage, photos of Human Body Model (HBM) ESD damage provided by Hi-Rel Laboratories, Inc. at 6116 N Freya, Spokane, Washington 99217 (509-325-5800 or www.hrlabs.com). Used with their permission.

ElectroStatic Discharge (ESD) Person Can Feel

It typically takes a ESD discharge greater than 2,000 or 3,000 volts for a person to feel the “zap”.

There is no exact voltage number where a person starts to feel a discharge. The ESD Association addresses this topic three times in the ESD Handbook ESD TR20.20 using these phrases:

  • “greater than 2000 volts”
  • “about 3,000 volts”
  • “exceed 3,000 volts”

The sensitivity of people is different and measuring the voltage is imprecise, so neither 2,000 nor 3,000 is to be an exact number.

Per ESD Handbook ESD TR20.20 Wrist Strap section 5.3.2.1 “Static electricity is a natural phenomenon that occurs in all climates and at all levels of relative humidity year round. Most people cannot feel an electrostatic discharge unless the static voltage is greater than 2000 volts.”

Per ESD Handbook ESD TR20.20 section 2.3 Nature of Static Electricity “The quantity, charge, is difficult for most people to visualize without some reference. As an example, an average person has a capacitance of about 100 picofarads (pF) and can feel a static discharge at their fingertips when the potential difference between their body and a grounded conductive object is about 3,000 volts (3 kV).”

Per ESD Handbook ESD TR20.20 ionizer section 5.3.6.5.3.3 Discharge Time and Product Sensitivity “Most personnel will not notice static discharges from the human body until they exceed 3,000 volts.”

The point, of course, is just because you cannot see or feel an ESD event, it does mean that ESD events are not occurring. Human beings are insensitive unless the ESD is several thousand volts. Many electronic components can be damaged by much smaller discharges.